Physics / mechanism
Solid-state batteries (SSBs) replace liquid/gel electrolyte with a solid ionic conductor — ceramic (oxide: LLZO, NASICON; sulfide: LGPS, argyrodite), polymer, or halide. Li⁺ transport occurs through lattice defects and grain boundaries rather than solvation shells. Key figures of merit: ionic conductivity (sulfides reach ~10⁻² S/cm at RT, approaching liquid electrolyte ~10⁻² S/cm), electrochemical stability window, interfacial resistance (typically 10–1000 Ω·cm² — the dominant unsolved problem), and critical current density before Li dendrite penetration. Energy density targets: >400 Wh/kg at cell level. State of art: Toyota, QuantumScape, Solid Power in late-stage prototype; sulfide systems lead on conductivity, oxides on stability.
Competitive landscape
Liquid electrolyte Li-ion (LFP, NMC) remains the incumbent — mature supply chain, $100–120/kWh at pack level, proven cycle life. Li-metal with liquid electrolyte (Sion Power, SES AI) offers an intermediate step: higher energy density without solid electrolyte manufacturing complexity. Na-ion competes at low-cost stationary. Key differentiation axes:
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.