WO2023206925A1

WO2023206925A1 - Lithium-ion battery

Info

Publication number: WO2023206925A1
Application number: PCT/CN2022/118991
Authority: WO
Inventors: 张昌明; 胡大林; 廖兴群; 李枫
Original assignee: 惠州市豪鹏科技有限公司
Priority date: 2022-04-26
Filing date: 2022-09-15
Publication date: 2023-11-02
Also published as: CN114784366A

Abstract

A lithium-ion battery, comprising a positive electrode plate, a negative electrode plate, a separator, and an electrolyte solution, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material; the positive electrode material comprises a lithium-supplementing additive LixMyOz, where 1 ≤ x ≤ 6, 1 ≤ y ≤ 6, 2 ≤ z ≤ 12, and M comprises one or more of Ni, Co, Fe, Cu, Al, Mn, Ti, P, Si and C; there is one or more types of the lithium-supplementing additive LixMyOz; the electrolyte solution comprises a nitrile-containing additive, and the nitrile-containing additive is selected from one or more of formula I below, and/or one or more of halides of formula I below, where (aa) in formula I is selected from one of substituted or unsubstituted C1-6 alkylene and substituted or unsubstituted C2-6 alkenylene.

Description

A lithium-ion battery

Technical field

The present invention relates to the technical field of secondary batteries, and in particular to a lithium-ion battery.

Background technique

Lithium-ion batteries are widely used in consumer electronics and power batteries due to their high specific energy, good fast charging and discharging capabilities, and low self-discharge. The working conditions of electronic products and power batteries are becoming more and more complex, and the requirements for lithium-ion batteries are also getting higher and higher, especially the requirements for battery capacity and life.

How to improve the energy density and cycle life of batteries is a long-standing issue in the lithium-ion battery (LIBs) industry. Current products are mainly improved from the perspective of the main material of the positive electrode, such as increasing the charging voltage of the positive electrode. However, after the charging voltage is increased, the amount of lithium removed from the cathode increases, and the structural stability deteriorates, which degrades the high-temperature storage and cycle performance of the battery.

technical problem

The purpose of the present invention is to provide a lithium-ion battery that improves the high-temperature storage and cycle performance of the lithium-ion battery.

Technical solutions

The invention discloses a lithium ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet includes a positive electrode current collector and a positive electrode material, and the positive electrode material includes a lithium supplement additive Li _x M _y O _z , where 1≤x≤ 6, 1≤y≤6, 2≤z≤12, M includes one or more of Ni, Co, Fe, Cu, Al, Mn, Ti, P, Si and C; lithium supplement additive Li _x MyO The types of _z include one or more than one type.

The electrolyte solution includes nitrile-containing additives, and the nitrile-containing additives are selected from one or more of the following formulas I to VI; and/or.

One or more types of halides selected from the following formulas I to VI.

.

Among them, the " "Selected from substituted or unsubstituted C1-6 alkylene, substituted or unsubstituted C2-6 alkenylene.

Optionally, the mass proportion of the lithium supplement additive in the cathode material is 0.01 to 10%.

Optionally, the mass proportion of nitrile-containing additives in the electrolyte is 0.01 to 10%.

Optionally, the mass proportion of nitrile-containing additives in the electrolyte is 0.05 to 5%.

Optionally, the lithium supplement additive is Li ₅ FeO ₄ , and the mass proportion of Li ₅ FeO ₄ in the positive electrode sheet is 1%; the nitrile-containing additive is adiponitrile, and the mass proportion of adiponitrile in the electrolyte is 2 %.

Optionally, in the positive electrode sheet and the negative electrode sheet, the mass proportion of the total content of N element is not less than 100 ppm.

Optionally, the positive active material includes one of lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, and ternary _{LiNixCoyMnzO2} material (where x ₊ y ₊ _z =1,x≥y) or more than one.

Optionally, the lithium salt in the electrolyte is selected from one or more types of organic electrolyte salts and inorganic electrolyte salts.

Optionally, the solvent of the electrolyte is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, and propyl propionate. , two or more types of methyl butyrate and tetrahydrofuran.

Optionally, the lithium salt in the electrolyte is selected from hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, lithium difluoro(trifluoromethylsulfonyl)imide, bis( One or more of lithium fluorosulfonyl imide and tris(trifluoromethanesulfonyl)methyllithium.

beneficial effects

Compared with the traditional positive electrode sheet, after adding the lithium supplement additive Li _x _My O _z to the lithium-ion battery of the present invention, the first efficiency of the battery is significantly improved, and as the amount of addition increases, the first efficiency increases. Nitrile-containing additives are used in the electrolyte. The simultaneous use of nitrile-containing additives and the lithium supplement additive Li _x M _y O _z can significantly improve the thermal stability of the battery, especially the high-temperature storage performance. This is mainly due to the improvement of the lithium supplement additive. The efficiency is related to the protection of the positive electrode surface by the nitrile-containing additives. Nitrile-containing additives can form a passivation film on the surface of cathode materials and lithium supplement additives. The CN group in nitrile-containing additives can chelate metal ions, which can not only increase the energy density of the battery, but also effectively stabilize the system and ensure the battery high temperature storage performance.

Best Mode of Carrying Out the Invention

It should be understood that the terminology used and the specific structural and functional details disclosed here are only for describing specific embodiments and are representative. However, the present invention can be specifically implemented in many alternative forms and should not be construed as merely are limited to the embodiments set forth herein.

The invention is described in detail below with reference to alternative embodiments.

As an embodiment of the present invention, a lithium ion battery is disclosed, including a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet includes a positive electrode current collector and a positive electrode material, and the positive electrode material includes a lithium supplement additive Li _x _My O _z , where 1≤x≤6, 1≤y≤6, 2≤z≤12, M includes one or more of Ni, Co, Fe, Cu, Al, Mn, Ti, P, Si and C; The types of lithium supplement Li _x My _O _z include one or more than one.

One or more types of halides selected from the following formulas I to VI.

.

Specifically, the positive electrode sheet includes a positive electrode current collector and a positive electrode material coated on the surface of the positive electrode current collector. The positive electrode current collector can be aluminum foil or the like. Cathode materials include cathode active materials, conductive agents, binders, and lithium supplement additives.

Optionally, the mass proportion of the lithium supplement additive in the cathode material is 0.01 to 10%. For example, it can be 0.01%, 0.05%, 0.08%, 0.1%, 0.13%, 0.17%, 2%, 2.6%, 3%, 3.4%, 4%, 4.7%, 5%, 6%, 7%, 8% ,9%,10%.

Optionally, the mass proportion of nitrile-containing additives in the electrolyte is 0.01 to 10%. For example, it can be 0.01%, 0.05%, 0.08%, 0.1%, 0.13%, 0.17%, 2%, 2.6%, 3%, 3.4%, 4%, 4.7%, 5%, 6%, 7%, 8% ,9%,10%.

Optionally, the mass proportion of nitrile-containing additives in the electrolyte is 0.05 to 5%. For example, it can be 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%.

Optionally, the lithium supplement additive is Li ₅ FeO ₄ , and the mass proportion of Li ₅ FeO ₄ in the cathode material is 1%; the nitrile-containing additive is adiponitrile, and the mass proportion of adiponitrile lactone in the electrolyte is is 2%.

Specifically, in the positive electrode sheet and the negative electrode sheet, the mass proportion of the total content of N element is not less than 100 ppm.

Specifically, the positive active material includes one of _lithium iron phosphate, lithium iron manganese phosphate, _lithium cobalt oxide, ternary _{LiNixCoyMnzO2} material (where x+y ₊ z=1,x≥y) or More than one type accounts for 80 to 99% of the mass ratio of cathode materials.

Specifically, the electrolyte consists of a solvent, a lithium salt, and a nitrile-containing additive. The lithium salt in the electrolyte is selected from one or more types of organic electrolyte salts and inorganic electrolyte salts. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ , Li ₂ B ₁₀ F ₁₀ , LiClO ₄ , LiCF ₃ SO ₃ , chelated orthoborate and chelated orthoborate Lithium salts of phosphates, such as lithium dioxaloborate [LiB(C ₂ O ₄ ) ₂ ], lithium dimalonate borate [LiB(O ₂ CCH ₂ CO ₂ ) ₂ ], bis(difluoromalonate) borate Lithium [LiB(O ₂ CCF ₂ CO ₂ ) ₂ ], (malonate oxalate) lithium borate [LiB(C ₂ O ₄ )(O ₂ CCH ₂ CO ₂ )], (difluoromalonate oxalate) lithium borate [LiB(C ₂ O ₄ )(O ₂ CCF ₂ CO ₂ )], lithium trioxalate phosphate [LiP(C ₂ O ₄ ) ₃ ], and lithium tris(difluoromalonate) phosphate [LiP(O ₂ CCF ₂ CO ₂ ) ₃ ], and any combination of two or more of the above lithium salts.

Specifically, in other embodiments, the lithium salt is selected from fluorine-containing lithium salts, for example, selected from hexafluorophosphate, hexafluoroarsenate, perchlorate, trifluorosulfonyllithium, difluoro(trifluoromethyl One or more of lithium bis(fluorosulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyllithium.

Specifically, the concentration of lithium salt in the electrolyte is 0.5M to 2M. When the lithium salt concentration is too low, the conductivity of the electrolyte is low, which will affect the rate and cycle performance of the entire battery system; when the lithium salt concentration is too high, the viscosity of the electrolyte is too high, which is also not conducive to improving the rate of the entire battery system. . In a more preferred embodiment, the lithium salt concentration is 0.9M~1.3M.

Specifically, the solvent is selected from non-aqueous organic solvents. In a preferred embodiment, the solvent of the electrolyte is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, and propylene carbonate. Two or more of propyl acid ester, methyl butyrate, and tetrahydrofuran.

Specifically, the electrolyte also includes other additives that promote the formation of the SEI film. Other additives include but are not limited to: vinylene carbonate and its derivatives, ethylene carbonate with non-conjugated unsaturated bonds in its side chain. Ester derivatives, cyclic carbonates substituted by halogens, and salts of chelated orthoborates and chelated orthophosphates. In a preferred embodiment, the additive includes one of vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate and bisfluoroethylene carbonate. Kind or variety.

The negative electrode sheet includes a negative electrode current collector and a negative electrode material located on the negative electrode current collector, where the negative electrode material includes a negative electrode active material, a negative electrode binder and a negative electrode conductive agent.

The negative active material is selected from graphite and/or silicon, such as natural graphite, artificial graphite, mesophase microcarbon balls (MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li- One or more of Sn-O alloy, Sn, SnO, SnO ₂ , spinel structure lithiated TiO2-Li4Ti5O12, and Li-Al alloy.

The present invention will be further described below through examples.

Example.

This example is used to illustrate the lithium ion battery disclosed in the present invention and its preparation method, which includes the following steps.

Preparation of electrolyte: Mix EC, DEC, and PC in a mass ratio of 1:1:1 as an organic solvent. Add the additive with the mass percentage content shown in Example 1 in Table 1 to the organic solvent. After mixing evenly, add LiPF ₆ to obtain an electrolyte solution with a LiPF ₆ concentration of 1.1 mol/L.

Production of the positive electrode sheet: Mix the positive active material lithium cobalt oxide (LiCoO ₂ ), the conductive agent CNT (Carbon Nanotube, carbon nanotube), the binder PVDF (polyvinylidene fluoride), and the lithium supplement additive in a mass ratio of 95: 1.5:1.5:2, where Table 1 shows the added amount of lithium supplement additive in the embodiment, and the total amount with the positive active material is 97%. Stir and mix thoroughly in N-methylpyrrolidone solvent to form a uniform positive electrode slurry. The slurry is coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.

Preparation of negative electrode sheet: Mix the negative active material graphite, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in an appropriate amount of deionized water solvent in a mass ratio of 96:1.2:1.5:1.3 Stir thoroughly to form a uniform negative electrode slurry. The slurry is coated on the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet.

Production of lithium-ion battery: PE porous polymer film is used as separator.

Stack the positive electrode piece, separator and negative electrode piece in order, so that the separator is between the positive and negative electrodes to play an isolation role, and then wind the stacked electrode piece and separator to obtain a winding core. Place the rolled core in the aluminum-plastic film bag that has been punched and molded. Inject the electrolyte prepared above into the baked and dried battery core. After vacuum packaging, standing, formation and other processes, the lithium-ion battery is completed. preparation.

.

Among them, ADN is adiponitrile, which is one of the specific compounds of formula I; DENE is 1,2-bis(cyanoethoxy)ethane, which is one of the specific compounds of formula II; HTCN is 1,2- Bis(cyanoethoxy)ethane is one of the specific compounds of formula III; BTTN is 3,3',3'',3''-(butane-1,2,3,4-tetraacyltetrakis (Oxy)) Tetraacrylonitrile is one of the specific compounds of formula VI.

Battery test.

First battery efficiency test.

After the battery is filled with electrolyte and left for a period of time, it is charged in an environment of 25±2°C. First, use a charging current of 0.02C and a charging time of 2H; secondly, use a charging current of 0.1C for a time of 5H, and finally use a charging current of 0.5C. Perform constant current and constant voltage charging to 4.45V, and the cut-off current is 0.02C. Discharge with 0.2C until the discharge cut-off voltage is 3.0V. The final first efficiency EF=DC/(CC+CV), where DC is the discharge capacity and CC+CV is the constant current capacity of charging plus the constant voltage section capacity.

45℃ cycle test.

The test method is: charge the lithium-ion battery to 4.45V at 1C constant current and constant voltage in a 45±2℃ thermostat, with a cut-off current of 0.05C, then discharge it to 3V at 1C, and perform multiple charge and discharge cycles according to the above conditions. Calculate the capacity retention rate after 300 and 500 battery cycles respectively, with 5 batteries in each group.

Capacity retention rate (%) = discharge capacity corresponding to the number of cycles (mAh) / discharge capacity of the third cycle (mAh) * 100%.

The average capacity retention rate of 5 batteries in each group after different cycles is recorded in Table 2.

.

Combining the data in Tables 1 and 2, it can be seen that compared with Comparative Example 1, Comparative Example 2 adds 1% lithium supplement additive Li ₂ NiO ₂ , the first efficiency of the battery is increased by 1.7%, and the high-temperature storage performance is slightly improved. In proportions 3 to 6, after adding nitrile-containing additives, the first efficiency decreased slightly, but the storage performance was improved. In Comparative Example 7, adding the lithium-replenishing additive Li ₂ NiO ₂ and the nitrile-containing additive ADN at the same time can significantly improve the storage performance. Compared with Comparative Example 7, in Examples 1 to 3, the contents of the lithium supplement additive Li ₂ NiO ₂ and the nitrile-containing additive ADN were adjusted. As the contents of the lithium supplement agent and ADN increased, the storage performance improved. The comprehensive effect of Li ₅ FeO ₄ in Example 4 on improving first-time efficiency and cycle performance is better than that of Li ₂ NiO ₂ .

The above content is a further detailed description of the present invention in combination with specific optional implementation modes, and it cannot be concluded that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all of them should be regarded as belonging to the protection scope of the present invention.

Claims

A lithium ion battery, characterized in that it includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet includes a positive electrode current collector and a positive electrode material, and the positive electrode material includes a lithium supplement additive Li x My O z , wherein 1≤x≤6, 1≤y≤6, 2≤z≤12, M includes one or more of Ni, Co, Fe, Cu, Al, Mn, Ti, P, Si and C; The types of lithium supplement additives Li x MyO z include one or more types;

The electrolyte includes a nitrile-containing additive, and the nitrile-containing additive is selected from one or more of the following formulas I to VI; and/or

One or more types of halides selected from the following formulas I to VI;

Among them, the " "Selected from substituted or unsubstituted C1-6 alkylene, substituted or unsubstituted C2-6 alkenylene.
The lithium-ion battery according to claim 1, wherein the mass proportion of the lithium replenishing additive in the cathode material is 0.01 to 10%.
The lithium-ion battery according to claim 2, wherein the mass proportion of the nitrile-containing additive in the electrolyte is 0.01 to 10%.
The lithium-ion battery according to claim 3, wherein the mass proportion of the nitrile-containing additive in the electrolyte is 0.05 to 5%.
The lithium-ion battery according to claim 4, wherein the lithium supplement additive is Li 5 FeO 4 , and the mass proportion of Li 5 FeO 4 in the positive electrode sheet is 1%; the nitrile-containing additive The additive is adiponitrile, and the mass proportion of adiponitrile in the electrolyte is 2%.
The lithium-ion battery according to claim 1, wherein the mass proportion of the total content of N element in the positive electrode sheet and the negative electrode sheet is not less than 100 ppm.
The lithium ion battery according to claim 1, wherein the positive active material includes lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide , and ternary LiNixCoyMnzO2 material (where x+y +z=1,x≥y) one or more.
The lithium ion battery according to claim 1, wherein the lithium salt in the electrolyte is selected from one or more organic electrolyte salts and inorganic electrolyte salts.
The lithium ion battery according to claim 1, wherein the solvent of the electrolyte is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, Two or more types of ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, and tetrahydrofuran.
The lithium ion battery according to claim 1, wherein the lithium salt in the electrolyte is selected from the group consisting of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, difluoride ( One or more of lithium trifluoromethanesulfonyl imide, lithium bis(fluoromethanesulfonyl)imide, and tris(trifluoromethanesulfonyl)methyllithium.