Battery cell, battery, and electric device

Abstract

The application discloses a kind of battery monomer, battery and electric device, the battery monomer includes: shell;At least two pole groups, the pole group is located in the shell and is distributed along the thickness direction of the shell;At least one buffer pole piece, the buffer pole piece is located in the shell and is arranged between two adjacent pole groups, the buffer pole piece includes conductive matrix and is arranged in the active material layer of at least one side surface of the conductive matrix;Electrolyte, the electrolyte is filled in the shell.The application increases buffer pole piece between two adjacent pole groups in the inside, so that internal pole group can extrude buffer pole piece to get expansion space to both sides in the process of battery monomer charging cycle;In addition, active material layer is arranged on buffer pole piece, active material layer can realize lithium ion insertion and extraction with pole group outside area material, makes full use of pole group outside area material, and can further improve battery capacity.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a battery cell, a battery, and an electrical device. Background Technology

[0002] With the rapid development of new energy technologies, lithium-ion batteries are becoming increasingly common in people's lives and work. However, compared with traditional lead-acid batteries, the material cost of lithium-ion batteries is still relatively high. In order to further reduce costs, the main method at present is to increase the capacity and energy of individual cells. The capacity of a cell with four poles connected in parallel is significantly higher than that of a cell with two poles connected in parallel, which reduces the average manufacturing cost and material cost.

[0003] During charge-discharge cycles, the positive and negative electrode materials expand due to lithium-ion insertion / extraction. For cells with two electrode assemblies, the electrode assemblies can expand outwards during cycling to ensure proper lithium insertion into the negative electrode. However, for cells with four electrode assemblies, the outer two electrode assemblies can expand freely, but the inner two electrode assemblies are constrained by the outer electrode assemblies and have no room to expand. This can cause difficulties in lithium insertion into the negative electrode during cycling, leading to risks such as lithium plating and affecting cycle performance.

[0004] Meanwhile, the outermost two sides of a typical electrode assembly are generally covered with a separator, and since these negative electrode materials do not participate in the cell's charging and discharging process because there is no corresponding positive electrode material for delithiation, they do not participate in the process. For a single cell with four electrode assemblies, there are a total of eight large negative electrode regions that do not participate in the reaction, resulting in significant capacity loss.

[0005] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a single battery cell, a battery, and an electrical device. Summary of the Invention

[0006] The purpose of this invention is to provide a single battery cell, a battery, and an electrical device to avoid lithium plating on the negative electrode and improve the cycle performance of the single battery cell.

[0007] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:

[0008] A single battery cell, the single battery cell comprising:

[0009] shell;

[0010] At least two electrode groups are located inside the housing and distributed along the thickness direction of the housing. Each electrode group includes a first electrode plate with a first polarity and a second electrode plate with a second polarity. The second electrode plate is located outside the electrode group. The first polarity is opposite to the second polarity.

[0011] At least one buffer electrode is located inside the housing and disposed between two adjacent electrode groups. The buffer electrode includes a conductive substrate and an active material layer disposed on at least one surface of the conductive substrate. The active material layer has a first polarity. The conductive substrate is electrically connected to the first electrode.

[0012] Electrolyte, which is filled inside the housing.

[0013] In some embodiments of the present invention, the conductive substrate is selected from porous materials with conductive properties.

[0014] In some embodiments of the present invention, the conductive substrate is a composite aluminum foam board, the composite aluminum foam board comprising an aluminum foam interlayer and a metal aluminum plate located on at least one side of the aluminum foam interlayer.

[0015] In some embodiments of the present invention, the thickness of the conductive substrate Greater than or equal to and less than or equal to ,in, The initial thickness of the electrode assembly. This refers to the compressibility of the conductive substrate. and These are the lower and upper limits of the cyclic expansion rate of the electrode group, respectively.

[0016] In some embodiments of the present invention, the compressibility of the conductive substrate The value is 30% to 80%; and / or, the lower limit of the cyclic expansion rate of the electrode group. It is 5% to 7%, with the upper limit. It is 14% to 16%.

[0017] In some embodiments of the present invention, the initial thickness of the conductive substrate With the initial thickness of the pole group ratio For (1~3):16; and / or, the initial thickness of the conductive substrate The thickness is 1mm to 3mm.

[0018] In some embodiments of the present invention, the initial thickness of the conductive substrate The compressibility of the conductive substrate is 1mm to 3mm. The initial thickness is 30% to 80%; further, the initial thickness of the conductive substrate is... The compressibility of the conductive substrate is 2mm~3mm. It ranges from 60% to 80%.

[0019] In some embodiments of the present invention, the thickness of the active material layer is 40 μm to 200 μm; and / or, the thickness of the active material layer on the surface of the conductive substrate is equal to the thickness of the active material layer in the first electrode; and / or, the material of the active material layer on the surface of the conductive substrate is the same as the material of the active material layer in the first electrode.

[0020] In some embodiments of the present invention, the electrode assembly is a wound electrode assembly, the first electrode is a positive electrode, the second electrode is a negative electrode, the wound electrode assembly is formed by winding the negative electrode, the separator and the positive electrode to form a straight portion and a corner portion, the second electrode is wrapped around the outside of the first electrode, and the active material layer on the surface of the conductive substrate covers the lithium intercalation region corresponding to the second electrode on the side electrode assembly surface.

[0021] In some embodiments of the present invention, the width m of the buffer electrode is greater than or equal to the width w of the straight portion and less than or equal to the total width x of the electrode group; and / or, the height n of the buffer electrode is greater than or equal to the height h of the first electrode and less than or equal to the total height y of the electrode group.

[0022] In some embodiments of the present invention, the electrode assembly further includes a first electrode tab electrically connected to the first electrode plate and a second electrode tab electrically connected to the second electrode plate. The outer casing is provided with a first electrode post and a second electrode post. The buffer electrode plate further includes a third electrode tab electrically connected to the conductive substrate. The first electrode tab and the third electrode tab are both electrically connected to the first electrode post, and the second electrode tab is electrically connected to the second electrode post.

[0023] In some embodiments of the present invention, an insulating coating is provided next to the active material layer on the surface of the conductive substrate, and the third electrode is located on one side of the insulating coating; further, the insulating coating is a ceramic coating with a thickness of 10μm~80μm.

[0024] In some embodiments of the present invention, the battery cell includes four electrode groups and three buffer electrodes, with a buffer electrode provided between each pair of adjacent electrode groups, and an active material layer provided on both sides of the conductive substrate in each buffer electrode.

[0025] The thickness of the individual battery cell is between 70mm and 80mm;

[0026] The width of the individual battery cell is between 250mm and 350mm;

[0027] The height of the individual battery cells is between 200mm and 300mm.

[0028] Another embodiment of the present invention provides the following technical solution:

[0029] A battery comprising the aforementioned individual battery cells.

[0030] Another embodiment of the present invention provides the following technical solution:

[0031] An electrical device comprising the battery described above.

[0032] Compared with the prior art, the present invention adds a buffer electrode between two adjacent electrode groups inside, so that the internal electrode groups can squeeze the buffer electrode to both sides to obtain expansion space during the charging cycle of the battery cell, which facilitates the lithium ion to complete lithium intercalation in the negative electrode and improves the cycle performance of the battery cell.

[0033] In addition, an active material layer is set on the buffer electrode. The active material layer can realize the insertion and extraction of lithium ions with the material in the outer region of the electrode group, making full use of the material in the outer region of the electrode group and further improving the cell capacity. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a three-dimensional structural diagram of a single battery cell according to one embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the exploded structure of a single battery cell according to one embodiment of the present invention;

[0037] Figure 3 This is a side view of the electrode assembly and buffer electrode sheet in one embodiment of the present invention.

[0038] Figure 4 for Figure 3 Enlarged structural diagram at point A;

[0039] Figure 5 This is a schematic diagram of the exploded structure of the electrode assembly and buffer electrode sheet in one embodiment of the present invention;

[0040] Figure 6 This is a three-dimensional structural diagram of the pole assembly in one embodiment of the present invention;

[0041] Figure 7 This is a three-dimensional structural diagram of the buffer electrode in one embodiment of the present invention;

[0042] Figure 8This is a schematic diagram of the planar structure of the buffer electrode before welding after cutting in one embodiment of the present invention;

[0043] Figure 9 This is a partial cross-sectional view of the buffer electrode in one embodiment of the present invention.

[0044] Figure 10 This is a physical image of a composite aluminum foam board according to one embodiment of the present invention.

[0045] Explanation of key figure labels:

[0046] 100-Cell cell, 11-Housing, 12-Cover plate, 121-First electrode post, 122-Second electrode post, 20-Electrode group, 21-First tab, 22-Second tab, 201-Straight section, 202-Corner section, 30-Buffer electrode, 31-Conductive substrate, 32-Active material layer, 33-Insulating coating, 34-Third tab, S-Lithium intercalation region. Detailed Implementation

[0047] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0048] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0049] In this invention, unless otherwise expressly specified and limited, the disclosed "range" is defined in the form of a lower limit and / or an upper limit. A given range is defined by selecting a lower limit and / or an upper limit, which defines the boundary of the particular range. Ranges defined in this way may include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with other lower limits to form an unspecified range. Similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower limit or upper limit and can be combined with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0050] In this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0051] In this invention, unless otherwise expressly specified and limited, all embodiments and optional embodiments, or all technical features and optional technical features, can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0052] Currently, the mainstream high-capacity 587 / 588Ah battery cells are becoming the primary development product for the next generation of energy storage cells, following the 314Ah battery cells. 587 / 588Ah battery cells typically employ a four-pole parallel connection technology, unlike the bipolar connection of the 314Ah battery cells. Compared to the 314Ah battery cells, the width of the 587 / 588Ah battery cells is significantly increased. Using high-efficiency winding technology, this saves on capacity loss due to radius (R-angle) space and avoids low production yields caused by excessively long electrode sheets in the electrode group.

[0053] During charge-discharge cycles, the positive and negative electrode materials expand due to lithium-ion insertion / extraction. In a 314Ah cell with only two electrode groups, these groups can expand outwards during cycling to ensure proper lithium insertion into the negative electrode. However, in 587 / 588Ah cells, while the outer two electrode groups can expand freely, the inner two electrode groups are constrained by the outer groups and lack expansion space. This can lead to difficulties in lithium insertion into the negative electrode during cycling, increasing the risk of lithium plating and affecting cycle performance.

[0054] Meanwhile, to ensure that all the lithium ions released from the positive electrode can be completely absorbed and inserted into the negative electrode, the negative electrode needs to completely wrap the positive electrode. Generally, the outermost two sides of the electrode group are coated with negative electrode materials by separators. Since there is no corresponding positive electrode material releasing lithium ions, these negative electrode materials do not participate in the charge-discharge process of the battery cell. For a battery cell monomer with four electrode groups, each electrode group has two large surfaces of negative electrode regions that do not participate in the reaction, and there are a total of eight large surfaces of negative electrode regions that do not participate in the reaction in the four electrode groups, which causes a large loss of the battery cell capacity.

[0055] In the present invention, a buffer electrode is added between two adjacent internal electrode groups, enabling the internal electrode groups to squeeze the buffer electrode towards both sides during the charge-discharge cycle of the battery cell monomer to obtain an expansion space, facilitating the insertion of lithium ions into the negative electrode and improving the cycle performance of the battery cell monomer.

[0056] In addition, an active material layer (positive electrode material) identical to the positive electrode is provided on the buffer electrode, and is connected to the positive electrode terminal through the corresponding tab. During the charging process of the battery cell, lithium ions in the active material layer on the buffer electrode are normally released and then inserted into the outermost negative electrode of the electrode group. Meanwhile, during the discharging process, the lithium ions are re-inserted, making full use of the negative electrode material in the large surface of the negative electrode region outside the electrode group and further improving the battery cell capacity.

[0057] See Figure 1 、 Figure 2 As shown, the present invention discloses a battery cell monomer 100, comprising:

[0058] A housing;

[0059] At least two electrode groups 20, which are located inside the housing and distributed along the thickness direction of the housing;

[0060] At least one buffer electrode 30, which is disposed between two adjacent electrode groups 20. The buffer electrode 30 includes a conductive substrate 31 and an active material layer 32 disposed on at least one surface of the conductive substrate;

[0061] An electrolyte (not shown), which is filled inside the housing.

[0062] In some embodiments of the present invention, the housing is in the shape of a cuboid, comprising a housing body 11 and a cover plate 12. There is a cavity with an open top inside the housing body 11, and the cover plate 12 is sealingly installed on the top of the housing body 11. The electrode group is fixedly installed on the cover plate 12 and located in the cavity.

[0063] [[ID=第31]]Exemplarily, see Figure 1 、 Figure 2 And in combination with Figure 3 And Figure 5As shown, taking a single cell 100 with four pole groups as an example, the casing has four identical pole groups 20 inside, and a buffer electrode 30 is provided between every two adjacent pole groups 20, for a total of three buffer electrodes 30.

[0064] In some embodiments of the present invention, taking a four-pole battery cell 100 as an example, the thickness a of the battery cell 100 is 70mm~80mm, the width c of the battery cell is 250mm~350mm, and the height b of the battery cell is 200mm~300mm.

[0065] The electrode assembly in this invention includes a first electrode with a first polarity and a second electrode with a second polarity, with the second electrode on the outside of the electrode assembly, and the first polarity being opposite to the second polarity.

[0066] In some embodiments of the present invention, references Figure 6 As shown, electrode assembly 20 is a wound electrode assembly. The first electrode is a positive electrode, and the second electrode is a negative electrode. The wound electrode assembly consists of the negative electrode, the separator, and the positive electrode, wound together. The second electrode (negative electrode) is wrapped around the outside of the first electrode (positive electrode). During the charging and discharging process of a single cell, active ions move back and forth between the positive and negative electrode, inserting and extracting. The separator is positioned between the positive and negative electrode to provide isolation.

[0067] In the electrode assembly 20 of the present invention, the positive electrode sheet typically includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material. The positive electrode current collector can be a conventional metal foil or a composite current collector (a composite current collector can be formed by depositing metal material on a polymer substrate). For example, the positive electrode current collector can be aluminum foil.

[0068] In this invention, the specific type of positive electrode active material is not limited; any active material known in the art that can be used for battery positive electrodes can be used, and those skilled in the art can select according to actual needs. For example, the positive electrode active material may include, but is not limited to, lithium transition metal oxides and / or lithium phosphates with olivine structures. The lithium transition metal oxides may include undoped and / or optionally doped modified lithium transition metal oxides, uncoated and / or coated modified lithium transition metal oxides, and the lithium phosphates with olivine structures may include undoped and / or optionally doped modified lithium phosphates, uncoated and / or coated modified lithium phosphates. The positive electrode active materials within the given range can be prepared or obtained commercially.

[0069] In some embodiments of the present invention, the positive electrode active material layer may optionally include a binder, a conductive agent, and other optional additives. Exemplarily, the conductive agent may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers. Exemplarily, the binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0070] In the electrode assembly 20 of the present invention, the negative electrode sheet typically includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material. The negative electrode current collector can be a conventional metal foil or a composite current collector (for example, a composite current collector can be formed by depositing metal material on a polymer substrate). Exemplarily, the negative electrode current collector can be a copper foil.

[0071] In some embodiments of the present invention, the battery cell 100 can be a lithium-ion battery cell. In this case, the specific type of negative electrode active material is not limited, and any active material known in the art that can be used for the negative electrode of a battery can be used. Those skilled in the art can flexibly select according to actual needs. Exemplarily, the negative electrode active material may include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials, and tin-based materials. Optionally, silicon-based materials may include one or more of elemental silicon, silicon oxide compounds (e.g., silicon suboxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Further optionally, tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode active materials within the given range can be prepared or obtained commercially.

[0072] In some embodiments of the present invention, the negative electrode active material layer may optionally include a binder, a conductive agent, and other optional additives. Exemplarily, the conductive agent may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Exemplarily, the binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). Exemplarily, other optional additives may include, but are not limited to, thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na), and PTC thermistor materials.

[0073] In some embodiments of the present invention, the diaphragm in the electrode assembly 20 may include, but is not limited to, a polyethylene porous membrane, a polypropylene porous membrane, a polyimide porous membrane, and a porous membrane formed by a composite of various polymers.

[0074] In some embodiments of the present invention, references Figure 2 , Figure 6 As shown, the electrode assembly 20 is provided with a first tab 21 and a second tab 22. The tabs are metallic conductors that lead out the positive and negative electrodes from the electrode assembly. For example, the first tab 21 can be a positive tab, and the second tab 22 can be a negative tab. The first tab 21 is welded to the positive current collector reserved on the positive electrode sheet, and the second tab 22 is welded to the negative current collector reserved on the negative electrode sheet. For example, the positive current collector in the positive electrode sheet is made of aluminum foil, and the first tab 21 can be made of aluminum strip; the negative current collector in the negative electrode sheet is made of copper foil, and the second tab 22 can be made of copper strip.

[0075] Accordingly, the cover plate 12 is provided with a first electrode post 121 and a second electrode post 122. The first electrode tab 21 is welded to the cover plate 12 and electrically connected to the first electrode post 121, and the second electrode tab 22 is welded to the cover plate 12 and electrically connected to the second electrode post 122.

[0076] In some embodiments of the present invention, references Figure 6 As shown, after the wound pole assembly is wound, it forms a straight portion 201 and corner portions 202 located on both sides of the straight portion 201. Optionally, the corner portions 202 are R-angles.

[0077] In some embodiments of the present invention, the height h of the negative electrode is slightly less than the total height y of the entire electrode assembly 20. This arrangement allows for sufficient space to accommodate the expansion of the negative electrode while preventing the edge of the negative electrode from contacting the edge of the positive electrode and causing a short circuit. In this case, the area corresponding to the negative electrode in the two opposite sides (large surfaces) of the straight portion 201 is the lithium intercalation region S, such as... Figure 6Medium shaded area.

[0078] The buffer electrode 30 between the electrode groups in this invention will be described in detail below.

[0079] In some embodiments of the present invention, references Figure 7 , Figure 9 As shown, the buffer electrode 30 includes a conductive substrate 31 and an active material layer 32 disposed on at least one side surface of the conductive substrate. Preferably, an active material layer 32 can be disposed on both sides of the conductive substrate 31, and the active material layer 32 on each side reacts with the outermost electrode of the electrode group on that side to improve the cell capacity.

[0080] During the cycling process of a single cell, the electrode assembly expands and presses against the buffer electrode on both sides. The electrolyte mainly wets the electrode assembly through a siphon effect. Excessive pressing force will affect the siphon effect between the electrode assembly and the buffer electrode, resulting in insufficient electrolyte absorption in the middle area of ​​the electrode assembly, which may lead to risks such as lithium plating. Therefore, the conductive substrate 31 needs to be made of a porous material. The pores in the porous material can store free electrolyte, thereby ensuring the amount of electrolyte required for long-term cycling and ensuring cycle performance. In addition, the buffer electrode participates in the reaction and needs to be electrically connected to the external electrode post like the electrode; therefore, the conductive substrate needs to have conductivity.

[0081] In addition, the conductive substrate 31 must be made of a material resistant to electrolyte corrosion. Meanwhile, after the electrode assembly 20 and the buffer electrode 30 are installed in the casing, they need to undergo a high-temperature baking process to completely remove moisture from the individual battery cells, creating a dry environment for electrolyte injection. The temperature of this high-temperature baking process is typically 75℃~100℃. Therefore, the buffer electrode is preferably made of a material that does not shrink at this process temperature.

[0082] In some embodiments of the present invention, the conductive substrate 31 is selected from a porous material that is resistant to electrolyte corrosion, does not shrink when heated at a temperature not exceeding 110°C, and has electrical conductivity. For example, the conductive substrate 31 is a composite aluminum foam board. Figure 10 As shown, the composite aluminum foam board includes an aluminum foam interlayer and a metal aluminum plate located on at least one side of the aluminum foam interlayer.

[0083] The foamed aluminum interlayer is a lightweight, porous metallic functional material with aluminum or aluminum alloy as the matrix and filled with numerous air bubbles. It can be prepared through processes such as melt foaming, powder metallurgy, and infiltration casting. Due to its aluminum or aluminum alloy matrix, it possesses certain electrical conductivity. Furthermore, foamed aluminum exhibits good dimensional stability. Below 600℃, its dimensional changes primarily follow the coefficient of linear expansion due to thermal expansion and contraction, rather than irreversible shrinkage. During the high-temperature baking process of the battery cell (75℃~100℃), the foamed aluminum board will not shrink.

[0084] The outer side of the foamed aluminum intermediate layer is a smooth metal aluminum plate. On the one hand, the aluminum plate can serve as the main conductive carrier of the buffer electrode. On the other hand, the smooth metal aluminum plate can better coat the positive electrode active material layer.

[0085] In some embodiments of the present invention, the aluminum foam interlayer has a relatively large thickness, for example, 0.5 mm to 3.0 mm, while the aluminum metal plate has a relatively small thickness, for example, 0.02 mm to 0.3 mm. For example, when a composite aluminum foam plate with a thickness of 1 mm is used, the thickness of the aluminum foam interlayer can be 0.974 mm, and the thicknesses of the two aluminum metal plates on both sides are 0.013 mm; when a composite aluminum foam plate with a thickness of 2 mm is used, the thickness of the aluminum foam interlayer can be 1.974 mm, and the thicknesses of the two aluminum metal plates on both sides are 0.013 mm; when a composite aluminum foam plate with a thickness of 3 mm is used, the thickness of the aluminum foam interlayer can be 2.974 mm, and the thicknesses of the two aluminum metal plates on both sides are 0.013 mm.

[0086] During the cycling process of a single battery cell, both the positive and negative electrode plates expand. The negative electrode plate, in particular, expands more significantly due to the continuous thickening of the graphite particles intercalating into lithium and the solid-liquid interface film on its surface. This causes the electrode assembly thickness to expand with each cycle. Therefore, it is necessary to select an appropriate composite aluminum foam plate thickness and compressibility based on the initial thickness of the electrode assembly and the cyclic expansion.

[0087] In some embodiments of the present invention, the initial thickness t and compressibility of the conductive substrate 31 are specified. Based on the initial thickness z and cyclic expansion rate of electrode group 20 Configure the settings.

[0088] Cyclic expansion rate Thickness measurement can be performed using a method similar to a digital micrometer or laser thickness gauge to directly measure the thickness change of a single cell. For example, using a 587 / 588Ah cell as an example, the lower limit of the electrode group's cyclic expansion rate after a certain number of cycles can be determined. It is 5% to 7%, with the upper limit. The cyclic expansion rate is 14% to 16%. Optionally, the cyclic expansion rate of the electrode assembly is 5% to 16%.

[0089] When the material of the conductive substrate 31 is selected as composite aluminum foam board, the compressibility is... It can be 30% to 80%, for example, 30%, 40%, 50%, 60%, 70%, 80%, etc., or it can be any range of the above values.

[0090] Initial thickness of conductive substrate 31 The initial thickness of the pole group 20 ratio = In some embodiments of the present invention, the ratio is (1~3):16, for example, it can be 1:16, 2:16, 3:16, etc.

[0091] Thickness of conductive substrate 31 Greater than or equal to and less than or equal to ,in, The initial thickness of the electrode group. This represents the compressibility of the conductive substrate. and These are the lower and upper limits of the electrode group's cyclic expansion rate, respectively. For example, when the lower limit of the electrode group's cyclic expansion rate is... and upper limit value 5% and 16% respectively, compressibility When the initial thickness z of the electrode assembly is 16 mm and the cyclic expansion rate is 50%, the thickness t of the conductive substrate is 1.6 mm to 5.12 mm. When the lower limit of the cyclic expansion rate of the electrode assembly is... and upper limit value 5% and 16% respectively, compressibility When the electrode thickness is 80% and the initial thickness z of the electrode group is 16 mm, the thickness t of the conductive substrate is 1 mm to 3.2 mm.

[0092] In some embodiments of the present invention, the initial thickness of the conductive substrate 31 is... The value can be 1mm to 3mm, for example, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, or any range of the above values.

[0093] Compressibility of conductive substrate 31 The porosity increases significantly with increasing porosity. Therefore, conductive substrates with a thin initial thickness and low compressibility cannot provide sufficient negative electrode expansion space during long-term cycling, resulting in decreased cycling performance. Therefore, in some preferred embodiments of the present invention, the conductive substrate 31 preferably has an initial thickness t of 2mm~3mm and a compressibility... It is a composite aluminum foam board with a content of 60% to 80%.

[0094] In this invention, the polarity of the active material layer 32 on the surface of the conductive substrate 31 is opposite to the polarity of the outer electrode sheet of the electrode assembly 20. Preferably, the electrode assembly is a wound electrode assembly, which uses a negative electrode sheet to wrap the positive electrode sheet, and the active material layer 32 on the surface of the conductive substrate 31 is a positive electrode active material layer.

[0095] In some embodiments of the present invention, the material of the active material layer 32 is the same as the positive electrode active material in the positive electrode sheet. The positive electrode active material has been described in detail above and will not be repeated here.

[0096] In some embodiments of the present invention, the thickness of the active material layer 32 may be the same as the thickness of the positive electrode active material in the positive electrode sheet.

[0097] In some embodiments of the present invention, the thickness of the active material layer 32 is 40 μm to 200 μm, for example, it can be 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, etc., or it can be a range of any of the above values.

[0098] By setting an active material layer on a conductive substrate, lithium ions in the positive active material layer on the buffer electrode are normally extracted during the charging process and then embedded into the outermost negative electrode of the electrode assembly. At the same time, lithium ion re-intercalation is completed during the discharge process, making full use of the negative electrode material of the electrode assembly and further improving the cell capacity.

[0099] In some embodiments of the present invention, when the wound electrode assembly uses a positive electrode sheet to wrap a negative electrode sheet, the material of the active material layer on the buffer electrode sheet is the same as the negative electrode active material in the negative electrode sheet. The negative electrode active material has been described in detail above and will not be repeated here.

[0100] In some embodiments of the present invention, references Figure 6 , Figure 7 As shown, the width m and height n of the buffer electrode 30 need to be rationally designed according to the electrode assembly 20. The active material layer 32 needs to cover the lithium intercalation region S of the flat portion 201 in the electrode assembly. The lithium intercalation region S corresponds to the negative electrode material on the large surface of the electrode assembly, ensuring that the lithium intercalation expansion area of ​​the negative electrode is within the coverage area of ​​the buffer electrode. Therefore, the width m of the buffer electrode 30 is greater than or equal to the width w of the flat portion and less than or equal to the total width x of the electrode assembly. The height n of the buffer electrode 30 is greater than or equal to the height h of the positive electrode and less than or equal to the total height y of the electrode assembly. For example, the width m of the buffer electrode 30 can be equal to the width w of the flat portion, the height n can be equal to the height h of the positive electrode, the width of the active material layer 32 is equal to the width m of the buffer electrode 30, and the height of the active material layer 32 is slightly less than the height n of the buffer electrode 30.

[0101] In this invention, the buffer electrode 30 serves as a buffer on one hand, and can also react with the electrode assembly to achieve charging and discharging on the other hand. Therefore, the buffer electrode 30 needs to be in electrical contact with the electrode post on the cover plate 12.

[0102] In some embodiments of the present invention, references Figure 4 , Figure 5 and Figure 7As shown, the buffer electrode 30 also includes a third electrode tab 34 electrically connected to the conductive substrate 31. Both the first electrode tab 21 and the third electrode tab 34 are electrically connected to the first electrode post 121 on the cover plate 12. Thus, the current generated by the chemical reaction between the active material layer 32 and the outermost electrode of the electrode group 20 can be collected through the third electrode tab 34 and conducted to the first electrode post 121.

[0103] In some embodiments of the present invention, references Figure 7 , Figure 9 As shown, an insulating coating 33 is provided next to the active material layer 32 on the surface of the conductive substrate 31, and the third electrode tab 34 is located on one side of the insulating coating 33. The insulating coating 33 can play an insulating role, preventing direct contact and short circuit between the positive and negative electrodes. At the same time, it can provide additional mechanical strength for the buffer electrode, reduce the risk of burrs piercing the surface membrane of the electrode assembly, and also help with electrolyte wetting and heat distribution, thereby improving the safety and stability of the battery cell.

[0104] For example, the insulating coating can be a ceramic coating with a thickness of 10μm to 80μm, such as 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 60μm, 80μm, etc., or it can be a range of any of the above values.

[0105] In some embodiments of the present invention, the material of the third electrode tab 34 is the same as the material of the conductive substrate 31. For example, the third electrode tab 34 and the conductive substrate 31 are an integrated composite aluminum foam board. First, an active material layer 32 and an insulating coating 33 are prepared on the composite aluminum foam board. Then, the buffer electrode is cut according to the aforementioned dimensions to obtain the desired result. Figure 8 The buffer electrode 30 shown.

[0106] Then as Figure 3 , Figure 4 As shown, the third tab 34 on the buffer electrode 30 and the first tab 21 in the electrode group 20 need to be welded to the first electrode post 121 in the cover plate 12 by ultrasonic welding or laser welding to achieve electrical connection between the third tab 34, the first tab 21 and the first electrode post 121.

[0107] The present invention also discloses a battery, which may include a single cell 100 or a battery module or battery pack composed of multiple cells 100.

[0108] In some embodiments of the present invention, the battery can be a battery module, and the number of individual battery cells contained in the battery module can be one or more, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0109] In some embodiments of the present invention, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0110] In addition, the present invention also discloses an electrical device comprising: the aforementioned battery. The battery, such as a single cell, battery module, or battery pack, can serve as both a power source and an energy storage unit for the electrical device.

[0111] In some embodiments of the present invention, the electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, and energy storage systems.

[0112] The present invention will be described in detail below with reference to specific embodiments.

[0113] Example 1:

[0114] In this embodiment, the battery cell 100 has a capacity of 588Ah and includes four electrode groups 20 and three buffer electrode plates 30, with a buffer electrode plate 30 disposed between every two adjacent electrode groups 20. The thickness a of the battery cell 100 is 72.5mm, the width c of the battery cell is 288.0mm, and the height b of the battery cell is 216.3mm.

[0115] The four pole groups 20 are identical, with each pole group having an initial thickness of 20. The total width of the electrode assembly is 16.0±0.5mm, the total width x of the electrode assembly is 284.0±1.0mm, the total height y of the electrode assembly is 205.0±1.0mm, the width w of the straight section is 268.0±1.0mm, and the height h of the positive electrode is 197.0±1.0mm.

[0116] The three buffer electrodes 30 are identical. The conductive substrate 31 in the buffer electrode 30 is a composite aluminum foam board with a thickness t of 2 mm. The thickness of the middle layer of the aluminum foam can be 1.974 mm. The thicknesses of the aluminum metal plates on both sides are 0.013 mm each. The width m of the active material layer 32 is 268.0 mm, the height n is 197.0 mm, and the compressibility is... It is 60%.

[0117] The preparation method of the battery cell 100 in this embodiment is as follows:

[0118] The positive and negative electrode sheets are wound together with the diaphragm on a winding machine, and the electrode assembly is obtained by hot pressing the electrode assembly.

[0119] Take a composite aluminum foam board, and uniformly coat both sides of the composite aluminum foam board with a positive electrode slurry of the same surface density as the positive electrode sheet to form an active material layer 32, and coat it with an insulating coating 33 of the same specifications as the positive electrode sheet.

[0120] The composite foam aluminum plate coated with active material layer 32 and insulating coating 33 is cut into buffer electrode sheets 30 of the same size, with the third electrode tab 34 reserved.

[0121] Take three buffer electrodes and place them between every two adjacent electrode groups. Then, weld the third tab 34 on the buffer electrode and the first tab 21 in the electrode group to the first electrode post 121 in the cover plate by ultrasonic welding or laser welding. Finally, glue the core together to obtain the bare cell.

[0122] After the bare battery cell is coated with a polyester film, it is placed in a housing, baked at high temperature, injected with electrolyte, and after separation and compatibility testing, a single battery cell 100 is obtained.

[0123] Example 2:

[0124] In this embodiment, the battery cell 100 has a capacity of 588Ah and includes four electrode groups 20 and three buffer electrode plates 30, with a buffer electrode plate 30 disposed between every two adjacent electrode groups 20. The thickness a of the battery cell 100 is 72.5mm, the width c of the battery cell is 288.0mm, and the height b of the battery cell is 216.3mm.

[0125] The four pole groups 20 are identical, with each pole group having an initial thickness of 20. The total width of the electrode assembly is 16.0±0.5mm, the total width x of the electrode assembly is 284.0±1.0mm, the total height y of the electrode assembly is 205.0±1.0mm, the width w of the straight section is 268.0±1.0mm, and the height h of the positive electrode is 197.0±1.0mm.

[0126] The three buffer electrodes 30 are identical. The conductive substrate 31 in the buffer electrode 30 is a composite aluminum foam board with a thickness t of 1 mm. The thickness of the middle layer of the aluminum foam can be 0.974 mm. The thicknesses of the aluminum metal plates on both sides are 0.013 mm each. The width m of the active material layer 32 is 268.0 mm, the height n is 197.0 mm, and the compressibility is... It is 30%.

[0127] The preparation method of the battery cell 100 in this embodiment is similar to that in Example 1, and will not be described again here.

[0128] Example 3:

[0129] In this embodiment, the battery cell 100 has a capacity of 588Ah and includes four electrode groups 20 and three buffer electrode plates 30, with a buffer electrode plate 30 disposed between every two adjacent electrode groups 20. The thickness a of the battery cell 100 is 72.5mm, the width c of the battery cell is 288.0mm, and the height b of the battery cell is 216.3mm.

[0130] The four pole groups 20 are identical, with each pole group having an initial thickness of 20. The total width of the electrode assembly is 16.0±0.5mm, the total width x of the electrode assembly is 284.0±1.0mm, the total height y of the electrode assembly is 205.0±1.0mm, the width w of the straight section is 268.0±1.0mm, and the height h of the positive electrode is 197.0±1.0mm.

[0131] The three buffer electrodes 30 are identical. The conductive substrate 31 in the buffer electrode 30 is a composite aluminum foam board with a thickness t of 3 mm. The thickness of the middle layer of the aluminum foam can be 2.974 mm. The thicknesses of the aluminum metal plates on both sides are 0.013 mm each. The width m of the active material layer 32 is 268.0 mm, the height n is 197.0 mm, and the compressibility is... It is 80%.

[0132] The preparation method of the battery cell 100 in this embodiment is similar to that in Example 1, and will not be described again here.

[0133] Comparative Example 1:

[0134] The battery cell 100 in this comparative example has a capacity of 588Ah, and includes four electrode groups 20 without buffer plates. The thickness a of the battery cell 100 is 72.5mm, the width c is 288.0mm, and the height b is 216.3mm.

[0135] The four pole groups 20 are identical, with each pole group having an initial thickness of 20. The total width of the electrode assembly is 16.0±0.5mm, the total width x of the electrode assembly is 284.0±1.0mm, the total height y of the electrode assembly is 205.0±1.0mm, the width w of the straight section is 268.0±1.0mm, and the height h of the positive electrode is 197.0±1.0mm.

[0136] The preparation method of the battery cell 100 in this comparative example is similar to that in Example 1, and will not be repeated here.

[0137] The discharge capacity, cycle performance, negative electrode interface condition after 1000 cycles under the 0.5P test condition, and thermal runaway test of the cell after 1000 cycles under the 0.5P test condition were compared between Examples 1-3 and Comparative Example 1 (refer to GB / T 36276-2023). The specific experimental data are shown in the table below.

[0138] Table 1: Cell discharge capacity under 0.5P test conditions

[0139]

[0140] Table 2: Cycle performance of cells under 0.5P test conditions

[0141]

[0142] Table 3: Negative electrode interface condition and cell thermal runaway test after 1000 cycles under 0.5P test conditions

[0143]

[0144] As can be seen from the comparison of Examples 1-3 and Comparative Example 1, the expansion of the internal electrode assembly of the quadruple electrode cell during cycling can compress the buffer electrode, ensuring that the negative electrode has room for expansion and that the electrodes remain in close contact. This allows lithium ions to be extracted from the positive electrode and stably embedded in the negative electrode, avoiding lithium plating problems on the negative electrode and thus improving cycle performance. Furthermore, during the thermal runaway test of the cell, it can ensure that the cell does not catch fire or explode, reducing the risk of cell safety failure.

[0145] In addition, an active material layer (positive electrode material) identical to that of the positive electrode is set on the buffer electrode and connected to the positive electrode post through a corresponding tab. During the charging process of the cell, lithium ions in the active material layer on the buffer electrode are normally extracted and then embedded into the outermost negative electrode of the electrode group. At the same time, lithium ion re-intercalation is completed during the discharge process, making full use of the large negative electrode material in the outer negative electrode area of ​​the electrode group. There are only two large negative electrode areas in the four electrode groups that do not participate in the reaction, thereby further improving the cell capacity.

[0146] Comparing Examples 1-3 reveals that buffer electrodes of different thicknesses and compressibility have varying effects on the cell's cycle performance and the lithium intercalation of the negative electrode. Buffer electrodes with smaller thickness and lower compressibility cannot provide sufficient expansion space for the negative electrode during later long-term cycling, resulting in decreased cycle performance and slight lithium plating on the negative electrode.

[0147] To provide expansion space for the electrode assembly, prevent lithium plating on the negative electrode, and simultaneously ensure the structural strength of the buffer electrode, as well as the storage and absorption of the electrolyte, thereby improving the cycle performance of the individual cell, the initial thickness of the conductive substrate in the buffer electrode is... The preferred thickness is 2mm to 3mm, and the compressibility is... The preferred value is 60% to 80%.

[0148] The above embodiments are all illustrated using a single cell with four pole groups as an example. The buffer electrode in this invention can also be applied to single cells with more than four pole groups, or to single cells with two pole groups.

[0149] It is worth noting that when the above-mentioned buffer electrode is used in a bipolar cell, since both electrode groups in the bipolar cell can expand to both sides of the casing, the negative electrode can be normally lithium-intercalated without the need for a buffer electrode. However, there are four large negative electrode areas that do not participate in the reaction between the two electrode groups. By setting the buffer electrode, the negative electrode material of the large negative electrode areas on both sides of the electrode group can be utilized to improve the cell capacity.

[0150] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0151] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A single battery cell, characterized in that, The battery cell unit includes: shell; At least two electrode groups are located inside the housing and distributed along the thickness direction of the housing. Each electrode group includes a first electrode plate with a first polarity and a second electrode plate with a second polarity. The second electrode plate is located outside the electrode group. The first polarity is opposite to the second polarity. At least one buffer electrode is located inside the housing and disposed between two adjacent electrode groups. The buffer electrode includes a conductive substrate and an active material layer disposed on at least one surface of the conductive substrate. The active material layer has a first polarity. The conductive substrate is electrically connected to the first electrode. Electrolyte, which is filled inside the housing.

2. The battery cell according to claim 1, characterized in that, The conductive substrate is made of a porous material with conductive properties.

3. The battery cell according to claim 2, characterized in that, The conductive substrate is a composite aluminum foam board, which includes an aluminum foam interlayer and a metal aluminum plate located on at least one side of the aluminum foam interlayer.

4. The battery cell according to claim 1, characterized in that, The thickness of the conductive substrate Greater than or equal to and less than or equal to ,in, The initial thickness of the electrode assembly. This refers to the compressibility of the conductive substrate. and These are the lower and upper limits of the cyclic expansion rate of the electrode group, respectively.

5. The battery cell according to claim 4, characterized in that, The compressibility of the conductive substrate 30% to 80%; and / or, The lower limit of the cyclic expansion rate of the pole group It is 5% to 7%, with the upper limit. It is 14% to 16%.

6. The battery cell according to claim 1 or 5, characterized in that, The initial thickness of the conductive substrate With the initial thickness of the pole group ratio For (1~3):16; and / or, The initial thickness of the conductive substrate The thickness is 1mm to 3mm.

7. The battery cell according to claim 1, characterized in that, The initial thickness of the conductive substrate The compressibility of the conductive substrate is 1mm to 3mm. The percentage is 30% to 80%.

8. The battery cell according to claim 7, characterized in that, The initial thickness of the conductive substrate The compressibility of the conductive substrate is 2mm~3mm. It ranges from 60% to 80%.

9. The battery cell according to claim 1, characterized in that, The thickness of the active material layer is 40 μm to 200 μm; and / or, The thickness of the active material layer on the surface of the conductive substrate is equal to the thickness of the active material layer in the first electrode; and / or, The material of the active material layer on the surface of the conductive substrate is the same as the material of the active material layer in the first electrode.

10. The battery cell according to claim 1, characterized in that, The electrode assembly is a wound electrode assembly, the first electrode is a positive electrode, and the second electrode is a negative electrode. The wound electrode assembly consists of a negative electrode, a separator, and a positive electrode, which are wound together to form a straight section and a corner section. The second electrode is wrapped around the outside of the first electrode. The active material layer on the surface of the conductive substrate covers the lithium intercalation region corresponding to the second electrode on the side surface of the electrode assembly.

11. The battery cell according to claim 10, characterized in that, The width m of the buffer electrode is greater than or equal to the width w of the straight portion and less than or equal to the total width x of the electrode group; and / or, The height n of the buffer electrode is greater than or equal to the height h of the first electrode and less than or equal to the total height y of the electrode group.

12. The battery cell according to claim 1, characterized in that, The electrode assembly further includes a first tab electrically connected to the first electrode and a second tab electrically connected to the second electrode. The outer casing is provided with a first electrode post and a second electrode post. The buffer electrode further includes a third tab electrically connected to the conductive substrate. The first tab and the third tab are both electrically connected to the first electrode post, and the second tab is electrically connected to the second electrode post.

13. The battery cell according to claim 12, characterized in that, An insulating coating is provided next to the active material layer on the surface of the conductive substrate, and the third electrode is located on one side of the insulating coating.

14. The battery cell according to claim 13, characterized in that, The insulating coating is a ceramic coating with a thickness of 10μm to 80μm.

15. The battery cell according to claim 1, characterized in that, The battery cell includes four electrode groups and three buffer electrodes. A buffer electrode is provided between each pair of adjacent electrode groups. An active material layer is provided on both sides of the conductive substrate in each buffer electrode. The thickness of the individual battery cell is between 70mm and 80mm; The width of the individual battery cell is between 250mm and 350mm; The height of the individual battery cells is between 200mm and 300mm.

16. A battery, characterized in that, The battery comprises any one of the cell units according to claims 1 to 15.

17. An electrical device, characterized in that, The electrical device includes the battery as described in claim 16.

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