A lithium-rich manganese oxide positive electrode material with non-stoichiometric regulation of Ni / Co / Mn content, and its preparation method and application

Abstract

The present invention discloses a lithium-rich manganese oxide positive electrode material with non-quantitative control of Ni / Co / Mn content and its preparation method and application, belonging to the field of battery technology. Its chemical formula is Li 1.2 Ni 0.132+ x Co 0.172+y Mn 0.492+z O2, wherein x=0~±0.1, y=0~±0.1, z=0~±0.1. The lithium-rich manganese-based positive electrode material provided by the present invention reduces cation mixing by increasing the content of Ni or reducing the content of Co and Mn, thereby suppressing the attenuation of voltage and capacity. By increasing the content of Ni or reducing the content of Co and Mn, the interlayer spacing of the (003) crystal plane is expanded, the lithium ion diffusion coefficient is increased, and the rate performance is significantly improved. In addition, based on charge balance, increasing the Ni content reduces the valence of Ni and Mn in the lithium-rich manganese material, the transition metal contributes more capacity, and the median voltage is greatly increased to 3.72V.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a lithium-rich manganese oxide positive electrode material with non-stoichiometrically regulated Ni / Co / Mn content, and a preparation method and application thereof. Background Art

[0002] In the existing energy storage battery system, lithium-ion batteries have been widely used in mobile phones, digital cameras, power tools, laptops and other fields due to their advantages such as high energy density, long cycle life, low self-discharge, no memory effect, wide operating temperature range and environmental friendliness, and are gradually expanding to new energy vehicles and energy storage fields.

[0003] Lithium-rich manganese oxide cathode materials have attracted considerable attention due to their high discharge capacity (>250 mAh / g), high average voltage (~3.6 V), abundant manganese resources, and low cost, making them the preferred cathode material for next-generation lithium-ion batteries. However, these materials still face challenges such as poor cycling stability and severe capacity and voltage decay, which have severely hampered their commercialization.

[0004] Element doping and surface coating are currently commonly used modification methods for the cycle stability of lithium-rich manganese-based positive electrode materials. In the patent specification with publication number CN117317192A, the inventors disclosed a method for preparing La-doped lithium-rich manganese-based positive electrode materials, which slows down the generation of oxygen vacancies through strong La-O bonds and blocks the migration path of transition metal ions, thereby enhancing the cycle and voltage stability of lithium-rich manganese-based positive electrode materials. In the patent specification with publication number CN117878308A, the inventors disclosed the introduction of a polyurethane material with a strong ligand on the surface of the main material of the lithium-rich manganese-based positive electrode material. During the charge and discharge cycle, the polyurethane material can establish a bonding effect with the oxygen framework on the surface of the main material, thereby stabilizing the lattice oxygen of the main material, inhibiting the irreversible release of oxygen during the charge and discharge cycle, and greatly improving the cycle stability of the lithium-rich manganese-based positive electrode material. However, the above schemes all introduce additional doping elements or coating layers, and have the defects of complex processing technology and difficulty in large-scale commercial application, and need to be improved. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a lithium-rich manganese oxide positive electrode material with non-stoichiometric control of Ni / Co / Mn content, and its preparation method and application, so as to solve the problems of introducing additional doping elements or coating layers and complex processing technology in the existing lithium-rich manganese positive electrode material modification methods.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is Li 1.2 Ni 0.132+x Co 0.172+y Mn 0.492+z O2, where x = 0 ~ ± 0.1, y = 0 ~ ± 0.1, z = 0 ~ ± 0.1.

[0008] The present invention provides a lithium-rich manganese-based cathode material with high specific capacity, effectively reducing voltage and capacity decay, low material cost, and no doping with any other elements. Simply by increasing the Ni content or reducing the Co and Mn contents, the voltage and capacity decay can be suppressed, improving the material's rate performance. Furthermore, increasing the Ni content partially reduces Ni and Mn, activating the electrochemical activity of more transition metals, providing more capacity, and significantly increasing the median voltage to 3.72V.

[0009] Furthermore, its chemical formula is Li 1.2 Ni 0.132+x Co 0.172+y Mn 0.492+z O2, wherein x=0, ±0.04 or ±0.1; y=0, ±0.04 or ±0.1; z=0, ±0.06 or ±0.1.

[0010] The method for preparing the above-mentioned lithium-rich manganese oxide positive electrode material with non-stoichiometric control of Ni / Co / Mn content comprises the following steps:

[0011] (1) Preparation of precursor solution

[0012] Lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate are mixed and added into water, and stirred to obtain a product;

[0013] (2) Preparation of precursor materials

[0014] The precursor solution obtained in step (1) is spray-dried to obtain;

[0015] (3) Preparation of positive electrode materials

[0016] The precursor material obtained in step (2) is heat-treated to obtain the product.

[0017] The beneficial effects of the present invention are: the preparation process of the present invention is simple, environmentally friendly, the preparation conditions are mild, and it is conducive to large-scale industrial production and application.

[0018] Furthermore, in step (1), the stoichiometric ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.2: (0.032-0.232): (0.072-0.272): (0.392-0.592), and 3% by mass of lithium acetate dihydrate is additionally added to compensate for lithium loss during the heat treatment process.

[0019] Furthermore, in the precursor solution of step (1), the total concentration of metal acetate is 0.1-0.2 mol / L, and the concentration of citric acid monohydrate is 0.2-0.5 mol / L.

[0020] Furthermore, in step (1), the stirring speed is 300-1000 rpm, the time is 0.5-2 h, and the temperature is 20-30°C.

[0021] Furthermore, in step (2), the inlet temperature of the spray drying is 200-250° C., the outlet temperature is 80-120° C., and the feed rate is 0.5-2 L / h.

[0022] The beneficial effects of adopting the above-mentioned further technical solution are as follows: the present invention adopts a one-step spray drying method in combination with the use of monohydrated citric acid to atomize the feed liquid through an atomizer to obtain fine droplets. By controlling the inlet and outlet temperatures and pressures of the spray dryer, more than 90 to 95% of the water in the small droplets is rapidly evaporated in an instant during contact with hot air, allowing the metal acetate and lithium ions to react quickly and uniformly, thereby improving the preparation efficiency, achieving better dispersibility, and further enhancing the electrochemical performance of the prepared electrode material.

[0023] Furthermore, the heat treatment conditions in step (3) are: in an air atmosphere, heating to 900-1100° C. at a heating rate of 1-5° C. / min, and keeping warm for 10-30 minutes.

[0024] Application of the above-mentioned lithium-rich manganese oxide positive electrode material with non-stoichiometric control of Ni / Co / Mn content in the preparation of lithium-ion batteries.

[0025] The present invention has the following beneficial effects:

[0026] (1) Without the need to introduce additional doping elements or coating layers, simply increasing the Ni content or reducing the Co and Mn contents inhibits cation mixing, improves structural stability, and thus suppresses voltage and capacity attenuation. At the same time, increasing the Ni content or reducing the Co and Mn content expands the interlayer spacing of the (003) crystal plane and improves the rate performance of the material. In addition, the increase in Ni content partially reduces Ni and Mn, activating more transition metal electrochemical activity, providing more capacity, and significantly increasing the median voltage from 3.25V to 3.72V.

[0027] (2) In the lithium-rich manganese-based positive electrode material prepared by the present invention, a one-step spray drying method is used in combination with the use of monohydrated citric acid, so that the feed liquid is atomized by an atomizer to obtain fine droplets. By controlling the inlet and outlet temperature and pressure of the spray dryer, more than 90% to 95% of the water can be rapidly evaporated in an instant during the contact process between the small droplets and the hot air, so that the metal acetate and the lithium salt react uniformly and form a lithium-rich manganese precursor material powder with good dispersibility.

[0028] (3) The preparation method of the lithium-rich manganese-based positive electrode material provided by the present invention has a simple synthesis process. A lithium-rich manganese-based positive electrode material with excellent electrochemical performance can be obtained simply by adjusting the content of Ni, Co, and Mn in the material chemical formula without doping with any other elements. It is low in cost, environmentally friendly, and conducive to large-scale production and application.

[0029] (4) The lithium-rich manganese oxide positive electrode material Li 1.2 Ni 0.132+x Co 0.172 Mn 0.492 The lithium-ion battery prepared by using O2 (x = -0.1 to 0.1) has a median voltage increased from 3.25V to 3.72V. When x = 0.1, the capacity retention rate of the lithium-rich manganese oxide positive electrode material is as high as 71.90% and the voltage retention rate is as high as 88.17% after 200 cycles at a current density of 200mA / g. 1.2 Ni 0.132 Co 0.172+y Mn 0.492 The lithium-ion battery assembled with the optimal component sample (y = -0.1) prepared by O2 has a capacity retention rate of up to 86.78% and a voltage retention rate of up to 82.99% after 500 cycles at a current density of 200 mA / g. 1.2 Ni 0.132 Co 0.172 Mn 0.492+z A lithium-ion battery assembled with the optimal composition sample (z = -0.6) prepared with O2 exhibited a capacity retention rate of 66.93% and a voltage retention rate of 75.79% after 350 cycles at a current density of 1000 mA / g. The lithium-rich manganese oxide positive electrode material obtained by regulating the Ni / Co / Mn composition in the present invention has electrochemical properties superior to most lithium-rich manganese-based positive electrode materials, improving the performance and effectiveness of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is an SEM image of the lithium-rich manganese oxide positive electrode material obtained in Example 1-13 of Experimental Example 1;

[0031] Figure 2 The XRD patterns of the lithium-rich manganese oxide positive electrode materials obtained in Examples 1-4 and Example 13 in Experimental Example 2;

[0032] Figure 3 XRD patterns of the lithium-rich manganese oxide positive electrode materials obtained in Examples 5-8 and Example 13 of Experimental Example 2;

[0033] Figure 4 The XRD patterns of the lithium-rich manganese oxide positive electrode materials obtained in Examples 9-13 of Experimental Example 2;

[0034] Figure 5 TEM images of the lithium-rich manganese oxide positive electrode materials obtained in Examples 1, 4, and 13 of Experimental Example 3;

[0035] Figure 6 This is the XPS O 1s graph of the lithium-rich manganese oxide positive electrode materials obtained in Examples 1-4 and Example 13 in Experimental Example 4;

[0036] Figure 7 The XPS Ni 2p diagram of the lithium-rich manganese oxide positive electrode materials obtained in Examples 1-4 and Example 13 in Experimental Example 4;

[0037] Figure 8 This is the XPS Mn 3s graph of the lithium-rich manganese oxide positive electrode materials obtained in Examples 1-4 and Example 13 in Experimental Example 4;

[0038] Figure 9 This is a graph showing the first charge and discharge curves of the lithium-rich manganese oxide positive electrode materials obtained in Examples 1-4 and Example 13 in Experimental Example 5;

[0039] Figure 10 This is a graph showing the first charge and discharge curves of the lithium-rich manganese oxide positive electrode materials obtained in Examples 5-8 and Example 13 of Experimental Example 5;

[0040] Figure 11 This is the first charge and discharge curve of the lithium-rich manganese oxide positive electrode material obtained in Examples 9-13 of Experimental Example 5;

[0041] Figure 12 This is a median voltage decay graph of the lithium-rich manganese oxide positive electrode material obtained in Examples 1-13 of Experimental Example 5;

[0042] Figure 13 This is a cycling stability diagram of the lithium-rich manganese oxide positive electrode material obtained in Example 1-13 of Experimental Example 5;

[0043] Figure 14 This is a rate performance diagram of the lithium-rich manganese oxide positive electrode material obtained in Examples 1-13 in Experimental Example 5. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not intended to limit the scope of the invention. In the embodiments, if specific conditions are not specified, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0045] Example 1:

[0046] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.232 Co 0.172 Mn 0.492 O2.

[0047] The preparation method comprises the following steps:

[0048] (1) Preparation of precursor solution

[0049] 18.914 g of lithium acetate dihydrate, 8.660 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The mixture was mechanically stirred at 500 rpm at room temperature for 1 h to obtain a precursor solution.

[0050] (2) Preparation of precursor materials

[0051] The precursor solution obtained in step (1) was sent to a spray dryer using a peristaltic pump. The inlet temperature of the spray dryer was set to 230°C, the outlet temperature was set to 100°C, and the feed rate was set to 1L / h. The precursor material was obtained by spray drying under high temperature and high pressure.

[0052] (3) Preparation of positive electrode materials

[0053] The precursor material obtained in step (2) was placed in an alumina crucible with a length of 120 mm, a width of 120 mm, and a height of 50 mm. The alumina crucible was placed in a box furnace and heated at a heating rate of 3°C / min in an air atmosphere. The crucible was heat treated at 1000°C for 20 min to obtain Li 1.2 Ni 0.232 Co 0.172 Mn 0.492 O2 positive electrode material, named Ni232.

[0054] Example 2:

[0055] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li1.2 Ni 0.172 Co 0.172 Mn 0.492 O2.

[0056] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 6.420 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Ni172.

[0057] Example 3:

[0058] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.092 Co 0.172 Mn 0.492 O2.

[0059] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 3.434 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water, and 63.042 g of citric acid monohydrate was added. 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment process; the mixture was mechanically stirred at 500 rpm for 1 hour at room temperature to obtain a precursor solution, and the remaining steps were the same as those of Example 1. The obtained positive electrode material was named Ni092.

[0060] Example 4:

[0061] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.032 Co 0.172 Mn 0.492 O2.

[0062] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 1.194 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water, and 63.042 g of citric acid monohydrate was added. Furthermore, 3% by mass of lithium acetate dihydrate was added to compensate for lithium loss during the heat treatment process. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The obtained positive electrode material was named NiO32.

[0063] Example 5:

[0064] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.272 Mn 0.492 O2.

[0065] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 10.162 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Co272.

[0066] Example 6:

[0067] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.212 Mn 0.492 O2.

[0068] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 7.920 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Co212.

[0069] Example 7:

[0070] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.132 Mn 0.492 O2.

[0071] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 4.932 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Co132.

[0072] Example 8:

[0073] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.072 Mn 0.492 O2.

[0074] The preparation method is the same as that of Example 1, except that when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 2.69 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate are weighed and dissolved in 1 L of deionized water, and 63.042 g of citric acid monohydrate is added. Furthermore, 3% by mass of lithium acetate dihydrate is added to compensate for lithium loss during the heat treatment process. The precursor solution is obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps are the same as those of Example 1. The obtained positive electrode material is named Co072.

[0075] Example 9:

[0076] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.592 O2.

[0077] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 21.764 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Mn592.

[0078] Example 10:

[0079] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.552 O2.

[0080] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 20.293 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Mn552.

[0081] Example 11:

[0082] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.432 O2.

[0083] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 15.882 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Mn432.

[0084] Example 12:

[0085] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.392 O2.

[0086] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 14.411 g of manganese acetate tetrahydrate were weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate was added, and 3% by mass of lithium acetate dihydrate was additionally added to compensate for lithium loss during the heat treatment. The precursor solution was obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps were the same as those of Example 1. The resulting positive electrode material was named Mn392.

[0087] Example 13:

[0088] A lithium-rich manganese oxide cathode material with non-stoichiometric control of Ni / Co / Mn content, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0089] The preparation method is the same as that of Example 1, except that, when preparing the precursor solution, 18.914 g of lithium acetate dihydrate, 4.927 g of nickel acetate tetrahydrate, 6.426 g of cobalt acetate tetrahydrate, and 18.088 g of manganese acetate tetrahydrate are weighed and dissolved in 1 L of deionized water. 63.042 g of citric acid monohydrate is added, and 3% by mass of lithium acetate dihydrate is additionally added to compensate for lithium loss during the heat treatment. The precursor solution is obtained by mechanically stirring at 500 rpm at room temperature for 1 hour. The remaining steps are the same as those of Example 1. The obtained positive electrode material is named Ni132, Co172, or Mn492.

[0090] Test Example 1: SEM test

[0091] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-13 were subjected to SEM testing to observe the morphology and size of the lithium-rich manganese-based positive electrode materials.

[0092] The experimental results are as follows Figure 1 As shown, it can be seen that the lithium-rich manganese-based positive electrode materials prepared in the embodiments of the present invention all have a spherical morphology, a smooth surface, and a size of about 400-700 nm.

[0093] Test Example 2: XRD test

[0094] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-13 were subjected to XRD testing to test the average structure of the lithium-rich manganese-based positive electrode materials.

[0095] The experimental results are as follows Figure 2-Figure 4 As shown in the figure, it can be seen that increasing the Ni content or decreasing the Co and Mn contents increases the I(003) / I(104) ratio and decreases the cation mixing. In addition, decreasing the Ni content or decreasing the Co and Mn content causes the spinel phase to appear in the lithium-rich manganese-based cathode material.

[0096] Test Example 3: TEM test

[0097] The lithium-rich manganese-based positive electrode materials prepared in Examples 1, 4 and 13 were subjected to TEM testing to test the local structure of the lithium-rich manganese-based positive electrode materials.

[0098] The experimental results are as follows Figure 5 It can be seen that as the Ni content of the lithium-rich manganese-based positive electrode material prepared in the embodiment of the present invention increases, the (003) crystal plane spacing increases continuously, which can improve the Li + Deintercalation kinetics during charge and discharge.

[0099] Test Example 4: XPS Test

[0100] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-4 and Example 13 were subjected to TEM testing to test the valence states of the elements in the lithium-rich manganese-based positive electrode materials.

[0101] The experimental results are as follows Figure 6-Figure 8 As shown. It can be seen that as the Ni content of the lithium-rich manganese-based positive electrode material provided in this embodiment increases, the oxygen vacancy content gradually decreases. 2+ The content gradually increases and the Mn valence gradually decreases.

[0102] Test Example 5: Electrochemical Performance Test

[0103] (1) Preparation of positive electrode sheet

[0104] The lithium-rich manganese-based cathode material prepared in Example 1-13 and Super P were weighed in a mass ratio of 8:1 and placed in a ball mill. Tungsten carbide ball milling beads were added to achieve a ball-to-material mass ratio of 100:1. Alcohol was added as a dispersant. After ball milling for 6 hours, the mixture was dried in a drying oven to obtain a mixture A.

[0105] Weigh 285 mg of mixture A and 1250 mg of 1.2% CMC solution, stir at room temperature for 2 h, ultrasonicate for 2 h, stir again for 2 h, use a 0.1 μm scraper to coat on aluminum foil, place in a vacuum drying oven at 110 ° C for 20 h, cut into electrodes with a diameter of 10 mm, and then transfer the cut electrodes to a vacuum oven at 115 ° C for 10 h for use.

[0106] (2) Assemble CR2025 stainless steel button battery

[0107] Using a metallic lithium sheet as the negative electrode, 200 μL of LBC-3045I(G) commercial electrolyte was dripped into the battery. CR2025 stainless steel button cells were assembled in a glove box filled with argon and with a moisture content of less than 0.01 ppm. The battery was then left at 45°C for 40 hours before its charge and discharge performance was tested.

[0108] CR2025 stainless steel button battery electrochemical performance test:

[0109] The cycling performance of the batteries prepared in Examples 1-13 was tested using a constant current charge and discharge method. The test temperature was 25°C, the voltage window was 2.0-4.8V, and the current densities tested were 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C, respectively, where 1C = 200mA / g.

[0110] like Figures 9-11 As shown in FIG, as the Ni content increases, the specific capacity contributed by the transition metal cations gradually increases, which is mainly because the increase in Ni content causes the transition metal cations Mn and Ni to be partially reduced. 1.2 Ni 0.112 Co 0.172 Mn 0.492 The lithium-ion battery prepared by O2 has a maximum first discharge specific capacity of 279.41 mAh / g at a current density of 20 mA / g.

[0111] like Figure 12 and Figure 13 As shown, the lithium-rich manganese oxide positive electrode material Li 1.2 Ni 0.232 Co 0.172 Mn 0.492 After 200 cycles at a current density of 200 mA / g, the lithium-ion battery prepared by O2 has a capacity retention rate of up to 71.90% and a voltage retention rate of up to 88.17%. This is mainly because the increased non-stoichiometric Ni will pre-occupy the Li sites in the Li layer after entering the lattice, and these interlayer Ni atoms will coordinate with the adjacent O, thereby improving the stability of the lattice oxygen. 1.2 Ni 0.132 Co 0.072 Mn 0.492 The lithium-ion battery prepared by O2 has a capacity retention rate of up to 86.78% and a voltage retention rate of up to 82.99% after 500 cycles at a current density of 200 mA / g. 1.2 Ni0.132 Co 0.172 Mn 0.432 The lithium-ion battery prepared by O2 has a capacity retention rate of up to 66.93% and a voltage retention rate of up to 75.79% after 350 cycles at a current density of 1000mA / g.

[0112] like Figure 14 As shown, the increase in Ni content expands the interlayer spacing of the (003) crystal plane, making the lithium-rich manganese oxide positive electrode material Li 1.2 Ni 0.232 Co 0.172 Mn 0.492 The lithium-ion battery prepared by O2 still provides 81.44mAh / g capacity at a current density of 2000mA / g. 1.2 Ni 0.132 Co 0.072 Mn 0.492 The lithium-ion battery prepared by O2 still provides a capacity of 103mAh / g at a current density of 2000mA / g. 1.2 Ni 0.132 Co 0.172 Mn 0.432 The lithium-ion battery prepared with O2 still provides a capacity of 90mAh / g at a current density of 2000mA / g.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lithium-rich manganese oxide positive electrode material with non-stoichiometric control of Ni / Co / Mn content, characterized in that: Its chemical formula is Li 1.2 Ni 0.232 Co 0.172 Mn 0.492 O2 or Li 1.2 Ni 0.132 Co 0.072 Mn 0.492 O2 or Li 1.2 Ni 0.132 Co 0.172 Mn 0.432 O2; The preparation method comprises the following steps: (1) Preparation of precursor solution Lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate are mixed and added into water, and stirred to obtain a product; (2) Preparation of precursor materials The precursor solution obtained in step (1) is spray-dried to obtain; (3) Preparation of positive electrode materials The precursor material obtained in step (2) is heat-treated to obtain a product.

2. The lithium-rich manganese oxide positive electrode material with non-stoichiometric control of Ni / Co / Mn content according to claim 1, characterized in that: In the step (1), the total concentration of metal acetate in the precursor solution is 0.1-0.2 mol / L, and the concentration of citric acid monohydrate is 0.2-0.5 mol / L.

3. The lithium-rich manganese oxide positive electrode material with non-stoichiometric control of Ni / Co / Mn content according to claim 1, characterized in that: In step (2), the inlet temperature of the spray drying is 200-250°C, the outlet temperature is 80-120°C, and the feed rate is 0.5-2 L / h.

4. Use of the lithium-rich manganese oxide positive electrode material with non-stoichiometrically controlled Ni / Co / Mn content according to any one of claims 1 to 3 in the preparation of lithium-ion batteries.

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