Li-ion Cells Research Articles

Towards Long-Term Monitoring of Commercial Lithium-Ion Batteries Enabled by Externally Affixed Fiber Sensors and Strain-Based Prognostic Strategies

Real-time monitoring of both continuous and spontaneous degradation in lithium-ion batteries is challenging due to the limited number of quantitative metrics available during cycling. In this regard, improved sensing approaches enabled by sensors of high accuracy, precision, and durability are key to achieving comprehensive state estimation and meeting rigorous safety standards. In this work, external temperature and strain monitoring in commercial Li-ion button cells was carried out using tandem pairs of polymer-based and silica-based optical fiber Bragg grating sensors. The decoupled data revealed that the sensors can reliably track strain and temperature evolution for over 500 cycles, as evidenced by periodic patterns with no sign of sensor degradation or loss of fidelity. Moreover, monitoring the strain signal enabled early detection of an anomalous cell over ∼60 cycles ahead of an electrochemical signature and abrupt drop in capacity, suggesting that mechanical sensing data may offer unique benefits in some cases. Detailed mechanical monitoring via incremental strain analysis suggests a parallel path toward understanding cell degradation mechanisms, regardless of whether they are continuous or discrete in nature. The accuracy and durability of such a package-level optical fiber sensing platform offers a promising pathway for developing robust real-time battery health monitoring techniques and prognostic strategies.

In Situ Electrophoretic Decorated Cactus-Type Metallic-Phase MoS2 on CaMn2O4 Nanofibers for Binder-Free Next-Generation LIBs.

Ternary manganese-based oxides, such as CaMn2O4 (CMO) nanofibers fabricated via the electrospinning technique, have the potential to offer higher reversible capacity through conversion reactions in comparison to that of carbon-based anodes. However, its poor electrical conductivity hinders its usage in lithium-ion batteries (LIBs). Hence, to mitigate this issue, controlled single-step in situ decoration of highly conducting metallic-phase MoS2@CMO nanofibers has been achieved for the first time via the electrophoretic deposition (EPD) technique and utilized as a binder-free nanocomposite anode for LIBs. Further, the composition of MoS2@CMO nanofibers has also been optimized to attain better electronic and ionic conductivity. The morphological investigation revealed that the flakes of MoS2 nanoflowers are successfully and uniformly decorated over the CMO nanofibers' surface, forming a cactus-type morphology. As a binder-free nanocomposite LIB anode, CMOMS-7 (7 wt % MoS2@CMO) demonstrates a specific capacity of 674 mA h g-1 after 60 cycles at 50 mA g-1 and maintains a capacity of 454 mA h g-1 even after 300 cycles at 1000 mA g-1. Further, the good rate performance (102 mA h g-1 at 5000 mA g-1) of CMOMS-7 can be ascribed to the enhanced electrical conductivity provided by the metallic-phase MoS2. Moreover, the feasibility of CMOMS-7 is thoroughly investigated by using a full Li-ion cell incorporating a binder-free cathode of LiNi0.3Mn0.3Co0.3O2 (NMC). This configuration showcases an impressive energy density of 154 Wh kg-1. Thus, the hierarchical and aligned structure of CMO nanofibers combined with highly conductive MoS2 nanoflowers facilitates charge transportation within the composite electrodes. This synergistic effect significantly enhances the energy density of the conversion-based nanocomposites, making them highly promising anodes for advanced LIBs.

Unravelling the safety improving and failure mechanisms of a 56.5 Ah high-energy–density Li-ion cell containing solid-state electrolyte

Safety issues of high-energy–density (HED) Li-ion cells have raised wide concerns and are impeding their application in electric vehicles (EVs). Developing the so-called quasi-solid or semi-solid Li-ion cells with solid-state electrolytes (SSEs) is a promising strategy but generally compromises the cell’s electric performance. Moreover, the safety improving and failure mechanisms remain not fully understood. This study demonstrates a large-format (56.5 Ah) HED (260 Wh kg−1) Li-ion cell with significantly improved safety and good electric performances, which is realized by partial substitution of the liquid electrolyte with lithium aluminium titanium phosphate (LATP) SSE and rational cell material matching. The cell can pass various penetration tests with minimal temperature rises (≤20 °C), showing extraordinarily high tolerances for mechanical abuses, and exhibited a retarded thermal runaway (TR) evolution process during the accelerating rate calorimetry (ARC) test, providing valuable time for deploying predicting, alarming, and preventing tactics for the battery management systems (BMSs). X-ray computed tomography and a large depth-of-field digital microscope were used to uncover the detailed failure behaviors of cell materials, which were correlated to the variation of detectable external cell signals (impedance, voltage, and temperature) that could serve as the basis for upgrading the BMS. We expect that the insights achieved could guide the rational design and management of safe HED Li-ion cells.

Analysis of the Distribution of Relaxation Times (DRT) Responses of Li-Ion Cells as a Function of Their Preparation Conditions

The distribution of relaxation times (DRT) approach was used to analyze the electrochemical impedance spectra obtained for lithium-ion cells as a function of their state of charge as well as the cell preparation conditions. The cells were made using LiFePO4 cathodes with PEDOT:PSS binder and Li anodes. The following parameters were varied: the load of the active mass with LiFePO4, the presence or absence of carbon nanotubes, the presence or absence of the carbon coating of the current collector, die-pressing of the active mass, as well as artificial degradation of the binder using thermal treatment. The results support the view adopted in the literature that the DRT response of Li-ion cells involves 4 main regions attributed to (i) contact resistance between the particles of the active mass or the particles and the current collector; (ii) ionic resistance of the active layer including that of SEI on the surface of the electrodes; (iii) faradaic resistance of the electrochemical charge transfer at the surface of the active material, and (iv) solid-state diffusion/transport of Li+ ions in the particles of active material. Moreover, we identified yet another contribution to the DRT spectra related to the ionic conductivity of the binder and electrolyte in the active mass of the cathode.

Controlling the structural features of tin dioxide nanoparticles embedded reduced graphene oxide on carbon cloth to serve as high stability fast charging anode for Li-ion cells

Tin dioxide or stannic oxide (SnO2) is an n-type semiconductor that has profound applications in gas sensors, solar cells, and energy storage devices like Li-ion batteries. Due to their high theoretical capacity (1494 mAh g−1) affordability, eco-friendliness, and safe operating conditions, SnO2 based anode materials are being extensively studied. Electrochemical capacity and stability for energy storage can be enhanced by embedding facet exposed SnO2 nanoparticles in reduced graphene oxide (rGO). In this study, SnO2 nanoparticles are synthesized and incorporated into rGO network via a simple solvo-thermal method is applied onto a carbon cloth substrate and used as anode for SnO2/rGO based Li-ion cell. The initial discharge capacity is found to be 1415 mAh g−1 and the charge capacity to be 1236 mAh g−1 with an initial Coulombic efficiency of 87 % at a current rate of 0.1 A g−1. The cell also exhibits excellent cycling stability and rate capability, with a discharge capacity of 1034 mAh g−1 and a charge capacity of 998 mAh g−1 at a current rate of 0.3 A g−1. This electrode is stable at a higher current rate of 2C (3 A g−1) and hence offers high prospects as anode material for application in fast-charging rechargeable cells.

Simulations-based investigation of the effectiveness of fire suppression techniques for safe, large-scale storage of Li-ion batteries

Thermal runaway and subsequent fire in Li-ion cells and battery packs is of much concern in the safety of practical electrochemical energy storage systems. While much of the past work in this direction has focused on single cells or small packs, there is a relative lack of understanding of thermal runaway related fire and fire suppression strategies for large-scale systems, for example in storage and transportation of Li-ion cells. This work presents a simulations-based investigation of strategies for effective prevention and suppression of thermal runaway propagation and resulting fire in pallets containing a large number of Li-ion cells. The impact of location, orientation and flowrate in sprinklers supplying a liquid coolant is quantitatively investigated. It is shown that a minimum flowrate is needed for effective fire containment, beyond which, additional flowrate does not offer much incremental benefit. The orientation of sprinklers with respect to the trigger pallet undergoing thermal runaway is found to strongly impact the effectiveness of fire suppression. Fire suppression in the case of vertically stacked pallets is also investigated. Interesting synergistic effects involving a combination of liquid coolant along with one or more suppressant gases is demonstrated. The key output of this work is a computational model that quantitatively predicts the effectiveness of fire suppression techniques for battery transportation and storage. Results presented here offer a fundamental understanding of an important practical problem in battery-based energy storage. Results may form the basis of design and optimization to ensure the safety of large-scale storage and transportation of Li-ion cells.

Improved lithium-ion battery health prediction with data-based approach

The accurate modeling and forecasting of Battery State of Health (SOH) is crucial for ensuring reliable performance and longevity of lithium-ion batteries. This article introduces a data-driven approach for SOH prediction using Gaussian Process Regression (GPR), selected for its ability to model complex data relationships and capture prediction uncertainty without relying on future load information. Recognizing the effect of reversible capacity recoveries on prediction accuracy, this work employs the ISEA-RWTH 48 Li-ion Cells dataset, deliberately devoid of such recoveries prior to training the GPR model. The GPR model was evaluated and compared with Support Vector Regression (SVR) using the publicly available dataset. First and second End of Life (EOL) scenarios were considered, relevant to primary and secondary battery applications. The results demonstrated the GPR model's superior performance. Particularly, mid-life and late-life predictions displayed better accuracy with GPR, showcasing higher R2 values and lower MAPE values (e.g., mid-life prediction: GPR's average R2 = 0.99, SVR's = 0.9789; GPR's average MAPE = 0.1916, SVR's = 1.3028). Moreover, GPR exhibited the ability to quantify uncertainty in capacity degradation and forecast first and second EOL instances effectively (e.g., mid-life predictions had 1.7 cycle error at 1st EOL and 8.9 cycle error at 2nd EOL). The research also offers valuable insights into the application of machine learning methods for predicting the health degradation of lithium-ion batteries.

Heterogeneity of Lithium Distribution in the Graphite Anode of 21700-Type Cylindrical Li-Ion Cells during Degradation

Structural and spatial aspects of cell degradation are studied using a combination of diffraction-and imaging-based tools applying laboratory X-rays, neutron scattering and synchrotron radiation with electrochemical and thermal characterization. Experimental characterization is carried out on cylindrical cells of 21700-type, where four regimes of cell degradation are identified, which are supplemented by an increased cell resistance and surface temperature during cell operation. The amount of intercalated lithium in the fully charged anodes in the fresh and aged states is determined by ex situ X-ray diffraction radiography and in situ X-ray diffraction computed tomography. The qualitatively similar character of the results revealed a loss of active lithium along with the development of a complex heterogeneous distribution over the electrode stripe.

The effect of liquid channels and cold plates on the performance of hybrid thermal management strategies for cylindrical Li-ion cells

In this paper, phase change material (PCM) based hybrid thermal management strategies are proposed for cylindrical Lithium-ion battery modules. Experimental and numerical studies are conducted to analyze the proposed strategies at a high discharge rate of 7 C. Three different types of thermal management configurations are developed. In all the configurations primary coolant is the PCM and secondary coolants are liquid and air. In one of the configuration vertical liquid coolant channels are placed between the PCM and airflow at the top of the cells. Whereas, in the two configurations different designs of cold plates are utilized in place of liquid channels. The experimental studies are conducted to obtain the temperature and heat flux profiles of the battery module. Moreover, a numerical model is developed and validated using the experimental data obtained. Using the numerical model, the thermal performance of the battery module was obtained for the proposed strategies. Based on the results, the maximum temperature of the battery module was limited to 29.1 °C and a high temperature uniformity was achieved by the end of the discharge cycle with the temperature difference limited to 1.2 °C. Additionally, the proposed hybrid thermal management strategy was capable of maintaining the required optimal thermal operating conditions without changing the phase of the PCM. Furthermore, it eliminates the requirement of a pump and reservoir since there is no flow of liquid within the battery module. This reduces the energy required for the operation of the thermal management system, thereby increasing the available energy for propulsion. Additionally, the developed strategy also increases the safety of the battery modules as it is capable of maintaining the required thermal environment in high discharge rates up to 7 C.

Forensic Analysis of Lithium-Ion Cells Involved in Fires

<div>The emerging use of rechargeable batteries in electric and hybrid electric vehicles and distributed energy systems, and accidental fires involving batteries, has heightened the need for a methodology to determine the root cause of the fire. When a fire involving batteries takes place, investigators and engineers need to ascertain the role of batteries in that fire. Just as with fire in general, investigators need a framework for determining the role that is systematic, reliant on collection and careful analysis of forensic evidence, and based on the scientific method of inquiry. This article presents a systematic scientific process to analyze batteries that have been involved in a fire. It involves examining Li-ion cells of varying construction, using a systematic process that includes visual inspection, x-ray, CT scan, and possibly elemental analysis and testing of exemplars. For the purposes of this article, we are mainly concentrating on the most common designs of consumer lithium-ion batteries, cylindrical and pouch. The methodology applies both scientific literature and observations gathered while investigating over a thousand incidents.</div>

Electrothermal modeling of lithium-ion batteries using an artificial intelligence technique-based approach for powerwall applications

The Powerwall, an innovative home battery powered by solar energy, is gaining popularity in the United States and Australia due to its ability to provide complete power to homes and serve as a backup during electrical supply interruptions. Recently, lithium-ion (Li-ion) battery technology has received significant attention from the industry and academia, standing out for offering greater energy capacity, power density, efficiency, and lower self-discharge rate compared to other technologies such as NiCd and NiMH batteries. Initially, this research aimed to model the Li-ion cells of the Powerwall using the equivalent circuit model (ECM). However, a detailed review of the literature indicated that a data-based approach, employing Deep Learning (DL) techniques or deep neural networks, represents the state of the art in the field. DL, a subset of machine learning and part of Artificial Intelligence (AI), offers notable advantages over ECM, including: i) high precision in estimating the non-linear relationships between voltage, current, temperature, and hidden variables such as the State of Charge (SOC); ii) the ability of a single artificial neural network to model the behavior of a Li-ion cell across different temperature ranges (example: from 0°C to 40°C); and iii) overcoming the challenge of identifying ECM parameters. Therefore, with the advancement of the research, the objective was updated to investigate and develop DL models, specifically feed-forward neural networks, for estimating the SOC of lithium-ion batteries in Powerwalls. The results obtained focus on the precise estimation of the SOC of Li-ion cells, underlining the efficacy and innovation of this methodological approach.

Interaction between LMFP and NCMA and Its Effect on Blending Cathode-Based Cells

Li-ion cells with a LiMnxFe1−xPO4 (LMFP) and LiNi1−x−y−zCoxMnyAlzO2 (NCMA) blending cathode show their benefits of lower cost and higher safety compared to barely NCMA cathode-based cells. However, the rate capability of LMFP material is relatively poor compared to NCMA or even LiFePO4, which is because of the low electronic conductivity of LMFP material and the 1D diffusion channel in its structure. This work discusses the effect on electrochemical performance when blends of various ratios of LMFP are used in an NCMA cathode, with data verified by a 5 Ah pouch cell. This work further investigated the interaction between NCMA and LMFP during charge/discharge. Combining results from experiment and simulation, it evidences that blending more LMFP does not always lead to worse discharge rate but reduces charge rate. Moreover, it is found that, in a constant current discharge/charge process, although the system is under continuous discharge/charge, LMFP works intermittently. This leads to different diffusion polarization states of LMFP in the discharge/charge process and further results in a difference in discharge/charge rate capability. Therefore, to improve rate capability, especially charging rate, using smaller-sized or doped LMFP to improve its diffusion coefficient is an optimized strategy.

Enhancement of ionic transport characteristics and cell performance through multi-layered separator microstructure in Li-ion cells

Enhancement of ionic transport characteristics and cell performance through multi-layered separator microstructure in Li-ion cells

Impact of Electrolyte Volume on the Cycling Performance and Impedance Growth of 18650 Li-ion Cells

We provide compelling evidence that the cycling performance of 18650 Li-ion cells is adversely affected by excessive amounts of electrolyte volume, with a noticeable decline observed within the initial 30 cycles, particularly at higher discharge rates. This “high-volume effect” imposes additional constraints on the optimization of cell manufacturing, highlighting the importance of identifying its underlying causes. The electrochemical impedance of 3.5 Ah 18650 cylindrical cells with varying levels of electrolyte volume was extensively measured using PEIS and GEIS techniques. The results indicate that, in general, the ohmic and charge transfer resistance(s) of the cells increase at a faster rate when excess electrolyte volume (9% and 18%) is present. During high discharge rate cycling, relaxation periods can effectively recover the lost capacity, but when high discharge rate cycling resumes, the trend in the capacity loss reappears. We hypothesize that a salt segregation effect in the electrolyte may contribute to the growth of both ohmic and charge transfer resistance, leading to capacity loss when excess electrolyte is present.

Binder-free Cu1.9Bi0.1Se@SWCNT hybrid anodes for lithium-ion and sodium-ion batteries

The rapid growth of portable electronic devices, electric vehicles, and grid-scale energy storage systems has accelerated the demand for enhancing existing materials and innovating new materials in rechargeable battery technologies. Li-ion batteries have dominated the energy storage field among the various battery systems. Na-ion batteries have emerged as promising candidates due to their similarities to Li-ion battery chemistry, low cost, and environmental sustainability. This study explores the potential advantages of synthesizing the binder-free Cu1.9Bi0.1Se@SWCNT heterostructure directly on the copper collector surface. A crucial aspect of this research is the intentional use of nanostructuring during synthesis. This technique capitalizes on the benefits of greater surface area, enhanced electron transport, and superior ionic conductivity. The synthesis method not only ensures excellent electrical and mechanical contact with the collector but also omits the need for a binder, offering a potential for improved overall performance in Li-ion and Na-ion batteries. The electrodes were synthesized using a simple and cost-effective physical vapor deposition method. The structural, morphological, and electrochemical properties of the electrodes were characterized. The binder-free Cu1.9Bi0.1Se@SWCNT electrode with 25 % SWCNT content exhibits excellent performance in Li-ion half cells, maintaining a high energy capacity of 556 mAh g−1 at 0.1 A g−1 over 100 cycles and 244 mAh g−1 at 0.5 A g−1 over 750 cycles. However, in the Na-ion battery system, the performance is notably poorer, revealing challenges and limitations. Most likely, the larger size of sodium ions posed difficulties in intercalation within the anode material structure.

Experimental Assessment of Different Air-Based Battery Thermal Management System for Lithium-Ion Battery Pack

<div>Lithium-ion (LI) batteries are widely used to power electric vehicles (EVs), owing to their high charge density, to minimize the environmental pollution caused by fossil fuel-based engines. It experiences an enormous amount of heat generation during charging and discharging cycles, which results in higher operating temperatures and thermal nonuniformity. This affects performance, useful battery life, and operating costs. This can be mitigated by an effective battery thermal management system (BTMS) to dissipate the heat there by safeguarding the battery from adverse thermal effects and ensuring high performance, safety, and longevity of the battery. This article presents a method to estimate the cooling requirement of a given battery pack using calorimetry and discusses the effect of airflow path, flow rate, and inlet air temperature on the thermal behavior of a 4S4P battery pack consisting of 18650 type lithium iron phosphate (LFP) cylindrical Li-ion cells each of 2.55 Ah capacity. In battery pack operation without a cooling system, it is found that the interior cells experience a 3°C higher cell temperature relative to the rest of the battery pack. The cooling performance of the different air BTMS, viz., natural convection cooling, single suction fan cooling, two-fan air cooling, centralized inlet air cooling, and wet jute-based single suction fan air cooling, is discussed. It is observed that the peak temperature rise of the cells in the battery pack was found to be the least in centralized inlet air cooling, unlike other cooling configurations. The wet jute-based single suction fan air cooling is superior by achieving the highest COP of 6, with an 8.9°C rise in battery pack peak temperature for a permissible peak discharge rate. It is observed that the temperature rise of the battery pack is profoundly influenced by the temperature of the inlet air compared to the flow rate.</div>

Reduction of Irreversible Capacity in Lithium-ion Batteries

This article is focused on a research of negative materials for Lithium-ion batteries. In the research are considered methods, which can lead to enhance capacity of Lithium-ion batteries. The increase of the battery capacity is based on reduction of irreversible capacity. The majority of Li-ion batteries which are used in this time has negative electrode make from graphite. On interface between electrolyte and graphite electrode originates the SEI layer (Solid-Electrolyte Interphase), this layer is the cause of irreversible capacity of graphite. This layer is indispensable for appropriate battery function but for creating this layer is consumed almost one-third potential capacity of Li-ion cell. In our research we attempted to prepare the material which would reduce these capacity losses. Was designed a concept where n-butyllithium (C4H9Li) reagent behaves as the source of lithium atoms and graphite acts like acceptor of lithium atoms. This process is called „lithiation“, our conception presents n-butyllithium like oxidative reagent which is able to reduce graphite material by Li atoms. Lithium atoms are intercalated between graphite sheets (as at charging process), resulting of this process is new lithiated electrode material which can be used for prepare of negative electrode for Li-ion cells.

Quantifying Electrochemical Degradation in Single-Crystalline LiNi0.8Mn0.1Co0.1O2 –Graphite Pouch Cells through Operando X-Ray and Postmortem Investigations

Layered nickel-rich lithium transition-metal oxides (LiNixMnyCo1−x−yO2; where ≥ 0.8), with single-crystalline morphology, are promising future high-energy-density Li-ion battery cathodes due to their ability to mitigate particle-cracking-induced degradation. This is due to the absence of grain boundaries in these materials, which prevents the build-up of bulk crystallographic strain during electrochemical cycling. Compared to their polycrystalline counterparts, there is a need to study single-crystalline Ni-rich cathodes using x-ray methods in uncompromised machine-manufactured industrylike full cells to understand their bulk degradation mechanisms as a function of different electrochemical cycling protocols. This can help us identify factors to improve their long-term performance. Here, through in-house x-ray studies of pilot-line-built LiNi0.8Mn0.1Co0.1O2–graphite A7 pouch cells, it is shown that their electrochemical-capacity fade under harsh conditions (2.5–4.4 V and 40 °C for 100 cycles at a C/3 rate) primarily stems from the high-voltage reconstruction of the cathode surface from a layered to a cubic (rock-salt) phase that impedes the Li+ kinetics and increases cell impedance. Postmortem electron and x-ray microscopy show that these cathodes can withstand severe anisotropic structural changes and show no cracking when cycled under such conditions. Comparing these results to those from commercial Li-ion cells with surface-modified single-crystalline Ni-rich cathodes, it is identified that cathode surface passivation can mitigate this type of degradation and prolong cycle life. In addition to furthering our understanding of degradation in single-crystalline Ni-rich cathodes, this work also accentuates the need for practically relevant and reproducible fundamental investigations of Li-ion cells and presents a methodology for achieving this. Published by the American Physical Society 2024

A proof-of-concept of direct recycling of anode and cathode active materials: From spent batteries to performance in new Li-ion cells

Recycling End-of-Life (EoL) Li-ion Batteries (LiBs) is a major target, driven mainly by recently published EU guidelines and by supply risks of primary resources for meeting the increasing demand of cell production. Even though LiBs recycling is technically feasible, it is limited by insufficient recycling efficiencies and high environmental impact of the currently available technologies. With moderate energy consumption and waste production, direct recycling is virtually the ideal approach in a circular economy perspective. However, the lack of verification of recycled materials under industrially relevant conditions hinders its attractiveness for large-scale applications. Here, we demonstrate direct recycling of NCM622 and graphite from spent cells and validate the recycled materials in new cells with commercially valid characteristics. We extend the recycling from the layered oxide cathode to the graphite anode with high efficiency and no toxic solvents used during the process. New cells with both recycled anode and cathode show very promising electrochemical performance comparable to those of commercially available active materials. The proof-of-concept of direct recycling offers the basis for identifying scalable routes and fast advancement of battery recycling.

Observation of preferential sputtering of Si/graphite anodes from Li-ion cells by GD-OES and its validation by neutron depth profiling

Although the loss of Li inventory (LLI) is a common aging mechanism in Li-ion batteries, there are only few methods capable of comprehensive depth profiling within the bulk of the electrode to locate the residual Li. Two post-mortem analytical methods, which can be used to obtain quantified Li depth profiles to depths greater than 10 μm from the electrode surface are neutron depth profiling (NDP) and glow discharge optical emission spectroscopy (GD-OES). In this work, the validation of GD-OES using NDP by examining the Si/graphite anodes of cylindrical 21700 cells is presented. One anode was in a pristine/fresh state, two anodes were aged to the state of health (SOH) 90% and 76% at 45 °C respectively, and suffered from heavy solid electrolyte interphase (SEI) growth, and the fourth anode was aged to SOH 60% at 0 °C and exhibited Li plating. It is demonstrated that Li plating leads to a faster sputter rate of the Li-rich anode surface. An adapted method is introduced to incorporate the changing sputter rate into the depth profile calculation. For the aged anodes, the progressive aging of the anodes leads to a higher amount of irreversibly bound Li on the anode surface.