Active material
A main object of the present disclosure is to provide an active material wherein an expansion upon intercalation of a metal ion such as a Li ion is suppressed. The present disclosure achieves the object by providing an active material comprising a silicon clathrate type crystal phase, and the active material includes a Na element, a Si element and a M element that is a metal element with an ion radius larger than the Si element, and a proportion of the M element to a total of the Si element and the M element is 0.1 atm % or more and 5 atm % or less.
1. An all solid state battery comprising an anode layer, a cathode layer, and a solid electrolyte layer including a solid electrolyte and formed between the cathode layer and the anode layer, wherein
one of the anode layer and the cathode layer includes an active material comprising a silicon clathrate type crystal phase,
the active material includes a Na element, a Si element and a Ge element,
a proportion of the Ge element to a total of the Si element and the Ge element is 0.5 atm % or more and 1 atm % or less,
an atomic part of the Na element to 136 atomic parts of the Si element is 2.0 parts or more and 5.4 parts or less, such that
the active material has a composition represented by Na w Ge z Si 136−z where [0<w, w≤24 and 0.136≤z≤6.8] 2.0≤w≤5.4 and 0.5≤z≤1.