Battery

Abstract

The invention relates to the field of batteries, in particular to a battery. The battery comprises a negative plate and an electrolyte, the negative plate comprises a negative current collector and a negative active material layer positioned on at least one side surface of the negative current collector, and the surface density of the negative active material layer is 9mg / cm < 2 >-14mg / cm < 2 >; the electrolyte comprises a first additive, the first additive comprises a substance shown as a formula I, R1, R2 and R3 are respectively and independently selected from at least one of substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C2-C5 alkenyl and substituted or unsubstituted C2-C4 alkynyl, and R2 and R3 are respectively and independently selected from at least one of substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C2-C5 alkenyl and substituted or unsubstituted C2-C4 alkynyl. The substituted group comprises at least one of phenyl, halogen, a sulfur-containing group, a phosphorus-containing group, trimethylsilyl, methoxyl, hydroxyl, carboxyl, aldehyde group, carbonyl and cyano. The battery provided by the invention has excellent cycle performance and furnace temperature safety performance.

Description

TECHNICAL FIELD

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

[0002] In recent years, with the rapid development of commercial application of lithium batteries, in order to meet the increasing requirements of terminal consumer application market for lithium batteries, new technologies of lithium batteries have emerged. At present, the graphite material has almost reached the theoretical capacity, in order to meet the demand of high energy density, the surface density of graphite negative electrode is increasing. However, with the increase of surface density, the wettability of negative electrode sheet to electrolyte becomes poor, the liquid retention of battery becomes low, which leads to the poor cycle performance of battery. And lithium is easy to be precipitated at the tab of battery, with the increase of surface density of negative electrode, the problem of lithium precipitation at the tab becomes more serious, which will further deteriorate the cycle performance of battery. In addition, it will also deteriorate the oven temperature safety performance of battery.

[0003] Therefore, it is necessary to solve the problem of deterioration of cycle performance and oven temperature safety performance of battery caused by the increase of surface density of negative electrode. SUMMARY

[0004] The present application aims to overcome the problem of deterioration of cycle performance and oven temperature safety performance of battery caused by the increase of surface density of negative electrode in the prior art, and provides a battery. The battery of the present application uses electrolyte in cooperation with negative electrode sheet, the first additive with specific structure in electrolyte can improve the wettability of electrolyte to negative electrode sheet while ensuring high surface density of negative electrode, and can improve the transmission efficiency of lithium ions at the tab, thereby improving the cycle performance of battery; in addition, it can also improve the oven temperature safety performance of battery.

[0005] In related art, the lithium battery with high surface density (for example, greater than or equal to 9 mg / cm 2The battery of the negative electrode sheet often has poor cycle performance and safety performance. The inventors of the present application found through long-term and large-scale research that the reasons for the above problems are as follows: (1) As the areal density of the negative electrode coating increases, the thickness and / or the compacted density of the negative electrode coating also increase. At this time, the penetration ability of the electrolyte to the negative electrode coating becomes poor, which causes the negative electrode coating near the negative electrode current collector to be unable to effectively contact with the electrolyte, thereby causing the cycle performance of the battery to become poor; (2) The current density is large at the tab (including the positive electrode tab and the negative electrode tab) of the battery, which causes the current distribution to be uneven near the tab. The increase of the areal density of the negative electrode coating exacerbates the unevenness of the current distribution. Such uneven current distribution not only increases the internal resistance of the battery, but also exacerbates the lithium precipitation problem near the tab, further deteriorating the cycle performance of the battery; (3) Due to the increase of the areal density of the negative electrode coating, the volume of the battery increases. In order to maintain the volume of the battery, the thickness of the separator or the thickness of the current collector is often thinned, which causes the oven temperature safety performance of the battery to become poor. Based on the above findings, the inventors believe that the electrolyte can be improved by improving the compatibility of the electrolyte to the high areal density negative electrode sheet, so as to improve the cycle performance and the oven temperature safety performance of the battery. Based on this, the inventors of the present application propose the following scheme:

[0006] The present application provides a battery, which comprises a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector, the areal density of the negative electrode active material layer is 9 mg / cm 2 -14 mg / cm 2 ; the electrolyte comprises a first additive, the first additive comprises a substance represented by formula I:

[0007]

[0008] wherein R1, R2 and R3 are each independently selected from at least one of substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C2-C5 alkenyl and substituted or unsubstituted C2-C4 alkynyl, and the substituted groups comprise at least one of phenyl, halogen, sulfur-containing group, phosphorus-containing group, trimethylsilyl group, methoxy group, hydroxyl group, carboxyl group, aldehyde group, carbonyl group and cyano group.

[0009] Firstly, the first additive has high stability due to its unique structure. Secondly, the first additive contains ether bond and can be preferentially reduced on the surface of the negative electrode to form a film to assist the formation of SEI film due to its high HUMO energy. The SEI film formed at this time can have high strength and toughness while having a thinner thickness. Therefore, when the electrolyte includes the first additive, the SEI film formed on the surface of the negative electrode can significantly improve the wettability of the electrolyte to the negative electrode sheet, thereby improving the liquid retention amount of the battery and improving the cycle performance of the battery. In addition, the SEI film formed on the surface of the negative electrode has a thinner thickness, which is beneficial to reduce the resistance of lithium ion transmission, uniform the current distribution of the negative electrode sheet, and improve the problem of lithium precipitation at the tab. In addition, the first additive includes a cyano group, which can complex with metal ions on the surface of the positive electrode sheet, thereby effectively protecting the positive electrode. Therefore, the first additive can form a protective film on the positive electrode and the negative electrode, thereby improving the problem of deterioration of the oven temperature safety performance caused by the thinning of the separator thickness and the current collector thickness.

[0010] Compared with the prior art, the battery of the present application has the following advantages: the battery of the present application has excellent cycle performance and oven temperature safety performance.

[0011] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the present application. Any numerical value, however, can be expressed as a range by either adding or subtracting a small percentage (e.g., 1-10%) from the stated value to account for variations, measurement inaccuracies, and the like. For numerical ranges expressed in the format "from X to Y," it is intended that embodiments "X," and "Y" are disclosed, as well as embodiments that are either greater than (or equal to) "X," or less than (or equal to) "Y" individually. As it is evident that "X" and "Y" are endpoints of a range, it is not intended that the range be limited to only the narrow range between "X" and "Y." It is also intended that the endpoints of a range are included in the range. It is therefore intended that a range include values that are either greater than (or equal to) the lower value or less than (or equal to) the upper value of the range. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 A scanning electron microscope (SEM) image of a negative electrode sheet in an example of the present application is shown.

[0013] Figure 2 A schematic diagram of the width of a groove in an example of the present application is shown.

[0014] Figure 3 A schematic diagram of the pitch of a groove in an example of the present application is shown. DETAILED DESCRIPTION

[0015] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and explanatory of the present application and are not intended to limit the present application.

[0016] A battery can include a negative electrode sheet and an electrolyte. The negative electrode sheet can include a negative electrode current collector and a negative electrode active material layer on at least one side surface of the negative electrode current collector. The negative electrode active material layer can have an area density of 9 mg / cm 2 - 14 mg / cm 2 , for example, 9 mg / cm 2 , 9.5 mg / cm 2 , 10 mg / cm 2 , 10.5 mg / cm 2 , 11 mg / cm 2 , 11.5 mg / cm 2 , 12 mg / cm 2 , 12.5 mg / cm 2 , 13 mg / cm 2 , 13.5 mg / cm 2 , or 14 mg / cm 2 . The electrolyte can include a first additive, which can include a substance represented by Formula I:

[0017]

[0018] wherein R1, R2, and R3 can each independently be selected from at least one of a substituted or unsubstituted C1-C8 (e.g., C1, C2, C3, C4, C5, C6, C7, or C8) alkyl group, a substituted or unsubstituted C2-C5 (e.g., C2, C3, C4, or C5) alkenyl group, and a substituted or unsubstituted C2-C4 (e.g., C2, C3, or C4) alkynyl group. The substituted group can include at least one of a phenyl group, a halogen, a sulfur-containing group, a phosphorus-containing group, a trimethylsilyl group, a methoxy group, a hydroxyl group, a carboxyl group, an aldehyde group, a carbonyl group, and a cyano group.

[0019] In the present disclosure, the C1-C8 alkyl group refers to an alkyl group having a carbon atom number of 1-8, and the like.

[0020] In the present disclosure, the content of the first additive is y, 0.1%≤y≤5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, based on the total weight of the electrolyte.

[0021] In an example, 0.3%≤y≤3.5%.

[0022] In an example, 0.5%≤y≤2%.

[0023] In the present application, the weight content of the first additive in the electrolyte can be tested by conventional methods in the art, for example by gas chromatography (GC).

[0024] The inventors of the present application found that when the weight content of the first additive in the electrolyte is within a certain range, the cycle performance and oven temperature safety performance of the battery can be further improved. The reason may be that the ether bond in the first additive can undergo a reduction reaction on the surface of the negative electrode to form a protective layer; at the same time, the cyano group in the first additive can complex with the metal active sites on the surface of the positive electrode sheet to form a protective layer. Therefore, the first additive forms a double protection in the battery. When the content of the first additive is too low (for example, less than 0.1%), the content of the first additive is too low to form an effective cover on the surface of the positive electrode sheet and the surface of the negative electrode sheet, or cannot repair the protective film on the surface of the positive electrode sheet and the surface of the negative electrode sheet in time when it is damaged, thereby affecting the cycle performance and oven temperature safety performance of the battery. When the content of the first additive is too high (for example, greater than 5%), the content of the first additive is too much, which not only increases the viscosity of the electrolyte and slows down the transmission of lithium ions, but also forms a relatively thick protective film on the surface of the positive electrode sheet, which increases the impedance of the battery and also affects the cycle performance of the battery.

[0025] In an example, the areal density of the negative electrode active material layer is 9.5 mg / cm 2 -11 mg / cm 2 .

[0026] In the present application, the surface of the negative electrode sheet can have recesses. As shown in Figure 1 The scanning electron microscope (SEM) image of the negative electrode sheet in an example of the present application is shown. As can be seen from the figure, the surface of the negative electrode sheet has recesses.

[0027] In the present application, the manufacturing method of the recesses is not particularly limited as long as the purpose of the present application can be achieved. For example, the manufacturing method of the recesses can include at least one of laser processing, mechanical processing and pore-forming agent processing. Taking laser processing to manufacture recesses as an example, a high-power density laser beam is used to irradiate the surface of the negative electrode sheet, so that the material on the surface of the negative electrode sheet is quickly heated to the vaporization temperature and evaporated to form recesses. At this time, the electrolyte can quickly spread to the inside of the negative electrode sheet through the recesses on the surface of the negative electrode sheet, so that the liquid retention of the battery is further increased, thereby reducing the impedance of each interface of the battery, accelerating the conduction of lithium ions, and avoiding the interface problems such as lithium precipitation in fast charging cycles.

[0028] However, laser processing to manufacture recesses has drawbacks, i.e. forming recesses by carbonizing the surface of the negative electrode sheet, which will cause the carbonized negative electrode active material to lose the ability to deintercalate lithium, resulting in partial capacity loss. Therefore, the above problem can be improved by controlling the power of the laser.

[0029] In the present application, the power of the laser can be 20-250 W, for example 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200 or 250 W.

[0030] In an example, the power of the laser is 40-200 W.

[0031] In the present application, the recess can include at least one of a groove and a hole.

[0032] In the present application, the width of the recess is w, in units of μm, the depth of the recess is h, in units of μm, and the pitch of the recess is g, in units of mm.

[0033] In the present application, the width of the recess has the conventional meaning in the art.

[0034] When the recess is a groove, the orthographic projection of the groove on the negative plate can include two long sides, and the width of the groove refers to the average distance from one long side to the other long side in the length direction or width direction of the negative plate. As shown in Figure 2 Fig. 1 shows a schematic diagram of the width of a groove in an example of the present application, wherein Figure 2 (a)- Figure 2 In (c), the two long sides of the groove are straight lines, but are not arranged in parallel, so the distance from any point on one long side to the other long side is not equal, at this time, the width of the groove can be taken as the average value, that is, on one long side, 50 points are selected at equal distances (i.e. the distance between each point is equal, so that the selected points can make the calculation result more accurate) based on the length of the long side, the width w1 corresponding to each point is measured, and the average value is taken as the width of the groove; in Figure 2 (d), the two long sides are curves, so the distance from any point on one long side to the other long side is not equal, at this time, the width of the groove can also be taken as the average value, that is, on one long side, 50 points are selected at equal distances (since Figure 2 (d), the two long sides are curves, so there is no Figure 2 (b), the two long sides are arranged in parallel, so the distance from any point on one long side to the other long side is equal in the length direction of the negative plate, at this time, the width of the groove is the distance w1 from any point on one long side to the other long side in the length direction or width direction of the negative plate; in Figure 2 (c), the two long sides of the groove are straight lines, but are not arranged in parallel, so the distance from any point on one long side to the other long side is not equal, at this time, the width of the groove can be taken as the average value, that is, on one long side, 50 points are selected at equal distances (i.e. the distance between each point is equal, so that the selected points can make the calculation result more accurate) based on the length of the long side, the width w1 corresponding to each point is measured, and the average value is taken as the width of the groove; in Figure 2 (d), the two long sides are curves, so the distance from any point on one long side to the other long side is not equal, at this time, the width of the groove can also be taken as the average value, that is, on one long side, 50 points are selected at equal distances (since Figure 2 (d), the two long sides are curves, so there is no Figure 2(c) the relationship between the two long edges in the middle, so 50 points can be randomly selected for measurement, and the width w1 corresponding to each point is measured to obtain the average value of the width of the groove. The width of the groove can be tested by conventional means in the art, such as SEM or 3D microscope.

[0035] When the recess is a hole, the shape of the hole in the orthographic projection on the surface of the negative electrode sheet can be regular or irregular, both of which can achieve good results. When the shape of the hole in the orthographic projection on the surface of the negative electrode sheet is circular, the width of the recess is the diameter of the circle; when the shape of the hole in the orthographic projection on the surface of the negative electrode sheet is non-circular, the width of the recess is the equivalent diameter of the diameter of a certain circle having the same area. The width of the hole can be tested by conventional means in the art, such as SEM.

[0036] In the present application, the depth of the recess has the conventional meaning in the art. The depth of the recess refers to the maximum value of the vertical distance from any point in the recess to the surface of the negative electrode sheet. The depth of the recess can be tested by conventional means in the art, such as SEM or 3D microscope.

[0037] In the present application, the pitch of the recess has the conventional meaning in the art.

[0038] When the recess is a groove, the pitch of the groove refers to the average distance between the adjacent two long edges of the adjacent two grooves on the negative electrode sheet in the length direction or width direction of the negative electrode sheet. As shown in Figure 3 Fig. 1 shows a schematic diagram of the pitch of the groove in an example of the present application, wherein, Figure 3 (a) is the case where the adjacent two long edges are straight lines and parallel, Figure 3 (b) is the case where the adjacent two long edges are straight lines but not parallel, Figure 3 (c) is the case where the adjacent two long edges are curves. In Figure 3 In (a), the adjacent two long edges are straight lines and are arranged in parallel, so the distance from any point on one long edge to the other long edge is equal in the length direction, and at this time, the pitch of the groove is the distance g1 from any point on one long edge to the other long edge in the length direction; in Figure 3 In (b), the adjacent two long edges are straight lines but are not arranged in parallel, so the distance from any point on one long edge to the other long edge is not equal, and at this time, the pitch of the groove can be taken as the average value, that is, 50 points are selected at equal distances on one long edge based on the length of the long edge (i.e., the distance between each point is equal, so that the selected points can make the calculation result more accurate), and the pitch g1 corresponding to each point is measured to obtain the average value of the pitch of the groove; in Figure 3In (c), the two long sides are curves, so the distance from any point on one long side to the other long side is not equal. In this case, the pitch of the grooves can also be taken as the average, i.e. 50 points are randomly selected on one long side (since the two long sides are not equal, the number of points selected on the two long sides can be different) and the pitch of the grooves is obtained by averaging the distances between the selected points. Figure 3 In (c), the two long sides are curves, so the distance from any point on one long side to the other long side is not equal. In this case, the pitch of the grooves can also be taken as the average, i.e. 50 points are randomly selected on one long side (since the two long sides are not equal, the number of points selected on the two long sides can be different) and the pitch of the grooves is obtained by averaging the distances between the selected points. Figure 3 In (b), the relationship between the two long sides is not equal, so 50 points can be randomly selected for measurement), and the pitch of each point is measured g1, and the average is taken to obtain the pitch of the grooves. The pitch of the grooves can be tested by conventional means in the art, such as by SEM or 3D microscope.

[0039] When the recesses are holes, the pitch of the holes refers to the shortest distance between the edges of two adjacent holes. The pitch of the holes can be tested by conventional means in the art, such as by SEM.

[0040] In the present application, the width w of the recess, the depth h of the recess and the pitch g of the recess satisfy: 30≤0.1×h+w / g≤3500, for example 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000 or 3500.

[0041] In an example, 600≤0.1×h+w / g≤1700.

[0042] In an example, 40≤0.1×h+w / g≤55.

[0043] When 0.1×h+w / g is small (for example less than 30), the width of the formed recess is small and the depth is shallow, and it is difficult for the electrolyte to penetrate into the inside of the negative electrode sheet. Too much electrolyte remaining on the surface of the negative electrode sheet can affect the adhesion of the separator, easily causing the "broken bridge" of the negative electrode sheet and the separator, affecting the capacity retention rate of the battery. When 0.1×h+w / g is large (for example greater than 3500), the width of the formed recess is large and the depth is deep, although the electrolyte can efficiently penetrate into the inside of the negative electrode sheet, but there are more and larger burrs around the recess, which has the risk of piercing the separator and causing micro-short circuit. And when the width of the recess on the surface of the negative electrode sheet is large and the depth is deep, it means that the loss of negative electrode active material is large, which will cause the first circle capacity to decrease significantly, affecting the energy density of the battery.

[0044] In the present application, the width w of the recess can be 30-200 μm, for example 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200.

[0045] In an example, the width w of the recess is 50-120.

[0046] In the present application, the depth h of the recess can be 5-30 μm, for example 5, 6, 7, 8, 9, 10, 15, 20, 25 or 30.

[0047] In an example, the depth h of the recess is 10-25.

[0048] In the present application, the pitch g of the recesses can be 0.01-5 mm, for example 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5.

[0049] In an example, the pitch g of the recesses is 1-3.

[0050] In an example, the pitch g of the recesses is 0.03-0.2.

[0051] In the present application, the depth h of the recess, the width w of the recess and the weight content y of the first additive in the electrolyte satisfy: -0.1≤20x y-0.3x h / w≤1, for example -0.1, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

[0052] In an example, 0.0375≤20x y-0.3x h / w≤0.34.

[0053] In an example, 0.04≤20x y-0.3x h / w≤0.339.

[0054] Manufacturing a recess on the surface of the negative electrode sheet will cause the surface of the negative electrode sheet to be uneven, which will not only increase the protrusions (burr) and cause the separator to be punctured, forming a micro-short circuit, but also cause uneven current distribution and exacerbate the lithium precipitation, resulting in poor cycle performance of the battery. The first additive not only can be oxidized to form a film on the positive electrode, but also can be preferentially reduced on the negative electrode due to its high HUMO energy; especially, it can form a film on the protrusions (burr) caused by the manufacturing of the recess, thereby reducing the risk of lithium precipitation and the risk of forming a micro-short circuit caused by uneven current distribution of the protrusions (burr). In addition, the first additive forms a film on the surface of the negative electrode sheet, making the surface smoother and reducing the specific surface area, which is beneficial to the deintercalation of lithium ions. Therefore, the parameters of the recess and the content of the first additive need to be regulated. When 20x y-0.3x h / w is small (for example, less than -0.1), y is relatively small with respect to h / w, the weight content of the first additive is low, and the recess forms more burrs. A low content of the first additive cannot effectively and completely form a film on the surface of the negative electrode sheet, resulting in precipitation; when 20x y-0.3x h / w is large (for example, greater than 1), y is relatively large with respect to h / w, the weight content of the first additive is high, and the depth of the recess is relatively small with respect to the width of the recess. A high content of the first additive reduces the fluidity of the electrolyte, and the small h / w reduces the liquid retention of the battery, which increases the risk of precipitation and diving during the cycle process.

[0055] In the present application, the battery can further include a positive electrode sheet, which can include a positive electrode tab, and the positive electrode sheet can further include a gum paper partially covering the positive electrode tab. The thickness t of the gum paper can be 0.05 mm-0.5 mm, for example, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm.

[0056] In an example, t is 0.1 mm-0.2 mm.

[0057] As the electrolyte continuously penetrates into the gum paper, the electrode sheet near the gum paper is in a liquid-poor state. During the overcharge of the battery, the lithium ions on the surface of the negative electrode sheet near the gum paper cannot be smoothly transported, causing interface blockage and lithium precipitation. In addition, the interface between the swelled gum paper and the surface of the positive electrode sheet has a small liquid-liquid contact angle, the interface impedance is reduced, and the positive electrode sheet and the gum paper will undergo an oxidation side reaction. Therefore, by controlling the thickness of the gum paper, on the one hand, the adhesion of the gum paper can be maintained to ensure the stability of the battery structure; on the other hand, the occurrence of side reactions can be reduced to ensure the stability of the battery system. When the thickness of the gum paper is relatively thin (for example, less than 0.05 mm), the gum paper cannot effectively play the role of adhesion, which is not conducive to the structural stability of the battery; when the thickness of the gum paper is relatively thick (for example, greater than 0.5 mm), the gum paper is more easily affected by the strong oxidizing positive electrode sheet and the swelling of the organic solvent in the electrolyte during the overcharge of the battery.

[0058] In the present application, the thickness of the adhesive tape can be tested by conventional methods in the art, for example, randomly selecting ten points on the adhesive tape, measuring the thickness of the adhesive tape at each point, and taking the average value.

[0059] In the present application, the weight content y of the first additive in the electrolyte and the thickness t of the adhesive tape satisfy: -0.1≤0.6xt-3xy≤0.3, for example, -0.1, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0, 0.1, 0.15, 0.2, 0.25 or 0.3.

[0060] In an example, 0≤0.6xt-3xy≤0.105.

[0061] In an example, 0.045≤0.6xt-3xy≤0.06.

[0062] During the charging process of the positive electrode, the lattice oxygen O 2- is oxidized to form molecular oxygen (O2), which is stabilized in the bulk phase by being trapped in the cavities in the bulk phase, but the molecular oxygen on the surface of the material is easy to escape, which on the one hand reacts violently with the electrolyte, and on the other hand oxidizes the swollen adhesive tape, causing the adhesive tape to gradually lose adhesion, become hard and brittle. The broken adhesive tape can even cause the tab adhesive to fall off, leading to the risk of battery swelling and leakage. The first additive can form a protective film on the surface of the positive electrode, allowing the molecular oxygen to stay in the positive electrode material. When the discharge reaction occurs, the molecular oxygen can re-form the lattice oxygen O 2- . Therefore, the first additive can prevent the escape of molecular oxygen, thereby preventing the oxidation of the adhesive tape, reducing the swelling rate of the adhesive tape, and protecting the interface near the tab to smoothly de-lithiate, thereby reducing the occurrence of lithium precipitation and ensuring the long cycle and safety of the battery. When 0.6xt-3xy is low (for example, less than -0.1), the content of the first additive is low, and the first additive cannot effectively form a film near the positive tab, resulting in a high swelling rate of the adhesive tape; it also cannot effectively prevent the escape of molecular oxygen, further causing the oxidation of the adhesive tape and increasing the risk of adhesive tape aging. When 0.6xt-3xy is high (for example, greater than 0.3), the content of the first additive is high, which can provide sufficient protection to the adhesive tape, but the increase in the content of the first additive will increase the viscosity of the electrolyte, thereby increasing the impedance of the battery and affecting the electrochemical performance of the battery.

[0063] In an example, R1, R2 and R3 can each independently be selected from at least one of substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C4 alkenyl and substituted or unsubstituted C2-C3 alkynyl.

[0064] In one example, the first additive includes at least one of 1,2,3-tris(cyanoethoxy)propane, 1,2,3,4-tetrakis(2-cyanoethoxy)butane, 1,2,3,4,5-pentakis(2-cyanoethoxy)pentane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, ethylene glycol bis(4-cyanobutyl) ether, and ethylene glycol (bis) propionitrile ether.

[0065] In one example, the first additive includes (1,2,3,4,5-pentakis(2-cyanoethoxy)pentane).

[0066] In the present application, the battery can include a wound battery.

[0067] In one example, the battery is a wound battery.

[0068] In the present application, the wound battery can include a circular arc region and a flat region. The radius of the positive electrode sheet located in the circular arc region is R 正 The radius of the negative electrode sheet adjacent to the positive electrode sheet near the winding center of the battery is R 负 , R 正 / R 负 ≤1.08.

[0069] For a wound battery, the circular arc is more prone to lithium precipitation than other positions. And with the increase of the negative electrode surface density, the risk of lithium precipitation at the circular arc will further increase, resulting in further reduction of the cycle performance of the battery. The inventors of the present application found that when the first additive is included in the electrolyte, by controlling the radius of the positive electrode sheet and the negative electrode sheet in the circular arc region, the problem of easy lithium precipitation in the circular arc region of the wound battery can be effectively improved. The reason can be that the circular arc region is poorly stressed during the formation stage, and the contact effect between the positive electrode sheet and the negative electrode sheet is not ideal. During the cycle process of the battery, not only is the lithium intercalation space insufficient in the negative electrode circular arc region, but also the poor contact between the positive electrode sheet and the negative electrode sheet makes the transmission resistance of lithium ions larger, and the region is prone to lithium precipitation in the later cycle, and with the intensification of lithium precipitation, the battery eventually deforms severely on the side and fails. The first additive can form a film on the surface of the positive electrode sheet and the negative electrode sheet, not only protecting the positive electrode sheet and the negative electrode sheet, but also reducing the transmission resistance of lithium ions and improving the transmission power of lithium ions on the surface of the negative electrode. On this basis, when R 正 / R 负 ≤1.08, the area of the positive electrode sheet in the circular arc region is balanced with the area of the negative electrode sheet, which can further reduce the transmission resistance of lithium ions and reduce the risk of lithium precipitation in the circular arc region.

[0070] In the present application, the radius of the positive electrode sheet at the circular arc region and the radius of the negative electrode sheet at the circular arc region can be tested by a method conventional in the art, for example, using a ruler.

[0071] In the present application, the CB value of the circular arc region can be 0.95-1.05, for example, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, or 1.05. The CB value of the flat region can be 1.01-1.07, for example, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, or 1.07.

[0072] In the present application, the thickness of the negative electrode active material layer can be 50 μm-80 μm, for example, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm.

[0073] In one example, the thickness of the negative electrode active material layer is 60 μm-70 μm.

[0074] In the present application, the thickness of the negative electrode active material layer refers to the thickness of the negative electrode active material layer on the side of the negative electrode current collector.

[0075] In the present application, the compaction density of the negative electrode active material layer can be 1.7 g / cm 3 -1.9 g / cm 3 , for example, 1.7 g / cm 3 , 1.8 g / cm 3 , or 1.9 g / cm 3 .

[0076] In one example, the compaction density of the negative electrode active material layer is 1.79 g / cm 3 -1.85 g / cm 3 .

[0077] In the present application, the negative active material layer can include a negative active material, a negative conductive agent, and a negative binder. The negative active material can include at least one of a carbon-based material and a silicon-based material. The carbon-based material can include at least one of natural graphite, artificial graphite, mesocarbon microbeads, soft carbon, and hard carbon. The silicon-based material can include at least one of silicon, silicon-oxygen, silicon-carbon, and silicon alloy. The silicon-oxygen has a conventional meaning in the art and is generally considered as a material including silicon and oxygen. The silicon-carbon also has a conventional meaning in the art and is generally considered as a material including silicon and carbon. The negative conductive agent can include a conductive agent conventionally used in the art, for example, including at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, and metal powder. The negative binder can include a binder conventionally used in the art, for example, including at least one of styrene butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, polyvinyl alcohol, and polyvinylidene fluoride.

[0078] In the present application, the content of the negative active material can be 90% to 99.8% (for example, 90%, 92%, 94%, 96%, 98%, 99%, or 99.8%) based on the total weight of the negative active material layer, the content of the negative conductive agent can be 0.1% to 5% (for example, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%), and the content of the negative binder can be 0.1% to 5% (for example, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%).

[0079] In an example, the content of the negative active material is 95% to 99.6%, the content of the negative conductive agent is 0.2% to 2.5%, and the content of the negative binder is 0.2% to 2.5% based on the total weight of the negative active material layer.

[0080] In the present application, the positive electrode sheet can include a positive current collector and a positive active material layer on at least one side surface of the positive current collector. The positive active material layer can include a positive active material, a positive conductive agent, and a positive binder. The positive active material can include a positive active material conventionally used in the art, for example, including at least one of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel cobalt manganese aluminate, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, and lithium-rich manganese-based material. The positive binder can include a binder conventionally used in the art, for example, including at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene butadiene rubber, polytetrafluoroethylene, and polyethylene oxide. The positive conductive agent can include a conductive agent conventionally used in the art, for example, including at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, and metal powder.

[0081] In the present application, the content of the positive electrode active material can be 90% to 99.8% (for example, 90%, 92%, 94%, 96%, 98%, 99%, or 99.8%) based on the total weight of the positive electrode active material layer, the content of the positive electrode conductive agent can be 0.1% to 5% (for example, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%), and the content of the positive electrode binder can be 0.1% to 5% (for example, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%).

[0082] In an example, the content of the positive electrode active material is 95% to 99.6%, the content of the positive electrode conductive agent is 0.2% to 2.5%, and the content of the positive electrode binder is 0.2% to 2.5% based on the total weight of the positive electrode active material layer.

[0083] In the present application, the electrolyte can further include a second additive. The second additive can include at least one of fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), 1,3-propylene carbonate (PST), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), succinonitrile (SN), and 1.3.6-hexanetricarbonitrile (HTCN). The content of the second additive can be ≤ 25%, for example, 25%, 20%, 15%, 10%, or 5% based on the total weight of the electrolyte.

[0084] In the present application, the electrolyte can further include a lithium salt. The lithium salt can include at least one of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluoro oxalate borate (LiDFOB), lithium bisfluorosulfonylimide (LiTFSI), lithium bis-trifluoromethylsulfonylimide, lithium difluorobisoxalate phosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide, and lithium bis(trifluoromethylsulfonyl)imide. The content of the lithium salt can be ≤ 21%, for example, 21%, 20%, 15%, 10%, or 5% based on the total weight of the electrolyte.

[0085] In the present application, the electrolyte can further include an organic solvent. The organic solvent can include at least one of ethylene carbonate (EC), propylene carbonate (PC), and the following solvents: propyl propionate (PP), ethyl propionate (EP), ethyl butyrate (EB), ethyl acetate (EA), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0086] The EC in the organic solvent can participate in the formation of the SEI film in the first charge-discharge cycle of the battery, can improve the efficiency of subsequent lithium ion deintercalation in the negative electrode, and reduce the occurrence of side reactions. PC has a high dielectric constant, which can promote the dissociation of lithium salt and greatly improve the ionic conductivity in the solution. The second additive can form a film on the surface of the positive electrode / negative electrode to protect the positive electrode / negative electrode. The lithium salt determines the basic physical and chemical properties of the electrolyte, and is the most important component in the electrolyte composition that affects the characteristics of the lithium ion battery. It can conduct lithium ions and increase the conductivity of the electrolyte.

[0087] In the present application, the battery can further comprise a separator, which can be selected from conventional separators used in the art, such as at least one of a polyethylene film and a polypropylene film.

[0088] It should be noted that the "first", "second" and the like numerical representation in the present application are only used to distinguish different substances or usage methods, and do not represent the difference in order.

[0089] The present application will be described in detail by the following examples. The examples described in the present application are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0090] In the following examples, the materials used are commercially available analytical pure unless otherwise specified.

[0091] The following examples are used to illustrate the battery of the present application.

[0092] Example 1

[0093] The battery is prepared according to the following method:

[0094] (1) Preparation of electrolyte

[0095] In a glove box (H2O<0.01ppm, O2<0.01ppm, Ar atmosphere), EC, PC, PP and EP were mixed uniformly according to the weight ratio of 12:10:58:20, 15% of fully dried LiPF6 based on the total weight of the electrolyte was added, 1.2% of the first additive (1,2,3,4,5-pentakis(2-cyanoethoxy)pentane) and 20% of the second additive (including 12% of FEC, 3% of PS, 2% of SN and 3% of HTCN) based on the total weight of the electrolyte were added, and stirred uniformly. After passing the water and free acid detection, the electrolyte was obtained;

[0096] (2) Preparation of negative electrode sheet

[0097] The negative active material (artificial graphite), conductive carbon black, butadiene rubber and sodium carboxymethyl cellulose are mixed uniformly according to the weight ratio of 98:1:0.5:0.5, deionized water is added, and the mixture is fully stirred to form a uniform negative electrode slurry; the negative electrode slurry is coated on a copper foil, dried, rolled, cut, cleaned, and a hole is made using a laser device to obtain a negative electrode sheet, wherein the areal density of the negative active material layer is 10.5 mg / cm 2 , the thickness of the negative active material layer is 70 μm, the compaction density of the negative active material layer is 1.77 g / cm 3 , the recess width w is 90 μm, the depth h is 15 μm, the pitch g is 0.1 mm, 0.1×h+w / g is 901.5, and 20×y-0.3×h / w is 0.19.

[0098] (3) Preparation of a positive electrode sheet

[0099] The positive active material (lithium cobaltate), conductive carbon black and polyvinylidene fluoride are mixed uniformly according to the weight ratio of 98:1.2:0.8, dispersed in N-methyl pyrrolidone (NMP), and fully stirred to form a uniform positive electrode slurry, which is coated on an aluminum foil, dried, rolled, cut, cleaned, and taped with adhesive paper to obtain a positive electrode sheet, wherein the thickness t of the adhesive paper is 0.15 mm, and 0.6×t-3×y is 0.054.

[0100] (4) Preparation of a battery

[0101] The negative electrode sheet prepared in step (2), the positive electrode sheet prepared in step (3) and a separator (a polypropylene substrate with a thickness of 5 μm, a ceramic layer with a thickness of 1 μm arranged on one side of the substrate, and a polyvinylidene fluoride adhesive layer with a thickness of 1 μm arranged on the other side of the substrate) are wound into a core according to a predetermined procedure, the electrolyte prepared in step (1) is injected, and the core is subjected to procedures such as vacuum sealing, standing, formation, sorting, secondary sealing, etc. to prepare a battery, wherein R 正 / R 负 ≤1.08, the CB value of the circular arc region is 1.01, and the CB value of the flat region is 1.04.

[0102] Example 2

[0103] A battery is prepared according to the following method:

[0104] (1) Preparation of an electrolyte

[0105] In a glove box (H2O < 0.01 ppm, O2 < 0.01 ppm, Ar atmosphere), EC, PC, PP and EP are mixed uniformly in a weight ratio of 12:10:58:20, 15% of fully dried LiPF6 based on the total weight of the electrolyte is added, 0.5% of the first additive (1,2,3,4,5-pentakis(2-cyanoethoxy)pentane) and 20% of the second additive (including 12% FEC, 3% PS, 2% SN and 3% HTCN) based on the total weight of the electrolyte are added, and stirred uniformly. After passing the moisture and free acid detection, the electrolyte is obtained.

[0106] (2) Preparation of negative electrode sheet

[0107] The negative electrode active material (artificial graphite), conductive carbon black, butadiene rubber and sodium carboxymethyl cellulose are mixed uniformly in a weight ratio of 98:1:0.5:0.5, deionized water is added, and the negative electrode slurry is formed by fully stirring. The negative electrode slurry is coated on a copper foil, dried, rolled, cut, cleaned, and the negative electrode sheet is obtained by using a laser device to form holes. The areal density of the negative electrode active material layer is 10.5 mg / cm 2 , the thickness of the negative electrode active material layer is 70 μm, the compaction density of the negative electrode active material layer is 1.77 g / cm 3 , the recess width w is 50 μm, the depth h is 10 μm, the pitch g is 0.03 mm, 0.1xh+w / g is 1667.7, and 20xy-0.3xh / w is 0.04.

[0108] (3) Preparation of positive electrode sheet

[0109] The positive electrode active material (lithium cobaltate), conductive carbon black and polyvinylidene fluoride are mixed uniformly in a weight ratio of 98:1.2:0.8, dispersed in N-methyl pyrrolidone (NMP), and fully stirred to form a uniform positive electrode slurry. The positive electrode slurry is coated on an aluminum foil, dried, rolled, cut, cleaned, and the positive electrode sheet is obtained by pasting adhesive paper. The thickness t of the adhesive paper is 0.1 mm, and 0.6xt-3xy is 0.045.

[0110] (4) Preparation of battery

[0111] The negative electrode sheet prepared in step (2), the positive electrode sheet prepared in step (3) and the separator (a polypropylene substrate with a thickness of 5 μm, a ceramic layer with a thickness of 1 μm arranged on one side of the substrate, and a polyvinylidene fluoride adhesive layer with a thickness of 1 μm arranged on the other side of the substrate) are wound into a core according to a predetermined procedure, the electrolyte prepared in step (1) is injected, and the battery is prepared after passing through the procedures of vacuum sealing, standing, formation, sorting, two-sealing and the like. The R 正 / R 负≤1.08, the CB value of the arc region is 1.01, and the CB value of the flat region is 1.04.

[0112] Example 3

[0113] The battery was prepared according to the following method:

[0114] (1) Preparation of electrolyte

[0115] In a glove box (H2O < 0.01 ppm, O2 < 0.01 ppm, Ar atmosphere), EC, PC, PP and EP were mixed uniformly according to a weight ratio of 12:10:58:20, 15% of fully dried LiPF6 based on the total weight of the electrolyte was added, 2% of the first additive (1,2,3,4,5-pentakis(2-cyanoethoxy)pentane) and 20% of the second additive (including 12% FEC, 3% PS, 2% SN and 3% HTCN) based on the total weight of the electrolyte were added, and stirred uniformly. After passing the moisture and free acid detection, the electrolyte was obtained;

[0116] (2) Preparation of negative electrode sheet

[0117] The negative electrode active material (artificial graphite), conductive carbon black, butadiene rubber and sodium carboxymethyl cellulose were mixed uniformly according to a weight ratio of 98:1:0.5:0.5, deionized water was added, and the negative electrode slurry was formed by fully stirring. The negative electrode slurry was coated on a copper foil, dried, rolled, cut, washed, and the ear rubber was attached. The negative electrode sheet was obtained by using a laser device to form holes, wherein the surface density of the negative electrode active material layer was 10.5 mg / cm 2 , the thickness of the negative electrode active material layer was 70 μm, the compaction density of the negative electrode active material layer was 1.77 g / cm 3 , the recess width w was 120 μm, the depth h was 25 μm, the pitch g was 0.2 mm, 0.1xh+w / g was 602.5, and 20x y-0.3xh / w was 0.34.

[0118] (3) Preparation of positive electrode sheet

[0119] The positive electrode active material (lithium cobaltate), conductive carbon black and polyvinylidene fluoride were mixed uniformly according to a weight ratio of 98:1.2:0.8, dispersed in N-methyl pyrrolidone (NMP), and fully stirred to form a uniform positive electrode slurry. The positive electrode slurry was coated on an aluminum foil, dried, rolled, cut, washed, and the adhesive tape was attached. The positive electrode sheet was obtained, wherein the thickness t of the adhesive tape was 0.2 mm, and 0.6xt-3xy was 0.06.

[0120] (4) Preparation of battery

[0121] The negative electrode sheet prepared in step (2), the positive electrode sheet prepared in step (3), and a separator (a polypropylene base material with a thickness of 5 μm, a ceramic layer with a thickness of 1 μm provided on one side of the base material, and a polyvinylidene fluoride adhesive layer with a thickness of 1 μm provided on the other side of the base material) were wound in a predetermined procedure to form a core, and the electrolyte prepared in step (1) was injected thereinto. Then, a battery was prepared by performing procedures such as vacuum sealing, standing, formation, sorting, and second sealing, wherein R 正 / R 负 ≤ 1.08, the CB value of the circular arc region was 1.01, and the CB value of the flat region was 1.04.

[0122] Example 4 Group

[0123] This group of examples was used to verify the effects of changes in the "areal density of the negative electrode active material layer".

[0124] This group of examples was performed with reference to Example 1, except that the areal density of the negative electrode active material layer was changed, as follows.

[0125] Example 4a: the areal density of the negative electrode active material layer was 9 mg / cm 2 , the thickness of the negative electrode active material layer was 60 μm, and the tap density of the negative electrode active material layer was 1.83 g / cm 3 .

[0126] Example 4b: the areal density of the negative electrode active material layer was 9.5 mg / cm 2 , the thickness of the negative electrode active material layer was 65 μm, and the tap density of the negative electrode active material layer was 1.8 g / cm 3 .

[0127] Example 4c: the areal density of the negative electrode active material layer was 11 mg / cm 2 , the thickness of the negative electrode active material layer was 70 μm, and the tap density of the negative electrode active material layer was 1.76 g / cm 3 .

[0128] Example 4d: the areal density of the negative electrode active material layer was 12 mg / cm 2 , the thickness of the negative electrode active material layer was 80 μm, and the tap density of the negative electrode active material layer was 1.74 g / cm 3 .

[0129] Example 5 Group

[0130] This group of examples was used to verify the effects of changes in "0.1 x h + w / g".

[0131] This group of examples was performed with reference to Example 1, except that the width w, the depth h, and the pitch g of the recesses were changed, as follows.

[0132] Example 5a, the recess width w is 30 μm, the depth h is 5 μm, the pitch g is 0.01 mm, 0.1 x h + w / g is 3000.5;

[0133] Example 5b, the recess width w is 200 μm, the depth h is 30 μm, the pitch g is 0.5 mm, 0.1 x h + w / g is 403, 20 x y - 0.3 x h / w is 0.195.

[0134] Example 6 group

[0135] This group of examples is used to verify the influence of the change of "the thickness t of the adhesive paper".

[0136] This group of examples is performed with reference to Example 1, except that the thickness t of the adhesive paper is changed, specifically as follows:

[0137] Example 6a, t is 0.05 mm, 0.6 x t - 3 x y is -0.006;

[0138] Example 6b, t is 0.5 mm, 0.6 x t - 3 x y is 0.264.

[0139] Example 7 group

[0140] This group of examples is used to verify the influence of the change of "the first additive".

[0141] This group of examples is performed with reference to Example 1, except that the first additive is changed, specifically as follows:

[0142] Example 7a, the first additive is replaced by 1,2,3,4-tetra(2-cyanoethoxy)butane of the same weight;

[0143] Example 7b, the first additive is replaced by 1,2,3-tri(cyanoethoxy)propane of the same weight.

[0144] Example 8 group

[0145] This group of examples is used to verify the influence of the change of "the weight content y of the first additive in the electrolyte".

[0146] This group of examples is performed with reference to Example 1, except that y is changed, specifically as follows:

[0147] Example 8a, y is 0.1%, 20 x y - 0.3 x h / w is -0.03, 0.6 x t - 3 x y is 0.087;

[0148] Example 8b, y is 0.3%, 20 x y - 0.3 x h / w is 0.01, 0.6 x t - 3 x y is 0.081;

[0149] Example 8c, y is 3.5%, 20 x y - 0.3 x h / w is 0.65, 0.6 x t - 3 x y is -0.015;

[0150] Example 8d, y is 5%, 20 x y - 0.3 x h / w is 0.95, 0.6 x t - 3 x y is -0.06.

[0151] Example 9 Group

[0152] This group of examples is for verifying the effect of the change in "20 x y - 0.3 x h / w".

[0153] This group of examples is conducted with reference to Example 2 or Example 3, except that 20 x y - 0.3 x h / w is changed by changing the width w, depth h and pitch g of the recesses, as follows:

[0154] Example 9a, conducted with reference to Example 2, except that the width w of the recesses is 120 μm, the depth h is 25 μm, the pitch g is 0.2 mm, and 20 x y - 0.3 x h / w is 0.0375.

[0155] Example 9b, conducted with reference to Example 3, except that the width w of the recesses is 50 μm, the depth h is 10 μm, the pitch g is 0.03 mm, and 20 x y - 0.3 x h / w is 0.34.

[0156] Example 10 Group

[0157] This group of examples is for verifying the effect of the change in "0.6 x t - 3 x y".

[0158] This group of examples is conducted with reference to Example 2 or Example 3, except that 0.6 x t - 3 x y is changed by changing the thickness t of the adhesive tape, as follows:

[0159] Example 10a, conducted with reference to Example 2, except that t is 0.2 mm, and 0.6 x t - 3 x y is 0.105.

[0160] Example 10b, conducted with reference to Example 3, except that t is 0.1 mm, and 0.6 x t - 3 x y is 0.

[0161] Example 11

[0162] This example is for verifying the effect of the change in "R 正 / R 负 ".

[0163] Conducted with reference to Example 1, except that R 正 / R 负, specifically as follows:

[0164] The areal density of the negative active material layer was 14 mg / cm 2 The thickness of the negative active material layer was 80 μm, and the compaction density of the negative active material layer was 1.83 g / cm 3 R 正 / R 负 > 1.08.

[0165] Example 12 group

[0166] This group of examples is used to verify the influence of the change in the "type of recess".

[0167] This group of examples is respectively made with reference to Examples 1-3, except that a laser device is used to make grooves on the surface of the negative plate, specifically as follows:

[0168] Example 12a, made with reference to Example 1, except that the recess width w is 90 μm, the depth h is 15 μm, the pitch g is 2 mm, and 0.1 x h + w / g is 46.5;

[0169] Example 12b, made with reference to Example 2, except that the recess width w is 50 μm, the depth h is 10 μm, the pitch g is 1 mm, and 0.1 x h + w / g is 51;

[0170] Example 12c, made with reference to Example 3, except that the recess width w is 120 μm, the depth h is 25 μm, the pitch g is 3 mm, and 0.1 x h + w / g is 42.5.

[0171] Example 13

[0172] Made with reference to Example 1, except that no holes are made on the surface of the negative plate.

[0173] In the above examples, except that the power of the laser used in Example 5 group is 20 W-250 W; Example 13 does not use laser to make holes; the power of the laser used in the rest of the examples is 40 W-200 W.

[0174] Comparative Example 1

[0175] Made with reference to Example 1, except that the first additive is not contained in the electrolyte.

[0176] Comparative Example 2

[0177] Made with reference to Example 1, except that the first additive is replaced by the same weight of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0178] Test Example

[0179] (1) Liquid retention coefficient test

[0180] The batteries prepared in the examples and comparative examples were extracted and packaged at the time of the second sealing process; the liquid retention amount was calculated, the liquid retention amount = the weight of the battery cell + the amount of electrolyte injection - the weight of the battery cell after the second sealing; the liquid retention coefficient = the liquid retention amount / battery capacity, and the results are recorded in Table 1.

[0181] (2) 1C cycle test

[0182] The batteries prepared in the examples and comparative examples were placed at 25°C, charged at 1C constant current to 4.48V, then converted to 0.7C to the upper limit voltage (4.53V), then charged at 4.53V constant voltage to 0.05C, and then placed for 5 minutes; then discharged at 0.7C constant current to 3V, and then placed for 5 minutes; this is one charge / discharge cycle; so charge / discharge 1000T, record the cycle capacity retention rate, and after the cycle, the battery is disassembled to observe the lithium precipitation, and the results are recorded in Table 1.

[0183] (3) 2C cycle test

[0184] The batteries prepared in the examples and comparative examples were placed at 25°C, charged at 2C constant current to 4.48V, then converted to 0.7C to the upper limit voltage (4.53V), then charged at 4.53V constant voltage to 0.05C, and then placed for 5 minutes; then discharged at 1C constant current to 3V, and then placed for 5 minutes; this is one charge / discharge cycle; so charge / discharge 1000T, record the cycle capacity retention rate, and after the cycle, the battery is disassembled to observe the lithium precipitation, and the results are recorded in Table 1.

[0185] (4) Furnace temperature test

[0186] The batteries prepared in the examples and comparative examples were placed at 25°C, charged at 1C constant current to 4.48V, then converted to 0.7C to the upper limit voltage (4.53V), then charged at 4.53V constant voltage to 0.05C, and then placed for 5 minutes; then the battery was placed in a 130°C furnace and observed for 60 minutes; if the battery did not catch fire and did not explode, it passed the test, and 10 batteries of each example or comparative example were tested, and the pass rate results are recorded in Table 1.

[0187] Table 1

[0188]

[0189]

[0190] As can be seen from Table 1, the battery of the present application has excellent cycle performance and furnace temperature safety performance compared with the comparative examples.

[0191] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A battery, characterized by, The battery includes a negative 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 surface of the negative electrode current collector, the negative electrode active material layer has a surface density of 9 mg / cm 2 -14 mg / cm 2 ; the electrolyte includes a first additive, the first additive includes a substance represented by Formula I: wherein R1, R2, and R3 are each independently selected from at least one of substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C2-C5 alkenyl, and substituted or unsubstituted C2-C4 alkynyl, the substituted groups including at least one of phenyl, halogen, sulfur-containing groups, phosphorus-containing groups, trimethylsilyl, methoxy, hydroxyl, carboxyl, aldehyde, carbonyl, and cyano.

2. The battery of claim 1, wherein, The content of the first additive is y, 0.1%≤y≤5%, based on the total weight of the electrolyte; Preferably, 0.5%≤y≤2%.

3. The battery according to claim 1 or 2, wherein The negative electrode sheet has a concave portion; the width of the concave portion is w, in units of μm, the depth of the concave portion is h, in units of μm, and the pitch of the concave portion is g, in units of mm; Preferably, w is 30-200, in units of μm; Preferably, h is 5-30, in units of μm; Preferably, g is 0.01-5, in units of mm.

4. The battery of claim 3, wherein, w, h, and g satisfy: 30≤0.1×h+w / g≤3500; Preferably, 40≤0.1×h+w / g≤55; Preferably, 600≤0.1×h+w / g≤1700.

5. The battery of claim 3, wherein, The depth h of the concave portion, the width w of the concave portion, and the weight content y of the first additive in the electrolyte satisfy: -0.1≤20×y-0.3×h / w≤1; Preferably, 0.04≤20×y-0.3×h / w≤0.

339.

6. The battery of claim 1 or 2, wherein, The battery further includes a positive electrode sheet, the positive electrode sheet includes a positive electrode tab, the positive electrode sheet further includes a gummed paper covering part of the positive electrode tab, and the thickness t of the gummed paper is 0.05mm-0.5mm.

7. The battery of claim 6, wherein, The weight content y of the first additive in the electrolyte and the thickness t of the gummed paper satisfy: -0.1≤0.6×t-3×y≤0.

3.

8. The battery of claim 1 or 2, wherein, R1, R2, and R3 are each independently selected from at least one of substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C4 alkenyl, and substituted or unsubstituted C2-C3 alkynyl; Preferably, the first additive includes at least one of 1,2,3-tris(cyanoethyloxy)propane, 1,2,3,4-tetrakis(2-cyanoethyloxy)butane, 1,2,3,4,5-pentakis(2-cyanoethyloxy)pentane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, ethylene glycol bis(4-cyanobutyl) ether, and ethylene glycol (bis) propionitrile ether; More preferably, the first additive includes 1,2,3,4,5-pentakis(2-cyanoethyloxy)pentane.

9. The battery of claim 1 or 2, wherein, The battery further comprises a positive electrode sheet; the battery comprises a winding type battery, the winding type battery comprises a circular arc region and a flat region; the radius of the positive electrode sheet located in the circular arc region is R 正 The radius of the negative electrode sheet adjacent to the positive electrode sheet and close to the winding center of the battery is R 负 , R 正 / R 负 ≤1.

08.

10. The battery of claim 1 or 2, wherein, The battery includes a jelly-roll battery, the jelly-roll battery includes a circular arc region and a flat region; the CB value of the circular arc region is 0.95-1.05, and the CB value of the flat region is 1.01-1.07.

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