Positive electrode sheet and its preparation method, as well as batteries and electrical equipment

Abstract

This application discloses a positive electrode sheet and its preparation method, as well as a battery and electrical device. The positive electrode sheet includes a positive current collector and a positive active material layer formed on at least one side of the positive current collector. The positive active material layer includes additives, which include at least one of elemental sulfur, sulfides, elemental selenium, selenides, elemental phosphorus, phosphides, elemental tellurium, elemental iodine, or elemental boron. The average particle size of the additives is greater than or equal to 2 μm. This passivates the additives, reduces their reactivity, decreases their solubility in the electrolyte, reduces the consumption of active ions by the oxidation products of the additives, and improves the cycle life of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to positive electrode sheets and their preparation methods, as well as batteries and electrical devices. Background Technology

[0002] Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. However, the SEI film (solid electrolyte interface) on the surface of the negative electrode of existing batteries has low toughness, which leads to continuous rupture and recombination of the SEI film during cycling, increasing the consumption of active ions and reducing the cycle life of the battery. Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application provides a positive electrode sheet that reduces the consumption of active ions and improves the cycle life of the battery.

[0004] A first aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive active material layer formed on at least one side of the positive current collector, the positive active material layer comprising an additive, the additive comprising at least one of elemental sulfur, sulfides, elemental selenium, selenides, elemental phosphorus, phosphides, elemental tellurium, elemental iodine or elemental boron, the additive having an average particle size greater than or equal to 2 μm.

[0005] The positive electrode sheet proposed in this application includes an additive, which has the following two functions: First, the additive can form organic segments with the cyclic solvent in the electrolyte. These organic segments can diffuse to the negative electrode and combine with active ions to form an SEI film. Second, the additive dissolves in the electrolyte, migrates to the negative electrode, and is reduced. The reduction product reacts with the organic solvent in the electrolyte to generate a PEO-like polymer, which then combines with active ions to form the SEI film. This improves the toughness of the formed SEI film, thereby reducing the DC internal resistance (DCR) of the battery and increasing its cycle life. By ensuring the average particle size of the additive is within the aforementioned range, the specific surface area of ​​the additive can be reduced, the number of reaction sites on the additive surface can be decreased, the additive can be passivated, its solubility in the electrolyte can be reduced, the probability of further oxidation of the additive can be reduced, the reaction between the oxidation products of the additive and active ions can be reduced, the consumption of active ions by the oxidation products of the additive can be reduced, and the cycle life of the battery can be improved.

[0006] According to some embodiments of this application, the average particle size of the additive is 3μm-30μm. This further passivates the additive, reduces its solubility in the electrolyte, decreases the consumption of active ions by the oxidation products of the additive, and improves the cycle life of the battery.

[0007] According to some embodiments of this application, the average particle size of the additive is 6μm-20μm. This further passivates the additive, reduces its solubility in the electrolyte, decreases the consumption of active ions by the oxidation products of the additive, and improves the cycle life of the battery.

[0008] According to some embodiments of this application, the sulfide includes at least one of lithium sulfide, sodium sulfide, selenium sulfide, cobalt sulfide, or nickel sulfide.

[0009] According to some embodiments of this application, the phosphide includes at least one of lithium phosphide or sodium phosphide.

[0010] According to some embodiments of this application, the selenide includes at least one of lithium selenide or sodium selenide.

[0011] Therefore, the aforementioned types of sulfides, phosphides, and selenides can participate in the formation of the SEI film, improve the toughness of the SEI film, and reduce the consumption of active ions by the oxidation products of the aforementioned additives by making the average particle size of the aforementioned types of sulfides, phosphides, and selenides greater than or equal to 2 μm, thereby improving the cycle life of the battery.

[0012] According to some embodiments of this application, the mass percentage of the additive is 0.1%-0.5% based on the total mass of the positive electrode active material layer. Therefore, by keeping the additive content within the above range, the additive can be slowly consumed during battery cycling, continuously forming an SEI film on the negative electrode, improving the toughness of the SEI film, reducing the battery's DCR, and increasing the battery's cycle life.

[0013] According to some embodiments of this application, the mass percentage of the additive is 0.1%-0.3% based on the total mass of the positive electrode active material layer. Therefore, during battery cycling, the additive can be slowly consumed, continuously forming an SEI film on the negative electrode, improving the toughness of the SEI film, reducing the battery's DCR, and increasing the battery's cycle life.

[0014] According to some embodiments of this application, the positive electrode active material layer includes a positive electrode active material, wherein the volume average particle size D of the positive electrode active material is... v The ratio of 50 to the average particle size of the additive is less than or equal to 1. This passivates the additive, reduces its reactivity, decreases its solubility in the electrolyte, reduces the consumption of active ions by the oxidation products of the additive, and improves the cycle life of the battery.

[0015] According to some embodiments of this application, at least a portion of the surface of the additive is coated with a coating layer. This coating layer passivates the additive, reducing its reactivity, decreasing the consumption of active ions by the additive's oxidation products, and improving the battery's cycle life.

[0016] According to some embodiments of this application, the ratio of the mass of the coating layer to the mass of the additive is 0.003-0.02, based on the total mass of the additive. This passivates the additive, reduces its reactivity, decreases the reaction between the additive and active ions, reduces the consumption of active ions, and improves the cycle life of the battery.

[0017] According to some embodiments of this application, the ratio of the mass of the coating layer to the mass of the additive is 0.008-0.02, based on the total mass of the additive. This further passivates the additive, reducing its reactivity, decreasing the reaction between the additive and active ions, reducing the consumption of active ions, and improving the battery's cycle life.

[0018] According to some embodiments of this application, the coating layer includes at least one of polyvinylidene fluoride, ethylene difluoropropylene-hexafluoropropylene copolymer, alumina, titanium dioxide, zirconium oxide, aluminum fluoride, titanium fluoride, sodium alginate, styrene-butadiene rubber, polyacrylic acid and its derivatives, polytetrafluoroethylene, polymethyl methacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinyl alcohol, or polyethylene glycol. Thus, the above materials can coat at least a portion of the surface of the additive, passivating the additive, reducing the reaction between the additive and active ions, reducing the consumption of active ions, and improving the cycle life of the battery.

[0019] According to some embodiments of this application, the ratio of the thickness of the positive electrode active material layer to the average particle size of the additive is greater than or equal to 2. This reduces the probability of scratches occurring during electrode processing.

[0020] A second aspect of this application provides a method for preparing a positive electrode sheet, comprising: forming a positive electrode active material layer on at least one side of a positive electrode current collector, the positive electrode active material layer comprising an additive, the additive comprising at least one selected from elemental sulfur, sulfides, elemental selenium, selenides, elemental phosphorus, phosphides, elemental tellurium, elemental iodine, or elemental boron, the average particle size of the additive being greater than or equal to 2 μm. The prepared positive electrode sheet comprises an additive that can participate in the formation of the negative electrode SEI film, improving the toughness of the SEI film, thereby reducing the DC internal resistance (DCR) of the battery and improving the cycle life of the battery. By ensuring the average particle size of the additive is within the aforementioned range, the additive can be passivated, reducing its solubility in the electrolyte, decreasing the consumption of active ions by the oxidation products of the additive, and improving the cycle life of the battery.

[0021] According to some embodiments of this application, the method further includes forming a coating layer on at least a portion of the surface of the additive. This coating layer passivates the additive, reducing its reactivity, decreasing the consumption of active ions by the additive's oxidation products, and improving the battery's cycle life.

[0022] A third aspect of this application provides a battery comprising a positive electrode sheet provided in the first aspect of this application or a positive electrode sheet prepared by the method provided in the second aspect of this application. This improves the energy density and cycle life of the battery.

[0023] According to some embodiments of this application, the battery further includes an electrolyte comprising a cyclic solvent. This can improve the cycle performance of the battery.

[0024] According to some embodiments of this application, the cyclic solvent may include at least one of vinylene carbonate, butylene carbonate, sulfolane, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, or 1,4-butyrolactone. This can improve the cycle performance of the battery.

[0025] The fourth aspect of this application provides an electrical device that includes the battery provided in the third aspect of this application. This improves the energy density and cycle life of the electrical device.

[0026] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0027] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0028] Figure 1 This is a schematic diagram of a battery according to one embodiment of this application.

[0029] Figure 2 yes Figure 1 An exploded view of a battery according to one embodiment of this application is shown.

[0030] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0031] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0032] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0033] Figure 6 This is a schematic diagram of an electrical device in which a battery is used as a power source according to one embodiment of this application.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1 Battery; 11 Housing; 12 Electrode assembly; 13 Cover plate; 2 Battery module; 3 Battery pack; 31 Upper casing; 32 Lower casing. Detailed Implementation

[0036] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0037] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0042] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing.

[0043] The SEI (solid electrolyte interface) film on the surface of the negative electrode of existing batteries has low toughness. During cycling, the SEI film continuously breaks down and reforms, increasing the consumption of active ions and reducing the cycle life of the battery. To improve the toughness of the SEI film, additives can be added to the positive electrode. These additives have two functions: ① The additive reacts with the cyclic solvent in the electrolyte to form organic segments that diffuse to the negative electrode and combine with active ions to form the SEI film; ② The additive dissolves in the electrolyte, migrates to the negative electrode, and is reduced. The reduction product reacts with the organic solvent in the electrolyte to generate a PEO-like polymer, which then combines with active ions to form the SEI film. Therefore, compared to the SEI film formed by inorganic carbonates and organic matter in related technologies, this method can improve the toughness of the negative electrode SEI film and reduce the battery's DC internal resistance (DCR). However, the additive is easily further oxidized at the positive electrode. The oxidation products readily combine with active ions. For example, when the additive is sulfur, the sulfur is further oxidized and reacts with active ions to form lithium sulfate, increasing the consumption of active ions and reducing the battery capacity.

[0044] The positive electrode proposed in this application can passivate the additives by making the average particle size of the additives greater than or equal to 2μm, thereby reducing the solubility of the additives in the electrolyte, reducing the probability of the additives being further oxidized, reducing the probability of the oxidation products of the additives reacting with active ions, reducing the consumption of active ions by the oxidation products of the additives, and improving the cycle life of the battery.

[0045] The positive electrode sheet disclosed in this application is applicable to lithium-ion batteries and sodium-ion batteries, and the battery disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0046] The first aspect of this application provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector; a positive active material layer formed on at least one side of the positive current collector, the positive active material layer comprising an additive, the additive comprising at least one of elemental sulfur, sulfide, elemental selenium, selenide, elemental phosphorus, phosphide, elemental tellurium, elemental iodine or elemental boron, the additive having an average particle size greater than or equal to 2 μm.

[0047] The positive electrode sheet proposed in this application includes an additive, which has the following two functions: First, the additive can form organic segments with the cyclic solvent in the electrolyte. These organic segments can diffuse to the negative electrode and combine with active ions to form an SEI film. Second, the additive dissolves in the electrolyte, migrates to the negative electrode, and is reduced. The reduction product reacts with the organic solvent in the electrolyte to generate a PEO-like polymer, which then combines with active ions to form the SEI film. This improves the toughness of the formed SEI film, thereby reducing the DC internal resistance (DCR) of the battery and increasing its cycle life. By ensuring the average particle size of the additive is within the aforementioned range, the specific surface area of ​​the additive can be reduced, the number of reaction sites on the additive surface can be decreased, the additive can be passivated, its solubility in the electrolyte can be reduced, the probability of further oxidation of the additive can be reduced, the reaction between the additive and active ions can be reduced, the consumption of active ions by the oxidation products of the additive can be reduced, and the cycle life of the battery can be improved.

[0048] In this application, the method for testing the average particle size of the additive is as follows: cut 10 positive electrode sheets of 5mm*5mm with ceramic scissors and place them in a plasma polishing machine. Polish them at 7.5kV for 50min. Then place the samples under a scanning electron microscope and use energy dispersive spectroscopy to mark the position of the additives. Then use a scanning electron microscope to measure the diameter of 50 additives on the 10 positive electrode sheets. The average value of the 50 diameters is the average particle size of the additive.

[0049] In this application, the active ions may include Li + Or Na + .

[0050] As an example, cyclic solvents may include at least one of vinylene carbonate, butylene carbonate, sulfolane, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, or 1,4-butyrolactone.

[0051] According to some embodiments of this application, the average particle size of the additive can be 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or 40 μm, or a range of any of the above values. According to some specific embodiments of this application, the average particle size of the additive can be 3 μm-30 μm. According to other specific embodiments of this application, the average particle size of the additive can be 6 μm-20 μm.

[0052] According to some specific embodiments of this application, the sulfide may include at least one of lithium sulfide, sodium sulfide, selenium sulfide, cobalt sulfide, or nickel sulfide. Specifically, when the additive is lithium sulfide, sodium sulfide, selenium sulfide, cobalt sulfide, or nickel sulfide, the formed anion is S. 2- S 2- It can form sulfur-containing organic segments with cyclic solvents.

[0053] According to some specific embodiments of this application, the phosphide may include at least one of lithium phosphide or sodium phosphide. Specifically, when the additive is lithium phosphide or sodium phosphide, the formed anion is P. 3- P 3- It can form phosphorus-containing organic segments with cyclic solvents.

[0054] According to some specific embodiments of this application, the selenide may include at least one of lithium selenide or sodium selenide. Specifically, when the additive is lithium selenide or sodium selenide, the formed anion is Se. 2- Se 2- It can form Se-containing organic segments with cyclic solvents.

[0055] Therefore, the aforementioned sulfides, selenides, and phosphides can form organic segments with cyclic solvents. These organic segments can diffuse to the negative electrode and combine with active ions to form an SEI film, thereby improving the toughness of the SEI film, reducing the battery's DCR, and increasing the battery's cycle life.

[0056] According to some embodiments of this application, the positive electrode active material layer includes a positive electrode active material, wherein the volume average particle size D of the positive electrode active material is... vThe ratio of the volume average particle size of the positive electrode active material to the average particle size of the additive is less than or equal to 1. For example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, or a range of any of the above values. Therefore, by keeping the ratio of the volume average particle size of the positive electrode active material to the average particle size of the additive within the above range, the difference between the volume average particle size of the positive electrode active material and the average particle size of the additive is reduced. This passivates the additive, reduces its activity, and makes the positive electrode slurry easier to filter during electrode processing, reducing the risk of scratches on the electrode, increasing the compaction density of the electrode, and improving the production efficiency of the electrode. According to some specific embodiments of this application, the volume average particle size D of the positive electrode active material... v The ratio of 50 to the average particle size of the additive can be 0.1-0.8.

[0057] In this application, D v 50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%. For example, according to standard GB / T 19077-2016 / ISO 13320:2009, the particle size is measured using a laser particle size analyzer (Malvern Master Size 2000). The specific testing procedure is as follows: scrape off the positive electrode active material layer powder from the positive electrode sheet, take an appropriate amount of powder and add it to 20 ml of deionized water (the sample concentration should be 8%-12% light-blocking level), and simultaneously sonicate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to the standard GB / T19077-2016 / ISO 13320:2009.

[0058] According to some embodiments of this application, at least a portion of the surface of the additive may be coated with a layer. This results in a larger average particle size for the additive, and the coating layer further passivates the additive, thereby reducing its reactivity, decreasing the reaction between the additive and active ions, reducing the consumption of active ions, and improving the cycle life of the battery.

[0059] According to some specific embodiments of this application, the coating layer is formed on the surface of each additive. This further passivates the additive, reduces its reactivity, decreases the reaction between the additive and active ions, reduces the consumption of active ions, and improves the cycle life of the battery.

[0060] According to some specific embodiments of this application, based on the total mass of the additives, the ratio of the mass of the coating layer to the mass of the additives can be 0.003-0.02, for example, it can be 0.003, 0.005, 0.01, 0.015, or 0.02, or any range of the above values. This passivates the additives, reduces their reactivity, decreases the reaction between the additives and active ions, reduces the consumption of active ions, and improves the cycle life of the battery. According to some specific embodiments of this application, based on the total mass of the additives, the ratio of the mass of the coating layer to the mass of the additives can be 0.008-0.02.

[0061] The method for testing the quality of the coating layer in this application is as follows: When the coating layer is an inorganic material, scrape off 2g of the positive electrode active material powder from the positive electrode sheet, digest it with aqua regia, and then use inductively coupled plasma atomic emission spectrometry to test the mass content w1 of the coating element. (w1 / relative atomic mass of the coating element) * relative molecular mass of the coating material can be used to obtain the mass of the coating material in 2g of powder. When the coating layer is an organic material, it can be tested by electron microscopy (EDS): cut the positive electrode sheet into 6mm*6mm pieces with ceramic scissors, attach it to the sample stage coated with paraffin wax, and make the sample slightly protrude (<1mm) from the edge of the sample stage; polish it at 7.5KV for 50min to obtain the cross-section of the electrode sheet, place the cross-section under a scanning electron microscope to find the location of the additive (the enriched area of ​​the additive element), and there is a ring of C element around it.

[0062] The method for testing the mass of the additives in this application is as follows: When the additive is an element, 2g of the positive electrode active material powder is scraped off from the positive electrode sheet, digested with aqua regia, and then the mass content of the additive is tested using an inductively coupled plasma atomic emission spectrometer (ICP-AES). When the additive is a compound, 2g of the positive electrode active material powder is scraped off from the positive electrode sheet, digested with aqua regia, and then the mass content w2 of the main element is tested using an ICP-AES. The mass of the compound in 2g of powder is obtained by multiplying (w2 / relative atomic mass of the main element) by the relative molecular mass of the compound. It should be noted that when the additive is a sulfide, the main element is sulfur; when the additive is a phosphide, the main element is phosphorus; and when the additive is a selenide, the main element is selenium.

[0063] According to some specific embodiments of this application, the coating layer may include at least one of polyvinylidene fluoride, ethylene difluoropropylene-hexafluoropropylene copolymer, alumina, titanium dioxide, zirconium oxide, aluminum fluoride, titanium fluoride, sodium alginate, styrene-butadiene rubber, polyacrylic acid and its derivatives, polytetrafluoroethylene, polymethyl methacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinyl alcohol, or polyethylene glycol. Thus, the above materials can coat at least a portion of the surface of the additive to form a passivation layer, thereby passivating the additive, reducing its reactivity, reducing its consumption of active ions, and improving the battery's cycle life.

[0064] According to some specific embodiments of this application, based on the total mass of the positive electrode active material layer, the mass percentage of the additive can be 0.1%-0.5%, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, or any range of the above values. Therefore, by keeping the additive content within the above range, the toughness of the SEI film is improved, the probability of reaction between the additive and active ions is reduced, the consumption of active ions is reduced, and the cycle life of the battery is improved. According to some specific embodiments of this application, based on the total mass of the positive electrode active material layer, the mass percentage of the additive is 0.1%-0.3%.

[0065] According to some embodiments of this application, based on the total mass of the positive electrode active material layer, the mass percentage of the coating layer can be 0.001%-0.05%, for example, it can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, or 0.05%, or a range of any of the above values. According to some specific embodiments of this application, based on the total mass of the positive electrode active material layer, the mass percentage of the coating layer can be 0.005%-0.01%. This further passivates the additives, reduces their reactivity, decreases the reaction between the additives and active ions, reduces the consumption of active ions, and improves the cycle life of the battery.

[0066] According to some embodiments of this application, the ratio of the thickness of the positive electrode active material layer to the average particle size of the additive is greater than or equal to 3. For example, it can be 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, or 31, or a range of any of the above values. Therefore, the average particle size of the additive can be adjusted according to the thickness of the positive electrode active material layer. By keeping the ratio of the thickness of the positive electrode active material layer to the average particle size of the additive within the above range, the risk of scratches during the processing of the positive electrode sheet can be reduced, and the processing efficiency of the positive electrode sheet can be improved. According to some specific embodiments of this application, the ratio of the thickness of the positive electrode active material layer to the average particle size of the additive is greater than or equal to 5.

[0067] According to some embodiments of this application, the positive electrode active material layer has pores, and the pore size can be 0.5μm-30μm, for example, it can be 0.5μm, 3μm, 5μm, 7μm, 10μm, 13μm, 15μm, 17μm, 20μm, 23μm, 25μm, 27μm or 30μm, or any range of the above values. Therefore, by making the pore size within the above range, the wetting effect of the electrolyte on the positive electrode sheet can be improved, the polarization of the positive electrode sheet can be reduced, thereby reducing the battery impedance, increasing the battery capacity, and reducing the battery temperature rise rate. According to some specific embodiments of this application, the pore size can be 0.5μm-10μm.

[0068] In this application, the method for testing the aperture is as follows: take the positive electrode sheet and use ion polishing to obtain the cross-section of the electrode sheet, then use a scanning electron microscope (SEM) to obtain a microscopic image and measure the aperture.

[0069] According to some embodiments of this application, the porosity of the positive electrode active material layer can be 30%-45%, for example, it can be 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, or 45%, or any range of the above values. Therefore, by keeping the porosity of the positive electrode active material layer within the above range, the wetting effect of the electrolyte on the positive electrode sheet can be improved, the polarization of the positive electrode sheet can be reduced, thereby reducing the battery impedance, increasing the battery capacity, and reducing the battery temperature rise rate. According to some specific embodiments of this application, the porosity of the positive electrode active material layer can be 35%-40%.

[0070] In this application, the porosity is calculated as follows: 1 - compaction density of the positive electrode active material layer (g / cm³) 3 *(Mass percentage of each material in the positive electrode active material layer (%) / True density of each material in the positive electrode active material layer (g / cm³)) 3 ))

[0071] As an example, the positive electrode includes a positive current collector having two surfaces opposite each other in its own thickness direction, and a layer of positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0072] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0073] In some embodiments, when the battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials 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 include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0074] In some embodiments, when the battery is a sodium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for use in sodium-ion batteries. As an example, the positive electrode active material may include, but is not limited to, at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0075] Examples of the aforementioned layered transition metal oxides include:

[0076] Na 1-x Cu h Fe k Mn l M 1 m O 2-y M 1 It is one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0077] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 It is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0078] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,0.67<d+e<0.8,b+c+d+e=1。

[0079] Examples of the aforementioned polyanionic compounds include:

[0080] A1 f M 3 g (PO4) i O j X 1 3-j , wherein A 1 is one or more of H, Li, Na, K, and NH4, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X 1 is one or more of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0081] Na n M 4 PO4X 2 , wherein M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, X 2 is one or more of F, Cl, and Br, 0 < n ≤ 2;

[0082] Na p M 5 q (SO4)3, wherein M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0083] Na s Mn t Fe 3-t (PO4)2(P2O7), wherein 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0084] As an example of the above-mentioned Prussian blue analogs, for example, the following can be listed:

[0085] A u M 6 v [M 7 (CN)6] w ·xH2O, wherein A is H + , NH4 + , an alkali metal cation, and an alkaline earth metal cation, M 6 and M 7 are each independently one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + , Li + , Na + , K +NH4 + 、Rb + Cs + 、Fr + Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ and Ra 2+ One or more of them, M 6 and M 7 Each is an independent cation of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W.

[0086] The modified compounds for the above materials can be used to modify the materials by doping and / or by surface coating.

[0087] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0088] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0089] A second aspect of this application provides a method for preparing a positive electrode sheet, comprising: forming a positive electrode active material layer on at least one side of a positive electrode current collector, the positive electrode active material layer comprising an additive, the additive comprising at least one selected from elemental sulfur, sulfides, elemental selenium, selenides, elemental phosphorus, phosphides, elemental tellurium, elemental iodine, or elemental boron, wherein the average particle size of the additive is greater than or equal to 2 μm. The prepared positive electrode sheet comprises an additive that can participate in the formation of the negative electrode SEI film, improving the toughness of the SEI film, thereby reducing the DC internal resistance (DCR) of the battery and improving the cycle life of the battery. By ensuring the average particle size of the additive is within the aforementioned range, the additive can be passivated, reducing its solubility in the electrolyte, reducing the reaction between the oxidation products of the additive and active ions, reducing the consumption of active ions, and improving the cycle life of the battery.

[0090] According to some embodiments of this application, the preparation method of the positive electrode sheet may include: forming a positive electrode slurry containing additives on a positive electrode current collector, drying and cold pressing to obtain the positive electrode sheet.

[0091] According to some embodiments of this application, the method further includes forming a coating layer on at least a portion of the surface of the additive. As a result, the additive has a larger average particle size, and the coating layer further passivates the additive, thereby reducing its reactivity, decreasing the reaction between the additive's oxidation products and active ions, reducing the consumption of active ions, and increasing the battery capacity.

[0092] A third aspect of this application provides a battery comprising a positive electrode sheet provided in the first aspect of this application or a positive electrode sheet prepared by the method provided in the second aspect of this application. This improves the energy density and cycle life of the battery.

[0093] According to some embodiments of this application, the battery further includes an electrolyte comprising a cyclic solvent. Thus, after the additive is oxidized, it can form organic segments with the cyclic solvent. These organic segments diffuse to the negative electrode and combine with active ions to form an SEI film, improving the toughness of the SEI film, thereby reducing the battery's DC internal resistance (DCR) and increasing the battery's cycle life.

[0094] As an example, the cyclic solvent may include at least one of vinylene carbonate, butylene carbonate, sulfolane, ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), or 1,4-butyrolactone.

[0095] According to some embodiments of this application, the electrolyte includes electrolyte salts and other solvents.

[0096] In some embodiments of this application, when the battery is a lithium-ion battery, the electrolyte salt may include 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate.

[0097] In some embodiments of this application, when the battery is a sodium-ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide.

[0098] In some embodiments of this application, other solvents may include at least one of diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, dimethyl sulfone, methyl ethyl sulfone, or diethyl sulfone.

[0099] In some embodiments of this application, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0100] As an example, a battery also includes a negative electrode and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0101] [Negative electrode plate]

[0102] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0103] As an example, the negative electrode current collector has two surfaces opposite each other in its own 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.

[0104] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0105] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0106] In some embodiments, the negative electrode film layer may optionally 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).

[0107] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0108] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0109] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0110] [Isolation membrane]

[0111] In some embodiments, the battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0112] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven 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.

[0113] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0114] In some embodiments, the battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0115] In some implementations, the battery's outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The battery's outer packaging can also be a soft pack, such as a pouch. The soft pack can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0116] This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is a square-structured battery 1 used as an example.

[0117] In some embodiments, battery 1 may include an outer packaging. The outer packaging is used to encapsulate the positive electrode, the negative electrode, and the electrolyte.

[0118] In some implementations, reference Figure 2 The positive electrode, negative electrode, and separator can be manufactured into electrode assembly 12 by winding or stacking processes.

[0119] In some implementations, reference Figure 2 The outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The shell 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed on the opening to close the receiving cavity.

[0120] In some embodiments, the outer packaging of battery 1 can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0121] The outer packaging of battery 1 can also be a soft package, such as a pouch. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0122] In some implementations, the battery 1 can be assembled into a battery module 2, and the battery module 2 can contain multiple batteries 1, the specific number of which can be adjusted according to the application and capacity of the battery module 2.

[0123] In some embodiments, the outer packaging of battery 1 may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0124] Figure 3 This is battery module 2 as an example. (See reference...) Figure 3 In battery module 2, multiple batteries 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other way. Furthermore, these multiple batteries 1 can be fixed in place using fasteners.

[0125] The battery module 2 may also include a housing with a receiving space in which multiple batteries 1 are housed. In some embodiments, the battery modules may also be assembled into a battery pack, the number of battery modules contained in the battery pack being adjustable according to the application and capacity of the battery pack.

[0126] Figure 4 and Figure 5This is battery pack 3 as an example. (See reference...) Figure 4 and 5 The battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box includes an upper box 31 and a lower box 32, with the upper box 31 covering the lower box 32 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0127] The fourth aspect of this application provides an electrical device that includes the battery provided in the third aspect of this application. This improves the energy density and cycle life of the electrical device.

[0128] As an example, a battery can be used as a power source for an electrical device or as an energy storage unit for that device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0129] As for the electrical equipment, the battery can be selected according to its usage requirements.

[0130] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0131] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0132] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0133] Example 1

[0134] 1. Preparation of positive electrode sheet

[0135] LiFePO4 (LFP), conductive carbon nanotubes, binder polyvinylidene fluoride, and additive S were thoroughly mixed in N-methylpyrrolidone solvent at a weight ratio of 96.8:0.7:2.2:0.3. The mixture was then coated on both surfaces of an aluminum foil with a thickness of 13 μm and a single layer of positive electrode active material with a thickness of 56.5 μm. The mixture was dried and cold-pressed to obtain the positive electrode sheet.

[0136] 2. Preparation of negative electrode sheet

[0137] The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) are mixed thoroughly in deionized water at a weight ratio of 96.5:0.7:1.8:1. The mixture is then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0138] 3. Preparation of electrolyte

[0139] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate and methyl ethyl carbonate were mixed at a mass ratio of 30:70 to obtain an organic solvent. The fully dried electrolyte salt LiPF6 was dissolved in the above solvent and mixed evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0140] 4. Separating membrane

[0141] Polypropylene film is used as the separator.

[0142] 5. Battery manufacturing

[0143] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrode assembly is then wound up. The electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is obtained.

[0144] The preparation methods of the batteries in Examples 2-19, Comparative Examples 1 and 2 are the same as those in Example 1, with the differences detailed in Table 1.

[0145] In Example 7, the weight ratio of positive electrode active material, conductive agent, binder, and additive was 97.05:0.7:2.2:0.05; in Example 8, the weight ratio was 97:0.7:2.2:0.1; in Example 9, the weight ratio was 96.6:0.7:2.2:0.5; and in Example 10, the weight ratio was 96.1:0.7:2.2:1.

[0146]

[0147] Performance testing

[0148] 1. DCR test

[0149] Maintain an ambient temperature of 25℃, charge and discharge at a rate of 0.33C for 3 cycles, with a cutoff voltage of 2.5V to 3.65V. Take the discharge capacity of the 3rd cycle as the standard capacity C0. Then charge at 0.33C0 to 50% C0 (50% SOC), let stand for 30 minutes, and then discharge at a current of I = 4C0 for 30 seconds. Record the voltage difference ΔU before and after the 4C0 discharge. DCR = ΔU / I.

[0150] 2. Capacity Testing Method

[0151] Maintain an ambient temperature of 25℃, charge and discharge at a rate of 0.33C for 3 cycles, with a cutoff voltage of 2.5V to 3.65V. Take the discharge capacity of the 3rd cycle as the standard capacity.

[0152] 3. Cyclic capacity retention test method

[0153] (1) At 45℃, the lithium-ion battery was charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, left to stand for 5 minutes, and then discharged at 1 / 3C to 2.5V. The discharge capacity C0 was recorded. (2) The lithium-ion battery was then charged at a constant current of 1.0C to 3.65V, left to stand for 5 minutes, and then discharged at 1 / 3C to 2.5V. The discharge capacity C1 was recorded. Step (2) was repeated 200 times. The discharge capacity C of the lithium-ion battery after the 200th cycle was recorded. 200 Capacity retention rate P200 = C 200 / C0×100%

[0154] The test results of the batteries in Examples 1-19 and Comparative Examples 1 and 2 are shown in Table 2.

[0155] Table 2

[0156]

[0157]

[0158] Conclusion: As shown in Table 2, the cycle capacity retention rates of Examples 1-19 are all higher than those of Comparative Examples 1 and 2, while the DCR of Examples 1-19 are all lower than those of Comparative Examples 1 and 2. This indicates that by adding additives to the positive electrode, the toughness of the negative electrode SEI film can be improved, and the battery DCR can be reduced. By passivating the additives, the reaction between the additives and active ions can be reduced, the consumption of active ions can be decreased, and the cycle capacity retention rate of the battery can be improved.

[0159] As can be seen from Examples 1-6 and Examples 14-18, the battery's cycle capacity retention rate can be improved and the battery's DCR can be reduced by increasing the particle size of the additive or by further coating the surface of the additive to passivate it.

[0160] As can be seen from Examples 7-10, the battery's cycle capacity retention rate can be improved and the battery's DCR can be reduced by adjusting the content of the additives.

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode sheet, characterized by, The positive electrode active material layer includes an additive, the additive includes at least one of a sulfur element, a sulfide, a selenium element, a selenide, a phosphorus element, a phosphide, a tellurium element, an iodine element, or a boron element, and an average particle diameter of the additive is greater than or equal to 2 μm. A mass ratio of the additive is 0.1%-0.5% based on a total mass of the positive electrode active material layer. The average particle diameter of the additive is 3 μm-30 μm. The average particle diameter of the additive is 6 μm-20 μm.

2. The cathode electrode of claim 1, wherein, At least one of the following conditions is satisfied:

3. The cathode electrode of claim 2, wherein, (1) the sulfide includes at least one of lithium sulfide, sodium sulfide, selenium sulfide, cobalt sulfide, or nickel sulfide; 4. The cathode electrode of claim 1, wherein, (2) the phosphide includes at least one of lithium phosphide or sodium phosphide; (3) the selenide includes at least one of lithium selenide or sodium selenide. The mass ratio of the additive is 0.1%-0.3%. At least a part of a surface of the additive is formed with a coating layer.

5. The cathode sheet of claim 1, wherein, A ratio of a mass of the coating layer to a mass of the additive is 0.003-0.02 based on a total mass of the additive.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized by, The positive electrode active material layer includes a positive electrode active material, the volume average particle diameter D v 50 the ratio of the average particle diameter of the additive is less than or equal to 1.

7. The positive electrode sheet according to any one of claims 1 to 5, characterized by, The ratio of the mass of the coating layer to the mass of the additive is 0.008-0.02 based on the total mass of the additive.

8. The cathode electrode of claim 7, wherein, The coating layer includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, aluminum oxide, titanium oxide, zirconium oxide, aluminum fluoride, titanium fluoride, sodium alginate, styrene butadiene rubber, polyacrylic acid and derivatives thereof, polytetrafluoroethylene, polymethyl methacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinyl alcohol, or polyethylene glycol.

9. The cathode electrode plate of claim 8, wherein, A ratio of a thickness of the positive electrode active material layer to the average particle diameter of the additive is greater than or equal to 2.

10. The cathode electrode of claim 7, wherein, The positive electrode active material layer includes an additive, the additive includes at least one of a sulfur element, a sulfide, a selenium element, a selenide, a phosphorus element, a phosphide, a tellurium element, an iodine element, or a boron element, and an average particle diameter of the additive is greater than or equal to 2 μm; 11. The positive electrode sheet according to any one of claims 1 to 5, characterized by A mass ratio of the additive is 0.1%-0.5% based on a total mass of the positive electrode active material layer.

12. A method of making a positive electrode sheet, characterized by, The method further includes forming a coating layer on at least a part of a surface of the additive. The battery further includes an electrolyte, the electrolyte includes a cyclic solvent. The cyclic solvent includes at least one of vinylene carbonate, butylene carbonate, sulfolane, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, or 1,4-butyrolactone.

13. The method of claim 12, wherein, The battery includes any one of claims 14-16.

14. A battery, characterized by The battery includes any one of claims 14-16.

15. The battery of claim 14, wherein, ​ 16. The battery of claim 15, wherein, ​ 17. An electrical device, characterized by ​

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