Non-aqueous electrolyte and lithium ion battery thereof

Abstract

The invention discloses a non-aqueous electrolyte and a lithium ion battery thereof. The non-aqueous electrolyte comprises a lithium salt, a non-aqueous organic solvent and an additive, the non-aqueous organic solvent comprises a carbonic ester compound, the additive comprises a compound A shown in a structural formula I, R1, R2 and R3 are independently selected from halogen and substituted or unsubstituted C1-C6 alkyl, X and Y are independently selected from S, P or C, m, n, a and b are independently selected from 0 or 1, and a, m, b and n are not 1 at the same time. The non-aqueous electrolyte comprises a compound A as shown in a structural formula I, the compound A is of a multi-connected parallel ring structure and can form a long-chain alkoxy lithium phosphate or alkoxy lithium sulfonate interface under high voltage, and the interface has good thermal stability and excellent lithium ion transmission characteristics; and the low-temperature performance, the high-temperature performance and the fast charging performance of the lithium ion battery can be effectively improved. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a non-aqueous electrolyte and a lithium ion battery thereof. Background Art

[0002] The rapid development of electric vehicles and portable electronic devices has placed higher demands on the performance of lithium-ion batteries. Fast charging capability, low-temperature performance, and high-temperature performance are key challenges currently facing lithium-ion batteries. During fast charging, the rapid insertion and extraction of lithium ions from the electrode material exacerbates polarization within the battery, shortening the battery's cycle life. Low temperatures reduce the electrolyte's ionic conductivity, increasing the battery's internal resistance and significantly reducing its charge and discharge capacity and efficiency. High temperatures accelerate the rate of chemical reactions within the battery, making it prone to electrolyte decomposition and gas generation, leading to increased internal battery pressure and potential safety hazards. High temperatures also accelerate structural damage and capacity decay in electrode materials, reducing the battery's cycle life and stability. Furthermore, high temperatures degrade the battery's interfacial stability, disrupting the transport of lithium ions at the interface and further impacting battery performance.

[0003] To address these performance deficiencies in lithium-ion batteries, researchers have extensively explored electrolyte additives. While some additives have been used in lithium-ion battery electrolytes to address these issues, their effectiveness remains to be seen. For example, these additives are prone to oxidative decomposition under high voltage conditions, preventing the formation of a stable and effective interfacial film. This not only limits battery performance improvements at high voltages but can also lead to significant gassing, further impacting battery safety and cycle life.

[0004] Therefore, there is an urgent need for a non-aqueous electrolyte and a lithium-ion battery thereof to address the deficiencies in the prior art. Summary of the Invention

[0005] The object of the present invention is to provide a non-aqueous electrolyte and a lithium ion battery thereof, wherein the non-aqueous electrolyte can effectively improve the high-temperature, low-temperature and fast-charging performance of the lithium ion battery.

[0006] To achieve the above object, the present invention provides a non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent and an additive, wherein the non-aqueous organic solvent comprises a carbonate compound, and the additive comprises compound A represented by structural formula I.

[0007] Wherein, R1, R2, and R3 are each independently selected from halogen, substituted or unsubstituted C1-C6 hydrocarbon group, X and Y are each independently selected from S, P or C, m, n, a, and b are each independently selected from 0 or 1, and a, m, b, and n are not 1 at the same time.

[0008] Compared with the prior art, the lithium ion battery electrolyte of the present invention includes the additive compound A shown in structural formula I. Compound A is a multi-ring structure with strong oxidation resistance, and the ring contains carbon, oxygen, phosphorus and / or sulfur elements. It can form a long-chain alkoxy lithium phosphate or alkoxy lithium sulfonate interface at high voltage. The interface has excellent lithium ion transmission characteristics and can significantly improve the low temperature and fast charging characteristics of the lithium ion battery. In addition, the long-chain interface has good thermal stability, is not easy to decompose at high voltage, and can improve the gas production of the battery to a certain extent. At the same time, the interface will not dissolve in carbonate solvents under high temperature and high voltage conditions, thereby improving the stability of the negative electrode interface, thereby improving the high temperature performance of the lithium ion battery at high voltage. Therefore, the lithium ion battery electrolyte of the present invention is applied to lithium ion batteries to effectively improve their low temperature performance, high temperature performance and fast charging characteristics.

[0009] As a preferred technical solution, R1, R2, and R3 are each independently selected from F, Cl, Br, I, and a substituted or unsubstituted C1-C6 alkyl group. When substituted, the substituent is selected from halogen, X and Y are selected from S, m and n are 0, and a and b are 0 or 1, X and Y are selected from P, m and n are 1, a and b are 0, and X and Y are selected from C, and m, n, a and b are 0.

[0010] As a preferred technical solution, the compound A is selected from at least one of compound 1 to compound 8, .

[0011] As a preferred technical solution, the mass percentage of the compound A in the non-aqueous electrolyte is 0.1% to 5%.

[0012] As a preferred technical solution, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium methanesulfonate, lithium trifluoromethylsulfonate, lithium fluorosulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, lithium difluorobis(oxalatophosphate), lithium diphosphate and lithium lower aliphatic carboxylate.

[0013] As a preferred technical solution, the non-aqueous organic solvent further includes at least one of a carboxylate compound and an ether compound.

[0014] As a preferred technical solution, it also includes an auxiliary agent, which is selected from vinylene carbonate, vinylene carbonate, fluoroethylene carbonate, vinyl sulfite, 1,3-propane sultone, 1,3-propylene sultone, 1,4-butane sultone, vinyl sulfate, succinic anhydride, maleic anhydride, 2-methylmaleic anhydride, methyl carbonate-2-propynyl ester, tetravinylsilane, triallyl isocyanurate, hexamethylene diisocyanate, o-phenanthroline, p-phenylene diisocyanate, 2,4-toluene At least one of diisocyanate, N-phenylbis(trifluoromethanesulfonyl)imide, vinyl bissulfate, phenyl methanesulfonate, vinyl bissulfate, bis-spiroallyl sulfate, hydroquinone difluorosulfonate, triallyl phosphate, tripropargyl phosphate, 2,4-butane sultone, isocyanoethyl methacrylate, methylene methanedisulfonate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, tris(vinyldimethylsilyl)phosphate, succinonitrile, adiponitrile, and 1,3,6-hexanetrinitrile.

[0015] Another aspect of the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, and the aforementioned non-aqueous electrolyte.

[0016] As a preferred technical solution, the active material of the positive electrode includes at least one of an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and modified compounds thereof.

[0017] As a preferred technical solution, the active material of the negative electrode includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode and a lithium negative electrode. DETAILED DESCRIPTION

[0018] The lithium ion battery of the present invention comprises a positive electrode, a negative electrode and a non-aqueous electrolyte.

[0019] Furthermore, the active material of the positive electrode of the present invention includes at least one of an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. The active material of the positive electrode of the present invention is not limited to these types, and other traditional materials that can be used as active materials for the positive electrode of the battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Specifically, examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Specifically, lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (structure such as LiNix Co y Mn 1-x-y M z O2, wherein 0.5≤x<0.9, x+y<1, 0≤z<0.08, and M is at least one of Al, Mg, Zr and Ti).

[0020] Furthermore, the active material of the negative electrode of the present invention includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials; the tin-based negative electrode may include tin, tin-carbon, tin-oxygen, and tin metal compounds; and the lithium negative electrode may include metallic lithium or a lithium alloy, wherein the lithium alloy may specifically be at least one of a lithium-silicon alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-aluminum alloy, a lithium-tin alloy, and a lithium-indium alloy.

[0021] Furthermore, the non-aqueous electrolyte of the present invention includes a lithium salt, a non-aqueous organic solvent, and an additive. Among them, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethylsulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium methanesulfonate (LiMS), lithium trifluoromethylsulfonate, lithium fluorosulfonate, lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), lithium diphosphate (Li2HPO4), and lower aliphatic lithium carboxylates. The lower aliphatic lithium carboxylates may be, but are not limited to, lithium acetate and lithium propionate. Lithium hexafluorophosphate has the characteristics of high conductivity, good electrochemical stability, and good compatibility with graphite negative electrodes, so the electrolyte lithium salt of the present invention is preferably lithium hexafluorophosphate.

[0022] Furthermore, the non-aqueous organic solvent of the present invention includes a carbonate compound. Carbonate compounds may include cyclic carbonates and chain carbonates. Specifically, cyclic carbonates may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), pentylene carbonate, vinylene carbonate (VC), or their derivatives; chain carbonates include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate. Furthermore, the non-aqueous organic solvent of the present invention also includes at least one of a carboxylate compound and an ether compound. Carboxylate compounds include at least one of cyclic carboxylate and chain carboxylate. Cyclic carboxylate compounds may specifically include, but are not limited to, at least one of γ-butyrolactone (GBL), γ-valerolactone (GVL), and δ-valerolactone (DVL); chain carboxylate compounds include, but are not limited to, methyl acetate (MAC), ethyl acetate (EA), propyl acetate (PA), butyl acetate (BA), propyl propionate (PP), and butyl propionate (BP). Ether compounds include cyclic ethers and chain ethers. Cyclic ethers include, but are not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). Chain ethers include, but are not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Carbonate, carboxylate, and ether compounds generally have good lithium salt solubility, ensuring a sufficiently high lithium ion concentration in the electrolyte, thereby providing good conductivity. In addition, carbonate compounds usually have a higher boiling point, which helps to improve the thermal stability of the electrolyte; carboxylate compounds have a lower viscosity, which can improve the fluidity and wettability of the electrolyte; ether compounds can remain liquid over a wider temperature range, which is beneficial for the use of batteries in high and low temperature environments. Therefore, by rationally selecting and proportioning these different types of non-aqueous organic solvents, the conductivity and cycle life of lithium-ion batteries can be optimized.

[0023] Furthermore, the non-aqueous electrolyte further comprises an auxiliary agent, which is selected from vinylene carbonate (VC), vinylene carbonate (VEC), fluoroethylene carbonate (FEC), vinyl sulfite (ES), 1,3-propane sultone (PS), 1,3-propylene sultone (PES), 1,4-butane sultone (BS), vinyl sulfate (DTD), succinic anhydride (SA), maleic anhydride (MA), 2-methylmaleic anhydride (MMA), methyl carbonate-2-propynyl ester (MPC), tetravinylsilane (TES), triallyl isocyanurate (TAIC), hexamethylene diisocyanate (HDI), o-phenanthroline, p-phenylene diisocyanate ( At least one of TDI, 2,4-toluene diisocyanate (MDI), N-phenylbis(trifluoromethanesulfonyl)imide (LiTFSI), diethylene sulfate (DES), phenyl methanesulfonate (BMS), dipropylene sulfate (DPS), hydroquinone difluorosulfonate, triallyl phosphate (TAP), tripropargyl phosphate (TPP), 2,4-butane sultone (BES), isocyanoethyl methacrylate, methylene methanedisulfonate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, tris(vinyldimethylsilyl)phosphate, succinonitrile (SN), adiponitrile (ADN), and 1,3,6-hexanetricarbonitrile (HTCN). By rationally selecting and proportioning additives, the high-temperature and low-temperature performance of lithium-ion batteries can be significantly improved. Preferably, the auxiliary agent of the present invention is selected from at least one of vinylene carbonate (VC), 1,3-propane sultone (PS), vinyl sulfate (DTD), succinonitrile (SN), adiponitrile (ADN), 1,3,6-hexanetrinitrile (HTCN) Furthermore, the mass percentage of the auxiliary agent in the lithium-ion battery electrolyte is 0.1% to 10%. For example, the content of the auxiliary agent may be, but is not limited to, 0.1%, 0.6%, 0.8%, 1.2%, 1.6%, 2%, 2.6%, 3.2%, 3.6%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0024] Furthermore, the additive includes compound A shown in structural formula I,

[0025] R1, R2, and R3 are each independently selected from halogen, a substituted or unsubstituted C1-C6 hydrocarbon group, X and Y are each independently selected from S, P, or C, m, n, a, and b are each independently 0 or 1, and a, m, b, and n are not simultaneously 1. Furthermore, R1, R2, and R3 are each independently selected from F, Cl, Br, I, or a substituted or unsubstituted C1-C6 alkyl group. When substituted, the substituent is selected from halogen, specifically F, Cl, Br, or I. X and Y are selected from S, m and n are 0, and a and b are 0 or 1. X and Y are selected from P, m and n are 1, and a and b are 0. X and Y are selected from C, and m, n, a, and b are 0. Furthermore, one of X and Y is selected from S, and the other is selected from C or S. One of X and Y is selected from P, and the other is selected from C or P. The mass percentage of compound A in the non-aqueous electrolyte is 0.1-5%. Specifically, the content of the additive may be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%. If the content is less than 0.1%, it is insufficient to form an effective interfacial film, while a content greater than 5% may cause the interfacial film to be too thick, thereby increasing internal resistance. Preferably, the mass percentage of the additive in the lithium-ion battery electrolyte is 0.1-2%. As an example, compound A may be selected from at least one of compounds 1 to 8, but is not limited thereto. Other compounds not listed herein are also applicable within the scope of the present invention.

[0026] .

[0027] Specifically, compounds 1 to 8 can be prepared according to the following synthetic routes:

[0028]

[0029]

[0030]

[0031]

[0032] .

[0033] In order to better illustrate the purpose, technical solutions and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0034] This embodiment provides a method for preparing a lithium-ion battery, comprising the following steps: (1) The positive electrode material LCO (LiCoO2), the conductive agent SuperP, the adhesive PVDF and the carbon nanotube (CNT) were mixed uniformly in a mass ratio of 96.5:1.5:1:1 to prepare a lithium-ion battery positive electrode slurry with a certain viscosity, which was then coated on the aluminum foil used for the current collector. The coating amount was 324 g / m 2 , dried at 85℃ and then cold pressed; then trimmed, cut into pieces, and slit; after slitting, dried at 85℃ for 4 hours under vacuum conditions, and the tabs were welded to make positive electrode sheets that meet the requirements; (2) Artificial graphite and silicon are mixed in a mass ratio of 90:10, and then mixed with a conductive agent SuperP, a thickener CMC, and an adhesive SBR (styrene-butadiene rubber emulsion) in a mass ratio of 95:1.5:1.0:2.5 to prepare a slurry, which is mixed evenly. The mixed slurry is applied to both sides of a copper foil, and then dried and rolled to obtain a negative electrode sheet that meets the requirements; (3) In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), ethylene carbonate (EC), propyl propionate (PP), propylene carbonate (PC), and propyl acetate (PA) were mixed in a mass ratio of 1:4:2:3 to obtain a mixed solvent as a non-aqueous organic solvent, and then the additive compound 1 was added to obtain a mixed solution. The mixed solution was sealed and packaged and placed in a quick freezer (-4°C) for 2 hours, then taken out. In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution, and after mixing evenly, a lithium-ion battery electrolyte was obtained; (4) The positive electrode sheet, negative electrode sheet and separator are laminated to form a lithium-ion battery with a thickness of 4.7 mm, a width of 55 mm and a length of 60 mm. The battery is vacuum-baked at 75°C for 10 h and the lithium-ion battery electrolyte is injected. After standing for 24 h, the battery is charged to 4.53 V at a constant current of 0.1 C (180 mA), and then charged at a constant voltage of 4.53 V until the current drops to 0.05 C (90 mA). The battery is then discharged to 3.0 V at 0.2 C (180 mA), and the charge and discharge cycle is repeated twice. Finally, the battery is charged to 3.8 V at 0.2 C (180 mA) to obtain a lithium-ion battery.

[0035] The formulas of the non-aqueous electrolytes and the positive electrode materials of Examples 1 to 19 and Comparative Examples 1 to 7 are shown in Table 1. When preparing the lithium-ion batteries of Example 12 and Comparative Example 5, the positive electrode material was replaced with NCM523 (LiNi 0.5 Co 0.2 Mn 0.3O2), the charging voltage was 4.4V, and the remaining steps were the same as in Example 1. When preparing the lithium-ion batteries of Example 13 and Comparative Example 6, the positive electrode material was replaced with LFP (LiFePO4), the charging voltage was 3.65V, and the remaining steps were the same as in Example 1. The preparation processes for the lithium-ion batteries of Examples 2-11, Examples 14-19, and Comparative Examples 1-4 were identical to those of Example 1.

[0036] Table 1 Compositions of the lithium-ion battery electrolytes of the examples and comparative examples

[0037] The structural formula of compound X is shown below:

[0038] Compound X The lithium-ion batteries prepared in Examples 1 to 19 and Comparative Examples 1 to 7 were subjected to high-temperature storage performance test, high-temperature cycle performance test, room-temperature cycle performance test, and low-temperature performance test under the following conditions. The results are shown in Table 2.

[0039] High temperature storage performance test : At room temperature (25°C), the lithium-ion battery was charged and discharged at 0.5C / 0.5C (the battery discharge capacity was recorded as C0), with an upper limit voltage of 4.53V. The battery was then charged to 4.53V under 0.5C constant current and constant voltage conditions, and the battery thickness was measured (the thickness was recorded as D0). The battery was placed in a 60°C oven for 30 days, taken out and the battery thickness was measured (the thickness was recorded as D1). The battery was placed in a 25°C environment and discharged at 0.5C (the discharge capacity was recorded as C1). The lithium-ion battery was further charged and discharged at room temperature (25°C) at 0.5C / 0.5C (the battery discharge capacity was recorded as C2), with an upper limit voltage of 4.53V. The capacity retention rate, capacity recovery rate, and thickness expansion rate were calculated.

[0040] Capacity retention rate = (C1 / C0) × 100% Capacity recovery rate = (C2 / C0) × 100% Thickness expansion rate = (D1 / D0) × 100% Normal temperature cycle performance test : At room temperature (25°C), the lithium-ion battery is charged and discharged once at 1.0C / 1.0C (the battery discharge capacity is C0) with an upper limit voltage of 4.53V. Then, it is charged and discharged at 1.0C / 1.0C for 500 cycles at room temperature (the battery discharge capacity is C1). Calculate the capacity retention rate.

[0041] Capacity retention rate = (C1 / C0) × 100% High temperature cycle test : At an elevated temperature (50°C), a lithium-ion battery is charged and discharged once at a 1.0C / 1.0C rate (discharge capacity = C0) with an upper voltage limit of 4.53V. Then, the battery is charged and discharged at a 1.0C / 1.0C rate for 400 cycles at room temperature (discharge capacity = C1). Calculate the capacity retention rate.

[0042] Capacity retention rate = (C1 / C0) × 100% Low temperature performance test : At room temperature (25°C), a lithium-ion battery is charged and discharged at a rate of 0.5C / 0.5 (battery cutoff voltage is 3.0V, discharge capacity is C0), with the upper voltage limit being 4.53V (cutoff current 0.05C). The battery is then fully charged at 0.5C to 4.53V (cutoff current 0.05C) at room temperature (25°C). The battery is then transferred to -20°C and left for 4 hours. It is then discharged at 0.5C to 3.0V, with the discharge capacity being C1. The capacity retention rate is calculated.

[0043] Capacity retention rate = (C1 / C0) × 100% Fast charging performance test: At room temperature (25°C), the lithium-ion battery is charged and discharged once at 4.0C / 1.0C (battery discharge capacity is C0) with an upper limit voltage of 4.53V. Then, it is charged and discharged at 4.0C / 1.0C for 300 cycles at room temperature (battery discharge capacity is C1), and the capacity retention rate is calculated.

[0044] Capacity retention rate = (C1 / C0) × 100% The above-mentioned high-temperature storage performance test, high-temperature cycle performance test, room-temperature cycle performance test, and low-temperature performance test are for 4.53V LCO lithium-ion batteries. When performing high-temperature storage performance test, high-temperature cycle performance test, room-temperature cycle performance test, and low-temperature performance test on 4.4V NCM523 and 3.65V LFP lithium-ion batteries, the charging voltage is replaced with 4.4V and 3.65V corresponding to their respective positive electrode materials.

[0045] Table 2 Lithium-ion battery performance test results

[0046] As shown in Table 2, compared with Comparative Examples 1 to 7, the lithium-ion batteries of Examples 1 to 19 have more excellent low-temperature performance, high-temperature performance and fast-charging characteristics. By comparing Examples 1 to 8 with Comparative Example 1, it can be seen that the addition of the additive compound A of the present invention can effectively improve the low-temperature performance, high-temperature performance and fast-charging performance of the LCO-based lithium-ion battery at a high voltage of 4.53V; this may be because the additive compound A of the present invention is a multi-ring structure, and the ring contains carbon, oxygen, phosphorus and / or sulfur elements, which can form a long-chain alkoxy lithium phosphate or alkoxy lithium sulfonate interface at high voltage. This interface has excellent lithium ion transport properties and can significantly improve the low-temperature and fast-charging characteristics of the lithium-ion battery. In addition, the long-chain interface has good thermal stability, is not easy to decompose at high voltage, and can improve the gas production of the battery to a certain extent. At the same time, the oxidation resistance of the compound A is strong, and the interface formed will not dissolve in carbonate solvents under high temperature and high voltage conditions, thereby improving the stability of the negative electrode interface, thereby improving the high-temperature performance of the lithium-ion battery at high voltage. Therefore, the lithium ion battery electrolyte of the present invention is applied to lithium ion batteries, and the lithium ion batteries have good low temperature performance, high temperature performance and fast charging characteristics at high voltage. At the same time, by comparing Example 12 with Comparative Example 5, and by comparing Example 13 with Comparative Example 6, it can be seen that the additive compound A of the present invention can also improve the low temperature performance, high temperature performance and fast charging characteristics of 4.4V NCM523 and 3.65V LFP system lithium ion batteries. It can be seen from Comparative Example 7 and Examples 1 to 8 that when the compound X shown in Comparative Example 7 is used, its performance is worse than that of Examples 1 to 8. This may be because compound X is a monocyclic structure of a cyclic and side chain, and the monocyclic and the cyclic are connected by a single bond. At a high voltage of 4.53V, the single bond structure is prone to breakage, and it is difficult to form a long chain interface on the negative electrode surface, which makes its room temperature cycle performance, high temperature cycle performance and fast charging cycle performance poor.

[0047] Comparing Example 11 with Examples 14 to 19, it can be seen that the introduction of auxiliary agents on the basis of additives can significantly improve the high-temperature performance and low-temperature performance of lithium-ion batteries.

[0048] Comparing Examples 14-16 with Examples 17-19, it is clear that the addition of a mixed additive containing SN, ADN, and HTCN significantly improves the high-temperature and low-temperature performance of the lithium-ion battery, and the expansion ratio is further improved. This is because SN, ADN, and HTCN can adsorb on the positive electrode surface, complexing the transition metal ions dissolved from the positive electrode and inhibiting the catalytic decomposition of the transition metal ions at the electrode-electrolyte interface. The additives of the present invention, combined with the mixed additive containing SN, ADN, and HTCN, can significantly improve the high-temperature and low-temperature performance of lithium-ion batteries.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent and an additive, characterized in that: The non-aqueous organic solvent includes a carbonate compound, and the additive includes compound A shown in structural formula I, Wherein, R1, R2, and R3 are each independently selected from halogen, substituted or unsubstituted C1-C6 hydrocarbon group, X and Y are each independently selected from S, P or C, m, n, a, and b are each independently selected from 0 or 1, and a, m, b, and n are not 1 at the same time.

2. The non-aqueous electrolyte according to claim 1, wherein R1, R2, and R3 are each independently selected from F, Cl, Br, I, and a substituted or unsubstituted C1-C6 alkyl group. When substituted, the substituent is selected from halogen, X and Y are selected from S, m and n are 0, and a and b are 0 or 1, X and Y are selected from P, m and n are 1, a and b are 0, and X and Y are selected from C, and m, n, a and b are 0.

3. The non-aqueous electrolyte according to any one of claims 1 or 2, wherein The compound A is selected from at least one of compound 1 to compound 8, 。 4. The non-aqueous electrolyte according to any one of claims 1 or 2, wherein The mass percentage of the compound A in the non-aqueous electrolyte is 0.1% to 5%.

5. The non-aqueous electrolyte according to any one of claims 1 or 2, wherein The lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium methanesulfonate, lithium trifluoromethylsulfonate, lithium fluorosulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, lithium difluorobis(oxalatophosphate), lithium diphosphate and lithium lower aliphatic carboxylate.

6. The non-aqueous electrolyte according to any one of claims 1 or 2, wherein The non-aqueous organic solvent further comprises at least one of a carboxylate compound and an ether compound.

7. The non-aqueous electrolyte according to any one of claims 1 or 2, wherein The auxiliary agent is selected from vinylene carbonate, vinylene carbonate, fluoroethylene carbonate, vinyl sulfite, 1,3 propane sultone, 1,3-propylene sultone, 1,4-butane sultone, vinyl sulfate, succinic anhydride, maleic anhydride, 2-methylmaleic anhydride, methyl carbonate-2-propynyl ester, tetravinylsilane, triallyl isocyanurate, hexamethylene diisocyanate, o-phenanthroline, p-phenylene diisocyanate, 2,4-toluene diisocyanate , N-phenylbis(trifluoromethanesulfonyl)imide, vinyl bissulfate, phenyl methanesulfonate, vinyl bissulfate, bis-spiroallyl sulfate, hydroquinone difluorosulfonate, triallyl phosphate, tripropargyl phosphate, 2,4-butane sultone, isocyanoethyl methacrylate, methylene methanedisulfonate, tris(trimethylsilyl)borate, tris(trimethylsilane)phosphate, tris(vinyldimethylsilane)phosphate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, at least one of.

8. A lithium-ion battery comprising a positive electrode and a negative electrode, characterized in that: Also includes the non-aqueous electrolyte according to any one of claims 1 to 7.

9. The lithium-ion battery according to claim 8, wherein The active material of the positive electrode includes at least one of an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and modified compounds thereof.

10. The lithium-ion battery according to claim 8, wherein The active material of the negative electrode includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode and a lithium negative electrode.

Images