Iron and halogen co-doped lithium-rich manganese-based cathode precursor, and preparation method and use thereof

Abstract

This invention provides an iron and halogen co-doped lithium-rich manganese-based cathode precursor, its preparation method, and its applications. The iron and halogen co-doped lithium-rich manganese-based cathode precursor includes a core and a coating layer covering the surface of the core. The material in the core includes a lithium-rich manganese-based precursor matrix material doped with halogen ions. The material in the coating layer includes a manganese-rich precursor material simultaneously doped with iron and halogen ions. The lithium-rich manganese-based cathode precursor provided by this invention, through the synergistic effect of halogen ion doping in the bulk phase of the precursor material and iron ion doping in the coating layer, increases the interlayer spacing of the cathode material, stabilizes the crystal structure, and enhances the formation of oxygen vacancies, suppressing excessive oxidation of lattice oxygen at high potentials and reducing irreversible oxygen release during cycling. This synergistic effect improves the electrochemical performance of the lithium-rich manganese-based cathode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to an iron and halogen co-doped lithium-rich manganese-based cathode precursor, its preparation method, and its uses. Background Technology

[0002] In recent years, lithium-ion batteries have been successfully applied in various fields, from portable electronics and electric vehicles to large-scale smart grids. However, with the increasing demand for energy storage, it is becoming increasingly necessary to develop lithium-ion batteries with better electrochemical performance. Lithium-rich manganese-based cathode materials have attracted widespread attention due to their high specific capacity exceeding 250 mAh / g at voltages of 2.0–4.8 V. However, lithium-rich manganese-based materials suffer from a series of problems such as irreversible redox reactions, transition metal migration, and structural transformations, resulting in low initial discharge specific capacity, severe voltage and capacity decay, and poor cycle stability. Therefore, there are few companies capable of stably and mass-producing lithium-rich manganese-based cathode materials, hindering their commercialization process.

[0003] Currently, structural design and doping modification are key to obtaining high-capacity, long-cycle lithium-rich manganese-based materials. The main methods used to modify lithium-rich manganese-based materials include ion doping, coating, and surface structure design. By doping with specific elements, structural regulation can be achieved, such as increasing interlayer spacing, improving metal ion migration, and stabilizing oxygen, thereby improving their electrochemical performance. For example, in CN113788500A, sintered lithium-rich manganese-based materials are mixed with a stannous salt solution and stirred. After sintering, a double-layer coating of a spinel phase layer and a SnO2 layer with oxygen vacancies is obtained. Due to the presence of oxygen vacancies, oxygen release is effectively suppressed, resulting in high first-cycle coulombic efficiency, discharge capacity, cycle stability, and rate performance of the cathode material. Another example is CN105655566A, where silica is coated onto the surface of lithium-rich manganese-based cathode materials and their precursors through the hydrolysis of tetraethyl orthosilicate. This effectively suppresses electrolyte decomposition, absorbs HF generated from LiPF6 decomposition, and improves the electrochemical performance of the lithium-rich manganese-based cathode material. Currently, the mainstream modification methods are to modify the materials based on the sintered finished products. Although this can improve the performance of the materials to a certain extent, it cannot change the fact that lithium-rich manganese-based materials are structurally unstable and prone to pulverization. Furthermore, lithium-ion batteries made using existing lithium-rich manganese-based materials are structurally unstable during cycling and have high manufacturing costs.

[0004] Therefore, obtaining high-performance, low-cost lithium-rich manganese-based cathode materials is a key challenge that needs to be overcome. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an iron and halogen co-doped lithium-rich manganese-based cathode precursor, its preparation method, and its applications. The lithium-rich manganese-based cathode precursor provided by this invention, through the synergistic effect of halogen ion doping in the bulk phase of the precursor material and iron ion doping in the coating layer, increases the interlayer spacing of the cathode material, stabilizes the crystal structure, and enhances the formation of oxygen vacancies, suppresses excessive oxidation of lattice oxygen at high potentials, and reduces irreversible oxygen release during cycling. These two synergistic effects further improve the electrochemical performance of the lithium-rich manganese-based cathode material.

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

[0007] In a first aspect, the present invention provides an iron and halogen co-doped lithium-rich manganese-based cathode precursor, the iron and halogen co-doped lithium-rich manganese-based cathode precursor comprising a core and a coating layer covering the surface of the core; the material in the core comprises a lithium-rich manganese-based precursor matrix material doped with halogen ions; the material in the coating layer comprises a manganese-rich manganese-based precursor material simultaneously doped with iron ions and halogen ions.

[0008] It should be noted that the halide ions in this invention are selected from at least one of chloride ions, fluoride ions, iodide ions, or bromide ions.

[0009] The lithium-rich manganese-based cathode precursor provided by this invention achieves this through the synergistic effect of halide ion doping in the bulk phase of the precursor material and trivalent iron ion doping in the coating layer. The iron doping in the surface shell mainly occupies the transition metal layer in the lithium-rich manganese material, which increases the interlayer spacing of the cathode material, enhances the bond energy between metal and oxygen, accelerates the lithium ion diffusion rate, and stabilizes the crystal structure. The trace iron doping can achieve Fe... 3+ and Fe 4+ The conversion of ferric ions in the surface layer and the doping of halogen anions in the entire structure increase the interlayer spacing of the cathode material and stabilize the crystal structure. They also increase the formation of oxygen vacancies, inhibit the excessive oxidation of lattice oxygen at high potentials, and reduce the release of oxygen during cycling, thus greatly improving the voltage decay performance and cycle stability of the lithium-rich manganese material. In other words, the doping of ferric ions in the surface layer and the doping of halogen anions in the entire structure in this application not only increase the interlayer spacing of the cathode material and stabilize the crystal structure, but also increase the formation of oxygen vacancies, inhibit the excessive oxidation of lattice oxygen at high potentials, and reduce the irreversible release of oxygen during cycling. The two work synergistically to improve the electrochemical performance of the lithium-rich manganese-based cathode material.

[0010] In this invention, if iron ions are also doped into the core, it will affect the electrochemical performance of the lithium-rich manganese-based cathode material, resulting in a lower overall charge and discharge capacity.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0012] Preferably, the difference between the median particle size D502 of the iron and halogen co-doped lithium-rich manganese-based cathode precursor and the median particle size D501 of the core satisfies: D502-D501=0.5~4μm, for example 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm or 4μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0013] Preferably, the median particle size D502 of the iron and halogen co-doped lithium-rich manganese-based cathode precursor is 6–12 μm, such as 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm or 12 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] In a second aspect, the present invention provides a method for preparing a lithium-rich manganese-based cathode precursor co-doped with iron and halogens as described in the first aspect, the method comprising the following steps:

[0015] The first mixed salt solution, the first precipitant solution, and the first complexing agent solution are added to the reaction vessel in parallel to carry out the first coprecipitation reaction, thereby obtaining a first mixed slurry containing a core.

[0016] The second mixed salt solution, iron salt solution, second precipitant solution, and second complexing agent solution are added concurrently to the first mixed slurry to carry out the second co-precipitation reaction, thereby obtaining the iron and halogen co-doped lithium-rich manganese-based cathode precursor.

[0017] The first mixed salt solution and the second mixed salt solution each independently include a manganese-containing mixed salt and a halide.

[0018] The preparation method provided by this invention can achieve uniform doping of halide ions in the bulk phase of lithium-rich manganese-based cathode precursor through a simple co-precipitation process. Furthermore, by controlling the stage of the co-precipitation reaction, iron ions are doped only on the surface layer of the lithium-rich manganese-based cathode precursor material. The preparation process is simple to operate, has low cost, and is more suitable for large-scale industrial production.

[0019] Preferably, in the first mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the molar concentration of the halide solution is (100-500):1, for example, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1 or 500:1, but it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0020] Preferably, the concentration of the manganese-containing mixed salt solution in the first mixed salt solution is 1 to 3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, in the second mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the molar concentration of the halide solution is (100-500):1, for example, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1 or 500:1, but it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0022] In this invention, by controlling the ratio of the molar concentration of the manganese-containing mixed salt solution to the molar concentration of the halide solution in the first mixed salt solution and / or the second mixed salt solution to be independently (100-500):1, it is more conducive to the doping of halide ions in the cathode precursor material, and further improves the cycle stability of the lithium-rich manganese-based cathode material.

[0023] Preferably, the halide includes sodium halide.

[0024] The present invention applies to all conventional halides, except sodium halide, that are soluble in manganese salt solutions and do not react with each other.

[0025] Furthermore, the sodium halide is selected from at least one of sodium chloride, sodium fluoride, sodium bromide, or sodium iodide.

[0026] Preferably, the concentration of the manganese-containing mixed salt solution in the second mixed salt solution is 1 to 3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the concentration of the iron salt solution is 0.001 to 0.02 mol / L, such as 0.001 mol / L, 0.005 mol / L, 0.008 mol / L, 0.01 mol / L, 0.013 mol / L, 0.015 mol / L, 0.018 mol / L, or 0.02 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] This invention achieves uniform doping of iron ions on the surface of lithium-rich manganese-based cathode precursors by using an iron salt solution concentration of 0.001–0.02 mol / L, which is more conducive to the diffusion of lithium ions and improves the discharge specific capacity of lithium-rich manganese materials. Furthermore, this invention does not impose any special limitation on the type of iron salt. Conventional trivalent iron salts that can be reasonably known by those skilled in the art are applicable to this invention. For example, the iron salts include, but are not limited to, at least one of ferric sulfate, ferric ammonium citrate, ferric citrate, or ferric nitrate.

[0029] Preferably, the concentrations of the first precipitant solution and the second precipitant solution are each independently 5 to 10 mol / L, such as 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but are not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] Preferably, the concentrations of the first complexing agent solution and the second complexing agent solution are each independently 0.3 to 3 mol / L, such as 0.3 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but are not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0031] Preferably, the pH values ​​of the first coprecipitation reaction and the second coprecipitation reaction are each independently 9 to 12, such as 9, 9.3, 9.5, 9.8, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8 or 12, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the rotation speeds of the first coprecipitation reaction and the second coprecipitation reaction are each independently 400 to 800 rpm, such as 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm or 800 rpm, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the difference between the median particle size D502 of the reaction product of the second coprecipitation reaction and the median particle size D501 of the core in the first mixed slurry satisfies: D502-D501 = 0.5~4μm, for example 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm or 4μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, during the second coprecipitation reaction, when the median particle size D502 of the reaction product reaches 6 to 12 μm, for example, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm or 12 μm, the reaction is stopped, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] In this invention, the median particle size D502 of the reaction product of the second coprecipitation reaction is the median particle size D50 of the final iron and halogen co-doped lithium-rich manganese-based cathode precursor; and this invention improves the electrochemical performance of the corresponding cathode material by controlling D502-D501 = 0.5~4μm.

[0036] Preferably, the mixed slurry obtained from the second coprecipitation reaction is sequentially washed and dried.

[0037] As a preferred technical solution, the preparation method includes the following steps:

[0038] A first mixed salt solution, a first precipitant solution with a concentration of 5–10 mol / L, and a first complexing agent solution with a concentration of 0.3–3 mol / L are added concurrently to a reaction vessel. In the first mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the halide solution is (100–500):1, and the concentration of the manganese-containing mixed salt solution is 1–3 mol / L. A first coprecipitation reaction is carried out to obtain a first mixed slurry containing a core.

[0039] A second mixed salt solution, an iron salt solution with a concentration of 0.001–0.02 mol / L, a second precipitant solution with a concentration of 5–10 mol / L, and a second complexing agent solution with a concentration of 0.3–3 mol / L are added concurrently to a first mixed slurry. In the second mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the halide solution is (100–500):1, and the concentration of the manganese-containing mixed salt solution is 1–3 mol / L. A second co-precipitation reaction is carried out to obtain the iron and halogen co-doped lithium-rich manganese-based cathode precursor.

[0040] The difference between the median particle size D502 of the reaction product of the second coprecipitation reaction and the median particle size D501 of the core in the first mixed slurry satisfies: D502-D501=0.5~4μm; during the second coprecipitation reaction, the reaction is stopped when the median particle size D502 of the reaction product reaches 6~12μm.

[0041] It should also be noted that, except for the above-mentioned limitations, the types of raw materials, preparation parameters, and preparation processes in the preparation method provided by this invention are all conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0042] Optionally, in the first mixed salt solution and the second mixed salt solution, the manganese-containing mixed salt may include at least one transition metal salt such as nickel salt, aluminum salt, and cobalt salt, in addition to manganese salt; and in the manganese-containing mixed salt solution, the molar percentage of manganese in the sum of the molar amounts of all metal elements is ≥60%, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99%; and the type of salt in the manganese-containing mixed salt solution is also a conventional technical solution, including but not limited to sulfates, nitrates, chlorides, or acetates.

[0043] Optionally, the precipitant includes, but is not limited to, sodium hydroxide and / or potassium hydroxide.

[0044] Optionally, the complexing agent includes, but is not limited to, at least one of ammonia, citric acid, sodium oxalate, or sodium tartrate.

[0045] Thirdly, the present invention provides a lithium-rich manganese-based cathode material, wherein the lithium-rich manganese-based cathode material is obtained by mixing and sintering a lithium source with an iron and halogen co-doped lithium-rich manganese-based cathode precursor as described in the first aspect or an iron and halogen co-doped lithium-rich manganese-based cathode precursor prepared by any of the preparation methods described in the second aspect.

[0046] This invention does not impose specific limitations on the preparation process of the cathode material. Conventional preparation processes that can be reasonably known to those skilled in the art are applicable to this invention.

[0047] By way of example, the present invention provides a method for preparing a cathode material:

[0048] The lithium source and the manganese-rich cathode precursor are mixed with a total molar ratio of lithium element in the lithium source to all metal elements in the manganese-rich cathode precursor of (1 to 1.6):1. After mixing, the mixture is sintered in an oxygen-containing atmosphere (such as an air atmosphere or an oxygen atmosphere) at a sintering temperature of 800 to 1200°C for 8 to 20 hours to obtain the lithium-rich manganese-based cathode material.

[0049] Furthermore, the lithium source includes at least one of LiOH, CH3COOLi, or Li2CO3.

[0050] Fourthly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the lithium-rich manganese-based cathode material as described in the third aspect.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The lithium-rich manganese-based cathode precursor provided by this invention, through the synergistic effect of halide ion doping in the bulk phase of the precursor material and trivalent iron ion doping in the coating layer, with the iron doping in the surface shell mainly occupying the transition metal layer in the lithium-rich manganese material, can increase the interlayer spacing of the cathode material, enhance the bond energy between metal and oxygen, accelerate the lithium ion diffusion rate, and stabilize the crystal structure; the trace amount of iron doping can achieve Fe during the charging and discharging process. 3+ and Fe 4+ The conversion of ferric ions in the surface layer and the doping of halogen anions in the entire structure increase the interlayer spacing of the cathode material and stabilize the crystal structure. They also increase the formation of oxygen vacancies, inhibit the excessive oxidation of lattice oxygen at high potentials, and reduce the release of oxygen during cycling, thus greatly improving the voltage decay performance and cycle stability of the lithium-rich manganese material. In other words, the doping of ferric ions in the surface layer and the doping of halogen anions in the entire structure in this application not only increase the interlayer spacing of the cathode material and stabilize the crystal structure, but also increase the formation of oxygen vacancies, inhibit the excessive oxidation of lattice oxygen at high potentials, and reduce the irreversible release of oxygen during cycling. The two work synergistically to improve the electrochemical performance of the lithium-rich manganese-based cathode material.

[0053] (2) The preparation method provided by the present invention can achieve uniform doping of halide ions in the bulk phase of lithium-rich manganese-based cathode precursor through a simple co-precipitation process, and achieves iron ion doping only on the surface layer of lithium-rich manganese-based cathode precursor material by controlling the stage of the co-precipitation reaction; and the preparation process is simple to operate, low in cost, and more suitable for large-scale industrial production. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of the present invention and should not be construed as limiting the invention.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having” and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0056] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0057] Example 1

[0058] This embodiment provides an iron and chloride co-doped lithium-rich manganese-based cathode precursor, which includes a core and a coating layer covering the surface of the core; the material in the core includes a lithium-rich manganese-based precursor matrix material doped with chloride ions; the material in the coating layer includes a manganese-rich precursor material doped with both iron ions and chloride ions.

[0059] When the median particle size D501 of the core is 6 μm, the median particle size D502 of the iron and chlorine co-doped lithium-rich manganese-based cathode precursor is 9 μm, and D502-D501=3 μm.

[0060] The preparation method of the iron and chlorine co-doped lithium-rich manganese-based cathode precursor is as follows:

[0061] (1) Weigh out nickel sulfate, cobalt sulfate, manganese sulfate crystals and sodium chloride crystals according to the metal molar ratio Ni:Co:Mn=30:10:70, add pure water and stir to prepare a mixed salt solution A, in which the molar concentration of the nickel cobalt manganese mixed salt solution is 1.5mol / L, the molar concentration of the sodium chloride solution is 0.005mol / L, and the molar concentration ratio of the nickel cobalt manganese mixed salt solution to the sodium chloride solution is 300:1; and prepare 6mol / L sodium hydroxide solution as precipitant B, 2mol / L ammonia solution as complexing agent C, and 0.005mol / L ferric sulfate as iron salt solution D.

[0062] (2) Add pure water and 6 mol / L sodium hydroxide solution to the reaction vessel as the reaction base liquid, control the initial pH value of the base liquid to be 12.0 to 12.5, and introduce nitrogen gas as a protective gas.

[0063] (3) The above mixed salt solution A, 6 mol / L sodium hydroxide solution B and 2 mol / L ammonia solution C are simultaneously added to the reactor by a metering pump. The stirring speed of the reactor is set to 600 rpm, and the pH is controlled between 9.5 and 10.5 to carry out the first coprecipitation reaction. When the median particle size D501 of the particles reaches 6 μm, the coprecipitation reaction is stopped to obtain the first mixed slurry.

[0064] (4) Continue to feed mixed salt solution A, 6 mol / L sodium hydroxide solution B and 2 mol / L ammonia solution C into the first mixed slurry. In addition, start to feed 0.005 mol / L ferric sulfate solution. Control the rotation speed at 600 rpm and the pH between 9.5 and 10.5 to continue the second coprecipitation reaction. When the median particle size D502 reaches 9 μm, stop feeding to obtain the second mixed slurry.

[0065] (5) After the reaction is complete, transfer the second mixed slurry to a vacuum filtration flask and wash it three times with alkaline solution and pure water respectively.

[0066] (6) The solid material obtained by vacuum filtration and washing is transferred to an oven and dried at 100°C to finally obtain the iron and chlorine co-doped lithium-rich manganese-based cathode precursor.

[0067] Example 2

[0068] This embodiment provides an iron and fluorine co-doped lithium-rich manganese-based cathode precursor, which includes a core and a coating layer covering the surface of the core; the material in the core includes a lithium-rich manganese-based precursor matrix material doped with fluorine ions; the material in the coating layer includes a manganese-rich precursor material doped with both iron ions and fluorine ions.

[0069] When the median particle size D501 of the core is 8 μm, the median particle size D502 of the iron and fluorine co-doped lithium-rich manganese-based cathode precursor is 10 μm, and D502-D501=2 μm.

[0070] The preparation method of the iron and fluorine co-doped lithium-rich manganese-based cathode precursor is as follows:

[0071] (1) Weigh out nickel sulfate, cobalt sulfate, manganese sulfate crystals and sodium fluoride crystals according to the metal molar ratio Ni:Co:Mn=33:13:64, add pure water and stir to prepare a mixed salt solution A, in which the molar concentration of the nickel cobalt manganese mixed salt solution is 2 mol / L, the molar concentration of the sodium fluoride solution is 0.01 mol / L, and the molar concentration ratio of the nickel cobalt manganese mixed salt solution to the sodium fluoride solution is 200:1; and prepare 7.5 mol / L sodium hydroxide solution as precipitant B, 1 mol / L citric acid solution as complexing agent C, and 0.005 mol / L ferric sulfate as iron salt solution D.

[0072] (2) Add pure water and 7.5 mol / L sodium hydroxide solution to the reaction vessel as the reaction base liquid, control the initial pH value of the base liquid to be 11.5 to 12.0, and introduce nitrogen gas as a protective gas.

[0073] (3) The above mixed salt solution A, 7.5 mol / L sodium hydroxide solution B and 1 mol / L citric acid solution C are simultaneously added to the reactor by a metering pump. The stirring speed of the reactor is set to 500 rpm, and the pH is controlled between 9.5 and 10 to carry out the first coprecipitation reaction. When the median particle size D501 of the particles reaches 8 μm, the coprecipitation reaction is stopped to obtain the first mixed slurry.

[0074] (4) Continue to feed mixed salt solution A, 7.5 mol / L sodium hydroxide solution B and 1 mol / L citric acid solution C into the first mixed slurry. In addition, start to feed 0.005 mol / L ferric sulfate solution. Control the rotation speed at 500 rpm and the pH between 9.0 and 10.0 to continue the second coprecipitation reaction. When the median particle size D502 reaches 10 μm, stop feeding to obtain the second mixed slurry.

[0075] (5) After the reaction is complete, transfer the second mixed slurry to a vacuum filtration flask and wash it three times with alkaline solution and pure water respectively.

[0076] (6) The solid material obtained by vacuum filtration and washing is transferred to an oven and dried at 100°C to finally obtain the iron and fluorine co-doped lithium-rich manganese-based cathode precursor.

[0077] Example 3

[0078] The difference between this embodiment and Embodiment 1 is that in Solution A of this embodiment, the molar concentration of sodium chloride solution is 0.015 mol / L, that is, the molar concentration ratio of the nickel-cobalt-manganese mixed salt solution to the molar concentration of sodium chloride solution is 100:1.

[0079] The remaining preparation methods and parameters are consistent with those in Example 1.

[0080] Example 4

[0081] The difference between this embodiment and Embodiment 1 is that in Solution A of this embodiment, the molar concentration of sodium chloride solution is 0.003 mol / L, that is, the molar concentration ratio of the nickel-cobalt-manganese mixed salt solution to the molar concentration of sodium chloride solution is 500:1.

[0082] The remaining preparation methods and parameters are consistent with those in Example 1.

[0083] Example 5

[0084] The difference between this embodiment and Embodiment 1 is that the concentration of the ferric sulfate solution in this embodiment is 0.001 mol / L.

[0085] The remaining preparation methods and parameters are consistent with those in Example 1.

[0086] Example 6

[0087] The difference between this embodiment and Embodiment 1 is that the concentration of the ferric sulfate solution in this embodiment is 0.02 mol / L.

[0088] The remaining preparation methods and parameters are consistent with those in Example 1.

[0089] Example 7

[0090] The difference between this embodiment and Embodiment 1 is that the median particle size D502 of the iron and chlorine co-doped lithium-rich manganese-based cathode precursor is 10 μm, and D502-D501 = 4 μm.

[0091] In the preparation method, during the adaptive adjustment of the second coprecipitation reaction, when the median particle size D502 reaches 10 μm, the feeding is stopped to obtain the second mixed slurry.

[0092] The remaining preparation methods and parameters are consistent with those in Example 1.

[0093] Example 8

[0094] The difference between this embodiment and Embodiment 1 is that the median particle size D502 of the iron and chlorine co-doped lithium-rich manganese-based cathode precursor is 6.5 μm, and D502-D501=0.5 μm;

[0095] In the preparation method, during the adaptive adjustment of the second coprecipitation reaction, when the median particle size D502 reaches 6.5 μm, the feeding is stopped to obtain the second mixed slurry.

[0096] The remaining preparation methods and parameters are consistent with those in Example 1.

[0097] Example 9

[0098] The difference between this embodiment and Embodiment 1 is that in Solution A of this embodiment, the molar concentration of sodium chloride solution is 0.03 mol / L, that is, the molar concentration ratio of the nickel-cobalt-manganese mixed salt solution to the molar concentration of sodium chloride solution is 50:1.

[0099] The remaining preparation methods and parameters are consistent with those in Example 1.

[0100] Example 10

[0101] The difference between this embodiment and Embodiment 1 is that in Solution A of this embodiment, the molar concentration of sodium chloride solution is 0.0025 mol / L, that is, the molar concentration ratio of the nickel-cobalt-manganese mixed salt solution to the molar concentration of sodium chloride solution is 600:1.

[0102] The remaining preparation methods and parameters are consistent with those in Example 1.

[0103] Example 11

[0104] The difference between this embodiment and Embodiment 1 is that the concentration of the ferric sulfate solution in this embodiment is 0.05 mol / L.

[0105] The remaining preparation methods and parameters are consistent with those in Example 1.

[0106] Example 12

[0107] The difference between this embodiment and Embodiment 1 is that the median particle size D502 of the iron and chlorine co-doped lithium-rich manganese-based cathode precursor is 6.3 μm, and D502-D501=0.3 μm;

[0108] In the preparation method, during the adaptive adjustment of the second coprecipitation reaction, when the median particle size D502 reaches 6.3 μm, the feeding is stopped to obtain the second mixed slurry.

[0109] The remaining preparation methods and parameters are consistent with those in Example 1.

[0110] Example 13

[0111] The difference between this embodiment and Embodiment 1 is that the median particle size D502 of the iron and chlorine co-doped lithium-rich manganese-based cathode precursor is 11 μm, and D502-D501=5 μm;

[0112] In the preparation method, during the adaptive adjustment of the second coprecipitation reaction, when the median particle size D502 reaches 11 μm, the feeding is stopped to obtain the second mixed slurry.

[0113] The remaining preparation methods and parameters are consistent with those in Example 1.

[0114] Comparative Example 1

[0115] The difference between this comparative example and Example 1 is that the lithium-rich manganese-based cathode precursor provided in this comparative example is not doped with chloride ions and iron ions.

[0116] In the preparation method, the mixed salt solution A contains only a nickel-cobalt-manganese mixed sulfate solution and does not contain a sodium chloride solution. Only the first coprecipitation reaction is carried out, and the iron salt solution D is not introduced in parallel. When the median particle size D502 reaches 10 μm, the feeding is stopped.

[0117] The remaining preparation methods and parameters are consistent with those in Example 1.

[0118] Comparative Example 2

[0119] The difference between this comparative example and Example 1 is that the lithium-rich manganese-based cathode precursor provided in this comparative example is not doped with iron ions.

[0120] In the preparation method, only the first coprecipitation reaction is carried out, and the iron salt solution D is not introduced in parallel. When the median particle size D502 reaches 10 μm, the feeding is stopped.

[0121] The remaining preparation methods and parameters are consistent with those in Example 1.

[0122] Comparative Example 3

[0123] The difference between this comparative example and Example 1 is that the lithium-rich manganese-based cathode precursor provided in this comparative example is not doped with chloride ions;

[0124] In the preparation method, the mixed salt solution A contains only a nickel-cobalt-manganese mixed sulfate solution and does not contain a sodium chloride solution.

[0125] The remaining preparation methods and parameters are consistent with those in Example 1.

[0126] The cathode precursors provided in Examples 1-13 and Comparative Examples 1-3 were uniformly mixed with lithium hydroxide at a molar ratio of 1:1.5 and sintered in air at 900°C for 12 hours to obtain the corresponding lithium-rich manganese-based cathode materials.

[0127] Battery fabrication: The lithium-rich manganese-based cathode materials prepared in Examples 1-13 and Comparative Examples 1-3, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were weighed at a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone (NMP) and mixed thoroughly. Then, the slurry was coated onto aluminum foil using a coater and dried in a vacuum drying oven at 80°C for 8 hours. Finally, the aluminum foil was stamped into 1.13 cm thick sheets. 2 The positive electrode is obtained by forming a circle.

[0128] The obtained electrode sheet was used as the positive electrode, the lithium metal sheet as the counter electrode, and the porous polypropylene membrane (Celgard2400) was used as the separator to separate the positive and counter electrodes. The electrolyte composition was: a mixture of 1 mol / L LiPF6 with EC, DMC and EMC (EC:DMC:EMC volume ratio = 1:1:1). The CR2032 button cell was assembled in an argon glove box.

[0129] The lithium-ion batteries provided in Examples 1-13 and Comparative Examples 1-3 were subjected to performance tests. The test conditions were as follows: at 25°C, the lithium-ion batteries were charged and discharged three times in a voltage range of 2V to 4.6V using a 0.1C (1C = 250mAh / g) charge-discharge system, and the specific capacity of the batteries was measured. The batteries were then cycled using a 0.1C current density charge-discharge system. After 100 cycles, the discharge capacity of the battery at this point was divided by the discharge capacity of the first cycle to obtain the battery's 100-cycle capacity retention rate. The test results are shown in Table 1.

[0130] Table 1

[0131]

[0132]

[0133] In summary, the lithium-rich manganese-based cathode precursor provided by this invention, through the synergistic effect of halide ion doping in the bulk phase of the precursor material and trivalent iron ion doping in the coating layer, allows the iron doping in the surface shell layer to mainly occupy the transition metal layer in the lithium-rich manganese material. This increases the interlayer spacing of the cathode material, enhances the bond energy between metal and oxygen, accelerates the lithium ion diffusion rate, and stabilizes the crystal structure. Furthermore, trace amounts of iron doping can achieve Fe... 3+ and Fe 4+ The conversion of ferric ions in the surface layer and the doping of halogen anions in the entire structure increase the interlayer spacing of the cathode material and stabilize the crystal structure. They also increase the formation of oxygen vacancies, inhibit the excessive oxidation of lattice oxygen at high potentials, and reduce the release of oxygen during cycling, thus greatly improving the voltage decay performance and cycle stability of the lithium-rich manganese material. In other words, the doping of ferric ions in the surface layer and the doping of halogen anions in the entire structure in this application not only increase the interlayer spacing of the cathode material and stabilize the crystal structure, but also increase the formation of oxygen vacancies, inhibit the excessive oxidation of lattice oxygen at high potentials, and reduce the irreversible release of oxygen during cycling. The two work synergistically to improve the electrochemical performance of the lithium-rich manganese-based cathode material.

[0134] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A lithium-rich manganese-based cathode precursor co-doped with iron and halogens, characterized in that, The iron and halogen co-doped lithium-rich manganese-based cathode precursor includes a core and a coating layer covering the surface of the core; the material in the core includes a lithium-rich manganese-based precursor matrix material doped with halogen ions; the material in the coating layer includes a lithium-rich manganese-based precursor material doped with both iron ions and halogen ions. The iron and halogen co-doped lithium-rich manganese-based cathode precursor is prepared by the following method: The first mixed salt solution, the first precipitant solution, and the first complexing agent solution are added to the reaction vessel in parallel to carry out the first coprecipitation reaction, thereby obtaining a first mixed slurry containing a core. The second mixed salt solution, iron salt solution, second precipitant solution, and second complexing agent solution are added concurrently to the first mixed slurry to carry out the second co-precipitation reaction, thereby obtaining the iron and halogen co-doped lithium-rich manganese-based cathode precursor. The first mixed salt solution and the second mixed salt solution each independently include a manganese-containing mixed salt and a halide; In the first mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the halide solution is (100~500):1; in the second mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the halide solution is (100~500):1; and the concentration of the iron salt solution is 0.001~0.02 mol / L.

2. The lithium-rich manganese-based cathode precursor co-doped with iron and halogens according to claim 1, characterized in that, The difference between the median particle size D502 of the iron and halogen co-doped lithium-rich manganese-based cathode precursor and the median particle size D501 of the core satisfies: D502-D501=0.5~4μm.

3. The lithium-rich manganese-based cathode precursor co-doped with iron and halogens according to claim 1, characterized in that, The median particle size D502 of the iron and halogen co-doped lithium-rich manganese-based cathode precursor is 6~12 μm.

4. A method for preparing an iron and halogen co-doped lithium-rich manganese-based cathode precursor as described in any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: The first mixed salt solution, the first precipitant solution, and the first complexing agent solution are added to the reaction vessel in parallel to carry out the first coprecipitation reaction, thereby obtaining a first mixed slurry containing a core. The second mixed salt solution, iron salt solution, second precipitant solution, and second complexing agent solution are added concurrently to the first mixed slurry to carry out the second co-precipitation reaction, thereby obtaining the iron and halogen co-doped lithium-rich manganese-based cathode precursor. The first mixed salt solution and the second mixed salt solution each independently include a manganese-containing mixed salt and a halide; In the first mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the halide solution is (100~500):1; in the second mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the halide solution is (100~500):1; and the concentration of the iron salt solution is 0.001~0.02 mol / L.

5. The preparation method according to claim 4, characterized in that, In the first mixed salt solution, the concentration of the manganese-containing mixed salt solution is 1~3 mol / L.

6. The preparation method according to claim 4, characterized in that, The halides include sodium halides.

7. The preparation method according to claim 4, characterized in that, In the second mixed salt solution, the concentration of the manganese-containing mixed salt solution is 1~3 mol / L.

8. The preparation method according to claim 4, characterized in that, The concentrations of the first precipitant solution and the second precipitant solution are each independently 5~10 mol / L.

9. The preparation method according to claim 4, characterized in that, The concentrations of the first complexing agent solution and the second complexing agent solution are each independently 0.3~3 mol / L.

10. The preparation method according to claim 4, characterized in that, The pH values ​​of the first coprecipitation reaction and the second coprecipitation reaction are each independently 9 to 12.

11. The preparation method according to claim 4, characterized in that, The rotation speeds of the first coprecipitation reaction and the second coprecipitation reaction are each independently 400~800 rpm.

12. The preparation method according to claim 4, characterized in that, The difference between the median particle size D502 of the reaction product of the second coprecipitation reaction and the median particle size D501 of the core in the first mixed slurry satisfies: D502-D501=0.5~4μm.

13. The preparation method according to claim 4, characterized in that, During the second coprecipitation reaction, the reaction is stopped when the median particle size D502 of the reaction product reaches 6~12μm.

14. The preparation method according to claim 4, characterized in that, The mixed slurry obtained from the second coprecipitation reaction was then washed and dried sequentially.

15. The preparation method according to claim 4, characterized in that, The preparation method includes the following steps: A first mixed salt solution, a first precipitant solution with a concentration of 5-10 mol / L, and a first complexing agent solution with a concentration of 0.3-3 mol / L are added concurrently to a reaction vessel. In the first mixed salt solution, the molar concentration ratio of the manganese-containing mixed salt solution to the halide solution is (100-500):1, and the concentration of the manganese-containing mixed salt solution is 1-3 mol / L. A first coprecipitation reaction is carried out to obtain a first mixed slurry containing a core. A second mixed salt solution, an iron salt solution with a concentration of 0.001~0.02 mol / L, a second precipitant solution with a concentration of 5~10 mol / L, and a second complexing agent solution with a concentration of 0.3~3 mol / L are added in parallel to the first mixed slurry. In the second mixed salt solution, the molar concentration ratio of the manganese mixed salt solution to the halide solution is (100~500):1, and the concentration of the manganese mixed salt solution is 1~3 mol / L. A second coprecipitation reaction is carried out to obtain the iron and halogen co-doped lithium-rich manganese-based cathode precursor. Wherein, the difference between the median particle size D502 of the reaction product of the second coprecipitation reaction and the median particle size D501 of the core in the first mixed slurry satisfies: D502-D501=0.5~4μm; during the second coprecipitation reaction, the reaction is stopped when the median particle size D502 of the reaction product reaches 6~12μm.

16. A lithium-rich manganese-based cathode material, characterized in that, The lithium-rich manganese-based cathode material is obtained by mixing and sintering a lithium-rich manganese-based cathode precursor co-doped with iron and halogens as described in any one of claims 1-3 or a lithium-rich manganese-based cathode precursor co-doped with iron and halogens prepared by any one of claims 4-15 with a lithium source.

17. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium-rich manganese-based cathode material as described in claim 16.

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