Battery

Abstract

The invention relates to the technical field of batteries, in particular to a battery. The battery comprises a shell, a cover plate and an electrode assembly, the electrode assembly comprises a positive plate, a diaphragm and a negative plate which are stacked, the negative plate comprises a negative current collector and a negative active layer, the negative active layer comprises a silicon-based material, and the weight ratio of silicon element in the negative active layer is 10-70%; the shell comprises a bottom wall and a side wall extending upwards from the bottom wall, an opening is formed in the side wall, the cover plate covers the opening, and the electrode assembly is located in the containing cavity of the shell; the battery also comprises an insulating layer which is positioned between the electrode assembly and the side wall; the battery meets the following relational expression: A / a is less than or equal to 2, A is the thickness of the insulating layer, and the unit is mm; and a is the distance between the edge of the positive plate and the insulating layer along the first direction when the battery is in 0% SOC, and the unit is mm. The battery provided by the invention can reduce the risk of short circuit of the battery with the metal shell in a drop test and / or a roller test.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery. Background Technology

[0002] As consumer electronics products continue to upgrade and diversify, higher demands are being placed on battery capacity and safety. Steel-cased batteries use steel as their outer shell, which has high mechanical strength and impact resistance, effectively protecting the internal structure of the battery, improving battery safety, and eliminating the need for extra space to prevent bulging. This allows for a larger battery capacity, making them widely used in the consumer electronics industry.

[0003] Currently, the energy density requirements for metal-cased batteries are constantly increasing, and the space utilization within the casing is becoming more efficient. With the increase in energy density, battery safety has become a key focus. Current efforts mainly concentrate on the insulation between the positive electrode and the casing, especially safety during drop and tumbling tests. This is primarily because the steel casing is usually negatively charged. During drop and tumbling tests, the battery cell frequently shakes within the metal casing, increasing the risk that the positive electrode may come into contact with the casing due to movement, leading to a short circuit, or even a fire or explosion. Summary of the Invention

[0004] To overcome the problem that metal-cased batteries are prone to short circuits and even fires and explosions during drop tests and / or roller tests, this invention provides a battery. The battery of this invention can reduce the risk of short circuits in metal-cased batteries during drop tests and / or roller tests.

[0005] To achieve the above objectives, the present invention provides a battery comprising a casing, a cover plate, and an electrode assembly. The electrode assembly comprises a positive electrode, a separator, and a negative electrode stacked together. The negative electrode comprises a negative current collector and a negative active layer located on at least one surface of the negative current collector. The negative active layer comprises a silicon-based material, wherein the weight percentage of silicon in the negative active layer is 10%-70%. The housing includes a bottom wall and a side wall extending upward from the bottom wall, the side wall having an opening, the cover plate closing the opening, and the electrode assembly located within a receiving cavity of the housing; the battery also includes an insulating layer formed on the side wall on the inner side of the housing, the insulating layer being located between the electrode assembly and the side wall; The battery satisfies the following relationship: A / a≤2, where A is the thickness of the insulating layer in mm; a is the distance between the edge of the positive electrode and the insulating layer along the first direction when the battery is at 0% SOC, in mm.

[0006] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: The battery of the present invention has a casing comprising a bottom wall and a side wall, the side wall having an opening, a cover plate closing the opening, an electrode assembly located within a receiving cavity formed by the cover plate and the side wall, and an insulating layer disposed on the inner surface of the side wall. The presence of the insulating layer prevents the positive electrode from contacting the casing during drop tests and roller tests, thereby avoiding the risk of short circuit. At the same time, the presence of the insulating layer also prevents the positive electrode from contacting the casing when the silicon-containing negative electrode expands, thereby improving the safety performance of the battery.

[0007] To further reduce the risk of contact between the positive electrode and the casing, the battery of the present invention also controls the weight ratio of silicon in the negative electrode active layer to 3%-70%, and the ratio of the thickness A of the insulating layer to the minimum value a of the distance between the edge line of the positive electrode and the surface of the insulating layer away from the sidewall when the battery is in a 0% SOC state, so that the battery satisfies the relationship: A / a≤2, thereby improving the matching degree between the thickness of the insulating layer and the weight ratio of silicon in the negative electrode active layer, so that the thickness of the insulating layer can withstand the expansion stress generated by silicon within the above range, ensuring that even if the expansion of the negative electrode causes the positive electrode to expand during the expansion process, there is always an insulating layer between the positive electrode and the sidewall of the casing, and the positive electrode will not contact the sidewall of the casing, thereby reducing or even avoiding the risk of short circuit.

[0008] Meanwhile, the insulating layer can also absorb the expansion stress of the positive and / or negative electrode sheets in the first direction, preventing excessive expansion stress and the negative electrode sheet from easily hitting the side wall of the casing, causing the negative electrode sheet to bend. Furthermore, A / a≤2 can also ensure that while the insulating layer plays its role in preventing the positive electrode sheet from contacting the casing and absorbing expansion stress, it can also reduce the occupancy rate of the insulating layer in the internal space of the casing, without affecting the insertion of the battery cell into the casing. This prevents the edge of the battery cell from overlapping with the insulating layer during the insertion process, which could cause wrinkles on the electrode sheet or separator at the edge of the battery cell, affecting the overall thickness of the battery or affecting the subsequent flange welding, leading to poor welding or missing welding. This gives the battery both high safety performance and high energy density. When A / a > 2, the thickness of the insulating layer is too large or the distance between the edge line of the positive electrode and the surface of the insulating layer away from the sidewall is too close. When the thickness of the insulating layer is too large, it will affect the space utilization of the battery, resulting in a decrease in the energy density of the battery, and will also increase the difficulty of inserting the cell into the casing. When the distance between the edge line of the positive electrode and the surface of the insulating layer away from the sidewall is too short, the short distance is not enough to effectively absorb the expansion stress of the positive and negative electrodes in the width and length directions. There is not enough expansion space for the expansion of the positive or negative electrode, which makes the electrode prone to bending and contact with the electrode of the other polarity during the cycle expansion process, causing a short circuit risk and reducing the safety performance of the battery.

[0009] Therefore, the insulating layer in the battery of the present invention can not only reduce or even avoid the risk of contact between the positive electrode and the casing during drop tests and / or roller tests, but also prevent the positive electrode and the casing from contacting each other during battery expansion. Furthermore, it can provide a buffer for the expansion of the positive and negative electrodes, reduce the risk of electrode bending, and further improve the safety performance of the battery, so that the battery has both high safety performance and high energy density.

[0010] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0011] 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

[0012] Figure 1 The diagram shown is a structural schematic of a battery according to an embodiment of the present invention.

[0013] Figure 2 The diagram shown is an exploded view of the battery structure according to an embodiment of the present invention.

[0014] Figure 3 The image shown is a partial cross-sectional view of a battery according to an embodiment of the present invention.

[0015] Figure 4 The image shown is an exploded view of the bottom shell and insulating layer according to an embodiment of the present invention. Detailed Implementation

[0016] 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 invention. Unless otherwise specified herein, data ranges include endpoints.

[0017] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0018] Currently, the energy density requirements for metal-cased batteries are constantly increasing, and the space utilization within the casing is becoming more efficient. With the increase in energy density, battery safety has become a key focus. Current efforts mainly concentrate on the insulation between the positive electrode and the casing, especially safety during drop and tumbling tests. This is primarily because the steel casing is usually negatively charged. During drop and tumbling tests, the battery cell frequently shakes within the metal casing, increasing the risk that the positive electrode may come into contact with the casing due to movement, leading to a short circuit, or even a fire or explosion.

[0019] Steel-cased batteries, due to their high mechanical strength and impact resistance, can meet the demands of high-energy-density batteries, such as those containing silicon anodes. Using steel-cased batteries with silicon anodes can provide higher energy density within the same volume, thus extending the device's battery life. However, research has found that batteries with silicon anodes expand significantly. During cycling, batteries containing silicon-doped anodes expand in both the X and Y directions (the length or width of the casing), gradually compressing the space between the electrode and the casing. This increases the risk of short circuits caused by contact between the positive electrode and the casing.

[0020] In view of the above situation, one embodiment of the present invention provides a battery, such as... Figures 1-4 As shown, battery 1 includes a casing 11, a cover plate 12, and an electrode assembly 13. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet stacked together. The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector. The negative electrode active layer includes a silicon-based material, and the weight percentage of silicon in the negative electrode active layer is 10%-70% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%). The casing includes a bottom wall and side walls extending upward from the bottom wall. The side walls have openings, and the cover plate closes the openings. The electrode assembly is located within the receiving cavity of the casing.

[0021] In this invention, the weight content of silicon in the negative electrode active layer can be obtained using conventional testing methods in the art, such as ICP. Specifically, after disassembling the lithium-ion battery, the negative electrode sheet is removed, soaked and rinsed with dimethyl carbonate, and dried. The dried negative electrode sheet is then subjected to high-temperature treatment at 400°C for 2 hours (e.g., in a tube furnace under nitrogen or argon atmosphere). The negative electrode active material layer can then be peeled off from the current collector, and the negative electrode active material can be collected. In the silicon content test, a thermogravimetric analyzer (e.g., a TGA 550 thermogravimetric analyzer) is used. The sample amount is 5mg-15mg. Under an air or oxygen atmosphere, the temperature is increased from room temperature to 900°C at a rate of 10°C / min, and held at 900°C for 40 minutes. This allows the non-silicon components in the negative electrode active layer to volatilize while the silicon is fully oxidized to silicon dioxide. The weight percentage at the end of the entire test process is the ash content of the negative electrode active layer; dividing this ash content by the molar mass of silicon dioxide and then multiplying it by the molar mass of silicon gives the percentage content of silicon in the negative electrode active layer.

[0022] In one specific example, along the length or width direction, the sidewall of the housing 11 extends outward to form a first flange edge 111, and the cover plate 12 forms a second flange edge 121 corresponding to the position of the first flange edge. The first flange edge 121 and the second flange edge 111 are aligned and connected, for example, by welding, to achieve a seal inside the housing. In another specific example, the upper and lower sidewalls of the housing both have first flange edges along the length and width directions, and the battery includes two cover plates located on the upper and lower sides of the housing. The cover plates form second flange edges corresponding to the positions of the first flange edges, and the two pairs of first flange edges and second flange edges are aligned and connected. In one specific example, the housing may be made of metal, such as steel, aluminum, or aluminum-plastic film. In other embodiments, the housing may be square, trapezoidal, polygonal, cylindrical, or other irregular shapes.

[0023] In a specific example, a first perforation 112 and a second perforation 113 are formed on the side wall of the housing 11. The first perforation contains a pole structure, which is connected to a certain polarity of the battery cell to lead to an external circuit. The second perforation is used to inject electrolyte into the battery cell and is sealed by a sealing element.

[0024] In a specific example, the positive electrode includes a positive current collector, a positive active layer on the positive current collector, and a positive electrode tab extending from one side of the positive current collector; the negative electrode includes a negative electrode tab extending from one side of the negative current collector, wherein the positive electrode tab and the positive current collector are integrally formed, and the negative electrode tab and the negative current collector are integrally formed.

[0025] In one specific example, the positive current collector may be, for example, aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector), and its thickness may be, for example, 6 μm-15 μm (e.g., 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm). In another specific example, the negative current collector may be, for example, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector. In one example, the thickness of the negative current collector may be, for example, 4 μm-10 μm (e.g., 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm).

[0026] In a specific example, the positive electrode active layer may include a positive electrode active material, such as lithium nickel cobalt manganese oxide (LiNi). 0.90 Co 0.05 Mn 0.05 O2 (NCM955), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 At least one of the following: O2 (NCM111)), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganese oxide, spinel-type lithium nickel manganese oxide, and lithium titanate.

[0027] In one specific example, the separator includes a base membrane and adhesive layers on both sides of the base membrane. In a further embodiment, a ceramic layer and an adhesive layer are sequentially formed on a first side of the base membrane, and an adhesive layer is formed on a second side. The first side surface of the base membrane is disposed opposite to the positive electrode, and the second side surface of the base membrane is disposed opposite to the negative electrode. In some embodiments, the thickness of the separator is 5 μm-20 μm (e.g., 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, or 20 μm).

[0028] In one specific example, the battery also includes an electrolyte comprising a lithium salt and a solvent, wherein the solvent comprises at least one selected from ethylene carbonate, diethyl carbonate, or fluoroethylene carbonate. In another embodiment, the electrolyte further includes a nitrile additive. The nitrile additive comprises a C3 percentage based on the total mass of the electrolyte. C3 is 0.5%-8%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%. In some embodiments, the nitrile additive comprises, for example, at least one selected from butadionitrile, adiponitrile, and 1,3,6-hexanetrionitrile.

[0029] In one specific example, the electrode assembly may be a core formed by stacking and winding a positive electrode, a separator, and a negative electrode; in other embodiments, the electrode assembly may be a stacked core formed by stacking a positive electrode, a separator, and a negative electrode. In a further embodiment, the stacked core includes a top layer and a bottom layer of electrodes along the thickness direction, the top layer and / or the bottom layer of electrodes may be single-sided negative electrodes, each including a negative current collector and a negative active layer on the surface of the negative current collector near the center of the electrode assembly. In some embodiments, the thickness of the current collector of the top layer of electrodes is greater than the thickness of the current collector of the same polarity electrodes in the middle of the stacked core, to prevent the top layer of electrodes from warping due to uneven stress during charging and discharging caused by the presence of an active layer on one side. In other embodiments, the negative electrode and the separators on both sides are thermally bonded together, i.e., the portions of the separators on both sides extending beyond the negative electrode are bonded to each other, such that the separators on both sides are bonded together to form a bag-like structure, enclosing the negative electrode within the bag-like structure.

[0030] The battery also includes an insulating layer 14 formed on the sidewall of the housing, located on one side of the housing. The insulating layer 14 is situated between the electrode assembly 13 and the sidewall of the housing 11. The battery satisfies the following relationship: A / a ≤ 2 (e.g., 2, 1.8, 1.5, 1.3, 1, 0.8, 0.5, 0.3, 0.1, 0.05, or 0.01), where A is the thickness of the insulating layer in mm; a is the distance between the edge of the positive electrode and the insulating layer along a first direction when the battery is at 0% SOC, in mm; in a specific example, the first direction refers to the length direction or the width direction of the battery; that is, a refers to the distance between the side of the positive electrode and the insulating layer along the length or width direction when the battery is fully discharged.

[0031] In this embodiment, the battery casing 11 includes a bottom wall 114 and a side wall 115. The side wall has an opening, which is closed by a cover plate. The electrode assembly is located in the receiving cavity formed by the cover plate and the side wall. An insulating layer is provided on the inner surface of the side wall. The presence of the insulating layer can prevent the positive electrode from contacting the casing during drop tests and roller tests, thereby avoiding the risk of short circuit. At the same time, the presence of the insulating layer can also prevent the positive electrode from contacting the casing when the silicon-containing negative electrode expands, thereby improving the safety performance of the battery.

[0032] To further reduce the risk of contact between the positive electrode and the casing, the battery of the present invention also controls the weight ratio of silicon in the negative electrode active layer to be 10%-70%, and the ratio of the thickness A of the insulating layer to the minimum value a of the distance between the edge line of the positive electrode and the surface of the insulating layer away from the sidewall when the battery is in a 0% SOC state, so that the battery satisfies the relationship: A / a≤2, thereby improving the matching degree between the thickness of the insulating layer and the weight ratio of silicon in the negative electrode active layer, so that the thickness of the insulating layer can withstand the expansion stress generated by silicon within the above range, ensuring that even if the expansion of the negative electrode causes the positive electrode to expand during the expansion process, there is always an insulating layer between the positive electrode and the sidewall of the casing, and the positive electrode will not contact the sidewall of the casing, thereby reducing or even avoiding the risk of short circuit.

[0033] Meanwhile, the insulating layer can also absorb the expansion stress of the positive and / or negative electrode sheets in the first direction, preventing excessive expansion stress and the negative electrode sheet from easily hitting the side wall of the casing, causing the negative electrode sheet to bend. Furthermore, A / a≤2 can also ensure that while the insulating layer plays its role in preventing the positive electrode sheet from contacting the casing and absorbing expansion stress, it can also reduce the occupancy rate of the insulating layer in the internal space of the casing, without affecting the insertion of the battery cell into the casing. This prevents the edge of the battery cell from overlapping with the insulating layer during the insertion process, which could cause wrinkles on the electrode sheet or separator at the edge of the battery cell, affecting the overall thickness of the battery or affecting the subsequent flange welding, leading to poor welding or missing welding. This gives the battery both high safety performance and high energy density. When A / a > 2, the insulation layer thickness is either too large or too close to the distance between the edge of the positive electrode and the surface of the insulation layer away from the sidewall. Excessive insulation layer thickness affects the battery's space utilization, leading to a decrease in energy density and increasing the difficulty of cell assembly. Conversely, insufficient distance between the edge of the positive electrode and the surface of the insulation layer away from the sidewall makes it difficult to effectively absorb the expansion stress of the positive and negative electrodes in both width and length directions. This lack of sufficient expansion space during cyclic expansion increases the risk of electrode bending and short circuits caused by contact between the electrodes of the opposite polarity, thus reducing battery safety.

[0034] Therefore, the insulating layer in the battery of the present invention can not only reduce or even avoid the risk of contact between the positive electrode and the casing during drop tests and / or roller tests, but also prevent the positive electrode and the casing from contacting each other during battery expansion. Furthermore, it can provide a buffer for the expansion of the positive and negative electrodes, reduce the risk of electrode bending, and further improve the safety performance of the battery, so that the battery has both high safety performance and high energy density.

[0035] In one possible implementation, the thickness A of the insulating layer is 0.01mm-0.5mm (e.g., 0.01mm, 0.03mm, 0.05mm, 0.08mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm or 0.5mm). This ensures that the insulating layer effectively prevents the positive electrode from contacting the side wall of the casing. It avoids the problem that if the thickness is too small, the positive electrode will repeatedly collide with the insulating layer during multiple charge and discharge cycles, and the insulating layer may easily fall off. At the same time, it avoids the problem that if the thickness is too large, it will affect the insertion of the battery cell into the casing.

[0036] In another possible implementation, when the battery is at 0% SOC, the distance 'a' between the edge of the positive electrode and the insulating layer along the first direction is 0.3 mm < a < 2 mm (e.g., 0.31 mm, 0.5 mm, 0.8 mm, 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 1.9 mm, or 1.95 mm), thereby ensuring that the positive and negative electrodes have sufficient expansion margin during charging and discharging.

[0037] In one possible implementation, the electrode assembly further includes a positive electrode tab assembly and a negative electrode tab assembly, and the sidewall of the housing is formed with a first perforation and an electrode post structure located on the first perforation, wherein the electrode post structure is connected to the positive electrode tab assembly.

[0038] In one specific example, the electrode structure includes a conductive element and an insulating structure. The conductive element includes a first pressing portion located on the outer side of the sidewall of the housing, a second pressing portion located on the inner side of the sidewall, and a conductive portion connecting the first pressing portion and the second pressing portion. The conductive portion passes through a first through-hole. In another specific example, the insulating structure includes a first insulating portion located between the first pressing portion and the sidewall of the housing, and a second insulating portion located between the second pressing portion and the sidewall of the housing, thereby preventing short circuits caused by contact between the first pressing portion and the sidewall of the housing or between the second pressing portion and the sidewall of the housing.

[0039] In another specific example, the pole structure includes a conductive element and an insulating layer located between the conductive element and the housing sidewall. In one example, the conductive element includes a straight portion and a conductive portion extending from the straight portion into a first through hole. The straight portion and the housing sidewall are bonded and sealed by the insulating layer. The positive electrode tab assembly is connected to the conductive portion.

[0040] In some specific examples, the positive electrode assembly includes several positive electrode tabs, a rigid positive electrode tab, and a positive electrode adapter. The positive electrode tabs are stacked, and after being bent, they connect to the rigid positive electrode tab. The end of the rigid positive electrode tab facing away from the positive electrode tab connects to the positive electrode adapter. The other end of the positive electrode adapter connects to the terminal post structure. In the width direction of the battery, the terminal post structure and the rigid positive electrode tabs are spaced apart, thus saving space in the length direction inside the casing. In one specific example, the positive electrode adapter has a U-shaped structure. In another specific example, the negative electrode assembly includes several negative electrode tabs and a rigid negative electrode tab. The negative electrode tabs are stacked, and after being bent, they connect to the rigid negative electrode tab. The end of the rigid negative electrode tab facing away from the negative electrode tab connects to the side wall of the casing and a fixing piece located outside the side wall of the casing.

[0041] The insulating layer 14 includes a first notch 141 and / or a second notch 142, with the first notch at least partially overlapping the area where the positive electrode tab assembly is located. In the specific example shown, the first notch is used to prevent the positive electrode hard tab, positive electrode adapter, and electrode post structure of the positive electrode tab assembly from passing through. That is, the length of the first notch is greater than or equal to the length of the positive electrode hard tab, positive electrode adapter, and electrode post structure (conductive and insulating structure) of the positive electrode tab assembly. In other words, in the length direction, the projection of the positive electrode hard tab, positive electrode adapter, and electrode post structure (conductive and insulating structure) of the positive electrode tab assembly onto the side wall of the housing is located within the first notch.

[0042] In another specific example, the second notch at least partially overlaps with the area where the negative electrode tab assembly is located. In the specific example shown in the figure, the second notch is used to avoid the negative electrode hard tab and fixing piece of the negative electrode tab assembly, that is, the length of the first notch is greater than or equal to the length of the negative electrode hard tab and fixing piece of the negative electrode tab assembly, or in other words, in the length direction, the projection of the negative electrode hard tab and fixing piece of the negative electrode tab assembly onto the side wall of the housing is located within the second notch.

[0043] By forming the first and second gaps, interference is prevented from the insulation layer on the installation or welding of the positive electrode tab assembly, electrode post structure, positive electrode adapter, negative electrode tab assembly or fixing piece. This avoids the problem of the insulation layer raising the positive and negative electrode tab assemblies, resulting in uneven interfaces and affecting the connection strength of the positive or negative electrodes.

[0044] In one possible implementation, the insulating layer further includes a first sub-insulating layer located in the area of ​​the cover plate corresponding to the positive electrode tab assembly. In a second direction, the first sub-insulating layer and the positive electrode tab assembly at least partially overlap. By providing the first sub-insulating layer, the positive electrode tab of the positive electrode tab assembly can be prevented from being subjected to the expansion stress of the battery cell during charging and discharging. The bend of the positive electrode tab near the cover plate is prone to being forced upward and making contact with the cover plate, resulting in a short circuit.

[0045] In one possible implementation, the insulating layer further includes a second sub-insulating layer 144 located between the first notch and the second notch, along the first direction X, between the second sub-insulating layer and the positive electrode tab assembly and the negative electrode tab assembly, thereby preventing the positive electrode tab and the negative electrode tab from easily coming into contact with each other and causing a short circuit during charging and discharging as the cell expands.

[0046] In one possible implementation, in the second direction Y of the battery, the end of the insulating layer near the cover plate is a first end 145, and the surface of the electrode assembly 13 near the cover plate is a first surface 131. For example, the current collector surface of the single-sided electrode sheet on the top surface of the electrode assembly is the first surface. In the second direction of the battery, the first end 145 protrudes from the first surface 131. In a specific example, the second direction may be, for example, the thickness direction of the battery. That is, the first end of the insulating layer will extend beyond the top surface of the top single-sided electrode sheet of the electrode assembly, thereby preventing the cell from expanding simultaneously along the thickness direction and the length and width directions during charging and discharging. The top of the insulating layer extends beyond the top of the top electrode sheet of the cell, which can prevent the top electrode sheet from contacting the casing after expanding along the thickness direction. At the same time, it can also prevent the separators stacked on both sides of the cell from accumulating near the flange edge, thereby affecting the welding of the flange edge.

[0047] In one possible implementation, such as Figure 4 As shown, the sidewall 115 includes a first sub-sidewall 1151 and a second sub-sidewall 1152, which are arranged adjacent to each other. The sidewall also includes an arc-shaped third sidewall 1153 located between the first sub-sidewall 1151 and the second sub-sidewall 1152. The third sidewall protrudes in the direction away from the electrode assembly and forms an R-angle. In a specific example, the sidewall includes a third sub-sidewall and a fourth sub-sidewall. Four arc-shaped third sidewalls are formed between the first sub-sidewall, the second sub-sidewall, the third sub-sidewall and the fourth sub-sidewall. The insulating layer at least partially covers the third sidewall, that is, the insulating layer at least partially covers one third sidewall, thereby preventing the R-angle of the third sidewall corresponding to the electrode from expanding during charging and discharging and squeezing the third sidewall, causing the third sidewall to break.

[0048] In one possible implementation, along a first direction, the sidewall 115 of the housing 11 extends outward to form a first flange edge 111, and the cover plate forms a second flange edge 121 corresponding to the position of the first flange edge. The first and second flange edges are aligned and connected. In a second direction of the battery, the first end 145 of the insulating layer 14 does not extend beyond the first flange edge 111. In a specific example, the second direction may be, for example, the thickness direction of the battery, that is, the first end of the insulating layer does not extend beyond the first flange edge in the thickness direction to avoid the insulating layer affecting the welding of the first and second flange edges. Specifically, if it extends beyond the first flange edge, the insulating layer will contaminate the area of ​​the first flange edge to be welded. When the laser irradiates this area, it will first ablate and carbonize the insulating layer, rather than directly acting on the metal surface. Consequently, the insulating layer will rapidly decompose at high temperatures, generating a large amount of gas. These gases are trapped in the molten metal and, upon cooling, will form pores, pinholes, or even burst points. These defects will severely compromise the tightness of the weld.

[0049] In one possible implementation, a first arcuate portion 1155 is formed between the first flange edge 111 and the sidewall 115, such as Figure 3 As shown, the first arc-shaped portion bends towards the electrode assembly. In the second direction of the battery, the first end 145 of the insulating layer does not extend beyond the lower edge of the first arc-shaped portion 1155. By ensuring the first end of the insulating layer does not extend beyond the lower edge of the first arc-shaped portion, in addition to further preventing contamination of the welding area, it also prevents the high temperature and energy during welding from causing the insulating layer to crack, carbonize, or even peel off from the casing surface. The peeled debris and carbonized particles would fall into the battery and float in the electrolyte. During battery charging and discharging, these conductive or semi-conductive particles may move between the positive and negative electrodes, easily causing micro-short circuits or even severe internal short circuits, leading to excessive self-discharge, overheating, or even thermal runaway. In a preferred example, in the second direction of the battery, the distance between the first end 145 of the insulating layer and the lower edge of the first arcuate portion 1155 is 0.01mm-0.5mm (e.g., 0.01mm, 0.03mm, 0.05mm, 0.08mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, or 0.5mm). This ensures that even with minor coating fluctuations or housing positioning deviations, no insulating material will ever come into contact with the welding area. This area must be an absolutely clean, uncontaminated metal surface.

[0050] In one possible implementation, in the second direction Y of the battery, the end of the insulating layer 14 near the bottom wall is designated as a second end 146, and a second arcuate portion 1156 is formed between the bottom wall 114 and the side wall 115. The second end 146 of the insulating layer covers the second arcuate portion 1156. This is mainly because the second arcuate portion is closest to the battery cell. If the battery cell comes into contact with this sharp second arcuate portion due to expansion or assembly tolerances, it will immediately cause an internal short circuit, and the battery will fail instantly or even trigger thermal runaway. In addition, the battery may be subjected to vibration or impact during transportation and use. The second arcuate portion covered by the insulating layer can become smoother, avoiding the risk of hard metal edges directly scratching or piercing the separator or electrode coating, thus playing a role in mechanical buffering and protection.

[0051] In one possible implementation, the orthographic projection of the second end 146 on the bottom wall 114 does not overlap with the orthographic projection of the electrode assembly on the bottom wall, preventing the insulation layer and the electrode assembly from stacking together, which would result in the thickness of the insulation layer and the electrode assembly being superimposed, causing the cell plane to be uneven and affecting the installation of the housing and cover plate.

[0052] In one possible implementation, the insulating layer is made of a first component, which includes one or more of boehmite, alumina, melamine, styrene-isoprene-styrene block copolymer, polypropylene, and polybutene. In another possible implementation, the insulating layer is also made of a second component, which includes one or more of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA). In yet another possible implementation, based on the total weight of the insulating layer, the first component constitutes 80%-100% by weight (e.g., 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98%, or 100%), and the second component constitutes 0%-20% by weight (e.g., 0%, 0.5%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, or 20%).

[0053] In another specific example, the sphericity of the silicon-based material is 0.85-1 (e.g., 0.85, 0.88, 0.9, 0.93, 0.95, 0.98, or 1), and when the battery is at 0% SOC, the difference b between the thickness of the electrode assembly and the depth of the casing is 0-0.1 mm (e.g., 0, 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, or 0.1 mm). By controlling the sphericity of the silicon-carbon particles and the difference b between the thickness of the electrode assembly and the depth of the casing, firstly, the sphericity can ensure the direction of expansion of the silicon-carbon particles, avoiding excessive expansion force in the XY direction. The expansion amount of silicon-carbon particles with higher sphericity in the thickness direction matches the reserved expansion space, preventing the cell from impacting the cover plate.

[0054] In this invention, the sphericity of silicon-based materials can be tested using the following method: Images of the particles on the surface of the negative electrode active layer are captured using a scanning electron microscope (SEM). Within an arbitrarily selected 100μm × 100μm area in the image, silicon-based particles are identified using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.), and the radius r of the equivalent circle representing the projected perimeter of a single silicon-based particle is calculated. 1 The radius r of the equivalent circle of the projected area of ​​silicon-based particles 2 The sphericity of a single silicon-based first particle = r 2 / r 1 The sphericity of 100 silicon-based particles was statistically analyzed and averaged. This process was repeated 5 times, and the average value was taken as the final test result. The scanning image was obtained by observing the surface of the negative electrode active layer using a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.).

[0055] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0056] The following examples illustrate the battery of the present invention.

[0057] Example 1 (1) Preparation of positive electrode sheet Lithium cobalt oxide, a positive electrode conductive agent (conductive carbon black and carbon nanotubes mixed at a mass ratio of 2:1), and a positive electrode binder (polyvinylidene fluoride) were mixed at a mass ratio of 97:1.5:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly to prepare a positive electrode slurry. The positive electrode slurry was coated on the surface of aluminum foil, dried, and rolled to obtain a positive electrode sheet.

[0058] (2) Preparation of negative electrode sheet Artificial graphite, silicon-carbon material (including a porous carbon matrix and silicon material located in the pores of the porous carbon matrix, with a sphericity of 0.93), carbon nanotubes, lithium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid were mixed in a mass ratio of 54.9:42:0.5:0.8:0.5:1.3, and deionized water was added to prepare a negative electrode slurry. The negative electrode slurry was coated on both sides of a copper foil, and then dried and rolled to obtain a negative electrode sheet. The elemental silicon content in the negative electrode active coating is 20%.

[0059] (3) Preparation of electrolyte In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), organic solvents (ethylene carbonate, propylene carbonate, propyl propionate, and ethyl propionate in a mass ratio of 15:15:50:20, totaling 71.5 parts by weight) were mixed to form a homogeneous solvent. Then, 15.5 parts by weight of lithium salt (LiPF6), 2 parts by weight of 1,3-propanesulfonyl lactone, 3 parts by weight of 1,3,6-hexanetrionitrile, and 8 parts by weight of fluoroethylene carbonate were slowly added. After thorough stirring, a lithium-ion battery electrolyte was obtained.

[0060] (4) Preparation of the diaphragm Polyethylene was selected as the 5μm substrate layer and polyvinylidene fluoride was selected as the adhesive layer. An alumina ceramic layer with a thickness of 2μm was set on the side of the adhesive layer close to the substrate layer to obtain a porous membrane.

[0061] (5) Preparation of lithium-ion batteries The positive electrode sheet prepared in step (1), the separator prepared in step (4), and the negative electrode sheet prepared in step (2) are stacked to obtain a core; after encapsulation, baking, liquid injection, formation, secondary sealing, sorting, and OCV, a lithium-ion battery is obtained. An insulating layer is provided on the inner surface of the shell sidewall. The first end of the insulating layer protrudes from the first surface of the electrode assembly, and the insulating layer covers the third sidewall. The second end of the insulating layer covers the second arc-shaped portion. The orthographic projection of the second end on the bottom wall does not overlap with the orthographic projection of the electrode assembly on the bottom wall. The insulating layer includes a first notch and a second notch. The first notch coincides with the area where the positive electrode tab assembly is located, and the second notch coincides with the area where the negative electrode tab is located. The insulating layer also includes a first sub-insulating layer and a second sub-insulating layer. The first sub-insulating layer coincides with the positive electrode tab assembly, and the second sub-insulating layer is located at the positive electrode... Between the tab assembly and the negative tab assembly, the insulating layer is made of polypropylene and has a thickness A of 0.1 mm. When the battery is at 0% SOC, the distance a between the edge of the positive electrode and the insulating layer along the first direction is 0.5 mm, and A / a = 0.2. In the second direction (thickness) of the battery, the distance between the first end of the insulating layer and the lower edge of the lower edge of the first arc-shaped portion is 0.26 mm. When the battery is at 0% SOC, the depth of the casing is greater than the thickness of the electrode assembly, and the difference b between the thickness of the electrode assembly and the depth of the casing is 0.3 mm.

[0062] Example 2 Example 2a The experiment was carried out in accordance with Example 1, except that the weight percentage of silicon in the negative electrode active layer was 10.3% and the sphericity of the silicon-based material was 0.86.

[0063] Example 2b The experiment was carried out in accordance with Example 1, except that the weight percentage of silicon in the negative electrode active layer was 69.2%, and the sphericity of the silicon-based material was 0.95.

[0064] Example 3 Group This set of examples illustrates the effects that occur when A / a changes.

[0065] This embodiment group is carried out with reference to Embodiment 1, except that A / a is changed, as detailed in Table 1-1.

[0066] Table 1-1 Example 4 group Example 4a Referring to Embodiment 1, the difference is that, in the second direction (thickness) of the battery, the distance between the first end of the insulating layer and the lower edge of the lower edge of the first arc-shaped portion is 0, that is, the first end is connected to the lower edge of the lower edge of the first arc-shaped portion.

[0067] Example 4b The same procedure is followed as in Example 1, except that the distance between the first end of the insulating layer and the lower edge of the lower edge of the first arcuate portion is 0.05 mm in the second direction (thickness) of the battery.

[0068] Example 4c The same procedure is followed as in Example 1, except that the distance between the first end of the insulating layer and the lower edge of the lower edge of the first arcuate portion is 0.5 mm in the second direction (thickness) of the battery.

[0069] Example 4d The same procedure is followed as in Example 1, except that the distance between the first end of the insulating layer and the lower edge of the lower edge of the first arcuate portion is 0.6 mm in the second direction (thickness) of the battery.

[0070] Example 5 group Example 5a The same procedure was followed as in Example 1, except that the insulating layer was made of boehmite and PVDF in a weight ratio of 90% to 10%.

[0071] Example 5b The same procedure was followed as in Example 1, except that the insulating layer was made of aluminum oxide and PMMA in a weight ratio of 90% to 10%.

[0072] Example 6 group Example 6a The same procedure was followed as in Example 1, except that when the battery was at 0% SOC, the difference b between the thickness of the electrode assembly and the depth of the casing was 1 mm.

[0073] Example 6b The same procedure was followed as in Example 1, except that when the battery was at 0% SOC, the difference b between the thickness of the electrode assembly and the depth of the casing was 0.01 mm.

[0074] Example 6c The same procedure was followed as in Example 1, except that when the battery was at 0% SOC, the difference b between the thickness of the electrode assembly and the depth of the casing was 0.

[0075] Example 6d The same procedure was followed as in Example 1, except that when the battery was at 0% SOC, the difference b between the thickness of the electrode assembly and the depth of the casing was 1.5 mm.

[0076] Comparative Example 1 The same procedure was followed as in Example 1, except that no insulating layer was provided on the inner surface of the sidewall of the housing.

[0077] Comparative Example 2 The same procedure was carried out as in Example 1, except that the thickness A of the insulating layer was 0.5 mm, and when the battery was at 0% SOC, the distance a between the edge of the positive electrode sheet and the insulating layer along the first direction was 0.22 mm, and A / a = 0.5 / 0.22 = 2.27.

[0078] Comparative Example 3 The same procedure was followed as in Example 1, except that the weight percentage of silicon in the negative electrode active layer was 72.6%.

[0079] Test case The batteries prepared by the examples and comparative examples were tested as follows.

[0080] 1. Drop test The batteries prepared in the examples and comparative examples were subjected to drop safety tests. The specific test methods are as follows: In an environment of 25℃±3℃, the battery is discharged at 0.2C to the lower limit voltage of 3.0V and left to stand for 10 minutes. Then, the battery is placed in a 25℃ constant temperature chamber and charged at a constant current of 0.7C to the upper limit voltage of 4.48V. After 50 cycles, the fully charged battery is subjected to a drop test within 12h-24h. The battery is dropped onto a concrete surface from a height of 1.5m, and each surface and corner is dropped once. During the test, the battery is dropped with a clamping arm for directional drop. The voltage is tested immediately after the drop test and again after resting for 12h. The battery is considered to have passed when it does not catch fire, explode, or emit smoke, the casing is not broken, and there is no leakage, and the voltage (the voltage tested immediately after the drop test and the voltage tested after resting for 12h) is not less than 90% of the voltage before the test. Each embodiment and comparative example tested 20 batteries, and the results were expressed as "number of passes / 20", where "20 / 20" means all 20 tests passed, "19 / 20" means 19 out of 20 tests passed, and so on. The results are recorded in Table 1.

[0081] 2. K-value test At 25℃, the open circuit potential of the lithium-ion batteries after sorting is measured to obtain V1. After standing for 24 hours, the open circuit potential of the battery is measured again to obtain V2. The K value of the battery is obtained by subtracting V2 from V1 and dividing by the standing time, with the unit being mV / H.

[0082] 3. Furnace temperature test The lithium-ion batteries were heated in a convection air chamber at an initial temperature of (25±3)℃ with a temperature change rate of (5±2)℃ / min, and then heated to (130±1)℃. The temperature was maintained for 60 minutes before the test was ended. The battery status was recorded. Twenty battery samples were tested for each example and comparative example. If the battery did not explode and / or catch fire, it was considered "passed". If it exploded or caught fire, it was considered "failed". The result was expressed as "number of passes / 20". For example, "20 / 20" means all passed, and "10 / 20" means 10 out of 20 batteries passed.

[0083] The results are recorded in Table 2.

[0084] Table 2 As can be seen from Table 2, by comparing the comparative example and the embodiment, the drop test pass rate of the battery in the embodiment is significantly improved, the K value is significantly reduced, and the furnace temperature pass rate of 130℃ is significantly improved. This indicates that by setting an insulating layer inside the side wall of the casing and controlling the battery to meet the relationship A / a≤2, the risk of the positive electrode plate contacting the casing is reduced, the furnace temperature pass rate is improved, and the safety performance of the battery is enhanced.

[0085] 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 battery includes a casing, a cover plate, and an electrode assembly. The electrode assembly includes a positive electrode, a separator, and a negative electrode stacked together. The negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector. The negative active layer includes a silicon-based material, and the weight percentage of silicon in the negative active layer is 10%-70%. The housing includes a bottom wall and side walls extending upward from the bottom wall, the side walls forming openings, the cover plate closing the openings, and the electrode assembly located within a receiving cavity of the housing; The battery also includes an insulating layer formed on the sidewall on one side of the housing, the insulating layer being located between the electrode assembly and the sidewall; The battery satisfies the following relationship: A / a≤2, where A is the thickness of the insulating layer in mm; a is the distance between the edge of the positive electrode and the insulating layer along the first direction when the battery is at 0% SOC, in mm.

2. The battery according to claim 1, characterized in that, The thickness A of the insulating layer is 0.01mm-0.5mm; And / or, when the battery is at 0% SOC, the distance a between the edge of the positive electrode and the insulating layer along the first direction is 0.2 mm < a < 2 mm; And / or, in the second direction of the battery, the end of the insulating layer near the cover plate is a first end, the surface of the electrode assembly near the cover plate is a first surface, and in the second direction of the battery, the first end protrudes from the first surface.

3. The battery according to claim 1, characterized in that, The sidewall includes a first sub-sidewall and a second sub-sidewall; The sidewall also includes an arc-shaped third sidewall located between the first sub-sidewall and the second sub-sidewall, and the insulating layer at least partially covers the third sidewall.

4. The battery according to claim 2, characterized in that, Along the first direction, the sidewall of the housing extends outward to form a first flange edge, and the cover plate forms a second flange edge corresponding to the position of the first flange edge, with the first flange edge and the second flange edge aligned and connected. In the second direction of the battery, the first end of the insulating layer does not extend beyond the first flange edge.

5. The battery according to claim 4, characterized in that, A first arcuate portion is formed between the first flange edge and the sidewall; In the second direction of the battery, the first end of the insulating layer does not extend beyond the lower edge of the first arcuate portion; Preferably, in the second direction of the battery, the distance between the first end of the insulating layer and the lower edge of the first arcuate portion is 0.01mm-0.5mm.

6. The battery according to claim 1, characterized in that, In the second direction of the battery, the end of the insulating layer near the bottom wall is the second end, and a second arc-shaped portion is formed between the bottom wall and the side wall; The second end of the insulating layer covers the second arcuate portion.

7. The battery according to claim 6, characterized in that, The orthographic projection of the second end on the bottom wall does not overlap with the orthographic projection of the electrode assembly on the bottom wall.

8. The battery according to claim 1, characterized in that, The electrode assembly further includes a positive electrode tab assembly and a negative electrode tab assembly, and the battery includes an electrode post structure connected to the positive electrode tab assembly; the insulating layer includes a first notch and / or a second notch, the first notch at least partially overlapping the area where the positive electrode tab assembly is located, and / or the second notch at least partially overlapping the area where the negative electrode tab assembly is located; And / or, the insulating layer further includes a first sub-insulating layer located in the region of the cover plate corresponding to the positive electrode tab assembly, wherein the first sub-insulating layer and the positive electrode tab assembly at least partially overlap in the second direction.

9. The battery according to claim 8, characterized in that, The insulating layer further includes a second sub-insulating layer, which is located between the first notch and the second notch, along the first direction, between the second sub-insulating layer and the positive electrode tab assembly and the negative electrode tab assembly.

10. The battery according to any one of claims 1-9, characterized in that, The insulating layer is made of one or more of the following materials: boehmite, alumina, melamine, styrene-isoprene-styrene block copolymer, polypropylene, and polybutene. And / or, the sphericity of the silicon-based material is 0.85-1; And / or, when the battery is at 0% SOC, the difference b between the thickness of the electrode assembly and the depth of the housing is 0-1 mm.

Images