Effect of Al and Zr co-doping on electrochemical performance of cathode Li[Li0.2Ni0.13Co0.13Mn0.54]O2 for Li-ion battery

Journal of Solid State Electrochemistry - The Li[Li0.2Ni0.13-x + y/3Co0.13-x + y/3Mn0.54-x + y/3]Al x Zr y O2 was synthesized via conventional solution...     

Influence of preparation method on structure, morphology, and electrochemical performance of spherical Li[Ni0.5Mn0.3Co0.2]O2

Spherical Li[Ni_0.5Mn_0.3Co_0.2]O₂ was prepared by both the continuous hydroxide co-precipitation method and continuous carbonate co-precipitation method under different calcined temperatures. The physical properties and electrochemical behaviors of Li[Ni_0.5Mn_0.3Co_0.2]O₂ prepared by two methods were characterized by X-ray diffraction, scanning electron microscope, and electrochemical measurements. It has been found that different preparation methods will result in the differences in the morphology (shape, particle size, and tap density), structure stability, and the electrochemical characteristics (shape of initial charge/discharge curve, cycle stability, and rate capability) of the final product Li[Ni_0.5Mn_0.3Co_0.2]O₂. The physical and electrochemical properties of the spherical Li[Ni_0.5Mn_0.3Co_0.2]O₂ prepared by continuous hydroxide co-precipitation is apparently superior to the one prepared by continuous carbonate co-precipitation method. The optimal sample prepared by continuous hydroxide co-precipitation at 820 °C exhibits a hexagonally ordered layer structure, high special discharge capacity, good capacity retention, and excellent rate capability. It delivers high initial discharge capacity of 175.2 mAh g^?1 at 0.2 C rate between 3.0 and 4.3 V, and the capacity retention of 98.8 % can be maintained after 50 cycles. While the voltage range is broadened up to 2.5 and 4.6 V vs. Li⁺/Li, the special discharge capacities at 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 10 C rates are as high as 214.3, 205.0, 198.3, 183.3, 160.1 and 135.2 mAh g^?1, respectively.     

Structural characterization and electrochemical intercalation of Li+ in layered Na0.65Ni0.5Mn0.5O2 obtained by freeze-drying method

New data on the structure and reversible lithium intercalation properties of sodium-deficient nickel–manganese oxides are provided. Novel properties of oxides determine their potential for direct use as cathode materials in lithium-ion batteries. The studies are focused on Na _x Ni_0.5Mn_0.5O₂ with x?=?2/3. Between 500 and 700 °C, new layered oxides Na_0.65Ni_0.5Mn_0.5O₂ with P3-type structure are obtained by a simple precursor method that consists in thermal decomposition of mixed sodium–nickel–manganese acetate salts obtained by freeze-drying. The structure, morphology, and oxidation state of nickel and manganese ions of Na_0.65Ni_0.5Mn_0.5O₂ are determined by powder X-ray diffraction, SEM and TEM analysis, and X-ray photoelectron spectroscopy (XPS). The lithium intercalation in Na_0.65Ni_0.5Mn_0.5O₂ is carried out in model two-electrode lithium cells of the type Li|LiPF₆(EC:DMC)|Na_0.65Ni_0.5Mn_0.5O₂. A new structural feature of Na_0.65Ni_0.5Mn_0.5O₂ as compared with well-known O3–NaNi_0.5Mn_0.5O₂ and P2–Na_2/3Ni_1/3Mn_2/3O₂ is the development of layer stacking ensuring prismatic site occupancy for Na⁺ ions with shared face on one side and shared edges on the other side with surrounding Ni/MnO₆ octahedra. The reversible lithium intercalation in Na_0.65Ni_0.5Mn_0.5O₂ is demonstrated and discussed.     

富锂正极材料Li[Li0.2Mn0.4Fe0.4]O2的表面包覆改性

用共沉淀法合成了富锂正极材料Li[Li0.2Mn0.4Fe0.4]O2,并对其表面进行Al2O3包覆。采用XRD、SEM和电化学测试等方法对样品进行表征。结果表明,与Li[Li0.2Mn0.4Fe0.4]O2相比,包覆改性后的Li[Li0.2Mn0.4Fe0.4]O2具有较好的电化学性能,其初始放电容量未明显降低,而循环寿命大大提高,4.0%Al2O3包覆处理的富锂正极材料经50次充放电循环后,容量衰减量在9%左右。     

Effect of synthesis routes on the electrochemical performance of Li[Ni0.6Co0.2Mn0.2]O2 for lithium ion batteries

The cathode-active materials, layered Li[Ni_0.6Co_0.2Mn_0.2]O₂, were synthesized by two different routes: spray-drying and solid-state methods. The influence of synthesis routes on the crystal structure, morphology, and electrochemical performance of the samples were characterized by X-ray diffraction, scanning electron microscope, and charge/discharge test. As a result, both samples showed a typical hexagonal structure with a single phase. However, the difference in synthesis route resulted in the difference in morphology and electrochemical performance, such as reversible capacity and the rate capability. The initial discharge capacity of sample synthesized by spray-drying method at room temperature and 50 °C were 173.1 and 181.2 mAh g^?1, respectively, which were higher than those of 166.8 and 177.5 mAh g^?1 for sample synthesized by solid-state method. The cycling performance was also evaluated. Sample synthesized by spray-drying method exhibits a higher discharge capacity and better cycling performance than those prepared by solid-state method, even at elevated temperature.     

Li-ion-conductive Li2TiO3-coated Li[Li0.2Mn0.51Ni0.19Co0.1]O2 for high-performance cathode material in lithium-ion battery

Journal of Solid State Electrochemistry - Li2TiO3 is used as a novel coating material to modify Li(Li0.2Mn0.51Ni0.19Co0.1)O2 electrode to enhance the electrochemical performance of the host...     

Synthesis of Li[Li0.2Ni0.2Mn0.6]O2 by radiated polymer gel method and impact of deficient Li on its structure and electrochemical properties

Layered Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li[Li_0.2Ni_0.2Mn_0.6]O₂ compounds were successfully synthesized by radiated polymer gel (RPG) method. The effect of deficient Li on the structure and electrochemical performance was investigated by means of X-ray diffraction, X-ray absorption near-edge spectroscopy and electrochemical cell cycling. The reduced Ni valence in Li[Li_0.16Ni_0.21Mn_0.63]O₂ leads to a higher capacity owing to faster Li⁺ chemical diffusivity relative to the baseline composition Li[Li_0.2Ni_0.2Mn_0.6]O₂. Cyclic voltammograms (CV) and a simultaneous direct current (DC) resistance measurement were also performed on Li/Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li/Li[Li_0.2Ni_0.2Mn_0.6]O₂ cells. Li[Li_0.16Ni_0.21Mn_0.63]O₂ shows better electrochemical performance with a reversible capacity of 158 mA hg⁻¹ at 1C rate at 20 °C.     

Carbon-coated high capacity layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathodes

Electrodes fabricated with the layered Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ have been coated with carbon by a thermal evaporation process and characterized. The carbon coating enhances the sample surface conductivity by 40% without degrading the layered oxide. The carbon-coated cathodes exhibit much improved rate capability and cycling performance than the bare cathode. Electrochemical impedance spectroscopy (EIS) data reveal that the improved electrochemical performances of the carbon-coated sample are due to the suppression of the solid-electrolyte interfacial (SEI) layer and faster kinetics of both the lithium-ion diffusion through surface layer and the charge transfer reaction.     

Prolonged lifespan of initial-anode-free lithium-metal battery by pre-lithiation in Li-rich Li2Ni0.5Mn1.5O4 spinel cathode

Anode-free lithium metal batteries (AF-LMBs) can deliver the maximum energy density. However, achieving AF-LMBs with a long lifespan remains challenging because of the poor reversibility of Li⁺ plating/stripping on the anode. Here, coupled with a fluorine-containing electrolyte, we introduce a cathode pre-lithiation strategy to extend the lifespan of AF-LMBs. The AF-LMB is constructed with Li-rich Li₂Ni_0.5Mn_1.5O₄ cathodes as a Li-ion extender; the Li₂Ni_0.5Mn_1.5O₄ can deliver a large amount of Li⁺ in the initial charging process to offset the continuous Li⁺ consumption, which benefits the cycling performance without sacrificing energy density. Moreover, the cathode pre-lithiation design has been practically and precisely regulated using engineering methods (Li-metal contact and pre-lithiation Li-biphenyl immersion). Benefiting from the highly reversible Li metal on the Cu anode and Li₂Ni_0.5Mn_1.5O₄ cathode, the further fabricated anode-free pouch cells achieve 350 W h kg⁻¹ energy density and 97% capacity retention after 50 cycles.

Benefiting from highly reversible structure evolution of pre-lithiated Li-rich Li₂Ni_0.5Mn_1.5O₄ cathode, the corresponding anode-free pouch cell delivers a considerable energy density of 350 W h kg⁻¹ and 97% capacity retention after 50 cycles.     

Local electronic structure of layered Li(x)Ni0.5Mn0.5O2 and Li(x)Ni(1/3)Mn(1/3)Co(1/3)O2

Samples of Li(x)Ni0.5Mn0.5O2 and Li(x)Ni(1/3)Mn(1/3)Co(1/3)O2 were prepared as active materials in electrochemical half-cells and were cycled electrochemically to obtain different values of Li concentration, x. Absorption edges of Ni, Mn, Co, and O in these materials of differing x were measured by electron energy loss spectrometry (EELS) in a transmission electron microscope to determine the changes in local electronic structure caused by delithiation. The work was supported by electronic structure calculations with the VASP pseudopotential package, the full-potential linear augmented plane wave code WIEN2K, and atomic multiplet calculations that took account of the electronic effects from local octahedral symmetry. A valence change from Ni2+ to Ni4+ with delithiation would have caused a 3 eV shift in energy of the intense white line at the Ni L3 edge, but the measured shift was less than 1.2 eV. The intensities of the "white lines" at the Ni L-edges did not change enough to account for a substantial change of Ni valence. No changes were detectable at the Mn and Co L-edges after delithiation either. Both EELS and the computational efforts showed that most of the charge compensation for Li+ takes place at hybridized O 2p states, not at Ni atoms.     

Enhanced electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2 composited with Ti3C2Tx MXene nanosheets

Journal of Solid State Electrochemistry - Li1.2Ni0.13Co0.13Mn0.54O2/Ti3C2Tx (LMR/TC) composite materials have been synthesized through mixing LMR particles with TC nanosheets. SEM result shows that...     

纳米Al2O3包覆富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的性能研究

采用纳米三氧化二铝(Al₂O₃)对富锂锰基正极材料Li_1.2Ni_0.13Co_0.13Mn_0.54O₂进行表面均匀包覆, 并考察了最优纳米Al₂O₃包覆量下材料的电化学性能. 扫描电子显微镜(SEM)和透射电子显微镜(TEM)显示了纳米Al₂O₃对富锂锰基正极材料表面均匀包覆, X射线衍射分析(XRD)结果表明包覆后富锂材料依然具有良好的层状结构. 恒流充/放电循环测试发现, 包覆后的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料的首次放电比容量为249.7 mA·h/g, 循环100次后的容量保持率为89.5%, 与未包覆的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料相比, 容量保持率提升约13%. 循环伏安(CV)和电化学阻抗(EIS)测试结果表明, 纳米Al₂O₃包覆可有效抑制材料极化, 降低界面阻抗和电荷转移阻抗, 进而提升富锂锰基正极材料的电化学性能.     

Preparation and cycle performance at high temperature for Li[Ni0.5Co0.2Mn0.3]O2 coated with LiFePO4

Li[Ni_0.5Co_0.2Mn_0.3]O₂ coated with LiFePO₄ was synthesized by a co-precipitation method. It consisted of the parent Li[Ni_0.5Co_0.2Mn_0.3]O₂ as the core and the LiFePO₄ as the coating material, with an average particle diameter of 500 nm. The LiFePO₄-coated Li[Ni_0.5Co_0.2Mn_0.3]O₂ showed no large initial capacity drop in the first cycle, which generally occurred with cathode materials bearing inactive coating layers such as Al₂O₃, ZnO, and MgO. Furthermore, it presented a remarkably improved cycle retention rate of over 89% until 400 cycles at 50 °C. We suggest that the LiFePO₄ coating technique is a very effective tool to improve the cycle performance of Li[Ni_0.5Co_0.2Mn_0.3]O₂ at high temperatures.     

Characterization of Li1−x Ni1+x O2 prepared by the thermal-assisted precipitation process

Li_1−x Ni_1+x O₂ was prepared by the thermal-assisted precipitation process of LiOH · H₂O and Ni(CH₃COO)₂ · 4H₂O at a pH of 6–13 followed by the high temperature calcination for a variety of prolonged times. Phases, morphologies and constituents were characterized using an x-ray diffractometer (XRD), a scanning electron microscope (SEM), an energy dispersive x-ray (EDX) analyzer an atomic absorption spectrophotometer (AAS) and titration. Maximum [I₍₀₀₃₎/I₍₁₀₄₎] and minimum [I_(006+102)/I₍₁₀₁₎] intensity ratios were used to determine the preparation conditions. In addition, possible formation reactions of the precursors and calcined products were proposed. The article was submitted by the authors in English.     

Coating of Al2O3 on layered Li(Mn1/3Ni1/3Co1/3)O2 using CO2 as green precipitant and their improved electrochemical performance for lithium ion batteries

Li(Mn_1/3Ni_1/3Co_1/3)O₂ cathode materials were fabricated by a hydroxide precursor method. Al₂O₃ was coated on the surface of the Li(Mn_1/3Ni_1/3Co_1/3)O₂ through a simple and effective one-step electrostatic self-assembly method. In the coating process, a NHCO₃-H₂CO₃ buffer was formed spontaneously when CO₂ was introduced into the NaAlO₂ solution. Compared with bare Li(Mn_1/3M_1/3Co_1/3)O₂, the surface-modified samples exhibited better cycling performance, rate capability and rate capability retention. The Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ electrodes delivered a discharge capacity of about 115 mAh·g^?1 at 2 A·g^?1, but only 84 mAh·g^?1 for the bare one. The capacity retention of the Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ was 90.7% after 50 cycles, about 30% higher than that of the pristine one.     

Preparation and Electrochemical Performance of Li[Ni1/3Co1/3Mn1/3]O2 Synthesized Using Li2CO3 as Template

Porous structure Li[Ni_1/3Co_1/3Mn_1/3]O₂ has been synthesized via a facile carbonate co‐precipitation method using Li₂CO₃ as template and lithium‐source. The physical and electrochemical properties of the materials were examined by many characterizations including TGA, XRD, SEM, EDS, TEM, BET, CV, EIS and galvanostatic charge‐discharge cycling. The results indicate that the as‐synthesized materials by this novel method own a well‐ordered layered structure α‐NaFeO₂ [space group: R‐3m(166)], porous morphology, and an average primary particle size of about 150 nm. The porous material exhibits larger specific surface area and delivers a high initial capacity of 169.9 mAh·g^?1 at 0.1 C (1 C=180 mA·g^?1) between 2.7 and 4.3 V, and 126.4, 115.7 mAh·g^?1 are still respectively reached at high rate of 10 C and 20 C. After 100 charge‐discharge cycles at 1 C, the capacity retention is 93.3%, indicating the excellent cycling stability.