High-entropy high-nickel single-crystal lithium-ion battery cathode material and preparation method thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and provides a high-entropy high-nickel single-crystal lithium ion battery positive electrode material and a preparation method thereof, to solve the problems existing in high-nickel lithium nickel cobalt manganese oxide positive electrode materials and improve the comprehensive performance thereof. In view of the modification requirement of high-nickel layered lithium nickel cobalt manganese oxide ternary positive electrode material, the application proposes a high-entropy alloy doping strategy based on combination design and component ratio design, and combines strict design of the preparation process on the basis of high-entropy alloy doping, so that the high-entropy doped positive electrode material presents a single-crystal morphology, and the specific molecular expression is: Li 1+δ [Ni 0.86±x Co 0.04±x / 2Mn 0.1±x / 2 (OH)2] 1‑z M z O2, wherein 0≤δ≤0.2, 0≤x≤0.06, and 0.005≤z≤0.25; M is at least five of Al, Mg, Ti, Zr, Ga, In, Y, La, B, Si, and Nb. In summary, the high-entropy high-nickel positive electrode material with a single-crystal morphology is synthesized by a high-temperature solid-phase method, and exhibits good electrochemical performance, and can exhibit good discharge specific capacity and cycle stability at a high voltage of 2.8-4.5 V.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to lithium-ion battery cathode materials, specifically providing a high-entropy, high-nickel single-crystal lithium-ion battery cathode material and its preparation method. Background Technology

[0002] With the rapid development of industrial technology, people's demand for energy is increasing, leading to a more severe fossil fuel crisis and corresponding environmental pollution problems. Therefore, the demand for new energy research and development has been growing in recent years. Among numerous new energy technology industries, lithium-ion batteries (LIBs) stand out due to their superior characteristics such as high energy density and high cycle stability. As a rechargeable battery, lithium-ion batteries have many significant advantages, becoming a dual focus of scientific research and industrialization. Furthermore, lithium-ion batteries are green, environmentally friendly, and pollution-free, thus finding widespread application in portable electronic devices, new energy vehicles, medical equipment, and many other fields. At the same time, this also means that people have increasingly higher requirements for the performance of lithium-ion batteries.

[0003] Currently, among commonly used lithium-ion battery cathode materials, high-nickel layered nickel-cobalt-manganese ternary cathode materials (NCM) are widely used. This material is a layered structure material with the chemical formula LiNi. x Co y Mn z O2 (x≥0.6) typically exhibits an α-NaFeO2-type layered structure, belonging to the hexagonal crystal system, R-3m space group; NCM is developed and modified from LiCoO2, LiNiO2, and LiMnO2 through combined research and development, leveraging the strengths and mitigating the weaknesses of each material, integrating the excellent properties of each, including the high capacity of lithium nickel oxide, the excellent stability of lithium cobalt oxide, and the high thermal stability of lithium manganese oxide, exhibiting excellent electrochemical performance with a capacity as high as 274 mAh·g. -1 The theoretical specific capacity is 3.6V with an average operating voltage. However, high-nickel lithium nickel cobalt manganese oxide cathode materials are usually formed by the agglomeration of numerous tiny primary particles into secondary composite polycrystalline particles. In this structure, during operation, as charging and discharging occur, Li... + The cations will continuously insert and extract into the internal lattice of the material, which will cause a series of structural changes and phase transitions over time. In addition, this ternary material also faces problems such as cation mixing, lattice defects, grain boundary cracks, and residual lithium compounds on the surface. These problems will have a huge impact on performance, resulting in short material life and poor safety. Moreover, due to its inability to withstand high-voltage charging, it also leads to low energy density, which greatly limits the further development and application of the material.

[0004] To address the series of problems existing in the aforementioned layered nickel-cobalt-manganese ternary cathode materials, various modification studies have been conducted, including but not limited to doping and coating. However, the overall performance after modification remains unsatisfactory. Therefore, combining multiple modification methods to improve the performance of lithium-ion batteries has become an important issue for the large-scale application of commercial lithium-ion batteries. Better and newer solutions are urgently needed to overcome the problems faced by high-nickel cathode materials and improve their overall performance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-entropy, high-nickel single-crystal lithium-ion battery cathode material and its preparation method, to solve many problems existing in high-nickel lithium nickel cobalt manganese oxide cathode materials, such as cation mixing, lattice defects, grain boundary cracks, and surface residual lithium compounds, and to improve its overall performance, which includes poor safety, short lifespan, poor resistance to high-voltage charging, and low energy density, thereby improving the overall electrochemical performance of lithium-ion batteries. Addressing the modification needs of high-nickel layered nickel cobalt manganese ternary cathode materials, this invention proposes high-entropy alloy doping based on combinatorial design and component ratio modulation design. Furthermore, based on high-entropy alloy doping and rigorous design of the preparation process, the cathode material exhibits a single-crystal morphology after high-entropy doping. The single-crystal morphology results in a cathode material with very high compaction density, possessing advantages such as high mechanical strength, low specific surface area, and low defect density, as well as superior electrochemical performance, including better safety performance, long cycle life, resistance to high-voltage charging, high compaction density, and high energy density. Furthermore, the single-crystal morphology reduces the accumulation of internal stress, making the extraction and insertion of lithium ions smoother, resulting in better reversibility and higher energy density. For high-entropy doped cathode materials, the high-entropy alloy exists as a solid solution within the material; this large configurational entropy gives the material better stability, exhibiting excellent cycle stability and a longer service life. This invention creatively combines these two modification methods effectively, using a high-temperature solid-state method to synthesize a single-crystal morphology high-entropy high-nickel lithium-ion battery cathode material, which exhibits excellent electrochemical performance and good specific capacity and stability at a high cutoff voltage of 2.8–4.5V. Moreover, the high-temperature solid-state method is simple, easy to control precisely, and suitable for large-scale industrial production.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A high-entropy, high-nickel single-crystal lithium-ion battery cathode material, characterized in that the lithium-ion battery cathode material has a single-crystal morphology, and its molecular formula is:

[0008] Li 1+δ [Ni 0.86±x Co 0.04±x / 2 Mn 0.1±x / 2 (OH)2] 1-z M zO2,

[0009] Where, 0≤δ≤0.2, 0≤x≤0.06, 0.005≤z≤0.25;

[0010] M is at least five of the following: Al, Mg, Ti, Zr, Ga, In, Y, La, B, Si, and Nb.

[0011] In particular: M = [Al+Ga+Ti+Y+Zr], [Al+In+Ti+Y+Zr], [La+Ga+Ti+Y+Zr] or [La+In+Ti+Y+Zr], where the molar ratio of (Al or La):(Ga or In):Ti:Y:Zr is 2:1:1:1:1.

[0012] Furthermore, the preparation method of the high-entropy, high-nickel single-crystal lithium-ion battery cathode material is characterized by comprising the following steps:

[0013] S1. Grind the lithium source (lithium hydroxide) and mix it evenly with the precursor and dopant to obtain a mixed raw material;

[0014] S2. Place the mixed raw materials in a tube furnace and heat them to 450℃~600℃ at a heating rate of 2~5℃ / min under an oxygen atmosphere. Hold the temperature for 4~8 hours to complete the pre-sintering and obtain the pre-fired material.

[0015] S3. Grind the pre-fired material evenly to obtain pre-fired powder;

[0016] S4. Place the pre-calcined powder in a tube furnace and heat it to 750℃~950℃ at a heating rate of 2~5℃ / min under an oxygen atmosphere. Hold the temperature for 12~24 hours to complete sintering and obtain high-entropy high-nickel single crystal lithium-ion battery cathode material.

[0017] Furthermore, in step S1, the molar ratio of lithium hydroxide, precursor, and dopant is: (1+δ):(1-z):z, 0≤δ≤0.2, 0.005≤z≤0.25.

[0018] Furthermore, in step S1, the precursor material is an 8-series ternary precursor with the chemical formula: Ni 0.86± x Co 0.04±x / 2 Mn 0.1±x / 2 (OH)₂, 0≤x≤0.06; typical composition is [Ni 0.86 Co 0.04 Mn 0.1 (OH)2].

[0019] Furthermore, in step S1, the doping material M is at least five oxides or hydroxides selected from Al, Mg, Ti, Zr, Ga, In, Y, La, B, Si, and Nb. Typical combinations of doping materials are [Al+Ga+Ti+Y+Zr], [Al+In+Ti+Y+Zr], [La+Ga+Ti+Y+Zr], or [La+In+Ti+Y+Zr], with a molar ratio of (Al or La):(Ga or In):Ti:Y:Zr of 2:1:1:1:1.

[0020] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0021] This invention proposes a high-entropy, high-nickel single-crystal lithium-ion battery cathode material and its preparation method, creatively achieving an effective combination of single-crystal morphology and high-entropy doping. The high-entropy, high-nickel single-crystal lithium-ion battery cathode material is prepared via a high-temperature solid-state method, exhibiting high reversible specific capacity and cycle stability. Using a high-temperature solid-state method, the lithium source, precursor, and dopant are mixed, pre-calcined, ground, and sintered. By strictly controlling the process conditions, a high-entropy cathode material with a single-crystal morphology is obtained, forming a uniformly distributed layered single-crystal particle material. This structure overcomes the lattice defects and grain boundary cracks encountered in traditional polycrystalline materials. High-entropy doping further refines the material's configuration, effectively suppressing cation mixing under the combined action of multiple elements and increasing the Li-Ni content. + The diffusion channels enable the material to have excellent cycling performance and structural stability.

[0022] In summary, the high-entropy, high-nickel single-crystal lithium-ion battery cathode material proposed in this invention can achieve a capacity of 181.0 mAh·g during charge-discharge at a rate of 0.5C. -1 After 100 cycles, the capacity retention rate was 86.4%; it also exhibited good specific capacity and stability at a high cutoff voltage of 2.8–4.5V, with a specific capacity reaching 191.8 mAh·g at a 0.5C rate. -1 After 100 cycles, the specific capacity is 149.3 mAh·g. -1 The capacity retention rate was 79.1%, compared to 147.8 mAh·g at 2.8–4.3 V. -1 The results are almost identical, proving that the material is fully capable of operating at higher cutoff voltages and has the ability to withstand high-voltage charging. Furthermore, the preparation process of the high-entropy, high-nickel single-crystal lithium-ion battery cathode material proposed in this invention is easy to control, the process is very simple and can be precisely controlled, and it has a very good application prospect and is expected to be put into large-scale industrial production. Attached Figure Description

[0023] Figure 1This is a process flow diagram for preparing the high-entropy, high-nickel single-crystal lithium-ion battery cathode material in this invention.

[0024] Figure 2 The image shows the XRD pattern of the high-entropy, high-nickel single-crystal lithium-ion battery cathode material in Example 1 of the present invention.

[0025] Figure 3 This is a SEM image of the high-entropy, high-nickel single-crystal lithium-ion battery cathode material in Example 1 of the present invention.

[0026] Figure 4 This is a graph showing the first charge-discharge curve of the high-entropy, high-nickel single-crystal lithium-ion battery cathode material at a 0.5C rate in Example 1 of the present invention.

[0027] Figure 5 This is a cycle performance curve of the high-entropy, high-nickel single-crystal lithium-ion battery cathode material of Example 1 of the present invention at a rate of 0.5C.

[0028] Figure 6 This is a cycle performance curve of the high-entropy, high-nickel single-crystal lithium-ion battery cathode material of Example 1 of the present invention at a working voltage of 2.8 to 4.5V at a 0.5C rate. Detailed Implementation

[0029] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material. This lithium-ion battery cathode material has a single-crystal morphology, and its molecular formula is: Li 1+δ [Ni 0.86±x Co 0.04±x / 2 Mn 0.1±x / 2 (OH)2] 1-z M z O2, δ=0.05, x=0, z=0.03, M=[Al+Ga+Ti+Y+Zr].

[0032] The preparation process of the high-entropy, high-nickel monocrystalline lithium-ion battery cathode material is as follows: Figure 1 As shown, using 8-series ternary precursors, lithium hydroxide, and dopants as raw materials, the specific steps include:

[0033] S1. Accurately weigh the following raw and auxiliary materials using an electronic analytical balance: lithium hydroxide, [Ni 0.86±x Co 0.04±x / 2Mn 0.1±x / 2 [OH)2] precursor (typically composed of [Ni 0.86 Co 0.04 Mn0.1 (OH)2), aluminum hydroxide, gallium oxide, titanium oxide, yttrium oxide, zirconium oxide, wherein, LiOH: precursor: Al 3+ Ga 2+ Ti 4+ Y 3+ Zr 4+ The molar ratio is 1.05:0.97:0.01:0.005:0.005:0.005:0.005;

[0034] Lithium hydroxide was carefully ground into uniform fine powder particles in an agate mortar. Then, the precursor and dopant materials (aluminum hydroxide, gallium oxide, titanium oxide, yttrium oxide, zirconium oxide) were added and stirred repeatedly until they were mixed evenly to obtain a mixed raw material.

[0035] S2. The mixed raw materials are loaded into a ceramic boat and placed in a tube furnace. An oxygen atmosphere is introduced, and the temperature is raised to 500°C at a heating rate of 5°C / min. The temperature is held for 5 hours to complete the pre-sintering and obtain the pre-fired material.

[0036] S3. Take out the pre-fired material and grind it carefully in an agate mortar until it becomes uniform fine powder particles to obtain pre-fired powder.

[0037] S4. The pre-fired powder is loaded into a ceramic boat and placed in a tube furnace. An oxygen atmosphere is introduced, and the temperature is raised to 800°C at a heating rate of 5°C / min. The temperature is held for 12 hours to complete sintering and obtain a high-entropy, high-nickel single-crystal lithium-ion battery cathode material.

[0038] The beneficial effects of the present invention will be described in detail below with reference to testing:

[0039] First, the structure of the material was characterized using X-ray diffraction (XRD), with a scanning range of 5°–90° and a scanning rate of 2°·min. -1 The result is as follows Figure 2 As shown in the figure, all the characteristic peaks correspond to the layered hexagonal α-NaFeO2 structure of the R-3m space group, and the splitting of the two sets of peaks (006) / (102) and (108) / (110) is very obvious, indicating that the material maintains a highly ordered layered structure and low cation mixing.

[0040] Then, scanning electron microscopy (SEM) was used to characterize the material and observe its morphology. The results are as follows: Figure 3 As shown in the figure, the material forms irregular polyhedral grains, which is a typical single crystal morphology.

[0041] Finally, the electrochemical performance of the cathode material was tested. The specific process for the electrochemical performance testing is as follows:

[0042] The aforementioned high-entropy, high-nickel single-crystal lithium-ion battery cathode material was mixed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride, PVDF) at a mass ratio of 85:10:5. The mixture was then thoroughly ground in an agate mortar until homogeneous, yielding a slurry. The slurry was then evenly coated onto a clean aluminum foil surface using a scraper, forming a 150µm coating. This coating was placed in an 80°C oven and dried for 5 hours. After drying, the foil was removed, cut into small round pieces with a diameter of 12mm, and then placed in a 100°C vacuum drying oven and dried overnight (approximately 12 hours). The resulting product was... The final electrode sheets were weighed and placed in an argon-atmospheric glove box for later use. The water and oxygen content in the glove box was less than 1 ppm. A CR2025 coin cell mold was used, with the prepared electrode sheet as the positive electrode and the lithium sheet as the negative electrode. GR-FH001 electrolyte and polyethylene separator were used, and the separator and spring sheet were assembled into a complete CR2025 coin cell. The battery was transferred to an air-conditioned room at 25°C and left to stand for 4 to 24 hours. Its electrochemical performance was tested using Xinwei Battery Equipment, with the working voltage set to 2.8 to 4.3V.

[0043] The electrochemical performance of the cathode material in this embodiment was tested at 0.5C, and the initial charge-discharge curve is shown below. Figure 4 As shown in the figure, the cycle performance curve is as follows: Figure 5 As shown in the figure, the battery prepared in this embodiment can achieve a maximum discharge specific capacity of 181.0 mAh·g during a 0.5C charge-discharge rate. -1 After 100 cycles, the battery retained 86.4% of its capacity, demonstrating good cycle stability. Cycle performance was tested at a 0.5C rate within a voltage range of 2.8–4.5V, with the following results: Figure 6 As shown in the figure, it can also operate stably at higher voltages and has a higher discharge specific capacity, reaching 191.8 mAh·g. -1 After 100 cycles, the capacity retention rate was 78.1%, which is almost the same as the discharge specific capacity after 100 cycles at 4.3V. This indicates that the material can withstand charge-discharge cycles at high cutoff voltages of 2.8 to 4.5V and exhibits excellent cycle stability.

[0044] Furthermore, the present invention also provides a comparative example, the preparation process of which differs from that of Example 1 in that: S1. The following raw and auxiliary materials are accurately weighed using an electronic analytical balance: lithium hydroxide, [Ni 0.86±x Co 0.04±x / 2 Mn 0.1±x / 2 [OH)2] precursor (typically composed of [Ni 0.86 Co 0.04 Mn 0.1(OH)2]), wherein the molar ratio of LiOH to precursor is 1.05:1.0; based on the same preparation process as in Example 1, the cathode material prepared in the comparative example is still a single crystal morphology, but without high entropy doping.

[0045] The cathode materials used in the comparative example were assembled into identical coin half-cells, and their electrochemical performance was tested at 0.5C. The battery prepared in the comparative example exhibited a discharge specific capacity of 185.3 mAh·g during a charge-discharge process at 0.5C. -1 After 100 cycles, the battery retained 66.2% of its capacity, exhibiting significantly worse cycle stability than the high-entropy, high-nickel monocrystalline lithium-ion battery cathode material in Example 1. By increasing the charging cutoff voltage and testing cycle performance at a rate of 0.5C within a voltage range of 2.8–4.5V, the capacity retention of the cathode material in the comparative example after 100 cycles was only 54.3%, far lower than the 78.1% capacity retention of the high-entropy, high-nickel monocrystalline lithium-ion battery cathode material in Example 1. This demonstrates that the high-entropy, high-nickel monocrystalline lithium-ion battery cathode material in Example 1 is better suited for operation at a high cutoff voltage of 2.8–4.5V and exhibits superior cycle stability.

[0046] Example 2

[0047] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, which is prepared in the same way as in Example 1. The only difference is that in step S1, gallium oxide is replaced with an equal molar amount of indium oxide. After electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0048] Example 3

[0049] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, which is prepared in the same way as in Example 1. The only difference is that in step S1, aluminum oxide is replaced with an equal molar amount of lanthanum oxide. After electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0050] Example 4

[0051] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, the preparation method of which is the same as that in Example 1, the only difference being: in step S1, LiOH: precursor: Al 3+ Ga 2+ Ti 4+ Y 3+ Zr 4+ The molar ratio is 1.08:0.97:0.01:0.005:0.005:0.005:0.005; after electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0052] Example 5

[0053] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, which is prepared in the same way as in Example 1. The only difference is that in step S4, the heating rate of the tube furnace is 2℃ / min. After electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0054] Example 6

[0055] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, which is prepared in the same way as in Example 1. The only difference is that the sintering temperature in step S4 is 750°C. After electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0056] Example 7

[0057] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, which is prepared in the same way as in Example 1. The only difference is that the sintering temperature in step S4 is 850°C. After electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0058] Example 8

[0059] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, which is prepared in the same way as in Example 1. The only difference is that in step S4, the heat preservation time is 15 hours. After electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0060] Example 9

[0061] This embodiment provides a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, the preparation method of which is the same as that in Example 1, the only difference being: the expression Li 1+δ [Ni 0.86±x Co 0.04±x / 2 Mn 0.1±x / 2 (OH)2] 1-z M z In O2, z = 0.09. In step S1, M = [Al + Ga + Ti + Y + Zr + Mg + Nb + B + Si], and the molar ratio Al:Ga:Ti:Y:Zr:Mg:Nb:B:Si = 2:1:1:1:1:1:1:0.5:0.5. After electrochemical performance testing, this embodiment has similar beneficial effects to Example 1.

[0062] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing a high-entropy, high-nickel single-crystal lithium-ion battery cathode material, characterized in that, Includes the following steps: S1. Lithium hydroxide is ground and then mixed evenly with the precursor and dopant to obtain a mixed raw material; The molar ratio of lithium hydroxide, precursor, and dopant is: (1+δ):(1-z):z, 0≤δ≤0.2, 0.005≤z≤0.25; The precursor material uses an 8-series ternary precursor with the chemical formula: Ni 0.86±x Co 0.04±x / 2 Mn 0.1±x / 2 (OH)₂, 0 ≤ x ≤ 0.06; The doped material is an oxide or hydroxide of the doping element; The doping elements are Al, Ga, Ti, Y, and Zr, with a molar ratio of Al:Ga:Ti:Y:Zr of 2:1:1:1:1; or Al, In, Ti, Y, and Zr, with a molar ratio of Al:In:Ti:Y:Zr of 2:1:1:1:1; or La, Ga, Ti, Y, and Zr, with a molar ratio of La:Ga:Ti:Y:Zr of 2:1:1:1:1; or La, In, Ti, Y, and Zr, with a molar ratio of La:In:Ti:Y:Zr of 2:1:1:1:1; or Al, Ga, Ti, Y, Zr, Mg, Nb, B, and Si, with a molar ratio of Al:Ga:Ti:Y:Zr:Mg:Nb:B:Si of 2:1:1:1:1:1:1:0.5:0.

5. S2. Place the mixed raw materials in a tube furnace and heat them to 450℃~600℃ at a heating rate of 2~5℃ / min under an oxygen atmosphere. Hold the temperature for 4~8 hours to complete the pre-sintering and obtain the pre-fired material. S3. Grind the pre-fired material evenly to obtain pre-fired powder; S4. Place the pre-calcined powder in a tube furnace and heat it to 750℃~950℃ at a heating rate of 2~5℃ / min under an oxygen atmosphere. Hold the temperature for 12~24 hours to obtain a high-entropy high-nickel single-crystal lithium-ion battery cathode material after sintering.

2. A high-entropy, high-nickel single-crystal lithium-ion battery cathode material, characterized in that, The lithium-ion battery cathode material has a single-crystal morphology and is prepared by the preparation method of the high-entropy high-nickel single-crystal lithium-ion battery cathode material according to claim 1.

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