Method for preparing lithium-rich manganese-based positive electrode material through sanding and spraying double coupling

Abstract

A method for preparing a lithium-rich manganese-based positive electrode material through sanding and spraying double coupling comprises the following steps: adding a lithium source, a nickel source, a cobalt source and a manganese source into deionized water, heating to dissolve the lithium source, the nickel source and the cobalt source in the deionized water, stopping heating, and continuing magnetic stirring to uniformly disperse the manganese source to obtain a metal salt precursor suspension; adding a dispersing agent into the metal salt precursor suspension liquid, sanding through a nano sand mill, and refining particles in the metal salt precursor suspension liquid until the particle size distribution D50 is 150nm + / -20nm; and carrying out high-temperature spray drying and high-temperature sintering on the refined metal salt precursor suspension to obtain the lithium-rich manganese-based positive electrode material. The method has the advantages of reasonable process, simplicity in operation, no need of introducing a modified coating material, low cost and environmental friendliness, and can improve the diffusion speed of lithium ions of the material in the positive electrode material, accelerate the diffusion kinetics of the lithium ions, improve the transmission channel of the lithium ions so as to improve the capacity and improve the energy density at the same time.

Description

Technical Field

[0001] The invention belongs to the field of lithium-ion batteries, and in particular relates to a method for preparing a lithium-rich manganese-based positive electrode material by sand milling and spraying dual coupling. Background Art

[0002] With the continuous enhancement of electronic product functionality, such as smartphones, tablets, and wearable devices, and the increasing diversification of electronic product application scenarios, such as portable devices, electric vehicles, and smart homes, the rapid development of these electronic products has placed higher demands on energy storage technology. As an important energy storage device, lithium-ion batteries play a vital role in various electronic products.

[0003] In lithium-ion batteries, the positive electrode material plays a decisive role in the capacity of the battery. At present, a variety of positive electrode materials have been developed and applied. Among them, lithium-rich manganese-based materials are regarded as strong candidates for the next generation of high energy density positive electrode materials because of their high energy density (more than 1000Wh / Kg) and large discharge specific capacity (about 280mAh / g) as well as average voltage (3.6V) and simple synthesis and preparation process. Its general formula is xLi2MnO3·(1-X)LiMO2, where M is a transition metal such as Ni, Co, and Mn. However, although lithium-rich manganese-based lithium-ion positive electrode materials have a high first discharge capacity of about 280mAh / g, their first coulombic efficiency is low. At the same time, due to the participation of the redox activity of anionic oxygen, Li in lithium-rich layered oxides + The diffusion capacity is relatively insufficient, which limits the cycle stability of the battery and affects the energy density of the battery.

[0004] At present, surfactants, organic polymers, inorganic salts, etc. are used to nanometerize lithium-rich manganese-based cathode materials. For example, polymer surfactant PVP is used to prepare nanosheet materials. The first-cycle efficiency of this material as an electrode material for lithium-ion batteries can be increased from 70% to 85%, which is attributed to surface passivation and uniform Li + However, PVP, as a surfactant, needs to be dissolved in an organic solvent and may remain on the surface or inside the nanosheet material during the preparation process. The residual PVP may hinder the diffusion of lithium ions, reduce the charge and discharge rate and capacity of the battery, and may also reduce the conductivity, affect the cycle stability, and increase the preparation cost. Therefore, although the nano-size of lithium-rich manganese-based positive electrode materials can be achieved by adjusting the interfacial tension, helping to narrow the particle distribution width and improve the uniformity of the particles, thereby improving the first coulombic efficiency and electrochemical performance to a certain extent, the modification method is complex, costly, and inefficient. Many surfactants are picky about solvent selection and are soluble in organic solvents such as ethanol and ether, and even require heating to dissolve. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing lithium-rich manganese-based positive electrode materials by sand grinding and spray dual coupling. The process is reasonable, the operation is simple, no modified coating materials need to be introduced, the cost is low, and it is good for the environment. It can increase the diffusion rate of lithium ions in the positive electrode material, accelerate the diffusion kinetics of lithium ions, improve the lithium ion transmission channel and thus increase the capacity, while also increasing the energy density.

[0006] The technical solution of the present invention is: A method for preparing a lithium-rich manganese-based positive electrode material by sand milling and spraying dual coupling comprises the following steps: Step 1: Add the lithium source, nickel source, cobalt source, and manganese source in a molar ratio of 1.515:0.165:0.165:0.665 to deionized water, heat to dissolve the lithium source, nickel source, and cobalt source in the deionized water, stop heating, and continue magnetic stirring to evenly disperse the manganese source to obtain a metal salt precursor suspension; Step 2: adding a dispersant to the metal salt precursor suspension, and grinding the metal salt precursor suspension with a nano sand mill to refine the particles to a particle size distribution D50 of 150 nm ± 20 nm; Step 3: The refined metal salt precursor suspension is spray-dried at high temperature to obtain a precursor powder; Step 4: Sinter the precursor powder at 850°C for 4-8 hours to obtain a lithium-rich manganese-based positive electrode material.

[0007] Furthermore, the lithium source is lithium hydroxide, the nickel source is nickel hydroxide, the cobalt source is cobalt hydroxide; and the manganese source is manganese dioxide.

[0008] Furthermore, the volume ratio of the total mass of the lithium source, nickel source, cobalt source, and manganese source to deionized water is 11:100 g / mL.

[0009] Furthermore, the dispersant is sodium carboxymethyl cellulose.

[0010] Furthermore, the mass volume ratio of the dispersant to the deionized water in step 1 is 1:300 g / mL.

[0011] Furthermore, in step 2, the inlet temperature of the spray drying is 230°C, the outlet temperature is 120°C, the peristaltic pump speed is 1500-2000 mL / h, the needle frequency is 20 Hz, and the spray pressure is 0.2 MPa; the atmosphere for the spray drying is air.

[0012] Furthermore, the nano sand mill used sand beads with a diameter of 0.3 mm and a composition of zirconium dioxide, with a rotation speed of 2000 rpm and a time of 15 min.

[0013] Furthermore, in step four, during high-temperature sintering, the obtained material precursor powder is placed in a crucible, sent into a muffle furnace, and heated from room temperature to 850°C at a heating rate of 3°C / min. After sintering at this temperature, the crucible is naturally cooled in the furnace.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a sand mill to grind and precisely control the particle fineness, and then couples it with a spray dryer for further atomization and granulation, successfully preparing nano-sized and uniform lithium-manganese-rich positive electrode material particles; this dual coupling method is not only simple and convenient, but also does not require the introduction of modified coating materials, thereby reducing costs, improving environmental protection, and ensuring high process repeatability, making it very suitable for industrial production.

[0015] (2) Through the above-mentioned dual coupling process and strict control of calcination conditions, the prepared lithium-rich manganese positive electrode material particles have stable properties, and their electrochemical performance avoids the influence of modified coating materials; during charging and discharging, the lithium ion embedding depth of the lithium-rich manganese positive electrode material particles is shallow and the diffusion path is short, which is conducive to the deintercalation of lithium ions in them, increases the diffusion rate of lithium ions in the material in the positive electrode material, accelerates the lithium ion diffusion kinetics, improves the lithium ion transmission channel and thus increases the capacity, while also increasing the energy density; the prepared lithium-rich manganese-based positive electrode material has a first-cycle capacity of up to 292.49mAh / g at a voltage of 4.8V, a first-cycle efficiency of up to 85.25%, and an energy density of 1047.47mWh / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a particle size D50 distribution curve of the lithium-rich manganese-based material of Example 1 of the present invention under 900g conditions; Figure 2 This is a particle size D50 distribution curve of the lithium-rich manganese-based material of Comparative Example 8 of the present invention under 800g conditions; Figure 3 7 is a particle size D50 distribution curve of the lithium-rich manganese-based material of Comparative Example 7 of the present invention under 700g conditions; Figure 4 This is a particle size D50 distribution curve of the lithium-rich manganese-based material of Comparative Example 6 of the present invention under 600g conditions; Figure 5 1 is an electrochemical first cycle charge and discharge curve diagram of the lithium-rich manganese-based positive electrode materials of Example 1 and Comparative Examples 6-8 of the present invention at 0.1C; Figure 6 The first electrochemical charge-discharge curves of the lithium-rich manganese-based positive electrode materials of Comparative Examples 1-3 and Examples 1-5 of the present invention at 0.1C are shown; Figure 7 1C electrochemical cycle discharge capacity curve of the lithium-rich manganese-based positive electrode materials of Comparative Examples 1-3 and Examples 1-5 of the present invention; Figure 8 1C electrochemical cycle median voltage curve of the lithium-rich manganese-based positive electrode materials of Comparative Examples 1-3 and Examples 1-5 of the present invention; Figure 9 1-3 and 1-5 of the present invention are XRD patterns of the lithium-rich manganese-based positive electrode materials of Comparative Examples 1-3 and Examples 1-5 of the present invention; Figure 10 is a scanning electron microscope image of the lithium-rich manganese-based positive electrode material of Comparative Example 5 of the present invention and Example 1 of the present invention; Figure 11 1-2 and 1-3 are impedance curves of the lithium-rich manganese-based positive electrode materials of Comparative Examples 1-2 and Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0017] Example 1 Synthetic material 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 )O2 1) Preparation of metal salt precursor suspension Weigh 9.60 g of lithium hydroxide, 4.05 g of nickel hydroxide, 4.06 g of cobalt hydroxide, and 15.30 g of manganese dioxide and add them to 300 mL of deionized water. Heat to 30°C-35°C to dissolve the lithium hydroxide, nickel hydroxide, and cobalt hydroxide in the deionized water. Stop heating and continue magnetic stirring for 1 hour to evenly disperse the manganese dioxide to obtain a metal salt precursor suspension. 2) Refine the metal salt precursor suspension 1 g of sodium carboxymethyl cellulose was added to the metal salt precursor suspension in step 1) as a dispersant, and the metal salt precursor suspension was fined by sand milling with a nano sand mill. During sand milling, the sand milling beads had a diameter of 0.3 mm, a composition of zirconium dioxide, and a weight of 900 g. The sand mill speed was 2000 rpm, and the sand milling time was 15 min. The particle size distribution D50 of the particles in the metal salt precursor suspension after sand milling was tested by a particle size analyzer and was 150 nm ± 20 nm. 3) Preparation of precursor powder The sand-milled metal salt precursor suspension was pumped into a spray dryer for spray drying. The spray drying atmosphere was air, the spray drying inlet temperature was 230°C, the outlet temperature was 120°C, the peristaltic pump speed was 1500-2000 mL / h, the needle frequency was 20 Hz, and the spray pressure was 0.2 MPa to obtain a precursor powder. 4) Preparation of lithium-rich manganese-based layered oxides The precursor powder was placed in a crucible and sent into a muffle furnace. The temperature was raised to 850°C at a heating rate of 3°C / min and calcined at 850°C in the muffle furnace for 5 hours. Fresh air was continuously introduced into the muffle furnace during the entire heating and calcining process. After calcination, the material was cooled with the furnace to obtain lithium-rich manganese-based layered oxide LRM-5.

[0018] The lithium-rich manganese-based layered oxide prepared in Example 1 was used as a lithium-rich manganese positive electrode material, and was mixed with a conductive agent (SuperP) and a binder (sodium carboxymethyl cellulose CMC) in a mass ratio of 85:10:5 to form a slurry (wherein CMC was added in the form of a CMC aqueous solution), and the CMC aqueous solution had a mass concentration of 1.6wt%. After stirring evenly, the slurry was coated on an aluminum foil current collector to obtain a lithium-rich manganese-based positive electrode sheet; and the lithium-rich manganese-based positive electrode sheet was assembled into a 2025 button battery in an argon-filled glove box with an oxygen and water content of less than 0.01ppm, and charge and discharge tests were performed on the Xinwei test system.

[0019] The 2025 button-type battery used a metal lithium sheet as the reference and counter electrodes, a Celgard-2400 separator, and an electrolyte consisting of LiPF6 (1 mol / L) / EC+DEC+EMC (solvent molar ratio 1:1:1). The battery was activated at 65°C for 20 hours. The test voltage window was 2.0-4.8V, and the test temperature was 27±1°C. The first three cycles were activated at a rate of 0.1C (1C = 200 mAh / g). Starting from the fourth cycle, a 1C rate was used. The performance test results are shown in Table 1.

[0020] Example 2 Step 1) to step 3) are the same as in Example 1; 4) Preparation of lithium-rich manganese-based layered oxides The precursor material was placed in a crucible and calcined in a muffle furnace. The temperature was raised to 850°C at a heating rate of 3°C / min and calcined at 850°C for 4 hours. Fresh air was continuously introduced into the muffle furnace during calcination. After cooling with the furnace, a lithium-rich manganese-based layered oxide LRM-4 was obtained.

[0021] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0022] Example 3 Step 1) to step 3) are the same as in Example 1; 4) Preparation of lithium-rich manganese-based layered oxides The precursor material was placed in a crucible and calcined in a muffle furnace. The temperature was raised to 850°C at a heating rate of 3°C / min and calcined at 850°C for 6 hours. Fresh air was continuously introduced into the muffle furnace during calcination. After cooling with the furnace, a lithium-rich manganese-based layered oxide LRM-6 was obtained.

[0023] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0024] Example 4 Step 1) to step 3) are the same as in Example 1; 4) Preparation of lithium-rich manganese-based layered oxides The precursor material was placed in a crucible and calcined in a muffle furnace. The temperature was raised to 850°C at a heating rate of 3°C / min and calcined at 850°C for 8 hours. Fresh air was continuously introduced into the muffle furnace during calcination. After cooling with the furnace, lithium-rich manganese-based layered oxide LRM-8 was obtained.

[0025] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0026] Comparative Example 1 Step 1) to step 3) are the same as in Example 1; 4) Preparation of lithium-rich manganese-based layered oxides The precursor material was placed in a crucible and calcined in a muffle furnace. The temperature was raised to 1000°C at a heating rate of 3°C / min and calcined at 1000°C for 20 minutes. Fresh air was continuously introduced into the muffle furnace during calcination. After cooling with the furnace, lithium-rich manganese-based layered oxide LRM-20 was obtained.

[0027] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0028] Comparative Example 2 Step 1) to step 3) are the same as in Example 1; 4) Preparation of lithium-rich manganese-based layered oxides The precursor material was placed in a crucible and calcined in a muffle furnace. The temperature was raised to 950°C at a heating rate of 3°C / min and calcined at 950°C for 2 hours. Fresh air was continuously introduced into the muffle furnace during calcination. After cooling with the furnace, a lithium-rich manganese-based layered oxide LRM-2 was obtained.

[0029] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0030] Comparative Example 3 Step 1) to step 3) are the same as in Example 1; 4) Preparation of lithium-rich manganese-based layered oxides The precursor material was placed in a crucible and calcined in a muffle furnace at a heating rate of 3°C / min to 850°C. Fresh air was continuously introduced into the muffle furnace during calcination. After cooling, the lithium-rich manganese-based matrix oxide LRM-3 was obtained. The slurry was prepared according to Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance tests. The performance test results are shown in Table 1.

[0031] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0032] Comparative Example 4 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 )O2 layered lithium-rich manganese-based positive electrode material preparation method is similar to comparative example 1, lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate were weighed 18.91g, 4.852g, 4.857g, 19.852g, respectively, dissolved in 1L of deionized water to form a mixed metal salt solution, and 61.04g of citric acid monohydrate was added, stirred for more than 1 hour until the mixture was uniform, and granulated only by spray drying to prepare a precursor of the layered lithium-rich manganese-based positive electrode material; the precursor was placed in an air-ventilated muffle furnace and sintered, and the temperature was increased from room temperature to 1000℃ at a heating rate of 3℃ / min and kept constant for 20min, and then naturally cooled to room temperature to obtain the lithium-rich manganese positive electrode material LRM-1.

[0033] 1) Preparation of Metal Salt Solution: Weigh 18.91 g of lithium acetate dihydrate, 4.852 g of nickel acetate tetrahydrate, 4.857 g of cobalt acetate tetrahydrate, and 19.852 g of manganese acetate tetrahydrate, respectively, and dissolve them in 1 L of deionized water. Add 61.04 g of citric acid monohydrate, and stir for at least 1 hour until the mixture is uniform to obtain a complexed metal salt solution. 2) Preparation of precursor powder The complexed metal salt solution was pumped into a spray dryer for spray drying. The spray drying atmosphere was air, the spray drying air inlet temperature was 230°C, the outlet temperature was 120°C, the peristaltic pump speed was 1500-2000 mL / h, the needle frequency was 20 Hz, and the spray pressure was 0.2 MPa to obtain a precursor powder. 3) Preparation of lithium-rich manganese-based layered oxides The precursor material was placed in a crucible and calcined in a muffle furnace. The temperature was raised to 1000°C at a heating rate of 3°C / min and calcined at 1000°C for 20 minutes. Fresh air was continuously introduced into the muffle furnace during calcination. After cooling with the furnace, the lithium-rich manganese positive electrode material RM-1 was obtained.

[0034] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0035] Comparative Example 5 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 ) The preparation method of O2 layered lithium-rich manganese-based positive electrode material is similar to that of Comparative Example 4, except that the temperature is raised from room temperature to 850°C at a heating rate of 3°C / min and calcined for 5 hours, and then naturally cooled to room temperature to obtain a lithium-rich manganese positive electrode material LRM-10.

[0036] 1) Preparation of metal salt precursor suspension Weigh 18.91 g of lithium acetate dihydrate, 4.852 g of nickel acetate tetrahydrate, 4.857 g of cobalt acetate tetrahydrate, and 19.852 g of manganese acetate tetrahydrate, respectively, and dissolve them in 1 L of deionized water. Add 61.04 g of citric acid monohydrate, and stir for at least 1 hour until the mixture is uniform, to obtain a complex metal salt solution. 2) Preparation of precursor powder The complexed metal salt solution was pumped into a spray dryer for spray drying. The spray drying atmosphere was air, the spray drying air inlet temperature was 230°C, the outlet temperature was 120°C, the peristaltic pump speed was 1500-2000 mL / h, the needle frequency was 20 Hz, and the spray pressure was 0.2 MPa to obtain a precursor powder. 3) Preparation of lithium-rich manganese-based layered oxides The precursor powder was placed in a crucible and sent into a muffle furnace. The temperature was raised to 850°C at a heating rate of 3°C / min and calcined at 850°C in the muffle furnace for 5 hours. Fresh air was continuously introduced into the muffle furnace during the entire heating and calcining process. After the calcination was completed, the furnace was cooled to obtain a lithium-rich manganese positive electrode material, LRM-10.

[0037] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0038] Comparative Example 6 Comparative Example 6 Preparation of 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 ) The method for preparing an O2 layered lithium-rich manganese-based positive electrode material is the same as in Example 1, except that a diameter of 0.3 mm, a weight of 600 g of sanding beads, a sand mill speed of 2000 rpm, and a sanding time of 15 min are used. The particle size distribution D50 of the metal salt precursor suspension after sanding is measured by a particle size analyzer and is 385 nm. The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0039] Comparative Example 7 Comparative Example 7 Preparation of 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 ) The method for preparing O2 layered lithium-rich manganese-based positive electrode material is similar to that of Example 1, except that a diameter of 0.3 mm, a sanding bead weight of 700 g, a sand mill speed of 2000 rpm, a sanding time of 15 min, and a particle size analyzer is used to test the particle size distribution D50 of the metal salt precursor suspension after sanding, which is 302 nm.

[0040] The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0041] Comparative Example 8 Comparative Example 8 Preparation of 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 ) The method for preparing an O2 layered lithium-rich manganese-based cathode material is the same as in Example 1, except that a diameter of 0.3 mm, a weight of 800 g of sanding beads, a sand mill speed of 2000 rpm, and a sanding time of 15 min are used. The particle size distribution D50 of the metal salt precursor suspension after sanding is measured by a particle size analyzer and is 217 nm. The slurry was prepared as in Example 1, and electrodes were assembled into batteries and subjected to the same electrochemical performance test. The performance test results are shown in Table 1.

[0042] 1. Physical and chemical properties and electrochemical performance tests of the embodiments of the present invention and the comparative examples The particle size D50 distribution curve of lithium-rich manganese-based materials under different conditions is as follows Figures 1-4 As shown, Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 The particle size D50 distribution curve of the lithium-rich manganese-based material under 900g conditions corresponding to Example 1, the particle size D50 distribution curve of the lithium-rich manganese-based material under 800g conditions of Comparative Example 8, the particle size D50 distribution curve of the lithium-rich manganese-based material under 700g conditions of Comparative Example 7, and the particle size D50 distribution curve of the lithium-rich manganese-based material under 600g conditions of Comparative Example 6 respectively; Figures 1-4 It can be seen that in Example 1, under the premise of a fixed sand mill speed of 2000 rpm, a time of 15 min, and a sand mill bead weight of 900 g, the particle size distribution D50 is 150 nm, which meets our requirements.

[0043] The electrochemical first cycle charge and discharge curves of lithium-rich manganese-based materials at 0.1C under different conditions are shown in the figure below. Figure 5 The electrochemical initial charge and discharge curves of lithium-rich manganese-based materials under different conditions are shown in Figure 6 As shown, from Figure 6 It can be seen that all materials meet the requirements of 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 ) O2 has a typical two-stage charging curve. Below 4.5V, there is a short platform where the redox reaction of transition metal cations occurs. Above 4.5V, there is a long platform where the redox reaction of oxygen anions occurs. Under the condition of 850℃-5h, that is, LRM-5, the first discharge capacity of the battery made of lithium-rich manganese-based positive electrode material can reach up to 292.49mAh / g. The 500-cycle discharge capacity curve of lithium-rich manganese-based material under different conditions is shown in the figure. Figure 7 As shown, from Figure 7 It can be seen that the positive electrode material of LRM-5 under the condition of 850℃-5h has only slight capacity decay after 500 cycles. The median voltage curve of 500 cycles of lithium-rich manganese-based materials under different conditions is as follows Figure 8 shown.

[0044] The XRD patterns of the lithium-rich manganese-based positive electrode materials of Comparative Examples 1-3 and Examples 1-5 of the present invention are as follows: Figure 9 As shown; Figure 9 The main diffraction peak of the sample is attributed to the NaFeO2 type layered structure of the R3-m space group, while the secondary peak at 20-25° is attributed to the ordered reflection of LiMn6, which is 0.5Li2MnO3·0.5Li(Ni 0.33 Co 0.33 Mn 0.33 ) Typical characteristics of O2 materials, the only difference is that the materials with too long and too short sintering time have poor crystallinity.

[0045] The scanning electron microscope images of the lithium-rich manganese-based positive electrode materials of Comparative Example 5 and Example 1 of the present invention are as follows: Figure 10 shown; from Figure 10 From the above, it can be seen that the lithium-rich manganese-based positive electrode material particles prepared by the sand milling and spraying dual coupling method in Example 1 of the present invention are spherical in morphology and uniform in particle size, while the particles prepared by the spraying method only in Comparative Example 5 are of different sizes, irregular in shape, and have poor particle size uniformity. The impedance curves of the lithium-rich manganese-based positive electrode materials of Comparative Examples 1-2 and Examples 1-3 of the present invention are as follows: Figure 11 shown. Figure 11This is the pre-cycling impedance curve for the lithium-rich manganese-based cathode material. The slope of the curve in the low-frequency region represents the lithium-ion diffusion capacity. Example 1: The lithium-ion diffusion capacity is strongest when the sand mill speed is fixed at 2000 rpm, the time is 15 minutes, the sand milling bead weight is 900g, and the calcination temperature is 850°C for 5 hours.

[0046] 2. Electrochemical Performance Data of Examples of the Invention and Comparative Examples

[0047] Table 1 First coulombic efficiency First discharge capacity Energy density Example 1 85.25％ 292.49mAh / g 1047.47mWh / g Example 2 84.40％ 282.25mAh / g 1001.39mWh / g Example 3 87.89％ 285.36mAh / g 1010.95mWh / g Example 4 85.60％ 283.51mAh / g 1015.48mWh / g Comparative Example 1 83.42％ 280.36mAh / g 1020.72mWh / g Comparative Example 2 84.24％ 261.30mAh / g 938.16mWh / g Comparative Example 3 82.19％ 273.74mAh / g 985.95mWh / g Comparative Example 4 78.83％ 275.12mAh / g 982.01mWh / g Comparative Example 5 71.76％ 279.36mAh / g 988.52mWh / g Comparative Example 6 80.19％ 223.38mAh / g 794.78mWh / g Comparative Example 7 83.38％ 244.90mAh / g 902.64mWh / g Comparative Example 8 85.14％ 260.14mAh / g 970.01mWh / g As can be seen from Table 1, Examples 1-4 show that the first discharge capacity of the battery prepared by the novel sanding and spraying dual-coupling method of the present invention for preparing lithium-rich manganese-based positive electrode materials can reach up to 288.60 mAh / g, the first Coulomb effect is as high as 85.36%, and the energy density is as high as 1034.00 mWh / g.

[0048] By comparison between Example 1 and Comparative Examples 6-8, it can be seen that in the process of preparing lithium-rich manganese-based positive electrode materials by a new sanding and spraying dual coupling method described in the present invention, under the same rotation speed and time conditions during sanding, the weight of the sanding beads increases from 600g, 700g, 800g to 900g, that is, when the ball-to-material ratio increases from 20:1, 23:1, 26:1 to 30:1, the particle size D50 distribution of the lithium-rich manganese-based positive electrode material meets 150nm.

[0049] By comparing Example 1 with Comparative Examples 1, 4, and 5, it can be seen that in the process of preparing lithium-rich manganese-based positive electrode materials using the novel sand milling and spraying dual coupling method described in the present invention, under the same sintering temperature and time conditions, the lithium-rich manganese-based positive electrode material battery prepared by the novel sand milling and spraying dual coupling method has a first-cycle discharge capacity of 292.49 mAh / g and a first-cycle coulombic efficiency of 85.25%, which are higher than those of Comparative Example 5 (279.36 mAh / g - 71.76%) using the spraying method alone; at the same time, the first-cycle discharge capacity of Comparative Example 1 is 280.36 mAh / g and the first-cycle coulombic efficiency is 83.42%, which are higher than the experimental results of Comparative Example 4 (275.12 mAh / g - 78.83%) using the spraying method alone. The novel sand milling and spraying dual coupling method described in the present invention refines the particle size of the lithium-rich manganese-based positive electrode material, which can improve the first coulombic efficiency and first discharge capacity of its lithium-rich layered oxide.

[0050] By comparing Examples 1, 2, 3, and 4 with Comparative Examples 2 and 3, it can be seen that in the process of preparing lithium-rich manganese-based positive electrode materials using the novel sand milling and spraying dual coupling method described in the present invention, within the range of sintering temperature of 850°C and time of 2-8h, the discharge capacity of the material fluctuates around 280mAh / g. The results show that at the same sintering temperature, the electrochemical performance of the lithium-rich layered oxide is lower when the calcination time is too long or too short. If the calcination time is too long, the refined grains will grow too large, and the lithium ion transmission will be too slow, resulting in a decrease in capacity (LRM-6: 850°C-6h discharge capacity is 285.36mAh / g; LRM-8: 850°C-8h discharge capacity is 283.51mAh / g); if the calcination time is too short, the layered structure of the material has not yet formed, and the electrochemical performance is poor (LRM-2: 850°C-2h discharge capacity is 282.25mAh / g). The optimal calcination temperature was 850°C for 5 hours, achieving a capacity of 292.49 mAh / g and a first-cycle coulombic efficiency of 85.25%. At this temperature, the lithium-rich manganese cathode material not only formed a well-crystalline layered structure but also maintained fine particles, which facilitated lithium ion transport. Consequently, high discharge capacity, first-cycle coulombic efficiency, and energy density were achieved under these conditions.

[0051] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling, characterized in that: The following steps are involved: Step 1: Add the lithium source, nickel source, cobalt source, and manganese source in a molar ratio of 1.515:0.165:0.165:0.665 to deionized water, heat to dissolve the lithium source, nickel source, and cobalt source in the deionized water, stop heating, and continue magnetic stirring to evenly disperse the manganese source to obtain a metal salt precursor suspension; Step 2: adding a dispersant to the metal salt precursor suspension, and grinding the metal salt precursor suspension with a nano sand mill to refine the particles to a particle size distribution D50 of 150 nm ± 20 nm; Step 3: The refined metal salt precursor suspension is spray-dried at high temperature to obtain a precursor powder; Step 4: Sinter the precursor powder at 850°C for 4-8 hours to obtain a lithium-rich manganese-based positive electrode material.

2. The method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling according to claim 1 is characterized in that: The lithium source is lithium hydroxide, the nickel source is nickel hydroxide, the cobalt source is cobalt hydroxide; and the manganese source is manganese dioxide.

3. The method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling according to claim 1 is characterized in that: The volume ratio of the total mass of the lithium source, nickel source, cobalt source, and manganese source to deionized water is 11:100 g / mL.

4. The method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling according to claim 1, characterized in that: The dispersant is sodium carboxymethyl cellulose.

5. The method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling according to claim 1, characterized in that: The mass volume ratio of the dispersant to the deionized water in step 1 is 1:300 g / mL.

6. The method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling according to claim 1, characterized in that: In step 2, the inlet temperature of the spray drying is 230° C., the outlet temperature is 120° C., the peristaltic pump speed is 1500-2000 mL / h, the needle frequency is 20 Hz, and the spray pressure is 0.2 MPa; the atmosphere for the spray drying is air.

7. The method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling according to claim 1, characterized in that: The nano sand mill used sand beads with a diameter of 0.3 mm and a composition of zirconium dioxide, with a rotation speed of 2000 rpm and a time of 15 min.

8. The method for preparing lithium-rich manganese-based positive electrode materials by sand milling and spraying dual coupling according to claim 1, characterized in that: In step 4, during high-temperature sintering, the obtained material precursor powder is placed in a crucible and sent into a muffle furnace, and the temperature is raised from room temperature to 850°C at a heating rate of 3°C / min. After sintering at this temperature, the material is naturally cooled in the furnace.

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