Method for preparing high-performance lithium manganate positive electrode material based on mixed lithium source

Abstract

The invention discloses a method for preparing a high-performance lithium manganate positive electrode material based on a mixed lithium source, and belongs to the technical field of lithium ion battery positive electrode materials. The method comprises the following steps: S1, weighing a mixed lithium source, Mn3O4, Al2O3, TiO2 and LiI according to a formula, and uniformly mixing the raw materials in a high-efficiency mixer; s2, the materials mixed in the step S1 are put into a sagger made of an aluminum oxide material, and the sagger is put into a muffle furnace to be sintered; and S3, crushing, screening and demagnetizing the sintered product in the step S2 to prepare the finished product lithium manganate material. By adopting the mixed lithium source of lithium oxide and lithium carbonate and introducing titanium, aluminum and iodine elements, not only can the cost be controlled, but also the generation of CO2 can be remarkably reduced, so that the oxygen defect problem in the material is improved, and the overall performance of the lithium manganate positive electrode material can be improved from two aspects of structure regulation and electrochemical performance optimization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery cathode materials, and particularly relates to a method for preparing high-performance lithium manganate cathode materials based on a mixed lithium source. BACKGROUND

[0002] Lithium manganate has become one of the hotspots of research on lithium ion battery cathode materials due to its advantages of abundant resources, relatively low cost and environmental friendliness. It has a high discharge voltage and a good discharge platform, and performs excellently in safety, thus having a broad development prospect.

[0003] Although lithium manganate has many advantages, it still has some challenges in practical application, especially problems related to oxygen defects. When lithium carbonate is used as a single lithium source for sintering, a large amount of carbon dioxide is released due to the excessively fast reaction rate between lithium carbonate and trimanganese tetraoxide; this fast reaction makes it difficult for oxygen to fully participate in the reaction, thus causing oxygen defects. Oxygen defects not only cause distortion of the crystal structure, making lithium manganate, which should be spinel structure, produce a heterogeneous phase, but also exacerbate the occurrence of Jahn-Teller effect, which has a negative impact on the capacity, cycle life and rate performance of the battery. In order to solve the problem of oxygen defects caused by lithium carbonate, researchers try to use lithium hydroxide as a lithium source, which has a lower decomposition temperature (about 450℃) and a relatively moderate reaction rate, thus reducing CO2 production; however, lithium hydroxide has extremely strong hygroscopicity and is easy to react with moisture in the air to generate Li2CO3 or LiOH·H2O during storage and batching, thus causing fluctuations in lithium content and affecting the stoichiometric ratio of the product; and the market price of lithium hydroxide is about 1.5-2 times that of lithium carbonate, and an additional moisture-proof process is required, which significantly increases the cost of industrial production.

[0004] Therefore, it is of great significance to develop a lithium manganate preparation technology that can effectively inhibit the formation of oxygen defects while taking into account cost and process feasibility for promoting the development of high-performance lithium ion batteries. SUMMARY

[0005] In view of this, the application discloses a method for preparing high-performance lithium manganate cathode materials based on a mixed lithium source. By using a mixed lithium source of lithium oxide (Li2O) and lithium carbonate and introducing titanium, aluminum and iodine elements, the application can not only significantly reduce CO2 generation while controlling cost, thus improving the problem of oxygen defects in the material, but also improve the overall performance of lithium manganate cathode materials from two aspects of structure regulation and electrochemical performance optimization.

[0006] To achieve the above-mentioned purpose, the application provides the following technical scheme:

[0007] The application provides a method for preparing high-performance lithium manganate cathode materials based on a mixed lithium source, comprising the following steps:

[0008] S1. According to the formula, the appropriate amount of mixed lithium source, manganese tetroxide (Mn3O4), aluminum oxide (Al2O3), titanium dioxide (TiO2), lithium iodide (LiI) is weighed, and the above raw materials are placed in a high-efficiency mixer for thorough mixing;

[0009] S2. The mixed material in step S1 is loaded into an alumina material box, and the box is placed in a muffle furnace for sintering;

[0010] S3. The product after sintering in step S2 is crushed, screened, and demagnetized to produce finished lithium manganate material, i.e., high-cycle lithium manganate positive electrode material.

[0011] Preferably, in step S1, the mixed lithium source is lithium carbonate (Li2CO3) and lithium oxide (Li2O), and the molar ratio of Li2CO3 to Li2O is 3:7.

[0012] Preferably, in step S1, the preparation method of Li2O is as follows: After sieving, lithium carbonate is placed in a platinum gold pan, and then placed in a muffle furnace and heated at a rate of 5-10℃ / min to 700-710℃ and kept for 10-24h for sintering. The sintered product is crushed and ground to obtain Li2O.

[0013] Preferably, in step S1, the preparation method of Li2O can also be as follows: Lithium carbonate and carbon are placed in a high-efficiency mixer in a molar ratio of 1:(1-1.2) for thorough mixing, and the mixture is loaded into a platinum gold pan and then placed in a muffle furnace under inert gas, heated at a rate of 5-10℃ / min to 400-600℃ and kept for 6-7h for sintering. The sintered product is crushed and ground to obtain Li2O.

[0014] Preferably, the carbon is one of coke, sugar, and graphite.

[0015] Preferably, in step S1, the molar ratio of lithium to manganese in the mixed lithium source and Mn3O4 is 1:1.98.

[0016] Preferably, in step S2, the sintering process in the muffle furnace is as follows: first, increase the temperature from room temperature (about 20℃) to 290℃ at a rate of 5℃ / min, then increase the temperature to 370℃ at a rate of 2.96℃ / min, and then continue to increase the temperature to 430℃ at a rate of 1.25℃ / min, and keep the temperature for 170 min; then, continue to increase the temperature to 520℃ at a rate of 0.32℃ / min, and keep the temperature for 60 min; then, increase the temperature to 690℃ at a rate of 1℃ / min, and keep the temperature for 120 min; after the temperature keeping, cool down to 580℃ at a rate of -1℃ / min, and keep the temperature for 240 min; finally, the furnace body is naturally cooled to room temperature from 580℃.

[0017] Preferably, in step S2, the sintering atmosphere in the muffle furnace adopts air atmosphere or oxygen atmosphere.

[0018] The application further discloses a high-performance lithium manganate positive electrode material prepared by the preparation method. x Al y Mn 2-x-y O 4-z I z , wherein 0 < x ≤ 0.008, 0 < y ≤ 0.012 and 0 < z ≤ 0.008.

[0019] The application further provides application of the high-performance lithium manganate positive electrode material in preparation of a lithium ion battery.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] (1) The application adopts a composite lithium source system of lithium oxide (Li2O) and lithium carbonate (Li2CO3), and realizes the solid-phase synthesis without CO2 release through a reaction formula: 6Li2O + 8Mn3O4 + 5O2 → 12LiMn2O4. The reaction path avoids CO2 gas generated by decomposition of lithium carbonate, and avoids the oxygen permeation pressure imbalance problem caused by gas expansion. By controlling the ratio of the two lithium sources, the high cost and storage difficulty of lithium oxide are reduced, and the formation of oxygen vacancies in the sintering process is effectively inhibited. At the same time, the mixed lithium source of lithium oxide and lithium carbonate is an economical and effective compromise solution, which can significantly reduce the generation of CO2 while controlling the cost, thereby improving the oxygen defect problem in the material and improving the specific capacity and cycle stability of the positive electrode material.

[0022] (2) The application dopes titanium (Ti), aluminum (Al) and iodine (I) elements in the lithium manganate material to synergistically improve the structural stability and electrochemical performance of the material.

[0023] ① The titanium element is in a tetravalent state (Ti4+ Introduced in the form of Mn, its ionic radius is approximately 0.0605 nm, similar to that of Mn. 4+ With a similar ionic radius (approximately 0.053 nm), it can replace Mn in the spinel structure. 4+ The octahedral positions of Ti form more stable Ti-O bonds; 4+ The larger ionic radius of Ti-O results in a higher bond energy than Mn-O, which inhibits the growth of Mn during high-temperature sintering. 4+ The reduction of (Mn) 4+ →Mn 3+ This reduces lattice distortion and phase transition, thereby improving the thermal stability of the material.

[0024] ② Aluminum element in the form of Al 3+ It is doped into the material in the form of Mn, with an ionic radius of approximately 0.0535 nm, slightly smaller than that of Mn. 3+ The ionic radius of Al is approximately 0.0649 nm. 3+ Able to partially replace Mn 3+ The position of Mn is suppressed through a charge compensation mechanism. 3+ The resulting Jahn-Teller effect (electron orbital distortion). This substitution effectively alleviates the Mn... 3+ The resulting crystal structure distortion reduces lattice oxygen loss during cycling, thus maintaining the material's long-cycle performance.

[0025] ③I - of -1 The decrease in valence state leads to a lower overall oxidation state, promoting the oxidation of Mn. 3+ The proportion increases, thereby improving the specific capacity of the material; the atomic radius of I- Greater than 0 2- Because the atomic radius of I- is greater than that of O 2- Its incorporation can increase the cell volume, reduce the structural stress during lithium ion insertion and extraction, and further improve the cycle stability and rate performance of the material.

[0026] In summary, by employing a mixed lithium source of lithium oxide and lithium carbonate and introducing elements such as titanium, aluminum, and iodine, this invention can not only effectively reduce the oxygen defect problem caused by CO2 release, but also improve the overall performance of lithium manganese oxide cathode materials from two aspects: structural regulation and electrochemical performance optimization, laying a solid foundation for their widespread application in high-safety, low-cost lithium-ion batteries.

[0027] (3) This invention utilizes a process combining segmented temperature control and rate regulation, along with a mixed lithium source (Li2O / Li2CO3) and multi-element doping (Ti / Al / I), to systematically optimize the synthesis pathway of lithium manganese oxide (LiMn2O4) materials. Specific analysis is as follows:

[0028] ①Low-temperature activation stage (20℃→290℃, 5℃ / min) and medium-temperature reaction stage (290℃→370℃, 2.96℃ / min): This process ensures that the atmosphere in the furnace, the saggar and the material as a whole are evenly heated, avoiding thermal stress and uneven reaction caused by temperature difference. During this period, Ti 4+ and Al 3+ ions begin to preliminarily diffuse into the Mn3O4 lattice, laying the foundation for subsequent structural reconstruction and doping.

[0029] ②Main reaction optimization stage (370℃→430℃, 1.25℃ / min): At this stage, Li2CO3 begins to decompose slowly to generate Li2O and release CO2. By controlling the heating rate, Li2O gradually participates in the solid-phase reaction, effectively alleviating the fluctuation of oxygen permeation pressure caused by the large amount of CO2 escaping, maintaining the stability of the reaction system. At the same time, this rate balances the reaction kinetics and the volatility of I-, promoting the uniform distribution of iodine ions in the precursor and creating conditions for their smooth entry into the lattice later.

[0030] ③Lattice optimization stage (430℃→520℃, 0.32℃ / min): Li2CO3 is fully decomposed into Li2O, and the loss of Li2O is reduced: At this stage, the slow heating promotes the complete decomposition of Li2CO3, reducing the high-temperature volatilization loss of Li2O; Li2O and Mn3O4 begin to react to generate LiMn2O4 precursor (6Li2O + 8Mn3O4 + 5O2→12LiMn2O4), and inhibit the formation of oxygen vacancies; I- gradually embeds into the lattice at this stage, regulates the Mn 3+ / Mn 4+ ratio, enhances the electronic conductivity and electrochemical activity of the material; This stage uses a slow heating rate of 0.32℃ / min to avoid sudden changes in lattice stress, promote Ti 4 to preferentially occupy octahedral sites, and Al3 + to replace Mn 3+ , inhibit the Jahn-Teller effect; holding at 520℃ for 60min further ensures the uniform distribution of doped elements in the lattice and enhances the structural stability.

[0031] ④High-temperature sintering stage (520℃→690℃, 1℃ / min): This stage densifies the spinel structure: High temperature promotes the formation of Ti-O bonds, increases the solid solubility of Al3 + , and I- further expands the lattice space; The holding platform at 690℃ is to make the unit cell continue to grow, and the material will also absorb a small amount of oxygen, thereby improving and compensating for the oxygen-deficient lithium manganate generated earlier.

[0032] ⑤ Cooling and stress release stage (690℃→580℃, -1℃ / min): This stage is slowly cooled at a rate of -1℃ / min to avoid thermal shock caused by lattice distortion, maintain the stable distribution of Ti / Al / I; keep at 580℃ for 240min to fully release the thermal stress and structural stress accumulated during sintering, stabilize the lattice position of Ti, Al, I and other doping elements, and significantly improve the mechanical integrity and cycle stability of the material.

[0033] In summary, the application constructs an efficient and stable synthesis path of lithium manganate positive electrode material through multi-dimensional parameter control of sintering curve process and element synergistic effect. Not only effectively solves the key technical problems such as oxygen defect, structure distortion and poor cycle stability, but also takes into account the cost control and process feasibility in industrial production, and provides strong support for the development of high-energy-density and high-safety lithium ion battery positive electrode materials. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 SEM image of the high cycle performance lithium manganate positive electrode material of Example 1 of the application;

[0035] Figure 2 Normal temperature cycle curve graph of lithium ion batteries made of the high cycle performance lithium manganate positive electrode material of Example 1 of the application and the lithium manganate positive electrode material of Comparative Example 1;

[0036] Figure 3 First charge-discharge curve graph of lithium ion batteries made of the high cycle performance lithium manganate positive electrode material of Example 1 of the application and the lithium manganate positive electrode material of Comparative Example 1. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0038] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0039] The materials and reagents used in the following examples can be obtained from commercial channels unless otherwise specified.

[0040] The application provides a method for preparing high-performance lithium manganate positive electrode material based on mixed lithium source, comprising the following steps:

[0041] S1. According to the formula, the appropriate amount of mixed lithium source (molar ratio of Li2CO3 and Li2O is 3:7), manganese tetroxide (Mn3O4), aluminum oxide (Al2O3), titanium dioxide (TiO2), lithium iodide (LiI) is weighed, and the above raw materials are placed in a high-efficiency mixer and mixed uniformly;

[0042] S2. The mixed material in step S1 is loaded into an alumina material box, and the box is placed in a muffle furnace for sintering.

[0043] S3. The product after sintering in step S2 is crushed, screened, and demagnetized to produce finished lithium manganate material, i.e., high-cycle lithium manganate positive electrode material.

[0044] The preparation method of the above Li2O is as follows: the sieved lithium carbonate is placed in a platinum gold pan, then placed in a muffle furnace, heated to 700-710°C at a rate of 5-10°C / min, and kept for 10-24h for sintering. The sintered product is crushed and ground to obtain Li2O.

[0045] The preparation method of the above Li2O can also be as follows: lithium carbonate and carbon (one of coke, sugar, and graphite) are placed in a high-efficiency mixer in a ratio of 1:(1-1.2) and mixed uniformly. The mixture is loaded into a platinum gold pan and placed in a muffle furnace under inert gas, heated to 400-600°C at a rate of 5-10°C / min, and kept for 6-7h for sintering. The sintered product is crushed and ground to obtain Li2O.

[0046] In the above step S1, the molar ratio of lithium and manganese in the mixed lithium source and Mn3O4 is 1:1.98.

[0047] In the above step S2, the sintering process in the muffle furnace is as follows: first, heat from room temperature (about 20°C) to 290°C at a rate of 5°C / min, then heat to 370°C at a rate of 2.96°C / min, then continue to heat to 430°C at a rate of 1.25°C / min, and keep the temperature for 170min; then continue to heat to 520°C at a rate of 0.32°C / min, and keep the temperature for 60min; then heat to 690°C at a rate of 1°C / min, and keep the temperature for 120min; after the heat preservation is over, cool to 580°C at a rate of -1°C / min, and keep the temperature for 240min; finally, the furnace body is naturally cooled to room temperature from 580°C.

[0048] The chemical formula of the high-performance lithium manganate positive electrode material prepared by the above preparation method is: LiTi x Al y Mn 2-x-y O 4-z Iz wherein: 0 < x < 0.008, 0 < y < 0.012, 0 < z < 0.008.

[0049] Application of the anion-cation co-doped high cycle performance lithium manganate cathode material in the preparation of lithium ion batteries.

[0050] The technical solutions of the present application will be further described below in combination with the drawings and specific embodiments:

[0051] Embodiment 1

[0052] The preparation method of the high-performance lithium manganate cathode material LiTi 0.008 Al 0.012 Mn 1.98 O 3.992 I 0.008 , the specific steps are as follows:

[0053] (1) Take 1200g of lithium carbonate (Li2CO3), use a vibrating screen to sieve, and place the sieved lithium carbonate in a platinum crucible, and put it into a muffle furnace, and heat it to 710℃ at a rate of 5℃ / min in a vacuum argon atmosphere and keep it for 12h for sintering, and then crush and grind the sintered product to obtain 486g of Li2O.

[0054] (2) Take a total of 847.31g of lithium source, including 375.05g of lithium carbonate and 472.26g of lithium oxide, and add it to a high-efficiency mixer and mix at a frequency of 35Hz for 25min to ensure that the two lithium sources are fully mixed and uniform, then add 5109.1g of trimanganese tetraoxide, 20.70g of aluminum oxide, 21.63g of titanium oxide, and 36.23g of lithium iodide to the high-efficiency mixer and mix at a frequency of 49Hz for 50min.

[0055] (3) Put the mixed material in step (2) into an alumina crucible, and place the crucible in a muffle furnace and sinter according to the following process: heat from room temperature (about 20℃) to 290℃ at a rate of 5℃ / min, then heat to 370℃ at a rate of 2.96℃ / min, then continue to heat to 430℃ at a rate of 1.25℃ / min, and keep the temperature for 170min; then, continue to heat to 520℃ at a rate of 0.32℃ / min, and keep the temperature for 60min; then heat to 690℃ at a rate of 1℃ / min, and keep the temperature for 120min; after the heat preservation is over, cool to 580℃ at a rate of-1℃ / min, and keep the temperature for 240min; finally, the furnace body is naturally cooled to room temperature from 580℃, wherein the atmosphere in the muffle furnace is oxygen atmosphere.

[0056] (4) The sintered product of step (3) is placed in a ball mill for 30 minutes of crushing, then sieved through a 300-mesh screen, removed from the magnet, and the finished lithium manganate material LiTi 0.008 Al 0.012 Mn 1.98 O 3.992 I 0.008 .

[0057] Figure 1 SEM image of the high-performance lithium manganate cathode material prepared for this example, from Figure 1 It can be seen that the high-performance lithium manganate cathode material prepared in this example exhibits a spherical or near-spherical shape, with uniform and consistent particle size, and moderate inter-particle porosity. Each particle is formed by the aggregation of numerous fine primary grains through the sintering process, forming secondary particles. The structure of the secondary particles and the close packing of the primary grains help to maintain the structural stability of the material during repeated charging and discharging, significantly extending the cycle life of the battery. The inter-particle porosity promotes contact between the electrolyte and the active material, enhancing ion transport efficiency. The high-performance lithium manganate cathode material prepared in this example has good sphericity, uniform particle size distribution, and reasonable porosity structure. These characteristics help to improve its electrochemical performance, including high-rate performance, cycle stability, and processing performance.

[0058] Example 2

[0059] The preparation method of the high-performance lithium manganate cathode material LiTi 0.008 Al 0.012 Mn 1.98 O 3.994 I 0.006 , the specific steps are as follows:

[0060] (1) Take 1200g of lithium carbonate (Li2CO3) and sieve it using a vibrating screen. Place the sieved lithium carbonate in a platinum crucible and place it in a muffle furnace. Heat it at a rate of 5°C / min to 710°C under a vacuum argon atmosphere and maintain the temperature for 12 hours for sintering. Grind the sintered product to obtain 486g of Li2O.

[0061] (2) Take a total of 847.31g of lithium source, including 375.05g of lithium carbonate and 472.26g of lithium oxide. Add them to a high-efficiency mixer and mix at a frequency of 35Hz for 25 minutes to ensure that the two lithium sources are fully mixed and uniform. Then, add 5109.1g of trimanganese tetraoxide, 20.70g of aluminum oxide, 21.63g of titanium oxide, and 27.17g of lithium iodide to the high-efficiency mixer and mix at a frequency of 49Hz for 50 minutes.

[0062] (3) Put the mixed material in step (2) into an alumina crucible, and place the crucible in a muffle furnace to sinter according to the following process: increase the temperature from room temperature (about 20°C) to 290°C at a rate of 5°C / min, then increase the temperature to 370°C at a rate of 2.96°C / min, then continue to increase the temperature to 430°C at a rate of 1.25°C / min, and keep the temperature at 430°C for 170 min; then, continue to increase the temperature to 520°C at a rate of 0.32°C / min, and keep the temperature at 520°C for 60 min; then increase the temperature to 690°C at a rate of 1°C / min, and keep the temperature at 690°C for 120 min; after the holding period, cool down to 580°C at a rate of -1°C / min, and keep the temperature at 580°C for 240 min; finally, the furnace body is naturally cooled to room temperature from 580°C, and the atmosphere in the muffle furnace is oxygen atmosphere.

[0063] (4) After the sintered product in step (3) is crushed in a ball mill for 30 min, it is sieved through a 300-mesh screen, and the magnetic particles are removed to obtain the finished lithium manganate material LiTi 0.008 Al 0.012 Mn 1.98 O 3.994 I 0.006 .

[0064] Example 3

[0065] The high-performance lithium manganate cathode material LiTi 0.005 Al 0.008 Mn 1.98 O 3.994 I 0.006 The preparation method comprises the following specific steps:

[0066] (1) Take 1200g of lithium carbonate (Li2CO3), and sieve it using a vibrating screen. Put the sieved lithium carbonate into a platinum-gold crucible, and place it in a muffle furnace to sinter at a rate of 5°C / min to 710°C under a vacuum argon atmosphere and keep the temperature for 12h. Crush and grind the sintered product to obtain 486g of Li2O.

[0067] (2) Take a total of 847.31g of lithium source, including 375.05g of lithium carbonate and 472.26g of lithium oxide, and add them to a high-efficiency mixer. Mix them at a frequency of 35Hz for 25min to ensure that the two lithium sources are fully mixed and uniform. Then, add 5109.1g of trimanganese tetraoxide, 13.79g of aluminum oxide, 13.52g of titanium oxide, and 27.17g of lithium iodide to the high-efficiency mixer, and mix them at a frequency of 49Hz for 50min.

[0068] (3) Put the mixed material in step (2) into an alumina crucible, and place the crucible in a muffle furnace to sinter according to the following process: increase the temperature from room temperature (about 20°C) to 290°C at a rate of 5°C / min, then increase the temperature to 370°C at a rate of 2.96°C / min, then continue to increase the temperature to 430°C at a rate of 1.25°C / min, and keep the temperature at 430°C for 170 min; then, continue to increase the temperature to 520°C at a rate of 0.32°C / min, and keep the temperature at 520°C for 60 min; then, increase the temperature to 690°C at a rate of 1°C / min, and keep the temperature at 690°C for 120 min; after the end of the heat preservation, cool to 580°C at a rate of -1°C / min, and keep the temperature at 580°C for 240 min; finally, the furnace body is naturally cooled from 580°C to room temperature, and the atmosphere in the muffle furnace is oxygen atmosphere.

[0069] (4) Put the sintered product in step (3) into a ball mill for 30 min, sieve through a 300-mesh screen, remove the magnetic material, and obtain the finished lithium manganate LiTi 0.005 Al 0.008 Mn 1.98 O 3.994 I 0.006 .

[0070] Comparative Example 1

[0071] The present example is a preparation method of lithium manganate LiMn2O4 as a positive electrode material for lithium ion batteries, and the specific steps are as follows:

[0072] (1) Put 399 g of lithium carbonate and 1601 g of trimanganese tetraoxide into a high-efficiency mixer and mix at 49 Hz for 50 min.

[0073] (2) Put the mixed material in step (1) into an alumina crucible, and place the crucible in a muffle furnace to sinter according to the following process: increase the temperature from room temperature (about 20°C) to 290°C at a rate of 5°C / min, then increase the temperature to 370°C at a rate of 2.96°C / min, then continue to increase the temperature to 430°C at a rate of 1.25°C / min, and keep the temperature at 430°C for 170 min; then, continue to increase the temperature to 520°C at a rate of 0.32°C / min, and keep the temperature at 520°C for 60 min; then, increase the temperature to 690°C at a rate of 1°C / min, and keep the temperature at 690°C for 120 min; after the end of the heat preservation, cool to 580°C at a rate of -1°C / min, and keep the temperature at 580°C for 240 min; finally, the furnace body is naturally cooled from 580°C to room temperature, and the atmosphere in the muffle furnace is oxygen atmosphere.

[0074] (3) Put the sintered product in step (2) into a ball mill for 30 min, sieve through a 280-mesh screen, remove the magnetic material, and obtain the finished lithium manganate LiMn2O4.

[0075] The lithium manganate positive electrode material prepared in Example 1 and Comparative Example 1 was made into a button cell, and electrochemical performance test was carried out, and the specific analysis is as follows.

[0076] Figure 2 The cycle performance curves of the lithium manganate positive electrode material prepared in Example 1 and Comparative Example 1 were made into a button cell at 1C current density for 33 cycles at room temperature, and it can be seen from the figure that: Example 1 showed more excellent cycle stability during the whole test period, especially in the middle and later stages, and its capacity retention rate was always slightly higher than that of Comparative Example 1, which indicated that the material or process design of Example 1 helped to slow down the capacity decay and prolong the battery life.

[0077] Figure 3 The first cycle charge-discharge curves of the lithium manganate positive electrode material prepared in Example 1 and Comparative Example 1 were made into a button cell at 2.7V-4.3V charge-discharge voltage range, 1C current density, and it can be seen from the figure that: with the increase of cycle number, both curves showed a downward trend, but the capacity decay rate of Example 1 was significantly lower than that of Comparative Example 1. Specifically: in the first 20 cycles, the discharge specific capacity of Example 1 was basically stable at 132-134mAh / g, showing excellent cycle stability; in contrast, the discharge specific capacity of Comparative Example 1 rapidly decreased to about 122mAh / g in the same period, indicating that its cycle stability was relatively poor. After more than 20 cycles, although both curves gradually tended to be flat, Example 1 showed better discharge specific capacity retention ability, and finally the discharge specific capacity of Example 1 stabilized at about 127mAh / g, while that of Comparative Example 1 decreased to below 122mAh / g. As can be seen, Example 1 showed more excellent cycle stability during the whole test period, especially in the middle and later stages, and its discharge specific capacity was always higher than that of Comparative Example 1, indicating that the material and process design adopted by Example 1 could effectively slow down the capacity decay and thus prolong the service life of the battery.

[0078] The method for preparing high-performance lithium manganate positive electrode material based on mixed lithium source disclosed in the present application is described in detail above. In this paper, specific examples are applied to explain the principles and implementation methods of the present application, and the above examples are only used to help understand the method and core idea of the present application. It should be pointed out that for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing high performance lithium manganate cathode material based on mixed lithium source, characterized in that, It comprises the following steps: S1. According to the formula, the appropriate amount of mixed lithium source, Mn3O4, Al2O3, TiO2, LiI is weighed, and the above raw materials are placed in a high-efficiency mixer for fully mixing; S2. The mixed material in step S1 is loaded into an alumina material box, and the box is placed in a muffle furnace for sintering; S3. The product after sintering in step S2 is crushed, screened, and demagnetized to obtain the finished lithium manganate material, i.e. high-cycle lithium manganate positive electrode material.

2. The method for preparing high-performance lithium manganate cathode material based on mixed lithium source according to claim 1, characterized in that, In step S1, the mixed lithium source is Li2CO3 and Li2O, and the molar ratio of Li2CO3 to Li2O is 3:

7.

3. The method for preparing high-performance lithium manganate cathode material based on mixed lithium source according to claim 2, characterized in that, In step S1, the preparation method of Li2O is as follows: after sieving, lithium carbonate is placed in a platinum gold pan, and then placed in a muffle furnace and heated at a rate of 5-10℃ / min to 700-710℃ and kept for 10-24h for sintering. The sintered product is crushed and ground to obtain Li2O. 4.The method for preparing high-performance lithium manganate cathode material based on mixed lithium source according to claim 2, characterized in that, In step S1, the preparation method of Li2O can also be as follows: lithium carbonate and carbon are placed in a high-efficiency mixer in a molar ratio of 1:(1-1.2) for fully mixing, and the mixture is loaded into a platinum gold pan and then placed in a muffle furnace under inert gas, heated at a rate of 5-10℃ / min to 400-600℃ and kept for 6-7h for sintering. The sintered product is crushed and ground to obtain Li2O.

5. The method for preparing high performance lithium manganate cathode material based on mixed lithium source according to claim 4, characterized in that, The carbon is one of coke, sugar and graphite.

6. The method for preparing high performance lithium manganate cathode material based on mixed lithium source according to claim 1, characterized in that, In step S1, the molar ratio of lithium to manganese in the mixed lithium source and Mn3O4 is 1:1.

98. 7.The method of claim 1, wherein the lithium source is a mixture of lithium hydroxide and lithium carbonate. In step S2, the sintering process in the muffle furnace is as follows: first, heated from room temperature (about 20℃) to 290℃ at a rate of 5℃ / min, then heated to 370℃ at a rate of 2.96℃ / min, then continued to heat to 430℃ at a rate of 1.25℃ / min, and kept at this temperature for 170min; then, continue to heat to 520℃ at a rate of 0.32℃ / min, and keep at this temperature for 60min; then, heat to 690℃ at a rate of 1℃ / min, and keep at 690℃ for 120min; After the end of the heat preservation, cool to 580℃ at a rate of-1℃ / min, and keep at this temperature for 240min; finally, the furnace body is naturally cooled to room temperature from 580℃. 8.The method for preparing high performance lithium manganate cathode material based on mixed lithium source according to claim 1, characterized in that, In step S2, the sintering atmosphere in the muffle furnace uses air atmosphere or oxygen atmosphere.

9. The high performance lithium manganate cathode material prepared according to the method of any one of claims 1 to 8, characterized in that, The high-performance lithium manganate positive electrode material has a chemical formula of: LiTi x AL y Mn 2-x-y O 4-z I z wherein: 0 < x ≤ 0.008, 0 < y ≤ 0.012, 0 < z ≤ 0.

008.

10. The use of the high-performance lithium manganate positive electrode material of claim 9 in the preparation of a lithium ion battery.

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