Modification method of ternary positive electrode material
By introducing rare earth elements to form a fast ion conductor coating during the co-precipitation process of the ternary positive electrode material precursor, the problem of side reactions when the ternary positive electrode material comes into contact with the electrolyte is solved, and the cycle stability and electrochemical performance of the material are improved.
Patent Information
- Application Number
- CN202510832600.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-20
- Publication Date
- 2025-09-26
AI Technical Summary
Existing ternary positive electrode materials undergo side reactions when in contact with electrolytes, resulting in active lithium consumption and transition metal dissolution, resulting in insufficient cycle performance.
Rare earth element sulfate is introduced during the co-precipitation process of the ternary positive electrode material precursor to form a rare earth hydroxide coating layer, and a fast ion conductor coating layer is formed by calcination. After simultaneous lithiation, a uniform coating layer is formed on the material surface.
The cycle stability and electrochemical performance of the positive electrode material are improved, the occurrence of side reactions is reduced, the 0.1C discharge specific capacity, first efficiency and high current density discharge capacity are increased, and the capacity retention rate after 50 cycles is significantly improved.
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Abstract
Description
Technical Field
[0001] The invention relates to a method for modifying a ternary positive electrode material, and belongs to the field of modification of positive electrode materials. Background Art
[0002] Lithium-ion batteries are highly regarded in the electric vehicle and energy storage systems due to their high capacity and long life. As one of the four main materials of lithium-ion batteries, the positive electrode material has a significant impact on the performance of the battery.
[0003] Although the energy density of the currently common ternary positive electrode materials is significantly superior to that of lithium iron phosphate, their cycle performance still severely restricts their use scenarios. The reason is that due to the direct contact between the positive electrode material and the electrolyte, a large number of side reactions occur on the surface of the material, which consumes active lithium while corroding the surface positive electrode material, thereby dissolving the transition metal. For this reason, the industry has carried out a large number of targeted modification measures on ternary materials to improve their service life. Currently, the commonly used modification methods include electrochemical regulation, surface modification, and bulk doping, among which surface coating is the most common. Traditional coating methods often require an additional calcination step to form a coating layer on the positive electrode surface, and due to the agglomeration, random distribution, and irregular particle shape of the material, it is impossible to form a low-thickness, uniform coating layer on the surface of the positive electrode particles. Summary of the Invention
[0004] The purpose of the present invention is to provide a method for coating and modifying a ternary positive electrode material and the obtained fast ion conductor coated ternary positive electrode material, so as to solve the problem of complicated steps in the existing fast ion conductor coating method.
[0005] The present invention adopts a synchronous physical and chemical method, and introduces rare earth element sulfate in the process of synthesizing a ternary material precursor by co-precipitation of transition metal sulfate. Since there is a significant difference in ionic radius between rare earth elements and transition metal elements Ni, Co, and Mn, and rare earth element sulfate is introduced after the dropwise addition of Ni, Co, and Mn element sulfates, the rare earth elements will form a layer of rare earth hydroxide on the surface of the precursor during the co-precipitation process, and will be simultaneously lithiated during the calcination process with the lithium source, thereby forming a fast ion conductor containing the rare earth element in situ on the surface of the positive electrode material.
[0006] Specifically, the method for coating and modifying a ternary cathode material provided by the present invention comprises the following steps:
[0007] S1. Co-precipitating a solution of a transition metal sulfate under an inert gas atmosphere; adding a solution of a sulfate of a rare earth element simultaneously during the co-precipitation process to form a ternary precursor having a surface coated with a rare earth hydroxide;
[0008] S2, mixing the ternary precursor obtained in step S1 with a lithium source, calcining under an air atmosphere, and cooling to obtain a ternary cathode material coated with a fast ion conductor;
[0009] The rare earth element is selected from one or more of the following: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu);
[0010] The transition metal sulfate is a soluble salt of Ni, Co, and Mn.
[0011] Preferably, the molar ratio of Ni, Co, and Mn in the transition metal sulfate is x:y:z, wherein 0.10≤x≤0.90, 0.04≤y≤0.33, 0.01≤z≤0.33, and x+y+z=1; the equivalent ratio may be 1:1:1, 5:2:3, 6:2:2, 7:1:2, or 8:1:1;
[0012] The coprecipitation reaction is carried out at a pH of 11-12.
[0013] Preferably, the inert atmosphere is nitrogen or argon.
[0014] Preferably, the molar ratio of the ternary precursor to the lithium source is 1:1.03-1.05, and they are mixed by dry method.
[0015] Preferably, the calcination temperature is 800-900°C and the time is 10-12 hours;
[0016] Preferably, the cooling is natural cooling.
[0017] The fast ion conductor coated ternary cathode material prepared by the method of the present invention has the chemical formula Li x (Ni a Co b Mn c )O2 / (LiMO2) d , wherein 1.00≤x≤1.09, 0.10≤a≤0.90, 0.04≤b≤0.33, 0.01≤c≤0.33, and a+b+c=1; 0.01≤d≤0.05, and M is a lanthanide rare earth element.
[0018] The thickness of the coating layer of the fast ion conductor coating the ternary cathode material is 3-5 nm.
[0019] The present invention adds rare earth element sulfate during the co-precipitation process to precipitate rare earth element hydroxide on the surface of the precursor, removes the lithium source and mixes evenly after filtering and drying, and obtains a ternary positive electrode material uniformly coated with a fast ion conductor containing rare earth elements after calcination, thereby reducing the occurrence of side reactions on the material surface and improving the cycle stability of the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 This is a scanning electron microscope image of the ternary positive electrode material prepared in Comparative Example 1 of the present invention.
[0021] Figure 2 This is a scanning electron microscope image of the ternary positive electrode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION
[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.
[0023] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.
[0024] Example 1:
[0025] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 1:1:1 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1 The amount of Er2(SO4)3 solution added was calculated based on the coating amount. After the addition was completed, the solution was aged for 5 minutes to obtain an Er(OH)3-coated precursor.
[0026] (2) The Er(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.33 Co 0.33 Mn 0.33 O2 / (LiErO2) 0.03 The coating layer thickness is 3-5nm.
[0027] Example 2:
[0028] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 1:1:1 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1Ce2(SO4)3 solution, the amount of solution added is calculated according to the coating amount, and after the addition is completed, it is aged for 5 minutes to obtain a Ce(OH)3-coated precursor;
[0029] (2) The Ce(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.33 Co 0.33 Mn 0.33 O2 / (LiCeO2) 0.03 The coating layer thickness is 3-5nm.
[0030] Example 3:
[0031] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 5:2:3 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1 Eu2(SO4)3 solution, the amount of solution added is calculated according to the coating amount, and after the addition is completed, it is aged for 5 minutes to obtain the Eu(OH)3-coated precursor;
[0032] (2) The Eu(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.5 Co 0.2 Mn 0.3 O2 / (LiEuO2) 0.03 The coating layer thickness is 3-5nm.
[0033] Example 4:
[0034] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 5:2:3 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1 The amount of Nd2(SO4)3 solution added was calculated based on the coating amount. After the addition was completed, the precursor was aged for 5 minutes to obtain the Nd(OH)3-coated precursor.
[0035] (2) The Nd(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.5 Co 0.2 Mn 0.3 O2 / (LiNdO2) 0.03 The coating layer thickness is 3-5nm.
[0036] Example 5:
[0037] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 6:2:2 in deionized water to prepare 2
[0038] mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1 The amount of Sm2(SO4)3 solution added was calculated based on the coating amount. After the addition was completed, the precursor was aged for 5 minutes to obtain the Sm(OH)3-coated precursor.
[0039] (2) The Sm(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.6 Co 0.2 Mn 0.2 O2 / (LiSmO2) 0.03 The coating layer thickness is 3-5nm.
[0040] Example 6:
[0041] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 6:2:2 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1 The amount of Pm2(SO4)3 solution added was calculated based on the coating amount. After the addition was completed, the precursor was aged for 5 minutes to obtain the Pm(OH)3-coated precursor.
[0042] (2) The Pm(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.6 Co 0.2 Mn 0.2O2 / (LiPmO2) 0.03 The coating layer thickness is 3-5nm.
[0043] Example 7:
[0044] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 8:1:1 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 12. After the transition metal sulfate solution was titrated, 1 mol L -1 The amount of solution added was calculated based on the coating amount. After the addition was completed, the precursor was aged for 5 minutes to obtain the Ho(OH)3-coated precursor.
[0045] (2) The Er(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 900°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 / (LiHoO2) 0.03 The coating layer thickness is 3-5nm.
[0046] Example 8:
[0047] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 8:1:1 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 12. After the transition metal sulfate solution was titrated, 1 mol L -1 The amount of solution added was calculated based on the coating amount. After the addition was completed, the precursor was aged for 5 minutes to obtain the Pr(OH)3-coated precursor.
[0048] (2) The Pr(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 900°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 / (LiPrO2) 0.03 The coating layer thickness is 3-5nm.
[0049] Example 9:
[0050] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 7:1:2 in deionized water to prepare 2 mol L -1The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1 The La2(SO4)3 solution was added, and the amount of solution added was calculated according to the coating amount. After the addition was completed, the precursor was aged for 5 minutes to obtain the La(OH)3-coated precursor.
[0051] (2) The La(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.7 Co 0.1 Mn 0.2 O2 / (LiLaO2) 0.03 The coating layer thickness is 3-5nm.
[0052] Example 10:
[0053] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 7:1:2 in deionized water to prepare 2 mol L -1 The coprecipitation experiment was carried out under a nitrogen atmosphere at pH = 11.5. After the transition metal sulfate solution was titrated, 1 mol L -1 The amount of Tb2(SO4)3 solution added was calculated based on the coating amount. After the addition was completed, the precursor was aged for 5 minutes to obtain the Tb(OH)3-coated precursor.
[0054] (2) The Tb(OH)3-coated precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.7 Co 0.1 Mn 0.2 O2 / (LiTbO2) 0.03 The coating layer thickness is 3-5nm.
[0055] Comparative Example 1:
[0056] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 1:1:1 in deionized water to prepare 2 mol L -1 A co-precipitation experiment was carried out with a sulfate solution at pH = 11.5 under a nitrogen atmosphere. After the transition metal sulfate solution was titrated, the precursor was filtered and dried.
[0057] (2) The precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.33 Co 0.33 Mn 0.33 O2.
[0058] Comparative Example 2:
[0059] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 5:2:3 in deionized water to prepare 2 mol L -1 A co-precipitation experiment was carried out with a sulfate solution at pH = 11.5 under a nitrogen atmosphere. After the transition metal sulfate solution was titrated, the precursor was filtered and dried.
[0060] (2) The precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.5 Co 0.2 Mn 0.3 O2.
[0061] Comparative Example 3:
[0062] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 6:2:2 in deionized water to prepare 2 mol L -1 A co-precipitation experiment was carried out with a sulfate solution at pH = 11.5 under a nitrogen atmosphere. After the transition metal sulfate solution was titrated, the precursor was filtered and dried.
[0063] (2) The precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.6 Co 0.2 Mn 0.2 O2.
[0064] Comparative Example 4:
[0065] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 8:1:1 in deionized water to prepare 2 mol L -1 A co-precipitation experiment was carried out with a sulfate solution at pH = 11.5 under a nitrogen atmosphere. After the transition metal sulfate solution was titrated, the precursor was filtered and dried.
[0066] (2) The precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2.
[0067] Comparative Example 5:
[0068] (1) Dissolve transition metal sulfate Ni:Co:Mn in a molar ratio of 7:1:2 in deionized water to prepare 2 mol L -1 A co-precipitation experiment was carried out with a sulfate solution at pH = 11.5 under a nitrogen atmosphere. After the transition metal sulfate solution was titrated, the precursor was filtered and dried.
[0069] (2) The precursor material obtained in step (1) was dry-mixed with lithium hydroxide in a molar ratio of 1.05:1, calcined at 850°C in an air atmosphere for 12 h, cooled to room temperature, and then ground and sieved to obtain LiNi 0.7 Co 0.1 Mn 0.2 O2.
[0070] Performance testing:
[0071] 1. Coating uniformity analysis, characterization using scanning electron microscopy
[0072] Figure 1 Shown is the SEM image of Comparative Example 1, which was not coated and had a smooth surface; Figure 2 What is shown is the coating effect diagram of Example 1. The coating almost completely covers the surface of the positive electrode material. The SEM images of other examples are similar to those of Example 2.
[0073] 2. Electrical performance analysis
[0074] 2032-type button cells were assembled in a glove box with a high-purity Ar atmosphere. The process was sequentially followed: positive electrode shell, 12mm positive electrode sheet, separator, negative electrode, and negative electrode shell. Electrolyte was added during the process. The assembled button cells were then tested for constant current charge and discharge performance on a Blue Battery Tester, operating at a voltage range of 2.8-4.4V.
[0075] Table 1 Performance of ternary positive electrode materials in various embodiments and comparative examples
[0076]
[0077]
[0078] By comparing the data of Examples 1 and 2 with that of Comparative Example 1, it can be seen that the 0.1C discharge specific capacity of the positive electrode material after LiErO2 and LiCeO2 coating is increased by about 10 mAh / g, the first efficiency is increased by about 5%, the high current density 1C discharge capacity is improved to varying degrees, and the capacity retention rate is significantly improved after 50 cycles.
[0079] By comparing the data of Examples 3 and 4 with that of Comparative Example 2, it can be seen that the 0.1C discharge specific capacity of the positive electrode material after LiEuO2 and LiNdO2 coating is increased by about 3.75mAh / g, the first efficiency is increased by about 2.75%, the high current density 1C discharge capacity is significantly increased by about 13mAh / g, and the capacity retention rate after 50 cycles is increased by about 8%.
[0080] By comparing the data of Examples 5 and 6 with that of Comparative Example 3, it can be seen that the 0.1C discharge specific capacity of the positive electrode material after LiSmO2 and LiPmO2 coating is increased by about 4.4mAh / g, the first efficiency is increased by about 3.05%, the high current density 1C discharge capacity is significantly increased by about 9.25mAh / g, and the capacity retention rate after 50 cycles is increased by about 9.7%.
[0081] By comparing the data of Examples 7 and 8 with that of Comparative Example 4, it can be seen that the 0.1C discharge specific capacity of the positive electrode material after LiHoO2 and LiPrO2 coating is increased by about 3.5mAh / g, the first efficiency is increased by about 0.85%, the high current density 1C discharge capacity is significantly increased by about 7.35mAh / g, and the capacity retention rate after 50 cycles is increased by about 11.15%.
[0082] By comparing the data of Examples 9 and 10 with that of Comparative Example 5, it can be seen that the 0.1C discharge specific capacity of the positive electrode material after LiLaO2 and LiTbO2 coating is increased by about 6.2mAh / g, the first efficiency is increased by about 1%, the high current density 1C discharge capacity is significantly increased by about 9.9mAh / g, and the capacity retention rate after 50 cycles is increased by about 13.4%.
[0083] Comprehensive analysis shows that since the electrochemical activity of LiErO2 and LiCeO2 is higher than that of other coating materials, the electrochemical performance of the materials is more significantly improved at low rates; since the surface of the positive electrode particles is coated with fast ion conductors, the active substances are isolated from direct contact with the electrolyte, effectively reducing the occurrence of interfacial side reactions, and the cycle performance of the materials is significantly improved.
[0084] The present invention first synthesizes the cathode material precursor through coprecipitation. During this process, rare metal elements are cleverly added, resulting in a coating of rare metal hydroxide on the precursor surface. This coating then undergoes a simultaneous lithiation reaction during the lithiation calcination step, transforming into a coating with fast ion conductivity. This technical solution results in a cathode material that not only retains its original electrochemical properties but also exhibits even superior electrochemical properties due to the presence of the fast ion conductor coating.
Claims
1. A method for coating and modifying a ternary cathode material, comprising the following steps: S1. A transition metal sulfate solution is subjected to a coprecipitation reaction under an inert atmosphere; a rare earth element sulfate solution is simultaneously added during the coprecipitation process to form a ternary precursor having a surface coated with a rare earth hydroxide; S2. Mix the ternary precursor obtained in step S1 with a lithium source, calcine under an air atmosphere, and cool to obtain a ternary positive electrode material coated with a fast ion conductor.
2. The method according to claim 1, wherein: The rare earth element is selected from one or more of the following: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.
3. The method according to claim 1 or 2, characterized in that: The transition metal sulfate is a soluble salt of Ni, Co, and Mn.
4. The method according to claim 3, wherein: The molar ratio of Ni, Co, and Mn in the transition metal sulfate is x:y:z, wherein 0.10≤x≤0.90, 0.04≤y≤0.33, 0.01≤z≤0.33, and x+y+z=1; The coprecipitation reaction is carried out at a pH of 11-12.
5. The method according to claim 1 or 2, characterized in that: The inert atmosphere is nitrogen or argon.
6. The method according to claim 1 or 2, characterized in that: The molar ratio of the ternary precursor to the lithium source is 1:1.03-1.
05.
7. The method according to claim 1 or 2, characterized in that: The calcination temperature is 800-900° C. and the calcination time is 10-12 hours.
8. A fast ion conductor coated ternary cathode material prepared by the method according to any one of claims 1 to 7; The chemical formula of the fast ion conductor coated ternary cathode material is Li x (Ni a Co b Mn c )O2 / ((LiMO2) d ,in, 1.00≤x≤1.09, 0.10≤a≤0.90, 0.04≤b≤0.33, 0.01≤c≤0.33, and a+b+c=1; 0.01≤d≤0.05, M is a lanthanide rare earth element.
9. The fast ion conductor coated ternary cathode material according to claim 8, characterized in that: The thickness of the coating layer of the fast ion conductor coating the ternary positive electrode material is 3-5 nm.