CN-116470125-B - Lithium ion secondary battery and design method and power utilization device thereof

CN116470125BCN 116470125 BCN116470125 BCN 116470125BCN-116470125-B

Abstract

The application discloses a lithium ion secondary battery, a design method thereof and an electric device, and belongs to the technical field of new energy. A lithium ion secondary battery comprises a positive electrode plate, a negative electrode plate, electrolyte and a diaphragm, wherein the positive electrode plate comprises a positive electrode current collector, a positive electrode active material layer and a protective film layer, the protective film layer contains boron compounds, the positive electrode active material layer comprises lithium cobalt-based ternary materials, the mass percentage of the boron compounds in the positive electrode active material layer is b and 0<b is less than or equal to 0.05%, the mass percentage of the boron compounds in the electrolyte is a and is more than or equal to 0.1% and less than or equal to 12%, the mass concentration of the boron elements in the positive electrode material layer and the mass concentration of the cobalt elements are met, the mass concentration of the boron elements in the positive electrode material layer and the mass concentration of the cobalt elements are controlled to be less than or equal to 750-32.54 are less than or equal to 1400- λ, the mass concentration of the boron elements in the positive electrode material layer and the mass concentration of the cobalt elements are controlled to be less than or equal to 32.54 are met to 750-1400- λ, and the mass concentration of the boron elements in the positive electrode layer and the mass concentration of the cobalt elements are ppm.

Inventors

FU JIALE
TIAN XIAODONG
LV GUOXIAN
CHU CHUNBO

Assignees

欣旺达电动汽车电池有限公司

Dates

Publication Date: 20260508
Application Date: 20230428

Claims (11)

1. The lithium ion secondary battery is characterized by comprising a positive electrode plate, a negative electrode plate, electrolyte and a diaphragm; The positive electrode plate comprises a positive electrode current collector, a positive electrode active material layer arranged on at least one surface of the positive electrode current collector and a protective film layer formed on the positive electrode active material layer, wherein the positive electrode active material layer and the protective film layer form a positive electrode material layer; the protective film layer contains a boron compound; the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium cobalt-based ternary material; The positive electrode active material layer contains a boron compound, the boron compound in the positive electrode active material layer comprises boric acid, and the mass percentage of the boron compound in the positive electrode active material layer is b, 0<b-0.05% based on the total mass of the positive electrode active material layer; the electrolyte contains boron compounds, and the mass percentage of the boron compounds in the electrolyte is a, which is more than or equal to 0.1% and less than or equal to 12% based on the total mass of the electrolyte; the mass concentration lambda of boron element and the mass concentration epsilon of cobalt element in the positive electrode material layer are satisfied that 750-lambda is less than or equal to 32.54ln (epsilon) is less than or equal to 1400-lambda, and the units of lambda and epsilon are ppm.
2. The lithium ion secondary battery according to claim 1, wherein the mass percentage of the boron compound in the electrolyte is a,0.1% or more and 6% or less.
3. The lithium ion secondary battery according to claim 1, wherein the boron compound in the electrolyte comprises at least one of lithium tetrafluoroborate, tris (trimethylsilane) borate, lithium dioxalate borate, and lithium difluorooxalate borate.
4. The lithium ion secondary battery according to claim 3, wherein the boron compound in the electrolyte comprises lithium tetrafluoroborate, tris (trimethylsilane) borate, lithium dioxalate borate and lithium difluorooxalate borate, wherein the mass percentage of lithium tetrafluoroborate in the electrolyte is a1,0.1% or less and 2.5% or less, the mass percentage of tris (trimethylsilane) borate in the electrolyte is a2,0.1% or less and 4.3% or less, the mass percentage of lithium dioxalate borate in the electrolyte is a3,0.1% or less and 6.2% or less, and the mass percentage of lithium difluorooxalate borate in the electrolyte is a4,0.1% or less and 9.5% or less, based on the total mass of the electrolyte.
5. The lithium ion secondary battery according to claim 1, wherein the boric acid is coated on the surface of the positive electrode active material.
6. The lithium ion secondary battery according to claim 1, wherein the total mass of the positive electrode material layer is N1, and the mass of the boron compound contained in the electrolyte is N2, wherein N2/n1=0.0002 to 0.3.
7. The lithium ion secondary battery of any one of claims 1-6, wherein the lithium cobalt-based ternary material comprises Li 1+x Ni a Co b Mn 1-a-b O 2-y A y ,-0.1≤x≤0.2,0<a<1,0≤b<1,0<a+b<1,0≤y<0.2,A comprising at least one of Mg, ti, cr, zr, al, V, rb, fe, zn or Ce.
8. The lithium ion secondary battery of claim 7 wherein the lithium cobalt-based ternary material comprises Li 1+ x Ni a Co b Mn 1-a-b O 2-y A y ,-0.1≤x≤0.2,0<a<1,0.01≤b<0.04,0<a+b<1,0≤y<0.2,A comprising at least one of Mg, ti, cr, zr, al, V, rb, fe, zn or Ce.
9. The lithium ion secondary battery according to claim 8, wherein the thickness of the protective film layer is 5 to 200nm.
10. A method for designing a lithium ion secondary battery, comprising the steps of: (1) Preparing a lithium ion secondary battery, wherein the lithium ion secondary battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, the positive pole piece, the diaphragm and the negative pole piece are arranged in a stacked manner, and the electrolyte is soaked in the positive pole piece, the negative pole piece and the diaphragm; The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector; the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium cobalt-based ternary material; The electrolyte comprises a boron compound and the positive electrode active material layer comprises the boron compound, wherein the mass percentage of the boron compound in the positive electrode active material layer is b, 0<b-0.05% based on the total mass of the positive electrode active material layer, the mass percentage of the boron compound in the electrolyte is a, 0.1-12% based on the total mass of the electrolyte, and the boron compound in the positive electrode active material layer comprises boric acid; (2) First charging the lithium ion secondary battery to form a protective film layer on the positive electrode active material layer, the positive electrode active material layer and the protective film layer constituting a positive electrode material layer; (3) Detecting the mass concentration lambda of boron element and the mass concentration epsilon of cobalt element in the positive electrode material layer, wherein the units of lambda and epsilon are ppm; (4) Judging whether lambda and epsilon meet 750-lambda is less than or equal to 32.54ln (epsilon) is less than or equal to 1400-lambda, if so, obtaining the target lithium ion secondary battery, and if not, adjusting the mass concentration of the boron compound in the electrolyte and the mass concentration of the boron compound in the positive electrode active material layer, and repeating the steps (1) - (4) until the conditions are met.
11. An electric device comprising the lithium ion secondary battery according to any one of claims 1 to 9 or the lithium ion secondary battery designed by the design method according to claim 10.

Description

Lithium ion secondary battery and design method and power utilization device thereof Technical Field The invention relates to the technical field of new energy, in particular to a lithium ion secondary battery, a design method thereof and an electric device. Background With the development of new energy automobiles, people have raised higher requirements on the endurance mileage and the cost, and the battery materials used are required to have both high energy density and low cost. The lithium cobalt-based ternary material is one of the currently commonly used anode active materials, has the advantages of high energy density and the like, contains cobalt element which is high in price, and is beneficial to controlling the cost of battery materials by reducing the cobalt content. However, a decrease in cobalt content results in a decrease in structural stability of the positive electrode active material, and an increase in oxygen release amount, thereby causing an increase in capacity fade during charge-discharge cycles and storage and an increase in high-temperature gas production. Therefore, there is a need to solve the above problems caused by the reduction of cobalt content. Disclosure of Invention Based on the defects existing in the prior art, the invention aims to provide a lithium ion secondary battery and a design method thereof, and aims to effectively solve the problem of reduced structural stability of a positive electrode material caused by reduced cobalt content. In a first aspect, the invention provides a lithium ion secondary battery, which comprises a positive electrode plate, a negative electrode plate, electrolyte and a diaphragm, wherein the positive electrode plate comprises a positive electrode current collector, a positive electrode active material layer arranged on at least one surface of the positive electrode current collector and a protective film layer formed on the positive electrode active material layer, the positive electrode active material layer and the protective film layer form the positive electrode material layer, the protective film layer contains a boron compound, the positive electrode active material layer comprises a positive electrode active material and the positive electrode active material comprises a lithium cobalt-based ternary material, the positive electrode active material layer contains the boron compound, the mass percentage of the boron compound in the positive electrode active material layer is b,0<b is less than or equal to 0.05% based on the total mass of the positive electrode active material layer, the mass percentage of the boron compound in the electrolyte is a,0.1 percent of less than or equal to 12% based on the total mass of the electrolyte, and the mass concentration of the boron compound in the electrolyte is a and the cobalt concentration in the positive electrode material layer is 53-1400-750 ppm. Further, the electrolyte contains a boron compound, and the mass percentage of the boron compound in the electrolyte is a, based on the total mass of the electrolyte, 0.1% or more and 12% or less. Further, the mass percentage of the boron compound in the electrolyte is a, and a is more than or equal to 0.1% and less than or equal to 6%. Further, the boron compound in the electrolyte includes at least one of lithium tetrafluoroborate, tris (trimethylsilane) borate, lithium dioxalate borate, and lithium difluorooxalato borate. Further, the boron compound in the electrolyte comprises lithium tetrafluoroborate, tris (trimethylsilane) borate, lithium dioxalate borate and lithium difluorooxalate borate, wherein the mass percentage of the lithium tetrafluoroborate in the electrolyte is a1, 0.1-2.5%, the mass percentage of the tris (trimethylsilane) borate in the electrolyte is a2, 0.1-4.3%, the mass percentage of the lithium dioxalate borate in the electrolyte is a3, 0.1-6.2%, and the mass percentage of the lithium difluorooxalate borate in the electrolyte is a4, 0.1-9.5%. Further, the boron compound contained in the positive electrode active material layer includes at least one of boron oxide and boric acid, which are coated on the positive electrode active material. Further, the total mass of the positive electrode material layer is N1, and the mass of the boron compound contained in the electrolyte is N2, wherein N2/n1=0.0002 to 0.3. Further, the lithium cobalt-based ternary material includes Li1+xNiaCobMn1-a-bO2-yAy,-0.1≤x≤0.2,0<a<1,0≤b<1,0<a+b<1,0≤y<0.2,A including at least one of Mg, ti, cr, zr, al, V, rb, fe, zn or Ce. Further, the lithium cobalt-based ternary material includes Li1+xNiaCobMn1-a-bO2-yAy,-0.1≤x≤0.2,0<a<1,0.01≤b<0.04,0<a+b<1,0≤y<0.2,A including at least one of Mg, ti, cr, zr, al, V, rb, fe, zn or Ce. Further, the thickness of the protective film layer is 5-200nm. The application provides a design method of a lithium ion secondary battery, which comprises the following steps of (1) preparing a lithium ion secondary battery, wherein th