A cathode material, its preparation method and application

Abstract

This invention provides a cathode material, its preparation method, and its application. The cathode material is Li(TM). 1‑a M a )O 2‑b N b (TM represents a transition metal, M represents a cation replacing the transition metal, and N represents an anion replacing oxygen, where 0.01 ≤ a < 1, 0.01 ≤ b < 2). At least one cation and one anion are doped at the interface of the cathode material using a coating-based heat treatment method. Co-doping of cations and anions is achieved at the interface of the cathode material using this method; the doping depth is 10–500 nm. Cation doping stabilizes the material lattice through strong M-O bonds, inhibiting transition metal migration; anion doping reduces oxygen activity and simultaneously adjusts the electronic band structure, improving electronic conductivity. Therefore, Li(TM) 1‑a M a )O 2‑b N b It has a synergistic optimization effect, which not only significantly improves the ion diffusion coefficient and thus optimizes the rate performance, but also improves the cycle stability by enhancing structural stability, thus having great application value and development prospects.

Description

Technical Field

[0001] This invention belongs to the field of positive material technology, and particularly relates to a positive electrode material, its preparation method and application. Background Technology

[0002] Since the actual energy density of commercially available lithium-ion batteries still cannot exceed 350 Wh / kg, it is far from meeting the growing demands of energy storage and electric vehicles. Therefore, improving the energy density and safety of batteries is currently the focus of lithium-ion battery research. The cathode material provides active lithium ions and is a direct factor affecting battery energy density. Therefore, improving the energy density of the cathode material is key to improving the overall energy density of the lithium-ion battery system. Increasing the capacity of the cathode material and enabling it to operate at high voltages can maximize its energy density. Common cathode materials include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), lithium nickel oxide (LiNiO2), and nickel-cobalt-manganese ternary cathodes (LiNiO2). x Co y Mn z O2, x+y+z=1). However, cathode materials experience severe capacity decay when operating at high voltages, along with problems such as heat generation and gas production, significantly reducing battery cycle life and safety, severely limiting the commercial application value and development prospects of cathode materials. The main reasons for these problems are the ease with which cation mixing and surface alkali residue occur during cathode material preparation, and the tendency for bulk oxygen escape, secondary particle breakage, and surface structural phase transitions and transition metal dissolution to occur during charge and discharge.

[0003] These issues cause the cathode material to undergo a phase transition during electrochemical processes, resulting in degradation to structures where lithium ions cannot rapidly intercalate and deintercalate, such as the rock salt phase. Simultaneously, these problems lead to extremely poor surface stability of the cathode material and make it prone to reacting with the electrolyte, causing electrolyte failure and gas generation. Furthermore, the dissolution of transition metals during electrochemical processes at the cathode causes electrolyte decomposition on the anode surface, affecting the nucleation kinetics of lithium ions on the anode surface and accelerating lithium dendrite formation, further reducing the battery's cycle stability and safety. Therefore, increasing the bulk and surface stability of the cathode material is crucial for improving its cycle life and safety.

[0004] Bulk doping is the most commonly used method to modify the bulk and interfacial physicochemical properties of materials. Bulk doping can alter the crystal structure of cathode materials by incorporating heteroatoms into the crystal lattice, thereby mitigating lattice distortion under high voltage and improving the stability of the bulk crystal structure. Simultaneously, the doped structure not only reduces side reactions between the cathode material and the electrolyte but also enhances the bond energy of the chemical bonds between metal and oxygen elements on the cathode surface, further improving the stability of the surface crystal structure. Cation doping stabilizes the lattice through strong bond energies, suppressing transition metal migration and oxygen evolution; anion doping reduces oxygen activity and adjusts the electronic band structure, improving electronic conductivity. Therefore, combining doping with different bulk elements can comprehensively improve the bulk lattice stability and interfacial structure stability of the cathode under high voltage. Their synergistic effect significantly improves the ion diffusion coefficient and cycle stability, thus significantly enhancing the cycle life and safety of lithium-ion batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a cathode material Li(TM) 1-a M a )O 2-b N b The proposed preparation method enables the control of the surface and interface of lithium-ion battery electrode materials, thereby addressing the issues of low energy density, power density, and safety of existing electrode materials caused by the limited optimization performance of single-element doping, poor structural stability, and severe oxygen release.

[0006] In a first aspect, the present invention provides a cathode material Li(TM) 1-a M a )O 2-b N b The cathode active material includes a positive electrode active material and a dopant element located at the interface of the positive electrode active material. The dopant element includes at least one of a cation that substitutes for a transition metal and an anion that substitutes for oxygen. The cation substitutes for the transition metal ion in the positive electrode material, and the anion substitutes for oxygen in the positive electrode material. The cation in the dopant element is Al. 3+ Mg 2+ 、Ti 4+ 、Zr 4+ 、Nb 5+ 、La 3+ , Hf 4+ At least one of the following, the anion including F - Cl - At least one of the following: TM is a transition metal, M is a cation, N is an anion, wherein 0.01 ≤ a < 1, 0.01 ≤ b < 2.

[0007] Furthermore, the positive electrode active material includes lithium nickel oxide (LiNiO2), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), and ternary materials (Li[Ni x Co y Mn z At least one of O2 and lithium iron phosphate (LiFePO4).

[0008] Furthermore, the doping elements at the surface of the positive electrode active material are doped with cations and anions by a coating and heat treatment method, and the doping thickness of the doping elements is 0.02-5 nm.

[0009] Secondly, this invention provides a method for preparing a cathode material. This method includes using precise nanofilm coating and doping technology to dope at least one type of cation and one type of anion at the surface and interface of the cathode material, thereby achieving the successful preparation of a material in which cations replace transition metals and anions replace oxygen. The specific preparation method includes the following steps:

[0010] (1) Place the positive electrode active material to be doped, i.e. the first electrode material, into the reactor of the ALD deposition equipment;

[0011] (2) The first set of precursor sources is introduced into the reactor. That is, the first gas-phase precursor source is introduced first, so that it is saturated and adsorbed onto the surface of the positive electrode active material of the material to be doped. Then the second gas-phase precursor source is introduced, so that the two precursor sources react and the product is deposited on the surface of the first electrode material to obtain the second electrode material. After each precursor source is deposited to the optimal amount, the next precursor source is deposited.

[0012] (3) The third set of precursor sources is introduced into the reactor. That is, the third gas-phase precursor source is introduced first, so that it is saturated and adsorbed onto the surface of the second electrode material to be doped. Then the fourth gas-phase precursor source is introduced, so that the two precursor sources react and the product is deposited on the surface of the second electrode material to obtain the third electrode material. After each precursor source is deposited to the optimal amount, the next precursor source is deposited.

[0013] (4) After deposition, the obtained electrode material is placed in a muffle furnace for heat treatment to obtain a cathode material in which cations replace transition metals and anions replace oxygen.

[0014] The precursor source includes an organic compound containing at least one of the metal elements lithium, aluminum, magnesium, titanium, zirconium, niobium, lanthanum, and hafnium. The precursor source also includes an inorganic compound containing at least one of the elements fluorine, chlorine, phosphorus, and oxygen that reacts with the organic compound containing the metal element.

[0015] Furthermore, the positive electrode active material includes lithium nickel oxide (LiNiO2), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), and ternary materials (Li[Ni x Co y Mn z At least one of the following materials: O2, lithium iron phosphate (LiFePO4), etc.

[0016] Furthermore, the thickness of the doped surface of the cathode material is 0.02-5 nm.

[0017] Furthermore, the precursor source contains Al cations. 3+ Mg 2+ 、Ti 4+ 、Zr 4+ 、Nb 5+ 、La 3+ , Hf 4+ At least one of the following, containing an anion F - Cl - At least one of the following.

[0018] Secondly, the present invention also provides a method for preparing a cathode material, comprising: a cathode active material and doping elements located at the interface of the cathode active material, wherein the doping elements include cations that substitute for transition metals and anions that substitute for oxygen. The lithium source of the gas-phase precursor is lithium tert-butoxide, the aluminum source is trimethylaluminum, the magnesium source is ethylmagnesium thiocene, the titanium source is titanium tetraisopropoxide, the zirconium source is tetra(dimethylamine)zirconium, the niobium source is niobium ethanol, the lanthanum source is tetramethylheptanedione lanthanum, the hafnium source is tetra(dimethylamine)hafnium, the fluorine source is pyridine hydrofluoric acid, the chlorine source is aluminum trichloride, and the phosphorus source is trimethyl phosphate.

[0019] Thirdly, the present invention also provides a method for preparing a positive electrode for a lithium-ion battery, the method comprising: uniformly mixing a positive electrode active material with conductive carbon black (SP), a binder (PVDF) and a solvent (NMP) in a ratio of 8:1:1:5 to prepare a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector (aluminum foil) and baking it successively in an 80°C forced-air oven for 1 hour and in a 120°C vacuum oven for 10 hours to obtain a positive electrode; characterized in that the method further comprises performing surface and interface doping on the positive electrode active material and / or the positive electrode using the method described in any one of claims 1-6.

[0020] The technical solution provided by this application has the following advantages compared with the prior art:

[0021] The cathode material proposed in this invention is a cathode material prepared using PNCD technology, in which cations replace transition metals and anions replace oxygen, thereby improving the overall electrochemical performance of the material in the following aspects:

[0022] (1) Cation doping stabilizes the material lattice through strong MO bonds, suppressing transition metal migration and oxygen evolution;

[0023] (2) Anion doping can reduce oxygen activity and at the same time adjust the electronic band structure to improve electronic conductivity;

[0024] (3) Improves thermal stability and facilitates material storage;

[0025] In summary, the cathode material and its preparation method proposed in this invention combine the doping of different bulk elements to improve the precision of element doping and enhance the synergistic optimization effect of anion and cation co-doping. This not only significantly improves the ion diffusion coefficient of the cathode material, thereby optimizing the rate performance, but also improves the cycle stability by enhancing its structural stability, thereby significantly improving the cycle life and safety of lithium-ion batteries. It has great application value and development prospects. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The results are the theoretical calculations of the energy required for Al doping to Ni sites and Li sites in the third cathode material obtained in Example 1.

[0029] Figure 2 They are respectively direct proofs of Al 3+ Doping into Ni sites, F - Calculation results for oxygen substitution;

[0030] Figure 3 For Al 3+ Replace Ni, F - Crystal structure model diagram of oxygen substitution;

[0031] Figure 4 Based on NCM523 and co-doped LiNi 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.983 F 0.016 Charge-discharge cycle test of a full cell with graphite as the positive electrode and graphite as the negative electrode under voltage conditions of 3.0-4.8 V;

[0032] Figure 5 The Ni90 powder, cation-doped Ni90-M, anion-doped Ni90-N, and cation- and anion-co-doped LiNi in Embodiment 2 of this invention are examples of this invention. 0.9-a Co 0.05 Mn 0.05 Nb a O 2-b F b Cyclic test diagrams of coin cells with four different powders as positive electrodes;

[0033] Figure 6 The matrix material (LiCoO2) and co-doped (LiCo) in Embodiment 3 of this invention are used. 1-a Mg a O 2-b F b The image shows the results of electron paramagnetic resonance (EPR) testing. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Example 1

[0036] This embodiment provides a cathode material LiNi 0.5a Co 0.2 Mn 0.3 Al a O 2-b F b The preparation method of (Al-substituted Ni, F-substituted O) is as follows:

[0037] (1) Weigh 10 g of medium-nickel ternary cathode material NCM523, considering its specific surface area of ​​0.35 m². 2 / g calculates the amount of precursor used in the ALD process;

[0038] (2) An aluminum source precursor was first deposited on the surface of NCM523 using ALD technology, followed by a fluorine source precursor. The reaction chamber temperature was 250 °C. The doping amount was controlled by adjusting the number of times the ALD coating procedure was executed in the preparation steps.

[0039] Using an ALD deposition system (a "step-type" spatial ALD powder coating system, Soft Power Technology Co., Ltd., ZL202410559402.9), when the vacuum in the reaction chamber reaches approximately 0.01-10 torr, heating begins on all components of the atomic layer deposition system. The temperature of the reaction chamber is controlled at 250℃. When the test temperature of each part of the system reaches the target temperature, degassing is performed to remove moisture from the reaction chamber. The temperatures of the aluminum and fluorine sources are maintained at 30℃ (room temperature or appropriate heating).

[0040] The preparation of synergistic doped materials includes the following steps:

[0041] Step (a): Place the substrate material of the first electrode, namely 10 g of medium-nickel ternary cathode material NCM523 powder, into the reaction chamber and evacuate the chamber until the vacuum reaches 10. -1 torr; set the nitrogen flow rate to 20 standard milliliters per minute (sccm), and spray the first gaseous precursor aluminum source (trimethylaluminum) gas in a pulse form, with nitrogen as the carrier gas flowing into the reaction chamber. Then the matrix material is left to stand for 5 seconds. During the standing process, trimethylaluminum is adsorbed onto the surface of the matrix material, and the unadsorbed trimethylaluminum gas in the reaction chamber is cleaned by nitrogen.

[0042] In step (b), the second gaseous precursor fluorine source (pyridine hydrofluoric acid) is sprayed out in a pulsed manner and flows into the reaction chamber with nitrogen as the carrier gas. Then, it is left to stand for 5 seconds. During the standing process, the fluorine source is adsorbed onto the matrix material and reacts with the aluminum source (trimethylaluminum) adsorbed in the previous step.

[0043] Steps (a) and (b) are executed sequentially, with the total number of cycles set to 2, 4, and 8, and the thickness of the deposit in each cycle being approximately 0.9-1 Å.

[0044] Step (c): Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and clean the excess pyridine hydrofluoric acid gaseous precursor in the reaction chamber to obtain the second electrode material with aluminum source and fluorine source precursor deposited.

[0045] Step (d): Remove the second electrode material from the ALD device cavity and place it in a muffle furnace. Heat the material to 600°C at a rate of 5°C / min and hold for 5 hours to obtain the cathode material LiNi, which is a cation-substituted transition metal and anion-substituted oxygen. 0.5a Co 0.2 Mn 0.3 Al a O 2-b F b .

[0046] To verify the optimal doping amount, the electrode materials obtained in Example 1 with different deposition times were subjected to powder conductivity tests under different pressures. The results are shown in Table 1. It can be seen that the powder with a total deposition time of 4 times has the highest conductivity, which is about 10 times higher than that of the original NCM523 powder.

[0047] In Table 1, PNCD refers to the method described in Example 2 of the existing patent CN113921776A: aluminum oxide is coated onto the surface of the medium-nickel ternary cathode material NCM532 by atomic layer deposition (ALD) at a temperature of 130-170℃ and a coating thickness of 0.1-0.5nm. After coating, the material is sintered at 200-600℃ for 1-8 hours to construct a heteroepitaxial structure on the material surface through a precise nanofilm coating doping (PNCD) process.

[0048] Table 1. Four-probe method powder conductivity test of Example 1, raw NCM523 powder, PNCD coated powder, Comparative Example 1 (using only Al precursor), and Comparative Example 2 (using only F precursor).

[0049]

[0050] Subsequently, the matrix material (NCM523) and the optimal co-doped sample LiNi were analyzed. 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.983 F 0.016 Theoretical calculations were performed, such as Figure 1 As shown, Al doping into Ni sites requires less energy than doping into Li sites, indicating that Al doping replaces the transition metal Ni.

[0051] First, based on the matrix material structure model using Al and F doping (total source insertion times of 8), the possible doping sites of Al and F atoms in the matrix material were obtained using the PyMagen program. For example, in the crystal structure of the matrix material, Al and F atoms might replace certain atomic positions in the matrix, or embed themselves in interstitial positions. Then, the Ewald energy of each doped structure was calculated using the PyMagen program. Ewald energy is a method used to describe the energy of electrostatic interactions in ionic crystals, taking into account long-range electrostatic interactions between ions. From numerous possible doped structures, 20 structures with the lowest Ewald energies were selected, such as... Figure 2 As shown. This is because a lower Ewald energy generally means that the structure is more stable in terms of electrostatic interactions, and is more likely to be a practically stable doped structure.

[0052] For the 20 selected structures, high-precision DFT calculations were performed. The DFT calculations considered the quantum behavior of electrons, calculating the total energy of each structure, including electron kinetic energy, the potential energy between electrons and atomic nuclei, and the interactions between electrons. Appropriate exchange-correlation functionals (such as PBE and LDA) and basis sets (such as plane-wave basis sets) were used in the calculations. Finally, the total energies of the DFT calculations of these 20 structures were compared, and the configuration with the lowest energy was determined. The configuration with the lowest energy is the most stable structure, indicating that the Al and F atom doping sites are most optimal.

[0053] like Figure 2 As shown, among all possible models, LiNi 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.983 F 0.016 The structure has the lowest energy, which directly proves that Al was successfully prepared through precise nanofilm coating and doping technology. 3+ Replacement of transition metals Ni and F - LiNi, a cathode material that replaces oxygen 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.983 F 0.016 Crystal structure model such as Figure 3 As shown.

[0054] Finally, NCM523 and co-doped LiNi 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.983 F 0.016 The charge-discharge cycle test of a full cell with graphite as the positive electrode and graphite as the negative electrode under voltage conditions of 3.0-4.8 V, such as... Figure 4 As shown, the initial discharge capacity of the battery with NCM523 as the positive electrode is 155.20 mAh / g, while even at 3.17 mAh / cm², the discharge capacity is significantly lower. 2 High areal capacity, LiNi 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.983 F 0.016 The initial discharge capacity of the battery with NCM523 as the positive electrode is 204.60 mAh / g, and the first-stage efficiency is improved from 84.12% (for a full cell with NCM523 as the positive electrode) to 92.14% (for LiNi doped batteries). 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.983F 0.016 (The image shows a full cell with the positive electrode as the cathode). After 100 cycles, the capacity retention rate increased from 61.45% for untreated NCM523 to 84.16% after co-doping, while the capacity retention rate after PNCD treatment was 77.42%. Both theoretical calculations and experimental results strongly demonstrate the optimization effect of co-doping on overall electrochemical performance.

[0055] Example 2

[0056] This embodiment provides a cathode material LiNi 0.9a Co 0.05 Mn 0.05 Nb a O 2-b F b The preparation method of (Nb-substituted Ni, F-substituted O) is as follows:

[0057] (1) Weigh 10g of high-nickel ternary cathode material Ni90, considering its specific surface area of ​​0.68 m². 2 / g calculates the amount of precursor used in the ALD process;

[0058] (2) A lithium source precursor was first deposited on the surface of NCM523, followed by an aqueous source precursor, then a niobium source precursor, and finally an aqueous source precursor. The reaction chamber temperature was 235℃.

[0059] (3) A lithium source precursor was first deposited on the NCM523 surface, followed by a fluorine source precursor. The doping amount was controlled by adjusting the number of times the program was executed in the preparation steps.

[0060] Using an ALD deposition system (a "step-type" spatial ALD powder coating system, Soft Power Technology Co., Ltd., ZL202410559402.9), when the vacuum in the reaction chamber reaches approximately 0.01-10 torr, heating begins on all components of the atomic layer deposition system. The temperature of the reaction chamber is controlled at 235℃. When the test temperature of each part of the system reaches the target temperature, the system is purged to remove moisture from the chamber. The lithium source precursor is heated to approximately 140-145℃, the niobium source precursor is heated to 155-160℃, and the water and fluorine sources are maintained at 30℃ (room temperature or appropriate heating).

[0061] The preparation method of synergistic doped materials includes the following steps:

[0062] Step (a): Place the substrate material of the first electrode, namely 10 g of high-nickel ternary cathode material Ni90 powder, into the reaction chamber and evacuate the chamber until the vacuum reaches 10. -1torr; Set the nitrogen flow rate to 20 standard milliliters per minute (sccm), and inject the first gaseous precursor lithium source (lithium tert-butoxide) gas in a pulse form. Use nitrogen as the carrier gas to flow into the reaction chamber, and then let it stand for 5 seconds. During the standing process, lithium tert-butoxide is adsorbed onto the surface of the matrix material, and the unadsorbed lithium tert-butoxide gas in the reactor is cleaned by nitrogen.

[0063] Step (b): The second gaseous precursor water source is sprayed out in a pulse form and flows into the reaction chamber with nitrogen as the carrier gas. Then it is left to stand for 5 seconds. During the standing process, the water source is adsorbed onto the matrix material and reacts with the lithium source (lithium tert-butoxide) adsorbed in the previous step.

[0064] Step (c): Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and wash away the excess water source precursor in the reactor to obtain the second electrode material with lithium source and water source precursor deposited.

[0065] Step (d): Place the second electrode material into the reaction chamber and evacuate the chamber until the vacuum reaches 10. -1 torr; set the nitrogen flow rate to 20 standard milliliters per minute (sccm), and spray the third gaseous precursor niobium source (niobium ethanol) in a pulsed manner. Nitrogen is used as the carrier gas to flow into the reaction chamber, and then it is left to stand for 5 seconds. During the standing process, niobium ethanol is adsorbed onto the surface of the second electrode material, and the excess unadsorbed niobium ethanol gas in the reaction chamber is cleaned by nitrogen.

[0066] In step (e), water source gas is sprayed out in a pulsed manner, and nitrogen is used as the carrier gas to flow into the reaction chamber. Then, it is left to stand for 5 seconds. During the standing process, water source is adsorbed onto the surface of the second electrode material and reacts with the niobium source adsorbed in the previous step.

[0067] Step (f): Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and wash away the excess water source precursor in the reactor to obtain the third electrode material with lithium source, water source and niobium source precursor deposited.

[0068] Steps (a) through (f) are performed sequentially, with 5 cycles set up, and the thickness of the deposited material in each cycle is approximately 1.8–1.9 Å.

[0069] Step (g): The lithium source (lithium tert-butoxide) gas is sprayed out in a pulse form and nitrogen is used as the carrier gas to flow into the reaction chamber. Then the matrix material is left to stand for 5 seconds. During the standing process, lithium tert-butoxide is adsorbed onto the surface of the matrix material, and the unadsorbed lithium tert-butoxide gas in the reaction chamber is cleaned by nitrogen.

[0070] Step (h) involves spraying the fourth gaseous precursor fluorine source (pyridine hydrofluoric acid) in a pulsed manner, with nitrogen as the carrier gas flowing into the reaction chamber, and then letting it stand for 5 seconds. During the standing process, the fluorine source is adsorbed onto the matrix material and reacts with the lithium source (lithium tert-butoxide) adsorbed in the previous step.

[0071] Step (i): Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and clean the excess pyridine hydrofluoric acid gaseous precursor in the reaction chamber to obtain the fourth electrode material with lithium source and fluorine source precursor deposited.

[0072] Steps (g) through (i) are executed sequentially, with the cycle number set to 10 times, meaning the lithium source and fluorine source are injected 10 times each. The deposition thickness per cycle is approximately 0.82–0.88 Å.

[0073] Step (j): Remove the electrode material obtained in the previous step from the ALD device cavity, place it in a muffle furnace, heat it to 300°C at a heating rate of 3°C / min, and hold it at that temperature for 4 hours to obtain the cathode material LiNi, which is a cation-substituted transition metal and anion-substituted oxygen. 0.9-a Co 0.05 Mn 0.05 Nb a O 2-b F b .

[0074] To verify the doping effect, the following materials were used: the original Ni90 powder from Example 2; the powder obtained by depositing only a niobium source and heat-treating it (electrode materials obtained by performing steps (a) to (f) and (j)) using only a Nb precursor; the powder obtained by depositing only an F precursor and heat-treating it (electrode materials obtained by performing steps (a) and (h) to (j)) using only an F precursor; the powder obtained by depositing only an F source and heat-treating it (electrode materials obtained by performing steps (a) and (h) to (j)) using only an F precursor; the untreated Ni90-A (the third electrode material powder obtained after performing steps (a) to (i) according to the above processing steps); and the deposited and heat-treated (i.e., co-doped) LiNi. 0.9a Co 0.05 Mn 0.05 Nb a O 2-b F b The powders were tested using a four-probe method with the same weight, and the results are shown in Table 2. It can be seen that although the conductivity of the untreated powder is higher than that of the original powder, the co-doped LiNi powder achieved after heat treatment... 0.9a Co 0.05Mn0.05 Nb a O 2-b F b Its powder conductivity is further improved.

[0075] Table 2. Raw Ni90 powder, using only Nb precursor, using only F precursor, deposited untreated Ni90-A, deposited and heat-treated LiNi 0.9a Co 0.05 Mn 0.05 Nb a O 2-b F b Four-probe method for powder conductivity testing

[0076]

[0077] Furthermore, coin cells using these three powders as positive electrodes were assembled and subjected to rate and cycle tests. Figure 5 As shown, under voltage conditions of 2.8–4.4 V and a C rate of 0.5, after 80 charge-discharge cycles, the capacity retention of the original Ni90 powder was 27.34%, while the capacity retention of the deposited but untreated Ni90-A increased to 48.06%. The capacity retention of the deposited and heat-treated (i.e., co-doped) LiNi... 0.9-a Co 0.05 Mn 0.05 Nb a O 2-b F b The capacity retention rate was significantly improved to 72.08%, which demonstrates the optimization effect of the synergistic doping strategy on the structural stability of the high-nickel ternary material Ni90.

[0078] Example 3

[0079] This embodiment provides a cathode material LiCo. 1-a Mg a O 2-b F b The preparation method of (Mg-substituted Co, F-substituted O) is as follows:

[0080] (1) Weigh 10 g of lithium cobalt oxide (LiCoO2), considering its specific surface area of ​​0.18 m². 2 / g calculates the amount of precursor used in the ALD process;

[0081] (2) Using ALD technology, a magnesium source precursor was first deposited on the LiCoO2 surface, followed by a water source precursor, then a lithium source precursor, and finally a fluorine source precursor. The chamber temperature was 200 ℃. The doping amount was controlled by adjusting the number of times the program was executed in the preparation steps.

[0082] Using an ALD deposition system (a "step-type" spatial ALD powder coating system, Soft Power Technology Co., Ltd., ZL202410559402.9), when the vacuum in the reaction chamber reaches approximately 0.01-10 torr, heating begins on all components of the atomic layer deposition system. The temperature of the reaction chamber is controlled at 200 ℃. When the test temperature of each part of the system reaches the target temperature, degassing is performed to remove moisture from the reaction chamber. The lithium source precursor is heated to approximately 140-145 ℃, the magnesium source precursor is heated to approximately 120 ℃, and the fluorine and water sources are maintained at 30 ℃ (room temperature or appropriate heating).

[0083] Precision nanofilm coating and doping technology includes the following steps:

[0084] Step (a): The substrate material of the first electrode, namely 10 g of lithium cobalt oxide (LiCoO2) powder, is placed into the reactor, and the reactor is evacuated until the vacuum in the reaction chamber reaches 10. -1 torr; Set the nitrogen flow rate to 20 standard milliliters per minute (sccm), and inject the first gaseous precursor magnesium source (ethyl magnesia) gas in a pulse form, with nitrogen as the carrier gas flowing into the reactor, and then let it stand for 5 seconds. During the standing process, ethyl magnesia is adsorbed onto the surface of the matrix material, and the unadsorbed ethyl magnesia gas in the reaction chamber is cleaned by nitrogen.

[0085] Step (b): The second gaseous precursor water source is sprayed out in a pulse form and flows into the reaction chamber with nitrogen as the carrier gas. Then it is left to stand for 5 seconds. During the standing process, the water source is adsorbed onto the matrix material and reacts with the magnesium source adsorbed in the previous step.

[0086] Step (c) Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and clean the excess water source vapor precursor in the reaction chamber to obtain the second electrode material with magnesium source and water source precursor deposited.

[0087] Steps (a) to (c) are executed sequentially, with the number of cycles set to 2, that is, the magnesium source and water source are injected 2 times each, and the thickness of the deposition in each cycle is approximately 1.3-1.4 Å.

[0088] Step (d): Place the second electrode material into the reaction chamber and evacuate the chamber until the vacuum reaches 10. -1 torr; Set the nitrogen flow rate to 20 standard milliliters per minute (sccm), and spray the third gaseous precursor lithium source (lithium tert-butoxide) in a pulsed manner. Use nitrogen as the carrier gas to flow into the reaction chamber, and then let it stand for 5 seconds. During the standing process, lithium tert-butoxide is adsorbed onto the surface of the second electrode material, and the excess unadsorbed lithium tert-butoxide gas in the reaction chamber is cleaned by nitrogen.

[0089] In step (e), the fourth gaseous precursor fluorine source (pyridine hydrofluoric acid) gas is injected in a pulse form and flows into the reaction chamber with nitrogen as the carrier gas. Then it is left to stand for 5 seconds. During the standing process, the fluorine source (pyridine hydrofluoric acid) is adsorbed onto the surface of the second electrode material and reacts with the lithium source adsorbed in the previous step.

[0090] Step (f): Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and clean the excess pyridine hydrofluoric acid gaseous precursor in the reaction chamber to obtain the third electrode material with magnesium source, water source, lithium source and fluorine source precursor deposited.

[0091] Steps (d) to (f) are executed sequentially, with the number of cycles set to 2, meaning that the lithium source and fluorine source are injected 2 times each, and the thickness of the deposition per cycle is approximately 0.82-0.88 Å.

[0092] Step (g): Remove the third electrode material from the ALD device cavity and place it in a muffle furnace. Heat the material to 600°C at a heating rate of 5°C / min and hold for 5 hours (heating scheme 1) to obtain the cathode material LiCo with cation-substituted transition metal and anion-substituted oxygen. 1-a Mg a O 2-b F b .

[0093] To verify the optimal doping temperature, the electrode material obtained in Example 3 was subjected to powder conductivity tests under different pressures. The results are shown in Table 3. It can be seen that the powder with the highest conductivity was obtained by heating to 600℃ at a heating rate of 5℃ / min and holding for 5 hours, which is about 4 times higher than that of the original LiCoO2 powder. In Table 3, heating scheme 2 is heating to 600℃ at a heating rate of 3℃ / min and holding for 5 hours, and heating scheme 3 is heating to 400℃ at a heating rate of 5℃ / min and holding for 5 hours.

[0094] Table 3. Conductivity test of LCO powder before and after composite coating in Example 3 using the four-probe method.

[0095]

[0096] Then, the matrix material (LiCoO2) and co-doping (LiCo) were studied. 1-a Mg a O 2-b F b Electron paramagnetic resonance (EPR) tests were performed, such as... Figure 6 As shown, LiCoO2 and LiCo 1-a Mg a O 2-b F bThe sample showed a similar signal at g=2.003, which is attributed to the formation of oxygen vacancies in the material, LiCo. 1-a Mg a O 2-b F b It has a stronger signal, i.e., higher conductivity, consistent with the results of powder conductivity tests.

[0097] Comparative Example 1

[0098] This embodiment refers to the method of Embodiment 1 to provide a cathode material LiNi with a cation-substituted transition metal. 0.5a Co 0.2 Mn 0.3 Al a The specific steps for preparing O2 (Al-substituted Ni) are as follows:

[0099] (1) Weigh 10 g of medium-nickel ternary cathode material NCM523, considering its specific surface area of ​​0.35 m². 2 / g calculates the amount of precursor used in the ALD process;

[0100] (2) An aluminum source precursor was first deposited on the NCM523 surface using ALD technology, followed by a water source precursor. The reaction chamber temperature was 250 °C. The doping amount was controlled by adjusting the number of times the program was executed in the preparation steps.

[0101] Using an ALD deposition system (a "step-by-step" spatial ALD powder coating system, manufactured by Soft Power Technology Co., Ltd.), when the vacuum in the reaction chamber reaches approximately 0.01-10 torr, heating begins on all components of the atomic layer deposition system. The temperature of the reaction chamber is controlled at 250℃. When the test temperature of each part of the system reaches the target temperature, the system is degassed to remove moisture from the reaction chamber. The temperatures of the aluminum source and water source are maintained at 30℃ (room temperature or appropriate heating). The precision nanofilm coating and doping technology includes the following steps:

[0102] Step (a): Place the substrate material of the first electrode, namely 10 g of medium-nickel ternary cathode material NCM523 powder, into the reaction chamber and evacuate the chamber until the vacuum reaches 10. -1 torr; set the nitrogen flow rate to 20 standard milliliters per minute (sccm), and spray the first gaseous precursor aluminum source (trimethylaluminum) in a pulse form. Nitrogen is used as the carrier gas to flow into the reaction chamber, and then let it stand for 5 seconds. During the standing process, trimethylaluminum is adsorbed onto the surface of the electrode material, and the excess unadsorbed trimethylaluminum gas in the reaction chamber is cleaned by nitrogen.

[0103] Step (b): The second gaseous precursor water source gas is sprayed out in a pulse form and flows into the reaction chamber with nitrogen as the carrier gas. Then it is left to stand for 5 seconds. During the standing process, the water source is adsorbed onto the surface of the second electrode material and reacts with the aluminum source adsorbed in the previous step.

[0104] Step (c): Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and clean the excess trimethylaluminum vapor precursor in the reaction chamber to obtain the second electrode material with deposited aluminum source and water source precursors.

[0105] Steps (a) and (c) are executed sequentially, with the number of cycles set to 2, 4, and 8, respectively. That is, the number of times the aluminum source and water source are injected are 2, 4, and 8, respectively, and the thickness of the deposition in each cycle is about 0.1 nm.

[0106] Step (d): Remove the second electrode material from the ALD device cavity, place it in a muffle furnace, heat it to 400°C at a heating rate of 3°C / min, and hold it for 4 hours to obtain the cation-substituted transition metal cathode material LiNi. 0.5-a Co 0.2 Mn 0.3 Al a O2.

[0107] Comparative Example 2

[0108] This embodiment refers to the method of Embodiment 1 to provide a cathode material LiNi with a cation-substituted transition metal. 0.5 Co 0.2 Mn 0.3 O 2-b F b The specific steps for preparing (F-substituted O) are as follows:

[0109] (1) Weigh 10 g of medium-nickel ternary cathode material NCM523, considering its specific surface area of ​​0.35 m². 2 / g calculates the amount of precursor used in the ALD process;

[0110] (2) A lithium source precursor was first deposited on the NCM523 surface using ALD technology, followed by a fluorine source precursor. The chamber temperature was 250 °C. The doping amount was controlled by adjusting the number of times the program was executed in the preparation steps.

[0111] Using an ALD deposition system (a "step-by-step" spatial ALD powder coating system, manufactured by Soft Power Technology Co., Ltd.), when the vacuum in the reaction chamber reaches approximately 0.01-10 torr, heating begins on all components of the atomic layer deposition system. The temperature of the reaction chamber is controlled at 250℃. When the test temperature of each part of the system reaches the target temperature, the system is degassed to remove moisture from the reaction chamber. The lithium source precursor is heated to 140-145℃, and the fluorine source temperature is maintained at 30℃ (room temperature or appropriate heating). The precise nanofilm coating and doping technology includes the following steps:

[0112] Step (a): The substrate material of the first electrode, namely 10 g of nickel-metal ternary cathode material NCM523 powder, is placed into the reactor, and the vacuum in the reaction chamber is evacuated to a vacuum of 10. -1 torr; Set the nitrogen flow rate to 20 standard milliliters per minute (sccm), and inject the first gaseous precursor lithium source (lithium tert-butoxide) gas in a pulse form. Use nitrogen as the carrier gas to flow into the reaction chamber, and then let it stand for 5 seconds. During the standing process, lithium tert-butoxide is adsorbed onto the surface of the matrix material, and the unadsorbed lithium tert-butoxide gas in the reactor is cleaned by nitrogen.

[0113] In step (b), the second gaseous precursor fluorine source (pyridine hydrofluoric acid) gas is injected in a pulse form and flows into the reaction chamber with nitrogen as the carrier gas. Then it is left to stand for 5 seconds. During the standing process, the fluorine source (pyridine hydrofluoric acid) is adsorbed onto the surface of the second electrode material and reacts with the lithium source adsorbed in the previous step.

[0114] Step (c): Let stand for 20 seconds, set the nitrogen flow rate to 40 standard milliliters per minute (sccm), and clean the excess pyridine hydrofluoric acid gaseous precursor in the reaction chamber to obtain the second electrode material with lithium source and fluorine source precursor deposited.

[0115] Steps (a) and (c) are executed sequentially, with the number of cycles set to 2, 4, and 8, respectively, meaning the lithium source and fluorine source are injected 2, 4, and 8 times, respectively, and the thickness of the deposited material per cycle is approximately 0.9-1.0 Å.

[0116] Step (d): Remove the second electrode material from the ALD device cavity, place it in a muffle furnace, heat it to 400°C at a heating rate of 3°C / min, and hold it for 4 hours to obtain the anion-substituted oxygen cathode material LiNi. 0.5-a Co 0.2 Mn 0.3 O 2-b F b .

[0117] To verify the doping effect, the final electrode material (LiNi) obtained in Example 1 was used. 0.4833 Co 0.2 Mn0.3 Al 0.01 6O 1.983 F 0.016 The cathode material powders obtained in Comparative Examples 1 and 2 were subjected to four-probe powder conductivity tests with the same weight. As shown in Table 1, the final electrode material (LiNi) obtained in Example 1 can be seen... 0.4833 Co 0.2 Mn 0.3 Al 0.016 O 1.98 3F 0.016 It has a greater improvement in electrical conductivity than other powders.

[0118] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0119] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A cathode material Li(TM) 1-a M a )O 2-b N b The preparation method of the [method] is characterized by, Specifically, it includes the following steps: Step (a): Ni90 powder, a high-nickel ternary cathode material, is placed in the reaction chamber, and lithium tert-butoxide gas is sprayed out in a pulsed manner. The unadsorbed lithium tert-butoxide gas in the reactor is cleaned by nitrogen. Step (b) involves spraying the second gaseous precursor water source in a pulsed manner and reacting it with the lithium tert-butoxide adsorbed in the previous step. Step (c) involves cleaning the excess water in the reactor to obtain the deposited second electrode material. Step (d) involves placing the second electrode material into the reaction chamber and spraying niobium ethanol in a pulsed manner. The niobium ethanol is adsorbed onto the surface of the second electrode material, and excess unadsorbed niobium ethanol gas in the reaction chamber is cleaned with nitrogen gas. In step (e), the water source gas is ejected in a pulsed manner, and the water source is adsorbed onto the surface of the second electrode material and reacts with the niobium ethanol adsorbed in the previous step. Step (f) involves cleaning excess water from the reactor to obtain the third electrode material; Steps (a) through (f) are executed sequentially, with 5 cycles set, and the thickness of the deposit in each cycle being 1.8-1.9 Å; Step (g) involves pulsating lithium tert-butoxide gas, which adsorbs onto the surface of the matrix material, and then purging the reaction chamber with nitrogen to remove any unadsorbed lithium tert-butoxide gas. Step (h) involves spraying pyridine hydrofluoric acid in a pulsed manner, where the pyridine hydrofluoric acid is adsorbed onto the matrix material and reacts with lithium tert-butoxide adsorbed in the previous step. Step (i): Clean the excess pyridine hydrofluoric acid in the reaction chamber to obtain the fourth electrode material; Steps (g) to (i) are executed sequentially, with the number of cycles set to 10, i.e., the lithium tert-butoxide and pyridine hydrofluoric acid are injected 10 times each, and the thickness of the deposition per cycle is 0.82-0.88 Å. Step (j): Place it in a muffle furnace to obtain the cathode material LiNi. 0.9-a Co 0.05 Mn 0.05 Nb a O 2-b F b .

Images