Dissolution Of Transition Metal Ions Research Articles

Interface Engineering via Manipulating Solvation Chemistry for Liquid Lithium-Ion Batteries Operated≥100 °C.

High-performance and temperature-resistant lithium-ion batteries (LIBs), which are able to operate at elevated temperatures (i.e., >60 °C) are highly demanded in various fields, especially in military or aerospace exploration. However, their applications were largely impeded by the poor electrochemical performance and unsatisfying safety issues, which were induced by the severe side reactions between electrolytes and electrodes at high temperatures. Herein, with the synergetic effects of solvation chemistry and functional additive in the elaborately designed weakly solvating electrolyte, a unique robust organic/inorganic hetero-interphase, composed of gradient F, B-rich inorganic components and homogeneously distributed Si-rich organic components, was successfully constructed on both cathodes and anodes, which would effectively inhibit the constant decomposition of electrolytes and dissolution of transition metal ions, thus highly enhancing the high-temperature electrochemical performance. As a result, both cathodes and anodes, without compromising their low-temperature performance, can operate at temperatures ≥100 °C, with excellent capacity retentions of 96.1 % after 500 cycles and 93.5 % after ≥200 cycles, respectively, at 80 °C. Ah-level LiCoO2||graphite full cells with a cut-off voltage of 4.3 V also exhibited superior temperature-resistance with a capacity retention of 89.9 % at temperature as high as 120 °C. Moreover, the fully charged pouch cells exhibited highly enhanced safety, demonstrating their potentials in practical applications at ultrahigh temperatures.

Failure analysis of ternary lithium-ion batteries throughout the entire life cycling at high temperature

The operation life is a key factor affecting the cost and application of lithium-ion batteries. This article investigates the changes in discharge capacity, median voltage, and full charge DC internal resistance of the 25Ah ternary (LiNi0.5Mn0.3Co0.2O2/graphite) lithium-ion battery during full life cycles at 45 °C and 2000 cycles at 25 °C for comparison. The batteries before and after cycling were disassembled, and the structure, morphology, interface characteristics, element content of the cathode and anode plates of the battery were characterized. By analyzing the failure factors of the performance of the ternary batteries during the 45 °C cycling, a reaction mechanism for the rapid decline of high-temperature cycling performance of ternary batteries has been proposed. The results show that the performance degradation of the ternary lithium-ion batteries in the whole life operated at high temperature is characterized by slow decline in the initial stage and rapid drop in the latter stage. Further analysis of physical and chemical performance revealed irreversible damage to both the cathode and anode. The dissolution of transition metal ions from the cathode and their deposition on the anode surface catalyze the decomposition of electrolyte solvents to produce a large amount of gas. Gassing, accompanied by the deposition of Li2CO3 and the thickening of SEI, leads to an increase in the internal resistance of the battery. The coupling between gassing and increased internal resistance is responsible for the rapid drop in the performance of the ternary batteries during high-temperature cycling.

Achievable dual-strategy to stabilize Li-rich layered oxide interface by a one-step wet chemical reaction towards long oxygen redox reversibility

Oxygen release and electrolyte decomposition under high voltage endlessly exacerbate interfacial ramifications and structural degradation of high energy-density Li-rich layered oxide (LLO), leading to voltage and capacity fading. Herein, the dual-strategy of CrxB complex coating and local gradient doping is simultaneously achieved on LLO surface by a one-step wet chemical reaction at room temperature. Density functional theory (DFT) calculations prove that stable B–O and Cr–O bonds through the local gradient doping can significantly reduce the high-energy O 2p states of interfacial lattice O, which is also effective for the near-surface lattice O, thus greatly stabilizing the LLO surface. Besides, differential electrochemical mass spectrometry (DEMS) indicates that the CrxB complex coating can adequately inhibit oxygen release and prevents the migration or dissolution of transition metal ions, including allowing speedy Li+ migration. The voltage and capacity fading of the modified cathode (LLO-CrB) are adequately suppressed, which are benefited from the uniformly dense cathode electrolyte interface (CEI) composed of balanced organic/inorganic composition. Therefore, the specific capacity of LLO-CrB after 200 cycles at 1C is 209.3 mA h g–1 (with a retention rate of 95.1%). This dual-strategy through a one-step wet chemical reaction is expected to be applied in the design and development of other anionic redox cathode materials.

Rational design of FeF2‐based cathode to realize high‐performance potassium storage

AbstractThe poor electronic conductivity of conversion‐type materials (CMs) and the dissolution/diffusion loss of transition metal (TM) ions in electrodes seriously hinder the practical applications of potassium ion batteries. Simply optimizing the electrode materials or designing the electrode components is no longer effective in improving the performance of CMs. Binders, as one of the electrode components, play a vital role in improving the electrochemical performance of batteries. Here we rationally designed FeF2 electrodes for the first time by optimizing electrode materials with the introduction of carbon nanotubes (CNTs) and combined with a sodium alginate (SA) binder based on strong interactions. We show that the FeF2@CNTs‐SA cathode does not suffer from TM ion dissolution and delivers a high capacity of 184.7 mAh g−1 at 10 mA g−1. Moreover, the capacity of FeF2@CNTs‐SA is as high as 99.2 mAh g−1 after 100 cycles at 100 mA g−1, which is a twofold increase compared to FeF2@CNTs‐PVDF. After calculating the average capacity decay rate per cycle of them, we find that FeF2@CNTs‐SA is about one‐third lower than FeF2@CNTs‐PVDF. Therefore, the SA binder can be broadly used for electrodes comprising several CMs, providing meaningful insights into mechanisms that lead to their improved electrochemical performances.

Revealing the degradation pathways of layered Li-rich oxide cathodes.

Layered lithium-rich transition metal oxides are promising cathode candidates for high-energy-density lithium batteries due to the redox contributions from transition metal cations and oxygen anions. However, their practical application is hindered by gradual capacity fading and voltage decay. Although oxygen loss and phase transformation are recognized as primary factors, the structural deterioration, chemical rearrangement, kinetic and thermodynamic effects remain unclear. Here we integrate analysis of morphological, structural and oxidation state evolution from individual atoms to secondary particles. By performing nanoscale to microscale characterizations, distinct structural change pathways associated with intraparticle heterogeneous reactions are identified. The high level of oxygen defects formed throughout the particle by slow electrochemical activation triggers progressive phase transformation and the formation of nanovoids. Ultrafast lithium (de)intercalation leads to oxygen-distortion-dominated lattice displacement, transition metal ion dissolution and lithium site variation. These inhomogeneous and irreversible structural changes are responsible for the low initial Coulombic efficiency, and ongoing particle cracking and expansion in the subsequent cycles.

Interface Engineering via Manipulating Solvation Chemistry for Liquid Lithium‐Ion Batteries Operated≥100 °C

AbstractHigh‐performance and temperature‐resistant lithium‐ion batteries (LIBs), which are able to operate at elevated temperatures (i.e., >60 °C) are highly demanded in various fields, especially in military or aerospace exploration. However, their applications were largely impeded by the poor electrochemical performance and unsatisfying safety issues, which were induced by the severe side reactions between electrolytes and electrodes at high temperatures. Herein, with the synergetic effects of solvation chemistry and functional additive in the elaborately designed weakly solvating electrolyte, a unique robust organic/inorganic hetero‐interphase, composed of gradient F, B‐rich inorganic components and homogeneously distributed Si‐rich organic components, was successfully constructed on both cathodes and anodes, which would effectively inhibit the constant decomposition of electrolytes and dissolution of transition metal ions, thus highly enhancing the high‐temperature electrochemical performance. As a result, both cathodes and anodes, without compromising their low‐temperature performance, can operate at temperatures ≥100 °C, with excellent capacity retentions of 96.1 % after 500 cycles and 93.5 % after ≥200 cycles, respectively, at 80 °C. Ah‐level LiCoO2||graphite full cells with a cut‐off voltage of 4.3 V also exhibited superior temperature‐resistance with a capacity retention of 89.9 % at temperature as high as 120 °C. Moreover, the fully charged pouch cells exhibited highly enhanced safety, demonstrating their potentials in practical applications at ultrahigh temperatures.

Mechanisms of Ni Dissolution from Ni-Rich Cathode in Li-Ion Batteries

Nickel-rich cathodes are the most promising candidates for realizing high-energy-density Li-ion batteries because of the high theoretical capacity. However, their structural instability detrimentally affects the battery performance during cell cycling, which restricts its large-scale commercial application. One impediment to their commercialization is the dissolution of transition metal ions, which can diffuse to the anode, corrupt the solid electrolyte interphase (SEI) films protecting the anode, and accelerate battery capacity fading. Here, we use ab initio molecular dynamics (AIMD) simulations to investigate the mechanism of Ni dissolution from the LiNiO2 cathode surfaces. Our calculations identified that the proton-transfer reactions between electrolytes and cathode surfaces cause the reduction of surface Ni atoms from Ni3+ to Ni2+, which weakened the Ni-O bonding. As the LiNiO2 cathode surface gets delithiated, more surface protonation reactions were observed, and the reduced Ni atoms were found to be dissolved from the cathode surfaces in the form of NiOOH, which is the fundamental origin of phase transition of LiNiO2 cathode from a layered to electrochemically inactive spinel-like structure, accompanied by H2O elimination and O2 evolution. Besides, we also studied the impact of various factors on Ni dissolution rates such as the presence of fluorine attachment and the coordination of Ni atoms and electrolyte species. These findings help inform future design of protective coatings, electrolytes, additives, and interfaces for Ni-rich cathode.

Study on the interface of high specific energy High stability

High nickel terterial oxide, with high specific capacity and low cost advantages, is the preferred positive electrode for high specific energy lithium-ion power batteries at present. However, the high nickel ternary cathode material is easy to have side reactions with the electrolyte in the high delithium state, which can not only lead to the dissolution of transition metal ions and the formation of the surface salt phase, but also cause the lattice oxygen loss and surface interface side reactions, resulting in rapid attenuation of electrode capacity. In this paper, the development history and structural characteristics of high nickel ternary cathode materials are introduced, and the surface interface problems leading to capacity attenuation and structural degradation are comprehensively analyzed. From this perspective, three effective strategies for improving electrochemical performance of high nickel ternary cathode materials are summarized. Finally, by describing the advantages and disadvantages of these layered cathode materials, the challenges faced by these layered cathode materials are discussed, and it is pointed out that in the future, composite modification strategies should be adopted to optimize their structures and improve their properties.

Tris(pentafluoro)phenylborane electrolyte additive regulates the highly stable and uniform CEI membrane components to improve the high-voltage behaviors of NCM811 lithium-ion batteries

Broadening the charging and discharging voltage window of high nickel cathode material NCM811 is the most expected method to improve the high specific energy density of batteries currently, yet the cathode-electrolyte interface (CEI) formed by the oxidized and decomposed products of carbonate-based electrolyte under high voltage are always so unsatisfied. Therefore, a voltage-stabilizer, TPFPB (Tris(pentafluoro)phenylborane), added into baseline electrolyte (1 M LiPF6 in EC:EMC:DMC=1:1:1 vol%) to promote the electrochemical performance of the battery at 4.5 V. The results interpret that the TPFPB-contained NCM811-Li half-cells exhibit high specific capacity (167.10 mAh/g), excellent capacity retention rate (CRR) (75.37 %), and high rate performance (173.3 mAh/g at 5C) during 4.5 V. Meanwhile, through the analysis of the physical characterization techniques. the B- and F-rich interfacial layer, named as CEI film, existing at the interface between the cathode and the electrolyte, produced under 4.5 V, is superior, resulting in impeding the structural collapse of the cathode material and the continued dissolution of transition metal ions (TMn+) from the cathode material, as well as, ameliorate the electrochemical polarization of the battery, ultimately, it can stabilize the electrochemical performance of the battery under high voltage. Therein, the present work elucidate a new and substantial approach to enhance the high-voltage performances of rich-Ni cathode materials.

High-entropy selenides derived from Prussian blue analogues as electrode materials for sodium-ion batteries

Transition metal selenides (TMS) have received much attention as anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacity and excellent redox reversibility. However, their further development is constrained by the dissolution of transition metal ions and substantial volume changes experienced during cycling. Herein, the high-entropy Prussian blue analogues were selenized by the vapor infiltration method, resulting in the formation of a core–shell structured high-entropy selenides (HESe-6). The core–shell structure with voids and abundant selenium vacancies on the surface effectively mitigates bulk expansion and enhances electronic conductivity. Furthermore, the high-entropy property endows an ultra-stable crystal structure and inhibits the dissolution of metal ions. The ex-situ EIS and in-situ XRD results show that HESe-6 is able to be reversibly transformed into highly conductive ultrafine metal particles upon Na+ embedding, providing more Na+ reactive active sites. In addition, despite the incorporation of up to seven different elements, it exhibits minimal phase transitions during discharge/charge cycles, effectively mitigating stress accumulation. HESe-6 could retain an ultralong-term stability of 765.83 mAh g−1 after 1000 loops even at 1 A g−1. Furthermore, when coupled with the Na3V2(PO4)2O2F cathode, it maintains a satisfactory charge energy density of 303 Wh kg−1 after 300 cycles, which shows promising application prospect in the future.

Effect of lithium-containing inorganic phosphate additives in stabilization of carbonate-based electrolyte for 5 V LiNi0.5Mn1.5O4-based lithium-ion batteries

High-voltage lithium-ion batteries (LIBs) with LiNi0.5Mn1.5O4 (LNMO) cathode are considered promising energy sources due to their high energy density. However, enhancing the stability of the electrode/electrolyte interface remains critical for the practical application of LIBs. In this work, lithium-containing inorganic phosphates (LiPO3, Li3PO4, and LiH2PO4) were used as multifunctional inorganic additives to improve the stability of the electrode/electrolyte interface in 5.0 V, LNMO-based LIBs with carbonate-based electrolytes. Based on theoretical calculations and experimental evaluations of the electrochemical performance, LiPO3 was selected as the optimal additive for further study in LNMO/Li and LNMO/Li4Ti5O12 cells. The LNMO/Li half-cells with LiPO3 delivered an initial discharge capacity of 108.8 mAh∙g−1 and retained a capacity of 94.9 % after 500 cycles at 5C, compared to 75.1 mAh∙g−1 and 79.4 % for the standard electrolyte. The increased cycling stability was ascribed to the ability of the multifunctional, film-forming LiPO3 additive to form stable interfacial films on both the cathode and anode, thus, inhibiting side reactions between the electrodes and electrolyte. Moreover, as an HF scavenger, LiPO3 reduced the HF content in the electrolyte to ensure the structural integrity of LNMO and inhibit the dissolution of transition metal ions. In the LNMO/Li4Ti5O12 full cells, the addition of LiPO3 effectively enhanced the cycling performance, and the capacity retention after 400 cycles at 5C was 79.1 %, compared to only 12.3 % for the standard electrolyte. Considering its simplicity, low cost, and feasibility, the addition of LiPO3 as a multifunctional electrolyte additive showed excellent prospects for commercial applications.

Boosting interface compatibility of high-voltage LiNi0.5Mn1.5O4 cathode materials with an ionic-conductive Li0.33La0.56TiO3 coating

High voltage LiNi0.5Mn1.5O4 (LNMO) is a crucial cathode material for lithium-ion batteries (LIBs) aiming at high energy densities. However, its performance is hindered by the dissolution of transition metal ions and the instability of the cathode electrolyte interface (CEI) film at elevated voltages. To address these issues, we report a solvothermal method to prepare LNMO coated with Li+-conductor Li0.33La0.56TiO3 (LNMO@LLTO). Our study reveals that the LLTO coating not only enhances ion diffusion at the interface, minimizing the Li+ concentration gradient, and acts as a barrier against Mn-ion dissolution. This coating minimizes side reactions, mitigates structural degradation, and promotes the formation of a stable and balanced CEI film that incorporates LLTO, thus ensuring the long-term cycle stability. When compared to bulk LNMO, the LNMO@LLTO cathode demonstrates superior performance, maintaining reversible capacities of 111.4 and 102.2 mAh·g−1 after 500 cycles at 2 and 5C at 25 °C, respectively. Even at 60 °C, the LNMO@LLTO maintains a high capacity of 94.3 mAh·g−1 with minimal electrochemical polarization after 200 cycles at 2C. This simple preparation technique, together with its performance promotion, offers new insights into the development of high voltage cathode materials for high energy density LIBs.

Molecular design of highly Li-ion conductive cathode-electrolyte interface enabling excellent rate performance for lithium-ion batteries

The structural stability and ionic conductivity of the cathode electrolyte interface (CEI) film at high voltages are crucial to the nickel-rich layered cathode in Li-ion batteries (LIBs). These characteristics are largely determined by electrolyte components. Herein, an air-stable organic cyclophosphate salt named lithium 1, 3, 2-dioxaphosphinan-2-olate-2-oxide (LiDOP) is designed and synthesized as a CEI forming additive. It preferentially oxidizes and undergoes opening-ring polymerization under charging to form an organic–inorganic hybrid polymers with –LiPO4 segments and –(CH2)3– alternately connected on the cathode surface. Such a structure endows CEI film with high ionic conductivity, flexibility and mechanical strength, which can ameliorate the structure phase transformation, suppress the transition metal ion dissolution and enhance the interfacial stability at high cut-off voltage. The electrolyte with 0.2 wt% LiDOP endows 4.3 V-charged Li||LiNi0.8Co0.1Mn0.1O2 battery with 83.2 % capacity retention after 200 cycles at 5C rate. The graphite||NCM811 pouch cell shows a capacity retention of 85.6 % after 150 cycles under a 4.5 V voltage, while the cell without LiDOP shows only 23.5 %. Our work demonstrates the effectiveness of covalently coupled P-O-Li compounds as CEI film in stabilizing the interface, which provides a guidance for the electrolyte design in high-voltage LIBs.

High-performance lithium batteries achieved by electrospun MXene-Enhanced cation-selective membranes

Conventional separators applied in lithium batteries face limitations like low porosity, poor electrolyte wettability, lower cation selectivity, and thermal instability, which impact battery performance and safety characteristics. Besides the challenge in separator design, transition metal ion migration from positive electrodes during cycling greatly accelerates capacity fading because of unrestricted diffusion of transition metal cation across the separator. This study explores an innovative strategy for the separator design by incorporating MXene (spraying MXene solution on both sides of the separator), a two-dimensional material, into electrospun Polyacrylonitrile/Polyetherimide membranes with the function of cation selection. Li+ can be accelerated, and its transference number increases along with the anion limitation in the MXene layer. Ni, Co, and Mn ion dissolution from the positive electrode is inhibited due to the cation selectivity of the MXene layer. Leveraging electrospinning advantages, the resultant membranes exhibit high porosity, excellent liquid absorption, mechanical strength, and superior thermal properties. Benefiting from MXene's layered structure and excellent adsorption ability, the membrane significantly inhibits the dissolution of transition metal ions while enabling smooth lithium deposition due to its cation selectivity. Eventually, the Li||NMC811 batteries deliver outstanding cyclic performance (91.3 % capacity retention after 200 cycles) and robust lithium dendrite suppression (800 h of stable cycling). Moreover, the MXene-modified membrane demonstrates exceptional electrolyte wettability, significantly improving ionic transference number (0.67) and conductivity (1.6 mS/cm). Modification of membrane surfaces with MXene offers insights into addressing transition metal ion migration from the positive electrode material perspective, providing a promising avenue for high-performance LIBs.

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.

Quenching-Induced Ultrathin LiF-Rich Interphases on LiNi0.8Co0.1Mn0.1O2 Cathode

Nickel-rich layered oxides (NCM) are a promising contender material for the cathode electrode of high-energy lithium-ion batteries (LIBs) due to their large reversible capacity and high operating voltage. However, the poor surface/interfacial stability and the dissolution of transition metal ions hinder the commercial application of NCM. To create an artificial cathode electrolyte interphase (CEI) with LiF-rich inorganic phase on the NCM surface, a practical and efficient way of quenching the NCM powder from high temperature in 1,1,2,2-Tetrafluoroethyl 2,2,2-trifluoroethyl ether (HFE) was devised. With this artificial CEI film, the side reactions between NCM and electrolytes are inhibited, and the dissolution of TM ions is retarded. The quenched-NCM achieved fantastic cycling performance and suppressed voltage decay. Our research offers an efficient and worthy approach for improving the surface/interfacial stabilization of nickel-rich cathode materials for high-energy-density LIBs.

Sodium Difluoro(oxalato)borate Additive‐Induced Robust SEI and CEI Layers Enable Dendrite‐Free and Long‐Cycling Sodium‐Ion Batteries

AbstractSodium‐ion batteries (SIBs) are a promising candidate for large‐scale energy storage due to the low cost and abundant sodium resources. However, the formation of sodium dendrites on the surface of hard carbon (HC) anodes is the most intractable challenge for full cells during charging, leading to severe performance degradation and safety hazards. Here, a robust additive‐induced borate and fluoride‐rich interphase is constructed by introducing sodium difluoro(oxalato)borate (NaDFOB) as additive in the ether‐based electrolyte to relieve the performance deterioration for SIBs. NaDFOB can participate in the passivation process of electrolyte‐electrode interfaces through preferential oxidation and reduction of DFOB− to effectively restrain the growth of sodium dendrites. Moreover, the electrolyte decomposition and dissolution of transition metal ions are effectively inhibited. Benefiting from that, FeMn‐based Prussian blue (FeMnHCF) || HC full cell with a negative/positive capacity ratio (N/P ratio) of 1.09 displays a capacity retention of 82.1%, especially with a low N/P ratio of 0.96 the cell still demonstrates a stable Coulombic efficiency of over 99.9% after 500 cycles via using NaDFOB as additive. As a practical demonstration, the designed 18650 full cells display enhanced cycling stability with NaDFOB additive. The findings provide insights into the additive‐induced inorganic‐rich interfacial layers for dendrite‐free SIBs.

Unlocking Electrode Performance of Disordered Rocksalt Oxides Through Structural Defect Engineering and Surface Stabilization with Concentrated Electrolyte

Abstract Li‐excess cation‐disordered rocksalt oxides can boost the energy density of rechargeable batteries by using anionic redox, but the inferior reversibility of anionic redox hinders its use for practical applications. Herein, a binary system of Li3NbO4–LiMnO2 is targeted and the systematic study on factors affecting electrode reversibility, i.e., percolation probability, electronic conductivity, defect concentrations, and electrolyte solutions, is conducted. A Mn‐rich sample, Li1.1Nb0.1Mn0.8O2, delivers a smaller reversible capacity compared with a Li‐rich sample, Li1.3Nb0.3Mn0.4O2, because of the limitation of ionic migration associated with insufficient percolation probability for disordered oxides. Nevertheless, a larger reversible capacity of Li1.3Nb0.3Mn0.4O2 originates from excessive activation of anionic redox, leading to the degradation of electrode reversibility. The superior performance of Li1.1Nb0.1Mn0.8O2, including Li ion migration kinetics and electronic transport properties, is unlocked by the enrichment of structural defects for nanosized oxides. Moreover, electrode reversibility is further improved by using a highly concentrated electrolyte solution with LiN(SO2F)2 through the surface stabilization on high‐voltage exposure. Superior capacity retention, >100 cycles, is achieved for nanosized Li1.1Nb0.1Mn0.8O2. The electrolyte decomposition and surface stabilization mechanisms are also carefully examined, and it is revealed that the use of highly concentrated electrolyte solution can effectively prevent lattice oxygen being further oxidized and transition metal ion dissolution.

Dual LiF/LiCl‐Rich Solid Electrolyte Interphases with Robust and Li+‐conductive Characteristics for 4.8 V Lithium Metal Batteries

AbstractLithium metal batteries, which are constructed by lithium‐rich manganese‐based oxide (LRMO) cathode and Li metal anode, have attracted intensive attention due to its high energy density. However, the instability of both cathode and anode limits the practical application due to undesirable electrolyte decomposition at high voltage. To address these issues, an electrolyte engineering strategy is proposed for constructing robust, highly Li+‐conductive solid electrolyte interphases on both cathode and anode with chlorobenzene as the additive. Due to the high mechanical stability and interface dynamics of the LiCl‐endorsed, LiF‐rich cathode electrolyte interphase, both the electrolyte decomposition and transition metal ion dissolution are effectively inhibited. Meanwhile, robust LiF/LiCl‐rich solid electrolyte interphase can effectively repress the overgrowth of Li dendrites. The Li||LRMO battery with optimized 2.0 wt.% chlorobenzene demonstrates a high‐capacity retention of 86.1% after 200 cycles at 0.5 C.

Advanced TiO2/Al2O3 Bilayer ALD Coatings for Improved Lithium-Rich Layered Oxide Electrodes.

Surface modification is a highly effective strategy for addressing issues in lithium-rich layered oxide (LLO) cathodes, including phase transformation, particle cracking, oxygen gas release, and transition-metal ion dissolution. Existing single-/double-layer coating strategies face drawbacks such as poor component contact and complexity. Herein, we present the results of a low-temperature atomic layer deposition (ALD) process for creating a TiO2/Al2O3 bilayer on composite cathodes made of AS200 (Li1.08Ni0.34Co0.08Mn0.5O2). Electrochemical analysis demonstrates that TiO2/Al2O3-coated LLO electrodes exhibit improved discharge capacities and enhanced capacity retention compared with uncoated samples. The TAA-5/AS200 bilayer-coated electrode, in particular, demonstrates exceptional capacity retention (∼90.4%) and a specific discharge capacity of 146 mAh g-1 after 100 cycles at 1C within the voltage range of 2.2 to 4.6 V. The coated electrodes also show reduced voltage decay, lower surface film resistance, and improved interfacial charge transfer resistances, contributing to enhanced stability. The ALD-deposited TiO2/Al2O3 bilayer coatings exhibit promising potential for advancing the electrochemical performance of lithium-rich layered oxide cathodes in lithium-ion batteries.