Study On Interface Of All-solid-state Lithium Batteries Based On PVC Polymer Electrolyte

With the widespread application of portable electronic products and new energy vehicles,people are increasingly studying lithium ion batteries.Among them,all-solid-state lithium batteries attract much attention due to their high safety and high energy density.However,the interface problem caused by the contact between solid electrolyte and electrode is the main factor hindering the development of solid-state lithium batteries.To solve interface problem,the PVC polymer electrolyte and Li 1.3Al0.3Ti1.7(PO4)3(LATP)inorganic solid electrolyte were studied in this paper.First of all,trimethyl phosphate(TMP)is used as additive to improve the interfacial contact of PVC polymer electrolyte and lithium anode,and then effectively inhibit the growth of lithium dendrites.Secondly,in-situ introduction of PVC+TEGDME polymer between the LATP inorganic solid electrolyte and electrode,which improve the interface contact between the inorganic solid electrolyte and electrode,greatly reduce the interface resistance,and effectively preven the reduction of LATP by Li electrode.The detailed research contents are as follows:(1)With the support of cellulose membrane,PVC-TMP solid electrolyte was prepared by in-situ polymerization with VC as monomer and TMP as plasticizer.The effects of different contents of TMP on electrolyte were studied.With the increase of TMP content,the ionic conductivity gradually increases,and the electrochemical stability window and the lithium ion transfer number increase first and then decrease.The presence of TMP reduces the degree of polymerization of PVC and accelerates the movement of PVC chain segment.What’s more,and TMP is conducive to the dissociation of lithium salt.When 10 wt%TMP is added,the PVC-TMP electrolyte shows a moderate ionic conductivity of 2.54×10-5 S cm-1(50℃).Moreover,TMP increases the flexibility of PVC and improves the contact between PVC and lithium anode.The initial impedance of solid-state lithium battery based on PVC-TMP polymer electrolyte is only 118 Ω at 50℃.Li/PVC-TMP/Li exhibit stable cycle for 1000 h at 0.05 mA cm-2 and 50℃.LiFePO4/PVC-TMP/Li battery maintains capacity retention of 79.7%after 150 cycles at 0.5 C.(2)Commercial LATP powder was used as raw material,which was pressed into LATP pellet and then sintered.First of all,the sintering temperature and time of LATP pellet were explored.The results show that when the sintering temperature and time are 850℃ and 2 h,the LATP pellet are obtained with moderate grain size,fewer grain boundaries,and no impurity phases.Then,PVC+TEGDME polymer electrolyte was introduced in-situ between LATP electrolyte and electrode.Compared with the pure LATP based solid-state lithium battery,the initial impedance of the modified LATP based solid-state lithium battery reduce from 5925 Ω to 286 Ω at 50℃.Li/LATP-PVC+TEGDME/Li exhibit stable cycle for 350 h at 0.09 mA cm-2 and 50℃,and the polarization voltage is only 0.0035 V.The LiFePO4/LATP-PVC+TEGDME/Li provides capacity retention of 94%after 100 cycles at 0.5 C.In addition,the averaged discharge specific capacity of NCM811/LATP-PVC+TEGDME/Li battery is 181.4 mAh g-1 at 0.1 C and 50℃.