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, a positive active material layer of the positive plate is provided with a tab groove, a positive tab is accommodated in the tab groove, and the surface of the positive tab is provided with first adhesive paper; a groove is formed in a negative active material layer of the negative plate, the tab groove and the groove are oppositely arranged in the thickness direction of the positive plate, second adhesive paper is arranged in the groove, and the orthographic projection area of the second adhesive paper in the thickness direction of the positive plate is S; the electrolyte comprises ethylene carbonate, fluoroethylene carbonate and 1, 3-propane sultone, the sum of the mass content percentage of the ethylene carbonate and the fluoroethylene carbonate in the electrolyte is w1, and the mass content percentage of the 1, 3-propane sultone in the electrolyte is w2; wherein S and w1 satisfy 0.5 < = w1 / S < = 25. According to the battery disclosed by the invention, excellent high-temperature cycling stability of the lithium battery can be ensured, and meanwhile, better battery safety performance can be met.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and more particularly to a battery and an electronic device including the battery. Background Technology

[0002] In conventional batteries, to prevent short circuits and improve safety, the positive electrode tab is covered with adhesive tape, and the corresponding negative electrode area is covered with insulating tape. However, because the positive electrode tab has both a tab and adhesive tape, and the corresponding negative electrode has insulating tape, this area is thicker than other areas. This affects the battery's consistency, causing unevenness on the electrodes, and ultimately impacting the battery's cycle stability and safety performance.

[0003] Currently, to reduce the impact of the tab adhesive and insulating tape on the overall thickness of the electrode sheet during battery design, a common approach is to pre-define a groove in the negative electrode area corresponding to the positive tab to address uneven thickness. This groove can accommodate excess tab adhesive and insulating tape, improving battery consistency. However, through practical verification, the inventors discovered that when this technology is applied to batteries operating in high-temperature / high-voltage environments, it easily causes the battery to bulge and deform. This is especially true for batteries that incorporate silicon-based materials into the negative electrode system to meet high energy density design requirements, leading to significant volume expansion and deformation. Furthermore, the large amount of gas generated inside the battery can concentrate in a specific area, such as the insulating tape area, causing the tape to detach and potentially triggering a series of battery safety issues.

[0004] Therefore, in order to solve the problems of high-temperature cycle stability and battery safety performance of high-voltage batteries, it is urgent to develop a new type of battery. Summary of the Invention

[0005] In view of the above problems, the present invention provides a battery and an electronic device including the battery. The battery of the present invention can ensure excellent high-voltage battery high-temperature cycle stability performance, and at the same time, it can prevent the insulating tape from falling off, thus meeting the requirements of superior battery safety performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention provides a battery comprising a negative electrode, a positive electrode, and an electrolyte, wherein the negative electrode comprises a negative current collector and a negative active material layer located on at least one side surface of the negative current collector, the negative active material layer comprising a silicon-based material, and the positive electrode comprises a positive current collector and a positive active material layer located on at least one side surface of the positive current collector.

[0008] A tab groove is provided on the positive electrode active material layer, a positive electrode tab is accommodated in the tab groove, and a first adhesive paper is provided on the surface of the positive electrode tab;

[0009] A groove is formed on the negative electrode active material layer. The tab groove is positioned opposite to the groove along the thickness direction of the positive electrode sheet. A second adhesive tape is placed in the groove. The total area of ​​the second adhesive tape projected along the thickness direction of the positive electrode sheet is S = 1 cm². 2 ≤S cm 2 ≤10cm 2 ;

[0010] The electrolyte comprises ethylene carbonate, fluoroethylene carbonate, and 1,3-propanesulfonyl lactone. The sum of the mass percentages of ethylene carbonate and fluoroethylene carbonate in the electrolyte is w1, 3% ≤ w1% ≤ 40%, and the mass percentage of 1,3-propanesulfonyl lactone in the electrolyte is w2, 0.5% ≤ w2% ≤ 6%.

[0011] Wherein, S and w1 satisfy 0.5≤w1 / S≤25.

[0012] A second aspect of the present invention provides an electronic device comprising the battery described in the first aspect of the present invention.

[0013] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0014] After the groove is formed at the negative electrode, the silicon-based material in the groove area will partially crack and be damaged, leading to violent side reactions and gas production. When a large amount of gas accumulates at the groove, a high-pressure zone is easily formed (because the adhesive tape blocks the gas diffusion path), causing the adhesive tape to be squeezed and deformed. In addition, the high temperature (50-90℃ during formation) softens the adhesive layer, reduces its compressive strength, and accelerates gas penetration, ultimately causing the adhesive tape to detach. Further research by the inventors of this invention revealed that the gas concentrated at the groove is mainly generated by fluoroethylene carbonate (FEC) and ethylene carbonate (EC). Therefore, this invention reduces the total amount of FEC and EC in the electrolyte and controls the total amount w1 of FEC and EC relative to the positive charge of the first adhesive tape. The shadow area S, satisfying 0.5≤w1 / S≤25, can effectively reduce electrolyte gas production and simultaneously improve the compressive strength of the adhesive tape, thereby inhibiting the deformation and detachment of the adhesive tape, slowing down battery expansion, reducing the risk of battery thermal runaway, and ensuring excellent high-voltage battery high-temperature cycle stability, thus improving battery safety performance. Moreover, the synergistic addition of 1,3-propanesulfonyl lactone (PS) to the electrolyte of this invention can inhibit EC / FEC decomposition, reduce the total amount of gas in the late stage of high-temperature cycling during the formation stage, thereby further reducing the expansion stress on the adhesive tape. In addition, PS can enhance the mechanical strength of the negative electrode SEI film and reduce the consumption of active lithium caused by SEI rupture at high temperatures, thereby further improving the high-temperature cycle performance and battery safety performance of the battery.

[0015] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-sectional structure of the positive electrode and the negative electrode provided in an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the cross-sectional structure of the groove of the negative electrode sheet provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures:

[0019] Negative electrode 100, negative electrode current collector 110, negative electrode active material layer 120, groove 130, first groove 131, second groove 132, positive electrode 200, positive electrode current collector 210, positive electrode active material layer 220, tab groove 230, positive electrode tab 240, first adhesive tape 250, second adhesive tape 300, third sub-adhesive tape 310, fourth sub-adhesive tape 320. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] It should be noted that the numerical designations such as "first" and "second" in this disclosure are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0022] 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, 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 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.

[0023] A first aspect of the present invention provides a battery comprising a negative electrode, a positive electrode, and an electrolyte, wherein the negative electrode comprises a negative current collector and a negative active material layer located on at least one side surface of the negative current collector, the negative active material layer comprising a silicon-based material, and the positive electrode comprises a positive current collector and a positive active material layer located on at least one side surface of the positive current collector.

[0024] A tab groove is provided on the positive electrode active material layer, a positive electrode tab is accommodated in the tab groove, and a first adhesive paper is provided on the surface of the positive electrode tab;

[0025] A groove is formed on the negative electrode active material layer. The tab groove is positioned opposite to the groove along the thickness direction of the positive electrode sheet. A second adhesive tape is placed in the groove. The total area of ​​the second adhesive tape projected along the thickness direction of the positive electrode sheet is S = 1 cm². 2 ≤S cm 2 ≤10cm 2 ;

[0026] The electrolyte comprises ethylene carbonate, fluoroethylene carbonate, and 1,3-propanesulfonyl lactone. The sum of the mass percentages of ethylene carbonate and fluoroethylene carbonate in the electrolyte is w1, 3% ≤ w1% ≤ 40%, and the mass percentage of 1,3-propanesulfonyl lactone in the electrolyte is w2, 0.5% ≤ w2% ≤ 6%.

[0027] Wherein, S and w1 satisfy 0.5≤w1 / S≤25.

[0028] like Figure 1 The diagram shows a cross-sectional view of a positive electrode and a negative electrode according to an embodiment of the present invention. The negative electrode 100 includes a negative current collector 110 and a negative active material layer 120 located on at least one side of the negative current collector 110. The positive electrode 200 includes a positive current collector 210 and a positive active material layer 220 located on at least one side of the positive current collector 210. A tab groove 230 is provided on the positive active material layer 220, and a positive tab 240 is accommodated in the tab groove 230. A first adhesive tape 250 is provided on the surface of the positive tab. A groove 130 is provided on the negative active material layer 120. The tab groove 230 and the groove 130 are arranged opposite to each other along the thickness direction of the positive electrode 200. A second adhesive tape 300 is provided in the groove 130, and the orthogonal projection area of ​​the second adhesive tape 300 along the thickness direction of the positive electrode is S, 1 cm². 2 ≤Scm 2 ≤10cm 2 For example, 1cm 2 1.1cm 2 1.2cm 2 1.3cm 2 1.4cm 2 1.5cm 2 1.6cm 2 1.7cm 2 1.8cm 2 1.9cm 2 2cm 2 2.1cm 2 2.2cm 2 2.3cm 2 2.4cm 2 2.5cm 2 2.6cm 2 2.7cm 2 2.8cm 2 2.9cm 2 3cm 2 Or it may fall within the range of any two of the above values. In the electrode assembly formed by winding or stacking positive electrode plates, negative electrode plates, and a separator, the tab groove and the recess are disposed on the active material layer between adjacent positive and negative electrode plates, such as... Figure 1In this design, the negative electrode sheet 100 located at the top along the thickness direction has a groove 130 only on the side of the negative electrode active material layer adjacent to the tab groove 230. Similarly, the negative electrode sheet 100 located at the bottom along the thickness direction also has a groove 130 only on the side of the negative electrode active material layer adjacent to the tab groove 230. The projected area of ​​the tab groove 230 overlapping with the groove 130 is greater than 80% of the projected area of ​​the tab groove 230, or the projected area of ​​the tab groove overlapping with the groove is 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%, 100%, or within any two of the above values. Furthermore, the thickness direction represents the thickness direction of the positive electrode sheet, and can also refer to the thickness direction of the negative electrode sheet or the battery cell. "Relatively arranged along the thickness direction of the positive electrode sheet" means that they are arranged relative to each other along the thickness direction of the positive electrode sheet, the negative electrode sheet, or the battery cell. Figure 1 As shown.

[0029] Further, the electrolyte of the present invention comprises ethylene carbonate (EC), fluoroethylene carbonate (FEC), and 1,3-propane sulpholactone (PS), wherein the sum of the mass percentages of the ethylene carbonate and the fluoroethylene carbonate in the electrolyte is w1, 3% ≤ w1% ≤ 40%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, etc. The 1,3-propanesulfonyl lactone in the electrolyte contains 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or within any two of the above values, and the mass percentage of w2 is 0.5% ≤ w2% ≤ 6%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%. %, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5. 2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, or within the range of any two of the above values; wherein, S and w1 satisfy 0.5≤w1 / S≤25, for example, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or within the range of any two of the above values.

[0030] This invention addresses the issue of uneven electrode thickness by creating grooves on the negative electrode active material layer on one side of the positive electrode tab groove, with the grooves opposite to the tab grooves. This reduces the impact of tab adhesive and insulating adhesive layers at the tabs on the overall thickness uniformity of the electrodes, thus improving the uniformity of electrode thickness and consequently enhancing the cycle performance and safety of the battery. However, when this technology is applied to batteries operating in extreme high-temperature / high-voltage environments, it can easily cause bulging and deformation of the battery appearance. This is especially true for batteries that incorporate silicon-based materials into the negative electrode system to meet high energy density design requirements, which can lead to large-scale volume expansion and deformation. Furthermore, the large amount of gas generated inside the battery can concentrate in a certain area, such as the insulating adhesive area, causing the adhesive to detach and potentially triggering a series of battery safety issues.

[0031] The inventors of this invention discovered that the aforementioned problems are primarily caused by the fact that the active material layer in the grooves obtained through laser cleaning or chemical cleaning of the negative electrode active material layer will suffer some degree of damage and numerous defects. This easily leads to an increase in electrolyte side reactions, resulting in the generation of a large amount of gas components during the formation stage or later stages of cycling. Consequently, this causes the battery to bulge and deform, and this situation is exacerbated in silicon-doped negative electrode systems. Furthermore, when gas accumulates in the grooves, it easily forms a high-pressure area (because the adhesive tape blocks the gas diffusion path), causing the adhesive tape to be squeezed and expand and deform. In addition, the high temperature (50-90°C during formation) softens the adhesive layer, reduces its compressive strength, accelerates gas penetration, and ultimately causes the adhesive tape to detach. The detachment of the adhesive tape will not be able to prevent metal burrs from piercing the separator, leading to a short circuit between the positive and negative electrodes, thus affecting the battery's safety performance.

[0032] The inventors of this invention further discovered that the gas concentrated in the groove is mainly generated by FEC and EC. At high temperatures, EC generates C2H4 (characteristic gas) and CO2 during negative electrode reduction, accompanied by H2 (moisture impurity reaction). FEC reduction generates HF and CO2. When these two gases generated by electrolyte solvents accumulate in the groove, the adhesive tape is easily squeezed and falls off, affecting the battery's safety performance. Moreover, when a large amount of gas is generated, the battery volume expands more rapidly, which leads to a decrease in the high-temperature cycle stability of the battery under high voltage and high temperature conditions, which does not meet the development requirements of high-temperature and high-energy-density battery technology. Based on this, the present invention reduces the total amount of FEC and EC in the electrolyte. The sum of the mass percentages of the ethylene carbonate and the fluoroethylene carbonate in the electrolyte is w1, where 3% ≤ w1% ≤ 40%. Reducing w1 can effectively reduce the side reaction gas production of the electrolyte. By controlling the total amount of FEC and EC w1 and the projected area S of the first adhesive paper to satisfy 0.5 ≤ w1 / S ≤ 25, the invention can effectively reduce the gas production caused by the decomposition of EC and FEC while enhancing the adhesive paper's resistance to gas pressure. This suppresses the deformation and detachment of the adhesive paper at the groove, reduces the risk of battery expansion and thermal runaway, and ensures excellent high-voltage battery high-temperature cycle stability, thereby improving battery safety performance.

[0033] When w1 / S < 0.5 (i.e., w1 is too small relative to S or S is too large): If w1 is too small relative to S, firstly, the decrease in w1 will lead to a decrease in the amount of gas produced by the electrolyte, because a decrease in w1 means a decrease in the total amount of EC and FEC, which directly reduces the gas production source (the decomposition reaction of EC and FEC is weakened). However, the decrease in the total amount of EC and FEC will also lead to insufficient electrolyte solvent, which will lead to incomplete internal reaction of the battery, making the electrolyte lack sufficient solvent to support the formation of a stable SEI film, and indirectly increasing other side reactions (such as the reaction of water impurities to generate H2), thus partially offsetting the benefits of reduced gas production source. It will still cause some reactive gas to accumulate in the groove, and the problem of the adhesive tape deforming and falling off in the groove will still exist.

[0034] The risk of thermal runaway in batteries is detrimental to the high-temperature cycle stability and safety performance of high-voltage batteries.

[0035] When w1 / S > 25 (i.e., w1 is too large relative to S or S is too small): When w1 is too large relative to S, the gas production increases significantly, directly aggravating the side reactions of the electrolyte. Moreover, EC and FEC decompose more violently at high temperatures, generating more gases (C2H4, CO2, HF, and H2), especially in the groove (where the active material is damaged, defects are more numerous, and side reactions are more likely to occur). At this time, when w1 is too large relative to S, the gas generation rate and total amount increase, causing gas to accumulate faster in the groove, forming a higher local pressure (high-pressure zone). The compressive strength of the adhesive paper is too small to resist this pressure. Under high-temperature conditions, the adhesive layer will be further softened, reducing its compressive strength, making it easier for gas to cause the adhesive paper to expand and deform. When S is too small, the compressive strength of the adhesive paper will be significantly reduced. When the adhesive paper is not strong enough, even if a small amount of gas accumulates in the groove, it is easy to form a local high-pressure zone, causing the adhesive paper to deform. Gas may penetrate the adhesive paper more quickly, causing local expansion.

[0036] Therefore, by controlling the ratio range of the total amount of FEC and EC w1 to the projected area S of the first adhesive paper, it is possible to effectively reduce the gas production caused by the decomposition of EC and FEC while enhancing the adhesive paper's resistance to gas pressure. This suppresses the deformation and detachment of the adhesive paper at the groove, reduces the risk of battery expansion and thermal runaway, and thus ensures excellent high-voltage battery high-temperature cycle stability and improves battery safety performance.

[0037] In addition, it should be noted that the total projected area S of the second adhesive tape along the thickness direction of the positive electrode sheet can be obtained by conventional testing methods in the field. After discharging the battery to 0% SOC, the negative electrode sheet is disassembled and removed. The negative electrode active coating of the negative electrode sheet is photographed from the thickness direction of the positive electrode sheet. The projected area S of the second adhesive tape can be obtained by analyzing the image with software.

[0038] Since the tab grooves of the positive electrode plate may be simultaneously formed on both sides of the positive electrode current collector and the positive electrode active material layer, the number N of the second adhesive strips may not be equal to 1, such as... Figure 1 In the case shown, there are two second adhesive strips, located on both sides of the positive electrode tab groove along the thickness direction. It should be noted that if there are multiple second adhesive strips, then the projected area S of the second adhesive strips represents the sum of the projected areas of the multiple second adhesive strips at different locations.

[0039] Furthermore, the synergistic addition of 1,3-propanesulfonyl lactone (PS) to the electrolyte of this invention can inhibit EC / FEC decomposition and reduce the total amount of gas generated during the high-temperature cycling phase of the battery formation stage. Specifically, PS preferentially reduces EC / FEC on the negative electrode surface, forming a stable SEI film containing sulfonic acid groups, blocking direct contact between EC / FEC and the electrode, thereby reducing gas generation from reduction and decomposition, and further alleviating the expansion stress on the adhesive tape. Moreover, PS can enhance the mechanical strength of the negative electrode SEI film, reducing the consumption of active lithium caused by SEI rupture at high temperatures. Furthermore, the PS-induced SEI film has a nanoscale layered structure with a higher elastic modulus than traditional SEI films, effectively buffering the stress caused by electrode volume changes and reducing the reduction and gas generation of EC / FEC at the negative electrode due to SEI film damage. In summary, the addition of PS can effectively reduce the gas generation from negative electrode side reactions in the electrolyte, alleviating the deformation and detachment of the adhesive tape at the groove from the source, mitigating battery expansion, reducing the risk of thermal runaway, thereby ensuring excellent high-voltage battery high-temperature cycling stability and improving battery safety performance.

[0040] In one example, 2.5cm 2 ≤S cm 2 ≤8cm 2 .

[0041] In one instance, 8% ≤ w1% ≤ 30%.

[0042] In one instance, 1% ≤ w2% ≤ 5%.

[0043] In one instance, S and w1 satisfy 1.5 ≤ w1 / S ≤ 18.

[0044] In one example, an empty foil area exists in the groove. It should be noted that the adhesion strength between the second adhesive tape and the negative electrode active material layer is lower than the adhesion strength between the second adhesive tape and the negative electrode current collector. By controlling the presence of an empty foil area (exposing the negative electrode current collector) in the groove, this invention can improve the adhesion strength between the second adhesive tape and the negative electrode foil, better fix the adhesive tape to the electrode surface, prevent it from falling off, and further improve the safety of the battery.

[0045] In one instance, such as Figure 2 As shown, Figure 2This is a schematic cross-sectional view of the groove in a negative electrode sheet according to an embodiment of the present invention. The groove 130 is divided into a first region and a second region along the thickness direction of the positive electrode sheet (the thickness direction of the positive electrode sheet is the same as that of the negative electrode sheet). In the first region, the surface of the negative electrode current collector 110 is provided with the negative electrode active material layer 120. In the second region, the bare negative electrode current collector 110 is exposed. It can be understood that a portion of the negative electrode active material layer will remain in a certain area within the groove. This type of area can be called the coating residue area, i.e., the first region. In another part of the area, the negative electrode active material is completely removed, directly exposing the negative electrode current collector inside the negative electrode active material layer. This part of the area can be called the empty foil area, i.e., the second region.

[0046] In one example, the projected area of ​​the second region along the thickness direction of the positive electrode sheet is 0.1 cm². 2 -2.5cm 2 For example, 0.1cm 2 0.2cm 2 0.3cm 2 0.4cm 2 0.5cm 2 0.6cm 2 0.7cm 2 0.8cm 2 0.9cm 2 1.0cm 2 1.1cm 2 1.2cm 2 1.3cm 2 1.4cm 2 1.5cm 2 1.6cm 2 1.7cm 2 1.8cm 2 1.9cm 2 2.0cm 2 2.1cm 2 2.2cm 2 2.3cm 2 2.4cm 2 2.5cm 2Or it may fall within the range of any two of the above values. Since the adhesive tape bonded more tightly to the metal foil than to the active material layer, and the amount of residual negative electrode active material in the groove is reduced, it helps to reduce gas generation in the groove area. Therefore, by adjusting the orthogonal projection area of ​​the second region within a suitable range, the adhesive strength of the tape can be improved, allowing the tape to be better fixed to the electrode surface, improving battery safety; and reducing gas generation in the groove, thus reducing the possibility of tape deformation and detachment. The method for measuring the orthogonal projection area of ​​the second region along the thickness direction of the positive electrode sheet can refer to the method for measuring the total orthogonal projection area S of the second adhesive tape. After discharging the battery to 0% SOC, disassemble and remove the negative electrode sheet. Take a picture of the negative electrode active coating of the negative electrode sheet from the thickness direction of the positive electrode sheet. Analyze the image using software to obtain the orthogonal projection area of ​​the second region where the negative electrode current collector foil protrudes from the groove. Furthermore, it should be noted that the orthogonal projection area of ​​the second region along the thickness direction of the positive electrode sheet refers to the orthogonal projection area of ​​the second region along the thickness direction of the positive electrode sheet in a single groove.

[0047] In one instance, such as Figure 1 As shown, the groove 130 includes a first groove 131 and a second groove 132. The first groove 131 and the second groove 132 are located on different negative electrode active material layers 120. The second adhesive tape 300 includes a third sub-adhesive tape 310 and a fourth sub-adhesive tape 320. The third sub-adhesive tape 310 is located in the first groove 131, and the fourth sub-adhesive tape 320 is located in the second groove 132 (that is, the second adhesive tape includes a third sub-adhesive tape and a fourth sub-adhesive tape located on both sides of the positive electrode tab groove along the thickness direction, and the third and fourth sub-adhesive tapes are respectively disposed in the corresponding first and second grooves). The third sub-adhesive tape 310 and the fourth sub-adhesive tape 320 satisfy at least one of the following conditions:

[0048] In one example, the thickness of the third sub-adhesive tape ranges from 5μm to 30μm, for example, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, or falls within the range of any two of the above values;

[0049] In one example, the thickness of the fourth sub-adhesive tape ranges from 5μm to 30μm, for example, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, or falls within the range of any two of the above values;

[0050] In one example, the thickness of the fourth sub-adhesive sheet is greater than the thickness of the third sub-adhesive sheet, and the thickness difference between the fourth sub-adhesive sheet and the third sub-adhesive sheet is 1μm-15μm, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or within any two of the above values.

[0051] The thicker fourth sub-adhesive paper is located on one side of the positive electrode tab groove, and the thinner third sub-adhesive paper is located on the other side of the positive electrode tab groove. During the process of winding or stacking the positive and negative electrode sheets to form an electrode assembly, the thinner third sub-adhesive paper will be located at the bottom of the electrode assembly, and the thicker fourth sub-adhesive paper will be located at the top of the electrode assembly. After the electrolyte is injected, the third sub-adhesive paper located at the bottom of the electrode assembly will be preferentially wetted by the electrolyte, and the liquid absorption will be higher. The fourth sub-adhesive paper located at the top of the electrode assembly will have a lower liquid absorption. Therefore, in order to keep the electrolyte wetting level in the negative electrode sheet on the inner and outer sides of the electrode assembly the same, the thickness of the fourth sub-adhesive paper can be increased to be greater than the thickness of the third sub-adhesive paper, thereby increasing the thickness of the outer adhesive paper to balance the electrolyte wetting amount on both sides of the positive electrode sheet, and further improving the safety performance and cycle performance of the battery.

[0052] In one example, the roughness Ra of the negative electrode current collector is 0.1 μm-10 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm or 10.0 μm.

[0053] Furthermore, in order to better fix the adhesive tape to the electrode surface, the present invention can also use a foil-squeezing method to roughen the foil material, improve the adhesion between the adhesive tape and the negative electrode current collector, and significantly enhance the mechanical interlocking effect. In one example, the roughness Ra of the negative electrode current collector is 0.1 μm-10 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or within any two of the above values. Meeting the above range effectively improves the safety performance of the battery. Among them, the arithmetic mean deviation of the profile (Ra) reflects the average height of the overall surface undulation, but is not sensitive to extreme peaks and valleys. The surface profile can be measured using a contact profilometer / laser scanner, or directly by a surface roughness meter. The specific testing method is as follows: using a high-powered microscope, lay the sample to be tested flat under the microscope lens, select a 10X magnification lens, and adjust the focus until the interface is clear; using 3D scanning, open the microscope operation interface, adjust the upper and lower limits of 3D scanning, and then click the "3D Scan" button to perform 3D scanning; after the 3D scan is completed, the roughness is automatically calculated.

[0054] In one example, the roughness Ra of the negative electrode current collector is 0.1 μm-4 μm.

[0055] To significantly improve the mechanical interlocking effect between the adhesive tape and the negative electrode sheet, the roughness Ra of the negative electrode current collector can be adjusted to the range of 0.1μm-10μm. However, when the roughness increases, it will lead to an increase in the interfacial contact resistance of the negative electrode sheet. Therefore, the roughness Ra of the negative electrode current collector surface should not be too large. In one example, the roughness Ra of the negative electrode current collector can be 0.1μm-4μm. By controlling the roughness of the negative electrode current collector surface within this range, the problem of increased adhesive area of ​​the adhesive tape and increased contact resistance of the negative electrode current collector surface can be balanced.

[0056] In one example, the silicon-based material includes at least one of silicon-carbon material, silicon-oxygen material, silicon alloy, and elemental silicon; the silicon-carbon material includes porous carbon and silicon material located within the porous carbon channels.

[0057] In one example, the sphericity of the silicon-based material is greater than 0.85. Silicon-based material particles with higher sphericity exhibit more uniform expansion stress distribution, resulting in a more dispersed direction of volume expansion of the negative electrode sheet. This reduces the problem of excessive expansion stress in the concentrated area of ​​the adhesive tape at the groove, further preventing the second adhesive tape at the groove from detaching and thus improving the battery's safety performance. The method for testing the sphericity of silicon-based materials may include the following steps: First, disassemble the lithium-ion battery, remove the negative electrode sheet, and soak and rinse it with dimethyl carbonate solvent to remove lithium salt and electrolyte solvent from the negative electrode sheet. After drying, obtain the cross-section of the negative electrode sheet by argon ion cutting. In the backscatter mode of a scanning electron microscope, silicon-based particles exhibit a brighter contrast, while graphite particles are darker. Therefore, image processing software (such as Image ProPlus) can be used to calculate the image of each bright particle in the SEM backscatter mode image of the negative electrode sheet at a certain magnification (such as 2500x) to obtain the perimeter and area of ​​each silicon-based particle. The perimeter equivalent radius r1 and area equivalent radius r2 of each particle are calculated respectively. Then, the sphericity b of each particle is b = r2 / r1. Finally, the sphericity of each particle is weighted and averaged to obtain the average sphericity b of the silicon-based material in the cross-section of the negative electrode sheet.

[0058] In one example, the particle size Dv50 of the silicon-based material is 5μm-15μm, for example, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or within any two of the above values. Large-particle silicon-based materials are prone to structural breakage (such as pulverization or fragmentation) of the negative electrode active material due to internal stress concentration, which can lead to the detachment of the second adhesive tape at the groove. In addition, the destruction of the active material structure can accelerate capacity decay. By controlling the particle size Dv50 within the range of 5μm-15μm, this invention can reduce the stress accumulation inside the negative electrode active material by optimizing the particle size, avoiding structural damage caused by uneven expansion, thereby maintaining the integrity of the material and the cycle stability of the high-voltage battery, and also improving the safety performance of the battery.

[0059] In this invention, the term "Dv50" refers to the particle size corresponding to a cumulative volumetric particle size distribution percentage of 50% for a sample. Dv50 can be tested using a laser particle size analyzer. The determination of the Dv50 value can be performed using a laser particle size analysis method. For example, it can be measured using a Malvern particle size analyzer. The specific testing steps include: dispersing the silicon-based material in deionized water containing a dispersant (e.g., nonylphenol polyoxyethylene ether, content 0.02-0.03 wt%) to form a mixture, sonicating the mixture for 2-5 minutes, and then placing it in a Malvern particle size analyzer for testing.

[0060] In one example, the maximum width of the groove is greater than the width of the tab groove.

[0061] In one instance, the width of the first adhesive tape is greater than the maximum width of the groove.

[0062] In one instance, the maximum width of the groove is greater than the width of the second adhesive tape.

[0063] It should be noted that the maximum width of the groove, the width of the tab groove, the width of the first adhesive strip, and the width of the second adhesive strip all refer to their dimensions in the width direction of the positive electrode sheet, such as... Figure 1 As shown.

[0064] This invention designs the maximum width of the groove to be greater than the width of the tab groove. This is to provide sufficient space to accommodate most of the first adhesive paper on the positive tab and the second adhesive paper set in the groove, thus solving the problem of uneven electrode thickness at the relative positions of the groove and the tab groove. Moreover, when there is enough space to accommodate the adhesive paper, it also provides space for the gas generated by a small amount of electrolyte and can prevent problems such as the edge of the adhesive paper lifting, thereby further preventing the adhesive paper from falling off and improving the safety performance of the battery.

[0065] By designing the width of the first adhesive tape to be greater than the maximum width of the groove, this invention can avoid the problem of direct contact and short circuit between the positive and negative electrode plates at the tab groove when the edge of the second adhesive tape is folded by the expansion stress inside the negative electrode active material. The larger the coverage width of the first adhesive tape, the better it is to prevent such problems from occurring, and further improve the safety performance of the battery.

[0066] This invention, by designing the maximum width of the groove to be greater than the width of the second adhesive strip, avoids the edge area of ​​the second adhesive strip in the groove being subjected to expansion stress in different directions. When the edge of the second adhesive strip along the width direction coincides with the two edges of the groove along the width direction, the two ends of the adhesive strip will be subjected not only to the upward expansion stress of the bottom active layer, but also to the expansion stress from both sides of the groove wall. After long-term cyclic expansion, the two ends of the second adhesive strip will be more likely to fall off. When the width of the second adhesive strip is greater than the maximum width of the groove, part of the adhesive strip still needs to be attached to the inner wall of the groove, which is more likely to fall off during cyclic expansion, affecting the safety performance of the battery.

[0067] In one example, the electrolyte includes a first additive, which comprises at least one of 2,2-difluoroethyl acetate (DFEA), ethyl 2,2-difluoroacetate, and methyltrifluoroethyl carbonate (FEMC). The first additive is present in the electrolyte at a mass percentage of w3, where 2% ≤ w3% ≤ 40%, for example, 2%, 3%, 4%, 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%, or within any two of the above values. This invention further adds at least one first additive selected from 2,2-difluoroethyl acetate (DFEA), ethyl 2,2-difluoroacetate, or methyltrifluoroethyl carbonate (FEMC) to the electrolyte. DFEA and ethyl 2,2-difluoroacetate are substances with good antioxidant properties, which can effectively improve the film quality of the negative electrode. FEMC can effectively optimize the SEI film structure. The content w3 of the first additive satisfies the following condition: 2% ≤ w3% ≤ 40%. When the first additive satisfies the above relationship, it can effectively improve the low-temperature and high-temperature cycling performance of the battery. The performance improvement is due to the synergistic effect of 2,2-difluoroethyl acetate (DFEA) and ethyl 2,2-difluoroacetate with a small amount of fluorinated additives such as FEC, which generate a "LiF-organic polymer" composite SEI film. The outer flexible organic layer can inhibit crack propagation, forming a composite SEI film that combines rigidity and flexibility, suppressing the expansion of the negative electrode and improving the low-temperature and cycle performance of the battery. FEMC can effectively optimize the SEI film structure, generating a dense film layer rich in lithium fluoride (LiF) and organic components, inhibiting electrolyte decomposition and reducing transition metal dissolution, thereby improving battery cycle life.

[0068] In one example, the electrolyte includes a boron-containing additive, wherein the boron-containing additive has a mass percentage (w4) in the electrolyte of 0.01% ≤ w4% ≤ 2%.

[0069] In one example, the boron-containing additive includes at least one of lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium oxalate borate.

[0070] Boron-containing additives form a composite SEI film containing borate and LiF. This film has high density (thickness <20 nm), which can suppress side reactions between EC / FEC and the negative electrode, reduce the gases such as HF generated during their decomposition, and the borate groups (BO) can capture free H+. + This inhibits the accumulation of HF, thereby reducing gas generation reactions caused by acid corrosion.

[0071] According to the battery of the present invention, the lithium-ion battery further includes a separator, which may also be a separator conventionally used in the art, such as PP film, PE film, etc.

[0072] According to the battery of the present invention, the positive electrode active material layer comprises a layered lithium composite oxide with the chemical formula 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.

[0073] According to the battery of the present invention, the negative electrode active material layer further comprises a carbon-based negative electrode material, wherein the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon and soft carbon.

[0074] According to the battery of the present invention, the electrolyte further comprises a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalato)phosphate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethanesulfonyl)imide, lithium di(pentafluoroethyl)imide, lithium tri(trifluoromethanesulfonyl)methyl, and lithium di(trifluoromethanesulfonyl)imide.

[0075] According to the battery of the present invention, the electrolyte also includes other organic solvents and other fluorinated solvents.

[0076] In one example, the other organic solvent includes at least one of propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, ethyl propionate, n-propyl propionate, methyl butyrate, ethyl butyrate, and n-ethyl butyrate.

[0077] In one example, the other fluorinated solvents include at least one selected from propylene fluoride carbonate, methyl ethyl fluoride carbonate, diethyl fluoride carbonate, dimethyl fluoride carbonate, ethyl fluoride carbonate, methyl fluoride propionate, ethyl fluoride propionate, propyl fluoride 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, fluorobenzene, 1,3-difluorobenzene, and 1,4-difluorobenzene.

[0078] In one example, the electrolyte also includes other additives, including one or more of vinylene carbonate, vinyl ethylene carbonate, vinyl sulfate, butadionitrile, glutaronitrile, adiponitrile, heptadionitrile, octadionitrile, sebaconitrile, 1,3,6-hexanetrionitrile, glycerol trionitrile, 1,2-bis(2-cyanoethoxy)ethane, and propenyl-1,3-sulfonyl lactone.

[0079] The battery of the present invention can be prepared using conventional methods in the art. Specifically, the positive electrode, separator, and negative electrode are stacked in sequence to ensure that the separator is between the positive and negative electrodes to provide isolation. Then, the unfilled bare cell is obtained by winding. The bare cell is placed in an outer packaging foil, and the electrolyte is injected into the dried bare cell. After vacuum sealing, settling, formation, shaping, and sorting, the desired lithium-ion battery is obtained.

[0080] A second aspect of the present invention provides an electronic device comprising the battery described in the first aspect of the present invention.

[0081] This invention does not limit the types of electronic devices, but may include, but is not limited to, laptops, input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0082] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0083] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0084] Example 1

[0085] The lithium-ion battery of the present invention is obtained by the following method:

[0086] 1) Preparation of positive electrode sheet

[0087] Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), super P (SP), and carbon nanotubes (CNT) were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until it formed a uniform and fluid positive electrode slurry. The positive electrode slurry was uniformly coated onto both surfaces of an aluminum foil. The coated aluminum foil was dried, and then rolled and slit to obtain the desired positive electrode sheet. The tab grooves on the surface of the positive electrode sheet were then laser-cleaned, and positive electrode tabs were welded into the tab grooves. A first adhesive tape was placed on the surface of the positive electrode tabs and the tab grooves. The dimension of the second adhesive tape in the width direction of the positive electrode sheet was larger than the dimension of the tab groove.

[0088] 2) Preparation of negative electrode sheet

[0089] Artificial graphite (anode active material), silicon-carbon material (comprising porous carbon and silicon within the porous carbon channels, with a sphericity of 0.95 and a particle size Dv50 of 10 μm), 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. Deionized water was added, and the mixture was stirred under vacuum to obtain anode active slurry. The slurry is uniformly coated on both surfaces of a copper foil (the roughness of the copper foil used is Ra = 3μm) to form a negative electrode active material layer. The coated copper foil is dried at room temperature, then transferred to an 80℃ oven for drying for 10 hours. After cold pressing and slitting, a negative electrode sheet with a thickness of 100μm is obtained. Then, grooves are pre-reserved on the surface of the negative electrode sheet by laser cleaning. The specific method is as follows: A high-energy laser beam is used to perform targeted cleaning on the surface of the negative electrode sheet to remove the coating or oxide layer in specific areas, exposing the substrate material. The laser parameters need to be adjusted according to the material characteristics to avoid damaging the substrate. The laser head moves along a preset path, and the depth is controlled by the XZ axis drive device. Shallow grooves are first engraved on the surface of the negative electrode active material layer on both sides of the negative electrode sheet (e.g., ...). Figure 2 The first groove layer in groove 130 is used to deposit a laser reflective film on the shallow groove slope, converting the vertical laser to a horizontal direction, and carving out a deeper inner groove (such as...). Figure 2 The second groove layer in groove 130, with negative electrode copper foil exposed at the bottom of the inner groove (the orthogonal projection area of ​​the exposed negative electrode copper foil along the thickness direction is 2 cm²). 2(i.e., the orthogonal projection area of ​​the second region along the thickness direction of the positive electrode sheet); Final shaping: After removing the reflective film, the residual reflective part is removed again with a laser to form the groove of the negative electrode sheet, including a first groove and a second groove located on the negative electrode active material layer on both sides of the negative electrode sheet respectively; the dimension of the groove in the maximum width direction of the positive electrode sheet is greater than the width dimension of the tab groove and smaller than the width dimension of the first adhesive tape. Then, a second adhesive tape is attached in the groove. The dimension of the second adhesive tape in the width direction of the positive electrode sheet is smaller than the maximum width dimension of the groove. The total orthogonal projection area of ​​the second adhesive tape along the thickness direction of the positive electrode sheet is S = 5 cm². 2 The second adhesive tape includes a third sub-adhesive tape and a fourth sub-adhesive tape. The thickness of the third sub-adhesive tape located in the first groove is 15 μm, the thickness of the fourth sub-adhesive tape located in the second groove is 15 μm, and the thickness difference between the two adhesive tapes is 0 μm.

[0090] 3) Preparation of electrolyte

[0091] In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the solvents ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) were mixed in a 1 / 1 / 1 / 7 ratio. Then, 13 wt% of fully dried lithium hexafluorophosphate (LiPF6) based on the total mass of the electrolyte was quickly added. Subsequently, 0.5 wt% of 1,4-dicyano-2-butene based on the total mass of the electrolyte was added, along with other additives including 2 wt% of 1,3,5-hexanetrionitrile (HTCN), 2 wt% adiponitrile (ADN), 1 wt% octanoic acid dinitrile (SN), 3 wt% 1,3-propanesulfonate lactone, and 15 wt% fluoroethylene carbonate additive. After thorough mixing and passing moisture and free acid tests, the desired electrolyte was obtained. The total mass percentage of ethylene carbonate and fluoroethylene carbonate in the electrolyte is w1 = 25%, and the total mass percentage of 1,3-propanesulfonyl lactone in the electrolyte is w2 = 3%.

[0092] 4) Preparation of lithium-ion batteries

[0093] The positive electrode sheet from step 1), the negative electrode sheet from step 2), and the separator are stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to obtain a battery cell. The battery cell is placed in an outer packaging aluminum foil, and the electrolyte from step 3) is injected into the outer packaging. After vacuum sealing, settling, formation, shaping, and sorting, a lithium-ion battery is obtained. The charge / discharge range of the battery of this invention is 3.0-4.58V.

[0094] Please refer to Tables 1 and 2 for details.

[0095] Example 2 group

[0096] This embodiment is based on Embodiment 1, except that the size of the second adhesive paper along the width of the positive electrode sheet is adjusted so that the projected area S of the second adhesive paper along the thickness of the positive electrode sheet is changed, as shown in Table 1.

[0097] Example 3 Group

[0098] This embodiment is based on Example 1, except that the mass percentage of ethylene carbonate and fluoroethylene carbonate in the electrolyte is changed, so that the sum of the mass percentages of ethylene carbonate and fluoroethylene carbonate in the electrolyte, w1%, is changed. See Table 1 for details.

[0099] Example 4 group

[0100] This embodiment is based on Example 1, except that the mass percentage of 1,3-propanesulfonyl lactone in the electrolyte is changed, so that the sum of the mass percentages of 1,3-propanesulfonyl lactone in the electrolyte, w2%, is changed. See Table 1 for details.

[0101] Comparative Example 1

[0102] This comparative example is based on Example 1, with the only difference being that the dimensions of the second adhesive paper along the width direction of the positive electrode sheet are adjusted to change the projected area S of the second adhesive paper along the thickness direction of the positive electrode sheet, and / or the mass percentage of ethylene carbonate, fluoroethylene carbonate, or 1,3-propanesulfonyl lactone in the electrolyte is changed, so that the sum of the mass percentages of ethylene carbonate and fluoroethylene carbonate in the electrolyte is w1%, and / or the mass percentage of 1,3-propanesulfonyl lactone in the electrolyte is changed w2, as detailed in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] Example 5 group

[0107] This embodiment is based on Embodiment 1, with the only difference being that the parameters of the groove laser etching are changed, thereby altering the projected area of ​​the second region in the groove along the thickness direction of the positive electrode sheet. Specifically:

[0108] Example 5-1: The projected area of ​​the second region along the thickness direction of the positive electrode sheet is 0.1 cm². 2 ;

[0109] Example 5-2: The projected area of ​​the second region along the thickness direction of the positive electrode sheet is 3.0 cm². 2 ;

[0110] Example 5-3: By changing the parameters and steps of the groove laser etching, without distinguishing between shallow and deeper grooves, a groove is directly etched on the surface of the negative electrode active material layer on both sides of the negative electrode sheet. The bottom of the groove does not expose the negative electrode copper foil. The projected area of ​​the second region along the thickness direction of the positive electrode sheet is 0 cm². 2 The negative electrode current collector foil was not exposed in the groove;

[0111] In Examples 5-4, the projected area of ​​the second region along the thickness direction of the positive electrode sheet is 3.2 cm². 2 .

[0112] Example 6

[0113] This embodiment is based on Example 1, except that a first additive is added to the electrolyte: 5% 2,2-difluoroethyl acetate and 5% methyltrifluoroethyl carbonate, with the addition amount w3% being 10%.

[0114] Example 7

[0115] This embodiment is based on Example 1, except that the first additive ethyl 2,2-difluoroacetate and the boron-containing additive lithium difluorooxalate borate are added to the electrolyte, with the addition amount w3% being 2% and the addition amount w4% being 0.01%.

[0116] Example 8

[0117] This embodiment is carried out with reference to Example 1, except that the first additive 2,2-difluoroethyl acetate and the boron-containing additive lithium difluorooxalate borate are added to the electrolyte, with the addition amount w3% being 40% and the addition amount w4% being 1%.

[0118] Example 9

[0119] This embodiment is based on Embodiment 1, except that by changing the parameters of the groove laser etching, the size of the groove in the width direction of the positive electrode is changed, so that the maximum width of the groove is smaller than the width of the tab groove.

[0120] Example 10

[0121] This embodiment is based on Embodiment 1, except that the dimensions of the first adhesive paper in the width direction of the positive electrode are changed so that the width of the first adhesive paper is smaller than the maximum width of the groove.

[0122] Example 11

[0123] This embodiment is based on Embodiment 1, except that the dimensions of the second adhesive paper in the width direction of the positive electrode are changed so that the width of the second adhesive paper is greater than the maximum width of the groove.

[0124] Example 12

[0125] This embodiment is based on Embodiment 1, except that the dimensions of the third and fourth sub-adhesive sheets in the second adhesive sheet are changed in the thickness direction of the positive electrode sheet, so that the thickness of the third sub-adhesive sheet located in the first groove and the thickness of the fourth sub-adhesive sheet located in the second groove are changed, as detailed in Table 2.

[0126] Example 13 group

[0127] This embodiment is based on Embodiment 1, with the only difference being that the roughness Ra of the negative electrode current collector is changed, and the thickness of the third sub-adhesive paper located in the first groove and the thickness of the fourth sub-adhesive paper in the second groove are also changed, as detailed in Table 2.

[0128] Example 14 group

[0129] This embodiment is based on Embodiment 1, with the only difference being that the sphericity and particle size Dv50 of the silicon-carbon material are changed, as detailed in Table 2.

[0130] Table 2

[0131]

[0132] Test case

[0133] 1) Cyclic performance test

[0134] The lithium-ion batteries obtained from all the above embodiments and comparative examples were subjected to charge-discharge cycles at 25°C with a discharge rate of 2C within the charge-discharge cutoff voltage range. The discharge capacity of the first cycle was measured as x1mAh, and the discharge capacity of the 600th cycle was measured as y1mAh. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate R1 = y1 / x1 of the 600th cycle. The results are recorded in Table 3.

[0135] 2) High-temperature storage test

[0136] The lithium-ion batteries prepared in all the above embodiments and comparative examples were subjected to high-temperature storage tests. The specific test methods are as follows:

[0137] At 25℃±3℃, the fully charged battery was discharged at 0.5C to the lower limit voltage of 3.0V, left to stand for 10 minutes, and then fully charged at a constant current of 0.5C with a cutoff current of 0.02C. After standing for 10 minutes, the thickness of the fully charged battery at 25℃±3℃ was measured. The battery was then placed in an environment of 85℃ for 6 hours and then removed. The battery thickness was measured and the thickness expansion rate (%) was recorded. The results are recorded in Table 3.

[0138] 3) Safety performance testing

[0139] The lithium-ion batteries obtained in all the above embodiments and comparative examples were discharged at 0.2C to the lower limit voltage of 3.0V at 25°C. After standing for 10 minutes, they were charged at 1C to the upper limit voltage of 4.55V with a cutoff current of 0.05C. At this time, the lithium-ion batteries were fully charged. Then, the fully charged lithium-ion batteries were placed in an oven, and the temperature inside the oven was increased at a rate of 5°C / min. When the temperature inside the oven reached 132°C, the temperature was kept constant for 60 minutes. The lithium-ion batteries were observed to see if they caught fire or exploded. If they did not catch fire or explode, the test was considered passed. A total of 10 tests were conducted, and the test results (10 PASS / 10) were recorded in Table 3.

[0140] Table 3

[0141]

[0142]

[0143] As shown in Table 3, this invention effectively reduces electrolyte gas production and simultaneously improves the compressive strength of the adhesive paper by reducing the total amount of FEC and EC in the electrolyte and controlling the total amount of FEC and EC w1 and the projected area S of the first adhesive paper to satisfy 0.5≤w1 / S≤25. This inhibits the deformation and detachment of the adhesive paper, slows down battery expansion, and ensures excellent high-temperature cycle stability of the battery, thereby improving battery safety performance. Furthermore, the synergistic addition of 1,3-propanesulfonyl lactone (PS) to the electrolyte of this invention can inhibit EC / FEC decomposition, further reduce the expansion stress on the adhesive paper, and improve the high-temperature cycle performance and battery safety performance of the battery.

[0144] 4) Low-temperature discharge test

[0145] The lithium-ion batteries prepared in Examples 1, 6-8, and the comparative examples were subjected to low-temperature discharge tests. The specific test methods are as follows:

[0146] At 25℃±3℃, a fully charged battery was discharged at 0.5C to the lower limit voltage of 3.0V, left to stand for 10 minutes, and the initial discharge capacity Q0 was recorded. The battery was then placed in a 0℃ constant temperature chamber and fully charged at a constant current of 0.5C, with a cutoff current of 0.02C. After storage for 6 hours, the battery was discharged at a constant current of 0.5C, and the discharge capacity Q1 was recorded. The low-temperature discharge capacity retention rate is calculated as Q1 / Q0 × 100%, and the results are recorded in Table 4.

[0147] Table 4

[0148]

[0149]

[0150] Analysis of Tables 3 and 4 shows that the present invention, by further adding the first additive, can effectively improve the low-temperature and cycle performance of the battery. In Example 7, the first additive also includes FEMC, which can effectively optimize the SEI film structure, inhibit electrolyte decomposition, and reduce transition metal dissolution, further improving the battery cycle life. In Example 8, the further addition of a boron-containing additive forms a composite SEI film containing borate and LiF, which can suppress the side reactions between EC / FEC and the negative electrode, reduce the gases generated by their decomposition, and thus further improve the battery cycle performance.

[0151] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The device includes a negative electrode, a positive electrode, and an electrolyte. The negative electrode includes a negative current collector and a negative active material layer located on at least one side of the surface of the negative current collector. The negative active material layer contains a silicon-based material. The positive electrode includes a positive current collector and a positive active material layer located on at least one side of the surface of the positive current collector. A tab groove is provided on the positive electrode active material layer, a positive electrode tab is accommodated in the tab groove, and a first adhesive paper is provided on the surface of the positive electrode tab; A groove is formed on the negative electrode active material layer. The tab groove is positioned opposite to the groove along the thickness direction of the positive electrode sheet. A second adhesive tape is placed in the groove. The total area of ​​the second adhesive tape projected along the thickness direction of the positive electrode sheet is S = 1 cm². 2 ≤S cm 2 ≤10cm 2 ; The electrolyte comprises ethylene carbonate, fluoroethylene carbonate, and 1,3-propanesulfonyl lactone. The sum of the mass percentages of ethylene carbonate and fluoroethylene carbonate in the electrolyte is w1, 3% ≤ w1% ≤ 40%, and the mass percentage of 1,3-propanesulfonyl lactone in the electrolyte is w2, 0.5% ≤ w2% ≤ 6%. Wherein, S and w1 satisfy 0.5≤w1 / S≤25.

2. The battery according to claim 1, characterized in that, 2.5cm 2 ≤S cm 2 ≤8cm 2 ; and / or, 8% ≤ w1% ≤ 30%; and / or, 1% ≤ w2% ≤ 5%; Preferably, S and w1 satisfy 1.5 ≤ w1 / S ≤ 18.

3. The battery according to claim 1, characterized in that, There is an empty foil area in the groove.

4. The battery according to claim 1, characterized in that, The groove is divided into a first region and a second region along the thickness direction of the positive electrode sheet. The surface of the negative electrode current collector in the first region is provided with the negative electrode active material layer, and the second region exposes the bare negative electrode current collector. Preferably, the projected area of ​​the second region along the thickness direction of the positive electrode sheet is 0.1 cm². 2 -3cm 2 .

5. The battery according to claim 1, characterized in that, The groove includes a first groove and a second groove, the first groove and the second groove being located on different layers of the negative electrode active material. The second adhesive tape includes a third sub-adhesive tape and a fourth sub-adhesive tape, the third sub-adhesive tape being located in the first groove and the fourth sub-adhesive tape being located in the second groove. The third sub-adhesive tape and the fourth sub-adhesive tape satisfy at least one of the following conditions: a. The thickness of the third sub-adhesive paper ranges from 5μm to 30μm; b. The thickness of the fourth sub-adhesive paper ranges from 5μm to 30μm; c. The thickness of the fourth sub-adhesive paper is greater than the thickness of the third sub-adhesive paper, and the thickness difference between the fourth sub-adhesive paper and the third sub-adhesive paper is 1μm-15μm.

6. The battery according to claim 1, characterized in that, The battery satisfies at least one of the following conditions: a. The roughness Ra of the negative electrode current collector is 0.1μm-10μm, preferably 0.1μm-4μm; b. The silicon-based material includes at least one of silicon-carbon material, silicon-oxygen material, silicon alloy, and elemental silicon; the silicon-carbon material includes porous carbon and silicon material located within the porous carbon channels; c. The sphericity of the silicon-based material is greater than 0.85; d. The particle size Dv50 of the silicon-based material is 5μm-15μm.

7. The battery according to claim 1, characterized in that, The maximum width of the groove is greater than the width of the tab groove; And / or, the width of the first adhesive tape is greater than the maximum width of the groove; And / or, the maximum width of the groove is greater than the width of the second adhesive tape.

8. The battery according to claim 1, characterized in that, The electrolyte includes a first additive, which includes at least one of 2,2-difluoroethyl acetate, 2,2-difluoroethyl acetate, and methyltrifluoroethyl carbonate. The mass percentage of the first additive in the electrolyte is w3%, where 2% ≤ w3% ≤ 40%.

9. The battery according to claim 1, characterized in that, The electrolyte includes a boron-containing additive, and the mass percentage of the boron-containing additive in the electrolyte is w4, where 0.01% ≤ w4% ≤ 2%. Preferably, the boron-containing additive includes at least one of lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate.

10. An electronic device, characterized in that, The electronic device includes the battery as described in any one of claims 1-9.

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