A high-nickel ternary positive electrode material, a preparation method thereof and a lithium ion battery
By forming a stable lithium titanate modified layer on the surface of high-nickel layered cathode material, the surface reaction problem during the preparation process and the structural degradation after long cycles are solved, thereby improving the cycle life and safety performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2026-04-07
AI Technical Summary
Existing high-nickel ternary cathode materials are prone to reacting with moisture and CO2 in the air during the preparation process to form strongly alkaline substances, resulting in residual lithium compounds on the surface, which affects the electrode preparation process and increases costs. At the same time, after long-term cycling, the structure degrades and the capacity decays. Conventional modification methods cannot guarantee the uniformity and precision of the modified layer.
Ti elements were directionally deposited on the surface of a high-nickel layered cathode material using the sol-gel method. By controlling the thickness and uniformity of the coating layer, a titanium oxide modified layer was formed. Then, the interdiffusion of elements was accelerated by recrystallization technology to form a stable lithium titanate surface modified layer, which prevented the material from contacting the electrolyte and reduced side reactions.
It improves the cycle performance and thermal stability of the material, enhances the stability of the electrode-electrolyte interface, reduces charge transfer impedance, and extends the cycle life and safety performance of lithium-ion batteries.
Smart Images
Figure CN119725438B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a high-nickel ternary positive electrode material, a preparation method thereof and a lithium ion battery. BACKGROUND
[0002] The lithium ion battery technology has been very mature today and is widely applied to fields including electric vehicles, energy storage, consumer electronics and the like. The performance of the negative electrode material of graphite and silicon-carbon material among the materials used by the lithium ion battery has basically approached the limit, and the cost is also relatively low, but the positive electrode material still has certain improvement space. In order to obtain a lithium ion battery with higher energy density, longer service life and higher safety, the phenomenon of lithium-nickel mixing often occurs in the process of using ternary materials. This is because the atomic radii of Li + and Ni 4+ are similar, so an excess of lithium salt is usually added during the production of high-nickel materials to inhibit the phenomenon of lithium-nickel mixing. However, the strong alkaline substances on the surface will further react with moisture and CO2 in the external air during the preparation process, and finally be converted into the main compounds of surface residual lithium, LiOH and Li2CO3. At the same time, the high-alkaline positive electrode material is easy to absorb moisture during the slurry preparation process, so that the slurry becomes a jelly-like state, which affects the process of preparing electrodes in industrial production and increases the cost of manufacturing battery cells.
[0003] In view of these problems, the material can be modified from aspects such as material structure design, doping and coating, among which the surface coating modification has the advantages of low cost and high controllability and is widely adopted. The surface treatment of the high-nickel ternary positive electrode material can improve the surface stability of the positive electrode material and effectively inhibit the side reaction of the high-energy positive electrode with the organic electrolyte, thereby becoming an important strategy and reliable way for the surface interface regulation of the positive electrode material.
[0004] The coating modification can effectively hinder the direct contact between the material and the electrolyte and reduce the side reaction between the high-activity Ni 4+ on the surface and the electrolyte, and the element introduced by the surface doping can effectively inhibit the oxygen precipitation, thereby inhibiting the degradation of the material surface from the layered structure to the defect spinel and disordered rock salt structure and improving the cycle performance of the material. However, the coating and doping means developed based on the conventional dry and wet processes cannot guarantee the uniformity of the modified layer and the precision of the atomic doping amount, so the capacity of the material after modification is usually reduced, and serious structural degradation and rapid capacity decay often occur after long cycle. SUMMARY
[0005] To overcome the deficiencies in the prior art, the purpose of the present application is to provide a high-nickel ternary positive electrode material, a preparation method thereof and a lithium ion battery, so as to improve the cycle life of the lithium ion battery.
[0006] To solve the above problems, the technical scheme adopted by the present application is as follows:
[0007] A high-nickel ternary positive electrode material, comprising an inner core and a coating layer, the inner core being a ternary positive electrode material, and the coating layer comprising a titanium oxide compound.
[0008] Preferably, the titanium oxide compound is at least one of TiO, TiO2, Ti2O3, Ti3O5, LiTiO2, Li2TiO3, Li4Ti5O 12 .
[0009] Preferably, the mass of the coating layer accounts for 0.01%-10% of the sum of the mass of the inner core and the coating layer. Further preferably, the mass of the coating layer accounts for 3% of the sum of the mass of the inner core and the coating layer.
[0010] A preparation method of a high-nickel ternary positive electrode material, comprising the following steps:
[0011] 1) mixing a titanium source, hydrogen peroxide and ammonia in water to obtain a mixed reaction solution; the titanium source is at least one of titanium propoxide, metatitanic acid, nano-titanium nitride, titanium tetrachloride and tetrabutyl titanate;
[0012] 2) uniformly mixing the mixed reaction solution obtained in step 1) with a mixed solvent to obtain a mixed solution; the mixed solvent is obtained by mixing ethanol and water;
[0013] 3) adding a ternary positive electrode material into the mixed solution obtained in step 2), uniformly mixing, and then treating at 25-150℃ for 5-40h to obtain a powder;
[0014] 4) obtaining the powder obtained in step 3) under an inert atmosphere at 300-1000℃ for 3-10h.
[0015] Preferably, the structure formula of the ternary positive electrode material in step 3) is LiNi x Co y Mn 1-x-y O2, 0.6≤x<1, 0<y≤0.2, x+y<1.
[0016] Further preferably, the ternary positive electrode material is LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.94 Co 0.03 Mn 0.03 O2.
[0017] Preferably, the ternary positive electrode material is a single-crystal ternary positive electrode material, a polycrystal ternary positive electrode material or a mixed material of a single-crystal ternary positive electrode material and a polycrystal ternary positive electrode material.
[0018] Preferably, the volume fraction of water in the mixed solvent in step 2) is 10%-50%.
[0019] Preferably, in step 1), the titanium source is mixed with hydrogen peroxide and ammonia in water to react by dispersing the titanium source evenly in water, then adding hydrogen peroxide solution and ammonia solution, and mixing for 0.5-1 h.
[0020] More preferably, in step 1), 2-55 mL of hydrogen peroxide solution is used for every 67.4-1685 mg of titanium source; the mass fraction of the hydrogen peroxide solution is 30%.
[0021] The preferred temperature for the treatment in step 3) is 75℃~90℃, and the treatment time is 20h-36h. More preferably, the temperature is 85℃, and the treatment time is 24h.
[0022] Preferably, the temperature for heat preservation in step 4) is 600-800℃, and more preferably, the heat preservation time is 6-8h.
[0023] A lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode includes a positive electrode current collector and a positive electrode material layer disposed on the positive electrode current collector, the positive electrode material layer includes a positive electrode active material, the positive electrode active material being the high-nickel ternary positive electrode material described above or a high-nickel ternary positive electrode material prepared by the preparation method described above.
[0024] The beneficial effects of this invention are:
[0025] This invention employs a sol-gel method to directionally deposit Ti elements on the surface of a high-nickel layered cathode material substrate. By adjusting the Ti element content, the proportion of the coating layer and its spatial distribution within the high-nickel material are controlled. The thickness of the modified layer is controlled by adjusting the recrystallization temperature and time, ultimately resulting in a titanium oxide-containing surface modified layer on the substrate material surface. The modified high-nickel layered cathode material is then subjected to post-annealing treatment to accelerate the interdiffusion of some metal elements in the titanium oxide-containing surface modified layer with elements on the surface of the high-nickel layered cathode material substrate, thereby improving the lattice oxygen stability at the substrate-modified layer interface.
[0026] This invention mainly investigates the effect of titanium oxide surface modification layer on the electrochemical performance of high-nickel layered cathode materials; the focus is on solving the battery performance degradation caused by surface structure decay during the cycling process of high-nickel layered cathode materials; the difficulty lies in the precise control of the thickness and uniformity of the titanium oxide surface modification layer. By using recrystallization technology, the titanium oxide surface modification layer is allowed to grow spontaneously on the cathode material, thereby making the coating layer of the high-nickel layered cathode material more stable and uniform.
[0027] The high-nickel layered cathode material of the present invention is coated with a titanium oxide surface modification layer, which can effectively prevent direct contact between the surface of the high-nickel layered cathode material and the electrolyte, reduce the side reactions between the electrode material and the electrolyte, prevent the electrolyte from penetrating into the interior of the secondary particles and causing microcracks, and maintain the structural stability of the cathode material during charging and discharging.
[0028] The lithium titanate coating formed by the surface residual alkali and titanium peroxide complex exhibits almost no volume expansion during charge and discharge, which can alleviate the volume expansion of high-nickel materials during charge and discharge, thereby improving their long-cycle performance and rate performance. Furthermore, lithium titanate materials possess excellent electronic conductivity, which can significantly improve the conductivity of the cathode material.
[0029] By consuming the surface residual lithium and titanium peroxide complex on the cathode material surface, a lithium titanate surface modification layer can be formed. This lithium titanate surface modification layer can effectively reduce the residual alkali content in high-nickel cathode materials, preventing the gelling phenomenon that occurs when the modified high-nickel cathode material is made into a slurry, thereby further improving the electrochemical performance of the modified high-nickel cathode material. It also enhances the electronic and ionic conductivity of the coating layer, thereby strengthening the electrode-electrolyte interface stability and reducing the charge transfer impedance of the battery during charge and discharge processes.
[0030] Therefore, the metal ions in the coating layer introduced into the subsurface of the high-nickel layered cathode material of the present invention can replace the original metal ions in the matrix material, thereby improving the stability of the lattice oxygen structure, thus improving the cycle performance and thermal stability of the material, and further improving the cycle life and safety performance of the lithium-ion battery. Attached Figure Description
[0031] Figure 1 This is a SEM image of the high-nickel ternary cathode material prepared in Example 1 of the present invention;
[0032] Figure 2 The image shows the XRD pattern of the high-nickel ternary cathode material prepared in Example 1 of this invention.
[0033] Figure 3 This is the EDS diagram of Ti element in the high-nickel ternary cathode material prepared in Example 1 of the present invention;
[0034] Figure 4 The images show the long-cycle curves of the high-nickel ternary cathode material prepared in Example 1 of this invention and the comparative sample. Detailed Implementation
[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0036] The ternary material LiNi in the following examples 0.8 Co 0.1 Mn 0.1O2 can be obtained from commercially available materials using existing technology, or from ternary materials such as LiNi prepared using the following preparation examples. 0.8 Co 0.1 Mn 0.1 O2.
[0037] The ternary material LiNi used in the following embodiments of the present invention 0.8 Co 0.1 Mn 0.1 The method for preparing O2 includes the following steps:
[0038] (1) Weigh out nickel sulfate hexahydrate (NiSO4·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O) and manganese sulfate monohydrate (MnSO4·H2O) according to the required stoichiometric ratio, and add them to a mixed solution containing sodium hydroxide (NaOH) and ammonia (NH3·H2O);
[0039] (2) Control the temperature, pH value, stirring speed and other parameters of the mixture, and obtain a pre-formed precipitate through reaction and aging;
[0040] (3) The precipitate obtained above was then washed with deionized water and dried overnight to finally obtain Ni. 0.8 Co 0.1 Mn 0.1 (OH)2 precursor;
[0041] (4) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ precursor and LiOH·H₂O were weighed at a molar ratio of 1:1.2 and thoroughly mixed by hand grinding in an agate mortar. The mixture was then heated at 500°C for 4 hours in an oxygen atmosphere in a tube furnace, followed by sintering at 800°C for 15 hours to finally obtain the ternary material LiNi. 0.8 Co 0.1 Mn 0.1 O2 (NCM811).
[0042] Example 1
[0043] The preparation method of the high-nickel ternary cathode material in this embodiment includes the following steps:
[0044] 1) Add 67.4 mg of TiN nanopowder to 3.8 mL of deionized water and stir until homogeneous. Then add 2.2 mL of hydrogen peroxide solution (30% by mass) and 0.8 mL of ammonia solution (25% by mass) to the homogeneous mixture. Stir magnetically for 0.5 hours. The mixture gradually transforms into a transparent yellow solution of titanium peroxide complex.
[0045] Add the mixed solvent to the above mixed solution and mix well to obtain a mixed solution; wherein the mixed solvent is composed of deionized water and ethanol, with the volume of deionized water being 50 mL and ethanol accounting for 70% of the volume of the mixed solvent;
[0046] 2) 49.9g of ternary material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was added to the above mixture and mixed evenly. Then the mixture was placed in an oven at 80°C for 30 hours to allow the titanium peroxide complex to nucleate and grow, resulting in a loose yellow powder.
[0047] 3) The obtained yellow powder is annealed at 800℃ for 7 hours in an argon atmosphere to form a titanium oxide surface modification layer of a certain thickness on the surface of NCM811 powder, thus obtaining the powder.
[0048] Example 2
[0049] The preparation method of the high-nickel ternary cathode material in this embodiment includes the following steps:
[0050] 1) Add 168.5 mg of TiN nanopowder to 9.4 mL of deionized water and stir until homogeneous. Then add 5.4 mL of hydrogen peroxide solution (30% by mass) and 2.0 mL of ammonia solution (25% by mass) to the homogeneous mixture. Stir magnetically for 0.5 hours. The mixture gradually transforms into a transparent yellow solution of titanium peroxide complex.
[0051] Add the mixed solvent to the above mixed solution and mix well to obtain a mixed solution; wherein the mixed solvent is composed of deionized water and ethanol, with the volume of deionized water being 50 mL and ethanol accounting for 70% of the volume of the mixed solvent;
[0052] 2) 49.75g of ternary material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was added to the above mixture and mixed evenly. Then the mixture was placed in an oven at 80°C for 30 hours to allow the titanium peroxide complex to nucleate and grow, resulting in a loose yellow powder.
[0053] 3) The obtained yellow powder is annealed at 800℃ for 7 hours in an argon atmosphere to form a titanium oxide surface modification layer of a certain thickness on the surface of NCM811 powder, thus obtaining the powder.
[0054] Example 3
[0055] The preparation method of the high-nickel ternary cathode material in this embodiment includes the following steps:
[0056] 1) Add 336.9 mg of TiN nanopowder to 18.9 mL of deionized water and stir until homogeneous. Then add 10.8 mL of hydrogen peroxide solution (30% by mass) and 4.0 mL of ammonia solution (25% by mass) to the homogeneous mixture. Stir magnetically for 0.5 hours. The mixture gradually transforms into a transparent yellow solution of titanium peroxide complex.
[0057] Add the mixed solvent to the above mixed solution and mix well to obtain a mixed solution; wherein the mixed solvent is composed of deionized water and ethanol, with the volume of deionized water being 50 mL and ethanol accounting for 70% of the volume of the mixed solvent;
[0058] 2) 49.5g of ternary material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was added to the above mixture and mixed evenly. Then the mixture was placed in an oven at 80°C for 30 hours to allow the titanium peroxide complex to nucleate and grow, resulting in a loose yellow powder.
[0059] 3) The obtained yellow powder is annealed at 800℃ for 7 hours in an argon atmosphere to form a titanium oxide surface modification layer of a certain thickness on the surface of NCM811 powder, thus obtaining the powder.
[0060] Example 4
[0061] The preparation method of the high-nickel ternary cathode material in this embodiment includes the following steps:
[0062] 1) Add 1.685 mg of TiN nanopowder to 94.3 mL of deionized water and stir until homogeneous. Then add 53.9 mL of hydrogen peroxide solution (30% by mass) and 20.2 mL of ammonia solution (25% by mass) to the homogeneous mixture. Stir magnetically for 0.5 hours. The mixture gradually transforms into a transparent yellow solution of titanium peroxide complex.
[0063] Add the mixed solvent to the above mixed solution and mix well to obtain a mixed solution; wherein the mixed solvent is composed of deionized water and ethanol, with the volume of deionized water being 50 mL and ethanol accounting for 70% of the volume of the mixed solvent;
[0064] 2) 47.5g of ternary material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was added to the above mixture and mixed evenly. Then the mixture was placed in an oven at 80°C for 30 hours to allow the titanium peroxide complex to nucleate and grow, resulting in a loose yellow powder.
[0065] 3) The obtained yellow powder is annealed at 800℃ for 7 hours in an argon atmosphere to form a titanium oxide surface modification layer of a certain thickness on the surface of NCM811 powder, thus obtaining the powder.
[0066] Comparative Example
[0067] Untreated ternary material LiNi obtained by the present invention 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was used as a control sample.
[0068] Experimental Example
[0069] (1) Morphological test
[0070] The ternary material prepared in Example 1 was subjected to SEM and XRD tests, and the results are as follows: Figure 1 , Figure 2 As shown.
[0071] from Figure 1 It can be seen that the cathode materials in the embodiments are all composed of secondary particles with a particle size of about 8 μm formed by the agglomeration of primary particles, and the modification has not changed the overall morphology of the cathode material.
[0072] from Figure 2 The elemental distribution diagram shows that Ti is uniformly distributed on the surface of the high-nickel cathode material, and the resulting coating layer is very uniform.
[0073] Further EDS elemental analysis was performed on the ternary material of Example 1. Figure 3 This is the EDS diagram of Ti element in the cathode material prepared in Example 1.
[0074] from Figure 3 It can be seen that the lithium titanate-modified cathode material exhibits a typical hexagonal α-NaFeO2 structure, belonging to the R-3m space group, corresponding to the standard PDF card (JCPDS#89-1979) for high-nickel ternary materials. Furthermore, the two pairs of clearly split peaks (006) / (102) and (108) / (110) confirm the material's good crystallinity and ordered layered structure. The intensity ratio of the (003) / (104) peak represents the cation mixing degree of the material; the ratio for all samples is greater than 1.2, indicating a low degree of cation mixing. Additionally, no shift in the peak position was observed in the magnified spectrum of the (003) peak, meaning that the titanium oxide surface modification layer coating exists only on the surface of the high-nickel NCM811 material and does not affect the internal crystal structure.
[0075] (2) Electrochemical performance testing
[0076] The high-nickel ternary cathode material prepared in Example 1 was used as a sample. The sample was mixed uniformly with polyvinylidene fluoride (PVDF), conductive carbon black, conductive carbon nanofibers (VGCF), and the solvent N-methylpyrrolidone (NMP) to obtain a cathode slurry. The mass ratio of the sample to PVDF, conductive carbon black, and conductive carbon nanofibers (VGCF) was 90:5:2.5:2.5. The cathode slurry was coated onto the surface of the cathode current collector, dried, and cut to form a cathode sheet. A lithium-ion battery was assembled using a lithium elemental metal sheet as the anode. The capacity retention after 200 cycles was tested under conditions of 1.0C (1C = 200 mA / g) and 3-4.3V. The results are as follows: Figure 4 As shown.
[0077] like Figure 4 As shown, the lithium-ion battery prepared with the material in Example 1 retained 80.2% of its capacity after 200 cycles. It is evident that the material in this example, compared to Comparative Example 1, exhibits significantly improved capacity retention and rate performance, demonstrating excellent electrochemical performance.
[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a high-nickel ternary cathode material, characterized in that, Includes the following steps: 1) A titanium source is mixed with hydrogen peroxide and ammonia in water to obtain a mixed reaction solution; the titanium source is nano-titanium nitride. 2) Mix the mixed reaction solution obtained in step 1) with the mixed solvent to obtain a mixed solution; the mixed solvent is obtained by mixing ethanol and water; 3) Add the ternary cathode material to the mixture obtained in step 2), mix thoroughly, and then treat at 75℃-90℃ for 20-36 hours to obtain powder; the ternary cathode material is LiNi. 0.8 Co 0.1 Mn 0.1 O2; 4) The powder obtained in step 3) is kept at 600-800℃ for 6-8 hours under an inert atmosphere to obtain the final product.
2. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, In step 2), the volume fraction of water in the mixed solvent is 10%-50%.
3. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, In step 1), the titanium source is mixed with hydrogen peroxide and ammonia in water to react. The titanium source is dispersed evenly in water, and then hydrogen peroxide solution and ammonia solution are added and mixed for 0.5-1h.
4. The method for preparing the high-nickel ternary cathode material according to claim 3, characterized in that, In step 1), 2-55 mL of hydrogen peroxide solution is used for every 67.4-1685 mg of titanium source; the mass fraction of the hydrogen peroxide solution is 30%.
5. A high-nickel ternary cathode material prepared by the preparation method according to any one of claims 1 to 4.
6. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode comprises a positive electrode current collector and a positive electrode material layer disposed on the positive electrode current collector, the positive electrode material layer comprising a positive electrode active material, characterized in that, The positive electrode active material is the high-nickel ternary positive electrode material as described in claim 5.