Secondary battery, battery module, battery pack, and electric apparatus

A secondary battery, comprising a positive electrode plate and a non-aqueous electrolyte, wherein

• the positive electrode plate comprises a positive electrode active material, wherein the positive electrode active material comprises a core and a shell enveloping the core;
• the core containing Li1+xMn1-yAyP1-zRzO4, wherein x=−0.100 to 0.100, y=0.001 to 0.500, z=0.001 to 0.100, A is one or more selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and optionally is one or more of Fe, Ti, V, Ni, Co, and Mg, and R is one or more selected from B, Si, N, and S;
• and
• the shell comprising a first coating layer enveloping the core and a second coating layer enveloping the first coating layer, wherein
• the first coating layer comprises a pyrophosphate MP2O7 and a phosphate XPO4, wherein M and X each are one or more independently selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, or Al;
• and
• the second coating layer contains carbon;
• and
• the non-aqueous electrolyte comprises an organic solvent, wherein the organic solvent comprises a first solvent, the first solvent comprising one or more of compounds represented by formula 1:
• wherein R1 and R2 are each independently one of C1 to C10 alkyl group and C1 to C10 haloalkyl group, and optionally R1 and R2 are each independently one of methyl, ethyl, propyl, butyl, pentyl, hexyl, fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, fluoropentyl, and fluorohexyl, and further optionally R1 and R2 are each independently one of methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl.