Constructing PTFE@LATP composite solid electrolytes with three-dimensional network for high-performance lithium batteries

Abstract

The NASICON-type lithium aluminum titanium phosphate (LATP) solid-state electrolytes is considered as a promising candidate for next-generation all-solid-state lithium batteries (ASSLBs) with high energy density. However, LATP possesses highly interfacial impedance, causing poor electrochemical performance of ASSLBs and seriously hindering its practical application. Herein, the (polytetrafluoroethylene) PTFE@LATP composite solid electrolytes with three-dimensional network have been constructed by combining sol-gel and solid state grinding methods. The electrochemical performance test results show that the introduction of 24 wt% PTFE can effectively reduce the interface impedance of LATP (LATP:2010.0 Ω, PTFE@LATP:126.9 Ω), increased ion conductivity of LATP (LATP:5.50 × 10−5 S∙cm−1, PTFE@LATP:7.56 × 10−4 S∙cm−1), further significantly improve the electrochemical window (LATP:3.2 V, PTFE@LATP:5.0 V), rate capability (corresponds to 95.2% of the initial discharge capacity) and cycling stability (the capacity of the full cell is changed from 140.1 mAh∙g−1 to 88.3 mAh∙g−1 after 500 cycles at 1 C) of ASSLBs. Mechanism research indicates that PTFE@LATP with the excellent electrochemical performance benefits from PTFE@LATP CSEs with three-dimensional network and electrode possess well interface compatibility, it conducive to preventing the occurrence of interface side reactions and promoting the rapid migration of lithium ions. This work provides a theoretical basis and practical guidance for the further development of CSEs with higher electrochemical performance.