AlF3-coated Li(Li0.17Ni0.25Mn0.58)O2 as cathode material for Li-ion batteries

Side Reactions/Changes in Lithium-Ion Batteries: Mechanisms and Strategies for Creating Safer and Better Batteries

Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and over-discharge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components.

Recent advances in lithium-rich manganese-based cathodes for high energy density lithium-ion batteries

The development of society challenges the limit of lithium-ion batteries (LIBs) in terms of energy density and safety. Lithium-rich manganese oxide (LRMO) is regarded as one of the most promising cathode materials owing to its advantages of high voltage and specific capacity (more than 250 mA h g^-1) as well as low cost. However, the problems of fast voltage/capacity fading, poor rate performance and the low initial Coulombic efficiency severely hinder its practical application. In this paper, we review the latest research advances of LRMO cathode materials, including crystal structure, electrochemical reaction mechanism, existing problems and modification strategies. In this review, we pay more attention to recent progress in modification methods, including surface modification, doping, morphology and structure design, binder and electrolyte additives, and integration strategies. It not only includes widely studied strategies such as composition and process optimization, coating, defect engineering, and surface treatment, but also introduces many relatively novel modification methods, such as novel coatings, grain boundary coating, gradient design, single crystal, ion exchange method, solid-state batteries and entropy stabilization strategy. Finally, we summarize the existing problems in the development of LRMO and put forward some perspectives on the further research.

Li-Deficient Materials-Decoration Restrains Oxygen Evolution Achieving Excellent Cycling Stability of Li-Rich Mn-Based Cathode

With the increasing demand for high energy density and rapid charging performance, Li-rich materials have been the up and coming cathodes for next-generation lithium-ion batteries. However, because of oxygen evolution and structural instability, the commercialization of Li-rich materials is extremely retarded by their poor electrochemical performances. In this work, Li-deficient materials Li_0.3NbO₂ and (Nb_0.62Li_0.15)TiO₃ are applied to functionalize the surface of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, aiming to suppress oxygen evolution and increase structural stability in LIBs. In addition, a fast Li-ion transport channel is beneficial to enhance Li⁺ diffusion kinetics. The results demonstrate that the electrodes decorated with Li_0.3NbO₂ and (Nb_0.62Li_0.15)TiO₃ materials exhibit more stable cycling stability after long-term cycling and outstanding rate capability.

Oxygen Loss in Layered Oxide Cathodes for Li-Ion Batteries: Mechanisms, Effects, and Mitigation

Layered lithium transition metal oxides derived from LiMO₂ (M = Co, Ni, Mn, etc.) have been widely adopted as the cathodes of Li-ion batteries for portable electronics, electric vehicles, and energy storage. Oxygen loss in the layered oxides is one of the major factors leading to cycling-induced structural degradation and its associated fade in electrochemical performance. Herein, we review recent progress in understanding the phenomena of oxygen loss and the resulting structural degradation in layered oxide cathodes. We first present the major driving forces leading to the oxygen loss and then describe the associated structural degradation resulting from the oxygen loss. We follow this analysis with a discussion of the kinetic pathways that enable oxygen loss, and then we address the resulting electrochemical fade. Finally, we review the possible approaches toward mitigating oxygen loss and the associated electrochemical fade as well as detail novel analytical methods for probing the oxygen loss.

Breaking Free from Cobalt Reliance in Lithium-Ion Batteries

The exponential growth in demand for electric vehicles (EVs) necessitates increasing supplies of low-cost and high-performance lithium-ion batteries (LIBs). Naturally, the ramp-up in LIB production raises concerns over raw material availability, where constraints can generate severe price spikes and bring the momentum and optimism of the EV market to a halt. Particularly, the reliance of cobalt in the cathode is concerning owing to its high cost, scarcity, and centralized and volatile supply chain structure. However, compositions suitable for EV applications that demonstrate high energy density and lifetime are all reliant on cobalt to some degree. In this work, we assess the necessity and feasibility of developing and commercializing cobalt-free cathode materials for LIBs. Promising cobalt-free compositions and critical areas of research are highlighted, which provide new insight into the role and contribution of cobalt.

Nanostructured Iron Fluoride Derived from Fe-Based Metal-Organic Framework for Lithium Ion Battery Cathodes

A comprehensive strategy for the morphological control of octahedral and spindle Fe-based metal-organic frameworks (Fe-MOFs) via microwave-assisted adjustment is proposed in this research. Afterward, in situ copyrolysis under N₂ atmosphere contributes to the fabrication of two shape-maintained FeF₃·0.33H₂O nanostructures (named O-FeF₃·0.33H₂O and S-FeF₃·0.33H₂O, respectively) with confined hierarchical porosity and graphitized carbon skeleton. The lithium storage performances for the MOF-derived octahedral O-FeF₃·0.33H₂O and spindle S-FeF₃·0.33H₂O composites are investigated, and the prospective lithium storage mechanism is discussed. As a result, the main product of the porous O-FeF₃·0.33H₂O structure is found to be a promising cathode material for lithium ion batteries owing to its advantageous electrochemical capability. Even after being cycled over 1000 times at 2 C (1 C = 237 mAh g^-1), the capacity attenuation rate of the as-prepared O-FeF₃·0.33H₂O electrode is as low as 0.039% per cycle. The combination of proper octahedral morphology and highly graphitized carbon modification can not only enhance the conductivity of the cathode but also promote the diffusion of Li⁺ effectively. The remarkable performance of octahedral O-FeF₃·0.33H₂O can be confirmed by the Li-ion diffusion coefficient (D_Li⁺) calculation analysis and kinetics analysis of lithium storage behavior.

Lithium-Rich Cobalt-Free Manganese-Based Layered Cathode Materials for Li-Ion Batteries: Suppressing the Voltage Fading

Lithium-rich layered oxides are recognized as promising materials for Li-ion batteries, owing to higher capacity than the currently available commercialized cathode, for their lower cost. However, their voltage decay and cycling instability during the charge/discharge process are problems that need to be solved before their practical application can be envisioned. These problems are mainly associated with a phase transition of the surface layer from the layered structure to the spinel structure. In this paper, we report the AlF3-coating of the Li-rich Co-free layered Li1.2Ni0.2Mn0.6O2 (LLNMO) oxide as an effective strategy to solve these problems. The samples were synthesized via the hydrothermal route that insures a very good crystallization in the layered structure, probed by XRD, energy-dispersive X-ray (EDX) spectroscopy, and Raman spectroscopy. The hydrothermally synthesized samples before and after AlF3 coating are well crystallized in the layered structure with particle sizes of about 180 nm (crystallites of ~65 nm), with high porosity (pore size 5 nm) determined by Brunauer–Emmett–Teller (BET) specific surface area method. Subsequent improvements in discharge capacity are obtained with a ~5-nm thick coating layer. AlF3-coated Li1.2Ni0.2Mn0.6O2 delivers a capacity of 248 mAh g−1 stable over the 100 cycles, and it exhibits a voltage fading rate of 1.40 mV per cycle. According to the analysis from galvanostatic charge-discharge and electrochemical impedance spectroscopy, the electrochemical performance enhancement is discussed and compared with literature data. Post-mortem analysis confirms that the AlF3 coating is a very efficient surface modification to improve the stability of the layered phase of the Li-rich material, at the origin of the significant improvement of the electrochemical properties.

Thermal Stability Enhancement through Structure Modification on the Microsized Crystalline Grain Surface of Lithium-Rich Layered Oxides

Lithium-rich layered oxides have been considered as the most promising candidate for offering a high specific capacity and energy density for lithium-ion batteries. However, their practical applications are still suffered by the cycle instability and also closely related thermal stability. Here, microsized crystalline grains with good dispersion of lithium-rich layered oxides are prepared by a molten-salt method, while a spinel structure is also introduced on a grain surface by following chemical oxidation and annealing process, and their thermal performance with different cutoff voltages during the charge process is systematically studied using differential scanning calorimetry method. Results have shown that thermal stability of microsized crystalline grains is better than that of spherical secondary agglomerates, the spinel structure introduction on the grain surface of microsized crystalline grains can contribute obviously to their thermal stability, in which the onset temperature of the exothermic peak has been increased by 103 °C, and the thermal release value can be reduced as much as about 40% when the battery was charged to 4.8 V. Furthermore, the electrochemical performance, especially cycle stability under a high temperature, has also been enhanced for spinel-modified microsized crystalline grains. This work not only develops the microsized crystalline grains with good dispersion of lithium-rich layered oxides, confirming the advantages of these materials compared to spherical secondary agglomerates, but also reveals the method to improve their thermal stability by grain surface structure modification, opening the way to optimize the comprehensive performance of electrode materials for batteries.

Method for Synthesis of Zeolitic Imidazolate Framework-Derived LiCoO2/CNTs@AlF3 with Enhanced Lithium Storage Capacity

Metal-organic framework-derived lithium cobaltate nanoparticles were fabricated by annealing of the ZIF-67 precursor with Li₂CO₃ under air, followed by homogeneous AlF₃ coating and carbon nanotubes (CNTs) wrapping. The as-prepared AlF₃-coated LiCoO₂/CNTs electrode can act as a potential cathode for enhanced lithium storage at both room temperature and an elevated temperature of 50 °C.

Surface Li+/K+ Exchange toward Double-Gradient Modification of Layered Li-Rich Cathode Materials

Surface coating and lattice doping are widely used to enhance the interfacial and structural stabilities of Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (LNCM). In this paper, KF is used to modify LNCM for the first time. A Li⁺/K⁺ exchange in the Li slabs is realized via a high-temperature treatment. Consequently, subsurface K⁺ gradient doping and surface K_1-xLi_xF gradient coating are obtained simultaneously on LNCM. Such an Li⁺/K⁺ exchange mechanism and double-gradient modification are clarified by X-ray diffraction, energy-dispersive spectrometry line scans, and high-resolution transmission electron microscopy analyses. As a result, the optimal 0.5 wt % KF-modified LNCM material shows markedly alleviated voltage degradation (0.0031 V@1 cycle), improved cycling stability (88%@100 cycles@0.5 C), and rate capability (108 mA h g^-1@10 C), revealing large application potential in high-energy materials.

Revealing the Electrochemical Mechanism of Cationic/Anionic Redox on Li-Rich Layered Oxides via Controlling the Distribution of Primary Particle Size

Lithium-manganese-rich layered oxides have sparked intense interest on high-energy-density lithium-ion batteries because of their unique anionic redox. While making efforts to adjust the primary particle size for the improved electrochemical kinetics, current research is insufficient to explain how the anionic/cationic interplay governs the electrochemical behavior except for ion diffusion. Here, fully ordered Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ spheres of shortened primary particle size were synthesized via the coprecipitation method for use as cathodes. A high discharge capacity of 303.2 mA h g^-1 was achieved for the first cycle. Optimized nanostructures reduce the lithium ion diffusion length and increase electronic conductivity unsurprisingly, contributing to excellent electrochemical activity and rate capability. Furthermore, the decreased primary particle size accelerated the redox reactivity of cations and the reversibility of anionic redox on path dependence. This work clarifies the electrochemical mechanism of cationic/anionic redox of these Li-rich layered oxides and provides a new vision for a unique design of high-energy cathode materials with better application.

The Role of Zr Doping in Stabilizing Li[Ni0.6 Co0.2 Mn0.2 ]O2 as a Cathode Material for Lithium-Ion Batteries

Ni-rich layered LiNi_1-x-y Co_x Mn_y O₂ systems are the most promising cathode materials for high energy density Li-ion batteries (LIBs). However, Ni-rich cathode materials inevitably suffer from rapid capacity fading and poor rate capability owing to structural instability and unstable surface side reactions. Zr doping has proven to be an effective method to enhance the cycle and rate performances by stabilizing the structure and increasing the Li⁺ diffusion rate. Herein, effects of Zr-doping on the structural stability and Li⁺ diffusion kinetics are thoroughly investigated in LiNi_0.6 Co_0.2 Mn_0.2 O₂ (LNCM) cathode material using atomic-resolution scanning transmission electron microscopy imaging, XRD Rietveld refinement, and density functional theory calculations. Zr doping mitigates the degree of cation mixing, decreases the structural transformation, and facilitates Li⁺ diffusion resulting in improved cyclic performance and rate capability. Based on the obtained results, an atomistic model is proposed to explain the effects of Zr doping on the structural stability and Li⁺ diffusion kinetics in LNCM cathode materials.

Chemical, Structural, and Electronic Aspects of Formation and Degradation Behavior on Different Length Scales of Ni-Rich NCM and Li-Rich HE-NCM Cathode Materials in Li-Ion Batteries

In order to satisfy the energy demands of the electromobility market, both Ni-rich and Li-rich layered oxides of NCM type are receiving much attention as high-energy-density cathode materials for application in Li-ion batteries. However, due to different stability issues, their longevity is limited. During formation and continuous cycling, especially the electronic and crystal structure suffers from various changes, eventually leading to fatigue and mechanical degradation. In recent years, comprehensive battery research has been conducted at Karlsruhe Institute of Technology, mainly aiming at better understanding the primary degradation processes occurring in these layered transition metal oxides. The characteristic process of formation and mechanisms of fatigue are fundamentally characterized and the effect of chemical composition on cell chemistry, electrochemistry, and cycling stability is addressed on different length scales by use of state-of-the-art analytical techniques, ranging from "standard" characterization tools to combinations of advanced in situ and operando methods. Here, the results are presented and discussed within a broader scientific context.

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.

Aegis of Lithium-Rich Cathode Materials via Heterostructured LiAlF4 Coating for High-Performance Lithium-Ion Batteries

Lithium-rich oxides have been regarded as one of the most competitive cathode materials for next-generation lithium-ion batteries due to their high theoretical specific capacity and high discharge voltage. However, they are still far from being commercialized due to low rate capability and poor cycling stability. In this study, we propose a heterostructured LiAlF₄ coating strategy to overcome those obstacles. The as-developed lithium-rich cathode material shows outstanding performance including a high reversible capacity (246 mA h g^-1 at 0.1C), excellent rate capability (133 mA h g^-1 at 5C), and ultralong cycling stability (3000 cycles). Comparing with those of pristine and AlF₃-coated lithium-rich cathode materials, the enhanced performances can be attributed to the introduction of the lithium-ion-conductive nanolayer and the generation of nonbonding O ^n- species in the active material lattice, which enable rapid and effective lithium ion transport and diffusion. Our work provides a new strategy to develop high-performance lithium-rich cathode materials for high-energy-density lithium-ion batteries.

A New Class of Ternary Compound for Lithium-Ion Battery: from Composite to Solid Solution

Searching for high-performance cathode materials is a crucial task to develop advanced lithium-ion batteries (LIBs) with high-energy densities for electrical vehicles (EVs). As a promising lithium-rich material, Li₂MnO₃ delivers high capacity over 200 mAh g^-1 but suffers from poor structural stability and electronic conductivity. Replacing Mn⁴⁺ ions by relatively larger Sn⁴⁺ ions is regarded as a possible strategy to improve structural stability and thus cycling performance of Li₂MnO₃ material. However, large difference in ionic radii of Mn⁴⁺ and Sn⁴⁺ ions leads to phase separation of Li₂MnO₃ and Li₂SnO₃ during high-temperature synthesis. To prepare solid-solution phase of Li₂MnO₃-Li₂SnO₃, a buffer agent of Ru⁴⁺, whose ionic radius is in between that of Mn⁴⁺ and Sn⁴⁺ ions, is introduced to assist the formation of a single solid-solution phase. The results show that the Li₂RuO₃-Li₂MnO₃-Li₂SnO₃ ternary system evolves from mixed composite phases into a single solid-solution phase with increasing Ru content. Meanwhile, discharge capacity of this ternary system shows significantly increase at the transformation point which is ascribed to the improvement of Li⁺/e^- transportation kinetics and anionic redox chemistry for solid-solution phase. The role of Mn/Sn molar ratio of Li₂RuO₃-Li₂MnO₃-Li₂SnO₃ ternary system has also been studied. It is revealed that higher Sn content benefits cycling stability of the system because Sn⁴⁺ ions with larger sizes could partially block the migration of Mn⁴⁺ and Ru⁴⁺ from transition metal layer to Li layer, thus suppressing structural transformation of the system from layered-to-spinel phase. These findings may enable a new route for exploring ternary or even quaternary lithium-rich cathode materials for LIBs.

Novel MOF shell-derived surface modification of Li-rich layered oxide cathode for enhanced lithium storage

Li-rich layered oxide materials have attracted increasing attention because of their high specific capacity (>250 mAh g^-1). However, these materials typically suffer from poor cycling stability and low rate performance. Herein, we propose a facile and novel metal-organic-framework (MOF) shell-derived surface modification strategy to construct NiCo nanodots decorated (∼5 nm in diameter) carbon-confined Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ nanoparticles (LLO@C&NiCo). The MOF shell is firstly formed on the surface of as-prepared Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ nanoparticles via low-pressure vapor superassembly and then is in situ converted to the NiCo nanodots decorated carbon shell after subsequent controlled pyrolysis. The obtained LLO@C&NiCo cathode exhibits enhanced cycling and rate capability with a capacity retention of 95% after 100 cycles at 0.4 C and a high capacity of 159 mAh g^-1 at 5 C, respectively, compared with those of LLO (75% and 105 mAh g^-1). The electrochemical impedance spectroscopy and selected area electron diffraction analyses after cycling demonstrate that the thin C&NiCo shell can endow LLO with high electronic conductivity and structural stability, indicating the undesired formation of the spinel phase initiated from the particle surface is efficiently suppressed. Therefore, this presented strategy may open a new avenue on the design of high-performance electrode materials for energy storage.

Au-doped Li1.2Ni0.7Co0.1Mn0.2O2 electrospun nanofibers: synthesis and enhanced capacity retention performance for lithium-ion batteries

Au-doped Li_1.2Ni_0.7Co_0.1Mn_0.2O₂ nanofibers, which exhibit better electrochemical performances, were fabricated by controlling the cationic ratio of Au.

Insight into the capacity fading of layered lithium-rich oxides and its suppression via a film-forming electrolyte additive

The capacity fading of layered lithium-rich oxide (Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, LLO) cathodes greatly hinders their practical application in next generation lithium ion batteries. It has been demonstrated in this work that the slow capacity fading of a LLO/Li cell within 120 cycles is mainly caused by electrolyte oxidation and LLO phase transformation with Ni dissolution. After 120 cycles, the dissolution of Mn becomes worse than that of Ni, leading to structural destruction of the generated spinel phase structure of LLO and fast capacity fading. Tripropyl borate (TPB) is proposed as a film-forming electrolyte additive, which shows a great capability to enhance the cycling stability of LLO/Li, with a capacity retention improvement from 21% to 78% after 250 cycles at 0.5C. Electrochemical and physical characterization demonstrated that the TPB-derived SEI film shows great capability to suppress electrolyte oxidation and the structural destruction of the generated spinel phase of LLO.

The capacity fading of layered lithium-rich oxide (Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, LLO) cathodes greatly hinders their practical application in next generation lithium ion batteries.

Multi-Functional Surface Engineering for Li-Excess Layered Cathode Material Targeting Excellent Electrochemical and Thermal Safety Properties

The Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2 cathode material is modified by a Li4M5O12-like heterostructure and a BiOF surface layer. The interfacial heterostructure triggers the layered-to-Li4M5O12 transformation of the material which is different from the layered-to-LiMn2O4 transformation of the pristine Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. This Li4M5O12-like transformation helps the material to keep high working voltage, long cycle life and excellent rate capability. Mass spectrometry, in situ X-ray diffraction and transmission electron microscope show that the Li4M5O12-like phase prohibits oxygen release from the material bulk at elevated temperatures. In addition, the BiOF coating layer protects the material from harmful side reactions with the electrolyte. These advantages significantly improve the electrochemical performance of Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. The material shows a discharge capacity of 292 mAh g(-1) at 0.2 C with capacity retention of 92% after 100 cycles. Moreover, a high discharge capacity of 78 mAh g(-1) could be obtained at 25 C. The exothermic temperature of the fully charged electrode is elevated from 203 to 261 °C with 50% reduction of the total thermal release, highlighting excellent thermal safety of the material.

Synthetic methods and electrochemical applications for transition metal phosphide nanomaterials

Recent developments and challenges in transition metal phosphide nanomaterials, with a focus on synthetic methods and their electrochemical applications, have been stated carefully.

Considering Critical Factors of Li-rich Cathode and Si Anode Materials for Practical Li-ion Cell Applications

In order to keep pace with increasing energy demands for advanced electronic devices and to achieve commercialization of electric vehicles and energy-storage systems, improvements in high-energy battery technologies are required. Among the various types of batteries, lithium ion batteries (LIBs) are among the most well-developed and commercialized of energy-storage systems. LIBs with Si anodes and Li-rich cathodes are one of the most promising alternative electrode materials for next-generation, high-energy batteries. Si and Li-rich materials exhibit high reversible capacities of <2000 mAh g(-1) and >240 mAh g(-1) , respectively. However, both materials have intrinsic drawbacks and practical limitations that prevent them from being utilized directly as active materials in high-energy LIBs. Examples for Li-rich materials include phase distortion during cycling and side reactions caused by the electrolyte at the surface, and for Si, large volume changes during cycling and low conductivity are observed. Recent progress and important approaches adopted for overcoming and alleviating these drawbacks are described in this article. A perspective on these matters is suggested and the requirements for each material are delineated, in addition to introducing a full-cell prototype utilizing a Li-rich cathode and Si anode.

Tunable and robust phosphite-derived surface film to protect lithium-rich cathodes in lithium-ion batteries

A thin, uniform, and highly stable protective layer tailored using tris(trimethylsilyl) phosphite (TMSP) with a high tendency to donate electrons is formed on the Li-rich layered cathode, Li1.17Ni0.17Mn0.5Co0.17O2. This approach inhibits severe electrolyte decomposition at high operating voltages during cycling and dramatically improves the interfacial stability of the cathode. The TMSP additive in the LiPF6-based electrolyte is found to preferentially eliminate HF, which promotes the dissolution of metal ions from the cathode. Our investigation revealed that the TMSP-derived surface layer can overcome the significant capacity fading of the Li-rich cathode by structural instability ascribed to an irreversible phase transformation from layered to spinel-like structures. Moreover, the superior rate capability of the Li-rich cathode is achieved because the TMSP-originated surface layer allows facile charge transport at high C rates for the lithiation process.

Enhanced high rate performance of Li[Li0.17Ni0.2Co0.05Mn0.58−xAlx]O2−0.5x cathode material for lithium-ion batteries

Pristine LNCM and LNCMA as Li-rich cathode materials for lithium ion batteries were synthesized via a sol–gel route. The Al-substituted LNCM sample exhibits an enhanced high rate performance and superior cyclability.

Performance improvement of Li-rich layer-structured Li1.2Mn0.54Ni0.13Co0.13O2 by integration with spinel LiNi0.5Mn1.5O4

Spinel LiNi_0.5Mn_1.5O₄ integration helps to suppress such degradation and that the integrated LiNi_0.5Mn_1.5O₄ “absorbs” the cations that would otherwise form a LiMn₂O₄-like phase.

Enhanced Li storage performance of LiNi(0.5)Mn(1.5)O(4)-coated 0.4Li(2)MnO(3)·0.6LiNi(1/3)Co(1/3)Mn(1/3)O(2) cathode materials for li-ion batteries

In this study, Li-rich cathode, 0.4Li2MnO3·0.6LiNi1/3Co1/3Mn1/3O2 was synthesized by a resorcinol formaldehyde assisted sol-gel method for the first time. Then, the surface of the as-prepared Li-rich cathode was modified with different amounts of LiNi0.5Mn1.5O4 (5, 10, and 20 wt %) through a simple dip-dry approach. The structural and electrochemical characterizations revealed that the spinel LiNi0.5Mn1.5O4 coating not only can prevent electrolytes from eroding the Li-rich core but also can facilitate fast lithium ion transportation. As a result, the 20 wt % coated sample delivered an initial discharge capacity of 298.6 mAh g(-1) with a Coulombic efficiency of 84.8%, compared to 281.1 mAh g(-1) and 70.2%, respectively, for the bare sample. Particularly, the coated sample demonstrates a Li storage capacity of 170.7 mAh g(-1) and capacity retention of 94.4% after 100 cycles at a high rate of 5 C (1250 mA g(-1)), showing a prospect for practical lithium battery applications. More significantly, the synthetic method proposed in this work is facile and low-cost and possibly could be adopted for large-scale production of surface-modified cathode materials.

Recent progress in Li-rich layered oxides as cathode materials for Li-ion batteries

This review systematically summarized Li-rich layered oxides and states the strategies to enhance such materials when used in Li-ion batteries.