SOLID STATE BATTERY

To provide a solid state battery using Si as a negative electrode active material, in which an increase in heating value hardly occurs.SOLUTION: A solid state battery 100 includes a positive electrode active material layer 10, a negative electrode active material layer 20, a solid electrolyte layer 30, and a polymer electrolyte layer 40. The solid electrolyte layer 30 is disposed between the positive electrode active material layer 10 and the negative electrode active material layer 20. The polymer electrolyte layer 40 is disposed at least one between the positive electrode active material layer 10 and the solid electrolyte layer 30 and between the negative electrode active material layer 20 and the solid electrolyte layer 30. The negative electrode active material layer 20 contains Si, as a negative electrode active material, the solid electrolyte layer 30 contains an inorganic solid electrolyte having Li, as a constituent element, and the polymer electrolyte layer 40 has an ionic conductivity at 120°C less than the ionic conductivity at 60°C.SELECTED DRAWING: Figure 1 【課題】負極活物質としてＳｉを用いた固体電池であって、発熱量の増大が生じ難い固体電池の提供。【解決手段】正極活物質層１０と、負極活物質層２０と、固体電解質層３０と、ポリマー電解質層４０とを備え、固体電解質層３０は、正極活物質層１０と負極活物質層２０との間に配置され、ポリマー電解質層４０は、正極活物質層１０と固体電解質層３０との間、及び、負極活物質層２０と固体電解質層３０との間、のうちの少なくとも一方に配置され、負極活物質層２０は、負極活物質としてＳｉを含み、固体電解質層３０は、構成元素としてＬｉを有する無機固体電解質を含み、ポリマー電解質層４０は、１２０℃におけるイオン伝導度が６０℃におけるイオン伝導度よりも小さい、固体電池１００。【選択図】図１