Battery cell, battery apparatus and electrical apparatus

Abstract

Provided are a battery cell, a battery apparatus and an electrical apparatus. The battery cell comprises an electrode assembly and an electrolyte, the electrolyte comprising an ether solvent; the electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a polymer layer located on at least one side of the negative electrode current collector; the polymer layer comprises a liquid-retaining polymer, the degree of swelling of the liquid-retaining polymer in the ether solvent being 100% to 500%. The negative electrode sheet exhibits a high liquid retention capacity, and can improve the cycle performance of the battery cell.

Description

Battery cell, battery device and electric device

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411076717.4, filed on August 7, 2024, entitled “Battery cell, battery device and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of battery technology, in particular to a battery cell, a battery device and an electric device. BACKGROUND

[0004] Metal battery cells have higher energy density compared to ion battery cells. Unlike the negative electrode of ion battery cells, metal battery cells generally do not have an active material layer on the negative electrode, or only have a carbon conductive layer on the negative electrode side, which results in a weaker liquid locking ability of the negative electrode of the metal battery cell to the electrolyte, which affects the cycle performance of the battery cell. SUMMARY

[0005] The present application provides a battery cell, a battery device and an electric device to improve the liquid locking ability of the negative electrode of the metal battery cell to the electrolyte and improve the cycle performance of the battery cell.

[0006] In a first aspect, the embodiments of the present application provide a battery cell, which comprises an electrode assembly and an electrolyte, the electrolyte comprising an ether solvent, and the electrode assembly comprising a negative electrode sheet.

[0007] The negative electrode sheet comprises a negative electrode current collector and a polymer layer on at least one side of the negative electrode current collector, and the polymer layer comprises a liquid-retaining polymer, and the liquid-retaining polymer has a swelling degree of 100% to 500% in the ether solvent.

[0008] In the present application, by providing a polymer layer comprising a liquid-retaining polymer on the surface of the negative electrode current collector, the liquid-retaining polymer has good liquid-retaining ability. After the negative electrode sheet is soaked with the electrolyte, small molecules in the electrolyte can penetrate into the interior of the liquid-retaining polymer, expand the molecular chains, and the small molecules in the electrolyte will continue to enter the gaps between the polymer molecular chains and be bound by the polymer, so that the negative electrode sheet can continuously maintain the state of being soaked with the electrolyte. Thus, the liquid-retaining ability of the negative electrode sheet can be improved, the uniformity of ion conduction during the charging and discharging cycle of the battery cell can be improved, the metal can be uniformly deposited on the negative electrode sheet, the internal short circuit of the battery cell caused by dendrite growth can be reduced, and the cycle performance of the battery cell can be improved.

[0009] In some embodiments, the liquid-retaining polymer has a swelling degree in the ether-based solvent of 200% to 400%. When the swelling degree of the liquid-retaining polymer in the ether-based solvent is within the above range, the polymer layer has good liquid-retaining capacity, and the battery cell has good cycle performance. Meanwhile, the polymer layer has a low expansion rate after absorbing liquid, the negative electrode sheet has a low volume change rate during the charging and discharging cycle of the battery cell, the capacity loss of the battery cell during the cycle can be reduced, and the battery cell has a high capacity retention rate.

[0010] In some embodiments, the contact angle between the polymer layer and the electrolyte is 2° to 30°. When the contact angle between the polymer layer and the electrolyte is within the above range, the electrolyte can better wet the surface of the polymer layer, which is conducive to further improving the liquid-retaining effect and electrolyte wettability of the negative electrode sheet, and thus improving the cycle performance of the battery cell.

[0011] In some embodiments, the molar content of active functional groups in the liquid-retaining polymer is less than or equal to 5%, and the active functional groups include one or more of carboxyl, phenolic hydroxyl, amide, carbon-carbon double bond, and carbon-nitrogen double bond. When the number of active functional groups in the liquid-retaining polymer is within the above range, the reaction between the material of the polymer layer and the deposited metal on the surface of the negative electrode sheet can be reduced, the consumption of active metal during the cycle of the battery cell can be reduced, and thus the capacity retention rate and cycle performance of the battery cell can be improved.

[0012] In some embodiments, the liquid-retaining polymer includes one or both of a polyether-based polymer and a polyester-based polymer. The above liquid-retaining polymer has good liquid-absorbing and liquid-retaining properties, which is conducive to further improving the liquid-retaining capacity of the negative electrode sheet and improving the cycle performance of the battery cell.

[0013] In some embodiments, the weight average molecular weight of the polyether-based polymer is 10,000 to 100,000.

[0014] In some embodiments, the weight average molecular weight of the polyester-based polymer is 100,000 to 400,000.

[0015] When the molecular weight of the polyether-based polymer and the polyester-based polymer is within the above range, the polymer has a suitable molecular size, which can make the formed polymer layer have a suitable network structure, which is conducive to improving the adsorption capacity of the polymer layer for the electrolyte, and thus improving the liquid-retaining capacity of the negative electrode sheet and improving the cycle performance of the battery cell.

[0016] In some embodiments, the polyether-based polymer includes one or more of polyethylene oxide, polymethyl ether, polypropylene oxide, and polyether ketone.

[0017] In some embodiments, the polyester-based polymer includes one or more of polymethyl methacrylate, polyethylene terephthalate, and polybutylene terephthalate.

[0018] In some embodiments, the polymer layer further comprises a conductive agent, and the mass percentage of the conductive agent in the polymer layer is 5% to 45% based on the total mass of the polymer layer. The addition of the conductive agent can improve the conductivity of the negative electrode sheet, which is conducive to reducing the internal resistance of the battery cell and improving the electrochemical performance of the battery cell.

[0019] In some embodiments, the conductive agent comprises one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0020] In some embodiments, the thickness of the polymer layer is 2 μm to 20 μm. Limiting the thickness of the polymer layer to the above range is conducive to improving the adsorption capacity of the polymer layer for the electrolyte, which can make the electrode sheet have a better liquid absorption and retention effect, thereby improving the cycle performance of the battery cell.

[0021] In some embodiments, the negative electrode sheet further comprises a conductive carbon layer, and the conductive carbon layer is located between the negative electrode current collector and the polymer layer.

[0022] In some embodiments, the thickness of the conductive carbon layer is 2 μm to 20 μm.

[0023] In some embodiments, the volume percentage of the ether-based solvent in the electrolyte is 90% to 97%.

[0024] Limiting the volume percentage of the ether-based solvent in the electrolyte to the above range is conducive to forming a thin and stable SEI film, and the electrolyte has a stable solvation structure, which has better reduction stability at the negative electrode, can reduce the decomposition of the electrolyte during the cycle of the battery cell, and makes the battery cell have higher cycle stability.

[0025] In some embodiments, the ether-based solvent comprises one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxy methane, 1,3-dioxolane, 2-methyl tetrahydrofuran, and tetrahydrofuran.

[0026] In a second aspect, the embodiments of the present application provide a battery device comprising the battery cell of the first aspect of the present application.

[0027] In a third aspect, the embodiments of the present application provide a power utilization device comprising the battery of the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced below. Those skilled in the art can obtain other drawings according to these drawings without creating any creative labor.

[0029] FIG. 1 is a schematic view of a battery cell according to some embodiments of the present application.

[0030] FIG. 2 is an exploded schematic view of a battery cell according to some embodiments of the present application.

[0031] FIG. 3 is a schematic view of a battery module according to some embodiments of the present application.

[0032] FIG. 4 is a schematic view of a battery pack according to some embodiments of the present application.

[0033] FIG. 5 is an exploded schematic view of the battery pack shown in FIG. 4.

[0034] FIG. 6 is a schematic view of an electric device according to some embodiments of the present application.

[0035] In the drawings, the drawings are not necessarily drawn to scale.

[0036] Reference signs are explained as follows: 1, battery pack; 2, upper case; 3, lower case; 4, battery module; 5, battery cell; 51, case; 52, electrode assembly; 53, cover plate. DETAILED DESCRIPTION

[0037] Hereinafter, specific embodiments of the electrode assembly, the battery cell, the battery, and the electric device according to the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are well known, repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0038] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the range, i.e., all ranges that fall between the upper and lower limits of the broader range. For example, a range of "60% to 120%" is intended to include any and all sub-ranges between (and including) the upper and lower limits of the broad range, e.g., 61-120%, 61- 119%, 61-118%,..., 61-1%, 62-120%, 62-119%, 62-118%,..., 62-1%,..., 1 19- 120%, 118-120%, 1-120%, etc. Also, a range such as "60% to 120%" is intended to include the end points 60% and 120% because the term "to" is used herein to be open- ended, i.e., generally meaning "starting from and up to." Further, a range such as "60% to 120%" is intended to include any and all individual independently selected values (e.g., 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, etc.) within the broader range. The same applies to ranges using single and double quotes (").

[0039] Unless otherwise specified, all embodiments and optional embodiments of the present application 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 the present application.

[0040] Unless otherwise specified, all technical features and optional technical features of the present application 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 the present application.

[0041] Unless otherwise specified, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0042] If there is no special indication, the terms "connected", "connection" in the present application should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection; it can be direct connection, or indirect connection through intermediate medium, or internal connection of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0043] "Multiple" appearing in the present application refers to more than two, including two. "Multiple" appearing in the present application refers to more than two, including two.

[0044] The battery device mentioned in the embodiments of the present application can include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of battery cells connected in series, parallel or mixed connection through a busbar component.

[0045] In some embodiments, the battery cell assembly is usually formed by arranging a plurality of battery cells; as an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with a cable tie.

[0046] The battery cell is the smallest unit that constitutes the battery device, which can realize the function of charging and discharging independently. The battery cell can be in the shape of a cylinder, a cuboid or other shapes, which are not limited in the embodiments of the present application. As an example, Fig. 1 is a battery cell 5 in the shape of a cuboid.

[0047] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Fig. 2 is a schematic diagram of a battery module 4 as an example. As shown in Fig. 2, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in other arbitrary ways. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0048] Optionally, the battery module 4 can also include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0049] In some embodiments, the above-mentioned battery module 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.

[0050] FIGS. 3 and 4 are schematic diagrams of the battery pack 1 as an example. As shown in FIGS. 3 and 4, the battery pack 1 can include a box body and a plurality of battery modules 4 arranged in the box body. The box body includes an upper box body 2 and a lower box body 3, the upper box body 2 is used to cover the lower box body 3 and forms a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the box body in any manner.

[0051] In some embodiments, the battery device can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0052] Embodiments of the present application provide a battery cell, which is a negative electrode-free battery cell, for example, can include at least one of a negative electrode-free lithium metal battery cell, a negative electrode-free sodium metal battery cell.

[0053] The negative electrode-free battery cell generally refers to a battery cell that does not actively set a negative active material layer on the negative electrode side during the manufacturing process of the battery cell, for example, does not set a layer or form a negative active material layer by a carbon active material layer at the negative electrode through a coating or deposition process during the manufacturing process of the battery cell. During the first charging, ions get electrons on the negative electrode side and deposit to form metal on the surface of the negative electrode current collector. During discharging, the metal can change into ions to return to the positive electrode, realizing the cycle of charging and discharging. Compared with other battery cells, the negative electrode-free battery cell does not have a negative active material layer, thereby achieving a higher energy density. In some embodiments, in order to improve the performance of the battery cell, the negative electrode side of the negative electrode-free battery cell can also be provided with some substances that can be used as negative active materials, such as carbon materials, etc. Although these substances have a certain capacity, due to their small amount, and they are not used as the main negative active material in the battery cell, the battery cell thus constituted can still be regarded as a negative electrode-free battery cell. The CB (Cell Balance) value of the negative electrode-free battery cell is usually very small, for example, in some embodiments, the CB value of the negative electrode-free battery cell can be less than or equal to 0.1. The CB value is the capacity per unit area of the negative electrode divided by the capacity per unit area of the positive electrode. Since the negative electrode-free battery cell does not contain or contains only a small amount of negative active material, the capacity per unit area of the negative electrode is small, and thus the CB value is very small, for example, usually less than or equal to 0.1.

[0054] The battery cell includes an electrode assembly. The electrode assembly can be a roll structure or a stack structure, and the embodiments of the present application are not limited thereto.

[0055] The electrode assembly generally includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0056] The battery cell can further include an outer package, which can be used to encapsulate the electrode assembly. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a pouch. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0057] In some embodiments, as shown in FIG. 5, the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The shell 51 has an opening in communication with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to requirements.

[0058] The anode-free battery cell has poor liquid locking ability of the negative electrode due to the absence of an active material layer on the negative electrode. During the charge and discharge cycle of the battery cell, the negative electrode has insufficient liquid retention capacity, and the electrolyte is difficult to infiltrate the upper part of the battery cell, resulting in insufficient electrolyte in the upper part of the battery cell during the cycle, uneven ion conduction distribution during charging and discharging, easy metal deposition on the negative electrode, and deterioration of dendrite growth, which may even cause internal short circuit of the battery cell, affecting the cycle performance and reliability of the battery cell.

[0059] In view of this, the embodiments of the present application can make the negative electrode sheet have higher liquid retention effect and electrolyte infiltration by setting a polymer layer with liquid retention capacity on the negative electrode sheet, thereby improving the cycle performance of the battery cell.

[0060] [Negative electrode sheet]

[0061] The negative electrode sheet includes a negative electrode current collector and a polymer layer located on at least one side of the negative electrode current collector, and the polymer layer contains a liquid retention polymer with a swelling degree of 100% to 500% in an ether solvent.

[0062] In the present application, the liquid retention polymer refers to a polymer with liquid retention capacity for electrolyte. The liquid retention polymer has good liquid retention capacity. After the negative electrode sheet is infiltrated with electrolyte, small molecules in the electrolyte can penetrate into the interior of the liquid retention polymer, expand the molecular chain, and the small molecules in the electrolyte will continue to enter the gap between the polymer molecular chains and be bound by the polymer, so that the negative electrode sheet can continuously maintain the state of being infiltrated with electrolyte, thereby improving the liquid retention capacity of the negative electrode sheet for electrolyte, improving the uniformity of ion conduction during the charge and discharge cycle of the battery cell, making the metal uniformly deposited on the negative electrode sheet, reducing the internal short circuit of the battery cell caused by dendrite growth, and improving the cycle performance of the battery cell.

[0063] In the present application, the swelling degree refers to the ratio of the volume after swelling to the volume before swelling when the polymer molecules adsorb the solvent to reach the swelling equilibrium. The swelling degree of the liquid-retaining polymer can be tested by a method known in the art. For example, the liquid-retaining polymer can be scraped on a glass plate to form a film, and a 1 cm x 1 cm polymer film piece is taken, the thickness of which is measured by a vernier caliper or a screw micrometer, and the volume thereof is calculated as V1. The polymer film piece is soaked in ethylene glycol dimethyl ether at room temperature for 12 h, and after being taken out, the length, width and height of the polymer film piece are measured, and the volume thereof is calculated as V2. Then, the swelling degree s of the liquid-retaining polymer is calculated according to the formula s = V2 / V1 x 100%.

[0064] In the present application, the swelling degree of the liquid-retaining polymer is measured at room temperature. The room temperature refers to the indoor temperature in the range of about 18°C to 30°C, for example, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C. In some embodiments, the room temperature can be a temperature of about 20°C ± 1°C, 20°C ± 2°C, 20°C ± 3°C; in some embodiments, the room temperature can also be 22°C or 25°C.

[0065] In some embodiments, the swelling degree of the liquid-retaining polymer can be 200% to 400%. The swelling degree of the liquid-retaining polymer in the ether solvent is in the above range, the polymer layer has good liquid-retaining capacity, and the battery monomer has good cycle performance; at the same time, the polymer layer has a low expansion rate after absorbing liquid, the negative electrode sheet has a low volume change rate during the charge and discharge cycle of the battery monomer, which can reduce the capacity loss during the cycle of the battery monomer, and the battery monomer has a high capacity retention rate.

[0066] Illustratively, the swelling degree of the liquid-retaining polymer can be 100%, 120%, 150%, 180%, 200%, 220%, 250%, 280%, 300%, 320%, 350%, 380%, 400%, 420%, 450%, 480%, 500%, or a range consisting of any of the above values.

[0067] In some embodiments, the electrolyte contact angle of the polymer layer can be 2° to 30°, optionally 4° to 20°.

[0068] Illustratively, the electrolyte contact angle of the polymer layer can be 2°, 5°, 8°, 10°, 12°, 13°, 15°, 18°, 20°, 22°, 25°, 28°, 30°, or a range consisting of any of the above values.

[0069] The electrolyte contact angle refers to the angle between the solid-liquid interface and the gas-liquid interface of a liquid drop formed by the electrolyte on the surface of the polymer layer, which can reflect the wettability of the electrolyte on the surface of the polymer layer.

[0070] In the present application, the contact angle can be measured by methods known in the art, for example, a contact angle measuring instrument can be used to measure the contact angle by manually or automatically dropping the liquid, ensuring that the volume of each drop is the same, using a high-resolution camera for optical measurement, and analyzing the test results in real time by measurement software. In the present application, the liquid used to measure the electrolyte contact angle is ethylene glycol dimethyl ether (DME).

[0071] In some embodiments, the molar content of active functional groups in the liquid-retaining polymer can be less than or equal to 5%, optionally less than or equal to 3%, and more optionally less than or equal to 1%. The active functional groups include one or more of carboxyl, phenolic hydroxyl, amide, carbon-carbon double bond, and carbon-nitrogen double bond.

[0072] In the present application, the active functional group refers to a functional group that can react with an active metal (Li, Na, etc.). During the charging and discharging cycle of the battery cell, the active metal in the battery cell will deposit on the surface of the negative electrode sheet, and the active functional group will react with the deposited active metal, consume the active metal in the battery cell, reduce the content of the active metal, and affect the electrochemical performance of the battery cell. Therefore, limiting the molar content of active functional groups in the liquid-retaining polymer within the above range can enable the battery to have a higher specific capacity during charging and discharging.

[0073] In some embodiments, the liquid-retaining polymer includes one or both of a polyether-based polymer and a polyester-based polymer.

[0074] In the present application, the polyether-based polymer refers to a polymer having an ether bond in the molecular structure of the polymer, and the polyester-based polymer refers to a polymer having an ester group in the molecular structure of the polymer. Both the polyether-based polymer and the polyester-based polymer have good electrolyte wettability and high liquid-retaining capacity, which can effectively improve the liquid-retaining capacity of the negative electrode sheet and further improve the cycle performance of the battery cell.

[0075] In some embodiments, the weight average molecular weight of the polyether-based polymer can be 10,000 to 100,000, and optionally 30,000 to 70,000.

[0076] In some embodiments, the weight average molecular weight of the polyester-based polymer can be 100,000 to 400,000, and optionally 120,000 to 320,000.

[0077] The molecular weight is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, gel permeation chromatography can be used, and reference can be made to GB / T 21863-2008 standard. Specifically, the following test steps can be referred to: using an ultra-high performance polymer chromatograph: ACQUITY APC; detector: ACQUITY differential refractive index detector. The test steps are as follows: (1) preheating after starting: install the chromatographic column and pipeline, turn on the console, test the power supply, etc., and open the test software Empower; (2) parameter setting, sample volume: 0 μL to 50 μL (determined according to sample concentration); pump flow rate: 0.2 mL / min; mobile phase: 30 mol / L LiBr NMP solution; sealing cleaning liquid: isopropyl alcohol; pre-column: PLgel 10um MiniMIX-B Guard (size: 50 mm x 4.6 mm x 2); analytical phase: PLgel 10um MiniMIX-B (size: 250 mm x 4.6 mm); standard: polystyrene kit; running time: 30 min; detector: ACQUITY differential refractive index (RI) detector; column oven temperature: 90°C; detector temperature: 55°C. (3) sample test: a. standard sample and test sample preparation: weigh 0.002 g to 0.004 g of standard sample / test sample into 2 mL of mobile phase liquid to prepare 0.1% to 0.5% mixed standard, and store in the refrigerator for >8 h; b. standard solution / sample test: edit the sample group to be tested, select the established sample group method, and click run queue after the baseline is stable, and start testing the sample; (4) data processing: according to the relationship between the retention time and the molecular weight, the calibration curve is established by using the chemical workstation, the sample spectrum is integrated and quantified, and the molecular weight and molecular weight distribution results are automatically generated by the chemical workstation.

[0078] The weight average molecular weight of the polyether polymer and the polyester polymer is in the above range, which has a more stable molecular structure, can adsorb and contain more electrolyte, thereby further improving the liquid retention capacity of the negative electrode sheet, and further improving the cycle performance of the battery cell.

[0079] In some embodiments, the polyether polymer includes one or more of polyethylene oxide, polymethyl ether, polypropylene oxide, and polyether ketone.

[0080] In some embodiments, the polyester polymer includes one or more of polymethyl methacrylate, polyethylene terephthalate, and polybutylene terephthalate.

[0081] The above-mentioned polyether polymer and polyester polymer both have good electrolyte wettability and stability, which can further improve the electrolyte wettability and liquid retention capacity of the negative electrode sheet, and improve the cycle performance of the battery cell.

[0082] In some embodiments, the polymer layer further comprises a conductive agent, and the mass percentage of the conductive agent based on the total mass of the polymer layer can be 5% to 45%, or alternatively 20% to 40%.

[0083] For example, the mass percentage of the conductive agent based on the total mass of the polymer layer can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or a range consisting of any of the above values.

[0084] The addition of the conductive agent can improve the conductivity of the battery cell, reduce the internal resistance of the battery cell, and further improve the electrochemical performance of the battery cell.

[0085] In some embodiments, the conductive agent can include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0086] In some embodiments, the thickness of the polymer layer can be 2 μm to 20 μm, or alternatively 2 μm to 6 μm.

[0087] For example, the thickness of the polymer layer can be 2 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, or a range consisting of any of the above values.

[0088] The thickness of the polymer layer within the above range can enable the negative electrode sheet to have better liquid retention capacity and improve the electrolyte wettability of the negative electrode sheet, thereby further improving the cycle performance of the battery cell.

[0089] In some embodiments, the negative electrode sheet can further comprise a conductive carbon layer, and the conductive carbon layer is located between the negative electrode current collector and the polymer layer.

[0090] The provision of the conductive carbon layer can reduce the internal resistance of the battery cell, and at the same time enable the active metal to be uniformly deposited on the surface of the negative electrode sheet, thereby further improving the electrochemical performance of the battery cell.

[0091] In some embodiments, the thickness of the conductive carbon layer can be 2 μm to 20 μm. For example, the thickness of the conductive carbon layer can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range consisting of any of the above values.

[0092] In some embodiments, the conductive carbon layer can be provided on the surface of the negative electrode current collector by means of magnetron sputtering, chemical plating, electroplating, or spraying.

[0093] In some embodiments, the polymer layer can be disposed on the surface of the negative current collector or the conductive carbon layer by gravure printing, roll coating, or the like.

[0094] In some embodiments, the material of the negative current collector includes one or more of copper, nickel, titanium, magnesium, aluminum, copper alloy, nickel alloy, titanium alloy, magnesium alloy, and aluminum alloy.

[0095] Optionally, the negative current collector can include a copper foil or a nickel foil, and more optionally, a copper foil.

[0096] [Positive electrode tab]

[0097] In some embodiments, the positive electrode tab includes a positive current collector and a positive film layer disposed on at least one surface of the positive current collector and including a positive active material. For example, the positive current collector has two surfaces opposite in the thickness direction of the positive current collector, and the positive film layer is disposed on either one or both of the two opposite surfaces of the positive current collector.

[0098] In some embodiments, the positive active material includes a material capable of deintercalating and intercalating lithium, so that a negative electrode-free lithium metal battery cell can be obtained.

[0099] By way of example, the positive active material can include, but is not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and modified compounds of each of the foregoing. Examples of the lithium transition metal oxides can include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and modified compounds of each of the foregoing. The lithium transition metal oxides can include, but are not limited to, one or more of layered structures, spinel structures. Examples of the lithium-containing phosphates can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and modified compounds of each of the foregoing.

[0100] In some embodiments, in order to further improve the energy density of the battery cell, the positive active material can include a compound having a general formula of Li a Ni b Co c M d O e D fOne or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0101] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining battery cells that balance high capacity and high reliability.

[0102] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2 O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0103] In some embodiments, the positive electrode active material includes a material capable of both sodium extraction and insertion. This results in a sodium-free negative electrode battery cell. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including, but not limited to, P2-type, O3-type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0104] In some embodiments, as an example, the positive electrode active material can include, but is not limited to, one or more of NaFe02, NaCo02, NaCr02, NaMn02, NaNi02, Na 0.67 MO2(M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, Mo), NaMO2(M includes at least two of Fe, Co, Ni, V, Ti, Mo), NaFeP04, NaMnP04, NaCoP04, Na4Fe3(P04)207, Na3V2(P04)2F3, Na3V2(P04)3, Prussian blue, Prussian white, and respective modified compounds thereof.

[0105] The modified compound of each of the above positive electrode active materials can be a doping modification and / or a surface coating modification of the positive electrode active material.

[0106] In some embodiments, the positive electrode film layer can further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent can include, but is not limited to, one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers.

[0107] In some embodiments, the positive electrode film layer can further optionally include a positive electrode binder. As an example, the positive electrode binder can include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorine-containing acrylate resin, styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS).

[0108] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be employed. The composite current collector can include a first layer of a polymer material and a layer of a metal material formed on at least one surface of the first layer of the polymer material. As an example, the metal material can include, but is not limited to, one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy. As an example, the first layer of the polymer material can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE).

[0109] The positive electrode film layer is generally formed by coating a positive electrode slurry on a positive electrode current collector, and then drying and cold-pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0110] [Separator]

[0111] The separator is located between the positive electrode and the negative electrode, and mainly functions to prevent internal short circuit.

[0112] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0113] In some embodiments, the material of the separator can include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different.

[0114] [Electrolyte]

[0115] The battery cell includes an electrolyte.

[0116] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and an organic solvent.

[0117] In some embodiments, the electrolyte solution includes anions, which can include one or more of bisfluorosulfonylimide anion (FSI - ), bis-trifluoromethanesulfonylimide anion (TFSI - ), bis-oxalate borate anion (BOB - ), difluoro-oxalate borate anion (DFOB - ), difluoro-bis-oxalate phosphate anion (DFOP - ), tetrafluoro-oxalate phosphate anion (TFOP - ), difluorophosphate anion (PO2F2 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), hexafluoroarsenate anion (AsF6 - ), trifluoromethanesulfonate anion (CF3SO3 - ).

[0118] In some embodiments, the electrolyte solution includes cations, which can include one or more of lithium ion, sodium ion.

[0119] In some embodiments, the concentration of the electrolyte salt can be 0.3 mol / L or more, optionally 0.7 mol / L or more, and the concentration of the electrolyte salt can further be 4 mol / L or less, optionally 2.5 mol / L or less, 1.7 mol / L or less. When the concentration of the electrolyte salt is within the above range, the electrolyte can have a suitable ionic conductivity.

[0120] The organic solvent can include, but is not limited to, one or more of esters, ethers, sulfones, nitriles, etc. The esters can include, but are not limited to, one or more of carbonates, phosphates, carboxylates, sulfates, sulfonates, etc. The carbonates can include cyclic carbonates and / or chain carbonates, and optionally, the carbonates can include both cyclic carbonates and chain carbonates. The chain carbonates can include polar chain carbonates with low viscosity, aliphatic branched chain carbonates, etc.

[0121] As an example, the organic solvent can include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraglyme (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9OCH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyldodecafluoropentyl methyl ether, 4-trifluoromethyldodecafluoropentyl ethyl ether, 4-trifluoromethyldodecafluoropentyl propyl ether, 5-trifluoromethyldodecafluorohexyl methyl ether, 5-trifluoromethyldodecafluorohexyl ethyl ether, 5-trifluoromethyldodecafluorohexyl propyl ether, 6-trifluoromethyltetradecafluoroheptyl methyl ether, 6-trifluoromethyltetradecafluoroheptyl ethyl ether, 6-trifluoromethyltetradecafluoroheptyl propyl ether, 7-trifluoromethylexahydrofluorooctyl methyl ether, 7-trifluoromethylexahydrofluorooctyl ethyl ether, 7-trifluoromethylexahydrofluorooctyl propyl ether.

[0122] In some embodiments, the organic solvent can contain an ether solvent, which can include one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxy methane, 1,3-dioxolane, 2-methyl tetrahydrofuran, tetrahydrofuran.

[0123] In some embodiments, the volume ratio of the ether solvent in the electrolyte can be 90% to 97%. Illustratively, the volume ratio of the ether solvent in the electrolyte can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or a range consisting of any of the above values.

[0124] The volume ratio of the ether solvent in the electrolyte within the above range is conducive to the formation of a thin and stable SEI film, and the electrolyte has a stable solvation structure, which has better reduction stability at the negative electrode, can reduce the decomposition of the electrolyte during the cycle of the battery cell, and makes the battery cell have higher cycle stability.

[0125] In some embodiments, the electrolyte can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, can also include a positive electrode film-forming additive, and can also include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, etc.

[0126] The preparation method of the battery cell is known. In some embodiments, the positive electrode, the separator, the negative electrode, and the electrolyte can be assembled to form the battery cell. As an example, the positive electrode, the separator, and the negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly can be placed in an outer package, and after drying, the above-mentioned electrolyte can be injected, and the battery cell can be obtained after processes such as vacuum packaging, standing, and formation. A plurality of battery cells can further be connected in series or in parallel or in a hybrid manner to form a battery module. A plurality of battery modules can further be connected in series or in parallel or in a hybrid manner to form a battery pack. In some embodiments, a plurality of battery cells can also be directly connected to form a battery pack.

[0127] Embodiments of the present application also provide a power utilization device, which includes the battery device provided by embodiments of the present application. The battery device can be used as a power source of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0128] The power utilization device can select the type of the battery device according to its use requirements, such as a battery cell, a battery module, or a battery pack.

[0129] FIG. 6 is a schematic view of an electric device as one example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the demand of the electric device for high power and high energy density, a battery pack or a battery module can be used.

[0130] The electric device as another example can be a mobile phone, a tablet, a notebook computer, etc. The electric device generally requires thinning, and a battery monomer can be used as a power source.

[0131] Embodiment

[0132] Hereinafter, the embodiments of the present application will be described. The following description of the embodiments of the technology or the like is exemplary and is for the purpose of explaining the present application only, and should not be construed as limiting the present application. In the embodiments, the specific conditions not mentioned are performed according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments used, for which the manufacturers are not mentioned, are all conventional products that can be obtained commercially.

[0133] Embodiment 1

[0134] Negative electrode sheet

[0135] The liquid-retaining polymer polyethylene oxide and the conductive agent conductive carbon were dispersed in water at a mass ratio of 7:3, mixed uniformly to form a slurry, and then coated on the surface of the negative electrode current collector copper foil by means of gravure printing. After drying, cold pressing, and slitting, the negative electrode sheet was obtained. The weight average molecular weight of the polyethylene oxide was 45,000, and the thickness of the polymer layer was 4 μm.

[0136] Positive electrode sheet

[0137] The positive electrode active material sodium pyrophosphate, the conductive agent carbon nanotube, and the binder hexafluorophosphoric acid were mixed uniformly in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 to obtain a positive electrode slurry. The positive electrode slurry was coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, and die cutting, the positive electrode sheet with a thickness of 200 μm was obtained. The coating mass of the positive electrode film layer in the positive electrode sheet was 350 mg / 1540 mm 2 .

[0138] Separator film

[0139] A commercial polyethylene (PE) separator film with a thickness of 12 μm was used.

[0140] Electrolyte

[0141] In an argon-filled glove box with a water content of <1 ppm, ethylene glycol dimethyl ether and tetrahydrofuran were mixed at a mass ratio of 1:3, and 1.0 mol / L sodium hexafluorophosphate (NaPF6) was added. After stirring uniformly, the electrolyte was obtained.

[0142] Battery cell

[0143] In an argon-protected glove box, the above positive electrode tab, negative electrode tab and separator film were stacked in order, with the separator film between the positive electrode tab and the negative electrode tab and capable of isolating the positive electrode tab from the negative electrode tab, and the stacked components were then wound to obtain an electrode assembly. The electrode assembly was placed in a shell, and after drying, an electrolyte was injected. After processes such as formation and standing, a sodium metal battery cell was obtained.

[0144] Examples 2 to 12

[0145] The difference from Example 1 is that the composition of the negative electrode tab is different, as shown in Table 1, and the rest is the same as Example 1.

[0146] Example 13

[0147] The difference from Example 1 is that the negative electrode tab includes a conductive carbon layer, which is prepared by the following method:

[0148] A commercially available two-dimensional copper foil with a thickness of 8 μm was used.

[0149] S10, 20wt% carbon nanotubes, 80wt% sodium carboxymethyl cellulose and an appropriate amount of deionized water were mixed to form a slurry, and then a conductive carbon layer with a thickness of 2 μm was formed on the surface of the copper foil by extrusion coating.

[0150] S20, the liquid-retaining polymer polyethylene oxide was dispersed in water to form a slurry, which was then coated on the surface of the negative electrode current collector copper foil by gravure printing. After drying, cold pressing and slitting, a negative electrode tab was obtained.

[0151] Example 14

[0152] The difference from Example 1 is that the positive electrode tab and the electrolyte are different, specifically:

[0153] Positive electrode tab

[0154] The positive electrode active material lithium iron phosphate, the conductive agent carbon black (Super P) and the binder polyvinylidene fluoride (PVDF) were mixed uniformly in an appropriate amount of solvent N-methyl pyrrolidone (NMP) at a weight ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry was coated on the positive electrode current collector aluminum foil, and after drying, a positive electrode tab was obtained.

[0155] Electrolyte

[0156] The electrolyte salt of the electrolyte is LiFSI with a concentration of 1 mol / L, and the solvent of the electrolyte is ethylene glycol dimethyl ether (DME).

[0157] The rest is the same as Example 1.

[0158] Comparative Example 1

[0159] The difference from Example 1 is that the negative electrode tab is not provided with a polymer layer, and the rest is the same as Example 1.

[0160] Comparative Example 2

[0161] The difference from Example 13 is that the negative electrode tab is not provided with a polymer layer, and the rest is the same as Example 1.

[0162] Comparative Examples 3-4

[0163] The difference from Example 1 is that the composition of the negative electrode tab is different, as shown in Table 1, and the rest is the same as Example 1.

[0164] Table 1

[0165] Test Part

[0166] 1. Electrolyte contact angle of polymer layer

[0167] Tested by contact angle tester, test liquid selected ethylene glycol dimethyl ether, droplet volume 1 μL, five positions tested for each sample, and average value taken.

[0168] 2. Liquid absorption capacity

[0169] The negative electrode tab was cut into a 10 cm x 1 cm strip sample, vertically immersed in electrolyte ethylene glycol dimethyl ether, and the lower end of the strip sample was immersed in electrolyte below the liquid surface by 2 cm. An ultra-high time resolution camera was used to record the height of the electrolyte rising on the sample.

[0170] 3. Swelling degree of polymer layer

[0171] The liquid-retaining polymer was scraped onto a glass plate to form a polymer layer, a 1 cm x 1 cm polymer film was taken, and its thickness was measured by vernier caliper or screw micrometer, and its volume was calculated as V1. The polymer film was soaked in ethylene glycol dimethyl ether at room temperature for 12 h, and the length, width, and height of the polymer film were measured after taking it out, and its volume was calculated as V2. Then the swelling degree s of the liquid-retaining polymer was calculated according to the formula s = V2 / V1 x 100%.

[0172] 4. Cell formation first efficiency

[0173] At 25°C, the cell was charged at 0.33C rate to a voltage equal to 3.65V, and the first charge capacity C1 was tested. Then it was discharged at 0.33C rate to a voltage equal to 1.5V, and the first discharge reversible capacity D1 was measured. The ratio of first discharge capacity D1 / C1 is the cell first efficiency.

[0174] 5. Cycle performance

[0175] The battery cell was charged at 0.33C rate to a voltage equal to 3.65V at 25℃, and then discharged at 0.33C rate to a voltage equal to 1.5V, and the reversible capacity was measured as C0. The charging and discharging was repeatedly performed until the discharge capacity Cn / C0of the battery cell was less than or equal to 80%, and the total cycle number was recorded. Wherein, Cnwas the reversible capacity at the n th cycle.

[0176] 6. Battery storage life

[0177] The battery cell was charged at 0.33C rate to a voltage equal to 3.65V at 25℃, and then discharged at 0.33C rate to a voltage equal to 1.5V, and the reversible capacity was measured as C0. The battery cell was then stored in an environment at 45℃, and every 30 days, the battery cell was charged at 0.33C rate to a voltage equal to 3.65V, and then discharged at 0.33C rate to a voltage equal to 1.5V, and the reversible capacity was measured as Cn, and the storage life decay rate of the battery cell was obtained according to Cn / C0. The storage and the repeated charging and discharging were continuously performed, and the capacity retention rate of the battery stored for 100 days was recorded.

[0178] The test results are shown in Table 2.

[0179] Table 2

[0180] In combination with the data in Table 2, the application examples can improve the liquid retention capacity of the negative electrode sheet by setting the polymer layer on the surface of the negative electrode sheet, and further improve the cycle performance of the battery cell.

[0181] Although the application has been described with reference to the preferred embodiments, various modifications can be made to the application without departing from the scope thereof, and equivalent parts can be substituted for the parts thereof. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising an electrode assembly and an electrolyte, the electrolyte comprising an ether-based solvent, the electrode assembly comprising a negative electrode tab; the negative electrode tab comprising a negative electrode current collector and a polymer layer on at least one side of the negative electrode current collector, the polymer layer comprising a liquid-retaining polymer, the liquid-retaining polymer having a swelling degree in the ether-based solvent of 100% to 500%.

2. The battery cell of claim 1, wherein, the liquid-retaining polymer having a swelling degree in the ether-based solvent of 200% to 400%.

3. The battery cell of claim 1 or 2, wherein, the polymer layer having a contact angle with the electrolyte of 2° to 30°.

4. The battery cell of any one of claims 1 to 3, wherein, the liquid-retaining polymer having a molar content of active functional groups of less than or equal to 5%, the active functional groups comprising one or more of carboxyl, phenolic hydroxyl, amide, carbon-carbon double bond, carbon-nitrogen double bond.

5. The battery cell of any one of claims 1 to 4, wherein, the liquid-retaining polymer comprising one or both of a polyether polymer and a polyester polymer.

6. The battery cell of claim 5, wherein, the polyether polymer having a weight average molecular weight of 10,000 to 1,000,000; and / or the polyester polymer having a weight average molecular weight of 100,000 to 400,000.

7. The battery cell of claim 5 or 6, wherein, the polyether polymer comprising one or more of polyethylene oxide, polymethyl ether, polypropylene oxide, polyether ketone; and / or the polyester polymer comprising one or more of polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate.

8. The battery cell of any one of claims 1 to 7, wherein, the polymer layer further comprising a conductive agent, the conductive agent having a mass percentage content of 5% to 45% based on the total mass of the polymer layer.

9. The battery cell of claim 8, wherein, the conductive agent comprising one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon nanotube, graphene, and carbon nanofiber.

10. The battery cell of any one of claims 1 to 9, wherein, the polymer layer having a thickness of 2μm to 20μm.

11. The battery cell of any one of claims 1 to 10, wherein, the negative electrode tab further comprising a conductive carbon layer between the negative electrode current collector and the polymer layer.

12. The battery cell of claim 11, wherein, the conductive carbon layer having a thickness of 2μm to 20μm.

13. The battery cell of any one of claims 1 to 12, wherein, the ether-based solvent having a volume percentage in the electrolyte of 90% to 97%.

14. The battery cell of claim 13, wherein, the ether-based solvent comprising one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxy methane, 1,3-dioxolane, 2-methyl tetrahydrofuran, tetrahydrofuran.

15. A battery device, wherein, comprising the battery cell of any one of claims 1 to 14.

16. An electrical device, comprising: comprising the battery device of claim 15.

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