TECHNICAL FIELD

The disclosure relates to an anode active material for all-solid-state batteries.

BACKGROUND

An active material (an alloy-based active material) containing a metal that can be alloyed with Li, such as Si, has large theoretical capacity per volume, compared to a carbon-based anode active material. Accordingly, an all-solid-state battery in which such an alloy-based active material is used in the anode, has been proposed.

An all-solid-state secondary battery is disclosed in Patent Literature 1, in which both a carbon-based anode active material and a Si-based anode active material are used in the anode active material layer. Patent Literature 1 describes that a decrease in discharge capacity is suppressed when the all-solid-state secondary battery is charged at high rate.

Patent Literature 1: Japanese Patent Application Laid-Open No. 2016-225187

However, it is difficult for the all-solid-state battery using the Si-based anode active material to suppress an increase in the resistance of the battery, with increasing the coulombic efficiency during initial charge and discharge of the battery.

SUMMARY

The disclosed embodiments were achieved in light of the above circumstances of the Si-based anode active material. An object of the disclosed embodiments is to provide an anode active material configured to achieve both an increase in the coulombic efficiency during initial charge and discharge of an all-solid-state battery, and suppression of an increase in the resistance of the all-solid-state battery.

In a first embodiment, there is provided an anode active material, wherein the anode active material is an anode active material for use in all-solid-state batteries; wherein the anode active material comprises a lithium-silicon alloy and elemental silicon; and wherein the anode active material has peaks at positions of 2θ=20.2°±0.5°, 23.3°±0.5°, 40.5°±0.5°, and 46.0°±0.5° in a XRD spectrum obtained by XRD measurement using CuKα radiation.

The element ratio of the lithium based on the silicon in the anode active material, may be from 0.20 to 4.0.

The lithium-silicon alloy and the elemental silicon may be particulate.

The elemental silicon may be crystalline.

The anode active material may further have peaks at positions of 2θ=28.5°±0.5°, 47.0°±0.5°, and 56.0°±0.5° in the XRD spectrum.

By using the anode active material of the disclosed embodiments in an all-solid-state battery, both an increase in the coulombic efficiency during initial charge and discharge of the all-solid-state battery, and suppression of an increase in the resistance of the all-solid-state battery, can be achieved.

