Battery and electronic device

Abstract

The present invention provides a battery and electronic device. The battery includes 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 side 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 side of the positive electrode current collector. The positive electrode active material layer is provided with a tab groove, in which a positive tab is accommodated, and a tab adhesive layer is provided on the surface of the positive tab. The negative electrode active material layer is provided with a groove, the tab groove and the groove are arranged opposite each other along a 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 of the fluorinated solvent in the electrolyte is m1, 5%≤m1≤50%. The battery of the present invention can provide the grooves in the negative electrode region with a certain degree of corrosion resistance, thereby improving the cycle life and safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a battery and an electronic device comprising the battery. Background Art

[0002] To prevent short circuits and improve battery safety, conventional batteries have tab glue applied to the positive tab surface and insulating tape applied to the corresponding negative electrode area. However, the presence of both the tab and tab glue, along with the insulating tape applied to the corresponding negative electrode, can lead to a thicker area in the positive tab, causing unevenness in the electrode.

[0003] At present, in order to reduce the impact of the tab glue and insulating tape layer on the overall thickness of the electrode during the battery design process, a structural method of pre-setting a groove in the negative electrode area corresponding to the positive tab is often adopted to solve the problem of uneven thickness. This groove can accommodate excess tab glue and insulating tape on the tab, and can also increase the liquid retention 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 other parts. The electrolyte stored in the groove is easy to react with the current collector and then corrode the current collector, causing safety hazards 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 provide the preset grooves in the negative electrode area with a certain corrosion resistance, thereby improving 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:

[0006] A first aspect of the present invention provides a battery, comprising 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 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 of the positive electrode current collector;

[0007] The positive electrode active material layer is provided with a tab groove, the positive electrode tab is accommodated in the tab groove, and the surface of the positive electrode tab is provided with a tab glue layer;

[0008] 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 rubber layer is provided in the groove;

[0009] The electrolyte includes a fluorinated solvent, and the mass content percentage of the fluorinated solvent in the electrolyte is m1%, 5%≤m1%≤50%.

[0010] A second aspect of the present invention provides an electronic device, comprising the battery according to the first aspect of the present invention.

[0011] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0012] The present invention provides a groove on the negative electrode active material layer on the side corresponding to the positive electrode tab groove, and the groove is arranged opposite to the tab groove, which can further solve the problem of uneven thickness of the electrode sheet and improve the consistency of the electrode sheet thickness, thereby improving the cycle performance and safety performance of the battery; but by providing a groove on the negative electrode active material layer on the side corresponding to the positive electrode tab groove, the electrolyte stored in the groove is easy to react with the current collector and thus corrode the current collector. Therefore, the electrolyte of the present invention includes a fluorinated solvent. Compared with traditional electrolyte solvents, the fluorinated solvent has better oxidation stability and is not easy to decompose. The fluorine element thereof will chemically react with the copper atoms on the surface of the current collector to generate a stable fluorinated passivation layer. This passivation layer usually has high thermal stability and chemical stability, can be tightly attached to the surface of the current collector, and give the tab groove a certain corrosion resistance. Moreover, by controlling the mass content percentage m1 of the fluorinated solvent in the electrolyte within an appropriate range, the corrosion resistance of the tab groove can be further improved, so that the cycle life and safety performance of the battery are effectively improved.

[0013] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the cross-sectional structure of a positive electrode sheet and a negative electrode sheet provided in one embodiment of the present invention.

[0015] Figure 2 This is a schematic top view of the negative electrode sheet provided in one embodiment of the present invention.

[0016] Description of reference numerals:

[0017] Negative electrode sheet 100 , negative electrode current collector 110 , negative electrode active material layer 120 , groove 130 , positive electrode sheet 200 , positive electrode current collector 210 , positive electrode active material layer 220 , tab groove 230 , positive tab 240 , tab adhesive layer 250 , insulating adhesive layer 300 . DETAILED DESCRIPTION

[0018] 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 used to illustrate and explain the present invention and are not intended to limit the present invention.

[0019] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, 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, 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 contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0020] A first aspect of the present invention provides a battery, comprising 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 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 of the positive electrode current collector;

[0021] The positive electrode active material layer is provided with a tab groove, the positive electrode tab is accommodated in the tab groove, and the surface of the positive electrode tab is provided with a tab glue layer;

[0022] 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 rubber layer is provided in the groove;

[0023] The electrolyte includes a fluorinated solvent, and the mass content percentage of the fluorinated solvent in the electrolyte is m1%, 5%≤m1%≤50%.

[0024] like Figure 1As shown, it is a schematic diagram of the cross-sectional structure of the positive electrode sheet and the negative electrode sheet provided in one embodiment of the present invention, wherein 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 side surface of the negative electrode current collector 110, and 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 side surface of the positive electrode current collector 210; the positive electrode active material layer 220 is provided with a tab groove 230, and a positive electrode tab 240 is accommodated in the tab groove 230, and a tab glue layer 250 is provided on the surface of the positive electrode tab; the negative electrode active material layer 120 is provided with a groove 130; the tab groove 230 and the groove 130 are connected along the third direction of the positive electrode sheet 200 The tab groove 230 and the groove 130 are arranged opposite each other along the third direction of the positive electrode sheet 200. The tab groove 230 and the groove 130 are arranged opposite each other along the third direction of the positive electrode sheet 200. This can be interpreted as the projected area of ​​overlap between the tab groove 230 and the groove 130 being greater than 80% of the projected area of ​​the tab groove 230, or the projected area of ​​overlap between the tab groove and the groove being greater than or equal to 80% of the projected area of ​​the groove, for example, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, the third direction can refer to the thickness direction of the positive or negative electrode sheet. "Relatively arranged along the third direction of the positive electrode sheet" means "relatively arranged along the thickness direction of the positive electrode sheet."

[0025] The present invention provides a groove on the negative electrode active material layer on the side corresponding to the positive electrode tab groove, and the groove is arranged opposite to the tab groove, which can reduce the influence of the tab glue and the insulating glue layer provided 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 consistency of the thickness 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 positive electrode tab groove will result in the groove gap between the two electrode sheets here storing a certain amount of electrolyte. When the electrolyte retention amount is high, the electrolyte stored in the groove is likely to react with the negative electrode current collector and thus corrode the negative electrode collector fluid, thereby causing safety hazards and affecting the cycle life of the battery; based on this, the electrolyte of the present invention includes a fluorinated solvent. Compared with traditional electrolyte solvents (carbonates or carboxylates), fluorinated solvents have better oxidation stability and are not easy to decompose. The fluorine element will chemically react with the copper atoms on the surface of the negative electrode current collector to form a stable fluorinated passivation layer. This passivation layer usually has high thermal stability and chemical stability, can be tightly attached to the surface of the negative electrode current collector, and give the groove at the pole ear a certain corrosion resistance, thereby alleviating the impact of structural designs such as grooves on battery performance, so that the cycle life and safety performance of the battery are effectively improved.

[0026] Furthermore, the mass content percentage of the fluorinated solvent in the electrolyte is m1%, 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 content percentage m1 of the fluorinated solvent in the electrolyte is too large, the fluorinated passivation layer generated on the surface of the negative electrode current collector will be too thick, which will hinder electron conduction and ion transport, and increase the internal resistance of the battery during charging and discharging. This will cause the battery to generate more heat during charging, thereby affecting the safety of the battery. Therefore, the mass content percentage 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 formed, the mass content percentage m1 of the fluorinated solvent in the electrolyte should not be too small, so as to avoid local overheating causing uneven temperature distribution inside the battery and weakened corrosion resistance, thereby further improving the safety performance of the battery's cycle life.

[0027] In one example, 10%≤m1%≤40%.

[0028] In the present invention, Figure 1 and Figure 2 As shown, Figure 2 This is a schematic diagram of the top structure of a negative electrode sheet provided in one embodiment of the present invention. Along the first direction of the negative electrode sheet, the length of the groove is L1, 5mm≤L1≤40mm, for example, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm or 40mm.

[0029] In one example, 10 mm ≤ L1 ≤ 30 mm.

[0030] In the present invention, Figure 2 As shown, along the second direction of the negative electrode sheet, the width of the groove is L2, 4mm≤L2≤30mm, for example, 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 28mm or 30mm.

[0031] In one example, 6 mm ≤ L2 ≤ 15 mm.

[0032] It can be understood that the first direction can refer to the width direction of the positive electrode sheet or the negative electrode sheet, the second direction can 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 the plane.

[0033] In the present invention, Figure 1 As shown, along the third direction of the negative electrode sheet, the depth of the groove is L3, 0.005mm≤L3≤0.15mm, for example, 0.005mm, 0.006mm, 0.007mm, 0.008mm, 0.009mm, 0.01mm, 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm or 0.15mm.

[0034] 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.

[0035] The groove on the negative electrode sheet needs to accommodate the positive electrode ear while accommodating the ear glue layer overflowing from the positive electrode ear and the overflow of the insulating glue layer set in the corresponding negative electrode area, so as to avoid uneven thickness at the ear. Therefore, its size in all directions should not be too small to obtain sufficient space to accommodate the overflow glue, but its size should not be too large, because when the size of the groove is too large, it will lead to excessive loss of the negative electrode active material layer, which will cause the battery capacity to decay and the impedance to increase, thereby affecting the overall performance of the battery.

[0036] In the present invention, Figure 1 and Figure 2 As shown, the orthographic projection area of ​​the groove 130 along the third direction of the negative electrode sheet is S mm 2 ,S mm 2 =L1*L2; the mass content percentage of the fluorinated solvent in the electrolyte is m1%; S and m1 satisfy m1≥S / 10.

[0037] Figure 2 This is a schematic diagram of the top view of the negative electrode sheet provided by one embodiment of the present invention. The positive projection of the groove is a rectangle. The area of ​​the rectangle can be obtained by the length × width of the rectangle mass content percentage, that is, S mm 2 =L1*L2.

[0038] When m1% of the fluorinated solvent in the electrolyte is equal to the projected area S of the groove (S mm 2=L1*L2) satisfies: when m1≥S / 10, the negative electrode sheet can better accommodate the insulating glue protruding from the tab and can store enough fluorinated solvent in the groove, which not only increases the liquid retention capacity of the negative electrode sheet, but also can be used to improve the corrosion resistance of the negative electrode sheet, thereby further improving the cycle life and thermal safety of the battery.

[0039] In the present invention, 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.

[0040] In one example, the fluorinated solvent includes at least one of ethyl methyl fluorinated carbonate, diethyl fluorinated carbonate, dimethyl fluorinated carbonate, ethyl fluorinated acetate, methyl fluorinated propionate, ethyl fluorinated propionate, propyl fluorinated propionate, 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 is understood that "fluorinated" can be monofluoro, difluoro, trifluoro, or the like, and the number of fluorinated substitutions is not limited, and the position of fluorinated substitutions is also not limited, and can be any substitutable position.

[0041] In the present invention, the electrolyte may further include electrolyte additives such as fluoroethylene carbonate and fluoropropylene carbonate.

[0042] In the present invention, the electrolyte may further include 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.

[0043] When unsaturated nitrile compounds are further added to the electrolyte containing fluorinated solvents, the combined use of fluorinated solvents and unsaturated nitrile compounds can reduce the interfacial side reactions between the electrolyte and the electrode, reduce the heat and gas generation inside the battery, and improve the thermal safety performance of the battery; specifically, the unsaturated nitrile compounds can form a protective layer on the electrode surface during the battery charging and discharging process. Compared with traditional nitrile compounds, unsaturated nitriles can undergo polymerization reactions. The polymerization reaction increases the reaction sites at the interface with the positive electrode, which can effectively prevent the shedding of the active material of the electrode and the decomposition of the electrolyte. In addition, the unsaturated nitrile compounds form a relatively stable solvation structure in the fluorinated solvent system, which can reduce the charge accumulation and ion agglomeration inside the battery, inhibit the side reactions inside the battery, and thus further improve the cycle stability and service life of the battery.

[0044] In one example, the mass content percentage of the unsaturated nitrile compound in the electrolyte is 0.1%-5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0045] In the present invention, Figure 1 As shown, the surface of the positive electrode tab 240 is provided with a tab glue layer 250. By providing the tab glue layer 250 on the surface of the positive electrode tab 240, a short circuit between the positive and negative electrodes can be prevented, but the dimensional design in each direction will affect the thickness flatness of the positive electrode tab. Although the grooves provided at the corresponding positions of the negative electrode sheet can improve this problem, if the volume of the tab glue layer exceeds the range that the grooves 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, 10mm≤a≤40mm, for example, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 25mm, 30mm, 35mm or 40mm. It should be noted that there may be a gap between the positive electrode tab and the positive active material layer along the third direction of the positive electrode sheet. Figure 1 The height difference shown in FIG. 1 is a diagram showing a height difference between the positive electrode sheet and the positive electrode sheet. However, the length a of the tab glue layer of the present invention only represents the length along the first direction of the positive electrode sheet.

[0046] In one example, 10 mm ≤ a ≤ 15 mm.

[0047] In the present invention, along the second direction of the positive electrode sheet, the width of the tab glue layer is b, 8mm≤b≤35mm, for example, 8mm, 9mm, 10mm, 11, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, 31mm, 32mm, 33mm, 34mm or 35mm.

[0048] In one example, 20 mm ≤ b ≤ 30 mm.

[0049] In the present invention, 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 , for example 150 mm 2 , 200 mm 2 , 250 mm 2 , 300 mm 2 , 350 mm2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 or 700 mm 2 .

[0050] In one embodiment, the positive projection area of ​​the tab glue layer along the third direction of the positive electrode sheet is 180 mm 2 -480 mm 2 .

[0051] If the area of ​​the ear glue layer covering the positive ear is too small, it may not be able to completely cover the positive ear, and there is a risk of short circuit; if the area of ​​the ear glue layer covering the positive ear is too large, the area of ​​the groove of the negative active material layer on the surface of the corresponding negative electrode sheet will be correspondingly expanded to avoid unevenness of the insulating glue at the ear. However, when the area of ​​the ear glue layer covering the positive ear is too large, the volume space inside the small area of ​​the groove is small and is not enough to accommodate the excessive overflow of the ear glue, so the area of ​​the groove needs to be increased accordingly. However, once the area of ​​the groove is increased, on the one hand, it will cause the loss of active material on the negative electrode side and reduce the energy density of the battery. On the other hand, it will also cause the corrodible area of ​​the negative electrode collector to increase, the corrosion of the negative electrode collector will be enhanced, and the cycle performance and thermal safety performance of the battery will be reduced. Therefore, the present invention can effectively improve the cycle stability of the battery by controlling the ear glue layer covering the ear to have a suitable area size, and can also avoid the risk of short circuit in the battery and improve the safety performance of the battery.

[0052] Furthermore, the fluorinated solvent has a good interaction with the tab glue layer, which can enhance the bonding performance between the tab glue layer and the positive electrode sheet, ensure the electrical conductivity and mechanical strength of the battery, thereby improving the overall performance of the battery and preventing risks such as short circuits and thermal runaway during the battery cycle. 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 and discharge efficiency of the battery; and good wettability and permeability help the fluorinated solvent better penetrate the surface of the tab glue layer, and can also enhance the bonding strength between the tab glue layer and the positive electrode current collector. This can not only improve the use effect of the tab glue layer, but may also reduce the safety issues of the battery caused by insufficient bonding strength to a certain extent.

[0053] In the present invention, 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%, and m1 and m2 satisfy m1≥m2.

[0054] In one example, based on the total mass of the negative electrode active material layer, the mass content of silicon element in the negative electrode active material layer is m2%, 2%≤m2%≤40%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35% or 40%.

[0055] In one example, 15%≤m2%≤30%.

[0056] When the mass content percentage m1 of the fluorinated solvent in the electrolyte is greater than the mass content m2 of the silicon element in the negative electrode active material layer, the fluorinated solvent helps to form a more stable solid electrolyte interface (SEI) film, reduces the decomposition of the electrolyte on the silicon negative electrode side, thereby effectively improving the cycle life of the battery, and at the same time can alleviate the mechanical stress caused by the silicon-based material contained in the negative electrode active material layer, reduce the possibility of rupture of the negative electrode active material layer material, thereby extending the cycle life of the battery and improving battery performance.

[0057] In the present invention, the particle size Dv50 of the silicon-based material is 5 μm-15 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0058] In one embodiment, the particle size Dv50 of the silicon-based material is 6 μm-10 μm.

[0059] In the present invention, the average sphericity q of the silicon-based material particles is 0.5-1, for example, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

[0060] In one example, the average sphericity q of the silicon-based material particles is 0.7-1.

[0061] Fluorinated solvents have low surface tension. By controlling the particle size Dv50 of the silicon-based material and the average sphericity q of the silicon-based material particles, the fluorinated solvents can better infiltrate the surface of the silicon negative electrode. The low surface tension of the outer layer makes it easier for the solvent molecules to spread on the surface of the silicon negative electrode, forming a uniform covering layer, reducing the interface resistance between the silicon negative electrode and the electrolyte, and helping to improve the transmission efficiency of lithium ions, thereby effectively improving the ionic conductivity of the negative electrode sheet, alleviating the volume change of the negative electrode sheet, and thus improving the cycle stability of the battery.

[0062] In the present invention, the negative electrode active material layer includes a primer layer close to the negative electrode current collector and a surface layer located on the surface of the primer layer away from the negative electrode current collector. The surface density s1 of the primer layer is greater than the surface density s2 of the surface layer.

[0063] Since setting grooves on the electrode inevitably leads to some capacity loss, coating the negative electrode active material layer with a double-layer coating technology can well compensate for this, so that the surface coating has a relatively high porosity structure and a small surface density s2, and the lower bottom coating has a relatively high compaction density structure and a large surface density s1, so that the density of the negative electrode active material in the negative electrode active material layer is distributed in a gradient, which can increase the energy density of the battery and improve the battery's ability to store electrical energy, thereby taking into account both high energy density and super fast charging performance.

[0064] 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 .

[0065] In one example, 1 mg / cm 2 ≤s1≤3 mg / cm 2 .

[0066] 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 .

[0067] In one example, 0.5 mg / cm 2 ≤s2≤2 mg / cm 2 .

[0068] In the present invention, the ratio of the surface density s1 of the primer layer to the surface density s2 of the topcoat layer is M, 1≤M≤2.5, for example, 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.

[0069] In one example, 1≤M≤1.5.

[0070] In the present invention, the thickness of the primer layer is 0.02 mm to 0.08 mm, for example, 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.

[0071] In one example, the thickness of the primer layer is 0.025 mm to 0.08 mm.

[0072] In the present invention, the thickness of the topcoat layer is 0.015 mm to 0.07 mm, for example, 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.

[0073] In one example, the thickness of the topcoat layer is 0.02 mm to 0.07 mm.

[0074] According to the battery of the present invention, the lithium-ion battery further comprises a separator, which may be a separator conventionally used in the art, such as a PP film, a PE film, and the like.

[0075] According to the battery of the present invention, the positive electrode active material layer includes a layered lithium composite oxide, the chemical formula of which 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.

[0076] For the battery according to the present invention, the negative electrode active material layer comprises a carbon-based negative electrode material, where the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon.

[0077] For the battery according to the present invention, the negative electrode active material layer comprises 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.

[0078] 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.

[0079] 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.

[0080] The battery of the present invention can be prepared by conventional methods in the art. Specifically, stack the positive electrode sheet, separator, and negative electrode sheet in sequence, ensure that the separator is between the positive and negative electrode sheets to play an isolation role, and then obtain an un-injected bare battery cell by winding; place the bare battery cell in an outer packaging foil, inject the electrolyte into the dried bare battery cell, and obtain the required lithium-ion battery through processes such as vacuum packaging, standing, forming, shaping, and sorting.

[0081] 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.

[0082] The present invention does not limit the types of electronic devices, and specifically includes but is not limited to laptop computers, input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0083] The present invention will be described in further detail below with reference to specific examples. It should be understood that the following examples are merely illustrative and explanations 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 encompassed within the scope of protection that the present invention is intended to protect.

[0084] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0085] Example 1

[0086] The lithium ion battery of the present invention is obtained by the following method:

[0087] 1) Cathode sheet preparation

[0088] The positive electrode active materials lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), SP (super P) and carbon nanotubes (CNT) are mixed in a mass ratio of 96:2:1.5:0.5, N-methylpyrrolidone (NMP) is added, and the mixture is stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode active slurry with uniform fluidity; the positive electrode active slurry is evenly coated on both surfaces of the aluminum foil; the coated aluminum foil is dried, and then rolled and cut to obtain the required positive electrode sheet, and then the tab groove on the surface of the positive electrode sheet is reserved by laser cleaning, the positive tab is welded in the tab groove, and the tab glue is coated on the surface of the positive tab, the length a of the tab glue layer is 12 mm, the width b is 24 mm, and the projection area of ​​the tab glue layer along the third direction of the positive electrode sheet is 288 mm 2 .

[0089] 2) Negative electrode preparation

[0090] The negative electrode active materials, artificial graphite, silicon carbon (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) were mixed in a mass ratio of 40:54.5:2.5:1.5:1:0.5, and deionized water was added to obtain a negative electrode active slurry 1 under the action of a vacuum mixer;

[0091] The negative electrode active materials, artificial graphite, silicon carbon (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) were mixed in a mass ratio of 54.5:40.5:1.5:1:0.5, and deionized water was added to obtain negative electrode active slurry 2 under the action of a vacuum mixer;

[0092] The negative electrode active slurry 1 and the negative electrode active slurry 2 were evenly coated on the two surfaces of the copper foil. The negative electrode active slurry 1 was used as the primer coating and the negative electrode active slurry 2 was used as the top coating. The thickness of the primer coating was 0.03 mm and the thickness of the top coating was 0.022 mm. The coated copper foil was dried at room temperature and then transferred to an 80°C oven for drying for 10 hours. The negative electrode sheet was then cold pressed and cut to obtain a negative electrode sheet with a thickness of 100 μm. The grooves on the surface of the negative electrode sheet were then reserved by laser cleaning. The dimensions of the grooves were as follows: L1 = 15 mm, L2 = 10 mm, and the groove depth L3 = 0.05 mm. In addition, the mass content of silicon element in the negative electrode active material layer was measured to be m2% = 25%, and the surface density of the primer coating was s1 = 2.3 mg / cm 2 , the density of the surface coating s2 = 1.74 mg / cm 2 , M=s1 / s2=1.32.

[0093] 3) Preparation of electrolyte

[0094] In an argon-filled glove box (H2O<0.1ppm, O2<0.1ppm), the solvents EC / PC / PP / difluoroethyl acetate (the fluorinated solvent is difluoroethyl acetate in fluoroethyl acetate) are mixed in a ratio of 1 / 1 / 2 / 3, and the mass content of difluoroethyl acetate in the electrolyte is m1%=30%. Then, 12.5wt% of fully dried lithium hexafluorophosphate (LiPF6) based on the total mass of the electrolyte is quickly added thereto, followed by 0.5wt% of 1,4-dicyano-2-butene based on the total mass of the electrolyte, and other additives such as 2wt% of 1,3,5-hexanetrionitrile (HTCN), 1wt% of adiponitrile (ADN), 4wt% of 1,3-propane sultone and 10wt% of fluoroethylene carbonate additives are added. After stirring evenly, the desired electrolyte is obtained after passing the moisture and free acid tests.

[0095] 4) Preparation of lithium-ion batteries

[0096] 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 form a battery cell. The battery cell is placed in an outer aluminum foil package, and the electrolyte from step 3) is injected into the outer packaging. After vacuum packaging, standing, forming, shaping, and sorting, a lithium-ion battery is obtained. The battery of the present invention has a charge and discharge range of 3.0-4.58V.

[0097] Example 2 group

[0098] This example is carried out with reference to Example 1, with the only difference being 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, or the type of the fluorinated solvent is changed at the same time. The type of the fluorinated solvent in Examples 2-1 and 2-3 remains unchanged, fluorobenzene is selected as the fluorinated solvent in Example 2-2, and difluoroethyl acetate and fluoroether (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) mixed in equal proportions are selected as the fluorinated solvent in Example 2-4. See Table 1 for details.

[0099] Example 3 group

[0100] This embodiment is carried out with reference to the embodiment 1, with the only difference being that, during the preparation of the negative electrode sheet, the size of the groove is changed by changing the laser cleaning parameters, as shown in Table 1.

[0101] Example 4 Group

[0102] This embodiment is carried out with reference to the embodiment 1, with the only difference being that, during the preparation of the negative electrode sheet, the mass content of silicon element m2% 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:

[0103] In Example 4-1, the mass content of silicon in the negative electrode active material layer is m2%=15%, the particle size Dv50=5 μm, and the average sphericity q=0.75;

[0104] In Example 4-2, the mass content of silicon in the negative electrode active material layer is m2%=30%, the particle size Dv50=15 μm, and the average sphericity q=1;

[0105] In Example 4-3, the mass content of silicon in the negative electrode active material layer is m2%=40%, the particle size Dv50=8 μm, and the average sphericity q=0.5;

[0106] See Table 1 for details.

[0107] Example 5

[0108] This embodiment is carried out with reference to the embodiment 1, the only difference being that the surface density of the primer layer and the top layer is changed, or the thickness of the primer layer and the top layer is changed simultaneously, specifically:

[0109] In Example 5-1, the negative electrode active material layer does not distinguish between the undercoat layer and the topcoat layer. The negative electrode active slurry adopts the negative electrode active slurry 1. The thickness and surface density of the undercoat layer and the topcoat layer remain unchanged, and the surface density is 2.3 mg / cm 2 ;

[0110] In Example 5-2, by changing the coating process of the negative electrode active material layer or the production process of the negative electrode sheet, the surface density and thickness of the base coat and the surface coat are changed. The thickness of the base coat is 0.08 mm, the thickness of the surface coat is 0.015 mm, and the surface density of the base coat is s1 = 0.5 mg / cm 2 , the density of the surface coating is s2=3mg / cm 2 ;

[0111] In Example 5-3, by changing the coating process of the negative electrode active material layer or the preparation process of the negative electrode sheet, the surface density and thickness of the base coat and the surface coat are changed. The thickness of the base coat is 0.02 mm, the thickness of the surface coat is 0.07 mm, and the surface density of the base coat is s1 = 5 mg / cm 2 , the density of the surface coating s2 = 0.2 mg / cm 2 ;

[0112] See Table 1 for details.

[0113] Example 6

[0114] This example is carried out with reference to Example 1, except 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:

[0115] In Example 6-1, the mass content percentage of 1,4-dicyano-2-butene is 0, and the unsaturated nitrile compound is not added;

[0116] The mass percentage of 1,4-dicyano-2-butene in Example 6-2 is 0.1;

[0117] The mass percentage of 1,4-dicyano-2-butene in Example 6-3 is 2;

[0118] The mass percentage of 1,4-dicyano-2-butene in Example 6-4 is 5;

[0119] See Table 1 for details.

[0120] Comparative Example 1

[0121] This comparative example was carried out with reference to Example 1, with the only difference being that, during the preparation of the electrolyte, the mass ratio of each solvent component was changed, so that the mass content percentage m1% of the fluorinated solvent in the electrolyte was changed, as shown in Table 1 for details.

[0122] Comparative Example 2

[0123] This comparative example was carried out with reference to Example 1, with the only difference being that no fluorinated solvent was added during the preparation of the electrolyte, as shown in Table 1.

[0124] Comparative Example 3

[0125] This comparative example was carried out with reference to Example 1, with the only difference being that, during the preparation of the negative electrode sheet, no groove corresponding to the tab groove was provided, as shown in Table 1 for details.

[0126] Table 1

[0127]

[0128] Test Case

[0129] 1) Cyclic performance test

[0130] The lithium-ion batteries obtained in the above examples and comparative examples were subjected to charge and discharge cycles at 25°C at a discharge rate of 2C within the charge and discharge cut-off voltage range. The discharge capacity in the first week of the test was calculated as x1mAh, and the discharge capacity in the Nth cycle was calculated as y1mAh. The capacity in the Nth week was divided by the capacity in the first week to obtain the cycle capacity retention rate R1=y1 / x1 in the Nth week. The number of battery cycles / T when the cycle capacity retention rate R1 was 80% was recorded, and the results were recorded in Table 2.

[0131] 2) Safety performance testing

[0132] The lithium-ion batteries obtained in the above examples and comparative examples were discharged at 0.2C to a lower voltage of 3.0V at 25°C. After standing for 10 minutes, they were charged at 1C to an upper voltage of 4.55V with a cutoff current of 0.05C. At this point, the lithium-ion batteries were fully charged. The fully-charged lithium-ion batteries were then placed in an oven, and the temperature in the oven was increased at a heating rate of 5°C / min. After the temperature in the oven reached 132°C, the temperature was maintained constant for 60 minutes. The lithium-ion batteries were observed to see if they caught fire or exploded. If no fire or explosion occurred, they were considered to have passed the test. A total of 10 tests were performed, and the test results are recorded in Table 2.

[0133] Table 2

[0134]

[0135] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection 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 of the 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 of the surface of the positive electrode current collector; The positive electrode active material layer is provided with a tab groove, the positive electrode tab is accommodated in the tab groove, and the surface of the positive electrode tab is provided with a tab glue layer; The negative electrode active material layer is provided with a groove, the tab groove and the groove are arranged opposite to each other along the third direction of the positive electrode sheet, an insulating rubber layer is provided in the groove, and the third direction of the positive electrode sheet is the thickness direction of the positive electrode sheet; The electrolyte includes a fluorinated solvent, the mass content of the fluorinated solvent in the electrolyte is m1%, 10%≤m1%≤40%; the fluorinated solvent includes ethyl fluoride; the fluorinated solvent forms a fluorinated passivation layer on the surface of the current collector in the groove; The positive projection area of ​​the groove along the third direction of the negative electrode sheet is S; S and m1 satisfy m1≥S / 10, where Smm 2 =L1*L2; along the first direction of the negative electrode sheet, the length of the groove is L1, 5mm≤L1≤40mm; along the second direction of the negative electrode sheet, the width of the groove is L2, 4mm≤L2≤30mm; wherein, the first direction of the negative electrode sheet is the width direction of the negative electrode sheet, the second direction of the negative electrode sheet is the length direction of the negative electrode sheet, and the third direction of the negative electrode sheet is the thickness direction of the negative electrode sheet.

2. The battery according to claim 1, characterized in that 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 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%.

4. 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 the first direction of the positive electrode sheet is the width direction of the positive electrode sheet.

5. The battery according to claim 1, characterized in that Along the second direction of the positive electrode sheet, the width of the tab glue layer is b, 8mm≤b≤35mm, and the second direction of the positive electrode sheet is the length direction of the positive electrode sheet.

6. The battery according to claim 1, characterized in that 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 a silicon-based material. 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%, and 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 facing 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 areal density s1 of the primer layer and the areal density s2 of the topcoat layer 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 to 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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