Battery and electronic device

Abstract

The invention provides a battery and an electronic device, the battery comprises a negative plate, a positive plate and an electrolyte, the negative plate comprises a negative current collector and a negative active material layer located on at least one side surface of the negative current collector, and the positive plate comprises a positive current collector and a positive active material layer located on at least one side surface of the positive current collector; a tab groove is formed in the positive active material layer, a positive tab is accommodated in the tab groove, and a tab adhesive layer is arranged on the surface of the positive tab; a groove is formed in the negative active material layer, the tab groove and the groove are oppositely arranged along the third direction of the positive plate, and an insulating adhesive layer is arranged in the groove; the electrolyte comprises a fluorinated solvent, the mass content percentage of the fluorinated solvent in the electrolyte is m1, and m1 is larger than or equal to 5% and smaller than or equal to 50%. According to the battery, certain corrosion resistance can be provided for the preset groove in the negative electrode area, so that the cycle life and the safety performance of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and particularly to a battery and an electronic device including the battery. Background Art

[0002] For the positive tab of a conventional battery, in order to prevent short circuit of the electrode sheet and improve the safety of the battery, an tab adhesive is provided on the surface of the positive tab, and an insulating adhesive tape is provided in the negative region corresponding to the positive tab. However, since both the tab and the tab adhesive are provided at the positive tab, and the insulating adhesive tape is provided on the corresponding negative electrode sheet, the thickness of this region will be relatively thick, resulting in unevenness of the electrode sheet.

[0003] Currently, in order to reduce the influence of the tab adhesive and the insulating adhesive layer provided at the positive tab during the battery design process on the overall thickness of the electrode sheet, a structure of presetting a groove in the negative region corresponding to the positive tab is often used to solve the problem of uneven thickness. This groove can accommodate the excess tab adhesive and insulating adhesive tape on the tab, and can also increase the liquid retention capacity of the negative electrode sheet. However, due to the groove between the two electrode sheets, a certain amount of electrolyte is often stored, and the active material in the groove is less than that in other parts. The electrolyte stored in the groove is likely to react with the current collector and corrode the current collector, posing a safety hazard and affecting the cycle life and safety performance of the battery. Summary of the Invention

[0004] Based on the above problems, the present invention provides a battery and an electronic device including the battery. The battery of the present invention can endow a preset groove in the negative region with a certain corrosion resistance, so as to improve the cycle life and safety performance of the battery.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: In a first aspect of the present invention, there is provided a battery, the battery including a negative electrode sheet, a positive electrode sheet and an electrolyte. The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one surface of the negative current collector. The positive electrode sheet includes a positive current collector and a positive active material layer located on at least one surface of the positive current collector; A tab groove is provided on the positive active material layer, and a positive tab is accommodated in the tab groove. An tab adhesive layer is provided on the surface of the positive tab; A groove is provided on the negative active material layer. The tab groove and the groove are oppositely arranged along a third direction of the positive electrode sheet. An insulating adhesive layer is provided in the groove; The electrolyte includes a fluorinated solvent, and the mass content percentage of the fluorinated solvent in the electrolyte is m1, 5% ≤ m1 ≤ 50%.

[0006] In a second aspect of the present invention, there is provided an electronic device, the electronic device including the battery according to the first aspect of the present invention.

[0007] Through the above technical solutions, the present invention has at least the following advantages compared with the prior art: By providing a groove on the negative electrode active material layer on the side corresponding to the ear groove of the positive electrode sheet, the groove is disposed opposite to the ear groove, the problem of uneven thickness of the electrode sheet can be further solved, the consistency of the thickness of the electrode sheet is improved, thereby improving the cycle performance and safety performance of the battery; however, by providing a groove on the negative electrode active material layer on the side corresponding to the ear groove of the positive electrode sheet, the electrolyte stored in the groove is likely to react with the current collector and then corrode the current collector. Therefore, the electrolyte of the present invention includes a fluorinated solvent. Compared with the traditional electrolyte solvent, the fluorinated solvent has better oxidation stability and is not easily decomposed. Its fluorine element will chemically react with the copper atoms on the surface of the current collector to form a stable fluorinated passivation layer. This passivation layer usually has high thermal stability and chemical stability, can closely adhere to the surface of the current collector, give a certain corrosion resistance to the ear groove, and by controlling the mass content percentage m1 of the fluorinated solvent in the electrolyte within a suitable range, the corrosion resistance of the ear groove can be further improved, so that the cycle life and safety performance of the battery are effectively improved.

[0008] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. Description of the Drawings

[0009] Figure 1 It is a schematic cross-sectional structure diagram of a positive electrode sheet and a negative electrode sheet provided by an embodiment of the present invention.

[0010] Figure 2 It is a schematic top view structure diagram of a negative electrode sheet provided by an embodiment of the present invention.

[0011] Description of the Reference Numerals: Negative electrode sheet 100, negative current collector 110, negative electrode active material layer 120, groove 130, positive electrode sheet 200, positive current collector 210, positive electrode active material layer 220, ear groove 230, positive ear 240, ear glue layer 250, insulating glue layer 300. Detailed Description of the Invention

[0012] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0013] In the specific embodiments and claims, a list of items connected by terms such as "at least one of", "at least one in", "at least one kind in", or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0014] A first aspect of the present invention provides a battery, the battery including a negative electrode sheet, a positive electrode sheet, and an electrolyte. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector; A pole ear groove is provided on the positive electrode active material layer, and a positive pole ear is accommodated in the pole ear groove. A pole ear adhesive layer is provided on the surface of the positive pole ear; A groove is provided on the negative electrode active material layer. The pole ear groove and the groove are oppositely arranged along the third direction of the positive electrode sheet, and an insulating adhesive layer is provided in the groove; The electrolyte includes a fluorinated solvent, and the mass content percentage of the fluorinated solvent in the electrolyte is m1, 5% ≤ m1 ≤ 50%.

[0015] As Figure 1As shown in the figure, it is a schematic cross-sectional structure diagram of a positive electrode sheet and a negative electrode sheet provided by an embodiment of the present invention. The negative electrode sheet 100 includes a negative electrode current collector 110 and a negative electrode active material layer 120 located on at least one surface of the negative electrode current collector 110. The positive electrode sheet 200 includes a positive electrode current collector 210 and a positive electrode active material layer 220 located on at least one surface of the positive electrode current collector 210. A tab groove 230 is provided on the positive electrode active material layer 220, and a positive electrode tab 240 is accommodated in the tab groove 230. A tab adhesive layer 250 is provided on the surface of the positive electrode tab. A groove 130 is provided on the negative electrode active material layer 120. The tab groove 230 and the groove 130 are oppositely arranged along the third direction of the positive electrode sheet 200. An insulating adhesive layer 300 is provided in the groove 130. Along the third direction of the positive electrode sheet 200, the fact that the tab groove 230 and the groove 130 are oppositely arranged along the third direction of the positive electrode sheet 200 can be interpreted as that the overlapping projection area of the tab groove 230 and the groove 130 is greater than 80% of the projection area of the tab groove 230, or the overlapping projection area of the tab groove and the groove is greater than or equal to 80% of the projection area of the groove, such as 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%. In addition, the third direction can refer to the thickness direction of the positive electrode sheet or the negative electrode sheet. Being oppositely arranged along the third direction of the positive electrode sheet means being oppositely arranged along the thickness direction of the positive electrode sheet.

[0016] In the present invention, by providing a groove on the negative electrode active material layer on the side corresponding to the tab groove of the positive electrode sheet, and the groove and the tab groove are oppositely arranged, it is possible to reduce the influence of the tab adhesive and the insulating adhesive layer at the tab between the electrode sheets on the overall thickness consistency of the electrode sheet, solve the problem of uneven thickness of the electrode sheet, thereby improving the thickness consistency of the electrode sheet, and further improving the cycle performance and safety performance of the battery. However, providing a groove on the negative electrode active material layer on the side corresponding to the tab groove of the positive electrode sheet will cause a groove gap between the two electrode sheets here, which will store a certain amount of electrolyte. When the electrolyte retention amount is high, the electrolyte stored in the groove is likely to react with the aluminum foil of the positive electrode current collector and then corrode the positive electrode current collector, thus causing a safety hazard and affecting the cycle life of the battery. Based on this, the electrolyte in the present invention includes a fluorinated solvent. Compared with traditional electrolyte solvents (carbonates or carboxylates), the fluorinated solvent has better oxidation stability and is not easily decomposed. Its fluorine element will chemically react with the copper atoms on the surface of the aluminum foil of the positive electrode current collector to form a stable fluorinated passivation layer. This passivation layer usually has high thermal stability and chemical stability and can tightly adhere to the surface of the positive electrode current collector, giving a certain corrosion resistance to the groove at the tab, thereby being able to alleviate the influence of structural designs such as grooves on the battery performance and effectively improving the cycle life and safety performance of the battery.

[0017] Further, the mass percentage content of the fluorinated solvent in the electrolyte is m1, where 5% ≤ m1 ≤ 50%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%. When the mass percentage content m1 of the fluorinated solvent in the electrolyte is too large, a too thick fluorinated passivation layer will be formed on the surface of the positive current collector aluminum foil, which will hinder electron conduction and ion transport, increase the internal resistance of the battery during charge and discharge, cause an increase in heat generation during battery charging, and thus affect the safety of the battery. Therefore, the mass percentage content m1 of the fluorinated solvent in the electrolyte should not be too large. At the same time, in order to ensure the uniformity of the thickness of the fluorinated passivation layer, the mass percentage content m1 of the fluorinated solvent in the electrolyte should not be too small to avoid uneven temperature distribution inside the battery caused by local overheating and weakened corrosion resistance, and further improve the safety performance of the battery's cycle life.

[0018] In one example, 10% ≤ m1 ≤ 40%.

[0019] In the present invention, as Figure 1 and Figure 2 shown, Figure 2 is a top view structural schematic diagram of the negative electrode sheet provided by an embodiment of the present invention. Along the first direction of the negative electrode sheet, the length of the groove is L1, where 5 mm ≤ L1 ≤ 40 mm, for example, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm or 40 mm.

[0020] In one example, 10 mm ≤ L1 ≤ 30 mm.

[0021] In the present invention, as Figure 2 shown, along the second direction of the negative electrode sheet, the width of the groove is L2, where 4 mm ≤ L2 ≤ 30 mm, for example, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm or 30 mm.

[0022] In one example, 6 mm ≤ L2 ≤ 15 mm.

[0023] It can be understood that the first direction may refer to the width direction of the positive electrode sheet or the negative electrode sheet, the second direction may refer to the length direction of the positive electrode sheet or the negative electrode sheet, the first direction and the second direction are perpendicular to each other in the same plane, and the third direction is perpendicular to this plane.

[0024] In the present invention, as Figure 1 shown, along the third direction of the negative electrode sheet, the depth of the groove is L3, 0.005 mm ≤ L3 ≤ 0.15 mm, for example, 0.005 mm, 0.006 mm, 0.007 mm, 0.008 mm, 0.009 mm, 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm or 0.15 mm.

[0025] In one example, along the third direction of the negative electrode sheet, the depth of the groove is 0.01 mm ≤ L3 ≤ 0.1 mm.

[0026] The groove on the negative electrode sheet needs to accommodate the positive electrode tab while also accommodating the overflowing tab glue layer at the tab of the positive electrode tab and the overflowing glue of the insulating glue layer provided in the corresponding negative electrode area, so as to avoid uneven thickness at the tab. Therefore, the dimensions in all directions should not be too small to obtain sufficient space to accommodate the overflowing glue, but the dimensions should not be too large either, because when the size of the groove is too large, it will cause excessive loss of the negative electrode active material layer, resulting in attenuation of the battery capacity and increase in impedance, and further affecting the overall performance of the battery.

[0027] In the present invention, as Figure 1 and Figure 2 shown, the orthographic projection area of the groove 130 along the third direction of the negative electrode sheet is S, S = L1 * L2; the mass content percentage of the fluorinated solvent in the electrolyte is m1; the S and m1 satisfy m1 ≥ S / 10.

[0028] Figure 2 It is a schematic top view structure diagram of the negative electrode sheet provided by an embodiment of the present invention. The orthographic projection of the groove is a rectangle, and the area of the rectangle can be obtained by multiplying the length × width of the rectangle mass content percentage, that is, S = L1 * L2.

[0029] When the m1 of the fluorinated solvent in the electrolyte and the projection area S (S = L1 * L2) of the groove satisfy: m1 ≥ S / 10, the negative electrode sheet can better accommodate the protruding insulating glue at the tab, and can store enough fluorinated solvent at the groove. While improving the liquid retention capacity of the negative electrode sheet, it can also be used to improve the corrosion resistance of the negative electrode sheet, thereby further improving the cycle life and thermal safety of the battery.

[0030] In the present invention, the fluorinated solvent includes at least one of fluorinated carbonate solvents, fluorinated carboxylate solvents, fluoroethers, and fluorobenzenes.

[0031] In one example, the fluorinated solvent includes at least one of ethyl methyl fluorocarbonate, diethyl fluorocarbonate, dimethyl fluorocarbonate, ethyl fluoroacetate, methyl fluoropropionate, ethyl fluoropropionate, propyl fluoropropionate, bis(2,2,2-trifluoroethyl) ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, methyl nonafluorobutyl ether, tris(trifluoroethoxy)methane, ethyl nonafluorobutyl ether, monofluorobenzene, and p-difluorobenzene. It should be understood that "fluorinated" can be monofluorinated, difluorinated, trifluorinated, etc. The number of fluorine substitutions is not limited, and the position of fluorine substitution is also not limited and can be any substitutable position.

[0032] In the present invention, the electrolyte may further include electrolyte additives such as fluorinated ethylene carbonate and fluorinated propylene carbonate.

[0033] In the present invention, the electrolyte may further include unsaturated nitrile compounds, and the unsaturated nitrile compounds include at least one of 1,4-dicyano-2-butene, 2-methyl-2-butenenitrile, and isopropylidenemalononitrile.

[0034] When unsaturated nitrile compounds are further added to the electrolyte containing fluorinated solvent, the combined use of fluorinated solvent and unsaturated nitrile compounds can reduce the interfacial side reactions between the electrolyte and the electrode sheet, reduce the generation of heat and gas inside the battery, and improve the thermal safety performance of the battery. Specifically, unsaturated nitrile compounds can form a protective layer on the electrode surface during the charge and discharge process of the battery. Compared with traditional nitrile compounds, unsaturated nitriles can undergo polymerization reactions, increasing the reaction sites at the interface with the positive electrode sheet through polymerization reactions, which can effectively prevent the shedding of the active material of the electrode sheet and the decomposition of the electrolyte. Moreover, under the fluorinated solvent system, unsaturated nitrile compounds can form a relatively stable solvation structure, reducing the charge accumulation and ion aggregation phenomena inside the battery, inhibiting the side reactions inside the battery, and thus further improving the cycle stability and service life of the battery.

[0035] In one example, the mass content percentage of the unsaturated nitrile compound in the electrolyte is 0.1% - 5%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0036] In the present invention, asFigure 1 As shown in the figure, a tab glue layer 250 is provided on the surface of the positive tab 240. By providing the tab glue layer 250 on the surface of the positive tab 240, short circuit between the positive and negative electrodes can be prevented, but the dimensional design in each direction will affect the thickness flatness at the positive tab. Although the groove provided at the corresponding position of the negative electrode sheet can improve this problem, if the volume of the tab glue layer exceeds the range that the groove can accommodate, it will still affect the uniformity of the thickness of the electrode sheet, thereby affecting the cycle life and safety performance of the battery. Based on this, further, in the present invention, along the first direction of the positive electrode sheet, the length of the tab glue layer is a, and 10 mm ≤ a ≤ 40 mm, for example, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 25 mm, 30 mm, 35 mm or 40 mm. It should be noted that there may be a height difference between the positive tab and the positive active material layer along the third direction of the positive electrode sheet, but the length a of the tab glue layer in the present invention only represents the length along the first direction of the positive electrode sheet. Figure 1 As shown in the figure.

[0037] In one example, 10 mm ≤ a ≤ 15 mm.

[0038] In the present invention, along the second direction of the positive electrode sheet, the width of the tab glue layer is b, and 8 mm ≤ b ≤ 35 mm, for example, 8 mm, 9 mm, 10 mm, 11, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm or 35 mm.

[0039] In one example, 20 mm ≤ b ≤ 30 mm.

[0040] In the present invention, the orthographic projection area of the tab glue layer along the third direction of the positive electrode sheet is 150 mm 2 -700 mm 2 , for example, 150 mm 2 , 200 mm 2 , 250 mm 2 , 300 mm 2 , 350 mm 2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2or 700 mm 2 。

[0041] In one example, the orthographic projection area of the tab glue layer along the third direction of the positive electrode sheet is 180 mm 2 -480 mm 2 。

[0042] If the area of the tab glue layer covering the positive tab is too small, it may not be able to completely cover the positive tab, posing a risk of short circuit; if the area of the tab glue layer covering the positive tab is too large, the area of the groove of the negative active material layer on the corresponding negative electrode sheet surface will correspondingly increase, avoiding unevenness of the insulating glue at the tab. However, when the area of the tab glue layer covering the positive tab is too large, the volume space inside the small-area groove is small and not enough to accommodate the excessive overflowing tab glue. Therefore, it is necessary to increase the area of the groove correspondingly. However, once the area of the groove is increased, on the one hand, it will cause loss of active material on the negative electrode side, reducing the energy density of the battery; on the other hand, it will also lead to an increase in the corrodible area of the negative current collector, strengthening the corrosion of the negative current collector and reducing the cycle performance and thermal safety performance of the battery. Therefore, by controlling the tab glue layer covering the tab to have a suitable area size, the present invention can effectively improve the cycle stability of the battery, avoid the risk of short circuit in the battery, and improve the safety performance of the battery.

[0043] Furthermore, there is a good interaction between the fluorinated solvent and the tab glue layer, which can enhance the bonding performance between the tab glue layer and the positive electrode sheet, ensure the conductivity and mechanical strength of the battery, thereby improving the overall performance of the battery and preventing risks such as short circuit and thermal runaway during the cycling process of the battery. At the same time, the high ionic conductivity of the fluorinated solvent can promote the migration of lithium ions inside the battery, and the combination of the tab glue layer and the solvent helps to maintain this performance, thereby improving the charge-discharge efficiency of the battery; moreover, good wettability and permeability help the fluorinated solvent to better penetrate the surface of the tab glue layer and can also enhance the adhesion between the tab glue layer and the positive current collector. This can not only improve the use effect of the tab glue layer but also reduce the safety problems of the battery caused by insufficient adhesion to a certain extent.

[0044] In the present invention, the negative active material layer contains a silicon-based material. Based on the total mass of the negative active material layer, the mass content of silicon element in the negative active material layer is m2, and m1 and m2 satisfy m1≥m2.

[0045] In one example, based on the total mass of the negative active material layer, the mass content of silicon element in the negative active material layer is m2, 2%≤m2≤40%, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35% or 40%.

[0046] In one example, 15% ≤ m2 ≤ 30%.

[0047] When the mass percentage content m1 of the fluorinated solvent in the electrolyte is greater than the mass content m2 of silicon element in the negative electrode active material layer, the fluorinated solvent helps to form a more stable solid electrolyte interface (SEI) film, reduce the decomposition of the electrolyte on the silicon negative electrode side, thereby effectively improving the cycle life of the battery. At the same time, it can relieve the mechanical stress brought by the silicon-based material in the negative electrode active material layer, reduce the possibility of the negative electrode active material layer material cracking, thereby prolonging the cycle life of the battery and improving the battery performance.

[0048] In the present invention, the particle size Dv50 of the silicon-based material is 5 μm - 15 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0049] In one example, the particle size Dv50 of the silicon-based material is 6 μm - 10 μm.

[0050] In the present invention, the average sphericity q of the silicon-based material particles is 0.5 - 1, such as 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

[0051] In one example, the average sphericity q of the silicon-based material particles is 0.7 - 1.

[0052] The fluorinated solvent has a low surface tension. By controlling the size of the particle size Dv50 of the silicon-based material and the average sphericity q of the silicon-based material particles, this helps the fluorinated solvent to better wet the surface of the silicon negative electrode. The low surface tension of the outer layer makes the solvent molecules easier to spread on the surface of the silicon negative electrode, forming a uniform covering layer, reducing the interfacial resistance between the silicon negative electrode and the electrolyte, helping to improve the lithium ion transport efficiency, thereby effectively improving the ionic conductivity of the negative electrode sheet, relieving the volume change of the negative electrode sheet, and further improving the cycle stability of the battery.

[0053] In the present invention, the negative electrode active material layer includes a bottom coating close to the negative electrode current collector and a surface coating located on the surface of the bottom coating away from the negative electrode current collector, and the areal density s1 of the bottom coating is greater than the areal density s2 of the surface coating.

[0054] Since setting grooves on the electrode inevitably results in a certain capacity loss, the double-layer coating technology can be used to coat the negative electrode active material layer to well compensate for this, achieving a relatively high-porosity structure for the surface coating with a small surface density s2, and a relatively high-compaction-density structure for the lower bottom coating with a large surface density s1, so that the density of the negative electrode active material in the negative electrode active material layer shows a gradient distribution, which can increase the energy density of the battery and improve the battery's ability to store electrical energy, thus taking into account both high energy density and super fast charging performance.

[0055] In the present invention, 0.5 mg / cm 2 ≤ s1 ≤ 5 mg / cm 2 , for example, 0.5 mg / cm 2 , 1 mg / cm 2 , 1.5 mg / cm 2 , 2 mg / cm 2 , 2.5 mg / cm 2 , 3 mg / cm 2 , 3.5 mg / cm 2 , 4 mg / cm 2 , 4.5 mg / cm 2 or 5 mg / cm 2 .

[0056] In one example, 1 mg / cm 2 ≤ s1 ≤ 3 mg / cm 2 .

[0057] In the present invention, 0.2 mg / cm 2 ≤ s2 ≤ 3 mg / cm 2 , for example, 0.2 mg / cm 2 , 0.5 mg / cm 2 , 1 mg / cm 2 , 1.5 mg / cm 2 , 2 mg / cm 2 , 2.5 mg / cm 2 or 3 mg / cm 2 .

[0058] In one example, 0.5 mg / cm 2 ≤ s2 ≤ 2 mg / cm 2 .

[0059] In the present invention, the ratio of the areal density s1 of the bottom coating to the areal density s2 of the surface coating is M, where 1 ≤ M ≤ 2.5, such as 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, or 2.5.

[0060] In one example, 1 ≤ M ≤ 1.5.

[0061] In the present invention, the thickness of the bottom coating is 0.02 mm - 0.08 mm, such as 0.02 mm, 0.021 mm, 0.022 mm, 0.023 mm, 0.024 mm, 0.025 mm, 0.026 mm, 0.027 mm, 0.028 mm, 0.029 mm, 0.03 mm, 0.031 mm, 0.032 mm, 0.033 mm, 0.034 mm, 0.035 mm, 0.036 mm, 0.037 mm, 0.038 mm, 0.039 mm, 0.04 mm, 0.05 mm, 0.055 mm, 0.06 mm, 0.065 mm, 0.07 mm, 0.075 mm, or 0.08 mm.

[0062] In one example, the thickness of the bottom coating is 0.025 mm - 0.08 mm.

[0063] In the present invention, the thickness of the surface coating is 0.015 mm - 0.07 mm, such as 0.015 mm, 0.016 mm, 0.017 mm, 0.018 mm, 0.019 mm, 0.02 mm, 0.021 mm, 0.022 mm, 0.023 mm, 0.024 mm, 0.025 mm, 0.026 mm, 0.027 mm, 0.028 mm, 0.029 mm, 0.03 mm, 0.031 mm, 0.032 mm, 0.033 mm, 0.034 mm, 0.035 mm, 0.04 mm, 0.045 mm, 0.05 mm, 0.055 mm, 0.06 mm, 0.065 mm, or 0.07 mm.

[0064] In one example, the thickness of the surface coating is 0.02 mm - 0.07 mm.

[0065] For the battery according to the present invention, the lithium-ion battery further includes a separator, and the separator can also be a separator commonly used in the art, such as a PP film, a PE film, etc.

[0066] For the battery according to the present invention, the positive electrode active material layer includes a layered lithium composite oxide, and its chemical formula is Li (1+x) Ni y Co z M(1-y-z) O 2 , wherein, -0.1 ≤ x ≤ 1; 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1; wherein, M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0067] For the battery according to the present invention, the negative electrode active material layer contains a carbon-based negative electrode material, wherein the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon.

[0068] For the battery according to the present invention, the negative electrode active material layer contains a silicon-carbon negative electrode material, and the silicon-carbon negative electrode material includes at least one of nano-silicon (Si), silicon oxide (SiO x (0 < x < 2)), and silicon-carbon.

[0069] For the battery according to the present invention, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalato)phosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyl, and lithium bis(trifluoromethylsulfonyl)imide.

[0070] For the battery according to the present invention, the electrolyte further includes an organic solvent, and the organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, ethyl propionate, n-propyl propionate, methyl butyrate, ethyl butyrate, and n-ethyl butyrate.

[0071] The battery of the present invention can be prepared by conventional methods in the art. Specifically, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence, ensuring that the separator is between the positive and negative electrode sheets to play an isolation role, and then the un-injected bare battery cell is obtained by winding; the bare battery cell is placed in an outer packaging foil, and the electrolyte is injected into the dried bare battery cell, and through processes such as vacuum packaging, standing, formation, shaping, and sorting, the required lithium-ion battery is obtained.

[0072] The second aspect of the present invention provides an electronic device, and the electronic device includes the battery described in the first aspect of the present invention.

[0073] The present invention does not limit the types of electronic devices, which may specifically include, but are not limited to, laptop computers, input-type computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0074] The following will further elaborate on the present invention in conjunction with specific embodiments. It should be understood that the following embodiments are only for illustrative and explanatory purposes of the present invention and should not be construed as limiting the protection scope 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.

[0075] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods; the reagents, materials, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0076] Example 1 The lithium-ion battery of the present invention is obtained in the following manner: 1) Preparation of the positive electrode sheet Mix the positive electrode active material lithium cobalt oxide (LiCoO 2 ), polyvinylidene fluoride (PVDF), SP (super P), and carbon nanotubes (CNT) in a mass ratio of 96:2:1.5:0.5, add N-methylpyrrolidone (NMP), and stir under a vacuum mixer until the mixed system becomes a homogeneous and fluid positive electrode active paste; uniformly coat the positive electrode active paste on both surfaces of the aluminum foil; dry the coated aluminum foil, and then obtain the required positive electrode sheet through rolling and slitting. Then, reserve the tab groove on the surface of the positive electrode sheet by laser cleaning, weld the positive tab in the tab groove, and coat the surface of the positive tab with tab glue. The length a of the tab glue layer is 12 mm, the width b is 24 mm, and the projected area of the tab glue layer in the third direction of the positive electrode sheet is 288 mm 2 .

[0077] 2) Preparation of the negative electrode sheet Mix the negative electrode active material artificial graphite, silicon carbide (particle size Dv50 = 8 μm, average sphericity q = 0.75), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP), and single-walled carbon nanotubes (SWCNTs) in a mass ratio of 40:54.5:2.5:1.5:1:0.5, add deionized water, and obtain negative electrode active paste 1 under the action of a vacuum mixer; Mix artificial graphite as the negative electrode active material, silicon carbide (particle size Dv50 = 8 μm, average sphericity q = 0.75), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) in a mass ratio of 54.5:40.5:1.5:1:0.5, add deionized water, and obtain negative electrode active paste 2 under the action of a vacuum mixer; Coat negative electrode active paste 1 and negative electrode active paste 2 evenly on both surfaces of the copper foil. Negative electrode active paste 1 is used as the bottom coating paint, and negative electrode active paste 2 is used as the surface coating paint. The thickness of the bottom coating is 0.03 mm, and the thickness of the surface coating is 0.022 mm; dry the coated copper foil at room temperature, then transfer it to an 80 °C oven and dry for 10 h, and then obtain a negative electrode sheet through cold pressing and slitting. The thickness of the negative electrode sheet is 100 μm, and then reserve a groove on the surface of the negative electrode sheet through laser cleaning. Among them, the dimensions of the groove are as follows: L1 = 15 mm, L2 = 10 mm, and the groove depth L3 = 0.05 mm; in addition, the mass content m2 of silicon element in the negative electrode active material layer is measured to be 25%, and the surface density s1 of the bottom coating is 2.3 mg / cm 2 , and the density s2 of the surface coating is 1.74 mg / cm 2 , M = s1 / s2 = 1.32.

[0078] 3) Preparation of electrolyte In a glove box filled with argon (H 2 O < 0.1 ppm, O 2 < 0.1 ppm), mix the solvents EC / PC / PP / difluoroethyl acetate (the fluorinated solvent is difluoroethyl acetate in fluoroethyl acetate) in a ratio of 1 / 1 / 2 / 3. The mass content percentage m1 of difluoroethyl acetate in the electrolyte is 30%, and then quickly add 12.5 wt% of fully dried lithium hexafluorophosphate (LiPF 6 ) based on the total mass of the electrolyte, and then add 0.5 wt% of 1,4-dicyano-2-butene based on the total mass of the electrolyte, as well as 2 wt% of 1,3,5-hexanetricarbonitrile (HTCN), 1 wt% of adiponitrile (ADN), 4 wt% of 1,3-propane sultone and 10 wt% of fluoroethylene carbonate additives. After stirring evenly and passing the moisture and free acid detection, the required electrolyte is obtained.

[0079] 4) Preparation of lithium-ion battery After laminating the positive electrode sheet in step 1), the negative electrode sheet in step 2), and the separator in the order of positive electrode sheet, separator, and negative electrode sheet, winding is then carried out to obtain an electrode core; the electrode core is placed in an outer packaging aluminum foil, and the electrolyte in step 3) is injected into the outer packaging. After processes such as vacuum packaging, standing, forming, shaping, and sorting, a lithium-ion battery is obtained. The charge and discharge range of the battery of the present invention is 3.0 - 4.58V.

[0080] Example 2 group This example is carried out with reference to Example 1. The only difference is that during the preparation process of the electrolyte, by changing the mass ratio of each solvent component, the mass content percentage m1 of the fluorinated solvent in the electrolyte is changed, or the type of the fluorinated solvent is changed simultaneously. Among them, the type of the fluorinated solvent in Example 2-1 and Example 2-3 does not change. The fluorinated solvent in Example 2-2 is fluorobenzene, and the fluorinated solvent in Example 2-4 is a mixture of difluoroethyl acetate and fluorinated ether (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) in equal proportions. See Table 1 for details.

[0081] Example 3 group This example is carried out with reference to Example 1. The only difference is that during the preparation process of the negative electrode sheet, by changing the parameters of laser cleaning, the size of the groove is changed. See Table 1 for details.

[0082] Example 4 group This example is carried out with reference to Example 1. The only difference is that during the preparation process of the negative electrode sheet, the mass content m2 of silicon element in the negative electrode active material layer is changed, or the particle size and average sphericity q of the silicon-based material are changed simultaneously. Specifically: In Example 4-1, the mass content m2 of silicon element in the negative electrode active material layer is 15%, the particle size Dv50 is 5μm, and the average sphericity q is 0.75; In Example 4-2, the mass content m2 of silicon element in the negative electrode active material layer is 30%, the particle size Dv50 is 15μm, and the average sphericity q is 1; In Example 4-3, the mass content m2 of silicon element in the negative electrode active material layer is 40%, the particle size Dv50 is 8μm, and the average sphericity q is 0.5; See Table 1 for details.

[0083] Example 5 This example is carried out with reference to Example 1. The only difference is that the surface density of the bottom coating and the surface coating is changed, or the thicknesses of the bottom coating and the surface coating are changed simultaneously. Specifically: Example 5-1: The negative electrode active material layer does not distinguish between the bottom coating and the surface coating. The negative electrode active paste used is negative electrode active paste 1. The thickness and surface density of the bottom coating and the surface coating remain unchanged, and the surface density is 2.3 mg / cm 2 ; Example 5-2: By changing the coating process of the negative electrode active material layer or the manufacturing process of the negative electrode sheet, the surface density and thickness of the bottom coating and the surface coating are changed. The thickness of the bottom coating is 0.08 mm, the thickness of the surface coating is 0.015 mm, the surface density s1 of the bottom coating = 0.5 mg / cm 2 , and the density s2 of the surface coating = 3 mg / cm 2 ; Example 5-3: By changing the coating process of the negative electrode active material layer or the manufacturing process of the negative electrode sheet, the surface density and thickness of the bottom coating and the surface coating are changed. The thickness of the bottom coating is 0.02 mm, the thickness of the surface coating is 0.07 mm, the surface density s1 of the bottom coating = 5 mg / cm 2 , and the density s2 of the surface coating = 0.2 mg / cm 2 ; See Table 1 for details.

[0084] 6 groups of examples This example is carried out with reference to Example 1. The only difference is that during the preparation of the electrolyte, the mass ratio of each solvent component is changed, so that the mass content percentage of the unsaturated nitrile compound 1,4-dicyano-2-butene is changed. Specifically: In Example 6-1, the mass content percentage of 1,4-dicyano-2-butene is 0, and this unsaturated nitrile compound is not added; In Example 6-2, the mass content percentage of 1,4-dicyano-2-butene is 0.1; In Example 6-3, the mass content percentage of 1,4-dicyano-2-butene is 2; In Example 6-4, the mass content percentage of 1,4-dicyano-2-butene is 5; See Table 1 for details.

[0085] 1 group of comparative examples This comparative example is carried out with reference to Example 1. The only difference is that during the preparation of the electrolyte, the mass ratio of each solvent component is changed, so that the mass content percentage m1 of the fluorinated solvent in the electrolyte is changed. See Table 1 for details.

[0086] Comparative Example 2 This comparative example is carried out with reference to Example 1. The only difference is that during the preparation of the electrolyte, the fluorinated solvent is not added. See Table 1 for details.

[0087] Comparative Example 3 This comparative example was carried out with reference to Example 1. The only difference is that during the preparation of the negative electrode sheet, the groove corresponding to the tab groove is not provided. See Table 1 for details.

[0088] Table 1 Test example 1) Cycle performance test The lithium-ion batteries obtained from the above examples and comparative examples were charged and discharged cyclically within the charge and discharge cut-off voltage range at a discharge rate of 2C at 25°C. The discharge capacity in the first week was measured as x 1 mAh, and the discharge capacity in the Nth cycle was measured as y 1 mAh; the capacity in the Nth week was divided by the capacity in the first week to obtain the cycle capacity retention rate R 1 =y 1 / x 1 , and the cycle capacity retention rate R was recorded 1 The cycle number of the battery when R was 80% was recorded as T, and the results were recorded in Table 2.

[0089] 2) Safety performance test The lithium-ion batteries obtained from the above examples and comparative examples were discharged at a rate of 0.2C to the lower limit voltage of 3.0V at 25°C. After standing for 10 minutes, they were charged at a rate of 1C to the upper limit voltage of 4.55V, with a cut-off current of 0.05C. At this time, the lithium-ion batteries were in a fully charged state; then the fully charged lithium-ion batteries were placed in an oven, and the temperature in the oven was increased at a rate of 5°C / min. When the temperature in the oven reached 132°C, the temperature was kept constant and continued for 60 minutes. Observe whether the lithium-ion batteries caught fire or exploded at this time. If they did not catch fire or explode, it was considered to pass the test. A total of 10 tests were carried out, and finally the test results were recorded in Table 2.

[0090] Table 2 The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A battery, characterized in that: The invention comprises a negative electrode sheet, a positive electrode sheet and an electrolyte, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector, and the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side surface of the positive electrode current collector; The positive electrode active material layer is provided with a tab groove, a positive electrode tab is accommodated in the tab groove, and a tab glue layer is provided on the surface of the positive electrode tab; The negative electrode active material layer is provided with a groove, the tab groove is arranged opposite to the groove along the third direction of the positive electrode sheet, and an insulating glue layer is arranged in the groove; The electrolyte includes a fluorinated solvent, and the mass content percentage of the fluorinated solvent in the electrolyte is m1, 5%≤m1≤50%.

2. The battery according to claim 1, characterized in that Along the first direction of the negative electrode sheet, the length of the groove is L1, 5mm≤L1≤40mm; and / or, along the second direction of the negative electrode sheet, the width of the groove is L2, 4mm≤L2≤30mm; And / or, along the third direction of the negative electrode sheet, the depth of the groove is L3, 0.005mm≤L3≤0.15mm.

3. The battery according to claim 1, characterized in that The positive projection area of ​​the groove along the third direction of the negative electrode sheet is S; the mass content percentage of the fluorinated solvent in the electrolyte is m1; The S and m1 satisfy m1≥S / 10, where S=L1*L2.

4. The battery according to claim 1, characterized in that The fluorinated solvent includes at least one of a fluorinated carbonate solvent, a fluorinated carboxylate solvent, a fluorinated ether solvent, and a fluorinated benzene solvent; And / or, the fluorinated solvent includes at least one of ethyl methyl fluorocarbonate, diethyl fluorocarbonate, dimethyl fluorocarbonate, ethyl fluoroacetate, methyl fluoropropionate, ethyl fluoropropionate, propyl fluoropropionate, bis(2,2,2-trifluoroethyl) ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, methyl nonafluorobutyl ether, tris(trifluoroethoxy)methane, ethyl nonafluorobutyl ether, monofluorobenzene, and p-difluorobenzene.

5. The battery according to claim 1, characterized in that The electrolyte further includes an unsaturated nitrile compound, wherein the unsaturated nitrile compound includes at least one of 1,4-dicyano-2-butene, 2-methyl-2-butenenitrile, and isopropylidenemalononitrile; The mass content percentage of the unsaturated nitrile compound in the electrolyte is 0.1%-5%.

6. The battery according to claim 1, characterized in that Along the first direction of the positive electrode sheet, the length of the tab glue layer is a, 10mm≤a≤40mm; And / or, along the second direction of the positive electrode sheet, the width of the tab glue layer is b, 8mm≤b≤35mm; And / or, the positive projection area of ​​the tab glue layer along the third direction of the positive electrode sheet is 150 mm 2 -700 mm 2 .

7. The battery according to claim 1, characterized in that The negative electrode active material layer contains silicon-based materials. Based on the total mass of the negative electrode active material layer, the mass content of silicon in the negative electrode active material layer is m2. The m1 and m2 satisfy m1≥m2, wherein 2%≤m2≤40%; And / or, the particle size Dv50 of the silicon-based material is 5 μm-15 μm; And / or, the average sphericity q of the silicon-based material particles is 0.5-1.

8. The battery according to claim 1, characterized in that The negative electrode active material layer includes a bottom coating layer close to the negative electrode current collector and a top coating layer located on a surface of the bottom coating layer away from the negative electrode current collector. The surface density s1 of the bottom coating layer is greater than the surface density s2 of the top coating layer.

9. The battery according to claim 8, characterized in that 0.5 mg / cm 2 ≤s1≤5 mg / cm 2 ; and / or, 0.2 mg / cm 2 ≤s2≤3 mg / cm 2 ; and / or, the ratio between the surface density s1 of the base coating and the surface density s2 of the top coating is M, 1≤M≤2.5; And / or, the thickness of the primer layer is 0.02 mm to 0.08 mm; And / or, the thickness of the topcoat layer is 0.015 mm-0.07 mm.

10. An electronic device, characterized in that: The electronic device comprises the battery according to any one of claims 1 to 9.

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