Cathode Electrolyte Interphase Layer Research Articles

Boron- and calcium-interspersed cathode-electrolyte interphases on Ni-rich layered oxide cathodes for advanced performance lithium-ion batteries

Although Ni-rich layered oxides (Ni-rich NCM) have become the preferred cathode materials in the electric vehicle market, their unsustainable cycling behavior arising from the extremely high reactivity at the interface has become a formidable challenge. To alleviate this problem, we propose modifying the cathode-electrolyte interphase (CEI) of Ni-rich L-NCM cathodes by incorporating B/Ca functional groups. Dual-functionalized CEI layers are prepared by heating boric acid (H3BO3) and calcium oxide (CaO) in a one-step process. Islands of B- and Ca-functionalized CEI layer are observed at the Ni-rich L-NCM cathode, and the thickness is controlled to approximately 2.4 nm. The B-functional group not only lowers the concentration of residual lithium but also compensates for the longer Li+ migration distance by providing a desirable pathway based on ion-hopping sites. The Ca functional groups increase the mechanical rigidity of the Ni-rich L-NCM cathode, which inhibits the appearance of microcracks. In terms of its cycling behavior, the capacity retention of the cell with the B/Ca-incorporated Ni-rich L-NCM cathode improves markedly (72.4%), whereas the bare Ni-rich L-NCM material only retains 44.3% of its capacity after 100 cycles.

Stable interphase inducer based on montmorillonite clay mineral to enhance stability and fire safety for lithium metal batteries

Heat buildup from factors like mechanical, electrical, or thermal stress is the main safety issue in lithium metal batteries (LMBs). Even without such stressors, however, LMBs may remain fire-prone because of the development of unstable electrode–electrolyte interphase on charge–discharge, potentially leading to internal short circuits. In this study, a stable cathode-electrolyte interphase inducer (SCEI-I) is proposed to tackle both the cycling stability issue and safety concerns. SCEI-I is synthesized by incorporating montmorillonite, a clay mineral, and methylphosphonic acid dimethyl ester, a flame-retardant material, onto a porous polyethylene film. On cycling, SCEI-I can induce a thin (<8 nm), uniform and robust cathode-electrolyte interphase layer, contributing to a steady and high Coulombic efficiency of 99.6%–99.8% with decreased impedance. SCE-I improves electrochemical performance by reducing the capacity degradation from ∼21.9% to ∼8.9% after 100 cycles. SCE-I also demonstrates strong thermal stability as the endothermic energy of SCEI-I is only –32.4 J/g (24 °C–280 °C), which is less than one-third of that of polypropylene separator (–118.9 J/g). Furthermore, when exposed to fire, the SCEI-I membrane instantly extinguished flames by disrupting combustion chain reaction. The present study proposes an interfacial engineering approach to improve the stability and safety of LMBs.

Anion-mediated interphase construction enabling high-voltage solid-state lithium metal batteries

Enhancing the interphase stability of polymer electrolytes with high-voltage cathodes is crucial for the development of high-energy-density lithium metal batteries (LMBs), especially in wearable devices area. Herein, lithium difluorophosphate (LiDFP) is incorporated into the solid polymer electrolyte of poly(ethylene oxide) (PEO) to enhance the formation of a robust cathode-electrolyte interphase (CEI) in high-voltage LiCoO2 LMBs. Through combining electrochemical measurements, spectroscopic techniques and theoretical calculations, the underlying modification mechanism is revealed. Due to its stronger anionic coordination with both polymer electrolyte chain and proton, and more oxidation-active resultant anion-coordinated polymer compared with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiDFP suppresses the formation of the strong acid HTFSI deriving from the deprotonated process of the terminal O-H group thus avoiding the further oxidative attack to the polymeric framework. Furthermore, under the synergetic decomposition of HDFP intermediate, the polymer-derived radical helps to reconstruct a chemo-mechanically stable and Li-conductive CEI layer, which consists of abundant LiF/Li3PO4/LixPOyFz inorganic species distributed in lithiated organic macromolecules. The in-situ constructed CEI effectively passivates catalytic sites on LiCoO2 directly against PEO, resulting in well-maintained layered structure during high-voltage cycling. The proposed interphasial chemistry that regulates CEI formation provides directive knowledge of electrolyte optimization for high-voltage solid-state batteries.

Tailoring Solvation Solvent in Localized High-Concentration Electrolytes for Lithium||Sulfurized Polyacrylonitrile.

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur (Li-S) batteries due to its significantly reduced polysulfide (PS) dissolution compared to that of elemental S cathodes. Although conventional carbonate-based electrolytes are stable with SPAN electrodes, they are unstable with Li metal anodes. Recently, localized high-concentration electrolytes (LHCEs) have been developed to improve the stability of Li anodes. Here, we report a new strategy to further improve the performance of Li||SPAN batteries by replacing the conventional solvating solvent 1,2-dimethoxyethane (DME) in LHCEs with a new solvating solvent, 1,2-diethoxyethane (DEE). The new optimal DEE-LHCE exhibits less reactivity against Li2S2, alleviates PS dissolution, forms a better cathode-electrolyte interphase layer on the SPAN cathode, and enhances SPAN structural reversibility even at elevated temperatures (45 °C). Compared to DME-LHCE, DEE-LHCE with the same salt and diluent leads to better performance in Li||SPAN batteries (with 82.9% capacity retention after 300 cycles at 45 °C), preservation of the SPAN cathode structure, and suppression of volume change of the Li metal anode. A similar strategy on tailoring the solvating solvents in LHCEs can also be used in other rechargeable batteries to improve their electrochemical performances.

Reconstructing Inorganic‐Rich Interphases by Nonflammable Electrolytes for High‐Voltage and Low‐Temperature LiNi0.5Mn1.5O4 Cathodes

AbstractCobalt‐free and spinel LiNi0.5Mn1.5O4 (LNMO) cathodes commonly suffer from undesirable solvent decomposition, serious transition‐metal dissolution, and unstable cathode electrolyte interphase (CEI) layers, incurring rapid capacity decay at high voltages and low temperatures. Herein, these issues are well addressed by utilizing fluorinated solvents with a low coordination number and ethyl propionate with a low melting point. A Li2CO3/LiF‐rich heterostructured CEI layer, which possesses good electron blocking capability of LiF, fast Li+ transport kinetics of Li2CO3 and good mechanical stability, is generated by the synergistic decomposition of hybrid solvents. The robust, homogeneous, and well‐balanced CEI layers subsequently prevent catalyzed parasitic side reactions, prohibit transition‐metal dissolution, and ensure fast interfacial reaction kinetics crossover to the LNMO cathode, thus improving its cycling stability. Consequently, the LNMO cathode delivers a high‐capacity retention of 95.8% over 500 cycles at 25 °C and 97.5% after 180 cycles at −20 °C. This work provides an encouraging alternative to design the high‐voltage and low‐temperature electrolyte for pushing the ongoing research to stabilize Co‐free LNMO materials toward practical applications.

Dual-anion ether electrolyte enables stable high-voltage Na3V2(PO4)2F3 cathode under wide temperatures

Na3V2(PO4)2F3 (denoted as NVPF) is an attractive cathode for sodium ion batteries (NIB) owning to its high theoretical capacity (128 mAh g−1) and high working potential (3.9 V vs Na/Na+). However, NVPF often suffers from low electronic conductivity and unstable cathode electrolyte interphase (CEI), seriously hindering its practical application. Here, a uniform NVPF microsphere assembled by carbon-coated NVPF nanosheets (HM-NVPF@CN) is prepared and subsequently an inorganic-rich B, F species CEI layer on its surface in dual-anion ether electrolyte is constructed to address above drawbacks. The carbon-coated NVPF nanosheets can shorten the diffusion pathway for both Na+ and e−, and provide large electrochemical reaction area. In addition, the robust CEI layer can enhance the Na+ transport and suppress the parasitic reactions. The optimized electrode exhibits a good cycling stability (70 mAh g−1 after 2000 cycles) and outstanding low temperature performance (99 mAh g−1 at −25 °C). The full cell fabricated with a hard carbon (HC) anode achieves a high capacity retention (88% after 930 cycles) and superior high temperature performance (60 °C, 72 mAh g−1 at 5C). This work provides a novel idea to regulate interfacial chemistry of cathodes for the high-voltage NIB.

Investigating Cathode Electrolyte Interphase Formation in NMC 811 Primary Particles through Advanced 4D-STEM ACOM Analysis

Investigating Cathode Electrolyte Interphase Formation in NMC 811 Primary Particles through Advanced 4D-STEM ACOM Analysis

Conductive Robust Interfaces with Fluoro-Borate Based Electrolyte Additive for 4.6V Well-Cycled LiNi0.90 Co0.06 Mn0.04 O2 ||Li Batteries.

Owing to the outstanding comprehensive properties of high energy density, excellent cycling ability, and reasonable cost, Ni-rich layered oxides (NCM) are the most promising cathode for lithium-ion batteries (LIBs). To further enhance the specific capacity of Ni-rich layered oxides, it is necessary to increase the cut-off voltage to a higher level. However, a higher cut-off voltage can lead to substantial structural changes and trigger interface side reactions, presenting significant challenges for practical applications (cycle life and safety). Herein, to solve above issues, tris(hexafluoroisopropyl)borate (TFPB) is introduced as a high voltage electrolyte additive for LiNi0.90 Co0.06 Mn0.04 O2 cathode. Based on detail in situ/ex situ characterization, this study proves that TFPB forms a protective solid-state interphase (SEI) layer on the Li-anode. Additionally, derivatives of TFPB are easily oxidatively decomposed to create a dense cathode electrolyte interphase (CEI) film on the cathode. This CEI film effectively prevents the continuous oxidation of the electrolyte and mitigates the adverse effects of HF on the battery. Benefit from the protective SEI and CEI layer, the LiNi0.90 Co0.06 Mn0.04 O2 ||Li battery with a TFPB-containing electrolyte maintains an unprecedented level of performance, with a capacity retention of 89.1% after 100 cycles under the ultrahigh cut-off voltage of 4.6V (vs Li/Li+ ).

Interior-Confined Vacancy in Potassium Manganese Hexacyanoferrate for Ultra-Stable Potassium-Ion Batteries.

Metal hexacyanoferrates (HCFs) are viewed as promising cathode materials for potassium-ion batteries (PIBs) because of their high theoretical capacities and redox potentials. However, the development of an HCF cathode with high cycling stability and voltage retention is still impeded by the unavoidable Fe(CN)6 vacancies (VFeCN) and H2O in the materials. Here, a repair method is proposed that significantly reduces the VFeCN content in potassium manganese hexacyanoferrate (KMHCF) enabled by the reducibility of sodium citrate and removal of ligand H2O at high temperature (KMHCF-H). The KMHCF-H obtained at 90 °C contains only 2% VFeCN, and the VFeCN is concentrated in the lattice interior. Such an integrated Fe-CN-Mn surface structure of the KMHCF-H cathode with repaired surface VFeCN allows preferential decomposition of potassium bis(fluorosulfonyl)imide (KFSI) in the electrolyte, which constitutes a dense anion-dominated cathode electrolyte interphase (CEI) , inhibiting effectively Mn dissolution into the electrolyte. Consequently, the KMHCF-H cathode exhibits excellent cycling performance for both half-cell (95.2 % at 0.2 Ag-1 after 2000 cycles) and full-cell (99.4 % at 0.1 Ag-1 after 200 cycles). This thermal repair method enables scalable preparation of KMHCF with a low content of vacancies, holding substantial promise for practical applications of PIBs.

Electrolyte Engineering with Tamed Electrode Interphases for High-Voltage Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) hold great promise for next-generation grid-scale energy storage. However, the highly instable electrolyte/electrode interphases threaten the long-term cycling of high-energy SIBs. In particular, the instable cathode electrolyte interphase (CEI) at high voltage causes persistent electrolyte decomposition, transition metal dissolution, and fast capacity fade. Here, this work proposes a balanced principle for the molecular design of SIB electrolytes that enables an ultra-thin, homogeneous, and robust CEI layer by coupling an intrinsically oxidation-stable succinonitrile solvent with moderately solvating carbonates. The proposed electrolyte not only shows limited anodic decomposition thus leading to a thin CEI,but also suppresses dissolution of CEI components at high voltage. Consequently, the tamed electrolyte/electrode interphases enable extremely stable cycling of Na3V2O2(PO4)2F (NVOPF) cathodes with outstanding capacity retention (>90%) over 3000 cycles (8 months) at 1 C with a high charging voltage of 4.3 V. Further, the NVOPF||hard carbon full cell shows stable cycling over 500 cycles at 1 C with a high average Coulombic efficiency (CE) of 99.6%. The electrolyte also endows high-voltage operation of SIBs with great temperature adaptability from -25 to 60°C, shedding light on the essence of fundamental electrolyte design for SIBs operating under harsh conditions.

A sacrificial separator facilitating in situ creation of a durable CEI layer and tailoring lithium dendrites for practical lithium metal batteries

The TBB–PE separator can form a robust and uniform boron-rich CEI (cathode electrolyte interphase) layer on the cathode surface via electrochemical oxidation as well as inhibit the growth of lithium dendrites by anion anchoring.

A facile approach to form an artificial CEI layer induced by residual Li compounds on LiNi0.9Co0.05Mn0.05O2 and Li6PS5Cl for all-solid-state batteries

All-solid-state batteries (ASSBs) are attracting significant attention as alternatives to conventional lithium-ion batteries due to their safety and higher energy density. However, electrochemical reactions between the solid electrolytes and active materials result in the degradation of electrochemical cell performances. A conventional approach is to employ protective layers onto the active materials, but this approach could have the drawback of being costly and time-consuming. The artificial cathode electrolyte interphase (CEI) layer generated by reactions between components within the electrode could provide a solution to these challenges. However, this approach can cause component degradation due to its intrinsically degradative nature of the forming process. In this study, we demonstrate the ASSBs with enhanced electrochemical performances by introducing lithium oxy-thiophosphate species (P-Ox-Sy-···Li+, LPOS) and LiCl artificial CEI layer, which could be spontaneously formed during heat treatment by chemical reactions between the solid electrolytes and residual Li compounds on the LiNi0.9Co0.05Mn0.05O2 (NCM) without the degradation. The LPOS-LiCl layer effectively suppresses the side reactions between solid electrolytes and NCM during the repeated electrochemical cyclings. As a result, the NCM full-cell (3.7 mAh cm−2) with the LPOS-LiCl artificial CEI layer exhibits 80.0 % cycle retention after 300 cycles at 0.2 C rate and room temperature. Moreover, it demonstrates 58 % higher Li-ion mobility and 36 % lower internal resistance after cycling compared to the NCM full-cell without the LPOS-LiCl artificial CEI layer.

Electrical Double Layer Formation at Intercalation Cathode–Organic Electrolyte Interfaces During Initial Lithium‐Ion Battery Reactions

AbstractInformation on the cathode/organic–electrolyte interface structure provides clues regarding the rate and reversibility of lithium intercalation reactions in lithium‐ion batteries. Herein, structural changes within the LiCoO2 electrode, throughout the interphase region, and in the LiPF6/propylene carbonate electrolyte are observed concurrently by in situ neutron reflectometry. The formation of an electrical double layer (EDL) during the early stages of charging and discharging is investigated and compared with that at an intercalation‐inactive Nb:SrTiO3 electrode. At the intercalation‐inactive interface between Nb:SrTiO3 and the electrolyte, a voltage‐dependent ionic distribution corresponding to the EDL forms on the electrolyte side without the formation of a cathode/electrolyte interphase (CEI) layer. In contrast, at the intercalation‐active LiCoO2/electrolyte interface, a CEI layer forms immediately after cell construction, and the ionic distribution in the electrolyte formed outside the CEI layer scarcely changes upon voltage application. The CEI/electrolyte interface is shielded from potential changes by the electronically insulating CEI; therefore, structural changes in the EDL are restricted. This supports the prevailing understanding that the CEI layer defines the rates of solvation/de‐solvation and adsorption/desorption reactions of lithium ions.

Promoting reversibility of layered potassium cathode through interstitial doping

With the increasing needs for large-scale and low-cost energy storage devices, Mn-based layered oxide cathodes have achieved considerable researching interests for potassium-ion batteries owing to their high energy density, abundant resource and low toxicity. However, their developments are challenged by the absence of suitable cathode materials to tolerate large-sized K-ion insertion/extraction and the presence of Jahn-Teller distortion of Mn3+. To address this issue, we present a strategy of embedding boron into interstitial tetrahedral sites to obtain a P3-K0.5Mn0.8Co0.2B0.1O2 cathode. Strong B-O covalent bonds facilitate the construction of robust orthorhombic framework and alleviate the undesired elongation of Mn-O bonds, contributing to excellent electrochemical performance. In addition, boron ions are verified to promote the formation of a homogeneous cathode electrolyte interphase layer, improving interfacial stability and realizing highly reversible cycling in a wide voltage range (1.4–4.3 V). This strategy provides a new pathway towards the development of high-performance cathode materials for potassium-ion batteries.

Trimethylsilyl Compounds for the Interfacial Stabilization of Thiophosphate-Based Solid Electrolytes in All-Solid-State Batteries.

Argyrodite-type Li6 PS5 Cl (LPSCl) has attracted much attention as a solid electrolyte for all-solid-state batteries (ASSBs) because of its high ionic conductivity and good mechanical flexibility. LPSCl, however, has challenges of translating research into practical applications, such as irreversible electrochemical degradation at the interface between LPSCl and cathode materials. Even for Li-ion batteries (LIBs), liquid electrolytes have the same issue as electrolyte decomposition due to interfacial instability. Nonetheless, current LIBs are successfully commercialized because functional electrolyte additives give rise to the formation of stable cathode-electrolyte interphase (CEI) and solid-electrolyte interphase (SEI) layers, leading to supplementing the interfacial stability between electrolyte and electrode. Herein, inspired by the role of electrolyte additives for LIBs, trimethylsilyl compounds are introduced as solid electrolyte additives for improving the interfacial stability between sulfide-based solid electrolytes and cathode materials. 2-(Trimethylsilyl)ethanethiol (TMS-SH), a solid electrolyte additive, is oxidatively decomposed during charge, forming a stable CEI layer. As a result, the CEI layer derived from TMS-SH suppresses the interfacial degradation between LPSCl and LiCoO2 , thereby leading to the excellent electrochemical performance of Li | LPSCl | LiCoO2 , such as superior cycle life over 2000 cycles (85.0% of capacity retention after 2000 cycles).

Solution-processed ZnO coated on LiNi0.8Mn0.1Co0.1O2(NMC811) for enhanced performance of Li-ion battery cathode

The LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material, widely used in Li-ion batteries (LIBs) for electric vehicles (EVs), has gained a fair amount of attention in the industry due to its advantages of high energy capacity and low production cost. However, during charge-discharge cycles, NMC811 cathode faces issues such as hydrofluoric acid (HF) attack, leaching of transition metals and unstable formation of the cathode electrolyte interphase (CEI), which leads to undermining cathode performance. To address these issues, extensive research has been conducted on coating materials based on metal oxides. In this study, our research team chose Li-doped ZnO (LZO) material, known for its high Li+ ion conductivity and structural stability. Employing sol-gel synthetic method, we successfully coated LZO material on commercial NMC811 particles, therefore ensuring its coating uniformity through X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy energy dispersive spectroscopy analyses. Evaluation of the coated samples (1 wt%, 2 wt%, and 3 wt% LZO on NMC811) revealed their superior electrochemical performance compared to bare NMC811; furthermore, the 2 wt% LZO-coated sample exhibited the highest cycling performance among the coated samples. These findings could be attributed to the lower charge transfer resistance verified by electrochemical impedance spectroscopy (EIS) analysis. Thus, we confirmed the LZO coating layers could provide stability for the NMC811 surface structure, mitigate the leaching of transition metal ions in the NMC811, and promote the formation of an enhanced CEI layer, therefore facilitating Li+ ion diffusion.

Carrageenan as A Sacrificial Binder for 5V LiNi0.5 Mn1.5 O4 Cathodes in Lithium-Ion Batteries.

5V-class LiNi0.5 Mn1.5 O4 (LNMO) with its spinel symmetry is a promising cathode material for lithium-ion batteries. However, the high-voltage operation of LNMO renders it vulnerable to interfacial degradation involving electrolyte decomposition, which hinders long-term and high-rate cycling. Herein, we overcome this longstanding challenge presented by LNMO by incorporating a sacrificial binder, namely, λ-carrageenan (CRN), a sulfated polysaccharide. This binder not only uniformly covers the LNMO surface via hydrogen bonding and ion-dipole interaction but also offers an ionically conductive cathode-electrolyte interphase layer containing LiSOx F, a product of the electrochemical decomposition of the sulfate group. Taking advantage of these two auspicious properties, the CRN-based electrode exhibited cycling and rate performance far superior to that of its counterparts based on the conventional poly(vinylidene difluoride) and sodium alginate binders. This study introduces a new concept, namely "sacrificial" binder, for battery electrodes known to deliver superior electrochemical performance but be adversely affected by interfacial instability. This article is protected by copyright. All rights reserved.

Boosting the “Solid–Liquid–Solid” Conversion Reaction via Bifunctional Carbonate‐Based Electrolyte for Ultra‐long‐life Potassium–Sulfur Batteries

AbstractPotassium–sulfur (K−S) batteries have attracted wide attention owing to their high theoretical energy density and low cost. However, the intractable shuttle effect of K polysulfides results in poor cyclability of K−S batteries, which severely limits their practical application. Herein, a bifunctional concentrated electrolyte (3 mol L−1 potassium bis(trifluoromethanesulfonyl)imide in ethylene carbonate (EC)) with high ionic conductivity and low viscosity is developed to regulate the dissolution behavior of polysulfides and induce uniform K deposition. The organic groups in the cathode electrolyte interphase layer derived from EC can effectively block the polysulfide shuttle and realize a “solid–liquid–solid” reaction mechanism. The KF‐riched solid‐electrolyte interphase inhibits K dendrite growth during cycling. As a result, the achieved K−S batteries display a high reversible capacity of 654 mAh g−1 at 0.5 A g−1 after 800 cycles and a long lifespan over 2000 cycles at 1 A g−1.

Boosting the "Solid-Liquid-Solid" Conversion Reaction via Bifunctional Carbonate-Based Electrolyte for Ultra-long-life Potassium-Sulfur Batteries.

Potassium-sulfur (K-S) batteries have attracted wide attention owing to their high theoretical energy density and low cost. However, the intractable shuttle effect of K polysulfides results in poor cyclability of K-S batteries, which severely limits their practical application. Herein, a bifunctional concentrated electrolyte (3 mol L-1 potassium bis(trifluoromethanesulfonyl)imide in ethylene carbonate (EC)) with high ionic conductivity and low viscosity is developed to regulate the dissolution behavior of polysulfides and induce uniform K deposition. The organic groups in the cathode electrolyte interphase layer derived from EC can effectively block the polysulfide shuttle and realize a "solid-liquid-solid" reaction mechanism. The KF-riched solid-electrolyte interphase inhibits K dendrite growth during cycling. As a result, the achieved K-S batteries display a high reversible capacity of 654 mAh g-1 at 0.5 A g-1 after 800 cycles and a long lifespan over 2000 cycles at 1 A g-1 .

Probing the Formation of Cathode-Electrolyte Interphase on Lithium Iron Phosphate Cathodes via Operando Mechanical Measurements.

Interfacial instabilities in electrodes control the performance and lifetime of Li-ion batteries. While the formation of the solid-electrolyte interphase (SEI) on anodes has received much attention, there is still a lack of understanding the formation of the cathode-electrolyte interphase (CEI) on the cathodes. To fill this gap, we report on dynamic deformations on LiFePO4 cathodes during charge/discharge by utilizing operando digital image correlation, impedance spectroscopy, and cryo X-ray photoelectron spectroscopy. LiFePO4 cathodes were cycled in either LiPF6, LiClO4, or LiTFSI-containing organic liquid electrolytes. Beyond the first cycle, Li-ion intercalation results in a nearly linear correlation between electrochemical strains and the state of (dis)-charge, regardless of the electrolyte chemistry. However, during the first charge in the LiPF6-containing electrolyte, there is a distinct irreversible positive strain evolution at the onset of anodic current rise as well as current decay at around 4.0 V. Impedance studies show an increase in surface resistance in the same potential window, suggesting the formation of CEI layers on the cathode. The chemistry of the CEI layer was characterized by X-ray photoelectron spectroscopy. LiF is detected in the CEI layer starting as early as 3.4 V and LixPOyFz appeared at voltages higher than 4.0 V during the first charge. Our approach offers insights into the formation mechanism of CEI layers on the cathode electrodes, which is crucial for the development of robust cathodes and electrolyte chemistries for higher-performance batteries.