A battery

Abstract

The application provides a battery, which comprises a positive electrode sheet, a negative electrode sheet, a separator and a non-aqueous electrolyte; the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive; wherein the non-aqueous organic solvent comprises methyl ethyl carbonate (EMC) and / or ethyl propionate (EP); the additive comprises LiPO2F2; the battery of the application has a small direct current internal resistance in a high SOC state, and the constant current charging time of the battery during the charging process can be greatly prolonged, so that the effect of fast charging is achieved. Furthermore, the consumption of the electrolyte salt in the electrolyte can be significantly reduced by introducing LiPO2F2, so that the fast charging performance of the battery does not decrease during the whole service life.

Description

Technical Field

[0001] This invention relates to a battery and belongs to the field of battery technology. Background Technology

[0002] Lithium-ion batteries, with their advantages of high operating voltage, high energy density, long cycle life, low self-discharge rate, no memory effect, and low environmental pollution, have been widely used in various consumer electronics markets and are the ideal power source for future electric vehicles and various power tools. However, lithium-ion batteries typically have a long charging time, often exceeding one hour, which severely limits the consumer experience. This is especially true in the electric vehicle sector; compared to traditional gasoline vehicles, which refuel in under 10 minutes, electric vehicles require over an hour to fully charge, significantly hindering their use and promotion. Summary of the Invention

[0003] In order to shorten the charging time of batteries and broaden their application fields, the present invention provides a battery with fast charging performance, which can be fully charged to 80% SOC in less than or equal to 20 minutes at a rate of 3C or higher.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte; the non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt, and additives.

[0006] The non-aqueous organic solvent includes ethyl methyl carbonate (EMC) and / or ethyl propionate (EP); the additive includes LiPO2F2.

[0007] The content of ethyl methyl carbonate (EMC) and / or ethyl propionate (EP) is A wt% of the total mass of the non-aqueous organic solvent; the content of LiPO2F2 is B wt% of the total mass of the non-aqueous electrolyte.

[0008] The thickness of the negative electrode sheet is C, and the unit is μm;

[0009] A, B, and C satisfy the following relationship: A + 100 × BC ≥ 0;

[0010] The discharge DC internal resistance of the battery at 25°C and 50% SOC is D; the discharge DC internal resistance of the battery at 25°C and 80% SOC is E, and D and E satisfy the following relationship: E / D≤2.

[0011] Typically, batteries are charged using a constant current / constant voltage charging method. However, due to the high DC internal resistance of the battery at high SOC (State of Charge), the battery exhibits significant polarization during charging, especially at high charging rates (e.g., 2C or higher). This causes the battery to quickly reach the charging cutoff voltage, rapidly transitioning from the constant current charging stage to the constant voltage charging stage, which significantly prolongs the charging time. In contrast, the battery provided by this invention has low DC internal resistance during discharge, particularly at high SOC (e.g., 80% SOC), which significantly improves the battery's charging performance.

[0012] According to the present invention, the content of ethyl methyl carbonate (EMC) and / or ethyl propionate (EP) as a mass percentage of the total mass of the non-aqueous organic solvent is A wt%, wherein A wt% ≥ 20 wt%, that is, the content of ethyl methyl carbonate (EMC) and / or ethyl propionate (EP) as a mass percentage of the total mass of the non-aqueous organic solvent is A wt% ≥ 20 wt%. For example, 80 wt% ≥ A wt% ≥ 20 wt%, for example, A wt% is 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, or 80 wt%.

[0013] According to the present invention, the non-aqueous organic solvent further includes one or more of the following solvents: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate, propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), methyl butyrate, and ethyl butyrate.

[0014] According to the present invention, the electrolyte salt is selected from at least one of lithium salt, sodium salt, magnesium salt, etc.

[0015] According to the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0016] According to the present invention, the content of electrolyte salt in the non-aqueous electrolyte is 1 mol / L to 2 mol / L.

[0017] According to the present invention, the conductivity of the non-aqueous electrolyte is ≥7 mS / cm @ 25℃.

[0018] According to the present invention, the content of LiPO2F2 accounts for a mass percentage of Bwt% of the total mass of the non-aqueous electrolyte, wherein Bwt% ≤ 1wt%; that is, the content of LiPO2F2 accounts for a mass percentage of Bwt% ≤ 1wt% of the total mass of the non-aqueous electrolyte. For example, 0.05wt% ≤ Bwt% ≤ 1wt%, and Bwt% is, for example, 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or 1wt%.

[0019] In this invention, the addition of LiPO2F2 to the non-aqueous electrolyte will cause a decrease in the conductivity of the non-aqueous electrolyte. For example, the decrease in conductivity of the non-aqueous electrolyte caused by the addition of LiPO2F2 is ≤1 mS / cm, that is, the change in conductivity of the non-aqueous electrolyte before and after the addition of LiPO2F2 is ≤1 mS / cm.

[0020] Studies have found that the following reactions occur in non-aqueous electrolytes (taking LiPF6 as an example).

[0021] LiPF6 + 2H2O → LiPO2F2 + 4HF

[0022] The presence of a certain amount of LiPO2F2 in the non-aqueous electrolyte inhibits the reaction from proceeding to the right, reducing the consumption of lithium salts in the non-aqueous electrolyte after battery use. This significantly reduces the performance degradation of the battery after long-term cycling. In other words, this invention controls the amount of LiPO2F2 added to the non-aqueous electrolyte to both form a low-resistance SEI film on the negative electrode surface and suppress the consumption of lithium salts in the non-aqueous electrolyte during long-term cycling, thus ensuring fast-charging performance throughout the battery's lifespan. However, when too much LiPO2F2 is added to the non-aqueous electrolyte, the conductivity of the non-aqueous electrolyte decreases significantly (decreased by >1 mS / cm), leading to a significant deterioration in the battery's fast-charging performance.

[0023] According to the present invention, the discharge DC internal resistance D of the battery at 25°C and 50% SOC is ≤65mΩ; the discharge DC internal resistance E of the battery at 25°C and 80% SOC is ≤100mΩ, and D and E satisfy the following relationship: E / D≤2.

[0024] According to the present invention, D and E satisfy the following relationship: 0.5≤E / D≤2; for example, D and E satisfy the following relationship: 1≤E / D≤1.8, or D and E satisfy: 1.2≤E / D≤1.6.

[0025] According to the present invention, the non-aqueous electrolyte may further include one or more of the following additives: vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfite, methane disulfonate, vinyl sulfate, succinic acid nitrile, glutaronitrile, adiponitrile, heptonitrile, octanoic acid nitrile, sebaconitrile, 1,3,6-hexanetrionitrile, 1,2-bis(2-cyanoethoxy)ethane, 3-methoxypropionitrile, 1,3-propanesulfonic acid lactone, and propenyl-1,3-sulfonic acid lactone.

[0026] According to the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer coated on one or both surfaces of the positive current collector, wherein the positive active material layer includes a positive active material, a conductive agent and a binder.

[0027] According to the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, a conductive agent and a binder.

[0028] According to the present invention, the mass percentage of each component in the positive electrode active material layer is: 80-99.8 wt% positive electrode active material, 0.1-10 wt% conductive agent, and 0.1-10 wt% binder.

[0029] Preferably, the mass percentage of each component in the positive electrode active material layer is: 90-99.6 wt% positive electrode active material, 0.2-5 wt% conductive agent, and 0.2-5 wt% binder.

[0030] According to the present invention, the mass percentage of each component in the negative electrode active material layer is: 80-99.8 wt% negative electrode active material, 0.1-10 wt% conductive agent, and 0.1-10 wt% binder.

[0031] Preferably, the mass percentage of each component in the negative electrode active material layer is: 90-99.6 wt% negative electrode active material, 0.2-5 wt% conductive agent, and 0.2-5 wt% binder.

[0032] According to the present invention, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0033] According to the present invention, the adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0034] According to the present invention, the negative electrode active material is selected from at least one of natural graphite, artificial graphite, hard carbon, soft carbon, mesophase microspheres, silicon-oxygen composite materials, and silicon-carbon negative electrode materials.

[0035] According to the present invention, the positive electrode active material is selected from one or more of layered lithium transition metal composite oxides, lithium manganese oxide, and lithium cobalt oxide mixed ternary materials; the chemical formula of the layered lithium transition metal composite oxide is Li. 1+ x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0036] According to the present invention, the thickness C of the negative electrode sheet is preferably ≤150μm, for example ≤120μm, such as ≤100μm. Exemplarily, the thickness C of the negative electrode sheet is 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm.

[0037] According to the present invention, the thicknesses of the negative electrode and the positive electrode have the following relationship: the thickness of the positive electrode / the thickness of the negative electrode is (0.93-1.48):1.

[0038] According to the present invention, the battery is a lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery.

[0039] The inventors of this application, through dedicated research, discovered that the fast-charging performance of a battery is related to the migration rate of ions (such as lithium ions) in the non-aqueous electrolyte, the diffusion rate of ions (such as lithium ions) in the SEI film, and the thickness of the negative electrode. Based on this, the inventors unexpectedly discovered that by adjusting the mass percentage (A wt%) of the content of ethyl methyl carbonate (EMC) and / or ethyl propionate (EP) relative to the total mass of the non-aqueous organic solvent; the mass percentage (B wt%) of the content of LiPO2F2 relative to the total mass of the non-aqueous electrolyte; and the thickness (C) of the negative electrode, the following relationship is satisfied: A + 100 × BC ≥ 0. Furthermore, the battery's discharge DC internal resistance at 25°C and 50% SOC is D; and the battery's discharge DC internal resistance at 25°C and 80% SOC is E. When D and E satisfy the following relationship: E / D ≤ 2, the obtained battery has fast-charging capability, achieving a charging time of less than or equal to 20 minutes to 80% SOC at a rate of 3C or higher.

[0040] The beneficial effects of this invention are:

[0041] This invention provides a battery that exhibits low DC internal resistance at high SOC, significantly extending the constant current charging time and achieving fast charging. Furthermore, the introduction of LiPO2F2 significantly reduces lithium salt consumption in the non-aqueous electrolyte, ensuring that the fast charging performance does not degrade throughout the battery's lifespan. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] It is understood that the battery of the present invention includes a negative electrode, an electrolyte, a positive electrode, a separator, and an outer packaging. The battery cell is obtained by stacking the positive electrode, separator, and negative electrode, or by stacking the positive electrode, separator, and negative electrode and then winding them. The battery cell is then placed in the outer packaging, and electrolyte is injected into the outer packaging to obtain the battery of the present invention.

[0046] Examples 1-12 and Comparative Examples 1-6

[0047] The batteries of Examples 1-12 and Comparative Examples 1-6 were prepared by the following steps:

[0048] 1) Preparation of positive electrode sheet

[0049] Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), super P (SP), and carbon nanotubes (CNT) were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until it formed a uniform and fluid positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil. The coated aluminum foil was dried, and then rolled and slit to obtain the desired positive electrode sheet.

[0050] 2) Preparation of negative electrode sheet

[0051] The negative electrode active materials graphite, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP), and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 96:1.5:1.5:0.9:0.1, and deionized water was added. The mixture was stirred in a vacuum mixer to obtain a negative electrode active slurry. The negative electrode active slurry was uniformly coated on both surfaces of a copper foil. The coated copper foil was dried at room temperature and then transferred to an 80°C oven for drying for 10 hours. After cold pressing and slitting, the negative electrode sheet was obtained.

[0052] 3) Preparation of electrolyte

[0053] In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), a non-aqueous organic solvent is mixed uniformly at a certain mass ratio. Then, 1 mol / L of fully dried lithium hexafluorophosphate (LiPF6) is quickly added and dissolved in the non-aqueous organic solvent. After that, 5 wt% of fluoroethylene carbonate, 3 wt% of 1,3-propanesulfonyl lactone, 1 wt% of 1,3,6-hexanetrionitrile, and LiPO2F2 (specific amounts are shown in Table 1) based on the total mass of the electrolyte are added. The mixture is stirred evenly, and after passing the tests for moisture and free acid, the desired electrolyte is obtained.

[0054] 4) Battery manufacturing

[0055] The positive electrode sheet from step 1), the negative electrode sheet from step 2), and the separator are stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to obtain a battery cell. The battery cell is placed in an outer packaging aluminum foil, and the electrolyte from step 3) is injected into the outer packaging. After vacuum sealing, settling, formation, shaping, and sorting, a battery is obtained. The battery of this invention has a charge / discharge range of 3.0-4.4V.

[0056] The batteries obtained in the examples and comparative examples were subjected to the following tests, and the test results are shown in Tables 2, 4 and 6.

[0057] 1) Cyclic performance test

[0058] The battery was charged and discharged for 100 cycles at 25°C within the charge and discharge cutoff voltage range at a rate of 2C. The discharge capacity of the first cycle and the discharge capacity of the 100th cycle were tested. The discharge capacity of the 100th cycle was divided by the discharge capacity of the first cycle to obtain the cycle capacity retention rate.

[0059] 2) Charging time test

[0060] (1) Under 25℃ conditions, charging: constant current charging at 0.5C to the cutoff voltage, then constant voltage charging, with a charging cutoff current of 0.1C; rest for 2 hours; discharging: discharging at 0.5C to the cutoff voltage. Repeat 3 times, and record the highest discharge capacity as Q0;

[0061] (2) At 25℃, constant current and constant voltage charging was used with a 3C rate, and the charging cutoff current was 0.02C. The capacity Q1 was recorded when the charging time was 20 minutes.

[0062] (3) Calculate the ratio of Q1 / Q0×100% and observe whether it is ≥80%.

[0063] 3) Discharge DC internal resistance (D) test under 25℃ and 50% SOC conditions

[0064] (1) a. Under 25℃ conditions, charge to the cutoff voltage using a constant current of 0.2C, then charge at a constant voltage. The charging cutoff current is 0.05C. Let stand for 10 minutes. Discharge to the cutoff voltage using a constant current of 0.2C. Let stand for 10 minutes. Record the initial discharge capacity C0. b. Under 25℃ conditions, charge to the cutoff voltage using a constant current of 0.2C, then charge at a constant voltage. The charging cutoff current is 0.05C. Let stand for 10 minutes. c. Under 25℃ conditions, discharge using a constant current of 0.2C. The discharge capacity is 50% C0.

[0065] (2) In the process of using the 0.2C discharge for 10s, the discharge end voltage is recorded as U1. Switch the current to 1C and discharge for 1s, the discharge end voltage is recorded as U2. Calculate DCIR from this. The DCIR calculation method is as follows: DCIR=(U1-U2) / (1-0.2)C.

[0066] 4) Discharge DC internal resistance (E) test under 25℃ and 80% SOC conditions

[0067] (1) a. Under 25℃ conditions, charge to the cutoff voltage using a constant current of 0.2C, then charge at a constant voltage with a charging cutoff current of 0.05C, let stand for 10 minutes, discharge to the cutoff voltage using a constant current of 0.2C, let stand for 10 minutes, and record the initial discharge capacity C0; b. Under 25℃ conditions, charge to the cutoff voltage using a constant current of 0.2C, then charge at a constant voltage with a charging cutoff current of 0.05C, and let stand for 10 minutes; c. Under 25℃ conditions, discharge using a constant current of 0.2C, and the discharge capacity is 20%C0.

[0068] (2) In the process of using the 0.2C discharge for 10s, the discharge end voltage is recorded as U1. Switch the current to 1C and discharge for 30s with 1C, the discharge end voltage is recorded as U2. Calculate DCIR from this. The DCIR calculation method is as follows: DCIR=(U1-U2) / (1-0.2)C.

[0069] Table 1. Composition and performance test results of the batteries in the examples and comparative examples.

[0070]

[0071] Table 2 shows the performance test results of the batteries in the examples and comparative examples.

[0072]

[0073]

[0074] As shown in Table 2, when A+100×BC≥0 and E / D≤2, the charging performance of the obtained battery is significantly improved, with a charging capacity ≥80% after 20 minutes of 3C charging and a capacity retention rate >90% after 100 cycles at room temperature. When A+100×BC<0 or E / D>2, the charging performance of the obtained battery is significantly reduced, failing to meet the requirement of a charging capacity ≥80% after 20 minutes of 3C charging, and the capacity retention rate after 100 cycles at room temperature is also low.

[0075] Table 3. Composition and performance test results of the batteries in the examples and comparative examples.

[0076]

[0077] Table 4. Performance test results of the batteries in the examples and comparative examples.

[0078]

[0079] As shown in Table 4, not adding LiPO2F2 affects the battery's charging performance after cycling. Adding too much will also significantly reduce the electrolyte's conductivity, affecting the battery's charging performance. Furthermore, when the electrolyte conductivity is <7 mS / cm, the battery's charging performance will also decrease substantially.

[0080] Table 5. Composition and performance test results of the batteries in the examples and comparative examples.

[0081]

[0082] Table 6 shows the performance test results of the batteries in the examples and comparative examples.

[0083] Example 8 yes 91.36％ Example 9 yes 92.37％ Example 10 yes 85.71％ Example 11 yes 85.18％ Example 12 yes 81.79％

[0084] As shown in Table 6, the battery performance gradually decreases as the thickness of the negative electrode increases. However, a battery with fast charging performance can still be obtained when the thickness of the negative electrode is controlled within 150 μm.

[0085] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte; wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt, and additives; Its features are, The non-aqueous organic solvent includes ethyl methyl carbonate (EMC) and / or ethyl propionate (EP); the additive includes LiPO2F2; The content of ethyl methyl carbonate (EMC) and / or ethyl propionate (EP) is Awt% of the total mass of the non-aqueous organic solvent; the content of LiPO2F2 is Bwt% of the total mass of the non-aqueous electrolyte. The thickness of the negative electrode sheet is C, and the unit is μm; A, B, and C satisfy the following relationship: A + 100 × BC ≥ 0; The discharge DC internal resistance of the battery at 25°C and 50% SOC is D; the discharge DC internal resistance of the battery at 25°C and 80% SOC is E, and D and E satisfy the following relationship: 0.5≤E / D≤2. The value of D is ≤65mΩ; the value of E is ≤100mΩ; 0.05 wt%≤B wt%≤1 wt%; 80 wt% ≥ A wt% ≥ 20 wt%; The thickness C of the negative electrode sheet is ≤150μm.

2. The battery according to claim 1, characterized in that, The non-aqueous organic solvent also includes one or more of the following solvents: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate, propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), methyl butyrate, and ethyl butyrate.

3. The battery according to claim 1 or 2, characterized in that, The electrolyte salt is selected from lithium salts; And / or, the lithium salt is selected from at least one of lithium hexafluorophosphate and lithium difluorosulfonylimide; And / or, the content of electrolyte salts in the non-aqueous electrolyte is 1~2 mol / L.

4. The battery according to claim 1 or 2, characterized in that, The addition of LiPO2F2 to the electrolyte causes a decrease in the electrolyte conductivity of ≤1mS / cm, that is, the change in electrolyte conductivity before and after the addition of LiPO2F2 is ≤1mS / cm. And / or, the conductivity of the non-aqueous electrolyte is ≥7 mS / cm @ 25℃.

5. The battery according to claim 1 or 2, characterized in that, The D and E satisfy the following relationship: 1≤E / D≤1.

8.

6. The battery according to claim 1 or 2, characterized in that, The D and E satisfy the following relationship: 1.2≤E / D≤1.

6.

7. The battery according to claim 1 or 2, characterized in that, The non-aqueous electrolyte also includes one or more of the following additives: vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfite, methane disulfonate, vinyl sulfate, succinic acid nitrile, glutaronitrile, adiponitrile, heptonitrile, octanoic acid nitrile, sebaconitrile, 1,3,6-hexanetrionitrile, 1,2-bis(2-cyanoethoxy)ethane, 3-methoxypropionitrile, 1,3-propanesulfonic acid lactone, and propenyl-1,3-sulfonic acid lactone.

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