Battery cell, battery, and electric apparatus

Abstract

The present application provides a battery cell, a battery, and an electric apparatus. In the battery cell, at least one of a positive electrode sheet, a separator, and a negative electrode sheet contains a gel electrolyte at a top thereof, so that a limiting electrolyte is kept at a top of the battery cell, reducing a risk of electrolyte extrusion, and lowering a risk of electrolyte deficiency at the top of the cell during a cycling process of the battery cell, thereby enabling the battery cell to maintain better cycle performance on the basis of improvements in energy density resulting from a larger size and / or a lower electrolyte injection factor of the battery cell.

Description

Battery cell, battery and electric device

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 2024111391106, filed on August 19, 2024, and entitled "Battery cell, battery and electric device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

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

[0004] Batteries such as lithium ion batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the expansion of the use of batteries, higher demands are placed on the performance of batteries. SUMMARY

[0005] The first aspect of the present application provides a battery cell, comprising a shell, an electrode assembly and a gel electrolyte, the shell has a receiving cavity inside, and the electrode assembly is arranged in the receiving cavity; the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet, and the separator is arranged between the positive electrode sheet and the negative electrode sheet; the gel electrolyte comprises a lyophilic polymer and a limiting electrolyte, and the limiting electrolyte is located inside the lyophilic polymer; in the direction of gravity, at least one of the positive electrode sheet, the separator and the negative electrode sheet contains the gel electrolyte at least at its top; the battery cell satisfies one or more of (1) to (2):

[0006] (1) the shell is a square shell, the height of the square shell in the direction of gravity is H1, and the length of the square shell perpendicular to the direction of gravity is L1, wherein H1≥L1, and H1≥100mm; or,

[0007] the shell is a square shell, the height of the square shell in the direction of gravity is H2, and the length of the square shell perpendicular to the direction of gravity is L2, wherein H2

[0008] the shell is a cylindrical shell, the axis of the cylindrical shell is perpendicular to the direction of gravity, the diameter of the cylindrical shell is D, and the length of the cylindrical shell along its axis is L3, wherein D

[0009] (2) in the battery cell, the ratio of the mass of the free electrolyte to the rated capacity of the battery cell is less than or equal to 0.2g / Ah.

[0010] In the design of the battery cell, on the one hand, when the size of the battery cell is large, the battery cell can accommodate more active materials, which is conducive to promoting the improvement of the energy density of the battery cell. On the other hand, when the battery cell contains less or no free electrolyte, it is also conducive to promoting the improvement of the energy density of the battery cell. However, during the charging process of the battery cell, the expansion of the active material will squeeze the electrolyte out of the electrode assembly. The squeezed electrolyte needs to be sucked back into the electrode assembly to maintain good wetting of the electrode assembly. At this time, due to the large size of the battery cell, the electrolyte needs to be sucked back for a long distance, and the electrolyte is difficult to be sucked back to the top of the battery cell in time, resulting in liquid deficiency at the top of the battery cell. Or because the battery cell contains less or no free electrolyte, less electrolyte is sucked back to the top of the battery cell, resulting in liquid deficiency at the top of the battery cell. When the top of the battery cell is short of liquid, the cycle performance of the battery cell will be affected.

[0011] In the above battery cell, at least one of the positive electrode sheet, the separator and the negative electrode sheet contains a gel electrolyte at the top thereof, which can keep the limited electrolyte at the top of the battery cell, reduce the risk of electrolyte being squeezed out, reduce the risk of liquid deficiency at the top of the battery cell during the cycle of the battery cell, and thus the battery cell can have good cycle performance on the basis of the improvement of the energy density brought by the large size and / or the small liquid injection coefficient.

[0012] In some embodiments, in the positive electrode sheet, the size percentage of the part containing the gel electrolyte in the size of the positive electrode sheet is 10% to 100% in the direction of gravity. The size percentage of the part containing the gel electrolyte in the size of the positive electrode sheet in this range can limit more electrolyte in the positive electrode sheet, so that the positive electrode sheet can have more sufficient contact with the electrolyte, and further improve the cycle performance of the battery cell. Alternatively, the size percentage of the part containing the gel electrolyte in the size of the positive electrode sheet is 20% to 100%.

[0013] In some embodiments, the gel electrolyte is uniformly distributed in the part of the positive electrode sheet containing the gel electrolyte. The uniform distribution of the gel electrolyte can make the contact between the electrolyte and the positive electrode sheet more uniform, which is conducive to further promoting the sufficient wetting of the electrolyte to the positive electrode sheet and further improving the cycle performance of the battery cell.

[0014] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on at least one surface of the positive electrode current collector, and the positive electrode active layer includes a gel electrolyte and a positive electrode active material; the gel electrolyte is distributed on the surface of the particles of the positive electrode active material. The gel electrolyte distributed on the surface of the particles of the positive electrode active material can protect the particles of the active material, reduce the side reaction between the particles of the positive electrode active material and the electrolyte, and further improve the cycle performance of the battery cell.

[0015] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the positive active material. At this time, more electrolyte can be confined in the positive electrode sheet, further improving the cycle performance of the battery cell.

[0016] In some embodiments, the mass percentage of the lyophilic polymer in the positive active layer is 0.1% to 2%. The mass percentage of the lyophilic polymer in the positive active layer in this range can make the confined electrolyte have a suitable amount in the positive active layer, making the confined electrolyte better adapt to the positive active material, further improving the cycle performance of the battery cell. Optionally, the mass percentage of the lyophilic polymer in the positive active layer is 0.1% to 1%.

[0017] In some embodiments, the positive active material includes one or more of lithium nickel manganese cobalt oxide and lithium-containing phosphate; in the lithium nickel manganese cobalt oxide, the molar percentage of nickel element is 50% to 95%, optionally 80% to 95%, in terms of the molar percentage of nickel element, manganese element and cobalt element. The lithium nickel manganese cobalt oxide with the molar percentage of nickel element in this range has a higher gram capacity, which is conducive to further improving the energy density of the battery cell.

[0018] In some embodiments, the density of the positive active layer is 2 g / cm 3 to 3.8 g / cm 3 .

[0019] In some embodiments, the positive active material includes lithium nickel cobalt manganese oxide, and the density of the positive active layer is 3.5 g / cm 3 to 3.8 g / cm 3 .

[0020] In some embodiments, the positive active material includes lithium-containing phosphate, and the density of the positive active layer is 2 g / cm 3 to 3 g / cm 3 .

[0021] In some embodiments, the mass energy density of the battery cell is 150 Wh / kg to 400 Wh / kg.

[0022] In some embodiments, in the negative electrode sheet, the size percentage of the part containing the gel electrolyte in the negative electrode sheet is 10% to 100% in the direction of gravity. The size percentage of the part containing the gel electrolyte in the negative electrode sheet in this range can make the negative electrode sheet confine more electrolyte, so that the negative electrode sheet can maintain more sufficient contact with the electrolyte, further improving the cycle performance of the battery cell. Optionally, in the negative electrode sheet, the size percentage of the part containing the gel electrolyte in the negative electrode sheet is 20% to 100%.

[0023] In some embodiments, the portion of the negative electrode tab containing the gel electrolyte is uniformly distributed. The uniform distribution of the gel electrolyte can make the contact between the electrolyte and the negative electrode tab more uniform, which is conducive to further promoting the full impregnation of the electrolyte to the negative electrode tab, and further improving the cycle performance of the battery cell.

[0024] In some embodiments, the negative electrode tab comprises a negative current collector and a negative active layer located on at least one surface of the negative current collector, and the negative active layer comprises a gel electrolyte and a negative active material; the gel electrolyte is distributed on the surface of the particles of the negative active material. The distribution of the gel electrolyte on the surface of the particles of the negative active material can protect the particles of the active material, reduce the side reaction between the particles of the negative active material and the electrolyte, and further improve the cycle performance of the battery cell.

[0025] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the negative active material. At this time, more electrolyte can be confined in the negative electrode tab, further improving the cycle performance of the battery cell.

[0026] In some embodiments, the mass percentage of the lyophilic polymer in the negative active layer is 1% to 5%. The mass percentage of the lyophilic polymer in the negative active layer in this range can make the confined electrolyte have a suitable amount in the negative active layer, and make the confined electrolyte better adapt to the negative active material, further improving the cycle performance of the battery cell. Alternatively, the mass percentage of the lyophilic polymer in the negative active layer is 2% to 4%.

[0027] In some embodiments, the density of the negative active layer is 1 g / cm 3 to 2 g / cm 3 , and optionally 1.3 g / cm 3 to 1.7 g / cm 3 .

[0028] In some embodiments, the size percentage of the portion containing the gel electrolyte in the separator in the direction of gravity is 10% to 100%. The size percentage of the portion containing the gel electrolyte in the separator in this range can confine more electrolyte in the positive electrode tab, so that the separator can maintain more sufficient contact with the electrolyte, further improving the cycle performance of the battery cell. Alternatively, the size percentage of the portion containing the gel electrolyte in the separator is 20% to 100%.

[0029] In some embodiments, the gel electrolyte is uniformly distributed in the part of the separator film containing the gel electrolyte. The uniform distribution of the gel electrolyte can make the contact between the electrolyte and the separator film more uniform, which is conducive to further promoting the full impregnation of the electrolyte to the separator film and further improving the cycle performance of the battery cell.

[0030] In some embodiments, the gel electrolyte is distributed at the pores of the separator film.

[0031] In some embodiments, the separator film comprises a separator film substrate and a coating layer located on at least one surface of the separator film substrate, and the coating layer contains a particulate filler. The coating layer containing the particulate filler has better heat resistance and higher strength, which can improve the heat resistance and strength of the separator film, so that the separator film maintains a relatively stable structure during the cycle of the battery cell, and promotes the further improvement of the cycle performance of the battery cell. Optionally, the particulate filler comprises one or more of boehmite, alumina, silica, and magnesium hydroxide.

[0032] In some embodiments, the thickness of the coating layer is 0.25 μm to 5 μm.

[0033] In some embodiments, the material of the separator film substrate comprises one or more of polyethylene, polypropylene, polyimide, and aramid.

[0034] In some embodiments, H1≥L1, and the liquid injection port of the battery cell is located at the top end of the shell.

[0035] In some embodiments, H1≥120 mm; optionally, 150 mm≤H1≤300 mm.

[0036] In some embodiments, 100 mm≤L1≤300 mm.

[0037] In some embodiments, H2

[0038] In some embodiments, L2≥120 mm; optionally, 220 mm≤L2≤350 mm.

[0039] In some embodiments, 50 mm≤H2≤150 mm.

[0040] In some embodiments, the lyophilic polymer comprises a fluorinated polymer; the fluorinated polymer has a crystallinity X c1 , 15%<X c1 ≤25%.

[0041] The fluorinated polymer has a melting temperature T m1 , which is in ℃, and 120 m1 ≤140.

[0042] In some embodiments, the lyophilic polymer comprises a fluorinated polymer; the fluorinated polymer has a cold crystallization degree X measured by differential scanning calorimetry c2 , 10% < X c2 ≤ 25%;

[0043] The fluorinated polymer has a cold crystallization temperature Tc2 in °C, 35 < T c2 ≤ 65.

[0044] In some embodiments, the monomers of the fluorinated polymer comprise hexafluoropropylene and vinylidene fluoride.

[0045] In some embodiments, the fluorinated polymer has a molar percentage of hexafluoropropylene of 6% to 13% based on the total molar ratio of hexafluoropropylene and vinylidene fluoride.

[0046] In some embodiments, the fluorinated polymer comprises at least one of a structural unit represented by Formula (AI) to a structural unit represented by Formula (AIII),

[0047] In Formula (AI) and Formula (AII), R 11 , R 12 , R 13 , and R 14 each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and at least one of R 11 , R 12 , R 13 , and R 14 comprises a fluorine atom; when substituted, the substituent comprises one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom;

[0048] In Formula (AIII), R 15 comprises a single bond, a substituted or unsubstituted C1-C3 alkyl group; when substituted, the substituent comprises one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; p is selected from positive integers of 1 to 3; n is each independently selected from positive integers of 1000 to 30000.

[0049] In some embodiments, the lyophilic polymer has a molecular weight of 1.2 x 10 5 g / mol to 1 x 10 6 g / mol.

[0050] In some embodiments, the gel electrolyte has a lithium ion transference number ≥ 0.4.

[0051] The second aspect of the present application provides a battery. The battery comprises the battery cell of the first aspect.

[0052] The third aspect of the present application provides a power consuming device. The power consuming device comprises the battery of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0053] For a better description and illustration of the embodiments or examples provided by the present application, reference can be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the presently described embodiments or examples, and the best mode presently contemplated of these applications. Moreover, in all the drawings, the same reference numbers are used to designate the same components. In the drawings:

[0054] FIG. 1 is a schematic view of a battery cell according to an embodiment of the present application.

[0055] FIG. 2 is an exploded view of the battery cell shown in FIG. 1 according to an embodiment of the present application.

[0056] FIG. 3 is a schematic view of a power consuming device using the battery cell according to an embodiment of the present application as a power source.

[0057] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0058] For the purpose of facilitating the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that the disclosure of the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing the specific embodiments and is not intended to limit the present application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0060] "ranges" disclosed herein can be defined, for example, by the lower and upper values. Any lower limit can independently be combined with any upper limit to define a range of any value. For example, if a range of 60-120 and 80-110 is listed, it is understood that a range of 60-110 and 80-120 is also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0061] In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0062] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated.

[0063] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment or implementation of the application. The appearances of the phrase that the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments. It is explicitly understood that the embodiments described herein are combinable with each other. Reference herein to "an implementation" has a similar understanding.

[0064] Those skilled in the art can understand that the order of writing each step in the method of each embodiment or example does not mean a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the present application can be performed in sequence or randomly. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can also comprise 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.

[0065] In the present application, "A, such as B" means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0066] In the present application, "optionally", "optional" and "optional" mean that it can or can not be present, that is, it means to select any one from the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified, and there is no contradiction or mutual restriction, each "option" is independent.

[0067] Generally, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting of the positive and negative electrodes, and at the same time to allow ions to pass through.

[0068] In the present application, "battery cell" means a basic unit capable of realizing mutual conversion between chemical energy and electrical energy. Further, it generally includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0069] An embodiment of the present application provides a battery monomer, comprising a shell, an electrode assembly and a gel electrolyte, the shell has a containing cavity inside, and the electrode assembly is arranged in the containing cavity; the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet, and the separator is arranged between the positive electrode sheet and the negative electrode sheet; the gel electrolyte comprises a lyophilic polymer and a limiting electrolyte, and the limiting electrolyte is located inside the lyophilic polymer; in the direction of gravity, at least one of the positive electrode sheet, the separator and the negative electrode sheet contains the gel electrolyte at least at the top of the at least one; the battery monomer satisfies one or more of (1) to (2):

[0070] (1) the shell is a square shell, the height of the square shell in the direction of gravity is H1, and the length of the square shell perpendicular to the direction of gravity is L1, wherein H1≥L1, and H1≥100 mm; or,

[0071] the shell is a square shell, the height of the square shell in the direction of gravity is H2, and the length of the square shell perpendicular to the direction of gravity is L2, wherein H2

[0072] the shell is a cylindrical shell, the axis of the cylindrical shell is perpendicular to the direction of gravity, the diameter of the cylindrical shell is D, and the length of the cylindrical shell along the axis is L3, wherein D

[0073] (2) in the battery monomer, the ratio of the mass of the free electrolyte to the rated capacity of the battery monomer is less than or equal to 0.2 g / Ah.

[0074] In the design of the battery cell, on the one hand, when the size of the battery cell is large, the battery cell can accommodate more active materials, which is conducive to promoting the improvement of the energy density of the battery cell. On the other hand, when the battery cell contains less or no free electrolyte, it is also conducive to promoting the improvement of the energy density of the battery cell. However, in the charging process of the battery cell, the expansion of the active material will squeeze the electrolyte out of the electrode assembly. And the squeezed electrolyte needs to be sucked back into the electrode assembly to keep the electrode assembly well soaked. At this time, due to the large size of the battery cell, the electrolyte needs to be sucked back for a long distance, and the electrolyte is difficult to be sucked back to the top of the battery cell in time, resulting in a lack of electrolyte at the top of the battery cell. Or because there is less or no free electrolyte, less electrolyte is sucked back to the top of the battery cell, resulting in a lack of electrolyte at the top of the battery cell. When the top of the battery cell is short of electrolyte, the cycle performance of the battery cell will be affected. In the battery cell of the present embodiment, at least one of the positive electrode sheet, the separator and the negative electrode sheet contains a gel electrolyte at the top thereof, which can keep the electrolyte at the top of the battery cell, reduce the risk of electrolyte being squeezed out, reduce the risk of electrolyte shortage at the top of the battery cell during the cycle of the battery cell, and thus the battery cell can improve the energy density brought by the larger size and / or smaller liquid injection coefficient, and keep the battery with good cycle performance.

[0075] It can be understood that when the shell is square, the direction of gravity can be the height direction of the shell, and the direction perpendicular to the direction of gravity is the length direction of the shell.

[0076] In some examples of the battery cell, the shell is a square shell, H1≥L1, and H1≥100 mm. At this time, the battery cell has a large size in the height direction, which can accommodate more active materials in the battery cell to improve the energy density of the battery cell. However, when the battery cell has a large size in the height direction, at the top of the battery cell, after the electrolyte in the electrode assembly is squeezed out, the electrolyte needs to climb a long distance during the electrolyte suction process, making it difficult for the electrolyte to be sucked back to the top of the electrode assembly in time, resulting in a lack of electrolyte at the top of the battery cell, and thus affecting the cycle performance of the battery cell. In the battery cell of the present embodiment, at least one of the positive electrode sheet, the separator and the negative electrode sheet contains a gel electrolyte at the top thereof, and in the gel electrolyte, the electrolyte can be limited to the top of the electrode assembly by the lyophilic polymer, which can reduce the risk of electrolyte being squeezed out at the top of the electrode assembly, improve the problem of electrolyte shortage at the top of the battery cell which is prone to occur in high battery cells, and thus the battery cell can have both high energy density and good cycle performance.

[0077] Optionally, H1≥L1, and the liquid injection port of the battery cell is arranged at the top end of the shell. For a battery cell with a large height, arranging the liquid injection port at the top end of the shell can make the injected electrolyte better soak the electrode assembly during the liquid injection process.

[0078] Optionally, H1≥L1, as some examples of H1, H1 can be 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, 260 mm, 270 mm, 280 mm, 290 mm, 300 mm, 310 mm, 320 mm, 330 mm, 340 mm, 350 mm, 360 mm, 370 mm, 380 mm, 390 mm, 400 mm, or any value within the range consisting of any two of the above values. Further optionally, H1≥120 mm. Still further optionally, 150 mm≤H1≤300 mm. As some examples of L1, 100 mm≤L1≤300 mm. Optionally, L1 can be 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, 260 mm, 270 mm, 280 mm, 290 mm, 300 mm, or any value within the range consisting of any two of the above values. Further optionally, 150 mm≤L1≤300 mm.

[0079] In some examples of the battery cell, the shell is a square shell, H2

[0080] Optionally, H2

[0081] Optionally, when H2

[0082] In some examples of the battery cell, the shell is a cylindrical shell, an axis of the cylindrical shell is perpendicular to the direction of gravity, D < L3, and a circumference of a circular face of the cylindrical shell is ≥ 140 mm. The large circumference and length of the circular face of the battery cell can accommodate more active materials inside the battery cell to increase the energy density of the battery cell. However, when the circumference of the circular face of the cylindrical shell of the battery cell has a large size, the electrolyte needs a long wicking distance to soak the electrode assembly. This also makes it difficult for the electrolyte to be timely sucked back and causes lack of electrolyte, which in turn affects the cycle performance of the battery cell. In the battery cell of the present embodiment, at least one of the positive electrode sheet, the separator, and the negative electrode sheet contains the gel electrolyte at the top thereof. In the gel electrolyte, the electrolyte can be confined to the top of the electrode assembly by the lyophilic polymer, which can reduce the risk of the electrolyte being squeezed out of the top of the electrode assembly, improve the top lack of electrolyte problem that is prone to occur in the battery cell, and thus enable the battery cell to have both high energy density and good cycle performance. Optionally, the circumference of the circular face of the cylindrical shell can be 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, or any value within a range defined by any two of the above values.

[0083] Further, the shell is a cylindrical shell, and the electrode assembly has a jelly-roll structure. At the innermost layer of the electrode assembly, at least one of the positive electrode sheet, the separator, and the negative electrode sheet contains the gel electrolyte, which can confine the electrolyte to the innermost layer of the electrode assembly by the lyophilic polymer, reduce the risk of lack of electrolyte in the innermost layer of the electrode assembly, and further improve the cycle performance of the electrode assembly.

[0084] In some examples of the battery cell, the ratio of the mass of the free electrolyte to the rated capacity of the battery cell is less than or equal to 0.2 g / Ah. At this time, the battery cell has less free electrolyte, which is conducive to reducing the mass of the battery cell, and thus the battery cell has a higher energy density. However, after the electrolyte in the electrode assembly is squeezed out, there is less electrolyte that is sucked back to the top of the battery cell due to the free electrolyte in the battery cell, which can also cause the battery cell to have top liquid deficiency, and thus affect the cycle performance of the battery cell. In the battery cell of the present embodiment, at least one of the positive electrode sheet, the separator, and the negative electrode sheet contains the gel electrolyte at the top thereof, and the electrolyte is confined at the top of the electrode assembly by the lyophilic polymer in the gel electrolyte, which can reduce the risk of the electrolyte at the top of the electrode assembly being squeezed out, improve the top liquid deficiency problem that is prone to occur in the battery cell with low electrolyte injection coefficient, and thus enable the battery cell to have a higher energy density and better cycle performance. Alternatively, the ratio of the mass of the free electrolyte to the rated capacity of the battery cell can be 0, 0.02 g / Ah, 0.05 g / Ah, 0.08 g / Ah, 0.1 g / Ah, 0.12 g / Ah, 0.15 g / Ah, 0.18 g / Ah, 0.2 g / Ah, or any value within a range defined by any two of the above values.

[0085] The rated capacity of the battery cell in the present application can be tested by the following method: charging the battery cell at 0.33 C to the upper limit voltage, and then charging at a constant voltage to the cutoff current of 0.05 C. Then discharge at 0.33 C to the lower limit voltage, and record the discharge capacity as the rated capacity of the battery cell, with the unit being Ah.

[0086] After the electrolyte is injected into the battery cell, the electrolyte mainly exists in the following forms: one is the electrolyte that can be adsorbed in the electrode assembly, two is the confined electrolyte inside the lyophilic polymer, and three is the free electrolyte that can be free in the battery cell.

[0087] The mass of the electrolyte injected into the battery cell and the mass of the free electrolyte in the battery cell of the present application can be tested by the following method: fully discharging a fresh battery cell to 0% SOC state of charge, weighing the battery cell, and the mass is M1. A hole with a diameter of 2 mm is opened at a local position of the battery cell, and the mass of the electrolyte in the hole is M2. The mass of the electrolyte injected into the battery cell is M1-M2, and the mass of the free electrolyte is M2. The battery monomer is placed above a container with a hole downward and right above the container, so that the free electrolyte inside the battery monomer can drip into the container below, and the battery monomer is thus placed for 3-5 hours, so that the free electrolyte inside can drip into the container, and then the remaining mass M2 of the battery monomer is weighed. Then the battery monomer is disassembled, and each part obtained by disassembly is dried at 60-95°C for 24-48 hours, and then each part is soaked in dimethyl carbonate (DMC) solvent, soaked for 12 hours, and then dried at 60-95°C for 24-48 hours; the soaking and drying are repeated twice, and each part after drying is weighed, and the total mass is recorded as M3. In the test method, the fresh battery monomer can be a battery monomer just out of the factory (after formation without charge-discharge cycle) or a battery monomer assembled on an electric device and used for less than 10 cycles. The mass of the electrolyte injected into the battery monomer is M1-M3, and the mass of the free electrolyte is M1-M2.

[0088] In some embodiments, the size of the part containing the gel electrolyte in the positive electrode tab accounts for 10-100% of the size of the positive electrode tab in the direction of gravity. The size of the part containing the gel electrolyte in the positive electrode tab accounts for 10-100% of the size of the positive electrode tab, which can limit more electrolyte in the positive electrode tab, so that the positive electrode tab can maintain more sufficient contact with the electrolyte, and further improve the cycle performance of the battery monomer. Alternatively, the size of the part containing the gel electrolyte in the positive electrode tab accounts for 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% of the size of the positive electrode tab, or any value within the range formed by any two of the above values. Further alternatively, the size of the part containing the gel electrolyte in the positive electrode tab accounts for 20-100% of the size of the positive electrode tab.

[0089] In some embodiments, the gel electrolyte is uniformly distributed in the part of the positive electrode tab containing the gel electrolyte. The uniform distribution of the gel electrolyte can make the contact between the electrolyte and the positive electrode tab more uniform, which is conducive to further promoting the full infiltration of the electrolyte to the positive electrode tab, and further improving the cycle performance of the battery monomer.

[0090] In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode active layer on at least one surface of the positive electrode current collector, and the positive electrode active layer includes a gel electrolyte and a positive electrode active material. The gel electrolyte is distributed on the surface of the particles of the positive electrode active material. The gel electrolyte distributed on the surface of the particles of the positive electrode active material can protect the particles of the active material, reduce the side reaction between the particles of the positive electrode active material and the electrolyte, and further improve the cycle performance of the battery monomer.

[0091] The gel electrolyte is distributed on the surface of the particles of the positive active material, which means that the gel electrolyte is located on the surface of the positive active layer away from the surface of the positive current collector. For example, the surface of the positive current collector forms a film layer including the positive active material, and the gel electrolyte is located on the surface of the film layer away from the surface of the positive current collector. Alternatively, the preparation of the positive electrode sheet with such a structure includes the following steps: coating the positive electrode slurry including the positive active material on the surface of the positive current collector, drying and curing to obtain the film layer, and then disposing the lyophilic polymer on the surface of the film layer. When the lyophilic polymer is in contact with the electrolyte, the lyophilic polymer adsorbs the electrolyte to form the gel electrolyte. Thus, the structure in which the gel electrolyte is distributed on the surface of the particles of the positive active material is obtained. It can be understood that the positive electrode slurry can further include a binder and a conductive agent, etc.

[0092] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the positive active material. At this time, more electrolyte can be confined in the positive electrode sheet, further improving the cycle performance of the battery cell. Alternatively, the preparation of the positive electrode sheet with such a structure includes the following steps: mixing the lyophilic polymer and the positive active material in a solvent to obtain a positive electrode slurry, then coating the positive electrode slurry on the surface of the positive current collector, and drying and curing to obtain a film layer. When the film layer is in contact with the electrolyte, the lyophilic polymer adsorbs the electrolyte to form the gel electrolyte. Thus, the structure in which the gel electrolyte is distributed at the pores between the particles of the positive active material is obtained. It can be understood that the positive electrode slurry can further include a binder and a conductive agent, etc.

[0093] In some embodiments, the mass percentage of the lyophilic polymer in the positive active layer is 0.1% to 2%. The mass percentage of the lyophilic polymer in the positive active layer within this range can make the confined electrolyte have a suitable amount in the positive active layer, so that the confined electrolyte and the positive active material are better adapted, further improving the cycle performance of the battery cell. Alternatively, the mass percentage of the lyophilic polymer in the positive active layer can be 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any value within the range formed by any two of the above values. Further alternatively, the mass percentage of the lyophilic polymer in the positive active layer is 0.1% to 1%.

[0094] In some embodiments, the positive active material includes one or more of lithium nickel manganese cobalt oxide and lithium-containing phosphate. The lithium nickel manganese cobalt oxide has a high specific capacity, which is beneficial to further improve the energy density of the battery cell. The lithium-containing phosphate has good cycle performance, which can further improve the cycle performance of the battery cell.

[0095] Alternatively, non-limiting examples of the lithium nickel manganese cobalt oxide can include LiNi 1 / 3 Co 1 / 3 Mn1 / 3 O2(referred to as: NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(referred to as: NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(referred to as: NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(referred to as: NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(referred to as: NCM 811 ), etc.

[0096] Optionally, non-limiting examples of the lithium-containing phosphate 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.

[0097] Optionally, in the lithium nickel manganese cobalt oxide, the molar percentage of the nickel element is 50% to 95% in terms of the molar percentage of the nickel element, the manganese element, and the cobalt element. Optionally, in the lithium nickel manganese cobalt oxide, the molar percentage of the nickel element can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any value within a range constituted by any two of the above values in terms of the molar percentage of the nickel element, the manganese element, and the cobalt element. Further optionally, in the lithium nickel manganese cobalt oxide, the molar percentage of the nickel element is 80% to 95% in terms of the molar percentage of the nickel element, the manganese element, and the cobalt element, and the lithium nickel manganese cobalt oxide with the molar percentage of the nickel element in this range has a higher gram capacity, which is conducive to further improving the energy density of the battery monomer.

[0098] In some embodiments, the density of the positive electrode active layer is 2 g / cm 3 to 3.8 g / cm 3 . The density of the positive electrode active layer in this range can make the battery monomer have a more appropriate weight and a higher energy density. For example, the density of the positive electrode active layer can be 2 g / cm 3 , 2.1 g / cm 3 , 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 32.7 g / cm3 3 2.8 g / cm3 3 2.9 g / cm3 3 3 g / cm3 3 3.1 g / cm3 3 3.2 g / cm3 3 3.3 g / cm3 3 3.4 g / cm3 3 3.5 g / cm3 3 3.6 g / cm3 3 3.7 g / cm3 3 3.8 g / cm3 3 or any value in a range defined by any two of the above values.

[0099] Optionally, the positive active material includes lithium nickel cobalt manganese oxide, and the density of the positive active layer is 3.5 g / cm3 3 3.8 g / cm3 3 .

[0100] Optionally, the positive active material includes lithium-containing phosphate, and the density of the positive active layer is 2 g / cm3 3 3 g / cm3 3 .

[0101] In some embodiments, the battery cell has a mass energy density of 150 Wh / kg to 400 Wh / kg. For example, the battery cell can have a mass energy density of 150 Wh / kg, 160 Wh / kg, 170 Wh / kg, 180 Wh / kg, 190 Wh / kg, 200 Wh / kg, 220 Wh / kg, 250 Wh / kg, 270 Wh / kg, 280 Wh / kg, 290 Wh / kg, 300 Wh / kg, 310 Wh / kg, 320 Wh / kg, 330 Wh / kg, 350 Wh / kg, 380 Wh / kg, 400 Wh / kg, or any value in a range defined by any two of the above values. Optionally, the battery cell has a mass energy density of 350 Wh / kg to 400 Wh / kg.

[0102] In some embodiments, the size of the portion of the negative electrode tab containing the gel electrolyte accounts for 10% to 100% of the size of the negative electrode tab in the direction of gravity. The size of the portion of the negative electrode tab containing the gel electrolyte accounting for 10% to 100% of the size of the negative electrode tab can limit more electrolyte in the negative electrode tab, enable the negative electrode tab to maintain more sufficient contact with the electrolyte, and further improve the cycle performance of the battery cell. Meanwhile, the gel electrolyte in the negative electrode tab can reduce the risk of electrolyte extrusion, reduce the lithium precipitation problem of the negative electrode tab due to liquid deficiency, and further improve the cycle performance of the battery cell. Alternatively, the size of the portion of the negative electrode tab containing the gel electrolyte accounts for 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% of the size of the negative electrode tab, or any value within the range formed by any two of the above values. Further alternatively, the size of the portion of the negative electrode tab containing the gel electrolyte accounts for 20% to 100% of the size of the negative electrode tab.

[0103] In some embodiments, the gel electrolyte is uniformly distributed in the portion of the negative electrode tab containing the gel electrolyte. The uniform distribution of the gel electrolyte can make the contact between the electrolyte and the negative electrode tab more uniform, which is conducive to further promoting the sufficient infiltration of the electrolyte into the negative electrode tab and further improving the cycle performance of the battery cell.

[0104] In some embodiments, the negative electrode tab includes a negative current collector and a negative active layer located on at least one surface of the negative current collector, and the negative active layer includes a gel electrolyte and a negative active material. The gel electrolyte is distributed on the surface of the particles of the negative active material. The distribution of the gel electrolyte on the surface of the particles of the negative active material can protect the particles of the active material, reduce the side reaction between the particles of the negative active material and the electrolyte, and further improve the cycle performance of the battery cell.

[0105] The gel electrolyte distributed on the surface of the particles of the negative active material means that the gel electrolyte is located on the surface of the negative active layer away from the negative current collector. For example, the surface of the negative current collector forms a film layer including the negative active material, and the gel electrolyte is located on the surface of the film layer away from the negative current collector. Alternatively, the preparation of the negative electrode tab with such a structure includes the following steps: coating a negative electrode slurry including a negative active material on the surface of a negative current collector, drying and solidifying to obtain a film layer, and then disposing a lyophilic polymer on the surface of the film layer. When the lyophilic polymer contacts with the electrolyte, the lyophilic polymer absorbs the electrolyte to form a gel electrolyte. Thus, the gel electrolyte is distributed on the surface of the particles of the negative active material. It can be understood that the negative electrode slurry can further include a binder and a conductive agent, etc.

[0106] In some embodiments, the gel electrolyte is distributed at the pores between the particles of the negative active material. In this case, more electrolyte can be confined in the negative electrode sheet, further improving the cycle performance of the battery cell. Alternatively, the preparation of the negative electrode sheet of this structure comprises the following steps: mixing the lyophilic polymer and the negative active material in a solvent to obtain a negative electrode slurry, then coating the surface of the negative electrode current collector with the negative electrode slurry, and drying and curing to obtain a film layer. When the film layer is in contact with the electrolyte, the lyophilic polymer absorbs the electrolyte to form a gel electrolyte. That is, a structure in which the gel electrolyte is distributed at the pores between the particles of the negative active material is obtained. It can be understood that the negative electrode slurry can also include a binder and a conductive agent, etc.

[0107] In some embodiments, in the negative active layer, the mass percentage of the lyophilic polymer in the negative active layer is 1% to 5%. The mass percentage of the lyophilic polymer in the negative active layer in this range can make the confined electrolyte have a suitable amount in the negative active layer, make the confined electrolyte better adapt to the negative active material, and further improve the cycle performance of the battery cell. Alternatively, the mass percentage of the lyophilic polymer in the negative active layer can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value within a range consisting of any two of the above values. Further alternatively, the mass percentage of the lyophilic polymer in the negative active layer is 2% to 4%.

[0108] In some embodiments, the density of the negative active layer is 1 g / cm 3 to 2 g / cm 3 . Alternatively, the density of the negative active layer can be 1 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 , 2 g / cm 3 or any value within a range consisting of any two of the above values. Further alternatively, the density of the negative active layer is 1.3 g / cm 3 to 1.7 g / cm 3 . Further alternatively, the negative active material includes graphite.

[0109] In some embodiments, the size of the portion of the separator film containing the gel electrolyte accounts for 10% to 100% of the size of the separator film in the direction of gravity. The size of the portion of the separator film containing the gel electrolyte accounting for 10% to 100% of the size of the separator film can limit the electrolyte in the cathode electrode sheet more, enable the separator film to maintain more sufficient contact with the electrolyte, and further improve the cycle performance of the battery cell. Alternatively, the size of the portion of the separator film containing the gel electrolyte accounts for 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% of the size of the separator film, or any value within a range defined by any two of the above values. Further alternatively, the size of the portion of the separator film containing the gel electrolyte accounts for 20% to 100% of the size of the separator film.

[0110] In some embodiments, the gel electrolyte is uniformly distributed in the portion of the separator film containing the gel electrolyte. The uniform distribution of the gel electrolyte can make the contact between the electrolyte and the separator film more uniform, which is conducive to further promoting the sufficient infiltration of the electrolyte into the separator film and further improving the cycle performance of the battery cell.

[0111] In some embodiments, the gel electrolyte is distributed at the pores of the separator film.

[0112] Alternatively, the separator film includes a substrate. Further alternatively, the substrate generally has a porous structure, and the gel electrolyte can be distributed at the pores of the substrate. Further alternatively, the separator film can further include a coating layer disposed on at least one surface of the substrate. Understandably, the gel electrolyte can also be distributed in the coating layer, and / or the gel electrolyte can also be distributed on the surface of the coating layer away from the substrate.

[0113] In some embodiments, the separator film includes a separator film substrate and a coating layer disposed on at least one surface of the separator film substrate, and the coating layer contains a particulate filler. Alternatively, the particulate filler includes one or more of boehmite, alumina, silica, and magnesium hydroxide. The coating layer containing the particulate filler has good heat resistance and high strength, which can improve the heat resistance and strength of the separator film, enable the separator film to maintain a relatively stable structure during the cycle of the battery cell, and further improve the cycle performance of the battery cell. Alternatively, the thickness of the coating layer is 0.25 μm to 5 μm. For example, the thickness of the coating layer can be 0.25 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value within a range defined by any two of the above values.

[0114] In some embodiments, the coating layer includes a solid-state electrolyte. The solid-state electrolyte is alternatively lithium aluminum titanium phosphate. Alternatively, the coating layer is disposed between the cathode electrode sheet and the separator film substrate.

[0115] Optionally, the coating of the separation membrane further comprises a binder. The use of the binder can improve the binding force between the coating and the substrate of the separation membrane, and further improve the structural stability of the separation membrane. Further optionally, the binder can be one or more of polyvinylidene fluoride and polyacrylate.

[0116] In some embodiments, the material of the separation membrane substrate comprises one or more of polyethylene, polypropylene, polyimide and aramid. Optionally, the thickness of the separation membrane substrate is 3 μm to 20 μm. For example, the thickness of the separation membrane substrate can be 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 any value within the range defined by any two of the above values. Further optionally, the thickness of the separation membrane substrate is 5 μm to 16 μm.

[0117] In some embodiments, the lyophilic polymer comprises one or more of fluorinated polymer, ether polymer, ester polymer and aldehyde ketone polymer.

[0118] fluorinated polymer

[0119] In some embodiments, the lyophilic polymer comprises fluorinated polymer; the crystallinity of the fluorinated polymer is X c1 , 15%≤X c1 ≤25%; the melting temperature of the fluorinated polymer is T m1 , which is in unit of ℃, 120≤T m1 ≤140.

[0120] The cold crystallinity of the fluorinated polymer is X c2 , 10%≤X c2 ≤25%; the cold crystallization temperature of the fluorinated polymer is Tc2, which is in unit of ℃, 35≤T c2 ≤65.

[0121] Crystallization refers to the process of ordering of atoms, ions or molecules in a material according to a certain spatial order. The conformation of the polymer in the crystallization is determined by both the intra-molecular and inter-molecular factors, and the inter-molecular force can affect the packing density between the molecular chains. The crystallinity X c1 is used to represent the degree of crystallization in a material, which can be measured by differential scanning calorimetry (DSC). Specifically, the test procedure is as follows: 0.5 g to 0.8 g of sample is taken and placed in a sample crucible, and the sample is subjected to temperature rising and falling treatment under nitrogen atmosphere, with a temperature rising rate of 10 ℃ / min, from an initial temperature of 20 ℃ lower than the intrinsic T g1 of the material to the intrinsic T m1The cut-off temperature of the high 20℃ process, the actual glass transition temperature T of the material is determined according to the endothermic and exothermic peak or transition point of the material in the process g1 and the melting temperature T m1 , etc.

[0122] Therefore, the fluorinated polymer has relatively low crystallinity and melting temperature, so that the molecular chain arrangement tends to be loose, the force between the molecular chains is small, the adjacent molecular chains are easy to be opened, and the chain segment movement is realized by intermolecular internal rotation, forming a molecular chain structure with high flexibility. And the fluorinated polymer and the electrolyte in the battery monomer can form a gel electrolyte, further improving the cycle performance of the battery monomer.

[0123] Exemplarily, the crystallinity X c1 of the fluorinated polymer measured by differential scanning calorimetry can be 20%, 21%, 22%, 23%, 24%, 25%, or any value within the range consisting of any two of the above values.

[0124] Exemplarily, the melting temperature T m1 of the fluorinated polymer can be 20℃, 50℃, 70℃, 90℃, 100℃, 120℃, 140℃, or any value within the range consisting of any two of the above values.

[0125] Exemplarily, the cold crystallinity X c2 of the fluorinated polymer measured by differential scanning calorimetry can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, or any value within the range consisting of any two of the above values.

[0126] Exemplarily, the cold crystallization temperature Tc2 of the fluorinated polymer can be 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, or any value within the range consisting of any two of the above values.

[0127] In some embodiments, the glass transition temperature of the fluorinated polymer is T g1 , which is in ℃, -150≤T g1 ≤60.

[0128] The glass transition temperature is the transition temperature of the segment of the polymer from freezing to motion, and the glass transition temperature has a certain influence on the flexibility of the polymer molecular chain. The lower the glass transition temperature, the better the flexibility of the polymer molecular chain at room temperature. The higher the glass transition temperature, the worse the flexibility of the molecular chain at room temperature. The glass transition temperature can be measured by differential scanning calorimetry (DSC). The glass transition temperature of the polymer is relatively low, the flexibility of the segment of the molecular chain is better, and the adjacent molecular chains are more easily opened. For example, the glass transition temperature of the fluorinated polymer can be -150°C, -120°C, -100°C, -80°C, -60°C, -30°C, 0°C, 30°C, 60°C, or any value within the range formed by any two of the above values.

[0129] In some embodiments, the monomers of the fluorinated polymer include hexafluoropropylene (HFP) and vinylidene fluoride (VDF). The design of the two monomers of hexafluoropropylene and vinylidene fluoride can make the fluorinated polymer have a lower crystallinity, which is beneficial to promote the diffusion and infiltration of the electrolyte in the fluorinated polymer, improve the affinity of the fluorinated polymer to the electrolyte, and improve the liquid retention capacity of the gel electrolyte. Alternatively, the molar percentage of hexafluoropropylene is 6% to 13% based on the total molar ratio of hexafluoropropylene and vinylidene fluoride. The molar percentage of hexafluoropropylene in this range can make the fluorinated polymer have a stable structure, while maintaining good affinity to the electrolyte, reducing the risk of the fluorinated polymer being dissolved by the electrolyte, further promoting the retention of the electrolyte in the fluorinated polymer, reducing the risk of the confined electrolyte in the gel electrolyte becoming free electrolyte, and further reducing the risk of liquid leakage of the battery cell. Alternatively, the molar percentage of hexafluoropropylene can be 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, or any value within the range formed by any two of the above values, based on the total molar ratio of hexafluoropropylene and vinylidene fluoride.

[0130] In some embodiments, the fluorinated polymer includes at least one of the structural units represented by formula (AI) to formula (AIII),

[0131] In formula (AI) and formula (AII), R 11 , R 12 , R 13 , and R 14 each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 , and R 14at least one of the R1to R6groups includes a fluorine atom; when substituted, the substituents include one or more of a nitrile group (abbreviated as: -CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom;

[0132] In formula (AIII), R 15 including a single bond, a substituted or unsubstituted C1-C3 alkyl group; when substituted, the substituents include one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; p is a positive integer selected from 1 to 3; each n is independently a positive integer selected from 1000 to 30000.

[0133] In some embodiments, R 11 , R 12 , R 13 , and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C2 alkyl group, or a substituted or unsubstituted C1-C2 alkoxy group; further optionally, R 11 , R 12 , R 13 , and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group.

[0134] In some embodiments, the fluoropolymer includes at least one of a structural unit represented by formula (AI-1) to a structural unit represented by formula (AI-11),

[0135] In some embodiments, the fluoropolymer includes at least one of a structural unit represented by formula (AII-1) to a structural unit represented by formula (AII-5),

[0136] In some embodiments, the fluoropolymer includes at least one of a structural unit represented by formula (AIII-1) to a structural unit represented by formula (AIII-3),

[0137] Exemplarily, the fluoropolymer includes one or more of polytetrafluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroalkoxy polymer PFA, perfluoropolyether PFPE, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE, and perfluoro(1-butene vinyl ether) polymer CYTOP.

[0138] Optionally, the fluorinated polymer comprises one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxy alkoxyethylene (PFA), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE).

[0139] The fluorinated polymer can be derived from one or more of fluorinated cycloethane, fluorinated ethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, and the like. Optionally, the fluorinated polymer can be derived from at least two of fluorinated cycloethane, fluorinated ethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene.

[0140] The fluorinated polymer employs short-chain monomers, which are conducive to polymerization to form linear or short-branched structures, and such structures have low entanglement, which is conducive to improving the flexibility of the molecular chains, and the molecular chains can be fully stretched in the electrolyte, thereby further improving the interface performance of the active material.

[0141] In some embodiments, n is each independently selected from positive integers from 5000 to 20000; and / or the molecular weight of the lyophilic polymer is 2 x 10 5 g / mol to 1.5 x 10 6 g / mol. When the molecular weight of the polymer is within the above range, the polymer can exhibit a certain solubility in the electrolyte, while not being easily completely dissolved and dispersed in the electrolyte, which is conducive to regulating the distribution and dispersion of the polymer on the surface of the active material; and the flexibility between the molecular chains of the polymer can be further improved, and the interaction between the molecular chains is relatively weak, which is conducive to the solvent molecules in the electrolyte opening the molecular chains and being wrapped by the molecular chains, thereby facilitating the active ions to enter the active material through the solvent, and realizing the smooth and rapid migration of the active ions.

[0142] For example, the molecular weight of the polymer can be 2 x 10 5 g / mol, 5 x 10 5 g / mol, 8 x 10 5 g / mol, 1 x 10 6 g / mol, 1.5 x 10 6 g / mol, or any value within a range defined by any two of the above values.

[0143] Ether-based polymers

[0144] The lyophilic polymer includes an ether polymer, wherein the ether polymer is made into a sheet structure; the sheet structure is tested by a dynamic frequency scanning test at (T m2 +20) ℃ to obtain an elastic modulus G'-dissipation modulus G" curve, a slope of the elastic modulus G'-dissipation modulus G" curve is K1,1 < K1 < ∞, and T m2 +20) ℃ represents a melting temperature of the ether polymer.

[0145] Specifically, the preparation process of the sheet structure is as follows: the ether polymer is vacuum dried at 80 ℃ for 12 h. The dried ether polymer is hot-pressed into a sheet by a flat curing machine, the hot-pressing temperature is set to (T m2 +20) ℃, the calendering thickness is 1 mm to 2 mm, the calendering time is 2 min, and the pressure is 8 MPa. After 2 min of calendering, the sample is taken out and cold-pressed on another curing machine of the same type, and the cold-pressing pressure is 10 MPa. A circular mold with a diameter of 25 mm is used to obtain a polymer disc with a fixed size, and the polymer disc is a sheet structure. Exemplarily, the sheet structure can be a disc with a thickness of 1 mm to 2 mm and a diameter of 25 mm; or the sample can be prepared according to the sample standard required by the test equipment.

[0146] According to the conclusion of classical linear viscoelasticity, for polymers, especially linear polymers, the elastic modulus G'-dissipation modulus G" in the terminal region of the elastic modulus G'-dissipation modulus G" curve is frequency-dependent, and the longest chain of the polymer plays a role in the viscoelastic behavior. The terminal region of the elastic modulus G'-dissipation modulus G" curve represents the interval range approaching the maximum angular velocity.

[0147] The specific steps of the dynamic frequency scanning test are as follows: the dynamic frequency scanning test is performed by using a TA-AR2000EX rotary rheometer, the parallel plate diameter is 25 mm, and the thickness is 0.9 mm. To ensure that the test is in the linear point elastic region, the strain during the dynamic frequency scanning test is 2%, the test temperature is (T m2 +20) ℃, and the frequency scanning range for testing is 500 rad / s≤w2≤0.05 rad / s, so as to obtain data in the lowest frequency range as possible.

[0148] The dynamic frequency scanning test can characterize the solid phase melting, that is, the entanglement degree of the molecular chain in the melt state. Compared with linear structures or short branched chain structures, long branched structures, network structures and low crosslinking structures have high entanglement degrees and will exhibit deviated linear terminal behavior, and the ether polymer exhibits solid phase behavior. When the ether polymer of the present application meets the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether polymer still maintains a certain molecular chain entanglement state, which can form a gel electrolyte with the electrolyte, and further improve the cycle performance of the battery monomer.

[0149] In some embodiments, 1 < K1≤ 100; optionally, 1 < K1≤ 10. Exemplarily, K1may be 1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or any value within a range between any two of the above-mentioned values.

[0150] In some embodiments, the glass transition temperature of the ether-based polymer is T g2 in ℃, -100≤ T g2 ≤ 50; optionally, -80≤ T g2 ≤ 30. Exemplarily, the glass transition temperature T g2 of the ether-based polymer can be -100℃, -80℃, -60℃, -30℃, 0℃, 30℃, 50℃, or any value within a range between any two of the above-mentioned values.

[0151] In some embodiments, the ether-based polymer comprises a structural unit represented by formula (BI),

[0152] In formula (BI), R 21 and R 22 each independently comprise a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R 23 comprises a substituted or unsubstituted C1-C5 alkylene group. Optionally, R 21 and R 22 each independently comprise a hydrogen atom, a substituted or unsubstituted C1-C2 alkyl group; and / or R 23 comprises a single bond, a substituted or unsubstituted C1-C4 methylene group.

[0153] In some embodiments, when substituted, the substituent group can comprise one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom.

[0154] Exemplarily, the ether-based polymer comprises at least one of a structural unit represented by formula (BI-1) to a structural unit represented by formula (BI-8),

[0155] In some embodiments, the ether-based polymer comprises a structural unit represented by formula (BII),

[0156] In formula (BII), R 24 to R 27 each independently comprise a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group, or an ether group, and R 24 to R27 at least one of R1to R4comprises a substituted or unsubstituted C1-C3alkyl group or ether group.

[0157] Optionally, R 24 to R 27 each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C2alkyl group, a substituted or unsubstituted C1-C2alkoxy group or ether group, and R 24 to R 27 at least one of R1to R4comprises a substituted or unsubstituted C1-C2alkyl group or ether group.

[0158] In some embodiments, the ether-based polymer comprises at least one of a structural unit represented by formula (BII-1) to a structural unit represented by formula (BII-7),

[0159] The monomer used in the above-mentioned ether-based polymer is a multi-ring structure such as a six-membered ring or less, or a short-chain monomer, which is beneficial to polymerization to form a high content of -O- structure, and this type of structure has a low degree of entanglement, which is beneficial to improving the flexibility of the molecular chain, and the molecular chain can be fully stretched in the electrolyte, easily forming a gel-like substance with the electrolyte, and further improving the cycle performance and storage performance of the battery cell.

[0160] The above-mentioned polymer is only an example of the structural group of the main molecular chain, and in the embodiments of the present application, the polymer can also be obtained by copolymerization of the above-mentioned structural group and other types of structural groups. Other types of structural groups may, for example, be olefin-based structural units, acrylonitrile-based structural units, etc.

[0161] When the above-mentioned group is substituted, the substituent group may, for example, comprise one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, and a halogen atom. The above-mentioned substituent group is a high-pressure resistant substituent group, which is more beneficial to stabilizing the structure of the polymer. The halogen atom may, for example, comprise a fluorine atom, a chlorine atom, a bromine atom, etc.

[0162] In some embodiments, n is each independently selected from a positive integer from 1500 to 25000.

[0163] Optionally, n is each independently selected from a positive integer from 3000 to 18000.

[0164] In some embodiments, the molecular weight of the polymer is 1.2 x 10 5 g / mol to 1.0 x 10 6 g / mol.

[0165] For example, the molecular weight of the polymer may, for example, be 1.2 x 10 5 g / mol, 2 x 10 5 g / mol, 5 x 10 5g / mol, 8x10 5 g / mol, 1x10 6 g / mol, or any value within a range defined by any two of the above values.

[0166] Ester polymer

[0167] In some embodiments, the lyotropic polymer comprises an ester polymer, wherein the ester polymer is made into a sheet structure; the sheet structure is subjected to a dynamic frequency sweep test at (T m3 +20) °C to obtain an elastic modulus G'-dissipation modulus G" curve, a slope of the elastic modulus G'-dissipation modulus G" curve is K2, 1 < K2 < ∞, T m3 °C represents a melting temperature of the ester polymer.

[0168] When the ester polymer of the present application satisfies the above range, the molecular chain entanglement state can be further reduced, which is beneficial to the diffusion of solvent molecules in the electrolyte between the molecular chains; and the ether polymer still maintains a certain molecular chain entanglement state, which can form a gel state substance with the electrolyte, further improving the cycle performance and storage performance of the battery cell.

[0169] In some embodiments, 1 < K2≤ 100; further optionally, 1 < K2≤ 10.

[0170] Exemplarily, K2may be 1.01, 1.1, 1.2, 1.5, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or any value within a range defined by any two of the above values.

[0171] In some embodiments, the glass transition temperature of the ester polymer is T g3 , in units of °C, -100≤ T g3 ≤ 50; optionally, -80≤ T g3 ≤ 30.

[0172] Exemplarily, the glass transition temperature of the ester polymer can be -100 °C, -90 °C, -80 °C, -60 °C, -30 °C, 0 °C, 30 °C, 50 °C, or any value within a range defined by any two of the above values.

[0173] In some embodiments, the ester polymer comprises a structural unit represented by formula (CI).

[0174] In formula (CI), R 31 , R 32 , and R 33 each independently comprise a hydrogen atom, or a substituted or unsubstituted C1-C8 alkyl group; R34 including substituted or unsubstituted C1-C8 alkyl, or substituted or unsubstituted C1-C8 hydroxyalkyl; optionally, R 34 including substituted or unsubstituted C1-C6 alkyl, or substituted or unsubstituted C1-C6 hydroxyalkyl.

[0175] including substituted or unsubstituted C1-C4 alkyl, or substituted or unsubstituted C1-C4 hydroxyalkyl. 31 including hydrogen atom, or substituted or unsubstituted methyl; R 32 and R 33 each independently including hydrogen atom; R 34 including substituted or unsubstituted C1-C4 alkyl, or substituted or unsubstituted C1-C4 hydroxyalkyl.

[0176] Exemplarily, the ester-based polymer includes at least one of structural units shown in formula (CI-1) to formula (CI-15).

[0177] In some embodiments, the ester-based polymer includes a structural unit shown in formula (CII).

[0178] In formula (CII), R 35 including substituted or unsubstituted C2-C6 methylene; optionally, R 35 each independently including substituted or unsubstituted C2-C4 methylene.

[0179] Exemplarily, the ester-based polymer includes at least one of structural units shown in formula (CII-1) to formula (CII-5).

[0180] The ester-based polymer described above has a low degree of entanglement of molecular chains, which is beneficial to improve the flexibility of the molecular chains, and the molecular chains can be fully stretched in the electrolyte and easily form a gel electrolyte with the electrolyte.

[0181] The polymer described above is only an example of the structural group of the main molecular chain, and in the embodiments of the present application, the polymer can also be the structural group described above and other types of structural groups. Other types of structural groups are, for example, olefin-based structural units, acrylonitrile-based structural units, maleic anhydride, and other types of monomers with functional groups.

[0182] When the above-mentioned groups are substituted, the substituents can include one or more of a nitrile group, a nitro group, a sulfonyl group, a carboxyl group, an ester group, a chlorine atom, a fluorine atom, and a bromine atom. The above-mentioned substituents are high-pressure resistant substituents, which are more beneficial to stabilize the structure of the polymer.

[0183] In some embodiments, n is each independently selected from positive integers from 800 to 20,000.

[0184] Optionally, each n is independently selected from positive integers from 1000 to 15000.

[0185] In some embodiments, the molecular weight of the polymer is from 1.2 x 10 5 g / mol to 1.0 x 10 6 g / mol.

[0186] Illustratively, the molecular weight of the polymer can be 1.2 x 10 5 g / mol, 2 x 10 5 g / mol, 5 x 10 5 g / mol, 8 x 10 5 g / mol, 1 x 10 6 g / mol, 1.5 x 10 6 g / mol, or any value within a range defined by any two of the above values.

[0187] Aldehyde-ketone polymer

[0188] In some embodiments, the lyophilic polymer comprises an aldehyde-ketone polymer, wherein the aldehyde-ketone polymer is made into a sheet-like structure; the sheet-like structure has a dynamic frequency scanning test at (T m4 + 20) °C to obtain an elastic modulus G' - energy dissipation modulus G" curve, the slope of the elastic modulus G' - energy dissipation modulus G" curve is K3, 0.8 ≤ K3 < ∞, T m4 °C represents the melting temperature of the aldehyde-ketone polymer.

[0189] In some embodiments, 0.8 ≤ K3 ≤ 100; optionally, 0.8 ≤ K3 ≤ 10.

[0190] Illustratively, K3 can be 0.8, 0.9, 1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or any value within a range defined by any two of the above values.

[0191] In some embodiments, the glass transition temperature of the aldehyde-ketone polymer is T g4 , in unit of °C, -100 ≤ T g4 ≤ 50; optionally, -80 ≤ T g4 ≤ 30.

[0192] Illustratively, the glass transition temperature of the aldehyde-ketone polymer can be -100 °C, -90 °C, -80 °C, -60 °C, -30 °C, 0 °C, 30 °C, 50 °C, or any value within a range defined by any two of the above values.

[0193] In some embodiments, the aldehyde ketone polymer includes a structural unit represented by Formula (DI) and / or a structural unit represented by Formula (DII),

[0194] In Formula (DI), R 41 includes a single bond, a substituted or unsubstituted C1-C6 methylene group; R 42 includes a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group.

[0195] Optionally, R 41 includes a single bond, a substituted or unsubstituted C1-C2 methylene group.

[0196] Optionally, R 42 includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0197] In the embodiments of the present application, a single bond indicates that the group is absent, and the atoms on both sides of the group are connected by a single bond, for example, R 41 is a single bond, indicating that the carbon atoms on both sides of R 41 are connected by a single bond.

[0198] Illustratively, the aldehyde ketone polymer includes at least one of a structural unit represented by Formula (DI-1) to a structural unit represented by Formula (DI-6).

[0199] In some embodiments, the aldehyde ketone polymer includes a structural unit represented by Formula (DII).

[0200] In Formula (DII), R 43 to R 46 each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s each independently are an integer selected from 0 to 5, and at least one of r and s is a positive integer. Optionally, R 43 to R 46 each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s each independently are an integer selected from 0 to 5, and at least one of r and s is a positive integer. Optionally, R

[0201] In some embodiments, the aldehyde ketone polymer includes at least one of a structural unit represented by Formula (DII-1) to a structural unit represented by Formula (DII-4).

[0202] The aldehyde-ketone polymer has a low degree of entanglement of molecular chains, which is beneficial to improve the flexibility of the molecular chains, and the molecular chains can be fully stretched in the electrolyte, which is beneficial to form a gel electrolyte with the electrolyte.

[0203] The above polymer is only an example of the structural group of the main molecular chain, and in the embodiments of the present application, the polymer can also be obtained by copolymerization of the above structural group and other types of structural groups. The other types of structural groups are, for example, olefin structural units, enol structural units, acrylonitrile structural units, etc.

[0204] When the above group is substituted, the substituent group can include one or more of a nitrile group, a nitro group, a sulfonyl group, a carboxyl group, an ester group, a chlorine atom, a fluorine atom, and a bromine atom. The above substituent group is a high-pressure resistant substituent group, which is more beneficial to stabilize the structure of the polymer.

[0205] In some embodiments, n is each independently selected from a positive integer from 500 to 15000.

[0206] Alternatively, n is each independently selected from a positive integer from 500 to 10000.

[0207] In some embodiments, the molecular weight of the lyophilic polymer is 1.2 x 10 5 g / mol to 1 x 10 6 g / mol.

[0208] For example, the molecular weight of the lyophilic polymer can be about 1.2 x 10 5 g / mol, about 2 x 10 5 g / mol, about 5 x 10 5 g / mol, about 8 x 10 5 g / mol, about 1 x 10 6 g / mol, or any value within a range consisting of any two of the above values.

[0209] The embodiments of the present application can further improve the cycle performance of the battery cell when the lyophilic polymer also satisfies one or more of the following conditions.

[0210] In some embodiments, the lyophilic polymer is added into the first solvent to form a polymer system at 70°C; the lyophilic polymer system is left to stand at 70°C for 8h, and left to stand at 25°C for ≥24h, after the two-stage standing treatment, part of the lyophilic polymer system is converted into a gel state substance through swelling and adsorption, and then the polymer system is filtered through a 200-mesh filter screen to obtain the first substance. The mass of the lyophilic polymer is n, and the unit is g; the mass of the first substance is m, and the unit is g; the polymer and the first substance satisfy: 5≤m / n≤1000; optionally, 10≤m / n≤1000; further optionally, 10≤m / n≤50. Exemplarily, m / n can be 5, 10, 20, 25, 28, 30, 32, 35, 40, 50, 80, 100, 200, 500, 1000 or any value within the range formed by any two of the above values.

[0211] Exemplarily, the ratio of the mass content of the lyophilic polymer to the mass content of the first solvent ranges from 1:100 to 1:10, for example, 3:50, based on the mass of the polymer system.

[0212] Exemplarily, the first solvent is the same as or similar to the solvent of the electrolyte, and the first solvent can include a carbonate solvent. For example, the carbonate solvent includes a cyclic carbonate solvent and / or a linear carbonate solvent.

[0213] As an example of the cyclic carbonate solvent, the cyclic carbonate solvent includes one or more of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinyl ethylene carbonate VEC and dioctyl carbonate CC.

[0214] As an example of the linear carbonate solvent, the linear carbonate solvent includes one or more of dimethyl carbonate DMC, diethyl carbonate DEC, ethyl methyl carbonate EMC, diphenyl carbonate DPC, methyl allyl carbonate MAC and polycarbonate VA.

[0215] Optionally, the first solvent can also contain lithium salt and electrolyte additives, such as lithium hexafluorophosphate, vinylene carbonate VC, fluoroethylene carbonate FEC, etc.

[0216] In this application, m / n is also referred to as the precipitation value, which characterizes the ability of the lyophilic polymer and the solvent to be converted into a gel state substance.

[0217] The first substance mainly includes the gel state substance formed by the lyophilic polymer and the first solvent, and in such a gel state substance, the molecular structure of the polymer does not change substantially.

[0218] In some embodiments, the first substance is dried at 80℃ for 12h to remove the first solvent in the first substance, and the dried first substance is detected by infrared spectrophotometry IR or nuclear magnetic resonance NMR test, and the main component of the first substance after drying is the lyophilic polymer as described above.

[0219] In the present application, the lyophilic polymer in the battery monomer can be obtained by discharging the battery monomer to 0% SOC, and then separately taking the positive electrode sheet, the negative electrode sheet and the separator. Taking the negative electrode sheet as an example: taking a negative electrode sheet with a mass of m1, washing it with a small amount of water to obtain a negative electrode powder, adding sufficient DMC solvent after drying at 80℃ for 4h, fully stirring to make the powder fully contact with the solvent, soaking at 60℃ for 24h, and then removing the solvent from the upper clear liquid by rotary evaporation to obtain a polymer film, and then obtaining the lyophilic polymer by washing, separating and other operations. The lyophilic polymer in the positive electrode sheet and the separator can be obtained in a similar manner.

[0220] The related parameters of the lyophilic polymer of the present application can be detected by the following method: the group of the lyophilic polymer of the present application can be detected by infrared spectrophotometry IR, specifically, the lyophilic polymer is tested by Thermo Nicolet Nexus 670 attenuated total reflection Fourier transform infrared spectrometer (abbreviated as: FTIR-ATR), and then tested according to the standard GB / T6040-2002, the test range is: ATR method 600cm -1 ~4000cm -1 ; repeatability: ±2cm -1 ; resolution: better than 4cm -1 ; transmission depth 0.2μm-0.6μm.

[0221] The structure of the lyophilic polymer of the present application can be tested by nuclear magnetic resonance NMR, specifically, 1H NMR and 13C NMR are tested on Varian Mercury Plus-400 nuclear magnetic resonance instrument, the test temperature is 20℃, TMS is internal standard, CDCl3 is used as solvent, and the proton resonance frequency is 400MHz.

[0222] The type of polymer monomer of the lyophilic polymer of the present application can be tested by pyrolysis-gas chromatography-mass spectrometry. The specific test steps are as follows: accurately take 0.5mg sample into the sample cup, fix it on the sample rod, and then put it into the pyrolyzer installed near the gas chromatography (abbreviated as: GC) sample inlet, after the pyrolyzer temperature reaches the set temperature, press the sample button, the sample cup falls into the pyrolysis furnace core by free fall, the volatile components are gasified instantly in the inert gas N2 atmosphere, and then carried into the gas chromatography column for separation, finally detected by flame ionization detector FID or mass spectrometer MS, so as to obtain the gas chromatogram or total ion current chromatogram.

[0223] The molecular weight of the lyotropic polymer of the embodiments of the present application is in the meaning known in the art and can be determined using devices and methods commonly used in the art, and can be tested using gel permeation chromatography (GPC). The specific testing procedure is as follows: an appropriate amount of the sample to be tested is taken, the sample concentration is ensured to be 8%-12% optical density, 20 ml of deionized water is added, and the sample is completely dispersed under ultrasonic treatment at 53 KHz / 120 W for 5 min. Then, the sample is determined according to the GB / T19077-2016 / ISO13320:2009 standard.

[0224] Alternatively, the sample is tested using a multi-angle laser light scattering instrument (MALLS). Specifically, a GPC instrument is used in combination with a Dawn Heleos II multi-angle laser light scattering device, an Optilab T-rEX refractive index detector, and a Visco Star II viscometer. The testing is performed at 30°C, tetrahydrofuran is used as the mobile phase, the flow rate is 1.0 ml / min, and the SEC-SAMLL data is processed using a commercial software ASTRA6 to obtain the molecular weight parameters.

[0225] In some embodiments, the lithium ion transference number of the gel electrolyte is ≥0.4. The gel electrolyte has a large lithium ion transference number, which can promote the movement of lithium ions and make the intercalation and deintercalation of lithium ions easier, thereby further improving the cycle performance of the battery cell. Optionally, the lithium ion transference number of the gel electrolyte is 0.4, 0.5, 0.7, 0.8, 0.9, 1, etc.

[0226] The lithium ion transference number can be measured by using a constant potential polarization method. Specifically, a Li / electrolyte / Li symmetric battery structure is assembled. A small and constant potential difference AV is applied to the measured symmetric battery, and the change of current with time is recorded. The lithium ion transference number calculation formula is as follows: wherein, t + is the lithium ion transference number, AV is the applied potential difference, I0 is the initial current, R0 is the interface impedance of the electrode and electrolyte before polarization, I ss is the steady-state current, and R ss is the interface impedance of the electrode and electrolyte after polarization.

[0227] In some embodiments, the limiting electrolyte includes a solvent and an electrolyte salt. Optionally, the solvent includes at least one of a cyclic carbonate, a chain carbonate, a carboxylic acid ester, a fluorinated carbonate, and a sulfite. The cyclic carbonate includes one or more of ethylene carbonate (abbreviated as: EC) and propylene carbonate (abbreviated as: PC). The chain carbonate includes one or more of dimethyl carbonate (abbreviated as: DMC), diethyl carbonate (abbreviated as: DEC), and methyl ethyl carbonate (abbreviated as: EMC).

[0228] The electrolyte salt includes a lithium salt. The lithium salt includes at least one of LiPF6, LiBF4, LiBOB, LiFSI, LiTFSI, Li2DFB, and LiODFB.

[0229] In some embodiments, the free electrolyte includes a solvent and an electrolyte salt. Optionally, the solvent includes at least one of a cyclic carbonate, a chain carbonate, a carboxylate, a fluorinated carbonate, and a sulfite. The cyclic carbonate includes one or more of ethylene carbonate (abbreviated as: EC) and propylene carbonate (abbreviated as: PC). The chain carbonate includes one or more of dimethyl carbonate (abbreviated as: DMC), diethyl carbonate (abbreviated as: DEC), and ethylmethyl carbonate (abbreviated as: EMC).

[0230] The electrolyte salt includes a lithium salt. The lithium salt includes at least one of LiPF6, LiBF4, LiBOB, LiFSI, LiTFSI, Li2DFB, and LiODFB.

[0231] Optionally, the limited electrolyte and the free electrolyte are the same.

[0232] The application also has an embodiment to provide a battery. The battery includes a battery cell.

[0233] The application also has an embodiment to provide an electric device. The electric device includes a battery.

[0234] The battery cell, the battery, and the electric device of the application are described below with appropriate reference to the accompanying drawings.

[0235] The positive electrode tab

[0236] The positive electrode tab includes a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector, the positive electrode active layer including a positive electrode active material.

[0237] As a non-limiting example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode active layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0238] In some embodiments, the cathode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material base material. Non-limiting examples of the metal material in the cathode current collector can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, and the like. Non-limiting examples of the polymer material base material in the cathode current collector can include one or more of a polypropylene (PP), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polystyrene (PS), a polyethylene (PE), and the like.

[0239] In some embodiments, in addition to the above-described lithium-containing phosphate and lithium nickel manganese cobalt oxide, the cathode active material can further include a cathode active material for a battery known in the art. As non-limiting examples, the cathode active material for a battery known in the art includes, but is not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof, and the like. Non-limiting examples of the lithium cobalt oxide can include LiCoO2; non-limiting examples of the lithium nickel oxide can include LiNiO2; non-limiting examples of the lithium manganese oxide can include LiMnO2, LiMn2O4, and the like; non-limiting examples of the lithium nickel cobalt aluminum oxide can include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0240] In some of the embodiments, the cathode active layer can further optionally include a binder. As non-limiting examples, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0241] In some of the embodiments, the cathode active layer can further optionally include a conductive agent. As non-limiting examples, the conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0242] In some embodiments, the positive electrode sheet can be prepared by dispersing the components described above for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector; and subjecting the positive electrode current collector to drying, cold pressing, or the like to obtain the positive electrode sheet. The solvent can be selected from, but is not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP for short). The positive electrode slurry can be coated on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The positive electrode slurry can be coated on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s.

[0243] The negative electrode sheet

[0244] The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector, the negative electrode active layer including a negative electrode active material.

[0245] As a non-limiting example, the negative electrode current collector has two surfaces opposite in the thickness direction of the negative electrode current collector, and the negative electrode active layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0246] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material base layer. Non-limiting examples of the metal material in the negative electrode current collector can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, and the like. Non-limiting examples of the polymer material base layer in the negative electrode current collector can include one or more of polypropylene (PP for short), polyethylene terephthalate (PET for short), polybutylene terephthalate (PBT for short), polystyrene (PS for short), polyethylene (PE for short), and the like.

[0247] In some embodiments, the negative active material can further include a negative active material known in the art for use in a battery. As a non-limiting example, the negative active material can include one or more of: other carbon-based materials other than the above-mentioned graphite, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as negative active materials for batteries can also be used. These negative active materials can be used alone or in combination with two or more.

[0248] In some embodiments, the negative active layer can further optionally include a binder. The binder can include one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0249] In some embodiments, the negative active layer can further optionally include a conductive agent. The conductive agent can include one or more of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0250] In some embodiments, the negative active layer can further optionally include other auxiliary agents, such as thickening agents, etc. The thickening agent can be sodium carboxymethyl cellulose (CMC-Na).

[0251] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent, such as deionized water, to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative electrode current collector; and drying, cold-pressing, etc., to obtain the negative electrode sheet. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s to 10000mPa·s.

[0252] Electrolyte

[0253] The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. The electrolyte can be in a liquid state, a gel state, or a full solid state.

[0254] In some embodiments, the limiting electrolyte and the free electrolyte of the present application include an electrolyte salt and a solvent.

[0255] In some embodiments, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro(bisoxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0256] In some embodiments, the solvent can include one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0257] In some embodiments, the electrolyte can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0258] In some embodiments, the additive in the electrolyte can include, but is not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0259] Separator film

[0260] In some embodiments, the separator film can be any known porous structure separator film having good chemical stability and mechanical stability.

[0261] In some embodiments, the material of the separator film can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0262] In some embodiments, the thickness of the separator film can be 6 μm to 40 μm, and can be 12 μm to 20 μm.

[0263] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator film can be used to form an electrode assembly through a winding process or a stacking process.

[0264] In some embodiments, the housing of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The housing of the battery cell can also be a soft pack, such as a pouch soft pack. The material of the soft pack can be plastic, and further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

[0265] The battery includes at least one battery cell. The battery can include one or more battery cells.

[0266] The shape of the battery cell is not particularly limited, and can be cylindrical, square, or any other shape. For example, FIG. 1 is a battery cell 1 in a square structure as an example.

[0267] In some embodiments, referring to FIG. 2, the outer package can include a housing 11 and a cover plate 13. The housing 11 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing 11 has an opening in communication with the receiving cavity, and the cover plate 13 can be arranged on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be used to form an electrode assembly 12 through a winding process or a stacking process. The electrode assembly 12 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 12. The number of the electrode assembly 12 included in the battery cell 1 can be one or more, and a person skilled in the art can select the appropriate number according to the actual needs.

[0268] The battery can be a battery module or a battery pack.

[0269] The battery module includes at least one battery cell. The number of the battery cells included in the battery module can be one or more, and a person skilled in the art can select the appropriate number according to the application and capacity of the battery module.

[0270] In the battery module, the plurality of battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells can be fixed by fasteners.

[0271] Optionally, the battery module can further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0272] In some embodiments, the battery module described above can be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the number can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0273] The battery pack can include a battery box and a plurality of battery modules arranged in the battery box. The battery box includes an upper box body and a lower box body, and the upper box body can be arranged on the lower box body to form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the battery box in any manner.

[0274] In addition, the application also provides a power utilization device, which includes the battery provided by the application. The battery can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device can be a mobile phone, a notebook computer, etc.; the electric vehicle can be 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., but is not limited thereto.

[0275] As the power utilization device, the battery can be selected according to the use requirement thereof.

[0276] FIG. 3 is a power utilization device 2 as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the battery for the power utilization device, a battery pack or a battery module can be used.

[0277] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a battery can be used as a power supply.

[0278] In order to make the technical problems, technical solutions and beneficial effects solved by the application clearer, the application will be further described in detail below in combination with embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the application and its application. Based on the embodiments in the application, all other embodiments obtained by a person skilled in the art without creative labor fall within the scope of protection of the application.

[0279] Unless otherwise specified in the examples, the techniques or conditions described in the literature or according to the product specifications were used. Unless otherwise specified, the reagents or instruments used were conventional products that can be obtained commercially.

[0280] Example 1

[0281] (1) Preparation of the positive electrode sheet

[0282] The positive electrode active material, the conductive agent carbon black, and the binder PVDF were mixed in N-methylpyrrolidone (abbreviated as NMP) at a mass percentage of 98.4%:0.4%:1.2% to prepare a positive electrode slurry. The positive electrode slurry was coated on an aluminum foil with a thickness of 12 pm and dried at 85°C, followed by cold pressing, then edge cutting, sheet cutting, and striping, and then dried at 85°C under vacuum for 4 h to prepare a positive electrode sheet. The density of the positive electrode active layer in the positive electrode sheet was 2.45 g / cm 3 .

[0283] (2) Preparation of the negative electrode sheet

[0284] The lyophilic polymer, graphite, conductive agent carbon black, binder styrene-butadiene rubber (abbreviated as SBR), and thickening agent sodium methyl cellulose (abbreviated as CMC-Na) were mixed in deionized water at a mass percentage of 3%:94%:0.5%:1.5%:1% to prepare a negative electrode slurry. The negative electrode slurry was coated on a copper foil with a thickness of 8 pm and dried at 85°C, followed by cold pressing, then edge cutting, sheet cutting, and striping, and then dried at 120°C under vacuum for 12 h to prepare a negative electrode sheet. The density of the negative electrode active layer in the negative electrode sheet was 1.6 g / cm 3 . In the negative electrode active layer, the lyophilic polymer accounted for 3% of the mass percentage of the negative electrode active layer.

[0285] (3) Separation film

[0286] A polyethylene substrate with a boehmite coating layer with a thickness of 2 pm on the surface was used.

[0287] (4) Preparation of the electrolyte

[0288] In an environment with a water content of less than 10 ppm, non-aqueous organic solvent ethylene carbonate DMC and methyl ethyl carbonate EMC were mixed at a mass ratio of 1:9 to obtain an electrolyte solvent, and then lithium salt LiPF6 and the mixed solvent were mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L, and 1% wt VC and 3% wt FEC additives were added.

[0289] (5) Preparation of the battery cell

[0290] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a separating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in a square aluminum shell, and after drying, an electrolyte is injected, and the battery monomer is obtained after processes such as vacuum packaging, standing, formation, and shaping. The ratio of the free electrolyte in the battery monomer to the rated capacity of the battery monomer is 0.1 g / Ah.

[0291] Examples 2-4

[0292] Compared with Example 1, the difference between Examples 2-4 is that the size of the shell of the battery monomer and the amount of the lyophilic electrolyte are different, as shown in Table 1.

[0293] Example 5

[0294] Compared with Example 1, the difference between Example 5 is that the shell of the battery monomer is a cylindrical shell. The axis of the cylindrical shell is perpendicular to the direction of gravity. The diameter of the circular surface of the cylindrical shell is 46 mm, and the length of the cylindrical shell along its axis is 95 mm.

[0295] Example 6

[0296] Compared with Example 1, the difference between Example 6 is that the monomer composition of the lyophilic polymer is different, as shown in Table 1.

[0297] Examples 7-9

[0298] Compared with Example 1, the difference between Examples 7-9 is that the positive active material is different, and the density of the positive active layer is 3.5 g / cm 3 .

[0299] Comparative Example 1

[0300] Compared with Example 1, the difference between Comparative Example 1 is that the battery monomer does not contain a lyophilic polymer.

[0301] Comparative Example 2

[0302] Compared with Example 5, the difference between Comparative Example 2 is that the battery monomer does not contain a lyophilic polymer.

[0303] Test Example

[0304] (1) The mass energy density of the battery monomer in the examples and comparative examples is tested, and the test method is: the battery monomer is charged at 0.33C constant current to the upper limit voltage, and then charged at constant voltage to the cutoff current 0.05C; then the battery monomer is discharged at 0.33C constant current to the lower limit voltage, and the discharge energy is recorded, the unit of discharge energy is Wh. The mass of the battery monomer is weighed, the unit of the mass of the battery monomer is kg, and the unit mass energy density of the battery monomer is calculated from the discharge energy / mass, the unit is Wh / kg.

[0305] (2) The cycle performance of the battery cells in the examples and comparative examples was tested by the following method: the capacity of the battery cell before cycling was tested; 0.33C charging to 10% SOC, 3C charging to 15% SOC, 2C charging to 20% SOC, 1.5C charging to 15% SOC, 1C charging to 20% SOC, and then 0.33C constant current charging to 100% SOC, upper voltage constant voltage charging to 0.05C; 0.5C discharging to 5% SOC; repeating 1600 cycles, the capacity of the battery after cycling was tested, and the cycle retention rate after cycling was calculated.

[0306] Table 1

[0307] In Table 1, X c2 represents the cold crystallinity of the lyophilic polymer. Tc2 represents the cold crystallization temperature of the lyophilic polymer, in °C. The unit of molecular weight is 104g / mol. a represents the mass percentage of the lyophilic polymer in the positive active layer. b represents the size percentage of the part containing the gel electrolyte in the separator film. The unit of height is mm. The unit of length is mm. The unit of thickness is mm. c represents the ratio of the mass of the free electrolyte in the battery cell to the rated capacity of the battery cell, in g / Ah. The unit of mass energy density is Wh / kg. VDF+HFP(91%:9%) represents the mole percentage of VDF and HFP, respectively, being 91% and 9% based on the total mole ratio of VDF and HFP monomers. VDF+HFP(94%:6%) represents the mole percentage of VDF and HFP, respectively, being 94% and 6% based on the total mole ratio of VDF and HFP monomers. The column of cycle performance, @ represents the cycle number, for example, @1600cls represents 1600 cycles.

[0308] As can be seen from Examples 1-9 and Comparative Examples 1-2, the use of lyophilic polymer in battery cells with larger size and less free electrolyte can effectively improve the cycle performance of the battery cells.

[0309] As can be seen from Examples 1 and 2, the cycle performance of the battery cells can be further improved when the separator film of the battery cell contains lyophilic polymer.

[0310] As can be seen from Examples 1, 7-9, the battery cells can maintain good cycle performance when the positive active material includes lithium nickel manganese cobalt oxide or lithium-containing phosphate.

[0311] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as there is no conflict, any combination of the technical features should be considered within the scope of the present disclosure.

[0312] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

A battery cell includes a housing, an electrode assembly, and a gel electrolyte, the housing has a receiving cavity inside, the electrode assembly is arranged in the receiving cavity; the electrode assembly includes a positive electrode sheet, a separator membrane, and a negative electrode sheet, the separator membrane is arranged between the positive electrode sheet and the negative electrode sheet; the gel electrolyte includes a lyophilic polymer and a limited electrolyte, the limited electrolyte is located inside the lyophilic polymer; at least one of the positive electrode sheet, the separator membrane, and the negative electrode sheet contains the gel electrolyte at least at the top thereof in the direction of gravity; the battery cell satisfies one or more of (1) to (2): (1) the shell is a square shell, a height of the square shell along a direction of gravity is H1, a length of the square shell along a direction perpendicular to the direction of gravity is L1, wherein, H1≥L1, H1≥100 mm; or, The housing is a square housing, the height of the square housing in the direction of gravity is H2, and the length of the square housing perpendicular to the direction of gravity is L2, wherein H2 The housing is a cylindrical housing, the axis of the cylindrical housing is perpendicular to the direction of gravity, the diameter of the cylindrical housing is D, and the length of the cylindrical housing along its axis is L3, wherein D (2) In the battery cell, the ratio of the mass of the free electrolyte to the rated capacity of the battery cell is less than or equal to 0.2 g / Ah. The battery cell of claim 1, wherein In the positive electrode sheet, the size percentage of the part containing the gel electrolyte in the positive electrode sheet is 10% to 100%, optionally 20% to 100%, in the direction of gravity; and / or, The gel electrolyte is uniformly distributed in the part of the positive electrode sheet containing the gel electrolyte. The battery cell according to claim 1 or 2, wherein, The positive electrode sheet includes a positive electrode current collector and a positive electrode active layer on at least one surface of the positive electrode current collector, and the positive electrode active layer includes the gel electrolyte and a positive electrode active material; The gel electrolyte is distributed on the surface of the particles of the positive electrode active material; and / or, The gel electrolyte is distributed at the pores between the particles of the positive electrode active material. The battery cell of claim 3, wherein, In the positive electrode active layer, the mass percentage of the lyophilic polymer in the positive electrode active layer is 0.1% to 2%, optionally 0.1% to 1%. The battery cell according to claim 3 or 4, wherein The positive electrode active material includes one or more of lithium nickel manganese cobalt oxide and lithium-containing phosphate; in the lithium nickel manganese cobalt oxide, the molar percentage of nickel element is 50% to 95%, optionally 80% to 95%, based on the molar percentage of nickel element, manganese element, and cobalt element. The battery cell according to claim 4 or 5, wherein The density of the positive electrode active layer is 2 g / cm 3 ~ 3.8 g / cm 3 ; Optionally, the positive active material includes lithium nickel cobalt manganese oxide, and the density of the positive active layer is 3.5 g / cm 3 ~ 3.8 g / cm 3 ; Optionally, the positive active material includes a lithium-containing phosphate, and the density of the positive active layer is 2 g / cm 3 ~ 3 g / cm 3 . The battery cell according to any one of claims 1 to 6, wherein The mass energy density of the battery cell is 150 Wh / kg to 400 Wh / kg. The battery cell according to any one of claims 1 to 7, wherein In the negative electrode sheet, the size percentage of the part containing the gel electrolyte in the negative electrode sheet is 10% to 100%, optionally 20% to 100%, in the direction of gravity; and / or, The gel electrolyte is uniformly distributed in the part of the negative electrode sheet containing the gel electrolyte. The battery cell according to any one of claims 1 to 8, wherein The negative electrode tab comprises a negative electrode current collector and a negative electrode active layer on at least one surface of the negative electrode current collector, the negative electrode active layer comprising the gel electrolyte and a negative electrode active material; the gel electrolyte is distributed on the surface of the particles of the negative electrode active material; and / or, The gel electrolyte is distributed at the pores between the particles of the negative electrode active material. The battery cell of claim 9, wherein, In the negative electrode active layer, the mass percentage of the lyophilic polymer in the negative electrode active layer is 1% to 5%, optionally 2% to 4%. The battery cell according to claim 9 or 10, wherein The density of the negative active layer is 1 g / cm 3 ~ 2 g / cm 3 , optionally 1.3 g / cm 3 ~ 1.7 g / cm 3 . The battery cell according to any one of claims 1 to 11, wherein In the direction of the gravity, the size percentage of the part containing the gel electrolyte in the separator film is 10% to 100%, optionally 20% to 100%; and / or, The gel electrolyte is uniformly distributed in the part of the separator film containing the gel electrolyte. The battery cell according to any one of claims 1 to 12, wherein The gel electrolyte is distributed at the pores of the separator film. The battery cell according to any one of claims 1 to 13, wherein The separator film comprises a separator film substrate and a coating layer on at least one surface of the separator film substrate, the coating layer containing a particulate filler; Optionally, the particulate filler comprises one or more of boehmite, alumina, silicon dioxide, and magnesium hydroxide; Optionally, the thickness of the coating layer is 0.25 μm to 5 μm; Optionally, the material of the separator film substrate comprises one or more of polyethylene, polypropylene, polyimide, and aramid. The battery cell according to any one of claims 1 to 14, wherein H1≥L1, the liquid injection port of the battery monomer is arranged at the top end of the shell. The battery cell of claim 15, wherein, H1≥120 mm; optionally, 150 mm≤H1≤300 mm. The battery cell according to claim 15 or 16, wherein 100 mm≤L1≤300 mm. The battery cell according to any one of claims 1 to 17, wherein H2<L2, in the direction perpendicular to the gravity, the liquid injection port of the battery monomer is arranged at both ends of the shell. The battery cell of claim 18, wherein, L2≥120 mm; optionally, 220 mm≤L2≤350 mm. The battery cell according to claim 18 or 19, wherein 50 mm≤H2≤150 mm. The battery cell according to any one of claims 1 to 20, wherein The lyophilic polymer comprises a fluorinated polymer; the fluorinated polymer has a crystallinity X measured by differential scanning calorimetry c1 , 15% < X c1 ≤ 25%. The melting temperature of the fluoropolymer is T m1 in °C, 120 < T m1 ≤ 140. The battery cell according to any one of claims 1 to 20, wherein The lyophilic polymer comprises a fluorinated polymer; the fluorinated polymer has a cold crystallization degree X measured by differential scanning calorimetry c2 , 10% < X c2 ≤ 25%. The cold crystallization temperature of the fluoropolymer is Tc2, in °C, 35 < T c2 ≤ 65. The battery cell according to claim 21 or 22, wherein, The monomer of the fluorinated polymer comprises hexafluoropropylene and vinylidene fluoride; Optionally, the mole percentage of the hexafluoropropylene is 6% to 13% based on the total mole ratio of the hexafluoropropylene and the vinylidene fluoride. The battery cell according to any one of claims 21 to 23, wherein The fluoropolymer includes at least one of a structural unit represented by Formula (AI) to a structural unit represented by Formula (AIII), In formula (AI) and formula (AII), R 11 , R 12 , R 13 , and R 14 each independently include a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 , and R 14 at least one of which includes a fluorine atom; when substituted, the substituent includes one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; In formula (AIII), R 15 including a single bond, substituted or unsubstituted C1-C3 alkyl; when substituted, the substituent includes one or more of a nitrile group, a nitro group, a sulfonic acid group, a sulfonyl group, an amide, a carboxyl group, an ester group, a halogen atom; p is a positive integer selected from 1 to 3; n is each independently a positive integer selected from 1000 to 30000. The battery cell according to any one of claims 1 to 24, wherein The lyotropic polymer has a molecular weight of 1.2 x 10 5 g / mol to 1 x 10 6 g / mol. The battery cell according to any one of claims 1 to 25, wherein The lithium ion transference number of the gel electrolyte is ≥0.

4. A battery comprising the battery monomer of any one of claims 1 to 26. An electric device comprising the battery of claim 27.

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