WO2023123842A1 - Additive, non-aqueous electrolyte solution containing said additive, and lithium-ion battery - Google Patents

Abstract

Provided are an additive, a non-aqueous electrolyte solution containing said additive, and a lithium-ion battery; the additive comprises a compound represented by the structural formula (1): wherein each of R₁ to R₆ is independently selected from a hydrogen atom, a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, and a C6-C10 aryl group. The additive can inhibit the oxidative decomposition of a non-aqueous electrolyte, improve the high-temperature storage performance and the high-temperature cycle performance of the lithium-ion battery in a high-voltage (especially 4.5 V) system, and also improve the low-temperature discharge performance of the lithium-ion battery.

Description

Additive and non-aqueous electrolytic solution and lithium ion battery containing the additive technical field

The application belongs to the technical field of lithium ion batteries, and in particular relates to an additive, a nonaqueous electrolyte containing the additive, and a lithium ion battery.

Background technique

Lithium-ion batteries are widely used in 3C digital, power tools, aerospace, energy storage, power vehicles and other fields due to their advantages such as high specific energy, no memory effect, and long cycle life. The ternary cathode material has become the preferred material for the cathode active material of the lithium-ion battery due to its good safety and low price.

In order to meet the needs of large mobile electrical equipment, the development of lithium-ion batteries with large specific capacity is imminent. The most common method is to increase the voltage of lithium-ion batteries, but all high-voltage cathode materials face a common problem: the decomposition of the electrolyte at high voltage, especially at a higher voltage of 4.5V, conventional electrolyte Oxidation and decomposition on the surface of the positive electrode of the battery are faster, especially under high temperature conditions, which will further accelerate the oxidation and decomposition of the electrolyte, and at the same time promote the deterioration reaction of the positive electrode material. More specifically, Japanese Patent JP2004071458A discloses an electrolyte solution containing a cyclic siloxane compound, which can improve the high-temperature storage characteristics and high-temperature cycle performance of lithium-ion batteries, but it is suitable for a voltage system of about 4.1V.

Therefore, there is an urgent need to develop an electrolyte that can withstand a high voltage of 4.5V to solve the shortcomings of the existing technical problems.

application content

The purpose of this application is to provide a kind of additive, this additive can suppress the oxidative decomposition of non-aqueous electrolytic solution, can improve the high-temperature storage performance and high-temperature cycle performance of lithium-ion battery under high voltage (especially when 4.5V) system, also can simultaneously It can improve the low-temperature discharge performance of lithium-ion batteries.

Another object of the present application is to provide a non-aqueous electrolyte, which can improve the high-temperature storage performance and high-temperature cycle performance of lithium-ion batteries under the 4.5V high-voltage system, and can also improve the low-temperature performance of lithium-ion batteries. discharge performance.

Another object of the present application is to provide a lithium-ion battery, which has better high-temperature storage performance, high-temperature cycle performance and low-temperature discharge performance in a high-voltage (especially 4.5V) system.

In order to achieve the above object, the application provides an additive, including a compound shown in structural formula 1:

Wherein R ₁ to R ₆ are each independently selected from a hydrogen atom, a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, and a C6-C10 aryl group.

Compared with the prior art, the additives of the present application include compounds shown in structural formula 1, that is, trisilylbenzene compounds with a special structure, which have an aromatic structure of planar silicon, in which carbon will form due to ^SP2 hybridization Strong π bond, and silicon will form a covalent σ bond due to SP ³ hybridization, so the σ-π conjugated structure between -Si=C- can make the additive form a kind of Stable dimer interface film, which can optimize the positive electrode/electrolyte interface, reduce the surface activity of the electrode and inhibit the oxidative decomposition of the electrolyte, so that the electrolyte remains stable under continuous high voltage, thereby improving the lithium-ion battery at high voltage ( Especially at 4.5V) high temperature storage performance and high temperature cycle performance under the system. At the same time, the dimer interface film has a good ability to conduct lithium ions and exhibits low internal resistance, so that the lithium ion battery has good low-temperature discharge performance.

Preferably, R ₁ , R ₃ , and R ₅ are the same, and R ₂ , R ₄ , and R ₆ are the same in the compound represented by the structural formula 1 of the present application. Further, R ₂ , R ₄ and R ₆ are all preferably hydrogen atoms.

Preferably, the compound represented by structural formula 1 of the present application is selected from at least one of compound 1 to compound 5:

In order to achieve the above purpose, the present application also provides a non-aqueous electrolytic solution, which includes a lithium salt, a non-aqueous organic solvent, and the above-mentioned additives.

Compared with the prior art, the non-aqueous electrolytic solution of the present application includes the compound shown in structural formula 1, so the non-aqueous electrolytic solution can remain stable under continuous high voltage, and then promote lithium ion battery at high voltage (especially when 4.5V) ) system under high-temperature storage performance and high-temperature cycle performance, and can also improve the low-temperature discharge performance of lithium-ion batteries.

Preferably, the mass percentage of the additive of the present application in the non-aqueous electrolyte is 0.1-5%, specifically but not limited to 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% %, 4%, 4.5%, 5%. Further, the mass percentage of the additive in the non-aqueous electrolyte is preferably 1-2%.

Preferably, the mass percentage of the lithium salt of the present application in the non-aqueous electrolyte is 6.5-15.5%.

Preferably, the lithium salt of the present application is selected from lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethylsulfonimide, lithium bisoxalate borate (LiBOB), lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate, and lithium bisfluorosulfonyl imide.

Preferably, the non-aqueous organic solvent of the present application is at least one of chain carbonate, cyclic carbonate and carboxylate. The non-aqueous organic solvent is more preferably selected from ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), butyl acetate (n-Ba), γ-butyrolactone (γ-Bt), propyl propionate (n-PP), ethyl propionate (EP) and ethyl butyrate (Eb). Preferably, the mass percentage of the non-aqueous organic solvent of the present application in the non-aqueous electrolyte is 60-80%.

In order to achieve the above object, the application also provides a lithium ion battery, including a positive electrode material, a negative electrode material, and the non-aqueous electrolyte mentioned above, and the positive electrode material is nickel-cobalt-manganese oxide or nickel-cobalt-aluminum oxide, and The highest charging voltage is 4.5V.

Compared with the prior art, the electrolyte of the lithium-ion battery of the present application includes a compound shown in structural formula 1, which can optimize the positive electrode/electrolyte interface as an additive, reduce the surface activity of the electrode and thereby inhibit the oxidative decomposition of the electrolyte, The electrolyte is kept stable under continuous high voltage, thereby improving the high-temperature storage performance and high-temperature cycle performance of the lithium-ion battery in a 4.5V high-voltage system, and at the same time improving the low-temperature discharge performance of the lithium-ion battery.

Preferably, the chemical formula of the nickel-cobalt-manganese oxide of the present application is LiNi _x Co _y Mn _z M _(1-xyz) O ₂ , and the chemical formula of the nickel-cobalt aluminum oxide is LiNi _x Co _y Al _z N _(1-xyz) O ₂ , wherein M and N are each independently selected from at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0<x<1, 0<y<1 , 0<z<1, x+y+z≤1.

Preferably, the negative electrode material of the present application is at least one selected from artificial graphite, natural graphite, lithium titanate, silicon-carbon composite material and silicon oxide.

Detailed ways

The purpose, technical solutions and beneficial effects of the present application will be further described below through specific examples, but this does not constitute any limitation to the present application. Those who do not indicate specific conditions in the examples can be carried out according to conventional conditions or conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products. Specifically, Compound 1, Compound 2, Compound 3, Compound 4, and Compound 5 used in the examples can be prepared through the following synthetic routes.

Compound 1 was prepared by dehydrogenation reaction between metal ions (Fe, Co, Ni) and trisilylcyclohexane in the gas phase, and then purified by recrystallization or column chromatography. More specifically, reference may be made to the prior art (Gasphasenreaktionen von M ⁺ und [CpM] ⁺ (M = Fe, Co, Ni) mit 1,3,5-Trisilacyclohexan: erste Hinweise auf die Bildung von 1,3,5-Trisilabenzol , Asgrir Bjarnason, Ingvar Arnason, Angewandte Chemie, 1992).

Compound 1 was reacted with methyl chloride under basic conditions, followed by recrystallization or column chromatography to obtain compound 2.

Compound 1 was reacted with ethyl chloride under basic conditions, followed by recrystallization or column chromatography to obtain compound 3.

Compound 1 was reacted with 2-chloropropane under basic conditions, and compound 4 was prepared by recrystallization or column chromatography purification.

Compound 1 was reacted with vinyl chloride under basic conditions, and compound 5 was prepared by recrystallization or column chromatography purification.

Example 1

(1) Preparation of non-aqueous electrolyte

In a glove box filled with argon (O ₂ <1ppm, H ₂ O<1ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were prepared according to the weight ratio of EC: Mix EMC:DEC=1:1:1 to obtain 86.5g of non-aqueous organic solvent, then add 1g of compound 1, dissolve and stir thoroughly, then add 12.5g of lithium hexafluorophosphate, and mix well to obtain an electrolyte.

(2) Preparation of positive electrode

LiNi _0.5 Co _{0.2 Mn 0.3 O 2 ternary material LiNi 0.5 Co 0.2} Mn _0.3 O ₂ , binder PVDF and conductive agent SuperP were uniformly mixed at a mass ratio of 95:1:4 to make a lithium ion battery positive electrode slurry with a certain viscosity. The prepared slurry was coated on both sides of the aluminum foil, dried and rolled to obtain a positive electrode sheet.

(3) Preparation of negative electrode

Prepare artificial graphite, conductive agent SuperP, thickener CMC, and adhesive SBR (styrene-butadiene rubber emulsion) in a mass ratio of 95:1.5:1.0:2.5 to make a slurry, mix evenly, and use the mixed slurry to coat After being clothed on both sides of the copper foil, the negative electrode sheet is obtained after drying and rolling.

(4) Preparation of lithium-ion batteries

The positive electrode, diaphragm and negative electrode are stacked into square batteries, packed with polymers, filled with the non-aqueous electrolyte of lithium-ion batteries prepared above, and made into lithium batteries with a capacity of 1000mAh after chemical formation and volume separation. ion battery.

The non-aqueous electrolyte formulations of Examples 2-8 and Comparative Example 1 are shown in Table 1, and the steps of preparing the non-aqueous electrolyte and preparing the lithium-ion battery are the same as those of Example 1.

The formula of table 1 non-aqueous electrolyte

group	Non-aqueous organic solvent/mass (g)	Lithium salt/mass (g)	Additive (g)
Example 1	EC/EMC/DEC＝1:1:1(86.5g)	LiPF6 (12.5g)	Compound 1 (1.0g)
Example 2	EC/EMC/DEC＝1:1:1(86.5g)	LiPF6 (12.5g)	Compound 2 (1.0g)
Example 3	EC/EMC/DEC＝1:1:1(86.5g)	LiPF6 (12.5g)	Compound 3 (1.0g)
Example 4	EC/EMC/DEC＝1:1:1(86.5g)	LiPF6 (12.5g)	Compound 4 (1.0g)
Example 5	EC/EMC/DEC＝1:1:1(86.5g)	LiPF6 (12.5g)	Compound 5 (1.0g)

Example 6	EC/EMC/DEC＝1:1:1(87.4g)	LiPF6 (12.5g)	Compound 5 (0.1g)
Example 7	EC/EMC/DEC＝1:1:1(82.5g)	LiPF6 (12.5g)	Compound 5 (5.0g)
Example 8	PC/EMC/DEC＝1:1:1(85.0g)	LiPF 6 (11.5g)+LiBOB (2.5g)	Compound 5 (1.0g)
Comparative example 1	EC/EMC/DEC＝1:1:1(87.5g)	LiPF6 (12.5g)	/

The lithium-ion batteries made in Examples 1-8 and Comparative Example 1 were tested for low-temperature discharge performance, high-temperature storage performance and high-temperature cycle performance respectively. The specific test conditions are as follows, and the performance test results are shown in Table 2.

Lithium-ion battery low temperature discharge performance test

At room temperature (25°C), charge and discharge the lithium-ion battery once at 0.5C/0.5C (the discharge capacity is denoted as C ₀ ), the upper limit voltage is 4.5V, and then the battery is charged and discharged under the condition of 0.5C constant current and constant voltage. Charge to 4.5V, put the lithium-ion battery in a low-temperature box at -20°C for 4 hours, and discharge it at 0.5C at -20°C (the discharge capacity is recorded as C ₁ ), and use the following formula to calculate the low-temperature discharge rate of the lithium-ion battery:

Low temperature discharge rate = C ₁ /C ₀ *100%

Lithium-ion battery high temperature storage performance test

At room temperature (25°C), charge and discharge the lithium-ion battery once at 0.3C/0.3C (the discharge capacity of the battery is recorded as C ₀ ), and the upper limit voltage is 4.5V; place the battery in an oven at 60°C for 7 days, Take out the battery, place the battery in an environment of 25°C, discharge at 0.3C, and record the discharge capacity as C ₁ ; then charge and discharge the lithium-ion battery once at 0.3C/0.3C (record the discharge capacity as C ₂ ), use The following formulas calculate the capacity retention rate and capacity recovery rate of lithium-ion batteries:

Capacity retention = C ₁ /C ₀ *100%

Capacity recovery rate = C ₂ /C ₀ *100%

Lithium-ion battery high temperature cycle performance test

Place the lithium-ion battery in a constant temperature box at 45°C and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature. Charge the battery at a constant current of 1C to a voltage of 4.5V, then charge at a constant voltage of 4.5V to a current of 0.05C, then discharge at a constant current of 1C to a voltage of 3.0V, and record the discharge capacity of the battery for the first cycle as C ₀ . This is a charge and discharge cycle. Then perform 1C/1C charge and discharge at 45°C for 300 cycles, and record the discharge capacity as C ₁ .

Capacity retention = C ₁ /C ₀ *100%

Table 2 Li-ion battery performance test results

As can be seen from the results in Table 2, the high-temperature storage performance, high-temperature cycle performance, and low-temperature discharge performance of the lithium-ion batteries of Examples 1-8 are all better than those of Comparative Example 1, because the electrolytes of the lithium-ion batteries of Examples 1-8 Including the compounds shown in structural formula 1, including trisilylbenzene compounds with a special structure, the compound has an aromatic structure of planar silicon, in which carbon will form a strong π bond due to SP ² hybridization, and silicon will form a strong π bond because of SP ³ is hybridized to form a covalent σ bond, so the σ-π conjugated structure between -Si=C- can make the additive form a stable dimer interface film at the electrode/electrolyte interface, which can Optimize the positive electrode/electrolyte interface, reduce the surface activity of the electrode and inhibit the oxidative decomposition of the electrolyte, so that the electrolyte remains stable under continuous high voltage, thereby improving the high temperature of lithium-ion batteries under high voltage (especially at 4.5V) systems Storage performance and high temperature cycle performance. At the same time, the dimer interface film has a good ability to conduct lithium ions and exhibits low internal resistance, so that the lithium ion battery has good low-temperature discharge performance.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application rather than limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that Modifications or equivalent replacements are made to the technical solutions of the present application without departing from the essence and scope of the technical solutions of the present application.

Claims (10)

1. An additive, is characterized in that, comprises the compound shown in structural formula 1:

   

   Wherein R ₁ to R ₆ are each independently selected from a hydrogen atom, a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, and a C6-C10 aryl group.
2. The additive according to claim 1, characterized in that R ₁ , R ₃ , and R ₅ are the same, and R ₂ , R ₄ , and R ₆ are the same.
3. The additive according to claim 1, wherein the compound represented by the structural formula 1 is selected from at least one of compound 1 to compound 5:

   
4. A kind of nonaqueous electrolytic solution, comprises lithium salt, nonaqueous organic solvent, is characterized in that, also comprises the additive as described in any one of claim 1～3.
5. The non-aqueous electrolytic solution according to claim 4, characterized in that, the mass percentage of the additive in the non-aqueous electrolytic solution is 0.1-5%.
6. The non-aqueous electrolytic solution according to claim 4, characterized in that, the mass percentage of the lithium salt in the non-aqueous electrolytic solution is 6.5-15.5%.
7. The non-aqueous electrolytic solution according to claim 4, wherein the lithium salt is selected from lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, bistrifluoromethylsulfonyl At least one of lithium amine, lithium bisoxalate borate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate and lithium bisfluorosulfonyl imide.
8. The nonaqueous electrolytic solution according to claim 4, wherein the nonaqueous organic solvent is at least one of chain carbonates, cyclic carbonates and carboxylates.
9. A lithium-ion battery, comprising a positive electrode material and a negative electrode material, is characterized in that it also includes the non-aqueous electrolyte according to any one of claims 4 to 8, and the positive electrode material is nickel-cobalt-manganese oxide or nickel-cobalt-aluminum Oxide, and the highest charging voltage is 4.5V.
10. The lithium ion battery as claimed in claim 9, wherein the chemical formula of the nickel-cobalt-manganese oxide _{is LiNixCoyMnzM (1-xyz) O2} , and the chemical formula _of the nickel-cobalt-aluminum oxide is LiNi _x Co _y Al _z N _(1-xyz) O ₂ , wherein M and N are each independently selected from at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti , 0<x<1, 0<y<1, 0<z<1, x+y+z≤1.