| Solid-state battery has attracted wide attention from researchers due to its high safety and high energy density,among which solid-state electrolyte is the technical focus of solid-state battery development.In this paper,PVDF-HFP with high dielectric constant was selected as polymer substrate to investigate the modification of separately or simultaneous addition of inorganic fillers and plasticizers.Firstly,the separately modification effect of inorganic fillers or plasticizers was studied.Based on the flame retardant effect of Mg2B2O5 and the Lewis acid-base interaction between cations in Mg2B2O5 and TFSI-,Mg2B2O5 was prepared by molten salt method and high temperature calcination method and added as an inert filler,the room temperature（RT）ionic conductivity and Li+transfer number(t Li+)of solid electrolyte（SE）were improved,and the capacity retention of Li|LFP at 0.5 C at RT was 92.9%.When SE was modified with active filler Li1.5Al0.5Ge1.5（PO4）3（LAGP）,infrared spectrum showed that the complexation of Ge atoms with N atoms in DMF could promote the chemical dehydrofluorination of the matrix,reduce activation energy（Ea）and increase t Li+.Li|LFP exerted specific capacity of 126.9 m Ah g-1 at0.5 C at RT.When SE was modified with plasticizer propylene carbonate（PC）,it was found by infrared spectrum that rotational vibration peak intensity of C-C decreased,which led to conformational distortion and stretching of the matrix,which inhibited the crystallization of polymer.The rate performance of Li|LFP was greatly improved,and the initial capacity reached 158 m Ah g-1 at 0.2 C at RT.The ionic conductivity at RT reached 9.78×10-4 S cm-1 with the addition of both PC and inert filler Mg2B2O5 at the optimal amount,t Li+inecreased to 0.42.The assembled Li|PVDF-HFP/Mg2B2O5/PC|LFP performed 90.3%capacity retention after 350 cycles at 0.5 C,while the control group was only 76.1%.When both PC and active filler LAGP were added to the PVDF-HFP solid-state electrolyte at the optimal addition,scanning electron microscope observation showed that plasticizer could connect loose inorganic fillers to polymer matrix,increase Li+transport channel,and increased the ionic conductivity at RT to 1.21×10-3 S cm-1 and Li+transfer number was reached up to 0.54.The assembled Li|PVDF-HFP/LAGP/PC|NCM delivered an initial capacity of 157 m Ah g-1 at 0.2 C and still reached 147 m Ah g-1 after 100 cycles,with a capacity retention of 93.6%,while the unmodified battery was only 64.8%.By studying the modification of solid electrolytes with inert filler,active filler and plasticizer,the electrochemical performance of solid electrolytes was improved,which provided new ideas for the modification of solid electrolytes. |
