Large Irreversible Capacity Loss Research Articles

Prelithiated Silicon Anodes for High-Energy and High-Power Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are pivotal in powering modern electronic devices and next-generation land and air electric vehicles. Silicon-based anodes are considered the next technology to replace traditional graphite anodes due to their high theoretical capacity. However, the inherent challenges associated with their large volume expansion and high irreversible capacity loss (IRCL) limit their practical application. This abstract explores our patented strategy of prelithiation as a viable approach to mitigate the IRCL limitations of SiOx dominant anodes. Prelithiation involves the precise addition of supplemental lithium into the anode, mitigating the adverse effects of initial lithiation and enhancing overall cyclability, energy, power, and extreme fast charge capability for silicon oxide dominant LIBs. Various prelithiation techniques, including Li powder, Li slurry, Li-foil, and the chemical doping of SiOx are examined to evaluate their effectiveness in providing supplemental lithium. The effectiveness of the prelithiation process is assessed by examining the impact on the structural stability, cycling performance, power capability, and rate capability of SiOx dominant anodes integrated into high-capacity (~30 Ah) pouch cells. Our focus is to emphasize prelithiation as a practical and scalable solution to enhance the electrochemical performance of SiOx dominant anodes, contributing to the development of high-energy and high-power LIBs enabling advanced air mobility and high-performance electric vehicles. The findings presented in this abstract contribute to the growing body of knowledge aimed at advancing the fundamental understanding and practical implementation of prelithiation as an enabler for SiOx-based anodes in LIBs. Figure 1

Modification Strategies of High-Energy Li-Rich Mn-Based Cathodes for Li-Ion Batteries: A Review.

Li-rich manganese-based oxide (LRMO) cathode materials are considered to be one of the most promising candidates for next-generation lithium-ion batteries (LIBs) because of their high specific capacity (250 mAh g-1) and low cost. However, the inevitable irreversible structural transformation during cycling leads to large irreversible capacity loss, poor rate performance, energy decay, voltage decay, etc. Based on the recent research into LRMO for LIBs, this review highlights the research progress of LRMO in terms of crystal structure, charging/discharging mechanism investigations, and the prospects of the solution of current key problems. Meanwhile, this review summarizes the specific modification strategies and their merits and demerits, i.e., surface coating, elemental doping, micro/nano structural design, introduction of high entropy, etc. Further, the future development trend and business prospect of LRMO are presented and discussed, which may inspire researchers to create more opportunities and new ideas for the future development of LRMO for LIBs with high energy density and an extended lifespan.

Doping Strategy to Improve the Electrochemical Behavior of Lithium Rich Transition Metal Oxides As Cathodes for Lithium-Ion Batteries

Lithium-rich transition metal oxides are considered a promising cathodic solutions in Li-ion batteries to meet the growing energetic demand, thanks to their high specific capacity and operational voltage [1-2]. Li-rich layered materials have a general stoichiometry Li1+xTM1-xO2, in which TM is a blend of transition metals, as Ni, Mn, Co [2]. They stand out due to their high lithium concentration and specific capacity [1-2]. The higher capacity of Lithium-Rich can be attributed to the specific anionic redox reaction in the bulk at above 4.5 V. Nevertheless, large irreversible capacity loss in the first cycle, poor rate capability, mean working potential decay upon cycling and cobalt content are still major drawbacks that are hindering commercialization. In order to make these materials up scalable to industrial production, it is important to consider the reduction of costs and the toxicity of raw materials, in particular cobalt. Cobalt reduction has been identified as major driver to improve the environmental benignity of batteries and the sustainability of the overall production-consumption-recycling lifecycle. Several efforts to reduce these problems have been made, including the development of different synthetic strategies, doping and surface modification. The most, widely explored, chemical strategy to mitigate the voltage decay and structural degradation in Lithium Rich cathodes is the doping. Elemental doping can be divided into cation and anion doping. As an example, incorporation of redox inactive metals, such as Al, Zr, Ti, has been proposed in order to stabilize the lattice as well as the partial replacement of lithium ions with other alkali cations, e.g. K and Na; or doping the oxygen anion sublattice. In this communication, we present our doping approaches. In particular, the simultaneous replacement of cobalt in the layered structure with aluminum and lithium (over-lithiation). Moreover, we present over-lithiated Co-free materials where the introduction of different amount of iron has been investigated. The characterization of these novel layered materials is reported in terms of composition, structure, morphology and electrochemical performances. These approaches can be applied as a strategy to mitigate the voltage decay and reduce the Cobalt content.[1] Ji, X. et al. Journal of Power Sources 487, (2021).[2] Zhao, S. et al. Angewandte Chemie - International Edition 60, 2208–2220 (2021).

Surficial structure regulation of SiOx material by high-energy ball milling and wet-alkali chemical reaction for lithium-ion batteries

The inhomogeneous nature of SiOx anode material on the atomic scale directly affects its electrochemical performance. A large irreversible capacity loss at the first cycle severely hinders the applications of SiOx materials in lithium ion batteries. The modification of SiOx by means of high-energy ball-milling and wet alkali chemical reaction can tune the ordering of amorphous silicon and silicon dioxide in SiOx materials, which is beneficial to the activation of nano silicon region and the surficial composition optimization of the lithiated products of SiOx during the first discharge process, and the formed Li2SiO3 phase and the increased O/Si ratio in the surface of SiOx contribute to the improved cyclic performance. This surface regulation approach is quite simple, efficient and suitable for large-scale applications of high-performance SiOx anode material.

Dry Pre‐Lithiation for Graphite‐Silicon Diffusion‐Dependent Electrode for All‐Solid‐State Battery

AbstractThe graphite/silicon‐based diffusion‐dependent electrodes (DDEs) are one of the promising electrode designs to realize high energy density for all‐solid‐state batteries (ASSBs) beyond conventional composite electrode design. However, the graphite/silicon‐based electrode also suffers from large initial irreversible capacity loss and capacity fade caused by significant volume change during cycling, which offsets the advantages of the DDEs in ful‐cell configuration. Herein, a new concept is presented for DDEs, dry pre‐lithiated DDEs (PL‐DDEs) by introducing Li metal powder. Since Li metal powder provides Li ions to graphite and silicon even in a dry state, the lithiation states of active materials is increased. Moreover, the residual Li within PL‐DDE further serves as an activator and a reservoir for promoting the lithiation reaction of the active materials and compensating for the active Li loss upon cycling, respectively. Based on these merits, ASSBs with PL‐DDE exhibit excellent cycling performance with higher columbic efficiency (85.2% retention with 99.6% CE at the 200th cycle) compared to bare DDE. Therefore, this dry lithiation process must be a simple but effective design concept for DDEs for high‐energy‐density ASSBs.

Highly activated oxygen redox enabling large-capacity Li-rich layered manganese-based oxide cathodes.

Li-rich Mn-based layered materials are considered the most promising next-generation high-energy-density cathode materials due to their high capacity, but their large irreversible capacity loss and severe voltage attenuation hinder their practical application. The limited operating voltage also makes it difficult to satisfy the increasing demand of high energy density in future applications. Inspired by the high voltage platform of Ni-rich LiNi0.8Co0.1Mn0.1O2, we design and prepare a Li1.2Ni0.32Co0.04Mn0.44O2 (LLMO811) cathode material with increased Ni content via the acrylic acid polymerization method and regulate the amounts of excess lithium of LLMO. It is found that LLMO-L3 with 3% excess lithium has the highest initial discharge capacity of 250 mA h g-1 with a coulombic efficiency of 83.8%. Taking advantage of a high operating voltage of about 3.75 V, the material achieves an impressive high energy density of 947 W h kg-1. Moreover, the capacity at 1C reaches 193.2 mA h g-1, which is higher than that of ordinary LLMO811. This large capacity is attributed to the highly reversible O redox reaction, and the strategy used to achieve this would throw some light on the exploration of high-energy-density cathodes.

Improved Cycling Performance of Cation-Disordered Rock-Salt Li1.2Ti0.4Mn0.4O2 Cathode through Mo-Doping and Al2O3-Coating

Cation-disordered rock-salt cathode material is a promising material for next-generation lithium-ion batteries due to their extra-high capacities. However, the drawbacks of large first-cycle irreversible capacity loss, severe capacity decay, and lower discharge voltage have undoubtedly hindered their application in commercial systems. In this study, cation doping (Mo4+) and atomic layer deposition (ALD) techniques were used to synthetically modify the Li1.2Ti0.4Mn0.4O2 (LTMO) material to improve the cycling stability. First, the optimal Mo-doped sample (Mo01) with the best electrochemical performance among the different doping amounts was selected for further study. Second, the selected sample was subsequently coated with an Al2O3 layer by the ALD technique to further optimize its electrochemical performance. Results show that the LTMMO/24Al2O3 sample, under optimal conditions, could obtain a specific discharge capacity of up to 228.4 mAh g−1 after 30 cycles, which is much higher than that of the unmodified LTMO cathode material. Our work has provided a new possible solution to address some of the capacity fading issues related to the cation-disordered rock-salt cathode materials.

SiOx/C anodes with high initial coulombic efficiency through the synergy effect of pre-lithiation and fluoroethylene carbonate for lithium-ion batteries

SiOx is considered to be a promising anode material for lithium-ion batteries (LIBs) due to the high lithium storage capacity. However, the large initial irreversible capacity loss and intensive volume change during cycling hinder its commercial applications. Prelithiation is an effective and convenient strategy to improve the initial Coulombic efficiency (ICE) of SiOx, while incomplete and unstable SEI on the prelithiated anode still results in rapid capacity decay. Herein, through the synergy effect of chemical pre-lithiation process and fluoroethylene carbonate reduction, a compact and stable LiF-rich SEI layer is in-situ formed on the surface of prelithiated SiOx anode. The modified SiOx anode exhibits a high ICE of 90.7% with good cycling performance. When paired with the commercial LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode, the assemble pre-Li-SiOx/C||NCM622 full cell exhibit a high ICE of 85.7% and stable cycling stability. This work provides a new insight in constructing favorable SEI in pre-lithiation process.

Li-incorporated porous carbon monoliths derived from carboxymethyl cellulose as anode material for high power lithium-ion batteries

In this study, a simple and effective pre-lithiation strategy is developed to resolve a large initial irreversible capacity loss and low initial Coulombic efficiency of porous carbon as anode material for Li-ion batteries. By using this strategy, Li-incorporated hierarchically porous carbon monoliths (PCMs) are successfully obtained from water-soluble carboxymethyl cellulose lithium salt. The prepared PCMs are found to have amorphous carbon structures and well-developed hierarchical pore architectures. In addition, Li is found to be homogeneously incorporated throughout the prepared PCMs. The electrochemical properties of the prepared Li-incorporated PCMs are studied in a half-cell configuration and exhibit lower initial irreversible capacity along with stable cycle life at high current densities. Generally, the resistance of LIB cell remarkably increases at the end of discharge. Here, the galvanostatic intermittent titration technique analyses reveal a higher diffusion coefficient of the prepared Li-incorporated PCMs, specifically at the end of discharge. Therefore, this inherent property of Li-incorporated PCMs is favorable for high-power LIB anode materials.

Sodium ion storage performance and mechanism in orthorhombic V2O5 single-crystalline nanowires

A fundamental understanding of the electrochemical reaction process and mechanism of electrodes is very crucial for developing high-performance electrode materials. In this study, we report the sodium ion storage behavior and mechanism of orthorhombic V2O5 single-crystalline nanowires in the voltage window of 1.0–4.0 V ( vs . Na/Na+). The single-crystalline nanowires exhibit a large irreversible capacity loss during the first discharge/charge cycle, and then show excellent cycling stability in the following cycles. At a current density of 100 mA g−1, the nanowires electrode delivers initial discharge/charge capacity of 217/88 mA h g−1, corresponding to a Coulombic efficiency of only 40.5%; after 100 cycles, the electrode remains a reversible discharge capacity of 78 mA h g−1 with a fading rate of only 0.09% per cycle compared with the 2nd cycle discharge capacity. The sodium ion storage mechanism was investigated, illustrating that the large irreversible capacity loss in the first cycle can be attributed to the initially formed single-crystalline α-Na x V2O5 (0.02 x via a single-phase (solid solution) reaction, leading to excellent cycling stability. The Na+ diffusion coefficient in α-Na x V2O5 ranges from 10−12 to 10−11.5 cm2 s−1 as evaluated by galvanostatic intermittent titration technique (GITT).

Revisiting the Na2/3Ni1/3Mn2/3O2 Cathode: Oxygen Redox Chemistry and Oxygen Release Suppression.

Sodium layered transition metal oxides have been considered as promising cathode materials for sodium ion batteries due to their large capacity and high operating voltage. However, mechanism investigations of chemical evolution and capacity failure at high voltage are inadequate. As a representative cathode, Na2/3Ni1/3Mn2/3O2, the capacity contribution at a 4.2 V plateau has long been assigned to the redox of the Ni3+/Ni4+ couple, while at the same time it suffers large irreversible capacity loss during the initial discharging process. In this work, we prove that the capacity at the 4.2 V plateau is contributed to the irreversible O2–/O2n–/O2 evolution based on in situ differential electrochemical mass spectrometry and density functional theory calculation results. Besides, a phenomenon of oxygen release and subsequent surface lattice densification is observed, which is responsible for the large irreversible capacity loss during the initial cycle. Furthermore, the oxygen release is successfully suppressed by Fe substitution due to the formation of a unique Fe-(O–O) species, which effectively stabilizes the reversibility of the O2–/O2n– redox at high operating voltage. Our findings provide a new understanding of the chemical evolution in layered transition metal oxides at high operating voltage. Increasing the covalency of the TM–O bond has been proven to be effective in suppressing the oxygen release and hence improving the electrochemical performance.

Improvement of the electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2 cathode material by Al2O3 surface coating

The layered Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 cathode materials have been synthesized by a facile approach and subsequently modified with different amount of Al2O3 nano layer. The microstructure and electrochemical performance of the pristine and Al2O3 coated samples were investigated systematically. It is found that the pristine particles are uniformly coated with Al2O3 layer. In particular, the 3 wt% Al2O3-coated cathode delivers the highest initial discharge capacity of 317.9 mAhg−1 at 25 mAg−1 in the voltage window 2.0–4.8 V, and best rate performance (317.9 mAhg−1 at 0.1 C, 105.6 mAhg−1 at 10 C), and best cyclability (discharge capacity of 164 mAhg−1 at 2 C after 200 cycles with capacity retention of 86.3%), which is much better than that of the pristine cathode (discharge capacity of 124 mAhg−1 at 2 C after 200 cycles with capacity retention of 73.3%). Electrochemical impedance spectroscopy (EIS) shows that the Al2O3 coating can reduce the charge transfer resistance during the cycle, which is attributed to the suppression of the side reactions and the stability of the surface structure of the active materials by Al2O3 oxide coating. These findings provide a research direction for solving serious defects such as large initial irreversible capacity loss and poor cycle stability of lithium-rich cathode materials for lithium ion batteries.

Li2ZrO3 Coating and Poly(3,4-ethylenedioxythiophene) Encapsulating on Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with the Stabilized Structure Interface Layer as cathode material

The wide application of Manganese-rich cathode materials have been severely restricted by the large initial irreversible capacity loss, poor cycling stability and low discharge capability at high rate. To ameliorate these severe challenges, the Li2ZrO3 and PEDOT materials were adopted to synthesize the Li2ZrO3 and PEDOT co-coated cathode by the sol-gel method with a calcination process. The SEM and TEM images revealed the Li2ZrO3 and PEDOT were uniformly covered on the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. The electrochemical properties of cathode were obviously enhanced by the Li2ZrO3 coating and PEDOT coating. The Li2ZrO3 coated cathode, PEDOT coated cathode and Li2ZrO3/PEDOT coated cathode respectively delivered the discharge capacities of 120.5, 113.5 and 128.6 mAhg−1, much higher than that (82.3 mAhg−1) of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. Besides, the pristine cathode merely retained a capacity of 156.7 mAhg−1 after 300 cycles at 45 °C. While a large discharge capacity of 201.4 mAh g−1 and a supernal capacity retention of 90.8% were acquired for Li2ZrO3/PEDOT coated cathode after 300 cycles. The electrochemical impedance spectroscopy (EIS) measurement implied the Li2ZrO3 coating and PEDOT coating layer could repress the growth of the charge transfer resistance and accelerate the Li+ diffusion during cycling.

Effect of the Direct Pre-Lithiation on Cycling Performance of Li Ion Battery with Silicon-Containing Anodes

The desire to advanced lithium ion battery is growing with the expansion of electronic markets. Therefore, studies on making electrode materials with high energy density and long cycle life are actively conducted. Among those materials, silicon containing anode is one of the most important materials in making high energy density batteries because of the high theoretical capacity of silicon (~4200mAh/g). However, silicon containing anodes have the disadvantage of large initial irreversible capacity and continuous capacity loss due to large volume change of silicon. Because Li ions transferred from the cathode to the anode disappear without being reversibly used for charging and discharging, the capacity of the full cell becomes significantly smaller than expected. To solve this problem, pre-lithiation has been proposed as a powerful method which can be done through several methods including chemical and electrochemical pre-lithiation and pre-lithiation by direct-contact to lithium [1]. Pre-lithiation studies show that the Coulombic efficiency and discharge capacity dramatically increased. In this research, we propose a method to improve a cycle life of Li ion batteries with silicon containing anodes by applying pre-lithiation to suppress the volume change of silicon. We applied a direct pre-lithation method to increase the cycle life through depositing Li onto the anode; which has an impact on the manufacturing process and the accurate controlling of Li amount. When the coin cell was fabricated with a high capacity cathode and a pre-lithiated silicon containing anode, we were able to obtain not only high discharge capacity (~18%) but also enhanced cycle life characteristics (~30%). In order to investigate the cause of improved cycle life of the cell, three electrode electrochemical experiments were conducted, and then the charged/discharged state of the anode and the cathode are separately extracted in the full cell profile. Analysis of the extracted profiles confirms that the end-voltage of the anode with accurate amount of extra Li is lowered, which means that the silicon in the anode did not completely shrink after discharge. This result demonstrates that the pre-lithiation method is effective in reducing the volume change of the silicon during cycling. Electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM) also supported the above results. We would like to share this result through the presentation and hope that this work will provide an effective method to build a long cycle life Li ion battery with silicon-containing anodes.

One-pot solvothermal synthesis of V2O5/MWCNT composite cathode for Li ion batteries

Composites of metal oxide with nanostructured carbons have been pursued intensively to evade issues like low intrinsic electronic conductivity, large irreversible capacity loss (IC), and poor coulombic efficiency (CE) of metal oxides in lithium-ion batteries (LIBs). In this report, we demonstrate one-pot solvothermal synthesis of V2O5 sheets using ethylene glycol and their composite with MWCNT by electrostatic self-assembly. The phase identification and morphological features were evaluated by XRD, FESEM, and HRTEM techniques, whereas structural properties were acquired from FTIR and Raman spectroscopy data. HRTEM of pristine V2O5 clearly confirms the formation of sheet-like morphology with few tens of nanometers thickness. Investigation of both the pristine V2O5 and V2O5/MWCNT composite materials as positive electrode in LIBs, the latter delivers a capacity of 265 mAh g−1 at 0.1C and 180 mAh g−1 at 1C rate which are higher than the performance of former (238 mAh g−1 at 0.1C rate). The improved electrochemical performance of the V2O5/MWCNT composite cathode in terms of specific capacity, coulombic efficiency, and cycle life stability is ascribed to good electronic and ionic conductivity as well as high lithium storage along both sides of basal plane of V2O5 sheets.

Improving Electrochemical Performance of 0.4Li2MnO3-0.6LiNi1/3Co1/3Mn1/3O2 Cathode Materials for Lithium Secondery Batteries with Coating LiNi0.5Mn1.5O4

Two components of the xLi2MnO3-yLiNi1/3Co1/3Mn1/3O2 have the same framework offer good structure compatibility, but exist large irreversible capacity loss[1] and structure transformation[ 2 ] when initially charged to 4.5V or higher. Hence there are many researchers focus their interest to investigate the possibility of integrating core-shell structure on reducing the irreversible capacity loss and improving cycle stability[3]. This paper is mainly on the improvement of electrochemical properties of 0.4Li2MnO3-0.6LiNi1/3Co1/3Mn1/3O2. The core cathode material was prepared from co-precipitation process. And the Shell material of LiNi0.5Mn1.5O2 has been integrated onto the surface of the core material using with assistance of PVP, since PVP has an effect of constraining particle size. After absolutely dried, both the coated and pristine samples were post-treated at the same thermal condition (Figure1).Figure 2(a). presents a compare of first charge-discharge process of the coated and pristine sample, a remarkable change in the activate process, as coating bring up first cycle efficiency from 73.3% to 83.7% operated at a voltage of 2.0~4.8V vs Li0 at an current rate of c/20(1c=250mAh/g).Figure 2(b). shows an enhancement of cycling properties after coated. Figure 1

Well-Wrapped Li-Rich Layered Cathodes by Reduced Graphene Oxide towards High-Performance Li-Ion Batteries.

Layered lithium-rich manganese oxide (LLO) cathode materials have attracted much attention for the development of high-performance lithium-ion batteries. However, they have suffered seriously from disadvantages, such as large irreversible capacity loss during the first cycle, discharge capacity decaying, and poor rate performance. Here, a novel method was developed to coat the surface of 0.4Li2MnO3∙0.6LiNi1/3Co1/3Mn1/3O2 cathode material with reduced graphene-oxide (rGO) in order to address these drawbacks, where a surfactant was used to facilitate the well-wrapping of rGO. As a result, the modified LLO (LLO@rGO) cathode exhibits superior electrochemical performance including cycling stability and rate capability compared to the pristine LLO cathode. In particular, the LLO@rGO with a 0.5% rGO content can deliver a high discharge capacity of 166.3 mAh g−1 at a 5C rate. The novel strategy developed here can provide a vital approach to inhibit the undesired side reactions and structural deterioration of Li-rich cathode materials, and should be greatly useful for other cathode materials to improve their electrochemical performance.

Preinserted Li metal porous carbon nanotubes with high Coulombic efficiency for lithium-ion battery anodes

Recently, many efforts have been devoted to enhance the capacity performance of porous carbon materials for lithium-ion battery (LIB) anodes. However, the low initial Coulombic efficiency (ICE) caused by the formation of solid electrolyte interphase (SEI) still remains unresolved. Here, we develop a facile and effective prelithiation strategy to compensate for the large irreversible capacity loss due to the formation of SEI. By this strategy, we not only obtain the high surface area and high active-porous carbon nanotubes (PCNTs) from polypyrrole nanotube (PPyNT) precusors, but also simultaneously achieve the satisfactory prelithiation for the PCNTs in which Li metal particles are well preinserted on its surface. This preinserted Li metal porous carbon nanotube (PCNTs@Li), as an anode material, shows a remarkably high ICE of 96% which is much larger than of the pure PCNTs (53%), and meanwhile delivers a high reversible capacity of 932 mAh g−1 at a current density of 20 mA g−1. Furthermore, it also possesses a desirable rate capability and cycling performance. That is, even at a large current density of 200 mA g−1 (namely 1 mA cm−2), the reversible capacity is still as high as 530 mAh g−1 after 230 cycles. With these distinguishing performance, the prepared PCNTs@Li is a promising anode material for LIBs.

Amide-Functionalized Porous Carbonaceous Anode Materials for Lithium-Ion Batteries.

Porous carbonaceous anode materials have received considerable attention as an alternative anode material, however, there is a critical bottleneck as it suffers from a large irreversible specific capacity loss over several initial cycles owing to undesired surface reactions. In order to suppress undesired surface reactions of porous carbonaceous anode material, here, we suggest a simple and convenient two-step surface modification approach that allows the embedding of an amide functional group on the surface of a porous carbonaceous anode, which effectively improves the surface stability. In this approach, the porous carbonaceous anode material is firstly activated by means of strong acid treatment comprising a combination of H2 SO4 and HNO3 , and it is subjected to further modification by means of an amide coupling reaction. Our additional systematic analyses confirm that the acid functional group effectively transforms into the amide functional group. The resulting amide-functionalized porous carbon exhibits an improved electrochemical performance: the initial discharge specific capacity is greatly reduced to less than 2,620 mA h g-1 and charge specific capacity is well still remained, indicating stabling cycling performance of the cell.

Tuning Anionic Redox Activity and Reversibility for a High‐Capacity Li‐Rich Mn‐Based Oxide Cathode via an Integrated Strategy

AbstractWhen fabricating Li‐rich layered oxide cathode materials, anionic redox chemistry plays a critical role in achieving a large specific capacity. Unfortunately, the release of lattice oxygen at the surface impedes the reversibility of the anionic redox reaction, which induces a large irreversible capacity loss, inferior thermal stability, and voltage decay. Therefore, methods for improving the anionic redox constitute a major challenge for the application of high‐energy‐density Li‐rich Mn‐based cathode materials. Herein, to enhance the oxygen redox activity and reversibility in Co‐free Li‐rich Mn‐based Li1.2Mn0.6Ni0.2O2 cathode materials by using an integrated strategy of Li2SnO3 coating‐induced Sn doping and spinel phase formation during synchronous lithiation is proposed. As an Li+ conductor, a Li2SnO3 nanocoating layer protects the lattice oxygen from exposure at the surface, thereby avoiding irreversible oxidation. The synergy of the formed spinel phase and Sn dopant not only improves the anionic redox activity, reversibility, and Li+ migration rate but also decreases Li/Ni mixing. The 1% Li2SnO3‐coated Li1.2Mn0.6Ni0.2O2 delivers a capacity of more than 300 mAh g−1 with 92% Coulombic efficiency. Moreover, improved thermal stability and voltage retention are also observed. This synergic strategy may provide insights for understanding and designing new high‐performance materials with enhanced reversible anionic redox and stabilized surface lattice oxygen.