A lithium-rich manganese-based positive electrode material with combined action of surface heterojunction and bulk doping, and a preparation method and application thereof

Abstract

The application belongs to the technical field of lithium-rich manganese-based positive electrodes, and discloses a lithium-rich manganese-based positive electrode material with surface heterojunction and bulk doping and a preparation method and application thereof. a (TiO3) b , 1<=a<=5, 1<=b<=5 and bulk Ti and M doped Li 1.2 Mn x Ni 0.2 Ti y M z O2, 0.3

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium-rich manganese-based positive electrodes, and more particularly relates to a lithium-rich manganese-based positive electrode material with a surface heterojunction and bulk doping and a preparation method and application thereof. BACKGROUND

[0002] Due to high energy density, long cycle life and environmental friendliness, lithium ion batteries (LIBs) have gradually become the main way to power portable electronic devices and electric vehicles. In these batteries, the positive electrode material is a key factor determining the performance, cost and safety of the battery. The specific capacity of the current main commercial positive electrode materials, such as LiCoO2, NCM and LiFePO4, is relatively low, making it difficult for lithium ion batteries to be widely used in many fields. Therefore, lithium-rich manganese-based materials have become the ideal candidate materials for the next generation of lithium ion batteries due to their high theoretical capacity (>250 mAh / g) and low cost. The high capacity characteristics of this type of positive electrode material are derived from the Li2MnO3 component which can be activated at a high voltage higher than 4.5 V to trigger an oxygen anion charge compensation mechanism, thereby providing additional capacity. It is this unique mixed anion-cation redox mechanism that makes LMRO a promising candidate positive electrode material for the next generation of high-energy lithium ion batteries.

[0003] However, lithium-rich manganese-based positive electrode materials at high voltage have problems such as low first coulombic efficiency, severe capacity and voltage decay, poor rate performance and poor cycle stability. In order to deal with these phenomena, researchers have been actively exploring various strategies, including element doping, surface treatment and structure optimization. However, the capacity and cycle stability of the current lithium-rich manganese-based positive electrode materials still need to be further improved, and there is great potential for practical application. SUMMARY

[0004] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the primary purpose of the present application is to provide a preparation method of a lithium-rich manganese-based positive electrode material with a surface heterojunction and bulk doping. The method uses a molten salt-assisted solvothermal method to prepare a lithium-rich manganese-based positive electrode material with a surface heterojunction M a (TiO3) b (1≤a≤5, 1≤b≤5) and bulk Ti and metal cation M doping, under the dual action of surface heterojunction and bulk doping mechanism, effectively inhibits the occurrence of interface reaction, reduces the generation of surface Li vacancies, and further slows down the migration rate of transition metal TM (Mn and Ni in lithium-rich) and the evolution process of heterostructure. By introducing metal cations to stabilize the lattice oxygen in the lithium-rich manganese material, the crystal structure stability of the material is improved, and the material has excellent cycle performance and structural stability, thereby improving the electrochemical performance of the battery.

[0005] Another object of the present application is to provide a lithium-rich manganese-based positive electrode material prepared by the above method, in which surface heterojunction and bulk doping jointly act. 1.2 Mn x Ni 0.2 Ti y M z O2, 0.3 < x ≤ 1.5, 0.0001 < y ≤ 0.001, 0.0001 < z ≤ 0.001, M = Na, K, Ba, Ca, Mg, Pb, Fe or Bi, is prepared by Ti and metal cation M coordination doping to prepare surface M a (TiO3) b (1 ≤ a ≤ 5, 1 ≤ b ≤ 5) heterojunction and bulk Ti and metal cation doping M lithium-rich manganese-based positive electrode material (Li 1.2 Mn 0.6 Ni 0.2 O2) with excellent voltage and capacity stability.

[0006] Still another object of the present application is to provide an application of the lithium-rich manganese-based positive electrode material prepared by the above surface heterojunction and bulk doping jointly acting.

[0007] The object of the present application is achieved by the following technical solutions:

[0008] A preparation method of a lithium-rich manganese-based positive electrode material prepared by surface heterojunction and bulk doping jointly acting, comprising the following steps:

[0009] S1. Stir a carbonate precursor Mn 0.75 Ni 0.25 CO3, anhydrous ethanol and tetrabutyl titanate at room temperature, and perform a solvothermal reaction at 120-180°C, and then filter, wash and dry to obtain a precursor in which Ti polymers cover the surface of Mn 0.75 Ni 0.25 CO3; the tetrabutyl titanate is 0.1-1 mol% of the carbonate precursor Mn 0.75 Ni 0.25 CO3, calculated according to Ti elements; and the molar ratio of the carbonate precursor Mn 0.75 Ni 0.25 CO3 to anhydrous ethanol is 0.008 mol:(50-100) mL.

[0010] S2. Stir the Ti polymer-covered Mn 0.75 Ni 0.25 CO3 precursor obtained in S1 at a molar ratio of 1:(1-1.1):(2-4):(0.001-0.01) to obtain a lithium-rich manganese-based positive electrode material.The precursor on the surface of CO3, lithium salt, molten salt and metal compound are uniformly ground, the mixed powder is sintered at 800-900 DEG C, cooled to room temperature, washed and dried at 180-200 DEG C to obtain a black powder;

[0011] S3. The black powder is dried at 300-400 DEG C, and cooled to room temperature to obtain a lithium-rich manganese-based positive electrode material with the cooperation of surface heterojunction and bulk doping, with a molecular formula of Li 1.2 Mn x Ni 0.2 Ti y M z O2, 0.3 < x < 1.5, 0.0001 < y < 0.001, 0.0001 < z < 0.001, wherein the surface heterojunction is M a (TiO3) b , 1 < a < 5, 1 < b < 5, the bulk doping is Ti and M doping, and M is Na, K, Ba, Ca, Mg, Pb, Fe or Bi.

[0012] Preferably, the lithium salt in step S2 is one or more of lithium carbonate, lithium hydroxide, lithium nitrate or lithium chloride; the molten salt is sodium chloride or / and potassium chloride; and the metal compound is a carbonate or / and chloride of Na, K, Ba, Ca, Mg, Pb, Fe or Bi.

[0013] Preferably, the heating rate of sintering at 800-900 DEG C in step S2 is 2-4 DEG C / min, and the sintering time is 10-20 h.

[0014] A lithium-rich manganese-based positive electrode material with the cooperation of surface heterojunction and bulk doping is prepared by the method.

[0015] The lithium-rich positive electrode material with the cooperation of surface heterojunction and bulk doping is applied to the preparation of lithium ion batteries.

[0016] The lithium-rich manganese-based positive electrode material with the cooperation of surface heterojunction and bulk doping is prepared by constructing a surface heterojunction M a (TiO3) b (1 < a < 5, 1 < b < 5) effectively inhibits the occurrence of interface reaction, reduces the generation of surface Li vacancies, and slows down the migration rate of transition metals Mn and Ni and the evolution process of heterostructure. The introduction of metal cations forms strong Ti-O bonds, M-O bonds and stable valence states to improve the electrochemical performance and lithium ion diffusion rate of the lithium-rich manganese-based positive electrode material, and the coordination of Ti and metal cations enhances the crystal structure and oxygen anion redox stability of the lithium-rich manganese-based layered positive electrode material, and significantly alleviates the surface interface reaction.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention employs a molten salt-assisted solvothermal method to prepare a surface heterostructure M by coordinated doping of Ti and metal cation M. a (TiO3) b (1≤a≤5, 1≤b≤5) and Li doped with bulk Ti and metal cation M. 1.2 Mn 0.6 Ni 0.2 In O2, the heterojunction effectively suppresses interfacial reactions and reduces the generation of surface Li vacancies, thereby slowing down the migration rate of transition metals and the evolution of the heterostructure. Doping with Ti and metal cations constructs Ti-O and MO bonds; the stronger bond energies suppress the Li-rich manganese-based material Li... 1.2 Mn 0.6 Ni 0.2 The structural phase transition of O2 during charging and discharging reduces the loss of lattice oxygen, thereby improving the efficiency of Li. 1.2 Mn 0.6 Ni 0.2 The stability and electrochemical performance of O2 cathode materials. Furthermore, the introduction of metals with larger ionic radii can act as a "pillar," stabilizing lithium-rich manganese-based materials such as Li. 1.2 Mn 0.6 Ni 0.2 The layered structure of O2 suppresses structural collapse and phase transition during charging and discharging, thereby improving the performance of Li. 1.2 Mn 0.6 Ni 0.2 The cycling stability of the O2 cathode material is ensured by the combined effect of surface heterojunction and bulk doping of Li. 1.2 Mn 0.6 Ni 0.2 O2 cathode materials possess excellent electrochemical performance. This method is simple; a molten salt-assisted solvothermal approach can be used to prepare lithium-rich manganese-based cathode materials with a dual-mechanism, namely, Li-based cathodes with the combined effects of surface heterojunction and bulk doping. 1.2 Mn 0.6 Ni 0.2 O2 has created favorable conditions for industrial application.

[0019] 2. The surface M prepared by this invention a (TiO3) b Electrochemical performance tests were conducted on a coin cell assembled from a lithium-rich manganese-based cathode material with heterojunction (1≤a≤5, 1≤b≤5) and bulk Ti and metal cation doping. The highest performance reached 206.9 mAh g⁻¹ at 2–4.8 V and 1 C. -1The capacity retention rate is 98.8% after 250 cycles. The lithium-rich manganese-based positive electrode material with the combined action of the surface heterojunction and the bulk doping has excellent cycle performance and structural stability, improves the electrochemical performance, and can be used for lithium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The XRD refinement figure and the partial enlarged view thereof of the lithium-rich manganese-based positive electrode material with the combined action of the surface heterojunction and the bulk doping prepared in Example 1 and the lithium-rich manganese-based positive electrode material of Comparative Example 1.

[0021] Figure 2 The voltage attenuation and discharge specific capacity cycle contrast figure of the lithium-rich manganese-based positive electrode material with the combined action of the surface heterojunction and the bulk doping prepared in Example 1 and the lithium-rich manganese-based positive electrode material of Comparative Example 1 under the condition of 1C (200 mA / g) and 4.8 V cut-off voltage.

[0022] Figure 3 The TEM image of the lithium-rich manganese-based positive electrode material with the combined action of the surface heterojunction and the bulk doping prepared in Example 1 and the lithium-rich manganese-based positive electrode material of Comparative Example 1 after 100 cycles.

[0023] Figure 4 The SEM photo of the lithium-rich manganese-based positive electrode material with the combined action of the surface heterojunction and the bulk doping prepared in Example 1 before cycle. DETAILED DESCRIPTION

[0024] The content of the present application is further illustrated in combination with specific examples, but should not be understood as a limitation to the present application. If not specifically indicated, the technical means used in the examples are the conventional means familiar to the person skilled in the art. Unless specifically indicated, the reagents, methods and equipment adopted in the present application are the conventional reagents, methods and equipment in the technical field.

[0025] Example 1

[0026] 1. 0.927 g of carbonate precursor (Mn 0.75 Ni 0.25 CO3) was placed in a polytetrafluoroethylene (PTFE) liner, 50 mL of anhydrous ethanol and 19 μL of tetrabutyl titanate were added. After stirring at room temperature for 30 min, it was placed in a reaction kettle for solvothermal reaction at 150 ℃ for 12 h. After the reaction was completed, the sample was taken out, filtered and washed with ethanol for 3 times, and then it was placed in a drying oven at 180 ℃ to obtain the precursor with Ti polymer uniformly covering the surface of Mn 0.75 Ni 0.25 CO3;

[0027] 2. Ti polymer uniformly covering Mn 0.75 Ni 0.25Precursor on the surface of CO3, 0.4655 g Li2CO3 (0.24 mol% relative to Mn 0.75 Ni 0.25 Precursor on the surface of CO3, 0.4655 g Li2CO3 (0.24 mol% relative to Mn

[0028] 3. The black powder was dried at 400 °C for 3 h and cooled to room temperature to obtain a lithium-rich manganese-based positive electrode material with the co-action of surface heterojunction BaTiO3 and bulk Ba and Ti doping, i.e., Li 1 .2 Mn 0.5925 Ni 0.2 Ti 0.005 Ba 0.005 O2positive electrode material.

[0029] Example 2

[0030] Different from Example 1 in that the temperature of the solvothermal reaction in Step 1 was 180 °C.

[0031] Example 3

[0032] Different from Example 1 in that the temperature of the solvothermal reaction in Step 1 was 120 °C.

[0033] Example 4

[0034] Different from Example 1 in that the content of tetrabutyl titanate and barium carbonate added in Steps 1 and 2 was both 0.4655 g Li2CO3 (5 mol% excess relative to Mn 0.75 Ni 0.25 CO3, to obtain a lithium-rich manganese-based positive electrode material with the co-action of surface heterojunction BaTiO3 and bulk Ba and Ti doping, i.e., Li 1 .2 Mn 0.5955 Ni 0.2 Ti 0.003 Ba 0.003 O2.

[0035] Example 5

[0036] Different from Example 1 in that the content of tetrabutyl titanate and barium carbonate added in Steps 1 and 2 was both 0.4655 g Li2CO3 (0.8 mol% relative to Mn 0.75 Ni 0.25 CO3, to obtain a lithium-rich manganese-based positive electrode material with the co-action of surface heterojunction BaTiO3 and bulk Ba and Ti doping, i.e., Li 1 .2 Mn 0.585 Ni 0.2 Ti 0.01Ba 0.01 O2.

[0037] Example 6

[0038] The difference from Example 1 is that the metal compound in Step 2 is K2CO3.

[0039] Example 7

[0040] The difference from Example 1 is that the metal compound in Step 2 is CaCO3.

[0041] Example 8

[0042] The difference from Example 1 is that the metal compound in Step 2 is MgCO3.

[0043] Example 9

[0044] The difference from Example 1 is that the sintering temperature in Step 2 is 830°C.

[0045] Example 10

[0046] The difference from Example 1 is that the sintering temperature in Step 2 is 870°C.

[0047] Comparative Example 1

[0048] 1. 0.927 g of carbonate precursor (Mn 0.75 Ni 0.25 CO3), 0.4655 g Li2CO3 (5 mol% excess relative to Mn 0.75 Ni 0.25 CO3), 1.8701 g NaCl and 3.5784 g KCl were uniformly ground, the mixed powder was sintered in air at 850°C for 12 h, cooled to room temperature, and the block solid was removed, washed with deionized water 3 times, filtered, and dried at 180°C to obtain a black powder.

[0049] 2. The black powder was sintered in air at 400°C for 3 h, cooled to room temperature, to obtain a Li 1.2 Mn 0.6 Ni 0.2 O2 cathode material.

[0050] Comparative Example 2

[0051] 1. 0.927 g of carbonate precursor (Mn 0.75 Ni 0.25 CO3), 0.004 g TiO2, 0.01 g BaCO3, 0.4655 g Li2CO3 (5 mol% excess relative to Mn 0.75 Ni 0.25CO3 5 mol%, 1.8701 g NaCl, 3.5784 g KCl were ground uniformly. The mixed powder was sintered in air at 850°C for 12 h, cooled to room temperature, the block solid was taken out, washed by deionized water for 3 times, filtered, dried at 180°C to get black powder.

[0052] 2. The black powder was sintered in air at 400°C for 3 h, cooled to room temperature to get bulk phase Ba and Ti doped Li-rich manganese-based positive electrode material, namely Li 1 .2 Mn 0.5925 Ni 0.2 Ti 0.005 Ba 0.005 O2.

[0053] Comparative Example 3

[0054] Different from Comparative Example 2 in that: the content of TiO2 and BaCO3 added in step 1 was 0.24 mol% of Mn 0.75 Ni 0.25 CO3, to prepare bulk phase Ba and Ti doped Li-rich manganese-based positive electrode material, namely Li 1 .2 Mn 0.5955 Ni 0.2 Ti 0.003 Ba 0.003 O2.

[0055] Comparative Example 4

[0056] Different from Comparative Example 2 in that: the content of TiO2 and BaCO3 added in step 1 was 0.8 mol% of Mn 0.75 Ni 0.25 CO3, to prepare bulk phase Ba and Ti doped Li-rich manganese-based positive electrode material, namely Li 1 .2 Mn 0.585 Ni 0.2 Ti 0.01 Ba 0.01 O2.

[0057] Comparative Example 5

[0058] Different from Comparative Example 2 in that: the metal compound in step 1 was K2CO3.

[0059] Comparative Example 6

[0060] Different from Comparative Example 2 in that: the metal compound in step 1 was CaCO3.

[0061] Comparative Example 7

[0062] Different from Comparative Example 2 in that: the metal compound in step 1 was MgCO3.

[0063] Comparative Example 8

[0064] The difference from Comparative Example 2 is that the sintering temperature in Step 1 is 830°C.

[0065] Comparative Example 9

[0066] The difference from Comparative Example 2 is that the sintering temperature in Step 1 is 870°C.

[0067] The positive electrode materials prepared from Examples 1-10 and Comparative Examples 1-9 were added with polyvinylidene fluoride binder, acetylene black conductive agent and N-methyl pyrrolidone cosolvent for homogenization, and the positive electrode materials were coated on metal aluminum sheets to form positive electrode sheets. Then the positive electrode sheets were assembled with polypropylene and polyethylene composite separators, 3036 electrolyte and lithium sheets to form batteries. The assembled batteries were connected to a charger for initial charging in a constant current and constant voltage charging mode. After charging, the capacity and cycle performance of the batteries were tested, and the test parameters of the batteries were as follows: 4.8V DCR first; 4.8V DCR cycle (1C), and the results are shown in Table 1.

[0068] Table 1 Electrochemical performance of batteries assembled with positive electrode materials of Examples 1-10 and Comparative Examples 1-9

[0069] Group Initial discharge specific capacity (mAh g -1 ])]] Initial coulombic efficiency Capacity retention after 250 cycles (%) Example 1 206.9 81.81 98.80 Comparative Example 1 235.7 73.86 42 Comparative Example 2 208.51 80.05 80.26 Example 2 202.93 78.46 91.24 Example 3 204.57 79.01 88.82 Example 4 213.45 80.64 77.56 Comparative Example 3 203.45 78.64 74.74 Example 5 198.51 77.72 81.86 Comparative Example 4 194.88 76.47 78.48 Example 6 223.66 77.09 65.25 Comparative Example 5 218.69 75.63 62.95 Example 7 215.98 80.85 67.10 Comparative Example 6 205.37 77.69 65.47 Example 8 202.65 81.96 69.34 Comparative Example 7 195.86 81.96 65.85 Example 9 191.30 82.17 67.40 Comparative Example 8 185.76 80.74 64.45 Example 10 208.70 79.84 85.28 Comparative Example 9 204.57 76.84 78.85

[0070] Table 1 is the electrochemical performance of lithium ion batteries assembled with lithium-rich manganese-based positive electrode materials of Examples 1-10 prepared by the surface heterojunction and bulk doping dual mechanism, and batteries assembled with lithium-rich manganese-based positive electrode materials of Comparative Example 1 and bulk doping lithium-rich manganese-based positive electrode materials of Comparative Examples 2-9. As can be seen from Table 1, Li 1 .2 Mn 0.5925 Ni 0.2 Ti 0.005 Ba 0.005 O2 of Example 1 reaches optimal performance, indicating that this method forms a heterojunction M a (TiO3) b (1≤a≤5, 1≤b≤5) effectively inhibits the occurrence of interface reactions, while reducing the generation of surface Li vacancies, thereby slowing down the migration rate of transition metals Mn and Ni and the heterostructure evolution process. The doping of Ti and metal cations constructs Ti-O bonds and M-O bonds, and the stronger bond energy inhibits the structural phase transition of Li 1.2 Mn 0.6 Ni 0.2 O2 in the charge and discharge process, reduces the loss of lattice oxygen, and thus improves the cycling performance of Li 1.2 Mn 0.6 Ni 0.2The stability and electrochemical performance of O2 cathode materials enhance the Li 1.2 Mn 0.6 Ni 0.2 The cycling stability and initial coulombic efficiency of the O2 cathode material at 4.8V. Lithium-ion batteries assembled from the lithium-rich manganese-based cathode materials prepared in Examples 1-10, which combine surface heterojunction and bulk doping, exhibit higher charge-discharge capacity, initial efficiency, and capacity retention compared to the battery assembled from the lithium-rich manganese-based cathode material in Comparative Example 1. The lithium-rich manganese-based cathode materials prepared in Examples 1-10 using the molten salt-assisted solvothermal method, which combine surface heterojunction BaTiO3 and bulk Ba and Ti doping, demonstrate better cycling stability and initial charge-discharge efficiency compared to the bulk-doped lithium-rich manganese-based cathode materials prepared in Comparative Examples 2-9 using the molten salt method.

[0071] Figure 1 The lithium-rich manganese-based cathode material Li, prepared in Example 1, is a result of the combined effects of a surface heterojunction (BaTiO3) and bulk Ba and Ti doping. 1 .2 Mn 0.5925 Ni 0.2 Ti 0.005 Ba 0.005 O2 and lithium-rich manganese-based cathode material Li (Comparative Example 1) 1.2 Mn 0.6 Ni 0.2 XRD pattern of O2 and its magnified view. From Figure 1 It can be seen that, due to the combined effect of surface heterojunction and bulk doping in Example 1, no impurity peaks appeared in the lithium-rich manganese-based cathode material, proving that Ba and Ti were successfully incorporated into the cathode material Li. 1.2 Mn 0.6 Ni 0.2 In O2, it is shown that the trace amounts of surface heterojunction BaTiO3 and the doping of Ba and Ti dopants do not affect the crystal structure of the material. Locally magnified XRD patterns show that after the combined effect of surface heterojunction BaTiO3 and the doping of Ba and Ti, the Li1 in Example 1... .2 Mn 0.5925 Ni 0.2 Ti 0.005 Ba 0.005 The O2 peaks 003 and 104 shift significantly to smaller angles, indicating that Ba 2+ The doping of Li affects the lattice constant of the material, expands the unit cell parameters of the sample, and is more conducive to the formation of Li. + diffusion. Figure 2 The graph shows a comparison of voltage decay (a) and discharge specific capacity (b) of the lithium-rich manganese-based cathode material prepared in Example 1, which combines surface heterojunction and bulk doping, with the lithium-rich manganese-based cathode material of Comparative Example 1, under 1C (200 mA / g) and 4.8V cutoff voltage conditions. Figure 2It can be seen that the Li 1.2 Mn 0.6 Ni 0.2 O2voltage decay (1.01 mV / cycle) within 50-250 cycles is much lower than that of Li 1.2 Mn 0.6 Ni 0.2 O2(2.22 mV / cycle), and the voltage stability is improved by more than 100%. The discharge capacity of the comparative example 1 after 250 cycles decreases significantly to 95.84 mAh g −1 , and the capacity retention rate is 42%. The discharge capacity of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material of the example 1 after 250 cycles is still as high as 204.4 mAh g −1 , and the capacity retention rate is 98.8%, indicating that the lithium-rich manganese-based positive electrode material with the surface heterojunction and bulk doping co-acting is greatly improved compared with the lithium-rich manganese-based positive electrode material. Figure 3 TEM images of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material (a and b) prepared in the example 1 and the lithium-rich manganese-based positive electrode material (c and d) of the comparative example 1 after 100 cycles. It can be seen that the material structure of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material of the example 1 after 100 cycles is compact, and there is no obvious corrosion; while the structure of the lithium-rich manganese-based positive electrode material of the comparative example 1 is loose and the electrolyte corrosion is serious, indicating that the lithium-rich manganese-based positive electrode material with the surface heterojunction BaTiO3 and Ba and Ti doping co-acting greatly improves the stability thereof. Figure 3 TEM images of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material (a and b) prepared in the example 1 and the lithium-rich manganese-based positive electrode material (c and d) of the comparative example 1 after 100 cycles. It can be seen that the material structure of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material of the example 1 after 100 cycles is compact, and there is no obvious corrosion; while the structure of the lithium-rich manganese-based positive electrode material of the comparative example 1 is loose and the electrolyte corrosion is serious, indicating that the lithium-rich manganese-based positive electrode material with the surface heterojunction BaTiO3 and Ba and Ti doping co-acting greatly improves the stability thereof. Figure 4 SEM images of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material of the example 1 before cycling. Among them, (a) is the SEM image of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material before cycling, and (b) is the EDX mapping. It can be seen that the heterojunction BaTiO3 formed on the surface effectively inhibits the occurrence of interface reaction. Figure 4 SEM images of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material of the example 1 before cycling. Among them, (a) is the SEM image of the surface heterojunction and bulk doping co-acting lithium-rich manganese-based positive electrode material before cycling, and (b) is the EDX mapping. It can be seen that the heterojunction BaTiO3 formed on the surface effectively inhibits the occurrence of interface reaction.

[0072] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement modes, and all shall be included in the protection scope of the present application.

Claims

1. A preparation method of a lithium-rich manganese-based positive electrode material with a combination of surface heterojunction and bulk doping, characterized in that, The method comprises the following steps: S1. 0.927 g of carbonate precursor Mn 0.75 Ni 0.25 CO3, 50 mL of anhydrous ethanol and 19 μL of tetrabutyl titanate were stirred at room temperature, and solvent-thermal reaction was carried out at 150°C for 12 h, to obtain Ti polymer-coated Mn 0.75 Ni 0.25 CO3 precursor on the surface of Ti S2. Uniformly coat Mn with Ti polymer. 0.75 Ni 0.25 The precursor on the CO3 surface, 0.4655 g Li2CO3, was used to uniformly cover Mn relative to the Ti polymer. 0.75 Ni 0.25 The precursors on the CO3 surface were uniformly ground in excess of 5 mol%, 1.8701 g NaCl, 3.5784 g KCl and 0.01 g BaCO3. The mixed powder was sintered in air at 850 °C for 12 h, cooled to room temperature, washed and dried at 180~200 °C to obtain a black powder. S3. Dry the black powder at 300-400℃, cool to room temperature to obtain a lithium-rich manganese-based positive electrode material with the cooperation of surface heterojunction and bulk doping, with a molecular formula of Li 1 .2 Mn 0.5925 Ni 0.2 Ti 0.005 Ba 0.005 O2.

2. The method for preparing lithium-rich manganese-based cathode material with the combined effect of surface heterojunction and bulk doping according to claim 1, characterized in that, The heating rate of the sintering in step S2 is 2-4 ℃ / min.

3. A lithium-rich manganese-based cathode material with the co-action of surface heterojunction and bulk doping, characterized in that, The lithium-rich manganese-based positive electrode material with the combined action of the surface heterojunction and the bulk doping is prepared by the method in claim 1 or 2.

4. Application of the lithium-rich positive electrode material with the combined action of the surface heterojunction and the bulk doping in claim 3 in the preparation of a lithium ion battery.

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