A non-aqueous electrolyte for a high-nickel ternary lithium-ion battery and the same for the high-nickel ternary lithium-ion battery.

Abstract

This invention discloses a non-aqueous electrolyte for a high-nickel ternary lithium-ion battery and the same for the high-nickel ternary lithium-ion battery. The non-aqueous electrolyte of this invention comprises a lithium salt, a non-aqueous organic solvent, and additives. The additives include compound A as shown in Formula 1, wherein R1, R2, and R3 are each independently selected from hydrogen or C1-C6 alkyl groups, R4 is [missing information], * indicates a connecting end, R [missing information]... 41 and R 42 Each is independently selected from phenyl or C1-C6 alkyl groups, or R 41 and R 42 They combine to form a ring structure. The high-nickel ternary lithium-ion battery non-aqueous electrolyte of this invention contains compound A with a special structure, which can effectively improve the electrochemical performance of lithium-ion batteries, especially the room temperature cycling, high temperature cycling, and high temperature storage performance of high-nickel ternary lithium-ion batteries. Formula 1

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a high-nickel ternary lithium-ion battery non-aqueous electrolyte and the high-nickel ternary lithium-ion battery thereof. Background Technology

[0002] Since its commercialization, lithium-ion batteries have rapidly replaced traditional nickel-cadmium and nickel-metal hydride batteries, becoming the core carrier in the field of new energy storage, thanks to their core advantages such as high energy density, long cycle life, and no memory effect. They are widely used in various scenarios such as new energy vehicles, portable electronic devices, and energy storage power stations.

[0003] Currently, ternary lithium-ion batteries have formed two major technology systems: NCM and NCA. Based on different nickel-cobalt ratios, they can be divided into a series of products such as 523, 622, and 811. Lithium-ion batteries containing 523 and 622 ternary cathode materials generally achieve an energy density of 200-300 Wh / kg, while high-nickel NCM811 and NCA systems can achieve a single-cell energy density exceeding 300-350 Wh / kg, finding wide application in new energy vehicles, special equipment, and high-end digital products.

[0004] To improve the energy density of ternary lithium-ion batteries, the mainstream methods in the market are to single-crystallize, increase voltage, and increase nickel content in ternary materials. Single-crystallization of ternary cathode materials can improve compaction density and cycle life. However, it places higher demands on the sintering process, and higher-temperature sintering can easily exacerbate lithium-nickel mixing. Increasing voltage refers to raising the charging cut-off voltage of the lithium battery, which can increase the specific capacity of the cathode material, thereby increasing the energy density of the lithium battery. However, increasing the charging voltage can easily cause surface structure reconstruction of the cathode material, dissolution and deposition of transition metals on the anode surface, and electrolyte oxidation. Increasing nickel content involves developing ternary cathode materials from low- to medium-nickel (5-series, 6-series) to high-nickel (8-series) and ultra-high-nickel (9-series). The main purpose of increasing nickel content is to improve specific capacity, but divalent nickel is difficult to oxidize in air, which places higher demands on the lithium source, sintering atmosphere, and production equipment. Furthermore, high-nickel materials are more reactive, have lower thermal stability, reduced cycle life, and are more prone to reaction with water and oxygen in the air.

[0005] Therefore, there is an urgent need for a non-aqueous electrolyte for high-nickel ternary lithium-ion batteries and a high-nickel ternary lithium-ion battery thereof to address the shortcomings of existing technologies. Summary of the Invention

[0006] In view of the above problems, the purpose of this invention is to provide a non-aqueous electrolyte for high-nickel ternary lithium-ion batteries and the high-nickel ternary lithium-ion battery thereof. The non-aqueous electrolyte contains compound A with a special structure, which can effectively improve the electrochemical performance of lithium-ion batteries, especially the room temperature cycling, high temperature cycling and high temperature storage performance of high-nickel ternary lithium-ion batteries.

[0007] To achieve the above objectives, the present invention provides a non-aqueous electrolyte for a high-nickel ternary lithium-ion battery, comprising a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive comprises compound A as shown in Formula 1.

[0008] Formula 1 R1, R2, and R3 are each independently selected from hydrogen or C1-C6 alkyl groups, and R4 is... * indicates the connection end, R 41 and R 42 Each is independently selected from phenyl or C1-C6 alkyl groups, or R 41 and R 42 They combine to form a ring structure.

[0009] Compared with the prior art, the electrolyte of the present invention includes a lithium salt, an organic solvent, and an additive. The additive includes a compound A with a special structure. Compound A has a benzene ring as the main structure and contains three different functional groups at positions 1, 3, and 4. At position 1, there is a five-membered ring structure composed of sulfur, nitrogen, and carbon atoms, and it also contains three terminal oxygen atoms, as well as two substituents, R1 and R2. At position 3, there is a sulfonyl group, whose main functionality lies in the nitrogen-containing group at position R4. At position 4 is an alkoxy group. Through the synergistic cooperation between the above groups, the battery can be oxidized on the positive electrode side during charging and discharging to form a CEI film rich in sulfur and nitrogen elements. At the same time, the oxygen atoms in the structure at positions 1 and 3 can form complexes with the metal ions of the positive electrode, stabilizing the positive electrode material. During battery cycling, on the one hand, it inhibits the continuous dissolution of nickel, manganese, and cobalt ions in the positive electrode and prevents the metal ion deposition on the negative electrode side from causing the SEI film to break. On the other hand, the robust CEI can isolate the highly active positive electrode from direct contact with the electrolyte, thereby reducing the side reactions and gas generation problems of the electrolyte, thus improving the room temperature cycling, high temperature cycling, and high temperature storage performance of high-nickel ternary lithium-ion batteries.

[0010] As a preferred technical solution, R1 and R2 are each independently selected from hydrogen or C1-C6 alkyl groups, R3 is selected from C1-C6 alkyl groups, and R4 is... * indicates the connection end, R 41 and R 42 Each is independently selected from phenyl or C1-C6 alkyl groups, or R 41 and R 42 They combine to form morpholine or tetrahydropyrrole structures.

[0011] As a preferred technical solution, compound A includes at least one of compounds 1 to 9.

[0012]

[0013] .

[0014] Specifically, the CAS number of compound 1 is 951980-78-2; the CAS number of compound 2 is 951995-90-7; the CAS number of compound 3 is 951975-48-7; the CAS number of compound 4 is 951975-66-9; the CAS number of compound 5 is 951937-93-2; the CAS number of compound 6 is 951942-08-8; the CAS number of compound 7 is 951981-28-5; the CAS number of compound 8 is 927963-71-1; and the CAS number of compound 9 is 919205-70-2.

[0015] As a preferred technical solution, the mass percentage of compound A in the non-aqueous electrolyte of a high-nickel ternary lithium-ion battery is 0.1% to 5.0%, preferably, the mass percentage of compound A in the non-aqueous electrolyte of a high-nickel ternary lithium-ion battery is 0.1% to 3.0%. As an example, the mass percentage of compound A in the non-aqueous electrolyte of a high-nickel ternary lithium-ion battery is 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0%, 2.2%, 2.5%, 3.0%, 3.2%, 3.5%, 3.8%, 4.0%, 4.2%, 4.5%, 4.8%, and 5.0%, but it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0016] As a preferred technical solution, the lithium salt of the present invention includes at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium di(oxalate)borate (C4BLiO8), lithium di(fluorooxalate)borate (C2BF2LiO4), lithium difluorophosphate (LiPO2F2), and lithium di(fluorobis(oxalate))phosphate (LiDFBP).

[0017] As a preferred technical solution, the mass percentage of the lithium salt in the non-aqueous electrolyte of the high-nickel ternary lithium-ion battery of the present invention is 5% to 37.5%. Preferably, the mass percentage of the lithium salt in the non-aqueous electrolyte of the high-nickel ternary lithium-ion battery is 6% to 20%, and more preferably, the mass percentage of the lithium salt in the non-aqueous electrolyte of the high-nickel ternary lithium-ion battery is 8% to 18%. As examples, the mass percentage of the lithium salt in the non-aqueous electrolyte of the high-nickel ternary lithium-ion battery is 5%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 20%, 25%, 28%, 30%, 32%, 34%, 35%, 37%, and 37.5%, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0018] As a preferred technical solution, the non-aqueous organic solvent includes at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), propyl propionate (PP), γ-butyrolactone (GBL), γ-valerolactone (GVL), 1,3-dioxolane (DOL), 1,4-dioxane (DX), tetrahydrofuran (THF), ethylene glycol di-n-butyl ether (EDB), and diethylene glycol dimethyl ether (DEGME), but the present invention is not limited thereto.

[0019] As a preferred technical solution, the high-nickel ternary lithium-ion battery non-aqueous electrolyte of the present invention further includes a film-forming aid, which is selected from vinylene carbonate (VC), vinylene carbonate (VEC), fluorovinyl carbonate (FEC), vinyl sulfite (ES), 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), 1,4-butanesulfonate lactone (1,4-BS), vinyl sulfate (DTD), succinic anhydride (SA), maleic anhydride (MA), tetraethylenesilane (TVSI), triallyl isocyanurate (TAIC), hexamethylene diisocyanate (HDI). HDI), o-phenanthroline, terephthalic diisocyanate (PPDI), 2,4-toluene diisocyanate (2,4-TDI), phenyl methanesulfonate (DBCO), ethylene disulfate (BIDTD), hydroquinone difluorosulfonate (HBFS), triallyl phosphate (TAP), triargyl phosphate, 2,4-butane sulcolone (2,4-BS), isocyanoethyl methacrylate (IEM), methylene disulfonate (MMDS), tri(trimethylsilane)borate (TMSB), tri(trimethylsilane) phosphate (TMSP), and tri(trimethylsilane) phosphite. Preferably, the adjuvant of the present invention is a combination of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0020] As a preferred technical solution, the mass percentage of the film-forming aid in the non-aqueous electrolyte of a high-nickel ternary lithium-ion battery is 0.1% to 5.0%. For example, the mass percentage of the aid in the non-aqueous electrolyte of a high-nickel ternary lithium-ion battery is 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%, but it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0021] Another aspect of the present invention provides a high-nickel ternary lithium-ion battery, comprising a positive electrode active material, a negative electrode active material, and the aforementioned non-aqueous electrolyte.

[0022] As a preferred technical solution, the positive electrode active material of the present invention is nickel cobalt manganese oxide, with the chemical formula LiNi. x Co y Mn (1-x-y) M z O2, where 0.6≤x≤0.9, x+y<1, 0≤z<0.08, and M is at least one of Al, Mg, Zr and Ti.

[0023] As a preferred technical solution, the negative electrode active material of the present invention is selected from carbon negative electrode materials, silicon negative electrode materials, or silicon-carbon negative electrode materials. Preferably, the negative electrode active material of the present invention is a silicon-carbon negative electrode material, and the mass ratio of carbon to silicon is 90:10. Detailed Implementation

[0024] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0025] Unless otherwise specified in the examples and comparative examples, the conditions may be performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all commercially available conventional products.

[0026] Example 1 1.1 Preparation of non-aqueous electrolyte for high-nickel ternary lithium-ion batteries: In a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm), dimethyl carbonate (DMC), ethyl acetate (EA), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed thoroughly in a mass ratio of 3:1:2:2 to obtain 87 g of a mixed solvent, which was then used as an organic solvent. 0.5 g of compound 1 was added to obtain a mixed solution. The mixed solution was sealed and packaged, then frozen in a freezer (-4°C) for 2 hours. After removal, 12.5 g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution in a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm). After thorough mixing, a high-nickel ternary lithium-ion battery non-aqueous electrolyte was prepared.

[0027] 1.2 Preparation of the positive electrode: LiNi nickel cobalt manganese ternary material LiNi 0.8 Co 0.1 Mn 0.1 Zr 0.03 O2, conductive agent Super P, binder PVDF and carbon nanotubes (CNT) are mixed evenly in a mass ratio of 97.5:1.5:1:1 to prepare a lithium-ion battery positive electrode slurry of a certain viscosity. The mixed slurry is coated on both sides of aluminum foil, dried and rolled to obtain the positive electrode sheet.

[0028] 1.3 Preparation of the negative electrode: Artificial graphite and silicon are mixed at a mass ratio of 90:10, and then mixed with conductive agent Super P, thickener CMC, and binder SBR (styrene-butadiene rubber latex) at a mass ratio of 95:1.5:1.0:2.5 to form a slurry. After being mixed evenly, the slurry is coated on both sides of copper foil, dried, and rolled to obtain a negative electrode sheet, thus producing a lithium-ion battery negative electrode sheet that meets the requirements.

[0029] 1.4 Preparation of high-nickel ternary lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence, and then layered as needed. After the tabs are welded, the battery is placed in the aluminum-plastic film of the outer packaging. The prepared electrolyte is injected into the dried bare cell, and vacuum sealing, standing, formation (0.05C constant current charging to 3.0V, then 0.1C constant current charging to 4.4V), capacity testing, and other processes are carried out in sequence to finally obtain a 1Ah high-nickel ternary lithium-ion battery.

[0030] The composition and content of the electrolytes in Examples 1-16 and Comparative Example 1 are shown in Table 1. The preparation processes of the non-aqueous electrolyte, positive electrode, negative electrode, and high-nickel ternary lithium-ion battery in Examples 2-16 and Comparative Example 1 are the same as those in Example 1.

[0031] Table 1. Composition of the electrolytes in the examples and comparative examples

[0032] The high-nickel ternary lithium-ion batteries prepared in Examples 1-16 and Comparative Example 1 were subjected to high-temperature cycling performance tests, room-temperature cycling performance tests, and high-temperature storage performance tests under the following conditions. The results are shown in Table 2.

[0033] ambient temperature cycling performance test : Under normal temperature (25℃) conditions, a lithium-ion battery is subjected to one 1.0C / 1.0C charge and discharge cycle (battery discharge capacity is C0), with an upper limit voltage of 4.4V. Then, under normal temperature conditions, it is subjected to 500 cycles of 1.0C / 1.0C charge and discharge (battery discharge capacity is C1), and the capacity retention rate is calculated.

[0034] Capacity retention rate = (C1 / C0) × 100% High temperature cycling test : Under high temperature (45℃) conditions, a lithium-ion battery is subjected to one 1.0C / 1.0C charge and discharge cycle (battery discharge capacity is C0), with an upper limit voltage of 4.4V. Then, it is subjected to 300 cycles of 1.0C / 1.0C charge and discharge at room temperature (battery discharge capacity is C1). The capacity retention rate is calculated.

[0035] Capacity retention rate = (C1 / C0) × 100% High-temperature storage test : Under normal temperature (25℃) conditions, the lithium-ion battery was subjected to one 0.3C / 0.3C charge and discharge cycle (the battery discharge capacity is recorded as C0), with an upper limit voltage of 4.4V; the battery was placed in a 60℃ oven for 30 days, then removed and placed in a 25℃ environment for 0.3C discharge, with the discharge capacity recorded as C1; then the lithium-ion battery was subjected to one 0.3C / 0.3C charge and discharge cycle (the battery discharge capacity is recorded as C2); Capacity retention rate = (C1 / C0) × 100% Capacity recovery rate = (C2 / C0) × 100% Table 2 Performance test results of lithium-ion batteries

[0036] As shown in Table 2, compared to Comparative Example 1, the lithium-ion batteries in Examples 1-16 exhibit better room-temperature cycling performance, high-temperature cycling performance, and high-temperature storage performance due to the use of additive compound A with a special structure in the electrolyte of this invention. Furthermore, Examples 5-7 and Comparative Example 1 show that in the ternary battery system, the room-temperature cycling performance of compounds 1-3 containing morpholine rings of this invention is on average improved by 24% compared to Comparative Example 1, and the high-temperature cycling performance is improved by 24.4%. Compounds 4-6 containing tetrahydropyrrole groups show a 32.3% improvement in room-temperature cycling performance and a 30.5% improvement in high-temperature cycling performance compared to Comparative Example 1. The performance improvement may be due to the cyclic -SO2-N- group and terminal carbonyl group at the 1-position of the benzene ring in the compound structure of this invention. On the one hand, the carbonyl group can complex metal ions at the positive electrode to form a protective layer rich in S and N elements; on the other hand, it is easily reduced at the negative electrode to form an inorganic-organic composite SEI film rich in Li2S and Li3N, thus enhancing the battery's cycling performance. Furthermore, the morpholine group and tetrahydropyrrole group at the 3 position of the benzene ring enhance this effect, thereby significantly improving the room temperature cycling and high temperature cycling performance of ternary batteries.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A non-aqueous electrolyte for a high-nickel ternary lithium-ion battery, comprising a lithium salt, a non-aqueous organic solvent, and additives, characterized in that, The additive includes compound A as shown in Formula 1. Formula 1 R1, R2, and R3 are each independently selected from hydrogen or C1-C6 alkyl groups, and R4 is... * indicates the connection end, R 41 and R 42 Each is independently selected from phenyl or C1-C6 alkyl groups, or R 41 and R 42 They combine to form a ring structure.

2. The high-nickel ternary lithium-ion battery non-aqueous electrolyte according to claim 1, characterized in that, R1 and R2 are each independently selected from hydrogen or C1-C6 alkyl groups, R3 is selected from C1-C6 alkyl groups, and R4 is... * indicates the connection end, R 41 and R 42 Each is independently selected from phenyl or C1-C6 alkyl groups, or R 41 and R 42 They combine to form morpholine or tetrahydropyrrole structures.

3. The high-nickel ternary lithium-ion battery non-aqueous electrolyte according to claim 1 or 2, characterized in that, Compound A includes at least one of compounds 1 to 9. 。 4. The high-nickel ternary lithium-ion battery non-aqueous electrolyte according to claim 1 or 2, characterized in that, The mass percentage of compound A in the non-aqueous electrolyte of the high-nickel ternary lithium-ion battery is 0.1% to 5.0%.

5. The high-nickel ternary lithium-ion battery non-aqueous electrolyte according to claim 1 or 2, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium di(oxalate)borate, lithium di(fluorooxalate)borate, lithium difluorophosphate, and lithium di(fluorobis(oxalate))phosphate.

6. The high-nickel ternary lithium-ion battery non-aqueous electrolyte according to claim 1 or 2, characterized in that, The non-aqueous organic solvent includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, butylene carbonate, methyl acetate, ethyl acetate, propyl acetate, propyl propionate, γ-butyrolactone, γ-valerolactone, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

7. The high-nickel ternary lithium-ion battery non-aqueous electrolyte according to claim 1 or 2, characterized in that, It also includes film-forming aids selected from at least one of vinylene carbonate, vinylene carbonate, fluorovinyl carbonate, vinyl sulfite, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, succinic anhydride, maleic anhydride, tetraethylenesilane, triallyl isocyanurate, hexamethylene diisocyanate, o-phenanthroline, terephthalic diisocyanate, 2,4-toluene diisocyanate, phenyl methanesulfonate, vinyl disulfate, hydroquinone difluorosulfonate, triallyl phosphate, triargyl phosphate, 2,4-butanesulfonate, isocyanoethyl methacrylate, methylene disulfonate, tris(trimethylsilane)borate, tris(trimethylsilane) phosphate, and tris(trimethylsilane) phosphite.

8. The high-nickel ternary lithium-ion battery non-aqueous electrolyte according to claim 7, characterized in that, The film-forming aid is present in the non-aqueous electrolyte of the high-nickel ternary lithium-ion battery at a mass percentage of 0.1% to 5.0%.

9. A high-nickel ternary lithium-ion battery, characterized in that, It includes positive electrode active materials, negative electrode active materials, and the non-aqueous electrolyte as described in any one of claims 1 to 8.

10. The high-nickel ternary lithium-ion battery according to claim 9, characterized in that, The positive electrode active material is nickel-cobalt-manganese oxide with the chemical formula LiNi. x Co y Mn (1-x-y) M z O2, where 0.6≤x≤0.9, x+y<1, 0≤z<0.08, and M is at least one of Al, Mg, Zr and Ti.

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