Advances of high-performance LiNi_(1-x-y)Co_(x)M_(y)O_(2) cathode materials and their precursor particles via co-precipitation process

Layered LiNi_(1-x-y)Co_(x)M_(y)O_(2)(M=Mn or Al)is a promising cathode material for lithium-ion batteries due to its high specific capacity and acceptable manufacturing cost.However,the polycrystalline LiNi_(1-x-y)Co_(x)M_(y)O_(2) cathode material suffers from disordered orientation of primary particles and poor geometric symmetry of secondary particles,which severely hampers the migration of Lit ions.Furthermore,the resulting anisotropy accelerates the disintegration of the secondary particle structure,significantly affecting the electrochemical performance of the polycrystalline cathode.In spite of less grain boundary,the single-crystal LiNi_(1-x-y)Co_(x)M_(y)O_(2) cathodes still suffer from severe microcracks generated by repeated planar gliding during cycling,which poses a great challenge to the cycling stability of single-crystal materials.It's worth noting that the microstructure of the cathode material is mainly inherited from its precursor.Therefore,it is necessary to deeply understand the influence of the microstructure of Ni_(1-x-y)Co_(x)M_(y)(OH)2 on the electrochemical properties of LiNi_(1-x-y)Co_(x)M_(y)O_(2) cathode materials,so as to optimize the production process of preparing high-performance cathode precursors.In this review,we summarize recent advances in the research and development of Ni-rich cathode precursor materials.Firstly,the challenges faced by the Ni-rich hydroxide precursor materials are presented,including the effect of primary particle morphology and arrangement on the electrochemical performance of cathode materials,the influence of secondary particle morphology on lithium insertion reactions in cathode,and the effect of particle size on the microcracking of single-crystal particles.Secondly,the presentation of the conventional co-precipitation reactor,the mechanism of precursor particle growth,and the influence of coprecipitation parameters are described in detail.Finally,the strategies are systematically discussed to solve the challenges of hydroxide precursors,such as the innovation and optimization on reactants,synthesis processes,and reaction equipment.To obtain satisfactory high-quality precursor materials,future work will require an in-depth understanding of the reaction mechanism,combined with simulation techniques such as flow field theory calculations to guide the synthesis of precursors.This review provides a comprehensive analysis of the current progresses on the producing technologies of highperformance cathode precursors and offers prospects for future industry developments.

Simultaneous extraction of DNA and RNA from Escherichia coli BL 21 based on silica-coated magnetic nanoparticles

The extraction of nucleic acid is recognized as one of the most essential steps in molecular biology for initiating other downstream applications such as sequencing, amplification, hybridization, and cloning. Many commercial kits and methods are currently available that allow the extraction of only one type of nucleic acids-DNA or RNA. However, in parallel clinical detection of several diseases, a method for simultaneous extraction of both DNA and RNA from the same source is needed in such cases. In this study, a method for simultaneous extraction of DNA and RNA from bacteria based on magnetic nanoparticles(MNPs) was described. Lysis buffers were prepared to help the nucleic acid released and adsorbed to MNPs. Then, two washing buffers were used to remove the contamination of proteins and carbohydrates. The nucleic acids were finally eluted by Deoxyribonuclease(DNase) and Ribonucleases(RNase) free water. Different factors which might affect the purification of the nucleic acid were investigated, and the quantity and quality parameters of the nucleic acid were also recorded. The DNA and RNA extracted from bacteria were then respectively subjected to polymerase chain reaction(PCR) and reverse transcription PCR(RT-PCR) to further confirm its quality. The results indicated that our method can be successfully used to simultaneously extract DNA and RNA from bacteria.

Granularity control enables high stability and elevated-temperature properties of micron-sized single-crystal LiNi_(0.5)Mn_(1.5)O_(4) cathodes at high voltage

The development of high energy density LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode materials for lithium-ion batteries are challenged by capacity degradation,which becomes more aggravated particularly at elevated temperatures.Thus,the practical strategy with facile craft and the viability of large-scale preparation for industrialized applications should be developed urgently.In this work,a micron-sized LNMO single crystals is synthesized by a facile two-step method consisting of an alcohol gel solvent method and a segmented sintering reaction.Results show that the truncated polyhedron LNMO-900 sample,with the moderate D50 characteristic value of 4.429 mm and the highest tap density of 2.31 g cm^(-3),provides a stable structural and chemical stability even at elevated testing temperature due to its moderate specific surface area and the few Fd-3m phase.The LNMO/Li half-cells display more excellent capacity retention(87.3% at 1C and 25℃ after 500 cycles)and better thermal stability(76.65% at 1C and 55℃ after 200 cycles)than those of the single crystals of LNMO-850 and LNMO-950.Besides,the XPS,in-situ EIS and electrochemical tests results also prove that the LNMO-900 exhibits the lowest electrolyte decomposition degree,owing to a thin and effective solid-electrolyte interfacial film formed after cycles.