Upgrading utilization method of waste low-nickel ternary positive electrode material

Abstract

The invention belongs to the field of recycling of lithium ion battery failure ternary positive electrode materials, and particularly discloses an upgrading utilization method of a waste low-nickel ternary positive electrode material. The method is used for upgrading a waste low-nickel ternary positive electrode into a single-crystal ultrahigh-nickel ternary positive electrode, and comprises the following steps: discharging and manually disassembling a waste ternary lithium battery, and carrying out high-temperature annealing, stripping and screening to obtain waste low-nickel ternary material powder; carrying out ball milling on the low-nickel ternary material, lithium hydroxide, nickel hydroxide and hafnium boride to obtain mixed powder; and carrying out high-temperature annealing on the mixed powder in oxygen to obtain the modified single-crystal ultrahigh-nickel ternary positive electrode. The process is novel and simple and has expandability, and low-cost upgrading of the ternary positive electrode can be achieved. Wherein Hf and B are uniformly doped in a positive electrode body phase and the surface of the positive electrode body phase is uniformly coated with the Li2HfO3 coating, so that mixed arrangement of lithium and nickel cations is reduced, the interface stability of the positive electrode is improved, and the upgraded ultrahigh nickel positive electrode shows excellent rate capability and cycling stability.

Description

Technical Field

[0001] This invention belongs to the field of battery cathode material technology, specifically relating to a method for upgrading and utilizing waste low-nickel ternary cathode materials. Background Technology

[0002] Lithium-ion batteries are currently the best choice to meet the energy density and cost requirements of the rapidly growing electric vehicle market. Global electric vehicle sales are projected to reach 38 million units annually by 2030. The market value of rechargeable lithium batteries is growing at a rate of nearly 15% annually, and is expected to reach $190 billion by 2032. However, after 5-8 years of use, lithium-ion batteries will inevitably face retirement due to capacity degradation. The continuous accumulation of degraded lithium-ion batteries exacerbates the pressure on the mineral resource supply chain and raises significant sustainability issues, necessitating the development of advanced battery recycling technologies to achieve closed-loop development of the industry. Among the various components of lithium-ion batteries, the cost of cathode materials accounts for more than one-third. This high contribution to battery cost highlights the importance of effective recycling of cathode materials, especially LiNi. x Co y Mn 1-x-y The high-value metals (such as lithium, cobalt, and nickel) in O2 ternary cathodes are unevenly distributed globally, making effective recycling strategies crucial for managing battery waste and reducing reliance on resource-intensive mining activities. Traditional recycling methods, including pyrometallurgy and hydrometallurgy, have seen widespread industrial application. Pyrometallurgy's high-temperature conditions lead to high energy consumption and the release of toxic gases. Hydrometallurgy requires acidic media to extract metal elements, resulting in acid pollution problems. Both methods are costly in terms of energy and chemical inputs and cause complete destruction of the microstructure of the degraded cathode. In recent years, non-destructive recycling methods have gained widespread attention due to their sustainability. These methods utilize degraded cathode powder as precursors for subsequent cathode resynthesis, such as restoring the original performance of the cathode through direct regeneration or improving the cathode grade through upgraded recycling. They repair structural defects without destroying the crystal structure, while avoiding high-temperature smelting and complex acid leaching.

[0003] In recent years, most research has focused on the direct regeneration of low-nickel or medium-nickel spent ternary cathodes, as these have already achieved large-scale production and will be among the first to face retirement in the ternary cathode series. With the continuous development of ternary cathodes, the market is gradually shifting towards high-nickel (Ni≥0.8) technology to overcome energy density barriers. Among them, ultra-high nickel cathodes (Ni≥0.9) possess high specific capacity and low cobalt content, and are considered ideal candidates for next-generation cathode materials. Upgrading degraded low-nickel cathodes to ultra-high nickel cathodes can maximize the recycling value of spent lithium-ion batteries. However, ultra-high nickel cathodes face long-term challenges at different scales, such as surface phase transitions, lattice oxygen loss, and microcracks, which will further exacerbate the degradation of the cathode under deep delithiation conditions. Therefore, overcoming the inherent limitations of ultra-high nickel cathodes and fully releasing the material's potential in long-life, high-energy battery systems is crucial. Designing technical solutions to address these issues is of great significance for upgrading spent low-nickel ternary cathode materials to ultra-high nickel ternary cathode materials. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing single-crystal ultra-high nickel ternary cathode materials from waste low-nickel ternary cathode materials. This invention maximizes the utilization of waste low-nickel ternary cathode materials, upgrading and regenerating them into Hf and B modified single-crystal ultra-high nickel ternary cathode materials (LiNi) through high-temperature sintering for lithium replenishment, uniform doping of Hf and B in the bulk phase, and uniform surface coating with Li2HfO3. 0.9 Co 0.05 Mn 0.05 O2 (U-NCM90HB). Hf and B are uniformly distributed in the bulk structure of the cathode, suppressing harmful phase transitions and lattice oxygen escape during charge and discharge. The Li2HfO3 coating alleviates the problem of residual lithium compounds on the surface, improves interfacial stability, and suppresses interfacial side reactions. The combination of bulk doping and surface coating enhances the cycle stability of the ultra-high nickel ternary cathode. Compared with commercial LiNi... 0.9 Co 0.05 Mn 0.05 Compared to O2 materials, the upgraded U-NCM90HB exhibits superior electrochemical performance. Furthermore, the upgraded recycling technology employed in this invention avoids the high energy consumption and environmental pollution associated with pyrometallurgical and hydrometallurgical processes.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for upgrading and utilizing waste low-nickel ternary cathode materials, comprising the following steps: S1, Collecting waste LiNi 0.33 Co 0.33 Mn 0.33O2 powder, i.e. waste NCM111 powder, is ball-milled with Ni(OH)2, HfB2 and LiOH·H2O to obtain a mixed powder; wherein the mass ratio of waste NCM111 powder to Ni(OH)2 and HfB2 is 1:(5.2-5.6):(0.03-0.11), and the amount of LiOH·H2O added is 1.05-1.2 times the molar amount of lithium deficiency in waste NCM111 powder; S2. The mixed powder is annealed at 450-650℃ for 3-6 hours, and then annealed at 700-900℃ for 12-18 hours to obtain the intermediate product. S3. The intermediate product is ball-milled, and then annealed for the third time at 700-900℃ for 6-12 hours to obtain the modified single-crystal ultra-high nickel ternary cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2, denoted as U-NCM90HB.

[0006] Further improvements were made to the method of upgrading and utilizing waste low-nickel ternary cathode materials: Preferred, waste LiNi 0.33 Co 0.33 Mn 0.33 The specific steps for collecting O2 powder are as follows: the waste ternary lithium battery is fully discharged, disassembled and separated, and the separated positive electrode sheet is calcined at a temperature of 400-700℃ for 2-5 h to remove the binder and conductive carbon black in the electrode sheet; the positive electrode powder is peeled off from the current collector aluminum foil and sieved to obtain waste NCM111 powder.

[0007] Preferably, before dismantling and separating the waste ternary lithium batteries, the waste ternary lithium batteries are immersed in a 0.1-2 mol / L NaCl aqueous solution for discharge.

[0008] Preferably, in step S1, the mixture is ball-milled at a speed of 300-600 rpm for 9-15 hours to obtain the mixed powder.

[0009] Preferably, in step S2, the mixed powder is annealed in a continuous oxygen stream at a heating rate of 2-10°C / min.

[0010] Preferably, in step S3, the intermediate product is ball-milled at a speed of 300-600 rpm for 5-10 hours.

[0011] Preferably, in step S3, the intermediate product after ball milling is annealed in a continuous oxygen stream at a heating rate of 2-10°C / min.

[0012] Preferably, in step S1, the mass ratio of waste NCM111 powder to Ni(OH)2 and HfB2 is 1:5.36:0.07.

[0013] Preferably, the modified single-crystal ultra-high nickel ternary cathode material is used as a cathode material in lithium-ion batteries for electrochemical performance testing.

[0014] The preferred steps for applying modified single-crystal ultra-high nickel ternary cathode material to electrochemical performance testing are as follows: S21. Weigh out single-crystal ultra-high nickel ternary cathode material, polyvinylidene fluoride (PVDF) binder and Super P conductive agent in a mass ratio of 8:1:1 and mix them. Add them to N-methylpyrrolidone (NMP) solvent and grind and mix to obtain a black slurry. S22. Using a scraper, evenly coat the black paste onto the aluminum foil. After vacuum drying at 70-120℃ for 8-18 hours, the loading of the positive electrode material on the aluminum foil per unit area is 2-3 mg / cm³. 2 The dried aluminum foil is then stamped into round sheets with a diameter of 14mm. S23. Using the above-mentioned disc as the positive electrode, lithium metal as the negative electrode, and Celgard 2500 as the separator between the positive and negative electrodes, LiPF6 is dissolved in a solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 to serve as the electrolyte. The concentration of LiPF6 is 0.8-1.2 M. The CR2025 button cell is then assembled for electrochemical performance testing.

[0015] The advantages of this invention compared to the prior art are as follows: 1) This invention provides a method for upgrading and recycling waste low-nickel ternary cathode material into single-crystal ultra-high nickel ternary cathode material. Waste low-nickel ternary cathode powder is ball-milled with Ni(OH)₂, LiOH·H₂O, and HfB₂ to obtain a mixed powder. The mixed powder is then ball-milled again after high-temperature annealing in an oxygen atmosphere, followed by a second annealing. This process upgrades the waste low-nickel ternary cathode material into a single-crystal ultra-high nickel ternary cathode material with a uniformly coated Li₂HfO₃ layer and bulk doped with Hf and B. Through simple ball milling and annealing, waste low-nickel ternary cathode material is upgraded and recycled into a product with performance superior to commercial LiNi. 0.9 Co 0.05 Mn 0.05The O2-based U-NCM90HB process not only reduces the use of harmful reagents and saves costs, but also alleviates the burden on battery raw material suppliers. Hf and B are uniformly distributed in the bulk structure of the cathode, suppressing harmful phase transitions and lattice oxygen escape during charge and discharge. The Li2HfO3 coating reduces residual lithium compounds on the surface, improves interfacial stability, and suppresses interfacial side reactions. The combination of bulk doping and surface coating enhances the cycle stability of the ultra-high nickel ternary cathode. Electrochemical performance tests of U-NCM90HB cathode materials assembled into coin cells show that U-NCM90HB exhibits excellent rate performance and cycle stability. This technical solution provides an effective method for directly upgrading and recycling spent low-nickel ternary cathode materials into high-energy-density batteries. Therefore, this invention not only maximizes the recycling of failed spent low-nickel ternary cathode materials, but also features a novel, simple, and scalable process, and the upgraded and recycled U-NCM90HB exhibits excellent electrochemical performance.

[0016] In order to ensure the safe dismantling of waste ternary lithium batteries, the waste ternary lithium batteries are first immersed in NaCl aqueous solution for discharge treatment, and then dismantled and separated. The waste low-nickel ternary cathode sheet is annealed to remove the binder and conductive carbon black, and the waste low-nickel ternary cathode powder is peeled off and screened from the aluminum foil.

[0017] 2) The U-NCM90HB material prepared in this invention is mixed with polyvinylidene fluoride (PVDF) binder, Super P conductive agent, and an appropriate amount of N-methylpyrrolidone (NMP) to prepare a black slurry. The black slurry is uniformly coated onto aluminum foil, vacuum dried, and then stamped into circular electrode sheets with a diameter of 14 mm, serving as the positive electrode of the battery. Lithium metal is used as the negative electrode, Celgard 2500 is used as the separator between the positive and negative electrodes, and 1.0 M LiPF6 (EC:DEC:DMC volume ratio of 1:1:1) is used as the electrolyte. The materials are then assembled into a CR2025 button cell. The electrochemical performance of the material is tested using a CHI660E electrochemical workstation and a LAND battery testing system. At room temperature, the electrochemical performance of the material was evaluated based on cyclic voltammetry (CV), cycling performance, and rate performance. This study confirmed that the present invention not only significantly improves the specific capacity of the cathode by upgrading and recycling waste low-nickel ternary cathode material into U-NCM90HB, but also alleviates the inherent problems in ultra-high nickel cathodes, including harmful phase transitions and microcrack formation, and exhibits excellent rate performance and cycling stability.

[0018] This invention relates to the technical field of recycling and upgrading of waste low-nickel ternary cathode materials, and in particular to a method for preparing single-crystal ultra-high nickel ternary cathode materials from waste low-nickel ternary cathode materials, as well as the application of the prepared single-crystal ultra-high nickel ternary cathode materials in electrochemical performance testing as cathode materials for lithium-ion batteries. Attached Figure Description

[0019] Figure 1 The images shown are electron microscope (EM) images of the U-NCM90HB material prepared in Example 1 of this invention, where (a) is a scanning electron microscope (SEM) image, (b) is a high-resolution transmission electron microscope (HRTEM) image, and (c)-(f) are HRTEM images of selected regions and corresponding fast Fourier transform images.

[0020] Figure 2 The X-ray diffraction patterns of U-NCM90HB prepared in Example 1 of the present invention, U-NCM90 prepared in Comparative Example 1, C-NCM90 in Comparative Example 2, and waste NCM111 are shown.

[0021] Figure 3 This is a cyclic volt-ampere curve of the CR2025 button cell assembled using U-NCM90HB in Embodiment 1 of the present invention.

[0022] Figure 4 This is a charge-discharge curve of the CR2025 button battery assembled using U-NCM90HB in Embodiment 1 of the present invention at a charging cutoff voltage of 4.3 V.

[0023] Figure 5 The diagram shows the cycle performance of CR2025 button batteries assembled using U-NCM90HB in Example 1 of the present invention, U-NCM90 in Comparative Example 1, and C-NCM90 and waste NCM111 in Comparative Example 2, respectively.

[0024] Figure 6 The rate performance diagrams show the CR2025 button batteries assembled using U-NCM90HB in Example 1 of the present invention, U-NCM90 in Comparative Example 1, and C-NCM90 and waste NCM111 in Comparative Example 2, respectively.

[0025] Figure 7 The rate performance diagrams are for the CR2025 button batteries assembled using U-NCM90HB from Example 1, U-NCM90HB-L from Example 2, and U-NCM90HB-H from Example 3, respectively. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Example 1

[0028] This embodiment provides a method for upgrading and utilizing waste low-nickel ternary cathode materials, specifically including the following steps: S1. Waste ternary lithium batteries are immersed in a NaCl aqueous solution (concentration 1 mol / L) for discharge. The batteries are then disassembled and separated. The positive electrode sheets of the waste ternary lithium batteries are recovered and annealed in a muffle furnace at 500℃ for 3 hours to remove binders and conductive carbon black. The positive electrode powder is peeled off from the current collector aluminum foil and sieved to obtain waste low-nickel ternary positive electrode LiNi. 0.33 Co 0.33 Mn 0.33 O2 powder is waste NCM111 powder; Waste NCM111 powder was ball-milled with Ni(OH)2, HfB2 and LiOH·H2O to obtain a mixed powder. The ball milling speed was 600 rpm and the time was 10 h. The mass ratio of waste NCM111 powder to Ni(OH)2 and HfB2 was 1:5.36:0.07, and the amount of LiOH·H2O added was 1.1 times the molar amount of lithium deficiency in the waste NCM111 powder. S2. The mixed powder is placed in a continuous oxygen flow and heated at a rate of 5℃ / min. It is annealed for the first time at 480℃ for 3 hours, and then heated to 700℃ for the second time for 12 hours to obtain the intermediate product. S3. The intermediate product was ball-milled (600 rpm, 6 h), heated to 700 °C at a rate of 5 °C / min in a continuous oxygen stream, and held at this temperature for a third annealing for 6 hours to obtain the modified single-crystal ultra-high nickel ternary cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2, denoted as U-NCM90HB.

[0029] Example 2

[0030] This embodiment provides a method for upgrading and utilizing waste low-nickel ternary cathode materials, specifically including the following steps: S1. Waste ternary lithium batteries are immersed in a NaCl aqueous solution (concentration 1 mol / L) for discharge. The batteries are then disassembled and separated. The positive electrode sheets of the waste ternary lithium batteries are recovered and annealed in a muffle furnace at 500℃ for 3 hours to remove binders and conductive carbon black. The positive electrode powder is peeled off from the current collector aluminum foil and sieved to obtain waste low-nickel ternary positive electrode LiNi. 0.33 Co 0.33 Mn 0.33 O2 powder is waste NCM111 powder; Waste NCM111 powder was ball-milled with Ni(OH)2, HfB2 and LiOH·H2O to obtain a mixed powder. The ball milling speed was 600 rpm and the time was 10 h. The mass ratio of waste NCM111 powder to Ni(OH)2 and HfB2 was 1:5.36:0.03, and the amount of LiOH·H2O added was 1.1 times the molar amount of lithium deficiency in the waste NCM111 powder. S2. The mixed powder is placed in a continuous oxygen flow and heated at a rate of 5℃ / min. It is annealed for the first time at 480℃ for 3 hours, and then heated to 700℃ for the second time for 12 hours to obtain the intermediate product. S3. The intermediate product was ball-milled (600 rpm, 6 h), heated to 700 °C at a rate of 5 °C / min in a continuous oxygen stream, and held for a third annealing for 6 h to obtain a single-crystal ultra-high nickel ternary cathode material LiNi modified with low Hf and B content. 0.9 Co 0.05 Mn 0.05 O2, denoted as U-NCM90HB-L.

[0031] Example 3

[0032] This embodiment provides a method for upgrading and utilizing waste low-nickel ternary cathode materials, specifically including the following steps: S1. Waste ternary lithium batteries are immersed in a NaCl aqueous solution (concentration 1 mol / L) for discharge. The batteries are then disassembled and separated. The positive electrode sheets of the waste ternary lithium batteries are recovered and annealed in a muffle furnace at 500℃ for 3 hours to remove binders and conductive carbon black. The positive electrode powder is peeled off from the current collector aluminum foil and sieved to obtain waste low-nickel ternary positive electrode LiNi. 0.33 Co 0.33 Mn 0.33 O2 powder is waste NCM111 powder; Waste NCM111 powder was ball-milled with Ni(OH)2, HfB2 and LiOH·H2O to obtain a mixed powder. The ball milling speed was 600 rpm and the time was 10 h. The mass ratio of waste NCM111 powder to Ni(OH)2 and HfB2 was 1:5.36:0.11, and the amount of LiOH·H2O added was 1.1 times the molar amount of lithium deficiency in the waste NCM111 powder. S2. The mixed powder is placed in a continuous oxygen flow and heated at a rate of 5℃ / min. It is annealed for the first time at 480℃ for 3 hours, and then heated to 700℃ for the second time for 12 hours to obtain the intermediate product. S3. The intermediate product was ball-milled (600 rpm, 6 h), heated to 700 °C at a rate of 5 °C / min in a continuous oxygen stream, and held for a third annealing for 6 h to obtain a high-Hf, B-modified single-crystal ultra-high nickel ternary cathode material, LiNi. 0.9 Co 0.05 Mn 0.05 O2, denoted as U-NCM90HB-H.

[0033] Example 4

[0034] In this embodiment, the modified single-crystal ultra-high nickel ternary cathode material prepared in Example 1 is used as the cathode material for lithium-ion batteries for electrochemical performance testing. The specific steps include the following: S1. Weigh U-NCM90HB material, polyvinylidene fluoride (PVDF) binder and Super P conductive agent in a mass ratio of 8:1:1, add them to N-methylpyrrolidone (NMP) solvent, and grind to obtain a black slurry; S2. Using a scraper, the black paste is evenly coated onto the aluminum foil. After vacuum drying at 100°C for 12 hours, the loading of the positive electrode material on the aluminum foil per unit area is 2.5 mg / cm². 2 The dried aluminum foil is then stamped into round sheets with a diameter of 14mm. S3. On the LAND battery testing system, the above-mentioned disc is used as the positive electrode, lithium metal as the negative electrode, Celgard 2500 as the separator between the positive and negative electrodes, and 1.0 M LiPF6 (the solvent is a mixture of EC: DEC: DMC in a volume ratio of 1:1:1) is used as the electrolyte. The CR2025 button cell is assembled for electrochemical performance testing.

[0035] Comparative Example 1

[0036] This comparative example provides a method for upgrading and recycling waste low-nickel ternary cathode material into single-crystal ultra-high nickel ternary cathode. The specific steps are the same as in Example 1, except that HfB2 is not added in step S2. The final upgraded material is an unmodified single-crystal ultra-high nickel ternary cathode, denoted as U-NCM90.

[0037] Following the method of assembling a CR2025 button cell in Example 2, U-NCM90 was assembled into a CR2025 button cell for electrochemical performance testing.

[0038] Comparative Example 2

[0039] This comparative example uses waste NCM111 powder collected in step S1 of Example 1 and commercially available C-NCM90 cathode powder. Following the method of assembling CR2025 button cells in Example 2, the waste NCM111 and C-NCM90 are assembled into CR2025 button cells for electrochemical performance testing.

[0040] Performance testing: (1) The morphology of the U-NCM90HB material prepared in Example 1 of this invention was characterized using a scanning electron microscope and a high-power transmission microscope, and the morphology was obtained as follows: Figure 1 The images shown are scanning electron microscope (SEM) images and high-resolution transmission electron microscope (TEM) images; among them, Figure 1 (a) is a scanning electron microscope image of the U-NCM90HB material prepared in Example 1 of the present invention; Figure 1 Image (b) is a high-resolution transmission electron microscope image of the U-NCM90HB material prepared in Example 1 of this invention; Figure 1 Images (c) and (e) are high-resolution transmission electron microscopy images of selected locations I and II. Figure 1 Images (d) and (f) are the corresponding Fast Fourier Transform images. From Figure 1 As can be seen in (a), the U-NCM90HB prepared in Example 1 of this invention has a single-crystal morphology and a smooth particle surface; Figure 1 In (b) and (c), it can be observed that the U-NCM90HB prepared in Example 1 of this invention has 0.234 nm lattice fringes, corresponding to the (01 2) crystal plane of lithium nickelate. Furthermore, a coating of approximately 2 nm thickness is clearly observed on the particle surface, with a clear boundary between it and the internal phase. The lattice fringes in the coating region correspond to the (-2 2 2) crystal plane of Li2HfO3, confirming the presence of Li2HfO3 in the coating.

[0041] (2) X-ray powder diffraction was used to analyze the composition of U-NCM90HB prepared in Example 1 of the present invention, U-NCM90 prepared in Comparative Example 1, and commercial C-NCM90 and waste NCM111 in Comparative Example 2, and the results were as follows. Figure 2 The X-ray diffraction pattern shown; where the horizontal axis represents the diffraction angle (2). The vertical axis represents intensity. Figure 2 It can be seen that all samples correspond to the LiNiO2 phase (JCPDS. 09-0063). Notably, U-NCM90HB shows characteristic peaks of Li2HfO3, confirming the formation of the Li2HfO3 phase on the surface.

[0042] (3) On a CHI660E electrochemical workstation, the CR2025 coin cell assembled in Example 4 was electrochemically tested using cyclic voltammetry, with a scan rate of 0.1-0.6 mV / s and a voltage range of 2.8-4.3 V. The results were as follows: Figure 3 The cyclic voltammetry curve is shown.

[0043] The CR2025 button cell assembled in Example 4 was subjected to charge-discharge tests using the LAND battery testing system, and the results were as follows: Figure 4 The charge / discharge curves shown are shown below. Figure 4 The chart shows the charge-discharge curves (40 cycles apart) of the CR2025 button cell assembled from the U-NCM90HB battery prepared in Example 1 of this invention at 0.5 C with a charging cutoff voltage of 4.3 V. Figure 4 It can be seen that the CR2025 button battery assembled by U-NCM90HB has a discharge specific capacity of 203.1 mAh / g in the voltage range of 2.8-4.3 V at 0.5 C. As the number of charge and discharge cycles increases, the discharge specific capacity shows a slight decreasing trend.

[0044] (4) The CR2025 button cells assembled in Example 4 and Comparative Examples 1 and 2 were subjected to cycle performance testing in the LAND test system, and the results were as follows: Figure 5 The cycle performance results of CR2025 button cells assembled from U-NCM90HB, U-NCM90, C-NCM90, and spent NCM111 are shown in (a) and (b) at 0.5 C with voltage ranges of 2.8–4.3 V and 2.8–4.5 V, respectively. Figure 5 As shown in (a) and (b), within the voltage range of 2.8–4.3 V, after 200 cycles, the discharge specific capacities of CR2025 button batteries assembled from U-NCM90HB, U-NCM90, C-NCM90, and recycled NCM111 remained at 159.3, 122.4, 102.8, and 70.8 mAh / g, respectively, with capacity retention rates of 78.4%, 61.6%, 37.6%, and 91.2%. Within the voltage range of 2.8–4.5 V, after 200 cycles, the discharge specific capacities of CR2025 button batteries assembled from U-NCM90HB, U-NCM90, and C-NCM90 remained at 135.1, 106.2, and 82.9 mAh / g, respectively, with capacity retention rates of 63%, 49.8%, and 39.7%. The upgraded and recycled U-NCM90HB material exhibits more stable cycle performance and a higher discharge specific capacity.

[0045] (5) Referring to the method for assembling CR2025 button cells in Example 4, the assembled CR2025 button cells were subjected to rate performance testing in the LAND battery testing system, and the results were as follows. Figure 6The rate performance of CR2025 button cells assembled from U-NCM90HB, U-NCM90, C-NCM90, and recycled NCM111 is shown at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 8 C. (The data is derived from...) Figure 6 It can be seen that within the voltage range of 2.8-4.3 V, the CR2025 coin cell assembled with U-NCM90HB outperforms other samples in terms of rate performance. Especially at high rates, the discharge capacity of U-NCM90HB is significantly improved compared with other samples.

[0046] (6) Referring to the method for assembling CR2025 button cells in Example 4, the U-NCM90HB-L and U-NCM90HB-H prepared in Examples 2 and 3 were assembled into CR2025 button cells and subjected to rate performance testing in the LAND battery testing system, yielding the following results: Figure 6 The rate performance of CR2025 coin cells assembled with U-NCM90HB, U-NCM90HB-L, and U-NCM90HB-H at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 8 C are shown. The test results indicate that, within the voltage range of 2.8–4.3 V, the CR2025 coin cell assembled with U-NCM90HB also outperforms other samples with increased or decreased HfB2 doping in terms of rate performance.

[0047] In summary, Embodiment 1 of this invention not only maximizes the value of waste low-nickel ternary cathodes by supplementing lithium and increasing nickel content, upgrading them into single-crystal ultra-high nickel ternary cathodes, but also ensures that Hf and B are uniformly distributed in the bulk structure of the cathode, suppressing harmful phase transitions and lattice oxygen escape during charge and discharge. The Li2HfO3 coating reduces residual lithium compounds on the surface, improves interfacial stability, and suppresses interfacial side reactions. The combination of bulk doping and surface coating enhances the cycle stability of the ultra-high nickel ternary cathode.

[0048] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for upgrading and utilizing waste low-nickel ternary cathode materials, characterized in that, Includes the following steps: S1, collecting waste LiNi 0.33 Co 0.33 Mn 0.33 O2 powder, i.e. waste NCM111 powder, is ball-milled with Ni(OH)2, HfB2 and LiOH·H2O to obtain a mixed powder; wherein the mass ratio of waste NCM111 powder to Ni(OH)2 and HfB2 is 1:(5.2-5.6):(0.03-0.11), and the amount of LiOH·H2O added is 1.05-1.2 times the molar amount of lithium deficiency in waste NCM111 powder; S2. The mixed powder is annealed at 450-650℃ for 3-6 hours, and then annealed at 700-900℃ for 12-18 hours to obtain the intermediate product. S3. The intermediate product is ball-milled, and then annealed for the third time at 700-900℃ for 6-12 hours to obtain the modified single-crystal ultra-high nickel ternary cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2, denoted as U-NCM90HB.

2. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 1, characterized in that, scrap LiNi 0.33 Co 0.33 Mn 0.33 The specific steps for collecting O2 powder are as follows: the waste ternary lithium battery is completely discharged, disassembled and separated, and the separated positive electrode sheet is calcined at a temperature of 400-700℃ for 2-5 hours to remove the binder and conductive carbon black in the electrode sheet; the positive electrode powder is peeled off from the current collector aluminum foil and sieved to obtain waste NCM111 powder.

3. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 2, characterized in that, Before dismantling and separating the waste ternary lithium batteries, the waste ternary lithium batteries are immersed in a 0.1-2 mol / L NaCl aqueous solution to discharge them.

4. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 1, characterized in that, In step S1, the mixture is ball-milled at 300-600 rpm for 9-15 hours to obtain a mixed powder.

5. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 1, characterized in that, In step S2, the mixed powder is annealed in a continuous oxygen stream at a heating rate of 2-10 °C / min.

6. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 1, characterized in that, In step S3, the intermediate product is ball-milled at 300-600 rpm for 5-10 hours.

7. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 1, characterized in that, In step S3, the ball-milled intermediate product is annealed in a continuous oxygen stream at a heating rate of 2-10 °C / min.

8. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 1, characterized in that, In step S1, the mass ratio of waste NCM111 powder to Ni(OH)2 and HfB2 is 1:5.36:0.

07.

9. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 1, characterized in that, The modified single-crystal ultra-high nickel ternary cathode material was prepared and used as a cathode material in lithium-ion batteries for electrochemical performance testing.

10. The method for upgrading and utilizing waste low-nickel ternary cathode materials according to claim 9, characterized in that, The specific steps for applying modified single-crystal ultra-high nickel ternary cathode materials to electrochemical performance testing are as follows: S21. Weigh out single-crystal ultra-high nickel ternary cathode material, polyvinylidene fluoride (PVDF) binder and Super P conductive agent in a mass ratio of 8:1:1 and mix them. Add them to N-methylpyrrolidone (NMP) solvent and grind and mix to obtain a black slurry. S22. Using a scraper, evenly coat the black paste onto the aluminum foil. After vacuum drying at 70-120℃ for 8-18 hours, the loading of the positive electrode material on the aluminum foil per unit area is 2-3 mg / cm³. 2 The dried aluminum foil is then stamped into round sheets with a diameter of 14mm. S23. Using the above-mentioned disc as the positive electrode, lithium metal as the negative electrode, and Celgard 2500 as the separator between the positive and negative electrodes, LiPF6 is dissolved in a solvent of ethylene carbonate EC, diethyl carbonate DEC, and dimethyl carbonate DMC mixed in a volume ratio of 1:1:1 to serve as the electrolyte. The concentration of LiPF6 is 0.8-1.2 M. The CR2025 button cell is then assembled for electrochemical performance testing.

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