Lithium battery electrolyte additive, electrolyte and lithium battery

Abstract

The present application relates to a kind of lithium battery electrolyte additive, electrolyte and lithium battery, belong to lithium battery technical field, the present application with sulfonyl borate compound as electrolyte additive, make boron compound additive fully decompose, form the compact and stable interface film containing boron and sulfur element on the surface of positive and negative, inhibit the decomposition of electrolyte, barrier HF to the corrosion damage of positive electrode interface, while inhibiting the dissolution of transition metal ion and the damage to negative, improve the cycle performance of lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium batteries, and particularly relates to a lithium battery electrolyte additive, an electrolyte and a lithium battery. BACKGROUND

[0002] Lithium ion batteries have many advantages such as high working voltage, long cycle life, large energy density, no memory effect and environmental friendliness, and are the most widely used and most promising secondary batteries in the current market. With the rapid development of China's economy, smart phones, notebook computers, digital cameras, camcorders and other products have put forward higher requirements for the safety performance, energy density and cycle life of lithium ion batteries, and lithium ion batteries are facing unprecedented challenges. Developing high-energy-density lithium ion batteries has become a research hotspot at home and abroad, and increasing the working voltage is an effective way to improve the energy density of lithium ion batteries. However, in the process of developing and applying high-voltage lithium ion batteries, the following two problems may be encountered:

[0003] Firstly, the conventional carbonate solvent electrolyte system will undergo irreversible oxidative decomposition when the voltage reaches 4.2V or above, and the decomposition products will form a thick medium layer on the positive and negative electrode surfaces, resulting in increased battery impedance and causing the battery cycle performance to deteriorate.

[0004] Secondly, at high voltage, the interface between the positive electrode material and the electrolyte will undergo a side reaction, and the HF produced by the reaction will damage the positive electrode interface and cause the dissolution of transition metal ions, which will migrate to the negative electrode and damage the interface film on the negative electrode surface, all of which will cause the electrochemical performance of the battery to deteriorate and the cycle performance to decline.

[0005] Therefore, it is necessary to develop a high-voltage electrolyte additive that can preferentially undergo oxidative decomposition and form a stable interface film on the positive and negative electrode interfaces, inhibit the decomposition of the electrolyte and the migration of transition metal ions, reduce impedance and improve the cycle performance of high-voltage lithium ion batteries. SUMMARY

[0006] The present application aims to provide a lithium battery electrolyte additive, an electrolyte and a lithium battery, in which a sulfonyl borate compound is used as an electrolyte additive, so that the boron-containing compound additive is fully decomposed to form a tight and stable interface film containing boron and sulfur elements on the surface of the positive and negative electrodes, inhibit the decomposition of the electrolyte, block the corrosion and damage of HF to the positive electrode interface, and inhibit the dissolution of transition metal ions and the damage to the negative electrode, thereby improving the cycle performance of the lithium ion battery.

[0007] The technical problems solved by the present application are as follows: Firstly, the conventional carbonate solvent electrolyte system will undergo irreversible oxidative decomposition when the voltage reaches 4.2V or above, and the decomposition products will form a thick medium layer on the positive and negative electrode surfaces, resulting in increased battery impedance and deteriorated battery cycle performance. Secondly, at high voltage, the interface between the positive electrode material and the electrolyte will undergo a side reaction, and the HF produced by the reaction will damage the positive electrode interface and cause the dissolution of transition metal ions, which will migrate to the negative electrode and damage the interface film on the negative electrode surface, all of which will cause the deterioration of the electrochemical performance of the battery and the decline of the cycle performance.

[0008] The object of the present application can be achieved by the following technical solutions:

[0009] The present application provides a lithium battery electrolyte additive, which has at least one of the following compounds 1 to 11:

[0010]

[0011]

[0012] The present application uses a sulfonyl borate compound as an electrolyte additive, which fully decomposes the boron-containing compound additive to form a tight and stable interface film containing boron and sulfur elements on the surface of the positive and negative electrodes, inhibits the decomposition of the electrolyte, blocks the corrosion and damage of HF to the positive electrode interface, and inhibits the dissolution of transition metal ions and the damage to the negative electrode, thereby improving the cycle performance of the lithium ion battery.

[0013] The present application provides a lithium battery electrolyte, which is composed of a lithium salt, an organic solvent and the above-mentioned lithium battery electrolyte additive, and the mass of the lithium battery electrolyte additive accounts for 0.01-5% of the total mass of the lithium battery electrolyte.

[0014] As a preferred scheme of the present application, the organic solvent is selected from one or more of carbonate organic solvents, carboxylate organic solvents, phosphate organic solvents, fluorinated ether organic solvents, fluorinated ester organic solvents and ether organic solvents.

[0015] As a preferred scheme of the present application, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate or lithium tetrafluoro(oxalato)phosphate, and the molar concentration of the lithium salt in the lithium battery electrolyte ranges from 0.05 to 3 mol / L.

[0016] The present application also provides a lithium battery, which comprises a positive electrode, a negative electrode, a separator and the above-mentioned lithium battery electrolyte.

[0017] As a preferred scheme of the present application, the positive material is LiNi 0.5 Mn 1.5 O4, LiCoO2, LiCoPO4, LiNiPO4, LiNi x Co y Mn 1-x-y O2, and LiNi x Co y Al 1-x-y O2, and the negative material is at least one of graphite, mesocarbon microbeads, silicon carbon, or metallic lithium.

[0018] The present application has the following beneficial effects:

[0019] In the technical scheme of the present application, the lithium battery electrolyte additive is a sulfonyl borate compound, which has a higher HOMO value than common electrolyte solvents, can be preferentially oxidized, and can form a stable oxidation film at the positive electrode interface to protect the positive material and slow down the structural damage; at the same time, the LUMO value of the additive is smaller than that of the common electrolyte solvent, can be preferentially reduced and decomposed on the surface of the graphite, silicon negative electrode, and metallic lithium negative electrode, and can form a more stable SEI film, which can effectively improve the cycle performance of the high-voltage lithium battery. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] Embodiment 1

[0022] A lithium battery electrolyte is composed of a lithium salt, an organic solvent, and an additive. The lithium salt LiPF6 is dissolved in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC), the mass ratio of EC, DMC, and EMC is 3:2:5, the lithium salt concentration is 1 mol / L, and 3% of the total mass of the electrolyte is added to the compound 1.

[0023] A lithium battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, and the electrolyte is the lithium ion battery electrolyte sample prepared above.

[0024] The preparation method of the lithium battery of the embodiment comprises: mixing negative electrode material graphite, conductive agent SP, binder CMC, and dispersant SBR according to a mass ratio of 94.5:1.5:1.5:2.5, adding a proper amount of deionized water, mixing into a uniform paste, then uniformly coating on a 9 μm copper foil, and drying to obtain a negative electrode sheet. The positive electrode material LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive agent SP, and binder PVDF are mixed according to a mass ratio of 96:2:2, a proper amount of NMP solvent is added, and a uniform paste is obtained, which is then uniformly coated on a 16 μm aluminum foil, and dried to obtain a positive electrode sheet. The positive electrode sheet, a separator, and a negative electrode sheet are sequentially wound on a winding machine to obtain a lithium ion battery cell. The battery prepared in this experiment is a 2.5 Ah cylindrical battery. After drying, 5 g of electrolyte is injected into the battery cell to obtain a corresponding battery sample.

[0025] Example 2

[0026] The lithium battery is manufactured by the same method as in Example 1, the electrolyte is prepared by dissolving lithium salt LiPF6 in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC), the mass ratio of EC, DMC, and EMC is 3:2:5, the concentration of lithium salt is 1 mol / L, and 3% of compound 2 is added to the total mass of the electrolyte.

[0027] Example 3

[0028] The lithium battery is manufactured by the same method as in Example 1, the electrolyte is prepared by dissolving lithium salt LiPF6 in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC), the mass ratio of EC, DMC, and EMC is 3:2:5, the concentration of lithium salt is 1 mol / L, and 3% of compound 3 is added to the total mass of the electrolyte.

[0029] Example 4

[0030] The lithium battery is manufactured by the same method as in Example 1, the electrolyte is prepared by dissolving lithium salt LiPF6 in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC), the mass ratio of EC, DMC, and EMC is 3:2:5, the concentration of lithium salt is 1 mol / L, and 3% of compound 4 is added to the total mass of the electrolyte.

[0031] Example 5

[0032] A lithium battery was manufactured in the same manner as in Example 1, and an electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L. Compound 5 was added to the electrolyte in an amount of 3% based on the total mass of the electrolyte.

[0033] Example 6

[0034] A lithium battery was manufactured in the same manner as in Example 1, and an electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L. Compound 6 was added to the electrolyte in an amount of 3% based on the total mass of the electrolyte.

[0035] Example 7

[0036] A lithium battery was manufactured in the same manner as in Example 1, and an electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L. Compound 7 was added to the electrolyte in an amount of 3% based on the total mass of the electrolyte.

[0037] Example 8

[0038] A lithium battery was manufactured in the same manner as in Example 1, and an electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L. Compound 8 was added to the electrolyte in an amount of 3% based on the total mass of the electrolyte.

[0039] Example 9

[0040] A lithium battery was manufactured in the same manner as in Example 1, and an electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L. Compound 9 was added to the electrolyte in an amount of 3% based on the total mass of the electrolyte.

[0041] Example 10

[0042] A lithium battery was produced in the same manner as in Example 1, except that the electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L, and 3% by mass of the compound 10 was added to the total mass of the electrolyte.

[0043] Example 11

[0044] A lithium battery was produced in the same manner as in Example 1, except that the electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L, and 3% by mass of the compound 11 was added to the total mass of the electrolyte.

[0045] Example 12

[0046] A lithium battery was produced in the same manner as in Example 1, except that the electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L, and 1.5% by mass of the compound 1 was added to the total mass of the electrolyte.

[0047] Example 13

[0048] A lithium battery was produced in the same manner as in Example 1, except that the electrolyte was prepared by dissolving a lithium salt composed of LiPF6and LiBF4(mass ratio 1:1) in an organic solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of 3:2:5, and the concentration of the lithium salt was 1 mol / L, and 3% by mass of the compound 1 was added to the total mass of the electrolyte.

[0049] Example 14

[0050] A lithium battery was produced in the same manner as in Example 1, except that the electrolyte was prepared by dissolving a lithium salt LiPF6in an organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a mass ratio of 1:1:3, and the concentration of the lithium salt was 1 mol / L, and 3% by mass of the compound 1 was added to the total mass of the electrolyte.

[0051] Comparative Example 1

[0052] The lithium ion battery was manufactured by the same method as Example 1, and the electrolyte was prepared by dissolving lithium salt LiPF6 in organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC), with the mass ratio of PC, EC, and DEC being 1:1:3, and the concentration of lithium salt being 1 mol / L, and 0.5% of tris(trimethylsilyl) borate (TMSB) was added to the total mass of the electrolyte.

[0053] Comparative Example 2

[0054] The lithium ion battery was manufactured by the same method as Example 1, and the electrolyte was prepared by dissolving lithium salt LiPF6 in organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC), with the mass ratio of PC, EC, and DEC being 1:1:3, and the concentration of lithium salt being 1 mol / L, and 0.5% of tris(trimethylsilyl) borate (TMSB) was added to the total mass of the electrolyte.

[0055] Comparative Example 3

[0056] The lithium ion battery was manufactured by the same method as Example 1, and the electrolyte was prepared by dissolving lithium salt LiPF6 in organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC), with the mass ratio of PC, EC, and DEC being 1:1:3, and the concentration of lithium salt being 1 mol / L, and 0.5% of tris(trimethylsilyl) borate (TMSB) was added to the total mass of the electrolyte.

[0057] Performance detection

[0058] At room temperature, the assembled battery was tested for 100 cycles of charge and discharge at 1C in the voltage range of 3.0-4.5V using a high-precision lithium battery charge and discharge device.

[0059] Table 1

[0060]

[0061]

[0062] As can be seen from the data in Table 1, the lithium ion battery provided by the present application has excellent cycle performance.

[0063] In the description of the specification, the description of the terms "one embodiment", "example", "specific example", and the like means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0064] The above merely illustrates and describes the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or adopt similar ways to replace, as long as the modifications or supplements do not deviate from the present application or exceed the scope defined by the present application, and should belong to the protection scope of the present application.

Claims

1. A lithium battery electrolyte additive, characterized by: The lithium battery electrolyte additive has at least one of compounds 1 to 11 as follows: 10 11。 2. A lithium battery electrolyte, characterized by: The lithium battery electrolyte additive is composed of a lithium salt, an organic solvent and the lithium battery electrolyte additive of claim 1.

3. The electrolyte for lithium battery according to claim 2, characterized by: The mass of the lithium battery electrolyte additive accounts for 0.01-5% of the total mass of the lithium battery electrolyte.

4. The lithium battery electrolyte of claim 2, wherein: The organic solvent is selected from one or more of carbonic acid ester organic solvents, carboxylic acid ester organic solvents, phosphoric acid ester organic solvents, fluorinated ether organic solvents, fluorinated ester organic solvents, and ether organic solvents.

5. The lithium battery electrolyte of claim 2, wherein: The lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, or lithium tetrafluoro(oxalato)phosphate.

6. The lithium battery electrolyte of claim 2, wherein: The molar concentration of the lithium salt in the lithium battery electrolyte is 0.05-3 mol / L.

7. A lithium battery, characterized by: The lithium battery electrolyte includes a positive electrode, a negative electrode, a separator, and the lithium battery electrolyte of any one of claims 2-6.

8. A lithium battery according to claim 7, wherein: The positive electrode material is LiNi 0.5 Mn 1.5 O4, LiCoO2, LiCoPO4, LiNiPO4.

9. The lithium battery of claim 7, wherein: The negative electrode material is at least one of graphite, mesocarbon microbeads, silicon-carbon, or metallic lithium.

Images