Battery Charging Research Articles

Designing a Hybrid Energy-Efficient Harvesting System for Head- or Wrist-Worn Healthcare Wearable Devices.

Battery power is crucial for wearable devices as it ensures continuous operation, which is critical for real-time health monitoring and emergency alerts. One solution for long-lasting monitoring is energy harvesting systems. Ensuring a consistent energy supply from variable sources for reliable device performance is a major challenge. Additionally, integrating energy harvesting components without compromising the wearability, comfort, and esthetic design of healthcare devices presents a significant bottleneck. Here, we show that with a meticulous design using small and highly efficient photovoltaic (PV) panels, compact thermoelectric (TEG) modules, and two ultra-low-power BQ25504 DC-DC boost converters, the battery life can increase from 9.31 h to over 18 h. The parallel connection of boost converters at two points of the output allows both energy sources to individually achieve maximum power point tracking (MPPT) during battery charging. We found that under specific conditions such as facing the sun for more than two hours, the device became self-powered. Our results demonstrate the long-term and stable performance of the sensor node with an efficiency of 96%. Given the high-power density of solar cells outdoors, a combination of PV and TEG energy can harvest energy quickly and sufficiently from sunlight and body heat. The small form factor of the harvesting system and the environmental conditions of particular occupations such as the oil and gas industry make it suitable for health monitoring wearables worn on the head, face, or wrist region, targeting outdoor workers.

A novel framework for low-temperature fast charging of lithium-ion batteries without lithium plating

This paper proposes a novel framework for low-temperature fast charging of lithium-ion batteries (LIBs) without lithium plating. The framework includes three key components: modeling, constraints, and strategy design. In the modeling phase, a new electro-thermal coupled model is introduced, which integrates both frequency-domain and time-domain electro-thermal coupled models. They optimize the bidirectional pulsed current (BPC) heating parameters and charging current, respectively. Terminal voltage boundaries and lithium plating serve as constraints. Terminal voltage is confined within upper and lower limits to prevent battery overcharge and overdischarge. Lithium plating avoidance entails setting a minimum frequency for BPC heating. During charging, lithium plating is mitigated by maintaining negative potential above 0 V. To obtain calculated negative electrode potential, a three-electrode battery is employed to calibrate the electro-thermal coupled model parameters. Subsequently, a novel low-temperature fast charging strategy is devised. This strategy enables intelligent switching between BPC heating and charging, while also synergistically optimizing BPC heating parameters and charging current. The strategy also achieves optimization of both charging speed and energy consumption. Charging the battery SOC from 0.2 to 0.9 in 42 min at −10 °C, without triggering lithium plating, is feasible with this proposed strategy. Compared to strategies focusing solely on current amplitude optimization, heating followed by charging, and traditional methods, this heating strategy exhibits the highest charging speed.

A novel joint estimation for core temperature and state of charge of lithium-ion battery based on classification approach and convolutional neural network

The core temperature (CT) of lithium-ion batteries (LIBs) is crucial for effective thermal management, and is significantly influenced by the state of charge (SOC) among other battery parameters. However, directly measuring CT and SOC poses challenges. This study introduces a novel joint estimation method for CT and SOC, in which classification approach is pioneeringly employed through a two-dimensional convolutional neural network (2D-CNN). SOC is initially estimated and subsequently utilized as an input to refine CT estimation. This process is facilitated by two 2D-CNNs that incorporate measured indices such as current, terminal voltage, surface temperature, and ambient temperature into their inputs. Techniques including data augmentation, sequential optimization, and Gaussian filtering are employed to enhance estimation effect. The methodology is validated using LIB charge/discharge data derived from experiments based on the urban dynamometer driving schedule (UDDS). Results demonstrate that the root-mean-square errors (RMSEs) for CT and SOC estimation are below 0.267 °C and 0.7 %, respectively, across a broad ambient temperature range of −15 °C–55 °C. Consequently, this study confirms the effectiveness of using classification for CT and SOC estimation, illustrating that the proposed method can precisely estimate CT and SOC of LIBs across a wide temperature spectrum. The effectiveness of the deep learning method based on classification in estimating CT and SOC has been validated. Furthermore, a comparative analysis reveals that incorporating SOC as an input for CT estimation notably reduces the training time required by the method.

Energy-efficient Vienna rectifier for electric vehicle battery charging stations

Global DC fast-charging infrastructure is being rapidly developed to accommodate the ever-increasing demand from the electric vehicle market. A major complication in the electric power system's process is the proliferation of ultra-fast charging (UFC) stations, which are known for their enormous power consumption and unpredictable, intermittent performance. By implementing grid-supportive features and ensuring an improved power consumption profile for the grid, installing regional energy storage can solve these challenges. This study presents a control approach for managing the grid-side AC/DC converters of rapid charging stations focused on future-oriented regulation. The paper primarily concentrates on various Vienna rectifier topologies. The technology, characteristics, benefits, and operational aspects of Vienna rectifier topologies are vital to improving the performance, efficiency, and grid integration of electric vehicle charging systems. Fast charging, grid stability, energy economy, and the smooth integration of electric vehicles into the electrical grid are all made possible by Vienna rectifiers. When used in battery energy storage systems (BESS) for electric vehicle charging infrastructure, Vienna rectifiers allow for effective discharge and charging of the batteries. The configurations and assessments of these converters are examined, assessed, and compared based on power output parameters, element count, power factor, THD, and efficiency. The Vienna rectifier has been identified as the best suitable DC fast-charging converter architecture for power levels exceeding 15 kW due to its exceptional efficiency, limited output voltage ripples, high power density, reduced current ripples, and reliable performance. Research on ways to improve electric vehicle charging infrastructure can be spurred by a better grasp of the Vienna rectifier's technological complexities and performance benefits, leading to greener and more efficient transportation options. As a result, the system's power density will eventually rise and elemental stress will decrease.

Visualizing Reaction Distributions for Materials Validation and Failure Analysis in Li-Ion Batteries

A real-time, high-throughput visualization technique for heterogeneity in lithium-ion battery (LIB) electrodes is necessary to understand battery performance on a mechanistic level. Our group, along with others, has seen that battery performance is governed by short range (<20 um) electron transfer between the active material and carbon binder domain (CBD) within electrodes [1]–[3]. Available imaging techniques for visualizing the electronic connectivity of LIB electrodes are limited to nanoscale, single particle resolutions using sophisticated synchrotron X-ray or electron microscopy [4]–[6]. Optical microscopy offers the correct spatial resolution for visualizing the submicron connection of active particles to CBD, but is limited by colorimetry of electrode materials- with graphite being the exception due to its visible color change during lithiation [7]. There is a rapidly growing body of research interested in studying the ionic diffusion pathways of Li-ion using operando optical microscopy, however none currently exist for studying the submicron electronic connectivity through a facile, operando approach- especially under a industrially applicable lens [8]. To the best of our knowledge, this study presents the first spatially- and time- resolved technique for visualizing the electronic connectivity of commercial LIB electrodes using operando electrochemical fluorescent microscopy (EFM). This technique relies on the principle of electrofluorochromism, which we use to our advantage for a simple electrochemical system involving heterogeneous electron transfer. This allows us to use fluorescence as a real-time tracker for electronic heterogeneity, where electronic ‘dead-zones’ present as non-fluorescent regions in 2D images.Using our technique, we visualize commonly used commercial LIB electrodes (carbon content 1-4%, regimented processing), including NMC (LiNixMnyCo1-x-yO2), LFP (LiFePO4), and LCO (LiCoO2) against formulaically similar in-house made LIB electrodes (< 3.5% carbon content) as a proof of concept. We first validate the efficacy of this technique by testing commercial NMC, with a flaked off piece of active material, to show that areas of electronic discontinuities can in fact be represented by non-fluorescence (Fig.1.) We also find that when compared to commercial electrodes, those which are fabricated in house reveal isolated active particles, agglomerated carbon islands, and dead zones, undiscernible by brightfield imaging (Fig. 2.) Global feature extraction is performed on post-processed images to quantify electrode topology and evaluate electronic connectivity of active particles of battery electrodes, as well as heterogeneous mapping to determine the heterogeneity index of electrodes imaged. Testing our technique on low- and high- performing electrodes from an established library of coin-cell data allows for a straightforward way of correlating performance metrics to heterogeneity features. This quick (<1hr), reproducible visualization technique is general enough to be used to study the electronic connectivity of emerging new battery electrodes, as well as verify commercially available ones. Using this approach to verify LIB electrodes prior to assembly could save months to years of battery testing by being used as an alternative to lengthy full cell testing.[1] S. L. Morelly, N. J. Alvarez, and M. H. Tang, “Short-range contacts govern the performance of industry-relevant battery cathodes,” Journal of Power Sources, vol. 387, pp. 49–56, May 2018, doi: 10.1016/j.jpowsour.2018.03.039.[2] R. M. Saraka, S. L. Morelly, M. H. Tang, and N. J. Alvarez, “Correlating Processing Conditions to Short- and Long-Range Order in Coating and Drying Lithium-Ion Batteries,” ACS Appl. Energy Mater., vol. 3, no. 12, pp. 11681–11689, Dec. 2020, doi: 10.1021/acsaem.0c01305.[3] J. Entwistle, R. Ge, K. Pardikar, R. Smith, and D. Cumming, “Carbon binder domain networks and electrical conductivity in lithium-ion battery electrodes: A critical review,” Renewable and Sustainable Energy Reviews, vol. 166, p. 112624, Sep. 2022, doi: 10.1016/j.rser.2022.112624.[4] S. Li et al., “Mutual modulation between surface chemistry and bulk microstructure within secondary particles of nickel-rich layered oxides,” Nat Commun, vol. 11, no. 1, Art. no. 1, Sep. 2020, doi: 10.1038/s41467-020-18278-y.[5] P.-C. Tsai et al., “Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries,” Energy Environ. Sci., vol. 11, no. 4, pp. 860–871, Apr. 2018, doi: 10.1039/C8EE00001H.[6] A. Singer et al., “Nucleation of dislocations and their dynamics in layered oxide cathode materials during battery charging,” Nat Energy, vol. 3, no. 8, Art. no. 8, Aug. 2018, doi: 10.1038/s41560-018-0184-2.[7] Y. Yamagishi, H. Morita, Y. Nomura, and E. Igaki, “Visualizing Lithiation of Graphite Composite Anodes in All-Solid-State Batteries Using Operando Time-of-Flight Secondary Ion Mass Spectrometry,” J. Phys. Chem. Lett., vol. 12, no. 19, pp. 4623–4627, May 2021, doi: 10.1021/acs.jpclett.1c01089.[8] A. J. Merryweather, C. Schnedermann, Q. Jacquet, C. P. Grey, and A. Rao, “Operando optical tracking of single-particle ion dynamics in batteries,” Nature, vol. 594, no. 7864, Art. no. 7864, Jun. 2021, doi: 10.1038/s41586-021-03584-2. Figure 1

Potential-Dependent BDAC Adsorption on Zinc Enabling ‘Selective’ Suppression of Zinc Corrosion for Energy Storage Applications

Utility-scale zinc (Zn) batteries are a promising solution to address the problem of intermittency of renewable energy sources[1],[2]; however, Zn-metal anodes in these batteries suffer from capacity loss due to spontaneous corrosion of the Zn especially when high-surface area anode configurations are employed[3]. Additionally, Zn dendrites are known to form during battery charging which limits the cycle-life of these batteries. Electrolyte additives have been explored that prevent the aforementioned issues[4],[5], but these too come at a cost, i.e., surface-blocking additives polarize the electrode surface leading to loss in the voltaic and energy efficiencies of the battery. In this presentation, a novel electrolyte additive, benzyldimethylhexadecylammonium chloride (BDAC), will be presented for its ability to suppresses corrosion of Zn in a mildly acidic (pH = 3) electrolyte. An attribute of BDAC distinct from previously studied additives is that it ‘selectively’ suppresses corrosion when the Zn electrode is held near its mixed potential; however, during high-rate Zn deposition (charging) or stripping (discharging), BDAC is essentially deactivated and thus does not appreciably polarize the electrode surface. This selective corrosion suppression behavior is explored using slow-scan cyclic voltammetry, which reveals a hysteretic response. The response implies a current-dependent BDAC adsorption mechanism in which BDAC reaches higher surface coverages when the partial currents at the Zn surface are low (e.g., at or near the corrosion mixed potential), but BDAC coverage is reduced considerably when the Zn deposition-stripping rates are increased. Numerical simulations of the BDAC diffusion-adsorption process are used to corroborate this model. Ramifications of our approach to the selective suppression of Zn dendrites will also be discussed.

Operando Electrochemical Fluorescent Microscopy to Predict Li-Ion Battery Performance

A real-time, high-throughput visualization technique for heterogeneity in lithium-ion battery (LIB) electrodes is necessary to understand battery performance on a mechanistic level. Our group, along with others, has seen that battery performance is governed by short range (<20 um) electron transfer between the active material and carbon binder domain (CBD) in electrodes [1]–[3]. Available imaging techniques for visualizing the electronic connectivity of LIB electrodes are limited to nanoscale, single particle resolutions using sophisticated synchrotron X-ray or electron microscopy [4]–[6]. Optical microscopy offers the correct spatial resolution for visualizing the submicron connections of active particles to CBD, but is limited by the colorimetry of electrode materials- with graphite being the exception due to its visible color change during lithiation [7]. There is a rapidly growing body of research interested in studying the ionic diffusion pathways of Li-ion using operando optical microscopy, however none currently exist for studying the submicron electronic connectivity using an operando approach- especially under a industrially applicable lens [8]. To the best of our knowledge, this study presents the first spatially- and time- resolved technique for visualizing the electronic connectivity of commercial LIB electrodes using operando electrochemical fluorescent microscopy (EFM). This technique relies on the principle of electrofluorochromism, which we use to our advantage for a simple electrochemical system involving heterogeneous electron transfer. This allows us to use fluorescence as a real-time tracker for electronic heterogeneity, where electronic ‘dead-zones’ present as non-fluorescent regions in 2D images.Using this technique, we visualize commonly used commercial LIB electrodes (carbon content 1-4%, regimented processing), including NMC (LiNixMnyCo1-x-yO2), LFP (LiFePO4), and LCO (LiCoO2) against formulaically similar in-house made LIB electrodes (< 3.5% carbon content) as a proof of concept. We first validate the efficacy of this technique by testing commercial NMC, with a flaked off piece of active material, to show that areas of electronic discontinuities can in fact be represented by non-fluorescence (Fig.1.) We also find that when compared to commercial electrodes, those which are fabricated in house reveal isolated active particles, agglomerated carbon islands, and dead zones, undiscernible by brightfield imaging (Fig. 2.) Global feature extraction is performed on post-processed images to quantify electrode topology and evaluate electronic connectivity of active particles of battery electrodes, as well as heterogeneous mapping to determine the heterogeneity index of electrodes imaged. Testing our technique on low- and high- performing electrodes from an established library of coin-cell data allows for a straightforward way of correlating performance metrics to heterogeneity features. This quick (<1hr), reproducible visualization technique is general enough to be used to study the electronic connectivity of emerging new battery electrodes, as well as verify commercially available ones. Using this approach to verify LIB electrodes prior to assembly could save months to years of battery testing by being used as an alternative to lengthy full cell testing.[1] S. L. Morelly, N. J. Alvarez, and M. H. Tang, “Short-range contacts govern the performance of industry-relevant battery cathodes,” Journal of Power Sources, vol. 387, pp. 49–56, May 2018, doi: 10.1016/j.jpowsour.2018.03.039.[2] R. M. Saraka, S. L. Morelly, M. H. Tang, and N. J. Alvarez, “Correlating Processing Conditions to Short- and Long-Range Order in Coating and Drying Lithium-Ion Batteries,” ACS Appl. Energy Mater., vol. 3, no. 12, pp. 11681–11689, Dec. 2020, doi: 10.1021/acsaem.0c01305.[3] J. Entwistle, R. Ge, K. Pardikar, R. Smith, and D. Cumming, “Carbon binder domain networks and electrical conductivity in lithium-ion battery electrodes: A critical review,” Renewable and Sustainable Energy Reviews, vol. 166, p. 112624, Sep. 2022, doi: 10.1016/j.rser.2022.112624.[4] S. Li et al., “Mutual modulation between surface chemistry and bulk microstructure within secondary particles of nickel-rich layered oxides,” Nat Commun, vol. 11, no. 1, Art. no. 1, Sep. 2020, doi: 10.1038/s41467-020-18278-y.[5] P.-C. Tsai et al., “Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries,” Energy Environ. Sci., vol. 11, no. 4, pp. 860–871, Apr. 2018, doi: 10.1039/C8EE00001H.[6] A. Singer et al., “Nucleation of dislocations and their dynamics in layered oxide cathode materials during battery charging,” Nat Energy, vol. 3, no. 8, Art. no. 8, Aug. 2018, doi: 10.1038/s41560-018-0184-2.[7] Y. Yamagishi, H. Morita, Y. Nomura, and E. Igaki, “Visualizing Lithiation of Graphite Composite Anodes in All-Solid-State Batteries Using Operando Time-of-Flight Secondary Ion Mass Spectrometry,” J. Phys. Chem. Lett., vol. 12, no. 19, pp. 4623–4627, May 2021, doi: 10.1021/acs.jpclett.1c01089.[8] A. J. Merryweather, C. Schnedermann, Q. Jacquet, C. P. Grey, and A. Rao, “Operando optical tracking of single-particle ion dynamics in batteries,” Nature, vol. 594, no. 7864, Art. no. 7864, Jun. 2021, doi: 10.1038/s41586-021-03584-2. Figure 1

Prediction of Lithium Deposition By Electrochemical Noise Method in Li-Ion Batteries

Electrochemical noise measurement methods have established a significant presence in corrosion literatures and through these measurements, it becomes feasible to discern the corrosion mode and make a clear distinction between localized and uniform corrosion types, particularly when examined alongside post-mortem studies.In recent years, the increase in the use of lithium-ion batteries demands that the tests to be performed on the batteries are faster, easier, cheaper and, if possible, non-destructive and non-perturbing. While some electrochemical noise studies on batteries have commenced, the existing literature on this subject is limited and questionable. Electrochemical noise measurement, in Lithium based batteries has the potential to serve as a non-invasive diagnostic tool for assessing battery health. One of our previous studies has demonstrated an increased voltage noise in non-rechargeable batteries with Li/MnO2 chemistry upon exposure to a short circuit, indicating detectable morphological changes in metallic lithium due to non-homogenous depletion of lithium anode through electrochemical noise measurement.In Lithium-Ion batteries, lithium deposition refers to the undesired formation of metallic lithium, commonly in the form of dendrites, on the battery’s anode during charge and discharge cycles. This phenomenon is a consequence of uneven lithium-ion plating and stripping, leading to localized overplating. This growth of lithium dendrites poses significant risk, including internal short circuits, compromised battery integrity, and the potential for thermal runaway. These issues can result in reduced battery performance, safety concerns, and shortened cycle life. Effectively addressing lithium deposition is essential for enhancing the safety and reliability of lithium-ion batteries in various applications.Similarly to our previous publication, the electrochemical noise method shows promise as a non-invasive approach to investigate the understand deposition of metallic lithium by monitoring the voltage noise during charge and discharge cycling of batteries. For this purpose, NMC/Graphite pouch and coin cells are employed. In this presentation, we will delve into the details of electrochemical noise in lithium-based batteries, discussing the method’s reliability in assessing lithium deposition in NMC/Graphite lithium-ion batteries and presenting preliminary results. Figure 1

Effective Lithium Polysulfides Anchoring on Vanadium Disulfide Facets for Lithium-Sulfur Batteries – A Computational Study

The commercialization of Li-S batteries is hindered by the shuttle effects of lithium polysulfides (LiPS) and the sluggish reaction kinetics. Hence, effectively trapping and promoting the conversion rates of LiPSs is of prime importance1. However, the fundamental kinetics of the electrocatalytic charging and discharging of Li-S batteries and the underlying mechanism have not been sufficiently explored yet.2 Therefore, by taking the 2D transition metal sulfide, VS2 as a model, we conducted a systematic investigation using density functional theory to study the ability of dominant exposed crystal planes of VS2 to trap LiPSs from leaching into electrolyte solvents and to act as an electrocatalyst to increase the Sulfur Reduction Reaction (SRR) kinetics3. To reflect a realistic environment of a battery, the effect of electrolyte solvents on the electrocatalytic activity was further investigated. Our calculations show that VS2 has moderate binding energy toward LiPSs which inhibits LiPS from leaching into electrolytes while fulfilling the key prerequisite to act as an electrocatalyst simultaneously.4 At the discharge, the conversion of S8 to the long chain Li2S8 was facile with a lower energy barrier while the rest of the reactions were sluggish explaining the accumulation of LiPSs. Further, the VS2 (001) facet exhibits excellent electrocatalytic activity for the SRR and Li2S decomposition reaction at charging compared to other dominant crystal planes, which significantly lowers the energy barriers of LiPS conversion during the charging and discharging process, ensuring high-rate performance and longer cycle life4. References Manthiram, A., Fu, Y., Chung, S.-H., Zu, C., & Su, Y.-S. (2014). Rechargeable Lithium–Sulfur Batteries. Chemical Reviews, 114(23), 11751–11787.Abraham, A. M., Thiel, K., Shakouri, M., Xiao, Q., Paterson, A., Schwenzel, J., Ponnurangam, S., & Thangadurai, V. (2022). Ultrahigh Sulfur Loading Tolerant Cathode Architecture with Extended Cycle Life for High Energy Density Lithium–Sulfur Batteries. Advanced Energy Materials, 2201494.Abraham, A. M., Boteju, T., Ponnurangam, S., & Thangadurai, V. (2022). A global design principle for polysulfide electrocatalysis in lithium–sulfur batteries—A computational perspective. Battery Energy, 20220003.Boteju, T., Abraham, A. M., Ponnurangam, S., & Thangadurai, V. (2023). Theoretical Study on the Role of Solvents in Lithium Polysulfide Anchoring on Vanadium Disulfide Facets for Lithium–Sulfur Batteries. The Journal of Physical Chemistry C.

Refractive Laser Beam Measuring Diffusion Coefficient of Concentrated Battery Electrolytes

A thorough understanding of electrolyte transport properties is crucial in the development of alternative battery technology. As a key parameter, the diffusion coefficient offers important insights into the behavior of electrolytes, especially for fast charge of high-energy batteries. Existing methods of measurement are often limited by redox species or offer questionable accuracy due to side reactions and/or disruption of the diffusion profile. A highly sensitive optical method was developed using a refractive laser beam through triangular diffusion column to measure the diffusion coefficient of concentrated battery electrolytes. The method based on Snell’s law can be applied to all liquid phase electrolytes since the refractive index is concentration dependent for all liquid electrolytes. This universal method relies on the deflection of a refractive laser beam passing through an electrolyte of a minor concentration gradient in a triangular diffusion column (Figure 1). A polarized HeNe laser was arranged to pass the beam through a right-angled triangular quartz precision cell, slightly rotated to the normal. The exact position of the refracted beam was located by a silicon photodiode-based position detector. Deflection calibration curves made simple conversion of beam position to concentration, and during the diffusion of two layered solutions, data points were collected every minute to produce a concentration profile descriptive of the 48-hour diffusion. Diffusion coefficients were calculated using a model based on OSM theory, accounting for multi-component concentrated systems in a restricted diffusion column.1 The measured diffusion coefficients are between 4.12x10-10 m2/s for 0.15 mol/kg ZnSO4 and 0.681x10-10 m2/s for 2.5 mol/kg ZnSO4 at 22.4 °C. The profile of concentration-dependent diffusion coefficients follows a non-linear inverse relationship described by the function D=4.943(1+m)-1.564 (Figure 2).Several other physicochemical properties of the same electrolytes were studied to correlate to the concentration-dependent diffusion coefficients, including refractive index, viscosity, conductivity, and microstructure analysis based on vibrational spectroscopy (Infrared and Raman). High concentration electrolytes with more ion pairs show increased viscosity which ultimately leads to smaller diffusion coefficients. A QCM-I instrument standard flow cell were used to determine the viscosity of ZnSO4 electrolyte and the concentration-dependent viscosity was fitted to the function η=1.06-0.476m+2.13m2-1.01m3+0.204m4. Interionic interactions also led to reduced conductivity at concentrations beyond 1.5mol/kg, despite the increased charge density of concentrated solutions. FT-IR spectrums allowed analyzation of increased charge density, which increased intensity of the O-H stretching peak in concentrated electrolytes, despite the decrease in the ratio of water. Competition between charge density and viscosity continues to challenge the efficiency of concentrated electrolytes.Lastly, we demonstrate the prototype in situ triangular cell to characterize the electrolyte in working batteries. The cell responds to short, low-voltage pulses with beam deflection and relaxation, and offers an opportunity as a novel in situ spectroscopic tool to characterize the battery electrolyte. Acknowledgments This work is supported by a grant from NSF (CBET-2243098).

Investigating Li-Ion Depletion during Fast Charging with Operando FTIR

Lithium-ion concentration polarization and slow ionic transport in the electrolyte phase hinder fast charging of electric vehicle batteries and can cause cell degradation. Although pseudo-2D (P2D) models capture concentration polarization phenomena during fast charging, experimental measurements of Li-ion concentration in the electrolyte phase have been limited. In this research, Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR) were used to collect operando optical measurements of Li-ion concentration in a high-loading graphite/NMC811 full cell with 1.2M LiPF6 in 3/7 (wt./wt.) ethylene carbonate (EC)/ethyl methyl carbonate (EMC). For this research, an optically accessible operando battery was developed that enables real-time measurements of Li-ion concentration at the back of the graphite anode near the current collector. Significant Li-ion concentration changes up to 0.5M were observed during charging at 1C, 2C, and 3C, as well as discharging at C/2, and compared with a P2D model. Both the model and the experiments showed Li-ion depletion and sinuous fluctuations at the graphite/current collector interface that indicate non-ideal behavior. These gradients likely develop due to insufficient electrolyte transport properties. This research enables novel Li-ion concentration measurements with FTIR. This research also validates P2D model physics for measuring and analyzing Li-ion concentration polarization at fast charging rates.

Novel Electrochemical Methodology for the Removal of HF from Carbonate-Based LiPF6-Containing Li-Ion Battery Electrolytes

Baseline Li-ion battery (LIB) electrolytes typically consist of LiPF6 salt dissolved in carbonate solvents. Due to trace amounts of water and the hydrolysis of PF6 - in carbonate solvents, these electrolytes always contain trace amounts of HF. [1] On the cathode, HF has negative effects, including transition metal dissolution and capacity fading. [2] On the anode, HF is involved in the formation and evolution of the solid electrolyte interphase (SEI). [3] The SEI originates in the thermodynamic instability of electrolyte moieties (salt, solvent, impurities) on the anode surface. As a result, electrolyte moieties are reduced and may then react with Li+ ions to form solid, insoluble products on the anode surface. This limits electron and solvent transport while permitting Li+ transport, kinetically stabilizing the interface. [4] The mechanism of nucleation and growth remains poorly understood despite their significance. The formation of LiF is one example. Although it is believed that direct PF6 - anion reduction is important, it is difficult to observe this reaction unambiguously because it frequently coexists with electrochemical signatures of electrocatalytic HF reduction or even acts in concert with one another. [5]The objective of this work is to remove ppm-levels of HF from carbonate-based LiPF6-containing electrolytes to enable foundational studies of SEI nucleation (e.g., direct PF6 - anionic direction) without interfering HF effects. We propose an electrochemical purification approach, which is complementary to conventional approaches using scavenging molecules. [6] Utilizing the knowledge that all other electrolyte moieties in baseline carbonate LiPF6-containing LIB electrolyte remain intact at relatively high potentials (significantly > 1.5 V vs. Li/Li+), we postulate to solely and selectively electrocatalytically reduce HF on metal electrodes. Therefore, our basic hypothesis is that all the HF in the electrolyte will be electrocatalytically reduced when an appropriate potential is applied to a high-surface area catalytically active electrode, while all other moieties essentially stay unchanged. To achieve this, we employed a porous Cu-foam working electrode that is integrated into a Teflon cone-type cell that has a second Pt working electrode. This allows us to use cyclic voltammetry (CV) to electrochemically test the HF concentration in the electrolyte. We report on the successful removal of HF to levels below a few ppm. Additionally, we observe CV features which we tentatively assign to direct anion reduction. Investigations are underway to gain deeper insight into the specifics of this reaction. We anticipate that the developed electrochemical method could lead to new opportunities for HF removal and basic research on the SEI reaction in electrolytes containing LiPF6.Literatur:[1] S.F. Lux, J. Chevalier, I.T. Lucas, R. Kostecki, HF Formation in LiPF6-Based Organic Carbonate Electrolytes, ECS Electrochemistry Letters, 2 (2013) A121.[2] C. Ye, W. Tu, L. Yin, Q. Zheng, C. Wang, Y. Zhong, Y. Zhang, Q. Huang, K. Xu, W. Li, Converting detrimental HF in electrolytes into a highly fluorinated interphase on cathodes, Journal of Materials Chemistry A, 6 (2018) 17642-17652.[3] D. Strmcnik, I.E. Castelli, J.G. Connell, D. Haering, M. Zorko, P. Martins, P.P. Lopes, B. Genorio, T. Østergaard, H.A. Gasteiger, F. Maglia, B.K. Antonopoulos, V.R. Stamenkovic, J. Rossmeisl, N.M. Markovic, Electrocatalytic transformation of HF impurity to H2 and LiF in lithium-ion batteries, Nature Catalysis, 1 (2018) 255-262.[4] A. Wang, S. Kadam, H. Li, S. Shi, Y. Qi, Review on modeling of the anode solid electrolyte interphase (SEI) for lithium-ion batteries, npj Computational Materials, 4 (2018) 15.[5] C. Cao, T.P. Pollard, O. Borodin, J.E. Mars, Y. Tsao, M.R. Lukatskaya, R.M. Kasse, M.A. Schroeder, K. Xu, M.F. Toney, H.-G. Steinrück, Toward Unraveling the Origin of Lithium Fluoride in the Solid Electrolyte Interphase, Chemistry of Materials, 33 (2021) 7315-7336.[6] J.-G. Han, M.-Y. Jeong, K. Kim, C. Park, C.H. Sung, D.W. Bak, K.H. Kim, K.-M. Jeong, N.-S. Choi, An electrolyte additive capable of scavenging HF and PF5 enables fast charging of lithium-ion batteries in LiPF6-based electrolytes, Journal of Power Sources, 446 (2020) 227366.

All Organic Quinone Solid State Batteries for Environmentally Friendly and Chemical Robust Alternatives Beyond Lithium-Ion Batteries

Introduction: Organic solid-state quinone batteries have unparalleled properties that can meet the most urgent challenges the industry faces. It can create an energy system that is environmentally friendly and electrochemically robust, while being cost efficient enough for industry to adopt and invest in. The inspiration for fully organic solid-state batteries came from extended studies on our all-organic aqueous redox flow batteries, where much of the science of organic redox coupling molecules were understood. Like redox flow batteries, organic solid state quinone batteries utilizes the breaking and reforming of bonds to generate electrical energy. However, it doesn’t require the constant flow of charge carrier solution like the flow batteries. Consequently, this avoids the cost of an extra pumping system and significantly reduce the size of the batteries compared to flow battery systems. Furthermore, the downsized battery system allows for the cell to be implemented into applications such as EV and portable devices. The redox species are directly deposited onto the electrodes. This deposition of active material on carbon paper enables higher surface area for charge transfer, which increases the capacity for fast charge and discharge compared to flow batteries. Additionally, the active materials are of organic quinone nature providing great robustness that other battery systems like lithium-ion batteries don’t allow. The redox chemistry of these quinones still happens in aqueous system, which allows us to use very small amount of aqueous electrolyte instead of the combustible organic solvent used in lithium batteries. Results and discussion: The appropriate quinone species for this solid-state battery must be electrochemically stable and dissolution free in the aqueous system. Various quinones with different substituents were tested. One of the promising redox couples discovered is 2-methylanthraquinone (MAQ) and duroquinone (DQ). The couple displayed a cell voltage of 400 mV (0.4 V) as shown in Figure 1. This value was found to correspond to the redox potential difference between DQ and MAQ. New methods of deposition of active materials onto the electrodes were developed. High conductivity was achieved by introducing CNT with appropriate binder, which resulted in improvements to the cell’s charge and discharge performance (Figure 2). Figure 1. Cyclic voltammetry study of 10 mM 2-Methylanthraquinone (MAQ) and 10 mM Duroquinone (DQ) in 1 M sulfuric acid with 20% ethanol, MSE reference electrode, glassy carbon, 50 mV/s. (Refer to image file) Figure 2: Charge and discharge of solid-state batteries of 2-Methylanthraquinone (MAQ) and Duroquinone (DQ) at 10 mA. (Refer to image file)For the positive side, 0.164 g of duroquinone was deposited on 25 cm2 carbon paper with 0.05 g of CNT. Correspondingly, 0.222 g of 2-Methylantroquinone was deposited for the negative side. The cell was assembled with Nafion 117 as separator and small amount of 1 M sulfuric acid as the supporting electrolyte. The initial charge and discharge curve of this cell showed 97% columbic efficiency. Long-term cycling to test the stability was performed and other redox couples also showed higher cell voltage with high efficiency.The next step for this study is to explore different redox couples that might have better compatibility and higher cell voltage compared to the current redox couple. This will be done through studying the large library of organic compounds including quinones and other redox active organic compounds. Figure 1

Enhancing the Performance of Electrochemical RAM (ECRAM) through Modeling Guided Device Engineering

Traditionally, the only ions allowed or welcomed by the microelectronic industry are those that act as fixed dopants. The issue of mobile ions became welcome primarily due to the memristor technology however, thin film transistor technologies benefit from them too. The electrochemical (transistor) random access memory (ECRAM) is emerging as a promising building block for multi-level neuromorphic computing. Using FAB-compatible materials we construct the ECRAM using CuOx as the gate and ions source (Cu+). The morphology of the HfOx gate insulator layer is tuned to render it ion transporting such that it can act as a uniform electrolyte layer. Lastly, the channel material is WOx with tungsten metal as the source/drain contact.While there are several reports of ECRAM devices, the operation mechanisms are not fully known/understood thus withholding progress of this field. Using the Sentaurus device simulator by Synopsis, including the hydrogen diffusion module, we simulate the mixed ionic electronic operation of the device. We have recently reported that by fitting the simulation to the device performance, we could identify the potentiation mechanism (i.e., insulator charging) and the occurrence of copper plating that takes place under high Cu+ ion flux (as in fast charging of Li batteries).[1]In the first part of the talk, we will expand on the chemical-physics details of the ECRAM device mentioned above. Next, we will present a new device architecture where we remove the WOx layer and study the ionic-electronic conduction of a modified HfOx layer. By fine-tuning the stoichiometry of the HfOx layer, it assumes both roles of ionic electrolyte and electronic conducting channel. Following detailed modelling of the measured properties, we introduce AlO2 as an ionic barrier layer at the WOx/HfOx interface to enhance the ionic retention of the HfOx layer. Using the above three device architectures in conjunction with the mixed ionic-electronic device simulation we reveal the role of the two memory mechanisms: a) Electric field-activated ion transport and b) Structure-induced trapping by ion-barrier layers.Reference[1] Nir Tessler, Nayeon Kim, Heebum Kang, Jiyong Woo; Switching mechanisms of CMOS-compatible ECRAM transistors—Electrolyte charging and ion plating. J. Appl. Phys. 21 August 2023; 134 (7): 074501. https://doi.org/10.1063/5.0154153 Figure 1

Why Charge Rate Capability Tests Fail to Characterize Structured Electrodes in Lithium-Ion Batteries and How to Modify Them

Fast charging is one of the most essential criteria for the user acceptance of battery electric vehicles. Especially for high-loaded electrodes used in automotive applications, the rate capability is limited due to the transport limitations of lithium ions in the pores.1 Electrode structuring is a powerful tool to overcome those limitations by creating additional directed diffusion channels for lithium ions.2 Despite the frequently described reduction of the transport limitation of lithium-ion batteries,3 there are hardly any charge rate capability tests in the literature that demonstrate the improvement through structuring. Instead, most studies present discharge rate capability tests showing the desired performance increase due to structuring.4-8 This study will explain why charge rate capability tests fail to characterize electrodes in the transport-limiting C-rate range. For this purpose, graphite anodes underwent “structure calendering”, where electrodes are simultaneously mechanically structured and calendered using an embossing roller. Thus, identical electrode properties, except for the lower tortuosity, can be achieved compared to the non-structured graphite anodes that were only calendered. Despite their different tortuosities, we will show that structured and non-structured graphite anodes exhibit minimal capacity differences in the charge rate capability test. This is attributed to lithium plating, which shifts the anode potential to similar values, regardless of the transport properties of the investigated electrode. We will modify the test to characterize the charge rate capability of electrodes in the transport-limiting regime where lithium plating occurs. For this purpose, in the charge rate capability test, the current is superimposed with a sinusoidal signal and the voltage response is measured. This allows the continuous estimation of the cell impedance during charging. Previous studies have shown that this method allows to track the onset of the lithium plating reaction.9-10 Applying the modified charge rate capability test will demonstrate that this detrimental side reaction occurs significantly later in structured electrodes. Günter, F. J., & Wassiliadis, N. (2022). State of the Art of Lithium-Ion Pouch Cells in Automotive Applications: Cell Teardown and Characterization. Journal of The Electrochemical Society, 169(3), 030515. https://doi.org/10.1149/1945-7111/ac4e11Pfleging, W. (2017). A review of laser electrode processing for development and manufacturing of lithium-ion batteries. Nanophotonics, 7(3), 549–573. https://doi.org/10.1515/nanoph-2017-0044Mai, W., Usseglio-Viretta, F. L. E., Colclasure, A. M., & Smith, K. (2020). Enabling fast charging of lithium-ion batteries through secondary-/dual- pore network: Part II - numerical model. Electrochimica Acta, 341, 136013. https://doi.org/10.1016/j.electacta.2020.136013Keilhofer, J., Schaffranka, L., Wuttke, A., Günter, F., Hille, L., Dorau, F., & Daub, R. (2023). Mechanical Structuring of Lithium‐Ion Battery Electrodes Using an Embossing Roller. Energy Technology. https://doi.org/10.1002/ente.202200869Dubey, R., Zwahlen, M. D., Shynkarenko, Y., Yakunin, S., Fuerst, A., Kovalenko, M. V., & Kravchyk, K. V. (2021). Laser Patterning of High-Mass-Loading Graphite Anodes for High-Performance Li-Ion Batteries. Batteries and Supercaps, 4(3), 464–468. https://doi.org/10.1002/batt.202000253Habedank, J. B., Kriegler, J., & Zaeh, M. F. (2019). Enhanced Fast Charging and Reduced Lithium-Plating by Laser-Structured Anodes for Lithium-Ion Batteries. Journal of The Electrochemical Society, 166(16), A3940–A3949. https://doi.org/10.1149/2.1241915jesHabedank, J. B., Kraft, L., Rheinfeld, A., Krezdorn, C., Jossen, A., & Zaeh, M. F. (2018). Increasing the Discharge Rate Capability of Lithium-Ion Cells with Laser-Structured Graphite Anodes: Modeling and Simulation. Journal of The Electrochemical Society, 165(7), A1563–A1573. https://doi.org/10.1149/2.1181807jesHille, L., Xu, L., Keilhofer, J., Stock, S., Kriegler, J., & Zaeh, M. F. (2021). Laser structuring of graphite anodes and NMC cathodes – Proportionate influence on electrode characteristics and cell performance. Electrochimica Acta, 392, 139002. https://doi.org/10.1016/j.electacta.2021.139002Koseoglou, M., Tsioumas, E., Ferentinou, D., Jabbour, N., Papagiannis, D., & Mademlis, C. (2021). Lithium plating detection using dynamic electrochemical impedance spectroscopy in lithium-ion batteries. Journal of Power Sources, 512(September), 230508. https://doi.org/10.1016/j.jpowsour.2021.230508Straßer, A., Adam, A., & Li, J. (2023). In operando detection of Lithium plating via electrochemical impedance spectroscopy for automotive batteries. Journal of Power Sources, 580(July), 233366. https://doi.org/10.1016/j.jpowsour.2023.233366

Effect of Mechanical Compression on Ionic Conductivity of PEO-LiTFSI Solid Polymer Electrolytes

In the field of energy storage materials, the development of robust solid polymer electrolytes for lithium-ion batteries necessitates an understanding of ionic conductivity when subjected to mechanical stress. Accurate determination of ionic conductivity requires knowing the electrolyte thickness, which is subject to volumetric changes during charging and discharging of solid-state batteries. However, compressive stress reduces the thickness of the electrolyte by an indeterminate amount.This work presents experimental measurements of ionic conductivity as a function of compressive stress, using poly(ethylene oxide) and with bis(trifluoromethane) sulfonimide (PEO-LiTFSI). In this study, we not only measure the stress-strain response of the electrolytes directly, but also monitor the extent of compression during electrochemical impedance spectroscopy (EIS). Compression was applied up to 50% strain for three consecutive cycles, and the typical thickness for the fabricated electrolytes was ~50 µm. EIS testing was performed by using an impedance analyzer, with the electrolyte placed between stainless steel blocking electrodes. Bulk resistance was determined by equivalent circuit modeling of impedance between 100 Hz and 2 MHz. Ionic conductivity κ was calculated from bulk resistance Rb , electrolyte thickness h, and cross-sectional area A, according to the equation κ = h/(Rb·A).In order to measure both stress and deformation simultaneously, a custom positioning stage was engineered to apply prescribed compression. The apparatus has an in-line load cell for force measurements and a laser triangulation sensor for position tracking with submicron resolution. We found that the bulk resistance at room temperature decreases exponentially, with magnitude reduced by approximately five-fold when subjected to compressive stress up to 10 MPa. Beyond ~7 MPa, bulk resistance values were no longer dependent on the amount of applied compression.In addition to mechanical measurements, changes in crystalline and amorphous regions were correlated to the magnitude of compressive stress and the measured ionic conductivity of the electrolyte. For optical imaging with simultaneous EIS measurements, glass slides coated with an indium tin oxide (ITO) film were used instead of stainless steel disks. The extent of crystallinity was visualized by optical microscopy of spherulites through a viewing window when compressed between rigid plates.Figure 1. Apparatus (left) and representative ionic conductivity vs. compressive stress (right) data for a PEO-LiTFSI polymer electrolyte. Figure 1

External Cooling and Degradation Interplay in Lithium-Ion Battery Fast Charging

Fast charging of Li-ion batteries involves key challenges such as lithium plating, mechanical stress formation, high temperature rise, and non-uniform temperature distributions. The advancement of thermal management systems to maintain an optimal cell temperature distribution and minimize degradation is critical to enable fast charging. This work analyzes the various degradation modes, including lithium plating, solid electrolyte interphase growth, and mechanical stresses in large-format Li-ion cells during fast charging, and delineates their dependence on external cooling conditions. Based on the cell design and operating conditions, unique attributes related to the evolution of internal thermal gradients, spatiotemporal lithium plating response, and the formation of mechanical stress hotspots are delineated. Further, optimal external cooling configurations that enable longer life and safety under fast charging conditions are determined. The study provides guidance toward the design of next-generation battery thermal management systems for Li-ion batteries with fast charging capabilities.

Measurement of Li-Ion Self-Diffusion in Laser Structured Electrodes

It is generally stated that a limiting factor in fast charging and high-power discharging of lithium-ion batteries (LiB) stems from the diffusion kinetics of Li+ in the electrode pore network. Numerous approaches in enabling fast charging of LiBs include active material development, electrolytes with high ionic conductivity and the management of the charging and discharging temperature. Another promising method is laser micro structuring to modify the electrode architecture regarding an enhanced lithium-ion diffusion kinetics. An increased high-rate capability and boost in cell lifetime have been demonstrated with such 3D electrodes [1, 2] but the related mechanisms leading to a substantial impact to diffusion kinetics are still poorly understood. Furthermore, it is imperative to find an optimal ablation pattern with regard to the desired application scenario that minimizes active mass loss in order to create the economic basis for efficient upscaling of the process.Nuclear Magnetic Resonance (NMR) measurements of longitudinal (T1) and transverse relaxation times (T2), as well as the T2/T2 exchange, are routinely used for the identification of different molecular species. The exchange NMR experiment is a well-known technique for studying local environments of nuclei such as liquids in pores and approximating their shapes and sizes [3]. The evolution of the transverse relaxation rate (T2) of a probed nuclei allows to determine if the specie is confined (shorter T2) or in liquid bulk (longer T2). In this work, so-called Exchange Nuclear Magnetic Resonance (T2/T2 exchange or EXSY), is conceptualized to study the impact of laser generated 3D patterns in pore self-diffusion of electrolyte species.Exchange NMR and T1 and T2 measurements were realized at various soaking times and electrolyte amounts for the following electrolyte species: Li+, PF6 -, ethyl carbonate (EC), and ethyl methyl carbonate (EMC), using laser structured, graphite-based electrodes casted on non-metallic substrates (to reduce RF interference). 2D exchange maps show the presence of confined species as well as the approximation of the diffusion properties. Using isotope exchange experiments with 6Li enriched electrolyte, concentration maps revealed the rate of 6LiPF6 intrusion into 7LiPF6 rich pre-soaked electrodes. The impact of laser generated 3D patterns in pore diffusion will be discussed in detail.[1]. Zheng, Y. et al. 3D silicon/graphite composite electrodes for high-energy lithium-ion batteries. Electrochim. Acta 317, 502–508 (2019).[2]. Smyrek, P., Pröll, J., Rakebrandt, J.-H., Seifert, H. J. & Pfleging, W. Manufacturing of advanced Li(NiMnCo)O2 electrodes for lithium-ion batteries . Laser-based Micro- Nanoprocessing IX 9351, 93511D (2015).[3]. Mitchell, J. et al. Validation of NMR relaxation exchange time measurements in porous media. J. Chem. Phys. 127, (2007).

Operando Visualization of Redox Flow Batteries Using Fluorescence Spectroscopy with Alizarin Red S Electrolyte

Redox flow batteries (RFBs) charge and discharge by transferring electrons between two pairs of redox species separated by a proton exchange membrane. Unlike traditional batteries that store energy in redox-active materials within an enclosed cell, RFBs store energy in liquid electrolytes housed in external reservoirs1. These electrolytes are pumped through the cell, enabling redox reactions on the surface of electrodes. The energy storage capacity of RFBs is determined by the concentration of the active species and the size of the reservoirs, making them a promising technology for large-scale energy storage applications2. While RFBs possess advantages such as long lifetime, flexible design for battery capacity and power, and rapid response, they suffer from drawbacks like low energy density, power density, and energy efficiency3. Efforts to address these issues have primarily focused on modifications to the electrode materials or the flow field4 , 5. However, evidence supporting performance enhancements often relies on global parameters such as energy efficiency, energy density, and voltage drop, lacking detailed mechanistic and microscopic studies. Real-time observation of the electrode-electrolyte interface during redox reactions and the transport of redox species in the flow field holds the potential to significantly contribute to understanding the electrode structure and mass transport phenomena in RFBs6. This understanding, in turn, facilitates prediction and purposeful enhancement of battery performance by developing desirable structures for both electrode and flow fields. Microscopy, particularly confocal microscopy, serves as a powerful tool for observing microscopic structures. Confocal microscopes yield sharper images with higher resolution than widefield microscopy, enabling rapid acquisition of high-resolution images.In this study, we employed a confocal laser scanning microscope for operando visualization of RFBs. We designed a transparent framework for the battery, allowing light to pass through, and covered its surface with a glass cover to visualize the porous carbon electrode. We selected a fluorescent redox-active species, Alizarin Red S to enable visualization using fluorescence spectroscopy. Leveraging its unique fluorescence properties, we established a correlation between fluorescence intensity and the state of charge. This innovative approach enables us to observe the distribution of electrolytes, the dynamics of redox reactions on the electrode surface (with fast speed of imaging ＜0.2s), the mass transfer behavior of the electrolyte on the electrode surface, and the uniformity of electrolyte flow in the flow field, including areas of stagnation or recirculation. Zhang, J. et al. An all-aqueous redox flow battery with unprecedented energy density. Energy Environ. Sci. 11, 2010–2015 (2018).Rubio-Garcia, J., Kucernak, A. & Charleson, A. Direct visualization of reactant transport in forced convection electrochemical cells and its application to redox flow batteries. Electrochem. commun. 93, 128–132 (2018).Tolmachev, Y. V. Flow Batteries From 1879 To 2022 And Beyond. Qeios 1–79 (2023).Wang, R. et al. Gradient-distributed NiCo2O4 nanorod electrode for redox flow batteries: Establishing the ordered reaction interface to meet the anisotropic mass transport. Appl. Catal. B Environ. 332, 122773 (2023).Kumar, S. & Jayanti, S. Effect of flow field on the performance of an all-vanadium redox flow battery. J. Power Sources 307, 782–787 (2016).Wong, A. A., Rubinstein, S. M. & Aziz, M. J. Direct visualization of electrochemical reactions and heterogeneous transport within porous electrodes in operando by fluorescence microscopy. Cell Reports Phys. Sci. 2, 100388 (2021).

Physics-Based State of Health Prediction of Lithium-Ion Battery during Fast Charging

Electrification of the transportation sector and increased use in consumer electronics have driven the increasing demand for lithium-ion batteries (LiBs) (1). Despite their high energy density and long service life, LiBs suffer from capacity degradation due to continuous growth of solid electrolyte interface (SEI) layer and plating of lithium on the anode surface. Graphite, the anode in most LiBs, has a high tendency to catalyze the degradation of the electrolyte consisting of LiPF6 and ethylene carbonate to form an SEI of Li-rich carbonate, phosphate, and fluoride compounds (2, 3). The SEI film grows during service due to the deposition of reaction products and repeated cycles of damage and reformation due to the contraction and expansion associated with volume changes during Li-ion intercalation and deintercalation. Additionally, fast or low-temperature charging of batteries results in lithium plating on the anode surface because the elevated concentration of Li+ on the anode surface results in graphite potential falling below 0V vs. Li+/Li and increased likelihood of Li deposition compared to intercalation (4). Lithium loss due to the side reactions of SEI growth and plating contributes to capacity loss and may increase the likelihood of battery failure. Hence, accurate modeling of the side reactions is required to determine the state of health (SOH) and predict the remaining capacity of LiBs during operation (5).We report an experimentally validated single particle model (SPM) to estimate the influence of SEI growth and Li plating on the capacity changes in Lithium Cobalt Oxide (LCO)/Carbon cells during repeated cycling (6-8). The SPM model idealizes each electrode as a single particle to approximate the cell response. A. Sarkar et al. (5) included the influence of SEI growth, plating, SEI fracture, and temperature in the SPM model to determine the influence of the side reactions on battery performance. The parameters corresponding to side reactions, such as the SEI film growth rate, conductivity of the SEI film, and reversibility of the plating reaction, were determined through comparison of numerical predictions of cell voltage and capacity change with experimental response measured at charging rates of 0.1C and fast charging rate of 2C on PowerStream 35 mAh LCO/C coin cells (Lir2032) as shown in Figure 1. In addition, the coin cells were subjected to charge/discharge experiments at charging rates varying from 0.1C – 5C for 100 cycles. Experimental measurements of the cell capacity changes were compared to model predictions for the different charging rates to validate the modeling assumptions and determine the efficacy of the estimated parameters in describing the cell degradation. The agreement between the model prediction and measured experimental response showed that the single particle model augmented with side reaction mechanisms can describe the cell degradation and is suitable for predicting the remaining capacity and safety of LiBs subjected to a range of charging rates. The model can also predict the accumulation of irreversibly plated lithium on the anode surface during repeated fast charging. The amount of plated lithium determines the severity of dendritic growth, and thus, model predictions of lithium accumulation may be used to estimate the likelihood of battery failure under fast charging conditions. Acknowledgment:This work was supported by the National Science Foundation, Iowa State University, and University of Connecticut.