Positive electrode plate and battery

Abstract

A positive electrode plate, wherein the positive electrode plate comprises a positive active material and a conductive agent; the positive active material comprises lithium iron phosphate; and in the positive electrode plate, within a unit area of 1 µm × 1 µm, the ratio of a number of lithium iron phosphate to a number of the conductive agent is 1:(0.5 to 50).

Claims

[1] A positive electrode plate, wherein the positive electrode plate comprises a positive active material and a conductive agent; the positive active material comprises lithium iron phosphate; and in the positive electrode plate, within a unit area of 1 µm × 1 µm, the ratio of a number of lithium iron phosphate to a number of the conductive agent is 1:(0.5 to 50). [2] The positive electrode plate according to claim 1, wherein in the positive electrode plate, within a unit area of 1 µm × 1 µm, the ratio of the number of lithium iron phosphate to the number of the conductive agent is 1:(5 to 40); preferably in the positive electrode plate a mass fraction of the positive active material is 90% to 95%; preferably in the positive electrode plate a mass fraction of the conductive agent is 2% to 5%. [3] The positive electrode plate according to claim 1, wherein a primary particle size of the lithium iron phosphate is denoted by A nm, an average particle size of the conductive agent is denoted by B nm, a ratio of A to B is (2 to 60):1, preferably (2.5 to 8):1; preferably the primary particle size A of the lithium iron phosphate is 100 nm to 600 nm, more preferably 140 nm to 300 nm; preferably the average particle size B of the conductive agent is 10 nm to 100 nm, more preferably 40 nm to 70 nm. [4] The positive electrode plate according to claim 3, wherein a surface resistance of the positive electrode plate is denoted by R Ωcm; the relationship between the primary particle size A of the lithium iron phosphate and the surface resistance R of the positive electrode plate satisfies 0.18 ≤ A / R ≤ 3; preferably, the surface resistance R of the positive electrode plate is 200 Ωcm to 600 Ωcm. [5] The positive electrode plate according to any one of claims 1 to 4, wherein the positive electrode plate further comprises a binder; a mass ratio of the conductive agent to the binder is 1:(0.3 to 2), preferably 1:(0.4 to 1.6); preferably a mass fraction of the binder in the positive electrode plate is 2% to 5%; preferably a peel strength of the positive electrode plate is 4 gf / mm to 25 gf / mm; preferably the binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyoxyethylene, sodium carboxymethylcellulose or styrene-butadiene rubber. [6] The positive electrode plate according to any one of claims 1 to 4, wherein a pressing density of the positive electrode plate is 1.8 g / cm 3 up to 2.5 g / cm 3 amounts; preferably a specific surface area C of the lithium iron phosphate 8 m 2 / g up to 15 m 2 / g; Preferably, the conductive agent comprises at least one of the following elements: conductive carbon black, conductive graphite, acetylene black, Keqin black, graphene, conductive carbon fiber, carbon nanotubes, metal powder, or carbon fiber. [7] A battery, the battery comprising the positive electrode plate according to any one of claims 1 to 6. [8] The battery according to claim 7, wherein the battery comprises a separator; the separator comprises a base film and an adhesive layer disposed on at least one side surface of the base film; preferably a projected area ratio of the adhesive layer on the base film is denoted by S, the primary particle size of the lithium iron phosphate is denoted by A nm, and the relationship between S and A: 0.03 ≤ S / A ≤ 0.35, preferably 0.1 ≤ S / A ≤ 0.25 is satisfied; preferably the projected area proportion S of the adhesive layer on the base film is 15% to 35%. [9] Battery according to claim 8, wherein the specific surface area of the lithium iron phosphate is C m 2 / g, a thermal shrinkage rate of the separator is denoted by L%, and the relationship between C and L satisfies 0.16 ≤ C / L ≤ 0.75; preferably the specific surface area C of the lithium iron phosphate 8 m 2 / g up to 15 m 2 / g; preferably the thermal shrinkage rate L of the separator is 20% to 50%. [10] The battery according to any one of claims 7 to 9, wherein the battery further comprises a negative electrode plate, the negative electrode plate comprising a negative active material; preferably the negative active material comprises at least one of graphite, hard carbon, mesocarbon microbeads, silicon carbide, silicon oxide, nanosilicon or a silicon alloy; more preferably the negative active material comprises graphite and hard carbon; Preferably, in the negative active material, a proportion of hard carbon is 0 wt% to 30 wt% and a proportion of graphite is 70 wt% to 100 wt%.

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