Positive pole piece, battery and electric equipment

Abstract

The invention relates to the technical field of batteries, in particular to a positive pole piece, a battery and electric equipment, the positive pole piece comprises a positive active material and a potassium salt additive, the positive active material comprises a phosphate positive material, and potassium ions are decomposed from potassium salt under the voltage of 3.1-4.2 V. The active ion loss of the battery can be reduced, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to positive electrode sheets, batteries, and electrical equipment. Background Art

[0002] With the development of modern technology, lithium-ion and sodium-ion batteries are considered the preferred green and environmentally friendly batteries due to their high energy density, long cycle life, and environmentally friendly performance. These batteries are widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in electric vehicles, power tools, military equipment, and aerospace applications.

[0003] Phosphate cathode materials, such as lithium iron phosphate and polyanion sodium electrolytes, are highly stable and widely used in secondary batteries. However, the lifespan of secondary batteries needs to be further improved. Summary of the Invention

[0004] In view of this, the main technical problem to be solved by this application is the problem of capacity attenuation in the early and late stages of the cycle of lithium iron phosphate or polyanion sodium battery. Thus, positive electrode sheets, batteries and electrical equipment are provided to improve the capacity attenuation when phosphate positive electrode materials are used as positive electrode active materials, thereby increasing the battery life.

[0005] In order to solve the above technical problems, a technical solution adopted in this application is: providing a positive electrode plate, the positive electrode plate includes a positive electrode film layer, the positive electrode film layer includes a positive electrode active material and an additive, the positive electrode active material includes a phosphate positive electrode material, and the additive includes a potassium salt, and the potassium salt decomposes into potassium ions at a voltage of 3.1V-4.2V.

[0006] In the technical solution of the embodiment of the present application, potassium salt is added as an additive in the positive electrode film layer, and the potassium salt decomposes potassium ions at a voltage of 3.1V-4.2V, so that after the positive electrode plate is assembled into a battery, in the formation stage, the potassium salt can decompose potassium ions; because the potassium ions decomposed by the potassium salt components are similar to the potential of lithium ions and sodium ions relative to reversible hydrogen, potassium ions can replace at least part of the lithium ions or sodium ions to participate in the formation of SEI film (solid electrolyte interface film) on the negative electrode plate, which can reduce the active ion loss of phosphate positive electrode materials such as lithium iron phosphate materials and / or polyanionic sodium electric materials in the positive electrode film layer, reduce the loss rate of active ions such as lithium ions and sodium ions, improve the capacity stability of the battery, reduce the occurrence of battery capacity decay, and improve the cycle life of the battery. In the embodiment of the present application, potassium salt decomposes potassium ions at a voltage of 3.1V-4.2V, and the voltage is low, which can reduce the occurrence of side reactions in the battery formation stage. In the embodiment of the present application, the cost of potassium salt is lower than that of lithium salt, so that the positive electrode plate of the embodiment of the present application can reduce the cost on the one hand, and on the other hand, it can reduce the occurrence of capacity decay in the early stage of battery formation or battery cycle. In addition, the negative electrode plate in the battery may expand or crack during the cycle process, and the negative electrode plate forms a new contact surface (the contact surface in direct contact with the electrolyte) or the SEI film ruptures, etc., which will re-form or repair the SEI film. The potassium salt in the embodiment of the present application can be used as an additive to participate in the repair of the SEI film during the battery cycle, reduce the loss of active ions such as lithium ions and sodium ions, improve the occurrence of battery capacity decay of phosphate positive electrode materials such as lithium iron phosphate and / or polyanionic sodium electric materials during the cycle, and improve the cycle stability of batteries made of phosphate positive electrode materials such as lithium iron phosphate and / or polyanionic sodium electric materials. On the other hand, in the embodiment of the present application, the additive is directly provided in the positive electrode film layer, so that the potassium ions in the additive can directly replace at least part of the lithium ions in the lithium iron phosphate positive electrode active material, and replace at least part of the sodium ions and other active ions in the polyanionic sodium electric material to participate in the formation of the SEI film on the negative electrode sheet.

[0007] In the embodiment of the present application, the voltage may be the charging voltage of the battery in the formation stage, that is, the voltage may be the formation voltage. In other embodiments, the voltage may also be the charging voltage of the battery during the cycle process.

[0008] In any embodiment, the mass ratio of potassium salt to positive electrode active material is (0.5-8):(90-97). In the embodiment of the present application, by controlling the mass ratio of potassium salt to positive electrode active material within the above range, the potassium salt in the positive electrode plate can, on the one hand, reduce the loss of active ions such as lithium ions and sodium ions, thereby improving the cycle performance of the battery; on the other hand, it can reduce the energy density loss of the positive electrode plate, thereby improving the electrochemical performance of the battery.

[0009] In any embodiment, the mass fraction of the potassium salt in the positive electrode film layer is 0.5%-8%. In the embodiment of the present application, by controlling the mass fraction of the potassium salt in the positive electrode film layer within the above range, the content of the potassium salt in the positive electrode film layer is preferably, the more large ion radius (potassium ions) in the positive electrode film layer, the larger the active ion diffusion channel, which is conducive to the escape of active lithium ions and the improvement of the capacity of the positive electrode plate; the mass fraction of the potassium salt in the positive electrode film layer within the above range can reduce the loss of active ions such as lithium ions and sodium ions, improve the cycle performance of the battery, reduce the energy density loss of the positive electrode plate, and improve the electrochemical performance of the battery.

[0010] In any embodiment, the additive includes potassium sulfide (K2S), potassium azide (KN3), potassium nitrite (KNO2), potassium citrate (KC6H5O7), potassium oxide (K2O), potassium peroxide (K2O2), potassium oxalate (K2C2O4), potassium squarate (K2C4O4), organic potassium oxides (K2C3O5, K2C4O6, K2C6O6), potassium thiosulfate (K2S2O3), potassium sulfite (K2SO3), potassium carbonate (K2CO3), potassium benzoate (KC6H5CO2), tripotassium citrate (C6H5K3O7) and potassium sodium citrate (C 12 H 10 K3Na3O 14 In the embodiment of the present application, the voltage at which the above-mentioned additive decomposes into potassium ions is relatively low, and the additive can be used as an additive for the positive electrode film layer.

[0011] In any embodiment, the volume average particle size DV50 of the potassium salt is 1 μm-30 μm. In the embodiment of the present application, by controlling the volume average particle size of the potassium salt within the above range, on the one hand, the specific surface area of ​​the potassium salt is improved, the polarization is reduced, and the potassium salt is easily decomposed under voltage to produce potassium ions; on the other hand, the manufacturability during the production process of the potassium salt slurry is improved, the polarization of the potassium salt is small, the power density is better, and the cycle performance is better. On the other hand, when the potassium salt slurry is made into a positive electrode film layer, the porosity of the positive electrode film layer is better, the compaction density is larger, and the positive electrode film layer is not easy to break.

[0012] In the embodiments of the present application, the volume average particle size DV50 is common knowledge in the art, has a meaning commonly known in the art, and can be measured by methods and instruments in the art.

[0013] In any embodiment, the volume average particle size DV50 of the potassium salt is 1 μm to 10 μm. By controlling the volume average particle size of the potassium salt within the above range, the specific surface area of ​​the potassium salt is improved, and the potassium salt is easily decomposed under voltage to produce potassium ions. In addition, the manufacturability of the potassium salt during the slurry production process is improved, the polarization of the potassium salt is reduced, the power density is improved, and the cycle performance is improved.

[0014] In any embodiment, during the initial cycle, the potassium ion content in the positive electrode plate is greater than or equal to 100 PPM. In the embodiment of the present application, after the positive electrode plate is assembled into a battery and undergoes formation and initial cycling, potassium ions still remain in the positive electrode plate, and the residual amount of potassium ions can be measured by inductively coupled plasma emission spectrometry (ICP).

[0015] In any embodiment, the positive electrode sheet includes a current collector, the positive electrode film layer includes a positive electrode active material layer and an additive layer, the additive layer is disposed on a side of the positive electrode active material layer facing away from the current collector, and the additive layer includes a potassium salt. In an embodiment of the present application, the potassium salt additive can form an additive layer disposed on a side of the positive electrode active material layer facing away from the current collector, so that the additive layer in the embodiment of the present application can also improve the loss of active ions such as lithium ions and sodium ions in the positive electrode active material layer, improve the occurrence of battery capacity decay during cycling, and improve the cycling stability of the battery.

[0016] In any embodiment, the positive electrode sheet includes a current collector, the positive electrode film layer includes a positive electrode active material layer, and the additive is dispersed in the positive electrode active material layer. This can simplify the manufacturing process, reduce the loss of active ions such as lithium ions and sodium ions in the positive electrode active material layer, reduce the occurrence of battery capacity decay during cycling, and improve the battery's cycling stability.

[0017] In any embodiment, the phosphate positive electrode material includes lithium iron phosphate material and / or polyanion sodium electrode material.

[0018] In any embodiment, the lithium iron phosphate material includes a structural formula of Li x Fe y M zPO4 material, wherein M includes any one or more of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B and Nb, 0.05≦x≦1.2, 0.2≦y≦1, 0≦z≦0.8. In the embodiment of the present application, the lithium iron phosphate material includes lithium iron phosphate or lithium iron phosphate doped with metal elements. Lithium iron phosphate is doped with the above-mentioned metal elements to improve the internal conductivity of the lithium iron phosphate particles. In the later stage of the battery cell in the embodiment of the present application, after formation or cycling, the number of P element atoms in a lithium iron phosphate material molecule can be greater than 1, or less than 1 and greater than 0, and the number of O element atoms can be greater than 4, or less than 4 and greater than 0.

[0019] In any embodiment, the lithium iron phosphate material includes a coating layer, the coating layer is provided on a surface of the lithium iron phosphate material having a structural formula of Li x Fe y M z In the embodiment of the present application, the surface of the lithium iron phosphate has a coating layer, for example, the coating layer includes a carbon-containing material layer, which can improve the conductivity of the lithium iron phosphate.

[0020] In any embodiment, the polyanionic sodium-based material includes Na x M y (X a O b )Z w , x=1-4, y=1-4, a=1-4, b=4-18, w=3 or 0, M includes one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Ca, Mg, Al, Nb, X=P, S, B, Mo, and Z includes F. The potassium salt additive can reduce the loss of active sodium ions in the above-mentioned polyanionic sodium battery, improve the capacity stability of the sodium battery, and increase the life of the sodium battery.

[0021] In any embodiment, the positive electrode film layer further comprises a conductive agent and a binder, and the mass ratio of the conductive agent, the binder, and the positive electrode active material is (1-5):(1-5):(90-97). In the embodiment of the present application, by controlling the mass ratio of the conductive agent, the binder, and the positive electrode active material within the above range, the bonding properties, conductivity, and energy density of the positive electrode film layer are improved.

[0022] A second aspect of the present application further provides a battery, comprising a positive electrode plate, the positive electrode plate comprising a positive electrode active material and an additive, the positive electrode active material comprising a phosphate positive electrode material, the additive comprising a potassium salt, and the potassium salt decomposing to produce potassium ions at a voltage of 3.1 V to 4.2 V. In an embodiment of the present application, the positive electrode plate in the battery comprises the additive, and during the battery formation process, the potassium salt can decompose to produce potassium ions, so that the positive electrode plate contains the potassium salt additive and potassium ions. The battery of the present application has the same advantages as the positive electrode plate of the first aspect.

[0023] In any embodiment, the phosphate positive electrode material includes a lithium iron phosphate material and / or a polyanion sodium electrode material.

[0024] In any embodiment, during the initial cycle, the content of potassium ions in the positive electrode sheet is greater than or equal to 100 PPM. In an embodiment of the present application, after the battery undergoes formation and the first cycle (initial cycle), potassium ions remain in both the positive electrode sheet and the negative electrode sheet, and the residual amount of potassium ions can be measured by an inductively coupled plasma emission spectrometer (ICP). When the mass ratio of potassium ions in the positive electrode sheet to the positive electrode film layer is greater than or equal to 100 PPM, it indicates that the potassium ions come from the potassium salt additive in the positive electrode film layer.

[0025] In any embodiment, the battery further includes a negative electrode sheet, the negative electrode sheet includes a negative electrode film layer, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite. In the embodiment of the present application, the negative electrode sheet includes a graphite negative electrode active material, so that the battery in the embodiment of the present application has better cycle stability.

[0026] In any embodiment, a negative electrode plate is further included, and the negative electrode plate includes metallic lithium or its alloy metal. In the embodiment of the present application, the use of metallic lithium or its alloy metal can significantly improve the volume energy density of the battery in the embodiment of the present application.

[0027] In any embodiment, the present invention further includes a negative electrode plate. At the end of the formation, the negative electrode plate includes a negative electrode film layer and a solid electrolyte interface film disposed on the negative electrode film layer, wherein the solid electrolyte interface film includes potassium ions. In the embodiment of the present application, the potassium salt additive in the positive electrode film layer can replace at least a portion of the lithium ions or sodium ions to participate in the formation of the SEI film (solid electrolyte interface film) on the negative electrode plate, so that the SEI film contains potassium ions.

[0028] The third aspect of the present application further provides an electrical device comprising the battery of the second aspect. The embodiment of the present application comprises the positive electrode sheet of the second aspect, and has at least the same advantages as the positive electrode sheet of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a positive electrode sheet provided in one embodiment of the present application;

[0030] Figure 2 This is a schematic structural diagram of a positive electrode sheet provided in another embodiment of the present application;

[0031] Figure 3 is a schematic structural diagram of a vehicle provided in one embodiment of the present application;

[0032] Figure 41 is a schematic diagram of the exploded structure of a battery provided in one embodiment of the present application;

[0033] Figure 5 It is a schematic diagram of the exploded structure of a battery cell provided in one embodiment of the present application. DETAILED DESCRIPTION

[0034] Below, the embodiments of the battery cells, batteries, and electrical equipment of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0035] " 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 special 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.

[0036] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] 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.

[0038] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates 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.

[0039] 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 indicate that other components not listed may also be included or that only the listed components are included.

[0040] 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).

[0041] During long cycles (more than 1,000 cycles), secondary batteries are prone to significant capacity decay, which affects the life and stability of the secondary batteries. The main reason is that during long cycles, the formation and repair of the SEI film of the negative electrode will continuously consume active ions (lithium ions or sodium ions), causing the battery capacity to decay rapidly. Among them, for lithium iron phosphate materials, the structure of lithium iron phosphate materials is very stable, and there is almost no structural change during the first charge and discharge process. The first charge and discharge efficiency is high, and the active lithium that is released basically returns to the positive electrode after the first discharge. However, the battery is still constantly consuming active lithium during the early use process, forming a relatively stable SEI film, which causes the lithium iron phosphate battery to have a faster capacity decay in the early cycle. During the middle and late use of the battery, the negative electrode is prone to expansion and increase in volume. In this process, active lithium will be consumed, and the SEI film will further form to achieve the effect of repairing the SEI film of the negative electrode, causing the lithium iron phosphate battery to be prone to capacity decay in the middle and late stages of the cycle. For polyanionic sodium-ion batteries, when used as positive electrode active materials in sodium batteries, the sodium batteries continuously consume active sodium during their early use and participate in the formation of the SEI film, resulting in a faster capacity decay in the early stages of the sodium-ion battery cycle.

[0042] To this end, the present application provides a positive electrode sheet, such as Figure 1As shown, the positive electrode plate includes a positive electrode film layer 32, which includes a positive electrode active material and an additive. The positive electrode active material includes a phosphate positive electrode material, and the additive includes a potassium salt. The potassium salt decomposes into potassium ions at a voltage of 3.1V-4.2V.

[0043] In the technical solution of the embodiment of the present application, by adding potassium salt as an additive to the positive electrode film layer 32, and the potassium salt decomposes potassium ions at a voltage of 3.1V-4.2V, so that after the positive electrode plate is assembled into a battery, in the formation stage, the potassium salt can decompose potassium ions; because the potassium ions decomposed by the potassium salt components are similar to the potential of lithium ions and sodium ions relative to reversible hydrogen, potassium ions can replace at least part of the lithium ions and sodium ions to participate in the formation of SEI film (solid electrolyte membrane) on the negative electrode plate, which can reduce the active ion loss of the phosphate positive electrode material in the positive electrode film layer 32, reduce the loss rate of active ions such as lithium ions and sodium ions, improve the capacity stability of the battery, and reduce the occurrence of battery capacity decay. In the embodiment of the present application, potassium salt decomposes potassium ions at a voltage of 3.1V-4.2V, and the voltage is low, which can reduce the occurrence of side reactions in the battery formation stage. In the embodiment of the present application, the cost of potassium salt is lower than that of lithium salt, so that the positive electrode plate of the embodiment of the present application can reduce costs on the one hand, and on the other hand, it can reduce the occurrence of battery formation or battery cycle early capacity decay. In addition, the negative electrode sheet in the battery may expand or crack during the cycle, and the negative electrode sheet forms a new contact surface (the contact surface in direct contact with the electrolyte) or the SEI film ruptures, and the SEI film will be formed again. The potassium salt in the embodiment of the present application can participate in the formation of the SEI film during the battery cycle as an additive, reduce the loss of active ions such as lithium ions and sodium ions, improve the occurrence of battery capacity decay when the phosphate positive electrode material is used as the positive electrode material during the cycle, and improve the cycle stability of the phosphate positive electrode material battery. On the other hand, in the embodiment of the present application, the additive is directly provided in the positive electrode film layer 32, so that the potassium ions in the additive can directly replace at least part of the lithium ions in the lithium iron phosphate positive electrode active material and / or replace at least part of the sodium ions and other active ions in the polyanionic sodium electric material to participate in the formation of the SEI film on the negative electrode sheet.

[0044] In some embodiments, the mass ratio of potassium salt to positive electrode active material is (0.5-8): (90-97). In the embodiment of the present application, by controlling the mass ratio of potassium salt to positive electrode active material in the above range, the potassium salt in the positive electrode plate can, on the one hand, reduce the loss of active ions such as lithium ions and sodium ions, thereby improving the cycle performance of the battery; on the other hand, the energy density loss of the positive electrode plate can be small, so that the electrochemical performance of the battery is better. In some embodiments of the present application, the mass ratio of potassium salt to positive electrode active material can be 0.5:90, 0.8:90, 0.5:92, 0.8:92, 1:93, 1.5:93, 2:93, 2.5:93, 3:93, 3.5:93, 4:93, 5:93, 0.5:94, 0.8:95, 1:96, 1.5:97, 3.5:97, etc. Or it can be a range value consisting of any two of the above values, for example, (0.5-0.8):(90-92), (0.8-1.5):(92-95), (1.5-3.5):(95-97), (0.5-3.5):(93-97), (3.5-5):(93-97), etc.

[0045] In the embodiment of the present application, the potassium salt additive is provided in the positive electrode film layer, the amount of the potassium salt provided is easy to control, the amount of the potassium salt is provided in a large amount, and the potassium salt can decompose potassium ions at a specific voltage, and the amount of potassium ions is also large. The potassium ions obtained by chemical decomposition are embedded in or removed from the positive electrode active material, which is conducive to participating in the formation of the SEI film. This is different from the effect achieved by introducing potassium doping into the positive electrode active material and adding potassium salt to the electrolyte in the related art; when potassium ion doping is introduced into the positive electrode active material, the potassium ions are not easily released, or the amount released is very small, and cannot participate in the formation of the SEI film, or the amount participating in the formation of the SEI film is also small; the solubility of the potassium salt in the electrolyte is small, and the amount of potassium salt that can be added to the electrolyte is also very small, and the amount participating in the formation of the SEI film is also small. The potassium salt additive is set in the positive electrode film layer. The amount of potassium salt is easy to control. The amount of potassium salt is set to be large, and the potassium salt can decompose potassium ions under a specific voltage. The amount of potassium ions is also large. The potassium ions obtained by chemical decomposition are embedded in or removed from the positive electrode active material, which is beneficial to participate in the formation of the SEI film, can greatly improve the battery capacity attenuation, and increase the cycle life of the battery.

[0046] In some embodiments, the mass fraction of potassium salt in the positive electrode film layer 32 is 0.5%-8%. In the embodiment of the present application, by controlling the mass fraction of potassium salt in the positive electrode film layer 32 within the above range, the content of potassium salt in the positive electrode film layer 32 is better in the embodiment of the present application, the more large ion radius (potassium ion) in the positive electrode film layer, the larger the active ion diffusion channel, which is conducive to the escape of active lithium ions and the improvement of the capacity of the positive electrode plate; the mass fraction of potassium salt in the positive electrode film layer is within the above range, which can reduce the loss of active ions such as lithium ions and sodium ions, improve the cycle performance of the battery, reduce the energy density loss of the positive electrode plate, and make the electrochemical performance of the battery better. In some embodiments of the present application, the mass fraction of potassium salt in the positive electrode film layer 32 can be 0.5%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.4%, 2.8%, 3%, 3.3%, 3.5%, 4%, 5%, 6%, 8%, etc. Or it can be a range value formed by any two of the above values, for example, 0.5%-1.2%, 1.2%-2.4%, 2.4%-3.5%, 0.5%-3.5%, 3.5%-5%, 5%-8%, etc.

[0047] In some embodiments, the additives include potassium sulfide (K2S), potassium azide (KN3), potassium nitrite (KNO2), potassium citrate (KC6H5O7), potassium oxide (K2O), potassium peroxide (K2O2), potassium oxalate (K2C2O4), potassium squarate (K2C4O4), organic potassium oxides (K2C3O5, K2C4O6, K2C6O6), potassium thiosulfate (K2S2O3), potassium sulfite (K2SO3), potassium carbonate (K2CO3), potassium benzoate (KC6H5CO2), tripotassium citrate (C6H5K3O7) and potassium sodium citrate (C 12 H 10 K3Na3O 14 In the embodiment of the present application, the voltage at which the above-mentioned additive decomposes into potassium ions is relatively low, and thus the additive can be used as an additive for the positive electrode film layer 32 .

[0048] In some embodiments, the volume average particle size DV50 of the potassium salt is 1 μm-30 μm. In the embodiment of the present application, by controlling the volume average particle size of the potassium salt within the above range, on the one hand, the specific surface area of ​​the potassium salt is better, the polarization is reduced, and the potassium salt is easy to decompose under voltage to produce potassium ions; on the other hand, the manufacturability during the production process of the potassium salt slurry is better, the polarization of the potassium salt is smaller, the power density is better, and the cycle performance is better. On the other hand, when the potassium salt slurry is made into a positive electrode film layer, the porosity of the positive electrode film layer is better, the compaction density is larger, and the positive electrode film layer is not easy to break. In some embodiments of the present application, the volume average particle size DV50 of the potassium salt can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 30 μm, etc., or a range value composed of any two of the above values, for example, 1 μm-8 μm, 8 μm-15 μm, 15 μm-30 μm, etc.

[0049] In some embodiments, the volume average particle size DV50 of the potassium salt is 1 μm-10 μm. By controlling the volume average particle size of the potassium salt within the above range, the specific surface area of ​​the potassium salt is improved, and the potassium salt is easily decomposed under voltage to produce potassium ions; on the other hand, the manufacturability of the potassium salt in the slurry production process is improved, the polarization of the potassium salt is small, the power density is better, and the cycle performance is better. In some embodiments of the present application, the volume average particle size DV50 of the potassium salt can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, etc., or a range value composed of any two of the above values, for example, 1 μm-3 μm, 3 μm-8 μm, 8 μm-10 μm, etc.

[0050] In some embodiments, during the initial cycle, the content of potassium ions in the positive electrode sheet is greater than or equal to 100PPM. In the embodiment of the present application, when the positive electrode sheet is assembled into a battery cycle and undergoes formation and initial cycles, the positive electrode sheet still has residual potassium ions, and the residual amount of potassium ions can be measured by inductively coupled plasma emission spectrometer (ICP). During the initial cycle, the content of potassium ions in the positive electrode sheet can be 100PPM, 300PPM, 500PPM, 1000PPM, 2000PPM, 5000PPM, 7000PPM, etc., or a range value composed of any two of the above values, such as 100PPM-300PPM, or. 300PPM-5000PPM, or 5000PPM-7000PPM, or the content of potassium ions in the positive electrode sheet can be greater than or equal to 7000PPM.

[0051] In some embodiments, as Figure 2As shown, the positive electrode sheet includes a current collector 31, and the positive electrode film layer 32 includes a positive electrode active material layer 321 and an additive layer 322. The additive layer 322 is disposed on the side of the positive electrode active material layer 321 facing away from the current collector 31, and the additive layer 322 includes a potassium salt. In an embodiment of the present application, the potassium salt additive can form the additive layer 322 and be disposed on the side of the positive electrode active material layer facing away from the current collector 31, so that the additive layer 322 in the embodiment of the present application can also improve the loss of active ions such as lithium ions and sodium ions in the positive electrode active material layer 321, improve the occurrence of battery capacity decay during the cycle, and improve the cycle stability of the battery.

[0052] In some embodiments, as Figure 1 As shown, the positive electrode sheet includes a current collector 31, and the positive electrode film layer 32 includes a positive electrode active material layer 321. The additive is dispersed in the positive electrode active material layer 321. This can simplify the manufacturing process, reduce the loss of active ions such as lithium ions and sodium ions in the positive electrode active material layer 321, reduce the occurrence of battery capacity decay during cycling, and improve the battery's cycling stability.

[0053] In some embodiments, the phosphate positive electrode material includes a lithium iron phosphate material and / or a polyanion sodium electrode material.

[0054] In some embodiments, the lithium iron phosphate material includes a structural formula of Li x Fe y M z PO4 material, wherein M includes any one or more of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B and Nb, 0.05≦x≦1.2, 0.2≦y≦1, 0≦z≦0.8. In the embodiment of the present application, the lithium iron phosphate material includes lithium iron phosphate or lithium iron phosphate doped with metal elements. Doping the lithium iron phosphate with the above-mentioned metal elements can improve the internal conductivity of the lithium iron phosphate particles. In the battery cell of the embodiment of the present application, after formation or cycling, the number of P element atoms in a lithium iron phosphate material molecule can be greater than 1, or less than 1 and greater than 0, and the number of O element atoms can be greater than 4, or less than 4 and greater than 0. For example, M can be Mn, and the lithium iron phosphate material includes lithium manganese iron phosphate; or M can also be any one or more of Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B and Nb.

[0055] In some embodiments, the lithium iron phosphate material includes a coating layer, the coating layer is provided on a surface of the lithium iron phosphate material. x Fe y M zIn the embodiment of the present application, the surface of the lithium iron phosphate has a coating layer, for example, the coating layer includes a carbon-containing material layer, which can improve the conductivity of the lithium iron phosphate.

[0056] In some embodiments, the polyanionic sodium-based material comprises Na x M y (X a O b )Z w ,x=1-4,y=1-4,a=1-4,b=4-18,w=3 or 0,M includes one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Ca, Mg, Al, Nb, X=P, S, B, Mo, Z includes F. Potassium salt additives can reduce the loss of active sodium ions in the above-mentioned polyanionic sodium electric materials, improve the capacity stability of sodium batteries, and increase the life of sodium batteries. Polyanionic sodium electric materials include compounds based on phosphoric acid and fluorophosphoric acid. Phosphoric acid-based compounds include Na x1 Fe y1 P m1 O n1 For example, sodium iron phosphate has a higher capacity, and sodium iron pyrophosphate has a higher voltage platform. Polyanionic sodium electric materials include one or more of sodium vanadium trifluorophosphate Na3V2(PO4)2F3, sodium vanadium fluorophosphate NaVPO4F, sodium vanadium phosphate Na3V2(PO4)3, Na4Fe3(PO4)2P2O7, NaFePO4, and Na3V2(PO4)3.

[0057] In some embodiments, the positive electrode film layer 32 further includes a conductive agent and a binder, and the mass ratio of the conductive agent, the binder to the positive electrode active material is (1-5): (1-5): (90-97). In the embodiment of the present application, by controlling the mass ratio of the conductive agent, the binder and the positive electrode active material within the above range, the bonding, conductivity and energy density of the positive electrode film layer 32 are better. In some embodiments of the present application, the mass ratio of the potassium salt to the positive electrode active material can be 1:1:90, 1:2:90, 1:5:93, 1:1:94, 1:2:95, 1:5:97, 2:1:93, 3:2:93, 5:5:93, 4:5:97, etc. Or it can be a range value composed of any two of the above values, for example, (1-2): (1-3): (90-94), (2-4): (3-4): (94-96), (4-5): (4-5): (96-97), etc.

[0058] A second aspect of the present application further provides a battery, comprising a positive electrode plate, the positive electrode plate comprising a positive electrode active material and an additive, the positive electrode active material comprising a phosphate positive electrode material, the additive comprising a potassium salt, and the potassium salt decomposing to produce potassium ions at a voltage of 3.1 V to 4.2 V. In an embodiment of the present application, the positive electrode plate in the battery comprises the additive, and during the battery formation process, the potassium salt can decompose to produce potassium ions, so that the positive electrode plate contains the potassium salt additive and potassium ions. The battery of the present application has the same advantages as the positive electrode plate of the first aspect.

[0059] In some embodiments, the phosphate cathode material includes a lithium iron phosphate material and / or a polyanionic sodium electrode material.

[0060] In some embodiments, during the initial cycle, the content of potassium ions in the positive electrode sheet is greater than or equal to 100 PPM. In the embodiment of the present application, after the battery undergoes formation and the first cycle (initial cycle), potassium ions remain in both the positive electrode sheet and the negative electrode sheet, and the residual amount of potassium ions can be measured by an inductively coupled plasma emission spectrometer (ICP). When the mass ratio of potassium ions in the positive electrode sheet to the positive electrode film layer is greater than or equal to 100 PPM, it indicates that the potassium ions come from the potassium salt additive in the positive electrode film layer.

[0061] In some embodiments, the battery further includes a negative electrode sheet, the negative electrode sheet including a negative electrode film layer, the negative electrode film layer including a negative electrode active material, and the negative electrode active material including graphite. In this embodiment of the present application, the negative electrode sheet includes a graphite negative electrode active material, which improves the cycle stability of the battery in this embodiment of the present application.

[0062] In some embodiments, a negative electrode plate is further included, and the negative electrode plate includes metallic lithium or its alloy metal. In the embodiment of the present application, the use of metallic lithium or its alloy metal can significantly improve the volume energy density of the battery in the embodiment of the present application.

[0063] In some embodiments, a negative electrode plate is further included. At the end of the formation, the negative electrode plate includes a negative electrode film layer and a solid electrolyte interface film disposed on the negative electrode film layer, wherein the solid electrolyte interface film includes potassium ions. In the embodiments of the present application, the potassium salt additive in the positive electrode film layer can replace at least a portion of the lithium ions or sodium ions to participate in the formation of the SEI film (solid electrolyte interface film) on the negative electrode plate, so that the SEI film contains potassium ions.

[0064] The third aspect of the present application further provides an electrical device comprising the battery of the second aspect. The embodiment of the present application comprises the positive electrode sheet of the second aspect, and has at least the same advantages as the positive electrode sheet of the second aspect.

[0065] The battery disclosed in the embodiments of the present application can be used in electrical devices that use the battery as a power source or various energy storage systems that use the battery as an energy storage element. The electrical devices may be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0066] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0067] Please refer to Figure 3 , Figure 3 A schematic structural diagram of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000. The battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000. For example, the battery 100 may serve as an operating power source for the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, to meet the power requirements for starting, navigating and driving the vehicle 1000.

[0068] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0069] Please refer to Figure 4 , Figure 4This is a schematic diagram of the exploded structure of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 is used to provide a storage space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space for the battery cell 20. The second portion 12 can be a hollow structure with one end open. The first portion 11 can be a plate-like structure, with the first portion 11 overlapping the open side of the second portion 12, so that the first portion 11 and the second portion 12 together define a storage space. The first portion 11 and the second portion 12 can also be hollow structures with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0070] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0071] Each battery cell 20 may be a secondary battery or a primary battery, and may also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0072] Please refer to Figure 5 , Figure 5 The following is a schematic diagram of the decomposition structure of a battery cell 20 provided in some embodiments of the present application. A battery cell 20 is the smallest unit that makes up a battery. Figure 5 The battery cell 20 includes an end cover 21, a shell 22, a battery cell assembly 23 and other functional components.

[0073] The end cap 21 is a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the end cap 21 can be adapted to the shape of the housing 22 to match the housing 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as an aluminum alloy). This prevents the end cap 21 from deforming when subjected to compression or collision, giving the battery cell 20 greater structural strength and improved safety. The end cap 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect to the battery cell assembly 23 to output or input electrical energy to the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for relieving internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cap 21 can also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application are not particularly limited in this regard. In some embodiments, an insulating member may be provided inside the end cap 21 to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be made of plastic, rubber, or the like.

[0074] The housing 22 is a component that cooperates with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can be used to accommodate the battery cell assembly 23, electrolyte, and other components. The housing 22 and end cap 21 can be separate components. An opening can be provided in the housing 22, and the end cap 21 is placed over the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and housing 22 can be integrated. Specifically, the end cap 21 and housing 22 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 22 needs to be enclosed, the end cap 21 is placed over the housing 22. The housing 22 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined based on the specific shape and size of the battery cell assembly 23. The housing 22 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this.

[0075] The cell assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more cell assemblies 23 may be contained in the housing 22. The cell assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the cell assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab 23a. The positive and negative electrode tabs may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tabs 23a connect the electrode terminals to form a current loop.

[0076] [Positive electrode]

[0077] In some embodiments, the positive electrode sheet includes the positive electrode sheet of the first aspect of the present application, and the positive electrode film layer is provided on at least one surface of a current collector. For the sake of distinction, the current collector is referred to as a positive electrode current collector.

[0078] 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.

[0079] 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.).

[0080] The positive electrode active material may also include one or more of phosphate positive electrode materials, sulfate positive electrode materials, silicate positive electrode materials, and borate positive electrode materials. x M(CN)6, where M is one or more of Fe, Mn, Co, Ni, Cu, Zn, Cr, Ti, V, Zr, and Ce, and where 0<x≤2. The positive electrode active material may include at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, and lithium manganese oxide.

[0081] In some embodiments, the positive electrode film layer includes a binder. 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.

[0082] In some embodiments, the positive electrode film layer includes a conductive agent. As an 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.

[0083] In some embodiments, the positive electrode sheet can be prepared by the following method: the components used to prepare the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, the potassium salt additive 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.

[0084] In another embodiment, the positive electrode sheet can also be prepared in the following manner: 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 dried to form a positive electrode active material layer; the potassium salt additive, the conductive agent and the binder are dispersed in a solvent (such as N-methylpyrrolidone) to form an additive slurry, and the additive slurry is coated on the positive electrode active material layer. After drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0085] [Negative electrode]

[0086] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material. In this embodiment, the battery cell is an ion battery. During the charge and discharge process of the battery, active ions (such as Li + 、Na + ) is embedded / deintercalated in the negative electrode active material.

[0087] As an example, the negative electrode current collector 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.

[0088] In some embodiments, the negative electrode current collector 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 material. 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.).

[0089] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0090] 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).

[0091] 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.

[0092] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0093] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, 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 current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0094] [Electrolytes]

[0095] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0096] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0097] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0098] In some embodiments, 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.

[0099] 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.

[0100] [Isolation film]

[0101] In some embodiments, the 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.

[0102] 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.

[0103] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into a battery cell assembly through a winding process or a lamination process.

[0104] In some embodiments, the housing 22 may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like.

[0105] The present application has no particular limitation on the shape of the battery cell 20 , which may be cylindrical, square, or any other shape.

[0106] The beneficial effects of the present application are further illustrated below with reference to the examples.

[0107] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0108] Example 1

[0109]

Preparation of positive electrode sheet

[0110] The positive electrode active material lithium iron phosphate (LiFePO4), potassium salt additive KC6H5O7, conductive carbon and polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 94.2:3:1.3:1.5, and then the solvent N-methylpyrrolidone (NMP) is added to adjust the solid content to 70%-80%. After stirring evenly, the positive electrode slurry is obtained, and then it is coated, dried, cold pressed and cut into positive electrode sheets.

[0111]

Preparation of negative electrode sheet

[0112] Graphite, conductive carbon SP, and binder SBR are dry-mixed at a ratio of 97:1:2, deionized water is added, and the solid content is adjusted to 45%-55%. After stirring evenly, the negative electrode slurry is obtained, which is then coated, dried, cold-pressed, and cut into negative electrode sheets.

[0113] Preparation of electrolyte

[0114] In an argon atmosphere glove box, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain a solvent, LiPF6 was added to the solvent at a mass percentage of 12.5% ​​and dissolved, and stirred to obtain an electrolyte.

[0115] [Diaphragm]

[0116] Polypropylene film is used as the isolation film.

[0117]

Battery preparation

[0118] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the cathode and anode to provide isolation. The cells are then wound to form a bare cell. The bare cell is then placed in an outer package, injected with the prepared electrolyte, and packaged, injected, formed, and vented to produce a lithium-ion battery.

[0119] Example 2

[0120] The difference from Example 1 lies in the preparation of the positive electrode sheet.

[0121] The positive electrode active material lithium iron phosphate (LiFePO4), conductive carbon and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 94.2:1:1, and then solvent N-methylpyrrolidone (NMP) was added to adjust the solid content to 70%-80%. After stirring, the positive electrode slurry was obtained, and then coated and dried to form a positive electrode active material layer. The surface loading of the positive electrode active material layer was 20 mg / cm 2 , i.e. 1cm 2 The mass of the positive electrode active material layer was 20 mg.

[0122] After the potassium salt additive KC6H5O7, conductive carbon and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 3:0.3:0.5, the solvent N-methylpyrrolidone (NMP) is added and the solid content is adjusted to 70%-80%. After stirring evenly, the additive slurry is obtained. The additive slurry is coated on the positive electrode active material layer, and then dried, cold pressed and cut into positive electrode sheets. The positive electrode sheet includes a positive electrode active material layer and an additive layer disposed on the positive electrode active material layer. The surface loading of the additive layer is 0.79 mg / cm 2 , i.e. 1cm 2 The mass of the additive layer is 0.79 mg. 2 The mass fraction of potassium salt in the positive electrode sheet accounts for 3% of the positive electrode film layer.

[0123] The rest is the same as in Example 1 and will not be described again here.

[0124] Example 3-Example 11

[0125] The difference from Example 1 lies in the positive electrode active material, potassium salt additive and its content, potassium salt particle size, etc., as shown in Table 1 for details.

[0126] Example 12

[0127] The positive electrode active material sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7), potassium salt additive KC6H5O7, conductive carbon and polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 94.2:3:1.3:1.5, and then the solvent N-methylpyrrolidone (NMP) is added to adjust the solid content to 70%-80%. After stirring evenly, the positive electrode slurry is obtained, and then it is coated, dried, cold pressed and cut into positive electrode sheets.

[0128]

Preparation of negative electrode sheet

[0129] Hard carbon, conductive carbon SP, and binder SBR are dry-mixed at a ratio of 97:1:2, deionized water is added, and the solid content is adjusted to 45%-55%. After stirring evenly, the negative electrode slurry is obtained, which is then coated, dried, cold-pressed, and cut into negative electrode sheets.

[0130] Comparative Example 1-Comparative Example 2

[0131] The difference from Example 1 is that no potassium salt additive is added. The positive electrode active material and content are detailed in Table 1. Other details are the same as Example 1.

[0132] Comparative Example 3

[0133] The difference from Example 12 is that no potassium salt additive is added. The positive electrode active material and content are detailed in Table 1. Other details are the same as Example 1.

[0134] The relevant parameter testing methods in the above embodiments and comparative examples are as follows:

[0135] 1) Volume average particle size Dv50 test

[0136] Equipment model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009, specific test process: Take an appropriate amount of the sample to be tested (the sample concentration is sufficient to ensure 8%-12% obscuration), add 20ml of deionized water, and simultaneously operate the external ultraviolet (53KHz / 120W) for 5 minutes to ensure that the sample is completely dispersed. Then, the sample is measured according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0137] 2) Battery performance test

[0138] 2.1) Cyclic Test of Example 1-Example 11, Comparative Example 1-Comparative Example 2

[0139] Step 1: Leave the battery at 25°C for 30 minutes, discharge at 0.33C to 2.5V, and leave it at 25°C for 30 minutes.

[0140] Step 2: Charge the battery at a constant current of 0.33C to 3.65V, then charge it at a constant voltage with a cutoff current of 0.05C and let it rest at 25°C for 30 minutes. Then, discharge it at 0.33C to 2.5V and let it rest at 25°C for 30 minutes. Repeat step 2 for n times until the battery cycle capacity remains at 80% of the battery capacity. Stop the cycle and record the number of cycles.

[0141] 2.2) Cyclic Performance Test of Example 12 and Comparative Example 2

[0142] Step 1: Let the battery stand at 25°C for 30 minutes, discharge at 0.33C to 1.5V, and let it stand at 25°C for 30 minutes.

[0143] Step 2: Charge the battery at a constant current of 0.33C to 3.65V, then charge it at a constant voltage with a cutoff current of 0.05C and let it rest at 25°C for 30 minutes. Then, discharge it at 0.33C to 1.5V and let it rest at 25°C for 30 minutes. Repeat step 2 for n times until the battery cycle capacity remains at 80% of the battery capacity. Stop the cycle and record the number of cycles.

[0144] 3) Potassium ion characterization test

[0145] Charge the battery to 3.75V (3.8V for sodium ion battery), then disassemble it in an inert atmosphere glove box, take out the positive electrode and negative electrode sheets respectively, and scrape off the powder on the positive electrode and negative electrode sheets respectively. Take out 50g of the powder from the positive electrode sheet, soak it in 100g of anhydrous ethanol, heat it to 80℃, stir and dissolve it for 4h, take 100mL of the supernatant, and dry it at 100℃ in vacuum to obtain the treated powder (weight is W). The treated powder is sent for XRD testing, and the test is carried out from 0 to 90℃ at a scan rate of 1℃ / min. The specific structure of the potassium salt can be determined by peak comparison with the XRD pattern card of the standard substance. The powder of the disassembled positive electrode sheet, the powder of the negative electrode sheet, and the battery electrolyte removed are sent for ICP testing respectively, and the content values ​​of each element in the positive electrode sheet, the negative electrode sheet, and the electrolyte can be obtained respectively. That is, the content values ​​of potassium ions in the positive electrode sheet, the negative electrode sheet, and the electrolyte can be obtained respectively. The K ion content of the positive electrode sheet and the negative electrode sheet is greater than 100ppm. At the same time, the powder of the negative electrode sheet is sent for XPS testing. XPS can detect the presence of K element. The presence of K peak in the XPS peak spectrum indicates the presence of trace amounts of undecomposed active ion compensation additives (potassium salt additives).

[0146] Table 1 Process and cycle performance parameters of the positive electrode sheets of various embodiments and comparative examples.

[0147]

[0148] Note: Content 1 indicates the mass fraction of the positive electrode active material in the positive electrode film layer; Content 2 indicates the mass fraction of the potassium salt in the positive electrode film layer; Mass ratio indicates the mass ratio of potassium salt to positive electrode active material; Voltage indicates that potassium salt can decompose potassium ions under the corresponding voltage; Setting mode indicates the setting mode of the additive in the positive electrode film layer, wherein, Mode 1 indicates that the additive is directly located in the positive electrode active material layer, Mode 2 indicates that the additive is located in the additive layer, and the additive layer is arranged on the side of the positive electrode active material layer away from the current collector; Number of cycles indicates the number of cycles when the battery cycle capacity is maintained at 80% of the battery capacity.

[0149] Table 2 Potassium ion characterization test data in Example 4 and Comparative Example 1.

[0150]

[0151] Note: The molar content of the positive electrode sheet Li:K after the cycle represents the molar ratio of Li ions in the positive electrode active material to K ions in the positive electrode sheet after the first cycle; the molar ratio of the negative electrode sheet Li:K after the cycle represents the molar ratio of Li ions in the positive electrode active material to K ions in the negative electrode sheet after the first cycle; the total molar content ratio Li:K after the cycle represents the molar ratio of Li ions in the positive electrode active material to the sum of K ions in the positive electrode sheet, negative electrode sheet and electrolyte after the first cycle.

[0152] It can be seen from the relevant data in Table 1 that, based on Comparative Example 1 and Comparative Example 2, when the cycle capacity retention rate of the battery formed by the positive electrode sheets of Examples 1-11 of the present application is maintained at 80% of the battery capacity, the number of cycles is 1900-4000 cycles, which is much higher than the 1500-1700 cycles of Comparative Examples 1-2. This shows that the positive electrode sheets of the embodiments of the present application can effectively reduce the loss of active lithium and improve the cycle stability of the battery by adding potassium salt additives.

[0153] Based on Comparative Example 3, when the cycle capacity retention rate of the battery formed by the positive electrode plate of Example 12 of the present application is maintained at 80% of the battery capacity, the number of cycles is increased from 1800 to 2300, and the number of cycles is significantly improved, indicating that the positive electrode plate of the embodiment of the present application can effectively reduce the loss of active sodium and improve the cycle stability of the battery by adding potassium salt additives.

[0154] As can be seen from Table 2, after the first cycle of the battery in Example 4 of the present application, the molar ratio of lithium ions in the positive electrode active material to the sum of potassium ions in the positive electrode sheet, the negative electrode sheet, and the electrode solution is 1:0.055, which can be used to indicate that the positive electrode sheet in Example 4 of the present application contains potassium ions. As long as the molar ratio of active ions (lithium ions and / or sodium ions) in the active material to the sum of potassium ions in the positive electrode sheet, the negative electrode sheet, and the electrode solution is between 1:0.04 and 1:0.06, it can be shown that the positive electrode sheet contains potassium ions.

[0155] The above is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A positive electrode plate, characterized in that: The positive electrode sheet includes a positive electrode film layer, which includes a positive electrode active material and an additive. The positive electrode active material includes a phosphate positive electrode material, and the additive includes a potassium salt. The potassium salt decomposes into potassium ions at a voltage of 3.1V-4.2V.

2. The positive electrode sheet according to claim 1, characterized in that: The mass ratio of the potassium salt to the positive electrode active material is (0.5-8):(90-97).

3. The positive electrode sheet according to claim 1 or 2, characterized in that: The mass fraction of the potassium salt in the positive electrode film layer is 0.5%-8%.

4. The positive electrode sheet according to any one of claims 1 to 3, characterized in that: The additives include K2S, KN3, KNO2, KC6H5O7, K2O, K2O2, K2C2O4, K2C4O4, K2C3O5, K2C4O6, K2C6O6, K2S2O3, K2SO3, K2CO3, KC6H5CO2, C6H5K3O7, C 12 H 10 K3Na3O 14 One or more of the .

5. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The volume average particle size DV50 of the potassium salt is 1 μm-30 μm.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The volume average particle size DV50 of the potassium salt is 1 μm-10 μm.

7. The positive electrode sheet according to any one of claims 1 to 6, characterized in that: When the initial cycle is completed, the potassium ion content in the positive electrode plate is greater than or equal to 100 PPM.

8. The positive electrode sheet according to any one of claims 1 to 7, characterized in that: The positive electrode plate includes a current collector; The positive electrode film layer comprises a positive electrode active material layer and an additive layer, wherein the additive layer is arranged on a side of the positive electrode active material layer away from the current collector, and the additive layer comprises the potassium salt; or The positive electrode film layer includes a positive electrode active material layer, and the additive is dispersed in the positive electrode active material layer.

9. The positive electrode sheet according to any one of claims 1 to 8, characterized in that: The phosphate positive electrode material includes lithium iron phosphate material and / or polyanion sodium electrode material; The lithium iron phosphate material includes a structural formula of Li x Fe y M z PO4 material, wherein M includes any one or more of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B and Nb, 0.05≦x≦1.2, 0.2≦y≦1, 0≦z≦0.

8.

10. The positive electrode sheet according to claim 9, characterized in that: The lithium iron phosphate material includes a coating layer, and the coating layer is arranged on the structure of Li x Fe y M z The outside of the PO4 material.

11. The positive electrode sheet according to any one of claims 1 to 8, characterized in that: The phosphate positive electrode material includes lithium iron phosphate material and / or polyanion sodium electric material, and the polyanion sodium electric material includes Na x M y (X a O b )Z w ,x=1-4, y=1-4, a=1-4, b=4-18, w=3 or 0, M includes one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Ca, Mg, Al, Nb, X=P, S, B, Mo, and Z includes F.

12. The positive electrode sheet according to any one of claims 1 to 10, characterized in that: The positive electrode film layer further includes a conductive agent and a binder, and the mass ratio of the conductive agent, the binder and the positive electrode active material is (1-5): (1-5): (93-97).

13. A battery, characterized in that: The invention comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode active material and an additive, wherein the positive electrode active material comprises a phosphate positive electrode material, and the additive comprises a potassium salt, and the potassium salt decomposes into potassium ions at a voltage of 3.1V-4.2V.

14. The battery according to claim 13, characterized in that The invention comprises a negative electrode plate. When the formation is completed, the negative electrode plate comprises a negative electrode film layer and a solid electrolyte interface film arranged on the negative electrode film layer, and the solid electrolyte interface film comprises potassium ions.

15. An electrical device, characterized in that: A battery comprising the battery according to claim 13 or 14.

Images