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

Abstract

The invention 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. Roasting the recycled ternary material to remove residual glue and carbon in the recycled ternary material, and weighing and grinding to obtain a regenerated ternary material; sampling the regenerated ternary material, measuring the content of metal elements in the regenerated ternary material, and supplementing the metal elements which do not meet the required stoichiometric ratio to obtain first powder; adding a fastening agent and a doping agent into the first powder, and performing fine grinding to obtain second powder; the second powder is placed in spray cracking equipment for spray cracking, and a lithium-rich manganese-based precursor is obtained; and roasting the lithium-rich manganese-based precursor in an oxygen-containing environment to obtain the single-crystal lithium-rich manganese-based material 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] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a preparation method of a single-crystal lithium-rich manganese-based material and the single-crystal lithium-rich manganese-based material. Background Art

[0002] With the rapid development of the low-altitude economy, the demand for lithium-ion battery energy density is also increasing. Lithium-rich manganese-based cathode materials, due to their high specific capacity and low cost, are considered the next generation of lithium-ion battery cathode materials after high-nickel ternary materials and have attracted widespread attention from researchers. However, lithium-rich manganese-based cathode materials currently have prominent problems that restrict their commercial application. These problems mainly focus on: low volumetric energy density, poor cycle stability, severe voltage decay, and poor rate performance, which hinder their commercial application. To address these issues such as volumetric energy density, single crystalization is a viable research direction.

[0003] In related technologies, according to current bond energy theory, since the Mn-O bond energy is higher than the Ni / Co-O bond energy and the proportion of Mn-O bonds in lithium-rich manganese materials is high, their high bond energy limits the dynamic adjustment ability of the lattice, resulting in the synthesis of single crystal morphology requiring higher energy input and special process conditions. Higher energy means higher calcination temperature, which will increase the degree of lithium-nickel mixing and weaken the high specific capacity characteristics of lithium-rich manganese-based materials. Summary of the Invention

[0004] In response to the above problems, the present invention reduces the solid-phase reaction activation energy by nano-sizing the raw materials, and solves the problem of uncontrollable particle size caused by nano-sizing the raw materials by using a fastening agent and a spray cracking device for rapid high-temperature cracking to prepare a precursor material with controllable particle size. As for the high activation energy barrier problem of the recycled ternary material itself, the nanoscale residual carbon existing on the surface of the recycled ternary nanoparticles after rapid cracking of the fastening agent is creatively used as an activator to create grain boundaries and crystal plane defects during the roasting process. According to theoretical calculations, the presence of the activator reduces the diffusion activation energy by 40-50%, greatly promoting the solid-solid diffusion rate and uniformity of the metal ions inside the ternary particles. Through the combination of the above methods, it is possible to use the recycled ternary material as the main raw material to prepare a single crystal morphology of lithium-rich manganese-based material with controllable particle size and good consistency. The single crystal material can effectively improve the compaction density of the lithium-rich manganese material, inhibit the formation and expansion of microcracks during the cycle, reduce the specific surface area, alleviate the side reaction with the electrolyte under high voltage, greatly reduce the amount of metal manganese dissolution, and greatly improve the life of the battery cell. At the same time, this process skips the traditional co-precipitation precursor process that takes dozens of hours, greatly shortens the production cycle and has no 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, preparing a fastening agent;

[0007] In the step 1, preparing the fastening agent comprises:

[0008] Step S1, placing absorbent cotton in a sodium hydroxide solution, heating and stirring, and then performing solid-liquid separation and washing to obtain a solid;

[0009] Step S2, adding dimethyl carbonate, niobium nitrate and deionized water to the solid matter, heating, stirring, filtering, washing, drying and crushing to obtain the fastening agent;

[0010] Step 2: calcining the recovered ternary material to remove residual glue and carbon in the recovered ternary material, and weighing and grinding the recovered ternary material to obtain a regenerated ternary material;

[0011] Step 3: sampling the recycled ternary material, determining the content of metal elements in the recycled ternary material, and supplementing the metal elements that do not meet the required stoichiometric ratio to obtain a first powder; adding the fastening agent and dopant to the first powder, and finely grinding to obtain a second powder; wherein the metal element includes at least one of nickel, cobalt, manganese, and lithium;

[0012] Step 4: placing 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 fastening agent is used to control the particle size of the lithium-rich manganese-based precursor;

[0013] Step 5: calcining the lithium-rich manganese-based precursor 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 the dimethyl carbonate is 4-7 times the mass of the solid matter, the mass of the niobium nitrate is 0.3-1.5 times the mass of the solid matter, the heating temperature is 60-80° C., and the stirring time is 6-12 h.

[0016] Optionally, the cracking product of the fastening agent is used as a solid-solid reaction activator to reduce the single crystal synthesis temperature.

[0017] Optionally, in step 3, the amount of the 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 cracking device is 500° C.-1000° C., and the atomization pressure of the spray cracking device is 0.3 MPa-0.8 MPa;

[0020] In the step 5, the roasting includes a primary roasting and a secondary roasting;

[0021] The primary calcination temperature is 300-600°C, and the primary calcination time is 1-3h;

[0022] The temperature of the secondary calcination is 600-900° C., and the time of the secondary calcination is 8-15 hours.

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

[0024] In the second aspect, the present invention also provides a single crystal lithium-rich manganese-based material, which is prepared by the method provided in the first aspect. The molecular formula of the single crystal lithium-rich manganese-based material is: xLi2MnO3·(1-x)LiMO2 molecular formula, 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 of .

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

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

[0027] The present invention provides a method for preparing a single-crystal lithium-rich manganese-based material and a single-crystal lithium-rich manganese-based material. The raw materials used to prepare the single-crystal lithium-rich manganese-based material are recycled ternary materials, which can not only solve the problem of low-cost application of retired batteries, but also produce new positive electrode materials to maximize economic benefits. In order to solve the problem of high activation energy barriers of recycled ternary materials themselves, a fastener is added in the process of preparing the single-crystal lithium-rich manganese-based material. The fastener is used to first form a colloidal substance during the rapid dehydration process of spray cracking, uniformly coat the metal oxide powder, and form homogeneous droplets, thereby reducing internal porosity, particle breakage and component segregation caused by differences in water loss rates of different components; in addition, during the continuous spray cracking process, most of the colloidal substances formed by the fastener and located inside the particles are decomposed into water and carbon dioxide, and the fastener is rapidly cracked during the spraying process to form a nano-lithium-rich manganese matrix. The nanoscale residual carbon on the surface of the particles reacts with the nano-lithium-rich manganese matrix in the subsequent calcination process, causing grain boundary and crystal surface defects, thereby greatly reducing the solid-solid reaction diffusion activation energy. Combined with the low activation energy characteristics of the nanoparticles inside the nano-lithium-rich manganese matrix particles, it greatly promotes the grain boundary fusion between the particles of the nano-lithium-rich manganese matrix, solves the problem of high bond energy activation energy barrier, improves the solid-solid diffusion speed and uniformity of the internal metal ions, and can form a single crystal morphology of lithium-rich manganese-based materials at a lower temperature, maintaining the material properties of high specific capacity of lithium-rich manganese materials. During the experiment, it was found that the use of high molecular weight fasteners in spray cracking can obtain stable small-particle lithium-rich manganese-based precursors, while the use of low molecular weight fasteners can obtain stable larger-sized precursor particles. This preparation method skips the traditional co-precipitation precursor process that takes dozens of hours, greatly shortens the production cycle and has no wastewater discharge, greatly reduces the cost of lithium-rich manganese-based materials, and increases the competitiveness of industrial production of materials.

[0028] The preparation method of the single-crystal lithium-rich manganese-based material provided by the present invention can form a single-crystal morphology material with controllable particle size. While maintaining the high specific capacity characteristics of the lithium-rich manganese-based material, it can effectively improve the positive electrode compaction density, thereby improving the volume energy density of the battery cell made using the single-crystal lithium-rich manganese-based material. There are fewer internal grain boundaries, more uniform stress distribution, and reduced stress accumulation at the grain boundaries, thereby inhibiting the formation and expansion of microcracks during the cycle. The single-crystal lithium-rich manganese-based material reduces the specific surface area of ​​the material, alleviates the side reaction between the single-crystal lithium-rich manganese-based material and the electrolyte under high voltage, significantly reduces the amount of metallic manganese dissolution, and greatly improves the life of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0032] Figure 4 This is a high-temperature cycle diagram of a lithium-ion battery corresponding to the single-crystal lithium-rich manganese-based material provided in Example 1. DETAILED DESCRIPTION

[0033] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features therein can be combined with each other in the absence of conflict.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0035] The present invention discloses a method for preparing a single-crystal lithium-rich manganese-based material. Figure 1 A schematic diagram of a process for preparing a single-crystal lithium-rich manganese-based material provided by the present invention is shown in FIG. Figure 1 As shown, the method includes the following steps:

[0036] Step 1: Prepare a fastening agent.

[0037] Optionally, step 1, preparing a fastening agent, comprises:

[0038] Step S1, placing absorbent cotton in a sodium hydroxide solution, heating and stirring, and then performing solid-liquid separation and washing to obtain a solid;

[0039] Step S2: adding dimethyl carbonate, niobium nitrate and deionized water to the solid matter, heating, stirring, filtering, washing, drying and crushing to obtain a fastening agent.

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

[0041] Illustratively, 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 may be, for example, 60-80° C., and the stirring time may be, for example, 6-12 h.

[0043] Specifically, 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, and ultimately affecting the particle size of the single crystal lithium-rich manganese-based material obtained subsequently.

[0044] Thus, the molecular weight of the fastener can be adjusted by the amount of niobium nitrate added. The more niobium nitrate is added, the higher the molecular weight of the fastener. A high molecular weight fastener can obtain a lithium-rich manganese-based precursor with a small median particle size during spray pyrolysis, while a low molecular weight fastener can obtain a lithium-rich manganese-based precursor with a large median particle size during 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 preparation method of the single-crystalline lithium-rich manganese-based material provided in this embodiment can achieve controllable adjustment of the particle size of the lithium-rich manganese-based precursor, and thus also achieves the regulation of the particle size of the single-crystalline lithium-rich manganese-based material, avoiding the problem of uncontrollable particle size caused by nano-sizing, and improving the morphology consistency of the single-crystalline lithium-rich manganese-based material.

[0045] Step 2: calcining the recovered ternary material to remove residual glue and carbon in the recovered ternary material, and weighing and grinding to obtain a regenerated ternary material.

[0046] For example, the recycled ternary material can be lithium nickel cobalt manganese oxide. To prevent residual glue and carbon in the recycled ternary material from affecting the purity of the subsequent preparation of single-crystal lithium-rich manganese-based materials, the recycled ternary material must first be calcined to remove the residual glue and carbon. Subsequently, the ternary material, free of residual glue and carbon, is weighed and ground until the median particle size D50 of the recycled ternary material is between 600nm and 900nm. Grinding is then stopped to obtain the regenerated ternary material.

[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 a first powder; add a fastener and a dopant to the first powder, and finely grind it to obtain a second powder; wherein the metal element includes at least one of nickel, cobalt, manganese and lithium.

[0048] Specifically, a small sample is taken from the recycled ternary material, the content of the metal elements in the recycled ternary material is measured, and the metal elements that do not meet the stoichiometric ratio are supplemented according to the desired stoichiometric ratio of the lithium-rich manganese-based material, thereby obtaining a first powder. For example, if the nickel element does not meet the desired stoichiometric ratio, a metal salt of the manganese element is supplemented to the recycled ternary material to ensure that the nickel element meets the desired stoichiometric ratio of the designed lithium-rich manganese-based material.

[0049] A dopant and a pre-prepared fastener are added to the first powder. The amount of the fastener 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 aluminum oxide, 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 mixed powder of the first powder, the fastening agent and the dopant is ground until the median particle size D50 of the mixed powder is between 50 nm and 150 nm.

[0051] Step 4: placing the second powder into a spray cracking device for spray cracking to obtain a lithium-rich manganese-based precursor; wherein the molecular weight of the fastening agent 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, thereby obtaining a lithium-rich manganese-based precursor. The temperature of the main reaction zone of the spray pyrolysis device can be, for example, 500°C to 1000°C, and the atomization pressure of the spray pyrolysis device is 0.3MPa to 0.8MPa. During the rapid dehydration process of the spray pyrolysis, a colloidal substance is first formed using a fastening agent, which uniformly coats the metal oxide powder to form homogeneous droplets, thereby reducing internal porosity, particle breakage, and component segregation caused by differences in water loss rates among different components.

[0053] Step 5: calcining the lithium-rich manganese-based precursor 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. The lithium-rich manganese-based precursor is first calcined once in an oxygen atmosphere at a temperature of 300-600°C and a calcination time of 1-3 hours. Then, it is calcined twice in an oxygen atmosphere at a temperature of 600-900°C and a calcination time of 8-15 hours. After the calcination is completed, the product is crushed, ground and sieved to obtain a single crystal lithium-rich manganese-based material. The product of the fastener in the spray pyrolysis process can be used as an activator for solid-solid reaction to reduce the temperature of single crystal synthesis.

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

[0056] Therefore, in the preparation method of the single crystal lithium-rich manganese-based material provided by the present invention, the raw material used to prepare the single crystal lithium-rich manganese-based material is recycled ternary material, which can not only solve the low-cost application problem of retired batteries, but also produce new positive electrode materials to maximize economic benefits. In order to solve the problem of high activation energy barrier of recycled ternary materials themselves, a fastener is added in the process of preparing single crystal lithium-rich manganese-based materials. The fastener is used to first form a colloidal substance during the rapid dehydration process of spray cracking, uniformly coat the metal oxide powder, and form homogeneous droplets, thereby reducing internal porosity, particle breakage and component segregation caused by the difference in water loss rates of different components; in addition, in the continuous spray cracking process, most of the colloidal substances located inside the particles formed by the fastener are decomposed into water and carbon dioxide, and the fastener is rapidly cracked during the spraying process to form a nano-lithium-rich manganese matrix. The nanoscale residual carbon on the surface of the particles reacts with the nano-lithium-rich manganese matrix in the subsequent calcination process, causing grain boundary and crystal surface defects, thereby greatly reducing the solid-solid reaction diffusion activation energy. Combined with the low activation energy characteristics of the nanoparticles inside the nano-lithium-rich manganese matrix particles, it greatly promotes the grain boundary fusion between the particles of the nano-lithium-rich manganese matrix, solves the problem of high bond energy activation energy barrier, improves the solid-solid diffusion speed and uniformity of the internal metal ions, and can form a single crystal morphology of lithium-rich manganese-based materials at a lower temperature, maintaining the material properties of high specific capacity of lithium-rich manganese materials. During the experiment, it was found that the use of high molecular weight fasteners in spray cracking can obtain stable small-particle lithium-rich manganese-based precursors, while the use of low molecular weight fasteners can obtain stable larger-sized precursor particles. This preparation method skips the traditional co-precipitation precursor process that takes dozens of hours, greatly shortens the production cycle and has no wastewater discharge, greatly reduces the cost of lithium-rich manganese-based materials, and increases the competitiveness of industrial production of materials.

[0057] The present invention also provides a single crystal lithium-rich manganese-based material, which is prepared by the method provided in the above embodiment, and thus has the technical effects of the above embodiment, which will not be described in detail 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 of .

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

[0059] In order to better understand the present invention, examples and comparative examples are provided below.

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

[0061] 100g of recovered NCM (nickel-cobalt-manganese) 111 type ternary material was calcined at 350℃ for 2h in an oxygen atmosphere, then heated to 700℃ and calcined for 2h. The weight was 96g and the mixture was ground into a sand mill to a particle size of 800nm. The metal content was measured and the metal content was calculated. 77g of lithium carbonate, 89g of manganese dioxide, 2.6g of a binder, 2g of aluminum oxide, 2g of boron oxide, and 2g of zirconium oxide were added and sand-milled to a median particle size of <100nm. The mixture was sprayed at an atomization pressure of 0.6MPa and a main reaction zone temperature of 880℃ to obtain Li-ion 2000 with a median particle size of 4.72μm. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 lithium-rich manganese-based precursor. 1.2 Ni 0.13 Co 0.13 Mn 0.54 The O2 lithium-rich manganese-based precursor was calcined at 500℃ for 1h and 850℃ for 12h in an oxygen atmosphere and then crushed to obtain a single crystal lithium-rich manganese-based Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 material.

[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 5 g, and the other preparation steps are the same as those in Example 1. The median particle size of the lithium-rich manganese-based precursor obtained after spray pyrolysis is 6.53 μm.

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

[0065] Comparative Example: The preparation steps are the same as those of Example 1, except that no fastening agent and dopant are 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 form a positive electrode slurry. This slurry was then coated onto aluminum foil to form a positive electrode sheet. After drying, the slurry was combined with a lithium metal negative electrode sheet, a polypropylene microporous membrane separator, and an electrolyte in a glove box to form a standard 2032-type button cell. After aging for 12 hours, the assembled cells were subjected to charge and discharge tests at a current density of 20 mA / g at 2.0-4.8 V. The physical, chemical, and electrochemical properties of the single-crystal lithium-rich manganese-based material are listed in Table 1.

[0067] Table 1 Test results of physical and chemical properties 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°C (%) 71.6 88.9 91.4 83.5 Manganese dissolution from negative electrode after high temperature cycling (ppm) 266 196 133 206

[0069] From the particle size test results of Example 1, Example 2 and Example 3, it can be seen that the particle size of the final 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 single-crystalline lithium-rich manganese-based material prepared using the present invention has a 0.1C discharge capacity greater than 280 mAh / g, a 2C discharge capacity / 1C discharge capacity ratio exceeding 70%, and a capacity retention rate exceeding 83% after 100 cycles at 45°C. The single-crystalline lithium-rich manganese-based material prepared in Example 2 has a capacity retention rate exceeding 90% after 100 cycles at 45°C. Furthermore, lithium-ion batteries prepared using the single-crystalline lithium-rich manganese-based material prepared according to the present invention significantly reduce manganese dissolution in the negative electrode after high-temperature cycling.

[0070] In summary, in the preparation method of the single crystal lithium-rich manganese-based material provided by the present invention, the raw material used to prepare the single crystal lithium-rich manganese-based material is recycled ternary material, which can not only solve the low-cost application problem of retired batteries, but also produce new positive electrode materials to maximize economic benefits. In order to solve the problem of high activation energy barrier of recycled ternary materials themselves, a fastener is added in the process of preparing single crystal lithium-rich manganese-based materials. The fastener is used to first form a colloidal substance during the rapid dehydration process of spray cracking, uniformly coat the metal oxide powder, and form homogeneous droplets, thereby reducing internal porosity, particle breakage and component segregation caused by the difference in water loss rates of different components; in addition, in the continuous spray cracking process, most of the colloidal substances located inside the particles formed by the fastener are decomposed into water and carbon dioxide, and the fastener is rapidly cracked during the spraying process to form a nano-lithium-rich manganese matrix. The nanoscale residual carbon on the surface of the particles reacts with the nano-lithium-rich manganese matrix in the subsequent calcination process, causing grain boundary and crystal surface defects, thereby greatly reducing the solid-solid reaction diffusion activation energy. Combined with the low activation energy characteristics of the nanoparticles inside the nano-lithium-rich manganese matrix particles, it greatly promotes the grain boundary fusion between the particles of the nano-lithium-rich manganese matrix, solves the problem of high bond energy activation energy barrier, improves the solid-solid diffusion speed and uniformity of the internal metal ions, and can form a single crystal morphology of lithium-rich manganese-based materials at a lower temperature, maintaining the material properties of high specific capacity of lithium-rich manganese materials. During the experiment, it was found that the use of high molecular weight fasteners in spray cracking can obtain stable small-particle lithium-rich manganese-based precursors, while the use of low molecular weight fasteners can obtain stable larger-sized precursor particles. This preparation method skips the traditional co-precipitation precursor process that takes dozens of hours, greatly shortens the production cycle and has no wastewater discharge, greatly reduces the cost of lithium-rich manganese-based materials, and increases the competitiveness of industrial production of materials.

[0071] The preparation method of the single-crystal lithium-rich manganese-based material provided by the present invention can form a single-crystal morphology material with controllable particle size. While maintaining the high specific capacity characteristics of the lithium-rich manganese-based material, it can effectively improve the positive electrode compaction density, thereby improving the volume energy density of the battery cell made using the single-crystal lithium-rich manganese-based material. There are fewer internal grain boundaries, more uniform stress distribution, and reduced stress accumulation at the grain boundaries, thereby inhibiting the formation and expansion of microcracks during the cycle. The single-crystal lithium-rich manganese-based material reduces the specific surface area of ​​the material, alleviates the side reaction between the single-crystal lithium-rich manganese-based material and the electrolyte under high voltage, significantly reduces the amount of metallic manganese dissolution, and greatly improves the life of the battery cell.

[0072] Although the present invention has been described above, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many variations without departing from the purpose of the present invention, and these are all protected by the present invention.

Claims

1. A method for preparing a single-crystal lithium-rich manganese-based material, characterized in that: The following steps are involved: Step 1, preparing a fastening agent; In the step 1, preparing the fastening agent comprises: Step S1, placing absorbent cotton in a sodium hydroxide solution, heating and stirring, and then performing solid-liquid separation and washing to obtain a solid; Step S2, adding dimethyl carbonate, niobium nitrate and deionized water to the solid matter, heating, stirring, filtering, washing, drying and crushing to obtain the fastening agent; Step 2: roasting the recovered ternary material to remove residual glue and carbon in the recovered ternary material, and weighing and grinding to obtain a regenerated ternary material; Step 3: sampling the recycled ternary material, determining the content of metal elements in the recycled ternary material, and supplementing the metal elements that do not meet the required stoichiometric ratio to obtain a first powder; adding the fastening agent and dopant to the first powder, and finely grinding to obtain a second powder; wherein the metal element includes at least one of nickel, cobalt, manganese, and lithium; Step 4: placing 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 fastening agent is used to control the particle size of the lithium-rich manganese-based precursor; Step 5: calcining the lithium-rich manganese-based precursor in an oxygen-containing environment to obtain a single crystal lithium-rich manganese-based material.

2. The method for preparing a single crystal lithium-rich manganese-based material according to claim 1, characterized in that: 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.

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

4. The method for preparing a single-crystal lithium-rich manganese-based material according to claim 1, wherein: The cracking product of the fastening agent is used as a solid-solid reaction activator to reduce the single crystal synthesis temperature.

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

6. The method for preparing a single crystal lithium-rich manganese-based material according to claim 1, characterized in that: In step 4, the temperature of the main reaction zone of the spray cracking device is 500° C.-1000° C., and the atomization pressure of the spray cracking device is 0.3 MPa-0.8 MPa; In the step 5, the roasting includes a primary roasting and a secondary roasting; The primary calcination temperature is 300-600°C, and the primary calcination time is 1-3h; The temperature of the secondary calcination is 600-900° C., and the time of the secondary calcination is 8-15 hours.

7. The method for preparing a single crystal lithium-rich manganese-based material 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.

8. A single crystal lithium-rich manganese-based material, characterized in that: The single crystal lithium-rich manganese-based material is prepared by the method according to any one of claims 1 to 7, 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 of .

9. A lithium-ion battery, characterized in that: Comprising the single crystal lithium-rich manganese-based material as claimed in claim 8.

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