Battery cell and manufacturing method therefor, battery, and electric device

Abstract

The present application discloses a battery cell and a manufacturing method therefor, a battery, and an electric device. The battery cell comprises a negative electrode sheet. The negative electrode sheet comprises a negative electrode current collector and a lithium metal layer arranged on at least one surface of the negative electrode current collector. The surface of the lithium metal layer is provided with a plurality of pits. The average size of the pits is 20 μm to 160 μm, and the number density of the pits is 208 / mm2 to 320 / mm2. The battery cell has a long cycle life.

Description

Battery cell, method for manufacturing the same, battery, and electric device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese Patent Application No. 202410888152.3, filed on July 3, 2024, entitled “Battery cell, method for manufacturing the same, battery, and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to a battery cell, a method for manufacturing the same, a battery, and an electric device. BACKGROUND

[0004] Lithium metal battery cells have higher energy density than lithium ion battery cells. However, due to the use of highly active lithium metal in lithium metal battery cells, and due to problems such as volume expansion, uneven deposition, and the like during lithium metal stripping and deposition, the cycle life of lithium metal battery cells is poor. SUMMARY

[0005] The present application provides a battery cell, a method for manufacturing the same, a battery, and an electric device, the battery cell having a long cycle life.

[0006] In a first aspect, the present application provides a battery cell, the battery cell comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a lithium metal layer disposed on at least one surface of the negative electrode current collector, the surface of the lithium metal layer having a plurality of pits, the average size of the pits being 20 μm-160 μm, the number density of the pits being 208 pits / mm 2 to 320 pits / mm 2 .

[0007] The average size of the pits on the surface of the lithium metal layer of the negative electrode sheet is 20 μm-160 μm, and the number density of the pits is 208 pits / mm 2 to 320 pits / mm 2 These pits expose fresh lithium metal, which can serve as preferential nucleation sites for subsequent lithium metal deposition. During subsequent charging, lithium metal will preferentially deposit at these nucleation sites, and can induce uniform and dense deposition of subsequent lithium metal, thereby reducing the formation of dead lithium, lithium dendrites, and the like, and also forming a lithium metal deposition morphology with a smaller specific surface area, reducing the consumption of electrolyte, and also reducing impedance and polarization. Therefore, the battery cell provided in the embodiments of the present application can have a long cycle life.

[0008] In some embodiments, the average size of the pits is 20 μm-45 μm. The average size of the pits in the above range can further improve the cycle life of the battery cell.

[0009] In some embodiments, the number density of the pits is 280 pits / mm 2 to 320 pits / mm 2 The number density of the pits in the above range can further improve the cycle life of the battery cell.

[0010] In some embodiments, the number ratio of pits with a maximum lateral dimension less than 50 pm is greater than or equal to 14%, and the number ratio of pits with a maximum lateral dimension greater than 100 pm is greater than 0 and less than or equal to 55%, based on the number of all pits. Alternatively, the number ratio of pits with a maximum lateral dimension less than 50 pm is greater than or equal to 48%, and the number ratio of pits with a maximum lateral dimension greater than 100 pm is greater than 0 and less than or equal to 18%, based on the number of all pits. The high number ratio of pits with a maximum lateral dimension less than 50 pm and the low number ratio of pits with a maximum lateral dimension greater than 100 pm can provide more preferential nucleation sites for the negative electrode tab, thereby further reducing the consumption of electrolyte and further improving the cycle life of the battery cell.

[0011] In some embodiments, the number density of pits with a maximum lateral dimension less than 50 pm is 30 pits / mm 2 to 202 pits / mm 2 The number density of pits with a maximum lateral dimension between 50 pm and 100 pm is 60 pits / mm 2 to 105 pits / mm 2 The number density of pits with a maximum lateral dimension greater than 100 pm is 14 pits / mm 2 to 114 pits / mm 2 Alternatively, the number density of pits with a maximum lateral dimension less than 50 pm is 130 pits / mm 2 to 202 pits / mm 2 The number density of pits with a maximum lateral dimension between 50 pm and 100 pm is 88 pits / mm 2 to 105 pits / mm 2 The number density of pits with a maximum lateral dimension greater than 100 pm is 14 pits / mm 2 to 50 pits / mm 2 The number density of pits with different sizes in the above range can further reduce the consumption of electrolyte and further improve the cycle life of the battery cell.

[0012] In some embodiments, the depth of the pits is greater than 10% of the thickness of the lithium metal layer and less than the thickness of the lithium metal layer.

[0013] In some embodiments, the sum of the areas of the plurality of pits is 20%-50% of the area of the lithium metal layer.

[0014] In some embodiments, the battery cell comprises a positive electrode tab, the positive electrode tab comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises one or more of lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds.

[0015] In some embodiments, the battery cell comprises an electrolyte, the concentration of the electrolyte is 1 mol / L-6 mol / L.

[0016] In a second aspect, the present application provides a preparation method of a battery cell, comprising the following steps: assembling a lithium-poor positive electrode tab and a negative electrode tab to obtain a battery cell, the negative electrode tab comprises a negative electrode current collector and a lithium metal layer disposed on at least one surface of the negative electrode current collector; performing pulse discharge on the battery cell to obtain a battery cell, a plurality of pits are formed on the surface of the lithium metal layer after the pulse discharge, the average size of the pits is 20 μm-160 μm, and the number density of the pits is 208 pits / mm 2 320 pits / mm 2 .

[0017] Performing pulse discharge on the battery cell assembled by the lithium-poor positive electrode tab and the negative electrode tab can cause the lithium metal on the surface of the negative electrode tab to peel off, thereby forming a plurality of pits on the surface of the lithium metal layer of the negative electrode tab in situ, and releasing part of the capacity of the lithium of the negative electrode into the lithium-poor positive electrode. Using the lithium-poor positive electrode tab to assemble the battery cell can also reduce the damage of the initial pulse discharge to the positive electrode active material. In addition, the preparation method of the battery cell provided in the embodiments of the present application is simple to operate and low in production cost.

[0018] In some embodiments, the initial current of the pulse discharge is less than or equal to 3C, and the cutoff current of the pulse discharge is 0.05C-0.50C. Alternatively, the initial current of the pulse discharge is less than or equal to 1C, and the cutoff current of the pulse discharge is 0.05C-0.10C. Using a small initial current to perform pulse discharge can make the negative electrode tab have a smaller pit size and a higher pit number density, thereby further improving the cycle life of the battery cell. The cutoff current of the pulse discharge is in the above range, which can reduce the pit size and increase the pit number density without damaging the positive electrode active material, thereby further improving the cycle life of the battery cell.

[0019] In some embodiments, the lithium-poor positive electrode plate comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a lithium-poor phase positive electrode active material, the lithium-poor phase positive electrode active material comprising one or more of a lithium-poor phase phosphate, a lithium-poor phase transition metal oxide, and respective modified compounds thereof.

[0020] In a third aspect, the present application provides a battery comprising the battery monomer of the first aspect of the present application or the battery monomer prepared by the preparation method of the second aspect of the present application.

[0021] In a fourth aspect, the present application provides an electric device comprising the battery of the third aspect of the present application.

[0022] The electric device of the present application comprises the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0024] FIG. 1 shows a schematic diagram of a battery monomer provided by some embodiments of the present application.

[0025] FIG. 2 shows a schematic diagram of a battery module provided by some embodiments of the present application.

[0026] FIG. 3 shows a schematic diagram of a battery pack provided by some embodiments of the present application.

[0027] FIG. 4 is an exploded schematic diagram of the battery pack shown in FIG. 3.

[0028] FIG. 5 shows a scanning electron microscope (SEM) image of a negative electrode plate provided by some embodiments of the present application.

[0029] FIG. 6 shows a schematic diagram of an electric device provided by some embodiments of the present application.

[0030] In the drawings, the drawings are not necessarily drawn according to the actual scale.

[0031] The reference signs are explained as follows: 1, battery pack; 2, upper box body; 3, lower box body; 4, battery module; 5, battery monomer. DETAILED DESCRIPTION

[0032] Hereinafter, specific embodiments of the battery cell and the method for manufacturing the same, the battery, and the electric device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known to those skilled in the art, repeated description of substantially identical configurations, is omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0033] The ranges disclosed herein are defined by their lower and upper limits. Ranges that include both endpoints are inclusive of the endpoints. Ranges that exclude both endpoints are not inclusive of the endpoints. Ranges that include one or both endpoints are inclusive of the endpoint(s) and ranges that exclude one or both endpoints are not inclusive of the endpoint(s). Ranges are defined by their lower and upper limits. Unless specifically stated otherwise, the use of a range of values for a parameter includes each and every value and sub-range within the range. Exemplary values for physical parameters, such as temperature and pressure, are included in ranges unless otherwise stated herein. All ranges and parameters, including those for quantities, are inclusive of the recited endpoint and endpoints, unless expressly stated otherwise. For example, a range of "about 1% to 20%" is inclusive of from 1% to 20% and is also inclusive of from 20% to 1%. All individual values and sub-ranges from the stated ranges for parameters are included and disclosed. When no range or specific value is given, the range of values, for example, useful in the application is contemplated, unless otherwise stated herein. For example, a parameter such as temperature can be in the range of 0-100°C, unless otherwise stated herein. In addition, when a parameter is stated to be an integer, it is understood that the parameter can be, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless specifically stated otherwise, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0035] Unless specifically stated otherwise, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0036] If not otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method comprising step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0037] If not otherwise specified, the terms "first", "second", etc. in the present application are used to distinguish different objects, rather than to describe a specific sequence or primary and secondary relationship.

[0038] In the present application, the terms "a plurality of" and "a plurality of kinds" refer to two or more than two.

[0039] In the description of the embodiments of the present application, if not otherwise specified, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be "above", "over" and "on" the second feature, which can be that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature can be "under", "below" and "underneath" the second feature, which can be that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0040] Unless otherwise specified, the terms used in the present application have the commonly known meanings understood by those skilled in the art.

[0041] Unless otherwise specified, the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art, for example, the test methods given in the embodiments of the present application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0042] The battery mentioned in the embodiments of the present application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application can comprise a battery cell, a battery module or a battery pack, etc.

[0043] The battery cell is the smallest unit that constitutes the battery, which can realize the function of charging and discharging by itself. The battery cell can be in the shape of a cylinder, a cuboid or other shapes, which are not limited in the embodiments of the present application. For example, FIG. 1 is a battery cell 5 in the shape of a cuboid as an example.

[0044] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in a mixed connection through a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body can be part of the chassis structure of the vehicle. For example, part of the box body can be at least part of the floor of the vehicle, or part of the box body can be at least part of the cross beam and longitudinal beam of the vehicle.

[0045] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0046] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. As shown in FIG. 2, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the multiple battery cells 5 can be fixed by fasteners.

[0047] Optionally, the battery module 4 can further include a shell having an accommodation space, and the multiple battery cells 5 are accommodated in the accommodation space.

[0048] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. As shown in FIGS. 3 and 4, the battery pack 1 can include a box body and multiple battery modules 4 arranged in the box body. The box body includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in the box body in any manner.

[0049] The battery cell provided by the embodiments of the present application includes a lithium metal battery cell. The battery cell includes an electrode assembly and an electrolyte, and the battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The electrode assembly can be a winding type structure or a stacking type structure, and the embodiments of the present application are not limited thereto. The battery cell further includes an outer package, which can be used to encapsulate the electrode assembly and the electrolyte. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag type soft package. The material of the soft package can be an aluminum plastic film or plastic, such as one or more of polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0050] Corrosion of the lithium metal negative electrode is one of the important reasons for the cycle failure of lithium metal battery cells. With the cycle charging and discharging of the battery cell, the lithium metal deposition and stripping on the surface of the lithium metal negative electrode will continuously occur, thereby forming a rough negative electrode surface, which is prone to cause problems such as dead lithium, electrolyte consumption, excessive polarization, and the like, thereby leading to poor cycle life of the battery cell.

[0051] Based on this, the embodiments of the present application start from the negative electrode sheet, and provide a battery cell with long cycle life.

[0052] The battery cell provided by the embodiments of the present application comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a lithium metal layer arranged on at least one surface of the negative electrode current collector, and the surface of the lithium metal layer has a plurality of pits. The average size of the pits is 20 μm-160 μm, and the number density of the pits is 208 pieces / mm 2 to 320 pieces / mm 2 .

[0053] As shown in FIG. 5, the surface of the lithium metal layer has a plurality of pits.

[0054] The average size of the pits on the surface of the lithium metal layer of the negative electrode sheet is 20 μm-160 μm, and the number density of the pits is 208 pieces / mm 2 to 320 pieces / mm 2 The pits expose fresh lithium metal, which can serve as a preferential nucleation site for subsequent lithium metal deposition. In the subsequent charging process, lithium metal will preferentially deposit on these nucleation sites, and can induce uniform and dense deposition of subsequent lithium metal, thereby reducing the generation of dead lithium, lithium dendrites, etc., and forming a lithium metal deposition morphology with smaller specific surface area, reducing electrolyte consumption, and reducing impedance and polarization. Therefore, the battery cell provided by the embodiments of the present application can have long cycle life.

[0055] The average size of the pits is 20 μm-160 μm, for example, can be 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 56 μm, 58 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, or a range composed of any of the above values.

[0056] Optionally, the average size of the dimples can be 20-120 μm, 20-100 μm, 20-90 μm, 20-80 μm, 20-70 μm, 20-60 μm, 20-50 μm, 20-45 μm, 20-40 μm, 22-100 μm, 22-90 μm, 22-80 μm, 22-70 μm, 22-60 μm, 22-50 μm, 22-45 μm, 22-40 μm.

[0057] The average size of the dimples in the above range can further improve the cycle life of the battery cell.

[0058] The number density of the dimples can be 208 / mm 2 to 320 / mm 2 , for example, 208 / mm 2 , 210 / mm 2 , 215 / mm 2 , 220 / mm 2 , 225 / mm 2 , 230 / mm 2 , 235 / mm 2 , 240 / mm 2 , 245 / mm 2 , 250 / mm 2 , 255 / mm 2 , 260 / mm 2 , 265 / mm 2 , 270 / mm 2 , 275 / mm 2 , 280 / mm 2 , 285 / mm 2 , 290 / mm 2 , 295 / mm 2 , 300 / mm 2 , 305 / mm 2 , 310 / mm 2 , 315 / mm 2 , 320 / mm 2 , or a range composed of any of the above values.

[0059] Optionally, the number density of the dimples can be 225 / mm 2 to 320 / mm 2 , 250 / mm 2 to 320 / mm 2 , 275 / mm 2 to 320 / mm2 280 / mm 2 to 320 / mm 2 285 / mm 2 to 320 / mm 2 290 / mm 2 to 320 / mm 2 295 / mm 2 to 320 / mm 2 300 / mm 2 to 320 / mm 2 .

[0060] The number density of the pits in the above range can further improve the cycle life of the battery cell.

[0061] In some embodiments, the number ratio of the pits with the maximum lateral dimension less than 50 pm can be greater than or equal to 14%, based on the number of all the pits.

[0062] Optionally, the number ratio of the pits with the maximum lateral dimension less than 50 pm can be greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 48%, greater than or equal to 52%, greater than or equal to 56%, greater than or equal to 60%.

[0063] In some embodiments, the number ratio of the pits with the maximum lateral dimension greater than 100 pm can be greater than 0 and less than or equal to 55%, based on the number of all the pits.

[0064] Optionally, the number ratio of the pits with the maximum lateral dimension greater than 100 pm can be greater than 0 and less than or equal to 50%, greater than 0 and less than or equal to 45%, greater than 0 and less than or equal to 40%, greater than 0 and less than or equal to 35%, greater than 0 and less than or equal to 30%, greater than 0 and less than or equal to 25%, greater than 0 and less than or equal to 20%, greater than 0 and less than or equal to 18%, greater than 0 and less than or equal to 15%, greater than 0 and less than or equal to 12%, greater than 0 and less than or equal to 10%, greater than 0 and less than or equal to 8%.

[0065] The high number ratio of the pits with the maximum lateral dimension less than 50 pm and the low number ratio of the pits with the maximum lateral dimension greater than 100 pm can provide more preferential nucleation sites for the negative electrode tab, thereby further reducing the consumption of electrolyte and further improving the cycle life of the battery cell.

[0066] In some embodiments, the number density of the pits with the maximum lateral dimension less than 50 pm can be 30 / mm 2 to 202 / mm 2 , for example, can be 30 / mm2 40 / mm 2 50 / mm 2 60 / mm 2 70 / mm 2 80 / mm 2 90 / mm 2 100 / mm 2 110 / mm 2 120 / mm 2 130 / mm 2 140 / mm 2 150 / mm 2 160 / mm 2 170 / mm 2 180 / mm 2 190 / mm 2 202 / mm 2 or a range of values formed by any of the above.

[0067] Optionally, the number density of pits having a maximum lateral dimension less than 50 pm can be 50 / mm 2 to 202 / mm 2 , 80 / mm 2 to 202 / mm 2 , 100 / mm 2 to 202 / mm 2 , 110 / mm 2 to 202 / mm 2 , 120 / mm 2 to 202 / mm 2 , 130 / mm 2 to 202 / mm 2 , 140 / mm 2 to 202 / mm 2 , 150 / mm 2 to 202 / mm 2 , 160 / mm 2 to 202 / mm 2 , 170 / mm 2 to 202 / mm 2 , 180 / mm 2 to 202 / mm 2 .

[0068] In some embodiments, the number density of pits having a maximum lateral dimension between 50 pm and 100 pm can be 60 / mm 2 to 105 / mm 2for example, 60 / mm 2 , 62 / mm 2 , 64 / mm 2 , 66 / mm 2 , 68 / mm 2 , 70 / mm 2 , 72 / mm 2 , 74 / mm 2 , 76 / mm 2 , 78 / mm 2 , 80 / mm 2 , 82 / mm 2 , 84 / mm 2 , 86 / mm 2 , 88 / mm 2 , 90 / mm 2 , 92 / mm 2 , 94 / mm 2 , 96 / mm 2 , 98 / mm 2 , 100 / mm 2 , 103 / mm 2 , 105 / mm 2 , or a range of values formed by any of the above.

[0069] Optionally, the number density of pits having a maximum lateral dimension between 50 pm and 100 pm can be 70 / mm 2 to 105 / mm 2 , 75 / mm 2 to 105 / mm 2 , 80 / mm 2 to 105 / mm 2 , 85 / mm 2 to 105 / mm 2 , 88 / mm 2 to 105 / mm 2 , 70 / mm 2 to 103 / mm 2 , 75 / mm 2 to 103 / mm 2 , 80 / mm 2 to 103 / mm 2 , 85 / mm 2 to 103 / mm 2 , 88 / mm 2 to 103 / mm 2 .

[0070] In some embodiments, the number density of pits having a maximum lateral dimension greater than 100 pm can be 14 pits / mm 2 up to 114 pits / mm 2 , for example, can be 14 pits / mm 2 , 16 pits / mm 2 , 18 pits / mm 2 , 20 pits / mm 2 , 22 pits / mm 2 , 24 pits / mm 2 , 26 pits / mm 2 , 28 pits / mm 2 , 30 pits / mm 2 , 32 pits / mm 2 , 34 pits / mm 2 , 36 pits / mm 2 , 38 pits / mm 2 , 40 pits / mm 2 , 45 pits / mm 2 , 50 pits / mm 2 , 55 pits / mm 2 , 60 pits / mm 2 , 65 pits / mm 2 , 70 pits / mm 2 , 75 pits / mm 2 , 80 pits / mm 2 , 90 pits / mm 2 , 100 pits / mm 2 , 114 pits / mm 2 , or a range of any of the above.

[0071] Optionally, the number density of pits having a maximum lateral dimension greater than 100 pm can be 14 pits / mm 2 up to 100 pits / mm 2 , 14 pits / mm 2 up to 80 pits / mm 2 , 14 pits / mm 2 up to 70 pits / mm 2 , 14 pits / mm 2 up to 60 pits / mm 2 , 14 pits / mm 2 up to 50 pits / mm 2 , 14 pits / mm 2 up to 45 pits / mm 2 , 14 pits / mm 2 up to 40 pits / mm 2 , 14 pits / mm 2 up to 35 pits / mm 2 .

[0072] The number density of the pits of different sizes in the above range can further reduce the consumption of electrolyte and further improve the cycle life of the battery cell.

[0073] In some embodiments, the depth of the pits can be more than 10% of the thickness of the lithium metal layer and less than the thickness of the lithium metal layer, for example, can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or a range consisting of any of the above values.

[0074] Alternatively, the depth of the pits can be 10%-95%, 20%-95%, 30%-95%, 40%-95%, 50%-95%, 10%-90%, 20%-90%, 30%-90%, 40%-90%, 50%-90% of the thickness of the lithium metal layer.

[0075] In some embodiments, the sum of the areas of the plurality of pits can be 20%-50% of the area of the lithium metal layer, for example, can be 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, or a range consisting of any of the above values.

[0076] Alternatively, the sum of the areas of the plurality of pits can be 24%-42% of the area of the lithium metal layer.

[0077] The number density of the pits can be obtained by scanning electron microscopy (SEM) observation. When testing, the negative electrode sheet can be disassembled from the battery cell, and then the number density of the pits on the surface of the negative electrode sheet is calculated. The maximum lateral size of each pit observed is taken as the size of each pit. When testing, the selected observation area has at least 100 complete pits in the field of view. In order to ensure accuracy, more than 3 observation areas can be selected, and then the average value is taken.

[0078] In some embodiments, the negative current collector can adopt a metal foil. Alternatively, as an example of the metal foil, a copper foil, a copper alloy foil, a nickel foil, a nickel alloy foil, etc. can be used.

[0079] In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material. Optionally, the positive electrode active material can include, but is not limited to, one or more of lithium-containing phosphates, lithium transition metal oxides, and respective modified compounds thereof. The lithium-containing phosphates can include, but are not limited to, one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and respective modified compounds thereof. The lithium transition metal oxides can include, but are 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 manganese oxide, lithium nickel cobalt aluminum oxide, and respective modified compounds thereof. The modified compounds of each of the above-mentioned positive electrode active materials can be a doping modification and / or a surface coating modification of the positive electrode active material.

[0080] In some embodiments, the positive electrode film layer can further include a positive electrode conductive agent. As an example, the positive electrode conductive agent can include, but is not limited to, one or more of super P, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] In some embodiments, the positive electrode film layer can further include a positive electrode binder. As an example, the positive electrode binder can include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic ester resin.

[0082] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0083] The positive electrode film layer can be formed by coating a positive electrode slurry on the positive electrode current collector, drying, and cold-pressing. The positive electrode slurry is generally formed by dispersing and uniformly stirring the positive electrode active material, the positive electrode conductive agent, the positive electrode binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0084] The isolation film can be arranged between the positive electrode tab and the negative electrode tab, and mainly functions to prevent internal short circuit. The type of the isolation film is not particularly limited in the present application, and any known porous structure film having good chemical stability and mechanical stability can be selected. In some embodiments, the material of the isolation film can include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and polyimide. The isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of the layers can be the same or different.

[0085] The electrolyte includes a lithium salt and an organic solvent. In some embodiments, the lithium salt can include, but is not limited to, one or more of lithium bisfluorosulfonylimide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethyl)sulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiOTF), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorodioxalate phosphate, and lithium tetrafluorodioxalate phosphate.

[0086] Optionally, the lithium salt includes lithium bisfluorosulfonylimide (LiFSI). The lithium salt can decompose on the surface of the negative electrode to form a SEI film component rich in inorganic fluorine, thereby facilitating long cycle life of the battery cell; meanwhile, the lithium salt also has good oxidation stability, and can support the cycle of the battery cell under high pressure.

[0087] In some embodiments, the organic solvent can include an ether solvent. The ether solvent can include one or more of a chain ether solvent and a cyclic ether solvent. The chain ether solvent can include, but is not limited to, one or more of diethyl ether, dipropyl ether, ethyl propyl ether, methyl butyl ether, dibutyl ether, ethyl butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol methyl ethyl ether, propylene glycol diethyl ether, butanediol dimethyl ether, butanediol methyl ethyl ether, and butanediol diethyl ether. The cyclic ether solvent can include, but is not limited to, one or more of tetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxolane, tetrahydropyran, 1,3-dioxane, and 1,4-dioxane.

[0088] In some embodiments, the electrolyte can further include a diluent. Optionally, the diluent can include, but is not limited to, one or more of benzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluoromethylbenzene, trifluoromethoxybenzene, decafluoropentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-dimethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(difluoromethoxy)ethane, 1,2-bis(trifluoromethoxy)ethane, 1,2-diethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl) ether, bis(2,2-difluoroethyl) ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, bis(1,1,2,2-tetrafluoroethyl) ether.

[0089] In some embodiments, the electrolyte can have a concentration of 1 mol / L to 6 mol / L, for example, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.4 mol / L, 3.6 mol / L, 3.8 mol / L, 4 mol / L, 4.2 mol / L, 4.4 mol / L, 4.6 mol / L, 4.8 mol / L, 5 mol / L, 5.2 mol / L, 5.4 mol / L, 5.6 mol / L, 5.8 mol / L, 6 mol / L, or a range formed by any of the above values.

[0090] Optionally, the electrolyte can have a concentration of 2 mol / L to 5 mol / L.

[0091] Increasing the concentration of the lithium salt can induce the lithium metal to deposit more densely and uniformly.

[0092] The present application also provides a method for preparing a battery cell, which can prepare the battery cell provided by the present application.

[0093] The method for preparing the battery cell comprises the following steps: assembling a lithium-poor positive electrode sheet and a negative electrode sheet to obtain a battery cell, the negative electrode sheet comprising a negative electrode current collector and a lithium metal layer arranged on at least one surface of the negative electrode current collector; and performing pulse discharge on the battery cell to obtain the battery cell, a plurality of pits being formed on the surface of the lithium metal layer after the pulse discharge, the average size of the pits being 20 μm-160 μm, and the number density of the pits being 208 pits / mm 2 to 320 pits / mm 2 .

[0094] After the lithium-poor positive electrode sheet and the negative electrode sheet are assembled into the battery cell, pulse discharge is performed, so that part of the lithium metal on the surface of the negative electrode sheet is peeled off, a plurality of pits are formed in situ on the surface of the lithium metal layer of the negative electrode sheet, and part of the lithium capacity of the negative electrode is released into the lithium-poor positive electrode. In addition, the use of the lithium-poor positive electrode sheet for assembling the battery cell can reduce the damage of the initial pulse discharge to the positive electrode active material. In addition, the method for preparing the battery cell provided in the embodiments of the present application is simple in operation and low in production cost.

[0095] In some embodiments, the initial current of the pulse discharge can be less than or equal to 3C. Alternatively, the initial current of the pulse discharge can be less than or equal to 2C, less than or equal to 1.5C, or less than or equal to 1C.

[0096] The use of a small initial current for pulse discharge can make the negative electrode sheet have a smaller pit size and a higher pit number density, so as to further improve the cycle life of the battery cell.

[0097] In some embodiments, the cutoff current of the pulse discharge can be 0.05C-0.50C. Alternatively, the cutoff current of the pulse discharge can be 0.05C-0.40C, 0.05C-0.30C, 0.05C-0.20C, or 0.05C-0.10C.

[0098] The cutoff current of the pulse discharge in the above range can reduce the pit size and increase the pit number density without damaging the positive electrode active material, so as to further improve the cycle life of the battery cell.

[0099] In some embodiments, the lithium-poor positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a lithium-poor phase positive electrode active material. After the pulse discharge, the lithium-poor phase positive electrode active material is converted into a conventional positive electrode active material, i.e., the positive electrode active material in the positive electrode sheet described above.

[0100] Optionally, the lithium-poor phase cathode active material can include one or more of a lithium-poor phase phosphate, a lithium-poor phase transition metal oxide, and respective modified compounds thereof. The lithium-poor phase phosphate can include, but is not limited to, one or more of a lithium-poor phase lithium iron phosphate, a lithium-poor phase lithium manganese phosphate, a lithium-poor phase lithium manganese iron phosphate, and respective modified compounds thereof. The lithium-poor phase transition metal oxide can include, but is not limited to, one or more of a lithium-poor phase lithium cobalt oxide, a lithium-poor phase lithium nickel oxide, a lithium-poor phase lithium manganese oxide, a lithium-poor phase lithium nickel cobalt oxide, a lithium-poor phase lithium manganese cobalt oxide, a lithium-poor phase lithium nickel manganese oxide, a lithium-poor phase lithium nickel cobalt manganese oxide, a lithium-poor phase lithium nickel cobalt aluminum oxide, and respective modified compounds thereof. The modified compounds of each of the aforementioned lithium-poor phase cathode active materials can be a doping modification and / or a surface coating modification to the lithium-poor phase cathode active material.

[0101] Optionally, the lithium-poor phase cathode active material can include Li a FePO4, Li b Ni 1-x-y Co x Mn y M z O c A d , one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A can include one or more of N, F, S, and Cl. a can be less than 1, optionally 0.2-0.9. b can be less than 1, optionally 0.2-0.9. x can be greater than 0 and less than 1. y can be greater than 0 and less than 1. z can be greater than 0 and less than 1. c can be 1-2. d can be greater than or equal to 0 and less than or equal to 1.

[0102] In some embodiments, the cutoff voltage of the pulse discharge can be greater than or equal to the lower cutoff voltage of the lithium-poor phase cathode active material.

[0103] The lower cutoff voltage of the cathode active material is a voltage known in the art.

[0104] For example, when the lithium-poor phase cathode active material includes Li b Ni 1-x-y Co x Mn y M z O c A d , the lower cutoff voltage can be 2.8 V, and the cutoff voltage of the pulse discharge can be greater than or equal to 2.8 V, for example, 2.8 V.

[0105] For example, when the lithium-poor phase cathode active material includes Li aWhen the FePO4 is used, the lower cut-off voltage can be 2.5 V, and the cut-off voltage of the pulse discharge can be greater than or equal to 2.5 V, for example, 2.5 V.

[0106] The application further provides a power utilization device comprising 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 be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0107] The power utilization device can select the type of the battery (such as a battery monomer, a battery module or a battery pack) according to the use requirement of the power utilization device.

[0108] FIG. 6 is a schematic diagram of a power utilization device 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 power utilization device, a battery pack or a battery module can be used.

[0109] The power utilization device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power utilization device usually requires thinning, and a battery monomer can be used as a power supply.

[0110] Embodiments

[0111] The following embodiments describe the present disclosure in more detail, which are only used for illustrative explanation, and various modifications and changes within the scope of the present disclosure are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods, and can be directly used without further treatment, and the instruments used in the embodiments are commercially available.

[0112] Embodiment 1

[0113] Preparation of the lithium-poor positive electrode sheet: the positive electrode active material Li 0.5 Ni 0.8 Co 0.1 Mn 0.1O2, positive electrode conductive agent acetylene black, positive electrode binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 98:1:1, added to the solvent N-methyl pyrrolidone (NMP) and stirred until the system was uniform, obtaining a positive electrode slurry; the positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, then transferred to an oven for further drying, and then cut into a 40mm x 50mm rectangle as a lithium-poor positive electrode tab for standby. The positive electrode surface capacity was 3.5mAh / cm 2 .

[0114] Preparation of negative electrode tab: a lithium foil with a thickness of 50μm was covered on a copper foil with a thickness of 12μm by rolling, and then cut into a 41mm x 51mm rectangle as a negative electrode tab for standby.

[0115] Preparation of separator film: a polyethylene porous film was cut into a 45mm x 55mm rectangle as a separator film for standby.

[0116] Preparation of electrolyte: 3.74g of lithium bisfluorosulfonylimide (LiFSI) was added to 4.33g of ethylene glycol dimethyl ether, and stirred thoroughly to form a colorless transparent electrolyte with a concentration of 4mol / L.

[0117] Preparation of battery monomer: a lithium-poor positive electrode tab and two negative electrode tabs were matched, with the above-mentioned separator film used to isolate the middle, and wrapped in an aluminum plastic film bag to form a battery monomer to be injected; 0.3g of electrolyte was injected into the above-prepared battery monomer to be injected, and then the aluminum plastic film bag was vacuum heat sealed and packaged, and the battery monomer was placed at 25℃ for more than 6 hours, with a capacity of 140mAh; then the battery monomer was subjected to pulse discharge, with a pulse discharge starting current of 1C (140mA), a cutoff current of 0.05C (7mA), and a cutoff voltage of 2.8V, and after the end, the battery monomer was obtained for cycle performance test.

[0118] The cycle performance test method is as follows: the prepared battery monomer was set to an environment temperature of 25℃, and after constant current charging to a cutoff voltage of 4.3V at 0.2C (28mA), 4.3V constant voltage charging was used until the current decayed to 0.1C (14mA); then constant current discharge was carried out at 1C (140mA) to 2.8V to obtain the first cycle discharge capacity. The above charging and discharging cycle was repeated, and the discharge capacity after each cycle was recorded. When the discharge capacity decays to 80% of the first cycle discharge capacity, the battery monomer life cutoff is considered, and the number of cycles experienced by the battery monomer is recorded.

[0119] The consumption amount test method of organic solvent and lithium salt is as follows.

[0120] The mass percentage of the organic solvent and the lithium salt in the electrolyte before injection was tested; the total mass of the battery monomer before injection was weighed, the total mass of the battery monomer after injection was weighed, the injection amount m0 of the electrolyte was obtained, the mass m1 of the organic solvent and the mass m2 of the lithium salt were calculated according to the mass percentage of the organic solvent and the lithium salt.

[0121] The battery monomer was subjected to 100 cycle charge-discharge tests according to the above method, after which the dirt on the surface of the battery monomer was wiped and the total mass m3 of the battery monomer was weighed; the electrolyte was taken out of the battery monomer and the mass percentage of the organic solvent and the lithium salt was tested; a separation film bag was made and its mass m4 was weighed; all the components obtained by disassembling were put into the separation film bag, and the solvent diethylene glycol dimethyl ether was added to the separation film bag for soaking and cleaning to remove the residual electrolyte; then the separation film bag together with all the components inside was heated and dried, and after the end, the total mass m5 of the separation film bag together with all the components inside was weighed. The remaining amount of the electrolyte is m3+m4-m5, and the remaining mass m6 of the organic solvent and the remaining mass m7 of the lithium salt are calculated according to the mass percentage of the organic solvent and the lithium salt.

[0122] The consumption amount of the organic solvent is m1-m6, and the consumption amount of the lithium salt is m2-m7.

[0123] Example 2

[0124] The preparation method of the battery monomer is the same as that of Example 1, except that the initial current of pulse discharge is 1.5C (210mA), the cutoff current is 0.05C (7mA), and the cutoff voltage is 2.8V.

[0125] Example 3

[0126] The preparation method of the battery monomer is the same as that of Example 1, except that the initial current of pulse discharge is 2C (280mA), the cutoff current is 0.05C (7mA), and the cutoff voltage is 2.8V.

[0127] Example 4

[0128] The preparation method of the battery monomer is the same as that of Example 1, except that the initial current of pulse discharge is 3C (420mA), the cutoff current is 0.05C (7mA), and the cutoff voltage is 2.8V.

[0129] Example 5

[0130] The preparation method of the battery monomer is the same as that of Example 1, except that the initial current of pulse discharge is 0.5C (70mA), the cutoff current is 0.05C (7mA), and the cutoff voltage is 2.8V.

[0131] Example 6

[0132] The preparation method of the battery cell is the same as that of Example 1, except that the initial current of the pulse discharge is 1C (140 mA), the cutoff current is 0.50C (70 mA), and the cutoff voltage is 2.8 V.

[0133] Example 7

[0134] The preparation method of the battery cell is the same as that of Example 1, except that the initial current of the pulse discharge is 1C (140 mA), the cutoff current is 0.25C (35 mA), and the cutoff voltage is 2.8 V.

[0135] Comparative Example 1

[0136] The preparation method of the battery cell is the same as that of Example 1, except that the pulse discharge is not performed.

[0137] Comparative Example 2

[0138] The preparation method of the battery cell is the same as that of Example 1, except that the initial current of the pulse discharge is 4C (560 mA), the cutoff current is 0.01C (1.4 mA), and the cutoff voltage is 2.8 V.

[0139] Comparative Example 3

[0140] The preparation method of the battery cell is the same as that of Example 1, except that the initial current of the pulse discharge is 4C (560 mA), the cutoff current is 1C (140 mA), and the cutoff voltage is 2.8 V.

[0141] Comparative Example 4

[0142] The preparation method of the battery cell is the same as that of Example 1, except that the constant current discharge is used before the battery cell is cycled.

[0143] Preparation of the battery cell: one piece of the cut lithium-poor positive electrode and two pieces of the cut negative electrode are matched, the above-mentioned separation film is used to isolate the middle, and is wrapped in an aluminum plastic film bag to form a battery cell to be injected; 0.3 g of electrolyte is injected into the above-mentioned prepared battery cell to be injected, and then the aluminum plastic film bag is vacuum hot-pressed and packaged, and is placed at 25°C for more than 6 hours, and the capacity of the battery cell is 140 mAh; then the battery cell is discharged at a constant current of 1C (140 mA), and the cutoff voltage is 2.8 V, and after the end, the battery cell is obtained, and the cycle performance test is performed.

[0144] As shown in Table 1, the pits on the surface of the lithium metal layer of the negative electrode meet the requirements of an average size of 20 μm-160 μm and a number density of 208 / mm 2 to 320 / mm 2 , which can make the battery cell have a longer cycle life.

[0145] It can also be seen from the test results of Examples 1 to 7 that further adjusting the pulse discharge starting current and / or the cutoff current can make the battery cell have a longer cycle life.

[0146] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical solution of the present application are also included in the technical scope of the present application. Furthermore, other modes obtained by applying various modifications to the embodiments or by combining part of the configuration elements of the embodiments within the scope of the gist of the present application are also included in the scope of the present application.

Claims

1. A battery cell, wherein, The battery cell includes a negative electrode tab including a negative electrode current collector and a lithium metal layer disposed on at least one surface of the negative electrode current collector, a surface of the lithium metal layer having a plurality of pits, an average size of the pits being 20 μm-160 μm, a number density of the pits being 208 pits / mm 2 to 320 pits / mm 2 . 2.The battery cell of claim 1, wherein, the average size of the pits is 20-45 μm; and / or, The number density of the pits is 280 pits / mm 2 up to 320 pits / mm 2 .

3. The battery cell of any one of claims 1-2, wherein, the number of pits with a maximum lateral dimension less than 50 μm accounts for more than 14% and the number of pits with a maximum lateral dimension greater than 100 μm accounts for more than 0 and less than or equal to 55% based on the number of all pits.

4. The battery cell of claim 3, wherein, the number of pits with a maximum lateral dimension less than 50 μm accounts for more than 48% and the number of pits with a maximum lateral dimension greater than 100 μm accounts for more than 0 and less than or equal to 18% based on the number of all pits.

5. The battery cell of any one of claims 1-4, wherein, The number density of pits having a maximum lateral dimension of less than 50 pm is 30 pits / mm 2 up to 202 pits / mm 2 The number density of pits having a maximum lateral dimension of between 50 pm and 100 pm is 60 pits / mm 2 up to 105 pits / mm 2 The number density of pits having a maximum lateral dimension of greater than 100 pm is 14 pits / mm 2 up to 114 pits / mm 2 .

6. The battery cell of claim 5, wherein, The number density of pits having a maximum lateral dimension less than 50 pm is 130 pits / mm 2 to 202 pits / mm 2 The number density of pits having a maximum lateral dimension between 50 pm and 100 pm is 88 pits / mm 2 to 105 pits / mm 2 The number density of pits having a maximum lateral dimension greater than 100 pm is 14 pits / mm 2 to 50 pits / mm 2 .

7. The battery cell of any one of claims 1-6, wherein, the depth of the pits is more than 10% of the thickness of the lithium metal layer and less than the thickness of the lithium metal layer.

8. The battery cell of any one of claims 1-7, wherein, the sum of the areas of the pits is 20-50% of the area of the lithium metal layer.

9. The battery cell of any one of claims 1-8, wherein, The battery cell comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises one or more of lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds.

10. The battery cell of any one of claims 1-9, wherein, The battery cell comprises an electrolyte, the concentration of the electrolyte is 1-6 mol / L. 11.A method for preparing a battery cell, comprising the following steps: assembling a lithium-poor positive electrode sheet with a negative electrode sheet to obtain a battery cell, the negative electrode sheet comprises a negative electrode current collector and a lithium metal layer disposed on at least one surface of the negative electrode current collector; The battery monomer is subjected to pulse discharge to obtain a battery monomer, a plurality of pits are formed on the surface of the lithium metal layer after the pulse discharge, the average size of the pits is 20-160 μm, and the number density of the pits is 208 / mm 2 to 320 / mm 2 .

12. The production method according to claim 11, wherein the initial current of the pulse discharge is less than or equal to 3C and the cutoff current of the pulse discharge is 0.05-0.50C.

13. The method of manufacturing according to claim 12, wherein, the initial current of the pulse discharge is less than or equal to 1C and the cutoff current of the pulse discharge is 0.05-0.10C.

14. The method of making according to any one of claims 11-13, wherein, The lithium-poor positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprises a lithium-poor phase positive electrode active material, the lithium-poor phase positive electrode active material comprises one or more of lithium-poor phase phosphates, lithium-poor phase transition metal oxides and their respective modified compounds. 15.A battery comprising the battery cell of any one of claims 1-10 or prepared by the method of any one of claims 11-14. 16.A device for using electricity, comprising the battery of claim 15.

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