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.     

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.     

Improving the electrochemical performance of single crystal LiNi0.5Mn1.5O4 cathode materials by Y–Ti doping and unannealing process

In recent years, due to the rising price of cobalt, people have been increasingly interested in LiNi_0.5Mn_1.5O₄ (LNMO) cathode materials, and many studies researches have been carried out on the preparation and modification of LNMO. However, the codoping of Y and Ti and the choice of annealing and unannealing processes after doping are less explored. In this study, single-crystal LNMO particles and Y, Ti-doped LiNi_0.45Mn_1.45O₄ particles were prepared by a simple sol-gel method under annealing and unannealing processes, respectively. Four samples were analyzed by X-ray powder diffraction, Raman spectra, Fourier transform infrared spectroscopy and electron paramagnetic resonance. By these means, it was found that the samples doped and not annealed had the largest amount of disordered structures and oxygen vacancies (OVs). Scanning electron microscopy showed that the doped and unannealed samples had more exposed (100) crystal planes than the other samples, and after multiple cycles, this sample had the smoothest surface morphology. Electrochemical tests show that the doped and unannealed samples exhibit excellent electrochemical performance, with a Coulombic efficiency of 93.94% in the first cycle, a specific capacity of 126.74 mAh?g^?1 after 500 cycles at a rate of 1 C, and a specific capacity of 126.74 mAh?g^?1 at a rate of 5 C. After 500 cycles, the specific capacity is 111.1 mAh?g^?1.     

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.     

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.     

Improving electrochemical performance of NCM811 cathodes for lithium-ion batteries via consistently arranging the hexagonal nanosheets with exposed {104} facets

Layered high-nickel LiNi_0.8Co_0.1Mn_0.1O₂ is a promising candidate of the next generation cathode materials for lithium-ion batteries. However, severe cycling instability and fast capacity drop induced by anisotropic structured change restrict its wide application. To address these defects, the structure design of cathodes is conducted. Herein, a hierarchical layered LiNi_0.8Co_0.1Mn_0.1O₂ cathode consisting of orderly stacking hexagonal nanosheets with exposed active {104} facets is successfully synthesized by an improved co-precipitation process and followed with a high temperature lithiation reaction. Benefiting from this unique texture, exposed active {104} facets with lower surface energy supply 3D barrier-free Li⁺ ion diffusion channels, significantly improving the efficiency of the Li⁺ diffusion. Moreover, the consistent arrangement of nanosheets in the manner of the {001} facets close attachment is beneficial to alleviate the stress caused by the anisotropic structured change. Thus, this cathode material presents both superior reversible capability (203.8 mAh g^?1 at 0.1C, 184.5 mAh g^?1 at 1 C, 173.0 mAh g^?1 at 5 C and 161.3 mAh g^?1 at 10 C) and stable cycling performance (capacity retention of 89.3% after 100 cycles at 1 C, 55.3% after 300 cycles at 5 C and 59.6% after 300 cycles at 10 C).     

Characterization of yttrium substituted LiNi0.33Mn0.33Co0.33O2 cathode material for lithium secondary cells

LiNi_0.33−xMn_0.33Co_0.33Y_xO₂ materials are synthesized by Y³⁺ substitute of Ni²⁺ to improve the cycling performance and rate capability. The influence of the Y³⁺ doping on the structure and electrochemical properties are investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and galvanostatic charge/discharge tests. LiNi_0.33Mn_0.33Co_0.33O₂ exhibits the capacity retentions of 89.9 and 87.8% at 2.0 and 4.0 C after 40 cycles, respectively. After doping, the capacity retentions of LiNi_0.305Mn_0.33Co_0.33Y_0.025O₂ are increased to 97.2 and 95.9% at 2.0 and 4.0 C, respectively. The discharge capacity of LiNi_0.305Mn_0.33Co_0.33Y_0.025O₂ at 5.0 C remains 75.7% of the discharge capacity at 0.2 C, while that of LiNi_0.33Mn_0.33Co_0.33O₂ is only 47.5%. EIS measurement indicates that LiNi_0.305Mn_0.33Co_0.33Y_0.025O₂ electrode has the lower impedance value during cycling. It is considered that the higher capacity retention and superior rate capability of Y-doped samples can be ascribed to the reduced surface film resistance and charge transfer resistance of the electrode during cycling.     

High-nickel and cobalt-free layered LiNi0.90Mn0.06Al0.04O2 cathode for lithium-ion batteries

In order to obtain superior cathode materials for lithium-ion batteries with lower cost and higher energy density, the research of nickel-based cathode materials trend towards high Ni, low Co or no Co composition. To demonstrate the feasibility of this compositional transformation, we introduce a Co-free LiNi_0.90Mn_0.06Al_0.04O₂ (NMA) cathode material with a Ni content of 90 mol%, ranging from LiNi_0.90Co_0.1O₂ (NC) to low Co LiNi_0.90Mn_0.06Co_0.04O₂ (NMC) composition transformation. All samples were synthesized by an organic amine coprecipitation method. The results show that the NMA cathode can provide the first discharge specific capacity of 223.1 mAh g^?1 at 0.1 C and 2.5–4.3 V, although is lower than that of NC and NMC, it has a higher average discharge voltage of 47 and 17 mV, respectively. At a high voltage window ranging from 2.5 to 4.5 V, the first discharge specific capacity up to 232.1 mAh g^?1, and the capacity retention rate of 100 cycles at 0.5 C is as high as 93.3%, which is much higher than the 66.9% of the NC. The dQ dV^?1 and discharge curves show that the NMA phase transition is gentler and the polarization is smaller during the high-voltage charge-discharge process, which also indicates that the destructive effect of Co on the layered structure is further enhanced at high potential. In conclusion, this work provides favorable support for NMA as a next-generation candidate for high-nickel and Co-free cathode materials.     

Inducing favorable dual-substitution reactivity by doping Mo6+ and F− to enhance electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathode materials

Lithium-ion batteries are a hot spot of modern energy research due to the advantage of capacity and cost. As a new type of green energy, lithium-ion batteries have a far-reaching influence on the sustainable development of the environment, and the wide application of it can effectively reduce the exploitation of fossil fuels. However, the high specific capacity is also accompanied by some irreversible problems, such as poor cyclic performance and the rapid decay of discharge capacity with high current density. In view of these problems, we employ a dual-modification strategy to co-dope LiNi_0.6Co_0.2Mn_0.2O₂ by Mo⁶⁺ and F^?. The addition of Mo⁶⁺ widens the interval layers and F^? was utilized to lessen the release of lattice oxygen with a purpose of enhancing cyclical stability. After 50 cycles, the dual-substitution of LiNi_0.6Co_0.2Mn_0.2O₂ displayed distinguished capacity retention of 89.6% with 137.7 mAh g^?1 at 0.5C. It's a feasible strategy to enhance the electrochemical performance of cathode materials.     

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.     

Performance of LiNi1/3Co1/3Mn1/3O2 prepared from spent lithium-ion batteries by a carbonate co-precipitation method

Spherical LiNi_1/3Co_1/3Mn_1/3O₂ cathode particles were resynthesized by a carbonate co-precipitation method using spent lithium-ion batteries (LIBs) as a raw material. The physical characteristics of the Ni_1/3Co_1/3Mn_1/3CO₃ precursor, the (Ni_1/3Co_1/3Mn_1/3)₃O₄ intermediate, and the regenerated LiNi_1/3Co_1/3Mn_1/3O₂ cathode material were investigated by laser particle-size analysis, scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), thermogravimetry–differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), inductively coupled plasma–atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the regenerated LiNi_1/3Co_1/3Mn_1/3O₂ was studied by continuous charge–discharge cycling and cyclic voltammetry. The results indicate that the regenerated Ni_1/3Co_1/3Mn_1/3CO₃ precursor comprises uniform spherical particles with a narrow particle-size distribution. The regenerated LiNi_1/3Co_1/3Mn_1/3O₂ comprises spherical particles similar to those of the Ni_1/3Co_1/3Mn_1/3CO₃ precursor, but with a narrower particle-size distribution. Moreover, it has a well-ordered layered structure and a low degree of cation mixing. The regenerated LiNi_1/3Co_1/3Mn_1/3O₂ shows an initial discharge capacity of 163.5 mA h g^?1 at 0.1 C, between 2.7 and 4.3 V; the discharge capacity at 1 C is 135.1 mA h g^?1, and the capacity retention ratio is 94.1% after 50 cycles. Even at the high rate of 5 C, LiNi_1/3Co_1/3Mn_1/3O₂ delivers the high capacity of 112.6 mA h g^?1. These results demonstrate that the electrochemical performance of the regenerated LiNi_1/3Co_1/3Mn_1/3O₂ is comparable to that of a cathode synthesized from fresh materials by carbonate co-precipitation.     

High-voltage electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode materials via Al concentration gradient modification

Al₂O₃-modified LiNi_0.5Co_0.2Mn_0.3O₂ cathode material is successfully synthesized via a facile carboxymethyl cellulose (CMC)-assisted wet method followed by a high-temperature calcination process. Al concentration gradient doping and accompanying formation of Al-coating are simultaneously accomplished in the modified samples. XRD and EDS analysis demonstrate that Al element is successfully doped into the crystal lattice with concentration gradient distribution inside the particles, reducing the Li/Ni cation mixing and stabilizing the layered structure. The compact distribution of Al on the surface forms a protective layer between the electrodes and the electrolyte, prohibiting the harmful side reactions and phase transition on the interphase. Compared with the pristine, the modified material with 2000?ppm Al₂O₃ (Al-2000) shows the best high-voltage performance with the capacity retention increased by ~13.3% from 138.3 to 163.0 mAh g^?1 at 1?C in 3.0–4.6?V after 100 cycles. Even under the high current rate of 8?C (1240 mAh g^?1) after 200 cycles, the Al-2000 still exhibits a capacity retention of 88.6%, greater than 80.3% for the pristine. Furthermore, results from the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) measurements confirm the roles of the Al₂O₃ modification in decreasing polarization and electrochemical resistances, contributing to the kinetic process of electrodes.     

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.     

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.     

Enhancing electrochemical performance and structural stability of LiNi0.5Mn1.5O4 cathode material for rechargeable lithium-ion batteries by boron doping

LiNi_0.5Mn_1.5O₄ cathode materials with a range of boron doping contents were successfully synthesized via an in situ solid-state method. The structures and grain morphologies were examined to elucidate the effect of boron doping on the electrochemical performance of LiNi_0.5Mn_1.5O₄. Scanning electron microscopy images show that the particle sizes of boron-doped LiNi_0.5-x/2B_xMn_1.5-x/2O₄ samples increase compared with those of pure LiNi_0.5Mn_1.5O₄. Characterization results confirm that boron doping could create more Mn³⁺ ions and increase the Mn³⁺ ions contents in LiNi_0.5-x/2B_xMn_1.5-x/2O₄ samples with increasing boron doping content. A greater number of Mn³⁺ ions could enhance the cationic disorder degree, thereby resulting in high electronic conductivities of LiNi_0.5-x/2B_xMn_1.5-x/2O₄ samples. Charge-discharge tests reveal that improvements in the electrochemical performance are achieved in LiNi_0.5-x/2B_xMn_1.5-x/2O₄ samples compared with that of pure LiNi_0.5Mn_1.5O₄. The boron-doped LiNi_0.495B_0.01Mn_1.495O₄ (denoted as LNMO-B0.01) cathode exhibits an excellent cycling stability with a capacity retention of 83.3% after 500 cycles at 3 C. Moreover, it also displays an optimal rate capability with discharge capacities of 136.1, 135.7, 130.3, 126.2, 123.1, 114.5, 104.5, and 82.9 mA h g^?1 at 0.2, 0.5, 1, 2, 3, 5, 7, and 10 C, respectively. The highest Li⁺ diffusion coefficient of LNMO-B0.01 determined from cyclic voltammetry tests indicates that an appropriate amount of boron doping could accelerate the Li⁺ diffusion in LNMO-B0.01. The lowest charge-transfer resistance obtained from the impedance spectra suggests that boron doping could promote kinetic charge transfer. As a result, this modification strategy can be utilized to enhance the electrochemical performance of LiNi_0.5Mn_1.5O₄ material.     

Nanoparticles constructed mesoporous coral-like Mn2O3 as high performance anode for lithium-ion batteries

As well established, the morphology and architecture of electrode materials greatly contribute to the electrochemical properties. Herein, a novel structure of mesoporous coral-like manganese (III) oxide (Mn₂O₃) is synthesized via a facile solvothermal method coupled with the carbonization under air. When fabricated as anode electrode for lithium-ion batteries (LIBs), the as-prepared Mn₂O₃ exhibits good electrochemical properties, showing a high discharge capacity of 1090.4 mAh g^?1 at 0.1 A g^?1, and excellent rate performance of 410.4 mAh g^?1 at 2 A g^?1. Furthermore, it maintains the reversible discharge capacity of 1045 mAh g^?1 at 0.1 A g^?1 after 380 cycles, and 755 mAh g^?1 at 1 A g^?1 after 450 cycles. The durable cycling stability and outstanding rate performance can be attributed to its unique 3D mesoporous structure, which is favorable for increasing active area and shortening Li⁺ diffusion distance.     

Sol-gel synthesis of nano Li1.2Mn0·54Ni0·13Co0·13O2 cathode materials using DL-lactic acid as chelating agent

Lithium-rich cathode materials Li_1·2Mn_0·54Ni_0·13Co_0·13O₂ (LMNCO) are prepared by sol-gel method using dl-lactic acid as chelating agent. The effect of pH on crystal structures, morphologies, particle sizes, and electrochemical properties of cathode materials are studied by X-ray diffractometry (XRD), scanning electron microscopy (SEM), nanoparticle analysis, charge–discharge tests, and electrochemical analysis. The Li_1·2Mn_0·54Ni_0·13Co_0·13O₂ cathodes exhibit well-ordered layered structures consisting of hexagonal LiMO₂ and monoclinic Li₂MnO₃ with smooth surfaces and well-crystallized particles (100–500 nm). LMNCO-7.0 exhibits smaller particle sizes than LMNCO-5.5 and LMNCO-8.5 and better electrochemical performance. The first discharge capacity and Coulombic efficiency of LMNCO-7.0 are 232.31 mAh g^?1 and 73.2%, respectively. After 50 cycles, discharge capacity of LMNCO-7.0 decrease to 194.93 mAh g^?1. LMNCO-7.0 cathode shows superior discharge capacity and rate performance due to its low charge transfer impedance and small average quasi-spherical particle diameter.     

Structure and morphology evolution in solid-phase synthesis lithium ion battery LiNi0.80Co0.15Al0.05O2 cathode materials with different micro-nano sizes of raw materials

The LiNi_0.80Co_0.15Al_0.05O₂ (NCA) cathode is endowed with a high energy density and excellent cycling performance. However, the preparation conditions for this material are quite harsh. Therefore, it is rather significant to obtain well-qualified NCA by simple solid-phase synthesis. In this study, the solid-phase synthesis of NCA cathode material is carried out by mixing two types of raw materials via stirring or sand milling. The effects of different particle sizes on the structure and morphology of NCA materials are analyzed. Owing to the different particle sizes of the raw materials, the diffusion path of Li⁺ between the solid phases differs greatly. The XRD results show that the samples mixed by stirring have a worse cation mixture than those mixed by sand milling due to the larger particle size, smaller sintering surface energy, and insufficient sintering strength. The electrochemical results show that the sample mixed by sand milling has a higher specific capacity at a low rate, the initial discharge capacity is 199.22?mAh?g^?1, and the capacity retention rate is 86.9% after 50 cycles. In contrast, the initial discharge capacity of the sample mixed by stirring is 184.86?mAh?g^?1, and the capacity is 171.93?mAh?g^?1 after 50 cycles with a 93.0% capacity retention rate.     

Zr-doped Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) as cathode material for lithium ion batteries

Layered Li[Ni_0.5−xMn_0.5−xZr_2x]O₂ (x = 0, 0.025) have been prepared by the mixed hydroxide and molten-salt synthesis method. The individual particles of synthesized materials have a sub-microsize range of 200-500 nm, and LiNi_0.475Mn_0.475Zr_0.05O₂ has a rougher surface than that of LiNi_0.5Mn_0.5O₂. The Li/Li[Ni_0.5−xMn_0.5−xZr_2x]O₂ (x = 0, 0.025) electrodes were cycled between 4.5 and 2.0 V at a current density of 15 mA/g, the discharge capacity of both cells increased during the first ten cycles. The discharge capacity of the Li/LiNi_0.475Mn_0.475Zr_0.05O₂ cell increased from 150 to 220 mAh/g, which is 50 mAh/g larger than that of the Li/LiNi_0.5Mn_0.5O₂ cell. We found that the oxidation of oxygen and the Mn³⁺ ion concerned this phenomenon from the cyclic voltammetry (CV). Thermal stability of the charged Li[Ni_0.5−xMn_0.5−xZr_2x]O₂ (x = 0, 0.025) cathode was improved by Zr doping.     

Fine-sized LiNi0.8Co0.15Mn0.05O2 cathode particles prepared by spray pyrolysis from the polymeric precursor solutions

Fine-sized LiNi_0.8Co_0.15Mn_0.05O₂ cathode particles with high discharge capacities and good cycle properties were prepared by spray pyrolysis from the polymeric precursor solutions. The cathode particles obtained from the spray solution without polymeric precursors had irregular morphology and hardly aggregated morphology. On the other hand, the cathode particles obtained from the spray solution with citric acid and ethylene glycol had fine size and regular morphologies. The cathode particles obtained from the spray solution containing adequate amounts of citric acid and ethylene glycol had several hundreds nanometer and narrow size distribution. The maximum discharge capacity of the cathode particles was 218 mAh/g when the excess of lithium component added to the spray solution was 6 mol% of the stoichiometric amount to obtain the LiNi_0.8Co_0.15Mn_0.05O₂ particles. The discharge capacities of the fine-sized LiNi_0.8Co_0.15Mn_0.05O₂ particles dropped from 218 to 213 mAh/g by the 50th cycle at a current density of 0.1 C.