Lithium ion battery electrolyte and lithium ion battery

Abstract

The present invention provides a lithium ion battery electrolyte and a lithium ion battery, belonging to the technical field of lithium ion batteries. The lithium ion battery electrolyte includes: 0.01 to 20 parts of electrolyte, 70 to 99.97 parts of aprotic organic solvent, 0.01 to 10 parts of film-forming additives and 0.01 to 5 parts of film-forming aids; the film-forming additive includes compound A, and the C-N six-membered ring and carbonyl group in compound A cooperate with each other, which can significantly reduce the interface impedance of the positive electrode and improve the rate performance of the battery, and the two cooperate with each other to improve the high-temperature storage and cycle performance of lithium ion batteries. When used in the battery, the battery has a 3C discharge rate of more than 91.53% at room temperature, a capacity retention of more than 82.60% after 50 days of storage at 60°C, a capacity recovery of more than 89.63%, a normal temperature thickness expansion of less than 5.9%, and a capacity retention rate of more than 92.1% after 800 weeks of high-temperature cycling at 45°C.

Description

Technical Field

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

[0002] In order to meet the urgent demand for higher mileage, the growing electric vehicle (EV) market urgently needs to use lithium-ion batteries with higher energy density, which poses a severe challenge to the reversibility and safety of lithium-ion batteries. The electrolyte is an important component of lithium-ion batteries, which plays a role in transmitting lithium ions between the positive and negative electrodes. The safety, charge and discharge cycle, operating temperature range and charge and discharge capacity of the battery are all closely related to the electrochemical properties of the electrolyte, so the modification of the electrolyte is an important factor in improving battery performance. Lithium battery electrolyte additives can greatly improve the rate, high temperature storage and cycle performance of lithium-ion batteries by adjusting the structure of the solid electrolyte interface film (CEI and SEI) and inhibiting the redox reaction of the electrolyte at the positive and negative electrodes. However, in the prior art, PS (1,3-propane sultone) and DTD (vinyl sulfate) are often added to lithium-ion battery electrolytes as additives, but the thermal stability of lithium-ion battery electrolytes with only PS and DTD added is poor, and it will bring environmental problems, and the application of the lithium-ion battery electrolyte in lithium-ion batteries is greatly hindered. Summary of the invention

[0003] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a lithium ion battery electrolyte and a lithium ion battery that can improve the rate performance and high temperature performance of the battery.

[0004] One of the purposes of the present invention is to provide a lithium ion battery electrolyte, the electrolyte comprising the following raw materials in parts by weight:

[0005] 0.01 to 20 parts of electrolyte, 70 to 99.97 parts of aprotic organic solvent, 0.01 to 10 parts of film-forming additive and 0.01 to 5 parts of film-forming aid;

[0006] The film-forming additives include compound A as shown in Formula 1 and other film-forming additives;

[0007]

[0008] Wherein, R1 is a C1-C5 alkyl group;

[0009] R2 and R3 are each independently selected from one of C2-C4 alkene groups or alkynyl groups.

[0010] Preferably, R2 and R3 are each independently selected from one of vinyl, propenyl, butenyl, butadienyl, ethynyl, propynyl, butenyl and butadiynyl.

[0011] Preferably, in compound A, R1 is -CH3, R2 is -CH=CH2, and R3 is -CH=CH2.

[0012] Preferably, the electrolyte comprises one or more of XClO4, XPF6, XBF4, XTFSI, XFSI, XBOB, XODFB, XCF3 SO3 or XAsF6;

[0013] Wherein, X includes any one of Li, Na or K.

[0014] Preferably, the aprotic organic solvent includes one or more of methyl propionate, methyl acetate, propyl propionate, methyl butyrate, ethyl butyrate, propyl acetate, butyl butyrate, acetonitrile, methyl propyl carbonate, ethyl propionate, γ-butyrolactone, cyclopentane, tetrahydrofuran, ethylene glycol dimethyl ether, 1,3-dioxolane, propylene carbonate, ethyl acetate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate or ethylene carbonate.

[0015] A second object of the present invention is to provide a lithium ion battery, wherein the lithium ion battery comprises the lithium ion battery electrolyte as described above.

[0016] Preferably, the lithium-ion battery comprises a battery casing, a battery core and an electrolyte, wherein the battery core and the electrolyte are sealed in the battery casing, and the battery core comprises a positive electrode, a negative electrode and a separator or a solid electrolyte layer arranged between the positive electrode and the negative electrode.

[0017] Preferably, the positive electrode material is LiNi x Co y Mn z L (1-x-y-z) O2、LiCo x' L (1-x') O2、LiNi x” L y' Mn (2-x”-y') O4 and or Li z' One or more of MPO4;

[0018] Wherein, L includes one or more of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe;

[0019] M is one or more of Fe, Mn or Co;

[0020] 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤x+y+z≤1, 0≤x'≤1, 0.3≤x”≤0.6, 0.01≤y’≤0.2, 0.5≤z’≤1.

[0021] Preferably, the negative electrode material includes silicon material and / or carbon material.

[0022] Preferably, the diaphragm or solid electrolyte is a composite diaphragm of one or more of polypropylene, polyethylene, glass fiber, vinylon or nylon.

[0023] The beneficial effects of the present invention include:

[0024] The electrolyte of the present invention adds compound A as shown in Formula 1 as a film-forming additive, and the three N atoms in the middle of the CN six-membered ring each have a pair of lone pairs of electrons, which cooperate with the carbonyl group to effectively improve the complexing ability of N with the high-valent metal atoms of the positive electrode, thereby significantly reducing the interfacial impedance of the positive electrode, which is beneficial to the migration of lithium ions at the positive electrode interface and significantly improving the rate performance of the battery. In addition, the complexing of N atoms with high-valent metal atoms can effectively reduce the oxidation activity of the positive electrode material to the electrolyte, and the two cooperate with each other to improve the Lewis alkalinity of the carbonyl group, and preferentially react with the by-product PF5 generated by the decomposition of lithium salts in the electrolyte system, thereby inhibiting the reaction of PF5 and the organic solvent, thereby effectively preventing the consumption of the solvent in the electrolyte system during the cycle, thereby improving the high-temperature storage and cycle performance of the lithium-ion battery. When used in a battery, many aspects of the resulting battery's performance are improved: the 3C discharge rate at room temperature is above 91.53%, the capacity is retained at above 82.60% after storage at 60°C for 50 days, the capacity recovery is above 89.63%, the thickness expansion at room temperature is below 5.9%, and the capacity retention rate is above 92.1% after 800 weeks of high-temperature cycling at 45°C, which can effectively improve the battery's rate performance and high-temperature performance. DETAILED DESCRIPTION

[0025] In the following description, certain specific details are included to provide a comprehensive understanding of each disclosed embodiment. However, one skilled in the relevant art will recognize that the embodiments can be implemented without one or more of these specific details, but with other methods, components, materials, etc.

[0026] Unless otherwise required herein, the words "include" and "comprising" should be interpreted as having an open and inclusive meaning, ie, "including but not limited to".

[0027] References to "one embodiment" or "an embodiment" or "a preferred embodiment" or "certain embodiments" throughout this specification mean that the specific referenced elements, structures or features described in connection with the embodiment are included in at least one embodiment. Therefore, the phrases "in one embodiment" or "in an embodiment" or "in a preferred embodiment" or "in certain embodiments" appearing in different places throughout the specification do not necessarily all refer to the same embodiment. In addition, the specific elements, structures or features may be combined in any appropriate manner in one or more embodiments.

[0028] According to a first aspect of the present invention, there is provided a lithium ion battery electrolyte, the electrolyte comprising the following raw materials in parts by weight:

[0029] 0.01 to 20 parts of electrolyte, 70 to 99.97 parts of aprotic organic solvent, 0.01 to 10 parts of film-forming additive and 0.01 to 5 parts of film-forming aid;

[0030] The film-forming additives include compound A as shown in Formula 1 and other film-forming additives;

[0031]

[0032] Wherein, R1 is a C1-C5 alkyl group;

[0033] R2 and R3 are each independently selected from one of C2-C4 alkene groups or alkynyl groups.

[0034] In the present invention, the electrolyte is, for example, 0.01 parts, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 15 parts, 16 parts, 18 parts or 20 parts.

[0035] The aprotic organic solvent is, for example, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, 92 parts, 94 parts, 96 parts, 98 parts or 99.7 parts.

[0036] The film-forming additive is, for example, 0.01 parts, 1 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts.

[0037] The film-forming aid is, for example, 0.01 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts.

[0038] R1 is, for example, -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)CH3, -CH2CH2CH2CH3, -CH(CH3)CH2CH3, -CH2CH(CH3)CH3, -C H2CH2CH2CH2CH3, -CH(CH3)CH2CH2CH3, -CH2CH(CH3)CH2CH3, -CH2CH2CH(CH3)CH3 or -CH(CH2CH3)CH2CH3.

[0039] R2 is, for example, ethenyl, propenyl, butenyl, ethynyl, propynyl or butynyl.

[0040] R3 is, for example, ethenyl, propenyl, butenyl, ethynyl, propynyl or butynyl.

[0041] In a preferred embodiment of the present invention, R2 and R3 are each independently selected from one of vinyl, propenyl, butenyl, butadienyl, ethynyl, propynyl, butenyl and butadiynyl.

[0042] In a preferred embodiment of the present invention, in the compound A, R1 is -CH3, R2 is -CH=CH2, and R3 is -CH=CH2.

[0043] In the present invention, the structure of the compound A is shown in Formula 1-1:

[0044]

[0045] In the present invention, the unsaturated double bonds can polymerize on the surface of the positive and negative electrodes, which can further promote the formation of a dense and uniform interface film, and can cooperate with the CN six-membered ring to further enhance the complexing ability of N, thereby further reducing the interfacial impedance of the positive electrode and further reducing the oxidation activity of the positive electrode material to the electrolyte.

[0046] In a preferred embodiment of the present invention, the electrolyte includes one or more of XClO4, XPF6, XBF4, XTFSI, XFSI, XBOB, XODFB, XCF3 SO3 or XAsF6.

[0047] Wherein, X includes any one of Li, Na or K.

[0048] In the present invention, the electrolyte includes one or more of LiClO4, NaClO4, KClO4, LiPF6, NaPF6, KPF6, LiBF4, NaBF4, KBF4, LiTFSI, NaTFSI, KTFSI, LiFSI, NaFSI, KFSI, LiBOB, NaBOB, KBOB, LiODFB, NaODFB, KODFB, LiCF3SO3, NaCF3SO3, KCF3SO3, LiAsF6, NaAsF6 or KAsF6.

[0049] Preferably, the electrolyte comprises one or more of LiPF6, LiAsF6, LiBOB or LiFSI. The electrolyte is, for example, LiPF6, LiAsF6, LiBOB, LiFSI, LiPF6 and LiAsF6, LiPF6 and LiBOB, LiPF6 and LiFSI, LiBOB and LiFSI, LiPF6, LiAsF6 and LiBOB, or a combination of LiAsF6, LiBOB and LiFSI.

[0050] In a preferred embodiment of the present invention, the aprotic organic solvent includes one or more of methyl propionate, methyl acetate, propyl propionate, methyl butyrate, ethyl butyrate, propyl acetate, butyl butyrate, acetonitrile, methyl propyl carbonate, ethyl propionate, γ-butyrolactone, cyclopentane, tetrahydrofuran, ethylene glycol dimethyl ether, 1,3-dioxolane, propylene carbonate, ethyl acetate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate or ethylene carbonate.

[0051] Preferably, the aprotic organic solvent comprises ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.

[0052] Preferably, the mass ratio of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate is 3:5:2.

[0053] In a preferred embodiment of the present invention, the other film-forming additives include one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate or methylene methane disulfonate.

[0054] In the present invention, the other film-forming additives are, for example, vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, methylene methanedisulfonate, vinylene carbonate and fluoroethylene carbonate, 1,3-propane sultone and vinylene carbonate, vinylene carbonate and methylene methanedisulfonate, vinylene carbonate, fluoroethylene carbonate and 1,3-propane sultone, vinylene carbonate, fluoroethylene carbonate and vinyl sulfate, or a combination of fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate and methylene methanedisulfonate.

[0055] Preferably, the other film-forming additives are vinylene carbonate and 1,3-propane sultone.

[0056] Preferably, the mass ratio of vinylene carbonate to 1,3-propane sultone is 1:1.

[0057] According to a second aspect of the present invention, a lithium ion battery is provided, wherein the lithium ion battery comprises the lithium ion battery electrolyte as described above.

[0058] In a preferred embodiment of the present invention, the lithium-ion battery comprises a battery housing, a battery cell and an electrolyte, wherein the battery cell and the electrolyte are sealed in the battery housing, and the battery cell comprises a positive electrode, a negative electrode and a separator or a solid electrolyte layer arranged between the positive electrode and the negative electrode.

[0059] In a preferred embodiment of the present invention, the positive electrode material is LiNi x Co y Mn z L (1-x-y-z) O2、LiCox' L (1-x') O2、LiNi x” L y' Mn (2-x”-y') O4 and or Li z' One or more of MPO4;

[0060] Wherein, L includes one or more of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe;

[0061] M is one or more of Fe, Mn or Co;

[0062] 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤x+y+z≤1, 0≤x'≤1, 0.3≤x”≤0.6, 0.01≤y'≤0.2, 0.5≤z'≤1.

[0063] In a preferred embodiment of the present invention, the negative electrode material includes silicon material and / or carbon material.

[0064] In a preferred embodiment of the present invention, the diaphragm or solid electrolyte is a composite diaphragm of one or more of polypropylene, polyethylene, glass fiber, vinylon or nylon.

[0065] In the present invention, the preparation method of the lithium ion battery comprises:

[0066] The positive electrode uses a binder, a composite conductive agent, a positive electrode material and a solvent, and adopts a wet slurry process to prepare a positive electrode slurry, and the viscosity of the positive electrode slurry is adjusted to 10000-13000mPa·s;

[0067] The negative electrode uses a negative electrode material, a conductive agent, a solvent, water and a binder, and adopts a wet slurry process to prepare a negative electrode slurry, and the viscosity of the negative electrode slurry is adjusted to 1500-3000mPa·s;

[0068] Then the positive electrode slurry and the negative electrode slurry are respectively subjected to processes such as coating, slicing, rolling, slitting, drying, taping, cell winding, and drying;

[0069] The electrolyte, the aprotic organic solvent and the film-forming additive are mixed to prepare a lithium-ion battery electrolyte;

[0070] The lithium-ion battery is then subjected to processes such as liquid filling and sealing, shelving for 24 hours, formation, primary final sealing, aging, and secondary final sealing to prepare a lithium-ion soft-pack battery.

[0071] Example

[0072] The present invention is further described in detail below in conjunction with the embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0073] In the following examples, unless otherwise specified, all raw materials are commercially available products.

[0074] First, prepare a film-forming additive compound A as shown in Formula 1-1:

[0075]

[0076] Then, the electrolyte, the aprotic organic solvent and the film-forming additive are mixed to prepare a lithium-ion battery electrolyte.

[0077] Among them, in Examples 1 to 9, Comparative Examples 1 and 3, the aprotic organic solvent uses ethylene carbonate, ethyl methyl carbonate and diethyl carbonate, and the mass ratio of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate is 3:5:2.

[0078] In Example 10 and Comparative Example 2, the aprotic organic solvent used was ethylene carbonate, propylene carbonate, propyl propionate and ethyl propionate, and the mass ratio of ethylene carbonate, propylene carbonate, propyl propionate and ethyl propionate was 17:13:30:40.

[0079] In Examples 1 to 10 and Comparative Examples 1 to 3, the film-forming aids are vinylene carbonate and 1,3-propane sultone, and the mass ratio of vinylene carbonate to 1,3-propane sultone is 1:1.

[0080] Specifically, in Examples 1 to 10 and Comparative Examples 1 to 3, the mass composition of the lithium ion battery electrolyte is as shown in Table 1.

[0081] Table 1 Electrolyte compositions of Examples 1 to 9 and Comparative Examples 1 to 3

[0082]

[0083] Then, the lithium ion battery electrolytes prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were used to prepare lithium ion batteries.

[0084] The positive electrode adopts a binder PVDF-S5130, a composite conductive agent Super-P / KS-6 (mass ratio Super-P: KS-6=2:1), a 523 nickel-cobalt-manganese ternary positive electrode material or a lithium cobalt oxide positive electrode material, and a solvent NMP (N-methyl-2-pyrrolidone). The positive electrode slurry is prepared by a wet pulping process, and the viscosity of the positive electrode slurry is adjusted to 10000-13000 mPa·s.

[0085] The negative electrode uses C-P15, conductive agent Super-P solvent CMC, H2O, and binder SBR as raw materials, and the negative electrode slurry is prepared by wet pulping process. The viscosity of the negative electrode slurry is adjusted to 1500-3000mPa·s;

[0086] The designed N / P ratio is 1.12, the capacity is 1671 mAh, and the process is through coating, slicing, rolling, slitting, drying at 140℃ for 8h, taping, winding the battery cell, and drying at 80℃ for 48h;

[0087] Then, the electrolytes of Examples 1 to 9, Comparative Examples 1 and 3 were added to a 1.6 Ah lithium-ion battery containing a graphite negative electrode material (Shanshan P15) and a NCM523 nickel-cobalt-manganese ternary material;

[0088] The electrolyte described in Example 10 and Comparative Example 2 was added to a battery whose negative electrode material was a silicon-carbon negative electrode material (Bai Te Rui S420) and whose positive electrode material was a 4.45V lithium cobalt oxide to prepare a 1.8Ah lithium-ion battery;

[0089] The lithium-ion battery is filled with liquid, sealed, left for 24 hours, formed, sealed once, aged, and sealed twice to prepare a lithium-ion soft-pack battery.

[0090] The battery is then tested for rate, cycle performance, safety performance, etc.

[0091] (1) Discharge rate performance: 1C current is 1.6A, 3C current is 4.8A; the charge and discharge potential range is 2.75V to 4.4V, and the 3C discharge rate at room temperature is the ratio of the 3C constant current discharge capacity C2 to the 1C constant current discharge capacity C1.

[0092] (2) High temperature storage performance: At room temperature, the formed battery was discharged at 1C (1.8A) constant current to 2.75V, and then charged at 1C constant current and constant voltage (cut-off current is 0.05C) / 1C constant current and discharged for three weeks. The discharge capacity in the third week was taken as the initial discharge capacity of the battery. The battery was then charged at 1C constant current and constant voltage to 3.85V with a cut-off current of 0.05C, and the initial DCIR of the battery was measured. The battery was then charged at 1C constant current and constant voltage to 4.4V with a cut-off current of 0.05C. After the battery was stored at 60°C for 50 days, it was discharged at 1C constant current to 2.75V, and the retention capacity of the battery was measured. The battery was then charged at 1C constant current and constant voltage to 4.4V with a cut-off current of 0.05C and discharged at 1C constant current to 2.75V, and the recovery capacity of the battery was measured. After another two weeks of 1C cycling, the battery was charged to 3.85V and the DCIR of the battery after storage was measured.

[0093] The calculation formulas for capacity retention rate, capacity recovery rate, and thickness expansion rate are as follows:

[0094] Battery capacity retention rate = retention capacity / initial capacity*100%

[0095] Battery capacity recovery rate = recovery capacity / initial capacity*100%

[0096] Battery thickness expansion = (thickness after 50 days - initial thickness) / initial thickness * 100%

[0097] (3) High temperature cycle performance: The battery was charged at a constant current and voltage of 1C (1.8A) to 4.4V (cut-off current was 0.05C), and then discharged at a constant current to 2.75V, and this charge and discharge cycle was repeated. The battery was placed in a 45°C environment using a Xinwei test cabinet. After this charge / discharge cycle, the capacity retention rate after the 600th cycle was calculated to evaluate its high temperature cycle performance.

[0098] The capacity retention rate after 600 cycles at 45°C is calculated as follows:

[0099] Capacity retention rate = (discharge capacity after 600th cycle / first discharge capacity)*100%.

[0100] In addition, the electrolytes described in Example 10 and Comparative Example 2 were added to a battery whose negative electrode material was a silicon-carbon negative electrode material (Bai Te Rui S420) and whose positive electrode material was a 4.45V lithium cobalt oxide to prepare a 1.8Ah lithium-ion battery; the following tests were performed:

[0101] (1) Discharge rate performance: 1C current is 1.8A, 3C current is 5.4A; the charge and discharge potential range is 2.75V to 4.45V, and the 3C discharge rate at room temperature is the ratio of the 3C constant current discharge capacity C2 to the 1C constant current discharge capacity C1.

[0102] (2) High temperature storage performance: At room temperature, the formed battery was discharged at 1C (1.8A) constant current to 2.75V, and then charged at 1C constant current and constant voltage (cut-off current is 0.05C) / 1C constant current and discharged for three weeks. The discharge capacity in the third week was taken as the initial discharge capacity of the battery. The battery was then charged at 1C constant current and constant voltage to 3.85V with a cut-off current of 0.05C, and the initial DCIR of the battery was measured. The battery was then charged at 1C constant current and constant voltage to 4.45V with a cut-off current of 0.05C. After the battery was stored at 60°C for 50 days, it was discharged at 1C constant current to 2.75V, and the retention capacity of the battery was measured. The battery was then charged at 1C constant current and constant voltage to 4.45V with a cut-off current of 0.05C and discharged at 1C constant current to 2.75V, and the recovery capacity of the battery was measured. After another two weeks of 1C cycling, the battery was charged to 3.85V and the DCIR of the battery after storage was measured.

[0103] The calculation formulas for capacity retention rate, capacity recovery rate, and thickness expansion at room temperature are as follows:

[0104] Battery capacity retention rate (%) = retention capacity / initial capacity * 100%

[0105] Battery capacity recovery rate (%) = recovery capacity / initial capacity * 100%

[0106] Battery room temperature thickness expansion (%) = (thickness after 50 days - initial thickness) / initial thickness * 100%

[0107] (3) High temperature cycle performance: The battery was charged at a constant current and voltage of 1C (1.8A) to 4.45V (cut-off current was 0.05C), and then discharged at a constant current to 2.75V, and this charge and discharge cycle was repeated. The battery was placed in a 45°C environment using a Xinwei test cabinet. After this charge / discharge cycle, the capacity retention rate after the 600th cycle was calculated to evaluate its high temperature cycle performance.

[0108] The capacity retention rate after 600 cycles at 45°C is calculated as follows:

[0109] Capacity retention rate = (discharge capacity after 600th cycle / first discharge capacity)*100%.

[0110] The room temperature discharge performance and high temperature storage performance of the lithium ion batteries prepared in Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 2.

[0111] The high temperature cycle performances of the lithium ion batteries prepared in Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 3.

[0112] Table 2 Tests of room temperature discharge performance and high temperature storage performance of Examples 1 to 10 and Comparative Examples 1 to 3

[0113]

[0114] Table 3 High temperature cycle performance of Examples 1 to 10 and Comparative Examples 1 to 3

[0115]

[0116]

[0117] As shown in Table 2 and Table 3, the electrolyte of the present invention improves the normal temperature discharge performance, high temperature storage performance and high temperature cycle performance of the obtained battery when used in the battery by adding compound A as a film-forming additive. The 3C discharge rate at room temperature is above 91.53%, the capacity is maintained at above 82.60% after 50 days of storage at 60°C, the capacity is recovered at above 89.63%, the normal temperature thickness expansion is below 5.9%, and the capacity retention rate is above 92.1% after 800 weeks of high temperature cycling at 45°C, which can effectively improve the rate performance and high temperature performance of the battery.

[0118] It can be seen from Comparative Example 1 and Example 3, and Comparative Example 2 and Example 10 that adding compound A to the electrolyte can improve the various performance of the battery, which is beneficial to the rate performance and high temperature performance of silicon-containing materials or graphite as negative electrodes and ternary materials or lithium cobalt oxide batteries.

[0119] The film-forming additive is reduced at a lithium potential of about 1.7V, and can preferentially form a dense and uniform SEI film on the surface of the battery negative electrode over other components of the electrolyte, thereby effectively inhibiting further decomposition of the electrolyte, effectively protecting the negative electrode interface, reducing irreversible reactions, and thereby improving performance.

[0120] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A lithium ion battery electrolyte, characterized in that: The electrolyte comprises the following raw materials in parts by weight: 0.01 to 20 parts of electrolyte, 70 to 99.97 parts of aprotic organic solvent, 0.01 to 10 parts of film-forming additive and 0.01 to 5 parts of film-forming aid; The film-forming additive includes a compound A as shown in Formula 1; In the compound A, R1 is -CH3, R2 is -CH=CH2, and R3 is -CH=CH2; The structure of the compound A is shown in Formula 1-1: 。 2. The lithium ion battery electrolyte according to claim 1, characterized in that The electrolyte includes one or more of XClO4, XPF6, XBF4, XTFSI, XFSI, XBOB, XODFB, XCF3SO3 or XAsF6; Wherein, X includes any one of Li, Na or K.

3. The lithium ion battery electrolyte according to claim 1, characterized in that The aprotic organic solvent includes one or more of methyl propionate, methyl acetate, propyl propionate, methyl butyrate, ethyl butyrate, propyl acetate, butyl butyrate, acetonitrile, methyl propyl carbonate, ethyl propionate, γ-butyrolactone, cyclopentane, tetrahydrofuran, ethylene glycol dimethyl ether, 1,3-dioxolane, propylene carbonate, ethyl acetate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate or ethylene carbonate.

4. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-ion battery electrolyte according to any one of claims 1 to 3.

5. The lithium ion battery according to claim 4, characterized in that The lithium-ion battery comprises a battery casing, a battery core and an electrolyte, wherein the battery core and the electrolyte are sealed in the battery casing, and the battery core comprises a positive electrode, a negative electrode and a separator or a solid electrolyte layer arranged between the positive electrode and the negative electrode.

6. The lithium ion battery according to claim 5, characterized in that The positive electrode is LiNi x Co y Mn z L (1-x-y-z) O2、LiCo x' L (1-x') O2、LiNi x'' L y' Mn (2-x''-y') O4 and or Li z' One or more of MPO4; Wherein, L includes one or more of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe; M is one or more of Fe, Mn or Co; 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤x+y+z≤1, 0≤x'≤1, 0.3≤x''≤0.6, 0.01≤y'≤0.2, 0.5≤z'≤1.

7. The lithium ion battery according to claim 5, characterized in that The negative electrode includes silicon material and / or carbon material.

8. The lithium ion battery according to claim 5, characterized in that The diaphragm or solid electrolyte is a composite diaphragm of one or more of polypropylene, polyethylene, glass fiber, vinylon or nylon.

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