A magnesium-doped cathode material precursor, its preparation method and its application

Abstract

This invention belongs to the field of battery materials technology, specifically a magnesium-doped cathode material precursor, its preparation method, and its application. It uses highly active nano-magnesium oxide with a nano-sized particle size and a specific surface area ≥20 m² / g as a multifunctional precursor raw material. This precursor is mixed with an acidic solution containing one or more transition metal ions. The high-activity magnesium oxide readily hydrolyzes to generate OH-. ‑ Its properties allow it to simultaneously serve as a precursor for both precipitants and dopants. The method of this invention is simple, combining precipitation and doping processes into one. The resulting precursor, after subsequent lithium or sodium mixing and calcination, can be successfully applied to the preparation of battery cathode materials, providing a novel technical route for cathode material preparation.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically a magnesium-doped cathode material precursor, its preparation method, and its application. Background Technology

[0002] Promoting the transition of the energy structure to clean and renewable energy has become an inevitable choice for global sustainable development. While the installed capacity of renewable energy sources such as solar and wind power continues to grow, their inherent intermittency, volatility, and uneven geographical distribution make it difficult to match power generation output with grid load in real time, severely restricting large-scale grid connection and efficient utilization. Against this backdrop, developing efficient, reliable, and low-cost large-scale energy storage technologies is considered a key pivot for smoothing renewable energy output, improving grid absorption capacity, and even constructing new power systems.

[0003] Meanwhile, the electrification transformation of the transportation sector is in full swing, and the widespread adoption of new energy vehicles has placed unprecedented high-performance demands on electrochemical energy storage devices. Range anxiety and safety concerns remain core issues affecting consumer confidence, and both essentially point to innovation in battery technology—namely, how to improve energy density and extend lifespan while ensuring extremely high safety and reliability. Among the core components of batteries, the cathode material is one of the key factors determining battery energy density, cost, and safety. Currently, whether it's commercially available lithium-ion batteries or promising sodium-ion batteries, layered transition metal oxides (such as Li[Ni)) are crucial. x Co y Mnz]O2 or Na[Ni x Co y Mnz]O2) are both mainstream cathode material systems that have attracted much attention. With their high reversible specific capacity and suitable operating voltage, they have become the preferred direction for pursuing high energy density batteries.

[0004] However, these materials, especially layered oxides with high nickel or manganese content, face a series of inherent challenges during repeated charge-discharge cycles in batteries. During lithium / sodium ion insertion / extraction, the materials are prone to harmful phase transitions, causing the crystal structure to transform from an ordered layered structure to a disordered rock salt or spinel phase, leading to irreversible capacity decay. Simultaneously, transition metal ions (especially Ni...) 3+ / Ni 4+ The migration of Na⁺ ions, oxygen evolution reactions under high voltage, and side reactions between the material surface and the electrolyte all exacerbate the instability of the electrode / electrolyte interface, not only reducing cycle life but also potentially leading to thermal runaway risks. Furthermore, for sodium-ion batteries, the large ionic radius of Na⁺ results in greater resistance to its migration within the crystal lattice, and certain phase transition volume effects are more pronounced, placing higher demands on the structural stability of the material.

[0005] To overcome the aforementioned bottlenecks, bulk doping of cathode materials is a widely recognized and effective modification strategy in both academia and industry. Introducing appropriate amounts of heterogeneous elements into the crystal structure can create a "pillar" effect, enhancing the metal-oxygen bond energy, suppressing transition metal layer slip and ion mixing, thereby improving structural stability and broadening ion transport channels. Mao et al. designed and prepared a novel nickel-rich LiNi co-doped with metal and non-metal ions. 0.74 Co 0.14 Mn 0.12 O2 cathode material. Doped Mg 2+ Ions enter the lithium layer, reducing the amount of Li in the material. + / Ni 2+ Cation mixing; acting as a pillar, stabilizing the layered framework. Currently, there are two main doping processes for cathode precursors: "dry" doping and "wet" doping. Dry doping typically involves physically and mechanically mixing the dopant (such as oxides, carbonates, etc.) with the lithium / sodium source and precursor after precursor synthesis, followed by high-temperature solid-state sintering. This method is simple, but the mixing uniformity between the dopant and the host material is extremely poor, often only achieving local or gradient doping on the particle surface, making it difficult to ensure atomic-level uniform distribution of the dopant element in the bulk phase of the material, resulting in limited and unstable modification effects. Wet doping, or co-precipitation doping, involves adding soluble dopant salts (such as magnesium sulfate, aluminum nitrate, etc.) along with the host metal salt solution to the reaction system during the precursor co-precipitation synthesis stage. Theoretically, this method can achieve molecular-level mixing, obtaining a more uniformly distributed precursor. However, it introduces a new, often overlooked, serious problem: the introduction and residue of impurity anions. For example, when using magnesium sulfate (MgSO4) as the magnesium source, a large amount of sulfate ions (SO4) will inevitably be introduced simultaneously. 2- These anions have a strong adsorption capacity on the surface and inside of precursor particles, and are difficult to completely remove even after repeated washing. During the subsequent high-temperature sintering process at hundreds or even thousands of degrees Celsius, the residual sulfates decompose and release gases. On the one hand, these gases create pores inside the material, damaging the compactness and mechanical strength of the particles; on the other hand, these gaseous side reactions may lead to increased alkalinity on the material surface and the formation of an electrochemically inert phase, severely impairing the battery's initial efficiency, rate performance, and long-term cycle stability.

[0006] Therefore, existing doping technologies face a dilemma: dry doping results in insufficient uniformity, while wet doping introduces new impurities. Developing a novel doping process that can achieve highly uniform distribution of dopant elements in the precursor stage while completely avoiding the introduction of harmful foreign anions is key to breaking through the current bottleneck in the development of high-performance cathode materials and meeting the stringent requirements for energy density, cycle life, and safety of next-generation energy storage devices.

[0007] Furthermore, when highly active nano-magnesium oxide is used as a precipitant in the reaction with the sulfate system, the reaction mechanism is completely different from that of sodium hydroxide. The Mg released during the hydrolysis of magnesium oxide... 2+ When magnesium sulfate combines with sulfate ions, the byproduct is magnesium sulfate (MgSO4), not sodium sulfate. This difference has significant economic and environmental value: magnesium sulfate is a high-value-added bulk chemical with wide applications in agriculture. Magnesium is a core component of chlorophyll molecules and an indispensable nutrient for plant photosynthesis. As a magnesium fertilizer, magnesium sulfate can be used to improve magnesium-deficient soils, significantly increasing crop yield and quality. Studies have shown that applying magnesium-containing fertilizers to crops such as rubber trees, fruit trees, tobacco, legumes, potatoes, and cereals can increase crop yields by 15-50%. Approximately 60% of China's arable land suffers from magnesium deficiency, and magnesium sulfate can increase the exchangeable magnesium content in the soil to ideal levels. The global market size for agricultural-grade magnesium sulfate is projected to exceed US$12 billion by 2025, with China accounting for 40% of the market share. Furthermore, magnesium sulfate can also be used in feed additives, pharmaceuticals, industrial auxiliaries, and many other fields.

[0008] Converting the low-value-added sodium sulfate byproduct of the co-precipitation reaction into the high-value-added magnesium sulfate enables resource utilization that "turns waste into treasure." Patent literature reports that co-producing potassium sulfate / magnesium sulfate potassium fertilizer during the preparation of magnesium oxide fibers can achieve zero industrial waste and pollutant generation, significantly improving the economic benefits of the products. Similarly, applying highly active magnesium oxide to the preparation of cathode material precursors holds promise for obtaining high-performance cathode materials while simultaneously recovering magnesium sulfate from the reaction mother liquor for use as agricultural fertilizer, achieving industrial synergy of "battery material production + agricultural fertilizer co-production."

[0009] Based on this, the present invention proposes a method for preparing a precursor of highly active nano-magnesium oxide as both a precipitant and a dopant. Utilizing the characteristics of high-activity magnesium oxide—small particle size, large specific surface area, and high hydration activity—it simultaneously acts as a magnesium source and precipitant in the co-precipitation reaction, through the release of OH- ions during hydrolysis. - The ions completely replace traditional alkaline solutions to provide an alkaline environment, while simultaneously releasing Mg. 2+ This method achieves atomic-scale uniform co-precipitation doping with transition metal ions. It not only simplifies the doping process and improves the uniformity of elemental distribution, but also transforms the reaction byproduct from low-value sodium sulfate to high-value magnesium sulfate, creating conditions for subsequent resource utilization and demonstrating significant economic and environmental benefits. Summary of the Invention

[0010] This invention aims to overcome the shortcomings of existing technologies and addresses the problems of single precipitant function, uneven distribution of dopant elements, low added value and high processing cost of sodium sulfate byproduct in the traditional co-precipitation method for preparing cathode material precursors using sodium hydroxide as a precipitant. It provides a method for preparing cathode material precursors using highly active magnesium oxide as both a precipitant and a dopant.

[0011] The technical solution adopted by this invention to solve its technical problem is: a method for preparing a magnesium-uniformly doped cathode material precursor, comprising the following steps:

[0012] A mixed aqueous solution of transition metal ions, a complexing agent, and a precipitant are fed concurrently into a reaction vessel containing a base liquid. The pH value is controlled to carry out a co-precipitation reaction. After the reaction, the precursor is obtained by aging, washing, and drying.

[0013] The precipitant is a highly active magnesium oxide suspension;

[0014] Highly active magnesium oxide serves as both a magnesium source and the sole precipitant in the reaction, and its surface releases OH- ions through in-situ hydrolysis. - The ions completely replace the traditional alkaline solution in providing the alkaline environment required for the precipitation reaction, while simultaneously releasing Mg. 2+ The ions precipitate simultaneously with the transition metal ions in the mixed salt solution, enabling uniform atomic-scale doping of magnesium with transition metal elements.

[0015] Preferably, the particle size of the highly active magnesium oxide is 30-200 nm, and its physical properties meet at least one of the following conditions: D50 is 0.05-3.0 μm, specific surface area is not less than 20 m² / g, and iodine uptake value is 120-250 g / kg.

[0016] Preferably, the complexing agent is an aqueous ammonia solution of 0.3-0.5 mol / L.

[0017] Preferably, the base solution is ammonia water with a pH of 10.6.

[0018] Preferably, the molar ratio of nickel, cobalt, and manganese in the mixed aqueous solution of transition metal ions is (0.6-0.9):(0.05-0.2):(0.05-0.2).

[0019] Preferably, the coprecipitation reaction is carried out at a temperature of 55°C, a pH of 10.8, a reaction time of 6 hours, and an aging time of 12 hours.

[0020] A magnesium-doped cathode material precursor was prepared by the above method. The chemical formula of the cathode material precursor is Ni. 0.83 Co 0.1 Mn 0.045 Mg 0.025 (OH)2, Ni0.9 Co 0.05 Mn 0.02 Mg 0.03 (OH)2 or Ni 0.63 Co 0.2 Mn 0.14 Mg 0.03 (OH)2.

[0021] Preferably, the cathode material prepared from this cathode material precursor has the chemical formula LiNi. 0.83 Co 0.1 Mn 0.045 Mg 0.025 O2, LiNi 0.9 Co 0.05 Mn 0.02 Mg 0.03 O2 or LiNi 0.63 Co 0.2 Mn 0.14 Mg 0.03 O2.

[0022] Preferably, the particle size of the cathode material precursor is no more than 10 μm; the particle size of the cathode material is no more than 15 μm; the initial discharge specific capacity of the cathode material at 0.1C rate is no less than 127 mAh / g; and the capacity retention rate after 50 cycles at 1C rate is no less than 85%.

[0023] An application of the magnesium-doped cathode material precursor prepared by the above method, wherein the magnesium-doped cathode material precursor is used as a battery cathode material.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention uses highly active magnesium oxide as both a precipitant and a magnesium source dopant, combining the steps of adding an alkaline solution and the dopant element separately in traditional processes into one. It eliminates the need for sodium hydroxide as a precipitant, simplifying the cleaning process. The OH- released during the hydrolysis of magnesium oxide... - The ions are directly used for the precipitation of transition metal ions, releasing Mg. 2+The ions then uniformly enter the precursor lattice as doping elements. This in-situ doping method avoids the inhomogeneity problems of subsequent mechanical mixing or secondary doping, achieving a uniform distribution of magnesium at the atomic scale, which is beneficial to improving the electrochemical performance of the final cathode material. Secondly, the byproduct is converted from sodium sulfate to magnesium sulfate, realizing resource utilization. When using a sulfate system for the reaction, the byproduct of the traditional sodium hydroxide process is sodium sulfate, which has low market value and high processing costs. This invention uses highly active magnesium oxide as a precipitant, where magnesium ions combine with sulfate ions to generate magnesium sulfate. Magnesium sulfate is an important agricultural fertilizer; magnesium is a core component of chlorophyll molecules and is crucial for crop photosynthesis. The magnesium sulfate in the supernatant after the reaction can be recycled for the production of magnesium fertilizer, which can be applied to crops such as rubber trees, fruit trees, tobacco, beans, potatoes, and cereals, increasing crop yields by 15-50%.

[0026] In summary, the method for preparing highly active magnesium oxide as a precursor for precipitants and dopants provided by this invention simplifies the process, improves doping uniformity, and enables the high-value utilization of by-products, resulting in good economic and environmental benefits. It provides a novel solution for the green preparation of cathode material precursors. Attached Figure Description

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] Figure 1 This is a SEM image of the precursor of Embodiment 1 of the present invention;

[0029] Figure 2 This is a SEM image of the cathode material in Example 1 of the present invention;

[0030] Figure 3 This is the XRD diffraction peak pattern of Embodiment 1 of the present invention;

[0031] Figure 4 This is a cycle performance diagram of the cathode material in Example 1 of the present invention;

[0032] Figure 5 This is a cycle performance diagram of the cathode material in Example 2 of the present invention;

[0033] Figure 6 This is a cycle performance diagram of the cathode material in Example 3 of the present invention. Detailed Implementation

[0034] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0035] Example 1

[0036] This invention provides a magnesium-doped cathode material precursor, the chemical formula of which is Ni. 0.83 Co 0.1 Mn 0.045 Mg 0.025 (OH)₂; the chemical formula of the cathode material is LiNi 0.83 Co 0.1 Mn 0.045 Mg 0.025 O2;

[0037] This invention also provides a method for preparing a magnesium-doped cathode material precursor, comprising the following steps:

[0038] Weigh out nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.8:0.1:0.1, dissolve them in deionized water, and prepare a 1 mol / L mixed aqueous solution of transition metal ions.

[0039] A base solution with a pH of 10.6 was prepared using ammonia water as a raw material; a 0.3 mol / L ammonia water solution was prepared as a complexing agent; and a highly active magnesium oxide suspension with a solid content of 2.5 g / L was prepared as a precipitating agent.

[0040] The base liquid was added to a sealed reactor, and argon gas was introduced to replace the air in the reactor. The solution temperature was adjusted to 55℃ and the stirring speed was 1200rpm. At the same time, 0.6 L of 0.3mol / L complexing agent, 0.5 L of 1.0mol / L mixed aqueous solution of transition metal ions, and 0.6 L of precipitant with a solid content of 2.5g / L were pumped in. The pH value of the solution in the reactor was adjusted to 10.8. After co-precipitation reaction for 6 hours, the mixture was aged for 12 hours to obtain the precursor slurry.

[0041] The slurry was pressure filtered and washed four times, and then dried at 80°C for 24 hours under vacuum to obtain the precursor.

[0042] The method for preparing cathode materials based on the above-described precursor in this invention includes the following steps:

[0043] The 2.0 g precursor obtained in this example was mixed and ground with 0.554 g of lithium hydroxide monohydrate, and then subjected to a two-stage heating and sintering process under an oxygen atmosphere: first, the temperature was increased to 480°C at a rate of 5°C / min and sintered for 5 h; then, the temperature was increased to 780°C at a rate of 5°C / min and sintered for 12 h. After cooling to room temperature, magnesium-doped triple cathode material LiNi was obtained. 0.83 Co 0.1 Mn 0.045 Mg 0.025 O2.

[0044] like Figure 1As shown, the precursor obtained in this embodiment is spherical with small particle size, and the particle diameter is less than 10 μm.

[0045] like Figure 2 As shown, the cathode material in this embodiment is LiNi. 0.83 Co 0.1 Mn 0.045 Mg 0.025 SEM image of O2, with particle size within 15μm and uniform distribution of elements.

[0046] Figure 3 The XRD diffraction peaks of this embodiment correspond to the characteristic peaks on the PDF card of lithium nickelate, indicating that the cathode material of this embodiment has a layered structure.

[0047] Example 2

[0048] This invention provides a magnesium-doped cathode material precursor, the chemical formula of which is Ni. 0.9 Co 0.05 Mn 0.02 Mg 0.03 (OH)₂; the chemical formula of the cathode material is LiNi 0.9 Co 0.05 Mn 0.02 Mg 0.03 O2;

[0049] This invention also provides a method for preparing a magnesium-doped cathode material precursor, comprising the following steps:

[0050] Weigh out nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.9:0.05:0.05, dissolve them in deionized water, and prepare a 1.0 mol / L mixed aqueous solution of transition metal ions.

[0051] A base solution with a pH of 10.6 was prepared using ammonia water as the raw material; a 0.5 mol / L ammonia water solution was prepared as the complexing agent; and a highly active magnesium oxide suspension with a solid content of 4.0 g / L was prepared as the precipitant.

[0052] The base liquid was added to a sealed reactor, and argon gas was introduced to replace the air in the reactor. The solution temperature was adjusted to 55℃ and the stirring speed was 1200 rpm. At the same time, 0.6 L of 0.5 mol / L complexing agent, 0.5 L of 1.0 mol / L mixed aqueous solution of transition metal ions and 0.6 L of precipitant with a solid content of 4.0 g / L were pumped in. The pH value of the solution in the reactor was adjusted to 10.8. After co-precipitation reaction for 6 h, the mixture was aged for 12 h to obtain the precursor slurry.

[0053] The slurry was pressure filtered and washed four times, and then dried at 80°C for 24 hours under vacuum to obtain the precursor.

[0054] The method for preparing cathode materials based on the above-described precursor in this invention includes the following steps:

[0055] The 2.0 g precursor obtained in this example was mixed and ground with 0.560 g of lithium hydroxide monohydrate, and then subjected to a two-stage heating and sintering process under an oxygen atmosphere: first, the temperature was increased to 480°C at a rate of 5°C / min and sintered for 5 h; then, the temperature was increased to 780°C at a rate of 5°C / min and sintered for 12 h. After cooling to room temperature, magnesium-doped triple cathode material LiNi was obtained. 0.9 Co 0.05 Mn 0.02 Mg 0.03 O2.

[0056] Example 3

[0057] This invention provides a magnesium-doped cathode material precursor, the chemical formula of which is Ni. 0.63 Co 0.2 Mn 0.14 Mg 0.03 (OH)₂; the chemical formula of the cathode material is LiNi 0.63 Co 0.2 Mn 0.14 Mg 0.03 O2;

[0058] This invention also provides a method for preparing a magnesium-doped cathode material precursor, comprising the following steps:

[0059] Weigh out nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.6:0.2:0.2, dissolve them in deionized water, and prepare a 1.0 mol / L mixed aqueous solution of transition metal ions.

[0060] A base solution with a pH of 10.6 was prepared using ammonia water as a raw material; a 0.5 mol / L ammonia water solution was prepared as a complexing agent; and a highly active magnesium oxide suspension with a solid content of 4.0 g / L was prepared as a precipitating agent.

[0061] The base liquid was added to a sealed reactor, and argon gas was introduced to replace the air in the reactor. The solution temperature was adjusted to 55℃, and the stirring speed was 1200 rpm. At the same time, 0.6 L of 0.5 mol / L complexing agent, 0.5 L of 1.0 mol / L mixed aqueous solution of transition metal ions, and 0.6 L of precipitant with a solid content of 4.0 g / L were pumped in. The pH value of the solution in the reactor was adjusted to 10.8. After co-precipitation reaction for 6 h, the mixture was aged for 12 h to obtain the precursor slurry.

[0062] The slurry was pressure filtered and washed four times, and then dried at 80°C for 24 hours under vacuum to obtain the precursor.

[0063] The method for preparing cathode materials based on the above-described precursor in this invention includes the following steps:

[0064] The 2.0 g precursor obtained in this example was mixed and ground with 0.560 g of lithium hydroxide monohydrate, and then subjected to a two-stage heating and sintering process under an oxygen atmosphere: first, the temperature was increased to 480°C at a rate of 5°C / min and sintered for 5 h; then, the temperature was increased to 780°C at a rate of 5°C / min and sintered for 12 h. After cooling to room temperature, magnesium-doped triple cathode material LiNi was obtained. 0.63 Co 0.2 Mn 0.14 Mg 0.03 O2.

[0065] It should be further noted that the high-activity magnesium oxide used in Examples 1-3 above has a particle size of 30-200 nm and its physical properties meet at least one of the following conditions: D50 is 0.05-3.0 μm, specific surface area is not less than 20 m² / g, and iodine uptake value is 120-250 g / kg.

[0066] Comparative Example 1

[0067] This invention provides a comparative example of preparing Ni using ordinary magnesium oxide as a precipitant. 0.83 Co 0.1 Mn 0.045 Mg 0.025 The method for using (OH)2 precursors aims to demonstrate that ordinary magnesium oxide cannot achieve effective co-precipitation due to insufficient activity. The preparation process includes the following steps.

[0068] The preparation method of the precursor in this comparative example is as follows:

[0069] Weigh out nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.80:0.10:0.10, dissolve them in deionized water, and prepare a 1.0 mol / L mixed aqueous solution of transition metal ions.

[0070] A base solution with a pH of 10.6 was prepared using ammonia water as raw material; a 0.3 mol / L ammonia water solution was prepared as a complexing agent; and a suspension of ordinary magnesium oxide with a solid content of 2.5 g / L was prepared as a precipitant. The ordinary magnesium oxide had an average particle size D50 of 15 μm and a BET specific surface area of ​​15 m² / g.

[0071] Add the base liquid to the sealed reactor, purge the air in the reactor with argon gas, adjust the solution temperature to 55℃, and the stirring speed to 1200 rpm; at the same time, pump in 0.6L of 0.3mol / L complexing agent, 0.5L of 1.0mol / L mixed aqueous solution of transition metal ions, and 0.6L of precipitant with a solid content of 2.5 g / L, and attempt to adjust the pH value of the solution in the reactor to 10.8.

[0072] During the reaction, it was found that the pH of the reaction system increased extremely slowly after the addition of ordinary magnesium oxide suspension. After 2 hours of reaction, the pH could not reach the same reaction pH of 10.8 as in Example 1, and the alkaline environment required for coprecipitation could not be achieved. Continuing the reaction for 6 hours resulted in only a small amount of precipitate forming in the reactor, with most transition metal ions remaining in the solution. After stopping the reaction, the product yield was less than 15%.

[0073] The 2.0 g precursor obtained in this comparative example was mixed and ground with 0.554 g of lithium hydroxide monohydrate, and then subjected to a two-stage heating and sintering process under an oxygen atmosphere: first, the temperature was increased to 480 °C at a rate of 5 °C / min and sintered for 5 h; then, the temperature was increased to 780 °C at a rate of 5 °C / min and sintered for 12 h. After cooling to room temperature, magnesium-doped triple cathode material LiNi was obtained. 0.83 Co 0.1 Mn 0.045 Mg 0.025 O2.

[0074] Comparative Example 2

[0075] This invention provides a comparative example of a method for preparing a cathode material precursor using highly active nano-magnesium oxide as a precipitant and dopant. The difference between this method and the cathode material precursor and cathode material preparation methods in Example 1 is that, in the precursor synthesis method, a highly active nano-magnesium oxide suspension with a solid content of 1.0 g / L is prepared as the precipitant. All other steps remain unchanged.

[0076] Performance testing

[0077] The performance of the cathode materials obtained in Examples 1-3 and Comparative Examples 1-2 was tested. Cathode materials, PVDF, and acetylene black prepared in different examples and comparative examples were weighed at a mass ratio of 8:1:1, and stirred evenly in N-methylpyrrolidone solution (NMP) to form a slurry. The slurry was then coated and dried to obtain the cathode sheet. Using lithium metal sheets as the counter electrode and 1 mol / L LiPF6 / EC:DMC:DEC (volume ratio 1:1:1) as the electrolyte, CR2032 coin cells were assembled. Charge-discharge performance tests were conducted at voltages of 2.8–4.3 V. The results are shown in Table 1: Cathode Material Performance Test Data.

[0078] Table 1: Test Data of Cathode Material Performance

[0079]

[0080] Analysis of the table above shows that the coin cell prepared from the precursor in Example 1 exhibits an initial discharge specific capacity of 127 mAh / g for the positive electrode material at a current density of 0.1C, and a capacity retention rate of 85.12% after 50 cycles at a current density of 1C. Figure 4 As shown.

[0081] Example 2: A coin cell was prepared from the precursor. At a current density of 0.1C, the initial discharge specific capacity of the positive electrode material was 137.5 mAh / g, and at a current density of 1C, the capacity retention rate of the positive electrode material after 50 cycles was 96.7%. Figure 5 As shown.

[0082] Example 3: A coin cell was prepared from the precursor. At a current density of 0.1C, the initial discharge specific capacity of the positive electrode material was 131.7 mAh / g, and at a current density of 1C, the capacity retention rate of the positive electrode material after 50 cycles was 95.5%. Figure 6 As shown.

[0083] In Comparative Example 1, a coin cell was prepared from the precursor. At a current density of 0.1C, the initial discharge specific capacity of the cathode material was almost 0. Ordinary magnesium oxide could not provide sufficient hydroxide ions, and the co-precipitation reaction could not be completed.

[0084] In Comparative Example 2, a coin cell was prepared from the precursor. At a current density of 0.1C, the initial discharge specific capacity of the cathode material was 94.98 mAh / g, and at a current density of 1C, the capacity retention rate of the cathode material after 50 cycles was 92.2%. This indicates that the high-activity nano-magnesium oxide with too low solid content does not provide sufficient hydroxide ions, resulting in poorer performance of the precursor material. The low crystallinity of the cathode material also leads to poorer electrochemical performance.

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a magnesium-uniformly doped cathode material precursor, characterized in that, Includes the following steps: A mixed aqueous solution of transition metal ions, a complexing agent, and a precipitant are simultaneously pumped into a reaction vessel containing a base liquid. The pH value is controlled to carry out a co-precipitation reaction. After the reaction, the precursor is obtained by aging, washing, and drying. The precipitant is a highly active magnesium oxide suspension with a solid content of 2.5 g / L; Highly active magnesium oxide serves as both a magnesium source and the sole precipitant in the reaction, and its surface releases OH- ions through in-situ hydrolysis. - The ions completely replace the traditional alkaline solution in providing the alkaline environment required for the precipitation reaction, while simultaneously releasing Mg. 2+ The ions precipitate simultaneously with the transition metal ions in the mixed salt solution, enabling uniform doping of magnesium and transition metal elements at the atomic scale. The particle size of highly active magnesium oxide is 30-200 nm, and its physical properties meet at least one of the following conditions: D50 is 0.05-3.0 μm, specific surface area is not less than 20 m² / g, and iodine adsorption value is 120-250 g / kg. The complexing agent is a 0.3-0.5 mol / L ammonia solution; The coprecipitation reaction was carried out at a temperature of 55℃, a pH of 10.8, a reaction time of 6 hours, and an aging time of 12 hours.

2. The method for preparing a magnesium-doped cathode material precursor according to claim 1, characterized in that, The base solution is ammonia water with a pH of 10.

6.

3. The method for preparing a magnesium-uniformly doped cathode material precursor according to claim 1, characterized in that, The molar ratio of nickel, cobalt, and manganese in a mixed aqueous solution of transition metal ions is (0.6-0.9):(0.05-0.2):(0.05-0.2).

4. A magnesium-doped cathode material precursor prepared by the method according to any one of claims 1-3, characterized in that, The chemical formula of the cathode material precursor is Ni. 0.83 Co 0.1 Mn 0.045 Mg 0.025 (OH)2 or Ni 0.63 Co 0.2 Mn 0.14 Mg 0.03 (OH) 2。 5. The magnesium-doped cathode material precursor according to claim 4, characterized in that, The cathode material prepared from this cathode material precursor has the chemical formula LiNi. 0.83 Co 0.1 Mn 0.045 Mg 0.025 O2 or LiNi 0.63 Co 0.2 Mn 0.14 Mg 0.03 O 2。 6. An application of a magnesium-doped cathode material precursor prepared by the method according to any one of claims 1-3, characterized in that, This magnesium-doped cathode material precursor is used in battery cathode materials; The particle size of the cathode material precursor is no more than 10 μm; the particle size of the cathode material is no more than 15 μm; the initial discharge specific capacity of the cathode material at 0.1C rate is no less than 127 mAh / g; and the capacity retention rate after 50 cycles at 1C rate is no less than 85%.

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