Modified lithium nickel manganese oxide cathode material, preparation method thereof and battery

Abstract

This invention discloses a modified lithium nickel manganese oxide cathode material, its preparation method, and a battery, belonging to the field of battery material technology. The preparation of the modified lithium nickel manganese oxide cathode material includes: spraying a nano-dispersion of a coating agent, dispersed by sand milling, into a fluidized bed via air atomization, mixing it with the flowing lithium nickel manganese oxide cathode material, and sintering; the particle size of the coating agent does not exceed 100 nm, and its amount does not exceed 10 wt% of the lithium nickel manganese oxide cathode material; the thickness of the coating layer is not less than 10 nm; the gas used to atomize the nano-dispersion of the coating agent is air, with a flow rate of 20 L / min to 50 L / min; the temperature of the hot air used to keep the lithium nickel manganese oxide cathode material in a flowing state is 100℃ to 130℃, and its inlet air volume is 0.2 m³ / min. 3 / min~0.5m 3 / min. This method can form a uniform, continuous, and dense thick coating layer on the surface of lithium nickel manganese oxide cathode material, thereby improving the capacity and cycle performance of the cathode material.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a modified lithium nickel manganese oxide cathode material, its preparation method, and a battery thereof. Background Technology

[0002] Lithium nickel manganese oxide (LNMO) cathode materials generally suffer from rapid capacity decline leading to short cycle life. The main reasons include: when cycling under high voltage conditions, the contact between the surface of the lithium nickel manganese oxide cathode material and the electrolyte, as well as the dissolution of manganese ions, will seriously affect the cycle and rate performance of the material; in addition, the surface of lithium nickel manganese oxide cathode materials has high activity and is prone to react with the electrolyte, which reduces cycle performance and safety.

[0003] Currently, coating the surface of lithium nickel manganese oxide cathode materials is often used to improve the above-mentioned problems, but existing coating methods have limited effect on improving cycle life and the corresponding capacity of the materials is low.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a modified lithium nickel manganese oxide cathode material, its preparation method, and a battery, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing a modified lithium nickel manganese oxide cathode material, comprising the following steps:

[0008] The coating agent nano-dispersion liquid, which has been dispersed by sand milling, is sprayed into a fluidized bed by airflow atomization and mixed with lithium nickel manganese oxide cathode material in a fluidized bed. The mixture is then sintered to obtain modified lithium nickel manganese oxide cathode material with a coating layer.

[0009] Among them, the particle size of the coating agent in the coating agent nano-dispersion is not more than 100 nm; the amount of coating agent is not more than 10 wt% of the lithium nickel manganese oxide cathode material; and the thickness of the coating layer is not less than 10 nm.

[0010] The gas used for atomizing the nano-dispersion of the coating agent is air, with a flow rate of 20 L / min to 50 L / min. Hot air is introduced into the fluidized bed to keep the lithium nickel manganese oxide cathode material in a flowing state. The temperature of the hot air is 100℃ to 130℃, and the inlet flow rate is 0.2 m³ / min. 3 / min~0.5m 3 / min.

[0011] In an optional embodiment, the thickness of the coating layer is 10 nm to 20 nm;

[0012] Alternatively, the amount of coating agent used is 1 wt% to 5 wt% of the lithium nickel manganese oxide cathode material.

[0013] In an optional embodiment, the coating agent includes at least one of yttrium oxide, tungsten oxide, and tantalum oxide.

[0014] In an optional embodiment, the concentration of the coating agent in the coating agent nanodispersion does not exceed 10 wt%.

[0015] In an optional embodiment, the sintering temperature is 500℃~800℃ and the sintering time is 6h~10h.

[0016] In an optional embodiment, the preparation of lithium nickel manganese oxide cathode material includes: mixing lithium nickel manganese oxide cathode material precursor with lithium source and then calcining it;

[0017] The general chemical formula of the lithium nickel manganese oxide cathode material precursor is Ni. x Mn y (OH)2, 0.2≤x≤0.3, y=1-x;

[0018] Lithium sources include lithium carbonate;

[0019] The ratio of the molar amount of Li in the lithium source to the total molar amount of Ni and Mn in the lithium nickel manganese oxide cathode material precursor is 0.5:1 to 0.55:1.

[0020] In an optional embodiment, the lithium nickel manganese oxide cathode material precursor is mixed with a lithium source and a dopant before calcination.

[0021] The dopant includes at least one of SrCO3, Sb2O3 and Nb2O5, and the amount of each dopant is 0.1wt% to 2wt% of the lithium nickel manganese oxide cathode material precursor.

[0022] In an optional embodiment, the calcination temperature is 900℃~1100℃ and the calcination time is 8h~15h.

[0023] Secondly, the present invention provides a modified lithium nickel manganese oxide cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0024] Thirdly, the present invention provides a battery, the raw materials for which the battery is prepared include the modified lithium nickel manganese oxide cathode material of the aforementioned embodiments.

[0025] The beneficial effects of this invention include:

[0026] This invention involves atomizing a milled and dispersed coating agent nano-dispersion into a fluidized bed using an airflow atomization. This mixture is then mixed with lithium nickel manganese oxide cathode material in a fluidized bed, sintered, and the temperature and flow rate of the hot air, the amount of coating agent nano-dispersion, and the airflow rate for atomizing the coating agent nano-dispersion are controlled. This process forms a uniform, continuous, dense, and relatively thick coating layer on the surface of the lithium nickel manganese oxide cathode material, which is beneficial for blocking Mn. 3+ The dissolution of the electrolyte prevents it from directly contacting the positive electrode surface, thus avoiding the electrolyte from eroding the surface of the positive electrode material during cycling and improving the capacity and cycle performance of the battery prepared from this lithium nickel manganese oxide positive electrode material. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 SEM image of the modified lithium nickel manganese oxide cathode material prepared in Example 1;

[0029] Figure 2 SEM image of the modified lithium nickel manganese oxide cathode material prepared in Example 2;

[0030] Figure 3 SEM image of the modified lithium nickel manganese oxide cathode material prepared in Comparative Example 1;

[0031] Figure 4 XPS images of the modified lithium nickel manganese oxide cathode materials prepared in Examples 1-2, Comparative Examples 1 and 3. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] The modified lithium nickel manganese oxide cathode material, its preparation method, and the battery provided by this invention will be described in detail below.

[0034] The inventors, through research, proposed that the limited effectiveness of existing coating methods in improving the cycle life of lithium nickel manganese oxide (LiMO) cathode materials stems from the fact that most existing methods involve mechanically mixing the coating agent with the LiMO cathode material, followed by high-temperature sintering to achieve the coating effect. For nano-sized metal oxide particles, the resulting coating typically exhibits an island-like, non-uniform distribution, making it difficult to obtain a thick coating layer. In other words, mechanical mixing rarely yields a uniform coating layer, making it difficult to achieve full coating of the LiMO cathode material. Furthermore, the coating layer obtained through mechanical mixing is prone to deformation during cycling due to the deformation of the LiMO cathode material and the presence of Li. + The insertion and removal of the material can lead to loss of the material, which reduces cycle performance and safety.

[0035] Unlike other cathode materials, lithium nickel manganese oxide cathode material contains Mn... 3+ Leaching is one of the main causes of cycle degradation. To effectively improve the cycle performance of lithium nickel manganese oxide cathode materials through coating, a continuous, dense, and uniform coating layer needs to be applied to the surface of the lithium nickel manganese oxide cathode material. This reduces the direct contact between the surface of the lithium nickel manganese oxide cathode material and the electrolyte, thus slowing down the dissolution of Mn. 3+ The dissolution of the lithium nickel manganese oxide cathode material improves its cycle performance.

[0036] Based on this, the present invention provides a method for preparing modified lithium nickel manganese oxide cathode material, comprising the following steps: spraying a coating agent nano-dispersion liquid dispersed by sand milling into a fluidized bed by airflow atomization, mixing it with lithium nickel manganese oxide cathode material in a fluidized bed in a flowing state, and sintering to obtain modified lithium nickel manganese oxide cathode material containing a coating layer.

[0037] The coating agent nano-dispersion is obtained by mixing a coating agent with water. The coating agent includes at least one selected from yttrium oxide, tungsten oxide, and tantalum oxide. The concentration of the coating agent in the coating agent nano-dispersion does not exceed 10 wt%, and can be, for example, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, or 0.5 wt%, or other values ​​within the range not exceeding 10 wt%. In some preferred embodiments, the concentration of the coating agent in the coating agent nano-dispersion is 1 wt% to 10 wt%.

[0038] The particle size of the coating agent in the nano-dispersion after sand milling should not exceed 100 nm. For example, it can be 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, or 10 nm, or other values ​​within the range of 100 nm. If the particle size of the coating agent in the nano-dispersion after sand milling exceeds 100 nm, it is not conducive to the density and uniformity of the coating, and affects the improvement of cycle performance.

[0039] The amount of coating agent used does not exceed 10 wt% of the lithium nickel manganese oxide cathode material. For example, it can be 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, or 0.5 wt%, or other values ​​within the range not exceeding 10 wt%. In some preferred embodiments, the amount of coating agent used is 1 wt% to 5 wt% of the lithium nickel manganese oxide cathode material. If the amount of coating agent exceeds 10 wt% of the lithium nickel manganese oxide cathode material, it will affect the normal insertion and extraction of lithium ions, leading to a significant decrease in the capacity of the modified lithium nickel manganese oxide cathode material.

[0040] The thickness of the coating layer is not less than 10 nm, for example, it can be 10 nm, 20 nm, 30 nm or 40 nm. In some preferred embodiments, the thickness of the coating layer is 10 nm to 20 nm. By setting the thickness of the coating layer to 10 nm to 20 nm, it is possible to effectively prevent manganese ion dissolution and prevent the electrolyte from directly contacting the positive electrode material. In addition, it can also avoid the insufficient capacity utilization that can easily lead to due to excessive coating layer thickness, which would affect the normal intercalation and deintercalation of lithium ions in the lithium nickel manganese oxide (LNMO) body.

[0041] In this invention, the gas used to atomize the coating agent nano-dispersion is air, and the air flow rate is 20 L / min to 50 L / min, such as 20 L / min, 25 L / min, 30 L / min, 35 L / min, 40 L / min, 45 L / min, or 50 L / min, or other values ​​within the range of 20 L / min to 50 L / min. If the air flow rate is too low, it is difficult to atomize the coating agent nano-dispersion, and the coating agent nano-dispersion will form droplets, resulting in poor coating effect; if the air flow rate is too high, it is not conducive to maintaining the integrity of the LNMO bulk morphology, and it is easy to form defects and micropowder on the surface, deteriorating the material properties.

[0042] In this invention, hot air is introduced into a fluidized bed to keep the lithium nickel manganese oxide cathode material in a fluidized state. The hot air can be introduced, exemplarily, from the bottom of the fluidized bed.

[0043] The temperature of the hot air can be between 100℃ and 130℃, such as 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, or 130℃, or other values ​​within the range of 100℃ to 130℃. By using hot air at the above temperatures, some of the water in the coating agent nano-dispersion can be evaporated upon contact with it, preventing excessive moisture from causing material agglomeration and uneven coating.

[0044] The intake volume of hot air can be 0.2m³. 3 / min~0.5m 3 / min, such as 0.2m3 / min, 0.25m 3 / min, 0.3m 3 / min, 0.35m 3 / min, 0.4m 3 / min, 0.45m 3 / min or 0.5m 3 / min, etc., can also be 0.2m. 3 / min~0.5m 3 Other values ​​within the / min range.

[0045] By setting the temperature and air intake of the hot air within the above range, combined with the amount of coating agent nano-dispersion and the air flow rate of the atomized coating agent nano-dispersion, it is beneficial for the coating agent to form a uniform, continuous, complete and dense coating on the surface of the lithium nickel manganese oxide cathode material.

[0046] In some alternative embodiments, the sintering temperature can be 500℃ to 800℃, such as 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, or other values ​​within the range of 500℃ to 800℃.

[0047] The sintering time can be 6h to 10h, such as 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h, or other values ​​within the range of 6h to 10h.

[0048] The above coating process is a continuous spray coating process.

[0049] Continuing from the above, this invention effectively blocks Mn by forming a uniform and relatively thick dense full coating on the surface of the lithium nickel manganese oxide cathode material. 3+ The dissolution of the electrolyte prevents it from directly contacting the positive electrode surface, thus preventing the electrolyte from eroding the surface of the positive electrode material during cycling.

[0050] In some optional embodiments, the preparation of lithium nickel manganese oxide cathode material may include: mixing lithium nickel manganese oxide cathode material precursor with a lithium source and then calcining it;

[0051] The general chemical formula of the lithium nickel manganese oxide cathode material precursor is Ni. x Mn y (OH)2, 0.2≤x≤0.3, y=1-x.

[0052] The lithium source includes lithium carbonate, and the ratio of the molar amount of Li in the lithium source to the total molar amount of Ni and Mn in the lithium nickel manganese oxide cathode material precursor is 0.5:1 to 0.55:1.

[0053] In other embodiments, the lithium nickel manganese oxide cathode material precursor can be mixed with a lithium source and a dopant before calcination. The dopant includes at least one of SrCO3, Sb2O3, and Nb2O5, and the amount of each dopant is 0.1wt% to 2wt% of the lithium nickel manganese oxide cathode material precursor, such as 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, or 2wt%, or other values ​​within the range of 0.1wt% to 2wt%.

[0054] In some optional embodiments, the calcination temperature can be between 900℃ and 1100℃, such as 900℃, 950℃, 1000℃, 1050℃, or 1100℃, or other values ​​within the range of 900℃ to 1100℃. The calcination time can be between 8h and 15h, such as 8h, 9h, 10h, 11h, 12h, 13h, 14h, or 15h, or other values ​​within the range of 8h to 15h.

[0055] It should be noted that lithium nickel manganese oxide cathode material precursors are also readily available for purchase. Furthermore, other conditions in the preparation process of lithium nickel manganese oxide cathode material precursors can be referenced from relevant existing technologies, and will not be elaborated upon or limited here.

[0056] Accordingly, the present invention also provides a modified lithium nickel manganese oxide cathode material, which is prepared by the above-described preparation method.

[0057] The modified lithium nickel manganese oxide cathode material includes lithium nickel manganese oxide cathode material and a coating layer covering the surface of the lithium nickel manganese oxide cathode material.

[0058] Furthermore, the present invention also provides a battery, the raw materials for which the modified lithium nickel manganese oxide cathode material described above is included. This battery exhibits high capacity and cycle retention.

[0059] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0060] Example 1

[0061] This embodiment provides a modified lithium nickel manganese oxide cathode material, the preparation method of which includes:

[0062] S1: Preparation of lithium nickel manganese oxide cathode material.

[0063] 1 kg of Ni 0.25 Mn 0.75 The (OH)₂ precursor was mixed with 207g of lithium carbonate and dopants (5g of SrCO₃, 5g of Sb₂O₃, and 5g of Nb₂O₅) and then calcined to obtain lithium nickel manganese oxide cathode material Li. 0.5 Ni 0.25 Mn 0.75O2, after being crushed by jaw crusher, is passed through a 400-mesh sieve for later use.

[0064] The heating rate during the calcination process is 3℃ / min, and the temperature is raised to 980℃ and held for 10 hours. The calcination is carried out in an air atmosphere.

[0065] S2: Coating of lithium nickel manganese oxide cathode material.

[0066] 500g of yttrium oxide nano-dispersion, which has been dispersed by sand milling, is atomized into a fluidized bed by airflow and mixed with 1kg of lithium nickel manganese oxide cathode material in a fluidized bed. The mixture is then sintered to obtain modified lithium nickel manganese oxide cathode material.

[0067] The concentration of yttrium oxide nano-dispersion was 10 wt%, and the particle size of yttrium oxide in the yttrium oxide nano-dispersion after sand milling was 50 nm. Air was used to atomize the yttrium oxide nano-dispersion at a flow rate of 35 L / min. Hot air was introduced into the fluidized bed to keep the lithium nickel manganese oxide cathode material in a flowing state; the temperature of the hot air was 115 °C, and the inlet flow rate was 0.35 m³ / min. 3 The heating rate during sintering was 3℃ / min, and the temperature was raised to 500℃ and held for 8 hours. Sintering was carried out in an air atmosphere. The thickness of the resulting coating layer was approximately 15nm.

[0068] Example 2

[0069] The difference between this embodiment and Embodiment 1 is that the amount of yttrium oxide nano-dispersion after sand milling is 100g.

[0070] Example 3

[0071] The difference between this embodiment and Embodiment 1 is that the coating agent is tantalum oxide.

[0072] Example 4

[0073] The difference between this embodiment and Embodiment 1 is that the coating agent is tungsten oxide.

[0074] Example 5

[0075] This embodiment provides a modified lithium nickel manganese oxide cathode material, the preparation method of which includes:

[0076] S1: Preparation of lithium nickel manganese oxide cathode material.

[0077] 1 kg of Ni 0.25 Mn 0.75 The (OH)₂ precursor is mixed uniformly with lithium carbonate and dopants (SrCO₃, Sb₂O₃, and Nb₂O₅) and then calcined to obtain lithium nickel manganese oxide cathode material Li. 0.5 Ni 0.25 Mn0.75 O2, after being crushed by jaw crusher, is passed through a 400-mesh sieve for later use.

[0078] The molar ratio of Li in lithium carbonate to the total molar ratio of Ni and Mn in the lithium nickel manganese oxide cathode precursor is 0.5:1. The amounts of SrCO3, Sb2O3, and Nb2O5 are all 0.1 wt% of the lithium nickel manganese oxide cathode precursor. The heating rate during calcination is 3 °C / min, and the temperature is raised to 900 °C and held for 15 h. Calcination is carried out in an air atmosphere.

[0079] S2: Coating of lithium nickel manganese oxide cathode material.

[0080] 500g of yttrium oxide nano-dispersion, which has been dispersed by sand milling, is atomized into a fluidized bed by airflow and mixed with 1kg of lithium nickel manganese oxide cathode material in a fluidized bed. The mixture is then sintered to obtain modified lithium nickel manganese oxide cathode material.

[0081] The concentration of yttrium oxide nano-dispersion was 10 wt%, and the particle size of yttrium oxide in the yttrium oxide nano-dispersion after sand milling was 100 nm. Air was used to atomize the yttrium oxide nano-dispersion at a flow rate of 50 L / min. Hot air was introduced into the fluidized bed to keep the lithium nickel manganese oxide cathode material in a flowing state; the temperature of the hot air was 100 °C, and the inlet flow rate was 0.5 m³ / min. 3 The heating rate during sintering was 3℃ / min, and the temperature was raised to 650℃ and held for 10 hours. Sintering was carried out in an air atmosphere. The thickness of the resulting coating layer was approximately 16nm.

[0082] Example 6

[0083] This embodiment provides a modified lithium nickel manganese oxide cathode material, the preparation method of which includes:

[0084] S1: Preparation of lithium nickel manganese oxide cathode material.

[0085] 1 kg of Ni 0.25 Mn 0.75 The (OH)₂ precursor is mixed uniformly with lithium carbonate and dopants (SrCO₃, Sb₂O₃, and Nb₂O₅) and then calcined to obtain lithium nickel manganese oxide cathode material Li. 0.5 Ni 0.25 Mn 0.75 O2, after being crushed by jaw crusher, is passed through a 400-mesh sieve for later use.

[0086] The molar ratio of Li in lithium carbonate to the total molar ratio of Ni and Mn in the lithium nickel manganese oxide cathode precursor is 0.55:1. The amounts of SrCO3, Sb2O3, and Nb2O5 are each 2 wt% of the lithium nickel manganese oxide cathode precursor. The heating rate during calcination is 3℃ / min, and the temperature is raised to 1100℃ and held for 8 hours. Calcination is carried out in an air atmosphere.

[0087] S2: Coating of lithium nickel manganese oxide cathode material.

[0088] 500g of yttrium oxide nano-dispersion, which has been dispersed by sand milling, is atomized into a fluidized bed by airflow and mixed with 1kg of lithium nickel manganese oxide cathode material in a fluidized bed. The mixture is then sintered to obtain modified lithium nickel manganese oxide cathode material.

[0089] The concentration of yttrium oxide nano-dispersion was 10 wt%, and the particle size of yttrium oxide in the yttrium oxide nano-dispersion after sand milling was 20 nm. Air was used to atomize the yttrium oxide nano-dispersion at a flow rate of 20 L / min. Hot air was introduced into the fluidized bed to keep the lithium nickel manganese oxide cathode material in a flowing state; the temperature of the hot air was 130 °C, and the inlet flow rate was 0.2 m³ / min. 3 The heating rate during sintering was 3℃ / min, and the temperature was raised to 800℃ and held for 6 hours. Sintering was carried out in an air atmosphere. The thickness of the resulting coating was approximately 14nm.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is that in S2, the mixing method of the materials is replaced by mechanical mixing, and the yttrium oxide nano-dispersion is replaced by 50g of nano-yttrium oxide powder.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 3 is that in S2, the mixing method of the materials is replaced by mechanical mixing, and the tantalum oxide nano-dispersion is replaced by 50g of nano-tantalum oxide powder.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 1 is that in S2, the amount of yttrium oxide nano-dispersion after sand milling is 50g.

[0096] Comparative Example 4

[0097] The difference between this comparative example and Example 1 is that in S2, the amount of yttrium oxide nano-dispersion after sand milling is 2000g.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 1 is that in S2, the particle size of yttrium oxide in the yttrium oxide nano-dispersion after sand milling is 150 nm.

[0100] Comparative Example 6

[0101] The difference between this comparative example and Example 1 is that in S2, the amount of yttrium oxide used is 15 wt% of the lithium nickel manganese oxide cathode material.

[0102] Comparative Example 7

[0103] The difference between this comparative example and Example 1 is that in S2, the air flow rate of the atomized coating agent nano-dispersion is 10 L / min.

[0104] Comparative Example 8

[0105] The difference between this comparative example and Example 1 is that in S2, the air flow rate of the atomized coating agent nano-dispersion is 60 L / min.

[0106] Comparative Example 9

[0107] The difference between this comparative example and Example 1 is that in S2, the temperature of the air in which the lithium nickel manganese oxide cathode material is in a flowing state is room temperature (approximately 25°C).

[0108] Comparative Example 10

[0109] The difference between this comparative example and Example 1 is that in S2, the intake volume of hot air that keeps the lithium nickel manganese oxide cathode material in a flowing state is 0.1 m³. 3 / min.

[0110] Test case

[0111] ① Taking Examples 1-2 and Comparative Example 1 as examples, the obtained modified lithium nickel manganese oxide cathode materials were observed by scanning electron microscopy (SEM). The SEM images are shown below. Figures 1 to 3 As shown.

[0112] Depend on Figures 1 to 3 It can be seen that, compared with the island-like thick coating during mechanical blending, using a fluidized bed to assist in coating the nano-dispersion of the coating agent can make the coating agent tightly, firmly and continuously coated on the surface of the lithium nickel manganese oxide cathode material, thereby playing a barrier role on the surface of the lithium nickel manganese oxide cathode material and preventing it from directly contacting the electrolyte.

[0113] ② Taking Examples 1-2 and Comparative Examples 1 and 3 as examples, XPS (X-ray photoelectron spectroscopy) tests were performed on the obtained modified lithium nickel manganese oxide cathode material and substrate (lithium nickel manganese oxide cathode material) to test the Mn element content on the material surface. The results are as follows: Figure 4 As shown.

[0114] Figure 4Taking the left-hand starting position as the reference, from top to bottom, they correspond to the substrate, Example 1, Example 2, Comparative Example 1, and Comparative Example 3.

[0115] Figure 4 In the test, a larger peak area indicates a higher Mn content on the surface of the tested material, with a testing depth of approximately 10 nm. Figure 4 As can be seen, the modified lithium nickel manganese oxide cathode materials obtained in Examples 1 and 2 show almost no detectable Mn element on the surface of the substrate (lithium nickel manganese oxide cathode material), indicating that the coating effect is dense and continuous, and the coating layer completely covers the cathode surface. In contrast, the conventional mechanical blending method in Comparative Example 1 yielded the same test results as the substrate (lithium nickel manganese oxide cathode material), indicating that mechanical blending cannot achieve continuous full coating. In Comparative Example 3, the insufficient amount of coating agent also resulted in a significantly worse coating effect.

[0116] ③ The modified lithium nickel manganese oxide cathode materials obtained in Examples 1-6 and Comparative Examples 1-10 were used to prepare 2025 coin cells and their electrochemical performance was tested. The preparation and testing methods are as follows:

[0117] The materials used in the preparation include: ternary cathode: carbon black: PVDF = 90:5:5, negative electrode is lithium metal, and electrolyte is Xinzhoubang (M10).

[0118] The test conditions included a charge / discharge voltage range of 3.5V to 4.95V, and one charge / discharge cycle at different rates (0.1C, 0.2C, 0.5C, 1C). Finally, the 1C capacity and cycle performance were tested at room temperature, and the results are shown in Table 1.

[0119] Table 1 Test Results

[0120]

[0121]

[0122] As can be seen from Table 1, the modified lithium nickel manganese oxide cathode materials obtained in Examples 1-6 are more conducive to improving the coin capacity and cycle retention rate of the battery than the modified lithium nickel manganese oxide cathode materials obtained in Comparative Examples 1-10.

[0123] In summary, the preparation method provided by this invention can form a uniform, continuous, dense, and relatively thick coating layer on the surface of lithium nickel manganese oxide cathode material, reducing the direct contact between the surface of the lithium nickel manganese oxide cathode material and the electrolyte, and slowing down the Mn content. 3+ The dissolution of [the substance] helps to improve the battery's capacity and cycle performance.

[0124] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a modified lithium nickel manganese oxide cathode material, characterized in that, Includes the following steps: The coating agent nano-dispersion liquid, which has been dispersed by sand milling, is sprayed into a fluidized bed by airflow atomization and mixed with lithium nickel manganese oxide cathode material in a fluidized bed. The mixture is then sintered to obtain modified lithium nickel manganese oxide cathode material with a coating layer. Wherein, the particle size of the coating agent in the coating agent nano-dispersion is not more than 100 nm; the amount of the coating agent is 1 wt% to 5 wt% of the lithium nickel manganese oxide cathode material; the thickness of the coating layer is 10 nm to 20 nm; and the coating agent is selected from at least one of yttrium oxide, tungsten oxide, and tantalum oxide. The gas used to atomize the coating agent nano-dispersion is air, and the air flow rate is 20 L / min to 50 L / min; hot air is introduced into the fluidized bed to keep the lithium nickel manganese oxide cathode material in a flowing state; the temperature of the hot air is 100℃ to 130℃; and the inlet volume of the hot air is 0.2 m³ / min. 3 / min~0.5m 3 / min.

2. The preparation method according to claim 1, characterized in that, The concentration of the coating agent in the coating agent nanodispersion does not exceed 10 wt%.

3. The preparation method according to claim 1, characterized in that, The sintering temperature is 500℃~800℃, and the sintering time is 6h~10h.

4. The preparation method according to claim 1, characterized in that, The preparation of the lithium nickel manganese oxide cathode material includes: mixing the lithium nickel manganese oxide cathode material precursor with a lithium source and then calcining it; The general chemical formula of the lithium nickel manganese oxide cathode material precursor is Ni. x Mn y (OH)2, 0.2≤x≤0.3, y=1-x; The lithium source includes lithium carbonate; The ratio of the molar amount of Li in the lithium source to the total molar amount of Ni and Mn in the lithium nickel manganese oxide cathode material precursor is 0.5:1 to 0.55:

1.

5. The preparation method according to claim 4, characterized in that, The lithium nickel manganese oxide cathode material precursor is mixed with the lithium source and dopant and then calcined. The dopant includes at least one of SrCO3, Sb2O3 and Nb2O5, and the amount of each dopant is 0.1wt% to 2wt% of the lithium nickel manganese oxide cathode material precursor.

6. The preparation method according to claim 4 or 5, characterized in that, The calcination temperature is 900℃~1100℃, and the calcination time is 8h~15h.

7. A modified lithium nickel manganese oxide cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

8. A battery, characterized in that, The raw materials for preparing the battery include the modified lithium nickel manganese oxide cathode material as described in claim 7.

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