Electrolyte and battery

Abstract

The present application relates to the field of batteries, and in particular to an electrolyte and a battery comprising the electrolyte. The electrolyte comprises a first additive, wherein the first additive comprises a substance shown in formula I and / or a substance shown in formula II. The electrolyte has the performance of inhibiting gas production, and can improve the safety performance and electrochemical performance of batteries.

Description

Electrolyte and battery Technical Field

[0001] The present disclosure relates to the field of batteries, and in particular to an electrolyte and a battery comprising the electrolyte. Background Art

[0002] Lithium-ion batteries, due to their long cycle life, fast charging speed, and high energy density, have become a key research area in the new energy sector. They are widely used in various fields, including consumer electronics, power tools, energy storage, and military applications. As a crucial component of lithium-ion batteries, the electrolyte has garnered significant attention. 1,3-Propane sultone (PS), a key electrolyte additive, exhibits excellent gas suppression properties. However, the toxicity of 1,3-Propane sultone limits its application.

[0003] Summary of the Invention

[0004] The present invention aims to overcome the above-mentioned problems existing in the prior art and provide an electrolyte and a battery including the electrolyte. The electrolyte disclosed in the present invention has the ability to inhibit gas production and has low toxicity, which can improve the safety and electrochemical performance of the battery.

[0005] The first aspect of the present disclosure provides an electrolyte. The electrolyte includes a first additive, the first additive including a substance represented by Formula I and / or a substance represented by Formula II:

[0006] wherein Y1, Y2, Y3 and Y4 are each independently selected from at least one of an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 1 to 10 carbon atoms, an alkynyl group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a fluoroalkenyl group having 1 to 10 carbon atoms, a fluoroalkynyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a nitrile group having 1 to 10 carbon atoms, and derivatives thereof;

[0007] n and m are each independently 0 or 1, M1 and M2 are each independently selected from At least one of, X1 and X2 are each independently selected from at least one of CH and O; R1 and R2 are each independently selected from H, halogen, unsubstituted or halogen-substituted hydrocarbon group with 1 to 5 carbon atoms, At least one of .

[0008] A second aspect of the present disclosure provides a battery, comprising the electrolyte described in the first aspect of the present disclosure.

[0009] Through the above technical solution, the present disclosure has at least the following advantages compared with the prior art: the electrolyte of the present disclosure has lower toxicity; and includes specific additives, which have the ability to inhibit gas production.

[0010] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. DETAILED DESCRIPTION

[0011] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0012] A first aspect of the present disclosure provides an electrolyte, wherein the electrolyte may include a first additive, and the first additive may include a substance represented by Formula I and / or a substance represented by Formula II:

[0013] wherein Y1, Y2, Y3 and Y4 are each independently selected from an alkyl group having 1 to 10 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms), an alkenyl group having 1 to 10 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms), an alkynyl group having 1 to 10 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms), an alkyl ... at least one of a fluoroalkyl group (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms), a fluoroalkenyl group having 1 to 10 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms), a fluoroalkynyl group having 1 to 10 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms), an alkoxy group having 1 to 10 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms), a nitrile group having 1 to 10 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms), and derivatives thereof;

[0014] n and m are each independently 0 or 1, M1 and M2 are each independently selected from At least one of, X1 and X2 are each independently selected from at least one of CH and O; R1 and R2 are each independently selected from H, halogen, unsubstituted or halogen-substituted hydrocarbon group having 1 to 5 carbon atoms (e.g., having 1, 2, 3, 4 or 5 carbon atoms), At least one of .

[0015] 1,3-Propane sultone (PS) as an electrolyte additive has excellent gas production inhibition performance. In order to improve the gas production inhibition performance of the battery, its addition concentration in the battery is generally >0.1% (this concentration is based on the weight of the battery, and the concentration of 1,3-propane sultone in the electrolyte is generally >1%). However, 1,3-propane sultone is toxic, and the inventors of the present disclosure have found that when the concentration of 1,3-propane sultone in the battery is >0.1% (the concentration of 1,3-propane sultone in the electrolyte is >1%), the polarization risk of the negative electrode sheet may increase. The reason may be that 1,3-propane sultone has a continuous film-forming ability. As the battery charge and discharge process proceeds, the volume of the negative electrode active material will expand and shrink. At this time, 1,3-propane sultone continues to form a thick and unstable interface film on the negative electrode surface, resulting in increased polarization of the negative electrode sheet and affecting the electrochemical performance. The inventors of the present disclosure further discovered that when the electrolyte includes a substance represented by Formula I and / or a substance represented by Formula II, even if the battery does not contain 1,3-propane sultone, it can also have excellent gas production suppression performance and can improve the volume expansion of the negative electrode active material (especially silicon-based materials). The polymer film generated by the substance represented by Formula I and / or the substance represented by Formula II has good stability and better compatibility with the negative electrode sheet, which can suppress the gas production problem caused by insufficient 1,3-propane sultone.

[0016] In the present disclosure, the substance represented by formula I and the substance represented by formula II can be obtained by conventional methods in the art, such as gas chromatography or ion chromatography.

[0017] The inventors of the present disclosure have discovered that when Y1, Y2, Y3 and Y4 in Formula I are selected from specific groups, a stable interface film can be formed on the surface of the positive electrode sheet and the surface of the negative electrode sheet (especially the surface of the negative electrode sheet), and the volume expansion of the negative electrode active material (especially the silicon-based material) can be effectively inhibited, thereby significantly improving the cycle performance of the battery.

[0018] In one example, Y1, Y2, Y3 and Y4 are each independently selected from at least one of an alkenyl group having ≤5 carbon atoms and an alkynyl group having ≤5 carbon atoms.

[0019] In one example, Y1, Y2, Y3 and Y4 are each independently selected from at least one of an alkenyl group having ≤3 carbon atoms and an alkynyl group having ≤3 carbon atoms.

[0020] In the present disclosure, the substance represented by formula I may include At least one of .

[0021] In one embodiment, the substance represented by formula I includes At least one of .

[0022] In one embodiment, the substance represented by formula I includes

[0023] In one embodiment, the substance represented by formula I includes

[0024] In one embodiment, the substance represented by formula I includes combination.

[0025] In the present disclosure, based on the total weight of the electrolyte, the content of the substance represented by formula I can be 0.05%-1.2%, for example, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1% or 1.2%.

[0026] The inventors of the present disclosure have discovered that when the content of the substance represented by Formula I in the electrolyte is within a specific range, the cycle performance of the battery can be effectively improved while also improving the safe storage performance.

[0027] In one example, based on the total weight of the electrolyte, the content of the substance represented by formula I is 0.3%-0.7%.

[0028] In the present disclosure, the content of the substance represented by Formula I in the electrolyte can be measured by conventional methods in the art, such as gas chromatography.

[0029] The inventors of the present disclosure have found that the substance shown in Formula II includes a polycyclic structure, has the properties of stable film formation and suppression of gas production, and can effectively reduce the interfacial impedance, improve the negative electrode interface conductivity, and improve the battery's cycle performance, high temperature storage performance and safety performance. The inventors of the present disclosure further found that when M1, M2, X1, X2, R1 and R2 in Formula II are selected from specific groups, a stable interfacial film can be formed on the surface of the positive electrode sheet and the surface of the negative electrode sheet, and the volume expansion of the negative electrode active material (especially silicon-based materials) can be suppressed, thereby improving the cycle performance of the battery and effectively improving the battery's safe storage performance.

[0030] In the present disclosure, the substance represented by formula II may include At least one of .

[0031] In one embodiment, the substance represented by formula II includes At least one of .

[0032] In one embodiment, the substance represented by formula II includes combination.

[0033] In the present disclosure, based on the total weight of the electrolyte, the content of the substance represented by formula II can be 0.1%-6%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% or 6%.

[0034] In one embodiment, based on the total weight of the electrolyte, the content of the substance represented by Formula II is 1%-3%.

[0035] In the present disclosure, the content of the substance represented by Formula II in the electrolyte can be measured by conventional methods in the art, such as gas chromatography.

[0036] In the present disclosure, the first additive includes the substance represented by Formula I and the substance represented by Formula II.

[0037] The inventors of the present disclosure have discovered that the substance represented by Formula I and the substance represented by Formula II have a synergistic effect, and the gas production inhibition ability of the two when used in combination is better than that of 1,3-propane sultone; and the two have a specific mass ratio, which can not only enhance the stability of the interface film formed on the surface of the positive electrode sheet and the surface of the negative electrode sheet, but also further inhibit the volume expansion of the negative electrode active material (especially silicon-based materials), thereby improving the cycle performance of the battery while improving the storage and safety performance.

[0038] In the present disclosure, the ratio of the content of the substance represented by formula II in the electrolyte to the content of the substance represented by formula I in the electrolyte can be (0.1-50):1, for example, 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1.

[0039] In one example, the ratio of the content of the substance represented by formula II in the electrolyte to the content of the substance represented by formula I in the electrolyte is (0.4-25):1.

[0040] In one example, the ratio of the content of the substance represented by formula II in the electrolyte to the content of the substance represented by formula I in the electrolyte is (3-4.5):1.

[0041] In the present disclosure, the electrolyte may further include 1,3-propane sultone.

[0042] Based on the total weight of the electrolyte, the content of 1,3-propane sultone is less than 1%, for example, 0.001%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95% or 0.99%.

[0043] In one example, based on the total weight of the electrolyte, the content of 1,3-propane sultone is ≤0.8%.

[0044] In one example, based on the total weight of the electrolyte, the content of 1,3-propane sultone is 0.1%-0.4%.

[0045] In the present disclosure, the content of 1,3-propane sultone in the electrolyte can be measured by conventional methods in the art, such as gas chromatography or gas chromatography-mass spectrometry.

[0046] The inventors of the present disclosure have discovered that the substance represented by Formula I, the substance represented by Formula II, and 1,3-propane sultone can produce a good synergistic effect, which can effectively improve the stability of the SEI film, reduce the interface instability and high polarization interface film caused by high expansion during charge and discharge, effectively improve the stability of the negative electrode interface conductive network, and reduce the volume expansion of the negative electrode material. It was further discovered that by limiting the content of the substance represented by Formula I, the content of the substance represented by Formula II, and the content of 1,3-propane sultone, it can be ensured that the addition amount of the substance represented by Formula I and the substance represented by Formula II does not result in high impedance, and can have the performance of suppressing gas production and improving cycle performance.

[0047] In the present disclosure, based on the total weight of the electrolyte, the content of 1,3-propane sultone is a%, the content of the substance represented by Formula I is b%, and the content of the substance represented by Formula II is c%, satisfying: 0.8+1.5×a≤1.8×b+0.5×c≤2+4×a.

[0048] In the present disclosure, the electrolyte may further include at least one of a lithium salt, an organic solvent, and a second additive.

[0049] In the present disclosure, the lithium salt may include at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium oxalatephosphate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bistrifluorosulfonylimide, and lithium bisfluorosulfonylimide.

[0050] In one example, the lithium salt includes lithium hexafluorophosphate and lithium bis(trifluorosulfonyl)imide.

[0051] In the present disclosure, the lithium salt can be a combination of lithium hexafluorophosphate and lithium bis(trifluorosulfonyl)imide, wherein the ratio of the molar concentration of lithium hexafluorophosphate to the molar concentration of lithium bis(trifluorosulfonyl)imide can be (0.7-10):1, for example, 0.7:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1.

[0052] In the present disclosure, the molar concentration of lithium hexafluorophosphate can be 0.7 mol / L-2 mol / L (e.g., 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2 mol / L); the molar concentration of lithium bis(trifluorosulfonyl)imide can be 0.2 mol / L-1 mol / L (e.g., 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L).

[0053] In the present disclosure, the molar concentration of lithium bis(fluorosulfonyl)imide may be 0.2 mol / L-1 mol / L (e.g., 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L).

[0054] In the present disclosure, the organic solvent may include organic solvents commonly used in the art, for example, at least one of ethylene carbonate, ethyl methyl carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate and γ-butyrolactone.

[0055] In the present disclosure, the second additive may include additives commonly used in the art, for example, at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, methylene methanedisulfonate, propylene sultone, maleic anhydride, diglycolic anhydride and succinic anhydride.

[0056] In the present disclosure, the lithium salt, the organic solvent and the second additive can be obtained by conventional testing methods in the art; for example, the lithium salt can be obtained by ion chromatography (IC) testing, the organic solvent can be obtained by gas chromatography (GC) testing, and the second additive can be obtained by GC testing.

[0057] The second aspect of the present disclosure provides a battery, which may include the electrolyte described in the first aspect of the present disclosure.

[0058] In the present disclosure, the battery may further include a negative electrode sheet, and the negative electrode sheet may include a silicon-based material.

[0059] During the charge and discharge process of the battery, the silicon negative electrode material will undergo a huge volume expansion, resulting in an aggravated side reaction with the electrolyte, seriously affecting the cycle life of the battery. The inventors of the present disclosure have found that using the electrolyte described in the first aspect of the present disclosure in combination with the silicon-based material can improve the volume expansion of the silicon-based material.

[0060] In the present disclosure, the silicon-based material may include at least one of silicon, silicon oxide (SiO x , 0 < x < 2), silicon carbide, and silicon alloy. The silicon carbide has its conventional meaning in the art, and generally, the silicon carbide is considered to be a composite material of silicon and carbon.

[0061] In the present disclosure, based on the total weight of the silicon-based material, the content of silicon element may be 30% - 80%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%.

[0062] The inventors of the present disclosure have found that there is a specific ratio between the content of silicon element in the silicon-based material and the sum of the contents of the substances shown in Formula I and Formula II in the electrolyte, which can further improve the volume expansion of the silicon-based material.

[0063] In the present disclosure, the ratio of the content of silicon element in the silicon-based material to the sum of the contents of the substances shown in Formula I and Formula II in the electrolyte may be (5 - 150):1, such as 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1, 95:1, 100:1, 110:1, 120:1, 130:1, 140:1, or 150:1.

[0064] In one example, the ratio of the content of silicon element in the silicon-based material to the sum of the contents of the substances shown in Formula I and Formula II in the electrolyte is (14 - 43):1.

[0065] In the present disclosure, the negative electrode sheet may further include a negative electrode current collector and a negative electrode coating on at least one surface of the negative electrode current collector. The negative electrode coating may include a negative electrode active material, and the negative electrode active material may include the silicon-based material.

[0066] In the present disclosure, the negative electrode active material may further include a carbon-based material. The carbon-based material includes at least one of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon and soft carbon. Based on the total weight of the negative electrode active material, the content of the carbon-based material may be 50%-97% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 97%), and the content of the silicon-based material may be 3%-50% (e.g., 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5% or 3%).

[0067] In the present disclosure, the negative electrode coating may further include a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent may include a conductive agent commonly used in the art, such as at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes. The negative electrode binder may be selected from a binder commonly used in the art, such as at least one of polyvinylidene fluoride (PVDF), styrene-butadiene rubber, sodium carboxymethyl cellulose, and polytetrafluoroethylene (PTFE).

[0068] In the present disclosure, based on the total weight of the negative electrode coating, the content of the negative electrode active material may be 80%-99% (for example, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%), the content of the negative electrode conductor may be 0.5%-10% (for example, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or 0.5%), and the content of the negative electrode binder may be 0.5-10% (for example, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or 0.5%).

[0069] Components of the battery other than the negative electrode sheet and the electrolyte (such as the positive electrode sheet and the separator, etc.) can be conventionally selected in the art.

[0070] In one example, the battery further includes a positive electrode sheet and a separator.

[0071] In the present disclosure, the positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer on at least one side of the positive electrode current collector, wherein the positive electrode active material layer may include a positive electrode active material. The positive electrode active material may be a conventional choice in the art, for example, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, and lithium-rich manganese oxide.

[0072] The positive electrode active material layer may further include a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent may be selected from those commonly used in the art, such as at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes. The positive electrode binder may be selected from those commonly used in the art, such as at least one of polyvinylidene fluoride (PVDF), styrene-butadiene rubber, sodium carboxymethyl cellulose (CMC-Na), and polytetrafluoroethylene (PTFE).

[0073] Based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be 70%-99% (for example, 70%, 75%, 80%, 85%, 90%, 95% or 99%), the content of the positive electrode conductor can be 0.5%-15% (for example, 15%, 10%, 5%, 1% or 0.5%), and the content of the positive electrode binder can be 0.5%-15% (for example, 15%, 10%, 5%, 1% or 0.5%).

[0074] In the present disclosure, the separator may be a separator commonly used in the art, such as at least one of a polyethylene film and a polypropylene film (PP).

[0075] In the present disclosure, the battery can be assembled in a conventional manner in the art.

[0076] It should be noted that the numerical expressions such as "first" and "second" in the present disclosure are only used to distinguish different substances or usage methods, and do not represent a difference in order.

[0077] The present disclosure will be described in detail below through examples. The examples described in this disclosure are only a portion of the examples of the present disclosure, not all of the examples. Based on the examples in this disclosure, all other examples obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this disclosure.

[0078] In the following examples, unless otherwise specified, all materials used were commercially available analytical grade.

[0079] Examples and Comparative Examples

[0080] Prepare the battery as follows:

[0081] (1) Preparation of electrolyte

[0082] In a glove box filled with inert gas (H2O<10ppm, O2<5ppm), ethylene carbonate, propylene carbonate and diethyl carbonate were mixed in a mass ratio of 1:2:4; to the above mixed solution was added a composition of lithium hexafluorophosphate and lithium bistrifluorosulfonyl imide at 14.5wt% based on the total weight of the electrolyte (wherein the ratio of the molar concentration of lithium hexafluorophosphate to the molar concentration of the lithium bistrifluorosulfonyl imide was 1:1), and after passing the moisture and free acid tests, a basic electrolyte was obtained; and different amounts of the substances in Table 1 were added to the above basic electrolyte to obtain an electrolyte.

[0083] (2) Preparation of positive electrode sheet

[0084] Lithium cobalt oxide (LCO), polyvinylidene fluoride (PVDF), conductive carbon black and single-walled carbon nanotubes are mixed in a weight ratio of 97.2:1.5:1.2:0.1, and N-methylpyrrolidone (NMP) is added with a solid content of 70wt%. A positive electrode slurry is obtained under the action of a vacuum mixer; the above positive electrode slurry is evenly coated on aluminum foil; and the above coated aluminum foil is dried, rolled, and cut to obtain a positive electrode sheet.

[0085] (3) Preparation of negative electrode sheet

[0086] The negative electrode active material (silicon carbon and artificial graphite mixed in a mass ratio of 1:9), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber and acetylene black are mixed in a weight ratio of 97:1:1:1, and deionized water is added, wherein the solid content is 50wt%, and the negative electrode slurry is obtained under the action of a vacuum mixer; the above negative electrode slurry is evenly coated on a high-strength carbon-coated copper foil, dried, rolled and cut to obtain a negative electrode sheet.

[0087] (4) Preparation of batteries

[0088] The positive electrode sheet obtained in step (2), the separator (9 μm thick PP film) and the negative electrode sheet obtained in step (3) are stacked in order, ensuring that the separator is between the positive and negative electrode sheets to play an isolating role, to obtain a bare battery cell, the above bare battery cell is placed in an aluminum-plastic film outer packaging, the electrolyte obtained in step (1) is injected into the dried battery, and the battery is packaged, allowed to stand, formed, shaped and capacity divided to obtain a battery.

[0089] Table 1

[0090] Note: In the batteries of Comparative Examples 1 to 3, the substance represented by Formula I and the substance represented by Formula II were not added to the electrolyte.

[0091] Test Case

[0092] (1) High temperature cycle performance test

[0093] The batteries prepared in the examples and comparative examples were subjected to high temperature cycle performance tests. The specific test methods are as follows:

[0094] At 45°C, charge the divided battery at 0.7C constant current and constant voltage to 4.48V, with a cut-off current of 0.05C, and then discharge it at 0.5C constant current to 3.0V. Repeat this cycle for 400 cycles. Calculate the capacity retention rate at the 400th week using the following formula:

[0095] The 400th cycle capacity retention rate (%) = (400th cycle discharge capacity / first cycle discharge capacity) × 100%. The results are recorded in Table 2.

[0096] (2) High temperature cyclic thickness expansion test

[0097] The batteries prepared in the examples and comparative examples were subjected to a high-temperature cyclic thickness expansion test. The specific test method is as follows:

[0098] At 45°C, charge the divided battery at a constant current and constant voltage of 0.7C to 4.48V, with a cut-off current of 0.05C, and then discharge it at a constant current of 0.5C to 3.0V. Repeat this cycle for 400 cycles. Calculate the thickness expansion rate at the 400th cycle using the following formula:

[0099] The thickness expansion rate at the 400th cycle (%) = (battery thickness after the 400th cycle / battery thickness after the first cycle - 1) × 100%. The results are recorded in Table 2.

[0100] (3) Thermal shock test

[0101] The batteries prepared in the examples and comparative examples were subjected to thermal shock tests. The specific test method is as follows:

[0102] At 25°C, charge the battery to 4.48V at a constant current of 0.5C. Continue charging the battery with a constant voltage (CV) charge to a current of 0.025C. Place the battery in a vertical position in a chamber and heat it to 120°C at a rate of 5±2°C, then continue heating at a rate of (2±1)°C until the battery ignites. The ignition temperature is considered the failure temperature of the battery in the thermal shock test. The results are recorded in Table 2.

[0103] (4) 60℃, 30d (days) high temperature storage test

[0104] The batteries prepared in the examples and comparative examples were subjected to a 30-day high-temperature storage test. The specific test method is as follows:

[0105] The battery was placed at room temperature (25°C) and charged and discharged once at 0.5C (4.48V-3.0V). The discharge capacity C0 of the battery before storage was recorded. The battery was then charged to a fully charged state of 4.48V using constant current and constant voltage. The thickness d1 of the battery before high-temperature storage was measured using a PPG battery thickness gauge (500g). The battery was placed in a 60°C constant temperature box and stored for 30 days. After storage, the battery was removed and the post-storage thermal thickness d2 was measured. The battery thickness expansion rate after storage at 60°C for 30 days was calculated using the following formula:

[0106] After storage at 60°C for 30 days, the thickness expansion ratio = (d2-d1) / d1×100%. The results are recorded in Table 2.

[0107] (5) Concentration test of 1,3-propane sultone in batteries

[0108] The specific test method is as follows: Based on the current system battery mass of 40g and the residual liquid volume of 4g, the concentration of 1,3-propane sultone in the battery is calculated as (a%×4)÷ / 40×1000000. The concentration of 1,3-propane sultone in the battery obtained by the test is the concentration before the chemical component sorting process. Taking into account the consumption of 1,3-propane sultone in the chemical component sorting process, the concentration of 1,3-propane sultone in the finished battery is generally slightly lower than the test value.

[0109] Table 2

[0110] As can be seen from Table 2, compared with the comparative example, the battery of the present disclosure has significantly improved high-temperature cycle capacity retention and thermal shock failure temperature, and significantly reduced 60°C storage thickness expansion rate, while ensuring a lower 1,3-propane sultone concentration.

[0111] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. An electrolyte, characterized in that, The electrolyte includes a first additive, and the first additive includes the substance shown in Formula I and / or the substance shown in Formula II: Among them, Y1, Y2, Y3, and Y4 are each independently selected from at least one of an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 1 to 10 carbon atoms, an alkynyl group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a fluoroalkenyl group having 1 to 10 carbon atoms, a fluoroalkynyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a nitrile group having 1 to 10 carbon atoms, and derivatives thereof; n and m are each independently 0 or 1, and M1 and M2 are each independently selected from at least one of, X1 and X2 are each independently selected from at least one of CH and O; R1 and R2 are each independently selected from H, halogen, an unsubstituted or halogen-substituted hydrocarbyl group having 1 to 5 carbon atoms, at least one of them.

2. The electrolyte according to claim 1, wherein, Y1, Y2, Y3, and Y4 are each independently selected from at least one of an alkenyl group having ≤5 carbon atoms and an alkynyl group having ≤5 carbon atoms; Preferably, Y1, Y2, Y3, and Y4 are each independently selected from at least one of an alkenyl group having ≤3 carbon atoms and an alkynyl group having ≤3 carbon atoms.

3. The electrolyte according to claim 1 or 2, wherein The substance represented by Formula I includes at least one of; Preferably, the substance represented by Formula I includes at least one of them; More preferably, the substance represented by Formula I includes combination.

4. The electrolyte according to any one of claims 1-3, wherein The substances represented by Formula II include at least one of; Preferably, the substance represented by Formula II includes at least one of them; More preferably, the substance represented by Formula II includes combination.

5. The electrolyte according to any one of claims 1-4, wherein, Based on the total weight of the electrolyte, the content of the substance represented by Formula I is 0.05% - 1.2%; preferably 0.3% - 0.7%; and / or, based on the total weight of the electrolyte, the content of the substance represented by Formula II is 0.1% - 6%; preferably 1% - 3%.

6. The electrolyte according to any one of claims 1-5, wherein, The first additive includes the substance represented by Formula I and the substance represented by Formula II; Preferably, the ratio of the content of the substance represented by Formula II in the electrolyte to the content of the substance represented by Formula I in the electrolyte is (0.1 - 50):1; More preferably, the ratio of the content of the substance represented by Formula II in the electrolyte to the content of the substance represented by Formula I in the electrolyte is (3 - 4.5):

1.

7. The electrolyte according to any one of claims 1-6, wherein, The electrolyte further includes 1,3 - propane sultone; Preferably, based on the total weight of the electrolyte, the content of 1,3 - propane sultone < 1%; More preferably, based on the total weight of the electrolyte, the content of 1,3 - propane sultone is 0.1% - 0.4%.

8. The electrolyte according to claim 7, wherein, Based on the total weight of the electrolyte, the content of 1,3 - propane sultone is a%, the content of the substance represented by Formula I is b%, and the content of the substance represented by Formula II is c%, satisfying: 0.8 + 1.5×a ≤ 1.8×b + 0.5×c ≤ 2 + 4×a.

9. The electrolyte according to any one of claims 1-8, wherein, The electrolyte further includes at least one of a lithium salt, an organic solvent, and a second additive; Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium oxalato phosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

10. The electrolyte according to claim 9, wherein, The lithium salt includes a combination of lithium hexafluorophosphate and lithium bis(trifluoromethanesulfonyl)imide; the ratio of the molar concentration of lithium hexafluorophosphate to the molar concentration of lithium bis(trifluoromethanesulfonyl)imide is (0.7 - 10):1; and / or, the molar concentration of lithium hexafluorophosphate is 0.7 mol / L - 0.2 mol / L, and the molar concentration of lithium bis(trifluoromethanesulfonyl)imide is 0.2 mol / L - 1 mol / L.

11. A battery, characterized in that, The battery includes the electrolyte according to any one of claims 1 - 10.

12. The battery according to claim 11, wherein, The battery further includes a negative electrode sheet, and the negative electrode sheet includes a silicon-based material; Preferably, the silicon-based material includes at least one of silicon, silicon oxide, silicon carbide, and silicon alloy; Preferably, based on the total weight of the silicon-based material, the content of silicon element is 30%-80%; Preferably, the ratio of the content of silicon element in the silicon-based material to the sum of the contents of the substances represented by Formula I and the substances represented by Formula II in the electrolyte is (5-150):1; preferably (14-43):

1.

13. The battery according to claim 12, wherein, The negative electrode sheet further includes a negative electrode current collector and a negative electrode coating on at least one side surface of the negative electrode current collector, and the negative electrode coating includes a negative electrode active material; based on the total weight of the negative electrode coating, the content of the negative electrode active material is 88%-99%.

14. The battery according to claim 13, wherein, The negative electrode active material includes the silicon-based material, and based on the total weight of the negative electrode active material, the content of the silicon-based material is 3%-50%.

15. The battery according to claim 13 or 14, wherein, The negative electrode active material further includes a carbon-based material, and the carbon-based material includes at least one of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, and soft carbon; based on the total weight of the negative electrode active material, the content of the carbon-based material is 50%-97%.

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