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, and
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 2.0≤w≤5.4 and 1<z≤1.36.