▎ 摘　　要

NOVELTY - Cathode piece of sodium ion battery comprises a cathode current collector, and a carbon material coating formed on at least part of the surface of the cathode current collector. The thickness of the carbon material coating is less than or equal to 10 microm; and the carbon material coating includes carbon material and polymer adhesive. USE - The cathode piece of sodium ion battery is useful in electrochemical device, and electronic device (all claimed). ADVANTAGE - The cathode piece: deposits metallic sodium on the surface of cathode current collector during the first charge, and the deposited metal sodium can adhere to the carbon material coating on the surface of cathode current collector. The carbon material coating: efficiently reduce the over-potential of sodium metal deposition; inhibits the formation of sodium dendrites; and improves the cycle performance of the battery. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for electrochemical device. The device utilizes anode piece.