Mitigating storage-induced degradation of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode material by surface tuning with phosphate

The Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂ layered oxide (NCM811) is attracting considerable attention as a high-capacity cathode material for rechargeable Li-ion batteries. However, due to its inherent structural/chemical/electrochemical instability, NCM811 with high Ni content suffers from significant performance degradation upon storage even in ambient atmospheres as well as during charge–discharge cycling. Herein, we demonstrate a simple but effective surface-tuning approach to mitigate storage-induced degradation of NCM811, which is based on the conversion of undesirable Li residues to a protective Li₃PO₄ nanolayer via phosphate treatment. The accelerated storage stability test shows that phosphate-modified NCM811 exhibits remarkably improved electrochemical performance (capacity, cycle life, and rate capability) over the pristine one after being stored under harsh environmental conditions. A combined analytical study indicates that surface tuning through phosphate treatment enhances the storage stability of NCM811 by eliminating impurity-forming Li residues and producing a Li₃PO₄ nanolayer that inhibits parasitic reactions at the electrode–electrolyte interface. Furthermore, Li₃PO₄ provides an effective barrier to H₂O and CO₂ infiltration into the particle agglomerates, thereby suppressing the loss of particle integrity.     

Improvement of electrochemical and thermal properties of Li[Ni0.8Co0.1Mn0.1]O2 positive electrode materials by multiple metal (Al, Mg) substitution

Al and/or Mg-substituted Li[Ni_0.8Co_0.1Mn_0.1−x−yAl_xMg_y]O₂ were prepared by a co-precipitation method and characterized by X-ray diffraction with Rietveld refinement, thermogravimetric analysis, differential scanning calorimetry (DSC), and electrochemical measurements. The Rietveld refinement results show that cation mixing of Al and/or Mg-substituted Li[Ni_0.8Co_0.1Mn_0.1−x−yAl_xMg_y]O₂ was reduced with increased doping amounts of Al and Mg. The Al and/or Mg substitution in Li[Ni_0.8Co_0.1Mn_0.1]O₂ also resulted in improved electrochemical cycling behavior, structural stability, and thermal stability compared to pristine Li[Ni_0.8Co_0.1Mn_0.1]O₂. The improvements of electrochemical and thermal properties resulted from the stabilized host structure by Al and/or Mg incorporation into Li[Ni_0.8Co_0.1Mn_0.1]O₂.     

High-voltage performance of concentration-gradient Li[Ni0.67Co0.15Mn0.18]O2 cathode material for lithium-ion batteries

A novel Li[Ni_0.67Co_0.15Mn_0.18]O₂ cathode material encapsulated completely within a concentration-gradient shell was successfully synthesized via co-precipitation. The Li[Ni_0.67Co_0.15Mn_0.18]O₂ has a core of Li[Ni_0.8Co_0.15Mn_0.05]O₂ that is rich in Ni, a concentration-gradient shell having decreasing Ni concentration and increasing Mn concentration toward the particle surface, and a stable outer-layer of Li[Ni_0.57Co_0.15Mn_0.28]O₂. The electrochemical and thermal properties of the material were investigated and compared to those of the core Li[Ni_0.8Co_0.15Mn_0.05]O₂ material alone. The discharge capacity of the concentration-gradient Li[Ni_0.67Co_0.15Mn_0.18]O₂ electrode increased with increasing upper cutoff voltage to 4.5 V, and cells with this cathode material delivered a very high capacity, 213 mAh/g, with excellent cycling stability even at 55 °C. The enhanced thermal and lithium intercalation stability of the Li[Ni_0.67Co_0.15Mn_0.18]O₂ was attributed to the gradual increase in tetravalent Mn concentration and decrease in Ni concentration in the concentration-gradient shell layer.     

Recent progress in coatings and methods of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials: A short review

LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) is a typical nickel (Ni)-rich ternary cathode material with several advantages, such as high specific capacity, low-cost, and environmentally friendly, making it a good candidate for use in lithium-ion batteries. However, its Ni content is as high as 80%; therefore, several new problems have emerged with gradually increasing applications. In this review, Li–Ni disorder and corresponding modification methods are first briefly reviewed, and then the origin of complex surface defect, which has a crippling effect on diffusion processes of Li⁺ at electrolyte/cathode interface, is discussed in detail. Analyses showed the importance of selecting appropriate surface modification material/technique for enhancing electrochemical properties. Therefore, popular surface coating materials and methods including metal oxides, fluorides, phosphates, fast ion conductors, and other compounds/elements used for the development of NCM811 are subjected to extensive and thorough research. Finally, several new perspectives and insights related to stability and safety at high voltages and temperatures, and the optimization of production process are also proposed.     

Synthetic optimization of spherical Li[Ni1/3Mn1/3Co1/3]O2 prepared by a carbonate co-precipitation method

A carbonate co-precipitation method was employed to prepare spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode material. The precursor, [Ni_1/3Co_1/3Mn_1/3]CO₃, was prepared using ammonia as chelating agent under CO₂ atmosphere. The spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ was prepared by mixing the precalcined [Ni_1/3Co_1/3Mn_1/3]CO₃ with LiOH followed by high temperature calcination. The preparation conditions such as ammonia concentration, co-precipitation temperature, calcination temperature and Li/[Ni_1/3Co_1/3Mn_1/3] ratio were varied to optimize the physical and electrochemical properties of the prepared Li[Ni_1/3Co_1/3Mn_1/3]O₂. The structural, morphological, and electrochemical properties of the prepared LiNi_1/3Co_1/3Mn_1/3O₂ were characterized by XRD, SEM, and galvanostatic charge-discharge cycling. The optimized material has a spherical particle shape and a well ordered layered structure, and it also has an initial discharge capacity of 162.7 mAh g^− 1 in a voltage range of 2.8-4.3 V and a capacity retention of 94.8% after a hundred cycles. The optimized ammonia concentration, co-precipitation temperature, calcination temperature, and Li/[Ni_1/3Co_1/3Mn_1/3] ratio are 0.3 mol L^− 1, 60 °C, 850 °C, and 1.10, respectively.     

Synthesis and improved electrochemical performance of Al (OH)3-coated Li[Ni1/3Mn1/3Co1/3]O2 cathode materials at elevated temperature

Spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ powders were synthesized from LiOH·H₂O and coprecipitated spherical metal hydroxide, (Ni_1/3Mn_1/3Co_1/3)(OH)₂ and coated with Al(OH)₃. The Al(OH)₃-coated Li[Ni_1/3Co_1/3Mn_1/3]O₂ showed a capacity retention of 80% at 320 mA g⁻¹ (2 C-rate) based on 20 mA g⁻¹ (0.1 C-rate), while the pristine Li[Ni_1/3Co_1/3Mn_1/3]O₂ delivered only 45% at the same current density. Also, unlike pristine Li[Ni_1/3Co_1/3Mn_1/3]O₂, the Al(OH)₃-coated Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode exhibits excellent rate capability and good thermal stability.     

Enhancing high-potential stability of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode with PrF3 coating

It is still a huge challenge to improve the safety and stability of Ni-rich (LiNi_0.8Co_0.1Mn_0.1O₂) cathode materials at elevated potential. Herein, the PrF₃ layer is employed to protect LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) via a simple wet chemical process. It was confirmed by XRD, HR-SEM, TEM, EDS, and XPS tests that PrF₃ is evenly covered throughout the surface of NCM811 without affecting the particle size and surface morphology. In particular, 1 wt% PrF₃ coated NCM811 exhibits excellent stability and rate capability with the capacity retention of 86.3% after 100 cycles at 1 C under a cut-off potential of 4.3 V, while the retention of pristine one is only 73.8%. Moreover, the capacity retention of 1 wt% PrF₃ coated samples enhances from 74.5% to 88.5% after 50 cycles at 1 C under higher cut-off voltage of 4.6 V. The superior performance for coated samples can be attributed to the fact that PrF₃ can effectively isolate the active material and the electrolyte from HF corrosion, and at the same time, reduce the generation of micro-cracks on the surface during prolonged cycles. Furthermore, as a physical barrier, PrF₃ alleviates the dissolution of transition metals in the electrolyte largely. These results suggest that the stability of NCM811 can be greatly upgraded at high voltage by PrF₃ coating.     

LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 and chlorine-rich argyrodite enabling high-performance all-solid-state lithium batteries at suitable stack pressure

All-solid-state lithium batteries (ASSLBs), which are consisted of Li_5.5PS_4.5Cl_1.5 electrolyte, metal lithium anode and LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811) cathode, are speculated as a promising next generation energy storage system. However, the unstable oxide cathode/sulfide-based electrolyte interface and the dendrite formation in sulfide electrolyte using the lithium metal anode hinder severely commercialization of the ASSLBs. In this work, the dendrite formation in sulfide electrolyte is investigated in lithium symmetric cell by varying the stack pressure (3, 6, 12, 24 MPa) during uniaxial pressing, and uniformly nanosized LiAlO₂ buffer layer was carefully coated on NCM811 electrode (LiAlO₂@NCM811) to improve the cathode/electrolyte interface stability. The result shows that lithium symmetrical cell has a steady voltage evolution over 400 h under 6 MPa stacking pressure, and the assembled LiAlO₂@NCM811/Li_5.5PS_4.5Cl_1.5/Li battery under the stack pressure of 6 MPa exhibits large initial discharge specific capacity and excellent cycling stability at 0.05 C and 25 °C. The feasibility of using the lithium metal anode in all-solid-state batteries (ASSBs) under suitable stack pressure combined with uniformly nanosized LiAlO₂ buffer layer coated on NCM811 electrode supply a facile and effective measures for constructing ASSLBs with high energy density and high safety.     

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.     

Synthesis and electrochemical properties of Li[Li0.07Ni0.1Co0.6Mn0.23]O2 as a possible cathode material for lithium-ion batteries

The layered Li[Li_0.07Ni_0.1Co_0.6Mn_0.23]O₂ materials were synthesized by sol-gel method with glycine or citric acid as chelating agent. The prepared materials were characterized by means of XRD, SEM and Raman spectroscopy. Li/Li[Li_0.07Ni_0.1Co_0.6Mn_0.23]O₂ cells were assembled and subjected to charge-discharge studies at different C rates, viz 0.2, 1, 2 and 4 C. Although the samples showed less discharge capacity at 4 C rate the fade in capacity per cycle is lesser than that of capacity fade at 0.2 C rate. The citric acid assisted sample is found to be superior in terms of discharge capacity, capacity retention rate and also in thermal stability to that of sample prepared with glycine as chelating agent.     

Effect of micron sized particle on the electrochemical properties of nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode materials

Particle size plays an important role in the electrochemical properties of cathode materials for lithium-ion battery, and the sizes of cathode powders are often designed to specific scales to obtain desired rate capacity, cyclic stability, etc. Nano-sized or micron-sized primary/secondary particles were both reported to be helpful to heighten the electrochemical properties of the same material system. However, the relationship between particle size and electrochemical properties of Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂ (NCM-811) has not been discussed in detail. Here, we prepared the pristine NCM-811 powders with various micro-sized particles by using solid state reaction, and investigated the influence of particle size on the electrochemical properties of typical NCM-811 cathode material, to clarify the importance of size effect. The result indicates that pristine NCM-811 cathode powders with D₅₀ = 7.7 μm displayed the best initial discharge specific capacity (224.5 and 169.1 mA h/g at 1/20 C and 1 C rate, respectively) and retention capacity (71.0% at 1 C rate) after 100th cycling at room temperature. The mutual acting mechanism in terms of layered structure, cation mixing degree, polarization state, charge-transfer resistance, and the diffusion ability of lithium-ion was confirmed by XRD, XPS, CV and EIS analyses, respectively.     

Characterization of high tap density Li[Ni1/3Co1/3Mn1/3]O2 cathode material synthesized via hydroxide co-precipitation

Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode material for lithium ion batteries was prepared by mixing metal hydroxide, (Ni_1/3Co_1/3Mn_1/3)(OH)₂, with 6% excess LiOH followed by calcinations. The (Ni_1/3Co_1/3Mn_1/3)(OH)₂ with secondary particle of about 12 μm was prepared by hydroxide co-precipitation. The tap density of the obtained Li[Ni_1/3Co_1/3Mn_1/3]O₂ powder was 2.56 ± 0.21 g cm⁻³. The powder was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), particle size distribution (PSD) and galvanostatic charge-discharge cycling. The XRD pattern of Li[Ni_1/3Co_1/3Mn_1/3]O₂ revealed a well ordered hexagonal layered structure with low cation mixing. Secondary particles with size of 13-14 μm and primary particles with size of about 1 μm can be identified from the SEM observations. In the voltage range of 2.8-4.3 V, the initial discharge capacity of the Li[Ni_1/3Co_1/3Mn_1/3]O₂ electrode was 166.6 mAh g⁻¹, and 96.5% of the initial capacity was retained after 50 charge-discharge cycling.     

Dual functions of three-dimensional hierarchical architecture on improving the rate capability and cycle performance of LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion battery

The main obstacles in lithium-ion battery are limited by rate performance and the rapid capacity fading of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). Herein, a novel three-dimensional (3D) hierarchical coating material has been fabricated by in situ growing carbon nanotubes (CNTs) on the surfaces of Ni–Al double oxide (Ni–Al-LDO) sheets (named as LDO&CNT) with Ni–Al double hydroxide (Ni–Al-LDH) as both the substrate and catalyst precursor. The resultant LDO&CNT nanocomposites are uniformly coated on the surfaces of NCM811 by the physical mixing method. The rate capability of the resultant cathode material retains to 78.80% at a current rate of 3C. Its capacity retention increases by 6.7–14.42% compared with pristine NCM811 after 100 cycles within a potential range of 2.75–4.3 V at 0.5C. The improved rate capability and cycle performance of NCM811 are assigned to the synergistic effects between Ni–Al-LDO and CNTs. The hierarchical LDO&CNT nanocomposites coating on the surface of NCM811 avoids the aggregation of conductive CNTs and the stacking of Ni–Al-LDO nanosheets. Furthermore, it accelerates Li⁺ and electrons shuttle and reduces the reaction of Li₂O with H₂O and CO₂ in air, which results in Li₂CO₃ and LiOH alkali formation on the NCM811 surface.     

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.     

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.     

Effect of synthesis condition on the structural and electrochemical properties of Li[Ni1/3Mn1/3Co1/3]O2 prepared by the metal acetates decomposition method

In order to get homogeneous layered oxide Li[Ni_1/3Mn_1/3Co_1/3]O₂ as a lithium insertion positive electrode material, we applied the metal acetates decomposition method. The oxide compounds were calcined at various temperatures, which results in greater difference in morphological (shape, particle size and specific surface area) and the electrochemical (first charge profile, reversible capacity and rate capability) differences. The Li[Ni_1/3Mn_1/3Co_1/3]O₂ powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry and SEM. XRD experiment revealed that the layered Li[Ni_1/3Mn_1/3Co_1/3]O₂ material can be best synthesized at temperature of 800 °C. In that synthesized temperature, the sample showed high discharge capacity of 190 mAh g⁻¹ as well as stable cycling performance at a current density of 0.2 mA cm⁻² in the voltage range 2.3-4.6 V. The reversible capacity after 100 cycles is more than 190 mAh g⁻¹ at room temperature.     

Electrochemical properties of Li[Ni1/3Mn1/3Al1/3−xCox]O2 as a cathode material for lithium ion battery

Layered Li[Ni_1/3Mn_1/3Al_1/3−xCo_x]O₂ (0 ≤ x ≤ 1/3) cathode materials are synthesized by a solvent evaporation method. Although XRD shows that Li[Ni_1/3Mn_1/3Al_1/3]O₂ has no obvious impurity phase, it has poor electrochemical properties. To improve its capability, part of Al in Li[Ni_1/3Mn_1/3Al_1/3]O₂ compound is replaced by Co in this study. The samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and charge–discharge test. The results indicate that the introduction of Co has a large influence on the morphology, structure and electrochemical performances of the samples, which become more excellent with an increase of Co content in compounds. Meanwhile, the high-temperature behavior of the samples is also investigated.     

Review of Computational Studies of NCM Cathode Materials for Li-ion Batteries

Lithium-ion based rechargeable batteries are considered among the most promising battery technologies because of the high energy- and power-densities of these electrochemical devices. Computational studies on lithium ion batteries (LIBs) facilitate rationalization and prediction of many important experimentally observed properties, including atomic structure, thermal stability, electronic structure, ion diffusion pathways, equilibrium cell voltage, electrochemical activity, and surface behavior of electrode materials. In recent years, Ni, Co and Mn-based (NCM) layered transition metal oxide positive electrode materials (LiNi_1-x-yCo_xMn_yO₂) have shown tremendous promise for high-energy density LIBs, and these NCM-based batteries are effectively commercialized. Here, we present an overview of recent theoretical work performed using first principles density functional theory on these layered cathode materials. This short review focuses on recent computational efforts of popular NCMs with increasing Ni content, ranging from NCM333 to NCM811.     

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.     

Effect of synthesis condition on the structure and electrochemical properties of Li[Ni1/3Mn1/3Co1/3]O2 prepared by hydroxide co-precipitation method

The layered Li[Ni_1/3Co_1/3Mn_1/3]O₂ powder with good crystalline and spherical shape was prepared by hydroxide co-precipitation method. The effects of pH value, NH₄OH amount, calcination temperature and extra Li amount on the morphology, structure and electrochemical properties of the cathode material were investigated in detail. SEM results indicate that pH value affected both the morphology and the property of the cathode material, and the highest discharge capacity in the first cycle of 163 mAh g⁻¹ (2.8-4.3 V) was obtained at pH value was 12. On the contrary, the NH₄OH amount, which was used as a chelating agent, only affected the particle size distribution of the material. The calcination temperatures caused great difference in the structure and property of layered Li[Ni_1/3Co_1/3Mn_1/3]O₂, and the best electrochemical properties were obtained at the calcination temperature of 800 °C. Extra Li amount not only caused difference in the material structure, but also affected their electrochemical properties. With increasing Li amount, the lattice parameters (a and c) increased monotonously, and the highest first cycle coulombic efficiency (the ratio of discharge capacity to charge capacity in the first cycle) was obtained with the Li/M of 1.10. Therefore, the optimum synthetic conditions for the hydroxide co-precipitation reaction were: pH value was 12, NH₄OH amount was 0.36 mol L⁻¹, calcination temperature was 800 °C and the Li/M molar ratio was 1.10.