Electrode-electrolyte Interphase Research Articles

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.

Constructing sulfur-rich interphase to promote the cycle stability of graphite/LiNi0.8Co0.1Mn0.1O2 pouch battery at elevated temperature

Lithium-ion batteries (LIBs) with LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes have a high energy density, but their long-cycle performance, especially at high temperature, should still be improved due to the instability of the NCM811 cathode-electrolyte interphase. In this work, 2, 2, 2-Trifluoroethyl p-Toluenesulfonate (TPTS) is introduced as a functional film-forming electrolyte additive design to improve the long-term stability of graphite/NCM811 batteries. The preferential redox reactions of TPTS molecules play a pivotal role in fostering the creation of a sulfur-riched interphase, characterized by low impedance. This interphase works to fortify the interfacial structure, effectively inhibiting the dissolution of transition metal ions. Therefore, in comparison to the graphite/NCM811 pouch batteries lacking additive, TPTS enhance the long-cycle capacity retention from 47 % to 80 % after 450 cycles at 45 °C. What's more, TPTS suppresses outgassing and demonstrates enhanced capacity maintenance for the battery even after storage at 60 °C. This work not only demonstrates the stabilizing impacts of TPTS on the electrode-electrolyte interphase and its enhancement of cycling performance at elevated temperatures but also introduces a novel approach for the practical utilization of functional electrolytes matching high-nickel LIBs.

Nonflammable Succinonitrile-Based Deep Eutectic Electrolyte for Intrinsically Safe High-Voltage Sodium-Ion Batteries.

Intrinsically safe sodium-ion batteries are considered as a promising candidate for large-scale energy storage systems. However, the high flammability of conventional electrolytes may pose serious safety threats and even explosions. Herein, a strategy of constructing a deep eutectic electrolyte is proposed to boost the safety and electrochemical performance of succinonitrile (SN)-based electrolyte. The strong hydrogen bond between S═O of 1,3,2-dioxathiolane-2,2-dioxide (DTD) and the α-H of SN endows the enhanced safety and compatibility of SN with Lewis bases. Meanwhile, the DTD participates in the inner Na+ sheath and weakens the coordination number of SN. The unique solvation configuration promotes the formation of robust gradient inorganic-rich electrode-electrolyte interphase, and merits stable cycling of half-cells in a wide temperature range, with a capacity retention of 82.8% after 800 cycles (25°C) and 86.3% after 100 cycles (60°C). Correspondingly, the full cells deliver tremendous improvement in cycling stability and rate performance.

Electrolyte solvent composition regulating endows CoSe2 hollow nanocage anode with stable potassium ion storage

Metal selenides are ideal anode materials for potassium-ion batteries (PIBs) due to their significant merits of favorable conductivity and ion transport property. However, the inevitable volume changes of metal selenides electrode during potassiation/depotassiation processes result in the fracture and reconstruction of the solid electrolyte interphase (SEI) layer, causing capacity decay and significantly limiting their practical applications. Reasonable morphology control accompanied by uniform and rigid SEI layer formation are key factors in improving the electrochemical cycling stability of metal selenides. In this paper, nano-hollow CoSe2 (CoSe2@CNC) anode materials are prepared using ZIF-67 as the precursor. The differences of electrochemical performances for CoSe2@CNC anode material in ester-based and ether-based electrolytes have been investigated in detail. Results demonstrate that the SEI layer formed in the ester-based electrolyte is loose and thick, leading to electrode pulverization and material detachment after several cycles, resulting in rapid degradation of cycle performance. In contrast, a thin and inorganic-rich SEI layer containing more inorganic components is formed in the ether-based electrolyte, effectively protecting the electrode from damage, facilitating electronic transfer at the electrode electrolyte interphase, and optimizing potassium ions storage performance.

Novel sulfur-based electrolyte additive for constructing high-quality sulfur-containing electrode-electrolyte interphase films in sodium-ion batteries

Sodium-ion batteries (SIBs) have been considered as the most promising grid-scale energy storage devices following lithium-ion batteries (LIBs). Similar to LIBs, the electrode–electrolyte interphase significantly impacts the cycling performance of the battery, and the presence of high-quality interphase films can greatly enhance the cycling performance of SIBs. In response to the interphase film challenges for SIBs, the investigation proposes the use of the sulfur-based additive 1,3-propanediol cyclic sulfate (PCS) to construct high-quality interphase films for improving electrochemical performance. Density functional theory (DFT) calculations indicate that PCS can preferentially undergo reduction–oxidation (Redox) reactions in conventional ester-based electrolyte systems, thereby forming sulfur-rich high-quality interphase films. The experimental results show that the capacity retention of NaNi1/3Fe1/3Mn1/3O2 (NFM)||hard carbon (HC) pouch cells increase from 33.94 % to 77.56 % after 300 cycles of long-term cycling at a current density of 0.5 C. Although the addition of PCS slightly reduces the ionic conductivity of the electrolyte (7.70 mS cm−1 vs. 8.09 mS cm−1), it lowers the activation energy (1.09 eV vs. 1.20 eV) and increases the Na+ transfer number (0.721 vs. 0.707) of the electrolyte, thereby improving the rate capability of NFM||HC pouch cells. This study demonstrates the potential application of PCS in SIBs and presents a forward-looking approach for exploring the film formation mechanism of sulfur-based additives.

Fluorinated solvent molecule tuning to improve electrochemical performances of low-concentration electrolyte

The development of low-concentration electrolyte has a favorable application prospect due to its advantages of saving lithium resources. However, the large-scale application is limited by the formation of high-impedance organic electrode/electrolyte interphase (EEI) and the higher desolvation energy of Li+. Herein, a mixed flurorinated solvents of ethyl difluoroacetate (2F) / ethyl trifluoroacetate (3F) (3:7, in volume ratio) is designed to adjust the interaction between Li+ and the solvents, so as to achieve performance improvements of the low-concentration electrolyte system containing 0.5 M LiPF6. Results shows that 2F solvent greatly weakens the interaction between Li+ and the solvents, and 3F solvent further promotes anions to enter the solvation sheath to form Li(2F)3.0(PF6−)2.3(3F)0.5 structure. It promotes the Li+ desolvation, and brings about the formation of a LiF-rich cathode-electrolyte interface film on the surface of LiFePO4 (LFP) cathode due to the HOMO of the 2F solvent in the solvation sheath of Li+ will be increase as the involvement of PF6− in the solvation sheath of Li+. As a result, the cycling stability and rate performance (130 mAh g−1 at 4 C) of the LFP/Li half-cell are significantly improved. This work provides a new strategy to improve the electrochemical performances of low-concentration electrolytes by fluorinated solvent molecule tuning.

Dual-Salt Electrolyte Additive Enables High Moisture Tolerance and Favorable Electric Double Layer for Lithium Metal Battery.

The carbonate electrolyte chemistry is a primary determinant for the development of high-voltage lithium metal batteries (LMBs). Unfortunately, their implementation is greatly plagued by sluggish electrode interfacial dynamics and insufficient electrolyte thermodynamic stability. Herein, lithium trifluoroacetate-lithium nitrate (LiTFA-LiNO3 ) dual-salt additive-reinforced carbonate electrolyte (LTFAN) is proposed for stabilizing high-voltage LMBs. We reveal that 1) the in situ generated inorganic-rich electrode-electrolyte interphase (EEI) enables rapid interfacial dynamics, 2) TFA- preferentially interacts with moisture over PF6 - to strengthen the moisture tolerance of designed electrolyte, and 3) NO3 - is found to be noticeably enriched at the cathode interface on charging, thus constructing Li+ -enriched, solvent-coordinated, thermodynamically favorable electric double layer (EDL). The superior moisture tolerance of LTFAN and the thermodynamically stable EDL constructed at cathode interface play a decisive role in upgrading the compatibility of carbonate electrolyte with high-voltage cathode. The LMBs with LTFAN realize 4.3 V-NCM523/4.4 V-NCM622 superior cycling reversibility and excellent rate capability, which is the leading level of documented records for carbonate electrode.

Dual‐Salt Electrolyte Additive Enables High Moisture Tolerance and Favorable Electric Double Layer for Lithium Metal Battery

AbstractThe carbonate electrolyte chemistry is a primary determinant for the development of high‐voltage lithium metal batteries (LMBs). Unfortunately, their implementation is greatly plagued by sluggish electrode interfacial dynamics and insufficient electrolyte thermodynamic stability. Herein, lithium trifluoroacetate‐lithium nitrate (LiTFA−LiNO3) dual‐salt additive‐reinforced carbonate electrolyte (LTFAN) is proposed for stabilizing high‐voltage LMBs. We reveal that 1) the in situ generated inorganic‐rich electrode‐electrolyte interphase (EEI) enables rapid interfacial dynamics, 2) TFA− preferentially interacts with moisture over PF6− to strengthen the moisture tolerance of designed electrolyte, and 3) NO3− is found to be noticeably enriched at the cathode interface on charging, thus constructing Li+‐enriched, solvent‐coordinated, thermodynamically favorable electric double layer (EDL). The superior moisture tolerance of LTFAN and the thermodynamically stable EDL constructed at cathode interface play a decisive role in upgrading the compatibility of carbonate electrolyte with high‐voltage cathode. The LMBs with LTFAN realize 4.3 V‐NCM523/4.4 V‐NCM622 superior cycling reversibility and excellent rate capability, which is the leading level of documented records for carbonate electrode.

Surface analysis insight note: Accounting for X‐ray beam damage effects in positive electrode‐electrolyte interphase investigations

We investigated the effects of X‐ray beam damage during X‐ray photoelectron spectroscopy measurement on LiNiO2 electrodes. The degree of damage induced by lab‐based and synchrotron X‐ray radiation has been compared between pristine and cycled electrodes, highlighting the role of positive solid electrode–electrolyte interphase to protect the cycled LiNiO2 surface from beam damage. The possible steps to avoid or at least reduce the beam‐induced effects are outlined.

Effect Temperature for improving the Li-ion conductivity of Li7La3Zr2O12

This study investigates the dissociation behavior of water-soluble salts of Li and La and the unique behavior of Zr sources, resulting in the generation of Li+, La3+, and Zr4+ ions in aqueous solutions. The specific conductivity of calcined SG1 and SG2 displays temperature-dependent variations, with SG1 consistently exhibiting higher conductivity (2.08 x 10-4 S/cm) across the temperature range. The closed-packed structure facilitates the controllable mass transfer of lithium, enhancing ionic conductivity. The constructed LiFePO4/LLZO/AC device using these electrolytes demonstrates an impressive energy density of 1.95 Wh/kg and a power density of 144.92 W/kg, showcasing an excellent solid electrode-electrolyte interphase. Over 10,000 cycles, cyclic stability, with an average performance of 86%, underscores the potential of LLZO as a solid electrolyte for advanced energy storage devices. The sol-gel synthesis and densification strategy is a simple and effective method for obtaining lithium-rich LLZO electrolytes. The enhanced ionic conductivity and electrochemical performance of the solid-state device emphasize the practical viability of this approach, contributing to the sustainable development of advanced energy storage technologies.

Additive‐guided Solvation‐regulated Flame‐retardant Electrolyte Enables High‐voltage Lithium Metal Batteries with Robust Electrode Electrolyte Interphases

AbstractWidening the voltage window of the nickel‐rich layered oxide cathode‐based lithium metal batteries (LMBs) can effectively improve the energy density of rechargeable batteries. However, serious safety issues associated with the high reactivity between LiNi0.8Co0.1Mn0.1O2 (NCM811) and electrolyte at high cut‐off voltage remains challenging. Herein, a flame‐retardant electrolyte with the ability to form a robust armor‐like electrode electrolyte interphase (EEI) with LiF and LixByOz compounds for stabilizing Li||NCM811 batteries is proposed. Such electrolyte exhibits the high thermal stability with flame‐retardant effect for ensuring the battery safety at high voltage. The armor‐like EEI can effectively protect both NCM811 and lithium (Li) for improving the battery cycling performance. As a result, the capacity retention rate of the NCM811 cathode with such electrolyte reached 68% after 150 cycles at 4.6 V. This work provides an effective reference for the reasonable design of high‐voltage, flame‐retardant electrolytes for LMBs.

Influence of Formation Temperature on Cycling Stability of Sodium-Ion Cells: A Case Study of Na3V2(PO4)2F3 | HC Cells

Sodium-ion batteries are cheaper and attractive alternatives to lithium-ion batteries, particularly for low energy applications.1 Moreover, the Na+ cation, with its larger ionic radius and lower charge density than Li+, exhibits a weaker interaction within the ionic framework of electrode materials, as well as in solution, resulting in the higher power-rate capability of sodium materials. Hence, sodium-ion batteries based on Na3V2(PO4)2F3 (NVPF) | hard carbon (HC) and Prussian blue analogs (PBA) I HC chemistries are primarily promoted for their high power applications (nearly 80% charging of the cell within 10min). Of particular interest is the NVPF|HC system, due to its high energy density (~120 Wh/kg achieved in 18650 cell level) and high structural stability of NVPF material for long cycling.Our studies, together with others published in recent years, show that the electrode-electrolyte interphase (EEI) formed in the Na-ion cell is not stable as it partly dissolves during rest or discharge periods, and re-forms when recharging the cell.2 This dissolution and reformation cycle can lead to poor cycling stability and an increase in EEI thickness. A thicker EEI results in a higher impedance, which decreases the performance of the cell at high charge/discharge rates. Thus, different strategies have been explored to modify the EEI properties and enhance its stability, mainly focused on the incorporation of SEI-forming additives like vinylene carbonate or fluoroethylene carbonate.3 These additives could eventually stabilize the interphase but with the cost of increasing the interfacial impedance, hence affecting the power rate capability of the Na-ion cells, as mentioned before. Thus, different strategies are needed that allow for the formation of a stable interphase displaying high ionic conductivity (less resistance).Here, we show that it is possible to achieve a stable, ionically conducting interphase modulating the temperature during formation cycles. First, we demonstrated that the nature and chemical composition of the interphase changes as a function of the temperature applied during the formation cycles. The temperature of the cell is expected to play a role in the dissolution or precipitation of different chemical components, which helps us to tune the formation protocol, producing a stable and conducting interphase with or without electrolyte additives. The cells subjected to the optimized formation protocol exhibit low impedance, high power rate capability and long cycling stability. The results presented in this study benefit in great measure the future commercialization of NVPF|HC cells, but also are expected to be of value for other sodium cells based on HC anodes, by providing a framework to optimize the EEI formation and characteristics. References Tarascon, J.-M. Na-ion versus Li-ion Batteries: Complementarity Rather than Competitiveness. Joule 4, 1616–1620 (2020).Ma, L. A., Mogensen, R., Naylor, A. J. & Younesi, R. Solid Electrolyte Interphase in Na-ion batteries. in Na-ion Batteries 243–264 (John Wiley & Sons, Ltd, 2021). doi:10.1002/9781119818069.ch6.Eshetu, G. G. et al. Electrolyte Additives for Room-Temperature, Sodium-Based, Rechargeable Batteries. Chem. – Asian J. 13, 2770–2780 (2018).

(Invited) Strategies for Enhancing the Stability of the Electrode-Electrolyte Interphase in Sulfide-Based Solid-State Batteries

In recent years, all solid-state batteries (SSBs) have gained significant attention as the next-generation energy storage device due to their high energy density, improved safety, and enhanced stability. Sulfide-based solid electrolytes (SEs) have garnered significant attention among various inorganic materials for their exceptional properties, including high ionic conductivity and robust mechanical properties. These features make them promising candidates for SSBs, ensuring both manufacturability and long-term cycle life. For example, Li-argyrodites (e.g., Li6PS5X, and X = Cl, Br, I) and Na-thioantimonate (e.g., Na2.88Sb0.88W0.12S4) offer high ionic conductivities (> 10-3 S/cm) that are comparable to those of liquid electrolytes. However, its practical application is still under-achieved due to a few technical challenges. Among the various issues, our focus is on the electrode-electrolyte interphase, which degrades the cycle life of the SSBs.At the cathode-electrolyte interphase, narrow electrochemical window (1.71 V – 2.01 V) of Li6PS5X unwantedly prompt the oxidative decomposition of solid-electrolyte. At the anode-electrolyte interphase, Li-argyrodite SEs can be easily reduced by Li metal or oxidized by cathode active materials because of its narrow electrochemical window (1.71 V – 2.01 V). The resulting byproducts at electrode-electrolyte interphases can unwantedly lead to capacity fading and an increase in cell resistance. Additionally, SSBs made with the Li-argyrodite SEs suffer from Li-dendrite penetration during repeated cycles and consequent internal short circuits.To address these challenges, we propose strategies for passivating the interphases between the cathode and the solid electrolyte, as well as between the metallic anode and the electrolyte in solid-state batteries (SSBs). Through a combinatorial study, we aim to elucidate the extent and severity of interfacial side reactions in solid-state batteries (SSBs). In addition, the optimal coating strategies of LiNbO3 for cathodes and Li3N coating on metallic Li anode will be discussed. The optimized Li3N as an artificial solid electrolyte interphase (SEI) layer on the metallic Li anode enables more than 5000 cycles without failure in symmetrical cells.Furthermore, we will also highlight a strategy for passivating the electrode-electrolyte interphases of Na-based solid-state batteries (SSBs) that employ thioantimoniate as the electrolyte material. The approaches to passivate the cathode and metallic Na anode will be presented. Comprehensive electrochemical and spectroscopic studies will be conducted to identify the source of degradation and elucidate the improvement mechanisms associated with each strategy.

Anionic Additive-Integrated Electrolyte Therapy: Enhancing High-Voltage Stability and Performance in Lithium-Ion Batteries

Significant endeavours have been undertaken to advance the development of eco-friendly, abundant, cost-effective, and high-performance cathode materials for lithium-ion batteries. Among the various contenders for next-generation energy storage systems, spinel LiNi0.5Mn1.5O4 has emerged as a leading high-voltage cathode candidate, owing to its aforementioned benefits. Nonetheless, the widespread adoption of LNMO-based lithium-ion batteries is substantially impeded by the electrochemical instability of conventional carbonate electrolytes above 4.5 V. High-voltage cycling of such batteries results in rapid capacity degradation and metal-ion dissolution from the LNMO electrode into the electrolyte, particularly at elevated temperatures, further causing deposition of metal-ions on anode electrode. Therefore, stabilizing the electrode/electrolyte interface is crucial to achieve improved electrochemical performance of the Li-ion cell at high voltages. The utilization of sacrificial electrolyte additives is regarded as a straightforward and efficacious method to accomplish this objective. These additives form a protective layer on the cathode surface, mitigating electrolyte decomposition and transition metal-ion dissolution and deposition on anode’s surface. Various additives facilitating high-voltage cathode materials have been documented, encompassing fluorides and sulfonates. However, borate salt-containing additives are particularly promising within this context.In the present study, we endeavour to elucidate the surface modifications transpiring on the electrode’s surface when minute quantities of borate-based salt are employed as an additive in the conventional EC:EMC electrolyte for high-voltage operation. We explored the impact of the additive salt in a standard LiPF6-EC/EMC base electrolyte on the discharge capacity and rate performance of the LiNi0.5Mn1.5O4/Graphite based Li-ion cell. The electrochemical behaviour, morphological behaviour, and electrode-electrolyte interphase layer stability on the electrode were meticulously examined using high-resolution transmission electron microscopy (HR-TEM), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These characterisations conformed the presence of an electrode-electrolyte interface forming a thin-layer via the sacrificial decomposition of the utilised additive. The introduction of this salt exhibits favourable effects on enhancing the electrochemical performance of the LiNi0.5Mn1.5O4/Graphite in high-voltage lithium-ion batteries. Notably, the utilised additive excels in mitigating irreversible capacity loss and reducing cycling fade, as it preferentially decomposes and forms a conductive, protective film that impedes subsequent electrolyte decomposition, thereby substantially enhancing cell performance.

Tuning Dopant Distribution for Stabilizing the Surface of High‐Nickel Layered Oxide Cathodes for Lithium‐Ion Batteries

AbstractLayered oxide cathodes with a high‐nickel (Ni ≥ 0.9) content exhibit great potential for enabling high‐energy‐density lithium‐ion batteries. However, their practical feasibility and cycle life are hampered by severe surface reactivity with the electrolyte. A LiNi0.90Co0.05Al0.05O2 cathode is presented enriched with Al on the surface (S‐NCA) and benchmark it against a LiNi0.90Co0.05Al0.05O2 cathode obtained by a conventional co‐precipitation method that has a uniform Al distribution throughout the bulk (B‐NCA). The S‐NCA cathode greatly outperform with an impressive capacity retention of 84% after 1000 cycles in pouch full cells with graphite anode compared to 62% retention for B‐NCA. Advanced surface characterization methodologies, including time‐of‐flight secondary‐ion mass spectrometry, reveal that the Al‐enriched surface morphology facilitates the formation of a robust, thin electrode‐electrolyte interphase (EEI), effectively suppressing the oxidative decomposition of the electrolyte, gas generation, and metallic dead lithium formation on graphite anode. The results illustrate that surface reactivity with the electrolyte is the primary factor limiting the cycle of cells with high‐Ni cathodes. The work provides valuable insights toward the practical viability of ultrahigh‐Ni cathodes in lithium‐ion batteries.

High Chaos Induced Multiple-Anion-Rich Solvation Structure Enabling Ultrahigh Voltage and Wide Temperature Lithium-Metal Batteries.

The optimal electrolyte for ultrahigh energy density (>400 Wh/kg) lithium-metal batteries with a LiNi0.8Co0.1Mn0.1O2 cathode is required to withstand high voltage (≥4.7 V) and be adaptable over a wide temperature range. However, the battery performance is degraded by aggressive electrode-electrolyte reactions at high temperature and high voltage, while excessive growth of lithium dendrites usually occurs due to poor kinetics at low temperature. Accordingly, the development of electrolytes has encountered challenges in that there is almost no electrolyte simultaneously meeting the above requirements. Herein, a high chaos electrolyte design strategy is proposed, which promotes the formation of weak solvation structures involving multiple anions. By tailoring a Li+-EMC-DMC-DFOB--PO2F2--PF6- multiple-anion-rich solvation sheath, a robust inorganic-rich interphase is obtained for the electrode-electrolyte interphase (EEI), which is resistant to the intense interfacial reactions at high voltage (4.7 V) and high temperature (45 °C). In addition, the Li+ solvation is weakened by the multiple-anion solvation structure, which is a benefit to Li+ desolventization at low temperature (-30 °C), greatly improving the charge transfer kinetics and inhibiting the lithium dendrite growth. This work provides an innovative strategy to manipulate the high chaos electrolyte to further optimize solvation chemistry for high voltage and wide temperature applications.

Modification of Al Surface via Acidic Treatment and its Impact on Plating and Stripping.

Amorphous Al2 O3 film that naturally exists on any Al substrate is a critical bottleneck for the cyclic performance of metallic Al in rechargeable Al batteries. The so-called electron/ion insulator Al oxide slows down the anode's activation and hinders Al plating/stripping. The Al2 O3 film induces different surface properties (roughness and microstructure) on the metal. Al foils present two optically different sides (shiny and non-shiny), but their surface properties and influence on plating and stripping have not been studied so far. Compared to the shiny side, the non-shiny one has a higher (~28 %) surface roughness, and its greater concentration of active sites (for Al plating and stripping) yields higher current densities. Immersion pretreatments in Ionic-Liquid/AlCl3 -based electrolyte with various durations modify the surface properties of each side, forming an electrode-electrolyte interphase layer rich in Al, Cl, and N. The created interphase layer provides more tunneling paths for better Al diffusion upon plating and stripping. After 500 cycles, dendritic Al deposition, generated active sites, and the continuous removal of the Al metal and oxide cause accelerated local corrosion and electrode pulverization. We highlight the mechanical surface properties of cycled Al foil, considering the role of immersion pretreatment and the differences between the two sides.

Differing Electrolyte Implication on Anion and Cation Intercalation into Graphite.

Emerging dual-graphite batteries (DGBs) capture extensive interest for their high output voltage and exceptional cost-effectiveness. Yet, developing electrolytes compatible with both the cathode and anode stands to be a tremendous challenge, and how electrolyte impacts anion and cation intercalation into graphite remains inexplicit or controversial. Herein, we have evaluated the performance of graphite anode and cathode in typical ethyl methyl carbonate (EMC) based electrolytes and unveiled their electrode-electrolyte interphase using Cryogenic transmission electron microscopy (Cryo-TEM). The addition of fluoroethylene carbonate (FEC) brings substantial improvement in cycle stability and Coulombic efficiency for both the graphite cathode and anode, but its implication on cation and anion intercalation differs. FEC is involved in anodic side reactions to produce a LiF-embedded solid-electrolyte interphase layer. It is much thinner and more uniform than that formed in the electrolyte without FEC, which is correlated with less graphite exfoliation and enhanced stability. As for the graphite cathode, both basal and edge planes are largely bare, and only few scattered byproducts are found. In addition, we also reveal layer bending and local lattice disordering of the graphite cathode based on multiple Cryo-TEM images, which are speculated to be caused by high lattice strain induced by anion intercalation and local oxidation under high voltage. The absence of cathode-electrolyte interphase (CEI) layers overturns the paradigm of attributing cathodic performance to CEI features and is regarded as a fundamental reason for severe self-discharge of graphite cathode. FEC helps to alleviate graphite exfoliation issues and enhance cycle stability, and we ascribe it to weakened solvation, which means reduced probability of solvent co-intercalation during charging, rather than compositional changes of cathodic byproducts.

Solid Electrolyte Interface Film-Forming and Surface-Stabilizing Bifunctional 1,2-Bis((trimethylsilyl)oxy) Benzene as Novel Electrolyte Additive for Silicon-Based Lithium-Ion Batteries.

The application of Si-based anodes in lithium-ion batteries (LIBs) has garnered significant attention due to their high theoretical specific capacity yet is still challenged by the substantial volume expansion of silicon particles during the lithiation process, resulting in the instability of the electrode-electrolyte interphase and deteriorative battery performance. Herein, an ortho(trimethylsilyl)oxybenzene electrolyte additive, 1,2-bis((trimethylsilyl)oxy) benzene (referred to as BTMSB), has been investigated as a bifunctional electrolyte additive for Si-based LIBs. The BTMSB can form a uniform and robust LiF-rich solid electrolyte interphase (SEI) on the surface of Si-based material particles, adapting the huge volume expansion of the Si-based electrode and facilitating lithium-ion transport. Additionally, the BTMSB demonstrates the ability to scavenge hydrofluoric acid (HF) to stabilize the electrode-electrolyte interphase. The SiOx/C∥Li batteries with 2% BTMSB exhibit improved cycle performance and current-rate capabilities, of which the capacity retention retains 69% after 400 cycles. Furthermore, Si-based anode cells with higher theoretical specific capacities (1C = 550 mAh g-1) and NCM523∥SiOx/C pouch cells are constructed and evaluated, displaying superior cycle performance. This work provides valuable insights for the development of effective electrolyte additives and the commercialization of high energy density LIBs with Si-based anodes.

Ultrahigh-Speed Aqueous Copper Electrodes Stabilized by Phosphorylated Interphase.

High-energy metal anodes for large-scale reversible batteries with inexpensive and nonflammable aqueous electrolytes promise the capability of supporting higher current density, satisfactory lifetime, nontoxicity, and low-cost commercial manufacturing, yet remain out of reach due to the lack of reliable electrode-electrolyte interphase engineering. Herein, in situ formed robust interphase on copper metal electrodes (CMEs) induced by a trace amount of potassium dihydrogen phosphate (0.05m in 1m CuSO4 -H2 O electrolyte) to fulfill all aforementioned requirements is demonstrated. Impressively, an unprecedented ultrahigh-speed copper plating/stripping capability is achieved at 100mA cm-2 for over 12000 cycles, corresponding to an accumulative areal capacity up to tens of times higher than previously reported CMEs. The use of solid-electrolyte interface-protection strategy brings at least an order of magnitude improvement in cycling stability for symmetric cells (Cu||Cu, 2800h) and full batteries with CMEs using either sulfur cathodes (S||Cu, 1000 cycles without capacity decay) or zinc anodes (Cu||Zn with all-metal electrodes, discharge voltage ≈1.02V). The comprehensive analysis reveals that the hydrophilic phosphate-rich interphase nanostructures homogenize copper-ion deposition and suppress nucleation overpotential, enabling dendrite-free CMEs with sustainability and ability to tolerate unusual-high power densities. The findings represent anelegantforerunnertoward the promising goal of metal electrode applications.