Lithium-rich manganese-based precursor and preparation method thereof, lithium-rich manganese-based positive electrode material, and lithium-ion battery

Abstract

The present invention provides a lithium-rich manganese-based precursor, which is a spherical or quasi-spherical secondary particle formed by agglomeration of primary particles. The precursor has good sphericity and comprises an inner core and an outer shell. The diameter of the primary particle of the inner core is 0.1-30 nm, the diameter of the primary particle of the outer shell is 60-200 nm, the particle size D50 of the secondary particle is 2.5-8.0 μm, the particle size interval is narrow, and the specific surface area is 15-35 m 2 / g, tap density is 1.0~1.7g / cm 3 . A preparation method of the precursor is also provided, which can synthesize a lithium-rich manganese-based precursor material with high sphericity, loose and porous structure, a large proportion of inner core, and uniform distribution of primary particles and secondary particles, which is helpful to improve the storage and release capacity of lithium ions in the positive electrode material, improve the capacity and cycle performance of the battery, and compared with the existing synthesis process, this method can save the wastewater ammonia nitrogen treatment process, reduce the cumbersome process, reduce energy consumption and production costs, and facilitate industrial application.

Description

Technical Field

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

[0002] With the rapid development of social economy, industries such as portable electronic devices and electric vehicles have put forward higher and higher requirements for energy storage equipment. As a new type of energy battery with high energy storage, green environmental protection and long cycle life, lithium-ion batteries have attracted the keen attention of many scientific workers. However, the more mature lithium battery positive electrode materials, such as lithium cobalt oxide layered materials, spinel phase lithium manganese oxide, olivine phase lithium iron phosphate and ternary NCM positive electrode materials, cannot meet the industry's high specific energy requirements for lithium-ion batteries (about 400Wh / Kg). Therefore, we urgently need to find a new positive electrode material with high specific energy, long life and environmental friendliness.

[0003] Lithium-rich manganese-based layered cathode material Li[Li 1-x-y Ni x Co y Mn z ]O2 has become the most promising lithium battery positive electrode material due to its high specific capacity (>250mAh / g), high platform voltage (up to 4.5V), low cost, high capacity, non-toxic and safe advantages. Lithium-rich materials are mainly composed of two parts, namely LiMO2 of R3-m space group and Li2MnO3 belonging to C / 2m space group. As the main component of the positive electrode material, the morphology and structure of the lithium-rich manganese-based precursor have an important influence on the structure and electrical properties of the positive electrode material. At present, the synthesis methods of lithium-rich manganese-based materials mainly include high-temperature solid phase method, sol-gel method, hydrothermal method, spray drying method, co-precipitation-sintering method, etc. Among them, the lithium-rich manganese-based precursor is prepared by co-precipitation reaction, and the material prepared by high-temperature lithiation co-precipitation-sintering method has uniform chemical composition, excellent and controllable morphology, uniform particle size distribution, and stable electrochemical performance. This method is simple and easy to scale up, and is highly consistent with the preparation technology of lithium-ion battery ternary positive electrode materials. It is an ideal choice for large-scale preparation of lithium-rich manganese-based materials.

[0004] However, it is difficult to synthesize lithium-rich manganese-based hydroxide precursors by coprecipitation, and it is easy to form too much solid solution Li2MnO3 phase, resulting in low capacity of lithium-rich manganese-based positive electrode materials. The general improvement measures are to start with improving the synthesis process, but it is difficult to obtain a morphology with good sphericity. Patent document CN 113998743 A discloses a manganese-rich hydroxide precursor and its preparation method and application, which mainly avoids the oxidation of manganese by dissolved oxygen in the raw materials by adding organic additives such as sodium borohydride, formaldehyde, sodium sulfite, etc. to the raw materials, ensuring that MnOOH is not generated during the synthesis process, and obtaining a non-oxidized high-capacity manganese-rich hydroxide precursor. However, the above-mentioned additives can strongly irritate human mucous membranes, upper respiratory tract, eyes and skin, easily causing harm to the human body, and can also cause harm to the environment during post-processing, which is not conducive to the industrial application of the product. In addition, the patent document discloses that in the synthesis process, the morphology of the precursor needs to be better controlled by adding a complexing agent ammonia water, and the ammonia water concentration is 5~25%. The high ammonia water concentration makes the post-processing process complicated.

[0005] CN 116605921 A discloses a lithium-rich manganese-based positive electrode precursor and its preparation method and application. The morphology and structure of the precursor are mainly controlled by two process means, namely, step-by-step precipitation and surface doping, so as to improve the thermal stability of the lithium-rich positive electrode material, reduce impedance, improve charge transfer ability, and thus improve cycle performance and rate performance. From the morphology disclosed in the patent document, it can be seen that the process does achieve morphology control, but the particle size of the synthesized product is large, the synthesis cycle is long, the step-by-step precipitation process is difficult, and two complexing agents, ammonia water and oxalic acid, are used for morphology control, which increases the difficulty of the entire precursor production process.

[0006] Therefore, it is crucial to develop a method for preparing lithium-rich manganese-based precursors that can be mass-produced, low-carbon and environmentally friendly, and has simple synthetic process control. Summary of the invention

[0007] In view of the above technical problems, the present invention provides a lithium-rich manganese-based precursor and a preparation method thereof, a lithium-rich manganese-based positive electrode material, and a lithium-ion battery.

[0008] To achieve the above object, the present invention proposes the following solution:

[0009] A lithium-rich manganese-based precursor, the chemical formula of which is Ni x Co y Mn z(OH)2, wherein 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.8, x+y+z=1, the precursor is a spherical or quasi-spherical secondary particle formed by the aggregation of primary particles, the sphericity Φ of the precursor is 1.2-1.8, wherein Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, and Dc is the minimum inscribed sphere radius of the same particle; the precursor comprises an inner core and an outer shell, the primary particle diameter of the inner core is 0.1-30nm, the primary particle diameter of the outer shell is 60-200nm, the secondary particles are loose and porous, the particle size D50 of the secondary particles is 2.5-8.0μm, the particle size distance is 0.60<(D90-D10) / D50<0.9, and the specific surface area is 15-35m 2 / g, tap density is 1.0~1.7g / cm 3 .

[0010] Preferably, the porosity of the outer wall is lower than that of the inner core.

[0011] Preferably, the sphericity of the precursor is 1.3 to 1.6.

[0012] Preferably, the volume proportion of the inner core of the precursor is 50 to 80%, more preferably 65 to 80%, and further preferably 65 to 75.5%.

[0013] As a general inventive concept, the present invention also provides a method for preparing a lithium-rich manganese-based precursor, comprising:

[0014] (1) In the presence of a non-oxidizing gas, a mixed metal salt solution and a precipitant solution are introduced into the bottom liquid of a reaction kettle in parallel to perform a coprecipitation reaction; the mixed metal salt solution is a solution of the general formula Ni x Co y Mn z A nickel-cobalt-manganese mixed metal salt solution prepared by (OH)2, wherein 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.7, x+y+z=1;

[0015] The coprecipitation reaction includes a nucleation stage and a particle growth stage. In the nucleation stage, the mixed metal salt solution is introduced at a flow rate of 5-15% / h of the reactor volume, and the pH value of the reaction system is controlled to be 11.0-12.0;

[0016] During the particle growth reaction, the pH value of the reaction system is controlled to be 9.5-10.5, and the flow rate of the mixed metal salt solution is increased in the late stage of the particle growth stage, and the reaction is continued until the reaction slurry reaches the target particle size; wherein, before the particle growth reaction is carried out, the pH value of the reaction system is adjusted to be linearly reduced to 9.5-10.5, and the rate of change of the linear reduction of the pH value of the reaction system is adjusted to V, 0.01 / min≤V≤0.05 / min;

[0017] (2) The obtained reaction slurry is subjected to solid-liquid separation, and the obtained solid phase is aged, washed, dried, and sieved to obtain a precursor.

[0018] Preferably, in step (1), the flow rate of the mixed metal salt solution is increased 1 to 4 times.

[0019] Preferably, in step (1), the single increase in the flow rate of the mixed metal salt solution is 5 to 30% of the flow rate of the mixed metal salt solution in the nucleation stage.

[0020] Preferably, in step (1), the total reaction time after the flow rate of the mixed metal salt solution is increased for the first time accounts for 40 to 70% of the total coprecipitation reaction time.

[0021] Preferably, in step (1), during the particle growth stage, before increasing the flow rate of the mixed metal salt solution, the mixed metal salt solution is introduced into the reactor at a flow rate of 5 to 15% of the volume of the reactor per hour.

[0022] Preferably, in step (1), the target particle size D50 is 2.5 to 8.0 μm.

[0023] Preferably, in step (1), during the particle growth stage, the pH is reduced to 9.8-10.2.

[0024] Preferably, in step (1), the total synthesis time of the coprecipitation reaction is 15 to 60 hours.

[0025] Preferably, in step (1), the duration of the nucleation stage is 20 to 60 minutes.

[0026] Preferably, in step (1), the particle growth phase lasts for 14 to 60 hours.

[0027] Preferably, in step (1), the temperature of the coprecipitation reaction is 45-65°C.

[0028] Preferably, in step (1), the method further comprises: preparing a reaction kettle bottom liquid, and introducing a non-oxidizing gas during the preparation of the reaction kettle bottom liquid.

[0029] Preferably, in step (1), during the preparation of the reactor bottom liquid and the coprecipitation reaction, the non-oxidizing gas is a nitrogen atmosphere, and the nitrogen flow rate is 8 to 60 L / h.

[0030] Preferably, the volume of pure water in the reactor bottom liquid is 15-35% of the volume of the reactor.

[0031] Preferably, the pH value of the reaction kettle bottom liquid is 11.0-12.0.

[0032] Preferably, the temperature of the bottom liquid of the reaction kettle is 45-65°C.

[0033] Preferably, the reaction kettle bottom liquid is prepared by pure water and alkali.

[0034] Preferably, in the mixed metal salt solution, the total metal ion concentration is 1.8 to 2.2 mol / L.

[0035] Preferably, the precipitant solution is an alkaline solution; the concentration of the alkaline solution is 3 to 11 mol / L;

[0036] Preferably, the alkaline solution is a sodium hydroxide solution.

[0037] Preferably, a dilute acid solution is used to adjust the pH value of the reaction system to decrease linearly; preferably, the dilute acid solution is a hydrochloric acid solution and / or a sulfuric acid solution; further preferably, the concentration of the dilute acid solution is 0.1 to 1 mol / L; preferably, the concentration of the dilute acid solution is 0.1 to 0.5 mol / L.

[0038] As a general inventive concept, the present invention also provides a lithium-rich manganese-based positive electrode material, which is obtained by mixing the aforementioned lithium-rich manganese-based precursor or the lithium-rich manganese-based precursor prepared by the aforementioned preparation method with a lithium source and then sintering;

[0039] Or the lithium-rich manganese-based precursor or the lithium-rich manganese-based precursor prepared by the aforementioned preparation method is mixed with a lithium source and an additive and then sintered;

[0040] The chemical formula of the lithium-rich manganese-based positive electrode material is Li 1+a Ni x Co y Mn z O2, where 0.3≤a≤0.5, 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.8, x+y+z=1.

[0041] As a general inventive concept, the present invention provides a lithium-ion battery comprising the aforementioned lithium-rich manganese-based positive electrode material.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The preparation method of the present invention can synthesize a lithium-rich manganese-based precursor material with high sphericity, loose and porous structure, a large proportion of inner core, good primary particle consistency, and uniform secondary particle distribution, which is helpful to improve the lithium ion storage and release capacity in the positive electrode material, and improve the capacity and cycle performance of the battery. Compared with the existing synthesis process, since the complexing agent ammonia water is not used in the synthesis process, the wastewater ammonia nitrogen treatment process is also omitted in the post-treatment process, which reduces the complicated process and high energy consumption in the industrial production process, reduces the production cost, and is convenient for industrial application.

[0044] 2. The preparation method of the present invention reasonably regulates the linear decrease of pH value during the co-precipitation process of preparing lithium-rich manganese-based precursors, so as to control the linear change of the growth rate of primary particles and secondary particles, which is beneficial to improve the consistency of primary particles of the material and improve the phenomenon of precursor morphology agglomeration and poor particle consistency caused by the wide diameter distance of the precursor, thereby improving the morphology structure of the lithium-rich manganese-based precursor.

[0045] 3. The present invention controls nucleation and growth in two stages. In the nucleation stage, the amount of nucleation is controlled by reasonably controlling the flow rate of metal salts and the pH value. At the same time, when the pH is at a high level, a weak acid is used to lower the pH, thereby reducing the risk of secondary nucleation when the pH changes from a high level to a low level above the seeding point, and better controlling the growth cycle of the synthesis; in addition, a low-carbon, clean and environmentally friendly preparation process is adopted in the entire synthesis process, reducing the use of complexing agent ammonia water, achieving a breakthrough innovation in the co-precipitation process of the lithium-rich manganese-based precursor, and reducing the production cost in the synthesis process; in addition, a weak acid is used to lower the pH in the high pH stage, and the nucleation stage and the particle growth stage are clearly separated to effectively improve the diameter distribution of the particle size, so that the particle size distribution of the lithium-rich manganese-based positive electrode material is uniform, which is more conducive to improving the Li in the lithium-rich manganese-based positive electrode material. + The migration ability of ions can improve the capacity characteristics of lithium-rich manganese-based cathode materials, and the voltage applied to each particle is relatively uniform, which is more conducive to improving the cycle and rate performance of lithium-rich manganese-based cathode materials. And by optimizing the flow of metal salts at each stage, it is beneficial to further improve the sphericity of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are 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.

[0047] Figure 1 The Ni prepared in Example 1 0.25 Mn 0.75 Morphology and cross-sectional electron microscope images of (OH)2 precursor.

[0048] Figure 2 The Ni prepared in Example 2 0.25 Co 0.9 Mn 0.66 Morphology and cross-sectional electron microscope images of (OH)2 precursor.

[0049] Figure 3 The Ni prepared in Example 4 and Comparative Example 1 0.25 Mn 0.75 SEM images of (OH)2 precursors, where (a) is the SEM image of the precursor of Example 4, and (b) is the SEM image of the precursor of Comparative Example 1.

[0050] Figure 4 The first charge-discharge curves and cycle performance diagrams of the positive electrode materials prepared from the precursors of Example 4 and Comparative Example 1, where (a) is the first charge-discharge curve and (b) is the cycle performance diagram. DETAILED DESCRIPTION

[0051] Some embodiments of the present invention provide a lithium-rich manganese-based precursor, the chemical formula of which is Ni x Co y Mn z(OH)2, wherein 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.8, further preferably 0.6≤z≤0.8, x+y+z=1, the precursor is a spherical or quasi-spherical secondary particle formed by the agglomeration of primary particles, the sphericity index Φ of the precursor is 1.2-1.8, for example, it can be 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, wherein Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, Dc is the minimum inscribed sphere radius of the same particle, the precursor comprises an inner core and an outer shell, the primary particle diameter of the inner core is 0.1-30nm, for example, it can be 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, etc., the primary particle diameter of the outer shell is 6 0 to 200 nm, for example, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, etc. The secondary particles are loose and porous, and the particle size D5 of the secondary particles is 0 is 2.5 to 8.0 μm, for example, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, the particle size distance is 0.60 < (D90-D10) / D50 < 0.9, for example, 0.65, 0.70, 0.75, 0.80, 0.85, etc., and the specific surface area is 15 to 35 m 2 / g, for example 15m 2 / g, 18m 2 / g, 20m 2 / g, 22m 2 / g, 25m 2 / g, 28m 2 / g, 30m 2 / g, 32m 2 / g, 35m 2 / g, etc., and the tap density is 1.0~1.7g / cm 3 , for example 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 wait.

[0052] According to a particularly preferred embodiment of the present invention, the sphericity of the precursor is 1.3 to 1.6.

[0053] In some preferred embodiments, the volume proportion of the precursor core is 50-80%, for example, 50%, 52%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, etc. The precursor provided by the present invention has the characteristics of loose and porous core and relatively dense outer wall, and the relatively dense outer wall means that compared with the core, the primary particles of the outer wall are more densely stacked and the looseness is lower than that of the core.

[0054] According to a particularly preferred embodiment of the present invention, the volume proportion of the core of the precursor is 50-80%, more preferably 65-80%, and further preferably 65-75.5%.

[0055] In some embodiments, the present invention provides a method for preparing a lithium-rich manganese-based precursor, comprising:

[0056] (1) In the presence of a non-oxidizing gas, a mixed metal salt solution and a precipitant solution are introduced into the bottom liquid of a reaction kettle in parallel to perform a coprecipitation reaction; the mixed metal salt solution is a solution of the general formula Ni x Co y Mn z A nickel-cobalt-manganese mixed metal salt solution prepared by (OH)2, wherein 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.7, x+y+z=1;

[0057] The coprecipitation reaction includes a nucleation stage and a particle growth stage. In the nucleation stage, the mixed metal salt solution is introduced at a flow rate of 5-15% / h of the reactor volume, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., and the pH value of the reaction system is controlled to be 11.0-12.0, such as 11.0, 11.3, 11.5, 11.8, 12.0, etc.;

[0058] During the particle growth reaction, the pH value of the reaction system is controlled to be 9.5-10.5, and the flow rate of the mixed metal salt solution is increased in the later stage of the particle growth reaction stage, and the reaction is continued until the reaction slurry reaches the target particle size; wherein, before the particle growth reaction is carried out, the pH of the reaction system is adjusted to be linearly reduced to 9.5-10.5, for example, 9.5, 9.8, 10.0, 10.2, 10.5, etc., so as to ensure that the growth of primary particles and secondary particles changes linearly, and the linear change rate is V, 0.01 / min≤V≤0.05 / min;

[0059] (2) The obtained reaction slurry is subjected to solid-liquid separation, and the obtained solid phase is aged, washed, dried, and sieved to obtain a precursor.

[0060] In some preferred embodiments, in step (1), the number of times the flow rate of the mixed metal salt is increased is 1 to 4 times, which can be 1 time, 2 times, 3 times or 4 times.

[0061] In some preferred embodiments, in step (1), the single increase in the flow rate of the mixed metal salt solution is 5 to 30% of the flow rate of the mixed metal salt solution in the nucleation stage, for example, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, etc.

[0062] In some preferred embodiments, in step (1), the total reaction time after the first increase in the flow rate of the mixed metal salt solution accounts for 40% to 70% of the total co-precipitation reaction time, for example, it can be 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, etc., wherein the total reaction time after the first increase in the flow rate of the mixed metal salt solution refers to the total time of the co-precipitation reaction after the first increase in the flow rate of the mixed metal salt solution.

[0063] In some preferred embodiments, in step (1), during the particle growth stage, the mixed metal salt solution is introduced into the reactor at a flow rate of 5 to 15% of the reactor volume / h before the flow rate of the mixed metal salt solution is increased.

[0064] In some preferred embodiments, in step (1), the target particle size D50 is 2.5 to 8.0 μm.

[0065] In some preferred embodiments, in step (1), during the particle growth stage, the pH is reduced to 9.8-10.2.

[0066] In some preferred embodiments, in step (1), the total synthesis time of the coprecipitation reaction is 15 to 60 h, for example, 20 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, etc.

[0067] In some preferred embodiments, in step (1), the duration of the nucleation stage is 20 to 60 min, for example, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0068] In some preferred embodiments, in step (1), the reaction time of the particle growth stage is 14 to 60 hours.

[0069] In some preferred embodiments, in step (1), the temperature of the coprecipitation reaction is 45-65°C.

[0070] In some preferred embodiments, during the preparation of the reactor bottom liquid and the co-precipitation reaction, the non-oxidizing gas is a nitrogen atmosphere, and the nitrogen flow rate is 8 to 60 L / h, for example, 8 L / h, 10 L / h, 12 L / h, 15 L / h, 18 L / h, 20 L / h, 25 L / h, 30 L / h, 35 L / h, 40 L / h, 45 L / h, 50 L / h, 55 L / h, 60 L / h, etc.

[0071] In some preferred embodiments, the volume of pure water in the bottom liquid of the reactor is 15-35% of the volume of the reactor, for example, it can be 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, etc.

[0072] In some preferred embodiments, the pH value of the bottom liquid of the reactor is 11.0-12.0, for example, 11.0, 11.3, 11.5, 11.8, 12.0, etc.

[0073] In some preferred embodiments, the temperature of the bottom liquid of the reaction kettle is 45-65°C.

[0074] In some preferred embodiments, the reaction kettle bottom liquid is prepared by pure water and alkali.

[0075] In some preferred embodiments, the total metal ion concentration in the mixed metal salt solution is 1.8 to 2.2 mol / L.

[0076] In some preferred embodiments, the precipitant solution is an alkaline solution; the concentration of the alkaline solution is 3 to 11 mol / L; preferably, the alkaline solution is a sodium hydroxide solution.

[0077] In some preferred embodiments, the pH value of the reaction system is linearly decreased by controlling the flow rate of the dilute acid solution; preferably, the dilute acid solution is a sulfuric acid solution and / or a hydrochloric acid solution; the concentration of the dilute acid solution is 0.1 to 1 mol / L; further preferably, the concentration of the dilute acid solution is 0.1 to 0.5 mol / L.

[0078] Some embodiments provide a lithium-rich manganese-based positive electrode material, which is obtained by mixing the aforementioned lithium-rich manganese-based precursor or the lithium-rich manganese-based precursor prepared by the aforementioned preparation method with a lithium source and sintering; or by mixing the aforementioned lithium-rich manganese-based precursor or the lithium-rich manganese-based precursor prepared by the aforementioned preparation method with a lithium source and an additive and sintering; the chemical formula of the lithium-rich manganese-based positive electrode material is Li 1+a Ni x Co y Mn zO2, where 0.3≤a≤0.5, 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.8, x+y+z=1. In the process of preparing lithium-rich manganese-based positive electrode materials, the amount of lithium salt can be determined according to the volatilization degree of lithium salt caused by temperature during the sintering process, and is usually 3-10wt% excess on the basis of the theoretical amount.

[0079] Some embodiments provide a lithium-ion battery comprising the aforementioned lithium-rich manganese-based positive electrode material.

[0080] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0081] Example 1

[0082] A method for preparing a lithium-rich manganese-based positive electrode material precursor, comprising:

[0083] (1) preparing a mixed salt solution containing nickel sulfate and manganese sulfate in a molar ratio of nickel to manganese metal ions of 25:75, wherein the total molar concentration of nickel and manganese metal ions in the mixed salt solution is 2 mol / L; preparing a 10 mol / L sodium hydroxide solution;

[0084] (2) Add pure water to a 300 L reactor, use sodium hydroxide solution as the bottom liquid, the volume of pure water is 100 L, adjust the temperature of the reactor to 55 °C, use sodium hydroxide to adjust the pH value to 11.83, and introduce nitrogen into the reactor for 3 h at a nitrogen flow rate of 10 L / h to prepare the reactor bottom liquid;

[0085] (3) After the preparation of the bottom liquid of the reactor is completed, the reaction is carried out. The temperature of the reaction system is controlled at 55°C during the entire reaction process, and nitrogen is continuously introduced during the entire reaction process. The metal salt solution and the alkaline solution are first injected simultaneously using a peristaltic pump. The total metal salt feed flow rate is controlled to be 360 ​​mL / min. The pH of the reaction system is controlled at 11.83 and maintained for 30 min to carry out the nucleation reaction;

[0086] After the nucleation reaction is completed, the feed is stopped, and the pH of the reaction system is slowly reduced from 11.83 to 10.00 using 0.2 mol / L dilute sulfuric acid. The pH at the beginning of the reaction is set to 11.83, and the pH value is controlled to decrease linearly. The pH value change rate V is 0.05 / min, and the pH is linearly reduced to 10.00 at the above rate; after the pH is stabilized, the metal salt solution and the alkaline solution are continuously injected for particle growth reaction. The pH in the particle growth reaction stage is controlled to be 10.00. During the entire reaction process, non-oxidizing atmosphere nitrogen is introduced until the reaction is completed. The nitrogen flow rate is 10 L / h. After 18 hours of the synthesis reaction, the total metal salt feed flow rate is increased from 360 mL / min to 450 mL / min. After the precursor particle size reaches 5.0 μm, the entire synthesis time is 58 hours. During the coprecipitation reaction, the supernatant solution in the reactor is discharged through a concentrator;

[0087] (4) After the reaction is completed, the prepared slurry is aged, washed, dried and sieved to obtain Ni 0.25 Mn 0.75 (OH)2 precursor product, the particle size D50 of the product is 5.23μm, TD is 1.63g / cm 3 , BET is 19.69m 2 / g, sphericity Φ is 1.3, the core accounts for 65.2%, where Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, and Dc is the minimum inscribed sphere radius of the same particle. The SEM image of the obtained product is shown in Figure 1 shown.

[0088] Example 2

[0089] A method for preparing a lithium-rich manganese-based positive electrode material precursor, comprising:

[0090] (1) preparing a mixed salt solution containing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of nickel, cobalt and manganese ions of 25:9:66, wherein the total molar concentration of the three metal ions of nickel, cobalt and manganese in the mixed salt solution is 2 mol / L; preparing a 10 mol / L sodium hydroxide solution;

[0091] (2) Pure water was added to a 300 L reactor, with sodium hydroxide solution as the bottom liquid. The volume of pure water was 65 L. The temperature of the reactor was regulated to 60 °C, and the pH value was regulated to 11.68 with sodium hydroxide. Nitrogen was introduced into the reactor for 3 h at a nitrogen flow rate of 10 L / h to prepare the bottom liquid of the reactor.

[0092] (3) After the preparation of the bottom liquid of the reactor is completed, the reaction is carried out. The temperature of the reaction system is controlled at 60°C during the entire reaction process, and nitrogen is continuously introduced during the entire reaction process. The metal salt solution and the alkaline solution are first injected simultaneously using a peristaltic pump. The total metal salt feed flow rate is controlled to 420 mL / min, and the pH of the reaction system is controlled at 11.68 for 40 min to carry out the nucleation reaction;

[0093] After the nucleation reaction is completed, the feed is stopped, and the pH of the reaction system is slowly reduced from 11.68 to 10.10 using 0.2 mol / L dilute sulfuric acid. The pH at the beginning of the reaction is set to 11.68, and the pH value is controlled to decrease linearly. The pH value change rate V is 0.03 / min, and the pH is linearly reduced to 10.10 at the above rate; after the pH is stabilized, the metal salt solution and the alkaline solution are continuously injected for particle growth reaction. The pH in the particle growth reaction stage is controlled to be 10.10. During the entire reaction process, non-oxidizing atmosphere nitrogen is introduced until the reaction is completed. The nitrogen flow rate is 10L / h. After 22h of the synthesis reaction, the total metal salt feed flow rate is increased from 420mL / min to 480mL / min. After the precursor particle size reaches 4.25μm, the entire synthesis time is 47h. During the coprecipitation reaction, the supernatant solution in the reactor is discharged through a concentrator;

[0094] (4) After the reaction is completed, the prepared slurry is aged, washed, dried and sieved to obtain Ni 0.25 Co 0.09 Mn 0.66 (OH)2 precursor product, the particle size D50 is 4.25μm, TD is 1.45g / cm 3 , BET is 18.89m 2 / g, sphericity Φ is 1.5, the core accounts for 73.7%, where Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, and Dc is the minimum inscribed sphere radius of the same particle. The SEM image of the obtained product is shown in Figure 2 shown.

[0095] Example 3

[0096] A method for preparing a lithium-rich manganese-based positive electrode material precursor, comprising:

[0097] (1) preparing a mixed salt solution containing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of nickel, cobalt and manganese ions of 16:16:68, wherein the total molar concentration of the three metal ions of nickel, cobalt and manganese in the mixed salt solution is 2 mol / L; preparing a 10 mol / L sodium hydroxide solution;

[0098] (2) Add pure water to a 300 L reactor, use sodium hydroxide solution as the bottom liquid, the volume of pure water is 50 L, the temperature of the reactor is regulated to 55 °C, the pH value is regulated to 11.87 with sodium hydroxide, and nitrogen is introduced into the reactor for 3 h at a nitrogen flow rate of 10 L / h to prepare the reactor bottom liquid;

[0099] (3) After the preparation of the bottom liquid of the reactor is completed, the reaction is carried out. The temperature of the reaction system is controlled to be 55°C during the entire reaction process, and nitrogen is continuously introduced during the entire reaction process. The metal salt solution and the alkaline solution are first injected simultaneously using a peristaltic pump. The total metal salt feed flow rate is controlled to be 360 ​​mL / min. The pH of the reaction system is controlled to be 11.87 and maintained for 50 min to carry out the nucleation reaction;

[0100] After the nucleation reaction is completed, the feed is stopped, and the pH of the reaction system is slowly reduced from 11.78 to 10.20 using 0.2 mol / L dilute sulfuric acid. The pH at the beginning of the reaction is set to 11.78, and the pH value is controlled to decrease linearly. The pH value change rate V is 0.02 / min, and the pH is linearly reduced to 10.20 at the above rate; after the pH is stabilized, the metal salt solution and the alkaline solution are continuously injected for particle growth reaction. The pH in the particle growth reaction stage is controlled to be 10.20. During the entire reaction process, non-oxidizing atmosphere nitrogen is introduced until the reaction is completed. The nitrogen flow rate is 10 L / h. After 20 hours of the synthesis reaction, the total metal salt feed flow rate is increased from 360 mL / min to 420 mL / min. After 26 hours of the synthesis reaction, the total metal salt feed flow rate is increased from 420 mL / min to 450 mL / min. After the precursor particle size reaches 3.03 μm, the entire synthesis time is 35 hours. During the coprecipitation reaction, the supernatant solution in the reactor is discharged through a concentrator;

[0101] (5) After the reaction is completed, the prepared slurry is aged, washed, dried and sieved to obtain Ni 0.16 Co 0.16 Mn 0.68 (OH)2 precursor product, the particle size D50 is 3.03μm, TD is 1.31g / cm 3 , BET is 22.59m 2 / g, the sphericity Φ is 1.5, and the inner core accounts for 73.5%, where Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, and Dc is the minimum inscribed sphere radius of the same particle.

[0102] Example 4

[0103] A method for preparing a lithium-rich manganese-based positive electrode material precursor, comprising:

[0104] (1) preparing a mixed salt solution containing nickel sulfate and manganese sulfate in a molar ratio of nickel to manganese metal ions of 25:75, wherein the total molar concentration of nickel, manganese and other metal ions in the mixed salt solution is 2 mol / L; preparing a 10 mol / L sodium hydroxide solution;

[0105] (2) Pure water was added to a 300 L reactor, with sodium hydroxide solution as the bottom liquid. The volume of pure water was 100 L. The temperature of the reactor was regulated to 55 °C, and the pH value was regulated to 11.63 with sodium hydroxide. Nitrogen was introduced into the reactor for 3 h at a nitrogen flow rate of 10 L / h to prepare the bottom liquid of the reactor.

[0106] (3) After the preparation of the bottom liquid of the reactor is completed, the reaction is carried out. The temperature of the reaction system is controlled to be 55°C during the entire reaction process, and nitrogen is continuously introduced during the entire reaction process. The metal salt solution and the alkaline solution are first injected simultaneously using a peristaltic pump. The total metal salt feed flow rate is controlled to be 360 ​​mL / min. The pH of the reaction system is controlled to be 11.63 and maintained for 50 min to carry out the nucleation reaction;

[0107] After the nucleation reaction is completed, the feed is stopped, and the pH of the reaction system is slowly reduced from 11.63 to 10.00 using 0.2 mol / L dilute sulfuric acid. The pH at the beginning of the reaction is set to 11.63, and the pH value is controlled to decrease linearly. The pH value change rate V is 0.05 / min, and the pH is linearly reduced to 10.00 at the above rate; after the pH is stabilized, the metal salt solution and the alkaline solution are continuously injected for particle growth reaction. The pH in the particle growth reaction stage is controlled to be 10.00. During the entire reaction process, non-oxidizing atmosphere nitrogen is introduced until the reaction is completed. The nitrogen flow rate is 10 L / h. After 18 hours of the synthesis reaction, the total metal salt feed flow rate is increased from 360 mL / min to 450 mL / min. After the precursor particle size reaches 3.0 μm, the entire synthesis time is 32 hours. During the coprecipitation reaction, the supernatant solution in the reactor is discharged through a concentrator;

[0108] (6) After the reaction is completed, the prepared slurry is aged, washed, dried and sieved to obtain Ni 0.25 Mn 0.75 (OH)2 precursor product, the particle size D50 is 3.0μm, TD is 1.04g / cm 3 , BET is 32.79m 2 / g, the sphericity Φ is 1.6, and the inner core accounts for 75.4%, where Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, and Dc is the minimum inscribed sphere radius of the same particle.

[0109] Comparative Example 1

[0110] A method for preparing a lithium-rich manganese-based positive electrode material precursor, comprising:

[0111] (1) preparing a mixed salt solution containing nickel sulfate and manganese sulfate in a molar ratio of nickel to manganese metal ions of 25:75, wherein the total molar concentration of nickel and manganese metal ions in the mixed salt solution is 2 mol / L; preparing a 10 mol / L sodium hydroxide solution; and preparing a 6 g / L ammonia solution;

[0112] (2) Pure water was added to a 300 L reactor, with sodium hydroxide solution as the bottom liquid. The volume of pure water was 100 L. The temperature of the reactor was regulated to 55 °C. Ammonia water was used to regulate the alkalinity of the reaction to 7 g / L. Sodium hydroxide was used to regulate the pH value to 11.63. Nitrogen was introduced into the reactor for 3 h at a nitrogen flow rate of 10 L / h to prepare the bottom liquid of the reactor.

[0113] (3) After the preparation of the bottom liquid of the reactor is completed, stop introducing nitrogen and proceed with the reaction. The temperature of the reaction system is controlled to be 55°C during the entire reaction process. First, a peristaltic pump is used to simultaneously inject metal salt solution, alkali solution, and ammonia solution. The total metal salt feed flow rate is controlled to be 360 ​​mL / min. The pH of the reaction system is controlled to be 11.63 and maintained for 50 min to carry out the nucleation reaction.

[0114] After the nucleation reaction is completed, 0.2 mol / L dilute sulfuric acid is used to slowly reduce the pH of the reaction system from 11.63 to 10.00. The pH at the beginning of the reaction is set to 11.63, and the pH value is controlled to decrease linearly. The pH value change rate V is 0.05 / min, and the pH is linearly reduced to 10.00 at the above rate; after the pH is stabilized, the metal salt solution, the alkaline solution, and the ammonia solution are continuously injected for particle growth reaction. The pH of the particle growth reaction stage is controlled to be 10.00. During the entire reaction process, non-oxidizing atmosphere nitrogen is introduced until the reaction is completed. The nitrogen flow rate is 10 L / h. After 18 hours of the synthesis reaction, the total metal salt feed flow rate is increased from 360 mL / min to 450 mL / min. After the precursor particle size reaches 4.05 μm, the entire synthesis time is 35 hours. During the coprecipitation reaction, the supernatant solution in the reactor is discharged through a concentrator;

[0115] (7) After the reaction is completed, the prepared slurry is aged, washed, dried and sieved to obtain Ni 0.25 Mn 0.75 (OH)2 precursor product, the particle size D50 of the product is 4.05μm, TD is 0.87g / cm 3 , BET is 43.46m 2 / g, the sphericity Φ is 1.7, and the inner core accounts for 82.8%, where Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, and Dc is the minimum inscribed sphere radius of the same particle.

[0116] Figure 1 The Ni prepared in Example 1 0.25 Mn 0.75 The morphology and cross-section electron microscope images of (OH)2 precursor, Figure 2 The Ni prepared in Example 2 0.25 Co 0.09 Mn 0.66 The morphology and cross-section electron microscope images of (OH)2 precursors, Figure 3 The morphology pictures of the precursors obtained in Example 4 and Comparative Example 1 are shown in FIG. 1 , wherein (a) is the morphology picture of the precursor obtained in Example 4, and (b) is the morphology picture of the precursor obtained in Comparative Example 1. Figure 4 The first charge and discharge curves and capacity attenuation images of the positive electrode materials corresponding to the precursors of Example 4 and Comparative Example 1 are shown.

[0117] As can be seen from the figure, the lithium-rich manganese-based precursor has a good sphericity under the ammonia-free process, and the secondary particles are orderly stacked into a multi-layered sheet structure. There are many large gaps between the layers, and it has an obvious loose porous structure, which is beneficial to the positive electrode material precursor in the lithium mixed roasting process. Figure 3 It can be seen from (a) and (b) that compared with the ammonia process, the precursor prepared by the ammonia-free process of the present invention has more uniform primary particles, better sphericity of secondary particles, and higher particle density. Higher sphericity means that the precursor particles are more regular in shape and more uniform in size, which improves the uniformity of the positive electrode material of the battery and ensures that the diffusion and embedding / de-embedding process of lithium ions in the material is more uniform and stable; and the high-sphericity precursor can provide a larger specific surface area and can provide more contact points for the embedding / de-embedding of lithium ions, thereby increasing the charge and ion transfer speed of the positive electrode material of the battery and improving the discharge rate and energy density of the battery; the precursor particles with higher sphericity have better chemical stability and structural stability, which can reduce the structural decomposition and capacity decrease of the material during the use of the battery, and improve the cycle life and capacity retention rate of the battery.

[0118] The precursor materials prepared in Example 4 and Comparative Example 1 were mixed with lithium carbonate according to the chemical formula Li 1.3 Mn 0.75 Ni 0.25 O2, and 5wt.% excess lithium (i.e., the amount of lithium used is 1.05 times the theoretical mass of the chemical formula) are mixed evenly to obtain a mixed lithium sintering precursor, and the mixed lithium sintering precursor is placed in an air atmosphere muffle furnace, and the temperature is increased to 500°C at 3°C / min and kept warm for 5 h; then the temperature is continued to be increased to 800°C at 3°C / min and kept warm for 10 hours to obtain a lithium-rich manganese-based (LLOs) positive electrode material.

[0119] The prepared LLOs positive electrode material, acetylene black, and PVDF were weighed in a mass ratio of 8: 1: 1, NMP was added, and mixed evenly in a mortar, and then coated on an aluminum foil current collector to form an electrode sheet. The electrode sheet was baked at 80°C in a vacuum oven for 8 hours, and then cut into a 10 mm diameter electrode sheet after drying, and stored in a vacuum for later use. The metal lithium sheet was used as the negative electrode, the separator was a PP separator, and the LiFP6 concentration was 1.0 mol·L -1 , the electrolyte with a mass ratio of EC to DMC of 1:1 (volume ratio) was assembled into a 2025-type button lithium-ion battery in an Ar atmosphere glove box.

[0120] The assembled button lithium-ion battery was charged and discharged at a rate of 0.1C (1C = 250mAh / g) and a voltage range of 2-4.8V. The battery was cycled at a rate of 1C and a voltage range of 2-4.8V. The results of the charge and discharge test at 0.1C and the cycle test at 1C are shown in Figure 1. Figure 4 As shown in (a) and (b).

[0121] The battery assembled with the positive electrode material obtained after calcining the precursor prepared in Example 4 and Comparative Example 1 has a charging specific capacity of 297.6 mAh / g and 255.8 mAh / g respectively at a rate of 0.1C (1C=250 mAh / g) and a voltage range of 2-4.8 V for the first charge and discharge, and the first coulombic efficiency is 89.70% and 70.82% respectively, which promotes the transfer of lithium ions and improves the first charge and discharge performance of the positive electrode material. It can be seen from the cycle performance diagram that the discharge specific capacity and cycle performance of the battery assembled with the positive electrode material obtained after calcining the precursor prepared in Example 4 at 1C for the first charge and discharge are significantly better than those in Comparative Example 1.

[0122] Table 1 shows the characteristic parameters of the precursors prepared in the embodiments of the present invention and the comparative examples. It can be seen that the precursors prepared in the present invention have a narrower diameter distribution, a higher tap density, and a better sphericity, which avoids the phenomenon of overcharge and over-discharge to varying degrees between large and small particles during the battery charging and discharging process, thereby improving the electrochemical performance and structural stability of the ternary positive electrode material and increasing the cycle life.

[0123] Table 1 Characteristic parameters of precursors in various embodiments and comparative examples

[0124]

[0125] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A lithium-rich manganese-based precursor, characterized in that: The chemical formula of the precursor is Ni x Co y Mn z (OH)2, wherein 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.8, x+y+z=1, the precursor is a spherical or quasi-spherical secondary particle formed by the aggregation of primary particles, the sphericity Φ of the precursor is 1.2-1.8, wherein Φ=Di / Dc, Di is the maximum inscribed sphere radius of the particle, and Dc is the minimum inscribed sphere radius of the same particle; the precursor comprises an inner core and an outer shell, the primary particle diameter of the inner core is 0.1-30nm, the primary particle diameter of the outer shell is 60-200nm, the secondary particles are loose and porous, the particle size D50 of the secondary particles is 2.5-8.0μm, the particle size distance is 0.60<(D90-D10) / D50<0.9, and the specific surface area is 15-35m 2 / g, tap density is 1.0~1.7g / cm 3 ; The porosity of the outer wall is lower than that of the inner core, and the volume of the inner core of the precursor accounts for 50 to 80%.

2. The lithium-rich manganese-based precursor according to claim 1, characterized in that: The sphericity of the precursor is 1.3 to 1.

6.

3. The lithium-rich manganese-based precursor according to claim 1 or 2, characterized in that: The core volume of the precursor accounts for 65-80%.

4. A method for preparing a lithium-rich manganese-based precursor using an ammonia-free process, characterized in that: include: (1) In the presence of a non-oxidizing gas, a mixed metal salt solution and a precipitant solution are introduced into the bottom liquid of a reaction kettle in parallel to perform a coprecipitation reaction; the mixed metal salt solution is a solution of the general formula Ni x Co y Mn z A nickel-cobalt-manganese mixed metal salt solution prepared by (OH)2, wherein 0.1≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.7, x+y+z=1; The coprecipitation reaction includes a nucleation stage and a particle growth stage. In the nucleation stage, the mixed metal salt solution is introduced at a flow rate of 5-15% / h of the reactor volume, and the pH value of the reaction system is controlled to be 11.0-12.0; During the particle growth reaction, the pH value of the reaction system is controlled to be 9.5-10.5, and the flow rate of the mixed metal salt solution is increased in the late stage of the particle growth stage, and the reaction is continued until the reaction slurry reaches the target particle size; wherein, before the particle growth reaction is carried out, the pH of the reaction system is adjusted to be linearly reduced to 9.5-10.5, and the rate of change of the linear reduction of the pH value of the reaction system is adjusted to be V, 0.01 / min≤V≤0.05 / min; the single increase in the flow rate of the mixed metal salt solution is 5-30% of the flow rate of the mixed metal salt solution in the nucleation stage; the total reaction time after the first increase in the flow rate of the mixed metal salt solution accounts for 40-70% of the total coprecipitation reaction time; (2) The obtained reaction slurry is subjected to solid-liquid separation, and the obtained solid phase is aged, washed, dried, and sieved to obtain a precursor.

5. The method for preparing a lithium-rich manganese-based precursor according to claim 4, characterized in that: In step (1), the flow rate of the mixed metal salt solution is increased 1 to 4 times.

6. The method for preparing a lithium-rich manganese-based precursor according to claim 4, characterized in that: The target particle size D50 is 2.5 to 8.0 μm.

7. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In step (1), during the particle growth stage, the mixed metal salt solution is introduced into the reactor at a flow rate of 5 to 15% of the volume of the reactor per hour before the flow rate of the mixed metal salt solution is increased.

8. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In step (1), during the particle growth stage, the pH is reduced to 9.8-10.

2.

9. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In step (1), the total synthesis time of the coprecipitation reaction is 15 to 60 hours.

10. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In step (1), the duration of the nucleation stage is 20 to 60 minutes.

11. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In step (1), the particle growth phase lasts for 14 to 60 hours.

12. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In step (1), the temperature of the coprecipitation reaction is 45-65°C.

13. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In step (1), the method further comprises: preparing a reaction kettle bottom liquid, and introducing a non-oxidizing gas during the preparation of the reaction kettle bottom liquid.

14. The method for preparing a lithium-rich manganese-based precursor according to claim 13, characterized in that: In step (1), during the preparation of the reactor bottom liquid and the co-precipitation reaction, the non-oxidizing gas is a nitrogen atmosphere, and the nitrogen flow rate is 8 to 60 L / h.

15. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: The volume of pure water in the bottom liquid of the reaction kettle is 15-35% of the volume of the reaction kettle.

16. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: The pH value of the reaction kettle bottom liquid is 11.0-12.

0.

17. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: The temperature of the bottom liquid of the reaction kettle is 45-65°C.

18. The method for preparing a lithium-rich manganese-based precursor according to claim 17, characterized in that: The reaction kettle bottom liquid is prepared by pure water and alkali.

19. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: In the mixed metal salt solution, the total metal ion concentration is 1.8-2.2 mol / L.

20. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: The precipitant solution is an alkaline solution; the concentration of the alkaline solution is 3-11 mol / L.

21. The method for preparing a lithium-rich manganese-based precursor according to any one of claims 4 to 6, characterized in that: The pH value of the reaction system was adjusted to decrease linearly by using a dilute acid solution.

22. The method for preparing a lithium-rich manganese-based precursor according to claim 21, characterized in that: The dilute acid solution is a sulfuric acid solution and / or a hydrochloric acid solution; the concentration of the dilute acid solution is 0.1-1 mol / L.

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