SECONDARY BATTERY, BATTERY MODULE, BATTERY PACK, AND ELECTRICAL DEVICE

1 . A secondary battery, comprising a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate, wherein the positive electrode plate comprises a positive electrode coating containing a positive electrode active material comprising a lithium iron phosphate material and a conjugated carbonyl compound.

2 . The secondary battery according to claim 1 , wherein

based on a total mass of the positive electrode active material, a mass percentage of the conjugated carbonyl compound is denoted as a %, wherein 2%≤a %≤13%.

3 . The secondary battery according to claim 1 , wherein

on a discharge curve of the positive electrode plate relative to graphite at a discharge rate of 0.33 C, a ratio of a discharge plateau capacity of the lithium iron phosphate material to a total discharge capacity of the positive electrode active material is W 1 , wherein 80%≤W 1 ≤99%; and/or

on a discharge curve of the positive electrode plate relative to graphite at a discharge rate of 0.33 C, a ratio of a discharge plateau capacity of the conjugated carbonyl compound to a total discharge capacity of the positive electrode active material is W 2 , wherein 1%≤W 2 ≤20%.

4 . The secondary battery according to claim 1 , wherein

a discharge curve of the lithium iron phosphate material relative to graphite at the discharge rate of 0.33 C has a discharge plateau voltage V 1 in V, wherein 3.2≤V 1 ≤3.45.

5 . The secondary battery according to claim 1 , wherein a discharge curve of the conjugated carbonyl compound relative to graphite at the discharge rate of 0.33 C has a discharge plateau voltage of V 2 in V, wherein 1.9≤V 2 ≤2.9.

6 . The secondary battery according to claim 1 , wherein

the conjugated carbonyl compound comprises one or more of a quinone compound or salt thereof, a conjugated carboxyl compound or salt thereof, a diimide salt, a dianhydride compound, and a rhodizonate;

optionally, the quinone compound or salt thereof comprises one or more of benzoquinone, anthraquinone, phenanthrenequinone, 1,4-dibenzoquinonylbenzene, 2,3,5,6-tetrachloro-1,4-benzoquinone, 2,5-dimethoxybenzoquinone, 1,3,4-trihydroxyanthraquinone, 1,5-dilithiumoxyanthraquinone, dipyridinobenzoquinone, dithiophenobenzoquinone, difuranobenzoquinone, nonylbenzohexaquinone, 5,7,12,14-pentaphenyltetraone, and 2,5-dihydroxybenzoquinone dilithium salt;

the conjugated carboxyl compound or salt thereof comprises one or more of terephthalic acid, 2,4-dialkenyladipic acid, vinyl dibenzoic acid, terephthalate lithium salt, 2,4-dialkenyladipate lithium salt, and vinyl dibenzoate lithium salt;

the diimide salt comprises a diphenylenetetramethylene diimide dilithium salt and/or a naphthalene tetramethylene diimide dilithium salt;

the dianhydride compound comprises one or more of pyromellitic anhydride, naphthalene tetracarboxylate dianhydride, and perylene tetracarboxylate dianhydride; and

the rhodizonate comprises rhodizonic acid dilithium salt and/or rhodizonic acid tetralithium salt.

7 . The secondary battery according to claim 1 , wherein

the negative electrode plate comprises a negative electrode coating containing a negative electrode active material comprising one or more of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, lithium titanate, and a lithium-aluminum alloy.

8 . The secondary battery according to claim 7 , wherein the negative electrode plate further comprises a lithium supplement layer disposed on the negative electrode coating.

9 . A battery module, comprising the secondary battery according to claim 1 .

10 . A battery pack, comprising the battery module according to claim 9 .

11 . An electrical device, comprising the battery pack according to claim 10 .