Modified cobalt-free positive electrode material and preparation method and application thereof
By modifying the material by doping with molybdenum bulk phase and coating the surface of LYTP fast ion conductor, the problems of Li/Ni mixing and low conductivity in cobalt-free cathode materials were solved, achieving excellent rate and capacity performance and improving the electrochemical performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- EVE ENERGY CO LTD
- Filing Date
- 2022-12-27
- Publication Date
- 2026-06-05
AI Technical Summary
Existing cobalt-free cathode materials suffer from problems such as Li/Ni mixing, numerous surface side reactions, and low conductivity. Single coating or doping methods have limited improvement effects.
A modification preparation method combining molybdenum bulk doping and LYTP fast ion conductor surface coating was adopted. By using molybdenum bulk doping and LYTP fast ion conductor surface coating, side reactions between material particles and electrolyte were reduced, Li/Ni mixing was suppressed, and lithium ion transport rate was accelerated.
It significantly improves the rate and capacity performance of cobalt-free binary cathode materials, with a first discharge specific capacity of over 188.3 mAh/g at 0.1C and over 97.6 mAh/g at 5C, and improves the structural stability and lithium-ion conduction rate of the material.
Smart Images
Figure CN116130656B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a modified cobalt-free cathode material, its preparation method, and its application. Background Technology
[0002] In recent years, the penetration rate of lithium-ion batteries in portable electronic devices, power tools and electric vehicles has been increasing year by year, which has brought strong demand for lithium-ion batteries. As a result, the demand for cathode materials, an important component of lithium-ion batteries, has also increased accordingly.
[0003] Currently, widely used cathode materials such as lithium cobalt oxide and ternary nickel-cobalt-manganese oxide all contain cobalt. However, due to the relative scarcity of domestic cobalt resources and the persistently high price of cobalt, the cost of lithium-ion batteries remains high. Therefore, developing cobalt-free cathode materials has become an important direction in the lithium battery field. Among these, layered binary cathode materials such as LiNi... 0.5 Mn 0.5 O2 has become an ideal candidate for cobalt-free cathode materials due to its advantages such as the absence of cobalt, high theoretical capacity, and ease of synthesis. However, like ternary cathode materials, this material also suffers from problems such as Li / Ni mixing, numerous surface side reactions, and high residual alkali. In addition, the absence of Co in the material results in low electrical conductivity.
[0004] CN113903895A discloses a method for coating a cobalt-free cathode material, the cobalt-free cathode material, and a lithium-ion battery. The method includes: 1) mechanically fusing a metal oxide and boric acid to obtain a composite coating agent; 2) mixing the cobalt-free cathode material and the composite coating agent, and calcining to obtain the coated cobalt-free cathode material.
[0005] CN112751026A discloses a modification method for synthesizing binary nickel manganese oxide lithium cathode material through doping. The method includes the following steps: (1) dissolving lithium acetate, nickel acetate, manganese acetate and strontium acetate in deionized water to obtain an acetate solution; (2) dissolving citric acid in ethylene glycol to obtain a citric acid ethylene glycol solution; (3) adding the acetate solution to the citric acid ethylene glycol solution, heating and stirring until the solution becomes a green gel; (4) drying the green gel, grinding it, and sintering it in air to obtain the binary nickel manganese oxide lithium cathode material.
[0006] The above solutions use coating or doping to address the problem of cobalt-free materials, but coating or doping alone can only solve one aspect of the problem, thus bringing limited improvement. Summary of the Invention
[0007] The purpose of this invention is to provide a modified cobalt-free cathode material, its preparation method, and its application. This invention improves upon the defects of cobalt-free binary cathode materials, such as Li / Ni mixing, numerous surface side reactions, and low conductivity. The proposed molybdenum bulk phase doping and LYTP fast ion conductor surface coating technology combine their respective advantages, enabling the obtained cobalt-free binary cathode material to exhibit excellent rate and capacity performance.
[0008] To achieve this objective, the present invention adopts the following technical solution:
[0009] In a first aspect, the present invention provides a method for preparing a modified cobalt-free cathode material, the method comprising the following steps:
[0010] (1) Mix nickel source, manganese source, urea and first solvent, add molybdenum source and heat to react to obtain molybdenum-doped precursor;
[0011] (2) Mix the first lithium source, iridium source, titanium source and phosphorus source with the second solvent, add the molybdenum doped precursor described in step (1), stir and evaporate the solvent to obtain the coated precursor;
[0012] (3) The coated precursor obtained in step (2) is mixed with the second lithium source and sintered to obtain the modified cobalt-free cathode material.
[0013] This invention addresses the problems of Li / Ni mixing, numerous surface side reactions, and poor conductivity in layered cobalt-free binary cathode materials. It provides a modification preparation method that combines bulk doping with fast ion conductor coating. This method reduces side reactions between material particles and electrolyte, suppresses Li / Ni mixing, and accelerates lithium ion transport rate by bulk doping of molybdenum and surface coating with LYTP fast ion conductor. As a result, the obtained cobalt-free binary cathode material exhibits excellent rate and capacity performance.
[0014] Preferably, the nickel source in step (1) includes nickel acetate.
[0015] Preferably, the manganese source includes manganese acetate.
[0016] Preferably, the molybdenum source comprises ammonium molybdate.
[0017] Preferably, the first solvent comprises ultrapure water.
[0018] Preferably, the heating reaction temperature in step (1) is 150 to 200°C, for example: 150°C, 160°C, 170°C, 180°C, 190°C or 200°C.
[0019] Preferably, the heating reaction time is 5 to 14 hours, for example: 5 hours, 8 hours, 10 hours, 12 hours or 14 hours.
[0020] Preferably, the heating reaction is followed by cooling, filtration, and drying.
[0021] Preferably, in step (2), the first lithium source includes lithium nitrate.
[0022] Preferably, the iridium source comprises iridium nitrate.
[0023] Preferably, the titanium source includes tetrabutyl titanate.
[0024] Preferably, the phosphorus source includes phosphoric acid.
[0025] Preferably, the second solvent includes ethanol.
[0026] Preferably, the temperature at which the solvent is stirred and evaporated in step (2) is 80 to 90°C, for example: 80°C, 82°C, 85°C, 88°C or 90°C.
[0027] Preferably, in step (3), the second lithium source includes lithium hydroxide and / or lithium carbonate.
[0028] Preferably, the sintering temperature is 750–1000°C, for example: 750°C, 820°C, 900°C, 950°C, or 1000°C.
[0029] Preferably, the sintering treatment time is 8 to 16 hours, for example: 8 hours, 10 hours, 12 hours, 14 hours or 16 hours.
[0030] Preferably, the atmosphere for the sintering process includes any one or a combination of at least two of oxygen, argon, or air.
[0031] In a second aspect, the present invention provides a modified cobalt-free cathode material, which is prepared by the method described in the first aspect. The modified cobalt-free cathode material includes a molybdenum-doped cobalt-free core and an LYTP fast ion conductor coating layer disposed on the surface of the molybdenum-doped cobalt-free core.
[0032] In the modified cobalt-free cathode material of this invention, the bulk doping of molybdenum forms Mo-O bonds, and the high bond energy of the Mo-O bonds improves the structural stability of the material and reduces the Li / Ni mixing. The surface coating of the LYTP fast ion conductor not only improves the lithium-ion conduction rate of the material, but also inhibits the erosion of material particles by HF in the electrolyte, thereby reducing the occurrence of surface side reactions. The two work synergistically to effectively improve the rate and capacity performance of the material.
[0033] Preferably, with the molar amount of the molybdenum-doped cobalt-free core being 100%, the molar fraction of the molybdenum element is 0.5% to 3%, for example: 0.5%, 0.8%, 1%, 2% or 3%, etc.
[0034] Preferably, based on the mass of the modified cobalt-free cathode material as 100%, the mass fraction of the LYTP fast ion conductor coating layer is 0.5% to 4%, for example: 0.5%, 0.8%, 1%, 2%, 3% or 4%, etc.
[0035] Preferably, the chemical formula of the LYTP fast ion conductor coating is Li. a Y b Ti c (PO4)3, where 1a + 3b + 4c = 9, 0 <a<2,0<b<2,0<c<2。
[0036] Thirdly, the present invention provides a positive electrode sheet comprising the modified cobalt-free positive electrode material as described in the second aspect.
[0037] Fourthly, the present invention provides a lithium-ion battery comprising a positive electrode as described in the third aspect.
[0038] Compared with the prior art, the present invention has the following beneficial effects:
[0039] (1) This invention develops a modified preparation method that combines bulk doping with fast ion conductor coating. This method reduces the side reactions between material particles and electrolyte by bulk doping of molybdenum and surface coating of LYTP fast ion conductor, suppresses Li / Ni mixing, accelerates the lithium ion transport rate, and enables the obtained cobalt-free binary cathode material to exhibit excellent rate and capacity performance.
[0040] (2) The battery made of the cobalt-free binary cathode material described in this invention can achieve a specific capacity of more than 188.3 mAh / g at the first discharge of 0.1C and more than 97.6 mAh / g at the first discharge of 5C. Attached Figure Description
[0041] Figure 1 This is a comparison chart of the charge-discharge curves of the cathode materials described in Example 1 and Comparative Example 1.
[0042] Figure 2 This is a comparison chart of the rate performance of the cathode materials described in Example 1 and Comparative Example 1. Detailed Implementation
[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.
[0044] Example 1
[0045] This embodiment provides a modified cobalt-free cathode material, and the preparation method of the modified cobalt-free cathode material is as follows:
[0046] (1) Dissolve 0.01 mol of nickel acetate tetrahydrate, manganese acetate tetrahydrate and urea in 50 ml of ultrapure water, then add 1 mol% of ammonium molybdate, dissolve completely and transfer to the liner of the reactor, react at 180 °C for 8 h, cool and remove, filter and dry to obtain Mo-doped precursor.
[0047] (2) Dissolve lithium nitrate, iridium nitrate hexahydrate, phosphoric acid, and tetrabutyl titanate in 50 ml of ethanol (the amount of lithium nitrate, iridium nitrate hexahydrate, phosphoric acid, and tetrabutyl titanate added is based on coating 2% wt Li 1.4 Y 0.8 Ti 1.3 (PO4)3 fast ion conductor calculation), then add the above-treated precursor, and evaporate the solvent while stirring at 85°C; finally, grind the evaporated precursor with lithium carbonate (5% excess) thoroughly, and calcine at 850°C for 10 hours in an oxygen atmosphere to obtain the modified cobalt-free cathode material.
[0048] Example 2
[0049] This embodiment provides a modified cobalt-free cathode material, and the preparation method of the modified cobalt-free cathode material is as follows:
[0050] (1) Dissolve 0.01 mol of nickel acetate tetrahydrate, manganese acetate tetrahydrate and urea in 50 ml of ultrapure water, then add 2 mol% of ammonium molybdate, dissolve completely and transfer to the liner of the reactor, react at 180 °C for 8 h, cool and remove, filter and dry to obtain Mo-doped precursor.
[0051] (2) Dissolve lithium nitrate, iridium nitrate hexahydrate, phosphoric acid, and tetrabutyl titanate in 50 ml of ethanol (the amount of lithium nitrate, iridium nitrate hexahydrate, phosphoric acid, and tetrabutyl titanate added is based on coating 1.5% wt Li). 1.4 Y 0.8 Ti 1.3 (PO4)3 fast ion conductor calculation), then add the above-treated precursor, and evaporate the solvent while stirring at 85°C; finally, grind the evaporated precursor with lithium carbonate (5% excess) thoroughly, and calcine at 850°C for 10 hours in an oxygen atmosphere to obtain the modified cobalt-free cathode material.
[0052] Example 3
[0053] The only difference between this embodiment and Embodiment 1 is that the molybdenum doping level in the core is 0.3%, while the other conditions and parameters are exactly the same as in Embodiment 1.
[0054] Example 4
[0055] The only difference between this embodiment and Embodiment 1 is that the molybdenum doping level in the core is 4%, while the other conditions and parameters are exactly the same as in Embodiment 1.
[0056] Example 5
[0057] The only difference between this embodiment and Embodiment 1 is that the mass fraction of the coating layer in the modified cobalt-free cathode material is 0.3%, while the other conditions and parameters are exactly the same as in Embodiment 1.
[0058] Example 6
[0059] The only difference between this embodiment and Embodiment 1 is that the mass fraction of the coating layer in the modified cobalt-free cathode material is 5%, while the other conditions and parameters are exactly the same as in Embodiment 1.
[0060] Comparative Example 1
[0061] This comparative example provides a cobalt-free cathode material, and the preparation method of the cobalt-free cathode material is as follows:
[0062] 0.01 mol of nickel acetate tetrahydrate, manganese acetate tetrahydrate, and urea were dissolved in 50 ml of ultrapure water, then transferred to the lining of a reaction vessel and reacted at 180 °C for 8 h. After cooling, the mixture was removed, filtered, and dried to obtain the precursor. The precursor was then thoroughly ground with lithium carbonate (5% excess) and calcined at 850 °C for 10 h in an oxygen atmosphere to obtain the cobalt-free cathode material.
[0063] Comparative Example 2
[0064] The only difference between this comparative example and Example 1 is that it does not contain molybdenum; all other conditions and parameters are exactly the same as in Example 1.
[0065] Comparative Example 3
[0066] The only difference between this comparative example and Example 1 is that the LYTP coating layer is not provided; all other conditions and parameters are exactly the same as in Example 1.
[0067] Comparative Example 4
[0068] The only difference between this comparative example and Example 1 is that the cobalt-free cathode material and LYTP are coated by mixing and grinding. All other conditions and parameters are exactly the same as in Example 1.
[0069] Performance testing:
[0070] LIR2430 coin cells were fabricated using the cathode materials obtained in the examples and comparative examples. The cathode material:PVDF:SP ratio was 80%:10%:10%, and the electrical performance was tested within a voltage window of 2.5-4.6V. The test results are shown in Table 1.
[0071] Table 1
[0072]
[0073]
[0074] As can be seen from Table 1, and from Examples 1-2, the battery made of the cobalt-free binary cathode material of the present invention can achieve a specific capacity of over 188.3 mAh / g at the first discharge of 0.1C and over 97.6 mAh / g at the first discharge of 5C.
[0075] A comparison of Examples 1 and 3-4 shows that the molybdenum doping amount in the core of the modified cobalt-free cathode material of the present invention affects its performance. Controlling the molybdenum doping amount to 0.5-3% of the core molar amount results in a modified cobalt-free cathode material with better performance. If the molybdenum doping amount is too high, it will reduce the number of redox sites, thereby reducing the capacity of the material. If the molybdenum doping amount is too low, the effect on reducing Li / Ni mixing is poor, which is also not conducive to the capacity utilization of the material.
[0076] A comparison of Examples 1 and 5-6 shows that the mass percentage of the coating layer in the modified cobalt-free cathode material of the present invention affects its performance. Controlling the mass percentage of the coating layer to 0.5-4% of the mass of the modified cobalt-free cathode material results in a material with better performance. If the mass percentage of the coating layer is too high, agglomeration will occur, which will hinder lithium-ion transport, increase the lithium-ion transport distance, and thus reduce the rate performance. If the mass percentage of the coating layer is too low, incomplete coating will occur, resulting in an insignificant modification effect.
[0077] The charge-discharge curves and rate performance comparison charts of the cathode materials described in Example 1 and Comparative Example 1 are shown below. Figure 1-2 As shown, by Figure 1-2 The comparison shows that the first discharge specific capacity of the modified cobalt-free cathode material of the present invention at a discharge rate of 0.1C is 189.6mAh / g, which is higher than the 181.9mAh / g of the comparative example. Even at a high discharge rate of 5C, Example 1 still maintains a discharge specific capacity of about 100mAh / g, which is much higher than the approximately 70mAh / g of the comparative example at this time.
[0078] As can be seen from the comparison between Example 1 and Comparative Example 2, in the modified cobalt-free cathode material of the present invention, the bulk doping of molybdenum forms Mo-O bonds, and the high bond energy of Mo-O bonds improves the structural stability of the material and also reduces the Li / Ni mixing of the material.
[0079] As can be seen from the comparison between Example 1 and Comparative Example 3, the surface coating of the LYTP fast ion conductor of the present invention not only improves the lithium ion conduction rate of the material, but also inhibits the erosion of material particles by HF in the electrolyte, thereby reducing the occurrence of surface side reactions. The two work together to effectively improve the rate and capacity performance of the material.
[0080] As can be seen from the comparison between Example 1 and Comparative Example 4, the present invention has the advantages of better coating uniformity and less agglomeration compared with the technical solution of directly using fast ion conductor grinding and coating, thus exhibiting better electrochemical performance.
[0081] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A method for preparing a modified cobalt-free cathode material, characterized in that, The preparation method includes the following steps: (1) A nickel source, a manganese source, urea and a first solvent are mixed, and a molybdenum source is added and heated to react to obtain a molybdenum-doped precursor; (2) Mix the first lithium source, iridium source, titanium source and phosphorus source with the second solvent, add the molybdenum doped precursor described in step (1), stir and evaporate the solvent to obtain the coated precursor; (3) The coated precursor and the second lithium source obtained in step (2) are mixed and sintered to obtain the modified cobalt-free cathode material; The modified cobalt-free cathode material includes a molybdenum-doped cobalt-free core and a coating layer disposed on the surface of the molybdenum-doped cobalt-free core; With the molar amount of the molybdenum-doped cobalt-free core being 100%, the molar fraction of molybdenum is 0.5% to 3%. Based on the mass of the modified cobalt-free cathode material as 100%, the mass fraction of the coating layer is 0.5~4%.
2. The preparation method according to claim 1, characterized in that, The nickel source in step (1) includes nickel acetate.
3. The preparation method according to claim 1, characterized in that, The manganese source includes manganese acetate.
4. The preparation method according to claim 1, characterized in that, The molybdenum source includes ammonium molybdate.
5. The preparation method according to claim 1, characterized in that, The first solvent includes ultrapure water.
6. The preparation method according to claim 1, characterized in that, The heating reaction in step (1) is carried out at a temperature of 150~200℃.
7. The preparation method according to claim 1, characterized in that, The heating reaction takes 5 to 14 hours.
8. The preparation method according to claim 1, characterized in that, The heating reaction is followed by cooling, filtration, and drying.
9. The preparation method according to claim 1, characterized in that, Step (2) The first lithium source includes lithium nitrate.
10. The preparation method according to claim 1, characterized in that, The iridium source includes iridium nitrate.
11. The preparation method according to claim 1, characterized in that, The titanium source includes tetrabutyl titanate.
12. The preparation method according to claim 1, characterized in that, The phosphorus source includes phosphoric acid.
13. The preparation method according to claim 1, characterized in that, The second solvent includes ethanol.
14. The preparation method according to claim 1, characterized in that, The temperature at which the solvent is stirred and evaporated in step (2) is 80~90℃.
15. The preparation method according to claim 1, characterized in that, Step (3) The second lithium source includes lithium hydroxide and / or lithium carbonate.
16. The preparation method according to claim 1, characterized in that, The sintering temperature is 750~1000℃.
17. The preparation method according to claim 1, characterized in that, The sintering process takes 8 to 16 hours.
18. The preparation method according to claim 1, characterized in that, The atmosphere for the sintering process includes any one or a combination of at least two of oxygen, argon, or air.
19. A modified cobalt-free cathode material, characterized in that, The modified cobalt-free cathode material is prepared by the method described in any one of claims 1-18, and the modified cobalt-free cathode material comprises a molybdenum-doped cobalt-free core and a coating layer disposed on the surface of the molybdenum-doped cobalt-free core; With the molar amount of the molybdenum-doped cobalt-free core being 100%, the molar fraction of molybdenum is 0.5% to 3%. Based on the mass of the modified cobalt-free cathode material as 100%, the mass fraction of the coating layer is 0.5~4%.
20. A positive electrode sheet, characterized in that, The positive electrode comprises the modified cobalt-free positive electrode material as described in claim 19.
21. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode as described in claim 20.