Cobalt-free, magnesium-doped lithium-rich manganese-based positive electrode material, preparation method therefor, and use thereof

Abstract

A cobalt-free, magnesium-doped lithium-rich manganese-based positive electrode material, a preparation method therefor, and a use thereof. The cobalt-free, magnesium-doped lithium-rich manganese-based positive electrode material has the following chemical formula: Li(NixMn1-x)MgyO2, where 0.1 ≤ x ≤ 0.5 and 0.01 ≤ y ≤ 0.1. The preparation method comprises: (1) mixing a nickel salt, a manganese salt, a magnesium salt, and deionized water to obtain a metal salt solution; (2) adding the metal salt solution, a precipitant solution, and a complexing agent solution into a base liquid in parallel flow and carrying out co-precipitation reaction, so as to obtain a lithium-rich manganese-based precursor; (3) mixing the lithium-rich manganese-based precursor and a lithium salt and performing primary calcination, so as to obtain a lithium-rich manganese-based intermediate; and (4) mixing the lithium-rich manganese-based intermediate and a lithium salt solution, and performing solid-liquid separation and then secondary calcination, so as to obtain a cobalt-free, magnesium-doped lithium-rich manganese-based positive electrode material. The provided cobalt-free, magnesium-doped lithium-rich manganese-based positive electrode material overcomes the shortcomings of conventional modification methods and improves the electrochemical performance of positive electrode materials.

Description

A cobalt-free, magnesium-doped, lithium-rich manganese-based cathode material, its preparation method and application Technical Field

[0001] This application belongs to the field of battery manufacturing technology, and relates to a lithium-rich manganese-based cathode material, and more particularly to a cobalt-free magnesium-doped lithium-rich manganese-based cathode material and its preparation method and application. Background Technology

[0002] In recent years, with the booming development of industries such as digital 3C products, new energy vehicles, and energy storage grids, the application of lithium-ion batteries has become increasingly widespread. Continuous progress in various industries has led to the increasing maturity of lithium battery technology, and people's expectations for battery performance have also risen accordingly. To meet the market demand for battery cathode materials with higher energy density and greater specific capacity, engineers have devoted considerable effort to extensive research and exploration.

[0003] Research has revealed that lithium-rich manganese-based cathode material aLi2MnO3·(1-a)LiMO2 (M = at least one of Ni, Mn, Al, V, Cr, Fe, and Ti) has high discharge specific capacity (>250mAh / g), high operating voltage (>3.5V), and also possesses advantages such as good thermal stability, wide charge / discharge voltage threshold range, low price, less susceptibility to mineral resource limitations, and environmental friendliness. These advantages have attracted widespread attention from industry experts and scholars, and it is hailed as an ideal choice for the next generation of high-energy-density power lithium batteries.

[0004] However, during the research process, technicians discovered that although lithium-rich manganese-based cathode materials have high specific capacity, they also have many problems in application, such as low initial coulombic efficiency (<80%) and significant voltage and capacity decay during cycling. Common modification methods for addressing these defects in lithium-rich manganese-based cathode materials mainly involve elemental doping and surface coating.

[0005] Elemental doping, primarily metal cation doping and fluorine anion doping, can enhance the structural stability of cathode materials to some extent. However, it suffers from uneven doping, with dopant elements distributed on the surface and in phase separation, easily forming impurity phases. Furthermore, elemental doping cannot solve the oxygen evolution problem under high voltage. Surface coating involves coating a protective layer onto the cathode material. This protective layer is generally electrochemically inert, which can suppress structural collapse caused by high-voltage charging and discharging, mitigate electrolyte corrosion of the electrode material, and improve conductivity. However, it suffers from uneven coating; if the coating is too thin, there are many blind spots, resulting in poor performance; if the coating is too thick, conductivity deteriorates, affecting capacity. Moreover, surface coating is a complex process that generates large amounts of toxic industrial wastewater, indicating significant room for improvement.

[0006] Therefore, how to provide a lithium-rich manganese-based positive electrode material and a preparation method thereof, overcome the drawbacks of traditional modification methods, and improve the electrochemical performance of the positive electrode material has become an urgent problem to be solved by those skilled in the art.

[0007] SUMMARY

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of protection of the claims.

[0009] The present application provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material, a preparation method thereof and an application thereof. The cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material overcomes the drawbacks of traditional modification methods and improves the electrochemical performance of the positive electrode material.

[0010] In a first aspect, the present application provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material, the chemical formula of which is: Li(Ni x Mn 1-x )Mg y O2; wherein 0.1≤x≤0.5 and 0.01≤y≤0.1.

[0011] In the present application, 0.1≤x≤0.5, for example, x can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, and further can be selected as 0.1≤x≤0.45, but is not limited to the listed values. Other values not listed in this range are also applicable.

[0012] In the present application, 0.01≤y≤0.1, for example, y can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, and further can be selected as 0.01≤y≤0.05, but is not limited to the listed values. Other values not listed in this range are also applicable.

[0013] Since cobalt is expensive and in short supply, the lithium-rich manganese-based positive electrode material provided by the present application does not contain cobalt, thereby significantly reducing the cost of raw materials and not being limited by mineral resources. The doping of magnesium can neutralize the effect of high-valence Mn 4+ , reduce the proportion of Ni 2+ , make the positive electrode material have lower Li + / Ni 2+ mixing arrangement, inhibit the local collapse between intercrystals, reduce the difficulty of Li + insertion and extraction during the charging and discharging process, thereby accelerating the insertion and extraction rate, improving the reversible capacity of the material, and also inhibiting Li +The transition metal layer is entered, and the electrochemical performance of the positive electrode material is significantly improved, which is conducive to large-scale popularization and application.

[0014] In a second aspect, the present application provides a preparation method of the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material according to the first aspect, and the preparation method comprises the following steps:

[0015] (1) mixing a nickel salt, a manganese salt, a magnesium salt and deionized water to obtain a metal salt solution;

[0016] (2) adding the metal salt solution, a precipitant solution and a complexing agent solution into a bottom liquid in a concurrent manner to perform a coprecipitation reaction, thereby obtaining a lithium-rich manganese-based precursor;

[0017] (3) mixing the lithium-rich manganese-based precursor and a lithium salt to perform a first calcination, thereby obtaining a lithium-rich manganese-based intermediate;

[0018] (4) mixing the lithium-rich manganese-based intermediate and a lithium salt solution, performing a solid-liquid separation and then performing a second calcination, thereby obtaining the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material.

[0019] The lithium-rich manganese-based precursor is prepared by using the coprecipitation method in the present application, and the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material is prepared through subsequent two calcinations. Before the second calcination, the lithium-rich manganese-based intermediate and the lithium salt solution are mixed, so that the lithium element volatilized in the first calcination process of the precursor is supplemented, and the capacity of the positive electrode material is further improved.

[0020] In one embodiment, the nickel salt, the manganese salt and the magnesium salt in step (1) are any one or a combination of at least two of the corresponding metal ion sulfate, nitrate, acetate or chloride salt, and typical but non-limiting combinations include a combination of sulfate and nitrate, a combination of nitrate and acetate, a combination of acetate and chloride, a combination of sulfate, nitrate and acetate, or a combination of nitrate, acetate and chloride.

[0021] In one embodiment, the molar ratio of nickel ions, manganese ions and magnesium ions in the metal salt solution in step (1) is (0.1-0.5):(0.5-0.9):(0.01-0.1), for example, it can be 0.1:0.5:0.01, 0.2:0.6:0.03, 0.3:0.7:0.05, 0.4:0.8:0.07 or 0.5:0.9:0.1, and further optionally (0.1-0.45):(0.55-0.9):(0.01-0.05), but is not limited to the listed values, and other values not listed in the range are also applicable.

[0022] In one embodiment, the total concentration of metal ions in the metal salt solution of step (1) is in the range of 1.5-5 mol / L, for example, it can be 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but is not limited to the listed values, other values not listed in this range are also applicable.

[0023] In one embodiment, the precipitant solution of step (2) comprises a sodium hydroxide solution and / or a sodium carbonate solution.

[0024] In one embodiment, the complexing agent solution of step (2) comprises any one or a combination of at least two of an ammonia solution, a sodium citrate solution or an ethylenediaminetetraacetic acid solution, typically but not limited to a combination of an ammonia solution and a sodium citrate solution, a sodium citrate solution and an ethylenediaminetetraacetic acid solution, an ammonia solution and an ethylenediaminetetraacetic acid solution, or an ammonia solution, a sodium citrate solution and an ethylenediaminetetraacetic acid solution.

[0025] In one embodiment, the bottom solution of step (2) is a mixed solution of the precipitant solution and the complexing agent solution.

[0026] In one embodiment, the pH value of the bottom solution of step (2) is in the range of 9.0-12.0, for example, it can be 9.0, 9.5, 10.0, 10.5, 11.0, 11.5 or 12.0, but is not limited to the listed values, other values not listed in this range are also applicable.

[0027] In one embodiment, the temperature of the co-precipitation reaction of step (2) is in the range of 25-75 °C, for example, it can be 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C or 75 °C, but is not limited to the listed values, other values not listed in this range are also applicable.

[0028] In one embodiment, the co-precipitation reaction of step (2) is carried out in a protective gas atmosphere, and the protective gas atmosphere comprises any one or a combination of at least two of nitrogen, helium or argon, typically but not limited to a combination of nitrogen and helium, helium and argon, nitrogen and argon, or nitrogen, helium and argon.

[0029] In one embodiment, the co-precipitation reaction of step (2) is accompanied by stirring, and the stirring rate is 150-500 rpm, for example, it can be 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, but not only limited to the listed values, other values not listed in the range are also applicable.

[0030] In one embodiment, the lithium salt of step (3) comprises lithium hydroxide and / or lithium carbonate.

[0031] In one embodiment, the molar ratio of the sum of metal ions in the lithium-rich manganese-based precursor of step (3) to lithium ions in the lithium salt is 1:(1.15-1.5), for example, it can be 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45 or 1.5, but not only limited to the listed values, other values not listed in the range are also applicable.

[0032] In one embodiment, the temperature of the first calcination of step (3) is 700-1000°C, for example, it can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, but not only limited to the listed values, other values not listed in the range are also applicable.

[0033] In this application, the temperature of the first calcination needs to be kept within a reasonable range. When the temperature is lower than 700°C, the sintered positive electrode material has low crystallinity, poor crystal structure and rich impurities, the primary particles are agglomerated and have no obvious edges and corners, the I 003 / I 104 strength is low, and the ion is severely disordered; when the temperature is higher than 1000°C, the lithium-nickel disordering and secondary crystallization are intensified, which reduces the battery cycle performance, and the lithium element is severely volatilized, thereby reducing the capacity of the positive electrode material.

[0034] In one embodiment, the heating rate of the first calcination of step (3) is 2-4°C / min, for example, it can be 2°C / min, 2.2°C / min, 2.4°C / min, 2.6°C / min, 2.8°C / min, 3°C / min, 3.2°C / min, 3.4°C / min, 3.6°C / min, 3.8°C / min or 4°C / min, but not only limited to the listed values, other values not listed in the range are also applicable.

[0035] In one embodiment, the holding time of the once calcination in step (3) is 8-16h, for example, it can be 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or 16h, but not limited to the listed values, other values not listed in the range are also applicable.

[0036] In one embodiment, the once calcination in step (3) is followed by crushing the lithium-rich manganese-based intermediate.

[0037] In one embodiment, the lithium salt solution in step (4) comprises lithium hydroxide solution and / or lithium carbonate solution.

[0038] In one embodiment, the concentration of the lithium salt solution in step (4) is 2-3mol / L, for example, it can be 2mol / L, 2.1mol / L, 2.2mol / L, 2.3mol / L, 2.4mol / L, 2.5mol / L, 2.6mol / L, 2.7mol / L, 2.8mol / L, 2.9mol / L or 3mol / L, but not limited to the listed values, other values not listed in the range are also applicable.

[0039] In one embodiment, the mixing in step (4) is accompanied by stirring until the lithium-rich manganese-based intermediate is fully wetted.

[0040] In one embodiment, the solid-liquid separation in step (4) comprises suction filtration.

[0041] In one embodiment, the solid-liquid separation in step (4) is followed by vacuum drying, and the temperature of the vacuum drying is 180-220℃, for example, it can be 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃ or 220℃, and the time is 6-10h, for example, it can be 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h, but not limited to the listed values, other values not listed in the range are also applicable.

[0042] In one embodiment, the temperature of the secondary calcination in step (4) is 400-500℃, for example, it can be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃ or 500℃, but not limited to the listed values, other values not listed in the range are also applicable.

[0043] In one embodiment, the secondary calcination in step (4) is performed for 3-5h, for example, it can be 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, 4.2h, 4.4h, 4.6h, 4.8h or 5h, but is not limited to the listed values, and other unlisted values within the range are also applicable.

[0044] As an optional technical solution of the second aspect of the application, the preparation method comprises the following steps:

[0045] (1) mixing nickel salt, manganese salt, magnesium salt and deionized water to obtain a metal salt solution with a total metal ion concentration of 1.5-5mol / L; the nickel salt, manganese salt and magnesium salt are each any one or a combination of at least two of the corresponding metal ion sulfate, nitrate, acetate or chloride salt, and the molar ratio of nickel ion, manganese ion and magnesium ion in the metal salt solution is (0.1-0.45):(0.55-0.9):(0.01-0.05);

[0046] (2) co-precipitation reaction of the metal salt solution, the precipitant solution and the complexing agent solution in the bottom solution with a pH value of 9.0-12.0 in a protective gas atmosphere at 25-75℃, accompanied by stirring at a speed of 150-500rpm, to obtain a lithium-rich manganese-based precursor; the precipitant solution comprises sodium hydroxide solution and / or sodium carbonate solution, the complexing agent solution comprises any one or a combination of at least two of ammonia, sodium citrate solution or ethylenediaminetetraacetic acid solution, and the bottom solution is a mixed solution of the precipitant solution and the complexing agent solution; the protective gas atmosphere comprises any one or a combination of at least two of nitrogen, helium or argon;

[0047] (3) mixing the lithium-rich manganese-based precursor and lithium salt, and performing primary calcination at 700-800℃ for 8-16h with a heating rate of 2-4℃ / min, and then crushing to obtain a lithium-rich manganese-based intermediate; the lithium salt comprises lithium hydroxide and / or lithium carbonate, and the molar ratio of the total metal ions in the lithium-rich manganese-based precursor to lithium ions in the lithium salt is 1:(1.15-1.5);

[0048] (4) mixing the lithium-rich manganese-based intermediate and lithium carbonate solution with a concentration of 2-3mol / L, stirring until the lithium-rich manganese-based intermediate is fully wet, then vacuum drying at 180-220℃ for 6-10h, and then secondary calcination at 400-500℃ for 3-5h to obtain a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material.

[0049] In a third aspect, the application provides a lithium ion battery comprising the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material as described in the first aspect.

[0050] The numerical ranges recited herein are inclusive of the endpoints and of any range that would be formed by including the endpoints. To the extent that numerical ranges are recited herein, the recitation of such ranges is intended to include the endpoints and to further include any range that would be formed by including the endpoints.

[0051] Compared with the related art, the application has the following beneficial effects:

[0052] (1) The lithium-rich manganese-based positive electrode material provided by the application does not contain cobalt elements, thereby significantly reducing the raw material cost and not being limited by mineral resources; the doping of magnesium elements can neutralize the action of high-valence Mn 4+ , reduce the proportion of Ni 2+ , make the positive electrode material have lower Li + / Ni 2+ mixing arrangement, inhibit the local collapse between intercrystals, reduce the difficulty of Li + insertion and extraction in the charging and discharging process, thereby accelerating the rate of insertion and extraction and improving the reversible capacity of the material, and also inhibiting Li + from entering the transition metal layer, thereby significantly improving the electrochemical performance of the positive electrode material and being conducive to large-scale popularization and application.

[0053] (2) The lithium-rich manganese-based precursor is prepared by the coprecipitation method in the application, and the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material is prepared by subsequent twice calcination, and the lithium-rich manganese-based intermediate and the lithium salt solution are mixed before the second calcination, thereby supplementing the lithium elements volatilized from the precursor in the first calcination process and further improving the capacity of the positive electrode material.

[0054] Other aspects can become apparent from the detailed description which follows, particularly when taken in conjunction with the drawings. DETAILED DESCRIPTION

[0055] The technical solutions of the application will be further described below through specific embodiments.

[0056] Embodiment 1

[0057] The embodiment provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof, the chemical formula of the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material is Li(Ni 0.3 Mn 0.7 )Mg 0.03 O2, and the preparation method comprises the following steps:

[0058] (1) mixing nickel sulfate, manganese sulfate, magnesium sulfate and deionized water to obtain a metal salt solution with a total metal ion concentration of 3.2 mol / L; the molar ratio of nickel ions, manganese ions and magnesium ions in the metal salt solution is 0.3:0.7:0.03;

[0059] (2) adding the metal salt solution, the sodium hydroxide solution and the ammonia water into a bottom solution with a pH value of 10±1 in a concurrent manner, the bottom solution being a mixed solution of the sodium hydroxide solution and the ammonia water, performing a co-precipitation reaction at 50°C in a nitrogen atmosphere, while stirring at a speed of 300 rpm, to obtain a lithium-rich manganese-based precursor;

[0060] (3) mixing the lithium-rich manganese-based precursor and lithium hydroxide, controlling a molar ratio of the sum of metal ions in the lithium-rich manganese-based precursor to lithium ions in the lithium hydroxide to be 1:1.3, performing a first calcination at 950°C for 12h, and a crushing to obtain a lithium-rich manganese-based intermediate;

[0061] (4) mixing the lithium-rich manganese-based intermediate and a lithium carbonate solution with a concentration of 2.5 mol / L, stirring until the lithium-rich manganese-based intermediate is fully wetted, performing vacuum drying at 200°C for 8h after suction filtration, and then performing a second calcination at 450°C for 4h, to obtain a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material.

[0062] Example 2

[0063] The embodiment provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof, the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material has a chemical formula of Li(Ni 0.45 Mn 0.55 )Mg 0.01 O2, and the preparation method comprises the following steps:

[0064] (1) mixing nickel nitrate, manganese nitrate, magnesium nitrate and deionized water to obtain a metal salt solution with a total metal ion concentration of 5 mol / L; a molar ratio of nickel ions, manganese ions and magnesium ions in the metal salt solution is 0.45:0.55:0.01;

[0065] (2) adding the metal salt solution, the sodium carbonate solution and the sodium citrate solution into a bottom solution with a pH value of 11±1 in a concurrent manner, the bottom solution being a mixed solution of the sodium carbonate solution and the sodium citrate solution, performing a co-precipitation reaction at 25°C in a helium atmosphere, while stirring at a speed of 500 rpm, to obtain a lithium-rich manganese-based precursor;

[0066] (3) mixing the lithium-rich manganese-based precursor and lithium carbonate, controlling a molar ratio of the sum of metal ions in the lithium-rich manganese-based precursor to lithium ions in the lithium carbonate to be 1:1.15, performing a first calcination at 800°C for 16h, and a crushing to obtain a lithium-rich manganese-based intermediate;

[0067] (4) mixing the lithium-rich manganese-based intermediate and a lithium hydroxide solution with a concentration of 2 mol / L, stirring until the lithium-rich manganese-based intermediate is fully wetted, vacuum drying at 180°C for 10h after suction filtration, and then secondary calcining at 400°C for 5h to obtain the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material.

[0068] Example 3

[0069] The present embodiment provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. The chemical formula of the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material is Li(Ni 0.25 Mn 0.75 )Mg 0.05 O2, and the preparation method comprises the following steps:

[0070] (1) mixing nickel chloride, manganese chloride, magnesium chloride and deionized water to obtain a metal salt solution with a total metal ion concentration of 1.5 mol / L; the molar ratio of nickel ions, manganese ions and magnesium ions in the metal salt solution is 0.25:0.75:0.05;

[0071] (2) adding the metal salt solution, a sodium hydroxide solution and an ethylenediaminetetraacetic acid solution into a bottom solution with a pH value of 10±1, the bottom solution being a mixed solution of the sodium hydroxide solution and the ethylenediaminetetraacetic acid solution, performing a co-precipitation reaction at 75°C in an argon atmosphere, while stirring at a speed of 150 rpm to obtain a lithium-rich manganese-based precursor;

[0072] (3) mixing the lithium-rich manganese-based precursor and lithium hydroxide, controlling the molar ratio of the total metal ions in the lithium-rich manganese-based precursor and lithium ions in the lithium hydroxide to be 1:1.5, performing primary calcination at 850°C for 8h, with a heating rate of 4°C / min, and then crushing to obtain a lithium-rich manganese-based intermediate;

[0073] (4) mixing the lithium-rich manganese-based intermediate and a lithium carbonate solution with a concentration of 3 mol / L, stirring until the lithium-rich manganese-based intermediate is fully wetted, vacuum drying at 220°C for 6h after suction filtration, and then secondary calcining at 500°C for 3h to obtain the cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material.

[0074] Example 4

[0075] The present embodiment provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that the molar ratio of nickel ions, manganese ions and magnesium ions in the metal salt solution in step (1) is adjusted to be 0.5:0.5:0.1, so that the chemical formula of the obtained cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material is Li(Ni 0.5 Mn 0.5 )Mg 0.1 O2, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0076] Example 5

[0077] This example provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that the nickel sulfate, manganese sulfate and magnesium sulfate in step (1) are replaced by nickel acetate, manganese acetate and magnesium acetate respectively, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0078] Example 6

[0079] This example provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that the temperature of the first calcination in step (3) is reduced to 650°C, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0080] Example 7

[0081] This example provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that the temperature of the first calcination in step (3) is increased to 1050°C, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0082] Example 8

[0083] This example provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that the temperature of the first calcination in step (3) is increased to 1050°C, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0084] Example 9

[0085] This example provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that the temperature of the second calcination in step (4) is reduced to 300°C, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0086] Example 10

[0087] This example provides a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that the temperature of the second calcination in step (4) is increased to 600°C, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0088] Comparative Example 1

[0089] This comparative example provides a lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that magnesium sulfate is not added in step (1), i.e., magnesium is not doped into the positive electrode material, the remaining steps and conditions are the same as those in Example 1, and thus are not described here.

[0090] Comparative Example 2

[0091] The comparative example provides a lithium-rich manganese-based positive electrode material and a preparation method thereof. Except that step (4) is not performed, i.e., the lithium-rich manganese-based intermediate after one-time calcination is directly used as the final lithium-rich manganese-based positive electrode material, the remaining steps and conditions are the same as those in example 1, and thus are not described herein.

[0092] Performance test

[0093] Lithium-ion button batteries were prepared by using the lithium-rich manganese-based positive electrode materials obtained in examples 1-10 and comparative examples 1-2. The specific preparation method comprises: according to the mass ratio of 8:1:1, the positive electrode material, acetylene black and polyvinylidene fluoride are dropped into N-methyl-2-pyrrolidone to prepare a solution, which is uniformly coated on an aluminum foil, dried, punched and made into a thin sheet; the battery electrode piece, lithium piece, glass fiber separator, electrolyte (LiClO4) gasket, spring and battery shell are assembled into a button battery in an argon glove box.

[0094] Table 1 below is the electrochemical performance test data of the button batteries prepared by using the lithium-rich manganese-based positive electrode materials obtained in examples 1-10 and comparative examples 1-2.

[0095] Table 1

[0096] It can be seen that the lithium-rich manganese-based positive electrode material provided by the present application does not contain cobalt element, thereby significantly reducing the raw material cost and not being limited by mineral resources; the doping of magnesium element can neutralize the action of high-valence Mn 4+ , reduce the proportion of Ni 2+ , make the positive electrode material have a lower Li + / Ni 2+ mixing arrangement, inhibit the local collapse between intercrystals, reduce the difficulty of Li + insertion and extraction in the charging and discharging process, thereby accelerating the insertion and extraction rate, improving the reversible capacity of the material, and also inhibiting Li + from entering the transition metal layer, thereby significantly improving the electrochemical performance of the positive electrode material, and being beneficial to large-scale popularization and application.

[0097] In addition, the present application uses a co-precipitation method to prepare a lithium-rich manganese-based precursor, and then obtains a cobalt-free magnesium-doped lithium-rich manganese-based positive electrode material after two-time calcination. Before the second-time calcination, the lithium-rich manganese-based intermediate and lithium salt solution are mixed, so as to supplement the lithium element volatilized from the precursor in the one-time calcination process, and further improve the capacity of the positive electrode material.

[0098] The above-described specific embodiments have further detailed the purposes, technical solutions and beneficial effects of the present application, and it should be understood that the above-described is only a specific embodiment of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A cobalt-free, magnesium-doped, lithium-rich manganese-based cathode material, wherein, The chemical formula of the cobalt-free, magnesium-doped, lithium-rich manganese-based cathode material is: Li(Ni x Mn 1-x )Mg y O2; where 0.1≤x≤0.5, 0.01≤y≤0.

1.

2. The cobalt-free, magnesium-doped, lithium-rich manganese-based cathode material according to claim 1, wherein, 0.1≤x≤0.45, 0.01≤y≤0.

05.

3. A method for preparing the cobalt-free, magnesium-doped, lithium-rich manganese-based cathode material as described in claim 1 or 2, comprising the following steps: (1) Mix nickel salt, manganese salt, magnesium salt and deionized water to obtain a metal salt solution; (2) The metal salt solution, precipitant solution and complexing agent solution were added to the bottom liquid in a co-precipitation reaction to obtain the lithium-rich manganese-based precursor. (3) Mix the lithium-rich manganese-based precursor and lithium salt and calcine them once to obtain the lithium-rich manganese-based intermediate; (4) Mix lithium-rich manganese-based intermediate and lithium salt solution, separate solid and liquid, and then calcine twice to obtain cobalt-free magnesium-doped lithium-rich manganese-based cathode material.

4. The preparation method according to claim 3, wherein, The nickel salt, manganese salt, and magnesium salt mentioned in step (1) are any one or a combination of at least two of the sulfate, nitrate, acetate, or chloride salts of the corresponding metal ions.

5. The preparation method according to claim 3 or 4, wherein, The molar ratio of nickel ions, manganese ions and magnesium ions in the metal salt solution in step (1) is (0.1-0.5):(0.5-0.9):(0.01-0.1), which can be selected as (0.1-0.45):(0.55-0.9):(0.01-0.05).

6. The preparation method according to any one of claims 3-5, wherein, The total concentration of metal ions in the metal salt solution in step (1) is 1.5-5 mol / L.

7. The preparation method according to any one of claims 3-6, wherein, The precipitant solution in step (2) includes sodium hydroxide solution and / or sodium carbonate solution.

8. The preparation method according to any one of claims 3-7, wherein, The complexing agent solution in step (2) includes any one or a combination of at least two of ammonia water, sodium citrate solution or ethylenediaminetetraacetic acid solution; Optionally, the bottom liquid in step (2) is a mixed solution of a precipitant solution and a complexing agent solution; Optionally, the pH value of the base solution in step (2) is 9.0-12.

0.

9. The preparation method according to any one of claims 3-8, wherein, The temperature for the coprecipitation reaction in step (2) is 25-75℃; Optionally, the coprecipitation reaction in step (2) is carried out in a protective gas atmosphere, and the protective gas atmosphere includes any one or a combination of at least two of nitrogen, helium or argon. Optionally, the coprecipitation reaction in step (2) is accompanied by stirring, and the stirring rate is 150-500 rpm.

10. The preparation method according to any one of claims 3-9, wherein, The lithium salt in step (3) includes lithium hydroxide and / or lithium carbonate; Optionally, the molar ratio of the total metal ions in the lithium-rich manganese-based precursor to the lithium ions in the lithium salt in step (3) is 1:(1.15-1.5).

11. The preparation method according to any one of claims 3-10, wherein, The calcination temperature in step (3) is 700-800℃; Optionally, the heating rate of the first calcination in step (3) is 2-4℃ / min; Optionally, the holding time for the first calcination in step (3) is 8-16 hours; Optionally, the lithium-rich manganese-based intermediate is pulverized after the first calcination in step (3).

12. The preparation method according to any one of claims 3-11, wherein, The lithium salt solution in step (4) includes lithium hydroxide solution and / or lithium carbonate solution; Optionally, the concentration of the lithium salt solution in step (4) is 2-3 mol / L; Optionally, the mixing in step (4) is accompanied by stirring until the lithium-rich manganese-based intermediate is fully wetted; Optionally, the solid-liquid separation in step (4) includes vacuum filtration; Optionally, step (4) includes vacuum drying between solid-liquid separation and secondary calcination, and the vacuum drying temperature is 180-220℃ and the time is 6-10h.

13. The preparation method according to any one of claims 3-12, wherein, The temperature of the secondary calcination in step (4) is 400-500℃; Optionally, the secondary calcination time in step (4) is 3-5 hours.

14. The preparation method according to any one of claims 3-13, comprising the following steps: (1) Mix nickel salt, manganese salt, magnesium salt and deionized water to obtain a metal salt solution with a total metal ion concentration of 1.5-5 mol / L; wherein the nickel salt, manganese salt and magnesium salt are any one or at least two of the sulfate, nitrate, acetate or chloride salts of the corresponding metal ions, and the molar ratio of nickel ions, manganese ions to magnesium ions in the metal salt solution is (0.1-0.45):(0.55-0.9):(0.01-0.05); (2) A metal salt solution, a precipitant solution, and a complexing agent solution are added concurrently to a base liquid with a pH of 9.0-12.

0. A co-precipitation reaction is carried out at 25-75°C under a protective gas atmosphere, accompanied by stirring at a rate of 150-500 rpm, to obtain a lithium-rich manganese-based precursor. The precipitant solution includes sodium hydroxide solution and / or sodium carbonate solution. The complexing agent solution includes any one or a combination of at least two of ammonia water, sodium citrate solution, or ethylenediaminetetraacetic acid solution. The base liquid is a mixed solution of the precipitant solution and the complexing agent solution. The protective gas atmosphere includes any one or a combination of at least two of nitrogen, helium, or argon. (3) Mix lithium-rich manganese-based precursor and lithium salt, calcine at 700-800℃ for 8-16h with a heating rate of 2-4℃ / min, and pulverize to obtain lithium-rich manganese-based intermediate; the lithium salt includes lithium hydroxide and / or lithium carbonate, and the molar ratio of the total metal ions in the lithium-rich manganese-based precursor to the lithium ions in the lithium salt is 1:(1.15-1.5). (4) Mix the lithium-rich manganese-based intermediate and a lithium salt solution with a concentration of 2-3 mol / L, and stir until the lithium-rich manganese-based intermediate is reached. The intermediate is fully wetted, filtered, and then vacuum dried at 180-220℃ for 6-10 hours, followed by secondary calcination at 400-500℃ for 3-5 hours to obtain a cobalt-free magnesium-doped lithium-rich manganese-based cathode material; the lithium salt solution includes lithium hydroxide solution and / or lithium carbonate solution.

15. A lithium-ion battery, wherein, The lithium-ion battery contains the cobalt-free, magnesium-doped, lithium-rich manganese-based cathode material as described in claim 1 or 2.

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