Cathode Materials For Lithium-ion Batteries Research Articles

Comprehensive Study of Zr-Doped Ni-Rich Cathode Materials Upon Lithiation and Co-Precipitation Synthesis Steps.

Ni-rich layered oxides LiNi1-x-yMnxCoyO2 (NMC811, x = 0.1 and y = 0.1) are considered promising cathode materials in lithium-ion batteries (LiBs) due to their high energy density. However, those suffer a severe capacity loss upon cycling at high delithiated states. The loss of performance over time can be retarded by Zr doping. Herein, a small amount of Zr is added to NMC811 material via two alternative pathways: during the formation of the transition metal (TM) hydroxide precursor at the co-precipitation step (0.1%-Zr-cp) and during the lithiation at the solid-state synthesis step (0.1%-Zr-ss). In this work, the crystallographic Zr uptake in both 0.1%-Zr-ss and 0.1%-Zr-cp is determined and quantified through synchrotron X-ray diffraction and X-ray absorption spectroscopy. We prove that the inclusion of Zr in the TM site for 0.1%-Zr-cp leads to an improvement of both specific capacity (156 vs 149 mAh/g) and capacity retention (85 vs 82%) upon 100 cycles compared to 0.1%-Zr-ss where the Zr does not diffuse into the active material and forms only an extra phase separated from the NMC811 particles.

LaCoO3@Fe3O4 as peroxymonosulfate activator derived from spent lithium battery cathode materials for degradation of sulfamethoxazole in water

To reduce the various hazards of SMX to aquatic ecosystems, in this study, magnetically separable LaCoO3@Fe3O4 catalysts for the degradation of sulfamethoxazole (SMX) in water by activated peroxymonosulfate (PMS) were successfully prepared by using cobalt oxalate recovered from spent batteries using sol–gel, hydrothermal, and high-temperature calcination methods. The main factors influencing the reaction and the effect of coexisting ions on the degradation efficiency of SMX were investigated. The results showed that under optimal conditions ([SMX] = 30 mg, [LaCoO3@Fe3O4] = 10 mg/L, [PMS] = 30 mg/L, pH (initial) = 7.02), the LaCoO3@Fe3O4/PMS system degraded SMX up to 93 % in 15 min. The degradation of SMX in the LaCoO3@Fe3O4/PMS system was shown to be achieved by a combination of radical (SO4•-/•OH/•O2–) and non-radical (1O2) pathways by quenching experiments and electron paramagnetic resonance spectroscopy (EPR) analysis. Then, three possible degradation pathways were proposed using LC-MS, and Ecological Constitutive Relationship (ECOSAR) analysis showed that the toxicity of the intermediate products was all lower than that of SMX, indicating that the system is feasible for SMX degradation. This study provides a new idea for activating PMS for the degradation of antibiotics in water by preparing catalysts using precious metals from recycled batteries.

Surface Pinning of Mn by Oxidation State Control for the Synthesis of Cobalt-Free, Ni-Rich, Core/Shell Structured Cathode Materials.

Motivated by the increasing cost, environmental concerns, and limited availability of Co, researchers are actively seeking alternative cathode materials for lithium-ion batteries. A promising strategy involves structure-modified materials, such as a NiMn core/shell system. This design leverages the high energy density of a Ni-rich core while employing an Mn-rich shell to enhance interfacial stability by suppressing unwanted reactions with the electrolyte. This approach offers improved cycling stability and reduced reliance on Co. However, the interdiffusion of Mn ions between the core and shell remains a significant challenge during synthesis. This work presents a facile approach to address the issue of Mn interdiffusion in core/shell cathode materials. The study demonstrates that partial oxidation of the precursor during the drying stage effectively enhances the Mn oxidation state. This strategy successfully suppresses Mn interdiffusion during subsequent calcination, leading to the preservation of the core/shell architecture in the final cathode material. This optimized structure mitigates interfacial reactions, enhances chemomechanical properties, and reduces crosstalk, a major contributor to rollover failure. This work presents a novel approach for synthesizing high-performance core/shell cathode materials for next-generation lithium-ion batteries.

Constructing High-performance Cobalt-based Environmental Catalysts from Spent Lithium-Ion Batteries: Unveiling Overlooked Roles of Copper and Aluminum from Current Collectors.

Converting spent lithium-ion batteries (LIBs) cathode materials into environmental catalysts has drawn more and more attention. Herein, we fabricated a Co3O4-based catalyst from spent LiCoO2 LIBs (Co3O4-LIBs) and found that the role of Al and Cu from current collectors on its performance is nonnegligible. The density functional theory calculations confirmed that the doping of Al and/or Cu upshifts the d-band center of Co. A Fenton-like reaction based on peroxymonosulfate (PMS) activation was adopted to evaluate its activity. Interestingly, Al doping strengthened chemisorption for PMS (from -2.615 eV to -2.623 eV) and shortened Co-O bond length (from 2.540 Å to 2.344 Å) between them, whereas Cu doping reduced interfacial charge-transfer resistance (from 28.347 kΩ to 6.689 kΩ) excepting for the enhancement of the above characteristics. As expected, the degradation activity toward bisphenol A of Co3O4-LIBs (0.523 min-1) was superior to that of Co3O4 prepared from commercial CoC2O4 (0.287 min-1). Simultaneously, the reasons for improved activity were further verified by comparing activity with catalysts doped Al and/or Cu into Co3O4. This work reveals the role of elements from current collectors on the performance of functional materials from spent LIBs, which is beneficial to the sustainable utilization of spent LIBs.

Balancing Ionic and Electronic Conduction at the LiFePO4 Cathode–Electrolyte Interface and Regulating Solid Electrolyte Interphase in Lithium‐Ion Batteries

AbstractRecently, in electric mobilities and stationary energy storage device applications, the development of long‐lasting, low‐cost, and high‐safety lithium‐ion batteries (LIBs) is widely studied. LiFePO4 (LFP) is a core cathode material for LIBs owing to its cost‐effectiveness and high safety. However, it exhibits low electronic conductivity and sluggish Li+ diffusion, hindering the application of LFP cathodes in high‐power battery industries. Herein, a triazole‐motivated electrolyte additive, 1‐(trimethylsilyl)−1H‐benzotriazole (TMSBTA) is presented, for mitigating iron dissolution via HF scavenging, reinforcing the robustness of the solid electrolyte interphase and constructing a cathode–electrolyte interface (CEI) to balance the ion and electron conduction of the CEI on the LFP cathode. Scanning probe microscopy performed in the conductive atomic force microscopy mode indicates that the electronically conductive CEI created by the oxidative decomposition of TMSBTA enables rapid and homogeneous lithiation and delithiation during cycling without morphological changes in the LFP particles. This study elucidates the design principles of the CEI on the LFP cathode and is expected to guide integrated electrolyte additive engineering for LFP‐containing LIBs.

Synergistic effect of interlayered doping and surface modification to improve the performance of Li-rich manganese-based cathode materials

Li-rich manganese-based oxides (LRMOs) with high energy density have been intensively studied, but their practical use as cathode materials for lithium-ion batteries is still impeded by the shortcomings such as low initial coulombic efficiency, voltage decay and poor rate capability. To address these issues, element Nb is selected to bulk dope and simultaneously surface modify the hierarchical Li1.20Mn0.54Co0.13Ni0.13O2 spheres in this work. Synergistic effect of Nb doping and surface modification on the crystalline structure and electrochemical performance of the resultant LRMOs is characterized in detail. The results suggest that Nb5+ ions are doped into the interlayer sites within the crystals while the LiMn2O4 and LiNb3O8 double layers are coated on the primary nanoparticles. The galvanostatic charge-discharge measurements reveal that the optimal LRMO-Nb2 sample can deliver the capacities of 286 and 167 mAh g−1 at the rates of 0.1 C and 5 C, respectively, and retains a capacity of 191 mAh g−1 at 1 C rate after 200 cycles. Ex-situ XRD patterns prove that the layered structure is strongly pillared by the interlayer-doped Nb5+ during the delithiation/lithiation processes. Especially, some lithium vacancies formed around Nb5+ ions can accelerate the diffusion of Li+ ions, which was proved by DFT calculations and experimental results. Our research demonstrates that cooperating of the interlayered doping of Nb5+ with surface coating of LiNb3O8 layer can improve rate capability and cyclability of the resultant LRMOs significantly.

Innovative green intense tetra-eutectic solvent (ITES) for recovery via occlusion co-precipitation at room temperature

Lithium iron phosphate (LiFePO4) is the widely used cathode material for safe and high-power lithium-ion batteries (LIBs) for electric vehicles (EVs). Therefore, numerous challenges to re-manufacturing, re-use, and recovery from spent LiFePO4/C are tolerated if evaluated early in the innovation process. Herein, innovative green intense tetra-eutectic solvent (ITES) has been used to recover a new Li-metal co-intercalation compound from spent LiFePO4/C cathode material, which is simple and cost-effective. The ITES leaching concerning organic solution with active hydrogen donor-acceptor salts creates a coordination environment through occlusion co-precipitate new co-intercalation compound at room temperature. Innovative green ITES-10 solution has successfully recovered a new Li-metal co-intercalation regarding the active hydrogen donor-acceptor bonding coordination environment of ITES adequate leaching solution and proposed recovery mechanism. The ICP-MS value of recovery metal (7Li) efficiency (%) of ITES-10 leaching for spent LiFePO₄/C cathode materials reaches approximately 0.452% at room temperature for recovery of new co-intercalation compound, besides the fresh LiFePO₄/C cathode materials (as reference), approximately 0.805%, respectively. Therefore, innovative ITES is considered to recover spent Li-based cathode materials in our future works concerning high leaching recovery rates below 100 °C in experimental conditions.

Lithium-Ion Conductive Coatings for Nickel-Rich Cathodes for Lithium-Ion Batteries.

Nickel (Ni)-rich cathodes are among the most promising cathode materials of lithium batteries, ascribed to their high-power density, cost-effectiveness, and eco-friendliness, having extensive applications from portable electronics to electric vehicles and national grids. They can boost the wide implementation of renewable energies and thereby contribute to carbon neutrality and achieving sustainable prosperity in the modern society. Nevertheless, these cathodes suffer from significant technical challenges, leading to poor cycling performance and safety risks. The underlying mechanisms are residual lithium compounds, uncontrolled lithium/nickel cation mixing, severe interface reactions, irreversible phase transition, anisotropic internal stress, and microcracking. Notably, they have become more serious with increasing Ni content and have been impeding the widespread commercial applications of Ni-rich cathodes. Various strategies have been developed to tackle these issues, such as elemental doping, adding electrolyte additives, and surface coating. Surface coating has been a facile and effective route and has been investigated widely among them. Of numerous surface coating materials, have recently emerged as highly attractive options due to their high lithium-ion conductivity. In this review, a thorough and comprehensive review of lithium-ion conductive coatings (LCCs) are made, aimed at probing their underlying mechanisms for improved cell performance and stimulating new research efforts.

Enabling Ultrastable Co-Free Li-Rich Oxides via TbF3 Treatment.

Co-free Li-rich Mn-based cathode materials (Co-free LRMOs) have become one of the most promising cathode materials in lithium-ion batteries for the next generation due to their low cost, high capacity, and environmental friendliness. Under high voltage, redox reactions involving anions can easily lead to various issues, including oxygen release, dissolution of transition metal elements (TMs), and structural collapse in these materials. The absence of the Co element further exacerbates this issue. Here, a simple one-step solid-phase reaction strategy is proposed to achieve nanoscale dual modification of the Co-free LRMOs with F and Tb doping. The dual modification has a relatively small impact on the cell parameters and Li+ diffusion ability of the LRMOs, leading to no significant improvement in its rate performance. The modified LRMOs only exhibited discharge capacities of 220.7, 200.1, 140.0, 115.5, and 90.9 mAh·g-1 at 0.1, 0.2, 1.0, 2.0, and 5.0 C, respectively. However, the modified Co-free LRMOs exhibit extremely strong structural stability and retain 95.1% of the initial capacity after 300 cycles, so far, the highest capacity retention rates among all Ni/Mn-based Li-rich materials. Mechanism studies have shown that the enhancement in structural stability of the Co-free LRMOs is attributed to the increased concentration of oxygen vacancies and Ni3+ ions through F doping. Furthermore, Tb doping not only hinders the release of O2 but also enhances the Li+ migration and electronic conductivity coefficient of the LRMOs.

Double gradient coupling heterostructure design accurately regulates the anion process of the Li-rich cathode

Lithium-rich layered oxides are regarded as the next generation of cathode materials for lithium-ion batteries due to their high capacity and high operating voltage. However, the release of oxygen at high voltage has caused serious failure problems, severely limiting the commercial application of lithium-rich cathode materials. As the irreversible release of oxygen occurs first at the surface of the particles, the change in structure at the surface is also more drastic. In response to the variability of anion redox processes from surface to interior in the particles, a coupling strategy of Al, oxygen vacancies double gradient and spinel heterostructure was designed. The high concentration of oxygen vacancies and Al on the surface inhibits excessive oxidation of lattice oxygen and oxygen release. The surface heterostructure improves the reaction kinetics and increases the activity and reversibility of the electrode process. The concentration of oxygen vacancies and Al in the interior ensures highly active anionic redox and further enhances structural stability. The specific capacity (0.13 mAh/g/cycle) and voltage (1.34 mV/cycle) decay of the modified material is greatly reduced. In-situ and ex-situ characterisations were used to analyse the modification mechanism, which can effectively guide the improvement of lithium-rich cathode material performance.

Effect of Subtle Changes in Ni2+/Ni3+ and Particle Surface Area in LiNi0.5Mn0.5−xCoxO2 (x = 0.1–0.3) Cathode Materials for Lithium-Ion Batteries

In Li[Ni,Mn,Co]O2 (NMC) cathode materials, small changes in transition metal ratio and particle surface area can significantly impact capacity retention. To understand the combined effect of transition metal ratio and the particle surface area, we studied LiNi0.5Mn0.5−xCoxO2 (x = 0.1–0.3) particles with two different morphologies: dense, spherical particles and high-surface area aggregates. All compositions in this series contain the same percentage of Ni but have differing amounts of Ni2+ and Ni3+. While Ni2+ tends to induce anti-site defects predominantly in the bulk, Ni3+ promotes particle surface reconstruction, both of which negatively impact capacity retention. Upon cycling to 4.4 V for 100 cycles, we observe that particles of high surface area with high Ni3+ concentration undergo the most severe capacity degradation. However, high surface area particles with high proportion of anti-site defects undergo sluggish capacity fade. Overall, with 60% of Ni2+ and 40% of Ni3+, spherical NMC 532 particles endure the detrimental effects of anti-site defects and surface reconstruction, but neither too prominently and thus emerges as the best candidate among the studied samples. This study highlights the synergy between transition metal ratio and particle surface area and how it determines the properties of the NMC cathode materials.

Zero Voltage-Degradation of Li2MnO3 with Ultrathin Amorphous Li─Mn─O Coating.

Manganese-based lithium-rich layered oxides (Mn-LLOs) are promising candidate cathode materials for lithium-ion batteries, however, the severe voltage decay during cycling is the most concern for their practical applications. Herein, an Mn-based composite nanostructure constructed Li2MnO3 (LMO@Li2MnO3) is developed via an ultrathin amorphous functional oxide LixMnOy coating at the grain surface. Due to the thin and universal LMO amorphous surface layer etched from the lithiation process by the high-concentration alkaline solution, the structural and interfacial stability of Li2MnO3 are enhanced apparently, showing the significantly improved voltage maintenance, cycle stability, and energy density. In particular, the LMO@Li2MnO3 cathode exhibits zero voltage decay over 200 cycles. Combining with ex situ spectroscopic and microscopic techniques, the Mn2+/4+ coexisted behavior of the amorphous LMO is revealed, which enables the stable electrochemistry of Li2MnO3. This work provides new possible routes for suppressing the voltage decay of Mn-LLOs by modifying with the composite functional unit construction.

Comparison of lithium sources on the electrochemical performance of LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

In order to fulfill the demand for high energy and capacity, an electrode with high-voltage capability, namely LiNi0.5Mn1.5O4 (LNMO) that has an operating potential of up to 4.7 V vs Li/Li+, is currently becoming popular in Li-ion battery chemistries. This research produced LNMO by using a solid-state method with only one-step synthesis route to compare its electrochemical performance with different lithium sources, including hydroxide (LNMO-LiOH), acetate (LNMO-LiAce), and carbonate (LNMO-LiCar) precursors. TGA/DSC was first performed for all three sample precursors to ensure the optimal calcination temperature, while XRD and SEM characterized the physical properties. The electrochemical measurements, including cyclic voltammetry and charge-discharge, were conducted in the half-cell configurations of LNMO//Li-metal using a standard 1 M LiPF6 electrolyte. LNMO-LiOH samples exhibited the highest purity and the smallest particle size, with values of 93.3% and 418 nm, respectively. In contrast, samples with higher impurities, such as LNMO-LiCar, mainly in the form of LixNi1-xO (LiNiO), displayed the largest particle size. The highest working voltage possessed by LNMO-LiOH samples was 4.735 V vs Li/Li+. The results showed that LNMO samples with LiNiO impurities would affect the reaction behavior that occurs at the cathode-electrolyte interface during the release of lithium-ions, resulting in high resistance at the battery operations and decreasing the specific capacity of the LNMO during discharging. The highest value, shown by LNMO-LiOH, was up to 92.75 mAh/g. On the other side, LNMO-LiCar only possessed a specific capacity of 44.57 mAh/g, indicating a significant impact of different lithium sources in the overall performances of LNMO cathode.

Effect of process conditions on the performance of LiNi0.815Co0.15Al0.035O2 positive electrode material powder synthesized by hydrothermal approach

LiNi0.815Co0.15Al0.035O2 (NCA) lithium-ion battery cathode material was prepared using a hydrothermal approach. XRD and SEM analyzed the crystal parameters and powder morphology of the cathode material. The results show that the nickel cobalt precursor exhibits a petal-like morphology, and the nanoneedle primary particles are randomly distributed. Accompanied by the increase in calcination temperature and time, the peak intensity ratio of I003/I104 tends to decrease and then increase. The peak intensity ratio reached a maximum when the NCA sample calcined at 750°C for 8 h, indicating the lowest extent of Li/Ni mixing and the best electrochemical performance of the positive electrode material.

Unveiling the vacancy-mediated charge kinetics and capacity fading mechanism in Mn-based cathode for lithium-ion battery

In the recent past, Li2MnSiO4 (LMS) has been considered a promising cathode material for high energy density lithium-ion batteries (LIBs). Extraction of the maximum amount of Li from the host LMS and reversibility of Li insertion and extraction is still challenging, probably because of poor conductivity and, thereby, poor Li-kinetics. To improve the Li-diffusion and ionic conductivity, oxygen vacancies (OVs) in pristine LMS (LMS180) have been created, and then their impact on the Li-reactivity of LMS is studied. The quantity of OVs is determined by X-ray photoelectron spectroscopy (XPS) and calculated to be 6.8% in LMS180 heated at 300 ºC in Ar (LMSA300) and ∼ 8.2% in LMS180 heated at 500° C in Ar (LMSA500), subsequently it is supported and validate by the electron paramagnetic response (EPR) and high-resolution transmission electron microscopy (HR-TEM). The best sample, i.e., LMSA500, exhibits a total conductivity of 8.06×10−6 S/cm, resulting in an initial charge capacity of 292 (±5) mAh/g at 10 mA/g. The OVs are found to facilitate the facile lithium-ion movement by providing the lowest migration energy. Furthermore, knowing the impacts of OVs presence in LMS and their effect on Li-diffusion enables us to address traditional capacity fading processes in LMS.

Hydrogen Reduction Behavior of NCM-based Lithium-ion Battery Cathode Materials

As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 °C and hydrogen partial pressure above 0.5 atm, Ni and Li2O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H2O, and Li2CO3, with about 0.02 wt% Al as an impurity.

A Study on the Microstructure Regulation Effect of Niobium Doping on LiNi0.88Co0.05Mn0.07O2 and the Electrochemical Performance of the Composite Material under High Voltage.

High-nickel ternary materials are currently the most promising lithium battery cathode materials due to their development and application potential. Nevertheless, these materials encounter challenges like cation mixing, lattice oxygen loss, interfacial reactions, and microcracks. These issues are exacerbated at high voltages, compromising their cyclic stability and safety. In this study, we successfully prepared Nb5+-doped high-nickel ternary cathode materials via a high-temperature solid-phase method. We investigated the impact of Nb5+ doping on the microstructure and electrochemical properties of LiNi0.88Co0.05Mn0.07O2 ternary cathode materials by varying the amount of Nb2O5 added. The experimental results suggest that Nb5+ doping does not alter the crystal structure but modifies the particle morphology, yielding radially distributed, elongated, rod-like structures. This morphology effectively mitigates the anisotropic volume changes during cycling, thereby bolstering the material's cyclic stability. The material exhibits a discharge capacity of 224.4 mAh g-1 at 0.1C and 200.3 mAh g-1 at 1C, within a voltage range of 2.7 V-4.5 V. Following 100 cycles at 1C, the capacity retention rate maintains a high level of 92.9%, highlighting the material's remarkable capacity retention and cyclic stability under high-voltage conditions. The enhancement of cyclic stability is primarily due to the synergistic effects caused by Nb5+ doping. Nb5+ modifies the particle morphology, thereby mitigating the formation of microcracks. The formation of high-energy Nb-O bonds prevents oxygen precipitation at high voltages, minimizes the irreversibility of the H2-H3 phase transition, and thereby enhances the stability of the composite material at high voltages.

Effect of Fe and Zn co-doping on LiCoPO4 cathode materials for High-Voltage Lithium-Ion batteries

Lithium cobalt phosphate (LiCoPO4) has great potential to be developed as a cathode material for lithium-ion batteries (LIBs) due to its structural stability and higher voltage platform with a high theoretical energy density. However, the relatively low diffusion of lithium ions still needs to be improved. In this work, Fe and Zn co-doped LiCoPO4: LiCo0.9-xFe0.1ZnxPO4/C is utilized to enhance the battery performance of LiCoPO4. The electrochemical properties of LiCo0.85Fe0.1Zn0.05PO4/C demonstrated an initial capacity of 118 mAh/g, with 93.4 % capacity retention at 1C after 100 cycles, and a good capacity of 87 mAh/g remained under a high current density of 10C. In addition, the diffusion rate of Li ions was investigated, proving the improvement of the materials with doping. The impedance results also showed a smaller resistance of the doped materials. Furthermore, operando X-ray diffraction displayed a good reversibility of the structural transformation, corresponding to cycling stability. This work provided studies of both the electrochemical properties and structural transformation of Fe and Zn co-doped LiCoPO4, which showed that 10 % Fe and 5 % Zn co-doping enhanced the electrochemical performance of LiCoPO4 as a cathode material in LIBs.

Novel synthesis of FeF3·0.33H2O@hollow acetylene black nanosphere and its long-life electrochemical properties as a cathode for lithium-ion batteries

Iron (III) fluoride (FeF3), characterized by high voltage and high specific capacity and emerges as a promising candidate for the forthcoming generation of cathode materials in lithium-ion batteries. This study employs a novel methodology by introducing Fe3+ sources into hollow acetylene black particles through a vacuum impregnation method. This innovative approach results in the synthesis of a composite material comprising FeF3∙0.33H2O encapsulated within hollow acetylene black nanospheres, denoted as the FeF3∙0.33H2O @hollow acetylene black nanosphere composite material (FF@HCN). The composite exhibits a shell composed of highly graphitized carbon and a core containing FeF3∙0.33H2O particles in the range of 10–20 nm. The proportion of active materials is 75.56 %. The acetylene black has chain-like structure and high specific surface area, significantly enhances the material's conductivity, contributing 74.4 % to the pseudocapacitance at a scan rate of 1 mV s−1. The cavity graphite shell plays a crucial role in restricting the expansion and pulverization decay of FeF3∙0.33H2O nanoparticles, thereby markedly improving the cycle stability. The initial capacity of the FF@HCN composite is 224.4 mAh g−1, and after 1000 cycles at 0.1 C, it maintains a capacity of 162.3 mAh g−1, resulting in a capacity retention rate of 72.3 % and decay per cycle of 0.027 %.

Regulation of surface structure to suppress voltage decay for high-stable Li-rich oxide cathodes

Layered lithium-rich manganese oxides (LMO) are promising cathode materials for high-energy density lithium-ion batteries due to their high specific capacity and working potential. However, serious voltage decay and undesirable cycle stability are big obstacles that hinder their industrialization and application. Herein, an innovative and industrially valuable strategy of constructing composite coatings and oxygen vacancies on the LMO surface is put forward to suppress voltage decay and enhance the cycling stability of LMO by precisely modulating NaBH4 treatment. The synergistic effect of surface spinel coating, NaBO2coating, and oxygen vacancies effectively inhibits the release of oxygen, impedes the occurrence of side reactions at the interface, inhibits the migration and dissolution of transition metals, suppresses the irreversible structure transformation and improves the reversibility of redox reaction. The capacity retention of the NaBH4-treated LMO material maintains 100 % after 200 cycles at 0.5C, as well as stable cycling at 2C with a discharge capacity of 180 mAh g−1 harvested. Moreover, the voltage decay is significantly suppressed by NaBH4 modification, especially the NaBH4-0.5 % sample exhibits a mere voltage decay of 1.73 mV per cycle in the 200 cycles. This study provides significant insights into the development of LMO cathodes with long-cycle performance.