Oxide cathode materials constructed with isotopic oxygen, their production methods and uses - Patents.com

Abstract

To relate to the field of lithium-ion battery technology and provide an oxide cathode material constructed with isotopic oxygen, and a manufacturing method and a use thereof.SOLUTION: Using 18O as a sole oxygen source, a precursor is prepared by a sol-gel method, and then solid-phase sintering is used to synthesize an oxide cathode material containing 18O as an oxygen element. Because the atomic mass of 18O is larger than that of 16O, the covalent bond energy between the transition metal atom and the lattice oxygen is increased, thereby raising the energy barrier for lattice oxygen diffusion. This allows the lattice oxygen in the oxide cathode material to be fixed under high voltage and temperature conditions. Furthermore, this effectively avoids problems such as oxygen escape from the lattice, which can cause crystal structure collapse and shorten the cycle life and safety of the oxide cathode material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to oxide cathode materials constructed with isotopes of oxygen, their manufacturing method and use, and is in the field of lithium-ion batteries. [Background technology]

[0002] Acid elements and their stable isotopes are major components of rocks and fluids in the crust and mantle, and are stable in nature (their relative abundances are 16 O: 99.756%, 17 O: 0.039%, 18 The difference between nuclides is due to the number of neutrons in the nucleus, which further creates the isotope effect and results in different physical, chemical and nuclear properties. For example, 18 O is 16 12.5% ​​heavier than O 18 The covalent bond formed by O is 16 It has a longer lifespan than O 16 It has a stronger bond energy than O.

[0003] In recent years, with the vigorous development of fields such as electric vehicles and energy storage power plants, high energy density and a wide operating temperature range are becoming the future development directions for lithium-ion batteries. Because the cathode is the core component of lithium-ion batteries, the development of materials that can withstand high voltage and high temperature conditions is key to improving battery energy density and extending the battery's operating temperature range. However, in the case of mainstream oxide cathode materials, the high voltage and high temperature operating environment can cause oxygen atoms in the lattice to become unstable, leading to their escape from the lattice and structural collapse, which further threatens the safety and electrochemical properties of the battery.

[0004] Currently, the mainstream modification method is zirconium element doping (Tina et al. Structural and electrochemical aspects of LiNi 0.8 Co 0.1 Mn 0.1These include near-surface doping, such as O2 cathode materials doped by various cations, ACS Energy Lett. 4 (2019) 508-516), and boron element doping (Chong et al. Surface reinforcement doping to suppress oxygen release of Li-rich layered oxides, J. Power Sources, Volume 503, 2021, 230048). This modification strategy achieves lattice oxygen stabilization of oxide cathodes under high voltages and temperatures by forming high-energy covalent bonds between oxygen atoms and doping atoms. Furthermore, to improve the thermal stability of oxide cathode materials, modification methods such as the fabrication of core-shell structures (Lee et al., Compositional core-shell design by nickel leaching on the surface of Ni-rich cathode materials for advanced high-energy and safe rechargeable batteries, J. Power Sources, Volume 400, 2018, Pages 87-95) and near-surface coating (Zou et al., Constructing a stable interfacial phase on single-crystalline Ni-rich cathode via chemical reaction with phosphomolybdic acid, Nano Energy, Volume 87, 2021, 106172) have been proposed. While these modification methods have some effectiveness, they still suffer from issues such as uneven modification and insufficient lattice oxygen stability, which affect the cycling stability and safety of batteries.

[0005] In view of the above problems, the present invention innovatively utilizes the isotope effect of oxygen to produce a non-radioactive ion beam with a long half-life. 18By constructing oxide cathode materials using O as the sole oxygen source, the covalent bond energy between the transition metal atoms and lattice oxygen is increased, while the energy barrier for lattice oxygen diffusion is also increased, thereby stabilizing the lattice oxygen in the crystal structure under high voltage and high temperature conditions. This method not only improves the energy density and cycle performance of oxide cathode materials, but also significantly enhances the inherent structural stability of the oxide cathode materials, thereby effectively improving their inherent safety characteristics. Furthermore, this process is characterized by its ease of operation and high compatibility with existing production lines. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a method for producing and using an oxide cathode material constructed with isotopic oxygen to overcome the shortcomings of the prior art. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention adopts the following technical solutions.

[0008] One of the objectives of the present invention is to develop a long half-life, non-radioactive 18 It is produced using O as the only oxygen source, and all lattice oxygen sites in the crystal structure are 18 The goal is to provide an oxide cathode material constructed with oxygen isotopes, dominated by O.

[0009] Preferably, the oxide cathode material is LiCoO2, LiNi x Co y M 1-x-y O2 (M=at least one of Mn and Al, 1≧1-xy≧0, 1≧x≧0, 1≧y≧0), LiMn2O4, xLi2MnO3·(1-x)LiMO2 (M=one or more of Ni, Co, and Mn, 1≧x≧0).

[0010] Another object of the present invention is to provide Transition metal salts and heavy oxygen water H2 required to produce the precursor of the oxide cathode 18 Prepare a transition metal salt solution using HO, organic acid, and deoxygenated water H2. 18 Step S1: preparing a complexing agent using O, adding a transition metal salt solution to the complexing agent, and heating and stirring until a sol-gel is formed; then vacuum drying the sol-gel to form a dried sol-gel, which is then vacuum ball-milled to obtain a precursor; Step S2: uniformly mixing the precursor obtained in step S1 with a lithium salt to obtain a blend; 18 In an O2 atmosphere, the blend in S2 is heated and kept at the temperature for a certain period of time to react. When the reaction is complete, 18 and step S3 of obtaining an oxide cathode material constructed of O. 18 The present invention provides a method for producing an oxide cathode material constructed of O.

[0011] Preferably, in step S1, the transition metal salt includes, but is not limited to, a transition metal salt having a metallic nickel ion, cobalt ion, manganese ion, etc. as a cation and a nitrate, sulfate, etc. as an anion, and the transition metal salt used does not have water of crystallization.

[0012] Preferably, the organic acid used in step S1 is one or more of organic acids such as citric acid, glycolic acid, or glycine, and the oxygen atoms in the organic acid molecule are 18 It is an O atom.

[0013] Preferably, in step S1, the molar ratio of total transition metal ions to organic acid molecules is 1:1.1 to 1.4.

[0014] Preferably, in step S1, the concentration of the transition metal salt solution is 0.01 to 5 mol L -1 The concentration of the organic acid in the complexing agent is 0.5 to 10 mol L -1 is.

[0015] Preferably, in step S1, the heating and stirring is carried out at 50 to 80° C. and 150 to 500 rpm.

[0016] Preferably, in step S1, the gel is vacuum dried by placing it in a vacuum oven at 120 to 200°C and leaving it for 5 to 12 hours, and the vacuum degree of the vacuum oven is 1 x 10 -1 ~1×10 -5 It is Pa.

[0017] Preferably, in step S1, the vacuum ball milling is performed by placing the dried sol-gel in a vacuum ball milling tank and ball milling it at 150 to 500 rpm for 1 to 10 hours to obtain a precursor having a particle size of 0.8 to 3 μm, and the vacuum degree of the vacuum ball milling tank is 1×10 -1 ~1×10 -5 It is Pa.

[0018] Preferably, in step S2, the molar ratio of the precursor to the lithium ions in the lithium salt is 1:1.1 to 1.3, and the lithium salt is such that all of the oxygen atoms are 18 The O atom is one or more of lithium hydroxide, lithium carbonate, and lithium acetate.

[0019] Preferably, in step S3, the reaction vessel is evacuated, and then: 18 O2 gas is introduced. 18 The vacuum level before introducing O2 gas was 1×10 -1 ~1×10 -5 Controlled by Pa, 18 The O2 gas flow rate is 20 to 50 mL min -1 is controlled by.

[0020] Preferably, in step S3, the heating is performed at 2 to 10°C min -1 The temperature is raised to 500 to 950°C at a rate of 100°C and kept at that temperature for 5 to 24 hours.

[0021] A further object of the present invention is to provide a method for manufacturing a lithium ion battery. 18 The present invention provides a method for manufacturing a cathode material using an oxide cathode material constructed of O. [Effects of the Invention]

[0022] The beneficial effects of the present invention are: Long half-life, non-radioactive 18 The precursor was prepared by the sol-gel method using O as the only oxygen source, and then sintered by solid-phase sintering. 18 In the present invention, an oxide cathode material containing O as the oxygen element is synthesized. 18 O 16 It has two more neutrons than O and its atomic mass is 16 Because the atomic mass of the transition metal is larger than that of O, it increases the covalent bond energy between the transition metal atom and the lattice oxygen while raising the energy barrier for lattice oxygen diffusion. This allows the lattice oxygen in the oxide positive electrode material to be fixed and stabilized in the crystal structure under high voltage and high temperature conditions. Furthermore, it effectively avoids problems such as oxygen escape from the lattice, which can cause the crystal structure to collapse, shorten the cycle life of the oxide positive electrode material, and reduce its safety. This method not only effectively improves the energy density and cycle performance of the oxide positive electrode material, but also significantly improves the inherent structural stability of the oxide positive electrode material, thereby effectively improving its inherent safety characteristics. Furthermore, this process is characterized by its simplicity and compatibility with conventional production processes. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is an SEM spectrum of the oxide positive electrode material produced in Example 1 of the present invention. [Figure 2] 1 is an XRD refinement spectrum of the oxide positive electrode material produced in Example 1 of the present invention. [Figure 3] 1 is a cycle characteristic curve of the battery manufactured in Example 1 of the present invention at a current density of 200 mAg −1 . [Figure 4] 1 is a cycle characteristic curve of a battery manufactured in Comparative Example 1 of the present invention at a current density of 200 mAg −1 . [Figure 5] FIG. 10 is a model diagram of four samples produced in Comparative Example 5 of the present invention. [Figure 6]FIG. 1 is an XRD diagram of four samples produced in Comparative Example 5 of the present invention. [Figure 7] 1 shows Raman spectra of four samples produced in Comparative Example 5 of the present invention. [Figure 8] FIG. 10 is a comparison diagram of the lithium ion diffusion coefficients of four samples prepared in Comparative Example 5 of the present invention. [Figure 9] 1 shows cyclic voltammetry curves of four samples prepared in Comparative Example 5 of the present invention. [Figure 10] FIG. 10 is a comparative diagram of the rate characteristics of four samples produced in Comparative Example 5 of the present invention. [Figure 11] FIG. 10 is a comparative diagram of cycle characteristics of four samples manufactured in Comparative Example 5 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] For ease of understanding, the technical solutions and embodiments of the present invention will be described more clearly, completely, and in detail below using specific examples and with reference to the drawings. It should be noted that the examples described in the present invention are implemented based on the technical solutions of the present invention and show detailed embodiments and specific operating procedures, but they are only some examples of the present invention, not all examples. The specific embodiments described are limited for the interpretation and explanation of the present invention, and do not limit the present invention. All other examples that can be obtained by those skilled in the art based on the examples of the present invention without creative work fall within the protection scope of the present invention.

[0025] Unless otherwise specified, all experimental methods used in the following examples are conventional methods, and all materials, reagents, etc. used in the examples are commercially available unless otherwise specified.

[0026] The preparation methods of some related substances according to the present invention are as follows.

[0027] Li 18 How OH is produced: 1: Prepare lithium foil and deuterated water in a molar ratio of 1:1.01. 2: Place the lithium foil in a sealed Erlenmeyer flask containing heavy oxygen water, heat and stir, and when the metallic lithium particles in the glass bottle disappear and the heavy oxygen water evaporates and condenses, Li 18 Obtain OH. Li2C 18 How O3 is produced: Li in the reaction flask 18 Excessive C in OH 18 After introducing O2, the Li2C 18 Get O3.

[0028] CH3C 18 O 18 How OLi is made: 1: Ethylene powder and heavy oxygen water are heated and stirred to obtain a heavy oxygen ethanol solution. 2: Copper and 18 Add O2, heat and stir to obtain deoxyacetic acid. 3. Remove the copper, add stoichiometric lithium powder to the deuterium acetic acid solution, and heat and stir at 200-300 rpm and 30-50°C for half an hour. When the metallic lithium particles in the glass bottle become long, the deuterium acetic acid will evaporate and condense, forming CH3C 18 O 18 Get OLi.

[0029] Citric acid (C6H8 18 O7) Manufacturing Method: 1: Anodic oxidation of heavy oxygen water to H2 18 Produces O2. 2: Hydrogen iodide, 1,2-ethylene dibromide, Na 18 OH to give cyclohexene, where Na 18 OH is obtained by reacting sodium powder with deuterated water. 3:H2 18 Cyclohexene is oxidized with O2 and H 18 O 18 OC(CH2)4C 18 O 18 Obtain OH. 4: Chloroacetic acid to Na 18OH to form sodium chloroacetate, which is reacted with KCN to give sodium α-cyanoacetate, followed by alkaline hydrolysis, calcium salt displacement, and acidification to give sodium α-cyanoacetate. 18 O 18 OCCH2 18 O 18 Obtain OH. 5: All oxygen elements 18 O adipic acid and malonic acid react with each other, and C6H8 18 Get O7.

[0030] Glycolic acid (H 18 OCH2C 18 O 18 OH) manufacturing method: 1: CH2 by methane oxidation 18 Manufacture O. 2:CH2 18 O and hydrocyanic acid are reacted at atmospheric pressure at 0-50°C while controlling the pH to 5-6 or 8-9, and the resulting dicyanomethanol is hydrolyzed at pH 3-5. The reaction temperature is controlled above 90°C, and the resulting product is extracted and crystallized. 18 OCH2C 18 O 18 Obtain OH.

[0031] Glycine (NH2CH2C 18 O 18 OH) manufacturing method: 1: CH2 by methane oxidation 18 Manufacture O. 2:CH2 18 Using O, HCN, and NH3 as raw materials, NH2CH2C 18 O 18 OH is produced. The present invention 18 O2 and H2 18 It was purchased from Isotop China, whose website is https: / / isotopechina.com / index.html.

[0032] Example 1: S1. Weigh out nickel sulfate, cobalt sulfate, and manganese sulfate so that the molar ratio of transition metal ions is 8:1:1, and add H2 18 O is used as a solvent with a concentration of 0.01 mol L -1 A transition metal salt solution was prepared. Then, the total transition metal ions and citric acid (C6H8 18 O7) was weighed out so that the molar ratio of H2 18 O with a concentration of 0.5 mol L -1 Next, the transition metal salt solution was added dropwise to the complexing agent at 60°C and stirred at 300 rpm to form a sol-gel, which was then placed in a vacuum oven at 120°C and dried after 12 hours (vacuum degree 1×10 -2 Pa), then placed in a vacuum ball milling tank and ball milled at 150 rpm for 10 h (vacuum degree 1×10 -5 Pa), a precursor with a particle size of approximately 1 μm was obtained. S2. The precursor obtained in S1 and Li 18 OH were weighed in a molar ratio of 1:1.1, mixed uniformly, and placed in a tube furnace. S3. 1×10 -1 After vacuum suction to Pa, 20 mL min -1 At a flow rate of 18 O2 was introduced and the temperature was maintained at 5°C for 5 min. -1 After the reaction was completed, the mixture was slowly cooled to room temperature and the LiNi 0.8 Co 0.1 Mn 0.1 18 Got O2. The obtained LiNi 0.8 Co 0.1 Mn 0.1 18 The SEM spectrum of O2 is shown in Figure 1, and the refined XRD spectrum is shown in Figure 2. 0.8 Co 0.1 Mn 0.1 18O2, carbon black conductive agent, and PVDF binder were mixed in a 90:5:5 ratio with an appropriate amount of NMP as a solvent to prepare a uniform slurry. This slurry was then applied to an aluminum foil, baked, and roll-pressed to obtain a positive electrode plate. This was then assembled with a lithium sheet as a counter electrode to form a CR2032 half cell. The first cycle capacity of the battery was 198.54 mAhg. -1 The 100-cycle capacity retention rate was 92.88% (30°C, 200mA g -1 , 3.0~4.5 V vs. Li + / Li), and the specific cycle characteristics are shown in FIG.

[0033] Example 2: S1. Cobalt nitrate and H2 18 The transition metal salt solution was prepared by weighing out H2 18 O is used as a solvent with a concentration of 1 mol L -1 A transition metal salt solution was prepared. Then, the total transition metal ions and glycolic acid (C2H4 18 Glycolic acid was weighed out so that the molar ratio of H2 to H3 was 1:1.4. 18 O and concentration is 5 mol L -1 Next, the transition metal salt solution was added dropwise to the complexing agent at 50°C and stirred at 500 rpm to form a sol-gel, which was then placed in a vacuum oven at 200°C and dried after 5 hours (vacuum degree 1×10). -1 Pa), then it was placed in a vacuum ball milling tank and ball milled at 300 rpm for 5 h (vacuum degree 1×10 -3 Pa), a precursor with a particle size of approximately 0.8 μm was obtained. S2. The precursor obtained in S1 and Li2C 18 O3 was weighed in a molar ratio of 1:0.6, mixed uniformly, and placed in a tube furnace. S3. 1×10 -5 After vacuum suction to Pa, 35 mL min -1 At a flow rate of 18 O2 was introduced and the temperature was maintained at 5°C for 5 min. -1 After the reaction was completed, the mixture was slowly cooled to room temperature and the LiCo 18 Got O2. The obtained LiCo 18 A slurry of O2, carbon black conductive agent, and PVDF binder was prepared in a ratio of 90:5:5, coated on aluminum foil, baked, and roll-pressed to obtain a positive electrode plate. This was then assembled with a lithium sheet as the counter electrode to form a CR2032 half cell. The first cycle capacity of the battery was 207.64 mAhg. -1 The 100-cycle capacity retention rate was 96.76% (30°C, 200mA g -1 , 3.0-4.6 V vs. Li + / Li).

[0034] Example 3 S1. Manganese sulfate and H2 18 The transition metal salt solution was prepared by weighing out H2 18 O is used as a solvent with a concentration of 5 mol L -1 A transition metal salt solution was prepared. Then, the total transition metal ions and glycine (C2H5N 18 Glycine was weighed out so that the molar ratio of H2 to O2 was 1:1.1. 18 O and concentration is 10 mol L -1 Next, the transition metal salt solution was added dropwise to the complexing agent at 80°C, and the mixture was stirred at 150 rpm to form a sol-gel, which was then placed in a vacuum oven at 150°C and dried after 8 hours (vacuum degree 1×10). -1 Pa), then it was placed in a vacuum ball milling tank and ball milled at 300 rpm for 5 h (vacuum degree 1×10 -5 Pa), a precursor with a particle size of approximately 3 μm was obtained. S2. The precursor obtained in S1 and Li 18 OH was weighed in a molar ratio of 1:1.3, then mixed uniformly and placed in a tube furnace. S3. 1×10 -1 After vacuum suction to Pa, 30 mL min -1 At a flow rate of 18 O2 was introduced and the temperature was maintained at 2°C for 2 min. -1 After the temperature was raised to 950°C at a rate of 100°C, the mixture was kept at the same temperature for 5 hours. After the reaction was completed, the mixture was slowly cooled to room temperature and the LiMn2 18 Got O4. The obtained LiMn2 18 A slurry of O4, carbon black conductive agent, and PVDF binder was prepared in a ratio of 90:6:4. The slurry was applied to aluminum foil, baked, and roll-pressed to obtain a positive electrode plate. A lithium sheet was used as the counter electrode, and these were assembled into a CR2032 half cell. The first cycle capacity of the battery was 138.5 mAhg. -1 The 100-cycle capacity retention rate was 93.78% (55°C, 200mA g -1 , 3.6-4.8 V vs. Li + / Li).

[0035] Example 4 S1. Weigh out nickel sulfate, cobalt sulfate, and manganese sulfate in the molar ratio of transition metal ions, and add H2 18 O is used as a solvent with a concentration of 4 mol L -1 A transition metal salt solution was prepared. Then, the total transition metal ions and citric acid (C6H8 18 O7) was weighed out so that the molar ratio of H2 18 O and concentration is 8 mol L -1 Next, the transition metal salt solution was added dropwise to the complexing agent at 60°C and stirred at 300 rpm to form a sol-gel, which was then placed in a vacuum oven at 500°C and dried after 5 hours (vacuum degree 1×10). -3 Pa), then it was placed in a vacuum ball milling tank and ball milled at 500 rpm for 1 h (vacuum degree 1×10 -1 Pa), a precursor with a particle size of approximately 1.8 μm was obtained. S2. The precursor obtained in S1 and lithium acetate C2H3 18 O2Li was weighed out in a molar ratio of 1:1.2, mixed uniformly, and then placed in a tube furnace. S3. 1×10 -2 After vacuum suction to Pa, 50 mL min -1 At a flow rate of 18 O2 was introduced and the temperature was increased to 10°C for 1 min. -1 After the temperature was raised to 900°C at a rate of 14 hours, the temperature was maintained. After the reaction was completed, the mixture was slowly cooled to room temperature. 1.2 Ni 0.16 Co0.08 Mn 0.56 18 Got O2. The obtained Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 18 A slurry of O2, carbon black conductive agent, and PVDF binder was prepared in a ratio of 90:5:5. The slurry was applied to aluminum foil, baked, and roll-pressed to obtain a positive electrode plate. A lithium sheet was used as the counter electrode, and these were assembled into a CR2032 half cell. The first cycle capacity of the battery was 243.7 mAhg. -1 The 100-cycle capacity retention rate was 92.56% (45°C, 200mA g -1 , 3.0-4.75 V vs. Li + / Li).

[0036] Comparative Examples 1 to 4 16 LiNi was prepared according to the process parameters of Examples 1 to 4, using O as the oxygen source. 0.8 Co 0.1 Mn 0.1 O2, LiCoO2, LiMn2O4, and Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 An O2 oxide cathode material was synthesized. The obtained oxide cathode material was assembled into a CR2032-type half cell according to the process parameters of Examples 1 to 4. The test environment and electrochemical parameters of this battery were the same as those of Examples 1 to 4, and the first cycle capacity and 100 cycle capacity retention rate of the battery were measured. These results are all shown in Table 1. The specific cycle characteristics of the battery of Comparative Example 1 are shown in Figure 4.

[0037] [Table 1]

[0038] Comparative Example 5 Taking lithium cobalt oxide (LCO) as an example, the inner and outer cathode materials 16 O and 18The four oxide positive electrode materials with different O atom distributions are compared to further reflect the effect of the present invention, which can also be applied to other oxide positive electrode materials described in the present invention. Sample No. 1: Inside and outside 16 O Sample No. 2: Core 16 O, shell is 18 O. Sample No. 3: Core 18 O, shell is 16 O. Sample No. 4: Inside and outside 18 O.

[0039] Model diagrams of the four oxide cathode materials are shown in Figure 5. The manufacturing methods are as follows. Sample No. 1: 18 All ingredients containing O are conventional 16 The samples were synthesized by substituting raw materials with natural abundance of O and employing the manufacturing method described in this invention. Sample No. 2: Sample No. 1 was used as the target for modification. 18 The surface is sintered by plasma sintering in an O atmosphere. 16 Part of O 18 Replace with O, 18 O-rich shell and 16 After many experiments, it was found that the modified sample with the core of O could be completely removed by extending the sintering time, increasing the sintering temperature, or using the high activity plasma sintering technique. 18 It was verified that it was still impossible to obtain sample No. 4, which was composed of O. Sample No. 3: Sample No. 4 was used as the denatured object. 16 Plasma sintering in an O atmosphere produces a surface 18 Part of O 16 Replace with O and 16 O, inside 18 Similarly, after many experiments, it was found that even if the sintering time or temperature was increased, the 18 All O 16 It has been verified that it is impossible to completely replace it with O. Sample No. 4: LiCo of Example 2 18 O2 is used as sample No. 4.

[0040] Test Example 1: Four samples exhibited the following characteristics: Feature (1): X-ray diffraction spectra (XRD) and structure refinement were employed to study the differences in the crystal structures of the four materials. As shown in Figure 6, the four different oxide cathode materials all maintain a clear layered structure and have similar crystal structures. The crystal structures were refined based on the obtained spectral data, and the unit cell parameters corresponding to the four samples are listed in Table 2. Based on the obtained crystal structure information, samples No. 2, No. 3, and No. 4 have: 16 Part of O 18 When replaced by O, 16 The c-axis contracted more than that of sample No. 1, which was composed of O, and sample No. 4 (completely 18 The most significant c-axis shrinkage was observed in lithium cobalt oxide cathodes (composed of 0 atoms). Typically, the lithium ion transport pathways in lithium cobalt oxide cathodes are perpendicular to the c-axis. The shrinkage of the c-axis narrows the spacing between adjacent ab planes, narrowing the lithium ion transport and diffusion pathways and slowing the electrochemical reaction rate of the material's lithium absorption / desorption. This modification is believed to have a negative impact on improving the electrochemical properties of the electrode material. However, the material of the present invention exhibits superior electrochemical properties. [Table 2]

[0041] Feature (2): To further clarify the differences in the microstructures among the four materials, Raman spectroscopy tests were conducted. As shown in Figure 7, the feature spectra of Samples No. 1 and No. 3 are similar, and the feature spectra of Samples No. 2 and No. 4 are also similar. Careful comparison of the Raman spectra of Samples No. 1 and No. 1 reveals that E g Vibration mode (O-Co-O bending vibration) and A 1gThe intensities of the vibrational modes (O-Co stretching vibrations) were shown to be similar, 16 O 18 Not replaced by O, or only a small portion near the surface 18 When replaced with O (note: the detection signal depth in the Raman spectrum is 100 nm), the oxide cathode material maintains its original vibrational modes. However, for samples No. 2 and No. 4, the E in these spectra g The vibration intensity of (O-Co-O bending vibration) is A 1g (O-Co stretching vibration) 1g The vibrational height of the O-Co stretching vibration has been reduced by half. g (O-Co-O bending vibration) and A 1g The intensity of the O-Co stretching vibration is much lower than that of samples No. 1 and No. 3. 16 O 18 When O is substituted, the two vibrational modes of the cobalt-oxygen bond in samples No. 2 and No. 4 are all 18 This indicates that the introduction of O suppresses the vibration. Furthermore, comparing the positions of the characteristic peaks in Figure 7, it was found that the characteristic peaks of Samples No. 2 and No. 4 are shifted toward lower wavenumbers compared to Samples No. 1 and No. 3. This indicates that the bond energy of the chemical bond (Co-O bond) corresponding to the two vibration modes is strengthened.

[0042] Feature (3): The results of testing the electronic conductivity of the above four materials and a commercially available lithium cobalt oxide cathode material are shown in Table 3. [Table 3] From Table 3, it can be seen that the electronic conductivity of Sample No. 1 is comparable to that of commercially available cathode materials, demonstrating that the manufacturing method described in this patent is reasonable and feasible. 16 Part or all of O 18 When replaced by O, the electronic conductivity of samples No. 2, No. 3, and No. 4 decreases to different degrees.16 O 18 When completely replaced by O, the electronic conductivity of sample No. 4 decreased by a factor of two compared to the commercially available cathode material. 16 O 18 It has been confirmed that the replacement of O with O has a significant effect on the electronic conductivity of the material. If the electronic conductivity of an electrode material is low, the material's electrical conductivity is poor, its electrochemical reaction activity is low, and it is considered to be unfavorable for the progress of the electrochemical reaction. However, the material of the present invention exhibits superior electrochemical properties.

[0043] Feature (4): Investigate the dynamic characteristics of lithium ion diffusion in four materials. The galvanostatic intermittent titration method is widely used to study the dynamics of lithium ion transport within electrode materials. First, multiple galvanostatic intermittent titration studies were conducted on the four positive electrode materials, and the lithium ion diffusion coefficients corresponding to the four positive electrode materials were carefully checked to ensure that the obtained data could be effectively reproduced. As shown in Figure 8, the changes in the lithium ion diffusion coefficients of the four positive electrode materials revealed 16 It was found that No. 1, No. 2, and No. 3, which contain oxygen atoms, all exhibited relatively similar lithium ion diffusion coefficients. However, surprisingly, 18 O 16 The complete replacement of O significantly improved the lithium ion diffusion coefficient of Sample No. 4, especially in the voltage platform range where the material undergoes redox reactions, resulting in a higher lithium ion diffusion flux. Therefore, it possesses better lithium ion transport dynamics. Combined with feature (1), it would seem that Sample No. 4's lithium ion diffusion coefficient is smallest because the lattice constant along the c-axis is smallest. However, the result of feature (4) is completely opposite, making it unpredictable.

[0044] Test Example 2: The electrochemical properties of four sample electrode materials were investigated as follows. The four materials were assembled into a battery according to the battery of Example 2, and the electrochemical properties were investigated based on the battery. (1) The electrochemical behavior of the four electrode materials was investigated by cyclic voltammetry at a scan rate of 0.1 mV / s and a scan range of 3.0 V to 4.8 V. As shown in Figure 9, Sample No. 1 had the poorest electrochemical reaction activity, 16 Part of O 18 The other two materials (Samples No. 2 and No. 3) in which O was substituted showed slight improvements. In contrast, Sample No. 4 exhibited a stronger redox peak current density and a sharper redox peak, indicating that Sample No. 4, an oxide positive electrode material of the present invention, has stronger redox activity than the other three materials and is more suitable as a positive electrode material for lithium-ion batteries.

[0045] (2) The applicant compared the rate characteristics of batteries using four samples at current densities of 20, 100, and 200 mA / g and voltages ranging from 3.0 V to 4.6 V. As shown in Figure 10, the discharge specific capacities of oxide cathode material samples No. 1, No. 2, and No. 3 at various rates were similar, and some capacity loss occurred after multiple cycles at high rates. On the other hand, the discharge specific capacity of oxide cathode material sample No. 4 at various rates was higher than that of samples No. 1, No. 2, and No. 3, and the reversible capacity was stable after multiple cycles at various rates, with no obvious loss. The above results suggest that the use of a high-performance oxide cathode material is essential when constructing an oxide cathode material. 16 O 18 It has been fully demonstrated that only a complete substitution with O can effectively improve the rate and cycle properties of the material, which is contrary to the relevant results and laws of electronic conductivity and is unpredictable.

[0046] (3) The applicant tested the cycle characteristics of the four samples at a current density of 200 mA / g and a voltage range of 3.0 V to 4.6 V. As shown in FIG. 11, the oxide cathode 18 O 16When O was partially replaced, regardless of whether the replaced portion was the core or shell of the positive electrode material, Samples 2 and 3 were the same as Sample 1 and could not achieve stable long-term cycling under high cutoff voltage conditions. However, Sample 4, an oxide positive electrode material of the present invention, showed very good cycling characteristics.

[0047] In summary, Sample No. 4 of the oxide positive electrode material described in the present invention exhibits a lattice arrangement structure unfavorable for lithium ion transport and has lower electronic conductivity, but exhibits excellent electrochemical reaction activity, excellent rate capability, and enhanced cycle stability.

[0048] From the above results, the advantages of the present invention are that it has a long half-life and is non-radioactive. 18 It has been found that the key to synthesizing oxide cathode materials is to use O as the sole oxygen source. On the one hand, it increases the covalent bond energy between transition metal atoms and lattice oxygen. On the other hand, it increases the energy barrier for lattice oxygen diffusion, thereby fixing the lattice oxygen in the oxide cathode material under high-voltage and high-temperature conditions, preventing oxygen from escaping from the lattice and causing the crystal structure to collapse. This method not only improves the energy density and cycle performance of the oxide cathode material, but also significantly enhances the inherent structural stability of the oxide cathode material, thereby effectively improving its inherent safety characteristics. Furthermore, this process is characterized by its ease of operation and high compatibility with existing production lines.

[0049] Although the present invention has been described in detail above through general descriptions, specific embodiments and experiments, it is not intended to limit the present invention in any way. Based on the present invention, some modifications or improvements are possible, which will be obvious to those skilled in the art. Therefore, all modifications or improvements made without departing from the spirit of the present invention belong to the scope of protection granted by the present invention.

Claims

1. １８ It is manufactured using O as the only oxygen source, and all of the lattice oxygen sites in its crystal structure are １８ Occupied by O, An oxide positive electrode material constructed with isotopes of oxygen, characterized in that it contains one or more elements satisfying the structure of LiCoO 2 , LiNi x Co y M 1-x-y O 2 (M=at least one of Mn and Al, 1≧1-x-y≧0, 1≧x≧0, 1≧y≧0), LiMn 2 O 4 , xLi 2 MnO 3 ·(1-x)LiMO 2 (M=one or more elements of Ni, Co, and Mn, 1≧x≧0).

2. A method for producing an oxide positive electrode material constructed of an isotope of oxygen in which all lattice oxygen sites in the crystal structure are occupied by 18O, the method being produced using 18O as the only oxygen source, Transition metal salts and heavy oxygen water H necessary for producing a precursor of an oxide positive electrode ２ １８ O was used to prepare a transition metal salt solution, and organic acids and heavy oxygen water H ２ １８ Step S1: preparing a complexing agent using O, adding a transition metal salt solution to the complexing agent, and heating and stirring until a sol-gel is formed; then vacuum drying the sol-gel to form a dried sol-gel, which is then vacuum ball-milled to obtain a precursor; Step S2: uniformly mixing the precursor obtained in step S1 with a lithium salt to obtain a blend; １８ O ２ The blend in S2 is heated in the atmosphere and kept at the temperature for a certain period of time to react. When the reaction is completed, １８ and step S3 of obtaining an oxide cathode material constructed of O.

3. In step S1, the transition metal salt includes a transition metal salt having at least one of metallic nickel ions, cobalt ions, and manganese ions as a cation and at least one of nitrates and sulfates as an anion, and the transition metal salt used does not have water of crystallization, and the concentration of the prepared transition metal salt solution is 0.01 to 5 mol L －１ The method for producing an oxide cathode material constructed with isotopes of oxygen according to claim 2, characterized in that:

4. The organic acid used in step S1 is one or more of citric acid, glycolic acid, and glycine, and the oxygen atom in the organic acid molecule is １８ O atoms, and the concentration of the organic acid in the prepared complexing agent is 0.5 to 10 mol L －１ The method for producing an oxide cathode material constructed with isotopes of oxygen according to claim 2, characterized in that:

5. 3. The method for producing an oxide cathode material constructed with isotope oxygen according to claim 2, wherein in step S1, the molar ratio of total transition metal ions to organic acid molecules is 1:1.1 to 1.

4.

6. 3. The method for producing an oxide cathode material constructed with isotopes of oxygen according to claim 2, wherein in step S1, the heating and stirring is performed at 50 to 80° C. and 150 to 500 rpm.

7. In step S2, the molar ratio of the precursor to the lithium ions in the lithium salt is 1:1.1 to 1.3, and the lithium salt is such that all of the oxygen atoms are １８ 3. The method for producing an oxide positive electrode material constructed with oxygen isotopes according to claim 2, characterized in that the oxygen isotopes are one or more of lithium hydroxide, lithium carbonate, and lithium acetate.

8. In step S3, the inside of the tubular furnace is evacuated, and then １８ O ２ A gas is introduced, where １８ O ２ The degree of vacuum before introducing the gas was 1×10 －１ ~1 x 10 －５ Controlled by Pa, １８ O ２ The gas flow rate is 20 to 50 mL min －１ is controlled by 2 to 10°C min －１ 3. The method for producing an oxide cathode material constructed with isotopes of oxygen according to claim 2, wherein the temperature is increased to 500 to 950°C at a rate of 1000 to 1500°C and maintained at that temperature for 5 to 24 hours.

9. Use of an oxide positive electrode material that is manufactured using 18O as the only oxygen source, and is constructed with isotopic oxygen in which all lattice oxygen sites in the crystal structure are occupied by 18O, Lithium-ion batteries and the use of oxide cathode materials constructed with isotopic oxygen in their manufacture.

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