A battery

Abstract

This invention relates to the field of battery technology, specifically to a battery. It includes a casing and a cell assembly, the cell assembly comprising a first cell and a second cell; the casing includes a first surface and a second surface, each comprising a first sub-surface, a second sub-surface, and a transition surface, disposed opposite each other along a second direction of the battery; the cell assembly includes a first adhesive member located between the first surface and the first cell, the projection of the first adhesive member in the second direction of the battery and the projection of the transition surface in the second direction at least partially overlapping; the first cell includes a first electrode, a first separator, and a second electrode; the second active layer of the second electrode has a silicon content of 1.5%-70% by mass; the first separator includes a first portion, and the first adhesive member is bonded to both the first portion and the first electrode; along the first direction, a first edge of the first adhesive member near the transition surface does not extend beyond the edge of the first portion. The battery of this invention possesses both high energy density and high safety performance.

Description

Technical Field

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

[0002] In recent years, with the rapid development of new energy technologies, batteries have been widely used in electronic devices, electric vehicles, electric two-wheelers, power tools, and other electrical terminals. As the integration of electrical terminals increases, the space reserved for battery compartments in these terminals is becoming smaller to facilitate the placement of various components, while at the same time, the energy density requirements for batteries are becoming higher and higher.

[0003] While irregularly shaped batteries can effectively improve the space utilization of the battery compartment and increase the energy density of the battery, their irregular structure can affect the overall structural stability of the battery and thus its safety performance. Summary of the Invention

[0004] To address the issue of simultaneously improving battery compartment space utilization while maintaining battery safety, this invention provides a battery. The battery of this invention not only improves battery compartment space utilization and energy density but also ensures battery safety.

[0005] To achieve the above objectives, the present invention provides a battery comprising a housing and a cell assembly located within the housing. The cell assembly includes a first cell and a second cell stacked together. Along a first direction of the battery, the length of the first cell is less than the length of the second cell. A first end of the second cell protrudes along the first direction of the battery from the end of the first cell corresponding to the first end of the second cell. The housing includes a first surface and a second surface disposed opposite to each other along a second direction of the battery. The first surface includes a first sub-surface, a second sub-surface, and a transition surface. Along the first direction of the battery, the first sub-surface protrudes from the second sub-surface, and the transition surface connects the first sub-surface and the second sub-surface. The cell assembly includes a first adhesive member located between the first surface of the housing and the first cell. The projection of the first adhesive member in the second direction of the battery and the projection of the transition surface in the second direction of the battery at least partially overlap. The first cell includes a first electrode, a first separator, and a second electrode near a first surface of the casing. The first separator is located between the first electrode and the second electrode. The second electrode includes a second current collector and a second active layer on the second current collector. The elemental silicon content in the second active layer is 1.5%-70% by mass. The first separator includes a first portion protruding from a first side of the first electrode along the first direction. The first adhesive is bonded to the first portion of the first separator and the first electrode, respectively. The first edge of the first adhesive near the transition surface does not extend beyond the edge of the first portion of the first separator.

[0006] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: In the battery of the present invention, the cell assembly includes a first cell and a second cell stacked together. Along a first direction of the battery, the length of the first cell is less than the length of the second cell. A first end of the second cell protrudes from the end of the first cell corresponding to the first end of the second cell along the first direction of the battery. The housing includes a first surface and a second surface disposed opposite to each other along a second direction of the battery. The first surface includes a first sub-surface, a second sub-surface, and a transition surface. Along the first direction of the battery, the second sub-surface protrudes from the first sub-surface. The transition surface connects the first sub-surface and the second sub-surface. That is, the cell assembly of the present invention is formed by stacking two cells with different widths one above the other. The first cell with a smaller width is located on top of the second cell with a larger width. By stacking the first cell and the second cell with the above-mentioned specific structure to form an irregularly shaped stacked battery, it is possible to achieve a depth fit with the space of the battery compartment, thereby improving the utilization rate of the limited space of the battery compartment. Moreover, the stacked battery can achieve an increase in battery capacity within the same area, thereby increasing the energy density of the battery.

[0007] Meanwhile, the cell assembly includes a first adhesive member located between the first surface of the casing and the first cell. The projection of the first adhesive member in the second direction of the battery and the projection of the transition surface in the second direction of the battery at least partially overlap. The first adhesive member is bonded to a first portion of the first separator and the first electrode, respectively. The first edge of the first adhesive member near the transition surface does not extend beyond the edge of the first portion of the first separator. That is, the first adhesive member is connected to both the first electrode and the first portion of the separator, and the coverage of the first adhesive member extends beyond the first electrode. This can reduce or even prevent the first electrode from stretching to a certain extent during battery cycling due to the large expansion of the cell with the silicon-doped second electrode. This stretching could easily cause the first electrode to fold towards the casing, thereby increasing the risk of the first electrode hitting the casing and causing damage to the casing, thus improving battery safety performance.

[0008] Furthermore, in the second direction, the first edge of the first adhesive member near the transition surface does not extend beyond the edge of the first portion of the first separator. That is, the first adhesive member is only bonded to the first separator and not to any other separators below it. It is understood that during battery cycling, the significant expansion of the cell with the silicon-doped second electrode in the first direction will cause the first separator to shift in that direction, resulting in misalignment between the first separator and the first electrode or between the first and second electrodes, causing misalignment between the first and second electrodes at certain locations. By removing the obstruction of the first separator, the first and second electrodes can easily come into contact with each other during cell expansion, causing a short circuit. By bonding the first adhesive member only to the first separator in the second direction, without bonding to other separators, it serves two purposes: firstly, it connects the first electrode and the first separator, fixing their relative arrangement and preventing misalignment; secondly, it reduces or even eliminates the risk of the first electrode becoming loose, deformed, wavy, or with raised edges in the later stages of battery cycling, thereby reducing the risk of lithium plating and further improving battery performance. Regarding the safety performance of the battery, the first adhesive component is only bonded to the first separator, which also avoids excessive binding of the electrode due to the first adhesive component being bonded to other separators. During charging and discharging, other separators will stretch under stress as the cell with the silicon-doped second electrode expands. If the first adhesive component is bonded to both the electrode and other separators, the first adhesive component will restrict the stretching of the electrode and other separators, making it difficult to release the expansion stress on the electrode and other separators. This can easily lead to tearing of the electrode or other separators, causing the active particles on the electrode to fall off easily. The torn portion of the separator penetrates into the electrode of the other polarity, leading to self-discharge. This results in a poor K-value for the battery or the inability to reach the termination current during charging, affecting the battery's cycle performance and lifespan. By bonding the first adhesive to the first separator, other separators and electrodes can expand and contract normally with the expansion of the cell with the silicon-doped second electrode during charging and discharging. This improves the stress state, prevents active particles from falling off, and reduces the K-value. During charging, the current can be smoothly reduced to the preset charging cutoff current according to the predetermined time, achieving a fully charged state.

[0009] Therefore, the battery of the present invention, formed by stacking a first cell and a second cell with a specific structure into an irregularly shaped stacked battery, can improve the utilization rate of the limited space of the battery compartment, thereby increasing the energy density of the battery. Moreover, the first adhesive is provided, which is bonded to a first portion of the first separator and the first electrode respectively; the first edge of the first adhesive near the transition surface does not extend beyond the edge of the first portion of the first separator; thereby fixing the single-sided first electrode and the first separator, improving the safety performance of the battery. At the same time, the first adhesive is only bonded to the first separator, which can also avoid excessive restraint of the first adhesive, further improving the cycle performance and service life of the battery.

[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 image shown is a top view of a battery according to one embodiment of the present invention.

[0013] Figure 2 The image shown is a top view of a battery according to another embodiment of the present invention.

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

[0015] Figure 4 As shown Figure 3 A magnified view of A in the middle. 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] One embodiment of this application provides a battery, such as Figures 1-4As shown, the battery includes a casing and a cell assembly located within the casing. In a specific example, the casing may be, for example, a steel casing, a titanium alloy casing, an aluminum casing, a stainless steel casing, an aluminum-plastic film, or a steel-plastic film.

[0019] The battery cell assembly 1 includes a first battery cell 11 and a second battery cell 12 stacked together. In one specific example, the thickness of the first battery cell and the thickness of the second battery cell are the same; in another specific example, the thickness of the first battery cell is greater than the thickness of the second battery cell. Along the first direction X of the battery, the length of the first battery cell 11 is less than the length 12 of the second battery cell, and the first end of the second battery cell protrudes along the first direction of the battery from the end of the first battery cell corresponding to the first end of the second battery cell. In one specific example, the first direction may be the width direction of the battery, and the width of the first battery cell is less than the width of the second battery cell, such as... Figure 2 As shown, the second cell includes a first end that protrudes from the edge of the first cell along its width direction. In another specific example, the first direction may be the length direction of the battery, that is, the length of the first cell is less than the length of the second cell, such as... Figure 1 As shown, the second cell includes a first end that extends along the length direction from the bottom edge of the first cell.

[0020] In this embodiment, such as Figure 4 As shown, the casing includes a first surface 21 and a second surface 22 disposed opposite to each other along the second direction Y of the battery. The first surface 21 includes a first sub-surface 211, a second sub-surface 212, and a transition surface 213. One end of the transition surface 213 is connected to the first sub-surface 211 by a first arc, and the other end of the transition surface 213 is connected to the second sub-surface 212 by a second arc. In a specific example, the included angle θ between the planes containing the transition surface 213 and the first sub-surface 211 is... 1 Satisfying 0°<θ 1 ≤45° (e.g., 1°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, or 45°); along the first direction X of the battery, the first sub-surface 211 protrudes beyond the second sub-surface 212, and the transition surface 213 connects the first sub-surface 211 and the second sub-surface 212. In a specific example, the second direction may be, for example, the thickness direction of the battery, and the first direction may be the width direction of the battery. That is, the first sub-surface, the transition surface, and the second sub-surface in the first surface are arranged along the width direction, wherein the first sub-surface protrudes beyond the second sub-surface in the thickness direction. In other words, the first sub-surface and the top surface of the first cell are arranged opposite each other, the second sub-surface and the surface of the second cell not covered by the first cell are arranged opposite each other, and the transition surface and the side surface of the first cell are arranged opposite each other.

[0021] The first cell 11 includes a first electrode 111 near a first surface 21 of the casing, a first separator 113, and a second electrode 112, with the first separator 113 located between the first electrode 111 and the second electrode 112. In one specific example, the first electrode is a positive electrode and the second electrode is a negative electrode; wherein the first electrode includes a first current collector, a first tab extending from one side of the first current collector, and a first active layer located on the first current collector. The second electrode includes a second current collector, a second active layer located on the second current collector, and a second tab extending from one side of the second current collector. In another specific example, the first electrode is a negative electrode and the second electrode is a positive electrode.

[0022] In some embodiments, the first current collector may comprise aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector). The composite current collector can be formed by depositing a metallic material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) onto a polymer substrate. In some embodiments, the thickness of the first current collector is 4 μm-12 μm (e.g., 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm).

[0023] In some embodiments, the first active layer includes a first active material, which may comprise lithium nickel cobalt manganese oxide (LiNi). 0.90 Co 0.05 Mn 0.05 At least one of the following: O2 (NCM955), NCM811, NCM622, NCM523, 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. In some embodiments, the thickness of the first active layer is 30 μm-110 μm (e.g., 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or 110 μm). It is understood that the thickness of the first active layer is the thickness of the first active layer on one side.

[0024] In some embodiments, the second current collector may include, but is not limited to, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collectors (e.g., carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.). In some embodiments, the thickness of the second current collector is 3μm-12μm (e.g., 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, or 12μm).

[0025] In some embodiments, the second active layer comprises a silicon-based material, which includes at least one of elemental silicon, silicon oxide, silicon carbon, and silicon alloys. The mass content of elemental silicon in the second active layer is 1.5%-70% (e.g., 1.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%).

[0026] In this invention, the weight content M of silicon in the second 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 (second electrode) is removed, soaked and rinsed with dimethyl carbonate, and dried. The dried negative electrode 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 second active 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 second 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 second 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 second active layer.

[0027] In some embodiments, the first 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 first 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 possible implementation, the first cell and / or the second cell may be, for example, a wound cell structure formed by stacking and winding a first electrode, a separator, and a second electrode; in another implementation, the first cell and / or the second cell may be a stacked cell structure formed by stacking a first electrode, a separator, and a second electrode.

[0029] In a further embodiment, the first cell has a stacked core structure, wherein the first electrode includes a single-sided electrode, the single-sided electrode includes a first current collector and a first active layer located on the surface of the first current collector away from the casing, thereby reducing the waste of active material. In another specific example, the thickness of the first current collector of the single-sided electrode is greater than the thickness of the first current collector of the first electrode of the same polarity, so that during charging and discharging, the single-sided electrode only has a first active layer on one side, and uneven stress on both sides can easily lead to warping problems.

[0030] In this embodiment, such as Figure 1 , Figure 2 and Figure 4 As shown, the battery cell assembly 1 includes a first adhesive member 131 located between the first surface 21 of the housing and the first battery cell 11. That is, the first adhesive member 131 is located between the first electrode 111 of the first battery cell 11 and the first surface 21. The first separator 113 includes a first portion 1131 protruding from the first side of the first electrode 111 along the first direction X. The first adhesive member 131 is bonded to the first portion 1131 of the first separator 113 and the first electrode 111 respectively. The first adhesive member 131 is bent downwards through the first electrode 111 and the first portion 1131 of the first separator 113. The first edge 1311 of the first adhesive member 131 near the transition surface 213 does not exceed the edge of the first portion 1131 of the first separator 113. In other words, the first adhesive member is located between the first electrode and the first separator and does not exceed the first separator, so that the first adhesive member will not bond with other separators of the first battery cell.

[0031] Furthermore, the projection of the first adhesive 131 onto the second direction Y of the battery and the projection of the transition surface 213 onto the second direction Y of the battery at least partially overlap. That is, part of the first adhesive 131 is located within the space formed between the side of the first cell 11 and the transition surface, thereby preventing the first adhesive from affecting the energy density and preventing the first adhesive from being too thick and easily pressing against the first surface of the casing. Moreover, since the expansion force of the first cell is a three-dimensional vector in the area formed between the side of the first cell and the transition surface, when the first cell expands and contracts during charging and discharging, it will simultaneously generate shear force and peeling force on the four surfaces of the casing: the first sub-surface, the transition surface, and the sides located on opposite sides of the first sub-surface. This can easily accelerate the aging, creep, and delamination of the sealant at the sealing edge, affecting the airtightness of the battery. By setting a first adhesive member that bonds the first electrode and the first part in the area formed between the side surface and the transition surface of the first cell, the first electrode is fixed and prevented from impacting the four surfaces of the casing, the transition surface and the sides on opposite sides of the first sub-surface as the cell expands, thus affecting the airtightness. Moreover, the first adhesive member being located in the area formed between the side surface and the transition surface of the first cell prevents local separation that is prone to occur under the complex stress caused by the expansion of the cell, thereby affecting heat dissipation or causing local abnormalities.

[0032] like Figure 3 and Figure 4 As shown, the battery cell assembly 1 in this embodiment includes a first battery cell 11 and a second battery cell 12 stacked together. Along the first direction X of the battery, the length of the first battery cell 11 is less than the length of the second battery cell 12. The first end of the second battery cell 12 protrudes along the first direction X of the battery from the end of the first battery cell 11 corresponding to the first end of the second battery cell 12. The housing includes a first surface 21 and a second surface 22 disposed opposite to each other along the second direction Y of the battery. The first surface 21 includes a first sub-surface 211, a second sub-surface 212, and a transition surface 213. Along the first direction X of the battery, the second sub-surface 211... Surface 212 protrudes from the first sub-surface 211, and the transition surface 213 connects the first sub-surface 211 and the second sub-surface 212. That is, the cell assembly of the present invention is formed by stacking two cells with different widths one on top of the other. The first cell with a smaller width is located on top of the second cell with a larger width. The irregularly shaped stacked battery formed by stacking the first and second cells with the above-mentioned specific structure can be adapted to the depth of the battery compartment space, thereby improving the utilization rate of the limited space of the battery compartment. Moreover, the stacked battery can achieve an increase in battery capacity within the same area, thereby improving the energy density of the battery.

[0033] Meanwhile, the cell assembly includes a first adhesive member located between the first surface of the casing and the first cell. The projection of the first adhesive member in the second direction of the battery and the projection of the transition surface in the second direction of the battery at least partially overlap. The first adhesive member is bonded to a first portion of the first separator and the first electrode, respectively. The first edge of the first adhesive member near the transition surface does not extend beyond the edge of the first portion of the first separator. That is, the first adhesive member is connected to both the first electrode and the first portion of the separator, and the coverage of the first adhesive member extends beyond the first electrode. This can reduce or even prevent the first electrode from stretching to a certain extent during battery cycling due to the large expansion of the cell with the silicon-doped second electrode. This stretching could easily cause the first electrode to fold towards the casing, thereby increasing the risk of the first electrode hitting the casing and causing damage to the casing, thus improving battery safety performance.

[0034] Furthermore, in the first direction, the first edge of the first adhesive member near the transition surface does not extend beyond the edge of the first portion of the first separator. That is, the first adhesive member is only bonded to the first separator and not to any other separators below it. It is understood that during battery cycling, the significant expansion of the cell with the silicon-doped second electrode in the first direction will cause the first separator to shift in that direction, resulting in misalignment between the first separator and the first electrode or between the first and second electrodes, causing misalignment between the first and second electrodes at certain locations. By removing the obstruction of the first separator, the first and second electrodes can easily come into contact with each other during cell expansion, causing a short circuit. By bonding the first adhesive member only to the first separator in the second direction, without bonding to other separators, it serves two purposes: firstly, it connects the first electrode and the first separator, fixing their relative arrangement and preventing misalignment; secondly, it reduces or even eliminates the risk of the first electrode becoming loose, deformed, wavy, or with raised edges in the later stages of battery cycling, thereby reducing the risk of lithium plating and further improving battery performance. Regarding the safety performance of the battery, the first adhesive component is only bonded to the first separator, which also avoids excessive binding of the electrode due to the first adhesive component being bonded to other separators. During charging and discharging, other separators will stretch under stress as the cell with the silicon-doped second electrode expands. If the first adhesive component is bonded to both the electrode and other separators, the first adhesive component will restrict the stretching of the electrode and other separators, making it difficult to release the expansion stress on the electrode and other separators. This can easily lead to tearing of the electrode or other separators, causing the active particles on the electrode to fall off easily. The torn portion of the separator penetrates into the electrode of the other polarity, leading to self-discharge. This results in a poor K-value for the battery or the inability to reach the termination current during charging, affecting the battery's cycle performance and lifespan. By bonding the first adhesive to the first separator, other separators and electrodes can expand and contract normally with the expansion of the cell with the silicon-doped second electrode during charging and discharging. This improves the stress state, prevents active particles from falling off, and reduces the K-value. During charging, the current can be smoothly reduced to the preset charging cutoff current according to the predetermined time, achieving a fully charged state.

[0035] Therefore, the battery of the present invention, formed by stacking a first cell and a second cell with a specific structure into an irregularly shaped stacked battery, can improve the utilization rate of the limited space of the battery compartment, thereby increasing the energy density of the battery. Moreover, the first adhesive is provided, which is bonded to a first portion of the first separator and the first electrode respectively; the first edge of the first adhesive near the transition surface does not extend beyond the edge of the first portion of the first separator; thereby fixing the single-sided first electrode and the first separator, improving the safety performance of the battery. At the same time, the first adhesive is only bonded to the first separator, which can also avoid excessive restraint of the first adhesive, further improving the cycle performance and service life of the battery.

[0036] In one possible implementation, along the first direction X of the battery, the dimension between the first edge 1311 of the first adhesive member 131 near the transition surface 213 and the first side edge of the first electrode 111 is L. 1 ;like Figure 4 As shown, this represents the actual size of the portion of the first adhesive element that extends beyond the first electrode. The second sub-surface 212 includes a first endpoint 2121 near the transition surface, i.e., the endpoint where the transition surface 213 and the second arc connect is the first endpoint 2121; the distance between the first endpoint 2121 and the first side edge of the first electrode 111 is L. 5 The following relationship is satisfied: 0.025≤L 1 / L 5 ≤3.6 (e.g., 0.025, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 3.6); where L 1 For 0.05mm-2mm (e.g., 0.05mm, 0.1mm, 0.3mm, 0.5mm, 0.8mm, 1mm, 1.3mm, 1.5mm, 1.8mm or 2mm); and / or, L 5 The thickness is 0.5mm-2mm (e.g., 0.5mm, 0.8mm, 1mm, 1.3mm, 1.5mm, 1.8mm or 2mm).

[0037] By controlling L 1 and L 5The ratio between them, through the portion of the first adhesive extending beyond the first electrode, effectively blocks the side of the first electrode from the casing, such as the cut of the current collector of the positive electrode. Usually, after cutting, the cut of the current collector of the positive electrode is prone to burrs, which can easily pierce the PP layer of the aluminum-plastic film. At the same time, it can also prevent the first electrode from extending along the first direction due to the expansion of the silicon-doped cell during charging and discharging, which would make the first electrode easily collide with the casing, causing damage to the PP layer of the casing, or causing the first electrode to bend after colliding with the casing, which could easily lead to contact with the second electrode and cause a short circuit. Moreover, the first adhesive causes the first electrode and the first separator to bend downwards. The edge of the projection of the first adhesive on the second cell is close to the first end point of the second sub-surface near the transition surface, thereby covering and pressing down the first cell. This prevents the electrolyte in the space between the first cell and the connection surface from being too much, which could easily cause the edge electrode of the first cell to delaminate under long-term immersion, leading to cycle failure or even lithium plating.

[0038] In one possible implementation, such as Figure 4 As shown, the first battery cell 11 includes a fifth electrode 115 near the second battery cell 12, and the second battery cell 12 includes a sixth electrode 126 near the first battery cell 11. The fifth electrode 115 and the sixth electrode 126 have the same polarity. The fifth electrode 115 and the sixth electrode 126 are bonded together by a second adhesive 132. In a specific example, both the fifth and sixth electrodes are positive electrodes, and each is a single-sided positive electrode. The fifth electrode includes a positive current collector and a positive active layer located on the surface of the positive current collector facing away from the second battery cell. The sixth electrode includes a positive current collector and a positive active layer located on the surface of the positive current collector facing away from the first battery cell. That is, the surfaces of the fifth and sixth electrodes facing each other are the surfaces of the positive current collector without a positive active layer, i.e., aluminum foil. The positive current collectors of the fifth and sixth electrodes are bonded together by the second adhesive. In a specific example, the second adhesive may be, for example, hot melt adhesive, polypropylene, or polyethylene.

[0039] In another possible implementation, the fifth and sixth electrodes have different polarities, and the battery includes a connecting membrane located between the fifth and sixth electrodes, which are bonded together by the connecting membrane.

[0040] In one specific example, the fifth electrode is a positive electrode, and the sixth electrode is a negative electrode. The fifth electrode includes a positive current collector and positive active layers on both sides of the current collector. The sixth electrode includes a negative current collector and negative active layers on both sides of the current collector. The negative active layer of the sixth electrode extends beyond the positive active layer of the fifth electrode, thus preventing lithium deposition at the interface. In a further example, the second cell includes connecting separators on opposite sides of the sixth electrode. Both connecting separators include extensions extending beyond the edge of the sixth electrode. The two connecting separators are thermally bonded together through these extensions, thereby enclosing the sixth electrode within the pouch space formed by the two connecting separators, preventing the sixth electrode from shifting during a drop. In this example, the sixth electrode and the two connecting separators are first thermally bonded, and then the first cell is thermally pressed onto the connecting separators. Bonding the fifth and sixth electrodes with connecting separators further improves the battery's energy density.

[0041] In one possible implementation, such as Figure 4 As shown, in the first direction X, the projection of the first edge 1311 of the first adhesive member 131 near the transition surface 213 onto the second cell 12 lies within the second adhesive member 132. That is, the first cell 11 includes a fifth electrode 115 near the second cell, and the second cell 12 includes a sixth electrode 126 near the first cell. The fifth and sixth electrodes have the same polarity. The fifth and sixth electrodes are bonded together by the second adhesive member. The first edge of the first adhesive member near the transition surface does not extend beyond the second adhesive member, preventing uneven thickness in the area between the fifth and sixth electrodes caused by the first edge of the first adhesive member near the transition surface extending beyond the second adhesive member, which would affect the flatness of the casing.

[0042] In one possible implementation, the first cell further includes a second electrode located on the side of the first separator opposite to the first electrode. The first and second electrodes have opposite polarities, and the dimension of the second electrode along a first direction exceeds the dimension of the first electrode along the ground direction. The second sub-surface includes a first endpoint near a transition surface. In the first direction, the projection of the edge of the first adhesive near the transition surface lies between the second electrode and the first endpoint of the first cell. That is, the portion of the first adhesive extending beyond the first electrode does not extend onto the second sub-surface, preventing the first adhesive from extending onto the second sub-surface and causing excessive thickness in a portion of the second sub-surface, resulting in a bulge in the casing. During charging and discharging, the casing in this area would experience excessive stress, leading to casing cracking and damage. Figure 4 As shown, in the first direction, the projection of the edge of the first adhesive near the transition surface lies within the range shown in L6.

[0043] In one possible implementation, such as Figure 2As shown, the first battery cell 11 also includes a first tab 117, which extends from the side of the first battery cell 11 and extends away from the first battery cell 11 in a third direction (Z). In a specific example, the first tab may be one of multiple flexible tabs integrally formed with the first current collector. The first separator 113 includes a second portion 1132 protruding from the first electrode sheet in a third direction. The first battery cell 11 includes a third adhesive member 133 that respectively adheres to the first electrode sheet 111 and the second portion 1132. In a specific example, the third direction is, for example, the length direction of the battery.

[0044] In a further example, such as Figure 2 As shown, the edge of the third adhesive 133 along its length is located between the edge of the first electrode and the edge of the second portion of the separator. In one specific example, the width of the third adhesive is 30%-70% of the width of the first electrode (e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%). In another specific example, the width of the third adhesive is greater than the width of the first electrode; that is, the third adhesive is disposed around the side of the first cell (e.g., ...). Figure 4 (As shown).

[0045] like Figure 2 As shown, in the second direction Y, the orthographic projection of the first adhesive member 131 onto the second cell 12 does not coincide with the orthographic projection of the third adhesive member 133 onto the second cell 12. In a specific example, such as Figure 2 As shown, the first adhesive 131 has its edge along the third direction Z located between the edge g of the first electrode and the edge f of the second portion of the separator. The first adhesive 131 adheres to the first electrode 111, the first portion 1131 of the separator, and the second portion 1132 of the separator, respectively. The width of the third adhesive is smaller than the width of the first electrode, and there is a gap between the third adhesive and the first adhesive along the first direction X. In another specific embodiment, the first adhesive adheres to the first electrode and the first portion of the separator, respectively. The third adhesive extends along the first direction to the area between the edge of the first electrode and the edge of the first portion of the separator. The third adhesive adheres to the first electrode, the first portion, and the second portion, respectively. There is a gap between the third adhesive and the first adhesive along the first direction, thereby preventing the first adhesive and the third adhesive from overlapping and causing local thickness accumulation, which can effectively improve the flatness of the battery and the energy density of the battery.

[0046] In one possible implementation, the portion of the first adhesive member covering the first electrode has a dimension L in the first direction. 7 The dimension of the first electrode in the first direction is L. 8 The battery satisfies the following relationship: 0.04 ≤ L 7 / L 8≤0.45 (e.g., 0.04, 0.08, 0.1, 0.13, 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, or 0.45); where L 7 2mm-10mm (e.g., 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm); and / or, L 8 The thickness is 20mm-100mm (e.g., 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, or 100mm). Because the area between the side and transition surface of the first cell is prone to abnormal pressure during hot pressing, and there may be uneven coverage or misalignment between the first electrode and the first separator, the side of the first cell may experience less pressure. The first adhesive component can increase the pressure on the edge of the first cell, thereby reducing the occurrence of black spots or lithium plating on the edge of the first cell, reducing battery thickness expansion during cycling, and improving battery cycle performance and lifespan. If L 7 / L 8 If L is too small, the bonding area of ​​the first adhesive component will be small, making it prone to peeling off during charging and discharging; if L... 7 / L 8 Excessive pressure can lead to excessive pressure on the sides of the first cell, resulting in uneven pressure distribution across the entire cell. During cycling, this uneven expansion of the cell's overall thickness can cause black spots and lithium plating later on.

[0047] In one possible implementation, in a first direction of the battery, the distance L between the end of the first adhesive member 131 facing away from the first electrode and the first endpoint of the second sub-surface 211 near the transition surface is... 9 0 < L 9 <2 (e.g., 0.1, 0.3, 0.5, 0.8, 1, 1.3, 1.5, 1.8 or 1.9) further prevents the first adhesive from extending to the second sub-surface, causing excessive thickness in some areas of the second sub-surface, resulting in a bulge in the casing. During charging and discharging, the casing in this area experiences excessive stress, leading to casing cracking and damage.

[0048] In one possible implementation, in the first direction, the end of the first adhesive member away from the first electrode is located within the space formed by the end of the second electrode of the first cell and the transition surface, thereby fixing the first electrode and preventing the first electrode from impacting the four surfaces of the housing—the first sub-surface, the transition surface, and the sides located on opposite sides of the first sub-surface—as the cell expands, thus affecting airtightness. Moreover, the first adhesive member is located in the area formed between the side surface of the first cell and the transition surface, preventing local separation that is prone to occur under the complex stress caused by cell expansion, which could affect heat dissipation or cause local abnormalities.

[0049] In one possible implementation, such as Figure 2 As shown, the first cell 11 includes a fourth adhesive member 134 disposed on a surface away from the second cell 12. The fourth adhesive member 134 and the first adhesive member 131 are spaced apart along a first direction X. In one specific example, the fourth adhesive member 134 extends beyond the edge g of the first electrode sheet along a third direction Z, but does not extend beyond the edge f of the first separator along a third direction; in another specific example, the edge of the fourth adhesive member along the first direction is located at the edge of the first electrode sheet and the third portion of the separator extending beyond the edge of the first electrode sheet along the first direction. In one specific example, the fourth adhesive member covers the end R-angle of the first electrode sheet (e.g., Figure 1 and Figure 2 (As shown). In another specific example, the first cell includes two fourth adhesive members, which are spaced apart along a third direction (e.g. Figure 1 and Figure 2 (As shown).

[0050] In one possible implementation, such as Figure 2 As shown, the second cell 12 includes a sixth electrode 126 adjacent to the first cell; a fifth adhesive member 135 is disposed on the surface of the sixth electrode 126 not covered by the first cell 11, the fifth adhesive member 135 and the first adhesive member 131 being spaced apart; the fifth adhesive member extends beyond the edge of the sixth electrode in a third direction, but does not extend beyond the edge of the adjacent separator of the sixth electrode in a third direction. In a specific example, the fifth adhesive member covers the radius (R) of the sixth electrode (e.g., ...). Figure 1 and Figure 2 (As shown). In another specific example, the fifth adhesive extends beyond the edge of the sixth electrode along the first direction, but does not extend beyond the edge of the adjacent diaphragm of the sixth electrode along the first direction. In another specific example, it includes two fifth adhesives spaced apart along a third direction (as shown). Figure 1 and Figure 2 (As shown).

[0051] 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.

[0052] The following examples illustrate the battery of the present invention.

[0053] 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.

[0054] (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%.

[0055] (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.

[0056] (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.

[0057] (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 first battery cell and a second battery cell of different sizes. The first battery cell and the second battery cell are arranged as follows: Figure 1 The cells are stacked in the manner shown to form a stacked core; after encapsulation, baking, liquid injection, formation, secondary sealing, sorting and OCV, a lithium-ion battery is obtained.

[0058] Among them, L 1 It is 0.7mm, L 5 It is 0.7mm, L 1 / L 5 =1,L 7 It is 5mm, L 8 It is 34mm, L 7 / L 8 =0.147.

[0059] Example 2 group Example 2a The same procedure was followed as in Example 1, except that the mass content of elemental silicon in the second active layer was 1.5%.

[0060] Example 2b The same procedure was followed as in Example 1, except that the elemental silicon content in the second active layer was 70%.

[0061] Example 3 Group This set of examples is used to illustrate when L 1 The impact of changes.

[0062] This embodiment group is carried out with reference to Embodiment 1, except that L is changed. 1 For details, please refer to Table 1-1.

[0063] Example 4 group This set of examples is used to illustrate when L 5 The impact of changes.

[0064] This embodiment group is carried out with reference to Embodiment 1, except that L is changed. 5 For details, please refer to Table 1-1.

[0065] Table 1-1 Example 5 group This set of examples is used to illustrate when L 7 The impact of changes.

[0066] This embodiment group is carried out with reference to Embodiment 1, except that L is changed. 7 See Table 1-2 for details.

[0067] Example 6 group This set of examples is used to illustrate when L 8 The impact of changes.

[0068] This embodiment group is carried out with reference to Embodiment 1, except that L is changed. 8 See Table 1-2 for details.

[0069] Table 1-2 Comparative Example 1 The same procedure was followed as in Example 1, except that the mass content of elemental silicon in the second active layer was 75%.

[0070] Comparative Example 2 The procedure is carried out in accordance with Example 1, except that there is no first adhesive component.

[0071] Comparative Example 3 The procedure is carried out in accordance with Example 1, except that the first adhesive is only bonded to the first electrode.

[0072] Comparative Example 4 The procedure is carried out with reference to Embodiment 1, except that the first edge of the first adhesive member near the transition surface extends beyond the edge of the first portion of the first diaphragm and is bonded to the other diaphragms below the first diaphragm.

[0073] Test case (1) Volumetric energy density: The battery was left to stand for 1 hour at (25±2)℃. It was then charged at a constant current of 0.5C to 4.53V, followed by constant voltage charging at 4.53V to a current of 0.05C, and left to stand for 10 minutes. Next, it was discharged at a constant current of 0.2C to 3V and left to stand for 10 minutes. The discharge capacity was recorded as Q, the average discharge plateau voltage as V, and the lithium-ion battery thickness as H, length as Y, width as Z, and volumetric energy density as (Q×V) / (H×Y×Z).

[0074] (2) Cyclic capacity retention, lithium plating, and safety performance tests at 25℃: At 25℃±2℃, the battery was charged at a constant current of 1.2C to 4.25V, then charged at 0.7C to the upper limit voltage of 4.53V, then continued to be charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.7C to 3V, left to stand for 5 minutes. The initial discharge capacity was recorded as C. 0 Cyclic charging method: Charge at a constant current of 1.2C to 4.25V, then switch to 0.7C charging to the upper limit voltage of 4.53V, then continue constant voltage charging to 0.05C, rest for 5 minutes, then discharge at a constant current of 0.7C to 3V. After 500 cycles, record the discharge capacity as C. 1The capacity retention rate is (C 1 / C 0 )×100%.

[0075] Lithium plating situation: After cycling 500T, the battery was charged to 4.53V at a constant current and constant voltage of 0.7C, with a cutoff current of 0.05C. After standing for 10 minutes, the battery was disassembled and the negative electrode was removed. The evaluation criteria for lithium plating on the negative electrode were: none < slight < moderate < severe. If no lithium plating or black spots appeared on the surface of the negative electrode, the result was "none". If lithium plating and / or black spots appeared on the surface of the negative electrode and the area of ​​lithium plating and / or black spots was greater than or equal to 1% to 5%, it was considered slight. If the area of ​​lithium plating and / or black spots on the surface of the negative electrode was greater than 5% to 20%, it was considered moderate. If the area of ​​lithium plating and / or black spots on the surface of the negative electrode was greater than 20%, it was considered severe.

[0076] Security performance test: After the battery is cycled at 25°C for 500T, if the casing is not damaged, the safety performance test is considered passed; if the battery casing is damaged, the safety performance test is considered failed. Each set of examples and comparative examples tests 20 batteries, and the number of batteries that pass is recorded as X. The result is recorded as "X / 20".

[0077] (3) Determination of K value: The lithium-ion batteries that have been sorted were placed in an environment of 45℃±5℃ and left to stand for 48 hours. Then, the batteries were transferred to an environment of 25℃±5℃ and left to stand for 48 hours. The open circuit potential was measured to obtain V. 1 After letting it stand for another 48 hours, the open-circuit potential of the battery was measured again to obtain V. 2 , with V 1 Subtract V 2 The difference is then divided by the resting time (48h) to obtain the battery's K value, in mV / h. The K value is the average of 100 batteries measured.

[0078] Table 2 As shown in Table 2, by comparing the comparative examples and the embodiments, the volumetric energy density is improved, the 25°C cycle capacity retention rate is improved, the lithium plating situation is significantly improved, the K value is reduced, and the safety performance test pass rate is improved. This indicates that by stacking the first cell and the second cell to form an irregularly shaped stacked battery, and by providing a first adhesive member, which is respectively bonded to the first part of the first separator and the first electrode, and the first edge of the first adhesive member near the transition surface does not exceed the edge of the first part of the first separator, the energy density of the battery is improved, the safety performance is enhanced, the room temperature cycle capacity retention rate of the battery is improved, and the K value is reduced.

[0079] 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 housing and a cell assembly located within the housing. The cell assembly includes a first cell and a second cell stacked together. Along a first direction of the battery, the length of the first cell is less than the length of the second cell. A first end of the second cell protrudes along the first direction of the battery from the end of the first cell corresponding to the first end of the second cell. The housing includes a first surface and a second surface disposed opposite to each other along a second direction of the battery. The first surface includes a first sub-surface, a second sub-surface, and a transition surface. Along the first direction of the battery, the first sub-surface protrudes from the second sub-surface, and the transition surface connects the first sub-surface and the second sub-surface. The cell assembly includes a first adhesive member located between a first surface of the housing and the first cell, wherein the projection of the first adhesive member in a second direction of the battery and the projection of the transition surface in the second direction of the battery at least partially overlap. The first cell includes a first electrode, a first separator, and a second electrode near a first side of the casing, wherein the first separator is located between the first electrode and the second electrode; The second electrode includes a second current collector and a second active layer located on the second current collector, wherein the mass content of elemental silicon in the second active layer is 1.5%-70%; The first diaphragm includes a first portion that protrudes from the first side of the first electrode in the first direction, and the first adhesive is bonded to the first portion of the first diaphragm and the first electrode respectively; Along the first direction, the first edge of the first adhesive near the transition surface does not extend beyond the edge of the first portion of the first diaphragm.

2. The battery according to claim 1, characterized in that, Along the first direction of the battery, the dimension between the first edge of the first adhesive member near the transition surface and the first side edge of the first electrode is L. 1 ; The second sub-surface includes a first endpoint near the transition surface, and the distance between the first endpoint and the first side edge of the first electrode is L. 5 The following relationship is satisfied: 0.025≤L 1 / L 5 ≤3.6; Among them, L 1 For 0.05-2mm; and / or, L 5 It is 0.5-2mm.

3. The battery according to claim 1, characterized in that, The first battery cell includes a fifth electrode near the second battery cell, and the second battery cell includes a sixth electrode near the first battery cell. The fifth electrode and the sixth electrode have the same polarity and are bonded together by a second adhesive. Alternatively, the fifth electrode and the sixth electrode may have different polarities, and the battery may include a connecting membrane located between the fifth electrode and the sixth electrode, which are bonded together by the connecting membrane.

4. The battery according to claim 3, characterized in that, In the first direction, the projection of the first edge of the first adhesive near the transition surface onto the second cell lies within the second adhesive.

5. The battery according to claim 3, characterized in that, The first cell further includes a second electrode, which is located on the side of the first separator opposite to the first electrode. The second sub-face includes a first endpoint near the transition surface. In the first direction, the projection of the edge of the first adhesive near the transition surface is located between the second electrode of the first cell and the first end point.

6. The battery according to claim 1, characterized in that, The first cell further includes a first electrode tab, which extends from the side of the first cell and extends away from the first cell in a third direction; the first separator includes a second portion that protrudes from the first electrode tab in the third direction. The first battery cell includes a third adhesive component that bonds the first electrode and the second portion respectively; In the second direction, the orthographic projection of the first adhesive on the second cell does not coincide with the orthographic projection of the third adhesive on the second cell.

7. The battery according to claim 1, characterized in that, The dimension of the portion of the first adhesive member covering the first electrode sheet in the first direction is L. 7 The dimension of the first electrode in the first direction is L. 8 The battery satisfies the following relationship: 0.04 ≤ L 7 / L 8 ≤0.45; Among them, L 7 2mm-10mm; and / or, L 8 The thickness ranges from 20mm to 100mm.

8. The battery according to claim 1, characterized in that, In a first direction of the battery, the distance L between the end of the first adhesive member facing away from the first electrode and the first endpoint of the second sub-surface near the transition surface is... 9 0 < L 9 <2.

9. The battery according to claim 1, characterized in that, In the first direction, the end of the first adhesive member away from the first electrode is located within the space formed by the end of the second electrode of the first cell and the transition surface.

10. The battery according to claim 1, characterized in that, The first battery cell includes a fourth adhesive member disposed on a side surface away from the second battery cell, and the fourth adhesive member and the first adhesive member are spaced apart along the first direction; The fourth adhesive extends beyond the edge of the first electrode in a third direction, but does not extend beyond the edge of the first diaphragm in a third direction. And / or, the second cell includes a sixth electrode near the first cell; The surface of the sixth electrode that is not covered by the first cell is provided with a fifth adhesive member, and the fifth adhesive member and the first adhesive member are provided at intervals. The fifth adhesive extends beyond the edge of the sixth electrode in a third direction, but does not extend beyond the edge of the adjacent diaphragm of the sixth electrode in a third direction.

Images