Ultrathin-Y2O3-coated LiNi0.8Co0.1Mn0.1O2 as cathode materials for Li-ion batteries: Synthesis,performance and reversibility

Nickel-rich lithium material LiNi_xCo_yMn_1-x-yO₂(x > 0.6) becomes a new research focus for the next-generation lithium-ion batteries owing to their high operating voltage and high reversible capacity. However, the rate performance and cycling stability of these cathode materials are not satisfactory. Inspired by the characteristics of Y₂O₃ production, a new cathode material with ultrathin-Y₂O₃ coating was introduced to improve the electrochemical performance and storage properties of LiNi_0.8Co_0.1Mn_0.1O₂ for the first time. XRD, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS) and XPS were used to mirror the crystal and surface of LiNi_0.8Co_0.1Mn_0.1O₂ particles, results i that a uniform interface formed on as-prepared material. The impacts on the electrochemical properties with or without Y₂O₃ coating are discussed in detail. Notably, galvanostatic discharge-charge tests appear that Y₂O_3-coated sample especially 3% coating displayed a better capacity retention rate of 91.45% after 100 cycles than the bare one of 85.07%.     

Effect of ZnO modification on the performance of LiNi0.5Co0.25Mn0.25O2 cathode material

ZnO was coated on LiNi_0.5Co_0.25Mn_0.25O₂ cathode (positive electrode) material for lithium ion battery via sol–gel method to improve the performance of LiNi_0.5Co_0.25Mn_0.25O₂. The X-ray diffraction (XRD) results indicated that the lattice structure of LiNi_0.5Co_0.25Mn_0.25O₂ was not changed distinctly after surface coating and part of Zn²⁺ might dope into the lattice of the material. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) proved that ZnO existed on the surface of LiNi_0.5Co_0.25Mn_0.25O₂. Charge and discharge tests showed that the cycle performance and rate capability were improved by ZnO coating, however, the initial capacity decreased dramatically with increasing the amount of ZnO. Differential scanning calorimetry (DSC) results showed that thermal stability of the materials was improved. The XPS spectra after charge–discharge cycles showed that ZnO coated on LiNi_0.5Co_0.25Mn_0.25O₂ promoted the decomposition of the electrolyte at the early stage of charge–discharge cycle to form more stable SEI layer, and it also can scavenge the free acidic HF species from the electrolyte. The electrochemical impedance spectroscopy (EIS) results showed ZnO coating could suppress the augment of charge transfer resistance upon cycling.     

A simple and effective method to synthesize layered LiNi0.8Co0.1Mn0.1O2 cathode materials for lithium ion battery

Nanocrystalline materials of Ni_0.8Co_0.1Mn_0.1(OH)₂ are successfully synthesized by fast co-precipitation method. The crystalline structure and morphology of the precursors and LiNi_0.8Co_0.1Mn_0.1O₂ materials are characterized by XRD, SEM and Rietveld refinement analyses. It is found that the nanocrystalline phase and low crystallinity of Ni_0.8Co_0.1Mn_0.1(OH)₂ could help achieve its uniform mixing with lithium source, and further attribute to highly ordered layered LiNi_0.8Co_0.1Mn_0.1O₂ with low cation mixing degree. Electrochemical studies confirm that the LiNi_0.8Co_0.1Mn_0.1O₂ exhibits a good electrochemical property with initial discharge specific capacity of 192.4 mAh g^− 1 at a current density of 18 mA g^− 1, and the capacity retention after 40 cycles is 91.56%. This method is a simple and effective method to synthesize cathode material.     

Effects of fast lithium-ion conductive coating layer on the nickel rich layered oxide cathode material

In this study, a series of ultra-thin fast ionic conductor (Li₃PO₄, Li₂ZrO₃, Li₄Ti₅O₁₂) layers were successfully deposited on the surface of LiNi_0.8Mn_0.1Co_0.1O₂. The effects of three typical ionic conductors were systemically compared for the first time. The influences of coating layers on the microstructures and electrochemical properties of the cathode material were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron spectroscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and electrochemical tests. Analysis indicated that the coating layers existed on the surface of the cathode material and did not cause any noticeable change in the crystal structure. Electrochemical tests proved that all the surface-modified samples exhibited excellent cycling performance and rate capability compared to the bared sample. The inferior electrochemical performances of the bared sample were related to the formation of thick solid-electrolyte inter-facial layer during cycling, while the coating layer could minimize the side-reactions between the cathode and electrolyte during cycling. The electrons transfer and Li⁺ diffusion coefficient of the Li₃PO₄ coated sample were superior to that of Li₂ZrO₃ and Li₄Ti₅O₁₂ coated samples, which were beneficial to the rate capability of LiNi_0.8Mn_0.1Co_0.1O₂.     

Ultrathin CeO2 coating for improved cycling and rate performance of Ni-rich layered LiNi0.7Co0.2Mn0.1O2 cathode materials

In this study, we have successfully coated the CeO₂ nanoparticles (CeONPs) layer onto the surface of the Ni-rich layered LiNi_0.7Co_0.2Mn_0.1O₂ cathode materials by a wet chemical method, which can effectively improve the structural stability of electrode. The X-ray powder diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) are used to determine the structure, morphology, elemental composition and electronic state of pristine and surface modified LiNi_0.7Co_0.2Mn_0.1O₂. The electrochemical testing indicates that the 0.3?mol% CeO₂-coated LiNi_0.7Co_0.2Mn_0.1O₂ demonstrates excellent cycling capability and rate performance, the discharge specific capacity is 161.7?mA?h?g^?1 with the capacity retention of 86.42% after 100 cycles at a current rate of 0.5?C, compared to 135.7?mA?h?g^?1 and 70.64% for bare LiNi_0.7Co_0.2Mn_0.1O₂, respectively. Even at 5?C, the discharge specific capacity is still up to 137.1?mA?h?g^?1 with the capacity retention of 69.0%, while the NCM only delivers 95.5?mA?h?g^?1 with the capacity retention of 46.6%. The outstanding electrochemical performance is assigned to the excellent oxidation capacity of CeO₂ which can oxidize Ni²⁺ to Ni³⁺ and Mn³⁺ to Mn⁴⁺ with the result that suppress the occurrence of Li⁺/Ni²⁺ mixing and phase transmission. Furthermore, CeO₂ coating layer can protect the structure to avoid the occurrence of side reaction. The CeO₂-coated composite with enhanced structural stability, cycling capability and rate performance is a promising cathode material candidate for lithium-ion battery.     

WO3 membrane-encapsulated layered LiNi0.6Co0.2Mn0.2O2 cathode material for advanced Li-ion batteries

Despite Nickel-rich materials have all the advantages of high capacity, long cycle life and low cost, there is still a disadvantage that the capacity decreases rapidly as the number of cycles increases. In order to solve this problem, WO₃ was uniformly coated on the surface of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials by wet coating, and its cycling performance was greatly improved with the higher capacity. The coated materials were analyzed by X-ray diffraction(XRD), Scanning electron microscope (SEM), high resolution Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS). The results showed that the coating thickness was around 3.15?nm, and some tungsten ions were doped into the lattice of the near surface area of the LiNi_0.6Co_0.2Mn_0.2O₂ material. In addition, the results of charge-discharge test showed that 1?wt%WO₃ coating LiNi_0.6Co_0.2Mn_0.2O₂ had the best performance, and delivered a discharge capacity of 140 mAh g^?1 (the capacity retention rate is 84.8%) in the potential interval of 2.8–4.3?V at 1?C (1?C?=?165?mA?g^?1) after 200 cycles, while the bare cathode material only delivered a discharge capacity of 120 mAhg^?1 (the capacity retention rate is 75%). The phenomenon indicates that the WO₃ coating plays a role in inhibiting the harmful side reactions between the cathode material and the electrolyte, improving the electrochemical and structure stability of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials.     

Synthesis and characterization of mono-dispersion LiNi0.8Co0.1Mn0.1O2 micrometer particles for lithium-ion batteries

LiNi_0.8Co_0.1Mn_0.1O₂ cathode material for lithium-ion battery exhibits high capacity, but it suffers from interfacial side reactions and structural/thermodynamic instability, which leads to capacity reduction and safety problems. Cubic brick (Ni_0.8Co_0.1Mn_0.1)C₂O₄·2H₂O particles with micron size are synthesized by co-precipitation method. The oxalic precursor is sintered with lithium hydroxide to obtain cubic mono-dispersion LiNi_0.8Co_0.1Mn_0.1O₂ micrometer particles. Structural stability, cycling performance, rate capability and compacting density of the cubic mono-dispersion material are investigated. Conventional spherical and irregular mono-dispersion LiNi_0.8Co_0.1Mn_0.1O₂ are also prepared for comparison. The results reveal that the cubic mono-dispersion LiNi_0.8Co_0.1Mn_0.1O₂ dramatically enhances the structural stability and cycling performance at a little cost of capacity and rate capability.     

Modification of LiNi0.5Co0.2Mn0.3O2 with a NaAlO2 coating produces a cathode with increased long-term cycling performance at a high voltage cutoff

A long-lived cycling property is an important factor for the extensive use of the lithium-ion batteries. In this study, a NaAlO₂ layer was initially coated on the LiNi_0.5Co_0.2Mn_0.3O₂ surface. Electrochemical tests indicate that the coated surface achieves better cycling stability and a higher capacity at 25 °C. In addition, the 1 wt % NaAlO₂-coated sample exhibits the best performance, and it also exhibits a discharge specific capacity of 189.6 mAh∙g⁻¹ at 0.1C in the first cycle. After 800 cycles at 1C, the capacity retention of the 1 wt % NaAlO₂-coated sample is approximately 73.31%, a value that is 21.26% higher than the pristine sample. The electrochemical impedance spectroscopy (EIS) analysis reveals a decrease in the LiNi_0.5Co_0.2Mn_0.3O₂ charge transfer impedance and a significant increase in lithium ion diffusion after the application of the NaAlO₂ coating. The high ion diffusion coefficient and low charge transfer impedance are conducive to the better rate performance of NaAlO₂-coated LiNi_0.5Co_0.2Mn_0.3O₂.     

Nano SIMS characterization of boron- and aluminum-coated LiNi1/3Co1/3Mn1/3O2 cathode materials for lithium secondary ion batteries

The LiNi_1/3Co_1/3Mn_1/3O₂ powders required for the present study, obtained by coprecipitation method has been surface coated with boron and aluminum. The morphology and crystal structure of powders have been characterized using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy techniques. The elemental distribution of the coated samples analyzed by transmission electron microscopy images and nano secondary ion mass spectrometry indicates a thin uniform layer of [B, Al]₂O₃ on the surface of spherical LiNi_1/3Co_1/3Mn_1/3O₂. The surface-modified LiNi_1/3Co_1/3Mn_1/3O₂ has been explored as a cathode material for lithium secondary ion battery applications. The electrochemical charge–discharge results reveal that the capacity retention rate of coated LiNi_1/3Co_1/3Mn_1/3O₂ after 40 cycles at 1 C rate maintains 93% of the initial discharge capacity while the rate of bare LiNi_1/3Co_1/3Mn_1/3O₂ maintains only 88%. It is noticed that the small amounts of boron and aluminum coatings on the surface of LiNi_1/3Co_1/3Mn_1/3O₂ can significantly improve the electrochemical properties of electrode materials because of the suppression of reaction between the cathode and the electrolytes.     

Properties of LiNi<Subscript>0.8</Subscript>Co<Subscript>0.1</Subscript>Mn<Subscript>0.1</Subscript>O<Subscript>2</Subscript> as a high energy cathode material for lithium-ion batteries

Nickel-rich layered materials are prospective cathode materials for use in lithium-ion batteries due to their higher capacity and lower cost relative to LiCoO₂. In this work, spherical Ni_0.8Co_0.1Mn_0.1(OH)₂ precursors are successfully synthesized through a co-precipitation method. The synthetic conditions of the precursors - including the pH, stirring speed, molar ratio of NH₄OH to transition metals and reaction temperature - are investigated in detail, and their variations have significant effects on the morphology, microstructure and tap-density of the prepared Ni_0.8Co_0.1Mn_0.1 (OH)₂ precursors. LiNi_0.8Co_0.1Mn_0.1O₂ is then prepared from these precursors through a reaction with 5% excess LiOH· H₂O at various temperatures. The crystal structure, morphology and electrochemical properties of the Ni_0.8Co_0.1Mn_0.1 (OH)₂ precursors and LiNi_0.8Co_0.1Mn_0.1O₂ were investigated. In the voltage range from 3.0 to 4.3 V, LiNi_0.8Co_0.1Mn_0.1O₂ exhibits an initial discharge capacity of 193.0mAh g^-1 at a 0.1 C-rate. The cathode delivers an initial capacity of 170.4 mAh g^-1 at a 1 C-rate, and it retains 90.4% of its capacity after 100 cycles.     

CeF3-modified LiNi1/3Co1/3Mn1/3O2 cathode material for high-voltage Li-ion batteries

A facile chemical deposition method has been adopted to prepare cerium fluoride (CeF₃) surface modified LiNi_1/3Co_1/3Mn_1/3O₂ as cathode material for lithium-ion batteries. Structure analyses reveal that the surface of LiNi_1/3Co_1/3Mn_1/3O₂ particles is uniformly coated by CeF₃. Electrochemical tests indicate that the optimal CeF₃ content is 1 wt%. The 1 wt% CeF₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ can deliver a discharge capacity of 107.1 mA h g⁻¹ even at 5 C rate, while the pristine does only 57.3 mA h g⁻¹. Compared to the pristine, the 1 wt% CeF₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ exhibits the greatly enhanced capacity and cycling stability in the voltage range of 3.0–4.5 V, which suggests that the CeF₃ coating has the positive effect on the high-voltage application of LiNi_1/3Co_1/3Mn_1/3O₂. According to the analyses from electrochemical impedance spectra, enhanced electrochemical performance is mainly because the stable CeF₃ coating layer can prevent the HF-containing electrolyte from continuously attacking the LiNi_1/3Co_1/3Mn_1/3O₂ cathode and retard the passivating layer growth on the cathode.     

Enhanced electrochemical performance of LiNi0.8Co0.1Mn0.1O2 via titanium and boron co-doping

Titanium and boron are simultaneously introduced into LiNi_0.8Co_0.1Mn_0.1O₂ to improve the structural stability and electrochemical performance of the material. X-ray diffraction studies reveal that Ti⁴⁺ ion replaces Li⁺ ion and reduces the cation mixing; B³⁺ ion enters the tetrahedron of the transition metal layers and enlarges the distance of the [LiO₆] layers. The co-doped sample has spherical secondary particles with elongated and enlarged primary particles, in which Ti and B elements distribute uniformly. Electrochemical studies reveal the co-doped sample has improved rate performance (183.1 mAh·g^-1 at 1 C and 155.5 mAh·g^-1 at 10 C) and cycle stability (capacity retention of 94.7% after 100 cycles at 1 C). EIS and CV disclose that Ti and B co-doping reduces charge transfer impedance and suppresses phase change of LiNi_0.8Co_0.1Mn_0.1O_2.     

Effects of surface modification on the cycling stability of LiNi0.8Co0.2O2 electrodes by CeO2 coating

A high-performance LiNi_0.8Co_0.2O₂ cathode was successfully fabricated by a sol-gel coating of CeO₂ to the surface of the LiNi_0.8Co_0.2O₂ powder and subsequent heat treatment at 700 °C for 5 h. The surface-modified and pristine LiNi_0.8Co_0.2O₂ powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), slow rate cyclic voltammogram (CV), and differential scanning calorimetry (DSC). Unlike pristine LiNi_0.8Co_0.2O₂, the CeO₂-coated LiNi_0.8Co_0.2O₂ cathode exhibits no decrease in its original specific capacity of 182 mAh/g (versus lithium metal) and excellent capacity retention (95% of its initial capacity) between 4.5 and 2.8 V after 55 cycles. The results indicate that the surface treatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium ion batteries.     

LiNi0.1Mn0.1Co0.8O2 electrode material: Structural changes upon lithium electrochemical extraction

We reported here on the synthesis, the crystal structure and the study of the structural changes during the electrochemical cycling of layered LiNi_0.1Mn_0.1Co_0.8O₂ positive electrode material. Rietveld refinement analysis shows that this material exhibits almost an ideal α-NaFeO₂ structure with practically no lithium-nickel disorder. The SQUID measurements confirm this structural result and evidenced that this material consists of Ni²⁺, Mn⁴⁺ and Co³⁺ ions.Unlike LiNiO₂ and LiCoO₂ conventional electrode materials, there was no structural modification upon lithium removal in the whole 0.42 ≤ x ≤1.0 studied composition range. The peaks revealed in the incremental capacity curve were attributed to the successive oxidation of Ni²⁺ and Co³⁺ while Mn⁴⁺ remains electrochemically inactive.     

Improving the electrochemical performance of Ni-rich cathode materials using a fast ion conductor coating of Li2O–B2O3–LiBr

The high-Ni layered metal oxide, LiNi_0.8Co_0.1Mn_0.1O₂ (LNCM811), has received widespread attention in the energy field because of its high specific capacity, but its large-scale applications are hindered due to severe capacity fading. Herein, a uniform and thin Li₂O–B₂O₃–LiBr-glass (LBBrO-glass) coating was deposited on LNCM811 by a liquid-phase coating and thermal treatment method. The experimental results suggested that the LBBrO-glass coating acted as a protective layer that inhibited transition metal dissolution and side reactions, which helped improve the electrochemical properties of LNCM811. Remarkably, after 200 cycles, the 2 wt% coating (LBBrO@LNCM-2) delivered a superior capacity retention of 88.9%, while only 71.8% was obtained for the pristine material (LNCM811). The discharge capacity of LBBrO@LNCM-2 was 163.5 mAh g^?1 at 5C, while it was only 139 mAh g^?1 for the pristine material.     

Electrochemical performance of all-solid-state lithium secondary batteries with Li-Ni-Co-Mn oxide positive electrodes

LiNi_1/3Co_1/3Mn_1/3O₂ was applied as a promising material to the all-solid-state lithium cells using the 80Li₂S·19P₂S₅·1P₂O₅ (mol%) solid electrolyte. The cell showed the first discharge capacity of 115 mAh g⁻¹ at the current density of 0.064 mA cm⁻² and retained the reversible capacity of 110 mAh g⁻¹ after 10 cycles. The interfacial resistance was observed in the impedance spectrum of the all-solid-state cell charged to 4.4 V (vs. Li) and the transition metal elements were detected on the solid electrolyte in the vicinity of LiNi_1/3Co_1/3Mn_1/3O₂ by the TEM observations with EDX analyses. The electrochemical performance was improved by the coating of LiNi_1/3Co_1/3Mn_1/3O₂ particles with Li₄Ti₅O₁₂ film. The interfacial resistance was decreased and the discharge capacity was increased from 63 to 83 mAh g⁻¹ at 1.3 mA cm⁻² by the coating. The electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ was compared with that of LiCoO₂, LiMn₂O₄ and LiNiO₂ in the all-solid-state cells. The rate capability of LiNi_1/3Co_1/3Mn_1/3O₂ was lower than that of LiCoO₂. However, the reversible capacity of LiNi_1/3Co_1/3Mn_1/3O₂ at 0.064 mA cm⁻² was larger than that of LiCoO₂, LiMn₂O₄ and LiNiO₂.     

Preparation of LiNi1/3Co1/3Mn1/3O2/polytriphenylamine cathode composites with enhanced electrochemical performances towards reversible lithium storage

A series of LiNi_1/3Co_1/3Mn_1/3O₂/polytriphenylamine composites were successfully synthesized by ultrasound dispersion method. LiNi_1/3Co_1/3Mn_1/3O₂/polytriphenylamine (5.0?wt%) composite with small and homogeneous particle size exhibited excellent electrochemical performance, which delivered an initial discharge capacity of 223.7?mAh g^?1 with a capacity retention of 84.39% after 100 cycles in the voltage range of 2.5–4.5?V and at a current density of 0.2C. Moreover, an excellent specific discharge capacity of 127.3?mAh g^?1 at a current density 5C indicates a superior rate performance of the LiNi_1/3Co_1/3Mn_1/3O₂/polytriphenylamine (5.0?wt%) composite. The good electrochemical performances of the composite can be attributed to the introduction of polytriphenylamine, which increased electrical conductivity, decreased charge transfer resistance and increased Li⁺ ion diffusion ability. These noteworthy results demonstrated that LiNi_1/3Co_1/3Mn_1/3O₂/polytriphenylamine composites might be potential cathode materials for lithium ion batteries.     

Realization of a high voltage Ni rich layer LiNi0.5Co0.2Mn0.3O2 single crystalline cathode for LIBs by surface modification

Single crystalline ternary cathode material LiNi_0.5Co_0.2Mn_0.3O₂(NCM523) can operate at extremely high voltages and could offer exceptional energy density. The single crystal morphology is less easy to form the cracks and could express better structure stability compared to the polycrystalline counterpart. However, irreversible parasitic side reactions in the interface during cycling may lead to rapid electrochemical degradations. Herein, a simple chemical wet method that modifies the single-crystal NCM523 particles with Al₂O₃ coating is proposed. The coating layer can effectively suppress the phase transformation and irreversible phase transition on the NCM surface during cycling. Furthermore, the cladding layer can prevent the erosion of by-products such as HF. As a result, the Al₂O₃ modified NCM523 delivers a high specific capacity of 192.5mAh g^?1, excellent cycling stability and rate capability. The capacity retention was 91.7% after 50 cycles even at ultra-high cut-off voltage of 4.7 V. This surface engineering strategy paves the way to promote the development of small size single crystal NCM523 materials for next generation LIBs.     

Effects of Co3(PO4)2 coatings on LiNi0.8Co0.16Al0.04O2 cathodes during application of high current

The electrochemical properties of bare and Co₃(PO₄)₂-coated LiNi_0.8Co_0.16Al_0.04O₂ electrodes after high current damage testing were characterized. Damage was induced by cycling with a high current density of 600 m Ag⁻¹. Co₃(PO₄)₂-coated LiNi_0.8Co_0.16Al_0.04O₂ electrodes exhibit lower capacity loss and better charge retention than bare LiNi_0.8Co_0.16Al_0.04O₂ electrodes after damage testing. The discharge capacity reduction of bare and Co₃(PO₄)₂-coated electrodes after damage testing were ∼27 and 15%, respectively. The impedance of cells containing bare electrodes remarkably increased after high current cycling, which may be induced by damage to the electrode surface. However, damage was successfully suppressed by the Co₃(PO₄)₂ coating. Bare LiNi_0.8Co_0.16Al_0.04O₂ electrodes developed large amounts of cracks and other extended defects after high current cycling. In contrast, Co₃(PO₄)₂-coated electrodes maintained stable features after high current cycling, indicating the coating layer effectively protected the surface of the LiNi_0.8Co_0.16Al_0.04O₂ powder.     

Structure and electrochemical characterization of LiNi<Subscript>0.3</Subscript>Co<Subscript>0.3</Subscript>Mn<Subscript>0.3</Subscript>Fe<Subscript>0.1</Subscript>O<Subscript>2</Subscript> cathode for lithium secondary battery

A lithium insertion material having the composition LiNi_0.3Co_0.3Mn_0.3Fe_0.1O₂ was synthesized by simple sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietvelt analysis of the XRD patterns shows that this compound can be classified as α-NaFeO₂ structure type (R3m; a=2.8689(5) Å and 14.296(5) Å in hexagonal setting). Rietvelt fitting shows that a relatively large amount of Fe and Ni ion occupy the Li layer (3a site) and a relatively large amount of Li occupies the transition metal layer (3b site). LiNi_0.3Co_0.3Mn_0.3Fe_0.1O₂ when cycled in the voltage range 4.3–2.8 V gives an initial discharge capacity of 120 mAh/g, and stable cycling performance. LiNi_0.3Co_0.3Mn_0.3Fe_0.1O₂ in the voltage range 2.8–4.5 V has a discharge capacity of 140 mAh/g, and exhibits a significant loss in capacity during cycling. Ex-situ XRD measurements were performed to study the structure changes of the samples after cycling between 2.8–4.3 V and 2.8–4.5 V for 20 cycles. The XRD and electrochemical results suggested that cation mixing in this layered structure oxide could be causing degradation of the cell capacity.