SECONDARY BATTERY, BATTERY MODULE, BATTERY PACK, AND ELECTRIC APPARATUS
A secondary battery, a battery module, a battery pack, and an electric apparatus are provided. The secondary battery includes a positive electrode plate and a non-aqueous electrolyte. The positive electrode plate includes a positive electrode active material, the positive electrode active material including a core and a shell enveloping the core, where the core contains Li 1+x Mn 1-y A y P 1-z R z O 4 , and the shell includes a first coating layer enveloping the core and a second coating layer enveloping the first coating layer. The first coating layer includes a pyrophosphate MP 2 O 7 and a phosphate XPO 4 , where 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. The non-aqueous electrolyte includes an organic solvent, where the organic solvent includes a first solvent, and the first solvent includes one or more of compounds represented by
1 . 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 Li 1+x Mn 1-y A y P 1-z R z O 4 , 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 MP 2 O 7 and a phosphate XPO 4 , 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 R 1 and R 2 are each independently one of C1 to C10 alkyl group and C1 to C10 haloalkyl group, and optionally R 1 and R 2 are each independently one of methyl, ethyl, propyl, butyl, pentyl, hexyl, fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, fluoropentyl, and fluorohexyl, and further optionally R 1 and R 2 are each independently one of methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl.
2 . The secondary battery according to claim 1 , wherein the first solvent comprises at least one of the following compounds:
3 . The secondary battery according to claim 1 , wherein based on a total mass of the organic solvent, a mass percentage of the first solvent is w1, w1 ranging from 20% to 80%.
4 . The secondary battery according to claim 1 , wherein the non-aqueous electrolyte further comprises a first additive, the first additive containing one or more from a group consisting of sultone and cyclic sulfate.
5 . The secondary battery according to claim 4 , wherein the sultone comprises at least one of compounds represented by formula 2:
wherein p represents 1, 2, or 3, R 11 represents one of a hydrogen atom, halogen atom, C1 to C12 alkyl group, C1 to C12 haloalkyl group, C1 to C12 alkoxy group, and C1 to C12 haloalkoxy group;
each R 12 independently represents one of a hydrogen atom, halogen atom, C1 to C12 alkyl group, C1 to C12 haloalkyl group, C1 to C12 alkoxy group, C1 to C12 haloalkoxy group, and 4- to 7-membered sultone group;
R 11 and R 12 may form a 5- to 10-membered cycloalkyl group with their respective attached carbon atoms;
R 13 represents one of a hydrogen atom, halogen atom, carbonyl group, C2 to C6 ester group, C1 to C12 alkyl group, C1 to C12 haloalkyl group, C2 to C12 alkenyl group, C1 to C12 alkoxy group, C1 to C12 haloalkoxy group, and C6 to C20 aryl group or benzyl group;
and/or
the cyclic sulfate comprises at least one of compounds represented by formula 3,
wherein q represents 1, 2, or 3,
R 14 represents one of a hydrogen atom, halogen atom, carbonyl group, C1 to C12 alkyl group, C1 to C12 haloalkyl group, C2 to C12 alkenyl group, C1 to C12 alkoxy group, C1 to C12 haloalkoxy group, C2 to C6 ester group, and 4- to 7-membered cyclic sulfate group, and optionally R 14 represents one of a hydrogen atom, halogen atom, carbonyl group, double bond, C1 to C6 alkyl group, C1 to C3 haloalkyl group, C1 to C3 alkoxy group, C1 to C3 haloalkoxy group, C2 to C3 easter group, and 4- to 5-membered cyclic sulfate group;
each R 15 independently represents one of a hydrogen atom, halogen atom, C1 to C12 alkyl group, C1 to C12 haloalkyl group, C1 to C12 alkoxy group, C1 to C12 haloalkoxy group, and C6 to C20 aryl group, and optionally each R 15 independently represents one of a hydrogen atom, halogen atom, C1 to C6 alkyl group, C1 to C3 haloalkyl group, C1 to C3 alkoxy group, C1 to C3 haloalkoxy group, and C6 to C10 aryl group; or
R 14 and R 15 each form a 4- to 7-membered cyclic sulfate group together with respective carbon atoms bonded thereto.
6 . The secondary battery according to claim 4 , wherein based on a total mass of the non-aqueous electrolyte, a proportion of the first additive is W3 and 0.01%≤W3≤20%.
7 . The secondary battery according to claim 1 , wherein the non-aqueous electrolyte further comprises a second additive, the second additive comprising one or more from a group consisting of a sulfite compound, a disulfonate compound, a nitrile compound, an aromatic compound, a phosphazene compound, a cyclic anhydride compound, a phosphite compound, a phosphate compound, and a borate compound.
8 . The secondary battery according to claim 7 , wherein based on the total mass of the non-aqueous electrolyte, a proportion of the second additive is W4, and 0.01%≤W4≤20%.
9 . The secondary battery according to claim 1 , wherein
based on a weight of the core, an application amount of the first coating layer is C1 wt %, C1 being greater than 0 and less than or equal to 7; and/or
based on the weight of the core, an application amount of the second coating layer is C2 wt %, C2 being greater than 0 and less than or equal to 6.
10 . The secondary battery according to claim 1 , wherein
a weight ratio of the pyrophosphate to the phosphate in the first coating layer ranges from 1:3 to 3:1.
11 . The secondary battery according to claim 1 , wherein
the phosphate in the first coating layer has an interplanar spacing of 0.345 nm to 0.358 nm and an included angle of 24.25° to 26.45° in the (111) crystal orientation; and
the pyrophosphate in the first coating layer has an interplanar spacing of 0.293 nm to 0.326 nm and an included angle of 26.410 to 32.57° in the (111) crystal orientation.
12 . The secondary battery according to claim 1 , wherein
a ratio of y to 1-y in the core ranges from 1:10 to 10:1; and/or
a ratio of z to 1-z in the core ranges from 1:9 to 1:999.
13 . The secondary battery according to claim 1 , wherein
a crystallinity of the pyrophosphate and a crystallinity of the phosphate each independently range from 10% to 100%.
14 . The secondary battery according to claim 1 , wherein
A is at least two selected from Fe, Ti, V, Ni, Co, and Mg.
15 . The secondary battery according to claim 1 , wherein
a Li/Mn anti-site defect concentration of the positive electrode active material is below 4%.
16 . The secondary battery according to claim 1 , wherein
a lattice change rate of the positive electrode active material is below 6%.
17 . The secondary battery according to claim 1 , wherein
a surface oxygen valence of the positive electrode active material is below −1.88.
18 . A battery module, comprising a secondary battery, wherein the secondary battery is the secondary battery according to claim 1 .
19 . A battery pack, comprising a battery module, wherein the battery module is the battery module according to claim 18 .