Abstract: The present disclosure relates to a solid state battery comprising silicon (Si) as a negative electrode active material. The solid state battery according to the present disclosure does not comprise a conductive material and a solid electrolyte in the negative electrode and comprise a minimum amount of binder. According to this structural feature, the battery according to the present disclosure has good electrical and chemical properties including heat resistant stability, energy density, life characteristics and Coulombic efficiency.

Abstract: A solid state battery is described, which has a negative electrode having a negative electrode active material layer including silicon (Si) as a negative electrode active material. The Si may be present as particles, e.g., microparticles, having an average particle size (D50) of 0.1 ?m to 10 ?m. The negative electrode active material layer may include the silicon (Si) in an amount of 75 wt % or more, 95 wt % or more, 99 wt % or more, or 99.9 wt % or more, based on 100 wt % of the negative electrode active material layer. The negative electrode active material layer can be free or substantially free of conductive material, carbon, solid state electrolyte, and/or binder. Preferably, after charge/discharge cycles, the negative electrode active material layer forms densified and interconnected large particles of Li—Si alloy, e.g., the Li—Si alloy may have at least one columnar structure and at least one void.