Positive electrode material, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a positive electrode material, and a preparation method therefor and the use thereof. The chemical formula of the positive electrode material is: Li1+nMnxAMyTMzO2-mQm, where n is 0-0.4, and x is 0.5-0.7; AM is Na and / or K, each y independently is 0.1-0.25, and the sum of all y is less than or equal to 0.4; TM is Zr, Cu, Mg, Ti, Fe, Al, etc., each z independently is 0.01-0.1, and the sum of n, x, all y and all z is 1; and Q is F, Cl, Br, I, etc., each m independently is 0.1-0.35, and the sum of all m is less than or equal to 0.4. During preparation, all the raw materials of the components are mixed and ground, and then sintered in one step. The preparation method is simple and easy to operate, and the prepared positive electrode material also has excellent electrochemical performance, which indicates that the present invention can avoid performing doping with a metal, such as Ni or Co, which has a relatively high price, thereby lowering the cost.

Description

A cathode material, its preparation method and application Technical Field

[0001] This invention relates to the field of energy storage technology, and more particularly to lithium-ion battery energy storage, specifically to a cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have become an important component of the electrochemical energy storage field due to their high energy density, lack of memory effect, and long cycle life, and are widely used in large-scale energy storage, portable devices, and electric vehicles. However, with further societal development, the demand for the energy density of lithium-ion batteries is increasing, and reducing the application cost of batteries has become one of the key focuses of lithium-ion battery development. Lithium-rich manganese-based layered cathode material (xLiTMO2·(1-x)Li[Li 1 / 3 Mn 2 / 3 LRM (Lithium-ion Reductant ore) exhibits additional specific capacity due to the activation of anions at high potentials (>4.5V) to undergo redox reactions. This results in a relatively high specific capacity for this material. Furthermore, the high Mn content of LRM contributes to its relatively low manufacturing cost. Therefore, LRM, possessing both high specific capacity and low cost, is a strong candidate for next-generation lithium-ion battery cathode materials.

[0003] However, this material still has the following problems: (1) Irreversible loss of oxygen anions at high potentials. To achieve high capacity, lithium-rich materials need to activate oxygen anions at a high cutoff voltage (>4.5V) to participate in charge compensation. However, oxygen anions in LRM are easily oxidized to oxygen at high potentials. This oxygen escapes from the material surface and attacks the liquid electrolyte, increasing the degree of interfacial side reactions, which in turn causes structural degradation and irreversible capacity loss. Therefore, the first-cycle coulombic efficiency of LRM is generally low; (2) Irreversible phase transition of crystal structure. Li + After insertion and extraction, vacancies are left in the lithium layer of the original material. At the same time, the irreversible loss of oxygen will aggravate the instability of the material's crystal structure, which will lead to the migration of transition metal ions (TM) and cause an irreversible phase transition from a layered structure to a spinel structure, resulting in a decrease in the material's cycle stability.

[0004] To address the problems of LMR (Layered Reduction) materials, current technical approaches mainly focus on doping, coating, and controlled synthesis methods. For example, selective growth of specific crystal planes can be achieved by controlling the synthesis atmosphere; sulfate ion groups induce the growth of spinel-layered composite phases; and ZrO2 coating materials improve the cycling stability of the material. These methods alleviate the aforementioned problems to some extent, but the processes are relatively cumbersome, often employing sol-gel methods, co-precipitation methods, or secondary coating methods, which are complex and difficult to operate. Furthermore, at the material design level, performance improvements are often achieved by introducing high-cost cobalt, impacting the cost of LMR. They also do not provide effective suppression of excessive redox reactions of oxygen anions, failing to fundamentally solve the problem of poor LMR cycling.

[0005] Furthermore, some researchers have attempted to improve cycle performance and address issues like low initial efficiency by preparing high-entropy doped layered cathode materials. However, in practice, they typically add more effective but more expensive metals such as Ni and Co to achieve a high-entropy state, which is not conducive to cost reduction. At the same time, in pursuit of better performance, multiple high-temperature calcinations are usually required, or further preparation methods such as co-precipitation are used. However, multiple calcinations are not only time-consuming and labor-intensive but also energy-intensive. In particular, co-precipitation requires a large amount of solvent, which easily generates industrial wastewater and necessitates additional wastewater treatment processes, which is not conducive to large-scale industrial production. There is a clear trade-off between these two approaches.

[0006] It should be noted that the information disclosed in the background section above is only for understanding the background of this application. Therefore, the background section of this invention may include background information about the problems or environment of this invention, and is not necessarily a description of prior art. Thus, the content included in the background section does not constitute an admission of prior art by the applicant. Summary of the Invention

[0007] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide a new cathode material that can have excellent electrochemical performance while avoiding the use of expensive metals such as Ni and Co for doping, and can also simplify the production process by requiring only one calcination step.

[0008] The novel cathode material provided by this invention is a low-cost, high-entropy, lithium-rich manganese-based layered cathode material that can effectively suppress the unstable activity of oxygen ions, delay the irreversible phase transition of the material, and overcome the problem of sacrificing some benefits for others in existing high-entropy doped layered cathode materials.

[0009] The present invention also provides a method for preparing the above-mentioned novel cathode material, which can achieve the preparation of cathode material with excellent electrochemical performance through simple operation. This shows that the design of the novel cathode material of the present invention reduces the requirements for processing technology, which is conducive to simplifying the processing process and further conducive to large-scale industrial production.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] A cathode material, wherein the chemical formula of the cathode material is: Li 1+n Mn x AM y TM z O 2-m Q m ;

[0012] Where n is 0-0.4 and x is 0.5-0.7;

[0013] AM is selected from one or more combinations of Na (sodium) and K (potassium), each y is independently 0.1-0.25, and when there are multiple AM, the sum of all y is less than or equal to 0.4;

[0014] TM is selected from one, two or more combinations of Zr (zirconium), Cu (copper), Mg (magnesium), Ti (titanium), Fe (iron), and Al (aluminum), each z is independently 0.01-0.1, and the sum of n, x, all y and all z is 1;

[0015] Q is selected from one, two or more combinations of F (fluorine), Cl (chlorine), Br (bromine), and I (iodine), each m is independently 0.1-0.35, and when Q has multiples, the sum of all m is less than or equal to 0.4.

[0016] In some embodiments of the present invention, AM is selected from a combination of Na and K.

[0017] In some embodiments of the present invention, each y is independently 0.1-0.2, for example, it can be 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, etc.

[0018] In some embodiments of the present invention, TM is selected from one, two or a combination of three of Zr, Cu and Mg.

[0019] In some embodiments of the present invention, TM is selected from a combination of Zr, Cu, and Mg.

[0020] In some embodiments of the present invention, TM comprises at least one selected from Zr, Cu, Mg, and a combination of one, two, or three selected from Ti (titanium), Fe (iron), and Al (aluminum).

[0021] In some embodiments of the present invention, each z is independently 0.01-0.07, for example, it can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, etc.

[0022] In some embodiments of the present invention, Q is selected from F.

[0023] In some embodiments of the present invention, each m is independently 0.15-0.30, for example, it can be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, etc.

[0024] According to some preferred aspects of the present invention, the chemical formula of the cathode material is: Li1[Li n Mn x Na y1 K y2 Zr z1 Cu z2 Mg z3 ]O 2-m1 F m1 ;

[0025] Where n and x are defined as before; y1 and y2 are independently 0.15-0.22, z1, z2, and z3 are independently 0.01-0.05, m1 is 0.15-0.35, and n+x+y1+y2+z1+z2+z3=1.

[0026] Furthermore, the numerical range "0.15-0.22" in "y1 and y2 are independently 0.15-0.22" can be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, etc.

[0027] Furthermore, the numerical range "0.01-0.05" in "z1, z2, z3 are independently 0.01-0.05" can be 0.01, 0.02, 0.03, 0.04, 0.05, etc.

[0028] According to some preferred aspects of the present invention, the chemical formula of the positive electrode material is:

[0029] Li1[Li n Mn x Na y3 K y4 Ti z4 Mo z5 Mg z6 Nb z7 ]O 2-m2 F m2;

[0030] Where n and x are defined as before; y3 and y4 are independently 0.15-0.22, z4, z5, z6, and z7 are independently 0.01-0.04, m2 is 0.15-0.25, and n+x+y3+y4+z4+z5+z6+z7=1.

[0031] Furthermore, the numerical range "0.15-0.22" in "y3 and y4 are independently 0.15-0.22" can be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, etc.

[0032] Furthermore, the numerical range "0.01-0.04" in "z4, z5, z6, z7 are independently 0.01-0.04" can be 0.01, 0.02, 0.03, 0.04, etc.

[0033] Furthermore, the numerical range "0.15-0.25" in "m2 is 0.15-0.25" can be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, etc.

[0034] According to the present invention, the cathode material has a layered structure and belongs to the C2 / m space group.

[0035] In some embodiments of the present invention, the entropy value of the cathode material is greater than or equal to 1.5R, further greater than or equal to 1.8R, and even further greater than or equal to 2.0R.

[0036] In this invention, the entropy value can be expressed as follows: configurational entropy (S) comfig The calculation formula is used to obtain:

[0037] Where R is the gas constant (approximately 8.314 J·mol⁻¹) -1 ·K -1 ), x i x represents the mole fraction of the i-th component at the cation-site, where N is the number of element types occupying the cation-site; j denoted as , where is the mole fraction of the j-th component at the anion site, and M is the number of element types occupying the anion site.

[0038] Another technical solution provided by the present invention is a method for preparing the above-mentioned cathode material, the method comprising: weighing each raw material according to the molecular weight ratio, mixing, adding solvent, grinding, drying the ground material, and then sintering to prepare the cathode material.

[0039] In some embodiments of the present invention, the raw materials include lithium salts as lithium sources and oxides, hydroxides or fluorides of the corresponding components.

[0040] In some embodiments of the present invention, the AM element can be added in the form of hydroxides, such as sodium hydroxide and / or potassium hydroxide.

[0041] In some embodiments of the present invention, the TM element can be added in the form of oxides, such as copper oxide, zirconium dioxide, magnesium oxide, titanium dioxide, iron oxide, aluminum oxide, etc.

[0042] In some embodiments of the present invention, the Mn element can be added in the form of an oxide, such as manganese dioxide.

[0043] In some embodiments of the present invention, for the Li (lithium) element, lithium salts may be added, such as lithium carbonate.

[0044] In some embodiments of the present invention, the Q element can be added in the form of lithium halide, for example, for fluorine, lithium fluoride can be added, and for chlorine, lithium chloride can be added.

[0045] In some embodiments of the present invention, the solvent is anhydrous ethanol.

[0046] In some embodiments of the present invention, the grinding is performed by ball milling. Further, during the ball milling process, the ball milling speed is 100-400 r / min, and the ball milling time is 12-16 h.

[0047] In some embodiments of the present invention, after grinding, the resulting powder raw material is pressed into sheets. Further, the pressing pressure is 5-30 MPa, and the holding time during pressing is 1-5 min.

[0048] In some embodiments of the present invention, the calcination is controlled to be carried out at 700-1100°C, for example, at 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C or 1100°C.

[0049] In some embodiments of the present invention, the calcination time is controlled to be 6-18 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, etc.

[0050] In some embodiments of the present invention, the calcination is a one-step sintering process.

[0051] In some embodiments of the present invention, the heating rate of the calcination is controlled to be 1-15°C / min, and more specifically 5-10°C / min.

[0052] In some embodiments of the present invention, the calcination is controlled to be carried out in an air atmosphere or an oxygen atmosphere.

[0053] This invention utilizes a simple high-temperature solid-state method, selecting oxides, hydroxides, fluorides of various metal ions, and lithium salts as lithium sources, and ball milling them together under the condition of using anhydrous ethanol as a dispersant. Then, through one-step sintering in a muffle furnace, a cathode material with a stable crystal structure can be obtained, and a material with multiple elements entering the material lattice to form a pure layered phase can be obtained without secondary processing, which is convenient and fast.

[0054] Another technical solution provided by the present invention is a positive electrode sheet, which includes a current collector and an active material, wherein the active material includes the positive electrode material, conductive agent and binder described above.

[0055] Furthermore, the current collector can be made of materials including, but not limited to, aluminum, copper, etc.

[0056] Furthermore, the conductive agent may include, but is not limited to, conductive carbon (SP), carbon nanotubes, carbon nanosheets, graphene, etc.

[0057] Furthermore, the adhesive may include, but is not limited to, polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polytetrafluoroethylene (PTFE), etc.

[0058] Furthermore, taking the total mass of the positive electrode material, conductive agent, and binder as 100%, the positive electrode material accounts for 50%-99%, the conductive agent accounts for 0.1%-35%, and the binder accounts for 0.1%-20%.

[0059] In some embodiments of the present invention, based on the total mass of the positive electrode material, conductive agent and binder as 100%, the positive electrode material accounts for 70%-98%, the conductive agent accounts for 0.2%-20%, and the binder accounts for 0.2%-20%.

[0060] In some embodiments of the present invention, based on the total mass of the positive electrode material, conductive agent and binder as 100%, the positive electrode material accounts for 80%-98%, the conductive agent accounts for 0.3%-15%, and the binder accounts for 0.3%-15%.

[0061] Another technical solution provided by the present invention is a lithium-ion battery, wherein the lithium-ion battery includes the positive electrode material described above.

[0062] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0063] Addressing the shortcomings of existing high-entropy doping designs, such as the need to introduce expensive metals like Ni and Co, the requirement for multiple high-temperature calcination processes, or the complexity of operation due to additional coating designs, the inventors of this invention, during extensive experimental research, unexpectedly discovered that by introducing specific amounts of alkali metals like sodium and / or potassium to replace manganese in the high-entropy doping design, and by using a high content of halogens to replace oxygen, the cathode material of this invention can achieve excellent electrochemical performance while avoiding the use of expensive metals like Ni and Co for doping. Furthermore, it simplifies the production process, requiring only a single calcination step. Further mechanistic studies suggest that the synergistic effect of multi-element substitution / doping in the material system of this invention eliminates the dependence on expensive nickel and cobalt, reducing the cost of LRM (Liquid Rational Metal Resin). Moreover, the combined effect of multi-element substitution / doping allows the material to obtain a stable, specific high-entropy structure in a single sintering step. This structure, in particular, effectively inhibits excessive redox reactions of oxygen anions and also significantly suppresses phase transitions, thereby improving the cycle stability of the cathode material. Attached Figure Description

[0064] Figure 1 shows the XRD patterns of the cathode material obtained in Example 1 and the cathode material obtained in Comparative Example 1. It can be seen that the cathode material obtained in Example 1 has a good layered structure, belonging to the C2 / m space group. The sharp diffraction peaks in the range of 20° to 30° belong to the LiMn6 superlattice of lithium-rich materials, indicating that the layered cathode material has very good crystallinity. It can also be seen that the material obtained in Comparative Example 1 has a layered structure, with the space group being C2 / m.

[0065] Figure 2 shows the charge-discharge curves of the cathode material obtained in Example 1 and the cathode material obtained in Comparative Example 1. The electrochemical curves of the two materials are similar, and an oxygen plateau appears above 4.5V during the first charge cycle. However, the electrochemical curve of Example 1 shows better capacity performance and cycle stability.

[0066] Figure 3 shows the cycle performance curves of the cathode material obtained in Example 1 and the cathode material obtained in Comparative Example 1. It can be seen that the cycle capacity of Comparative Example 1 decays rapidly, while the cycle capacity of the material in Example 1 increases with each cycle.

[0067] Figure 4 shows the first charge-discharge curve of the positive electrode material obtained in Example 2 of the present invention;

[0068] Figure 5 shows the cycle performance curve of the cathode material obtained in Example 2 of the present invention;

[0069] Figure 6 shows the first charge-discharge curve of the cathode material obtained in Comparative Example 2 of the present invention.

[0070] Figure 7 shows the first charge-discharge curve of the cathode material obtained in Comparative Example 3 of the present invention. It can be seen that the first discharge capacity is low.

[0071] Figure 8 shows the first charge-discharge curve of the cathode material obtained in Comparative Example 4 of the present invention. It can be seen that the first discharge capacity is low.

[0072] Figure 9 shows the first charge-discharge curve of the cathode material obtained in Comparative Example 5 of the present invention. It can be seen that the first discharge capacity is low.

[0073] Figure 10 shows the cycle performance curves of the cathode materials obtained in Comparative Examples 3, 4, and 5 of this invention. It can be seen that there is an activation trend during the cycle process, but the capacity is much lower than the discharge specific capacity in the examples. Detailed Implementation

[0074] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0075] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0076] Example 1:

[0077] This example provides a cathode material and its preparation method, which includes:

[0078] According to the molecular formula Li[Na] 0.2 K 0.2 Mn 0.535 Zr 0.015 Cu 0.025 Mg 0.025 ]O 1.7 F 0.3Weigh out 1.0862 g of lithium carbonate, 1.8604 g of manganese dioxide, 0.3112 g of lithium fluoride, 0.4488 g of potassium hydroxide, 0.32 g of sodium hydroxide, 0.0739 g of zirconium dioxide, 0.07955 g of copper oxide, and 0.0403 g of magnesium oxide (at a 0.04 mol ratio) and place them in a mortar. Grind by hand for 30 minutes, then pour the mixture into a ball mill jar. Add zirconium beads at a mass ratio of 1:4 (raw material: zirconium beads), then add 15 mL of anhydrous ethanol. Place the jar in a planetary ball mill and ball mill at 200 r / min for 12 hours. The mixed raw materials were placed in an oven and dried at 80°C for 12 hours. The powder was then ground into powder using an agate mortar and pestle. 0.5g of the powder was weighed and placed in a tableting mold. The tablets were pressed at 10MPa for 2 minutes to obtain 3mm discs. The discs were placed in a 15mL corundum crucible and placed in a muffle furnace. The temperature was increased to 900°C at a rate of 5°C / min and held for 12 hours. The temperature was then reduced to 200°C and allowed to cool naturally to obtain a dark brown layered cathode material. The entropy value of the material was calculated to be 1.65R, which is a high-entropy cathode material.

[0079] The materials prepared above were assembled into coin cells for electrochemical performance characterization. The specific steps are as follows: The prepared positive electrode material, conductive carbon (SP), and binder PVDF were uniformly mixed in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) was added to form a slurry, which was then coated onto Al foil. After vacuum drying at 120℃ for 12 hours, the slurry was cut into 10mm diameter electrode sheets. In a glove box (H2O < 0.01ppm, O2 < 0.01ppm), lithium metal was used as the negative electrode, and a high-voltage electrolyte (5V high-voltage perfluorinated lithium-ion electrolyte from Duoduo Chemical) was used to assemble CR2025 coin cells. The cells were placed in the Xinwei electrochemical testing system at 10mA·g -1 The current density for charging and discharging is 2.0-4.9V, with a voltage range of 2.0-4.9V (vs. Li). + / Li).

[0080] Figure 1 shows the XRD pattern of the cathode material obtained in this example. It can be seen that the cathode material obtained in Example 1 has a good layered structure, belongs to the C2 / m space group, and the sharp diffraction peaks in the range of 20° to 30° belong to the LiMn6 superlattice of lithium-rich materials. It can be seen that the layered cathode material has very good crystallinity.

[0081] Figure 2 shows the charge-discharge curves of the cathode material obtained in this example. These electrochemical curves demonstrate good capacity utilization and cycle stability. Figure 3 shows the cycle performance curves of the cathode material obtained in this example. It can be seen that the cycle capacity of the material in Example 1 increases with each cycle.

[0082] Furthermore, the cathode material obtained in this example exhibits a relatively long oxygen plateau above 4.6V during the first charge cycle, achieving an initial charging capacity of 270mAh·g.-1 Discharge capacity 173mAh·g -1 Furthermore, the capacity increases with cycling, reaching a discharge specific capacity of 273 mAh·g after 30 cycles. -1 .

[0083] Example 2:

[0084] This example provides a cathode material and its preparation method, which includes:

[0085] According to the molecular formula LiNa 0.2 K 0.2 Mn 0.53 Ti 0.02 Mo 0.02 Mg 0.02 Nb 0.01 O 1.8 F 0.2 Weigh out 1.2413 g of lithium carbonate, 1.8431 g of manganese dioxide, 0.4488 g of potassium hydroxide, 0.32 g of sodium hydroxide, 0.06392 g of titanium dioxide, 0.0531 g of niobium pentoxide, 0.03224 g of magnesium oxide, 0.1151 g of molybdenum trioxide, and 0.2075 g of lithium fluoride (at a 0.04 mol ratio) and place them in a mortar. Grind by hand for 30 minutes, then pour the mixture into a ball mill jar. Add zirconium beads at a mass ratio of 1:4 (raw material: zirconium beads), then add 15 mL of anhydrous ethanol. Place the jar in a planetary ball mill at 20 °C. The mixture was ball-milled at 0 r / min for 12 h. The mixed raw materials were then placed in an oven and dried at 80 °C for 12 h. The powder was then ground into powder using an agate mortar. 0.5 g of the powder was weighed and placed in a tableting mold. The tablets were pressed at 10 MPa for 1 min to obtain 3 mm discs. The discs were placed in a 15 mL corundum crucible and heated to 900 °C in a muffle furnace at a heating rate of 5 °C / min. The temperature was held for 6 h and then naturally cooled to obtain a bright orange layered cathode material. The entropy value of the material was calculated to be 1.58R, which is a high-entropy cathode material.

[0086] Figure 4 shows the first charge-discharge curve of the cathode material in this example; Figure 5 shows the cycle performance curve of the cathode material obtained in this example, which shows that the cycle performance is very stable.

[0087] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material had a first-cycle discharge capacity of 183.32 mAh·g. -1 The discharge capacity after 30 cycles is 181.12 mAh / g, with a retention rate of 98.8%.

[0088] Example 3:

[0089] This example provides a cathode material and its preparation method, which includes:

[0090] According to the molecular formula LiNa 0.2 K 0.15 Mn 0.56 Zr 0.015 Cu 0.025 Mg 0.05 O 1.8 F 0.2 Weigh out 1.2413 g of lithium carbonate, 2.2081 g of manganese dioxide, 0.32 g of sodium hydroxide, 0.3366 g of potassium hydroxide, 0.0739 g of zirconium dioxide, 0.07955 g of copper oxide, 0.0322 g of magnesium oxide, and 0.2075 g of lithium fluoride in a mortar. Grind by hand for 30 minutes, then pour into a ball mill jar. Add zirconium beads at a mass ratio of raw material to zirconium beads of 1:4. Then add 15 mL of anhydrous ethanol and place in a planetary ball mill at 200 rpm. The mixture was ball-milled at a speed of 1 / min for 12 hours. The mixed raw materials were then placed in an oven and dried at 80℃ for 12 hours. The powder was then ground into powder using an agate mortar. 0.5g of the powder was weighed and placed in a tableting mold. The tablets were pressed at 10MPa for 1 minute to obtain 3mm discs. The discs were placed in a 15mL corundum crucible and placed in a muffle furnace. The temperature was increased to 900℃ at a rate of 5℃ / min and held for 12 hours. The material was then naturally cooled to obtain a brown layered cathode material. The entropy value of the material was calculated to be 1.56R.

[0091] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material had a first-cycle discharge capacity of 177.69 mAh·g. -1 After 30 activation cycles, it can reach 202 mAh·g. -1 .

[0092] Example 4:

[0093] This example provides a cathode material and its preparation method, which includes:

[0094] According to the molecular formula LiNa 0.15 K 0.15 Mn 0.635 Zr 0.015 Cu 0.025 Mg 0.025 O 1.7 Cl 0.3Weigh out 1.0862 g of lithium carbonate, 2.2082 g of manganese dioxide, 0.3367 g of potassium hydroxide, 0.24 g of sodium hydroxide, 0.0739 g of zirconium dioxide, 0.07955 g of copper oxide, 0.0403 g of magnesium oxide, and 0.5086 g of lithium chloride (at a 0.04 mol ratio) and place them in a mortar. Grind by hand for 30 minutes, then pour the mixture into a ball mill jar. Add zirconium beads at a mass ratio of raw material to zirconium beads of 1:4. Then add 15 mL of anhydrous ethanol and place the mixture in a planetary ball mill at 200 rpm. The mixture was ball-milled at a speed of min for 12 hours. The mixed raw materials were then placed in an oven and dried at 80°C for 12 hours. The powder was then ground into powder using an agate mortar. 0.5 g of the powder was weighed and placed in a tableting mold. The tablets were pressed at 10 MPa for 1 minute to obtain 3 mm discs. The discs were placed in a 15 mL corundum crucible and placed in a muffle furnace. The temperature was raised to 900°C at a rate of 5°C / min and held for 6 hours. The material was then naturally cooled to obtain an orange layered cathode material. The entropy value of the material was calculated to be 1.53R.

[0095] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material had a first-cycle discharge capacity of 85 mAh·g. -1 After 30 activation cycles, it can reach 120mAh·g. -1 .

[0096] The results indicate that in the cathode material system of the present invention, when halogens are used to replace part of the oxygen, especially when the halogen content is high, the effect of chlorine substitution is worse than that of fluorine substitution in Example 1.

[0097] Comparative Example 1:

[0098] This example provides a cathode material and its preparation method, which includes:

[0099] According to the molecular formula Li[Li 0.33 Mn 0.67 Weigh 2.474 g of lithium hydroxide monohydrate and 3.0806 g of manganese carbonate (0.04 mol) and hand-mill for 30 min. Pour the mixture into a ball mill jar and add zirconium beads at a mass ratio of 1:4 (raw material: zirconium beads). Then add 15 mL of anhydrous ethanol and place the mixture in a planetary ball mill at 200 r / min for 12 h. Place the mixed raw material in an oven and dry it at 80 °C for 12 h. Then grind the powder into powder using an agate mortar and pestle. Weigh 0.5 g of the powder raw material and place it in a tableting mold. Press it at 10 MPa for 2 min to obtain a 3 mm disc. Place the disc in a 15 mL corundum crucible and place it in a muffle furnace. Heat it to 700 °C at a heating rate of 5 °C / min and hold it for 24 h. After natural cooling, obtain a bright orange cathode material. The entropy value of this material is calculated to be 0.63R.

[0100] Figure 1 shows the XRD pattern of the cathode material obtained in Comparative Example 1. It can be seen that the material obtained in Comparative Example 1 also belongs to the layered structure with the space group C2 / m.

[0101] Referring to Figure 2, which shows the charge-discharge curves of the cathode material obtained in Example 1 and the cathode material obtained in Comparative Example 1, the electrochemical curves of the two materials are similar. An oxygen plateau appears above 4.5V during the first charge cycle. However, the electrochemical curve of Example 1 shows better capacity performance and cycle stability.

[0102] Referring to Figure 3, which shows the cycle performance curves of the cathode material obtained in Example 1 and the cathode material obtained in Comparative Example 1, it can be seen that the cycle capacity of Comparative Example 1 decays rapidly, while the cycle capacity of the material in Example 1 increases with each cycle.

[0103] Specifically, the electrochemical performance was characterized by assembling coin cells using the same method as in Example 1. The results showed that although the material exhibited a first-cycle discharge specific capacity of 263 mAh·g... -1 However, the capacity decays extremely quickly, and after five cycles, the capacity retention rate is less than 60%.

[0104] Comparative Example 2:

[0105] This example provides a cathode material and its preparation method, which includes:

[0106] According to the molecular formula Li[Li 0.434 Mn 0.566 ]O 1.7 F 0.3 Weigh out 1.7596 g of lithium carbonate, 1.9682 g of manganese dioxide, and 0.3112 g of lithium fluoride (at a 0.04 mol rate). Grind by hand for 30 min and pour into a ball mill jar. Add zirconium beads at a mass ratio of 1:4 (raw material: zirconium beads). Then add 15 mL of anhydrous ethanol and place in a planetary ball mill at 200 r / min for 12 h. Place the mixed raw material in an oven and dry it at 80 °C for 12 h. Then grind the powder into powder using an agate mortar. Weigh out 0.5 g of the powder and place it in a tableting mold. Press it at 10 MPa for 2 min to obtain a 3 mm disc. Place the disc in a 15 mL corundum crucible and place it in a muffle furnace. Heat it to 700 °C at a heating rate of 5 °C / min and hold for 24 h. Then cool it naturally to obtain an orange cathode material. The entropy value of this material is calculated to be 1.107R.

[0107] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material's first-cycle discharge capacity was only 110 mAh·g. -1 Furthermore, the capacity decays rapidly after 10 cycles, indicating poor stability. The first-cycle charge-discharge curve of the cathode material obtained in this example is shown in Figure 6.

[0108] Comparative Example 3:

[0109] This example provides a cathode material and its preparation method, which includes:

[0110] According to the molecular formula Li[Li 0.4 Mn 0.535 Zr 0.015 Cu 0.025 Mg 0.025 ]O 1.7 F 0.3 Weigh out 1.7068 g of lithium carbonate, 1.8604 g of manganese dioxide, 0.3112 g of lithium fluoride, 0.0739 g of zirconium dioxide, 0.07955 g of copper oxide, and 0.0403 g of magnesium oxide (0.04 mol). Place them in a mortar and grind by hand for 30 minutes. Then pour the mixture into a ball mill jar. Add zirconium beads at a mass ratio of raw material to zirconium beads of 1:4. Then add 15 mL of anhydrous ethanol and place the mixture in a planetary ball mill. Mill at 200 r / min for 1 minute. 2h; The mixed raw materials were placed in an oven and dried at 80℃ for 12h. Then, the powder was ground into powder using an agate mortar. 0.5g of powder raw material was weighed and placed in a tableting mold. The tablets were pressed at 10MPa for 1min to obtain 3mm discs. The discs were placed in a 15mL corundum crucible and placed in a muffle furnace. The temperature was increased to 900℃ at a rate of 5℃ / min and held for 12h. After natural cooling, the positive electrode material was obtained. The entropy value of the material was calculated to be 1.37R.

[0111] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material's first-cycle discharge capacity was only 64.87 mAh·g. -1 The capacity is relatively low. The first charge-discharge curve of the cathode material obtained in this example is shown in Figure 7, which shows that the first discharge capacity is relatively low.

[0112] Comparative Example 4:

[0113] This example provides a cathode material and its preparation method, which includes:

[0114] According to the molecular formula Li[Na] 0.217 K 0.217 Mn 0.566 ]O 1.7 F 0.3Weigh 1.0862 g of lithium carbonate, 1.9682 g of manganese dioxide, 0.4870 g of potassium hydroxide, 0.3472 g of sodium hydroxide, and 0.3112 g of lithium fluoride (0.04 mol) and place them in a mortar. Grind by hand for 30 min and then pour into a ball mill jar. Add zirconium beads at a mass ratio of raw material to zirconium beads of 1:4. Then add 15 mL of anhydrous ethanol and place in a planetary ball mill at a speed of 200 r / min for 12 h. Place the mixed raw material in an oven and dry it at 80 °C for 12 h. Then grind the powder into powder using an agate mortar. Weigh 0.5 g of the powder raw material and place it in a tableting mold. Press it at 15 MPa for 1 min to obtain a 3 mm disc. Place the disc in a 15 mL corundum crucible and place it in a muffle furnace. Heat it to 900 °C at a heating rate of 5 °C / min and hold it for 12 h. Then cool it naturally to obtain the cathode material. The entropy value of the material is calculated to be 1.41R.

[0115] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material's first-cycle discharge capacity was only 19.27 mAh·g. -1 The capacity is extremely low. The first charge-discharge curve of the cathode material obtained in this example is shown in Figure 8, which shows that the first discharge capacity is low.

[0116] Comparative Example 5:

[0117] This example provides a cathode material and its preparation method, which includes:

[0118] According to the molecular formula LiNa 0.15 K 0.15 Mn 0.635 Zr 0.015 Cu 0.025 Mg 0.025 Weigh out 1.5517g of lithium carbonate, 2.2081g of manganese dioxide, 0.3367g of potassium hydroxide, 0.24g of sodium hydroxide, 0.0739g of zirconium dioxide, 0.07955g of copper oxide, and 0.0403g of magnesium oxide in a mortar. Grind by hand for 30 minutes, then transfer to a ball mill jar. Add zirconium beads at a mass ratio of 1:4 (raw material: zirconium beads), then add 15mL of anhydrous ethanol. Place the mixture in a planetary ball mill at 200 rpm. The mixture was ball-milled at a speed of 1000 for 12 hours. The mixed raw materials were then placed in an oven and dried at 80°C for 12 hours. The powder was then ground into powder using an agate mortar. 0.5 g of the powder was weighed and placed in a tableting mold. The tablets were pressed at 15 MPa for 1 minute to obtain 3 mm discs. The discs were placed in a 15 mL corundum crucible and placed in a muffle furnace. The temperature was increased to 900°C at a rate of 5°C / min and held for 12 hours. The material was then naturally cooled to obtain the cathode material. The entropy value of the material was calculated to be 1.10R.

[0119] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material's first-cycle discharge capacity was only 52.8 mAh·g. -1 The capacity is relatively low. The first charge-discharge curve of the cathode material obtained in this example is shown in Figure 9, which shows that the first discharge capacity is relatively low.

[0120] Furthermore, Figure 10 shows the cycle performance curves of the cathode materials obtained in Comparative Examples 3, 4, and 5. It can be seen that there is an activation trend during the cycling process, but the capacity is much lower than the discharge specific capacity in the examples.

[0121] Comparative Example 6:

[0122] This example provides a cathode material and its preparation method, which includes:

[0123] According to the molecular formula Li[Na] 0.217 K 0.217 Mn 0.5 Zr 0.017 Cu 0.027 Mg 0.025 ]O 1.7 F 0.3 Weigh out 1.0862 g of lithium carbonate, 1.7387 g of manganese dioxide, 0.4870 g of potassium hydroxide, 0.3472 g of sodium hydroxide, 0.0837 g of zirconium dioxide, 0.0859 g of copper oxide, 0.0403 g of magnesium oxide, and 0.3112 g of lithium fluoride (0.04 mol) and place them in a mortar. Grind by hand for 30 minutes, then pour into a ball mill jar. Add zirconium beads at a mass ratio of raw material to zirconium beads of 1:4. Then add 15 mL of anhydrous ethanol and place in a planetary ball mill at 200 rpm. The mixture was ball-milled at a speed of min for 12 hours. The mixed raw materials were then placed in an oven and dried at 80°C for 12 hours. The powder was then ground into powder using an agate mortar. 0.5 g of the powder was weighed and placed in a tableting mold. The tablets were pressed at 10 MPa for 1 minute to obtain 3 mm discs. The discs were placed in a 15 mL corundum crucible and placed in a muffle furnace. The temperature was increased to 900°C at a rate of 5°C / min and held for 12 hours. The material was then naturally cooled to obtain an orange layered cathode material. The entropy value of the material was calculated to be 1.69R.

[0124] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material had an initial discharge capacity of approximately 32.3 mAh·g. -1 Its capacity is extremely low.

[0125] Comparative Example 7:

[0126] This example provides a cathode material and its preparation method, which includes:

[0127] According to the molecular formula Li[Li 0.4Mn 0.535 Zr 0.015 Ti 0.025 Mo 0.025 ]O 1.7 F 0.3 Weigh out 1.7068 g of lithium carbonate, 1.8604 g of manganese dioxide, 0.3112 g of lithium fluoride, 0.0739 g of zirconium dioxide, 0.0799 g of titanium dioxide, and 0.1439 g of molybdenum trioxide (at a 0.04 mol) and place them in a mortar. Grind by hand for 30 minutes, then pour the mixture into a ball mill jar. Add zirconium beads at a mass ratio of raw material to zirconium beads of 1:4. Then add 15 mL of anhydrous ethanol and place the jar in a planetary ball mill. Mill at 200 r / min for 12 minutes. h; The mixed raw materials were placed in an oven and dried at 80℃ for 12 hours. Then, the powder was ground into powder using an agate mortar. 0.5g of powder raw material was weighed and placed in a tableting mold. The tablets were pressed at 10MPa for 1 minute to obtain 3mm discs. The discs were placed in a 15mL corundum crucible and placed in a muffle furnace. The temperature was increased to 900℃ at a rate of 5℃ / min and held for 12 hours. After natural cooling, an orange layered cathode material was obtained. The entropy value of the material was calculated to be 1.37R.

[0128] Electrochemical performance was characterized by assembling the material into coin cells using the same method as in Example 1. The results showed that the material's first-cycle discharge capacity was approximately 93 mAh·g. -1 .

[0129] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0130] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A positive electrode material, characterized in that, The chemical formula of the cathode material is: Li 1+n Mn x AM y TM z O 2-m Q m ; Where n is 0-0.4 and x is 0.5-0.7; AM is selected from one or more combinations of Na and K, each y is independently 0.1-0.25, and when there are multiple AM, the sum of all y is less than or equal to 0.4; TM is selected from one, two or more combinations of Zr, Cu, Mg, Ti, Fe, and Al, each z is independently 0.01-0.1, and the sum of n, x, all y and all z is 1; Q is selected from one, two or more combinations of F, Cl, Br, and I, each m is independently 0.1-0.35, and when there are multiple Q, the sum of all m is less than or equal to 0.

4.

2. The cathode material according to claim 1, characterized in that, AM is selected from the combination of Na and K.

3. The cathode material according to claim 1, characterized in that, Each y is independently 0.1-0.

2.

4. The cathode material according to claim 1, characterized in that, TM is selected from one, two, or a combination of three of Zr, Cu, and Mg.

5. The positive electrode material according to claim 1, characterized in that, TM contains at least one selected from Zr, Cu, Mg, and a combination of one, two, or three selected from Ti (titanium), Fe (iron), and Al (aluminum).

6. The cathode material according to claim 1, characterized in that, TM is selected from a combination of Zr, Cu, and Mg.

7. The cathode material according to claim 1, characterized in that, Each z is independently between 0.01 and 0.

07.

8. The positive electrode material according to claim 1, characterized in that, Q is selected from F.

9. The positive electrode material according to claim 1, characterized in that, Each m is independently 0.15-0.

30.

10. The cathode material according to claim 1, characterized in that, The chemical formula of the cathode material is: Li1[Li n Mn x Na y1 K y2 Zr z1 Cu z2 Mg z3 ]O 2-m1 F m1 ; Where n is 0-0.4, x is 0.5-0.7; y1 and y2 are independently 0.15-0.22, z1, z2 and z3 are independently 0.01-0.05, m1 is 0.15-0.35, and n+x+y1+y2+z1+z2+z3=1.

11. A positive electrode material, characterized in that, The chemical formula of the cathode material is: Li1[Li n Mn x Na y3 K y4 Ti z4 Mo z5 Mg z6 Nb z7 O 2-m2 F m2 ; Where n is 0-0.4, x is 0.5-0.7; y3 and y4 are independently 0.15-0.22, z4, z5, z6 and z7 are independently 0.01-0.04, m2 is 0.15-0.25, and n+x+y3+y4+z4+z5+z6+z7=1.

12. The cathode material according to any one of claims 1-11, characterized in that, The cathode material has a layered structure and belongs to the C2 / m space group.

13. The cathode material according to any one of claims 1-11, characterized in that, The entropy value of the cathode material is greater than or equal to 1.5R.

14. The cathode material according to claim 13, characterized in that, The entropy value of the cathode material is greater than or equal to 1.8R.

15. The cathode material according to claim 14, characterized in that, The entropy value of the cathode material is greater than or equal to 2.0R.

16. The cathode material according to any one of claims 1-11, characterized in that, The entropy value of the cathode material is 1.5R-2.0R.

17. A method for preparing the cathode material according to any one of claims 1-16, characterized in that, The preparation method includes: weighing each raw material according to the molecular weight ratio, mixing, adding solvent, grinding, drying the ground material, and then sintering to produce a positive electrode material.

18. The method for preparing the cathode material according to claim 17, characterized in that, The raw materials include lithium salts as a lithium source and corresponding oxides, hydroxides, or fluorides; and / or, The solvent is anhydrous ethanol; and / or, The grinding is performed using ball milling; and / or, The calcination is controlled to be carried out at 700-1100°C; and / or, The calcination time is controlled to be 6-18 hours; and / or, The calcination is a one-step sintering process; and / or, The heating rate of the calcination is controlled to be 1-15℃ / min; and / or, The calcination is controlled to be carried out in an air atmosphere or an oxygen atmosphere.

19. The method for preparing the cathode material according to claim 17, characterized in that, The heating rate of the calcination is controlled to be 5-10℃ / min.

20. An electrode sheet comprising a current collector and an active material, said active material comprising a conductive agent and a binder, characterized in that, The active material further comprises the cathode material as described in any one of claims 1-16.

21. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in any one of claims 1-16 or the electrode sheet as described in claim 20.

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