What are the technical challenges in developing solid-state batteries for EVs?

Solid-state battery challenges include: Interface resistance between solid electrolyte and electrodes (limiting power density), mechanical stability during cycling (volume changes causing contact loss or cracking), lithium dendrite formation through solid electrolyte (safety concern), scalable manufacturing of thin solid electrolyte layers, operating temperature sensitivity (some electrolytes require 60-80C), and cost of current materials. Solutions being developed include: Sulfide vs oxide vs polymer electrolytes with different tradeoffs, interfacial engineering, and hybrid semi-solid designs. Benefits when achieved include higher energy density (>400 Wh/kg), improved safety, and faster charging.