Three-dimensional networking binders prepared in situ during wet-slurry process for all-solid-state batteries operating under low external pressure

Abstract

For all-solid-state Li batteries (ASLBs), the external operating pressure offsets the detrimental electrochemo-mechanical effects. In this work, a new scalable in situ protocol to reinforce binders for sulfide-electrolyte-based ASLBs operating under low or no external pressures is reported. The vulcanization of butadiene rubber (BR) using elemental sulfur proceeds in situ during the wet-slurry fabrication process for electrodes, forming a mechanically resilient crosslinked structure. The electrochemical performance of LiNi0.70Co0.15Mn0.15O2 electrodes fabricated using pristine or vulcanized BR diverge significantly as the operating pressure is lowered from 70 MPa to a practically acceptable value of 2 MPa. Complementary analysis using cross-sectional scanning electron microscopy and operando electrochemical pressiometry measurements confirms that the vulcanization of BR suppresses the electrochemo-mechanical degradation of electrodes, which suggests that the scaffolding structure of the vulcanized BR helps maintain the microstructural integrity of the electrodes upon charge and discharge. The significantly enhanced performance of the vulcanized BR is also demonstrated for pouch-type LiNi0.70Co0.15Mn0.15O2/Li4Ti5O12 full cells operated under no external pressure (reversible capacity of 121 vs. 150 mA h g−1 at 0.2C for electrodes with pristine vs. vulcanized BR, respectively).