▎ 摘　　要

NOVELTY - An electrochemical device comprises a positive pole piece comprising a positive active material layer comprising a positive active material, and a negative pole piece comprising a negative active material layer comprising a negative active material (N1) and a negative active material (N2), where the efficiency of the material (N2) is lower than the efficiency of the material (N1). Based on the total weight of the materials (N1) and (N2), the mass percentage omega of the negative electrode active material (N2) satisfies specific relation. USE - Electrochemical device e.g. lithium on battery used for electronic device (claimed). ADVANTAGE - The electrochemical device has suppressed problem of overcharging lithium precipitation during initial charging by mixing the negative electrode active material (N2) with lower primary efficiency in an appropriate ratio in the negative electrode active material layer. DETAILED DESCRIPTION - An electrochemical device comprises a positive pole piece comprising a positive active material layer comprising a positive active material, and a negative pole piece comprising a negative active material layer comprising a negative active material (N1) and a negative active material (N2), where the efficiency of the material (N2) is lower than the efficiency of the material (N1). Based on the total weight of the materials (N1) and (N2), the mass percentage omega of the negative electrode active material (N2) satisfies the relation: x-0.03less than or equal toomegaless than or equal tox+0.1, where x = (C2-C1)/((C4-D4)xyxD1/((1-x)D3+xD4)), C1 is the charging gram capacity of the positive electrode active material at V1, C2 is the charging gram capacity of the positive electrode active material at V2, D1 is the discharge gram capacity of the positive electrode active material after being overcharged by V2 to V3 and then charged to V1, D3 is the discharge gram capacity of the material (N1), C4 is the charged gram capacity of the material (N2), D4 is the discharge gram capacity of the material (N2), y is the CB value of the electrochemical device, V1 is the upper limit of the use voltage of the electrochemical device, V2 is (V1+0.1 V)-(V1+0.5 V), and V3 is the positive electrode potential of the electrochemical device at the lower limit of the use voltage.