Preparation method of single-crystal lithium-rich manganese-based material and single-crystal lithium-rich manganese-based material

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a preparation method of a single-crystal lithium-rich manganese-based material and the single-crystal lithium-rich manganese-based material. The method comprises the following steps: preparing a fastening agent; roasting recycled ternary materials to remove residual glue and carbon in the recycled ternary materials, weighing and grinding to obtain regenerated ternary materials; sampling the regenerated ternary materials, determining the content of metal elements in the regenerated ternary materials, supplementing metal elements that do not meet the required stoichiometric ratio to obtain a first powder; adding the fastening agent and a dopant to the first powder and finely grinding to obtain a second powder; spraying and cracking the second powder in a spraying and cracking device to obtain a lithium-rich manganese-based precursor; and roasting the lithium-rich manganese-based precursor in an oxygen-containing environment, so that the single-crystal lithium-rich manganese-based material is obtained after roasting. According to the technical scheme, the production cost of the single-crystal lithium-rich manganese-based material is reduced, and the electrochemical performance of the single-crystal lithium-rich manganese-based material is improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and specifically relates to a method for preparing a single-crystal lithium-rich manganese-based material and the single-crystal lithium-rich manganese-based material. Background Technology

[0002] With the rapid development of the low-altitude economy, the demand for lithium-ion battery energy density is constantly increasing. Lithium-rich manganese-based cathode materials, due to their high specific capacity and low cost, are considered the next-generation lithium-ion battery cathode material after high-nickel ternary materials and have attracted widespread attention from researchers. However, current lithium-rich manganese-based petroleum materials also have significant problems that restrict their commercial application, mainly focusing on: low volumetric energy density, poor cycle stability, severe voltage decay, and poor rate performance, hindering their commercial application. To solve the problems of volumetric energy density, single crystallization is a feasible research direction.

[0003] In related technologies, according to current bond energy theory, the Mn-O bond energy is higher than the Ni / Co-O bond energy, and the Mn-O bond ratio is high in lithium-rich manganese materials. This high bond energy limits the dynamic adjustment capability of the crystal lattice, resulting in the need for higher energy input and special process conditions to synthesize single-crystal morphologies. Higher energy means higher calcination temperatures, and increased temperatures will increase the degree of lithium-nickel mixing, weakening the high specific capacity characteristics of lithium-rich manganese-based materials. Summary of the Invention

[0004] To address the aforementioned issues, this invention reduces the activation energy of solid-state reactions through raw material nano-sizing. The uncontrollable particle size issue arising from raw material nano-sizing is resolved by using a fastener and a spray pyrolysis device for rapid, high-temperature pyrolysis to prepare precursor materials with controllable particle size. Regarding the high activation energy barrier of the recycled ternary materials themselves, this invention creatively utilizes the nanoscale residual carbon remaining on the surface of the recycled ternary nanoparticles after rapid pyrolysis with the fastener as an activator to create grain boundaries and crystal plane defects during calcination. Theoretical calculations show that the presence of the activator reduces the diffusion activation energy by 40-50%, significantly promoting the solid-solid diffusion rate and uniformity of metal ions within the ternary particles. By combining these methods, it is possible to use recycled ternary materials as the main raw material to prepare lithium-rich manganese-based materials with controllable particle size and good uniformity in single-crystal morphology. This single-crystal material effectively increases the compaction density of lithium-rich manganese materials, inhibits the formation and propagation of microcracks during cycling, reduces specific surface area to alleviate side reactions with the electrolyte under high voltage, significantly reduces the amount of manganese metal leaching, and greatly improves cell lifespan. Meanwhile, this process skips the traditional co-precipitation precursor process that takes tens of hours, significantly shortens the production cycle, eliminates wastewater discharge, greatly reduces the cost of lithium-rich manganese-based materials, and increases the competitiveness of industrial production of materials.

[0005] In a first aspect, the present invention provides a method for preparing a single-crystal lithium-rich manganese-based material, comprising the following steps:

[0006] Step 1: Prepare the fastener;

[0007] In step 1, the preparation of the fastener includes:

[0008] Step S1: Place the degreased cotton in a sodium hydroxide solution, heat and stir, then perform solid-liquid separation and washing to obtain a solid product;

[0009] Step S2: Add dimethyl carbonate, niobium nitrate and deionized water to the solid material, and then heat, stir, filter, wash, dry and pulverize to obtain the fastener;

[0010] Step 2: Roast the recycled ternary material to remove the residual glue and carbon in the recycled ternary material, and weigh and grind it to obtain the recycled ternary material;

[0011] Step 3: Sample the recycled ternary material, determine the content of metal elements in the recycled ternary material, supplement the metal elements that do not meet the required stoichiometric ratio, and obtain the first powder; add the fastener and dopant to the first powder, and grind it finely to obtain the second powder; wherein the metal elements include at least one of nickel, cobalt, manganese and lithium.

[0012] Step 4: Place the second powder into a spray pyrolysis device for spray pyrolysis to obtain a lithium-rich manganese-based precursor; wherein, the molecular weight of the fastener is used to control the particle size of the lithium-rich manganese-based precursor;

[0013] Step 5: The lithium-rich manganese-based precursor is calcined in an oxygen-containing environment to obtain a single-crystal lithium-rich manganese-based material.

[0014] Optionally, the amount of niobium nitrate added is used to control the molecular weight of the fastener, thereby affecting the particle size of the lithium-rich manganese-based precursor obtained after spray pyrolysis in step 4, and ultimately determining the particle size of the single-crystal lithium-rich manganese-based material obtained in step 5.

[0015] Optionally, in step S2, the mass of dimethyl carbonate is 4-7 times the mass of the solid, the mass of niobium nitrate is 0.3-1.5 times the mass of the solid, the heating temperature is 60-80℃, and the stirring time is 6-12h.

[0016] Optionally, the pyrolysis products of the fastener are used as solid-solid reaction activators to reduce the single crystal synthesis temperature.

[0017] Optionally, in step 3, the amount of fastener added is 0.5%-1.5% of the mass of the first powder.

[0018] In step 3, the dopant is one or more of aluminum oxide, zirconium oxide, boron oxide, tungsten oxide, magnesium oxide, yttrium oxide, calcium oxide, molybdenum oxide, and titanium oxide.

[0019] Optionally, in step 4, the temperature of the main reaction zone of the spray pyrolysis equipment is 500℃-1000℃, and the atomization pressure of the spray pyrolysis equipment is 0.3MPa-0.8MPa;

[0020] In step 5, the roasting includes a first roasting and a second roasting;

[0021] The temperature of the first roasting is 300-600℃, and the roasting time is 1-3 hours.

[0022] The secondary roasting temperature is 600-900℃, and the secondary roasting time is 8-15h.

[0023] Optionally, the median particle size D50 of the single-crystal lithium-rich manganese-based material is 2.5-8 μm.

[0024] Secondly, the present invention also provides a single-crystal lithium-rich manganese-based material, prepared by the method provided in the first aspect, wherein the molecular formula of the single-crystal lithium-rich manganese-based material is: xLi2MnO3·(1-x)LiMO2, wherein 0 <x<1,M=Ti、Cr、Al、Ni、Mn、Co、Fe、Ni 1 / 2 Mn 1 / 2 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 One or more combinations thereof.

[0025] Thirdly, the present invention also provides a lithium-ion battery comprising the single-crystal lithium-rich manganese-based material as provided in the second aspect.

[0026] The technical solution provided by this invention has the following advantages compared with the prior art:

[0027] This invention provides a method for preparing a single-crystal lithium-rich manganese-based material and the single-crystal lithium-rich manganese-based material itself. The raw material used in preparing the single-crystal lithium-rich manganese-based material is recycled ternary material, which can solve the problem of low-cost application of retired batteries and produce new cathode materials, thereby maximizing economic benefits. To address the high activation energy barrier of recycled ternary materials, a binder is added during the preparation of the single-crystal lithium-rich manganese-based material. During the rapid dehydration process of spray pyrolysis, the binder first forms a colloidal substance that uniformly coats the metal oxide powder, forming homogeneous droplets. This reduces internal porosity, particle breakage, and component segregation caused by differences in the water loss rates of different components. Furthermore, during continuous spray pyrolysis, most of the colloidal substance formed by the binder within the particles decomposes into water and carbon dioxide, and the binder rapidly decomposes during spraying, forming a nano-sized lithium-rich manganese matrix. The nanoscale residual carbon on the surface of the particles reacts with the nano-sized lithium-rich manganese matrix during subsequent calcination, creating grain boundaries and crystal plane defects. This significantly reduces the solid-solid reaction diffusion activation energy. Combined with the low activation energy characteristics of the nanoparticles within the nano-sized lithium-rich manganese matrix, this greatly promotes grain boundary fusion between the particles, solving the high bond energy activation barrier problem and improving the solid-solid diffusion rate and uniformity of internal metal ions. This allows for the formation of single-crystal morphology of lithium-rich manganese-based materials at lower temperatures, maintaining the high specific capacity of the materials. Experiments revealed that using a high-molecular-weight binder in spray pyrolysis yields stable small-particle lithium-rich manganese-based precursors, while using a low-molecular-weight binder yields stable, larger-particle precursor particles. This preparation method skips the traditional co-precipitation precursor process that requires tens of hours, significantly shortening the production cycle and eliminating wastewater discharge. This greatly reduces the cost of lithium-rich manganese-based materials and increases their competitiveness in industrial production.

[0028] The method for preparing single-crystal lithium-rich manganese-based materials provided by this invention can form single-crystal materials with controllable particle size. While maintaining the high specific capacity characteristics of lithium-rich manganese-based materials, it can effectively improve the cathode compaction density, thereby increasing the volumetric energy density of the battery cell made using this single-crystal lithium-rich manganese-based material. It also results in fewer internal grain boundaries, a more uniform stress distribution, and reduced stress accumulation at grain boundaries, thus suppressing the formation and propagation of microcracks during cycling. The single-crystal lithium-rich manganese-based material reduces the specific surface area of ​​the material, alleviates the side reactions between the single-crystal lithium-rich manganese-based material and the electrolyte under high voltage, significantly reduces the amount of manganese metal leaching, and greatly improves the battery cell lifespan. Attached Figure Description

[0029] Figure 1 A schematic flowchart illustrating a method for preparing a single-crystal lithium-rich manganese-based material provided by the present invention;

[0030] Figure 2SEM image of the single-crystal lithium-rich manganese-based material provided in Example 1;

[0031] Figure 3 The first charge-discharge curve of the lithium-ion battery corresponding to the single-crystal lithium-rich manganese-based material provided in Example 1 is shown.

[0032] Figure 4 The high-temperature cycling diagram is for the lithium-ion battery corresponding to the single-crystal lithium-rich manganese-based material provided in Example 1. Detailed Implementation

[0033] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0034] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0035] This invention discloses a method for preparing single-crystal lithium-rich manganese-based materials. Figure 1 This is a schematic flowchart of a method for preparing a single-crystal lithium-rich manganese-based material provided by the present invention, as shown below. Figure 1 As shown, the method includes the following steps:

[0036] Step 1: Prepare the fastener.

[0037] Optionally, step 1, preparing the fastener, includes:

[0038] Step S1: Place the degreased cotton in a sodium hydroxide solution, heat and stir, then perform solid-liquid separation and washing to obtain a solid product;

[0039] Step S2: Add dimethyl carbonate, niobium nitrate and deionized water to the solid material, and then heat, stir, filter, wash, dry and pulverize to obtain the fastener.

[0040] For example, the molar concentration of the sodium hydroxide solution in step S1 can be 2-10 mol / L, the heating temperature can be 40-60°C, and the stirring time can be 4-8 h.

[0041] For example, in step S2, the mass of dimethyl carbonate is 4-7 times the mass of the solid obtained in step S1, and the mass of niobium nitrate is 0.3-1.5 times the mass of the solid obtained in step S1.

[0042] The heating temperature in step S2 can be, for example, 60-80℃, and the stirring time can be, for example, 6-12h.

[0043] Specifically, the amount of niobium nitrate added is used to control the molecular weight of the fastener, which in turn affects the particle size of the lithium-rich manganese-based precursor obtained after spray pyrolysis, and ultimately affects the particle size of the subsequently obtained single-crystal lithium-rich manganese-based material.

[0044] Therefore, the molecular weight of the fastener can be adjusted by the amount of niobium nitrate added. The more niobium nitrate added, the higher the molecular weight of the fastener. High molecular weight fasteners can obtain stable lithium-rich manganese-based precursors with smaller median particle size in spray pyrolysis, while low molecular weight fasteners can obtain stable lithium-rich manganese-based precursors with larger median particle size in spray pyrolysis. That is, the median particle size of the lithium-rich manganese-based precursor is negatively correlated with the amount of niobium nitrate added. Therefore, the method for preparing single-crystal lithium-rich manganese-based materials provided in this embodiment can achieve controllable adjustment of the particle size of lithium-rich manganese-based precursors, and thus also achieve particle size control of single-crystal lithium-rich manganese-based materials, avoiding the problem of uncontrollable particle size caused by nano-sizing and improving the morphological consistency of single-crystal lithium-rich manganese-based materials.

[0045] Step 2: Roast the recycled ternary material to remove residual glue and carbon, and then weigh and grind it to obtain the recycled ternary material.

[0046] For example, the recycled ternary material can be lithium nickel cobalt manganese oxide. To avoid the residual glue and carbon in the recycled ternary material affecting the purity of the subsequent preparation of single-crystal lithium-rich manganese-based materials, the recycled ternary material needs to be calcined first to remove the residual glue and carbon. Subsequently, the ternary material after removing the residual glue and carbon is weighed and ground until the median particle size D50 of the recycled ternary material is between 600nm and 900nm, at which point the grinding is stopped, and the regenerated ternary material is obtained.

[0047] Step 3: Sample the recycled ternary material, determine the content of metal elements in the recycled ternary material, supplement the metal elements that do not meet the required stoichiometric ratio, and obtain the first powder; add a binder and a dopant to the first powder, and grind it finely to obtain the second powder; wherein the metal elements include at least one of nickel, cobalt, manganese and lithium.

[0048] Specifically, a small sample is taken from the recycled ternary material, and the content of metal elements in the recycled ternary material is determined. Based on the required stoichiometry of the lithium-rich manganese-based material, metal elements that do not meet the stoichiometry are added to obtain the first powder. For example, if the nickel element does not meet the required stoichiometry, a manganese metal salt is added to the recycled ternary material to ensure that the nickel element meets the required stoichiometry of the designed lithium-rich manganese-based material.

[0049] Add a dopant and a pre-prepared binder to the first powder. The amount of binder added can be, for example, 0.5%-1.5% of the mass of the first powder. The dopant can be, for example, one or more of alumina, zirconium oxide, boron oxide, tungsten oxide, magnesium oxide, yttrium oxide, calcium oxide, molybdenum oxide, and titanium oxide. The dopant is used to achieve the function of fluxing and reduce the sintering temperature of the material.

[0050] The mixture of the first powder, the binder, and the dopant is ground until the median particle size D50 of the mixture is between 50 nm and 150 nm.

[0051] Step 4: Place the second powder into a spray pyrolysis device for spray pyrolysis to obtain a lithium-rich manganese-based precursor; wherein, the molecular weight of the fastener is used to control the particle size of the lithium-rich manganese-based precursor.

[0052] Specifically, the precursor solution is placed in a spray pyrolysis device for spray pyrolysis to obtain a lithium-rich manganese-based precursor. The temperature of the main reaction zone of the spray pyrolysis device can be, for example, 500℃-1000℃, and the atomization pressure of the spray pyrolysis device is 0.3MPa-0.8MPa. During the rapid dehydration process of spray pyrolysis, a binder is used to first form a colloidal substance, which uniformly coats the metal oxide powder, forming homogeneous droplets. This reduces internal porosity, particle breakage, and component segregation caused by differences in the water loss rates of different components.

[0053] Step 5: The lithium-rich manganese-based precursor is calcined in an oxygen-containing environment to obtain a single-crystal lithium-rich manganese-based material.

[0054] Specifically, the lithium-rich manganese-based precursor prepared by spray pyrolysis is calcined in an oxygen-containing environment. First, the precursor is calcined once in an oxygen atmosphere at a temperature of 300-600℃ for 1-3 hours. Then, a second calcination is performed in an oxygen atmosphere at a temperature of 600-900℃ for 8-15 hours. After calcination, the product is pulverized, ground, and sieved to obtain single-crystal lithium-rich manganese-based material. The product of the fastener in the spray pyrolysis process can be used as an activator for the solid-solid reaction to lower the temperature of single-crystal synthesis.

[0055] During the experiment, it was found that using a high molecular weight fastener in spray pyrolysis can yield stable small-particle lithium-rich manganese-based precursors, while using a low molecular weight fastener can yield stable, larger-sized precursor particles. This allows the particle size of the lithium-rich manganese-based precursors to be controlled by adjusting the molecular weight of the fastener. The method for adjusting the molecular weight of the fastener can be understood by referring to the above description.

[0056] Therefore, the method for preparing single-crystal lithium-rich manganese-based materials provided by this invention uses recycled ternary materials as raw materials, which can solve the problem of low-cost application of retired batteries and produce new cathode materials, thereby maximizing economic benefits. To address the high activation energy barrier of recycled ternary materials, a binder is added during the preparation of single-crystal lithium-rich manganese-based materials. The binder first forms a colloidal substance during the rapid dehydration process of spray pyrolysis, uniformly coating the metal oxide powder and forming homogeneous droplets. This reduces internal porosity, particle breakage, and component segregation caused by differences in the water loss rates of different components. Furthermore, during continuous spray pyrolysis, most of the colloidal substance formed by the binder inside the particles decomposes into water and carbon dioxide, and the binder rapidly decomposes during spraying, forming a nano-sized lithium-rich manganese matrix. The nanoscale residual carbon on the surface of the particles reacts with the nano-sized lithium-rich manganese matrix during subsequent calcination, creating grain boundaries and crystal plane defects. This significantly reduces the solid-solid reaction diffusion activation energy. Combined with the low activation energy characteristics of the nanoparticles within the nano-sized lithium-rich manganese matrix, this greatly promotes grain boundary fusion between the particles, solving the high bond energy activation barrier problem and improving the solid-solid diffusion rate and uniformity of internal metal ions. This allows for the formation of single-crystal morphology of lithium-rich manganese-based materials at lower temperatures, maintaining the high specific capacity of the materials. Experiments revealed that using a high-molecular-weight binder in spray pyrolysis yields stable small-particle lithium-rich manganese-based precursors, while using a low-molecular-weight binder yields stable, larger-particle precursor particles. This preparation method skips the traditional co-precipitation precursor process that requires tens of hours, significantly shortening the production cycle and eliminating wastewater discharge. This greatly reduces the cost of lithium-rich manganese-based materials and increases their competitiveness in industrial production.

[0057] This invention also provides a single-crystal lithium-rich manganese-based material, prepared using the method described in the above embodiments, and therefore possesses the technical effects of the above embodiments, which will not be elaborated further here. The molecular formula of the single-crystal lithium-rich manganese-based material is: xLi₂MnO₃·(1-x)LiMO₂, where 0 <x<1,M=Ti、Cr、Al、Ni、Mn、Co、Fe、Ni 1 / 2 Mn 1 / 2 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 One or more combinations thereof.

[0058] The present invention also provides a lithium-ion battery comprising the single-crystal lithium-rich manganese-based material provided in the above embodiments, and thus has the technical effects of the above embodiments, which will not be elaborated here.

[0059] To better understand the present invention, embodiments and comparative examples are also provided below.

[0060] Example 1: 10g of degreased cotton was placed in an 8M sodium hydroxide solution at 50℃ and stirred for 4h. After solid-liquid separation and washing, 50g of dimethyl carbonate and 10g of niobium nitrate were added to 100mL of water. The mixture was stirred slowly at 80℃ for 10h. After filtration, washing, drying and pulverizing, the fastener was obtained.

[0061] 100g of recycled NCM (nickel-cobalt-manganese) 111 type ternary material was calcined at 350℃ for 2 hours in an oxygen atmosphere, then calcined at 700℃ for 2 hours, yielding 96g. This 96g material was then ground in a sand mill to a particle size of 800nm. Samples were taken to determine the metal content. Based on calculations, 77g of lithium carbonate, 89g of manganese dioxide, 2.6g of fastener, 2g of alumina, 2g of boron oxide, and 2g of zirconium oxide were added and milled together until the median particle size D50 < 100 nm. The mixture was then sprayed under an atomization pressure of 0.6MPa and a main reaction zone temperature of 880℃ to obtain Li₂ with a median particle size D50 of 4.72μm. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2-rich lithium-manganese-based precursor. Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 The O2-rich lithium-manganese-based precursor was calcined at 500℃ for 1 h and then at 850℃ for 12 h in an oxygen atmosphere, followed by pulverization to obtain single-crystal lithium-rich manganese-based Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 materials.

[0062] like Figure 2 As shown, the single-crystal lithium-rich manganese-based material prepared in Example 1 has a single-crystal morphology.

[0063] Example 2: The only difference from Example 1 is that the amount of niobium nitrate added in Example 2 is 5g. All other preparation steps are the same as in Example 1. The median particle size of the lithium-rich manganese-based precursor obtained after spray pyrolysis is 6.53μm.

[0064] Example 3: The only difference from Example 1 is that the amount of niobium nitrate added in Example 3 is 14g. All other preparation steps are the same as in Example 1. The median particle size of the lithium-rich manganese-based precursor obtained after spray pyrolysis is 3.2μm.

[0065] Comparative example: The preparation steps are the same as in Example 1, except that no fastener or dopant is added during the preparation process.

[0066] The positive electrode materials prepared in Examples 1, 2, 3, and the comparative example were mixed with a conductive agent (carbon black) and a binder (polyvinylidene fluoride) in a ratio of 90:5:5 to prepare a positive electrode slurry, which was then coated onto aluminum foil to form a positive electrode sheet. After drying, the slurry was assembled with a lithium metal negative electrode sheet, a polypropylene microporous membrane separator, and an electrolyte in a glove box to form a standard 2032 button cell. After aging for 12 hours, the assembled cells were subjected to charge-discharge tests at a current density of 2.0-4.8V and 20mA / g. The physicochemical and electrochemical performance test results of the single-crystal lithium-rich manganese-based material are listed in Table 1.

[0067] Table 1. Test results of physicochemical and electrochemical properties of single-crystal lithium-rich manganese-based materials

[0068] project Comparative Example Example 1 Example 2 Example 3 Median particle size D50 (μm) 9.35 4.41 6.37 3.07 <![CDATA[Powder Compaction Density (g / cm 3 ).]]> 2.74 2.93 3.08 2.99 0.1C discharge specific capacity (mAh / g) 272.1 288.3 281.5 297.3 1C discharge specific capacity (mAh / g) 220.3 235.7 221.3 266.5 2C discharge capacity / 1C discharge capacity (%) 60.1 77.2 71.1 91.3 Capacity retention rate (%) after 100 cycles at 45℃ 71.6 88.9 91.4 83.5 Manganese leaching from the negative electrode after high-temperature cycling (ppm) 266 196 133 206

[0069] The particle size test results from Examples 1, 2, and 3 show that the particle size of the final prepared single-crystal lithium-rich manganese-based material can be controlled by adjusting the amount of niobium nitrate used during the preparation process, and the compaction density of the powder is significantly improved. In the electrochemical performance test, combined with Table 1, Figure 3 and Figure 4 The monocrystalline lithium-rich manganese-based material prepared using this invention exhibits a 0.1C discharge specific capacity greater than 280 mAh / g, a 2C discharge capacity / 1C discharge capacity ratio exceeding 70%, and a capacity retention rate of over 83% after 100 cycles at 45°C. The monocrystalline lithium-rich manganese-based material prepared in Example 2 achieves a capacity retention rate of over 90% after 100 cycles at 45°C. Furthermore, lithium-ion batteries prepared using the monocrystalline lithium-rich manganese-based material of this invention show significantly reduced manganese dissolution from the negative electrode after high-temperature cycling.

[0070] In summary, the method for preparing single-crystal lithium-rich manganese-based materials provided by this invention uses recycled ternary materials as raw materials, which can solve the problem of low-cost application of retired batteries and produce new cathode materials, thereby maximizing economic benefits. To address the high activation energy barrier of recycled ternary materials, a binder is added during the preparation of single-crystal lithium-rich manganese-based materials. During the rapid dehydration process of spray pyrolysis, the binder first forms a colloidal substance that uniformly coats the metal oxide powder, forming homogeneous droplets. This reduces internal porosity, particle breakage, and component segregation caused by differences in the water loss rates of different components. Furthermore, during continuous spray pyrolysis, most of the colloidal substance formed by the binder within the particles decomposes into water and carbon dioxide, and the binder rapidly decomposes during spraying, forming a nano-sized lithium-rich manganese matrix. The nanoscale residual carbon on the surface of the particles reacts with the nano-sized lithium-rich manganese matrix during subsequent calcination, creating grain boundaries and crystal plane defects. This significantly reduces the solid-solid reaction diffusion activation energy. Combined with the low activation energy characteristics of the nanoparticles within the nano-sized lithium-rich manganese matrix, this greatly promotes grain boundary fusion between the particles, solving the high bond energy activation barrier problem and improving the solid-solid diffusion rate and uniformity of internal metal ions. This allows for the formation of single-crystal morphology of lithium-rich manganese-based materials at lower temperatures, maintaining the high specific capacity of the materials. Experiments revealed that using a high-molecular-weight binder in spray pyrolysis yields stable small-particle lithium-rich manganese-based precursors, while using a low-molecular-weight binder yields stable, larger-particle precursor particles. This preparation method skips the traditional co-precipitation precursor process that requires tens of hours, significantly shortening the production cycle and eliminating wastewater discharge. This greatly reduces the cost of lithium-rich manganese-based materials and increases their competitiveness in industrial production.

[0071] The method for preparing single-crystal lithium-rich manganese-based materials provided by this invention can form single-crystal materials with controllable particle size. While maintaining the high specific capacity characteristics of lithium-rich manganese-based materials, it can effectively improve the cathode compaction density, thereby increasing the volumetric energy density of the battery cell made using this single-crystal lithium-rich manganese-based material. It also results in fewer internal grain boundaries, a more uniform stress distribution, and reduced stress accumulation at grain boundaries, thus suppressing the formation and propagation of microcracks during cycling. The single-crystal lithium-rich manganese-based material reduces the specific surface area of ​​the material, alleviates the side reactions between the single-crystal lithium-rich manganese-based material and the electrolyte under high voltage, significantly reduces the amount of manganese metal leaching, and greatly improves the battery cell lifespan.

[0072] Although the present invention has been described above, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit of the present invention, and these modifications are all within the protection scope of the present invention.

Claims

1. A method for preparing a single-crystal lithium-rich manganese-based material, characterized in that, Includes the following steps: Step 1: Prepare the fastener; In step 1, the preparation of the fastener includes: Step S1: Place the degreased cotton in a sodium hydroxide solution, heat and stir, then perform solid-liquid separation and washing to obtain a solid product; Step S2: Add dimethyl carbonate, niobium nitrate and deionized water to the solid material, and then heat, stir, filter, wash, dry and pulverize to obtain the fastener; Step 2: The recycled ternary material is roasted to remove residual glue and carbon, and then weighed and ground to obtain recycled ternary material; the recycled ternary material is lithium nickel cobalt manganese oxide material; Step 3: Sample the recycled ternary material, determine the content of metal elements in the recycled ternary material, supplement the metal elements that do not meet the required stoichiometric ratio, and obtain the first powder; add the fastener and dopant to the first powder, and grind it finely to obtain the second powder; wherein the metal element is at least one of nickel, cobalt, manganese and lithium. Step 4: Place the second powder into a spray pyrolysis device for spray pyrolysis to obtain a lithium-rich manganese-based precursor; wherein, the molecular weight of the fastener is used to control the particle size of the lithium-rich manganese-based precursor; Step 5: The lithium-rich manganese-based precursor is calcined in an oxygen-containing environment to obtain a single-crystal lithium-rich manganese-based material. The dopant is one or more of aluminum oxide, zirconium oxide, and boron oxide.

2. The method for preparing single-crystal lithium-rich manganese-based materials according to claim 1, characterized in that, The amount of niobium nitrate added is used to control the molecular weight of the fastener, which in turn affects the particle size of the lithium-rich manganese-based precursor obtained after spray pyrolysis in step 4, and ultimately determines the particle size of the single-crystal lithium-rich manganese-based material obtained in step 5.

3. The method for preparing single-crystal lithium-rich manganese-based materials according to claim 1, characterized in that, In step S2, the mass of dimethyl carbonate is 4-7 times the mass of the solid, the mass of niobium nitrate is 0.3-1.5 times the mass of the solid, the heating temperature is 60-80℃, and the stirring time is 6-12h.

4. The method for preparing single-crystal lithium-rich manganese-based materials according to claim 1, characterized in that, The pyrolysis products of the fastener serve as activators for the solid-solid reaction, used to lower the single-crystal synthesis temperature.

5. The method for preparing single-crystal lithium-rich manganese-based materials according to claim 1, characterized in that, In step 3, the amount of fastener added is 0.5%-1.5% of the mass of the first powder.

6. The method for preparing single-crystal lithium-rich manganese-based materials according to claim 1, characterized in that, In step 4, the temperature of the main reaction zone of the spray pyrolysis equipment is 500℃-1000℃, and the atomization pressure of the spray pyrolysis equipment is 0.3MPa-0.8MPa. In step 5, the roasting includes a first roasting and a second roasting; The temperature of the first roasting is 300-600℃, and the roasting time is 1-3 hours. The secondary roasting temperature is 600-900℃, and the secondary roasting time is 8-15h.

7. The method for preparing single-crystal lithium-rich manganese-based materials according to claim 1, characterized in that, The median particle size D50 of the single-crystal lithium-rich manganese-based material is 2.5-8 μm.

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