Iron and halogen co-doped lithium-rich manganese-based positive electrode precursor as well as preparation method and application thereof

Abstract

The invention provides an iron and halogen co-doped lithium-rich manganese-based positive electrode precursor as well as a preparation method and application thereof. The iron and halogen co-doped lithium-rich manganese-based positive electrode precursor comprises an inner core and a coating layer coating the surface of the inner core, the material in the inner 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 doped with iron ions and halogen ions at the same time. According to the lithium-rich manganese-based positive electrode precursor provided by the invention, through synergistic cooperation of halogen ion doping in the bulk phase of the precursor material and iron ion doping in the coating layer, the interlayer spacing of the positive electrode material is increased, and the crystal structure is stabilized; the lithium-rich manganese-based positive electrode material prepared by the method can be used for improving the electrochemical performance of the lithium-rich manganese-based positive electrode material, improving the formation of oxygen vacancies, inhibiting excessive oxidation of lattice oxygen under high potential and reducing irreversible release of oxygen in a circulating process, and the electrochemical performance of the lithium-rich manganese-based positive electrode material is further improved through the synergistic effect.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium-ion batteries and relates to an iron- and halogen-co-doped lithium-rich manganese-based positive electrode precursor and a preparation method and use thereof. Background Art

[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 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 of more than 250mAh / g at a voltage of 2.0-4.8V. However, lithium-rich manganese-based materials have a series of problems such as irreversible redox, transition metal migration and structural transformation, resulting in low first discharge specific capacity, severe voltage and capacity attenuation, and poor cycle stability. Therefore, there are few companies that can stably and mass-produce lithium-rich manganese-based cathode materials, which hinders their commercialization process.

[0003] At present, structural design and doping modification are the key to obtain high-capacity and long-cycle lithium-rich manganese-based materials. At present, lithium-rich manganese-based materials are mainly modified by ion doping, coating and surface structure design. By doping with specific elements, structural regulation such as increasing interlayer spacing, improving metal ion migration, and stabilizing oxygen can be achieved, thereby improving its electrochemical performance. For example, in CN113788500A, the sintered lithium-rich manganese-based material is mixed with a stannous salt solution and stirred, and a surface coated with a double layer of a spinel phase layer and a SnO2 layer with oxygen vacancies is obtained after sintering. Due to the presence of oxygen vacancies, the release of oxygen is effectively suppressed, so that the positive electrode material has a higher first-cycle coulomb efficiency, discharge capacity, cycle stability and rate performance; for example, in CN105655566A, silicon dioxide is coated on the surface of lithium-rich manganese-based positive electrode materials and their precursors by hydrolyzing tetraethyl orthosilicate, which can effectively suppress the decomposition of the electrolyte, absorb the HF generated by the decomposition of LiPF6, and improve the electrochemical performance of lithium-rich manganese-based positive electrode materials. The current mainstream modification method is to modify the material based on the sintered finished product. Although it can improve the performance of the material to a certain extent, it cannot change the fact that the lithium-rich manganese-based material is structurally unstable and easy to pulverize. In addition, the lithium-ion battery prepared using the existing lithium-rich manganese-based material has an unstable structure during the cycle process and has a high production cost.

[0004] Therefore, how to obtain high-performance and low-cost lithium-manganese-rich based positive electrode materials is a difficult challenge that needs to be overcome at present. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a lithium-rich manganese-based positive electrode precursor co-doped with iron and halogen, as well as a preparation method and use. The lithium-rich manganese-based positive electrode precursor provided by the present invention not only increases the interlayer spacing of the positive electrode material and stabilizes the crystal structure through the synergistic coordination of the doping of halogen ions in the bulk phase of the precursor material and the doping of iron ions in the coating layer; it can also increase the formation of oxygen vacancies, inhibit excessive oxidation of lattice oxygen at high potentials, and reduce the irreversible release of oxygen during the cycle. The two act synergistically with each other, thereby improving the electrochemical performance of the lithium-rich manganese-based positive electrode material.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a lithium-rich manganese-based positive electrode precursor co-doped with iron and halogen, wherein the lithium-rich manganese-based positive electrode precursor co-doped with iron and halogen comprises a core and a coating layer coated on 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 doped with both iron ions and halogen ions.

[0008] It should be noted that the halogen ion in the present invention is at least one selected from chloride ion, fluoride ion, iodide ion or bromide ion.

[0009] The lithium-rich manganese-based positive electrode precursor provided by the present invention cooperates with the doping of halogen ions in the bulk phase of the precursor material and the doping of trivalent iron ions in the coating layer. The surface shell iron doping mainly occupies the transition metal layer in the lithium-rich manganese material, which can increase the interlayer spacing of the positive electrode material, enhance the bond energy of the metal and oxygen, accelerate the diffusion rate of lithium ions, and stabilize the crystal structure; a trace amount of iron doping can achieve Fe 3+ and Fe 4+ conversion, thereby improving the discharge specific capacity of the lithium-rich manganese material; halogen anion doping mainly replaces oxygen ions in the lithium-rich manganese material, increases the formation of oxygen vacancies, inhibits excessive oxidation of lattice oxygen at high potentials, reduces the release of oxygen during the cycle, and greatly improves the voltage decay performance and cycle stability of the lithium-rich manganese material; that is, the trivalent iron ion doping in the surface layer and the halogen anion doping in the entire structure in the present application not only increase the interlayer spacing of the positive electrode material and stabilize the crystal structure; but also increase the formation of oxygen vacancies, inhibit excessive oxidation of lattice oxygen at high potentials, and reduce the irreversible release of oxygen during the cycle. The two work synergistically with each other, thereby improving the electrochemical properties of the lithium-rich manganese-based positive electrode material.

[0010] In the present invention, if iron ions are also doped into the core, it will affect the electrochemical properties of the lithium-rich manganese-based positive electrode 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. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, the difference between the median particle size D502 of the iron and halogen co-doped lithium-manganese-rich positive electrode 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, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0013] Preferably, the median particle size D502 of the iron and halogen co-doped lithium-manganese-based positive electrode precursor is 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, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

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

[0015] Adding the first mixed salt solution, the first precipitant solution and the first complexing agent solution into a reaction container in parallel to perform a first coprecipitation reaction to obtain a first mixed slurry containing a core;

[0016] Adding the second mixed salt solution, the iron salt solution, the second precipitant solution and the second complexing agent solution into the first mixed slurry in parallel to perform a second coprecipitation reaction to obtain the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor;

[0017] Wherein, the first mixed salt solution and the second mixed salt solution independently include manganese-containing mixed salt and halide.

[0018] The preparation method provided by the present invention can achieve uniform doping of halogen ions in the bulk phase of the lithium-rich manganese-based positive electrode precursor through a simple coprecipitation process, and by regulating the stage of the coprecipitation reaction, it is achieved that the iron ions are only doped on the surface layer of the lithium-rich manganese-based positive electrode precursor material; and the preparation process is simple to operate, low in cost, and more suitable for large-scale industrial production.

[0019] Preferably, in the first mixed salt solution, the ratio of the molar concentration of the solution containing the manganese mixed salt 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, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0021] Preferably, in the second mixed salt solution, the ratio of the molar concentration of the solution containing the manganese mixed salt 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0023] Preferably, the halide comprises sodium halide.

[0024] Among the halides provided by the present invention, except for sodium halide, other conventional substances that are soluble in manganese salt solutions and do not react with each other are also applicable to the present invention.

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

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

[0027] Preferably, the concentration of the iron salt solution is 0.001-0.02 mol / L, for example, 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, and other unlisted values ​​within the numerical range are also applicable.

[0028] The present invention achieves uniform doping of iron ions on the surface of the lithium-rich manganese-based positive electrode precursor by setting the concentration of the iron salt solution to 0.001 to 0.02 mol / L, which is more conducive to the diffusion of lithium ions and improves the discharge specific capacity of the lithium-rich manganese material. The present invention does not specifically limit the type of iron salt, and the present invention is applicable to conventional trivalent iron salts that can be known to technicians in this field within a reasonable range. For example, the iron salt includes but is not limited to at least one of ferric sulfate, ammonium ferric citrate, ferric citrate or ferric nitrate.

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

[0030] Preferably, the concentrations of the first complexing agent solution and the second complexing agent solution are independently 0.3 to 3 mol / L, for example, 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, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical 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, for example 9, 9.3, 9.5, 9.8, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8 or 12, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the rotation speeds of the first coprecipitation reaction and the second coprecipitation reaction are each independently 400-800 rpm, for example, 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, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the difference between the median particle size D502 of the reaction product of the second co-precipitation reaction and the median particle size D501 of the inner 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, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In the present 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 positive electrode precursor; and the present invention better improves the electrochemical properties of the corresponding positive electrode material by regulating D502-D501=0.5~4μm.

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

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

[0038] A first mixed salt solution, a first precipitant solution with a concentration of 5 to 10 mol / L, and a first complexing agent solution with a concentration of 0.3 to 3 mol / L are added in parallel to a reaction container, wherein the molar concentration of the manganese-containing mixed salt solution and the molar concentration of the halide solution in the first mixed salt solution are in a ratio of (100 to 500):1, and the concentration of the manganese-containing mixed salt solution is 1 to 3 mol / L, and a first coprecipitation reaction is performed 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 to 0.02 mol / L, a second precipitant solution with a concentration of 5 to 10 mol / L, and a second complexing agent solution with a concentration of 0.3 to 3 mol / L are added in parallel to the first mixed slurry, wherein the molar concentration of the manganese-containing mixed salt solution and the molar concentration of the halide solution in the second mixed salt solution are (100 to 500):1, and the concentration of the manganese-containing mixed salt solution is 1 to 3 mol / L, and a second coprecipitation reaction is performed to obtain the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor;

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

[0041] It should also be noted that, in the preparation method provided by the present invention, except for the above limitations, the material types, preparation parameters and preparation processes of the remaining raw materials are all conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments based on 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 of transition metal salts such as nickel salts, aluminum salts, cobalt salts, etc. in addition to manganese salts; and in the manganese-containing mixed salt solution, the molar proportion of manganese in the sum of the molar amounts of all metal elements is ≥60%, for example, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 99%, etc.; 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, etc.

[0043] Optionally, the precipitating agent 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 water, citric acid, sodium oxalate or sodium tartrate.

[0045] In a third aspect, the present invention provides a lithium-rich manganese-based positive electrode material, which is obtained by mixing and sintering the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor as described in the first aspect or the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor prepared by the preparation method described in any one of the second aspects with a lithium source.

[0046] The present invention does not impose any special limitation on the specific preparation process of the positive electrode material, and the present invention is applicable to any conventional preparation process that can be known within a reasonable range by those skilled in the art.

[0047] Exemplarily, the present invention provides a method for preparing a positive electrode material:

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

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

[0050] In a fourth aspect, the present invention further provides a lithium-ion battery, wherein the lithium-ion battery comprises the lithium-rich manganese-based positive electrode 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 positive electrode precursor provided by the present invention, by synergistically coordinating the doping of halogen ions in the bulk phase of the precursor material and the doping of trivalent iron ions in the coating layer, the surface shell iron doping mainly occupies the transition metal layer in the lithium-rich manganese material, which can increase the interlayer spacing of the positive electrode material, enhance the bond energy of the metal and oxygen, accelerate the diffusion rate of lithium ions, and stabilize the crystal structure; trace iron doping can achieve Fe during the charge and discharge process 3+ and Fe 4+ conversion, thereby improving the discharge specific capacity of the lithium-rich manganese material; halogen anion doping mainly replaces oxygen ions in the lithium-rich manganese material, increases the formation of oxygen vacancies, inhibits excessive oxidation of lattice oxygen at high potentials, reduces the release of oxygen during the cycle, and greatly improves the voltage decay performance and cycle stability of the lithium-rich manganese material; that is, the trivalent iron ion doping in the surface layer and the halogen anion doping in the entire structure in the present application not only increase the interlayer spacing of the positive electrode material and stabilize the crystal structure; but also increase the formation of oxygen vacancies, inhibit excessive oxidation of lattice oxygen at high potentials, and reduce the irreversible release of oxygen during the cycle. The two work synergistically with each other, thereby improving the electrochemical properties of the lithium-rich manganese-based positive electrode material.

[0053] (2) The preparation method provided by the present invention can achieve uniform doping of halogen ions in the bulk phase of the lithium-rich manganese-based positive electrode precursor through a simple co-precipitation process, and by regulating the stage of the co-precipitation reaction, it is achieved that the iron ions are only doped on the surface layer of the lithium-rich manganese-based positive electrode precursor material; and the preparation process is simple to operate, low in cost, and more suitable for large-scale industrial production. DETAILED DESCRIPTION

[0054] The technical scheme of the present invention is further illustrated by specific examples below. Those skilled in the art should understand that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0056] In the description of this application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0057] Example 1

[0058] The present embodiment provides a lithium-rich manganese-based positive electrode precursor co-doped with iron and chlorine, wherein the lithium-rich manganese-based positive electrode precursor co-doped with iron and chlorine comprises a core and a coating layer coated on the surface of the core; the material in the core comprises a lithium-rich manganese-based precursor matrix material doped with chloride ions; the material in the coating layer comprises a manganese-rich manganese-based precursor material doped with iron ions and chloride ions at the same time;

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

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

[0061] (1) nickel sulfate, cobalt sulfate, manganese sulfate crystals and sodium chloride crystals are weighed according to a metal molar ratio of Ni:Co:Mn=30:10:70, and pure water is added and stirred to finally obtain a mixed salt solution A, wherein the molar concentration of the nickel-cobalt-manganese mixed salt solution is 1.5 mol / L, the molar concentration of the sodium chloride solution is 0.005 mol / L, and the ratio of the molar concentration of the nickel-cobalt-manganese mixed salt solution to the molar concentration of the sodium chloride solution is 300:1; 6 mol / L sodium hydroxide solution is prepared as a precipitant B, 2 mol / L ammonia solution is prepared as a complexing agent C, and 0.005 mol / L ferric sulfate is prepared as an iron salt solution D;

[0062] (2) adding pure water and 6 mol / L sodium hydroxide solution as reaction bottom liquid into the reaction kettle, controlling the initial pH value of the bottom liquid to be 12.0-12.5, and introducing nitrogen as protective gas;

[0063] (3) adding the mixed salt solution A, 6 mol / L sodium hydroxide solution B and 2 mol / L ammonia solution C into the reactor simultaneously through a metering pump, setting the stirring speed of the reactor to 600 rpm, controlling the pH to be between 9.5 and 10.5 to carry out a first coprecipitation reaction, and stopping the coprecipitation reaction when the median particle size D501 of the particles reaches 6 μm to obtain a first mixed slurry;

[0064] (4) continuing to introduce the mixed salt solution A, 6 mol / L sodium hydroxide solution B and 2 mol / L ammonia solution C into the first mixed slurry, and additionally beginning to introduce 0.005 mol / L ferric sulfate solution, controlling the rotation speed to 600 rpm and the pH to be between 9.5 and 10.5 to continue the second coprecipitation reaction, and stopping the feeding when the median particle size D502 reaches 9 μm to obtain a second mixed slurry;

[0065] (5) After the reaction is completed, the second mixed slurry is transferred to a suction filtration bottle, and filtered and washed three times with alkali solution and pure water respectively;

[0066] (6) The solid material obtained by 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 positive electrode precursor.

[0067] Example 2

[0068] The present embodiment provides an iron- and fluorine-co-doped lithium-rich manganese-based positive electrode precursor, wherein the iron- and fluorine-co-doped lithium-rich manganese-based positive electrode precursor comprises a core and a coating layer coated on the surface of the core; the material in the core comprises a lithium-rich manganese-based precursor matrix material doped with fluorine ions; the material in the coating layer comprises a manganese-rich manganese-based precursor material doped with both iron ions and fluorine ions;

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

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

[0071] (1) nickel sulfate, cobalt sulfate, manganese sulfate crystals and sodium fluoride crystals are weighed according to a metal molar ratio of Ni:Co:Mn=33:13:64, and pure water is added and stirred to finally obtain a mixed salt solution A, wherein 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 ratio of the molar concentration of the nickel-cobalt-manganese mixed salt solution to the molar concentration of the sodium fluoride solution is 200:1; 7.5 mol / L sodium hydroxide solution is prepared as a precipitant B, 1 mol / L citric acid solution is prepared as a complexing agent C, and 0.005 mol / L ferric sulfate is prepared as an iron salt solution D;

[0072] (2) adding pure water and 7.5 mol / L sodium hydroxide solution as reaction base liquid into the reaction kettle, controlling the initial pH value of the base liquid to be 11.5-12.0, and introducing nitrogen as protective gas;

[0073] (3) adding the mixed salt solution A, 7.5 mol / L sodium hydroxide solution B and 1 mol / L citric acid solution C into the reactor simultaneously through a metering pump, setting the stirring speed of the reactor to 500 rpm, controlling the pH to be between 9.5 and 10 to carry out a first coprecipitation reaction, and stopping the coprecipitation reaction when the median particle size D501 of the particles reaches 8 μm to obtain a first mixed slurry;

[0074] (4) continuing to introduce the 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, and additionally beginning to introduce 0.005 mol / L ferric sulfate solution, controlling the rotation speed to 500 rpm and the pH to be between 9.0 and 10.0 to continue the second coprecipitation reaction, and stopping the feeding when the median particle size D502 reaches 10 μm to obtain a second mixed slurry;

[0075] (5) After the reaction is completed, the second mixed slurry is transferred to a suction filtration bottle, and filtered and washed three times with alkali solution and pure water respectively;

[0076] (6) The solid material obtained by 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 positive electrode 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 the sodium chloride solution is 0.015 mol / L, that is, the ratio of the molar concentration of the nickel-cobalt-manganese mixed salt solution to the molar concentration of the sodium chloride solution is 100:1.

[0079] The rest of the preparation methods and parameters were the same as 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 the sodium chloride solution is 0.003 mol / L, that is, the ratio of the molar concentration of the nickel-cobalt-manganese mixed salt solution to the molar concentration of the sodium chloride solution is 500:1.

[0082] The rest of the preparation methods and parameters were the same as 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 rest of the preparation methods and parameters were the same as 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 rest of the preparation methods and parameters were the same as 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 positive electrode 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 rest of the preparation methods and parameters were the same as 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 positive electrode 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 rest of the preparation methods and parameters were the same as 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 the sodium chloride solution is 0.03 mol / L, that is, the ratio of the molar concentration of the nickel-cobalt-manganese mixed salt solution to the molar concentration of the sodium chloride solution is 50:1.

[0099] The rest of the preparation methods and parameters were the same as 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 the sodium chloride solution is 0.0025 mol / L, that is, the ratio of the molar concentration of the nickel-cobalt-manganese mixed salt solution to the molar concentration of the sodium chloride solution is 600:1.

[0102] The rest of the preparation methods and parameters were the same as those in Example 1.

[0103] Embodiment 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 rest of the preparation methods and parameters were the same as 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 positive electrode 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 rest of the preparation methods and parameters were the same as 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 positive electrode 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 rest of the preparation methods and parameters were the same as 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 positive electrode 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 only contains a nickel-cobalt-manganese mixed sulfate solution and does not contain a sodium chloride solution. Only the first coprecipitation reaction is carried out without concurrently flowing in an iron salt solution D. When the median particle size D502 reaches 10 μm, the feeding is stopped.

[0117] The rest of the preparation methods and parameters were the same as 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 positive electrode 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 without concurrently feeding the iron salt solution D. When the median particle size D502 reaches 10 μm, the feeding is stopped.

[0121] The rest of the preparation methods and parameters were the same as 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 positive electrode precursor provided in this comparative example is not doped with chloride ions;

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

[0125] The rest of the preparation methods and parameters were the same as those in Example 1.

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

[0127] Battery preparation: The lithium-rich manganese-based positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) prepared in Examples 1-13 and Comparative Examples 1-3 were weighed in a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone (NMP) and mixed evenly; then, the slurry was applied on aluminum foil with an applicator and dried in a vacuum drying oven at 80°C for 8h; finally, the aluminum foil was punched into 1.13 cm 2 The positive electrode is obtained by forming a circular shape.

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

[0129] The performance test of the lithium ion batteries provided in Examples 1-13 and Comparative Examples 1-3 was performed under the following test conditions: at 25°C, the lithium ion batteries were charged and discharged three times in a voltage range of 2V to 4.6V at a charge and discharge rate of 0.1C (1C = 250 mAh / g), and the battery specific capacity was measured; the battery was cycled at a current density of 0.1C, and after 100 cycles, the discharge capacity of the battery at this time was divided by the discharge capacity of the first cycle, which was the 100-cycle capacity retention rate of the battery. The test results are shown in Table 1.

[0130] Table 1

[0131]

[0132]

[0133] In summary, the lithium-rich manganese-based positive electrode precursor provided by the present invention, through the synergistic coordination of halogen ion doping in the bulk phase of the precursor material and trivalent iron ion doping in the coating layer, the surface shell iron doping mainly occupies the transition metal layer in the lithium-rich manganese material, which can increase the interlayer spacing of the positive electrode material, enhance the bond energy of the metal and oxygen, accelerate the lithium ion diffusion rate, and stabilize the crystal structure; trace iron doping can achieve Fe during the charge and discharge process 3+ and Fe 4+ conversion, thereby improving the discharge specific capacity of the lithium-rich manganese material; halogen anion doping mainly replaces oxygen ions in the lithium-rich manganese material, increases the formation of oxygen vacancies, inhibits excessive oxidation of lattice oxygen at high potentials, reduces the release of oxygen during the cycle, and greatly improves the voltage decay performance and cycle stability of the lithium-rich manganese material; that is, the trivalent iron ion doping in the surface layer and the halogen anion doping in the entire structure in the present application not only increase the interlayer spacing of the positive electrode material and stabilize the crystal structure; but also increase the formation of oxygen vacancies, inhibit excessive oxidation of lattice oxygen at high potentials, and reduce the irreversible release of oxygen during the cycle. The two work synergistically with each other, thereby improving the electrochemical properties of the lithium-rich manganese-based positive electrode material.

[0134] The applicant declares that the above is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. An iron-and halogen-co-doped lithium-rich manganese-based positive electrode precursor, characterized in that: The iron and halogen co-doped lithium-manganese-based positive electrode precursor includes a core and a coating layer coated on 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 manganese-based precursor material doped with both iron ions and halogen ions.

2. The iron and halogen co-doped lithium-rich manganese-based positive electrode precursor 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 positive electrode precursor and the median particle size D501 of the core satisfies: D502-D501=0.5-4 μm; Preferably, the median particle size D502 of the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor is 6 to 12 μm.

3. A method for preparing an iron and halogen co-doped lithium-rich manganese-based positive electrode precursor as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: Adding the first mixed salt solution, the first precipitant solution and the first complexing agent solution into a reaction container in parallel to perform a first coprecipitation reaction to obtain a first mixed slurry containing a core; Adding the second mixed salt solution, the iron salt solution, the second precipitant solution and the second complexing agent solution into the first mixed slurry in parallel to perform a second coprecipitation reaction to obtain the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor; Wherein, the first mixed salt solution and the second mixed salt solution independently include manganese-containing mixed salt and halide.

4. The preparation method according to claim 3, characterized in that: In the first mixed salt solution, the ratio of the molar concentration of the solution containing the manganese mixed salt to the molar concentration of the solution containing the halide is (100-500):1; Preferably, in the first mixed salt solution, the concentration of the manganese-containing mixed salt solution is 1 to 3 mol / L.

5. The preparation method according to claim 3 or 4, characterized in that: In the second mixed salt solution, the ratio of the molar concentration of the solution containing the manganese mixed salt to the molar concentration of the solution containing the halide is (100-500):1; Preferably, the halide comprises sodium halide; Preferably, in the second mixed salt solution, the concentration of the manganese-containing mixed salt solution is 1 to 3 mol / L; Preferably, the concentration of the iron salt solution is 0.001-0.02 mol / L; Preferably, the concentrations of the first precipitant solution and the second precipitant solution are independently 5 to 10 mol / L; Preferably, the concentrations of the first complexing agent solution and the second complexing agent solution are independently 0.3 to 3 mol / L.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The pH values ​​of the first coprecipitation reaction and the second coprecipitation reaction are independently 9 to 12; Preferably, the rotation speeds of the first coprecipitation reaction and the second coprecipitation reaction are independently 400 to 800 rpm; 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 inner core in the first mixed slurry satisfies: D502-D501=0.5-4 μm; Preferably, during the second coprecipitation reaction, when the median particle size D502 of the reaction product reaches 6 to 12 μm, the reaction is stopped.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The mixed slurry obtained by the second coprecipitation reaction is sequentially washed and dried.

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

9. A lithium-rich manganese-based positive electrode material, characterized in that: The lithium-rich manganese-based positive electrode material is obtained by mixing and sintering the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor as described in claim 1 or 2 or the iron-and-halogen co-doped lithium-rich manganese-based positive electrode precursor prepared by the preparation method as described in any one of claims 3-8 with a lithium source.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-rich manganese-based positive electrode material as claimed in claim 9.

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