Improving electrochemical performance of Ni-rich layered oxide cathodes via one-step dual modification strategy

A one-step overall strategy from surface to bulk was proposed to simultaneously synthesize the Nb-doped and LiNbO_(3)-coated LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2) cathode materials.The incorporation of LiNbO_(3) coating can regulate the interface and facilitate the diffusion of Li-ions.Simultaneously,the stronger Nb—O bond can effectively suppress Li^(+)/Ni^(2+) cation mixing and strengthen the stability of crystal structure,which helps to mitigate the anisotropic variations of lattice parameters during Li^(+) de/intercalation.The results showed that the dual-modified materials exhibited good structural stability and distinguished electrochemical performance.The optimal NCM-Nb2 sample showed an excellent capacity retention of 90.78%after 100 cycles at 1C rate between 2.7 and 4.3 V,while only 67.90%for the pristine one.Meanwhile,it displayed a superior rate capability of 149.1 mA·h/g at the 10C rate.These results highlight the feasibility of one-step dual modification strategy to synchronously improve the electrochemical performance of Ni-rich layered oxide cathodes.

Fabrication of electrospun bilayer separators for lithium-sulfur batteries:A surface and structure dual modification strategy

The severe shuttle effect problem of soluble polysulfides greatly hinders the development of long-life lithium-sulfur(Li-S)batteries,which can be improved by separator modification.This study develops a bilayer separator based on an effective surface and structure dual modification strategy.This bilayer separator(named as TCNFs/SPNFs)is constructed by the integration of a carbon-based nanofiber layer(surface modification layer)with a polymer-based nanofiber layer(structure modification layer)through a facile electrospinning process.The excellent electrolyte wettability of the nanofibers accelerates lithium-ion migration,while the good electronic conductivity of the carbon layer facilitates fast electron conduction.The TiO_(2)and SiO_(2)nanoparticles embedded in the separator provide abundant active sites for immobilizing the polysulfides.Owing to these synergistic effects,this multi-functional separator helps inhibit the shuttling problem and thus enhances the active sulfur utilization.The as-prepared battery with the TCNFs/SPNFs separator delivers significantly enhanced the electrochemical performances,producing a low capacity decay rate of 0.061%per cycle at 1 C over 1000 cycles and an admirable rate capacity of 886.7 mAh g^(-1)at 2 C.Even with a high sulfur loading of 4.8 mg cm^(-2),a remarkable areal capacity of 6.0 mAh cm^(-2)is attained.This work is believed to provide a promising strategy to develop novel separators for high-performance Li-S batteries.

Damage mechanisms and recent research advances in Ni-rich layered cathode materials for lithium-ion batteries

Nickel-rich cathode is considered to be the cathode material that can solve the short-range problem of electric vehicles with excellent elec-trochemical properties and low price.However,microcracks,lithium–nickel hybridization,and irreversible phase transitions during cycling limit their commercial applications.These issues should be resolved by modifications.In recent years,it has been favored by researchers to solve a large number of problems by combining multiple modification strate-gies.Therefore,this paper reviews recent developments in various modification techniques for nickel-rich cathode materials that have improved their electrochemical characteristics.The summary of multiple modifications of nickel-rich materials will play a guiding role in future development.

Integrating trace Ti-doping and LiYO2-coating to stabilize Ni-rich cathodes for lithium-ion batteries

Ni-rich layered cathodes have become the promising candidates for the next-generation high-energy Liion batteries due to their high energy density and competitive cost.However,they suffer from rapidcapacity fading due to the structural and interfacial instability upon long-term operation.Herein,the Tidoped and LiYO2-coated Ni-rich layered cathode has been synthesized via a facile one-step sinteringstrategy,which significantly restrains the interfacial parasitic side reactions and enhances the structuralstability.Specifically,the trace Ti^(4+)doping greatly stabilizes the lattice oxygen and alleviates the Li/Nidisorder while the LiYO_(2) coating layer can prevent the erosion of the cathode by the electrolyte duringcycles.As a result,the Ti-NCM83@LYO delivers a high specific capacity of 135 mAh g^(-1) even at 10C andthere is almost no capacity loss at 1C for 100 cycles.This work provides a simple one-step dual-modification strategy to meet the commercial requirements of Ni-rich cathodes.