Lithium-rich manganese-based positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a lithium-rich manganese-based positive electrode material and a preparation method and application thereof.According to the preparation method of the lithium-rich manganese-based positive electrode material, a core-shell structure of the lithium-rich manganese-based material is designed through collaborative design of an inner core (nickel-cobalt-manganese precursor) and an outer shell (cerium-tungsten source); high capacity (rich lithium manganese base) of the inner core and high stability of the shell can be realized at the same time, and circulating voltage attenuation is relieved. The pseudo bonding effect of cerium can stabilize the main body structure, and the coating of tungsten further improves the diffusion efficiency of lithium ions by forming a high-conductivity interface layer. Tungsten and cerium mixed coating achieves collaborative optimization with a high-conductivity interface layer of tungsten through the structural stability and built-in electric field effect of cerium, and the cycling stability, voltage platform attenuation and first efficiency of the lithium-rich manganese-based material are remarkably improved.

Description

Technical Field

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

[0002] Lithium-rich manganese-based materials typically have the molecular formula xLi₂MnO₃·(1-x)LiMO₂ (M=Ni,Mn,Co), exhibiting a layered structure and high specific capacity (>250mAh·g). -1 The theoretical specific capacity can reach 300 mAh·g. -1 The above far surpasses traditional ternary materials (such as LiNi). 0.8 Co 0.1 Mn 0.1 O2 has shown great potential in the demand for high-energy-density batteries and has become a research hotspot in the field of cathode materials for lithium-ion batteries.

[0003] The core advantage of lithium-rich manganese-based materials lies in their unique composite structure. The Li₂MnO₃ phase provides high-capacity Li insertion / extraction channels, while the LiMO₂ phase maintains structural stability. This composite structure can achieve a high voltage plateau (>4.5V) during charge and discharge, significantly improving battery energy density. Furthermore, lithium-rich manganese-based materials are lower in cost (due to abundant Mn resources) and have better safety than cobalt-based materials, meeting the demand for low cost and high safety in new energy vehicles and energy storage systems. However, their industrialization still faces many technical challenges. Irreversible anionic redox leads to lattice oxygen loss, resulting in low initial charge / discharge efficiency (60-80%). The transformation of the layered structure into the spinel phase causes capacity decay, leading to cycle voltage decay. Current technologies address this through single doping (such as Mg). 2+ / Zr 4+ It only inhibits 40% of manganese leaching; although ternary material composites can improve cycle stability, the specific capacity is limited (<250mAh / g); coating with V2O5 can improve the initial efficiency to 94%, but the rate performance is not improved. These problems urgently need to be solved to promote the large-scale application of lithium-rich manganese-based batteries.

[0004] The related technology discloses a cathode material and its preparation method, and a lithium-ion battery. Specifically, the cathode material includes secondary particles, which are formed by the aggregation of multiple primary particles. The secondary particles include a matrix material with the general chemical formula Li. a Ni x Co y M z N bO2, wherein 0.95≤a≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, ≤b<0.4, x+y+z+b=1, M is Mn and / or Al, N includes at least one of Zr, Mg, Sr, V, Y, Nb, B, S, Ba, Ti and Ta; and a first coating material located on the surface of the matrix material, the first coating material including lithium tungstate and / or lithium molybdate; the cathode material also includes a second coating material located on the surface of the secondary particles, the second coating material being located between and / or on the surface of the primary particles on the surface of the secondary particles; the second coating material includes at least one of Al2O3, TiO2, MgO, CeO2, ZrO2 and their corresponding lithium-containing metal compounds. The cathode material of this application can reduce the overpotential in the battery electrode and improve its cycle performance and rate performance; however, the interface stress and impedance of ordinary nickel-cobalt-manganese precursor sintered cathode materials are relatively large, which is not conducive to the transport of lithium ions, and the transition metal in the internal lattice is prone to migration and structural distortion, resulting in poor first charge and discharge efficiency, voltage decay and cycle life.

[0005] Therefore, how to effectively optimize and modify lithium-rich manganese-based cathode materials and their preparation methods to improve their initial charge-discharge efficiency, voltage decay, and cycle life is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing lithium-rich manganese-based cathode materials to solve the problems of low initial charge-discharge efficiency, voltage decay and short cycle life in the prior art.

[0007] In a first aspect, the present invention provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps:

[0008] (1) Prepare first and second solutions of different concentrations using nickel, cobalt, and manganese sources respectively; add the second solution to the first solution at a first rate to carry out the reaction, and obtain nickel-cobalt-manganese precursor;

[0009] (2) The nickel-cobalt-manganese precursor and the lithium source are mixed and then subjected to a first sintering to obtain the matrix material;

[0010] (3) The matrix material is immersed in the coating liquid and sintered for the second time to obtain a lithium-rich manganese-based cathode material, wherein the coating liquid includes a cerium source and a tungsten source.

[0011] In some optional embodiments, the cerium source is calculated as cerium element, the tungsten source is calculated as tungsten element, and the molar ratio of cerium element to tungsten element is 1:(1.5-2.5).

[0012] In some alternative embodiments, in the first solution, the nickel source is calculated as nickel element, the cobalt source is calculated as cobalt element, the manganese source is calculated as manganese element, and the molar ratio of the nickel element, the cobalt element, and the manganese element is (0.10-0.14):(0.10-0.14):(0.72-0.76).

[0013] In some alternative embodiments, in the second solution, the nickel source is calculated as nickel element, the cobalt source is calculated as cobalt element, the manganese source is calculated as manganese element, and the molar ratio of the nickel element, the cobalt element, and the manganese element is (0.02-0.06):(0.02-0.06):(0.88-0.96).

[0014] In some alternative embodiments, the molar ratio of nickel in the first solution to nickel in the second solution is (0.10-0.14):(0.02-0.09).

[0015] In some alternative embodiments, the concentration of the cerium source in the coating solution is 0.5 mol / L to 1 mol / L.

[0016] In some alternative embodiments, the concentration of the tungsten source in the coating solution is 0.5 mol / L to 1 mol / L.

[0017] In some optional embodiments, the lithium source is calculated as lithium element, the nickel-cobalt-manganese precursor is calculated as nickel element, cobalt element and manganese element, and the molar ratio of the total number of moles of lithium element to the total number of moles of nickel element, cobalt element and manganese element is 1:(1.20-1.35).

[0018] In some alternative embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, and lithium nitrate.

[0019] In some alternative embodiments, the cerium source includes at least one of cerium nitrate, cerium chloride, and cerium carbonate.

[0020] In some alternative embodiments, the tungsten source includes at least one of ammonium tungstate, tungsten chloride, and tungsten oxide.

[0021] In some alternative embodiments, the first sintering temperature is 920℃-980℃ and the time is 12h-14h.

[0022] In some alternative embodiments, the second sintering temperature is 450°C-500°C and the time is 5h-8h.

[0023] In some alternative implementations, the immersion time is 8-12 hours.

[0024] In some alternative implementations, step (1) further includes adding a complexing agent, which includes ammonia.

[0025] In some alternative implementations, in step (1), the pH is adjusted to 7.8-8.2.

[0026] In some alternative embodiments, the reaction is carried out at a temperature of 50°C-65°C for a duration of 4-6 hours.

[0027] In some alternative embodiments, the reaction is further accompanied by stirring at a speed of 700 rpm to 1000 rpm.

[0028] In some alternative embodiments, the first rate is 3 mL / min to 10 mL / min.

[0029] In some optional embodiments, the chemical formula of the nickel-cobalt-manganese precursor is [(Ni a Co b Mn c ) 1-z (Ni d Co e Mn f ) z CO3, where 0.10≤a≤0.14, 0.10≤b≤0.14, 0.72≤c≤0.76, 0.02≤d≤0.06, 0.02≤e≤0.06, 0.88≤f≤0.96, 0.1≤z≤0.5, a+b+c=1, d+e+f=1.

[0030] In some alternative embodiments, the chemical formula of the matrix is ​​Li. w Mn x Ni y Co z O2, where w≤1.35, 0<x<0.60, 0<y<0.20, x+y+z=1.

[0031] In a second aspect, the present invention provides a lithium-rich manganese-based cathode material, which is prepared by the preparation method described in the first aspect.

[0032] Thirdly, the present invention provides an application of a lithium-rich manganese-based cathode material prepared by the preparation method described in the first aspect or the lithium-rich manganese-based cathode material described in the second aspect in a lithium-ion battery.

[0033] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0034] 1. The method for preparing lithium-rich manganese-based cathode material provided by the present invention includes the following steps: preparing a nickel source, a cobalt source, and a manganese source into a first solution and a second solution of different concentrations, respectively; adding the first solution and the second solution to a reaction vessel for reaction to obtain a nickel-cobalt-manganese precursor; mixing the nickel-cobalt-manganese precursor and a lithium source and performing a first sintering to obtain a matrix material; mixing the matrix material and a coating solution and performing a second sintering to obtain a lithium-rich manganese-based cathode material, wherein the coating solution includes a cerium source and a tungsten source. The second solution is added to the first solution at a first rate to create different growth rates for the core-shell particles, forming a core-shell structured nickel-cobalt-manganese precursor. On one hand, the nickel-cobalt-manganese precursor has a high ion diffusion coefficient, which helps lithium ions to quickly insert and de-insert into the material. On the other hand, when the core-shell structured nickel-cobalt-manganese precursor is sintered with the lithium source, the lamellar monomers of the outer shell can effectively promote the penetration of the lithium source, forming a well-crystallized, rounded single-crystal material. This not only improves the density of the cathode material but also reduces its interfacial impedance and enhances the overall electrochemical performance. In addition, the nickel-cobalt-manganese precursor has a gradient transition layer that can suppress interfacial stress.

[0035] Furthermore, the core-shell structure of lithium-rich manganese-based materials, through the synergistic design of the core (nickel-cobalt-manganese precursor) and the shell (cerium-tungsten source), can simultaneously achieve high core capacity (lithium-rich manganese-based) and high shell stability, mitigating cycle voltage decay. The introduction of tungsten (W) can form oxide layers such as Li₂WO₄ through surface coating, while cerium doping, by stimulating pseudo-bonding, can stabilize the lattice oxygen evolution process of lithium-rich manganese-based materials, suppress transition metal migration and structural distortion, construct a conductive network, and inhibit the dissolution of transition metal ions. Simultaneously, tungsten source coating can also improve the Li₂O₃ content of lithium-rich manganese-based materials. + Conductivity (such as forming a fast-ion conductor) improves the rate performance and cycle stability of lithium-rich manganese-based cathode materials. Cerium (Ce) 3+ / Ce 4+ The addition of cerium can replace some transition metal ions (such as Mn and Ni), stabilizing the crystal structure through charge compensation and suppressing lattice oxygen loss and phase transitions during cycling. In this invention, the pseudo-bonding of cerium stabilizes the main structure, while the coating of tungsten further enhances lithium-ion diffusion efficiency by forming a highly conductive interface layer. The mixed coating of tungsten and cerium achieves synergistic optimization through the structural stability and built-in electric field effect of cerium and the highly conductive interface layer of tungsten, significantly improving the cycling stability, voltage plateau decay, and first-pass efficiency of lithium-rich manganese-based materials.

[0036] 2. The method for preparing lithium-rich manganese-based cathode material provided by the present invention controls parameters such as reaction temperature, pH, stirring rate and / or reaction time to achieve different growth rates of core-shell particles, thereby better forming a core-shell structured nickel-cobalt-manganese precursor. Detailed Implementation

[0037] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0038] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0039] To address the problems existing in the aforementioned related technologies, according to a first aspect of the present invention, a method for preparing a lithium-rich manganese-based cathode material is provided, comprising the following steps:

[0040] (1) Nickel source, cobalt source, and manganese source are respectively prepared into a first solution and a second solution with different concentrations; the second solution is added to the first solution at a first rate to obtain a nickel-cobalt-manganese precursor; in the first solution, the nickel source is calculated as nickel element, the cobalt source as cobalt element, and the manganese source as manganese element, and the molar ratio of nickel element, cobalt element, and manganese element is (0.10-0.14):(0.10-0.14):(0.72-0.76); in the second solution, the nickel source is calculated as nickel element, the cobalt source as cobalt element, and the manganese source as manganese element, and the molar ratio of nickel element, cobalt element, and manganese element is (0.0... 2-0.06):(0.02-0.06):(0.88-0.96); the molar ratio of nickel in the first solution to that in the second solution is (0.10-0.14):(0.02-0.09); step (1) also includes adding a complexing agent, which includes ammonia; adjusting the pH to 7.8-8.2; the reaction temperature is 50℃-65℃, and the time is 4h-6h; the reaction also includes stirring at a speed of 700rpm-1000rpm; the first rate is 3mL / min-10mL / min; the chemical formula of the nickel-cobalt-manganese precursor is [(Ni a Co b Mn c ) 1-z (Ni d Co e Mn f ) zCO3, wherein 0.10≤a≤0.14, 0.10≤b≤0.14, 0.72≤c≤0.76, 0.02≤d≤0.06, 0.02≤e≤0.06, 0.88≤f≤0.96, 0.1≤z≤0.5, a+b+c=1, d+e+f=1; the nickel source includes at least one of nickel sulfate, nickel nitrate, and nickel acetate; the cobalt source includes at least one of cobalt sulfate, cobalt nitrate, and cobalt acetate; the manganese source includes at least one of manganese sulfate, manganese nitrate, and manganese acetate.

[0041] (2) The nickel-cobalt-manganese precursor and the lithium source are mixed and subjected to a first sintering to obtain a matrix material; the lithium source is calculated based on lithium element, and the nickel-cobalt-manganese precursor is calculated based on nickel, cobalt, and manganese elements, with a molar ratio of lithium element to the total molar number of nickel, cobalt, and manganese elements of 1:(1.20-1.35); the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, and lithium nitrate; the first sintering temperature is 920℃-980℃, and the time is 12h-14h; the chemical formula of the matrix is ​​Li w Mn x Ni y Co z O2, where w≤1.35, 0<x<0.60, 0<y<0.20, x+y+z=1;

[0042] (3) The matrix material is immersed in a coating solution and then sintered for the second time to obtain a lithium-rich manganese-based cathode material. The coating solution includes a cerium source and a tungsten source. The cerium source is calculated as cerium element, the tungsten source is calculated as tungsten element, and the molar ratio of cerium element to tungsten element is 1:(1.5-2.5). In the coating solution, the concentration of the cerium source is 0.5mol / L-1mol / L. In the coating solution, the concentration of the tungsten source is 0.5mol / L-1mol / L. The cerium source includes at least one of cerium nitrate, cerium chloride, and cerium carbonate. The tungsten source includes at least one of ammonium tungstate, tungsten chloride, and tungsten oxide. The immersion time is 8h-12h. The temperature of the second sintering is 450℃-500℃, and the time is 5h-8h.

[0043] In this invention, TM represents the three metals Ni, Co, and Mn in the gradient precursor.

[0044] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0047] (1) NiSO4, CoSO4, and MnSO4 were weighed out in a molar ratio of 0.13:0.13:0.74 and mixed to prepare a core solution; NiSO4, CoSO4, and MnSO4 were weighed out in a molar ratio of 0.05:0.05:0.90 and mixed to prepare a shell solution; 500 mL of the core solution was added to the reaction vessel, and then 500 mL of the shell solution was added dropwise at a rate of 5 mL / min to carry out the reaction. During the reaction, ammonia was used to adjust the pH to 8.0, the reaction temperature was 55℃, the reaction time was 5 h, and the stirring speed was 800 rpm to generate [(Ni 0.13 Co 0.13 Mn 0.74 ) 0.5 (Ni 0.05 Co 0.05 Mn 0.90 ) 0.5 CO3, a gradient precursor;

[0048] (2) The gradient precursor and Li2CO3 were mixed at a Li / TM molar ratio of 1.25 and sintered at 950℃ for 12 h under an oxygen atmosphere to obtain the matrix; wherein, the chemical formula of the matrix is ​​Li 1.25 Mn 0.54 Ni 0.33 Co 0.13 O2;

[0049] (3) Weigh out Ce(NO3)3 and (NH4) according to a Ce to W molar ratio of 1:1.5. 10 W 12 O 41 The mixture was dissolved in ethanol and ultrasonically dispersed to prepare a coating solution; in the coating solution, Ce(NO3)3 and (NH4)3 were present. 10 W 12 O 41 The concentrations were 0.5 mol / L and 0.5 mol / L, respectively;

[0050] (4) The substrate was immersed in the coating solution for 10 h, dried at 80 °C, and then coated and sintered at 500 °C for 6 h to form CeO2@Li2WO4 coating, thus preparing lithium-rich manganese-based cathode material.

[0051] Example 2

[0052] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 1, except that in step (3), the molar ratio of Ce to W is 1:2.

[0053] Example 3

[0054] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 1, except that in step (3), the molar ratio of Ce to W is 1:2.5.

[0055] Example 4

[0056] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 1, except that Ce(NO3)3 is replaced with the same number of moles of CeCl3, and (NH4)3 is used instead. 10 W 12 O 41 Replace with the same number of moles of WCl6.

[0057] Example 5

[0058] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0059] (1) Ni(NO3)2, Co(CH3COO)2, and Mn(NO3)2 were weighed out in a molar ratio of 0.12:0.14:0.74 and mixed to prepare a core solution; NiSO4, CoSO4, and MnSO4 were weighed out in a molar ratio of 0.02:0.06:0.92 and mixed to prepare a shell solution; 500 mL of the core solution was added to the reaction vessel, and then 625 mL of the shell solution was added dropwise at 3 mL / min to carry out the reaction. During the reaction, ammonia water was used to adjust the pH to 7.8, the reaction temperature was 65℃, the reaction time was 6 h, and the stirring speed was 900 rpm to generate [(Ni 0.12 Co 0.14 Mn 0.74 ) 0.5 (Ni 0.02 Co 0.06 Mn 0.92 ) 0.5 CO3, a precursor for nickel, cobalt, and manganese;

[0060] (2) The nickel-cobalt-manganese precursor and Li₂CO₃ were mixed at a Li / TM molar ratio of 1.2 and sintered at 920°C for 14 h under an oxygen atmosphere to obtain the matrix; wherein, the chemical formula of the matrix is ​​Li 1.2 Mn 0.54 Ni 0.33 Co 0.13 O2;

[0061] (3) Weigh out Ce(NO3)3 and (NH4) according to a Ce to W molar ratio of 1:1.5. 10 W 12 O 41The solution was dissolved in ethanol and ultrasonically dispersed to prepare a coating solution. In the coating solution, the concentration of Ce(NO3)3 was 0.75 mol / L, and the concentration of (NH4)3 was... 10 W 12 O 41 The concentration is 1 mol / L;

[0062] (4) The substrate was immersed in the coating solution for 12 hours, dried at 80°C, and then sintered at 450°C for 8 hours to form CeO2@Li2WO4 coating, thus preparing lithium-rich manganese-based cathode material.

[0063] Example 6

[0064] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0065] (1) Ni(CH3COO)2, Co(NO3)2, and Mn(CH3COO)2 were weighed out in a molar ratio of 0.14:0.14:0.72 and mixed to prepare a core solution; NiSO4, CoSO4, and MnSO4 were weighed out in a molar ratio of 0.03:0.02:0.95 and mixed to prepare a shell solution; 500 mL of the core solution was added to the reaction vessel, and then 750 mL of the shell solution was added dropwise at a rate of 9 mL / min to carry out the reaction. During the reaction, ammonia was used to adjust the pH to 8.2, the reaction temperature was 50℃, the reaction time was 6 h, and the stirring speed was 1000 rpm to generate [(Ni 0.14 Co 0.14 Mn 0.72 ) 0.5 (Ni 0.03 Co 0.02 Mn 0.95 ) 0.5 CO3, a precursor for nickel, cobalt, and manganese;

[0066] (2) The nickel-cobalt-manganese precursor was mixed with Li₂CO₃ at a Li / TM molar ratio of 1.35 and sintered at 980℃ for 13 h under an oxygen atmosphere to obtain the matrix; wherein, the chemical formula of the matrix is ​​Li 1.35 Mn 0.54 Ni 0.33 Co 013 O2;

[0067] (3) Weigh cerium chloride and tungsten oxide according to a Ce to W molar ratio of 1:1.5, dissolve them in ethanol, and disperse them by ultrasonication to prepare a coating solution. In the coating solution, the concentration of Ce(NO3)3 is 1 mol / L, and the concentration of (NH4)3 is 1 mol / L. 10 W 12 O 41 The concentration was 0.75 mol / L;

[0068] (4) The substrate was immersed in the coating solution for 8 hours, dried at 80°C, and then sintered at 500°C for 5 hours to form CeO2@Li2WO4 coating, thus preparing lithium-rich manganese-based cathode material.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 1, except that in step (3), Ce(NO3)3 is replaced with the same number of moles of (NH4). 10 W 12 O 41 .

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 1, except that in step (3), (NH4) is used. 10 W 12 O 41 Replace with the same number of moles of Ce(NO3)3.

[0073] Comparative Example 3

[0074] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 1, except that in step (3), Ce(NO3)3 and (NH4) are added. 10 W 12 O 41 Replace with the same number of moles of Na2S.

[0075] Comparative Example 4

[0076] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 1, except that in step (3), Ce(NO3)3 and (NH4) are added. 10 W 12 O 41 Replace with the same number of moles of Li3VO4.

[0077] Comparative Example 5

[0078] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material, which is basically the same as the steps in Example 3, except that in step (1), NiSO4, CoSO4 and MnSO4 are weighed directly according to a molar ratio of 0.18:0.18:1.64, mixed to obtain a lithium-rich manganese-based precursor, and the pH is controlled at 8.0, the temperature at 55℃, and the stirring speed at 800 rpm to generate Ni 0.18 Co 0.18 Mn 1.64 CO3 precursor.

[0079] Experimental Example

[0080] The cathode materials prepared in Examples 1-6 and Comparative Examples 1-5 were used to prepare coin cells. The specific preparation method was as follows: cathode materials, polyvinylidene fluoride (PVDF) and conductive agent acetylene black were weighed at a mass ratio of 90:5:5 and coated into an electrode sheet. A lithium metal sheet was used as the counter electrode, and the separator was Celgard 2500. A 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC to DMC volume ratio of 1:1) was used as the electrolyte. The cells were assembled into CR2032 coin cells in an argon glove box (where water <0.01 ppm and oxygen <0.01 ppm). Finally, the cells were placed in the Blue Electric Test System for electrical performance testing. The electrical performance test conditions are as follows: the charge / discharge voltage range is 2.0V-4.8V, the test temperature is 25℃, the battery's initial charge / discharge performance is tested by 1 cycle at 0.1C / 0.1C, and the battery's cycle performance is tested by 50 cycles at 1C / 1C.

[0081] Table 1. Performance test results of button batteries prepared from the cathode materials of each embodiment and comparative example.

[0082]

[0083] As can be seen from the table above, the discharge specific capacity of the button batteries prepared with the cathode materials prepared in Examples 1-6 is 240 mAh g. -1 -246mAh g -1 The first-stage efficiency was 74%-77%, and the capacity retention rate was 93%-97%. Comparative Example 1 only added Ce(NO3)3, which could not further improve the diffusion efficiency of lithium ions, resulting in a decrease in discharge specific capacity, first-stage efficiency, and capacity retention rate. Comparative Example 2 only added (NH4). 10 W 12 O 41 Lattice oxygen loss leads to low initial charge / discharge efficiency; Comparative Example 3 uses Ce(NO3)3 and (NH4)3. 10 W 12 O 41 Replacing the coating with the same number of moles of Na2S did not provide more active ions on the surface, resulting in a decrease in discharge specific capacity, first-time efficiency, and capacity retention. Comparative Example 4 used Ce(NO3)3 and (NH4)2... 10 W 12 O 41When replaced with the same number of moles of Li3VO4, the Li3VO4 coating did not stabilize the material structure, resulting in a decrease in discharge specific capacity, first efficiency, and capacity retention. In Comparative Example 5, no gradient precursor was formed, and the uniform high-nickel material surface was more active. During cycling, especially under high voltage, the electrolyte continued to oxidize and decompose on the surface, forming a thick and unstable CEI film that consumed active lithium. At the same time, the high nickel content on the particle surface led to severe transition metal migration and irreversible phase transitions, eroding from the surface inwards and destroying structural integrity, resulting in a decrease in discharge specific capacity, first efficiency, and capacity retention.

[0084] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: (1) Prepare first and second solutions of different concentrations by using nickel, cobalt and manganese sources respectively; add the second solution to the first solution at a first rate to obtain nickel-cobalt-manganese precursor; (2) The nickel-cobalt-manganese precursor and the lithium source are mixed and then subjected to a first sintering to obtain the matrix material; (3) The matrix material is immersed in the coating liquid and sintered for the second time to obtain a lithium-rich manganese-based cathode material, wherein the coating liquid includes a cerium source and a tungsten source.

2. The method for preparing lithium-rich manganese-based cathode material according to claim 1, characterized in that, The cerium source is calculated based on cerium element, the tungsten source is calculated based on tungsten element, and the molar ratio of cerium element to tungsten element is 1:(1.5-2.5).

3. The method for preparing lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the first solution, the nickel source is calculated as nickel element, the cobalt source is calculated as cobalt element, the manganese source is calculated as manganese element, and the molar ratio of nickel element, cobalt element and manganese element is (0.10-0.14):(0.10-0.14):(0.72-0.76); And / or, in the second solution, the nickel source is calculated as nickel element, the cobalt source is calculated as cobalt element, the manganese source is calculated as manganese element, and the molar ratio of the nickel element, the cobalt element, and the manganese element is (0.02-0.06):(0.02-0.06):(0.88-0.96); And / or, the molar ratio of nickel in the first solution to nickel in the second solution is (0.10-0.14):(0.02-0.09).

4. The method for preparing lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the coating solution, the concentration of the cerium source is 0.5 mol / L to 1 mol / L; And / or, in the coating solution, the concentration of the tungsten source is 0.5 mol / L to 1 mol / L; And / or, the lithium source is calculated as lithium element, the nickel-cobalt-manganese precursor is calculated as nickel element, cobalt element and manganese element, and the molar ratio of the total molar number of lithium element to the total molar number of nickel element, cobalt element and manganese element is 1:(1.20-1.35).

5. The method for preparing the lithium-rich manganese-based cathode material according to claim 1 or 4, characterized in that, The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, and lithium nitrate; And / or, the cerium source includes at least one of cerium nitrate, cerium chloride, and cerium carbonate; And / or, the tungsten source includes at least one of ammonium tungstate, tungsten chloride, and tungsten oxide.

6. The method for preparing lithium-rich manganese-based cathode material according to claim 1, characterized in that, The first sintering temperature is 920℃-980℃, and the time is 12h-14h; And / or, the second sintering temperature is 450℃-500℃, and the time is 5h-8h; And / or, the immersion time is 8h-12h.

7. The method for preparing lithium-rich manganese-based cathode material according to claim 1, characterized in that, Step (1) also includes adding a complexing agent, which includes ammonia. And / or, in step (1), adjust the pH to 7.8-8.2; And / or, the reaction is carried out at a temperature of 50°C-65°C for a time of 4-6 hours; And / or, the reaction also includes stirring at a speed of 700 rpm to 1000 rpm; And / or, the first rate is 3 mL / min-10 mL / min.

8. The method for preparing lithium-rich manganese-based cathode material according to any one of claims 1-7, characterized in that, The chemical formula of the nickel-cobalt-manganese precursor is [(Ni a Co b Mn c ) 1-z (Ni d Co e Mn f ) z CO3, where 0.10≤a≤0.14, 0.10≤b≤0.14, 0.72≤c≤0.76, 0.02≤d≤0.06, 0.02≤e≤0.06, 0.88≤f≤0.96, 0.1≤z≤0.5, a+b+c=1, d+e+f=1; And / or, the chemical formula of the matrix is ​​Li w Mn x Ni y Co z O2, where w≤1.35, 0<x<0.60, 0<y<0.40, x+y+z=1.

9. A lithium-rich manganese-based cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the lithium-rich manganese-based cathode material prepared by any one of claims 1-8 or the lithium-rich manganese-based cathode material of claim 9 in a lithium-ion battery.

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