Modified nickel cobalt lithium manganate positive electrode material and preparation method and application thereof
By generating a Co-doped modified barium strontium titanate coating layer on the surface of a single-crystal nickel-cobalt-manganese cathode material, the problems of lattice deformation and coating inhomogeneity in high-nickel ternary materials were solved, thereby improving lithium-ion transport efficiency and reducing transition metal dissolution, thus improving the cycle life and storage performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-12
- Publication Date
- 2026-03-24
AI Technical Summary
During cycling, high-nickel ternary materials experience lattice oxygen escape due to lattice deformation and electron transfer, leading to phase transitions and a decline in electrochemical performance. Meanwhile, traditional coating methods suffer from inhomogeneity and weak bonding.
Co-doped barium strontium titanate coating layer was generated in situ on the surface of single-crystal nickel-cobalt-manganese cathode material. The titanium source, strontium source and barium source were uniformly reacted by sol-gel method to form a uniform and dense coating layer, which enhances lithium-ion transport and reduces transition metal dissolution.
It improves the cycle life and storage time of the material, enhances lithium-ion transport efficiency, reduces the dissolution of transition metals, and improves the overall performance of the battery.
Smart Images
Figure CN121726362A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of cathode material technology, and more specifically, to a modified lithium nickel cobalt manganese oxide cathode material, its preparation method, and its application. Background Technology
[0002] To increase energy density and reduce cost, current cathode materials tend to have higher nickel content. However, NCM811 cathode materials have some problems, such as microcracks caused by lattice deformation during cycling, and Co... 3+ / 4+ The t2g band and O 2- The 2p orbitals overlap significantly at the top, resulting in a high potential (>4.3V vs Li / Li). + ) below Co 3+ During oxidation, electrons will be transferred from Co. 4+ The t2g orbital was transferred to O 2- The 2p orbital triggers lattice oxygen escape. Furthermore, in highly delithiated cathodes, high-valence transition metal cations (TM, especially Ni) are present. 4+ Electrons spontaneously transfer from the TM orbital to the 2p orbital of lattice oxygen, further exacerbating the release of lattice O. This escape can cause TM cations to migrate to adjacent Li plates, leading to a phase transition from a layered structure to a spinel structure. This hinders lithium-ion diffusion, resulting in poor electrochemical performance. Furthermore, the released O2 reacts violently with organic electrolytes, leading to thermal runaway.
[0003] To address these issues, researchers have explored various modification methods to improve the performance of high-nickel ternary materials. Surface coating is an effective modification strategy; however, traditional coating methods, such as solid-phase mechanical coating or CVD coating, suffer from problems like uneven coating and high costs. Furthermore, the coating layer formed by directly mixing and sintering metal oxides with the cathode material using traditional processes not only has poor uniformity but also weak adhesion to the substrate. During battery cycling, it is prone to peeling off due to volumetric deformation of the electrode material, leading to a decline in cycle performance and safety.
[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 cobalt manganese oxide cathode material, its preparation method and application, so as to solve or improve the above-mentioned technical problems.
[0006] This invention can be implemented as follows: In a first aspect, the present invention provides a method for preparing a modified lithium nickel cobalt manganese oxide cathode material, comprising the following steps: dissolving a barium source and a strontium source in a first solvent and heating to form a first solution; dissolving a titanium source, a single-crystal lithium nickel cobalt manganese oxide cathode material, and a cobalt source in a second solvent to form a second solution; adding the first solution to the second solution and stirring to obtain a mixed solution; adding deionized water dropwise to the mixed solution to carry out a hydrolysis reaction; after the reaction is completed, gelling the reaction mixture and then aging it; drying and heat-treating the aged material to obtain the modified lithium nickel cobalt manganese oxide cathode material.
[0007] In an optional embodiment, the preparation of the single-crystal nickel-cobalt-manganese cathode material includes: mixing nickel-cobalt-manganese hydroxide with a lithium source and then sintering it.
[0008] In an optional embodiment, the molecular formula of nickel-cobalt-manganese hydroxide is Ni x Co y Mn z (OH)2, where 0.6≤x≤0.8, 0.1≤y≤0.2, and x+y+z=1.
[0009] In an optional embodiment, the lithium source includes at least one of lithium hydroxide and lithium carbonate.
[0010] In an optional embodiment, sintering includes: heating to 850°C to 950°C at a heating rate of 2°C / min to 4°C / min, and holding at that temperature for 8h to 10h.
[0011] In an optional embodiment, the total concentration of barium and strontium in the first solution is 0.05 mol / L to 0.2 mol / L.
[0012] Alternatively, heating may be carried out at 75℃~85℃ with stirring for 0.5h~1h.
[0013] In an optional embodiment, the barium source includes at least one of barium acetate and barium carbonate.
[0014] In an optional embodiment, the strontium source includes at least one of strontium acetate and strontium carbonate.
[0015] In an optional embodiment, the first solvent includes at least one of acetic acid and anhydrous ethanol.
[0016] In an optional embodiment, the molar ratio of barium in the barium source to strontium in the strontium source is 0.6:0.4.
[0017] In an optional embodiment, the ratio of the sum of the molar amounts of barium in the barium source and strontium in the strontium source to the molar amounts of titanium in the titanium source is 1:1 to 1:1.2.
[0018] In an optional embodiment, the molar ratio of cobalt in the cobalt source to the total molar ratio of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.05:100 to 0.2:100.
[0019] In an optional embodiment, the titanium source includes at least one of tetrabutyl titanate and titanium tetrachloride.
[0020] In an optional embodiment, the cobalt source includes at least one of cobalt nitrate and cobalt acetate.
[0021] In an optional embodiment, the second solvent includes at least one of anhydrous ethanol and acetic acid.
[0022] In an optional embodiment, after the deionized water is added dropwise, stirring is continued for 1 to 2 hours to ensure the hydrolysis reaction is complete.
[0023] In an optional embodiment, gelation is carried out in a water bath at 75°C to 85°C; And / or, the aging time is 1h to 3h.
[0024] In an optional embodiment, drying is carried out at 115°C to 125°C for 20 to 28 hours; And / or, the heat treatment is carried out at 750℃~850℃ for 1h~3h.
[0025] Secondly, the present invention provides a modified lithium nickel cobalt manganese oxide cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.
[0026] Thirdly, the present invention provides a battery comprising the modified lithium nickel cobalt manganese oxide cathode material of the aforementioned embodiments.
[0027] The beneficial effects of this invention include: This invention creatively generates a Co-doped modified barium strontium titanate coating layer in situ on the surface of a single-crystal nickel-cobalt-manganese cathode material. This Co-doped modified barium strontium titanate coating layer is formed by heat treatment of a Co-doped modified barium strontium titanate coating agent. The aforementioned Co-doped modified barium strontium titanate coating agent exhibits piezoelectric properties; during battery charging and discharging, the material undergoes minute expansion and contraction due to changes in interatomic spacing, generating an additional electric field that accelerates lithium-ion transport efficiency. This invention utilizes a sol-gel method to ensure uniform reaction of the titanium, strontium, and barium sources, resulting in the in-situ growth of a uniform, dense, and continuous coating layer. Lithium ions can pass through the coating layer normally during charging and discharging without affecting the cathode capacity. Simultaneously, this coating layer reduces the direct contact between the nickel-cobalt-manganese cathode material and the electrolyte, effectively reducing the dissolution of transition metals, thereby significantly improving the material's cycle life and storage time. Attached Figure Description
[0028] 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.
[0029] Figure 1 The image shows a SEM image of the modified lithium nickel cobalt manganese oxide cathode material prepared in Example 1. Figure 2 SEM image of the modified lithium nickel cobalt manganese oxide cathode material prepared in Example 8; Figure 3 Here is a SEM image of the cathode material prepared in Comparative Example 1; Figure 4 The image shows the XRD pattern of the modified lithium nickel cobalt manganese oxide cathode material prepared in Example 1. Detailed Implementation
[0030] 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.
[0031] The modified lithium nickel cobalt manganese oxide cathode material, its preparation method, and its application provided by this invention will be described in detail below.
[0032] This invention provides a method for preparing a modified lithium nickel cobalt manganese oxide cathode material, comprising the following steps: S1: Dissolve the barium source and strontium source in the first solvent and heat to form the first solution.
[0033] In some alternative implementations, the barium source may exemplary include at least one of barium acetate and barium carbonate.
[0034] Strontium sources may, by way of example, include at least one of strontium acetate and strontium carbonate.
[0035] The first solvent may, by way of example, include at least one of acetic acid and anhydrous ethanol.
[0036] In some alternative embodiments, the total concentration of barium and strontium in the first solution can be 0.05 mol / L to 0.2 mol / L, such as 0.05 mol / L, 0.1 mol / L, 0.15 mol / L or 0.2 mol / L, or other values within the range of 0.05 mol / L to 0.2 mol / L.
[0037] The molar ratio of barium in the barium source to strontium in the strontium source can be 0.6:0.4.
[0038] If the total concentration of barium and strontium in the first solution is too low, it is not conducive to the formation of a uniform coating layer on the surface of lithium nickel cobalt manganese oxide material; if the total concentration of barium and strontium in the first solution is too high, it is not conducive to the reaction between the barium source and the strontium source. If the amount of barium source and strontium source exceeds their solubility in the solvent, they will be directly converted into impurity phase.
[0039] In some alternative embodiments, heating can be carried out at 75°C to 85°C (e.g., 75°C, 80°C, or 85°C) and with stirring for 0.5h to 1h (e.g., 0.5h or 1h). Stirring can be performed using magnetic stirring.
[0040] S2: Dissolve the titanium source, single-crystal nickel-cobalt-manganese cathode material, and cobalt source in the second solvent to form a second solution.
[0041] In some alternative embodiments, the titanium source may exemplary include at least one of tetrabutyl titanate and titanium tetrachloride.
[0042] The cobalt source may, by way of example, include at least one of cobalt nitrate and cobalt acetate.
[0043] The second solvent may, by way of example, include at least one of acetic acid and anhydrous ethanol.
[0044] The preparation of single-crystal nickel-cobalt-manganese cathode material includes: mixing nickel-cobalt-manganese hydroxide with a lithium source and sintering it, followed by jaw crusher and roller airflow pulverization for later use.
[0045] The molecular formula of nickel cobalt manganese hydroxide is Ni x Co y Mn z (OH)₂, 0.6≤x≤0.8, 0.1≤y≤0.2, x+y+z=1. For example, nickel-cobalt-manganese hydroxide can be Ni 0.8 Co 0.1 Mn 0.1 (OH)2, and the corresponding single-crystal nickel-cobalt-manganese cathode material is LiNi. 0.8 Co 0.1 Mn 0.1 O2.
[0046] The lithium source may, by way of example, include at least one of lithium hydroxide and lithium carbonate.
[0047] In some alternative embodiments, sintering may include: heating to 850°C to 950°C (e.g., 850°C, 900°C, or 950°C) at a heating rate of 2°C / min to 4°C / min (e.g., 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, or 4°C / min), and holding at that temperature for 8h to 10h (e.g., 8h, 8.5h, 9h, 9.5h, or 10h).
[0048] It should be noted that the preparation of nickel cobalt manganese hydroxide can also refer to the relevant existing technologies in this field, and no further limitations are imposed here.
[0049] The ratio of the sum of the molar amounts of barium in the barium source and strontium in the strontium source to the molar amounts of titanium in the titanium source is 1:1 to 1:1.2.
[0050] The ratio of the molar amount of cobalt in the cobalt source to the total molar amount of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material can be from 0.05:100 to 0.2:100, such as 0.05:100, 0.1:100, 0.15:100, or 0.2:100, or other values within the range of 0.05:100 to 0.2:100.
[0051] Co is mainly used for doping and modifying barium strontium titanate, refining its grain size, and optimizing its microstructure. Furthermore, Co doping significantly improves the dielectric and ferroelectric properties of barium strontium titanate, enhancing its functionality. In this invention, excess Co... 2+ It can react with Li and residual lithium salts (such as Li2CO3) on the surface of nickel-cobalt-manganese cathode materials to form lithium cobalt oxide. Lithium cobalt oxide is an excellent fast ion conductor, which is beneficial to improving the transport dynamics of lithium ions at the interface, thereby comprehensively improving the overall performance of the battery.
[0052] It should be noted that in this invention, S1 and S2 can be performed by performing S1 first and then S2, or by performing S2 first and then S1.
[0053] S3: Add the first solution to the second solution and stir to obtain a mixed solution.
[0054] The stirring time can be, for example, 0.5h to 1h.
[0055] S4: Add deionized water dropwise to the mixed solution to carry out the hydrolysis reaction.
[0056] In some alternative embodiments, deionized water is added dropwise to the mixed solution at room temperature. After the deionized water is added, stirring is continued for 1 to 2 hours (e.g., 1 hour, 1.5 hours, or 2 hours) to ensure that the hydrolysis reaction is complete.
[0057] S5: After the reaction is complete, the reaction mixture is gelled and then aged.
[0058] In some alternative embodiments, gelation can be carried out in a water bath at 75°C to 85°C (e.g., 75°C, 80°C, or 85°C).
[0059] Aging can be carried out at room temperature, and the aging time can be 1h to 3h, such as 1h, 1.5h, 2h, 2.5h or 3h, or other values within the range of 1h to 3h.
[0060] S6: The aged material is dried and heat-treated to obtain modified lithium nickel cobalt manganese oxide cathode material.
[0061] In some alternative embodiments, drying can be carried out at 115°C to 125°C (e.g., 115°C, 120°C, or 125°C) for 20 to 28 hours (e.g., 20 hours, 24 hours, or 28 hours).
[0062] In some alternative embodiments, the heat treatment can be carried out at 750°C to 850°C (e.g., 750°C, 800°C, or 850°C) for 1 hour to 3 hours (e.g., 1 hour, 2 hours, or 3 hours). The heat treatment process can be carried out in an oxygen atmosphere.
[0063] Building upon the above, this invention creatively generates a Co-doped modified barium strontium titanate coating layer in situ on the surface of a single-crystal nickel-cobalt-manganese cathode material. This Co-doped modified barium strontium titanate coating layer is formed by heat treatment of a Co-doped modified barium strontium titanate coating agent. The aforementioned Co-doped modified barium strontium titanate coating agent possesses piezoelectric properties; during battery charging and discharging, the material undergoes minute expansion and contraction due to changes in interatomic spacing, generating an additional electric field that accelerates lithium-ion transport efficiency. This invention utilizes a sol-gel method to ensure uniform reaction of the titanium, strontium, and barium sources, resulting in the in-situ growth of a uniform, dense, and continuous coating layer. Lithium ions can pass normally through the coating layer during charging and discharging without affecting the cathode capacity. Simultaneously, this coating layer reduces the direct contact between the nickel-cobalt-manganese cathode material and the electrolyte, effectively reducing the dissolution of transition metals, thereby significantly improving the material's cycle life and storage time.
[0064] Accordingly, the present invention also provides a modified lithium nickel cobalt manganese oxide cathode material, which is prepared by the above-described preparation method.
[0065] In addition, the present invention also provides a battery comprising the above-described modified lithium nickel cobalt manganese oxide cathode material.
[0066] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0067] Example 1 This embodiment provides a modified lithium nickel cobalt manganese oxide cathode material, the preparation method of which includes: S1: Dissolve barium acetate and strontium acetate in 50 mL of acetic acid, heat to 80 °C, and stir magnetically for 0.5 h to obtain the first solution.
[0068] The total concentration of Ba and Sr in the first solution is 0.1 mol / L, and the molar ratio of Ba to Sr is 0.6:0.4.
[0069] S2: Tetrabutyl titanate is mixed with 100g of single-crystal nickel-cobalt-manganese cathode material LiNi 0.8 Co 0.1 Mn 0.1 O2 and cobalt acetate are dissolved in a measured amount of acetic acid and stirred thoroughly for 0.5 hours to form a homogeneous second solution.
[0070] The molar ratio of Ba in the barium source to the sum of Sr in the strontium source and Ti in the titanium source is 1:1. The molar ratio of Co in the cobalt source to the total molar ratio of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.05:100.
[0071] Among them, the single-crystal nickel-cobalt-manganese cathode material LiNi 0.8 Co 0.1 Mn 0.1 The preparation of O2 includes: adding 3 kg of Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor was mixed evenly with 1.41 kg of lithium hydroxide, and then heated to 900 °C at a heating rate of 3 °C / min and held for 10 h. After being crushed by a jaw crusher and a double-roller air jet mill, single-crystal nickel-cobalt-manganese cathode material LiNi was obtained. 0.8 Co 0.1 Mn 0.1 O2.
[0072] S3: Add the first solution to the second solution and stir thoroughly for 0.5 hours to obtain a mixed solution.
[0073] S4: At room temperature, add deionized water dropwise to the mixed solution. After the addition is complete, continue stirring for 1.5 hours to ensure the hydrolysis reaction is complete.
[0074] S5: After the hydrolysis reaction is completed, the reaction mixture is placed in an 80°C water bath for gelation, and then aged at room temperature for 2 hours.
[0075] S6: The aged material is dried at 120℃ for 24 hours, and then heat-treated at 800℃ for 2 hours in a box furnace under oxygen atmosphere protection to obtain the modified lithium nickel cobalt manganese oxide cathode material, denoted as Co-Ba. 0.6 Sr 0.4 TiO3-coated NCM811.
[0076] Example 2 The difference between this embodiment and Embodiment 1 is that the molar ratio of Co in the cobalt source to the total molar ratio of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.1:100.
[0077] Example 3 The difference between this embodiment and Embodiment 1 is that the molar ratio of Co in the cobalt source to the total molar ratio of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.15:100.
[0078] Example 4 The difference between this embodiment and Embodiment 1 is that the molar ratio of Co in the cobalt source to the total molar ratio of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.2:100.
[0079] Example 5 The difference between this embodiment and Embodiment 1 is that the cobalt source is replaced with cobalt nitrate.
[0080] Example 6 The difference between this embodiment and Example 1 is that the total concentration of Ba and Sr elements in the first solution is 0.05 mol / L.
[0081] Example 7 The difference between this embodiment and Example 1 is that the total concentration of Ba and Sr elements in the first solution is 0.15 mol / L.
[0082] Example 8 The difference between this embodiment and Example 1 is that the total concentration of Ba and Sr elements in the first solution is 0.2 mol / L.
[0083] Example 9 The difference between this embodiment and Embodiment 1 is that the ratio of the sum of the molar amounts of Ba in the barium source and Sr in the strontium source to the molar amounts of Ti in the titanium source is 1:1.2.
[0084] Comparative Example 1 The difference between this comparative example and Example 1 is that the single-crystal nickel-cobalt-manganese cathode material LiNi 0.8 Co 0.1 Mn 0.1 O2 was not coated and was directly sintered at 800℃ for 2 hours.
[0085] Comparative Example 2 The difference between this comparative example and Example 1 is that the coating layer does not contain Co, that is, cobalt acetate was not added to S2.
[0086] Comparative Example 3 The difference between this comparative example and Example 1 is that the coating layer does not contain Sr, and the Sr portion is replaced with Ba. That is, the coating layer is Co-doped barium titanate.
[0087] Comparative Example 4 The difference between this comparative example and Example 1 is that the coating layer does not contain Ba, and the Ba portion is replaced with Sr. That is, the coating layer is Co-doped strontium titanate.
[0088] Comparative Example 5 The difference between this comparative example and Example 1 is that the molar ratio of barium in the barium source to strontium in the strontium source is 0.5:0.5.
[0089] Comparative Example 6 The difference between this comparative example and Example 1 is that the molar ratio of barium in the barium source to strontium in the strontium source is 0.7:0.3.
[0090] Comparative Example 7 The difference between this comparative example and Example 1 is that the molar ratio of cobalt in the cobalt source to the total molar ratio of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.02:100.
[0091] Comparative Example 8 The difference between this comparative example and Example 1 is that the molar ratio of cobalt in the cobalt source to the total molar ratio of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.4:100.
[0092] Test case (1) Taking Example 1, Example 8 and Comparative Example 1 as examples, the obtained cathode materials were observed by scanning electron microscopy, and their SEM images are as follows: Figures 1 to 3 As shown.
[0093] Depend on Figures 1 to 3 It can be seen that, compared with Comparative Example 1, the surface of the cathode materials in Examples 1 and 8 both have Co-Ba... 0.6 Sr 0.4 TiO3 coating layer, and the thickness of the coating layer gradually increases with the increase of coating amount.
[0094] (2) The modified lithium nickel cobalt manganese oxide cathode material prepared in Example 1 was subjected to XRD testing, and the results are as follows: Figure 4 As shown.
[0095] Depend on Figure 4 It can be seen that after coating, the lithium nickel cobalt manganese oxide cathode material exhibits a hexagonal α-NaFeO2 structure with an R-3m spatial structure, and no impurity phases were found, indicating that the coating did not have a significant impact on the layered structure of the lithium nickel cobalt manganese oxide cathode material.
[0096] (3) The ternary cathode materials obtained in Examples 1-9 and Comparative Examples 1-8 were assembled into 2032 coin cells and their electrochemical performance was tested.
[0097] The assembly method of the coin cell is as follows: it is carried out in a glove box with oxygen content <0.1ppm and water content <0.1ppm, with lithium sheet as negative electrode, PE separator, electrolyte obtained by mixing EC and DEC in a volume ratio of 1:1, and 1mol of LiPF6 is added to assemble a 2032 type coin cell.
[0098] The conditions for the button cell test included: a charging voltage range of 3.0V to 4.3V, charge-discharge tests at 0.1C, 0.2C, 0.5C, and 1C at a room temperature of 25℃, and finally, performance tests at a high temperature of 45℃ to evaluate the 1C capacity and cycle performance. The results for 0.1C capacity at 25℃, first-time efficiency, and 1C cycle performance at 45℃ are shown in Table 1.
[0099] Table 1 Test Results
[0100] As can be seen from Table 1, the modified lithium nickel cobalt manganese oxide cathode materials prepared in Examples 1-9 are more conducive to improving the coin capacity and cycle retention rate of the battery than the cathode materials prepared in Comparative Examples 1-8.
[0101] Comparing Examples 1-4, it can be seen that the capacity of the modified cathode material first increases and then decreases with the increase of Co doping amount. The main mechanism may be that: in the low doping stage, Co can inhibit the excessive growth of barium strontium titanate grains, refine their size, thereby improving the uniformity and bonding state of the coating layer, which is beneficial to improving the lithium-ion transport kinetics and structural stability of the ternary cathode material, and the capacity increases accordingly; however, when the Co doping amount further increases, it may cause abnormal coarsening of barium strontium titanate grains, resulting in uneven distribution of the coating layer, increased interfacial impedance, and thus capacity decay.
[0102] Comparing Examples 1 and 5, it can be seen that the Co source has little impact on capacity and cycling performance. Comparing Examples 1 and 6-8, it can be seen that as the coating amount increases, the capacity first increases and then decreases, while the cycling performance gradually increases. This may be because the coating layer is too thick, affecting the capacity and lithium-ion conduction. Comparing Examples 2 and 9, it can be seen that when the ratio of the sum of the molar amounts of Ba in the barium source and Sr in the strontium source to the molar amounts of Ti in the titanium source is 1:1.2, the impact on the experiment is small. Among Examples 1-9, Example 2 has the best overall effect.
[0103] In summary, this invention creatively generates a Co-doped modified barium strontium titanate coating layer in situ on the surface of a single-crystal nickel-cobalt-manganese cathode material. This Co-doped modified barium strontium titanate coating layer is formed by heat treatment of a Co-doped modified barium strontium titanate coating agent. The aforementioned Co-doped modified barium strontium titanate coating agent possesses piezoelectric properties; during battery charging and discharging, the material undergoes minute expansion and contraction due to changes in interatomic spacing, generating an additional electric field that accelerates lithium-ion transport efficiency. This invention utilizes a sol-gel method to enable uniform reaction of the titanium, strontium, and barium sources, resulting in the in-situ growth of a uniform, dense, and continuous coating layer. Lithium ions can pass normally through the coating layer during charging and discharging without affecting the cathode capacity. Simultaneously, this coating layer reduces the direct contact between the nickel-cobalt-manganese cathode material and the electrolyte, effectively reducing the dissolution of transition metals, thereby significantly improving the material's cycle life and storage time.
[0104] 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 cobalt manganese oxide cathode material, characterized in that, Includes the following steps: A barium source and a strontium source are dissolved in a first solvent and heated to form a first solution. A titanium source, a single-crystal nickel-cobalt-manganese cathode material, and a cobalt source are dissolved in a second solvent to form a second solution. The first solution is added to the second solution and stirred to obtain a mixed solution. Deionized water is added dropwise to the mixed solution to carry out a hydrolysis reaction. After the reaction is completed, the reaction mixture is gelled and then aged. The aged material is dried and heat-treated to obtain the modified nickel-cobalt-manganese lithium cathode material.
2. The preparation method according to claim 1, characterized in that, The preparation of the single-crystal nickel-cobalt-manganese cathode material includes: mixing nickel-cobalt-manganese hydroxide with a lithium source and then sintering it; Preferably, the molecular formula of the nickel-cobalt-manganese hydroxide is Ni x Co y Mn z (OH)2, where 0.6≤x≤0.8, 0.1≤y≤0.2, x+y+z=1; Preferably, the lithium source includes at least one of lithium hydroxide and lithium carbonate; Preferably, sintering includes: heating to 850°C to 950°C at a heating rate of 2°C / min to 4°C / min, and holding at that temperature for 8h to 10h.
3. The preparation method according to claim 1, characterized in that, The total concentration of barium and strontium in the first solution is 0.05 mol / L to 0.2 mol / L; Alternatively, heating may be carried out at 75℃~85℃ with stirring for 0.5h~1h; Preferably, the barium source includes at least one of barium acetate and barium carbonate; Preferably, the strontium source includes at least one of strontium acetate and strontium carbonate; Preferably, the first solvent includes at least one of acetic acid and anhydrous ethanol; Preferably, the molar ratio of barium in the barium source to strontium in the strontium source is 0.6:0.
4.
4. The preparation method according to claim 1, characterized in that, The ratio of the sum of the molar amounts of barium in the barium source and strontium in the strontium source to the molar amounts of titanium in the titanium source is 1:1 to 1:1.
2.
5. The preparation method according to claim 1, characterized in that, The ratio of the molar amount of cobalt in the cobalt source to the total molar amount of nickel, cobalt, and manganese in the single-crystal nickel-cobalt-manganese cathode material is 0.05:100 to 0.2:100; Preferably, the titanium source includes at least one of tetrabutyl titanate and titanium tetrachloride; Preferably, the cobalt source includes at least one of cobalt nitrate and cobalt acetate; Preferably, the second solvent includes at least one of acetic acid and anhydrous ethanol.
6. The preparation method according to claim 1, characterized in that, After the deionized water has been added dropwise, continue stirring for 1 to 2 hours to ensure the hydrolysis reaction is complete.
7. The preparation method according to claim 1, characterized in that, Gelation was carried out in a water bath at 75℃~85℃; And / or, the aging time is 1h to 3h.
8. The preparation method according to claim 1, characterized in that, Drying is carried out at 115℃~125℃ for 20h~28h; And / or, the heat treatment is carried out at 750℃~850℃ for 1h~3h.
9. A modified lithium nickel cobalt manganese oxide cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.
10. A battery, characterized in that, The battery comprises the modified lithium nickel cobalt manganese oxide cathode material as described in claim 9.