Positive electrode material and preparation method and application thereof

Abstract

The invention discloses a positive electrode material as well as a preparation method and application thereof. 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 to 0.4, and x is 0.5 to 0.7; aM is Na and / or K, each y independently ranges from 0.1 to 0.25, and the sum of all y is smaller than or equal to 0.4; tM is Zr, Cu, Mg, Ti, Fe, Al or the like, each z is independently 0.01-0.1, and the sum of n, x, all y and all z is 1; q is F, Cl, Br, I and the like, each m independently ranges from 0.1 to 0.35, and the sum of all m is smaller than or equal to 0.4; during preparation, all the raw materials are mixed, ground and sintered in one step, the preparation method is simple and easy to operate, and the prepared positive electrode material also has excellent electrochemical performance, so that doping of metals such as Ni and Co which are relatively high in price can be avoided, 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 laminated positive electrode materials (xLiTMO2·(1-x)Li[Li 1 / 3Mn 2 / 3 ]O2, LRM) can activate anions to undergo redox reactions at high potentials (>4.5V) to exert additional specific capacity, making the specific capacity of this material relatively high. At the same time, the high Mn content of LRM itself makes its preparation cost relatively low. Therefore, LRM, which has both high specific capacity and low cost, has become a strong candidate for the next generation of lithium-ion battery positive electrode materials.

[0003] However, this material still has the following significant problems: (1) Irreversible loss of oxygen anions at high potentials. In order for lithium-rich materials to exert their high capacity, they need to activate oxygen anions at a higher cutoff voltage (>4.5V) to participate in charge compensation. The oxygen anions in LRM are easily oxidized to oxygen at high potentials. This oxygen will escape from the surface of the material and 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] In response to the problems existing in LMR, the existing technical means are mainly concentrated on doping, coating, and regulating synthesis methods. For example, the preferential growth of specific crystal faces can be achieved by regulating the synthesis atmosphere; sulfate ion groups induce the growth of spinel-layered composite phases; ZrO2 coating materials improve the cyclic stability of materials, etc. These methods have alleviated the above problems to a certain extent, but the processing methods are relatively cumbersome, mostly using sol-gel method or co-precipitation method and secondary coating method, with complicated steps and difficult to operate; at the same time, at the material design level, performance is often improved by introducing high-cost cobalt, which affects the cost of LRM; there is no good inhibitory effect on the excessive redox of oxygen anions, and the problem of poor LRM cycle cannot be fundamentally solved.

[0005] In addition, some researchers have prepared high-entropy doped layered positive electrode materials to improve cycle performance and low initial efficiency. However, in actual operations, they generally add metals such as Ni and Co that have better effects but are 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 the use of 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 the addition of wastewater post-treatment processes. This is not conducive to large-scale industrial production and there is an obvious problem of losing one thing while gaining another.

[0006] It should be noted that the information disclosed in the above background technology section is only used to understand the background of the present application, so the background technology section of the present invention may contain background information about the problem or environment of the present invention, but not necessarily describe the prior art. Therefore, the content contained in the background technology section is not an admission of the applicant to 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 to provide a new positive electrode material which 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 one calcination step.

[0008] The novel positive electrode material provided by the present invention is a low-cost high-entropy lithium-manganese-rich layered positive electrode 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 losing one thing while gaining another in the existing high-entropy doped layered positive electrode materials.

[0009] The present invention also provides a method for preparing the above-mentioned new positive electrode material, which can be simply operated to prepare the 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 one or more combinations 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 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 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 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, 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 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.

[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 preparation 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 a 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 element 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 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 min.

[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 conducts ball milling mixing under the condition of a solvent such as anhydrous ethanol as a dispersant. Then, through a one-step sintering method in a muffle furnace, a positive electrode material with a stable crystal structure can be obtained, and a variety of elements enter the material lattice to form a pure layered phase material, without the need for secondary treatment, which is convenient and quick.

[0046] Another technical solution provided by the present invention is a lithium-ion battery, wherein the lithium-ion battery comprises 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 the existing high entropy doping design, such as the need to introduce expensive metals such as Ni and Co, the need to cooperate with the processing process of multiple high-temperature calcinations, or the need for additional coating design to make the operation complicated, the inventors of the present invention unexpectedly found in a large number of experimental studies 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 avoid the use of expensive metals such as Ni and Co for doping while having excellent electrochemical properties, and can also simplify the production process, only one step of calcination is required; after further mechanism research, it is analyzed that it should be that under the material system of the present invention, the substitution / doping of multiple elements has a synergistic effect, thereby getting rid of the dependence on expensive nickel and cobalt, reducing the use cost of LRM, and the substitution / doping of multiple elements works together, so that the material obtains a stable specific high entropy structure in a one-step sintering process, especially the 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 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. It can be seen 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 belongs to a layered structure, and the space group is C2 / m.

[0050] Figure 2 The charge and 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 in electrochemical curves. An oxygen platform appears above 4.5V in the first cycle of charging, 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] Fig. 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] Fig.10 The cycle performance curves of the positive electrode materials obtained in Comparative Examples 3, 4 and 5 of the present invention show that there is an activation trend during the cycle, but the capacities are far lower than the discharge specific capacities in the embodiments. DETAILED DESCRIPTION

[0059] The above scheme is further described below in conjunction with 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 adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0060] Unless otherwise specified in the following examples, all raw materials are commercially available 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(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 and 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 material was weighed and placed in a tablet pressing mold, and maintained at a pressure of 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 maintained for 12 hours, then cooled to 200°C and naturally cooled 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 uniformly mixed in a mass ratio of 7:2:1, an appropriate amount of N-methylpyrrolidone (NMP) was added to make a slurry, applied on Al foil, vacuum dried at 120°C for 12 hours, and 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 the 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 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 (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 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 and grind for 20 min. The mixed raw materials were ball milled at a speed of 0r / min for 12h; the mixed raw materials were placed in an oven and dried with air at 80℃ for 12h, and then the powder was ground into powder with an agate mortar, 0.5g of the powder raw material was 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℃ at a rate of 5℃ / min, and kept warm for 6h, and then naturally cooled to obtain a bright orange layered positive electrode material. After calculation, the entropy value of the material is 1.58R, which is a high entropy positive electrode material.

[0069] The electrochemical performance of the button 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 181.12 mAh / g, and the 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(0.04mol) Weigh 1.2413g of lithium carbonate, 2.2081g of manganese dioxide, 0.32g of sodium hydroxide, 0.3366g of potassium hydroxide, 0.0739g of zirconium dioxide, 0.07955g of copper oxide, 0.0322g of magnesium oxide and 0.2075g of lithium fluoride in a mortar, grind by hand for 30min, pour into a ball mill, add zirconium beads according to the mass ratio of raw materials: zirconium beads = 1:4, then add 15mL of anhydrous ethanol, place in a planetary ball mill and grind at 200r / min ball milling for 12h; the mixed raw materials were placed in an oven and dried at 80℃ for 12h, 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 1min to obtain a 3mm disc; the disc was placed in a 15mL corundum crucible, placed in a muffle furnace, and heated to 900℃ at a rate of 5℃ / min for 12h, 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 button 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 0.3Weigh 1.0862g of lithium carbonate, 2.2082g of manganese dioxide, 0.3367g of potassium hydroxide, 0.24g of sodium hydroxide, 0.0739g of zirconium dioxide, 0.07955g of copper oxide, 0.0403g of magnesium oxide and 0.5086g of lithium chloride (0.04mol) in a mortar, grind by hand for 30min, pour into a ball mill, add zirconium beads according to the mass ratio of raw materials: zirconium beads = 1:4, then add 15mL of anhydrous ethanol, place in a planetary ball mill and grind at 200r / min for 12 h; the mixed raw materials were placed in an oven and dried with air at 80 ° C for 12 h, 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 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, and kept warm for 6 h, 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 button 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, compared with the fluorine substitution in Example 1, the effect of chlorine substitution is worse than that of fluorine substitution.

[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 (0.04 mol) weighed 2.474 g of lithium hydroxide monohydrate and 3.0806 g of manganese carbonate, hand-milled for 30 min, poured into a ball mill, added zirconium beads according to the mass ratio of raw material: zirconium beads = 1:4, and then added 15 mL of anhydrous ethanol, placed in a planetary ball mill and ball milled at 200 r / min for 12 h; the mixed raw materials were placed in an oven and dried with air at 80 ° C for 12 h, and then 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 maintained at a pressure of 10 MPa for 2 min to obtain a 3 mm disc; the disc was placed in a 15 mL corundum crucible, placed in a muffle furnace, heated to 700 ° C at a rate of 5 ° C / min, and kept warm for 24 h, and then naturally cooled to obtain a bright orange positive electrode material. After calculation, the entropy value of the material is 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 (according to 0.04 mol) were weighed, hand-milled for 30 min, and then poured into a ball mill, zirconium beads were added according to the mass ratio of raw material: zirconium beads = 1:4, and then 15 mL of anhydrous ethanol was added, and the mixture was placed in a planetary ball mill for ball milling at a speed of 200 r / min for 12 h; the mixed raw materials were placed in an oven for forced air drying at 80°C for 12 h, 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 min to obtain a 3 mm disc; the disc was placed in a 15 mL corundum crucible, placed in a muffle furnace, heated to 700°C at a rate of 5°C / min, and kept warm for 24 h, and then naturally cooled to obtain an orange positive electrode material. After calculation, the entropy value of the material was 1.107R.

[0086] The electrochemical performance of the button 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, 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 a speed of 200 r / min for 1 2h; put the mixed raw materials into an oven and dry them with air at 80℃ for 12h, then grind the powder into powder with an agate mortar, weigh 0.5g of the powder raw material and put it into a tablet pressing mold, and keep the pressure at 10MPa for 1min to obtain a 3mm disc; put the disc in a 15mL corundum crucible, put it in a muffle furnace and heat it to 900℃ at a rate of 5℃ / min for 12h, then cool it naturally to obtain the positive electrode material. After calculation, the entropy value of the material is 1.37R.

[0090] The electrochemical performance of the button 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 (0.04mol) 1.0862g of lithium carbonate, 1.9682g of manganese dioxide, 0.4870g of potassium hydroxide, 0.3472g of sodium hydroxide and 0.3112g of lithium fluoride were weighed and placed in a mortar. After hand grinding for 30min, they were poured into a ball mill. Zirconium beads were added according to the mass ratio of raw material: zirconium beads = 1:4, and then 15mL of anhydrous ethanol was added. The mixture was placed in a planetary ball mill and ball milled at a speed of 200r / min for 12h; the mixed raw materials were placed in an oven and dried with air at 80℃ for 12h, and then the powder was ground into powder with an agate mortar. 0.5g of the powder raw material was weighed and placed in a tablet pressing mold. The pressure was maintained at 15MPa for 1min to obtain a 3mm disc; the disc was placed in a 15mL corundum crucible, placed in a muffle furnace, heated to 900℃ at a rate of 5℃ / min, and kept for 12h, and then naturally cooled to obtain a positive electrode material. After calculation, the entropy value of the material was 1.41R.

[0094] The electrochemical performance of the button 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 , the capacity is extremely low.

[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-grinded 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 ball mill was placed in a planetary ball mill at 200 r / m in speed for 12 h; the mixed raw materials were placed in an oven and dried with air at 80°C for 12 h, 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 15 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 for 12 h, and then naturally cooled to obtain the positive electrode material. After calculation, the entropy value of the material is 1.10R.

[0098] The electrochemical performance of the button 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(0.04mol) 1.0862g of lithium carbonate, 1.7387g of manganese dioxide, 0.4870g of potassium hydroxide, 0.3472g of sodium hydroxide, 0.0837g of zirconium dioxide, 0.0859g of copper oxide, 0.0403g of magnesium oxide and 0.3112g of lithium fluoride were weighed and placed in a mortar. After hand grinding for 30min, 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 15mL of anhydrous ethanol was added. The mixture was placed in a planetary ball mill and pulverized at 200r / min. min for 12 h; the mixed raw materials were placed in an oven and dried with air at 80°C for 12 h, 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 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 for 12 h, 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 button 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 , the capacity is extremely low.

[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 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 (0.04 mol) 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 and grind at a speed of 200 r / min for 12 h; put the mixed raw materials into an oven and dry them with air at 80°C for 12h, then grind the powder into powder with an agate mortar, weigh 0.5g of the powder raw material and put it into a tablet pressing mold, and keep the pressure at 10MPa for 1min to obtain a 3mm disc; put the disc in a 15mL corundum crucible, put it in a muffle furnace and heat it to 900°C at a rate of 5°C / min, keep it for 12h, and then cool it naturally to obtain an orange layered positive electrode material. After calculation, the entropy value of the material is 1.37R.

[0106] The electrochemical performance of the button 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 only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0108] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

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 selected from a combination of one or more 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 or more combinations of F, Cl, Br, and I, each m is independently 0.1-0.35, and when Q has a plurality of elements, the sum of all m is less than or equal to 0.

4.

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 TM is selected from the group consisting of Zr, Cu, and Mg; and / or, 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, 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 claim 1, 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 and x are the same as those in claim 1; 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.

7. 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 1.5R, further greater than 1.8R, and further greater than 2.0R.

8. A method for preparing the positive electrode material according to any one of claims 1 to 7, characterized in that: The preparation method comprises: weighing various raw materials according to the molecular weight ratio, mixing, adding solvent, grinding, drying the ground materials, and then sintering to prepare positive electrode materials.

9. The method for preparing the positive electrode material according to claim 8, 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 carried out by ball milling; and / or, Controlling the calcination to be carried out at 700-1100° C.; and / or, Controlling the calcination time to be 6-18h; and / or, The calcination is a one-step sintering; and / or, Controlling the heating rate of the calcination to be 1-15°C / min, further to be 5-10°C / min; and / or, The calcination is controlled to be performed in an air atmosphere or an oxygen atmosphere.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the positive electrode material according to any one of claims 1 to 7.

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