Lithium nickel oxide cathode material and its manufacturing method and use

Abstract

A lithium nickel oxide positive electrode material and its manufacturing method and use, wherein the positive electrode material has the chemical formula L i1+x Ni 1-x O2, where 0.02≦x≦0.08, and its crystal structure is an α-NaFeO2-type hexagonal layered structure and the space group is R-3m. Li, which is in stoichiometric excess over Ni, occupies the octahedral voids in the Ni layers and is randomly distributed in the octahedral voids. The preparation method includes: (1) reacting a nickel source and a lithium source with oxygen in the presence of a molten salt additive to obtain a lithium nickel oxide-containing product; and (2) purifying the lithium nickel oxide-containing product to obtain a lithium nickel oxide-containing powder, which is then placed in an oxygen environment to obtain a lithium nickel oxide positive electrode material. When used in lithium-ion batteries, this positive electrode material can achieve high energy density and exhibit excellent cycling and thermal stability.

Description

[Technical Field]

[0001] The present invention relates to the field of lithium ion technology, and more particularly to lithium nickel oxide positive electrode materials and their manufacturing methods and uses. [Background technology]

[0002] Ternary materials, such as lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide, offer good energy and power densities and are widely used in the manufacture of power batteries. Increasing the nickel content can increase the energy density of ternary cathode materials, but can also reduce the material's cycling and thermal stability. Lithium nickel oxide (LiNiO2) has a high energy density (>900 Wh / kg material level), but this type of material is typically lithium-deficient (the ratio of Li to Ni is less than 1) due to the difficulty in obtaining a phase that matches the theoretical stoichiometry during synthesis. During electrochemical cycling, this material is prone to structural transformation from the layered phase to the rocksalt phase, resulting in the loss of lattice oxygen, resulting in poor cycling stability and reduced power performance due to the structural transformation. In order to improve the energy density, various kinds of lithium-rich positive electrode materials (usually with a ratio of Li to transition metals greater than 1.1:0.9) have been proposed in the prior art. However, the conventional lithium-rich positive electrode materials are composed of two structural units, namely, R-3m (layered structure LiMO2, M=Ni, Co, Mn, etc. transition metal) and c / 2m (monoclinic structure Li2MO3, M=Mn, Co, or Ni) structural units. However, due to their thermodynamic properties, materials containing c / 2m units (Li2MO3 units, M=Mn, Co, or Ni) require high voltages (>4.5V vs Li) to extract more lithium ions and achieve high energy density. + / Li). Such high voltages exceed the stability window of the electrolyte, reducing the stability of the material interface and affecting its cycle life. In other words, it is difficult to achieve high energy density, excellent cycle stability, and excellent thermal stability with conventional positive electrode materials. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention addresses the shortcomings and deficiencies of the prior art by providing a lithium nickel oxide positive electrode material that, when used in a lithium ion battery, simultaneously provides the lithium ion battery with high energy density, excellent cycling stability, and excellent thermal stability. [Means for solving the problem]

[0004] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0005] A lithium nickel oxide positive electrode material, the lithium nickel oxide positive electrode material having a chemical formula of Li 1+x Ni 1-x O2, where 0.02≦x≦0.08, the lithium nickelate positive electrode material has a crystalline structure of an α-NaFeO2-type hexagonal layered structure, the space group of the crystalline structure of the lithium nickelate positive electrode material is an R-3m type, and in the crystalline structure of the lithium nickelate positive electrode material, Li in stoichiometric excess over Ni occupies and is randomly distributed in the octahedral voids in the Ni layers of the layered structure.

[0006] The molar ratio of Li to Ni in the lithium nickelate positive electrode material is slightly greater than 1:1, and the positive electrode material is in a state of slight excess of lithium.

[0007] In some embodiments, 0.03≦x≦0.06.

[0008] In some embodiments, 0.04≦x≦0.05.

[0009] In some embodiments, the crystal structure does not contain any Li2NiO3 units of space group c / 2m as detected by neutron diffraction.

[0010] The present invention further provides a lithium nickel oxide positive electrode material, the lithium nickel oxide positive electrode material having the chemical formula Li 1+x Ni 1-x O2, where 0.02≦x≦0.08, and the lithium nickel oxide positive electrode material has a crystal structure of an α-NaFeO2-type hexagonal layered structure, and the space group of the crystal structure is an R-3m type.

[0011] In some embodiments, 0.03≦x≦0.06.

[0012] In some embodiments, 0.04≦x≦0.05.

[0013] In some embodiments, in the crystal structure of the lithium nickelate cathode material, Li in stoichiometric excess over Ni occupies and is randomly distributed in the octahedral voids in the Ni layers of the layered structure.

[0014] In some embodiments, the crystal structure is not detected by neutron diffraction to contain Li2NiO3 units in the space group c / 2m.

[0015] In the present invention, when the surface is evaluated by neutron diffraction testing, no superstructure peaks are observed, i.e., no Li2NiO3 unit with space group c / 2m is detected, which confirms that the crystalline structure of the lithium nickel oxide positive electrode material does not contain Li2NiO3 unit with space group c / 2m.

[0016] The present invention further provides a lithium nickel oxide positive electrode material, the lithium nickel oxide positive electrode material having the chemical formula Li 1+x Ni 1-xO2, where 0.02≦x≦0.08, and the lithium nickelate positive electrode material is produced by a production method including: (1) reacting a nickel source and a lithium source with oxygen in the presence of a molten salt additive to obtain a lithium nickelate-containing product; and (2) purifying the lithium nickelate-containing product to obtain a powder containing lithium nickelate, and placing the powder in an oxygen environment to obtain the lithium nickelate positive electrode material.

[0017] In the present invention, the molten salt additive refers to an additive capable of forming a eutectic mixture having a lower eutectic point together with a lithium source in the reaction raw materials, and the molten salt additive may be a molten salt containing lithium or a molten salt not containing lithium.

[0018] The present invention further provides a method for producing the aforementioned lithium nickelate positive electrode material, which can stably produce a lithium nickelate positive electrode material having a slight excess of lithium. (1) reacting a nickel source, a lithium source with oxygen in the presence of a molten salt additive to obtain a lithium nickel oxide-containing product; (2) purifying the lithium nickelate-containing product to obtain a powder containing lithium nickelate, and placing the powder in an oxygen environment to obtain the lithium nickelate positive electrode material.

[0019] The lithium nickelate-containing product obtained in the above-mentioned step (1) typically contains an excess lithium source and a molten salt additive in addition to lithium nickelate.

[0020] The purification process in step (2) described above can remove excess lithium source and molten salt additives, but this process may damage the surface structure of the lithium nickel oxide. In step (2), the powder is placed in an oxygen environment to repair the surface structure of the lithium nickel oxide. As a result, the crystal structure of the finally obtained lithium nickel oxide positive electrode material has a perfect layered structure with a space group of only R-3m.

[0021] In some embodiments, the nickel source is one or more selected from the group consisting of NiO, Ni(OH) 2 , and NiCO 3 .

[0022] In some embodiments, the lithium source is selected from LiOH or LiOH·H2O.

[0023] The molten salt additive is one or more selected from the group consisting of Li2SO4, Na2SO4, and K2SO4.

[0024] In some embodiments, the molten salt additive is Li2SO4.

[0025] In some embodiments, the ratio of the amount of substance of the lithium source to the amount of substance of the nickel source is 1.1 to 1.7:1.

[0026] In some embodiments, the ratio of the amount of the lithium source to the amount of the nickel source is 1.3 to 1.5:1.

[0027] In some embodiments, the ratio of the amount of substance of the molten salt additive to the amount of substance of the nickel source is 0.1 to 0.5:1.

[0028] In some embodiments, the ratio of the amount of substance of the molten salt additive to the amount of substance of the nickel source is 0.27-0.5:1.

[0029] In some embodiments, in step (1), the reaction temperature is 550 to 650°C.

[0030] In some embodiments, in step (1), the reaction time is 10 to 20 hours.

[0031] In some embodiments, in step (2), the temperature of the oxygen environment is 450 to 550°C.

[0032] In some embodiments, in step (2), the residence time in the oxygen environment is 2 to 5 hours.

[0033] In some embodiments, in step (2), the purification comprises washing and filtering.

[0034] In some embodiments, the method further comprises grinding the lithium nickelate-containing product prior to the purification.

[0035] In some embodiments, the method further comprises: (1) A nickel source, a lithium source, and a molten salt additive are uniformly mixed to obtain a mixture, the mixture is placed in a reactor, oxygen is injected into the reactor, and the temperature is raised to cause a reaction, thereby producing nickel. obtaining a lithium oxide-containing product; (2) crushing, washing, and filtering the lithium nickelate-containing product to obtain a powder containing lithium nickelate, placing the powder in a reactor, injecting oxygen into the reactor, and increasing the temperature to obtain the lithium nickelate positive electrode material. The washing can remove excess lithium source and molten salt additives.

[0036] In some embodiments, in step (1), the oxygen injection flow rate is 0.1 to 0.5 L / min.

[0037] In some embodiments, in step (1), the temperature increase rate is 2 to 10° C. / min.

[0038] In some embodiments, in step (1), the reaction is followed by cooling, and preferably the cooling rate is 2 to 10° C. / min.

[0039] In some embodiments, in step (2), the oxygen injection flow rate is 0.1 to 0.5 L / min.

[0040] In some embodiments, in step (2), the temperature increase rate is 2 to 10° C. / min.

[0041] In some embodiments, in step (2), after the temperature increase, further cooling is performed, and preferably the cooling rate is 2 to 10° C. / min.

[0042] In some embodiments, the reactor is a tube furnace.

[0043] The present invention further provides the use of the aforementioned lithium nickelate positive electrode material in a lithium ion battery.

[0044] The present invention further provides a lithium-ion battery including a cathode containing the aforementioned lithium nickelate cathode material. In some embodiments, the lithium-ion battery has a first-discharge energy density of 904 Wh / kgV or greater at 0.1 C scaling.

[0045] In some embodiments, the lithium ion battery has a discharge specific capacity retention rate of 92.3% or more after 100 charge / discharge cycles at 1C magnification in a voltage range of 4.3 to 2.8V.

[0046] In some embodiments, the thermal runaway temperature T2 of the lithium ion battery (the temperature at which the temperature rise due to self-heating exceeds 1°C / min) is 253.2°C or higher.

[0047] Compared with the prior art, the present invention has the following technical advantages:

[0048] The lithium nickel oxide positive electrode material of the present invention has a thermodynamically stable α-NaFeO2-type hexagonal layered structure, and its crystal structure has a space group of R-3m type and does not contain a Li2NiO3 unit of space group c / 2m. This overcomes the drawback of conventional positive electrode materials that cannot simultaneously achieve excellent cycle stability and high power-conversion performance. The lithium nickel oxide positive electrode material of the present invention simultaneously has high cycle stability, high power-conversion performance, and high thermal stability.

[0049] In the present invention, lithium ions are introduced into the nickel layer of the layered structure of lithium nickel oxide by a method of molten salt chemistry in a slight excess of the stoichiometric ratio, without changing the layered crystal structure. When a lithium nickel oxide positive electrode material with a slight excess of lithium is obtained and used in a lithium ion battery positive electrode, the lithium ion battery + / Li), an energy density of >900Wh / kg can be achieved, and the cycle stability and power consumption performance are both excellent. [Brief explanation of the drawings]

[0050] [Figure 1] 1 shows the results of a neutron diffraction test of positive electrode material 1 in Example 1. [Figure 2] 1 is a scanning transmission electron microscope photograph of a positive electrode material 1 in Example 1. [Figure 3] 1 shows the results of an electrochemical charge-discharge test of a positive electrode material 1 in Example 1 and a comparative positive electrode material 1 in Comparative Example 1. [Figure 4] 1 shows the results of a magnification test of a positive electrode material 1 in Example 1 and a comparative positive electrode material 1 in Comparative Example 1. [Figure 5] 1 shows the initial charge-discharge curve of positive electrode material 1 in Example 1. [Figure 6] 1 shows the results of a thermal safety test in a charged state for positive electrode material 1 in Example 1 and comparative positive electrode material 1 in Comparative Example 1. [Figure 7] 1 shows the results of an oxygen release test for a positive electrode material 1 in Example 1 and a lithium-deficient lithium nickel oxide according to the prior art. [Figure 8] 1 is a scanning transmission electron microscope image of a positive electrode material 1 in Example 1. FIG. [Figure 9] FIG. 10 is a neutron diffraction diagram of the positive electrode material in Comparative Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0051] Lithium nickel oxide (LiNiO2) has a high energy density (>900Wh / kg), but this type of material is difficult to obtain a phase that matches the theoretical stoichiometric ratio during synthesis, and is usually lithium-deficient (the ratio of Li to Ni is less than 1). During the electrochemical cycling process, this material is prone to structural transformation from the layered phase to the rocksalt phase, and is prone to losing lattice oxygen, resulting in low cycle stability and low power performance due to the structural transformation.

[0052] Traditional lithium nickel oxide is usually produced by solid-state reaction, and the obtained lithium-deficient lithium nickel oxide is, 1-y Ni 1+y O2, and to improve the performance of the lithium nickel oxide, the structure is usually modified by lattice doping or surface coating.

[0053] The chemical formula is Li 1+x Ni 1-x A lithium nickel oxide positive electrode material with a slight excess of lithium, i.e., O, cannot be produced by conventional solid-state reaction production methods, and although possible phases of the material can be predicted from the Li-Ni-O phase diagram, it cannot actually be produced and obtained experimentally.

[0054] There are other types of lithium-rich positive electrode materials in the prior art. These materials usually have a ratio of Li to transition metals greater than 1.1:0.9. However, the crystal structure of these materials contains not only layered R-3m structural units but also c / 2m (monoclinic Li2NiO3) structural units. Therefore, these materials can achieve high energy density at high pressure, but their cycle stability is poor.

[0055] In the present invention, when lithium nickel oxide is synthesized creatively by the method of molten salt chemistry, a molten salt additive is added to prepare a layered structure lithium nickel oxide positive electrode material containing only R-3m structural units and a slight excess of lithium, whose chemical formula is Li 1+x Ni 1-xWhen this positive electrode material is used in a lithium ion battery, the lithium ion battery simultaneously has high energy density, excellent cycling stability and thermal stability.

[0056] Example 1 Ni(OH)2 was mixed uniformly with LiOH and Li2SO4 (ratio of the amounts of the three substances: 1:1.3:0.27). The mixed powder was then placed in a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min. The temperature was increased to 600°C at a rate of 5°C / min, and the temperature was maintained at 600°C for 15 hours, after which the temperature was decreased to room temperature at a rate of 5°C / min.

[0057] The cooled powder is then removed and mechanically crushed, then added to deionized water to dissolve excess LiOH and Li2SO4, filtered, and the solid portion is removed and blast-dried at 60°C. The dried powder is then re-added to a corundum porcelain boat and placed in a tube furnace. Pure oxygen is injected at a flow rate of 0.2 L / min, and the temperature is increased to 500°C at a rate of 5°C / min. After maintaining at 500°C for 5 hours, the temperature is reduced to room temperature at a rate of 5°C / min to obtain cathode material 1.

[0058] The crystalline structure of the cathode material 1 was characterized by neutron diffraction (Figure 1), which confirmed that it has a layered structure, a space group of R-3m, and no c / 2m Li2NiO3 units. Since no superstructure peaks were observed, the term "superstructure" refers to an in-plane superstructure formed by the regular arrangement of Li and Ni to form Li@Ni6, which corresponds to the Li2NiO3 units with c / 2m symmetry. Furthermore, scanning transmission electron microscopy (STEM) imaging confirmed the random distribution of extra Li ions in the Ni layer. The results are shown in Figure 8. Li is lighter than Ni, resulting in darker contrast. As can be seen in Figure 8, the relatively dark spots correspond to the presence of Li atoms replacing Ni in the Ni layer, and are randomly distributed (indicated by arrows in Figure 8). The STEM image also confirms the layered structure of the material (Figure 2). The elemental composition of the material was analyzed by ICP, and the ratio of the amount of Li to Ni was 1.04:0.96 (i.e., the chemical formula Li 1+x Ni 1-x The results are shown in Table 1.

[0059] Example 2 Ni(OH)2 was mixed uniformly with LiOH and Li2SO4 (ratio of the amounts of the three substances: 1:1.1:0.27). The mixed powder was then placed in a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.5 L / min. The temperature was increased to 650°C at a rate of 2°C / min, and the temperature was maintained at 650°C for 15 hours, after which the temperature was decreased to room temperature at a rate of 2°C / min.

[0060] The cooled powder was then removed and mechanically crushed, then added to deionized water to dissolve excess LiOH and Li2SO4. After filtering, the solid portion was removed and blast-dried at 60°C. The dried powder was then re-added to a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.5 L / min, and the temperature was increased to 450°C at a rate of 2°C / min. After holding at 450°C for 2 hours, the temperature was reduced to room temperature at a rate of 2°C / min to obtain cathode material 2. The elemental composition of the material was analyzed by ICP, and the results are shown in Table 1.

[0061] Example 3 Ni(OH)2 was mixed uniformly with LiOH and Li2SO4 (ratio of the amounts of the three substances: 1:1.7:0.27). The mixed powder was then placed in a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.1 L / min. The temperature was increased to 550°C at a rate of 10°C / min, and the temperature was maintained at 550°C for 15 hours. After that, the temperature was decreased to room temperature at a rate of 10°C / min.

[0062] The cooled powder is then taken out and mechanically crushed, then added to deionized water to dissolve excess LiOH and Li2SO4, filtered, and the solid portion is taken out and blast-dried at 60°C. The dried powder is then placed in a corundum porcelain boat and placed in a tube furnace, where it is heated with pure acid. The element was injected at a flow rate of 0.1 L / min, the temperature was raised to 550°C at a rate of 10°C / min, and the temperature was maintained at 550°C for 4 hours, after which it was cooled to room temperature at a rate of 10°C / min to obtain cathode material 3. The elemental composition of the material was analyzed by ICP, and the results are shown in Table 1.

[0063] Example 4 Ni(OH)2 was mixed uniformly with LiOH and Li2SO4 (ratio of the amounts of the three substances: 1:1.5:0.1). The mixed powder was then placed in a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min. The temperature was increased to 600°C at a rate of 5°C / min, and the temperature was maintained at 600°C for 15 hours, after which the temperature was decreased to room temperature at a rate of 5°C / min.

[0064] The cooled powder was then removed and mechanically crushed, then added to deionized water to dissolve excess LiOH and Li2SO4. After filtering, the solid portion was removed and blast-dried at 60°C. The dried powder was then re-added to a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min, and the temperature was increased to 500°C at a rate of 5°C / min. After holding at 500°C for 5 hours, the temperature was reduced to room temperature at a rate of 5°C / min to obtain cathode material 4. The elemental composition of the material was analyzed by ICP, and the results are shown in Table 1.

[0065] Example 5

[0066] Ni(OH)2 was mixed with LiOH and Li2SO4 uniformly (the ratio of the amounts of the three was 1:1.5:0.5). The mixed powder was then placed in a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min. The temperature was increased to 600°C at a rate of 5°C / min, and the temperature was maintained at 600°C for 15 hours, after which the temperature was decreased to room temperature at a rate of 5°C / min.

[0067] The cooled powder was then removed and mechanically crushed, then added to deionized water to dissolve excess LiOH and Li2SO4. After filtering, the solid portion was removed and blast-dried at 60°C. The dried powder was then re-added to a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min, and the temperature was increased to 500°C at a rate of 5°C / min. After maintaining at 500°C for 5 hours, the temperature was reduced to room temperature at a rate of 5°C / min to obtain cathode material 5. The elemental composition of the material was analyzed by ICP, and the results are shown in Table 1.

[0068] Example 6 NiO was mixed uniformly with LiOH·H2O and Li2SO4 (ratio of the amounts of the three components: 1:1.3:0.27). The mixed powder was then placed in a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min. The temperature was increased to 600°C at a rate of 5°C / min, and the temperature was maintained at 600°C for 15 hours. After that, the temperature was decreased to room temperature at a rate of 5°C / min.

[0069] The cooled powder was then removed and mechanically crushed, then added to deionized water to dissolve excess LiOH·H2O and Li2SO4. After filtering, the solid portion was removed and blast-dried at 60°C. The dried powder was then re-added to a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min, and the temperature was increased to 500°C at a rate of 5°C / min. After maintaining at 500°C for 5 hours, the temperature was reduced to room temperature at a rate of 5°C / min to obtain cathode material 6. The elemental composition of the material was analyzed by ICP, and the results are shown in Table 1.

[0070] Example 7 NiCO3 was mixed with LiOH and Li2SO4 uniformly (ratio of the amounts of the three substances: 1:1.3:0.27), and then the mixed powder was placed in a corundum porcelain boat and heated in a tube furnace. Pure oxygen is injected at a flow rate of 0.2 L / min, the temperature is increased to 600°C at a rate of 5°C / min, the temperature is maintained at 600°C for 15 hours, and then the temperature is decreased to room temperature at a rate of 5°C / min.

[0071] The cooled powder was then removed and mechanically crushed, then added to deionized water to dissolve excess LiOH and Li2SO4. After filtering, the solid portion was removed and blast-dried at 60°C. The dried powder was then re-added to a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min, and the temperature was increased to 500°C at a rate of 5°C / min. After maintaining at 500°C for 5 hours, the temperature was reduced to room temperature at a rate of 5°C / min to obtain cathode material 7. The elemental composition of the material was analyzed by ICP, and the results are shown in Table 1.

[0072] Comparative Example 1 Ni(OH)2 was mixed uniformly with LiOH (at a ratio of 1:1.02). The resulting powder was then placed in a corundum porcelain boat and placed in a tube furnace. Pure oxygen was injected at a flow rate of 0.2 L / min. The temperature was increased to 485°C at a rate of 5°C / min, held for 3 hours, then increased to 700°C, held for 20 hours, and then cooled to room temperature at a rate of 5°C / min. Comparative cathode material 1 was obtained. The elemental composition of the material was analyzed by ICP, and the results are shown in Table 1.

[0073] Performance test: Electrochemical cycle stability: The cathode material 1 of Example 1 was assembled into a button cell in an argon-protected glove box together with a lithium sheet, a diaphragm, and an electrolyte (a solution of lithium hexafluorophosphate dissolved in dimethyl carbonate and fluoroethylene carbonate in a 1:1 volume ratio, with the lithium hexafluorophosphate concentration at 1 mol / L). The battery was charged and discharged at 1C over a voltage range of 4.3 to 2.8 V. The cathode material 1 of Comparative Example 1 was similarly operated and tested. The electrochemical cycle stability results are shown in Figure 3.

[0074] Separately, the charging and discharging performance of both materials was evaluated using the same button battery described above. The battery was charged to 4.3 V at 0.2 C charging rate and then discharged at 0.5 to 10 C charging rates. The test results are shown in Figure 4. Here, the initial discharge energy density of the battery corresponding to the positive electrode material 1 of Example 1 was obtained by integrating the charge and discharge curves and was 904 Wh / kg (Figure 5).

[0075] Example 8 (Thermal Safety Test) The positive electrode material 1 of Example 1 was used to assemble a soft pack battery and evaluate its thermal safety. Assembly method: (1) Preparation of positive electrode piece: The active material (positive electrode material 1 of Example 1), conductive agent (carbon black), and adhesive (5 wt% polyvinylidene fluoride / N-methylpyrrolidone solution) were mixed in a mass ratio of 94:3:3, and N-methylpyrrolidone (NMP) was added to adjust the solid concentration to 65%. The mixture was applied to a 13 μm aluminum foil, dried, and then punched into pieces measuring 55 mm x 35 mm (H x W) using a punching machine. After rolling, the pieces were cut into 1 (2) Preparation of negative electrode pieces: Active material (graphite), conductive agent (carbon black), and adhesive (5 wt% polyvinylidene fluoride / N-methylpyrrolidone solution) were mixed in a mass ratio of 94:3:3, and NMP was added to adjust the solids concentration to 45%. This mixture was then applied to 10 μm copper foil and dried. After drying, pieces measuring 57 mm x 37 mm (H x W) were punched out using a punching machine. The resulting pieces were rolled and vacuum dried at 80°C for 12 hours. (3) Preparation of soft-pack battery cells: 16 μm PE diaphragms and positive and negative electrodes were stacked to form battery cells. Each positive electrode was matched to a corresponding negative electrode. The outermost layer was wrapped in a diaphragm and then sealed with polyamide tape. Aluminum and nickel tabs were then welded to the exposed tabs of the positive and negative electrodes using an ultrasonic welder. Polyamide tape was then applied to the soldered areas. The outer layer of the battery cell is wrapped in aluminum plastic film, leaving an opening for injecting the electrolyte. The fabricated battery cell is dried in a vacuum at 60°C for 6 hours. The capacity is set to 30mAh. (4) Battery fabrication: 0.5g of electrolyte (1.2M lithium hexafluorophosphate solution, solvent: ethylene carbonate EC and ethyl methyl carbonate EMC mixed solvent in a weight ratio of 3:7, containing 2% vinylene carbonate VC) is pipetted into the battery cell, and the inlet is sealed using a sealing machine. The battery is placed flat and left to stand for 10 hours before testing. (5) Cell formation and testing: The battery is clamped and tested using a charge-discharge tester. It is charged to 4.25V at a constant current of 0.1C (22mA / g of positive electrode active material mass, same below), and then charged at a constant voltage of 0.05C. It is discharged to 2.75V at 0.1C, and the above process is repeated three times to complete cell formation.

[0076] Thermal safety evaluation method: Two soft-pack batteries were each charged at a constant current of 0.1C to 4.25V, then charged at a voltage of 0.05C, and then allowed to stand. The accelerating rate calorimeter chamber was opened, and the tip of a thermocouple was attached to the center of one battery with aluminum tape. Then, the other battery was placed on top of the battery, and the two batteries were attached with aluminum tape and fixed in a dedicated test rack inside the chamber. The accelerating rate calorimeter cover was closed, and the accelerating rate calorimeter process was started for testing. Specific test process: Starting at 25°C, the test was first switched to heating mode, and the chamber was heated for 5°C each time (10 minutes), and the battery temperature was monitored. After 30 minutes, the test was stopped and the test mode was entered. If the temperature rise rate was slower than 0.02°C / min, heating resumed after the test. If the temperature rise rate was faster than 0.02°C / min, the test mode was entered, and the chamber was no longer heated, and only the temperature change was recorded. The test is completed by switching to a cooling mode until the temperature exceeds 300°C. The test results are shown in Figure 6. The battery equipped with the cathode material 1 of Example 1 has a relatively high T2 temperature (thermal runaway temperature, the temperature at which the temperature rise due to self-heating exceeds 1°C / min) of 253.2°C.

[0077] Comparative Example 2 (Thermal Safety Test) The soft-pack battery assembly method and thermal safety evaluation method were the same as those in Example 8, except that the cathode material 1 in Example 1 was simply replaced with comparative cathode material 1 in Comparative Example 1. The test results are shown in Figure 6, and the T2 temperature (thermal runaway temperature, the temperature at which the temperature rise due to self-heating exceeds 1°C / min) was 179.0°C. Therefore, Comparative Example 2 is more susceptible to thermal runaway than Example 8.

[0078] Using in situ differential electrochemical mass spectrometry (DEMS), oxygen and carbon dioxide release tests were conducted on the lithium nickel oxide positive electrode material of Example 1 and the lithium-deficient lithium nickel oxide positive electrode material of the prior art. The test conditions were the first charge at a charge rate of 0.1C. The results are shown in FIG. 7, where A is the general lithium nickel oxide (LNO) and B is the lithium nickel oxide of Example 1 (LR-LNO with a slight lithium excess). As can be seen, the general lithium nickel oxide generates 4.2 μmol / g of O and 86.5 μmol / g of CO when lithium is removed, while the lithium nickel oxide of Example 1 essentially does not release oxygen.

[0079] Example 9 This is almost the same as Example 1, except that Li2SO4 is simply replaced with Na2SO4.

[0080] Example 10 This is almost the same as Example 1, except that Li2SO4 is simply replaced with K2SO4.

[0081] Comparative Example 3 This is almost the same as Example 1, except that Li2SO4 is not added.

[0082] Comparative Example 4 This is almost the same as Example 1, except that the ratio of the amounts of Ni(OH)2, LiOH, and Li2SO4 is 1:1.05:0.27.

[0083] Comparative Example 5 This is almost the same as Example 1, except that the ratio of the amounts of Ni(OH)2, LiOH, and Li2SO4 is 1:2:0.27.

[0084] Comparative Example 6 The solution of the embodiment in JP2015082345A (Japanese Patent Publication No. 2015-82345) is specifically as follows.

[0085] Lithium peroxide (Li2O2) and nano-sized nickel oxide are used as starting materials. These raw materials are crushed and mixed in a molar ratio of Li / Ni = 1.9. The mixture is then loaded into a platinum tank and sintered for 1 hour at 700°C under a pressure of 4 GPa using a cubic anvil-type high-pressure apparatus to obtain lithium-rich lithium nickel oxide. The average particle size is around 50-100 nm, and the amount of each element is analyzed by emitting a spectrum using ICP, and the components are identified as Li. 1.30 Ni 0.70 Figure 2 (neutron diffraction diagram) of the patent is shown in Figure 9, which shows that the positive electrode material has a layered structure, and the space group contains c / 2m Li2NiO3 units in addition to R-3m. In Figure 9, there is a very prominent superstructure peak (2θ in the range of 20 to 25°, corresponding to the dotted box), which corresponds to c / 2m Li2NiO3 (where M=Ni) units, i.e., the regular arrangement of Li@Ni6 is within the Ni layer.

[0086] The elemental components of the materials of Examples 9 to 10 and Comparative Examples 3 to 5 were analyzed by ICP, and the results are shown in Table 1.

[0087] [Table 1]

Claims

1. A lithium nickel oxide positive electrode material, The lithium nickel oxide positive electrode material has the chemical formula Li １＋ｘ Ni １－ｘ O ２ where 0.02≦x≦0.08, and the lithium nickel oxide cathode material has a crystal structure of α-NaFeO ２ The lithium nickelate positive electrode material has a hexagonal layered structure, and the space group of the crystal structure of the lithium nickelate positive electrode material is an R-3m type. In the crystal structure of the lithium nickelate positive electrode material, Li in a stoichiometric excess relative to Ni occupies octahedral voids in the Ni layers of the layered structure and is randomly distributed in the octahedral voids. A lithium nickel oxide positive electrode material characterized by:

2. 03≦x≦0.06 2. The lithium nickelate positive electrode material according to claim 1.

3. 04≦x≦0.05 2. The lithium nickelate positive electrode material according to claim 1.

4. The lithium nickel oxide positive electrode material has the chemical formula Li １＋ｘ Ni １－ｘ O ２ where 0.02≦x≦0.08, and the lithium nickel oxide cathode material has a crystal structure of α-NaFeO ２ The crystal structure has a hexagonal layer structure, and the space group of the crystal structure is an R-3m type. A lithium nickel oxide positive electrode material characterized by:

5. In the crystalline structure of the lithium nickelate cathode material, Li in stoichiometric excess relative to Ni occupies octahedral voids in the Ni layers of the layered structure and is randomly distributed in the octahedral voids.

5. The lithium nickelate positive electrode material according to claim 4.

6. Neutron diffraction revealed that the crystal structure contained Li with a space group of c / 2m. ２ NiO ３ No units detected containing The lithium nickelate positive electrode material according to claim 1 or 4.

7. A lithium nickel oxide positive electrode material, The lithium nickel oxide positive electrode material has the chemical formula Li １＋ｘ Ni １－ｘ O ２ wherein 0.02≦x≦0.08, and the lithium nickelate positive electrode material is produced by a production method including: (1) reacting a nickel source and a lithium source with oxygen in the presence of a molten salt additive to obtain a lithium nickelate-containing product; and (2) purifying the lithium nickelate-containing product to obtain a powder containing lithium nickelate, and placing the powder in an oxygen environment to obtain the lithium nickelate positive electrode material. A lithium nickel oxide positive electrode material characterized by:

8. A method for producing the lithium nickelate positive electrode material of any one of claims 1 to 6. The method comprises: (1) reacting a nickel source, a lithium source with oxygen in the presence of a molten salt additive to obtain a lithium nickelate-containing product; (2) purifying the lithium nickelate-containing product to obtain a powder containing lithium nickelate, and placing the powder in an oxygen environment to obtain the lithium nickelate positive electrode material. A method characterized by:

9. The nickel source is NiO, Ni(OH) ２ and NiCO ３ One or more selected from the group consisting of 9. The method of claim 8.

10. The lithium source is LiOH or LiOH.H ２ Selected from O 9. The method of claim 8.

11. The molten salt additive is Li ２ SO ４ , Na ２ SO ４ and K. ２ SO ４ One or more selected from the group consisting of 9. The method of claim 8.

12. The molten salt additive is Li ２ SO ４ is 9. The method of claim 8.

13. The ratio of the amount of the lithium source to the amount of the nickel source is 1.1 to 1.7:1, and / or the ratio of the amount of the molten salt additive to the amount of the nickel source is 0.1 to 0.5:

1.

9. The method of claim 8.

14. The ratio of the amount of the lithium source to the amount of the nickel source is 1.3 to 1.5:1, and / or the ratio of the amount of the molten salt additive to the amount of the nickel source is 0.27 to 0.5:

1.

9. The method of claim 8.

15. In step (1), the reaction temperature is 550 to 650°C, and / or in step (1), the reaction time is 10 to 20 hours, and / or in step (2), the temperature of the oxygen environment is 450 to 550°C, and / or in step (2), the residence time in the oxygen environment is 2 to 5 hours.

9. The method of claim 8.

16. In step (2), the purification includes washing and filtering, and / or the method further includes grinding the lithium nickelate-containing product before the purification.

9. The method of claim 8.

17. The method comprises: (1) uniformly mixing a nickel source, a lithium source, and a molten salt additive to obtain a mixture, placing the mixture in a reactor, injecting oxygen into the reactor, and increasing the temperature to react and obtain a lithium nickel oxide-containing product; (2) crushing, washing, and filtering the lithium nickel oxide-containing product to obtain a powder containing lithium nickel oxide; placing the powder in a reactor; injecting oxygen into the reactor; and heating the reactor to obtain the lithium nickel oxide positive electrode material.

9. The method of claim 8.

18. In step (1), the oxygen injection flow rate is 0.1 to 0.5 L / min, and / or in step (1), the temperature increase rate is 2 to 10° C. / min.

18. The method of claim 17.

19. In step (2), the oxygen injection flow rate is 0.1 to 0.5 L / min, and / or in step (2), the temperature increase rate is 2 to 10° C. / min.

18. The method of claim 17.

20. The lithium nickel oxide according to any one of claims 1 to 7 in a lithium ion battery. Use of positive electrode materials.

21. A cathode comprising the lithium nickelate cathode material of any one of claims 1 to 7. A sodium-ion battery characterized by:

22. The lithium ion battery has an initial discharge energy density of 904 Wh / kgV or more at a 0.1 C multiplication rate, and / or the lithium ion battery has a discharge specific capacity retention rate of 92.3% or more after 100 charge / discharge cycles at a 1 C multiplication rate in a voltage range of 4.3 to 2.8 V.

22. The lithium ion battery of claim 21.

Images