Synthesis and properties of single-crystal Ni-rich cathode materials in Li-ion batteries

Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigated by X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical performance was characterized by long-term cycling, cyclic voltammetry, and in-situ impedance spectroscopy. The results indicated that high temperature rendered layered oxides to lose lithium/oxygen in the interior and exterior, and induced cationic disordering. Besides, the solid-phase synthesis process promoted phase transformation for electrode materials, causing the coexisting multi-phase in a single particle. High temperature can foster the growth of single particles, but it caused unstable structure of layered phase.

Boosting cell performance of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode material via structure design

Ni-rich cathodes exhibit appealing properties,such as high capacity density,low cost,and prominent energy density.However,the inferior ionic conductivity and bulk structural degradation become bottlenecks for Ni-rich cathodes and severely limit their commercial utilization.Traditional coating and doping methods suffer fatal drawbacks in functioning as a unit and cannot radically promote material performance to meet the needs of Li-ion batteries(LIBs).Herein,we successfully devised an ingenious and facile synthetic method to establish Ni-rich oxides with a La_(2)Zr_(2)O_(7) coating and Zr doping.The coating layer improves the ion diffusion kinetics and enhances Li-ion transportation while Zr doping effectively suppresses the phase transition of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode.Owing to the synergetic effect of Zr doping and La_(2)Zr_(2)O_(7) coating,the modified material shows prominent initial discharge capacity of 184.7 m Ah g^(-1) at 5℃ and maintains 177.5 m Ah g^(-1) after 100 cycles at 1℃.Overall,the proposed feasible electrode design method can have a far-reaching impact on further fabrication of advanced cathodes for high-performance LIBs.

Synthesis and characterization of Li_4Ti_5O_(12) via a hydrolysis process from TiCl_4 aqueous solution

Spinel-type lithium and titanium composite oxide Li4TisO12 was successfully synthesized via a novel hydrolysis method followed by calcination using titanium tetrachloride （TIC14） and lithium hydroxide （LiOH.H2O） as raw materials. Three major factors, including LiOH con- centration, LiOH dosage, and hydrolysis temperature were studied for optimizing the synthetic conditions to obtain a phase-pure Li4Ti5012. The physical and electrochemical properties of samples were characterized by X-ray dif- fraction （XRD）, thermogravimetric analysis （TGA）, fourier transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, and constant current discharge-charge test. The FT-IR results indicate the presence of [TiO6] octahedra. The SEM images show that the Li4Ti5O12 pre- cursor obtained is an amorphous solid with an irregular and rough morphology. It is revealed that the phase-pure spinel Li4Ti5O12 powders with well crystallization and regular morphology can be obtained by calcining the precursor at 800 ℃ for 6 h. The constant current discharge-charge tests indicate that the Li4TisO12 material delivers an excellent cycling ability, maintaining 93.8 % of its initial specific capacity after 60 cycles at a current density of 0.5C.

Single-Crystal Nickel-Based Cathodes:Fundamentals and Recent Advances

Lithium-ion batteries(LIBs)represent the most promising choice for meeting the ever-growing demand of society for various electric applications,such as electric transportation,portable electronics,and grid storage.Nickel-rich layered oxides have largely replaced LiCoO_(2)in commercial batteries because of their low cost,high energy density,and good reliability.Traditional nickel-based oxide particles,usually called polycrystal materials,are composed of microsized primary particles.However,polycrystal particles tend to suffer from pulverization and severe side reactions along grain boundaries during cycling.These phenomena accelerate cell degradation.Single-crystal materials,which exhibit robust mechanical strength and a high surface area,have great potential to address the challenges that hinder their polycrystal counterparts.A comprehensive understanding of the growing body of research related to single-crystal materials is imperative to improve the performance of cathodes in LIBs.This review highlights origins,recent developments,challenges,and opportunities for single-crystal layered oxide cathodes.The synthesis science behind single-crystal materials and comparative studies between single-crystal and polycrystal materials are discussed in detail.Industrial techniques and facilities are also reviewed in combination with our group’s experiences in single-crystal research.Future development should focus on facile production with strong control of the particle size and distribution,structural defects,and impurities to fully reap the benefits of single-crystal materials.