Preparation And Properties Of Li₂O-V₂O₅-SiO₂-B₂O₃ Glass As Cathode Material For Lithium Ion Batteries

At present,most researches on cathode materials for lithium-ion batteries focus on crystalline materials with an inherent theoretical capacity.However,it is very difficult to break through the capacity limitation.What's more,the crystalline materials always suffer from phase transition and structural collapse in long-cycles,which destroy their cycling stability.Therefore,a new concept of amorphous cathode materials has been proposed.The capacity of amorphous materials can be changed by changing the composition.And a free volume adapting to lattice distortion can also improve cycling performance.This paper proposed a new system of Li₂O-V₂O₅-Si O₂-B₂O₃?named as LVSB?quaternary amorphous material,and made judgement about whether it is expected to be used as a cathode material for lithium-ion batteries.Firstly,LVSB amorphous materials were prepared by sol-gel method and melt-quenching method,and their morphology,structure and electrochemical properties were analyzed.It showed that the sol-gel method cannot satisfy both amorphous property and electrochemical activity,while the melt-quenching method could.Furthermore,the samples obtained by different melting processes were characterized.It was found that the samples with a melting temperature of 1000°C or 1100°C and a holding time of 30 min or 60 min exhibited better electrochemical performance while maintaining the amorphous state.Considering the energy consumption and other factors,melting at 1000°C for 30min is the best preparation process.Secondly,based on the optimal preparation process,the electrochemical performance of LVSB quaternary amorphous materials with different compositions were compared.They were prepared by changing the ratio of Li₂O/V₂O₅ and Si O₂/B₂O₃.After detailed structural characterization and electrochemical analysis,it was found that when the ratio of Li₂O:V₂O₅:Si O₂:B₂O₃ was 2:3:4:1,the obtained sample showed the best electrochemical performance maintaining amorphous.Finally,the samples obtained under the optimal ratio and the best preparation process were ball milled,and the electrochemical properties of the samples before and after ball milling were compared.As a result,the sample after ball milling had a larger capacity?158.1 m Ah/g for the first cycle?,and the cycling performance was improved?the capacity retention rate increased from 26.9%to 56.5%after one hundred cycles?,the rate performance was also more desirable.And the results of ex-situ XPS can reveal that LVSB amorphous cathode materials present an insertion mechanism.This work prepared Li₂O-V₂O₅-Si O₂-B₂O₃ quaternary amorphous materials by a simple one-step method,and the possibility of the new system as a cathode material for lithium ion batteries was fully verified.The electrochemical properties of the material can be significantly improved through a simple physical method?ball milling?,which makes it hope to become one of the new materials in the next generation of energy storage devices.