Phosphate-based positive electrode material, method for preparing same, and use thereof
By using LiCl and MnCl2 fluxes in the sintering process of phosphate-based cathode materials, the problem of impurity phases caused by doped metal ions was solved, achieving high electrical conductivity and good cycle performance, making the materials suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN DYNANONIC CO LTD
- Filing Date
- 2024-02-29
- Publication Date
- 2026-07-03
AI Technical Summary
Existing phosphate-based cathode materials are prone to generating impurity phases during the doping process with metal ions, which affects their electrochemical performance.
Phosphate-based cathode materials were prepared by mixing LiCl and MnCl2 as fluxes with phosphate-based precursor components and then sintering them. This process assisted in metal ion doping and suppressed the generation of impurity phases, resulting in a uniform particle structure.
It improves the electronic conductivity, Li-ion diffusion rate and structural stability of phosphate-based cathode materials, thereby enhancing the energy density, cycle performance and stability of the battery.
Smart Images
Figure CN118145618B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of battery materials technology, and in particular relates to a phosphate-based cathode material, its preparation method and application. Background Technology
[0002] Lithium-ion batteries, due to their high volumetric energy density, gravimetric energy density, and excellent cycle performance, are internationally recognized as ideal energy storage and output power sources, playing an increasingly important role in various fields. As a crucial component of lithium-ion batteries, the performance of the cathode material directly affects various performance indicators, occupying a core position in lithium-ion battery technology. Currently, there are many known cathode materials for lithium-ion batteries on the market. Among them, lithium iron phosphate has become the preferred cathode material for lithium-ion batteries due to its advantages such as large discharge capacity, long lifespan, low price, non-toxicity, no environmental pollution, wide availability of raw materials, stable voltage platform, excellent safety performance, and superior cycle performance.
[0003] Phosphate-based cathode materials such as lithium iron phosphate, with an olivine-type crystalline structure, exhibit high stability and undergo Li+ ionization during charge and discharge. + The insertion and extraction of Li can maintain its basic structure, which gives it high safety, but it also leads to a decrease in its ionic conductivity, resulting in low capacity. Furthermore, with repeated charge and discharge cycles, Li precipitates at the battery film interface, causing Li in the crystal to precipitate. + Misalignment leads to poor cycle performance.
[0004] To change this phenomenon, the electrochemical performance of phosphate-based cathode materials can be improved by doping with metal ions; however, phosphate-based cathode materials are prone to generating impurity phases during the doping process, which affects the morphology of the product particles and also affects the electrochemical performance of the product. Summary of the Invention
[0005] The purpose of this application is to provide a phosphate-based cathode material, its preparation method, and its application, aiming to solve to some extent the problem that impurity phases are easily generated during the doping of metal ions in existing phosphate-based cathode materials, which affects the electrochemical performance of the product.
[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:
[0007] In a first aspect, this application provides a method for preparing a phosphate-based cathode material, comprising the following steps:
[0008] A solid precursor is prepared by mixing phosphate-based precursor components and flux; wherein the flux includes LiCl and MnCl2, and the phosphate-based precursor components include a doped metal source, the doped metal source including a nickel source.
[0009] The solid precursor was sintered to obtain a phosphate-based cathode material.
[0010] In some possible implementations, the molar ratio of LiCl to MnCl2 in the flux is 1:(0.18~0.23).
[0011] In some possible implementations, the phosphate-based precursor components may further include at least an iron source, a lithium source, and a phosphorus source.
[0012] In some possible implementations, a dispersant and a first carbon source are also added during the mixing process.
[0013] In some possible implementations, the molar ratio of lithium in the lithium source, iron in the iron source, metal in the doped metal source, and metal in the flux is (0.90~0.96):(0.92~0.99):(0.03~0.05):0.1.
[0014] In some possible implementations, the amount of dispersant added is 10% to 30% of the theoretical yield of the phosphate-based cathode material.
[0015] In some possible implementations, the amount of the first carbon source added is 6% to 13% of the theoretical yield of the phosphate-based cathode material.
[0016] In some possible implementations, the mixing process includes: mixing the iron source, the phosphorus source, the lithium source, the doped metal source and the flux, then adding the dispersant and the first carbon source and mixing them, and mixing them at a temperature of 160°C to 220°C for 8 to 18 hours to obtain the dried solid precursor.
[0017] In some possible implementations, the sintering process includes: after performing a first sintering process on the solid precursor, mixing the sintered material with a second carbon source and performing a second sintering process to obtain a phosphate-based cathode material.
[0018] In some possible implementations, the conditions for the first sintering treatment include: heating to 520°C to 560°C at a heating rate of 1°C / min to 5°C / min under an inert atmosphere, and holding at that temperature for 4h to 7h.
[0019] In some possible implementations, the conditions for the second sintering process include: heating to 700°C to 760°C at a heating rate of 1°C / min to 5°C / min under an inert atmosphere, and holding at that temperature for 6 to 11 hours.
[0020] In some possible implementations, the amount of the second carbon source added is 1% to 3% of the theoretical yield of the phosphate-based cathode material.
[0021] In some possible implementations, the iron source includes at least one of ferrous oxalate, ferric nitrate, ferrous sulfate, ferric phosphate, and ferrous sulfate.
[0022] In some possible implementations, the phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid.
[0023] In some possible implementations, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxide, lithium acetate, and lithium acetate.
[0024] In some possible implementations, the nickel source includes at least one of nickel nitrate, nickel acetate, nickel oxalate, nickel carbonate, nickel oxide, and nickel chloride.
[0025] In some possible implementations, the dispersant includes water and / or ethanol.
[0026] In some possible implementations, the first carbon source includes at least one of glucose, sucrose, citric acid, and polyethylene glycol.
[0027] In some possible implementations, the second carbon source includes at least one of glucose, starch, citric acid, sucrose, polyethylene, and polyethylene glycol.
[0028] Secondly, this application provides a phosphate-based cathode material, which is prepared according to the above method.
[0029] Thirdly, this application provides a positive electrode sheet, including a current collector and an active layer formed on the surface of the current collector, wherein the active layer contains the aforementioned phosphate-based positive electrode material.
[0030] Fourthly, this application provides a secondary battery that includes the aforementioned positive electrode plate.
[0031] The method for preparing phosphate-based cathode materials provided in the first aspect of this application involves adding fluxes including LiCl and MnCl2 to the raw material components to form a solid precursor. This not only assists in the doping effect of doped metal ions such as nickel sources in the phosphate-based cathode material, preventing the formation of impurity phases, but also effectively inhibits the agglomeration of product particles, resulting in uniform, intact, and well-dispersed product particles, thereby improving the electronic conductivity, Li ion diffusion rate, and structural stability of the phosphate-based cathode material. Simultaneously, LiCl and MnCl2 in the flux can also act as raw materials and dopant sources, respectively. Furthermore, doping elements such as nickel replace Fe sites, forming metal-oxygen bonds, which have a synergistic effect in the phosphate-based cathode material. Therefore, the doping of metal elements can effectively improve the conductivity and diffusion coefficient of the phosphate-based cathode material. By sintering the solid precursor, the phosphate-based cathode material can be obtained. The preparation process is simple and suitable for large-scale industrial production and application. The phosphate-based cathode material produced has good performance in terms of processing performance, discharge capacity and cycle performance, and can provide high-quality cathode material for new energy battery manufacturers to produce high-capacity and long-life phosphate-based batteries.
[0032] The phosphate-based cathode material provided in the second aspect of this application, prepared by the above-described method, utilizes a flux added during the preparation process to assist sintering. This flux not only aids in metal doping and reduces the formation of impurity phases, but LiCl / MnCl2 also serves as both a raw material and a dopant source, resulting in excellent metal ion doping in the phosphate-based cathode material and the absence of impurity phase products. Simultaneously, the flux effectively inhibits the agglomeration of product particles, resulting in uniform, intact, and well-dispersed particles in the phosphate-based cathode material. Therefore, the phosphate-based cathode material provided in this application exhibits superior electrochemical properties, including good electronic conductivity, Li ion diffusion rate, and structural stability.
[0033] The positive electrode provided in the third aspect of this application uses the aforementioned phosphate-based positive electrode material in the active layer. This phosphate-based positive electrode material has good electrochemical properties such as electronic conductivity, Li ion diffusion rate and structural stability, and the particles are uniform in size, intact and well dispersed. Therefore, it improves the stability, energy density, rate performance, cycle performance and other electrochemical properties of the positive electrode.
[0034] The secondary battery provided in the fourth aspect of this application improves the energy density, cycle stability, and other electrochemical performance of the secondary battery by including a positive electrode sheet with excellent electrochemical performance such as good stability, high energy density, good rate performance, and good cycle stability. Attached Figure Description
[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0036] Figure 1 This is a schematic flowchart of the preparation method of the phosphate-based cathode material provided in the embodiments of this application;
[0037] Figure 2 These are XRD patterns of the phosphate-based cathode materials provided in Examples 1, 5, and 6 of this application and Comparative Examples 1-5;
[0038] Figure 3 This is a comparison chart of the discharge capacity of the phosphate-based cathode materials provided in Examples 1, 5, and 6 of this application and Comparative Examples 1-5 under 1C discharge.
[0039] Figure 4 These are comparison charts showing the capacity retention rates under 1C discharge provided in Examples 1, 5, and 6 of this application and Comparative Examples 1-5. Detailed Implementation
[0040] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0041] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.
[0042] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.
[0043] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.
[0044] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.
[0045] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as µg, mg, g, or kg.
[0046] The first aspect of this application provides a method for preparing a phosphate-based cathode material, as shown in the attached figure. Figure 1 As shown, it includes the following steps:
[0047] S10. A solid precursor is prepared by mixing phosphate-based precursor components and flux; wherein the flux includes LiCl and MnCl2, and the phosphate-based precursor components include a doped metal source, the doped metal source including a nickel source.
[0048] S20. The solid precursor is sintered to obtain a phosphate-based cathode material.
[0049] The method for preparing phosphate-based cathode materials provided in the first aspect of this application involves adding fluxes including LiCl and MnCl2 to the raw material components to form a solid precursor. This not only assists in the doping effect of doped metal ions such as nickel sources in the phosphate-based cathode material, preventing the formation of impurity phases, but also effectively inhibits the agglomeration of product particles, resulting in uniform, intact, and well-dispersed product particles, thereby improving the electronic conductivity, Li ion diffusion rate, and structural stability of the phosphate-based cathode material. Simultaneously, LiCl and MnCl2 in the flux can also act as raw materials and dopant sources, respectively. Furthermore, doping elements such as nickel replace Fe sites, forming metal-oxygen bonds, which have a synergistic effect in the phosphate-based cathode material. Therefore, the doping of metal elements can effectively improve the conductivity and diffusion coefficient of the phosphate-based cathode material. The phosphate-based cathode material can be obtained by sintering the solid precursor. The preparation process is simple and suitable for large-scale industrial production and application. The phosphate-based cathode material produced has good performance in terms of processing performance, discharge capacity and cycle performance, and can provide high-quality cathode material for new energy battery manufacturers to produce high-capacity and long-life phosphate-based batteries.
[0050] In step S10 above:
[0051] In some possible implementations, the molar ratio of LiCl to MnCl2 in the flux is 1:(0.18~0.23). With this ratio, LiCl and MnCl2 in the flux can better improve the doping effect of the doped metal ions in the phosphate-based cathode material and avoid the formation of impurity phases. For example, the molar ratio of LiCl to MnCl2 can be 1:0.18, 1:0.19, 1:0.2, 1:0.21, 1:0.22, 1:0.23, etc.
[0052] In some possible implementations, the phosphate-based precursor raw material components also include at least an iron source, a lithium source, and a phosphorus source. In some embodiments, the iron source, lithium source, and phosphorus source are obtained according to the stoichiometric ratio of the elements in the phosphate-based cathode material, wherein the stoichiometric ratio can be the molar ratio of the raw material components or the mass ratio calculated based on the molar ratio.
[0053] In some possible implementations, the molar ratio of lithium in the lithium source, iron in the iron source, metal in the doped metal source, and metal in the flux is (0.90~0.96):(0.92~0.99):(0.03~0.05):0.1. This ratio allows for better doping of transition metals in phosphate-based cathode materials, avoiding the formation of impurity phases, and ensuring the overall performance of the phosphate-based cathode material, including its bonding stability, electrochemical performance, and stability. For example, the molar ratios of lithium in the lithium source, iron in the iron source, metal in the doped metal source, and metal in the flux can be 0.9:(0.92~0.99):(0.03~0.05):0.1, 0.91:(0.92~0.99):(0.03~0.05):0.1, 0.92:(0.92~0.99):(0.03~0.05):0.1, 0.93:(0.92~0.99):(0.03~0.05):0.1, 0.94:(0.92~0.99):(0.03~0.05):0.1, 0.96:(0.92~0.99):(0.03~0.05):0.1, (0.90 ... 6): 0.92: (0.03~0.05): 0.1, (0.90~0.96): 0.94: (0.03~0.05): 0.1, (0.90~0.96): 0.96: (0.03~0.05): 0.1, (0.90~0.96): 0.98: (0.03~0.05): 0.1, (0.90~0.96): 0.99: (0.03~0.05): 0.1, (0.90~0.96): (0.92~0.99): 0.03: 0.1, (0.90~0.96): (0.92~0.99): 0.04: 0.1, (0.90~0.96): (0.92~0.99): 0.05: 0.1, etc.
[0054] In some possible implementations, the iron source includes at least one of ferrous oxalate, ferric nitrate, ferrous sulfate, ferric phosphate, and ferrous sulfate.
[0055] In some possible implementations, the phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid.
[0056] In some possible implementations, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxide, lithium acetate, and lithium acetate.
[0057] In some possible implementations, the nickel source includes at least one of nickel nitrate, nickel acetate, nickel oxalate, nickel carbonate, nickel oxide, and nickel chloride.
[0058] Each raw material component in the above embodiments of this application has good solubility, and the anionic components in the raw materials can be volatilized and removed at high temperature during the subsequent sintering process. This will not introduce impurity elements or form impurity phases in the phosphate-based cathode material, which is beneficial to improving the purity of the phosphate-based cathode material product and improving the overall performance of the cathode material.
[0059] In some possible implementations, a dispersant and a first carbon source are added during the mixing process. The dispersant improves the mixing effect of the phosphate-based precursor components and the flux, ensuring thorough and uniform mixing of the components. The first carbon source protects the components from oxidation during the solid precursor formation and sintering processes, and facilitates the in-situ carbon coating on the outer surface of the phosphate-based cathode material. This not only improves the structural stability of the phosphate-based cathode material but also enhances its electrical conductivity.
[0060] In some possible implementations, the amount of dispersant added is 10% to 30% of the theoretical yield of phosphate-based cathode materials. At this level, the dispersant ensures thorough and uniform mixing of the phosphate-based precursor components and fluxing agents, thereby improving the preparation efficiency of the phosphate-based cathode materials. For example, the amount of dispersant added is 10%, 15%, 20%, 25%, or 30% of the theoretical yield of phosphate-based cathode materials.
[0061] In some possible implementations, the dispersant includes water and / or ethanol; these dispersants can improve the mixing effect of phosphate-based precursor components and fluxes, ensuring that the raw material components are fully and uniformly mixed, without introducing additional impurities into the reaction system.
[0062] In some possible implementations, the amount of the first carbon source added is 6% to 13% of the theoretical yield of the phosphate-based cathode material. At this level, the first carbon source can protect the raw material components from oxidation during the solid precursor formation and sintering processes, and facilitates the subsequent in-situ formation of a carbon coating layer on the outer surface of the phosphate-based cathode material. For example, the amount of the first carbon source added is 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, etc., of the theoretical yield of the phosphate-based cathode material.
[0063] In some possible implementations, the first carbon source includes at least one of glucose, sucrose, citric acid, and polyethylene glycol; these carbon sources can be fully dispersed in the mixture, protecting the raw material components from oxidation during the preparation of solid precursors and sintering, and facilitating the in-situ formation of a coating layer on the surface of the phosphate-based cathode material through subsequent sintering, thereby improving the structural stability and electrochemical properties such as conductivity of the phosphate-based cathode material.
[0064] In some possible implementations, the mixing process includes: mixing an iron source, a phosphorus source, a lithium source, a doped metal source, and a flux; then adding a dispersant and a first carbon source for further mixing; and mixing at a temperature of 160℃~220℃ for 8h~18h to obtain a dry solid precursor. In this embodiment, the iron source, phosphorus source, lithium source, doped metal source, and flux are mixed, and simultaneously a dispersant and a first carbon source are added for further mixing to ensure thorough and uniform mixing of all raw material components. Then, the mixture is treated at a temperature of 160℃~220℃ for 8h~18h to allow the dissolved and volatilized components to be removed, resulting in a dry solid precursor. Exemplarily, the mixing temperature can be 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, etc., and the treatment time can be 8h, 9h, 10h, 12h, 14h, 15h, 16h, 18h, etc.
[0065] In step S20 above:
[0066] In some possible implementations, the sintering process includes: after a first sintering of the solid precursor, mixing the first sintered material with a second carbon source and then performing a second sintering to obtain the phosphate-based cathode material. This application's embodiment employs a two-stage sintering method, which can better optimize the grain size of the phosphate-based cathode material, better ensure its structural stability, and thus improve its cycle performance. The added second carbon source forms a carbon-coated shell in situ through subsequent high-temperature sintering, which not only improves the conductivity of the lithium iron phosphate-based cathode material but also enhances its structural stability and inhibits the growth of lithium iron phosphate particles, resulting in uniform, complete, and well-dispersed product particles. This, in turn, improves the electronic conductivity, Li-ion diffusion rate, and structural stability of the phosphate-based cathode material.
[0067] In some possible implementations, the conditions for the first sintering treatment include: heating to 520℃~560℃ at a heating rate of 1℃ / min~5℃ / min under an inert atmosphere, and holding at that temperature for 4h~7h. Under these conditions, the solid precursor is initially converted into a phosphate-based cathode material. With the synergistic effect of the flux, nickel and other doping metal ions are uniformly and stably doped into the phosphate-based cathode material without generating impurity phases. The inert atmosphere can be at least one of nitrogen, argon, and helium.
[0068] In some possible implementations, the conditions for the second sintering treatment include: heating to 700℃~760℃ at a heating rate of 1℃ / min~5℃ / min under an inert atmosphere, and holding at that temperature for 6h~11h. Under these conditions, the second carbon source forms a carbon coating layer in situ on the surface of the phosphate-based cathode material, resulting in uniform, intact, and well-dispersed product particles, thereby improving the electronic conductivity, Li ion diffusion rate, and structural stability of the phosphate-based cathode material. Furthermore, the high-temperature treatment optimizes the grain size of the phosphate-based cathode material, better ensuring its structural stability and thus improving its cycle performance. The inert atmosphere can be at least one of nitrogen, argon, and helium.
[0069] In some possible implementations, the amount of the second carbon source added is 1% to 3% of the theoretical yield of the phosphate-based cathode material. In this case, the amount of the second carbon source added sufficiently ensures the formation of a carbon coating layer on the surface of the phosphate-based cathode material, optimizes the particle size and uniformity of the phosphate-based cathode material product particles, improves the conductivity of the phosphate-based cathode material, and enhances the electrochemical performance of the lithium-containing phosphate-based cathode material. For example, the amount of the second carbon source added could be 1%, 2%, 3%, etc., corresponding to the theoretical yield of the phosphate-based cathode material.
[0070] In some possible implementations, the second carbon source includes at least one of glucose, starch, citric acid, sucrose, polyethylene, and polyethylene glycol. These carbon sources can be converted in situ into amorphous carbon materials at high temperatures during sintering, coating the surface of the phosphate-based cathode material to form an amorphous carbon coating layer. This optimizes the particle size of the phosphate-based cathode material and improves its electrochemical performance.
[0071] Secondly, embodiments of this application provide a phosphate-based cathode material, which is prepared according to the above method.
[0072] The phosphate-based cathode material of this application, prepared by the above method, utilizes a flux added during the preparation process to assist sintering. This flux not only aids in metal doping and reduces the formation of impurity phases, but LiCl / MnCl2 also serves as both a raw material and a dopant source, resulting in excellent metal ion doping and the absence of impurity phases in the phosphate-based cathode material. Furthermore, the flux effectively inhibits particle agglomeration, leading to uniform, intact, and well-dispersed particles in the phosphate-based cathode material. Therefore, the phosphate-based cathode material provided in this application exhibits superior electrochemical properties, including excellent electronic conductivity, Li ion diffusion rate, and structural stability.
[0073] In some possible implementations, the phosphate-based cathode material in this application uses lithium iron phosphate as the substrate, is uniformly doped with metal ions such as nickel and manganese, has no impurity phase generated, and has an amorphous carbon coating layer formed on the surface.
[0074] Thirdly, embodiments of this application provide a positive electrode sheet, including a current collector and an active layer formed on the surface of the current collector, wherein the active layer contains the aforementioned phosphate-based positive electrode material.
[0075] The positive electrode sheet of this application uses the above-mentioned phosphate-based positive electrode material in the active layer. This phosphate-based positive electrode material has good electrochemical properties such as electronic conductivity, Li ion diffusion rate and structural stability, and the particles are uniform in size, intact and well dispersed. Therefore, it improves the stability, energy density, rate performance and cycle performance of the positive electrode sheet.
[0076] In some possible implementations, the preparation of the active layer includes the following steps: mixing the above-mentioned phosphate-based positive electrode material, conductive agent and binder to form an electrode slurry, coating the electrode slurry onto the current collector, and then preparing the positive electrode sheet through steps such as drying, rolling and die cutting.
[0077] In some possible implementations, the mass percentage of phosphate-based cathode material in the active layer of the cathode sheet is 90% to 95%. Specifically, the mass percentage of the modified cathode material in the cathode active material layer can be 90%, 91%, 92%, 93%, 94%, 95%, etc.
[0078] In some possible implementations, the current collector of the positive electrode includes, but is not limited to, any one of copper foil or aluminum foil.
[0079] In some possible implementations, the binder content in the positive electrode active material layer is 2 wt%-5 wt%. In specific embodiments, the binder content can be typical but not limited to 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc.
[0080] In some possible implementations, the binder includes one or more of the following: polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.
[0081] In some possible implementations, the conductive agent content in the positive electrode active material layer is 1 wt%-5 wt%. In specific embodiments, the conductive agent content can be typical but not limited to 3 wt%, 4 wt%, 5 wt%, etc.
[0082] In some possible implementations, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes.
[0083] Fourthly, embodiments of this application provide a secondary battery that includes the aforementioned positive electrode plate.
[0084] The secondary battery provided in this application embodiment has improved the energy density, cycle stability and other electrochemical performance of the secondary battery because it contains a positive electrode sheet with excellent electrochemical performance such as good stability, high energy density, good rate performance and good cycle stability.
[0085] This application does not specifically limit the negative electrode, electrolyte, separator, etc. in the secondary battery of the embodiments, and can be applied to any battery system.
[0086] In some possible implementations, the negative electrode active material of the secondary battery includes, but is not limited to, carbon materials such as graphite, soft carbon (e.g., coke), and hard carbon, or nitrides, tin-based oxides, tin alloys, and nano-anode materials. The current collector includes, but is not limited to, any one of copper foil and aluminum foil.
[0087] In some possible implementations, the steps for making the negative electrode sheet include: mixing the negative electrode active material with conductive agents such as conductive carbon black, binders such as carboxymethyl cellulose and styrene-butadiene rubber, and solvents such as water in a mass ratio of (80~99):(1~5):(2~10):100 to make a positive electrode mixed slurry, then degassing under vacuum, discharging the material, coating it on a coating machine, and obtaining the negative electrode sheet after rolling, slitting, and die-cutting.
[0088] In some possible implementations, the membrane is capable of blocking electrons while allowing ions to pass through. Exemplary membranes include, but are not limited to, at least one material selected from polypropylene fibers, polyacrylonitrile fibers, polyvinyl formal fibers, poly(ethylene glycol terephthalate), polyethylene terephthalate, polyamide fibers, and poly(p-phenylene terephthalamide).
[0089] In some possible implementations, the electrolyte comprises at least one soluble metal salt. In some specific embodiments, the metal salt includes LiClO4, LiBF4, LiPF6, LiAsF6, LiCF3SO3, LiTDI, Li[(CF3SO2)2N], Li[(FSO2)2N], Li[(C m F 2m+1 SO2)(C n F 2n+1 At least one of SO2(N)[m, n], where m and n are natural numbers. These electrolytic salts can ensure high ionic conductivity of the electrolyte and do not undergo harmful side reactions with electrode materials, electrolyte, diaphragm, etc., and have good chemical stability.
[0090] In some possible implementations, the secondary battery includes at least one of a battery cell, a battery module, and a battery pack.
[0091] In some possible implementations, the battery cell types include lithium-ion batteries, as well as novel batteries such as lithium-air batteries and lithium metal batteries.
[0092] In some possible implementations, the battery cells of this application can be assembled into a battery module. The battery module can contain multiple battery cells, the specific number of which can be adjusted according to the application and capacity of the battery module. Furthermore, the battery module may also include a housing with a receiving space in which multiple battery cells are received.
[0093] In one possible implementation, battery cells and / or battery modules can also be assembled into a battery pack, and the number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
[0094] To enable those skilled in the art to clearly understand the above-described implementation details and operations of this application, and to demonstrate the significant advancements in the performance of the phosphate-based cathode materials, their preparation methods, and applications in the embodiments of this application, the following examples illustrate the above technical solutions.
[0095] Example 1
[0096] A phosphate-based cathode material LiFe 0.93 Ni 0.05 Mn 0.02 PO4, its preparation includes the following steps:
[0097] ① A mixture of lithium carbonate, ammonium dihydrogen phosphate, ferrous oxalate, nickel acetate, and LiCl-MnCl2 was prepared, wherein the molar ratio of LiCl to MnCl2 was 1:0.2; the molar ratio of lithium in the lithium source: phosphorus in the phosphorus source: iron in the iron source: nickel in the nickel source: and the metal elements in LiCl-MnCl2 was 0.92:1.00:0.93:0.05:0.1. Then, 15 wt% of ethanol dispersant (based on the theoretical yield of the prepared lithium iron phosphate) and 8 wt% starch were added, and the mixture was heated at 160℃ for 10 h to obtain a solid precursor.
[0098] ② The precursor was placed in a nitrogen atmosphere and heated to 550°C at a rate of 4°C / min. After holding at this temperature for 6 hours, it was cooled and pulverized to obtain a calcined material.
[0099] ③ The raw materials were mixed with sucrose, with the sucrose addition amount being 1 wt% of the lithium iron phosphate produced. The resulting mixture was heated to 750°C in a nitrogen atmosphere at a heating rate of 3°C / min, held at that temperature for 8 hours, and then cooled. After pulverization, the phosphate-based cathode material LiFe was obtained. 0.93 Ni 0.05 Mn 0.02 PO4.
[0100] Example 2
[0101] A phosphate-based cathode material LiFe 0.95 Ni 0.03 Mn 0.02 PO4, its preparation includes the following steps:
[0102] ① A mixture of lithium hydroxide, ammonium dihydrogen phosphate, ferric nitrate, nickel acetate, and LiCl-MnCl2 was prepared, wherein the molar ratio of LiCl to MnCl2 was 1:0.2; the molar ratio of lithium in the lithium source: phosphorus in the phosphorus source: iron in the iron source: nickel in the nickel source: and the metal elements in LiCl-MnCl2 was 0.92:1.00:0.95:0.03:0.1. Then, 15 wt% of ethanol dispersant (based on the theoretical yield of the prepared lithium iron phosphate) and 8 wt% starch were added, and the mixture was heated at 160℃ for 10 h to obtain a solid precursor.
[0103] ② The precursor was placed in a nitrogen atmosphere and heated to 560°C at a rate of 3°C / min. After holding at this temperature for 5 hours, it was cooled and then pulverized to obtain a calcined material.
[0104] ③ The raw materials were mixed with sucrose at a concentration of 0.8 wt% of the lithium iron phosphate produced. The resulting mixture was heated to 740°C at a rate of 4°C / min under a nitrogen atmosphere, held at that temperature for 8 hours, and then cooled. After pulverization, the phosphate-based cathode material LiFe was obtained. 0.95 Ni 0.03 Mn 0.02 PO4.
[0105] Example 3
[0106] A phosphate-based cathode material LiFe 0.94 Ni 0.04 Mn 0.02 PO4, its preparation includes the following steps:
[0107] ① A mixture of lithium hydroxide, ammonium dihydrogen phosphate, iron nitrate, nickel nitrate, and LiCl-MnCl2 was prepared, wherein the molar ratio of LiCl to MnCl2 was 1:0.2; the molar ratio of lithium in the lithium source: phosphorus in the phosphorus source: iron in the iron source: nickel in the nickel source: and the metal elements in LiCl-MnCl2 was 0.92:1.00:0.95:0.03:0.1. Then, 15 wt% of ethanol dispersant (based on the theoretical yield of the prepared lithium iron phosphate) and 8 wt% starch were added, and the mixture was heated at 160℃ for 10 h to obtain a solid precursor.
[0108] ② The precursor was placed in a nitrogen atmosphere and heated to 540°C at a rate of 3.5°C / min. After holding at this temperature for 5 hours, it was pulverized to obtain a calcined material.
[0109] ③ A mixture of glucose and calcined materials, with the glucose content being 0.8 wt% of the prepared lithium iron phosphate, was heated to 750°C in a nitrogen atmosphere at a heating rate of 2°C / min, held at this temperature for 7 hours, cooled, and then pulverized to obtain the phosphate-based cathode material LiFe. 0.94 Ni 0.04 Mn 0.02 PO4.
[0110] Example 4
[0111] A phosphate-based cathode material LiFe 0.94 Ni 0.04 Mn 0.02 PO4, its preparation includes the following steps:
[0112] ① A mixture of lithium carbonate, ammonium dihydrogen phosphate, iron nitrate, nickel oxide, and LiCl-MnCl2 was prepared, wherein the molar ratio of LiCl to MnCl2 was 1:0.2; the molar ratio of lithium in the lithium source: phosphorus in the phosphorus source: iron in the iron source: nickel in the nickel source: and the metal elements in LiCl-MnCl2 was 0.92:1.00:0.95:0.03:0.1. Then, 15 wt% of ethanol dispersant (based on the theoretical yield of the prepared lithium iron phosphate) and 8 wt% starch were added, and the mixture was heated at 160℃ for 10 h to obtain a solid precursor.
[0113] ② The precursor was placed in a nitrogen atmosphere and heated to 520°C at a rate of 2°C / min. After holding at this temperature for 6 hours, it was cooled and pulverized to obtain a calcined material.
[0114] ③ A mixture of polyethylene glycol (PEG) and lithium iron phosphate (LiFePO4) was prepared. The PEG was added at 2 wt% of the raw material. The resulting mixture was heated to 730°C at a rate of 4°C / min under a nitrogen atmosphere, held at that temperature for 9 hours, cooled, and then pulverized to obtain the phosphate-based cathode material LiFePO4. 0.94 Ni0.04 Mn 0.02 PO4.
[0115] Example 5
[0116] A phosphate-based cathode material differs from Example 1 in that: in step ①, lithium carbonate, ammonium dihydrogen phosphate, iron nitrate, nickel nitrate, and LiCl-MnCl2 are mixed, wherein the molar ratio of lithium in the lithium source: phosphorus in the phosphorus source: iron in the iron source: nickel in the nickel source: and the metal elements in LiCl-MnCl2 is 0.82:1.00:0.93:0.05:0.1; and the molar ratio of LiCl to MnCl2 is 2:0.2, i.e., LiCl is added in excess. Other operations are consistent with the example, yielding lithium iron phosphate (LiFe). 0.93 Ni 0.05 Mn 0.02 PO4.
[0117] Example 6
[0118] A phosphate-based cathode material differs from Example 1 in that: in step (1), lithium carbonate, ammonium dihydrogen phosphate, iron nitrate, nickel nitrate, and LiCl-MnCl2 are mixed, wherein the molar ratio of lithium in the lithium source: phosphorus in the phosphorus source: iron in the iron source: nickel in the nickel source: and the molar ratio of metal elements in LiCl-MnCl2 is 0.92:1.00:0.93:0.05:0.1, and the molar ratio of LiCl:MnCl2 is 1:0.4, that is, the added MnCl2 is in excess. Other operations are the same as in the example, to obtain lithium iron phosphate (LiFe). 0.93 Ni 0.05 Mn 0.04 PO4.
[0119] Comparative Example 1
[0120] A phosphate-based cathode material differs from Example 1 in that: no LiCl-MnCl2 flux is added, and the molar ratio of lithium in the lithium source: phosphorus in the phosphorus source: iron in the iron source: nickel in the nickel source is 1.02:1.00:0.93:0.05. Other operating steps are the same as in Example 1, resulting in a material with Ni... 12 Phosphate materials with P5 impurity phase.
[0121] Comparative Example 2
[0122] A phosphate-based cathode material differs from Example 1 in that only LiCl is added as a flux, without the addition of MnCl2. All other operational steps are the same as in Example 1, resulting in a material with Ni... 12 Phosphate materials with P5 impurity phase.
[0123] Comparative Example 3
[0124] A phosphate-based cathode material differs from Example 1 in that only MnCl2 is added as a flux, without LiCl. All other operational steps are the same as in Example 1, resulting in a material with Ni... 12 Phosphate materials with P5 impurity phase.
[0125] Comparative Example 4
[0126] A phosphate-based cathode material differs from Example 1 in that the manganese source in the flux is MnSO4, while the other operating steps are the same as in Example 1, resulting in a material with Ni... 12 Phosphate materials with P5 impurity phase.
[0127] Comparative Example 5
[0128] A phosphate-based cathode material differs from Example 1 in that the manganese source in the flux is Mn(NO3)2, while the other operating steps are the same as in Example 1, resulting in a material with Ni... 12 Phosphate materials with P5 impurity phase.
[0129] To verify the progressiveness of the embodiments of this application, the following performance tests were performed on the above embodiments and comparative examples:
[0130] 1. X-ray powder diffraction tests were performed on the phosphate-based cathode materials prepared in Examples 1, 5, 6, and Comparative Examples 1 to 5. The test results are shown in the attached figure. Figure 2 The XRD spectra of Examples 1, 5, 6, and Comparative Examples 1 to 5 are shown. The test results show that the phosphate-based cathode materials prepared by adding LiCl-MnCl2 flux in Examples 1, 5, and 6 of this application do not contain Ni. 12 P5 impurity phase. Comparative Examples 1 to 5 all contain Ni. 12 P5 impurity phase.
[0131] Furthermore, through refinement of the XRD spectra, the results are shown in Table 1 below. The phosphate-based cathode materials prepared in Examples 1, 5, and 6 of this application do not contain Ni. 12 The P5 impurity phase was relatively high in Comparative Example 1 without the addition of LiCl-MnCl2 flux. Comparative Examples 2 and 3, with the addition of LiCl and MnCl2 respectively, still showed significant impurities. Comparative Examples 4 and 5, with the addition of LiCl-MnSO4 and LiCl-Mn(NO3)2 respectively, still showed significant Ni impurities. 12 The presence of the P5 impurity phase indicates that the LiCl-MnCl2 flux is a superior combination.
[0132] Table 1
[0133]
[0134] 2. The phosphate-based cathode materials obtained in Examples 1 to 6 and Comparative Examples 1 to 5 were prepared into cathode slurries. The processing properties of the cathode slurries, such as solid content, viscosity, thixotropic index, and recovery rate, were tested as follows:
[0135] ① The calculation method for solid content is: (active substance + polyvinylidene fluoride + carbon black conductive agent) / (active substance + polyvinylidene fluoride + carbon black conductive agent + N-methylpyrrolidone) * 100%.
[0136] ② Viscosity test method: obtained by NDJ-8S digital viscometer.
[0137] ③Thixotropic index test method: obtained by Anton Pear rheometer, the calculation is the ratio of viscosity at shear force of 1 / s and 50 / s.
[0138] ④ Recovery rate test method: The recovery rate is obtained by testing with an Anton Pear rheometer. The recovery rate is the ratio of the viscosity at 185s and 60s on the thixotropic curve.
[0139] The test results are shown in Table 2 below:
[0140] Table 2
[0141]
[0142] As can be seen from the test results in Table 2 above, compared with Comparative Examples 1-5, the phosphate-based cathode material prepared into cathode slurry in the embodiments of this application has a higher solid content and more active material per unit volume, which can improve the electrochemical performance of the material; the lower thixotropic index indicates that the slurry performance is more stable and less prone to sedimentation and stratification; the higher recovery rate indicates that the slurry has better coating performance.
[0143] 3. Comparison of the discharge capacity of the phosphate-based cathode materials prepared in Examples 1, 5, 6, and Comparative Examples 1 to 5 at 1C discharge (as shown in the attached table). Figure 3 (as shown) and a comparison of capacity retention (as attached) Figure 4 (As shown in the figure). The test results show that the phosphate-based cathode material in this application has better electrochemical performance.
[0144] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for producing a phosphate-based positive electrode material, characterized by, Includes the following steps: A solid precursor is prepared by mixing phosphate-based precursor components and a flux; wherein the flux comprises LiCl and MnCl2 in a molar ratio of 1:(0.18~0.23), the phosphate-based precursor components include a doped metal source, the doped metal source being a nickel source; the flux can also function as both a raw material and a dopant source; the flux can simultaneously suppress the generation of impurity phases and the agglomeration of product particles; The solid precursor was sintered to obtain a phosphate-based cathode material.
2. The method for producing a phosphate-based cathode material according to claim 1, wherein The phosphate-based precursor components also include at least an iron source, a lithium source, and a phosphorus source; And / or, a dispersant and a first carbon source are also added during the mixing process.
3. The method for producing a phosphate-based cathode material according to claim 2, wherein The molar ratio of lithium in the lithium source, iron in the iron source, metal in the doped metal source, and metal in the flux is (0.90~0.96):(0.92~0.99):(0.03~0.05):0.1; And / or, the amount of the dispersant added is 10% to 30% of the theoretical yield of the phosphate-based cathode material; And / or, the amount of the first carbon source added is 6% to 13% of the theoretical yield of the phosphate-based cathode material.
4. The method for preparing the phosphate-based cathode material as described in claim 3, characterized in that, The mixing process includes: mixing the iron source, the phosphorus source, the lithium source, the doped metal source and the flux, then adding the dispersant and the first carbon source and mixing them, and mixing them at a temperature of 160℃~220℃ for 8h~18h to obtain the dry solid precursor. And / or, the sintering process includes: after performing a first sintering process on the solid precursor, mixing the sintered material with a second carbon source and then performing a second sintering process to obtain a phosphate-based cathode material.
5. The method for preparing the phosphate-based cathode material as described in claim 4, characterized in that, The conditions for the first sintering treatment include: heating to 520℃~560℃ at a heating rate of 1℃ / min~5℃ / min under an inert atmosphere, and holding at that temperature for 4h~7h. And / or, the conditions for the second sintering treatment include: heating to 700℃~760℃ at a heating rate of 1℃ / min~5℃ / min under an inert atmosphere, and holding at that temperature for 6h~11h; And / or, the amount of the second carbon source added is 1% to 3% of the theoretical yield of the phosphate-based cathode material.
6. The method for preparing the phosphate-based cathode material as described in claim 4 or 5, characterized in that, The iron source includes at least one of ferrous oxalate, ferric nitrate, ferric phosphate, and ferrous sulfate. And / or, the phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid; And / or, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxide, and lithium acetate; And / or, the nickel source includes at least one of nickel nitrate, nickel acetate, nickel oxalate, nickel carbonate, nickel oxide, and nickel chloride; And / or, the dispersant comprises water and / or ethanol; And / or, the first carbon source includes at least one of glucose, sucrose, citric acid, and polyethylene glycol; And / or, the second carbon source includes at least one of glucose, starch, citric acid, sucrose, polyethylene, and polyethylene glycol.
7. A phosphate-based cathode material, characterized in that, The phosphate-based cathode material is prepared by the method according to any one of claims 1 to 6.
8. A positive electrode plate, characterized in that, It includes a current collector and an active layer formed on the surface of the current collector, the active layer containing the phosphate-based cathode material as described in claim 7.
9. A secondary battery, characterized in that, The secondary battery includes the positive electrode as described in claim 8.