A lithium-rich manganese-based positive electrode material and its precursor and preparation method

Abstract

The present invention relates to a lithium-rich manganese-based positive electrode material and its precursor and preparation method, belonging to the field of battery technology. The problems of low ion diffusion coefficient, poor rate performance and poor cycle performance of existing lithium-rich manganese-based positive electrode materials are solved. The preparation method of the present invention comprises the following steps: firstly, a transition metal salt, a precipitant and a complexing agent are uniformly mixed with water to obtain a transition metal salt solution, a precipitant solution and a complexing agent solution; then, the precipitant solution and the complexing agent solution are used to regulate the pH of the bottom liquid in the reactor; then, under the protection of an inert atmosphere, the reactor is fed with liquid, and the nucleation-growth process of the primary particles is regulated by dynamically adjusting the pH, temperature and stirring speed of the system, and the crystal plane orientation, particle size and stacking mode of the primary particles are controlled, thereby regulating the morphology of the secondary particles; after the liquid is fed, the precursor is obtained after aging, filtration, washing and drying. The positive electrode material prepared by the precursor has both rate performance and high energy density performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a lithium-rich manganese-based positive electrode material and a precursor and a preparation method thereof. Background Art

[0002] With the growing demand for fast charging and battery life in the consumer market, the development of new fast-charging, high-energy-density lithium-ion batteries has become a new trend. As one of the key components, the gram capacity and kinetic performance of the positive electrode material are lower than those of the negative electrode material, which has become a shortcoming that currently restricts the development of lithium-ion batteries.

[0003] The gram capacity of lithium-rich manganese-based positive electrode materials can reach more than 280mAh / g, which can significantly improve the energy density of the battery, thereby meeting the needs of electric vehicles and energy storage systems for high endurance, and is an ideal choice for future lithium-ion batteries.

[0004] However, the special anion reaction mechanism of lithium-rich manganese-based cathode materials during charging and discharging leads to low initial efficiency, poor kinetic performance, and poor cycle performance; at the same time, the poor electrochemical activity of the local structure of Li2MnO3 in the bulk phase, the particle morphology, and the size of the primary particles also affect the diffusion process of lithium ions. Under the combined effect, the ion diffusion coefficient of lithium-rich manganese-based cathode materials is lower than that of traditional ternary cathode materials, resulting in poor rate performance; at the same time, the uneven distribution of internal stress and side reactions during the cycle will also cause structural deterioration, resulting in poor cycle performance, and the existing performance cannot meet the needs of the consumer market.

[0005] In the prior art, the main methods for improving the rate performance and cycle performance of lithium-rich manganese-based cathode materials are modification methods such as doping and coating. However, the doping and coating strategies mainly optimize the local structure of the cathode material bulk and the cathode particle-electrolyte interface structure, and cannot regulate the intrinsic structural characteristics of the secondary sphere (such as the crystal plane orientation of the primary particles, the secondary spherical core-growth process, etc.), and fundamentally improve the kinetic performance and structural stability of lithium-rich manganese-based cathode particles.

[0006] Therefore, starting from optimizing the intrinsic structural characteristics of the precursor, preparing a lithium-rich manganese-based positive electrode material and its precursor with stable structure and rapid lithium ion diffusion is the research focus in this field. Summary of the invention

[0007] The purpose of the present invention is to solve the technical problems of low ion diffusion coefficient, poor rate performance, poor cycle performance, etc. of lithium-rich manganese-based positive electrode materials in the prior art, and to provide a lithium-rich manganese-based positive electrode material and its precursor and preparation method.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a lithium-rich manganese-based positive electrode material precursor, comprising the following steps:

[0010] S1. mixing a transition metal salt and water to obtain a transition metal salt solution, wherein the transition metal salt includes a manganese salt;

[0011] S2. The precipitant and the complexing agent are mixed with water to obtain a precipitant solution and a complexing agent solution;

[0012] S3. Using a precipitant solution and a complexing agent solution to control the pH of the bottom liquid in the reactor;

[0013] S4. Under the protection of an inert atmosphere, liquids are introduced into the reactor, wherein the liquids are transition metal salt solution, precipitant solution and complexing agent solution. During the liquid introduction process, the nucleation-growth process of the primary particles is regulated by dynamically adjusting the pH, temperature and stirring speed of the system, and the crystal plane orientation, particle size and stacking mode of the primary particles are controlled, thereby regulating the morphology of the secondary particles;

[0014] S5. After the liquid is added, aging;

[0015] S6. After aging, the lithium-rich manganese-based positive electrode material precursor is obtained through filtration, washing and drying.

[0016] Preferably, in step S1, the transition metal salt further comprises one or more of nickel salt and cobalt salt;

[0017] More preferably, in step S1, the manganese salt is one or more of manganese nitrite, manganese nitrate, manganese sulfate, and manganese acetate; the nickel salt is one or more of nickel nitrite, nickel nitrate, nickel sulfate, and nickel acetate; the cobalt salt is one or more of cobalt nitrite, cobalt nitrate, cobalt sulfate, and cobalt acetate;

[0018] More preferably, in step S1, in the transition metal salt solution, the molar ratio of manganese, nickel and cobalt is x:y:z, 1 / 3≤x<1, 0≤y≤1 / 2, 0≤z≤1 / 2.

[0019] Preferably, in step S1, the total concentration of the transition metal salt in the transition metal salt solution is 0.1-4M.

[0020] Preferably, in step S2, the precipitant is one or more of sodium hydroxide, sodium bicarbonate, sodium carbonate, and oxalic acid; and in the precipitant solution, the concentration of the precipitant is 0.1-10M.

[0021] Preferably, in step S2, the complexing agent is one or more of ethylenediaminetetraacetic acid (EDTA), ammonia water, citric acid, ammonium sulfate, and ammonium chloride; and the concentration of the complexing agent in the complexing agent solution is 0.1-5M.

[0022] Preferably, in step S2, the base liquid contains ≤5wt% of additives, and the additives are one or more of polyethylene glycol (PEG), sodium dodecylbenzene sulfonate, ammonium dodecyl sulfate, and hexadecyldimethylammonium chloride.

[0023] Preferably, in step S3, the pH of the bottom liquid in the reaction kettle is regulated to be 7.3-12.0 using a precipitant solution and a complexing agent solution.

[0024] Preferably, in step S4, the process of dynamically adjusting the pH, temperature and stirring speed of the system to adjust the nucleation-growth process of the primary particles, control the crystal plane orientation, particle size and stacking mode of the primary particles, and then regulate the morphology of the secondary particles is:

[0025] ① Regulate pH, temperature and stirring speed to make nucleation greater than growth and generate primary particles in the system. When it is observed that the primary particles are about to agglomerate, proceed to ②;

[0026] ② Regulate pH, temperature and stirring speed to make the growth greater than the nucleation, so that the primary particles continue to grow along the (001) crystal plane until they begin to be radially arranged and stacked. If the size of the secondary particles does not reach the target requirement, proceed to step ③. If the size of the secondary particles reaches the target requirement, proceed to step ④.

[0027] ③ Regulate pH, temperature and stirring speed, and then regulate the growth rate of primary particles until the particle size of the secondary particles reaches the target requirement, and then enter ④;

[0028] ④ Regulate the pH, temperature and stirring speed to make nucleation greater than growth, until the confinements between the primary particle plates are filled with newly nucleated primary particles, and the surface of the secondary particles is observed to be dense. Stop adding liquid to obtain secondary particles with controllable particle size, a moderate proportion of chemically non-active (003) crystal faces of the primary particles, and (010) crystal faces oriented outward with a nano-confinement structure.

[0029] Preferably, in step S4, the inert atmosphere is one or both of nitrogen and argon.

[0030] Preferably, in step S4, the precipitant solution and the complexing agent solution are introduced separately or in combination.

[0031] Preferably, in step S4, the pH is adjusted in the range of 7.3-12.0, the temperature is adjusted in the range of 25-80° C., and the stirring speed is adjusted in the range of 100-3000 r / min.

[0032] Preferably, in step S4, the liquid inlet is divided into several stages.

[0033] Preferably, in step S5, the aging pH is 7.3-12.0, the temperature is 25-80°C, the stirring speed is 100-3000r / min, and the time is 1-24h.

[0034] Preferably, the precipitant solution and the complexing agent solution are replaced by a precipitant-complexing agent solution, in which the concentration of the precipitant is 0.1-10 M, the concentration of the complexing agent is 0.1-5 M, and the solvent is water.

[0035] In a second aspect, the present invention also provides a lithium-rich manganese-based positive electrode material precursor prepared by the above preparation method.

[0036] In a third aspect, the present invention also provides a method for preparing a lithium-rich manganese-based positive electrode material, the steps of which are as follows: uniformly mixing a lithium-rich manganese-based positive electrode material precursor and a lithium salt, heating and keeping warm in an oxygen-containing atmosphere to obtain a lithium-rich manganese-based positive electrode material.

[0037] Preferably, the lithium salt is one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalatoborate).

[0038] Preferably, the molar ratio of the lithium element in the lithium salt to the transition metal element in the lithium-rich manganese-based positive electrode material precursor is 1.25:0.8-1.12:0.8.

[0039] Preferably, the insulation temperature is 750-950° C., and the insulation time is 10-24 hours.

[0040] Preferably, the oxygen-containing atmosphere is one or both of air and oxygen.

[0041] In a fourth aspect, the present invention also provides a lithium-rich manganese-based positive electrode material prepared by the above preparation method.

[0042] The principle of the present invention is: in the preparation process of the lithium-rich manganese-based positive electrode material precursor of the present invention, the pH, temperature and stirring speed of the reaction system synergistically affect the process of transition metal element deposition. If the regulation causes nucleation to be much greater than growth, more small-sized primary particles will be produced. If the regulation causes growth to be much greater than nucleation, the primary particles will preferentially grow along the (001) crystal plane to increase the size, and the stacking mode of primary particles of different sizes is also different. The present invention controls the nucleation-growth process and stacking mode of the primary particles by feeding the liquid in stages, and then regulates the morphology of the secondary particles to obtain secondary particles with controllable particle size, moderate proportion of non-chemically active (003) crystal planes and primary particles (010) crystal planes facing outwards and oriented arrangement with nano-confined structures. The lithium-rich manganese-based positive electrode material inherits the morphology of the precursor, has a controllable particle size, a moderate proportion of non-chemically active (003) crystal planes and a special structure of primary particles (010) crystal planes facing outwards, improves the stability of the bulk structure, promotes the lithium ion mass transfer process, and ultimately improves the electrochemical properties of the lithium-rich manganese-based positive electrode material.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The lithium-rich manganese-based positive electrode material precursor of the present invention realizes controllable regulation of the precursor nucleation-growth process by repeatedly adjusting the process parameters during liquid feeding, thereby increasing the proportion of stable crystal planes, constructing directional fast ion mass transfer crystal planes and confined filling high specific surface area structures, and ultimately realizing the preparation of lithium-rich manganese-based positive electrode materials with both rate performance and high energy density performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 The precursor Mn prepared in Example 1 of the present invention 4 / 6 Ni 1 / 6 Co 1 / 6 SEM image of (OH)2;

[0047] Figure 2 This is a scanning electron microscope image of the lithium-rich manganese-based positive electrode material prepared in Example 1 of the present invention;

[0048] Figure 3 This is the rate performance of the lithium-rich manganese-based positive electrode material prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0049] In order to further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0050] The method for preparing a lithium-rich manganese-based positive electrode material precursor of the present invention comprises the following steps:

[0051] S1. Mixing the transition metal salt and water to obtain a transition metal salt solution;

[0052] S2. The precipitant and the complexing agent are mixed with water to obtain a precipitant solution and a complexing agent solution;

[0053] Alternatively, the precipitant and the complexing agent are mixed uniformly with water to obtain a precipitant-complexing agent solution;

[0054] S3. The pH of the bottom liquid in the reactor is regulated by using a precipitant solution, a complexing agent solution or a precipitant-complexing agent solution;

[0055] S4. Under the protection of an inert atmosphere, liquids are introduced into the reactor, wherein the liquids introduced are all transition metal salt solutions, precipitant solutions and complexing agent solutions, or the liquids introduced are all transition metal salt solutions and precipitant-complexing agent solutions, and the nucleation-growth process of the primary particles is regulated by dynamically adjusting the pH, temperature and stirring speed of the system, and the crystal plane orientation, particle size and stacking mode of the primary particles are controlled, thereby regulating the morphology of the secondary particles;

[0056] S5. After the liquid is added, aging;

[0057] S6. After aging, the lithium-rich manganese-based positive electrode material precursor is obtained through filtration, washing and drying.

[0058] In some embodiments, in step S1, the transition metal salt includes a manganese salt and one or more of a nickel salt and a cobalt salt; the manganese salt is one or more of a manganese nitrite, a manganese nitrate, a manganese sulfate, and a manganese acetate; the nickel salt is one or more of a nickel nitrite, a nickel nitrate, a nickel sulfate, and a nickel acetate; the cobalt salt is one or more of a cobalt nitrite, a cobalt nitrate, a cobalt sulfate, and a cobalt acetate. In the transition metal salt solution, the molar ratio of manganese, nickel, and cobalt is x:y:z, 1 / 3≤x<1, 0≤y≤1 / 2, 0≤z≤1 / 2. In the transition metal salt solution, the total concentration of the transition metal salt is 0.1-4M. Preferably, deionized water is used.

[0059] In some embodiments, in step S2, the precipitant is one or more of sodium hydroxide, sodium bicarbonate, sodium carbonate, and oxalic acid, and the complexing agent is one or more of EDTA, ammonia, citric acid, ammonium sulfate, and ammonium chloride; in the precipitant solution or the precipitant-complexing agent solution, the concentration of the precipitant is 0.1-10 M; in the complexing agent solution or the precipitant-complexing agent solution, the concentration of the complexing agent is 0.1-5 M. Preferably, the water is deionized water.

[0060] In some embodiments, in step S3, the base liquid contains additives, the addition amount is ≤5wt%, and the additives are one or more of polyethylene glycol, sodium dodecylbenzene sulfonate, ammonium dodecyl sulfate, and hexadecyldimethylammonium chloride.

[0061] In some embodiments, in step S3, the pH of the bottom liquid in the reaction kettle is adjusted to 7.3-12.0 using a precipitant solution, a complexing agent solution or a precipitant-complexing agent solution.

[0062] It should be noted that dynamically adjusting the pH, temperature and stirring speed of the system is the core innovation of the present invention. During this process, the system undergoes the following processes: ① regulating the pH, temperature and stirring speed so that nucleation is greater than growth, and primary particles are generated in the system. When it is observed that the primary particles are about to agglomerate, proceed to ②; ② regulating the pH, temperature and stirring speed (destroying the system equilibrium process) so that growth is greater than nucleation, prompting the primary particles to continue to grow along the (001) crystal plane until they begin to be radially arranged and stacked. If the particle size of the secondary particles does not reach the target requirement, proceed to ③. If the particle size of the secondary particles reaches the target requirement, , enter ④; ③ adjust pH, temperature and stirring speed (destroy system equilibrium process), and then adjust the growth rate of primary particles until the size of the secondary particles reaches the target requirement, enter ④; ④ adjust pH, temperature and stirring speed (destroy system equilibrium process), make nucleation greater than growth, until the confinement between the primary particle plates is filled with newly nucleated primary particles, observe that the surface of the secondary particles is dense, stop feeding, and obtain secondary particles with controllable particle size, moderate proportion of non-chemically active (003) crystal planes of primary particles, and (010) crystal planes facing outwards with nano-confined structure. The purpose of this dynamic adjustment can be divided into: ① control particle size, ② adjust the proportion of non-chemically active (003) crystal planes of primary particles, ③ adjust the directional arrangement of (010) crystal planes of primary particles facing outwards, and ④ confined filling of nanoparticles between primary particle plates. Among them, purpose ① can regulate the mass transfer path and mass transfer site, purpose ② can use the (003) crystal plane stability to regulate the material cycle stability, purpose ③ can construct a radial arrangement morphology of primary particles, and the (010) crystal plane directly contacts the electrolyte to promote the lithium ion mass transfer process, and purpose ④ can regulate the porosity between primary particles and improve the initial efficiency of the material.

[0063] In some embodiments, the preferred pH adjustment range is 7.3-12.0, the temperature adjustment range is 25-80°C, and the stirring speed adjustment range is 100-3000r / min; the precipitant solution and the complexing agent solution are fed separately or in combination; the inert atmosphere is one or both of nitrogen and argon.

[0064] In some embodiments, the pH, temperature and stirring speed of the dynamic adjustment system of the present invention are achieved by segmented liquid feeding, including but not limited to three to five stages, taking three-stage segmented liquid feeding as an example: that is, in the first stage of liquid feeding, a certain pH, temperature and stirring speed are maintained, and part of the transition metal salt solution, the precipitant solution and the complexing agent solution (or the precipitant-complexing agent solution) are passed into the reactor until the first stage of liquid feeding is completed; in the second stage of liquid feeding, a certain pH, temperature and stirring speed are maintained, and part of the transition metal salt solution, the precipitant solution and the complexing agent solution (or the precipitant-complexing agent solution) are passed into the reactor until the second stage of liquid feeding is completed; in the third stage of liquid feeding, a certain pH, temperature and stirring speed are maintained, and part of the transition metal salt solution, the precipitant solution and the complexing agent solution (or the precipitant-complexing agent solution) are passed into the reactor until the third stage of liquid feeding is completed.

[0065] In some embodiments, in step S4, three stages of liquid inflow are adopted. During the first stage of liquid inflow, the stirring speed is set to 1500 rpm, the pH value is maintained at 10.3, and the temperature is 60°C; during the second stage of liquid inflow, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.7, and the temperature is 50°C; during the third stage of liquid inflow, the stirring speed is set to 750 rpm, the pH value is maintained at 10.7, and the temperature is 50°C;

[0066] Alternatively, three-stage liquid inlet is used. During the first stage of liquid inlet, the stirring speed is set to 1500 rpm, the pH value is maintained at 7.6, and the temperature is 50°C; during the second stage of liquid inlet, the stirring speed is set to 1000 rpm, the pH value is maintained at 7.8, and the temperature is 40°C; during the third stage of liquid inlet, the stirring speed is set to 500 rpm, the pH value is maintained at 8.0, and the temperature is 45°C;

[0067] Alternatively, three-stage liquid inlet is adopted. During the first stage of liquid inlet, the stirring speed is set to 2000 rpm, the pH value is maintained at 10.5, and the temperature is 50°C; during the second stage of liquid inlet, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.5, and the temperature is 50°C; during the third stage of liquid inlet, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.7, and the temperature is 50°C;

[0068] Alternatively, a four-stage liquid inlet is used. During the first stage of liquid inlet, the stirring speed is set to 1500 rpm, the pH value is maintained at 10.3, and the temperature is 50°C; during the second stage of liquid inlet, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.5, and the temperature is 45°C; during the third stage of liquid inlet, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.3, and the temperature is 45°C; during the fourth stage of liquid inlet, the stirring speed is set to 500 rpm, the pH value is maintained at 10.7, and the temperature is 40°C;

[0069] Alternatively, a five-stage liquid inlet is adopted: during the first stage of liquid inlet, the stirring speed is set to 1500 rpm, the pH value is maintained at 10.3, and the temperature is 55°C; during the second stage of liquid inlet, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.3, and the temperature is 50°C; during the third stage of liquid inlet, the stirring speed is set to 500 rpm, the pH value is maintained at 10.5, and the temperature is 50°C; during the fourth stage of liquid inlet, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.7, and the temperature is 45°C; during the fifth stage of liquid inlet, the stirring speed is set to 500 rpm, the pH value is maintained at 10.9, and the temperature is 45°C.

[0070] In some embodiments, in step S5, the aging pH is 7.3-12.0, the temperature is 25-80° C., the stirring speed is 100-3000 r / min, and the time is 1-24 h.

[0071] The lithium-rich manganese-based positive electrode material precursor prepared by the preparation method of the present invention can be used to prepare lithium-rich manganese-based positive electrode materials.

[0072] The preparation method of the lithium-rich manganese-based positive electrode material of the present invention comprises the following steps: uniformly mixing a lithium-rich manganese-based positive electrode material precursor and a lithium salt, and heating and heat preservation in an oxygen-containing atmosphere to obtain the lithium-rich manganese-based positive electrode material.

[0073] In some embodiments, the lithium salt is one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium dioxalatoborate; the molar ratio of the lithium element in the lithium salt to the transition metal element in the lithium-rich manganese-based positive electrode material precursor is 1.25:0.8-1.12:0.8.

[0074] In some embodiments, the insulation temperature is 750-950° C., and the insulation time is 10-24 h.

[0075] In some embodiments, the oxygen-containing atmosphere is one or both of air and oxygen.

[0076] The lithium-rich manganese-based positive electrode material prepared by the preparation method of the present invention has both rate performance and high energy density performance.

[0077] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments.

[0078] In the following examples, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, devices, instruments, equipment, etc. used in the following examples can be obtained from commercial sources.

[0079] Example 1

[0080] MnSO4·H2O, NiSO4·6H2O and CoSO4·7H2O were dissolved in deionized water at a molar ratio of Mn:Ni:Co=4:1:1 to prepare a 1.5 mol / L mixed uniform transition metal salt solution, which was kept warm to 50°C in advance;

[0081] Dissolve the coprecipitant NaOH and the complexing agent NH3·H2O in deionized water to prepare a mixed uniform solution of 2.0 mol / L NaOH and 0.5 mol / L NH3·H2O, and keep the temperature at 50°C in advance;

[0082] Add 200 mL of deionized water and 0.5 wt% of PEG to the reactor, and add an appropriate amount of precipitant-complexing agent solution to adjust the pH value to 10.3, and keep the temperature at 50 °C in advance;

[0083] Nitrogen was introduced as protective gas 20 minutes in advance;

[0084] The transition metal salt solution and the precipitant-complexing agent mixed solution are pumped into the coprecipitation reactor at the same time, and the liquid is fed in four stages: during the first stage of liquid feeding, the stirring speed is set to 1500 rpm, the pH value is maintained at 10.3, and the temperature is 50°C; during the second stage of liquid feeding, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.5, and the temperature is 45°C; during the third stage of liquid feeding, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.3, and the temperature is 45°C; during the fourth stage of liquid feeding, the stirring speed is set to 500 rpm, the pH value is maintained at 10.7, and the temperature is 40°C;

[0085] After the liquid was added, aging was carried out, and the aging parameters were pH 10.7, temperature 40°C, stirring speed 500r / min, and time 24h;

[0086] After aging, the mother liquor was filtered, washed and dried at 120 ° C for 24 h to obtain a three-in-one precursor Mn with oriented crystal plane arrangement, high stable crystal plane ratio and confined filling structure. 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2, SEM image Figure 1 As shown;

[0087] The precursor Mn 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2 and lithium carbonate (Li:TM=1.15:0.8, TM represents transition metal element) powders were mixed evenly, and then kept at 850℃ for 15h to obtain high-performance lithium-rich manganese-based positive electrode materials. The scanning electron microscope image is shown in Figure 2 shown.

[0088] from Figure 1 and Figure 2 It is explained that the present invention controls the nucleation-growth process and stacking mode of the primary particles through a dynamic adjustment system, thereby regulating the morphology of the secondary particles, and obtaining a precursor with a nano-confined filling structure having a controllable particle size, a moderate proportion of non-chemically active (003) crystal planes, and primary particles with (010) crystal planes oriented outward. The lithium-rich manganese-based positive electrode material inherits the morphology of the precursor and has a special structure with a controllable particle size, a moderate proportion of non-chemically active (003) crystal planes, and primary particles with (010) crystal planes oriented outward.

[0089] The lithium-rich manganese-based positive electrode material was assembled into a 2032 half-cell for testing. When cycled at a 5C rate, the discharge capacity of the lithium-rich manganese-based positive electrode material was 180mAh / g; after 200 cycles, the capacity retention rate was 93.2%.

[0090] Example 2

[0091] MnSO4·H2O, NiSO4·6H2O and CoSO4·7H2O were dissolved in deionized water at a molar ratio of Mn:Ni:Co=4:1:1 to prepare a 2.0 mol / L mixed uniform transition metal salt solution, which was kept warm to 55°C in advance;

[0092] Dissolve the coprecipitant NaOH and the complexing agent NH3·H2O in deionized water to prepare a mixed uniform solution of 2.0 mol / L NaOH and 1.0 mol / L NH3·H2O, and keep the temperature at 55°C in advance;

[0093] Add 200 mL of deionized water to the reactor, add an appropriate amount of precipitant-complexing agent solution to adjust the pH value to 10.3, and keep the temperature at 55°C in advance;

[0094] Nitrogen was introduced as protective gas 20 minutes in advance;

[0095] The transition metal salt solution and the precipitant-complexing agent mixed solution were simultaneously pumped into the coprecipitation reactor, and the liquid was fed in three stages: during the first stage of liquid feeding, the stirring speed was set to 1500 rpm, the pH value was maintained at 10.3, and the temperature was 60°C; during the second stage of liquid feeding, the stirring speed was set to 1000 rpm, the pH value was maintained at 10.7, and the temperature was 50°C; during the third stage of liquid feeding, the stirring speed was set to 750 rpm, the pH value was maintained at 10.7, and the temperature was 50°C;

[0096] After the liquid was added, aging was carried out, and the aging parameters were pH 10.8, temperature 45°C, stirring speed 1000r / min, and time 4h;

[0097] After aging, the mother liquor was filtered, washed and dried at 120 °C for 24 h to obtain a three-in-one precursor Mn with oriented crystal plane arrangement, high stable crystal plane ratio and confined filling structure. 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2;

[0098] The precursor Mn 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2 and lithium carbonate (Li:TM=1.15:0.8) powders were mixed evenly and then kept at 850°C for 15h to obtain a high-performance lithium-rich manganese-based positive electrode material.

[0099] The lithium-rich manganese-based positive electrode material was assembled into a 2032 half-cell for testing. The first-cycle discharge capacity was 268 mAh / g when activated at 0.1C. After 200 cycles at 1C, the capacity retention rate was 89.6%, and the discharge capacity at 5C was 178 mAh / g.

[0100] Example 3

[0101] MnSO4·H2O, NiSO4·6H2O and CoSO4·7H2O were dissolved in deionized water at a molar ratio of Mn:Ni:Co=4:1:1 to prepare a 0.5 mol / L mixed uniform transition metal salt solution, which was kept warm to 50°C in advance;

[0102] Dissolve the coprecipitant NaOH and the complexing agent NH3·H2O in deionized water to prepare a mixed uniform solution of 2.0 mol / L NaOH and 0.4 mol / L NH3·H2O, and keep the temperature at 50°C in advance;

[0103] Add 200 mL of deionized water and 0.1 wt% of sodium dodecylbenzene sulfonate to the reactor, and add an appropriate amount of precipitant-complexing agent solution to adjust the pH value to 10.3, and keep the temperature at 50 °C in advance;

[0104] Nitrogen was introduced as protective gas 20 minutes in advance;

[0105] The transition metal salt solution and the precipitant-complexing agent mixed solution are pumped into the coprecipitation reactor at the same time, and the liquid is fed in five stages: when the liquid is fed in the first stage, the stirring speed is set to 1500 rpm, the pH value is maintained at 10.3, and the temperature is 55°C; when the liquid is fed in the second stage, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.3, and the temperature is 50°C; when the liquid is fed in the third stage, the stirring speed is set to 500 rpm, the pH value is maintained at 10.5, and the temperature is 50°C; when the liquid is fed in the fourth stage, the stirring speed is set to 1000 rpm, the pH value is maintained at 10.7, and the temperature is 45°C; when the liquid is fed in the fifth stage, the stirring speed is set to 500 rpm, the pH value is maintained at 10.9, and the temperature is 45°C;

[0106] After the liquid was added, aging was carried out, and the aging parameters were pH 11.0, temperature 45°C, stirring speed 2000r / min, and time 24h;

[0107] After aging, the mother liquor was filtered, washed and dried at 120 °C for 24 h to obtain a three-in-one precursor Mn with oriented crystal plane arrangement, high stable crystal plane ratio and confined filling structure. 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2;

[0108] The precursor Mn 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2 and lithium carbonate (Li:TM=1.15:0.8) powders were mixed evenly and then kept at 850°C for 15h to obtain a high-performance lithium-rich manganese-based positive electrode material.

[0109] The lithium-rich manganese-based cathode material was assembled into a 2032 half-cell for testing, and its rate performance was shown in Figure 3 .

[0110] Example 4

[0111] Mn(NO3)2, Ni(NO3)2 and Co(NO3)2 were dissolved in deionized water at a molar ratio of Mn:Ni:Co=4:1:1 to prepare a 3.0 mol / L mixed uniform transition metal salt solution, which was kept warm to 60°C in advance;

[0112] Dissolve the coprecipitant NaOH and the complexing agent NH3·H2O in deionized water to prepare a mixed uniform solution of 1.0 mol / L NaOH and 0.8 mol / L NH3·H2O, and keep the temperature at 60°C in advance;

[0113] Add 200 mL of deionized water and 0.1 wt% of EDTA to the reactor, and add an appropriate amount of precipitant-complexing agent solution to adjust the pH value to 10.5, and keep the temperature at 60 °C in advance;

[0114] Nitrogen was introduced as protective gas 20 minutes in advance;

[0115] The transition metal salt solution and the precipitant-complexing agent mixed solution were simultaneously pumped into the coprecipitation reactor, and the liquid was fed in three stages: during the first stage of liquid feeding, the stirring speed was set to 2000 rpm, the pH value was maintained at 10.5, and the temperature was 50°C; during the second stage of liquid feeding, the stirring speed was set to 1000 rpm, the pH value was maintained at 10.5, and the temperature was 50°C; during the third stage of liquid feeding, the stirring speed was set to 1000 rpm, the pH value was maintained at 10.7, and the temperature was 50°C;

[0116] After the liquid was added, aging was carried out, and the aging parameters were pH 10.7, temperature 55°C, stirring speed 3000r / min, and time 1h;

[0117] After aging, the mother liquor was filtered, washed and dried at 120 ° C for 20 h to obtain a three-in-one precursor Mn with oriented crystal plane arrangement, high stable crystal plane ratio and confined filling structure. 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2;

[0118] The precursor Mn 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2 and lithium carbonate (Li:TM=1.20:0.8) powders were mixed evenly and then kept at 900°C for 15h to obtain a high-performance lithium-rich manganese-based positive electrode material.

[0119] Example 5

[0120] MnSO4·H2O, NiSO4·6H2O and CoSO4·7H2O were dissolved in deionized water at a molar ratio of Mn:Ni:Co=4:1:1 to prepare a 1.0 mol / L mixed uniform transition metal salt solution, which was kept warm to 50°C in advance;

[0121] Dissolve the coprecipitant Na2CO3 and the complexing agent NH3·H2O in deionized water to prepare a mixed uniform solution of 2.0 mol / L Na2CO3 and 0.5 mol / L NH3·H2O, and keep the temperature at 50°C in advance;

[0122] Add 200 mL of deionized water to the reactor, and add an appropriate amount of precipitant-complexing agent solution to adjust the pH value to 7.6, and keep the temperature at 50°C in advance;

[0123] Nitrogen was introduced as protective gas 20 minutes in advance;

[0124] The transition metal salt solution and the precipitant-complexing agent mixed solution were simultaneously pumped into the coprecipitation reactor, and the liquid was fed in three stages: during the first stage of liquid feeding, the stirring speed was set to 1500 rpm, the pH value was maintained at 7.6, and the temperature was 50°C; during the second stage of liquid feeding, the stirring speed was set to 1000 rpm, the pH value was maintained at 7.8, and the temperature was 40°C; during the third stage of liquid feeding, the stirring speed was set to 500 rpm, the pH value was maintained at 8.0, and the temperature was 45°C;

[0125] After the liquid was added, aging was carried out, and the aging parameters were pH 8.0, temperature 45°C, stirring speed 500r / min, and time 24h;

[0126] After aging, the mother liquor was filtered, washed and dried at 120 °C for 24 h to obtain a three-in-one precursor Mn with oriented crystal plane arrangement, high stable crystal plane ratio and confined filling structure. 4 / 6 Ni 1 / 6 Co 1 / 6 CO3;

[0127] The precursor Mn 4 / 6 Ni 1 / 6 Co 1 / 6 CO3 and lithium carbonate (Li:TM=1.14:0.8) powders were mixed evenly and then kept at 850°C for 15h to obtain a high-performance lithium-rich manganese-based positive electrode material.

[0128] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A method for preparing a lithium-rich manganese-based positive electrode material precursor, characterized in that: The following steps are involved: S1. mixing a transition metal salt and water to obtain a transition metal salt solution, wherein the transition metal salt includes a manganese salt; S2. The precipitant and the complexing agent are mixed with water to obtain a precipitant solution and a complexing agent solution; S3. Using a precipitant solution and a complexing agent solution to control the pH of the bottom liquid in the reactor; S4. Under the protection of an inert atmosphere, liquids are introduced into the reactor, wherein the liquids are transition metal salt solution, precipitant solution and complexing agent solution. During the liquid introduction process, the nucleation-growth process of the primary particles is regulated by dynamically adjusting the pH, temperature and stirring speed of the system, and the crystal plane orientation, particle size and stacking mode of the primary particles are controlled, thereby regulating the morphology of the secondary particles; S5. After the liquid is added, aging; S6. After aging, the precursor of the lithium-rich manganese-based positive electrode material is obtained by filtration, washing and drying; Among them, in step S4, the process of dynamically adjusting the pH, temperature and stirring speed of the system to adjust the nucleation-growth process of the primary particles, control the crystal plane orientation, particle size and stacking mode of the primary particles, and then regulate the morphology of the secondary particles is: ① Regulate pH, temperature and stirring speed to make nucleation greater than growth and generate primary particles in the system. When it is observed that the primary particles are about to agglomerate, proceed to ②; ② Regulate pH, temperature and stirring speed to make the growth greater than the nucleation, so that the primary particles continue to grow along the (001) crystal plane until they begin to be radially arranged and stacked. If the size of the secondary particles does not reach the target requirement, proceed to step ③. If the size of the secondary particles reaches the target requirement, proceed to step ④. ③ Regulate pH, temperature and stirring speed, and then regulate the growth rate of primary particles until the particle size of the secondary particles reaches the target requirement, and then enter ④; ④ Regulate the pH, temperature and stirring speed to make nucleation greater than growth, until the confinements between the primary particle plates are filled with newly nucleated primary particles, and the surface of the secondary particles is observed to be dense. Stop adding liquid to obtain secondary particles with controllable particle size, a moderate proportion of chemically non-active (003) crystal faces of the primary particles, and (010) crystal faces oriented outward with a nano-confinement structure.

2. The method for preparing a lithium-rich manganese-based positive electrode material precursor according to claim 1, characterized in that: In step S1, the transition metal salt further comprises one or more of a nickel salt and a cobalt salt; the manganese salt is one or more of a manganese nitrite, a manganese nitrate, a manganese sulfate, and a manganese acetate; the nickel salt is one or more of a nickel nitrite, a nickel nitrate, a nickel sulfate, and a nickel acetate; the cobalt salt is one or more of a cobalt nitrite, a cobalt nitrate, a cobalt sulfate, and a cobalt acetate; in the transition metal salt solution, the total concentration of the transition metal salt is 0.1-4M, and the molar ratio of manganese, nickel, and cobalt is x:y:z, 1 / 3≤x<1, 0≤y≤1 / 2, 0≤z≤1 / 2; In step S2, the precipitant is one or more of sodium hydroxide, sodium bicarbonate, sodium carbonate, and oxalic acid; in the precipitant solution, the concentration of the precipitant is 0.1-10M; The complexing agent is one or more of ethylenediaminetetraacetic acid, ammonia water, citric acid, ammonium sulfate and ammonium chloride; in the complexing agent solution, the concentration of the complexing agent is 0.1-5M.

3. The method for preparing a lithium-rich manganese-based positive electrode material precursor according to claim 1, characterized in that: In step S2, the base liquid contains ≤5wt% of additives, and the additives are one or more of polyethylene glycol, sodium dodecylbenzene sulfonate, ammonium dodecyl sulfate, and hexadecyldimethylammonium chloride.

4. The method for preparing a lithium-rich manganese-based positive electrode material precursor according to claim 1, characterized in that: In step S3, the pH of the bottom liquid in the reaction kettle is regulated to be 7.3-12.0 using a precipitant solution and a complexing agent solution; In step S4, the inert atmosphere is one or both of nitrogen and argon; The precipitant solution and the complexing agent solution are fed separately or in combination; The pH adjustment range is 7.3-12.0, the temperature adjustment range is 25-80°C, and the stirring speed adjustment range is 100-3000r / min; In step S5, the aging pH is 7.3-12.0, the temperature is 25-80°C, the stirring speed is 100-3000r / min, and the time is 1-24h.

5. The method for preparing a lithium-rich manganese-based positive electrode material precursor according to claim 1, characterized in that: The precipitant solution and the complexing agent solution are replaced with a precipitant-complexing agent solution, wherein the concentration of the precipitant is 0.1-10 M, the concentration of the complexing agent is 0.1-5 M, and the solvent is water.

6. A lithium-rich manganese-based positive electrode material precursor prepared according to the preparation method according to any one of claims 1 to 5.

7. A method for preparing a lithium-rich manganese-based positive electrode material using the lithium-rich manganese-based positive electrode material precursor according to claim 6, characterized in that: The lithium-rich manganese-based positive electrode material precursor and the lithium salt are evenly mixed, and heated and kept warm in an oxygen-containing atmosphere to obtain the lithium-rich manganese-based positive electrode material.

8. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 7, characterized in that: The lithium salt is one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalatoborate); The molar ratio of the lithium element in the lithium salt to the transition metal element in the lithium-rich manganese-based positive electrode material precursor is 1.25:0.8-1.12:0.8; The insulation temperature is 750-950°C and the insulation time is 10-24h; The oxygen-containing atmosphere is one or both of air and oxygen.

9. The lithium-rich manganese-based positive electrode material prepared by the method for preparing a lithium-rich manganese-based positive electrode material according to claim 7.

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