▎ 摘　　要

NOVELTY - Negative electrode piece comprises a current collector (1), and an active material layer (2) located on the current collector. The active layer comprises a silicon-based material. The minimum value of the mass ratio of the silicon element in the active layer at the same area and different positions is X1, the maximum value is X2, the value of X1/X2 is M, where M is not less than 0.7, and the weight loss ratio minimum value (Y1) of the thermal gravimetric analysis (TG) at 800 degrees C is Y1, where Y1/Y2 is N. USE - Negative electrode piece used in an electrochemical device for electronic device (all claimed). ADVANTAGE - The cathode pole piece improves the silicon-based material distribution uniformity in the carbon material. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for an electrochemical device, which comprises a positive pole piece, a negative pole piece, a separator arranged between the positive pole piece and the negative pole piece, where the negative pole piece is the negative pole piece. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the cathode polepiece. Current collector (1) Active material layer (2)