Graphite Battery Research Articles

Environment Friendly Synthesis of Reduced Graphene Oxide from Spent Lithium-Ion Battery Graphite and Its Nanocomposite with MoO3 Nanorods for Photocatalytic Hydrogen Evolution

Environment Friendly Synthesis of Reduced Graphene Oxide from Spent Lithium-Ion Battery Graphite and Its Nanocomposite with MoO₃ Nanorods for Photocatalytic Hydrogen Evolution

High-Energy Sodium Ion Batteries Enabled by Switching Sodiophobic Graphite into Sodiophilic and High-Capacity Anodes.

Owing to the crustal abundance of sodium element, sodium ion batteries (SIBs) are considered a promising complementary to lithium-ion battery for stationary energy storage applications. The cointercalation chemistry enables the use of cost-effective graphite as anodes, whereas the low capacity (<130 mAh g-1) and high redox potential (>0.6 V vs. Na/Na+) of graphite significantly limit the energy density of SIBs. Herein, we induce the high-capacity Na metal into sodiophilic ternary graphite intercalation compounds (t-GICs) via co-intercalation and deposition reactions, thereby achieving Na/t-GIC anodes with high capacities and low working voltage (0.18 V). The new anodes exhibit high coulombic efficiencies of above 99.7 % over 550 cycles and a high-rate capacity of 588.4 mAh g-1 at 6 C (10 min per charge). When it is paired with Na3V2(PO4)2F3 (NVPF) cathodes, the SIBs demonstrate a high energy density of 259 Wh kg-1 both electrodes surpassing that of commercial LiFePO4//graphite batteries. The outstanding anode performance is attributed to the tailored sodiophilicity of graphite through manipulating the ether solvents and the in situ generated space among t-GIC flakes to stably accommodate Na metal. Our findings for stable Na plating/striping on sodiophilic graphite materials provide an effective approach for developing advanced SIBs.

High‐Energy Sodium Ion Batteries Enabled by Switching Sodiophobic Graphite into Sodiophilic and High‐Capacity Anodes

AbstractOwing to the crustal abundance of sodium element, sodium ion batteries (SIBs) are considered a promising complementary to lithium‐ion battery for stationary energy storage applications. The cointercalation chemistry enables the use of cost‐effective graphite as anodes, whereas the low capacity (&lt;130 mAh g−1) and high redox potential (&gt;0.6 V vs. Na/Na+) of graphite significantly limit the energy density of SIBs. Herein, we induce the high‐capacity Na metal into sodiophilic ternary graphite intercalation compounds (t‐GICs) via co‐intercalation and deposition reactions, thereby achieving Na/t‐GIC anodes with high capacities and low working voltage (0.18 V). The new anodes exhibit high coulombic efficiencies of above 99.7 % over 550 cycles and a high‐rate capacity of 588.4 mAh g−1 at 6 C (10 min per charge). When it is paired with Na3V2(PO4)2F3 (NVPF) cathodes, the SIBs demonstrate a high energy density of 259 Wh kg−1both electrodes surpassing that of commercial LiFePO4//graphite batteries. The outstanding anode performance is attributed to the tailored sodiophilicity of graphite through manipulating the ether solvents and the in situ generated space among t‐GIC flakes to stably accommodate Na metal. Our findings for stable Na plating/striping on sodiophilic graphite materials provide an effective approach for developing advanced SIBs.

Photodiode-based focus monitoring in ultrashort-pulsed laser structuring of graphite anodes for lithium-ion batteries

In recent years, there has been an increased demand for elaborate monitoring techniques in laser material processing. This has been driven by the need for fast and cost-efficient quality assurance processes. At the same time, ultrashort-pulsed (USP) laser radiation has emerged as a promising technology for creating intricate microstructures in lithium-ion battery graphite anodes due to its high precision and negligible thermal impact. However, the integration of process monitoring in USP laser applications for graphite anode structuring is still unexplored. There is a lack of clarity on suitable sensors, observable parameters, and extractable process-relevant insights. The presented study addressed this gap by demonstrating the capability of state-of-the-art photodiode-based monitoring systems in collecting process-relevant data and deriving valuable insights. A sensor equipped with three photodiodes was employed to address these challenges. Exploratory data analysis and machine learning methodologies were leveraged to develop a data pipeline for processing the acquired information. The data were used to train convolutional neural networks that could accurately predict the focal position. At the same time, the limitations of traditional regression approaches could be shown. The findings advanced the understanding of the possibilities of process monitoring in USP laser applications and emphasized the significance of data-driven approaches in optimizing manufacturing processes.

An unsaturated chain carbonate additive contributing to high-performance LiFePO4//graphite battery at broad temperature range

Vinylene carbonate (VC) electrolyte additive can extend the cycle life of lithium-ion batteries (LIBs) by the polymerization of CC bonds and ring opening at the electrode/electrolyte interface. However, the interface film produced by VC exhibits extremely high impedance at low temperatures (LT), leading to a rapid deterioration in battery performance. In this work, butyl 2-acetylene 1, 4-diethoxycarbonate (BAEC) additive, a chain carbonate with CC bond, is designed for the first time to overcome the fatal low-temperature defect of VC. The higher unsaturation CC bond endows BAEC with an elevated REDOX activity for film forming. When BAEC is collaborated with VC which has better cathodic compatibility, the LiFePO4//Graphite pouch cells demonstrate an ultrahigh capacity retention of 105.8 % after 300 cycles at 0 °C and 101.2 % after 130 cycles at −10 °C. In contrast, the VC system fails only after 10 cycles at 0 °C and cannot achieve normal charge and discharge at −10 °C. Moreover, BAEC + VC system exhibits an enhanced capacity retention of 85.7 % at the 500th cycle at 45 °C. Deep exploration reveals that in addition to the intrinsic factors of the higher unsaturation which are the guarantee of reactivity and uniformity for film generation, BAEC can regulate the initial Li+ solvation structure through steric hindrance and interaction with the solvent which contributes to preeminent interface film stability and conductivity. This work proves that unsaturated chain carbonates are worthwhile additives which can promote the development of LIBs with strong environmental adaptability.

Predictive pretrained transformer (PPT) for real-time battery health diagnostics

Modeling and forecasting the evolution of battery systems involve complex interactions across physical, chemical, and electrochemical processes, influenced by diverse usage demands and dynamic operational patterns. In this study, we developed a predictive pre-trained Transformer (PPT) model equipped with 1,871,114 parameters that enhance identification of both short-term and long-term patterns in time-series data. This is achieved through the integration of convolutional layers and probabilistic sparse self-attention mechanisms, which collectively enhance prediction accuracy and efficiency in diagnosing battery health. Moreover, the customized hybrid-model fusion supports parallel computing and employs transfer learning, reducing computational costs while enhancing scalability and adaptability. Consequently, this allows for precise real-time health estimations across various battery cycles. We validated this method using a public dataset of 203 commercial lithium iron phosphate (LFP)/graphite batteries charged at rates ranging from 1C to 8C. By using only partial charge data—from an 80 % state of charge to the maximum charging voltage (3.6 V for LFP batteries, 4.2 V for ternary batteries)—and avoiding complex feature engineering, error metrics were achieved below 0.3 % for root mean square error (RMSE), weighted mean absolute percentage error (WMAPE), and mean absolute error (MAE), with an R2 of 98.9 %. The generalization capabilities were further demonstrated across 36 different testing protocols, encompassing 23,480 cycles throughout the entire life cycle, with a total inference time of 9.88 s during the testing phases. Further experiments on 30 nickel cobalt aluminum (NCA) batteries and 36 nickel cobalt manganese (NCM) batteries, across different battery types and operational scenarios, resulted in RMSE, WMAPE, and MAE all below 0.9 %, with R2 values of 94.1 % and 94.4 %, respectively. These findings highlight the potential of our customized deep transfer neural networks to enhance diagnostic accuracy, accelerate training, and improve generalization in real-time applications.

High energy density potassium-based dual graphite battery with high concentration carbonate electrolyte

Dual ion batteries (DIBs) differ from traditional lithium-ion and sodium-ion batteries in that the electrolyte acts as a significant source of active materials in DIBs, directly influencing the specific capacity, charge-discharge efficiency, and cycle life. Traditional potassium (K)-based dual ion batteries use electrolytes with concentrations below 1 m (mol kg−1), which exhibit a comparatively low oxidation potential of ∼4.4 V versus K/K+. This limits the operational longevity and energy density of the batteries. To enhance the electrochemical stability of the electrolyte and improve the capacity and reversibility of anions/cations intercalating into graphite electrodes, this study introduces a 10.0 m potassium bis(fluorosulfonyl)imide (KFSI) in carbonate ester electrolytes. The results show that increasing the electrolyte concentration effectively raises the oxidation potential to 6.1 V vs. K/K+. A K-dual graphite dual ion battery (K-DGDIB) is assembled using 10.0 m KFSI/ethylene carbonate (EC):dimethyl carbonate (DMC) electrolyte and incorporates both a graphite cathode and a graphite anode. This battery provides a discharge capacity of 94.2 mAh g−1 at 100 mA g−1, a discharge medium voltage of ∼4.24 V, and an energy density of ∼5.8 Wh kg−1 considering the total mass of all added electrolyte and the total mass of the active materials.

LiNi0.5Mn1.5O4 Addition to Anion-Storing Graphite Cathode Yields Multifaceted Benefits to Dual Graphite Batteries

Dual graphite batteries (DGBs) yield an output voltage of ∼4.5 V vs Li+/Li by functioning on the “scissor-cutting” type dual-ion storing mechanism. However, they lack capacity, suffer from poor cycling efficiency, and exhibit insufficient cycle life. The improvement strategies reported in the literature ameliorate only the targeted parameter but downgrade the rest. Herein, the approach of blending LiNi0.5Mn1.5O4 (LNMO) spinel oxide with graphite at cathode is demonstrated as a multifunctional remedy. LNMO represents an additional lithium reservoir that replenishes the depleted lithium at anode during cycling, thereby boosting cycling efficiency. It acts as a sacrificial salt that compensates for the irreversibly consumed Li+ from its stock during parasitic reactions, thus reducing the self-discharge rate of dual-graphite full cell. Further, the Ni4+/2+ redox couple at ∼4.75 V vs Li+/Li in LNMO enhances capacity, upshifts average discharge voltage, and increases the energy output of the full cell. The interaction between de/intercalating Li+ and PF6− during the “cooperated scissor-cutting mechanism” functional at blended cathode decreases charge transfer resistance. The presence of LNMO enriches the interfacial composition in inorganic components that benefit long-term cycling. Moreover, the physical properties like tap density, durability, and pore structure are reinforced in graphite/ LNMO blended cathode.

An integrated simulation and experimental study of calendering process in water-based manufacturing of lithium-ion battery graphite electrode

Lithium-ion batteries produced from water-based manufacturing processes are favored for their environmental and economic advantages, while currently sacrificing some technical performance. This paper reports an integrated study on the calendering process of water-based manufacturing of lithium-ion battery graphite electrode, aiming to improve electrochemical performance of the manufactured lithium-ion batteries. The interactive mechanism between the calendering process and the porous microstructure of the produced graphite electrode was systematically investigated. It reveals that the graphite electrode with 40 % of porosity produced under 79,509 N/m calendering force achieves an optimal 333 mAh/g of specific capacity and 91.2 % of capacity retention after 100 cycles.

Thermal Performance of a Cylindrical Li[Ni0.6Co0.2Mn0.2]O2/Graphite Battery based on the Electrochemical-Thermal Coupling Model

The thermal safety of lithium-ion batteries has garnered significant attention due to its pivotal role in the field of new energy. In this work, a three-dimensional electrochemical-thermal coupling model based on the P2D model was established for predicting the thermal performance. The charge-discharge and temperature rise experiments via 18650 cylindrical Li[Ni0.6Co0.2Mn0.2]O2 / graphite batteries are designed to confirm the rationality of the model. The simulation results show that the highest temperature of the battery surface during discharging at 1 C and 4 C are 42.85 °C and 61.25 °C, and the experimental results are 42.50 °C and 62.85 °C, respectively. The electrode heat generation mainly comes from the reaction heat of cathode and anode during 1 C charge process, the maximum power is 1.2 W and 0.6 W, respectively. In the discharge process, the cathode dominates the reaction contribution of 1.02 W and the reaction heat power from the anode is only 0.016 W. The capacity of heat dissipation can be increased by enhancing the convective heat transfer coefficient and air velocity within a reasonable range. The proposed electrochemical-thermal coupling model is valuable to evaluate the heat behavior and promote the battery development.

Decoration of recycled battery graphite functionalized with gold nanoparticles/poly(nicotinic acid) for detection of bifenazate pesticide in tea and food samples

Bifenazate (BF), is a type of carbamate acaricide effective at controlling mite parasites on crops and ornamental plants. In this work, a recycled dry zinc-carbon battery graphite electrode decorated with gold nano particles/poly nicotinic acid, AuNPs/poly(NA)-BGE, was applied as the working electrode for the electrochemical measurement of bifenazate (BF). The working electrode (BGE) was functionalized by 10 electropolymerization voltammetric cycles of poly nicotinic acid poly (NA) following by 30 s of amperometric deposition of gold nanoparticles (AuNPs) to produce the final AuNPs/poly(NA)-BGE electrode in a two-step procedure. “Electrochemical and morphological characterization of the sensor at its different production steps was performed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX) techniques and Transmission electron microscopy (TEM).” The highest peak current response was attained using pH 6.0 in 0.1 M phosphate buffer. The sensor exhibited a linearity range from (1 × 10−4–1 × 10−8 M) that is equivalent to 30.035–3.00 × 10−3 µg/mL with limits of detection LOD and quantification 3.3 × 10−11 M (9.91 × 10−6 µg/mL) and 1.00 × 10−10 M (3.00 × 10−5 µg/mL), respectively. Finally, with a recovery range of (96.3 %–102.6 %) and an RSD of (0.17 %–0.64 %), BF in Kenyan green and black tea, strawberry, tomato, cucumber and its commercial formulation Duramite® 24 %SC was successfully quantified which indicates the promising applicability of the presented sensor in different matrixes.

Development, characterization and validation of a novel physics-informed equivalent circuit model for silicon–graphite battery cells

The widespread deployment of electric vehicles (EVs), as well as the growing requirements both from manufacturers and consumers, necessitate an increase in energy density with regard to current lithium-ion batteries (LIBs). In this regard, one of the most promising alternatives is the addition of silicon to conventional graphite anodes, thus giving rise to energy-dense LIBs. However, this entails a significant increment in modeling, parameterization and computational complexities due to the interactions between both negative electrode materials. In this article, we present a novel physics-informed equivalent circuit model for cells with blended electrodes, which is able to provide accurate results with respect to a state-of-the-art electrochemical model, not only for the output voltage (≤25 mV RMS), but also internal states, namely active material particle surface concentrations (≤1.2 %) and current distribution (≤2.6 %) at a much lower computational cost. Furthermore, this formulation also allows for a notable simplification of model parameterization. Hence, we describe thorough static and dynamic parameterization processes from half-cell experimental data and impedance measurements. Finally, we validate the proposed model in constant-current as well as dynamic operation, highlighting the influence that the choice of hysteresis model has on the latter. We understand that the presented model is an interesting alternative for the modeling of cells with blended electrodes, and is also suitable for its implementation in Battery Management Systems (BMSs) in EVs.

Low-cost ionic liquid electrolytes based on low-molecular-weight primary and secondary alkylamine hydrochlorides for rechargeable Al batteries

Rechargeable batteries with Al metal as the negative electrode are promising candidates for post‑lithium-ion batteries. However, the cost of the most commonly used electrolytes, chloroaluminate ionic liquids based on 1-ethyl-3-methylimidazolium chloride (EMICl), is prohibitive. Herein, we report a novel, low-cost chloroaluminate ionic liquid electrolyte based on primary and secondary alkylamine hydrochlorides, namely, ethylamine hydrochloride (EtNH3Cl) and dimethylamine hydrochloride (Me2NH2Cl). The advantages of these alkylamine hydrochlorides over their tertiary amine counterparts (Me3NHCl and Et3NHCl) are their lower cost, odorless nature, and a lower molecular weight that would reduce the battery weight. Although the binary systems of EtNH3Cl–AlCl3 and Me2NH2Cl–AlCl3 are not liquids at room temperature, mixing the two systems results in an ionic liquid at room temperature. The electrodeposition of Al and intercalation of AlCl4− into graphite in this electrolyte system are demonstrated. The alkylammonium cations decompose only at potentials below −0.3 V vs. Al. The performance of Al–graphite batteries incorporating this low-cost electrolyte is comparable to that of batteries using the conventional expensive EMICl-based electrolytes under typical charge-discharge conditions. The low-cost EtNH3Cl–Me2NH2Cl–AlCl3 electrolyte is expected to advance Al batteries toward practical application and commercialization.

Towards Understanding and Control of Thermal Processes in Lithium-Ion Batteries

Despite lithium-ion batteries (LIBs) being state-of-the-art commercial rechargeable batteries, there are still significant challenges. For example, heat generation during cycling can lead to performance degradation and safety issues1-2. During the process of charging and discharging, the heat that is generated from the chemical reactions taking placing is ideally distributed uniformly in space, to dissipate out the cell easily. However, in practice, heat generation tends to be heterogeneous throughout the battery, leading to localized overheating3. This phenomenon can result in e.g. decomposition of the solid-state electrolyte interphase (SEI) layer, triggering electrode reactions with the electrolyte and degradation of the electrolyte (producing combustible gases) and even melting of the separator4. Hence, comprehending the origins of temperature generation and its heterogeneity is crucial.To address this challenge, operando X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are applied to monitor the structural changes in the electrode materials during charge and discharge, while simultaneous temperature measurements are conducted using a thermal camera, as such obtaining spatial resolved structure/temperature/performance relationships. We have focused on state-of-the-art nickel rich NMC (Nickel Manganese Cobalt Oxide) versus graphite batteries and by comparing the structural changes of the electrode materials during cycling in ‘hot’ versus ‘cool’ areas of the electrode and battery, we were able to establish a structure-temperature relationships, on top of the electrochemical structure-performance relationships and as such unravel “heat-generation” process and reactions. The real-time temperature distribution was compared to the computational models using COMSOL, and insights in thermal processes and their possible control measures could be obtained.References Lain, M. & Kendrick, E. Understanding the limitations of lithium-ion batteries at high rates. Journal of Power Sources. Volume 493, 229690 (2021).Ma, S., et al. Temperature effect and thermal impact in lithium-ion batteries: A review. Progress in Natural Science: Materials International. Volume 28, Issue 6, Pages 653-666 (2018).Rafael, M., et al. Operando Radiography and Multimodal Analysis of Lithium–Sulfur Pouch Cells—Electrolyte Dependent Morphology Evolution at the Cathode. Adv. Energy Mater. 2103432 (2022).Joris, J., et al. A comprehensive review of future thermal management systems for battery electrified vehicles. Journal of Energy Storage 31, 101551(2020).

Temperature‐Inert Interface Enables Safe and Practical Energy‐Dense LiNi0.91Co0.07Mn0.02O2 Pouch Cells

AbstractSafety concerns significantly hinder the practical implementation of ultrahigh‐nickel cathodes in lithium‐ion batteries. The solid electrolyte interphase (SEI) derived from conventional ester‐based electrolyte is susceptible to thermal decomposition, resulting in battery safety degradation. Herein, a temperature‐inert and inorganic‐rich SEI is developed for the ultrahigh‐nickel LiNi0.91Co0.07Mn0.02O2|graphite (NCM91|Gr) battery by employing a flame‐retardant diluted weakly solvated electrolyte. Temperature‐dependent X‐ray photoelectron spectroscopy reveals that SEI's inorganic components of LiF, Li2SO3, Li2SO4, and Li3N exhibit exceptional thermotolerance under thermal attack. Further evidence from temperature‐dependent X‐ray diffraction indicates that this thermally stable interface effectively mitigates the anode phase transition from the original LiC6 to LiC12 state, resulting in a remarkable improvement in intrinsic safety and a 32% reduction in gas emission for battery. The 1.2 Ah NCM91|Gr pouch cell exhibits a thermal failure onset temperature as high as 183.1 °C and maintains stability at 180 °C for 60 min. Furthermore, a 360 Wh kg−1 12.3 Ah LiNi0.92Co0.06Mn0.02O2|graphite@20% silicon dioxide cell experiences no thermal runaway even at 200 °C. The 1.2 Ah NCM91|Gr pouch cell also delivers outstanding capacity retention of 90.5% after 1200 cycles with enhanced electrochemical performance. This study provides a promising approach for developing safer energy‐dense batteries through electrolyte and interface design.

Electrolyte Design Enables Rechargeable LiFePO4/Graphite Batteries from -80°C to 80°C.

Lithium iron phosphate (LFP)/graphite batteries have long dominated the energy storage battery market and are anticipated to become the dominant technology in the global power battery market. However, the poor fast-charging capability and low-temperature performance of LFP/graphite batteries seriously hinder their further spread. These limitations are strongly associated with the interfacial Li-ion transport. Here we report a wide-temperature-range ester-based electrolyte that exhibits high ionic conductivity, fast interfacial kinetics and excellent film-forming ability by regulating the anion chemistry of Li salt. The interfacial barrier of the battery is quantitatively unraveled by employing three-electrode system and distribution of relaxation time technique. The superior role of the proposed electrolyte in preventing Li0 plating and sustaining homogeneous and stable interphases are also systematically investigated. The LFP/graphite cells exhibit rechargeability in an ultrawide temperature range of -80°C to 80°C and outstanding fast-charging capability without compromising lifespan. Specially, the practical LFP/graphite pouch cells achieve 80.2% capacity retention after 1200 cycles (2 C) and 10-min charge to 89% (5 C) at 25°C and provides reliable power even at -80°C.

Electrolyte Design Enables Rechargeable LiFePO4/Graphite Batteries from −80°C to 80°C

Lithium iron phosphate (LFP)/graphite batteries have long dominated the energy storage battery market and are anticipated to become the dominant technology in the global power battery market. However, the poor fast‐charging capability and low‐temperature performance of LFP/graphite batteries seriously hinder their further spread. These limitations are strongly associated with the interfacial Li‐ion transport. Here we report a wide‐temperature‐range ester‐based electrolyte that exhibits high ionic conductivity, fast interfacial kinetics and excellent film‐forming ability by regulating the anion chemistry of Li salt. The interfacial barrier of the battery is quantitatively unraveled by employing three‐electrode system and distribution of relaxation time technique. The superior role of the proposed electrolyte in preventing Li0 plating and sustaining homogeneous and stable interphases are also systematically investigated. The LFP/graphite cells exhibit rechargeability in an ultrawide temperature range of −80°C to 80°C and outstanding fast‐charging capability without compromising lifespan. Specially, the practical LFP/graphite pouch cells achieve 80.2% capacity retention after 1200 cycles (2 C) and 10‐min charge to 89% (5 C) at 25°C and provides reliable power even at −80°C.

Revealing the materials, design, and performance of Ni-rich LiNi1-x-yCoxMnyO2/graphite pouch cells

Among lithium-ion batteries (LIBs), Ni-rich LiNi1-x-yCoxMnyO2/Graphite batteries hold a dominant position in electric vehicles due to high energy density, good cycling stability, and low content of Co element. In this work, Ni-rich LiNi1-x-yCoxMnyO2 (LiNi0.83Co0.07Mn0.10O2, NCM83)/Graphite pouch cells with a capacity of around 2.1 Ah are designed and manufactured. The structure and micromorphology of NCM83 as well as graphite are revealed. The XRD Rietveld refinement method clarifies the lattice parameters of NCM83. The PE separator modified by Al2O3 and PVDF (PE/Al2O3/PVDF) is used in the cells. The design parameters, formation, and aging processes are disclosed as well. Charge-discharge tests demonstrate that the NCM83/Graphite pouch cells have good electrochemical performance. Notably, the cell delivers an initial discharge capacity of 2.158 Ah at 1 A and 25 °C, and retains a high reversible discharge capacity of 1.715 Ah after 500 cycles with a capacity retention of close to 80 %. Additionally, the polarization characteristics during charging and discharging are discussed in detail, demonstrating that a good linear relationship exists between polarization voltage and cycle number. This work systematically reveals the materials, and design technology of NCM83/Graphite battery cells and helps deepen the understanding of commercial LIBs based on Ni-rich LiNi1-x-yCoxMnyO2 cathode materials.

Digital Twin‐Assisted Degradation Diagnosis and Quantification of NMC Battery Aging Effects During Fast Charging

AbstractA comprehensive understanding of aging mechanisms and degradation diagnosis under fast charging in battery electric vehicles is needed. However, there is a lack of tools to capture both macroscopic and microscopic parameters, still focusing on experiment results analysis. To get a comprehensive degradation insight for improved service life, this study explores aging mechanisms in LiNi0.5Co0.2Mn0.3O2 graphite batteries under different fast charging conditions (0.6C to 2C) for up to 1000 equivalent full cycles (EFCs). An improved digital twin is used to quantify aging effects and identify aging modes, combining electrochemical techniques with post‐mortem analysis for assessing chemical and structural degradation. After 1000 EFCs, the dominant aging modes are loss of active material (LAM) in the negative electrode and loss of lithium inventory (LLI), surpassing LAM in the positive electrode. Compared to constant current charging, multistep fast charging effectively mitigates Li plating effects and graphite cracking, resulting in a 13% reduction in LAM. Additionally, optimizing the depth of discharge leads to at least 4% reductions in LLI and 16% in LAMpos. This study proves the electrochemical digital twin's potential for quantifying aging effects and serves as a basis for future physics‐informed machine learning to predict aging behavior and modes.

Operando Raman observation of lithium-ion battery graphite composite electrodes with various densities and thicknesses

Understanding the mechanisms of inhomogeneous charging and discharging reactions in an electrode is critical to improving the rate capability of lithium-ion batteries. Various methods have been developed to observe the distribution of electrode structure or lithium ions within an electrode; however, most of these methods require large-scale equipment or entail complex procedures. To simplify reaction distribution measurements within electrodes, this study developed specially designed cells and conducted operando observations of reaction distribution in graphite composite electrodes using Raman spectroscopy. Behaviors on both the electrolyte and current collector sides of the electrodes were compared, and electrodes of various densities and thicknesses were examined. For electrodes with low density, the changes in graphite structure were almost simultaneous on the electrolyte and current collector sides and were hardly dependent on the electrode thickness. In contrast, the changes in electrode structure with increased density were dependent on their thickness. This implies that the ion transportation length is responsible for the reaction distribution in the electrodes when ion channels connecting the current collector and electrolyte sides decrease owing to the increased electrode density. The simple method developed in this study is expected to further contribute to the understanding of the distribution of reactions within graphite composite electrodes.