Battery monomer, battery and electric device

Abstract

The embodiment of the invention provides a battery monomer, a battery and an electric device. The battery monomer comprises a negative pole piece, the negative pole piece comprises a negative pole current collector and a composite negative pole active material layer coated on at least one side of the negative pole current collector, and the composite negative pole active material layer comprises a first negative pole active material and a second negative pole active material; the electrolyte comprises electrolyte salt, and the electrolyte salt comprises at least one of lithium salt, sodium salt or potassium salt; wherein in the electrolyte, the content x of the lithium salt is greater than or equal to 0 mol / L and less than 0.8 mol / L, the content y of the potassium salt is greater than or equal to 0 mol / L and less than 3 mol / L, the content z of the sodium salt is greater than or equal to 0 mol / L and less than 3 mol / L, and the sum of the content of the sodium salt and the content of the potassium salt is y + z which is greater than 0 mol / L. According to the technical scheme provided by the invention, the production cost of the battery is reduced while the battery is ensured to have relatively good cycle performance and rate capability.

Description

Battery cells, batteries and electrical devices Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Art

[0002] In recent years, lithium-ion batteries have found an increasingly broad range of applications, including energy storage and power supply applications such as wind, hydro, thermal, and solar power plants, as well as electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. While lithium-ion batteries have experienced significant growth, higher demands have been placed on their performance and production costs.

[0003] Therefore, how to make lithium-ion batteries have both good performance and low production costs is an urgent problem that needs to be solved.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery and an electrical device, so that the battery has good cycle performance, rate performance and low production cost.

[0006] The first aspect of the present application provides a battery cell, comprising: a negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a composite negative electrode active material layer coated on at least one side of the negative electrode current collector, the composite negative electrode active material layer comprising a first negative electrode active material and a second negative electrode active material; an electrolyte, comprising an electrolyte salt, the electrolyte salt comprising at least one of a lithium salt, a potassium salt or a sodium salt; wherein, in the electrolyte, the content x of the lithium salt is 0 mol / L≤x<0.8 mol / L, the content y of the potassium salt is 0 mol / L≤y<3 mol / L, the content z of the sodium salt is 0 mol / L≤z<3 mol / L, and the sum of the contents of the potassium salt and the sodium salt is y+z>0 mol / L.

[0007] In an embodiment of the present application, a battery cell includes a negative electrode plate and an electrolyte. The negative electrode plate is coated with a composite negative electrode active material layer comprising a first negative electrode active material and a second negative electrode active material. The electrolyte includes at least one of a sodium salt, a potassium salt, and a lithium salt. In the electrolyte, the sum of the sodium and potassium salt contents is in the range of y+z>0 mol / L, the lithium salt content x is in the range of 0 mol / L≤x<0.8 mol / L, the potassium salt content y is in the range of 0 mol / L≤z<3 mol / L, and the sodium salt content z is in the range of 0 mol / L≤y<3 mol / L. On the one hand, by making the battery include a first negative electrode active material and a second negative electrode active material, wherein the first negative electrode active material is used for deintercalation of lithium ions and the second negative electrode active material is used for deintercalation of sodium ions or potassium ions; on the other hand, by adding potassium salt or sodium salt to the electrolyte, the potassium salt or sodium salt replaces the lithium salt to play the role of transferring charge, which can ensure that the lithium ions still have a high ionic conductivity in the electrolyte, thereby ensuring that the battery has good cycle performance and rate performance while reducing the production cost of the battery.

[0008] In a possible implementation, the content of the electrolyte salt is 0 mol / L<x+y+z<5 mol / L, optionally, 1.0 mol / L<x+y+z<3 mol / L.

[0009] In the embodiments of the present application, by limiting the content of the electrolyte salt x+y+z in the electrolyte to 0 mol / L<x+y+z<5 mol / L, especially 1.0 mol / L<x+y+z<3 mol / L, the battery can maintain good cycle performance and rate performance.

[0010] In one possible embodiment, the first negative electrode active material includes at least one of a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of forming an alloy with lithium, optionally graphite.

[0011] In an embodiment of the present application, by adopting at least one of a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, silicon-based materials, tin-based materials, lithium titanate or other metals that can form alloys with lithium as the first negative electrode active material of the battery, especially graphite, it is possible to ensure the normal extraction and embedding of lithium ions in the first negative electrode active material, thereby enabling the normal conversion of chemical energy and electrical energy in the battery.

[0012] In one possible embodiment, the second negative electrode active material includes at least one of hard carbon, dipotassium benzoate, germanium and its alloys, tin and its alloys, lead and its alloys, antimony metal and its alloys, bismuth and its alloys, and metal oxides.

[0013] In the embodiment of the present application, by adopting at least one of hard carbon, dipotassium benzoate, germanium and its alloys, tin and its alloys, lead and its alloys, antimony metal and its alloys, bismuth and its alloys, and metal oxides as the second negative electrode active material, the normal extraction and embedding of sodium ions or potassium ions in the second negative electrode active material can be ensured, thereby ensuring that the battery has good cycle performance and rate performance.

[0014] In one possible implementation, the composite negative electrode active material layer includes a mixture of the first negative electrode active material and the second negative electrode active material.

[0015] In the embodiment of the present application, the composite negative electrode active material layer is obtained by directly mixing the first negative electrode active material and the second negative electrode active material. This method is simple to operate and easy to process, and is conducive to wide application in production.

[0016] In a possible implementation, the composite negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer.

[0017] In the embodiment of the present application, by coating the first negative electrode active material and the second negative electrode active material on the negative electrode current collector respectively, lithium ions can be better deintercalated in the first negative electrode active material, and sodium and potassium ions can be better deintercalated in the second negative electrode active material, thereby further improving the performance of the battery.

[0018] In a possible implementation, the first negative electrode active material layer is disposed between the negative electrode current collector and the second negative electrode active material layer.

[0019] In an embodiment of the present application, the first negative electrode active material layer is arranged between the negative electrode current collector and the second negative electrode active material layer, that is, the thinner second negative electrode active material layer is coated on the relatively thicker first negative electrode active material layer, which facilitates the processing of the negative electrode plate and the penetration of the electrolyte into the negative electrode plate.

[0020] In a possible implementation, the thickness of the composite negative electrode active material layer is 30-300 um, optionally, 50-200 um.

[0021] In the embodiments of the present application, if the composite negative electrode active material layer is too thin, the effective surface area of ​​the negative electrode plate can be reduced, resulting in waste of active material and affecting the battery's performance at high currents. If the composite negative electrode active material layer is too thick, the amount of active material per unit volume in the battery can be reduced and the polarization voltage can be increased, resulting in a reduction in battery capacity. By maintaining the thickness of the composite negative electrode active material layer within 30-300 μm, and particularly within 50-200 μm, a normal amount of active material on the negative electrode plate can be maintained, thereby ensuring normal rate performance of the battery.

[0022] In a possible implementation manner, the thickness of the second negative electrode active material layer is 1-80 um, optionally, 20-50 um.

[0023] In the embodiment of the present application, by maintaining the thickness of the second negative electrode active material layer at 1-80 μm, especially 20-50 μm, the second negative electrode active material can be normally deintercalated and deintercalated with sodium and potassium ions.

[0024] In a possible implementation, the thickness of the first negative electrode active material layer is 50-300 um, optionally, 100-200 um.

[0025] In the embodiment of the present application, by maintaining the thickness of the first negative electrode active material layer at 50-300 um, especially at 100-200 um, the first negative electrode active material can normally intercalate and deintercalate lithium ions.

[0026] In a possible embodiment, in the composite negative electrode active material layer, the ratio of the mass content w1 of the first negative electrode active material to the mass content w2 of the second negative electrode active material is 1000:1-10:1, optionally, 99:1-9:1.

[0027] In the embodiments of the present application, the composite negative electrode active material layer includes a first negative electrode active material for lithium insertion and a second negative electrode active material for sodium or potassium insertion. By maintaining the mass ratio of the first negative electrode active material to the second negative electrode active material in the range of 1000:1 to 10:1, particularly 99:1 to 9:1, sufficient space for lithium insertion can be ensured in the composite negative electrode active material layer.

[0028] In a possible embodiment, the compaction density g of the negative electrode sheet satisfies: g=g1*w1+g2*w2,

[0029] Wherein, g1 is the compaction density of the first negative electrode active material, and g2 is the compaction density of the second negative electrode active material.

[0030] In the embodiments of the present application, the composite negative electrode active material on the negative electrode sheet includes a first negative electrode active material and a second negative electrode active material. Differences in the mass content and compaction density of the first and second negative electrode active materials will result in variations in the compaction density of the entire negative electrode sheet. By correlating the compaction density of the negative electrode sheet with the content and compaction density of the first and second negative electrode active materials, the compaction density of the entire negative electrode sheet can be more accurately calculated.

[0031] In a possible embodiment, the compaction density of the negative electrode sheet is in the range of 0.1-5 g / cm 3, optionally, 0.5-3.0 g / cm 3 .

[0032] In the embodiment of the present application, the compaction density of the negative electrode sheet is set to 0.1-5 g / cm 3 , especially 0.5-3.0g / cm 3 , which can avoid the electrolyte being unable to penetrate due to the high compaction density of the negative electrode and the low battery capacity due to the low compaction density.

[0033] In one possible embodiment, the compaction density of the first negative electrode active material is in the range of 0.5-3 g / cm 3 , optionally, 1.0-1.8 g / cm 3 .

[0034] In the embodiment of the present application, the compaction density of the first negative electrode active material is 0.5-3 g / cm 3 , especially 1.0-1.8g / cm 3 , which can avoid the electrolyte from being unable to penetrate due to the high compaction density of the first negative electrode active material and the low battery capacity due to the low compaction density.

[0035] In one possible embodiment, the compaction density of the second negative electrode active material is in the range of 0.1-5 g / cm 3 , optionally, 1.0-3.0 g / cm 3 .

[0036] In the embodiment of the present application, the compaction density of the second negative electrode active material is 0.1-5 g / cm 3 , especially 1.0-3.0g / cm 3 , which can avoid the electrolyte from being unable to penetrate due to the high compaction density of the second negative electrode active material and the low battery capacity due to the low compaction density.

[0037] In one possible embodiment, the coating weight of the composite negative electrode active material layer is 0.5-50 mg / cm 2 , optionally, 5-30 mg / cm 2 .

[0038] In the embodiment of the present application, the coating weight of the composite negative electrode active material layer is kept at 0.5-50 mg / cm 2 , especially 5-30mg / cm 2 , the coating weight of the composite negative electrode active material layer can be kept within a reasonable range.

[0039] In one possible embodiment, the anion of the electrolyte salt includes at least one of perchlorate, tetrafluoroborate, hexafluoroarsenate, hexafluorophosphate, bistrifluoromethylsulfonyl imide, difluorophosphate, bisdifluorosulfonyl imide, bisoxalatoborate, and difluorooxalatoborate.

[0040] In the embodiments of the present application, by using at least one of perchlorate, tetrafluoroborate, hexafluoroarsenate, hexafluorophosphate, bis(trifluoromethylsulfonylimide), difluorophosphate, bis(difluorosulfonylimide), bis(oxalatoborate) and difluorooxalatoborate as the anion of the electrolyte salt, the chemical energy and electrical energy in the battery can be successfully converted.

[0041] A second aspect of the present application provides a battery, comprising the battery cell described in any one of the embodiments in the first aspect of the present application.

[0042] The third aspect of the present application provides an electrical device, comprising the battery described in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0044] FIG1 is a schematic structural diagram of a battery cell according to an embodiment of the present application;

[0045] FIG2 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present application;

[0046] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0047] FIG4 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0048] FIG5 is a schematic structural diagram of an electric device according to an embodiment of the present application;

[0049] Reference numerals:

[0050] Housing 11, electrode assembly 12, negative electrode sheet 13, cover plate 14;

[0051] Battery cell 100 , negative electrode current collector 131 , composite negative electrode active material layer 132 , first negative electrode active material / first negative electrode active material layer 133 , second negative electrode active material / second negative electrode active material layer 134 , motor 400 , battery 500 , upper case 501 , lower case 502 , controller 600 . DETAILED DESCRIPTION

[0052] The following describes in detail embodiments of the battery cell, battery, and electrical device of the present application, with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. Furthermore, the accompanying drawings and the following description are provided to facilitate a thorough understanding of the present application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0053] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of specific range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0055] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0056] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0057] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0058] The terms "above", "below", "greater than" or "less than" as used in this application are inclusive of the number, for example, "at least one" means one or more, and "at least one of A and B" means "A", "B" or "A and B".

[0059] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0060] Lithium batteries are widely used in consumer electronics due to their high energy density, power density, and long cycle life. In recent years, with the continuous development of electric vehicles and energy storage systems, people's requirements for battery performance and production costs have also continued to increase.

[0061] For existing lithium batteries, the salts contained in their electrolytes are generally lithium salts. However, the cost of lithium salts is much higher than that of other salts, such as sodium salts and potassium salts. Therefore, there are methods such as adding sodium salts and potassium salts to the electrolyte of lithium batteries to improve the problem of high lithium salt costs. However, since the negative electrode materials of lithium batteries are mostly made of carbon materials such as graphite, the amount of sodium ions or potassium ions embedded in them is very limited, so that most of the sodium salts and potassium salts in the electrolyte cannot play the role of transferring charge, resulting in low conductivity of lithium ions in the electrolyte, and the performance of lithium batteries, such as cycle performance and rate performance, will also be reduced. Therefore, how to develop a large-scale energy storage system with good cycle performance and rate performance while having low production costs is particularly important.

[0062] The battery cell, battery, and electrical device of the present application are described below with reference to the accompanying drawings.

[0063] The present application has no limitation on the type of battery, and the battery may be a lithium-ion battery, a lithium metal battery, or a sodium-ion battery, etc. The following embodiments are described using a lithium-ion battery as an example.

[0064] [Battery Cell]

[0065] A first aspect of the present application provides a battery cell. FIG1 is a schematic structural diagram of a battery cell according to an embodiment of the present application. The battery cell 100 includes an electrode assembly 12 , and the electrode assembly 12 includes a positive electrode sheet and a negative electrode sheet.

[0066] Figure 2 is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of the present application. As shown in Figures 1 and 2, the battery cell 100 includes: a negative electrode sheet 13, which includes a negative electrode current collector 131 and a composite negative electrode active material layer 132 coated on at least one side of the negative electrode current collector 131, wherein the composite negative electrode active material layer 132 includes a first negative electrode active material 133 and a second negative electrode active material 134; an electrolyte solution including an electrolyte salt, wherein the electrolyte salt includes at least one of a lithium salt, a sodium salt, or a potassium salt; wherein, in the electrolyte solution, the lithium salt content x is 0 mol / L ≤ x < 0.8 mol / L, the potassium salt content y is 0 mol / L ≤ y < 3 mol / L, the sodium salt content z is 0 mol / L ≤ z < 3 mol / L, and the sum of the sodium and potassium salt contents is y + z > 0 mol / L.

[0067] Research has found that adding at least one of sodium salt or potassium salt to the electrolyte can allow sodium salt or potassium salt to replace lithium salt to play the role of charge transmission, that is, it can maintain the high ionic conductivity of lithium ions in the electrolyte, thereby reducing costs while ensuring that the battery has good cycle performance and rate performance.

[0068] In the above embodiment, the battery cell 100 includes a negative electrode plate 13 and an electrolyte. The negative electrode plate 13 is coated with a composite negative electrode active material layer 132 comprising a first negative electrode active material 133 and a second negative electrode material 134. The electrolyte includes at least one of a lithium salt, a sodium salt, and a potassium salt. In the electrolyte, the sum of the sodium and potassium salt contents is within the range of y+z>0 mol / L, the lithium salt content x is within the range of 0 mol / L≤x<0.8 mol / L, the potassium salt content y is within the range of 0 mol / L≤y<3 mol / L, and the sodium salt content z is within the range of 0 mol / L≤z<3 mol / L. On the one hand, by making the battery include a first negative electrode active material 133 and a second negative electrode active material 134, the first negative electrode active material 133 is used for lithium ion deintercalation and the second negative electrode active material 134 is used for potassium ion or sodium ion deintercalation; on the other hand, by adding potassium salt or sodium salt to the electrolyte, potassium salt or sodium salt replaces lithium salt to play the role of transferring charge, that is, ensuring that lithium ions have a higher ionic conductivity in the electrolyte, thereby ensuring that the battery has better cycle performance and rate performance, while also reducing the production cost of the battery.

[0069] It should be noted that the concentration of lithium salt, potassium salt or sodium salt in the electrolyte defined in this application refers to the concentration in the initial state of the battery cell. The "initial state" refers to the battery after the SEI film is formed and before the charge and discharge process.

[0070] Typically, a battery cell 100 includes a positive electrode sheet, a separator, a negative electrode sheet 13, and an electrolyte. During the battery's charge and discharge processes, active ions are intercalated and released between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0071] In some embodiments, the content of the electrolyte salt is 0 mol / L<x+y+z<5 mol / L, optionally, 1.0 mol / L<x+y+z<3 mol / L.

[0072] In the above scheme, by limiting the content of electrolyte salt x+y+z in the electrolyte to 0mol / L<x+y+z<5mol / L, especially 1.0mol / L<x+y+z<3mol / L, the battery can maintain good cycle performance and rate performance.

[0073] In some embodiments, the first negative electrode active material 133 includes at least one of graphite, soft carbon, hard carbon, carbon fiber, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of forming an alloy with lithium, and optionally, graphite.

[0074] In the above scheme, by adopting at least one of a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, silicon-based materials, tin-based materials, lithium titanate or other metals that can form alloys with lithium as the first negative electrode active material 133 of the battery, especially graphite, it is possible to ensure the normal extraction and embedding of lithium ions in the first negative electrode active material 133, thereby enabling the normal conversion of chemical energy and electrical energy in the battery.

[0075] In some embodiments, the second negative active material 134 includes at least one of hard carbon, dipotassium terephthalate, germanium and its alloys, tin and its alloys, lead and its alloys, antimony metal and its alloys, bismuth and its alloys, and metal oxides.

[0076] In the above scheme, by using at least one of hard carbon, dipotassium benzoate, germanium and its alloys, tin and its alloys, lead and its alloys, antimony metal and its alloys, bismuth and its alloys, and metal oxides as the second negative electrode active material 134, the normal extraction and embedding of sodium ions or potassium ions in the second negative electrode active material 134 can be ensured, thereby ensuring that the battery has good cycle performance and rate performance.

[0077] It should be noted here that the concentration of the electrolyte salt will change as the battery is continuously charged and discharged. During the charging process of the battery, the potassium and sodium ions in the electrolyte are transferred to the surface of the negative electrode plate 13, react with the second negative electrode active material 134, and then enter the negative electrode plate 13. In addition, the lithium ions in the positive electrode gradually escape and diffuse into the electrolyte, replacing the sodium ions or potassium ions in the electrolyte. In this process, the sodium ions or potassium ions in the electrolyte serve as the main carriers of charge transfer in the electrolyte, and the concentration of lithium ions gradually increases from x mol / L to (x+y+z) mol / L, and the concentration of potassium ions or sodium ions decreases from y mol / L and z mol / L to 0 mol / L, respectively. The discharge process is the opposite.

[0078] In addition, the metal oxide here refers to metal oxides such as MnO2 and SnO2.

[0079] In some embodiments, the composite negative electrode active material layer 132 includes a first negative electrode active material 133 and a second negative electrode active material 134 mixed.

[0080] In the above solution, the composite negative electrode active material layer 132 is obtained by directly mixing the first negative electrode active material 133 and the second negative electrode active material 134 . This method is simple to operate and easy to process, and is conducive to wide application in production.

[0081] 2 , in some embodiments, the composite negative electrode active material 132 includes a first negative electrode active material layer 133 and a second negative electrode active material layer 134 .

[0082] In the above scheme, by coating the first negative electrode active material 133 and the second negative electrode active material 134 on the negative electrode current collector 131 respectively, lithium ions can be better deintercalated in the first negative electrode active material 133, and sodium and potassium ions can be better deintercalated in the second negative electrode active material 134, so as to further improve the performance of the battery.

[0083] In some embodiments, the first negative active material layer 133 is coated on the negative current collector 131 , and the second negative active material layer 134 is coated on the first negative active material layer 133 .

[0084] In the above scheme, the first negative electrode active material layer 133 is coated on the negative electrode current collector 131, and the second negative electrode active material layer 134 is coated on the first negative electrode active material layer 133, that is, the thinner second negative electrode active material layer 134 is coated on the thicker first negative electrode active material layer 133, which facilitates the processing of the negative electrode plate 13 and the penetration of the electrolyte on the negative electrode plate 13.

[0085] In some embodiments, the thickness of the composite negative electrode active material layer 132 is 30-300 um, optionally, 50-200 um.

[0086] In the above scheme, if the thickness of the composite negative electrode active material layer 132 is too thin, it can easily reduce the effective surface area of ​​the negative electrode plate 13, resulting in waste of active material and affecting the battery's performance at high currents. If the thickness of the composite negative electrode active material layer 132 is too thin, it can easily reduce the active material per unit volume of the battery and increase the polarization voltage, thereby reducing the battery capacity. By maintaining the thickness of the composite negative electrode active material layer 132 between 30-300 μm, and particularly between 50-200 μm, a normal amount of active material on the negative electrode plate 13 can be maintained, thereby ensuring normal rate performance of the battery.

[0087] In the embodiment of the present application, the thickness of the composite negative electrode active material layer 132 may be 30 um, 100 um, or 200 um. As long as the thickness is within the above range, the present application does not impose any particular limitation thereto.

[0088] In some embodiments, the thickness of the second negative electrode active material layer 134 is 1-80 um, optionally, 20-50 um.

[0089] In the above solution, by maintaining the thickness of the second negative electrode active material layer 134 at 1-80 μm, especially 20-50 μm, the second negative electrode active material 134 can normally deintercalate sodium and potassium ions.

[0090] In the embodiment of the present application, the thickness of the second negative electrode active material layer 134 may be 10 um, 25 um, or 40 um. As long as the thickness is within the above range, the present application does not impose any particular limitation thereto.

[0091] In some embodiments, the thickness of the first negative electrode active material layer 133 is 50-300 um, and optionally, 100-200 um.

[0092] In the above solution, by maintaining the thickness of the first negative electrode active material layer 133 at 50-300 μm, especially at 100-200 μm, the first negative electrode active material 133 can normally intercalate and deintercalate lithium ions.

[0093] In the embodiment of the present application, the thickness of the first negative electrode active material layer 133 may be 50 um, 100 um, or 150 um. As long as the thickness is within the above range, the present application does not impose any particular limitation thereto.

[0094] In some embodiments, in the composite negative electrode active material layer 132 , the ratio of the mass content w1 of the first negative electrode active material 133 to the mass content w2 of the second negative electrode active material 134 is 1000:1-10:1, or alternatively, 99:1-9:1.

[0095] In the above embodiment, the composite negative electrode active material layer 132 includes a first negative electrode active material 133 for inserting lithium and a second negative electrode active material 134 for inserting sodium or potassium ions. By maintaining the mass ratio of the first negative electrode active material 133 to the second negative electrode active material 134 in the range of 1000:1 to 10:1, particularly 99:1 to 9:1, sufficient space for inserting lithium can be ensured in the composite negative electrode active material layer 132.

[0096] In the embodiment of the present application, the mass ratio of the first negative electrode active material 133 to the second negative electrode active material 134 can be 100:1, 50:1 or 30:1. As long as the value range is within the above range, the present application does not make any special limitation on this.

[0097] In some embodiments, the compaction density g of the negative electrode sheet 13 satisfies: g=g1*w1+g2*w2,

[0098] Wherein, g1 is the compaction density of the first negative electrode active material 133 , and g2 is the compaction density of the second negative electrode active material 134 .

[0099] In the above solution, the composite negative electrode active material 132 on the negative electrode sheet 13 includes a first negative electrode active material 133 and a second negative electrode active material 134. The difference in mass content and compaction density of the first negative electrode active material 133 and the second negative electrode active material 134 will result in a change in the compaction density of the entire negative electrode sheet 13. By correlating the compaction density of the negative electrode sheet 13 with the content and compaction density of the first negative electrode active material 133 and the second negative electrode active material 134, the compaction density of the entire negative electrode sheet 13 can be more accurately calculated.

[0100] In some embodiments, the compaction density of the negative electrode sheet 13 is in the range of 0.1-5 g / cm 3 , optionally, 0.5-3.0 g / cm 3 .

[0101] In the above solution, the compaction density of the negative electrode sheet 13 is set to 0.1-5 g / cm 3 , especially 0.5-3.0g / cm 3 , which can avoid the electrolyte from being unable to penetrate due to the negative electrode plate 13 being too compacted and the battery capacity from being low due to the compacted density being too small.

[0102] In some embodiments, the compaction density of the first negative electrode active material 133 is in the range of 0.5-3 g / cm 3 , optionally, 1.0-1.8 g / cm 3 .

[0103] In the above scheme, by making the compaction density of the first negative electrode active material 133 0.5-3 g / cm 3 , especially 1.0-1.8g / cm 3 , which can avoid the electrolyte from being unable to penetrate due to the high compaction density of the first negative electrode active material 133 and the battery from having low capacity due to the low compaction density.

[0104] In the embodiment of the present application, the compaction density of the first negative electrode active material layer 133 can be 0.6 g / cm 3 , 1.0g / cm 3 or 1.5g / cm 3 As long as its value range is within the above range, this application does not make any special limitations on it.

[0105] In some embodiments, the compaction density of the second negative electrode active material 134 is in the range of 0.1-5 g / cm 3 , optionally, 1.0-3.0 g / cm 3 .

[0106] In the above scheme, by making the compaction density of the second negative electrode active material 134 0.1-5 g / cm 3 , especially 1.0-3.0g / cm 3 , which can avoid the electrolyte from being unable to penetrate due to the high compaction density of the second negative electrode active material 134 and the battery from having low capacity due to the low compaction density.

[0107] In the embodiment of the present application, the compaction density of the second negative electrode active material layer 134 can be 0.6 g / cm 3 , 2.0g / cm 3 or 3.5g / cm 3 As long as its value range is within the above range, this application does not make any special limitations on it.

[0108] In some embodiments, the coating weight of the composite negative active material layer 132 is 0.5-50 mg / cm 2 , optionally, 5-30 mg / cm 2 .

[0109] In the above scheme, the coating weight of the composite negative electrode active material layer 132 is kept at 0.5-50 mg / cm 2 , especially 5-30mg / cm 2, the coating weight of the composite negative electrode active material layer 132 can be kept within a reasonable range.

[0110] In the embodiment of the present application, the coating weight of the composite negative electrode active material layer 132 can be 5.0 mg / cm 2 、10.0mg / cm 2 or 20.5 mg / cm 2 As long as its value range is within the above range, this application does not impose any special limitation on it.

[0111] In some embodiments, the anion of the electrolyte salt includes at least one of perchlorate, tetrafluoroborate, hexafluoroarsenate, hexafluorophosphate, bistrifluoromethylsulfonyl imide, difluorophosphate, bisdifluorosulfonyl imide, bisoxalatoborate, and difluorooxalatoborate.

[0112] In the above scheme, by adopting at least one of perchlorate, tetrafluoroborate, hexafluoroarsenate, hexafluorophosphate, bis(trifluoromethylsulfonylimide), difluorophosphate, bis(difluorosulfonylimide), bis(oxalatoborate) and difluorooxalatoborate as the anion of the electrolyte salt, the chemical energy and electrical energy in the battery can be successfully converted.

[0113] In the above embodiments, sodium salt or potassium salt is added to the electrolyte instead of lithium salt to play the role of transferring charge, that is, to maintain the good conductivity of lithium ions in the electrolyte. The technical solution of the present application can also be analogized to magnesium and aluminum batteries. For example, in magnesium batteries, potassium salt or sodium salt can also be added to replace magnesium salt to play the role of transferring charge, thereby maintaining the good conductivity of magnesium ions in the electrolyte. The above is only for illustration, and this application will not go into details here.

[0114] [Positive electrode]

[0115] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0116] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0117] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0118] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0119] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one 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.

[0120] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0121] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0122] [Negative electrode]

[0123] The negative electrode sheet includes a negative electrode current collector 131 and a negative electrode film layer disposed on at least one surface of the negative electrode current collector 131 . The negative electrode film layer includes the composite negative electrode active material layer 132 in any of the above embodiments.

[0124] As an example, the negative electrode current collector 131 has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector 131 .

[0125] In some embodiments, the negative electrode current collector 131 may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0126] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one 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).

[0127] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0128] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0129] In some embodiments, the negative electrode sheet 13 can be prepared by the following method: the components for preparing the negative electrode sheet 13, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector 131, and after drying, cold pressing and other processes, the negative electrode sheet 13 can be obtained.

[0130] [Electrolyte]

[0131] The electrolyte serves to conduct ions between the positive electrode and the negative electrode. In an embodiment of the present application, the electrolyte includes the electrolyte salt described in any of the above embodiments, wherein the electrolyte salt includes at least one of a lithium salt, a sodium salt, or a potassium salt, and in the electrolyte, the lithium salt content x is 0 mol / L ≤ x < 0.8 mol / L, the potassium salt content y is 0 mol / L ≤ y < 3 mol / L, the sodium salt content z is 0 mol / L ≤ z < 3 mol / L, the sum of the sodium salt and potassium salt contents is y + z > 0 mol / L, and the electrolyte salt content is 0 mol / L < x + y + z < 3 mol / L.

[0132] In some embodiments, the electrolyte further comprises a solvent. The solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0133] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0134] [Isolation film]

[0135] In some embodiments, the lithium-ion battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0136] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0137] In some embodiments, the positive electrode sheet, the negative electrode sheet 13 and the separator can be formed into the electrode assembly 12 by a winding process or a lamination process.

[0138] In some embodiments, the battery cell 100 may include an outer packaging that can be used to encapsulate the electrode assembly 12 and the electrolyte.

[0139] In some embodiments, the outer packaging of the battery cell 100 may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell 100 may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0140] The present application has no particular limitation on the shape of the battery cell 100 , which may be cylindrical, square, or any other shape. For example, FIG3 shows a battery cell 100 with a square structure as an example.

[0141] In some embodiments, referring to Figure 1, the outer packaging may include a shell 11 and a cover plate 14. The shell 11 may 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 shell 11 has an opening connected to the receiving cavity, and the cover plate 14 can be covered on the opening to close the receiving cavity. The positive electrode, the negative electrode and the solid electrolyte can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The number of electrode assemblies 12 contained in the battery cell 100 can be one or more, and those skilled in the art can select according to specific actual needs.

[0142] FIG4 is a schematic diagram of the structure of a battery according to one embodiment of the present application. As shown in FIG4 , in a battery 500, multiple battery cells 100 may be arranged sequentially along the length of the battery 500. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 100 may be secured together using fasteners.

[0143] Continuing with Figure 4 , the battery 500 may include a battery box and a plurality of battery cells 100 disposed within the battery box. The battery box includes an upper box body 501 and a lower box body 502. The upper box body 501 can cover the lower box body 502 and form an enclosed space for accommodating the battery cells 100. The plurality of battery cells 100 may be arranged in any manner within the battery box.

[0144] In some embodiments, battery cells may be assembled into a battery module first. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0145] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0146] In some embodiments, the above-mentioned battery modules or battery packs can also be assembled into a battery. The number of battery modules or batteries contained in the battery can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery.

[0147] That is to say, in the embodiments of the present application, the battery may include any one of a battery cell, a battery module or a battery pack.

[0148] In addition, the present application also provides an electric device, which includes at least one of the battery cells and batteries provided in the present application. The battery cells or batteries can be used as the power source of the electric device, and can also be used as the energy storage unit of the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0149] For example, Figure 5 is a structural diagram of a vehicle according to an embodiment of the present application. As shown in Figure 5, vehicle 1 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 400, a controller 600 and a battery 500 can be provided inside the vehicle 1, and the controller 600 is used to control the battery 500 to supply power to the motor 400. For example, a battery 500 can be provided at the bottom, front or rear of the vehicle 1. The battery 500 can be used to power the vehicle 1. For example, the battery 500 can be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements of the vehicle 1 during startup, navigation and operation. In another embodiment of the present application, the battery 500 can not only serve as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0150] As the electrical device, a battery cell or a battery can be selected according to its usage requirements.

[0151] The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device's requirements for high power and high energy density of the battery, a battery cell or a battery can be used.

[0152] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use the battery cell 100 as a power source.

[0153] [Example]

[0154] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0155] [Example 1]

[0156] 1. Preparation of lithium-ion batteries

[0157] 1.1) Preparation of the Positive Electrode: Dissolve the positive electrode active material, lithium iron phosphate (LiFePO4, LFP), the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) at a weight ratio of 95%:3%:2%. Stir thoroughly and mix thoroughly to prepare a positive electrode slurry. The positive electrode slurry is evenly coated on Al foil, dried at 85°C for 4 hours, and then cold-pressed. The sheet is then trimmed and cut to obtain the positive electrode.

[0158] 1.2) Preparation of the Negative Electrode Sheet: Disperse the first negative electrode active material, graphite; the second negative electrode active material, hard carbon; the conductive agent, Super P; the binder, styrene-butadiene rubber (SBR); and the thickener, CMC-Na, in deionized water at a mass ratio of 90%:2%:3%:1.5%:1.5%. After thorough mixing, a negative electrode slurry is obtained. The negative electrode slurry is applied to the negative electrode current collector, Cu foil, and dried under vacuum at 120°C for 12 hours. The negative electrode sheet is then cold-pressed, trimmed, and cut into sheets.

[0159] 1.3). Isolation film: 16μm polyethylene film is used as the isolation film.

[0160] 1.4) Electrolyte: Evenly mix 0.8 mol / L lithium hexafluorophosphate and 0.2 mol / L EC / DMC (1:1 vol%) solution.

[0161] 1.5) Assembly: The positive electrode sheet, separator, and negative electrode sheet prepared in the above steps are stacked in order, with the separator positioned between the positive and negative electrodes to provide isolation. Winding is done to form an electrode assembly, and the tabs are welded. The electrode assembly is then placed in the housing. The prepared electrolyte solution is poured into the dried battery cells. After packaging and allowing them to rest, they are slowly formed and then shaped to produce a lithium-ion battery.

[0162] [Example 2]

[0163] The preparation process of the lithium-ion battery of Example 2 is basically the same as that of Example 1, except that the electrolyte is a uniform mixture of 0.8 mol / L lithium hexafluorophosphate, 0.1 mol / L EC / DMC and 0.1 mol / L (1:1 vol%) solution.

[0164] [Example 3]

[0165] The preparation process of the lithium-ion battery of Example 3 is basically the same as that of Example 1, except that in the negative electrode plate, the ratio of the first negative electrode active material graphite to the second negative electrode active material hard carbon is 82%:10%, and the electrolyte is a uniform mixture of 0.5 mol / L EC / DMC and 0.5 mol / L sodium hexafluorophosphate solution.

[0166] [Example 4]

[0167] The preparation process of the lithium-ion battery of Example 4 is substantially the same as that of Example 3, except that the electrolyte is a 1 mol / L sodium hexafluorophosphate solution.

[0168] [Example 5]

[0169] The preparation process of the lithium-ion battery of Example 5 is basically the same as that of Example 1, except that the negative electrode plate contains only the first negative electrode active material graphite, and the electrolyte is a uniform mixture of 0.8 mol / L lithium hexafluorophosphate, 0.1 mol / L EC / DMC, and 0.1 mol / L (1:1 vol%) solution.

[0170] [Example 6]

[0171] The preparation process of the lithium-ion battery of Example 6 is basically the same as that of Example 5, except that the electrolyte is a uniform mixture of 0.5 mol / L EC / DMC and 0.5 mol / L sodium hexafluorophosphate solution.

[0172] [Example 7]

[0173] The preparation process of the lithium-ion battery of Example 7 is basically the same as that of Example 5, except that the electrolyte is a 1 mol / L sodium hexafluorophosphate solution.

[0174] [Example 8]

[0175] The preparation process of the lithium-ion battery of Example 8 is basically the same as that of Example 5, except that the electrolyte is a 1 mol / L EC / DMC solution.

[0176] [Example 9]

[0177] The preparation process of the lithium-ion battery of Example 9 is basically the same as that of Example 1, except that the ratio of the first negative electrode active material graphite to the second negative electrode active material hard carbon is 30%:1%, and the electrolyte is a uniform mixture of 0.7 mol / L lithium hexafluorophosphate and 0.3 mol / L EC / DMC.

[0178] [Example 10]

[0179] The preparation process of the lithium-ion battery of Example 10 is basically the same as that of Example 1, except that the ratio of the first negative electrode active material graphite to the second negative electrode active material hard carbon is 30%:2%, and the electrolyte is 1 mol / L EC / DMC solution.

[0180] [Comparative Example 1]

[0181] The preparation process of the lithium ion battery of Comparative Example 1 is basically the same as that of Example 1, except that the ratio of the first negative electrode active material graphite to the second negative electrode active material hard carbon is 90%:2%, and the electrolyte is a 1 mol / L lithium hexafluorophosphate solution.

[0182] [Comparative Example 2]

[0183] The preparation process of the lithium ion battery of Comparative Example 2 is basically the same as that of Example 1, except that the ratio of the first negative electrode active material graphite to the second negative electrode active material hard carbon is 15%:1%, and the electrolyte is a 1 mol / L lithium hexafluorophosphate solution.

[0184] [Comparative Example 3]

[0185] The preparation process of the lithium-ion battery of Comparative Example 3 is substantially the same as that of Example 1, except that the negative electrode active material is only graphite and the electrolyte is a 1 mol / L lithium hexafluorophosphate solution.

[0186] 2. Performance characterization of negative electrode

[0187] 2.1) Thickness measurement: Use X / β-ray microspot density meter (CDM thickness and density measurement all-in-one machine) to measure.

[0188] 2.2) Measurement of compacted density: Take the prepared negative electrode sheet and cut a section with a circular or square cutter. Measure the thickness and weigh it. Wash away the negative electrode material with an acetone-alcohol mixture and dry it. Weigh and measure the mass and thickness of the remaining Cu foil. Divide the difference between the two weights by the area to calculate the areal density. Divide the areal density by the thickness difference to obtain the compacted density.

[0189] 3. Performance characterization of lithium-ion batteries

[0190] 3.1) Cycling Performance: Under normal temperature conditions, maintain the battery charge and discharge voltage range between 2.5-3.65V, cycle 100 times at a current density of 0.5C, and calculate the capacity retention rate. See Table 1 for test results.

[0191] 3.2) Rate performance: Under normal temperature conditions, maintain the battery charge and discharge voltage range at 2.5-3.65V, charge and discharge at a current density of 2C for 10 cycles, and calculate the charge and discharge specific capacity at this rate.

[0192] Table 1 Lithium ion battery performance test table of Examples 1-10 and Comparative Examples 1-3

[0193] It can be seen from the above-mentioned lithium-ion battery performance test that compared with batteries in which the negative electrode active material only uses graphite and the electrolyte only includes lithium salt, the lithium-ion battery provided in this application has a negative electrode active material that is a composite negative electrode active material including graphite and hard carbon, and the electrolyte includes lithium salt, potassium salt or sodium salt. This reduces the production cost while ensuring better cycle performance and rate performance of the battery.

[0194] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising: A negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a composite negative electrode active material layer disposed on at least one side of the negative electrode current collector, the composite negative electrode active material layer comprising a first negative electrode active material and a second negative electrode active material; An electrolyte solution including an electrolyte salt, wherein the electrolyte salt includes at least one of a lithium salt, a sodium salt or a potassium salt; Wherein, in the electrolyte, the content x of the lithium salt is 0mol / L≤x<0.8mol / L, the content y of the potassium salt is 0mol / L≤y<3mol / L, the content z of the sodium salt is 0mol / L≤z<3mol / L, and the sum of the contents of the potassium salt and the sodium salt is y+z>0mol / L.

2. The battery cell according to claim 1, wherein: The content of the electrolyte salt is 0 mol / L<x+y+z<5 mol / L, optionally, 1.0 mol / L<x+y+z<3 mol / L.

3. The battery cell according to claim 1 or 2, wherein: The first negative electrode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming an alloy with lithium, and optionally, graphite.

4. The battery cell according to any one of claims 1 to 3, wherein: The second negative electrode active material includes at least one of hard carbon, dipotassium terephthalate, germanium and its alloys, tin and its alloys, lead and its alloys, antimony metal and its alloys, bismuth and its alloys, and metal oxides.

5. The battery cell according to any one of claims 1 to 4, wherein: The composite negative electrode active material layer includes the first negative electrode active material and the second negative electrode active material mixed.

6. The battery cell according to any one of claims 1 to 4, wherein: The composite negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer.

7. The battery cell according to claim 6, wherein: The first negative electrode active material layer is disposed between the negative electrode current collector and the second negative electrode active material layer.

8. The battery cell according to claim 6 or 7, wherein: The thickness of the composite negative electrode active material layer is 30-300 um, and optionally, 50-200 um.

9. The battery cell according to any one of claims 6 to 8, wherein: The thickness of the second negative electrode active material layer is 1-80 um, and optionally, 20-50 um.

10. The battery cell according to any one of claims 6 to 9, wherein: The thickness of the first negative electrode active material layer is 50-300 um, and optionally, 100-200 um.

11. The battery cell according to any one of claims 1 to 10, wherein: In the composite negative electrode active material layer, the ratio of the mass content w1 of the first negative electrode active material to the mass content w2 of the second negative electrode active material is 1000:1-10:1, and optionally, is 99:1-9:

1.

12. The battery cell according to claim 11, wherein: The compaction density g of the negative electrode sheet satisfies: g=g1*w1+g2*w2, Wherein, g1 is the compaction density of the first negative electrode active material, and g2 is the compaction density of the second negative electrode active material.

13. The battery cell according to claim 12, wherein: The compaction density of the negative electrode sheet is in the range of 0.1-5 g / cm 3 , optionally, 0.5-3.0 g / cm 3 .

14. The battery cell according to claim 12 or 13, wherein: The compaction density of the first negative electrode active material is in the range of 0.5-3 g / cm 3 , optionally, 1.0-1.8 g / cm 3 .

15. The battery cell according to any one of claims 12 to 14, wherein: The compaction density of the second negative electrode active material ranges from 0.1 to 5 g / cm 3 , optionally, 1.0-3.0 g / cm 3 .

16. The battery cell according to any one of claims 1 to 15, wherein: The coating weight of the composite negative electrode active material layer is 0.5-50 mg / cm 2 , optionally, 5-30 mg / cm 2 .

17. The battery cell according to any one of claims 1 to 16, wherein: The anion of the electrolyte salt includes at least one of perchlorate, tetrafluoroborate, hexafluoroarsenate, hexafluorophosphate, bistrifluoromethylsulfonyl imide, difluorophosphate, bisdifluorosulfonyl imide, bisoxalatoborate, and difluorooxalatoborate.

18. A battery comprising a plurality of battery cells according to any one of claims 1 to 17.

19. An electrical device comprising the battery according to claim 18, wherein the battery is used to provide electrical energy.

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