Solid Electrolyte Interphase Growth Research Articles

Design, perspectives, and challenges of modification strategies for alkali metal anodes

Abstract. The alkali metal anode has emerged as a focal point of research due to its extremely low oxidation-reduction potential and high theoretical specific capacity. However, challenges such as unstable solid electrolyte interphase (SEI), infinite volume expansion, and uncontrollable dendrite growth result in low coulombic efficiency and irreversible losses during the deposition and stripping processes. To address these issues, various effective strategies have been proposed to protect the alkali metal anode and achieve dendrite-free growth. In this review, we summarize recent advancements in enhancement strategies for alkali metal anodes, including the construction of three-dimensional current collectors and interface engineering. Specifically, we delve into the development of carbon-based current collectors with various dimensions and structures and the application of interface engineering techniques to tackle the challenges of unstable SEI, volume changes, and dendrite growth. Furthermore, we explore advanced characterization techniques that provide deeper insights into the reaction mechanisms and behavior of these enhancement strategies. Finally, we discuss the current limitations and future research directions in protecting alkali metal anodes, aiming to provide valuable insights into the study of dendrite growth and the development of effective protection strategies for alkali metal anodes.

Quantifying the Effect of Degradation Modes on Li-ion Battery Thermal Instability and Safety

Understanding the thermal stability of lithium-ion (Li-ion) cells is critical to ensuring optimal safety and reliability for various applications such as portable electronics and electric vehicles. In this work, we demonstrate a combined modeling and experimental framework to interrogate and quantify the role of different degradation modes on the thermal stability and safety of Li-ion cells. A physics-based Li-ion cell aging model is developed to describe the underpinning role of degradation mechanisms such as Li plating, solid electrolyte interphase growth, and the loss of electrode active material on the resulting capacity fade during cycling. By incorporating mechanistic degradation descriptors from the aging model, we develop a degradation-aware cell-level thermal stability framework that captures key safety characteristics such as thermal runaway (TR) onset temperature, self-heating rate, and peak TR temperature for different cycling conditions. Additionally, we perform electrochemical and accelerating rate calorimetry (ARC) experiments to evaluate the thermo-kinetic parameters associated with the various exothermic reactions during TR of pristine and aged Li-ion cells. Through a synergistic integration of thermo-electrochemical characteristics from the ARC experiments and degradation insights from the cell aging model, the proposed aging-coupled safety framework provides a baseline to quantify the thermal stability of Li-ion cells subject to a wide range of operating conditions and degradation scenarios.

Unraveling the Complex Temperature-Dependent Performance and Degradation of Li-Ion Batteries with Silicon-Graphite Composite Anodes

Competing effects of graphite and Si result in a complex temperature dependent performance and degradation of Li-ion batteries with Si-graphite composite anodes. This study examines the influence of varying the Si content (0 to 20.8 wt%) in Si-graphite composite anodes with consistent areal capacity and N/P ratio in full cells containing NMC622 cathodes. One hundred pilot-scale double-layer pouch cells were built and cycle aged in the temperature range from −10 to 55 °C. Electrochemical characterization demonstrated that increasing Si contents enhance capacity and mitigate internal resistance at low temperatures. On the other hand, high Si contents decrease charge-discharge energy efficiency and cycle life, particularly at elevated temperatures. Post-mortem analysis of aged electrodes, including physico-chemical characterization (scanning electron microscopy, energy-dispersive X-ray analysis, thickness measurements) and cell reconstruction revealed significant solid electrolyte interphase growth and increased loss of active material in anodes with high Si content. The optimum temperature for longest cycle life as derived from Arrhenius plots decreased from 30 °C for graphite anodes to 10 °C for cells with moderate Si content up to 5.8 wt%. These findings allow the design of optimized cells by balancing the Si content versus operating temperature in order to achieve lowest cell aging.

A Comparison of Standard SEI Growth Models in the Context of Battery Formation

Growth of the Solid Electrolyte Interphase (SEI) layer on negative electrode particles during the formation cycle is one of the most complex and least understood steps of lithium-ion battery manufacturing. This initial SEI formation significantly impacts battery performance, lifetime, and degradation. Zero-dimensional models, which reduce the complexity of SEI’s morphology, material, and structure, are commonly used to study long-term SEI growth rates and capacity fade. These models are derived based on limiting mechanisms. We aim to compare the most common SEI growth models, focusing on the first few cycles at low C-rates representing formation protocols. Using consistent parameters across models, we seek to understand if they can capture the dynamics of SEI formation. We conducted qualitative comparisons with experimental measurements of Coulombic efficiency in 2032-type coin cells at low C-rate. Our analysis shows that the models predict SEI growth in the first cycle to be higher than in subsequent cycles. However, the difference between cycles in these models is insufficient to explain the experimental results, which indicate a capacity fade during the first cycle that is two orders of magnitude higher than in later cycles. This suggests new models are needed to accurately describe the physics of the formation cycle.

Evolution of aging mechanisms and performance degradation of lithium-ion battery from moderate to severe capacity loss scenarios

The aging mechanisms of Nickel-Manganese-Cobalt-Oxide (NMC)/Graphite lithium-ion batteries are divided into stages from the beginning-of-life (BOL) to the end-of-life (EOL) of the battery. The corresponding changes in the battery performance across these stages have been analyzed, and a digital twin model is established to quantify the primary parameters that influence these aging mechanisms. Post-mortem analysis is applied to validate the results. This paper compares the aging mechanisms from BOL to EOL using two charging protocols: a multi-step fast charge protocol and a common constant-current fast charge protocol that applies the average current of multi-step currents. Notably, a transition from a linear to a non-linear degradation trend in capacity fade is observed, beginning from a 10% capacity reduction to EOL. From BOL to 10% degradation, the resistance of solid electrolyte interphase (SEI) grows steadily. The graphite anode’s crack depth exhibits a significant increase, accompanied by an evident collapse of cathode materials in all the test cases following a 10% degradation until EOL. This phenomenon can be attributed to one primary reason—the expansion of the corresponding simulated resistance of charge transfer (Rct). Post-mortem analysis revealed the change in morphology, structure, and composition of various degradation conditions. This analysis proved that the primary driver of the linear aging stage is the SEI growth. Furthermore, it is evident that the transition to a non-linear aging degradation is dominated by electrode defects resulting from continuous mechanical stress during long-term aging.

Modeling Particle Versus SEI Cracking in Lithium-Ion Battery Degradation: Why Calendar and Cycle Aging Cannot Simply be Added

Degradation models are important tools for understanding and mitigating lithium-ion battery aging, yet a universal model that can predict degradation under all operating conditions remains elusive. One challenge is the coupled influence of calendar and cycle aging phases on degradation mechanisms, such as solid electrolyte interphase (SEI) formation. In this work, we identify and systematically compare three different SEI interaction theories found in the literature, and apply them to experimental degradation data from a commercial lithium-ion cell. In a step-by-step process, and after careful data selection, we show that SEI delamination without any cracking of the active particles, and SEI microcracking, where cycling only affects SEI growth during the cycle itself, are both unlikely candidates. Instead, the results indicate that upon cycling, both the SEI and the active particle crack, and we provide a simple, 4-parameter equation that can predict the particle crack rate. Contrary to the widely-accepted Paris’ law, the particle crack rate decreases with increasing cycles, potentially due to changing intercalation dynamics resulting from the increasing surface-to-volume ratio of the active particles. The proposed model predicts SEI formation accurately at different storage conditions, while simply adding the degradation from pure calendar and cycle aging underestimates the total degradation.

External short circuit of lithium-ion battery after high temperature aging

The microscopic and macroscopic changes of lithium-ion batteries after high temperature cycling and their effect on external short circuit (ESC) are studied in this study. The results indicate that solid electrolyte interphase and cathode electrolyte interphase cover the surface of anode and cathode. Transition metal, Mn is dissolved from the cathode. Capacity and resistance decreases and increases after cycling at high temperature. The safety of batteries after ESC is ranked as: 70 % state of health (SOH) > 100 % SOH > 80 % SOH > 90 % SOH. Thermal runaway only occurs to battery with 90 % SOH after ESC. Increase of resistance after cycling affects heat generation during ESC less. Onset temperature and thermal runaway temperature increases and decreases owing to solid electrolyte interphase growth and Mn dissolution. Compared to fresh battery, safety of battery with 70 % SOH after ESC increases. Fast discharging causes side reactions for aged batteries, which also generate heat. The heat generation effect of fast discharging decreases with the decrease of SOH after 90 % SOH. Local micro internal short circuit causes more heat generation for aged batteries. The results are important for safety control of lithium-ion battery.

Investigating Temperature-Dependent Dynamics of SEI Growth and Battery Degradation

Several studies have contributed to the current understanding of the temperature-dependent behavior of solid-electrolyte interphase (SEI) formation in lithium-ion batteries and its impact on battery capacity and lifespan. Liu et al. developed a thermal-electrochemical model that revealed the complex interplay between diffusivity, reaction kinetics, and temperature on SEI growth1. Leng et al. presented an electrochemistry-based electrical model to examine the temperature's effect on battery aging2. Alipour et al. reviewed temperature-dependent electrochemical properties3, while Lubhani Mishra et al. provided a detailed physics-based analysis of battery degradation and temperature inhomogeneities4. These studies collectively indicate higher temperatures accelerating and promoting growth of compact and less permeable SEI structures leading to an increase in capacity loss and cell resistance, and lower temperatures resulting in slow ionic transport through the SEI also causing higher ohmic loss. In the present work, we study SEI growth and resulting effect on battery capacity fade using continuum scale modeling under the assumption of constant battery cell temperature as well as considering actual dynamically changing temperature data from experiments. SEI growth under these two considerations is compared and the comparison is used in determining scenarios where considering dynamically varying temperature is crucial for accuracy. The detailed analysis of the internal states from the simulation results contributes to the understanding of the effect of the thermal dynamics on battery cell degradation due to SEI growth. To achieve these objectives, a physics-based model, specifically the Single Particle Model (SPM), is utilized. The model uses temporal temperature data obtained from past experimental studies as well as temperature dependent properties of SEI provided in the literature as inputs for this investigation. The ultimate aim of this study is to better understand how temperature influences SEI characteristics, thereby contributing to improved battery performance and longevity across diverse thermal environments. References Liu, L., Park, J., Lin, X., Sastry, A. M., & Lu, W. (2014). A thermal-electrochemical model that gives spatial-dependent growth of solid electrolyte interphase in a Li-ion battery. Journal of power sources, 268, 482-490.Leng, F., Tan, C. M., & Pecht, M. (2015). Effect of temperature on the aging rate of Li-ion battery operating above room temperature. Scientific reports, 5(1), 12967.Alipour, M., Ziebert, C., Conte, F. V., & Kizilel, R. (2020). A review on temperature-dependent electrochemical properties, aging, and performance of lithium-ion cells. Batteries, 6(3), 35.Mishra, L., Subramaniam, A., Jang, T., Garrick, T. R., & Subramanian, V. R. (2022, October). Model Development for Temperature-Dependent Degradation in Large Format Lithium-Ion Batteries. In Electrochemical Society Meeting s 242 (No. 28, pp. 1075-1075). The Electrochemical Society, Inc.

A Data-Driven Approach for Predicting the Lifetime of Lithium-Metal Batteries

Lithium-metal batteries (LMBs) are promising candidates for accelerating the implementation of electric vehicles in our society. LMBs comprise of a lithium-metal anode that possesses the highest theoretical specific capacity (3860 mAh/g) and the lowest redox potential (-3.04V vs standard hydrogen electrode).1 LMBs undergo repeated plating and stripping of lithium ions on the anode surface. The non-homogenous stripping process leads to the isolation of metallic lithium from the anode surface, forming dead-lithium.2 The parasitic reaction between the lithium-metal anode and the electrolyte leads to the formation of the solid electrolyte interphase (SEI) layer. These phenomena lead to the reduction of available lithium and a rise in cell impedance, causing a rapid reduction of lifetime for these batteries.3 , 4 In this talk, we present a diverse dataset collected from different LMBs of different capacities and voltage ranges, that includes features from the initial formation cycle, rest voltages and CV charging during cycling. A data-driven model from the LMB cycling data is presented to predict the remaining useful lifetime (RUL) of these cells. Insights from the model can be used to determine the bad cells in a batch, improve the designs of the cells and derive optimal charging protocols for their implementation in the BMS. References Lin, D., Liu, Y. & Cui, Y. Reviving the lithium metal anode for high-energy batteries. Nat. Nanotechnol. 12, 194 (2017).Xu, S., Chen, K.-H., Dasgupta, N. P., Siegel, J. B. & Stefanopoulou, A. G. Evolution of Dead Lithium Growth in Lithium Metal Batteries: Experimentally Validated Model of the Apparent Capacity Loss. J. Electrochem. Soc. 166, A3456–A3463 (2019).Liu, G. & Lu, W. A Model of Concurrent Lithium Dendrite Growth, SEI Growth, SEI Penetration and Regrowth. J. Electrochem. Soc. 164, A1826–A1833 (2017).Gao, N. et al. Fast Diagnosis of Failure Mechanisms and Lifetime Prediction of Li Metal Batteries. Small Methods 5, 1–11 (2021).

Operando Electrochemical Liquid Cell STEM Investigation of the Growth and Evolution of the Mosaic Solid Electrolyte Interphase for Lithium-Ion Batteries

The solid electrolyte interphase (SEI) is a key component of a lithium-ion battery forming during the first few dis-/charge cycles at the interface between the anode and the electrolyte. The SEI passivates the anode-electrolyte interface by inhibiting further electrolyte decomposition extending the battery's cycle life. Insights into SEI growth and evolution in terms of structure and composition remain difficult to access. To unravel the formation of the SEI layer during the first cycles, operando electrochemical liquid cell scanning transmission electron microscopy (ec-LC-STEM) is employed to monitor in real time the nanoscale processes that occur at the anode-electrolyte interface in their native electrolyte environment [1]. The results show that the formation of the SEI layer is not a one-step process, but comprises multiple steps. The growth of the SEI is initiated at low potential during the first charge by decomposition of electrolyte leading to the nucleation of inorganic nanoparticles. Thereafter, the growth continues during subsequent cycles by forming an island-like layer. Eventually, a thick dense layer is formed with a mosaic structure composed of larger inorganic patches embedded in a matrix of organic compounds. While the mosaic model for the structure of the SEI is generally accepted, our observations document for the first time how the complex structure of the SEI is built up during dis-/charge cycling.[1] W. Dachraoui, R. Pauer, C. Battaglia, R. Erni, ACS Nano 2023, 17, 20434

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.

Binary Cation Matrix Electrolyte and Its Effect on Solid Electrolyte Interphase Suppression and Evolution of Si Anode.

An unstable solid electrolyte interphase (SEI) has been recognized as one of the biggest challenges to commercializing silicon (Si) anodes for high-energy-density batteries. This work thoroughly investigates a binary cation matrix of Mg2++Li+ electrolyte and its role in SEI development, suppression, and evolution of a Si anode. Findings demonstrate that introducing Mg ions dramatically reduces the SEI growth before lithiation occurs, primarily due to the suppression of solvent reduction, particularly ethylene carbonate (EC) reduction. The Mg2+ alters the Li+ cation solvation environment as EC preferably participates in the oxophyllic Mg2+ solvation sheath, thereby altering the solvent reduction process, resulting in a distinct SEI formation mechanism. The initial SEI formation before lithiation is reduced by 70% in the electrolyte with the presence of Mg2+ cations. While the SEI continues to develop in the postlithiation, the inclusion of Mg ions results in an approximately 80% reduction in the postlithiation SEI growth. Continuous electrochemical cycling reveals that Mg2+ plays a crucial role in stabilizing the deep-lithiated Si phases, which effectively mitigates side reactions, resulting in controlled SEI growth and stable interphase while eliminating complex LixSiy formation. Mg ions promote the development of a notably more rigid and homogeneous SEI, characterized by a reduced dissipation (ΔD) in the Mg2++Li+ ion matrix compared to the solely Li+ system. This report reveals how the Mg2++Li+ ion matrix affects the SEI evolution, viscoelastic properties, and electrochemical behavior at the Si interface in real time, laying the groundwork for devising strategies to enhance the performance and longevity of Si-based next-generation battery systems.

Elucidating the Transport of Electrons and Molecules in a Solid Electrolyte Interphase Close to Battery Operation Potentials Using a Four-Electrode-Based Generator-Collector Setup.

In lithium-ion batteries, the solid electrolyte interphase (SEI) passivates the anode against reductive decomposition of the electrolyte but allows for electron transfer reactions between anode and redox shuttle molecules, which are added to the electrolyte as an internal overcharge protection. In order to elucidate the origin of these poorly understood passivation properties of the SEI with regard to different molecules, we used a four-electrode-based generator-collector setup to distinguish between electrolyte reduction current and the redox molecule (ferrocenium ion Fc+) reduction current at an SEI-covered glassy carbon electrode. The experiments were carried out in situ during potentiostatic SEI formation close to battery operation potentials. The measured generator and collector currents were used to calculate passivation factors of the SEI with regard to electrolyte reduction and with regard to Fc+ reduction. These passivation factors show huge differences in their absolute values and in their temporal evolution. By making simple assumptions about molecule transport, electron transport, and charge transfer reaction rates in the SEI, distinct passivation mechanisms are identified, strong indication is found for a transition during SEI growth from redox molecule reduction at the electrode | SEI interface to reduction at the SEI | electrolyte interface, and good estimates for the transport coefficients of both electrons and redox molecules are derived. The approach presented here is applicable to any type of electrochemical interphase and should thus also be of interest for interphase characterization in the fields of electrocatalysis and corrosion.

Two-Step Growth Mechanism of the Solid Electrolyte Interphase in Argyrodyte/Li-Metal Contacts.

The structure and growth of the solid electrolyte interphase (SEI) region between an electrolyte and an electrode is one of the most fundamental yet less well-understood phenomena in solid-state batteries. We present an atomistic simulation of the SEI growth for one of the currently promising solid electrolytes (Li6PS5Cl), based on ab initio-trained machine learning interatomic potentials, for over 30,000 atoms during 10 ns, well beyond the capabilities of conventional molecular dynamics. This unveils a two-step growth mechanism: a Li-argyrodite chemical reaction leading to the formation of an amorphous phase, followed by a kinetically slower crystallization of the reaction products into a 5Li2S·Li3P·LiCl solid solution. The simulation results support the recent, experimentally founded hypothesis of an indirect pathway of electrolyte reduction. These findings shed light on the intricate processes governing SEI evolution, providing a valuable foundation for the design and optimization of next-generation solid-state batteries.

Physics-Informed Design of Hybrid Pulse Power Characterization Tests for Rechargeable Batteries

Industry-standard diagnostic methods for rechargeable batteries, such as hybrid pulse power characterization (HPPC) tests for hybrid electric vehicles, provide some indications of state of health (SoH), but lack a physical basis to guide protocol design and identify degradation mechanisms. We develop a physics-based theoretical framework for HPPC tests, which are able to accurately determine specific mechanisms for battery degradation in porous electrode simulations. We show that voltage pulses are generally preferable to current pulses, since voltage-resolved linearization more rapidly quantifies degradation without sacrificing accuracy or allowing significant state changes during the measurement. In addition, asymmetric amounts of information gain between charge /discharge pulses are found from differences in electrode kinetic scales. We demonstrate our approach of physics-informed HPPC on simulated Li-ion batteries with nickel-rich cathodes and graphite anodes. Multivariable optimization by physics-informed HPPC rapidly determines kinetic parameters that correlate with degradation phenomena at the anode, such as solid-electrolyte interphase (SEI) growth and lithium plating, as well as at the cathode, such as oxidation-induced cation disorder. If validated experimentally, standardized voltage protocols for HPPC tests could play a pivotal role in expediting battery SoH assessment and accelerating materials design by providing new electrochemical features for interpretable machine learning of battery degradation.

Long‐Life High‐Voltage Sodium‐Ion Batteries Enabled by Electrolytes with Cooperative Na+‐Solvation

AbstractStabilizing the electrode interphases is urgently required to enhance the lifetime of high‐voltage sodium‐ion batteries (SIBs). However, the continuous anode solid–electrolyte interphase (SEI) growth associated with electron leakage and the fragile cathode–electrolyte interphase (CEI) lead to capacity fade at high voltage; and yet the solvation‐interphase‐performance relationship is inadequately addressed. Herein, a cooperative Na+‐solvation strategy is reported to stabilize the interphases by a holistic design of electrolytes combining soft and moderate co‐solvents. The rationally regulated Na+‐solvation leads to CEI/SEI with the desired thickness and component stability. As such, remarkable cycling stability is achieved for 4.3‐V Na3V2O2(PO4)2F (NVOPF) cathodes with 83.3% capacity retention over 3000 cycles at 1 C, significantly outperforming the carbonate counterpart (41.6% capacity retention). Meanwhile, the restrained SEI growth via reducing the formation of electron‐leaking Na2CO3 stabilizes the long‐term cycling of the hard carbon (HC) anode. The assembled NVOPF||HC full cells achieve superior rate capability (up to 15 C) and stable cycling stability over 500 cycles. The demonstrated engineering of electrolyte chemistry, Na+‐solvation, and interphase structure/component contributes toward the rational establishment of design rules for high‐voltage SIBs and possibly other similar chemistries.

Flexible bidirectional pulse charging regulation achieving long-life lithium-ion batteries

Typical application scenarios, such as vehicle to grid (V2G) and frequency regulation, have imposed significant long-life demands on lithium-ion batteries. Herein, we propose an advanced battery life-extension method employing bidirectional pulse charging (BPC) strategy. Unlike traditional constant current charging methods, BPC strategy not only achieves comparable charging speeds but also facilitates V2G frequency regulation simultaneously. It significantly enhances battery cycle ampere-hour throughput and demonstrates remarkable life extension capabilities. For this interesting conclusion, adopting model identification and postmortem characterization to reveal the life regulation mechanism of BPC: it mitigates battery capacity loss attributed to loss of lithium-ion inventory (LLI) in graphite anodes by intermittently regulating the overall battery voltage and anode potential using a negative charging current. Then, from the perspective of internal side reaction, the life extension mechanism is further revealed as inhibition of solid electrolyte interphase (SEI) and lithium dendrite growth by regulating voltage with a bidirectional pulse current, and a semi-empirical life degradation model combining SEI and lithium dendrite growth is developed for BPC scenarios health management, the model parameters are identified by genetic algorithm with the life simulation exhibiting an accuracy exceeding 99%. This finding indicates that under typical rate conditions, adaptable BPC strategies can extend the service life of LFP battery by approximately 123%. Consequently, the developed advanced BPC strategy offers innovative perspectives and insights for the development of long-life battery applications in the future.

Lignin‐derived hard carbon anode with a robust solid electrolyte interphase for boosted sodium storage performance

AbstractHard carbon is regarded as a promising anode candidate for sodium‐ion batteries due to its low cost, relatively low working voltage, and satisfactory specific capacity. However, it still remains a challenge to obtain a high‐performance hard carbon anode from cost‐effective carbon sources. In addition, the solid electrolyte interphase (SEI) is subjected to continuous rupture during battery cycling, leading to fast capacity decay. Herein, a lignin‐based hard carbon with robust SEI is developed to address these issues, effectively killing two birds with one stone. An innovative gas‐phase removal‐assisted aqueous washing strategy is developed to remove excessive sodium in the precursor to upcycle industrial lignin into high‐value hard carbon, which demonstrated an ultrahigh sodium storage capacity of 359 mAh g−1. It is found that the residual sodium components from lignin on hard carbon act as active sites that controllably regulate the composition and morphology of SEI and guide homogeneous SEI growth by a near‐shore aggregation mechanism to form thin, dense, and organic‐rich SEI. Benefiting from these merits, the as‐developed SEI shows fast Na+ transfer at the interphases and enhanced structural stability, thus preventing SEI rupture and reformation, and ultimately leading to a comprehensive improvement in sodium storage performance.

Anionic and cationic co-driving strategy for enhanced lithium storage and migration on Si-based anodes

Alloy-based anodes are considered to be a promising choice for next-generation high-energy density devices; nevertheless, lithiation-induced anisotropic swelling and ongoing solid electrolyte interphase growth and cracking severely limit practical applicability. Herein, an anionic and cationic co-driving strategy is proposed for the alloy-based (Si) anode that aims to improve structural stability with controlled ion migration pathways and enhanced reaction kinetics, eventually leading to better capacity, high-rate performance, and cycle performance for lithium storage. Ex-situ tests and density functional theory simulations show that Co-HHTP has both anionic and cationic co-storage capabilities. Furthermore, the strong interactions between Co-HHTP and anionic species may impede anion transport towards the silicon surface, hence mitigating the recurrent degradation of the solid electrolyte interphase. As a proof of concept, the Si-based anode, fitted with Co-HHTP, delivers a high initial Coulombic efficiency of 80.4 %, a large reversible capacity (1648.0 mAh g−1 at 0.2 A g−1), and an ultralow attenuation rate of 0.034 % per cycle over 1000 cycles. The proposed approach provides a new strategy for a high-performance anode through functional coating structural construction coupled with anionic and cationic co-storage that confine anion diffusion and facilitate lithium storage and migration.

Interface engineering of Si-based anodes with fluorinated binder enabling lean-additive lithium-ion batteries

Silicon (Si) is a promising alternative to graphite anode for increasing the energy density of litihum-ion batteries owing to its high theoretical capacity. However, the severe volume change of Si during cycling leads to unstable solid electrolyte interphase (SEI) growth, resulting in rapid capacity fading, particularly under lean-additive electrolyte conditions. In this study, we introduce an innovative approach to interface engineering of Si anodes using a fluorinated binder, a method that forms a stable and uniform lithium fluoride (LiF)-based SEI layer under lean-additive electrolyte conditions without the need for common additives. The LiF layer not only improves the structural stability of Si electrodes but also enhances the electrolyte stability, thereby preventing undesired SEI growth by electrolyte decomposition. Benefiting from this proposed binder, the Si-based anode retains a high reversible capacity (93.7 %) after 400 cycles at 0.9 A g−1 and the full cell, pairing with LiNi0.8Co0.1Mn0.1O2 cathode, delivers a high areal capacity of 4.23 mAh cm−2 (93.4 % retention) after 200 cycles under a lean-additive electrolyte (only 3 wt% additive). The interface stabilization by fluorinated binder provides insights into the rational design of a binder for the application of Si anodes in high-energy-density lithium-ion batteries.