A composite cathode material precursor, a preparation method and application thereof

Abstract

A composite cathode material precursor, its preparation method, and its application are disclosed. The composite cathode material precursor comprises an N-doped iron phosphate core and an M-doped iron phosphate coating layer covering the surface of the iron phosphate core. The N element includes at least one selected from Mn, Ni, Co, Cr, V, Mg, Sr, Nb, La, Nd, Ce, and Y, and the M element includes at least one selected from Al, Ti, and Zr. By introducing doping elements N and M into the core and coating layer of the cathode material precursor, respectively, the crystal structure of iron phosphate can be adjusted, improving its conductivity and ion diffusion rate. Furthermore, the doping elements N and M form a synergistic effect in the composite cathode material precursor, comprehensively improving the structural stability, cycle life, ion transport rate, and electrochemical performance of the cathode material by optimizing the crystal nucleus structure, enhancing the stability of the coating layer, and regulating the electronic structure.

Description

Technical Field

[0001] This disclosure belongs to the field of battery materials technology, specifically relating to a composite cathode material precursor, its preparation method, and its application. Background Technology

[0002] Iron phosphate is an important cathode material precursor, widely used in lithium-ion batteries and other energy storage devices. However, lithium iron phosphate materials synthesized from traditional iron phosphate precursors have certain limitations in terms of compaction, cycle performance, and electrochemical performance. Due to the inherent limitations of the material, lithium iron phosphate materials suffer from poor conductivity, slow lithium-ion diffusion rate, and low specific capacity. Currently, these problems are mainly addressed through methods such as structural optimization, doping modification, and surface coating of lithium iron phosphate materials.

[0003] To improve the uniformity and controllability of doping and coating in lithium iron phosphate, and to enhance the electrochemical performance and stability of lithium iron phosphate, it is necessary to develop a method for preparing iron phosphate, a precursor for cathode materials, in order to improve the performance and stability of lithium iron phosphate materials. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0005] To address the shortcomings of existing technologies, the present disclosure aims to provide a composite cathode material precursor, its preparation method, and its applications. This disclosure introduces doping elements N and M into the core and coating layer of the cathode material precursor, respectively, thereby regulating the crystal structure of iron phosphate and improving its conductivity and ion diffusion rate. Furthermore, the doping elements N and M form a synergistic effect in the composite cathode material precursor, comprehensively improving the structural stability, cycle life, ion transport rate, and electrochemical performance of the cathode material by optimizing the crystal nucleus structure, enhancing the stability of the coating layer, and regulating the electronic structure. This design concept provides a potential innovative approach for the development of materials in novel lithium-ion batteries and other electrochemical devices.

[0006] To achieve this objective, the present disclosure adopts the following technical solution:

[0007] In a first aspect, this disclosure provides a composite cathode material precursor, the composite cathode material precursor comprising an N-doped iron phosphate core and an M-doped iron phosphate coating layer covering the surface of the iron phosphate core;

[0008] The N element includes at least one of Mn, Ni, Co, Cr, V, Mg, Sr, Nb, La, Nd, Ce, and Y, and the M element includes at least one of Al, Ti, and Zr.

[0009] This disclosure introduces doping elements N and M into the core and coating layer of the cathode material precursor, respectively, which can regulate the crystal structure of iron phosphate and improve its conductivity and ion diffusion rate. Secondly, the doping elements N and M form a synergistic effect in the composite cathode material precursor, which comprehensively improves the structural stability, cycle life, ion transport rate and electrochemical performance of the cathode material by optimizing the crystal nucleus structure, enhancing the stability of the coating layer and regulating the electronic structure. This design concept provides a potential innovative approach for the development of materials in novel lithium-ion batteries and other electrochemical devices.

[0010] In this disclosure, the dopant element M introduced into the coating layer can, to a certain extent, alter the electron cloud density and crystal state of the coating layer, thereby affecting the surface reactivity and stability of iron phosphate and playing a supporting and stabilizing role in the interlayer structure of iron phosphate. The dopant element N introduced into the core provides additional charge compensation, alters the conductivity and ion diffusion performance of the crystal nucleus, and helps to improve the conductivity and ion transport rate of the material, thus appropriately increasing the specific capacity of the material. Therefore, different ions play different functions at different positions in the material; the core dopant element provides additional charge compensation, increasing the specific capacity of the material, while the coating layer dopant element plays a stabilizing role.

[0011] In this disclosure, different dopants in the core and coating layer lead to the formation of an interface between them. The interfacial interaction of different elements can optimize the band structure of the interface. By using a reasonable doping combination, the band bending and electronic density of states at the interface can be adjusted, thereby improving the carrier transport efficiency at the interface, promoting electron transfer, and improving the conductivity of the material. Furthermore, this interfacial interaction can increase the electron transport rate between the electrode and the electrolyte, enhance the electrochemical activity of the electrode, and also enhance the bonding strength and stability of the interface. During electrochemical cycling, the electrode material undergoes volume expansion and contraction, which leads to stress and shear forces between the core and coating layer. Therefore, by enhancing the interfacial strength and stability, delamination and damage at the interface can be effectively prevented, thus improving the cycle life of the material.

[0012] In this disclosure, different doping elements in the core and cladding layer cause changes in the concentration of charge carriers such as free electrons and holes. By controlling the concentration of charge carriers, the conductivity and electron mobility of the material can be altered. Furthermore, elemental doping can change the band gap, energy level barrier, and Fermi level position of the material, making it easier for valence band electrons to transition to the conduction band. Effective control of the Fermi level in both the core and shell layers can promote charge transfer and improve the conductivity at the interface. The synergistic effect of different doping elements in the core and cladding layer enhances the overall performance of the material.

[0013] Specifically, the doping elements Al, Ti, and Zr in the coating layer have the following advantages: ① They can enhance the thermal stability of the structure and extend the service life of the material; ② The doped ions replace some of the positions of iron ions, which can increase the vacancies and defects in the crystal structure, thereby improving the migration rate of lithium ions in the crystal; ③ They can improve the electronic and ionic conductivity of the material, thereby improving the charge and discharge rate and performance of the battery. Titanium doping can affect the growth rate and size of the crystal, forming smaller crystal particles, which helps to improve the compaction performance and capacity retention of the battery. The doping elements Mn, Ni, Co, Cr, V, Mg, Sr, Nb, La, Nd, Ce, and Y in the core have the following advantages: They can improve the lithium ion diffusion rate and electron mobility, and improve the rate performance and capacity of the material. However, since these ions are prone to a certain degree of dissolution, they can exacerbate the side reactions with the electrolyte. To suppress the occurrence of dissolution, constructing a core-shell structure can realize the interaction between the inner and outer doped ions. The outer layer doping can suppress the stability of the core doped elements and reduce the dissolution phenomenon.

[0014] In this disclosure, N and M elements can be combined in various ways, including Mn+Ti, Mn+Al, Mn+Zr, Co+Al, Co+Zr, V+Al, and V+Zr. In the Mn+Ti combination, Mn doping improves ionic conductivity and intercalation / deintercalation capability, increasing the material's capacity. Simultaneously, Mn doping introduces additional electronic energy levels into the core, increasing the electronic density of states and allowing more electrons to transition from the valence band to the conduction band, thus improving the material's conductivity. Ti stabilizes the crystal structure and suppresses side reactions. Ti doping controls crystal growth size while increasing the material's compaction performance. Furthermore, Ti introduces additional electronic energy levels, resulting in a superimposed electronic density of states at the interface between the inner and outer layers. This increases the likelihood of band shift at the interface, affecting electron transport and conductivity.

[0015] As an optional technical solution of this disclosure, the thickness of the iron phosphate coating layer is 0.1-4μm, for example, it can be 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 3μm, 4μm, 5μm, etc.

[0016] In this disclosure, if the thickness of the iron phosphate coating layer is too small, the surface of the core layer cannot be uniformly coated, the coating is incomplete, and the performance cannot be maximized; if the thickness of the iron phosphate coating layer is too large, it will reduce the lithium-ion insertion / extraction performance, hinder the material activity, prevent the expression of the inner layer structure performance, and reduce the electrochemical performance.

[0017] In one embodiment, the particle size D50 of the composite cathode material precursor is 1-10 μm, for example, it can be 1 μm, 3 μm, 5 μm, 7 μm or 9 μm, etc.

[0018] As an optional technical solution of this disclosure, the chemical formula of the iron phosphate core is Fe. y N 1-y PO4, the general chemical formula of the iron phosphate coating is Fe x M 1-x PO4, 0.9≤x<1, 0.9≤y<1.

[0019] In this disclosure, 0.9 ≤ x < 1, for example, can be 0.9, 0.92, 0.94, 0.96 or 0.98, etc., and 0.9 ≤ y < 1, for example, can be 0.9, 0.92, 0.94, 0.96 or 0.98, etc.

[0020] In this disclosure, if the doping amount of N element is too large, it will easily cause crystal structure distortion. During the discharge process of synthesized lithium iron phosphate, more N element will dissolve out, affecting the conductivity and ion diffusion coefficient of the material, thereby affecting the rate performance. If the doping amount of M element is too large, it will inhibit the growth of small particles, resulting in a decrease in compaction performance. At the same time, the M atoms will hinder the diffusion channels of ions, resulting in a decrease in the capacity of lithium iron phosphate.

[0021] In one implementation, 0.95 ≤ x < 1 and 0.95 ≤ y < 1.

[0022] In this disclosure, within the range of 0.95≤x<1 and 0.95≤y<1, the conductivity and lithium-ion diffusion performance can be improved from within the material, the structural stability can be enhanced, the element dissolution can be reduced, and the electrochemical performance of the material can be improved.

[0023] In one embodiment, the molar ratio of the N element to the M element is (0.25-1):(1-0.25), wherein the N element is selected in the range of "0.25-1", for example, 0.25, 0.5 or 0.75, and the M element is selected in the range of "1-0.25", for example, 1, 0.75 or 0.25.

[0024] In this disclosure, if the molar ratio of N to M elements is too large, the dopant elements are easily dissolved, blocking the diffusion channels of lithium ions and affecting the electrochemical performance of the cathode material; if the molar ratio of N to M elements is too small, the doping effect cannot be achieved, the carrier concentration between the valence band and conduction band decreases, the conductivity deteriorates, and the electrochemical performance decreases.

[0025] In a second aspect, this disclosure provides a method for preparing a composite cathode material precursor as described in the first aspect, the method comprising the following steps:

[0026] (1) Mix the first iron source, the N-containing dopant and the first solvent to obtain liquid metal A, and mix the second iron source, the phosphorus source, the oxidant, the M-containing dopant and the second solvent to obtain liquid metal B;

[0027] (2) Adjust the pH of the liquid metal A and perform heat treatment to obtain solid C. Then, mix the solid C with an activator and activate it to obtain a slurry.

[0028] (3) The slurry and liquid metal B are mixed and heat-treated to obtain the composite cathode material precursor.

[0029] The preparation method disclosed herein can synthesize doped@coated precursors. The dopant element M introduced into the coating layer plays a supporting and stabilizing role in the interlayer structure of iron phosphate. The dopant element N introduced into the core provides additional charge compensation, changes the conductivity and ion diffusion performance of the crystal nucleus, helps to improve the conductivity and ion transport rate of the material, and can appropriately increase the specific capacity of the material.

[0030] As an optional technical solution of this disclosure, the N-doped agent in step (1) includes at least one of the compounds containing Mn, Ni, Co, Cr, V, Mg, Sr, Nb, La, Nd, Ce and Y elements, such as manganese sulfate, nickel sulfate, cobalt acetate, magnesium sulfate, cobalt acetate tetrahydrate, lanthanum nitrate or cerium carbonate, etc.

[0031] It should be noted that N-doped agents must be soluble in acid.

[0032] In one embodiment, the M-containing dopant in step (1) includes at least one of compounds containing Al, Ti and Zr elements, such as titanium trichloride, aluminum trichloride hexahydrate, aluminum nitrate, aluminum sulfate or zirconium carbonate.

[0033] It should be noted that M-doped agents must be soluble in acid.

[0034] In one implementation, step (1) includes either a divalent iron source or a trivalent iron source.

[0035] It should be noted that if the first and second iron sources are only ferrous iron sources, an oxidant needs to be added to oxidize them and turn them into ferric iron sources.

[0036] In one embodiment, the divalent iron source includes ferrous sulfate, and the trivalent iron source includes at least one of ferric sulfate, ferric chloride, ferric oxalate, and ferric nitrate.

[0037] In one embodiment, the phosphorus source in step (1) includes at least one of phosphoric acid, ammonium dihydrogen phosphate, monohydrogen phosphate, sodium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, and potassium phosphate.

[0038] It should be noted that if the phosphorus source is ammonium dihydrogen phosphate or ammonium monohydrogen phosphate, the phosphorus source can not only provide phosphorus but also regulate pH.

[0039] In one embodiment, the oxidant in step (1) includes hydrogen peroxide and / or sodium peroxide.

[0040] In one embodiment, in step (1), both the first solvent and the second solvent are water.

[0041] In one embodiment, the method for adjusting the pH of the metal liquid A in step (2) includes the following steps:

[0042] Under stirring conditions, the pH adjuster is added dropwise to the molten metal A.

[0043] In this disclosure, adjusting the pH of the metal liquid A can bring the pH to the precipitation pH of ferric phosphate.

[0044] In one embodiment, the pH adjuster comprises a phosphorus-containing compound, which includes at least one selected from phosphoric acid, ammonium dihydrogen phosphate, monohydrogen phosphate, sodium phosphate, sodium dihydrogen phosphate, and potassium phosphate.

[0045] It should be noted that if the phosphorus-containing compound is ammonium dihydrogen phosphate or ammonium monohydrogen phosphate, then the phosphorus source can not only provide phosphorus but also play a role equivalent to that of an alkaline solution.

[0046] In one embodiment, the pH adjuster further includes an alkaline solution, which includes at least one of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, NaOH, ammonia, and urea.

[0047] In this disclosure, the alkaline solution can regulate the pH of the reaction solution and control the synthesis of ferric phosphate precipitate.

[0048] In one embodiment, the pH adjuster further includes an oxidant, which includes hydrogen peroxide and / or sodium peroxide.

[0049] In this disclosure, the purpose of adding an oxidizing agent is to oxidize the ferrous iron in the reaction solution to ferric iron. Ferrous iron and phosphoric acid cannot form a precipitate, so ferrous iron needs to be oxidized.

[0050] In one embodiment, the dripping rate is (0.05-0.25)×V1 g / min, where V1 is the volume of the liquid metal A, and can be, for example, 0.05V1 g / min, 0.1V1 g / min, 0.15V1 g / min, 0.2V1 g / min, or 0.25V1 g / min, etc.

[0051] In this disclosure, the dropping rate is (0.05-0.25)×V1 g / min, which helps to control the precipitation rate of the molten metal and regulate the particle size and morphology of the product.

[0052] In one embodiment, after adjusting the pH of the metal liquid A in step (2), the pH value of the metal liquid A is 1.6-2.1, for example, it can be 1.6, 1.7, 1.8, 1.9, 2 or 2.1, etc.

[0053] In this disclosure, if the pH value of the metal liquid A is too low, it cannot reach the precipitation pH of ferric phosphate, and the metal liquid A will not precipitate; if the pH value of the metal liquid A is too high, it is easy to reach the precipitation pH of ferric hydroxide, resulting in ferric hydroxide precipitation, which affects the uniformity and consistency of the product.

[0054] In one embodiment, the temperature of the heat treatment in step (2) is 60-100℃, for example, it can be 60℃, 70℃, 80℃, 90℃ or 100℃, and the time is 0.5-5h, for example, it can be 0.5h, 1.5h, 2.5h, 3.5h or 4.5h.

[0055] In this disclosure, if the heat treatment temperature is too low, the conversion of iron phosphate crystals will be incomplete, resulting in a poor activation effect. If the heat treatment temperature is too high, the conversion will be easier to complete, resulting in a better activation effect. There is no obvious adverse effect, but the energy consumption will increase, which is not conducive to cost reduction and efficiency improvement. At the same time, the material may become too loose, which will easily clog the filter cloth during filtration and affect the continuity of production.

[0056] As an optional technical solution of this disclosure, the activator in step (2) is an acid-alcohol mixed solution.

[0057] This disclosure uses an acid-alcohol mixture as an activator, which can dissolve small particles on the surface of seed crystals and form a porous structure, improving the hydrophilicity, dispersibility and crystal growth rate of iron phosphate. This porous structure can adjust the structure and morphology of the product, increase its surface area, and facilitate the interaction between the electrode material and the electrolyte, thereby optimizing its electrochemical performance and application performance.

[0058] In one embodiment, the acid in the acid-alcohol mixture includes at least one of sulfuric acid, phosphoric acid, and nitric acid.

[0059] In this disclosure, the acid in the acid-alcohol mixture can dissolve small particles on the surface of the seed crystal, forming a porous structure and adjusting the product structure and morphology.

[0060] In one embodiment, the molar concentration of the acid in the acid-alcohol mixture is 0.1-0.4 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L or 0.4 mol / L, etc.

[0061] In this disclosure, the molar concentration of acid is 0.1-0.4 mol / L, which can achieve excellent activation effect. Too high a concentration will result in overactivation and dissolution of too many small particles; too low a concentration will result in incomplete activation and failure to meet the activation requirements.

[0062] In one embodiment, the alcohol in the acid-alcohol mixture includes at least one selected from methanol, ethanol, ethylene glycol, propylene glycol, and glycerol.

[0063] In this disclosure, the alcohol in the acid-alcohol mixture can improve the surface properties of the seed crystal, enhance its hydrophilicity and dispersibility, promote seed crystal induction, and improve the crystal growth rate and product quality.

[0064] In one embodiment, the molar ratio of acid to alcohol in the acid-alcohol mixture is 1:(0.5-3), for example, it can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc.

[0065] In this disclosure, if the molar ratio of acid to alcohol is too small, it is easy to cause particle agglomeration and poor dispersibility; if the molar ratio of acid to alcohol is too large, it is easy to cause poor activation effect.

[0066] In one embodiment, the activation method in step (2) includes mechanical activation or immersion activation.

[0067] In one embodiment, the activation temperature in step (2) is 40-70°C, for example, 40°C, 50°C, 60°C or 70°C, and the activation time is 0.5-2h, for example, 0.5h, 1h, 1.5h or 2h.

[0068] In this disclosure, selecting appropriate activation temperature and activation time helps to accelerate the reaction rate and increase the interaction between the seed crystal and the acidic solution, thereby optimizing the activation effect.

[0069] As an optional technical solution of this disclosure, the amount of slurry added in step (3) is ((0.10-1.00)×Fe mass concentration of liquid metal B×V2) / solid content of slurry, where V2 is the volume of liquid metal B, and can be, for example, 0.1×Fe mass concentration of liquid metal B×V2) / solid content of slurry, 0.3×Fe mass concentration of liquid metal B×V2) / solid content of slurry, 0.5×Fe mass concentration of liquid metal B×V2) / solid content of slurry, 0.7×Fe mass concentration of liquid metal B×V2) / solid content of slurry or 0.9×Fe mass concentration of liquid metal B×V2) / solid content of slurry, etc.

[0070] In this disclosure, the amount of slurry added satisfies the above-mentioned relationship, which can effectively control the core-shell thickness and product particle size.

[0071] In one embodiment, the heat treatment temperature in step (3) is 80-95°C, for example, 80°C, 85°C, 90°C or 95°C, and the time is 3-5h, for example, 3h, 3.5h, 4h, 4.5h or 5h.

[0072] In this disclosure, selecting appropriate heat treatment temperature and time is beneficial to improving the crystallization degree of iron phosphate while increasing the specific surface area of ​​the product, and without causing excessive energy waste.

[0073] It should be noted that the heat treatment process is the same as the aging process.

[0074] In one embodiment, after the heat treatment described in step (3) is completed, solid-liquid separation, washing, drying and dehydration steps are also performed.

[0075] As an optional technical solution of this disclosure, the preparation method includes the following steps:

[0076] (I) Mix the first iron source, the N-containing dopant and the first solvent to obtain liquid metal A; mix the second iron source, the phosphorus source, the oxidant, the M-containing dopant and the second solvent to obtain liquid metal B; mix the alkaline solution, the phosphorus-containing compound and the oxidant to obtain a pH adjuster.

[0077] (II) Using liquid metal A as the base liquid, under stirring conditions, pH adjuster is added dropwise to liquid metal A to adjust its pH value to 1.6-2.1, then the temperature is raised to 60-100℃ and aged for 0.5-5.0h, and solid C is obtained after filtration;

[0078] The dropping rate is (0.05-0.25)×V1 g / min, where V1 is the volume of the molten metal A.

[0079] (III) The solid C and the acid-alcohol mixture are mixed and ground, and activated at 40-70℃ for 0.5-2h to obtain a slurry;

[0080] The acid molar concentration of the acid-alcohol mixture is 0.1-0.4 mol / L, and the molar ratio of acid to alcohol is 1:(0.5-3).

[0081] (IV) The slurry and liquid metal B are mixed and heat-treated at 80-95℃ for 3-5 hours. After the heat treatment, the solid and liquid are separated to obtain a filter cake. After washing, drying and dehydration, the filter cake is used to obtain the composite cathode material precursor.

[0082] Wherein, the amount of slurry added = ((0.10-1.00) × Fe mass concentration of molten metal B × V2) / solid content of slurry, where V2 is the volume of molten metal B.

[0083] Thirdly, this disclosure provides a lithium iron phosphate cathode material, which is prepared from the composite cathode material precursor described in the first aspect.

[0084] The lithium iron phosphate cathode material prepared based on the composite cathode material precursor provided in this disclosure exhibits excellent electrochemical performance and stability.

[0085] Fourthly, this disclosure provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery comprises lithium iron phosphate positive electrode material prepared from the composite positive electrode material precursor as described in the third aspect.

[0086] The numerical range described in this disclosure includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this disclosure will not exhaustively list the specific point values ​​included in the range.

[0087] Compared with the prior art, this disclosure has the following beneficial effects:

[0088] This disclosure introduces doping elements N and M into the core and coating layer of the cathode material precursor, respectively, which can regulate the crystal structure of iron phosphate and improve its conductivity and ion diffusion rate. Secondly, the doping elements N and M form a synergistic effect in the composite cathode material precursor, which comprehensively improves the structural stability, cycle life, ion transport rate and electrochemical performance of the cathode material by optimizing the crystal nucleus structure, enhancing the stability of the coating layer and regulating the electronic structure. This design concept provides a potential innovative approach for the development of materials in novel lithium-ion batteries and other electrochemical devices.

[0089] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0090] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0091] Figure 1 This is a SEM image of the iron phosphate core in the composite cathode material precursor prepared in Example 1 of this disclosure.

[0092] Figure 2 This is a SEM image of the iron phosphate coating layer in the composite cathode material precursor prepared in Example 1 of this disclosure.

[0093] Figure 3 This is a SEM image of the iron phosphate core in the composite cathode material precursor prepared in Example 3 of this disclosure.

[0094] Figure 4This is a SEM image of the iron phosphate coating layer in the composite cathode material precursor prepared in Example 3 of this disclosure. Detailed Implementation

[0095] The technical solutions of this disclosure will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as specific limitations thereof.

[0096] Example 1

[0097] This embodiment provides a composite cathode material precursor, which includes an N-doped iron phosphate core and an M-doped iron phosphate coating layer covering the surface of the iron phosphate core; the N element is Mn and the M element is Ti.

[0098] The thickness of the iron phosphate coating is 1.5 μm, and the particle size D50 of the composite cathode material precursor is 5 μm.

[0099] The general chemical formula of the iron phosphate core is Fe. 0.998 Mn 0.002 PO4, the general chemical formula of the iron phosphate coating is Fe 0.998 Ti 0.002 The molar ratio of PO4 to N and M elements is 1:1.

[0100] This embodiment also provides a method for preparing the above-mentioned composite cathode material precursor, the preparation method comprising the following steps:

[0101] (1) Dissolve 1112g of the first iron source and 8g of Mn dopant in 4L of the first solvent to obtain metal liquid A (where Fe = 55.64g / L and Mn = 0.30g / L). Dissolve 1588g of the second iron source, 660g of the phosphorus source, 460g of the oxidant and 31.3g of Ti dopant in 8L of the second solvent to obtain metal liquid B (where the concentrations of Fe, P and Ti are 39.95g / L, 21.53g / L and 0.11g / L, respectively). Mix 414g of alkaline solution, 70g of phosphorus compound and 310g of oxidant in 4L of pure water, filter and obtain pH adjuster (where the concentration of P is 26.65g / L).

[0102] Among them, the first iron source is ferrous sulfate heptahydrate, the Mn dopant is manganese sulfate, the first solvent is pure water, the second iron source is ferrous sulfate heptahydrate, the phosphorus source is phosphoric acid, the Ti dopant is titanium trichloride, the second solvent is pure water, the alkaline solution is ammonium dihydrogen phosphate, the phosphorus compound is phosphoric acid, and the oxidant in the metal liquid B and the oxidant in the pH adjuster are both hydrogen peroxide.

[0103] (2) Using a volume of liquid metal A of volume V1 as the base liquid, a pH adjuster is added dropwise to liquid metal A under stirring conditions to adjust its pH value to 1.8. Then, the temperature is raised to 90℃ and aged for 3 hours. After filtration, solid C is obtained with a water content of about 38%.

[0104] The dropping rate is 0.15 × V1 g / min, where V1 is the volume of the molten metal A, which is 4 L.

[0105] (3) 40g of 98% concentrated sulfuric acid and 58g of 95% ethanol were added to 1.9L of pure water to prepare an activator (containing 0.2mol / L sulfuric acid and 0.6mol / L ethanol). 1000g of the solid C was added to 1.5L of the activator and mixed and ground until D50 was 1μm. Then, it was activated at 50℃ for 1h to obtain a slurry.

[0106] The molar ratio of acid to alcohol is 1:3;

[0107] (4) 1 kg of the slurry is added to 8 L of liquid metal B and heat-treated at 95 °C for 2 h. After the heat treatment, solid and liquid are separated to obtain filter cake. After washing, drying and dehydration, the filter cake is used to obtain the composite cathode material precursor.

[0108] The amount of slurry added is calculated as follows: (0.2 × Fe mass concentration of liquid metal B × V2) / solid content of slurry, where V2 is the volume of liquid metal B (8L), the Fe mass concentration of liquid metal B is 39.95g / L, and the solid content of slurry is 40%.

[0109] Figure 1 and Figure 2 SEM images of the iron phosphate core and iron phosphate coating layer in the composite cathode material precursor prepared in this embodiment are shown respectively. Figure 1 It can be seen that the iron phosphate core has a plate-like structure with a diameter of 1 μm. Figure 2 It can be seen that the diameter of the iron phosphate particles induced by the core is 4μm, indicating that the coating layer thickness is 1.5μm.

[0110] Example 2

[0111] This embodiment provides a composite cathode material precursor, which includes an N-doped iron phosphate core and an M-doped iron phosphate coating layer covering the surface of the iron phosphate core; the N element is Mn and the M element is Al.

[0112] The thickness of the iron phosphate coating layer is 1 μm, and the particle size D50 of the composite cathode material precursor is 3 μm.

[0113] The general chemical formula of the iron phosphate core is Fe. 0.998 Mn 0.002PO4, the general chemical formula of the iron phosphate coating is Fe 0.998 Al 0.002 The molar ratio of PO4 to N and M elements is 1:1.

[0114] This embodiment also provides a method for preparing the above-mentioned composite cathode material precursor, the preparation method comprising the following steps:

[0115] (1) Dissolve 1112g of the first iron source and 8g of Mn dopant in 4L of the first solvent to obtain metal liquid A (where Fe = 56.55g / L and Mn = 0.31g / L). Dissolve 1588g of the second iron source, 660g of the phosphorus source, 460g of the oxidant and 31.3g of Al dopant in 8L of the second solvent to obtain metal liquid B (where the concentrations of Fe, P and Ti are 40.55g / L, 21.74g / L and 0.212g / L, respectively). Mix 414g of alkaline solution, 70g of phosphorus compound and 310g of oxidant in 4L of pure water, filter and obtain pH adjuster (where the concentration of P is 26.81g / L).

[0116] Among them, the first iron source is ferrous sulfate heptahydrate, the Mn dopant is manganese sulfate, the first solvent is pure water, the second iron source is ferrous sulfate heptahydrate, the phosphorus source is phosphoric acid, the Al dopant is aluminum trichloride hexahydrate, the second solvent is pure water, the alkaline solution is ammonium dihydrogen phosphate, the phosphorus compound is phosphoric acid, and the oxidant in the metal liquid B and the oxidant in the pH adjuster are both hydrogen peroxide.

[0117] (2) Using a volume of liquid metal A of volume V1 as the base liquid, a pH adjuster was added dropwise to liquid metal A under stirring conditions to adjust its pH value to 1.6. Then the temperature was raised to 90℃ and aged for 4 hours. After filtration, solid C was obtained with a water content of about 38%.

[0118] The dropping rate is 0.05 × V1 g / min, where V1 is the volume of the molten metal A, which is 4 L.

[0119] (3) 30g of 98% concentrated sulfuric acid and 43g of 95% ethanol were added to 1.9L of pure water to prepare an activator (containing 0.15mol / L sulfuric acid and 0.45mol / L ethanol). 1000g of the solid C was added to 1.5L of the activator and mixed and ground until D50 was 1μm. Then, it was activated at 40℃ for 1h to obtain a slurry.

[0120] The molar ratio of acid to alcohol is 1:3;

[0121] (4) 0.5 kg of the slurry was added to 8 L of liquid metal B and heat-treated at 95 °C for 2 h. After the heat treatment, solid and liquid were separated to obtain filter cake. After washing, drying and dehydration, the filter cake was used to obtain the composite cathode material precursor.

[0122] The amount of slurry added is calculated as follows: (0.4 × Fe mass concentration of liquid metal B × V2) / solid content of slurry, where V2 is the volume of liquid metal B (8L), the Fe mass concentration of liquid metal B is 39.95g / L, and the solid content of slurry is 40%.

[0123] Example 3

[0124] This embodiment provides a composite cathode material precursor, which includes an N-doped iron phosphate core and an M-doped iron phosphate coating layer covering the surface of the iron phosphate core; the N element is Mg and the M element is Al.

[0125] The thickness of the iron phosphate coating layer is 1 μm, and the particle size D50 of the composite cathode material precursor is 3 μm.

[0126] The general chemical formula of the iron phosphate core is Fe. 0.9985 Mg 0.0015 PO4, the general chemical formula of the iron phosphate coating is Fe 0.9975 Al 0.0025 The molar ratio of PO4 to N and M elements is 1:1.

[0127] This embodiment also provides a method for preparing the above-mentioned composite cathode material precursor, the preparation method comprising the following steps:

[0128] (1) Dissolve 1200g of the first iron source and 7g of Mg-containing dopant in 4L of the first solvent, and filter to obtain metal liquid A (where Fe = 59.19g / L and Mn = 0.24g / L). Dissolve 1588g of the second iron source, 660g of phosphorus source, 460g of oxidant and 20g of Al-containing dopant in 8L of the second solvent to obtain metal liquid B (where the concentrations of Fe, P and Ti are 39.99g / L, 21.84g / L and 0.266g / L, respectively). Mix 850g of alkaline solution, 500g of phosphorus-containing compound and 350g of oxidant in 4L of pure water, and filter to obtain pH adjuster (where the concentration of P is 32.60g / L).

[0129] Among them, the first iron source is ferrous sulfate heptahydrate, the Mg dopant is magnesium sulfate monohydrate, the first solvent is pure water, the second iron source is ferrous sulfate heptahydrate, the phosphorus source is phosphoric acid, the Al dopant is aluminum trichloride hexahydrate, the second solvent is pure water, the alkaline solution is sodium hydroxide, the phosphorus compound is phosphoric acid, and the oxidant in the metal liquid B and the oxidant in the pH adjuster are both hydrogen peroxide.

[0130] (2) Using a volume of liquid metal A of volume V1 as the base liquid, a pH adjuster was added dropwise to liquid metal A under stirring conditions to adjust its pH value to 2.1. Then the temperature was raised to 90℃ and aged for 4 hours. After filtration, solid C was obtained with a water content of about 38%.

[0131] The dropping rate is 0.25 × V1 g / min, where V1 is the volume of the molten metal A, which is 4 L.

[0132] (3) 30g of 98% concentrated sulfuric acid and 43g of 95% ethanol were added to 1.9L of pure water to prepare an activator (containing 0.15mol / L sulfuric acid and 0.45mol / L ethanol). 1000g of the solid C was added to 1.5L of the activator and mixed and ground until D50 was 1μm. Then, it was activated at 70℃ for 1h to obtain a slurry.

[0133] The molar ratio of acid to alcohol is 1:3;

[0134] (4) 0.5 kg of the slurry was added to 8 L of liquid metal B and heat-treated at 95 °C for 2 h. After the heat treatment, solid and liquid were separated to obtain filter cake. After washing, drying and dehydration, the filter cake was used to obtain the composite cathode material precursor.

[0135] The amount of slurry added is calculated as follows: (0.2 × Fe mass concentration of molten metal × V2) / solid content of slurry. V2 is the volume of molten metal B (8L), the Fe mass concentration of molten metal B is 39.99g / L, and the solid content of slurry is 40%.

[0136] Figure 3 and Figure 4 SEM images of the iron phosphate core and iron phosphate coating layer in the composite cathode material precursor prepared in this embodiment are shown respectively. Figure 1 It is known that the diameter of the kernel layer is 0.5-1 μm, from Figure 2 It is known that the diameter of the shell is about 3-4 μm, and the thickness of the coating layer is about 1.5-2 μm.

[0137] Example 4

[0138] The difference between this embodiment and Embodiment 1 is that the thickness of the iron phosphate coating layer is 0.05 μm by adjusting the amount of molten metal B added.

[0139] The remaining preparation methods and parameters are consistent with those in Example 1.

[0140] Example 5

[0141] The difference between this embodiment and Embodiment 1 is that the thickness of the iron phosphate coating layer is 6 μm by adjusting the amount of metal liquid B added.

[0142] The remaining preparation methods and parameters are consistent with those in Example 1.

[0143] Example 6

[0144] The difference between this embodiment and Embodiment 1 is that, by adjusting the amount of Mn-containing dopant added, the chemical formula of the iron phosphate core is Fe. 0.8 Mn 0.2 PO4.

[0145] The remaining preparation methods and parameters are consistent with those in Example 1.

[0146] Example 7

[0147] The difference between this embodiment and Embodiment 1 is that, by adjusting the amount of Ti dopant added, the chemical formula of the iron phosphate coating layer is Fe. 0.8 Ti 0.2 PO4.

[0148] The remaining preparation methods and parameters are consistent with those in Example 1.

[0149] Example 8

[0150] The difference between this embodiment and Embodiment 1 is that, by adjusting the amount of Mn dopant and Ti dopant added, the molar ratio of N to M elements in the composite cathode material precursor is 0.1:1.

[0151] The remaining preparation methods and parameters are consistent with those in Example 1.

[0152] Example 9

[0153] The difference between this embodiment and Embodiment 1 is that, by adjusting the amount of Mn dopant and Ti dopant added, the molar ratio of N to M elements in the composite cathode material precursor is 1:0.1.

[0154] The remaining preparation methods and parameters are consistent with those in Example 1.

[0155] Example 10

[0156] The difference between this embodiment and embodiment 1 is that no pH adjuster is added in step (2), that is, no pH adjuster is prepared in step (1).

[0157] The remaining preparation methods and parameters are consistent with those in Example 1.

[0158] Example 11

[0159] The difference between this embodiment and embodiment 1 is that no activator is added in step (3).

[0160] The remaining preparation methods and parameters are consistent with those in Example 1.

[0161] Example 12

[0162] The difference between this embodiment and embodiment 1 is that the activator in step (3) contains only concentrated sulfuric acid, that is, 58g of ethanol is replaced with 58g of concentrated sulfuric acid.

[0163] The remaining preparation methods and parameters are consistent with those in Example 1.

[0164] Example 13

[0165] The difference between this embodiment and embodiment 1 is that the activator in step (3) contains only ethanol, that is, 40g of concentrated sulfuric acid is replaced with 40g of ethanol.

[0166] The remaining preparation methods and parameters are consistent with those in Example 1.

[0167] Comparative Example 1

[0168] The difference between this comparative example and Example 1 is that the chemical formula of the iron phosphate core is Fe. 0.998 Ti 0.002 PO4, the general chemical formula of the iron phosphate coating is Fe 0.998 Mn 0.002 PO4 involves swapping the Mn-containing dopant in liquid metal A and the Ti-containing dopant in liquid metal B. The specific steps include:

[0169] 1112g of the first iron source and 21.4g of Ti-containing dopant were dissolved in 4L of the first solvent to obtain metal liquid A (where Fe = 56.01g / L and Ti = 0.30g / L). 1588g of the second iron source, 660g of the phosphorus source, 460g of the oxidant, and 10g of Mn-containing dopant were dissolved in 8L of the second solvent to obtain metal liquid B (where the concentrations of Fe, P, and Ti are 40.61g / L, 21.78g / L, and 0.11g / L, respectively).

[0170] The remaining preparation methods and parameters are consistent with those in Example 1.

[0171] Comparative Example 2

[0172] The difference between this comparative example and Example 1 is that the chemical formula of both the iron phosphate core and the iron phosphate coating is Fe. 0.998 Ti 0.002 PO4, which means replacing 8g of Mn-containing dopant with 24.1g of titanium trichloride.

[0173] The remaining preparation methods and parameters are consistent with those in Example 1.

[0174] Comparative Example 3

[0175] The difference between this comparative example and Example 1 is that the chemical formula of both the iron phosphate core and the iron phosphate coating is Fe. 0.998 Mn 0.002 PO4, that is, replacing 31.3g of Ti-doped agent with 10g of manganese sulfate.

[0176] The remaining preparation methods and parameters are consistent with those in Example 1.

[0177] Comparative Example 4

[0178] The difference between this comparative example and Example 1 is that the chemical formula of the iron phosphate core is FePO4, that is, the core is not doped, and no Mn dopant is added in step (1).

[0179] The remaining preparation methods and parameters are consistent with those in Example 1.

[0180] Comparative Example 5

[0181] The difference between this comparative example and Example 1 is that the chemical formula of the iron phosphate coating is FePO4, that is, the coating is not doped, and no Ti dopant is added in step (1).

[0182] The remaining preparation methods and parameters are consistent with those in Example 1.

[0183] Performance testing

[0184] I. The physicochemical properties of the composite cathode material precursors prepared in the above embodiments and comparative examples were tested. The specific elemental data were obtained by ICP-AES equipment, and the test results are shown in Table 1.

[0185] Table 1

[0186]

[0187]

[0188]

[0189] analyze:

[0190] As shown in Table 1, the (Fe+M+N) / P ratio of the iron phosphate products prepared in Examples 1-3 meets the design ratio (Fe / P = 0.97-0.98). Furthermore, the BET of the iron phosphate synthesized in Examples 1-3 is higher than that in Comparative Examples 1-3, which is beneficial for improving the activity of the synthesized lithium iron phosphate and improving the compaction performance of the product.

[0191] Using the composite cathode material precursors prepared in the above examples and comparative examples as raw materials, lithium iron phosphate cathode materials were synthesized. Simultaneously, commercially available lithium iron phosphate cathode materials were used as controls to fabricate lithium-ion batteries, and electrochemical performance tests were conducted: 1) Initial discharge specific capacity and initial efficiency were tested at room temperature (25°C) with a charge / discharge voltage of 2.0-3.65V and an initial charge / discharge rate of 0.1C; 2) Cycle performance and powder compaction performance were tested at room temperature (25°C) with a charge / discharge voltage of 2.0-3.65V and a charge / discharge rate of 1C. The test results are shown in Table 2.

[0192] Table 2

[0193]

[0194]

[0195] analyze:

[0196] As shown in Table 2, by doping N and M elements in the iron phosphate core and coating layer respectively, doped@coated iron phosphate can be constructed, which improves the powder characteristics and can increase the compaction density and discharge specific capacity of the synthesized lithium iron phosphate.

[0197] A comparison of the data results from Examples 1 and 4-5 shows that if the thickness of the iron phosphate coating layer is too small, the coating uniformity will be poor, the dopant elements will be easily dissolved, and the synthesis of lithium iron phosphate will easily lead to a decrease in cycle life and rate performance; if the thickness of the iron phosphate coating layer is too large, the lithium ion diffusion channels will be easily blocked after the synthesis of lithium iron phosphate, and small particles will not be able to grow, thereby reducing the compaction performance.

[0198] A comparison of the data results from Examples 1 and 6-7 shows that if the doping amount of Mn in the iron phosphate core or the doping amount of Ti in the iron phosphate coating layer is too large, the synthesis of lithium iron phosphate will easily block the lithium-ion diffusion channels and inhibit the growth of small particles, resulting in compaction and reduced capacity.

[0199] A comparison of the data results from Examples 1 and 8-9 shows that if the molar ratio of N to M elements is too small, there will be too many inner layer dopants, which will easily lead to more Mn dissolution, inhibiting particle growth and resulting in low capacity and compaction. If the molar ratio of N to M elements is too large, the outer layer dopants will easily block the lithium-ion diffusion channels, resulting in low capacity of the synthesized lithium iron phosphate.

[0200] A comparison of the data results from Example 1 and Example 10 shows that without the addition of a pH adjuster, precipitation cannot be obtained, thus making it impossible to synthesize the composite cathode material precursor.

[0201] A comparison of the data results from Example 1 and Example 11 shows that if no activator is added, the slurry activity is poor, and the iron phosphate particles synthesized by induction are large. Although the product has high compaction, its capacity is relatively low.

[0202] A comparison of the data results from Examples 1 and 12-13 shows that if the activator contains only concentrated sulfuric acid or ethanol, the synthesized iron phosphate BET is likely to be too small and the activity is insufficient, which will result in low compaction or low capacity after the synthesis of lithium iron phosphate.

[0203] A comparison of the data results from Example 1 and Comparative Example 1 shows that if the doping positions of N and M elements are exchanged, it is easy for M element to dissolve, resulting in slightly poorer discharge and compaction performance of the cathode material.

[0204] A comparison of the data results from Example 1 and Comparative Example 2 shows that if both the core and shell are doped with Ti, the interfacial carrier concentration decreases after the synthesis of lithium iron phosphate, resulting in a slightly lower capacity despite high compaction performance.

[0205] A comparison of the data results from Example 1 and Comparative Example 3 shows that if both the core and shell are doped with Mn, although the discharge specific capacity of the material can be improved, the compaction performance is lower than that of Example 1 because Mn may dissolve during the synthesis process.

[0206] A comparison of the data results from Example 1 and Comparative Examples 4-5 shows that if the iron phosphate core is not doped, the synthesized lithium iron phosphate has a slightly lower capacity; if the iron phosphate coating layer is not doped, the synthesized lithium iron phosphate has a slightly lower capacity and lower compaction performance.

Claims

1. A composite cathode material precursor, comprising an N-doped iron phosphate core and an M-doped iron phosphate coating layer covering the surface of the iron phosphate core; The N element includes at least one of Mn, Ni, Co, Cr, V, Mg, Sr, Nb, La, Nd, Ce and Y, and the M element includes at least one of Al, Ti and Zr; The general chemical formula of the iron phosphate core is Fe. y N 1-y PO4, the general chemical formula of the iron phosphate coating is Fe x M 1-x PO4, 0.9≤x<1, 0.9≤y<1.

2. The composite cathode material precursor according to claim 1, wherein, The thickness of the iron phosphate coating is 0.1-4 μm.

3. The composite cathode material precursor according to claim 1, wherein, The particle size D50 of the composite cathode material precursor is 1-10 μm.

4. The composite cathode material precursor according to claim 1, wherein, The general chemical formula of the iron phosphate core is Fe. y N 1-y PO4, the general chemical formula of the iron phosphate coating is Fe x M 1-x PO4, 0.95≤x<1, 0.95≤y<1.

5. The composite cathode material precursor according to claim 1, wherein, The molar ratio of N to M elements is (0.25-1):(1-0.25).

6. A method for preparing a composite cathode material precursor as described in any one of claims 1-5, comprising the following steps: (1) Mix the first iron source, the N-containing dopant and the first solvent to obtain liquid metal A, and mix the second iron source, the phosphorus source, the oxidant, the M-containing dopant and the second solvent to obtain liquid metal B; (2) Adjust the pH of the liquid metal A and perform heat treatment to obtain solid C. Then mix the solid C with an activator and activate it to obtain a slurry. (3) The slurry and liquid metal B are mixed and heat-treated to obtain the composite cathode material precursor.

7. The preparation method according to claim 6, wherein, The method for adjusting the pH of liquid metal A in step (2) includes the following steps: Under stirring conditions, the pH adjuster is added dropwise to the molten metal A.

8. The preparation method according to claim 7, wherein, The pH adjuster includes a phosphorus-containing compound, which includes at least one of phosphoric acid, ammonium dihydrogen phosphate, monohydrogen phosphate, sodium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, and potassium phosphate.

9. The preparation method according to claim 7, wherein, The pH adjuster also includes an alkaline solution, which includes at least one of ammonium phosphate, NaOH, ammonia, and urea.

10. The preparation method according to claim 7, wherein, The pH adjuster also includes an oxidizing agent, which includes hydrogen peroxide and / or sodium peroxide.

11. The preparation method according to claim 6, wherein, After adjusting the pH of the metal liquid A as described in step (2), the pH value of the metal liquid A is 1.6-2.

1.

12. The preparation method according to claim 6, wherein, The heat treatment in step (2) is performed at a temperature of 60-100℃ for 0.5-5 hours.

13. The preparation method according to claim 6, wherein, The activator in step (2) is an acid-alcohol mixture solution.

14. The preparation method according to claim 13, wherein, In the acid-alcohol mixture, the acid includes at least one of sulfuric acid, phosphoric acid, and nitric acid.

15. The preparation method according to claim 13, wherein, In the acid-alcohol mixture, the molar concentration of the acid is 0.1-0.4 mol / L.

16. The preparation method according to claim 13, wherein, In the acid-alcohol mixture, the alcohol includes at least one of methanol, ethanol, ethylene glycol, propylene glycol, and glycerol.

17. The preparation method according to claim 13, wherein, In the acid-alcohol mixture, the molar ratio of acid to alcohol is 1:(0.5-3).

18. The preparation method according to claim 6, wherein, The activation temperature in step (2) is 40-70℃ and the activation time is 0.5-2h.

19. The preparation method according to claim 6, wherein, The amount of slurry added in step (3) = ((0.10-1.00) × Fe mass concentration of metal liquid B × V2) / solid content of slurry, where V2 is the volume of metal liquid B.

20. The preparation method according to claim 6, wherein, The heat treatment in step (3) is performed at a temperature of 80-95℃ for 3-5 hours.

21. The preparation method according to claim 6, wherein, After the heat treatment described in step (3) is completed, solid-liquid separation, washing, drying and dehydration steps are also performed.

22. The preparation method according to claim 6, wherein, The preparation method includes the following steps: (I) Mix the first iron source, the N-containing dopant and the first solvent to obtain liquid metal A; mix the second iron source, the phosphorus source, the oxidant, the M-containing dopant and the second solvent to obtain liquid metal B; mix the alkaline solution, the phosphorus-containing compound and the oxidant to obtain a pH adjuster. (II) Using liquid metal A as the base liquid, under stirring conditions, pH adjuster is added dropwise to liquid metal A to adjust its pH value to 1.6-2.1, then the temperature is raised to 60-100℃ and aged for 0.5-5h, and solid C is obtained after filtration; (III) The solid C and the acid-alcohol mixture are mixed and ground, and activated at 40-70℃ for 0.5-2h to obtain a slurry; The acid molar concentration of the acid-alcohol mixture is 0.1-0.4 mol / L, and the molar ratio of acid to alcohol is 1:(0.5-3). (IV) The slurry and liquid metal B are mixed and heat-treated at 80-95℃ for 3-5 hours. After the heat treatment, the solid and liquid are separated to obtain a filter cake. The filter cake is washed, dried and dehydrated to obtain the composite cathode material precursor. Wherein, the amount of slurry added = ((0.10-1.00) × Fe mass concentration of molten metal B × V2) / solid content of slurry, where V2 is the volume of molten metal B.

23. A lithium iron phosphate cathode material prepared from the composite cathode material precursor according to any one of claims 1-5.

24. A lithium-ion battery comprising the lithium iron phosphate cathode material as described in claim 23.

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