A positive electrode material, a preparation method and application thereof

Abstract

The application discloses a positive electrode material and a preparation method and application thereof, and the chemical formula of the positive electrode material is Li 1+n Mn x AM y TM z O 2‑ m Q m ; n is 0-0.4, x is 0.5-0.7; AM is Na and / or K, each y is independently 0.1-0.25, and the total sum of all y is less than or equal to 0.4; TM is Zr, Cu, Mg, Ti, Fe, Al and the like, each z is independently 0.01-0.1, and the total sum of n, x, all y and all z is 1; Q is F, Cl, Br, I and the like, each m is independently 0.1-0.35, and the total sum of all m is less than or equal to 0.4; during preparation, the raw materials of the components are mixed and ground, and then one-step sintering is carried out, so that the preparation method is simple and easy to operate; moreover, the prepared positive electrode material also has excellent electrochemical performance, which indicates that the application can avoid doping of the metals such as Ni and Co which are relatively expensive, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, in particular to lithium-ion battery energy storage, and specifically to a positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become an important part of the electrochemical energy storage field due to their high energy density, no memory effect and long cycle life. They are widely used in large-scale energy storage, portable devices and power vehicles. However, with the further development of society, people's demand for the energy density of lithium-ion batteries has further increased. At the same time, reducing the application cost of batteries has also become one of the development focuses of lithium-ion batteries. Lithium-rich manganese-based layered cathode materials (xLiTMO2·(1-x)Li[Li 1 / 3Mn 2 / 3 ]O2, LRM (LRM) has a relatively high specific capacity due to the redox reaction of activated anions at high potentials (>4.5V), resulting in additional specific capacity. At the same time, the high Mn content of LRM itself makes its preparation cost relatively low. Therefore, LRM, with its combination of high specific capacity and low cost, has become a promising candidate for the next generation of lithium-ion battery cathode materials.

[0003] However, this material still has the following significant problems: (1) Irreversible loss of oxygen anions at high potential. In order for lithium-rich materials to achieve high capacity, it is necessary to activate oxygen anions at a higher cutoff voltage (>4.5V) to enable them to participate in charge compensation. The oxygen anions in LRM are easily oxidized to oxygen at high potential. This part of oxygen will escape from the surface of the material and will also attack the liquid electrolyte, increasing the degree of interfacial side reactions and causing structural degradation of the material and irreversible loss of capacity. Therefore, the first-cycle coulombic efficiency of LRM is generally low; (2) Irreversible phase change of crystal structure. Li + After deintercalation, vacancies will be 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, thereby leading to the migration of transition metal ions (TM), causing an irreversible phase transition from a layered structure to a spinel structure, resulting in a decrease in the material's cyclic stability.

[0004] To address the problems of LRM, existing technical approaches primarily focus on doping, coating, and regulating synthesis methods. For example, regulating the synthesis atmosphere to achieve preferential growth of specific crystal planes; inducing the growth of spinel-layered composite phases with sulfate ion groups; and improving the cycling stability of materials by coating ZrO2 materials. These methods alleviate the aforementioned issues to some extent, but the processing is relatively cumbersome, often utilizing sol-gel or co-precipitation methods and secondary coating methods, resulting in lengthy and difficult procedures. Furthermore, performance improvements are often achieved through the introduction of high-cost cobalt in material design, impacting LRM costs. Furthermore, the excessive redox of oxygen anions is not effectively suppressed, failing to fundamentally address the issue of poor LRM cycling.

[0005] In addition, some researchers have prepared high-entropy doped layered positive electrode materials to improve cycle performance and low first efficiency. However, in actual operation, they generally add metals such as Ni and Co, which are more effective but more expensive, to form a high-entropy state, which is not conducive to reducing costs. At the same time, in order to pursue better results, it is basically necessary to undergo multiple high-temperature calcinations, or further combine them with the co-precipitation method for preparation. However, multiple calcinations are not only time-consuming and labor-intensive, but also have high energy consumption. In particular, the co-precipitation method requires the use of a large amount of solvents, which is prone to produce industrial wastewater and requires additional wastewater post-treatment processes. This is not conducive to large-scale industrial production, and there is an obvious problem of losing sight of one thing while focusing on another.

[0006] It should be noted that the information disclosed in the background section is only used to understand the background of the present application. Therefore, the background section of the present invention may include background information about the problem or environment of the present invention, but does not necessarily describe the prior art. Therefore, the content included in the background section does not constitute an admission by the applicant of the prior art. Summary of the Invention

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

[0008] The novel cathode material provided by the present invention is a low-cost, high-entropy, lithium-rich manganese-based layered cathode material, which can effectively inhibit the unstable activity of oxygen ions and delay the irreversible phase change of the material, thus overcoming the problem of the existing high-entropy doped layered cathode materials that have to compromise on one thing while focusing on another.

[0009] The present invention also provides a method for preparing the above-mentioned new positive electrode material, which can be simply operated to prepare a positive electrode material with excellent electrochemical properties, indicating that the design of the new positive electrode material of the present invention reduces the requirements for processing technology, is conducive to simplifying the processing process, and is further conducive to large-scale industrial production.

[0010] In order to achieve the above object, a technical solution adopted by the present invention is:

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

[0012] Wherein, n is 0-0.4, x is 0.5-0.7;

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

[0014] TM is selected from a combination of one or more 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 a combination of one or more of F (fluorine), Cl (chlorine), Br (bromine), and I (iodine), each m is independently 0.1-0.35, and when Q has multiple, 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 invention, each y is independently 0.1-0.2.

[0018] In some embodiments of the present invention, TM is selected from the group consisting of Zr, Cu, and Mg.

[0019] In some embodiments of the invention, each z is independently 0.01-0.07.

[0020] In some embodiments of the present invention, Q is selected from F.

[0021] In some embodiments of the present invention, each m is independently 0.15-0.30.

[0022] According to some preferred aspects of the present invention, the chemical formula of the positive electrode material is:

[0023] Li1[Li n Mn x Na y1 K y2 Zr z1 Cu z2Mg z3 ]O 2-m1 F m1 ;

[0024] Wherein, n and x are the same as above; 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.

[0025] According to some preferred aspects of the present invention, the chemical formula of the positive electrode material is:

[0026] Li1[Li n Mn x Na y3 K y4 Ti z4 Mo z5 Mg z6 Nb z7 ]O 2-m2 F m2 ;

[0027] Wherein, n and x are the same as above; 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.

[0028] According to the present invention, the positive electrode material has a layered structure and belongs to the C2 / m space group.

[0029] In some embodiments of the present invention, the entropy value of the positive electrode material is greater than 1.5R, further greater than 1.8R, and further greater than 2.0R.

[0030] Another technical solution provided by the present invention is a method for preparing the positive electrode material described above, the method comprising: weighing the raw materials according to the molecular weight ratio, mixing, adding a solvent, grinding, drying the ground material, and then sintering to prepare the positive electrode material.

[0031] In some embodiments of the present invention, the raw material includes a lithium salt as a lithium source and an oxide, hydroxide or fluoride of the corresponding component.

[0032] In some embodiments of the present invention, the AM element may be added in the form of hydroxide, for example, sodium hydroxide and / or potassium hydroxide may be added.

[0033] In some embodiments of the present invention, the TM elements may be added in the form of oxides, for example, copper oxide, zirconium dioxide, magnesium oxide, titanium dioxide, iron oxide, aluminum oxide, etc. may be added.

[0034] In some embodiments of the present invention, the Mn (manganese) element may be added in the form of an oxide, such as manganese dioxide.

[0035] In some embodiments of the present invention, for the Li (lithium) element, a lithium salt may be added, for example, lithium carbonate.

[0036] In some embodiments of the present invention, the Q element may be added in the form of lithium halide. For example, for fluorine, lithium fluoride may be added, and for chlorine, lithium chloride may be added.

[0037] In some embodiments of the present invention, the solvent is anhydrous ethanol.

[0038] In some embodiments of the present invention, the grinding is performed by ball milling. Furthermore, during the ball milling process, the rotation speed of the ball milling is 100-400 r / min, and the ball milling time is 12-16 h.

[0039] In some embodiments of the present invention, after grinding, the powdered raw material is pressed into tablets. Further, the pressure used for pressing is 5-30 MPa, and the holding time during pressing is 1-5 minutes.

[0040] In some embodiments of the present invention, the calcination is controlled to be performed at 700-1100°C.

[0041] In some embodiments of the present invention, the calcination time is controlled to be 6-18 hours.

[0042] In some embodiments of the present invention, the calcination is a one-step sintering.

[0043] In some embodiments of the present invention, the heating rate of the calcination is controlled to be 1-15° C. / min, further 5-10° C. / min.

[0044] In some embodiments of the present invention, the calcination is controlled to be performed in an air atmosphere or an oxygen atmosphere.

[0045] The present invention utilizes a simple high-temperature solid-phase method to select oxides, hydroxides, fluorides of various metal ions and lithium salts as a lithium source, and ball-mills the mixture in a solvent such as anhydrous ethanol as a dispersant. The mixture is then sintered in a muffle furnace in one step to obtain a positive electrode material with a stable crystal structure. Furthermore, multiple elements enter the material lattice to form a pure layered phase, eliminating the need for secondary processing and making the process quick and convenient.

[0046] Another technical solution provided by the present invention is a lithium-ion battery, comprising the positive electrode material described above.

[0047] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0048] Based on the defects of existing high-entropy doping designs, such as the need to introduce expensive metals such as Ni and Co, the need to cooperate with multiple high-temperature calcination processes, or the need for additional coating designs that complicate operations, the inventors of the present invention unexpectedly discovered during extensive experimental research that by introducing a specific content of alkali metal sodium and / or potassium to replace manganese in the high-entropy doping design, and using a high content of halogen to replace oxygen, the positive electrode material of the present invention can have excellent electrochemical properties while avoiding the use of expensive metals such as Ni and Co for doping, and can also simplify the production process, requiring only a single calcination step. After further mechanistic research, it is analyzed that it is because the substitution / doping of multiple elements in the material system of the present invention plays a synergistic role, thereby getting rid of the dependence on expensive nickel and cobalt, reducing the cost of using LRM, and the combined effect of the substitution / doping of multiple elements enables the material to obtain a stable specific high-entropy structure in a one-step sintering process. In particular, this structure has an excellent inhibitory effect on the excessive redox of oxygen anions and also has an excellent inhibitory effect on the phase change of the material, thereby improving the cycle stability of the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The XRD spectra of the positive electrode material obtained in Example 1 of the present invention and the positive electrode material obtained in Comparative Example 1 show that the positive electrode material obtained in Example 1 has a good layered structure and belongs to the C2 / m space group. The sharp diffraction peak in the range of 20° to 30° belongs to the LiMn6 superlattice of the lithium-rich material. It can be seen that the layered positive electrode material has very good crystallinity. It can be seen that the material obtained in Comparative Example 1 also has a layered structure and the space group is C2 / m.

[0050] Figure 2 The charge-discharge curves of the positive electrode material obtained in Example 1 of the present invention and the positive electrode material obtained in Comparative Example 1 are similar. An oxygen plateau appears above 4.5V during the first charge cycle, but the electrochemical curve of Example 1 shows better capacity and cycle stability.

[0051] Figure 3 The cycle performance curves of the positive electrode material obtained in Example 1 of the present invention and the positive electrode material obtained in Comparative Example 1 show that the cycle capacity of Comparative Example 1 decays rapidly, while the cycle capacity of the material in Example 1 increases cycle by cycle.

[0052] Figure 4 This is the first cycle charge and discharge curve of the positive electrode material obtained in Example 2 of the present invention;

[0053] Figure 5This is the cycle performance curve of the positive electrode material obtained in Example 2 of the present invention;

[0054] Figure 6 This is the first cycle charge and discharge curve of the positive electrode material obtained in Comparative Example 2 of the present invention;

[0055] Figure 7 This is the first cycle charge and discharge curve of the positive electrode material obtained in Comparative Example 3 of the present invention. It can be seen that the first cycle discharge capacity is relatively low;

[0056] Figure 8 This is the first cycle charge and discharge curve of the positive electrode material obtained in Comparative Example 4 of the present invention. It can be seen that the first cycle discharge capacity is relatively low;

[0057] Figure 9 This is the first cycle charge and discharge curve of the positive electrode material obtained in Comparative Example 5 of the present invention. It can be seen that the first cycle discharge capacity is relatively low;

[0058] Figure 10 These are the cycle performance curves of the positive electrode materials obtained in Comparative Examples 3, 4, and 5 of the present invention. It can be seen that there is an activation trend during the cycle, but the capacity is far lower than the discharge specific capacity in the examples. DETAILED DESCRIPTION

[0059] The above scheme is further described below in conjunction with specific examples; it should be understood that these examples 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 examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are generally the conditions in routine experiments.

[0060] Unless otherwise specified in the following examples, all raw materials were purchased from commercial sources or prepared by conventional methods in the art.

[0061] Example 1

[0062] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0063] 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 0.3(According to 0.04 mol) Weigh 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 in a mortar, grind by hand for 30 min, pour into a ball mill, add zirconium beads according to the mass ratio of raw materials: zirconium beads = 1:4, then add 15 mL of anhydrous ethanol, place in a planetary ball mill at a speed of 200 r / min for 12 h ; The mixed raw materials were placed in an oven and dried at 80°C for 12 hours, then ground into powder with an agate mortar, 0.5g of the powder raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 10MPa for 2 minutes to obtain a 3mm disc; the disc was placed in a 15mL corundum crucible, placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min and kept warm for 12 hours, then cooled to 200°C and cooled naturally to obtain a dark brown layered positive electrode material. After calculation, the entropy value of the material was 1.65R, which is a high-entropy positive electrode material.

[0064] The materials prepared above were assembled into button cells for characterization of electrochemical performance. The specific steps are as follows: the prepared positive electrode material, conductive carbon (SP) and binder PVDF were evenly mixed in a mass ratio of 7:2:1, an appropriate amount of N-methylpyrrolidone (NMP) was added to form a slurry, coated on Al foil, vacuum dried at 120°C for 12 hours, and then cut into pole pieces with a diameter of 10 mm. In a glove box (H2O < 0.01ppm, O2 < 0.01ppm), lithium metal was used as the negative electrode and high-voltage electrolyte (Duoduo Chemical's lithium perfluorinated 5V high-voltage electrolyte) was assembled into CR2025 button cells. The battery was placed in a Xinwei electrochemical test system, 10mA·g -1 The current density is charged and discharged, and the voltage range is 2.0-4.9V (vs.Li + / Li).

[0065] The material has a long oxygen platform above 4.6V in the first cycle, and the first charge capacity reaches 270mAh·g -1 , discharge capacity 173mAh·g -1 , and the capacity increases with the cycle, and the discharge capacity can reach 273mAh·g after 30 cycles. -1 .

[0066] Example 2

[0067] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0068] According to the molecular formula LiNa 0.2 K 0.2 Mn 0.53 Ti 0.02 Mo0.02 Mg 0.02 Nb 0.01 O 1.8 F 0.2 (According to 0.04 mol) Weigh 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 into a mortar, grind by hand for 30 min and pour into a ball mill jar, add zirconium beads according to the mass ratio of raw materials to zirconium beads = 1:4, then add 15 mL of anhydrous ethanol, place in a planetary ball mill and grind for 20 min. The raw materials were ball-milled at a speed of 0 r / min for 12 h; the mixed raw materials were placed in an oven and dried at 80 ° C for 12 h, and then ground into powder with an agate mortar. 0.5 g of the powder raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 10 MPa for 1 min to obtain a 3 mm disc; the disc was placed in a 15 mL corundum crucible, placed in a muffle furnace, and heated to 900 ° C at a rate of 5 ° C / min. The temperature was kept for 6 h and then naturally cooled to obtain a bright orange layered positive electrode material. The entropy value of the material was calculated to be 1.58R, which is a high entropy positive electrode material.

[0069] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was 183.32 mAh·g -1 , 30-cycle discharge capacity is 181.12mAh / g, and retention rate is 98.8%.

[0070] Example 3

[0071] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0072] 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(0.04 mol) Weigh 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 into a mortar, grind by hand for 30 min and pour into a ball mill, add zirconium beads according to the mass ratio of raw materials: zirconium beads = 1:4, then add 15 mL of anhydrous ethanol, place in a planetary ball mill and grind at 200 r / min ball milling for 12 hours; the mixed raw materials were placed in an oven and dried at 80°C for 12 hours, then ground into powder with an agate mortar, 0.5g of the powder raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 10MPa for 1 minute to obtain a 3mm disc; the disc was placed in a 15mL corundum crucible, placed in a muffle furnace and heated to 900°C at a rate of 5°C / min, kept warm for 12 hours, and then naturally cooled to obtain a brown layered positive electrode material. The entropy value of the material was calculated to be 1.56R.

[0073] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was 177.69 mAh·g -1 , after 30 cycles of activation, it can reach 202mAh·g -1 .

[0074] Example 4

[0075] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0076] 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 0.3(According to 0.04 mol) Weigh 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 in a mortar, grind by hand for 30 min, pour into a ball mill, add zirconium beads according to the mass ratio of raw materials: zirconium beads = 1:4, then add 15 mL of anhydrous ethanol, place in a planetary ball mill at 200 r / min. min ball milling for 12 hours; the mixed raw materials were placed in an oven and dried at 80 ° C for 12 hours, and then ground into powder with an agate mortar, 0.5 g of the powder raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 10 MPa for 1 minute to obtain a 3 mm disc; the disc was placed in a 15 mL corundum crucible, placed in a muffle furnace, and heated to 900 ° C at a rate of 5 ° C / min. The temperature was kept for 6 hours and then naturally cooled to obtain an orange layered positive electrode material. The entropy value of the material was calculated to be 1.53R.

[0077] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was 85 mAh·g -1 After 30 cycles of activation, it can reach 120mAh g -1 .

[0078] The results show that in the cathode material system of the present invention, when halogen is 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.

[0079] Comparative Example 1

[0080] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0081] According to the molecular formula Li[Li 0.33 Mn 0.67 ]O2 (according to 0.04 mol) weighed 2.474 g of lithium hydroxide monohydrate and 3.0806 g of manganese carbonate, hand-milled for 30 minutes, and poured into a ball mill jar, and zirconium beads were added according to the mass ratio of raw materials: zirconium beads = 1:4, and then 15 mL of anhydrous ethanol was added, and the mixture was placed in a planetary ball mill and ball milled at a speed of 200 r / min for 12 hours; the mixed raw materials were placed in an oven and air-dried at 80°C for 12 hours, and then the powder was ground into powder with an agate mortar, 0.5 g of the powder raw material was weighed and placed in a tablet pressing mold, and the pressure was maintained at 10 MPa for 2 minutes to obtain a 3 mm disc; the disc was placed in a 15 mL corundum crucible, placed in a muffle furnace, and heated to 700°C at a rate of 5°C / min. The temperature was kept at this temperature for 24 hours, and then naturally cooled to obtain a bright orange positive electrode material. The entropy value of the material was calculated to be 0.63R.

[0082] The electrochemical performance of the button cell was characterized by assembling it in the same way as in Example 1. The results showed that although the first cycle discharge capacity of the material was 263 mAh·g -1 , but it decays very quickly, and the capacity retention rate after five cycles is less than 60%.

[0083] Comparative Example 2

[0084] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0085] According to the molecular formula Li[Li 0.434 Mn 0.566 ]O 1.7 F 0.3 1.7596 g of lithium carbonate, 1.9682 g of manganese dioxide, and 0.3112 g of lithium fluoride (based on 0.04 mol) were weighed, hand-milled for 30 minutes, and poured into a ball mill. Zirconium beads were added according to the mass ratio of raw materials: zirconium beads = 1:4, and then 15 mL of anhydrous ethanol was added. The mixture was placed in a planetary ball mill and ball milled at a speed of 200 r / min for 12 hours; the mixed raw materials were placed in an oven and air-dried at 80°C for 12 hours, and then the powder was ground into powder with an agate mortar. 0.5 g of the powdered raw material was weighed and placed in a tablet pressing mold. The pressure was maintained at 10 MPa for 2 minutes to obtain a 3 mm disc; the disc was placed in a 15 mL corundum crucible, placed in a muffle furnace, and heated to 700°C at a rate of 5°C / min. The temperature was kept for 24 hours and then naturally cooled to obtain an orange positive electrode material. The entropy value of the material was calculated to be 1.107R.

[0086] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was only 110 mAh·g -1 , and the capacity decays rapidly after 10 cycles, and the stability is poor.

[0087] Comparative Example 3

[0088] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0089] 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(0.04 mol) Weigh 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 in a mortar. Grind by hand for 30 min and pour into a ball mill. Add zirconium beads according to the mass ratio of raw materials to zirconium beads = 1:4. Then add 15 mL of anhydrous ethanol and place in a planetary ball mill at a speed of 200 r / min for 1 minute. 2h; the mixed raw materials were placed in an oven and dried at 80°C for 12h, then the powder was ground into powder with an agate mortar, 0.5g of the powder raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 10MPa for 1min to obtain a 3mm disc; the disc was placed in a 15mL corundum crucible, placed in a muffle furnace and heated to 900°C at a rate of 5°C / min for 12h, and then naturally cooled to obtain the positive electrode material. The entropy value of the material was calculated to be 1.37R.

[0090] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was only 64.87 mAh·g -1 , lower capacity.

[0091] Comparative Example 4

[0092] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0093] According to the molecular formula Li[Na 0.217 K 0.217 Mn 0.566 ]O 1.7 F 0.3 (0.04 mol) 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 were weighed and placed in a mortar. After hand grinding for 30 minutes, the mixture was poured into a ball mill. Zirconium beads were added according to the mass ratio of raw materials: zirconium beads = 1:4, and then 15 mL of anhydrous ethanol was added. The mixture was placed in a planetary ball mill and ball milled at a speed of 200 r / min for 12 hours. The mixed raw materials were placed in an oven and air-dried at 80 ° C for 12 hours. The powder was then ground into powder using an agate mortar. 0.5 g of the powdered raw material was weighed and placed in a tablet pressing mold. The pressure was maintained at 15 MPa for 1 minute to obtain a 3 mm disc. The disc was placed in a 15 mL corundum crucible, placed in a muffle furnace, and heated to 900 ° C at a rate of 5 ° C / min. The temperature was kept for 12 hours and then naturally cooled to obtain the positive electrode material. The entropy value of the material was calculated to be 1.41R.

[0094] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was only 19.27 mAh·g -1 , very low capacity.

[0095] Comparative Example 5

[0096] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0097] According to the molecular formula LiNa 0.15 K 0.15 Mn 0.635 Zr 0.015 Cu 0.025 Mg 0.025 O2 (0.04 mol) was weighed. 1.5517 g of lithium carbonate, 2.2081 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 and 0.0403 g of magnesium oxide were placed in a mortar, hand-milled for 30 min, and then poured into a ball mill. Zirconium beads were added according to the mass ratio of raw materials: zirconium beads = 1:4, and then 15 mL of anhydrous ethanol was added. The mixture was placed in a planetary ball mill at 200 r / m in ball milling speed for 12 hours; the mixed raw materials were placed in an oven and dried at 80°C for 12 hours, then ground into powder with an agate mortar, 0.5g of the powder raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 15MPa for 1 minute to obtain a 3mm disc; the disc was placed in a 15mL corundum crucible, placed in a muffle furnace, and heated to 900°C at a rate of 5°C / min for 12 hours, and then naturally cooled to obtain the positive electrode material. The entropy value of the material was calculated to be 1.10R.

[0098] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was only 52.8 mAh·g -1 , lower capacity.

[0099] Comparative Example 6

[0100] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0101] 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(0.04 mol) Weigh 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 into a mortar, grind by hand for 30 min and pour into a ball mill jar, add zirconium beads according to the mass ratio of raw materials: zirconium beads = 1:4, then add 15 mL of anhydrous ethanol, place in a planetary ball mill at 200 r / min. min ball milling for 12 hours; the mixed raw materials were placed in an oven at 80 ° C for 12 hours, and then the powder was ground into powder with an agate mortar. 0.5 g of the powder raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 10 MPa for 1 minute to obtain a 3 mm disc; the disc was placed in a 15 mL corundum crucible, placed in a muffle furnace and heated to 900 ° C at a rate of 5 ° C / min for 12 hours, and then naturally cooled to obtain an orange layered positive electrode material. The entropy value of the material was calculated to be 1.69R.

[0102] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was about 32.3 mAh·g -1 , very low capacity.

[0103] Comparative Example 7

[0104] This example provides a positive electrode material and a preparation method thereof, the preparation method comprising:

[0105] According to the molecular formula Li[Li 0.4 Mn 0.535 Zr 0.015 Ti 0.025 Mo 0.025 ]O 1.7 F 0.3 (0.04 mol) Weigh 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 in a mortar, grind by hand for 30 min, and pour into a ball mill. Add zirconium beads according to the mass ratio of raw materials to zirconium beads = 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; the mixed raw materials were placed in an oven and dried at 80°C for 12 hours, then ground into powder using an agate mortar, 0.5g of the powdered raw materials were weighed and placed in a tablet pressing mold, and the pressure was maintained at 10MPa for 1 minute to obtain a 3mm disc; the disc was placed in a 15mL corundum crucible, placed in a muffle furnace and heated to 900°C at a rate of 5°C / min, kept warm for 12 hours, and then naturally cooled to obtain an orange layered positive electrode material. The entropy value of the material was calculated to be 1.37R.

[0106] The electrochemical performance of the coin cell was characterized by assembling it in the same manner as in Example 1. The results showed that the first cycle discharge capacity of the material was about 93 mAh·g -1 .

[0107] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0108] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A positive electrode material, characterized in that The chemical formula of the positive electrode material is: Li 1+n Mn x AM y TM z O 2-m Q m ; Wherein, n is 0-0.4, x is 0.5-0.7; AM is selected from a combination of one or more of Na and K, each y is independently 0.1-0.25, and when there are multiple AMs, the sum of all y is less than or equal to 0.4; TM is a combination of Zr, Cu, and Mg, 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 a combination of one or more of F, Cl, Br, and I, each m is independently 0.1-0.35, and when Q has multiple members, the sum of all m is less than or equal to 0.4; The entropy value of the positive electrode material is greater than 1.5R.

2. The positive electrode material according to claim 1, characterized in that AM is selected from a combination of Na and K; and / or, each y is independently 0.1-0.

2.

3. The positive electrode material according to claim 1, characterized in that Each z is independently 0.01-0.

07.

4. The positive electrode material according to claim 1, characterized in that Q is selected from F; and / or, each m is independently 0.15-0.

30.

5. The positive electrode material according to claim 1, characterized in that The chemical formula of the positive electrode material is: Li1[Li n Mn x The y1 K y2 Zr z1 The z2 Mg z3 ]O 2-m1 F m1 ; Wherein, n and x are the same as those in claim 1; 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.

6. The positive electrode material according to any one of claims 1 to 5, characterized in that The positive electrode material has a layered structure and belongs to the C2 / m space group; and / or the entropy value of the positive electrode material is greater than 1.8R.

7. The positive electrode material according to any one of claims 1 to 5, characterized in that The entropy value of the positive electrode material is greater than 2.0R.

8. The positive electrode material according to any one of claims 1 to 5, characterized in that The entropy value of the positive electrode material is greater than 1.5R and less than or equal to 2.0R.

9. A positive electrode material, characterized in that The chemical formula of the positive electrode material is: Li1[Li n Mr x So y3 K y4 Tea z4 Mo z5 Mg z6 No z7 ]O 2-m2 F m2 ; Wherein, 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.

10. The positive electrode material according to claim 9, characterized in that The positive electrode material has a layered structure and belongs to the C2 / m space group; and / or the entropy value of the positive electrode material is greater than 1.5R.

11. The positive electrode material according to claim 9, characterized in that The entropy value of the positive electrode material is greater than 1.8R.

12. The positive electrode material according to claim 11, characterized in that The entropy value of the positive electrode material is greater than 2.0R.

13. The positive electrode material according to claim 9, characterized in that The entropy value of the positive electrode material is greater than 1.5R and less than or equal to 2.0R.

14. A method for preparing the positive electrode material according to any one of claims 1 to 13, characterized in that: The preparation method comprises: weighing raw materials according to molecular weight ratio, mixing, adding solvent, grinding, drying the ground materials, and then sintering to prepare positive electrode materials.

15. The method for preparing the positive electrode material according to claim 14, characterized in that: The raw materials include lithium salt as a lithium source and oxides, hydroxides or fluorides of corresponding components; and / or, The solvent is anhydrous ethanol; and / or, The grinding is performed by ball milling; and / or, Controlling the calcination to be carried out at 700-1100° C.; and / or, Controlling the calcination time to be 6-18 hours; and / or, The calcination is a one-step sintering; and / or, Controlling the heating rate of the calcination to be 1-15°C / min; and / or, The calcination is controlled to be carried out in an air atmosphere or an oxygen atmosphere.

16. The method for preparing the positive electrode material according to claim 14, wherein: The heating rate of the calcination is controlled to be 5-10°C / min.

17. A lithium ion battery, characterized in that: The lithium-ion battery comprises the positive electrode material according to any one of claims 1 to 13.

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