Abstract: Provided is a composite active material for a secondary battery with improved initial coulombic efficiency and capacity retention rate of a negative electrode active material, and a secondary battery containing the composite active material for a secondary battery. The composite active material for a secondary battery has silicon particles with an average particle size of 150 nm or less, a matrix phase in which the silicon particles are dispersed, and a silicate compound of at least one metal selected from Li, K, Na, Ca, Mg, and Al. The composite active material for a second battery has the silicate compound in a near-surface of the silicon particles. The silicate concentration in the near-surface of the silicon particles is higher than the silicate concentration in the matrix phase. The composite active material for a secondary battery further has silicon dioxide in the near-surface of the silicon particles.

Abstract: A present invention is a power supply device, comprising a battery unit, a heater configured to generate heat on the basis of power of the battery unit, and a driving unit configured to drive the heater with a driving force according to a temperature of the battery unit.