battery

Abstract

The application relates to the field of batteries, in particular to a battery. The battery comprises a pole piece and an electrolyte; the pole piece comprises a current collector and a tab arranged on the current collector, the distance from the head edge of the current collector to the side of the tab close to the head edge of the current collector is D, the distance from the tail edge of the current collector to the side of the tab close to the tail edge of the current collector is L, and 0.097<=D / (D+L)<=0.894; the electrolyte comprises lithium hexafluorophosphate, and the content of the lithium hexafluorophosphate is x% by weight based on the total weight of the electrolyte, and [(D+L) / D]x%*100>=9.8. The battery can improve the fast charging performance under the premise of ensuring the safety performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a battery. BACKGROUND

[0002] Lithium ion battery as an excellent energy storage device is widely used in portable electronic devices, electric vehicles and energy storage and other fields. In recent years, the rapid development of electric vehicles has brought great convenience to people's travel, but due to the long charging time of lithium ion batteries, it seriously affects the use experience of consumers, so the field has been committed to improving the charging speed of lithium ion batteries, but improving the charging speed of lithium ion batteries is easy to cause internal thermal runaway of the battery, and even cause explosion, which has safety hazards.

[0003] Therefore, it is very important to find a battery that can improve the charging speed and has safety performance. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned problems existing in the prior art, and to provide a battery. The battery of the present application produces a synergistic effect by adjusting the position of the tab on the pole piece and adjusting the composition of the electrolyte, reduces the polarization of the pole piece, increases the charging capacity of the battery, and ensures the safety performance of the battery.

[0005] The inventors of the present application found that by adjusting the position of the tab and adjusting the composition of the electrolyte, a synergistic effect can be unexpectedly produced, so that the battery can maintain safety performance while improving the charging speed, which may be due to the following reasons: by adjusting the position of the tab on the pole piece, the distribution of current density on the pole piece is changed, and by adjusting the composition of the electrolyte, the content of lithium salt in the electrolyte is changed, the current density at each place on the pole piece and the content of lithium salt in the electrolyte have a certain synergistic effect, which increases the fast charging capacity of the battery and improves the safety performance of the battery.

[0006] The present application provides a battery, which comprises a pole piece and an electrolyte; the pole piece comprises a current collector and a tab provided on the current collector, the distance from the head edge of the current collector to the side of the tab close to the head edge of the current collector is D, the distance from the tail edge of the current collector to the side of the tab close to the tail edge of the current collector is L, then 0.097≤D / (D+L)≤0.894; the electrolyte comprises lithium hexafluorophosphate, the content of lithium hexafluorophosphate is x% by weight based on the total weight of the electrolyte, and [(D+L) / D]x%*100≥9.8 is satisfied.

[0007] By the above technical solution, the battery of the present application has at least the following advantages compared with the prior art: by adjusting the position of the tab on the pole piece and adjusting the composition of the electrolyte, the fast charging capacity of the battery is increased and the safety performance of the battery is improved.

[0008] The endpoints of the ranges and any values described herein are not limited to the precise values recited as should be understood, the ranges or values are understood to include values approximately around the recited value. For ranges, the endpoints are included within the range, between the endpoints, and between the endpoints and the individual points within the range, as well as the individual points themselves. New ranges can be created by combining the endpoints of the ranges or individual points with the endpoints of other ranges or individual points. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 A schematic view of tab position of an example of the present application is shown.

[0010] BRIEF DESCRIPTION OF DRAWINGS

[0011] 1 - current collector;

[0012] 2 - tab. DETAILED DESCRIPTION

[0013] The specific embodiments of the present application will now be described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and explanatory and are not intended to limit the present application.

[0014] The present application provides a battery, the battery comprising a tab and an electrolyte; the tab comprising a current collector and a tab disposed on the current collector, the distance from the head edge of the current collector to the side of the tab close to the head edge of the current collector is D, the distance from the tail edge of the current collector to the side of the tab close to the tail edge of the current collector is L, then 0.097≤D / (D+L)≤0.894 (for example, D / (D+L) is equal to 0.097, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85 or 0.894); the electrolyte can comprise lithium hexafluorophosphate, the content of the lithium hexafluorophosphate is x% by weight based on the total weight of the electrolyte, satisfying [(D+L) / D]x% x 100≥9.8.

[0015] The tab position of the tab of the battery described in the present application will be described below with reference to the accompanying drawings, such as Figure 1 A schematic view of tab position of an example of the present application is shown, the tab comprising a current collector 1 and a tab 2 disposed on the current collector 1, the distance from the head edge of the current collector 1 to the side of the tab 2 close to the head edge of the current collector 1 is D, the distance from the tail edge of the current collector 1 to the side of the tab 2 close to the tail edge of the current collector 1 is L.

[0016] In the present application, the term "head" refers to winding the pole piece starting from the end of the "head", which is the end winding inside the battery; the term "tail" refers to the end winding outside the battery.

[0017] In an example, 0.195≤D / (D+L)≤0.793.

[0018] Alternatively, xwt%=8-20wt%. That is, the content of lithium hexafluorophosphate is 8-20wt%, for example, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%, based on the total weight of the electrolyte.

[0019] The inventors of the present application found through a large number of experimental studies that lithium hexafluorophosphate has a specific content that allows better synergy between the electrolyte and the pole piece, further improving the fast charging performance of the battery.

[0020] Preferably, xwt%=11.3-18.7wt%. That is, the content of lithium hexafluorophosphate is 11.3-18.7wt%, based on the total weight of the electrolyte.

[0021] The inventors of the present application found that when the electrolyte contains lithium bisfluorosulfonylimide and the lithium bisfluorosulfonylimide and lithium hexafluorophosphate have a specific ratio, the prepared battery has more excellent fast charging performance.

[0022] The electrolyte can also include lithium bisfluorosulfonylimide, and the content of lithium bisfluorosulfonylimide is ywt%, based on the total weight of the electrolyte, and 0.001≤y / x≤10, for example, y / x is equal to 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0023] In an example, 0.005≤y / x≤0.5.

[0024] The electrolyte can further comprise a component T, which can be present in an amount of 0.05 to 10 wt.%, for example 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, or 10 wt.%, based on the total weight of the electrolyte.

[0025] In one example, the component T is present in an amount of 0.09 to 7.8 wt.%, based on the total weight of the electrolyte.

[0026] In one example, the component T is present in an amount of 0.2 to 5 wt.%, based on the total weight of the electrolyte.

[0027] The component T is a compound having the following general formula (I),

[0028]

[0029] wherein R1and R2may each independently be selected from the group consisting of F- substituted or unsubstituted C1-C18alkane, F-substituted or unsubstituted C1-C18alkene, F-substituted or unsubstituted C1-C18alkyne, F-substituted or unsubstituted C1-C18silane, and derivatives thereof.

[0030] Optionally, R1and R2are each independently selected from the group consisting of F- substituted or unsubstituted C1-C8alkane, F-substituted or unsubstituted C1-C8alkene, F-substituted or unsubstituted C1-C8alkyne, or F-substituted or unsubstituted C1-C8silane.

[0031] In one example, R1and R2are each independently selected from the group consisting of F-substituted C1-C4alkane, F-substituted C1-C4alkene, F-substituted C1-C4alkyne, or unsubstituted C1-C4silane.

[0032] In one example, the component T is selected from the group consisting of

[0033] at least one of the group consisting of

[0034] The component T is a combination of T1and T2, wherein the mass ratio of T1to T2may be 1 : (0.5 to 2), for example 2: 1, 1: 1, 2:3, or 1:2.

[0035] In one example, the component T is a combination of T1and T2, wherein the mass ratio of T1to T2is 2:3.

[0036] The electrolyte can further comprise lithium difluorophosphate.

[0037] The content of the lithium difluorophosphate can be less than the content of the component T.

[0038] The inventors of the present application found that the component T and the lithium difluorophosphate have a synergistic effect at a specific composition, further improving the fast charging performance of the battery.

[0039] In an example, the content of the lithium difluorophosphate is less than the content of the component T.

[0040] The inventors of the present application found that when the content of the lithium difluorophosphate is greater than the content of the component T, the fast charging performance of the battery becomes poor, which can be due to the fact that when the content of the lithium difluorophosphate is greater than the content of the component T, the component T forms a film, affecting the exertion of its effect.

[0041] The electrolyte can also contain other components or additives commonly used in electrolytes in the art, such as solvents and functional additives, which also belong to the protection scope of the present application.

[0042] The content of the solvent is 60-90% by weight based on the total weight of the electrolyte.

[0043] The content of the functional additive is 0-30% by weight based on the total weight of the electrolyte.

[0044] Optionally, the solvent is selected from at least one of carbonates, carboxylates, ethers, and fluorides thereof.

[0045] The carbonates can include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate.

[0046] The carboxylates can include γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, n-butyl propionate, methyl butyrate, or ethyl n-butyrate.

[0047] The ethers can include 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, ethyl propyl ether, or ethylene glycol dimethyl ether.

[0048] The fluorides thereof can be one fluorine substitution or multiple fluorine substitutions.

[0049] Optionally, the functional additive is selected from at least one of 1,3-propane sultone, 1,3-propene sultone, butanedinitrile, hexanedinitrile, glycerol trinitrile, 1,3,6-hexanetricarboxylic acid, lithium difluoro(oxalato)borate, lithium difluorodioxalatephosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium bistrifluoromethylsulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium 4,5-dicyano-2-trifluoromethyl-imidazole, lithium triflate, and lithium perfluorobutylsulfonate.

[0050] In the present application, the electrolyte is prepared by including the following steps:

[0051] The solvent, lithium hexafluorophosphate, lithium bisfluorosulfonylimide, component T, lithium difluorophosphate, and the functional additive are mixed.

[0052] The mixing temperature can be 10-15°C.

[0053] The mixing method can be stirring and / or ultrasonic mixing.

[0054] In the present application, the tab and the current collector can be the tab and the current collector commonly used in the art.

[0055] For example, the negative electrode tab contains nickel element.

[0056] For another example, the positive electrode tab contains aluminum element.

[0057] The current collector can be a substance having conductivity and not causing adverse chemical changes during charging and discharging, for example, at least one selected from copper, stainless steel, aluminum, nickel, titanium, carbon cloth, or a composite thereof.

[0058] The electrode sheet further includes an active material layer disposed on the outer surface of the current collector. The active material layer can include a positive electrode active material or a negative electrode active material.

[0059] Optionally, the positive electrode active material is selected from at least one of lithium transition metal composite oxides.

[0060] The lithium transition metal composite oxides can include LiMO2(M is Ni, Co, or Mn), LiMn2O4, LiMPO4(M is Fe, Mn, or Co), LiNi x Mn 1-x O2(M is Co or Mn), LiNi x Co y M 1-x-y O2(x≥0, y≤1, x+y≤1, M is at least one of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, Zr, Ta, W, B, F, and Si).

[0061] Optionally, the negative active material is selected from at least one of lithium metal, a carbon-based material, a silicon-based material, and lithium titanate.

[0062] The carbon-based material can include artificial graphite, natural graphite, hard carbon, soft carbon, or mesophase microspheres.

[0063] The silicon-based material can include silicon and oxides of silicon, such as SiO x (0 < x < 2).

[0064] The battery further includes a separator, which can be a separator commonly used in the art.

[0065] Optionally, the separator is selected from at least one of a porous polymer film, a polymer coating coated on a surface of the porous polymer film, or an oxide coating coated on a surface of the porous polymer film.

[0066] The porous polymer film can include at least one of a polyolefin-based polymer film (e.g., including polyethylene, polypropylene, ethylene-butene copolymer, ethylene-methacrylate copolymer), a glass fiber film, a polytetrafluoroethylene film, a cellulose film, a polyimide film, a polyamide film, aramid, and spandex.

[0067] The polymer coating can include at least one of polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluorochloroethylene copolymer, and polyoxyethylene.

[0068] The oxide coating can include at least one of Al2O3 and MO2 (M is Si, Ti, Zn, Mg, Ca, Zr, Mn, or W).

[0069] The battery of the present application can improve fast charging performance while ensuring safety performance.

[0070] The present application will be described in detail below through examples. The examples described in the present application are only a part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0071] In the following examples, the materials used are commercially available analytical pure unless otherwise specified.

[0072] In the following examples, the negative electrode sheet is taken as an example to illustrate the electrode sheet described in the present application, and the positive electrode sheet is also applicable.

[0073] Example 1

[0074] (1) Preparation of electrolyte:

[0075] In an argon-filled glove box (H2O < 1 ppm, O2 < 1 ppm), 68.05 wt% of organic solvent (mass ratio of ethylene carbonate, propylene carbonate and propyl propionate is 2:2:6), 15 wt% of lithium hexafluorophosphate, 9 wt% of functional additive (mass ratio of 1,3-propane sultone, 1,3,6-hexanetricarbonitrile and fluoroethylene carbonate is 2:2:5), 3.75 wt% of lithium bisfluorosulfonylimide, 3.5 wt% of component T (mass ratio of T1 and T2 is 2:3) and 0.7 wt% of lithium difluorophosphate were mixed and stirred uniformly at 15°C.

[0076] (2) Preparation of the negative electrode:

[0077] The artificial graphite, sodium carboxymethyl cellulose, styrene butadiene rubber and acetylene black were mixed in a mass ratio of 95:1.5:2:1.5, deionized water was added and stirred uniformly to obtain a negative electrode slurry, the negative electrode slurry was uniformly coated on a copper foil, dried in an oven at 80°C for 10 h, rolled, cut to obtain a negative electrode sheet, and a nickel tab was welded. The total length of the negative electrode sheet was 1000 mm, the tab width was 5 mm, D = 487 mm and L = 508 mm.

[0078] (3) Preparation of the positive electrode:

[0079] The lithium cobaltate, polyvinylidene fluoride and acetylene black were mixed in a mass ratio of 97:1.5:1.5, N-methylpyrrolidone was added and stirred uniformly to obtain a positive electrode slurry, the positive electrode slurry was uniformly coated on an aluminum foil, dried in an oven at 120°C for 8 h, rolled, cut to obtain a positive electrode sheet, and an aluminum tab was welded.

[0080] (4) The separator was a polypropylene separator.

[0081] (5) Preparation of the battery:

[0082] The positive electrode sheet, the separator and the negative electrode sheet prepared above were wound to obtain a bare cell, the bare cell was placed in an outer aluminum plastic film, the electrolyte prepared above was injected into the battery in a glove box, and the lithium ion battery was obtained after standing, pre-charging, aging and capacity distribution.

[0083] Examples 2-7 and Comparative Examples 1-2 refer to Example 1, except for the tab position and the composition of the electrolyte, as shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] Test Example

[0088] (1) Cycle performance test

[0089] The batteries of the examples and the comparative examples were cycled at 25℃ at a rate of 1C for 100 cycles, and the capacity of the 100th cycle was divided by the capacity of the 1st cycle to obtain the cycle capacity retention rate, and the test results are recorded in Table 2.

[0090] (2) Temperature shock test

[0091] The batteries of the examples and the comparative examples were placed in an oven at 4.45V, and the temperature was increased from room temperature to 130℃ and 132℃ at a rate of 5℃ / min, respectively, and whether ignition and explosion occurred at 130℃ and 132℃, respectively, was observed, and the test results are recorded in Table 2.

[0092] (3) Rate charge test

[0093] The batteries of the examples and the comparative examples were first charged to 3.0V at 25℃, then charged to 4.5V at a rate of 1C, and then disassembled to observe whether lithium precipitation occurred; if lithium precipitation did not occur, then the rate was increased by 0.5C successively at 1.5C, 2C, and 2.5C until the rate at which lithium precipitation occurred was found, and the rate at which lithium precipitation occurred is recorded in Table 2.

[0094] Table 2

[0095]

[0096] As can be seen from Table 2, the battery of the present application has significantly improved cycle capacity retention rate, safety performance, and rate at which lithium precipitation occurs compared with the comparative examples, and the battery of the present application can improve the fast charging performance while ensuring safety performance.

[0097] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A battery, characterized by, The battery comprises a pole piece and an electrolyte; The pole piece comprises a current collector and a tab provided on the current collector, a distance from a head edge of the current collector to the tab near a side of the tab close to the head edge of the current collector is D, a distance from a tail edge of the current collector to the tab near a side of the tab close to the tail edge of the current collector is L, and 0.097≤D / (D+L)≤0.894; The electrolyte comprises lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium difluorophosphate and component T, a content x of the lithium hexafluorophosphate is 11.3-18.7% by weight based on the total weight of the electrolyte, and 18.9≤[(D+L) / D]×x%×100≤76.9 is satisfied; a content y of the lithium bisfluorosulfonylimide satisfies 0.005≤y / x≤0.7 with x; and a content of the lithium difluorophosphate is less than a content of the component T; said component T is in combination, wherein the mass ratio of the components T and U is 1 : (0.5-2); The pole piece further comprises an active material layer provided on an outer surface of the current collector, the active material layer comprises a positive electrode active material or a negative electrode active material, the positive electrode active material comprises lithium cobaltate, and the negative electrode active material comprises artificial graphite.

2. The battery of claim 1, wherein, 0.195≤D / (D+L)≤0.

793.

3. The battery of claim 1, wherein, 0.005≤y / x≤0.

5.

4. The battery according to claim 1 or 2, wherein A content of the component T is 0.05-10% by weight based on the total weight of the electrolyte.

5. The battery of claim 4, wherein, A content of the component T is 0.2-5% by weight based on the total weight of the electrolyte.

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