Sn-doped high-voltage lithium nickel manganese oxide cathode materials, their preparation methods and applications

Abstract

This invention discloses a Sn-doped high-voltage lithium nickel manganese oxide cathode material, its preparation method, and its application, belonging to the field of lithium-ion battery cathode materials. The preparation method involves: 1) dissolving a lithium source, a nickel source, a manganese source, and a tin source in water, wherein the lithium source, nickel source, manganese source, and tin source are all acetates, then adding a complexing agent, citric acid, and stirring the reaction mixture; 2) drying the resulting mixture by spray drying to obtain a solid powder; 3) pre-sintering the obtained solid powder, grinding it, then sintering and grinding it again to obtain the Sn-doped high-voltage lithium nickel manganese oxide cathode material. The obtained high-voltage lithium nickel manganese oxide cathode material has high purity, excellent uniform particle size, and a good truncated octahedral crystal structure. Sn doping effectively improves structural stability, exhibiting excellent lithium-ion and electronic conductivity, and demonstrating high specific capacity and cycle stability. Furthermore, the preparation process is simple, involves few steps, has high production efficiency, and uses inexpensive and readily available raw materials, which is beneficial for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to a Sn-doped high-voltage nickel-manganese lithium cathode material, its preparation method, and its application. Background Technology

[0002] LiNi 0.5 Mn 1.5 O4 (LNMO), as a high-voltage cathode material, has attracted much attention in the field of lithium-ion batteries due to its high energy density, high operating voltage, low cost, and environmental friendliness. LNMO boasts an operating voltage as high as 4.7V and an energy density as high as 650Wh / kg, making it an ideal choice for improving battery energy density.

[0003] Furthermore, LNMO possesses three-dimensional lithium-ion diffusion channels, thereby forming rapid ion diffusion kinetics, enabling Li... + LNMO exhibits faster ion migration rates in the electrolyte and at the electrolyte-electrode interface. However, during charge-discharge, the two-phase transition leads to decreased structural stability, resulting in poor cycle performance. Furthermore, during cycling, transition metals (Mn) readily dissolve from the LNMO lattice and migrate into the electrolyte, causing the spinel-type structure of the LNMO electrode to collapse and increasing charge transfer impedance, thus severely degrading battery performance. Moreover, the Jahn-Teller effect in the Mn-O framework induces structural distortion in the LNMO cathode, easily leading to structural degradation and rapid capacity decay. Therefore, high structural stability and optimized electrochemical performance are key requirements for achieving high-energy-density lithium-ion battery energy storage for LNMO cathode materials.

[0004] The structural basis of LNMO comprises two distinct polymorphs: a cationic ordered phase (space group P4332, referred to as o-LNMO) and a cationic disordered phase (space group Fd-3m, referred to as d-LNMO). These structures differ at the atomic scale, and these differences affect the electrochemical performance of the material; the main differences between o-LNMO and d-LNMO in electrochemical performance are rate performance and cycle stability. The ordered phase o-LNMO exhibits better structural stability and a lower lithium-ion migration activation energy, theoretically beneficial for improving the material's conductivity and ion diffusion coefficient. However, in practical applications, it has been found that d-LNMO, due to its disordered structure, may be more conducive to lithium-ion transport, exhibiting better rate performance. Therefore, current LNMO synthesis primarily focuses on the disordered phase. To improve the performance of LNMO, researchers have adopted various strategies, such as bulk doping, coating, and morphology control, to optimize the material structure.

[0005] In-situ doping effectively incorporates trace elements into specific sites within the LNMO lattice to stabilize it and prevent structural collapse, demonstrating significant efficacy. Currently, solid-state doping is commonly employed. However, this method typically involves mechanically mixing lithium, manganese, and nickel sources followed by high-temperature calcination, which can lead to uneven mixing of raw materials, thus affecting electrochemical performance. Furthermore, materials synthesized using solid-state methods often exhibit irregular morphologies, potentially impacting electrical conductivity and ion diffusion properties. Summary of the Invention

[0006] The purpose of this invention is to provide a Sn-doped high-voltage lithium nickel manganese oxide cathode material, its preparation method, and its application. The preparation process is simple, the raw materials are inexpensive and readily available, and the resulting cathode material, when used as a positive electrode active material for lithium-ion batteries, exhibits excellent lithium-ion and electronic conduction properties, as well as high specific capacity and cycle stability.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing Sn-doped high-voltage lithium nickel manganese oxide cathode material is provided, comprising the following steps:

[0009] 1) Dissolve lithium, nickel, manganese and tin sources in water, wherein the lithium, nickel, manganese and tin sources are all acetates, and then add citric acid as a complexing agent and stir to react;

[0010] 2) The mixture obtained in step 1) is dried by spray drying to obtain a solid powder;

[0011] 3) The solid powder obtained in step 2) is pre-sintered, ground, sintered again, and ground again to obtain Sn-doped high-voltage lithium nickel manganese oxide cathode material.

[0012] According to the above scheme, in step 1), the lithium source, nickel source, manganese source, and tin source are selected according to the chemical formula LiNi. 0.5 Mn 1.5-x Sn x The stoichiometric ratio of O4 is used for feeding, where x is 0.035 to 0.045.

[0013] Preferably, the lithium source is in excess by 4-6%, and a slight excess of lithium acetate is used to compensate for lithium loss during high-temperature sintering.

[0014] According to the above scheme, in step 1), the molar volume ratio of nickel source to water is 0.005 mol: 150 mL to 200 mL.

[0015] According to the above scheme, in step 1), the molar ratio of citric acid to transition metal ions is 0.8 to 1:1, wherein the transition metals are Ni, Mn and Sn.

[0016] According to the above scheme, in step 1), the stirring reaction time is 12-18 hours.

[0017] According to the above scheme, in step 2), the spray drying outlet temperature is set to 190-210℃.

[0018] According to the above scheme, in step 3), the pre-sintering process is: pre-sintering at 500℃~600℃ for 4h~6h; preferably, the heating rate is 3~5℃min. -1 .

[0019] According to the above scheme, in step 3), the grinding time after pre-sintering is 1 to 1.5 hours.

[0020] According to the above scheme, in step 3), the sintering process is: sintering at 800-900℃ for 8-10 hours; preferably, the heating rate is 3-5℃ / min. -1 .

[0021] According to the above scheme, in step 3), the grinding time after sintering is 1 to 1.5 hours.

[0022] By adjusting the pre-sintering and sintering conditions, the particle size distribution and morphology of LNMO materials can be modified, significantly improving the material's structural and interfacial chemical stability as well as its interfacial charge transfer kinetics.

[0023] A Sn-doped high-voltage lithium nickel manganese oxide cathode material prepared by the above method is provided, which has a truncated octahedral crystal morphology and a three-dimensional lithium-ion diffusion channel.

[0024] This invention provides an application of the aforementioned Sn-doped high-voltage nickel-manganese lithium cathode material in lithium-ion batteries.

[0025] A lithium-ion battery is provided, comprising the above-mentioned Sn-doped high-voltage lithium nickel manganese oxide cathode material.

[0026] This invention provides a method for preparing Sn-doped high-voltage lithium nickel manganese oxide cathode materials. This method employs a one-step spray drying technique, achieving direct conversion from solution to dried product, significantly simplifying the preparation process and improving production efficiency. Through this technology, the lithium source can deeply penetrate the interior of the precursor particles, avoiding subsequent lithium doping steps and ensuring the uniformity and consistency of the material. Furthermore, the one-step spray drying method atomizes raw material droplets into fine droplets, achieving uniform mixing of the raw materials at the molecular level, improving material uniformity, and enhancing its compaction density and ion transport performance. This method also allows for precise control of the physical conditions during the drying process, thereby preparing particles with specific morphologies, ensuring precise control of the precursor's stoichiometry, and achieving the desired chemical composition and structure.

[0027] This invention selects metal acetate salts, utilizing their high solubility to facilitate the preparation of precursor solutions with high solid content, reducing solvent evaporation during spray drying and improving drying efficiency. Simultaneously, acetate can form uniform complexes in solution, which is beneficial for forming uniform droplets during spray drying, thereby producing cathode materials with uniform particle size distribution. Furthermore, using acetate raw materials reduces the introduction of other ions, such as SO42-. 2- or Cl - This avoids the negative impact of impurity ions on battery performance.

[0028] This invention selects citric acid as a complexing agent. On one hand, citric acid is a multidentate chelating agent that can form stable chelates with multiple metal ions, helping to ensure the uniform distribution of metal ions (such as nickel and manganese) in the solution. This results in the formation of uniform precursor particles during spray drying, thus contributing to the acquisition of a cathode material with a uniform chemical composition. On the other hand, citric acid can influence the crystallization process of the precursor, facilitating the formation of cathode materials with specific morphologies and particle size distributions, and reducing the introduction of other impurity ions, which has a positive impact on the electrochemical performance of the battery. Simultaneously, citric acid is relatively stable during heating and does not easily decompose, which helps maintain the homogeneity of the solution during spray drying, thereby obtaining a uniform cathode material. Furthermore, in the subsequent heat treatment process, the gas generated by the decomposition of citric acid helps remove moisture and other volatile impurities from the material, improving its purity.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. This invention provides a method for preparing Sn-doped high-voltage lithium nickel manganese oxide cathode material. Using lithium, nickel, manganese, and tin sources in acetate form as raw materials, and citric acid as a complexing agent, the Sn-doped high-voltage lithium nickel manganese oxide cathode material is prepared by a one-step spray drying method. The obtained high-voltage lithium nickel manganese oxide cathode material has high purity, excellent uniform particle size, and a good truncated octahedral crystal structure. Sn doping effectively improves structural stability, exhibiting excellent lithium-ion and electronic conductivity, and demonstrating high specific capacity and cycle stability, particularly at 100 mA g. -1 At a current density, it exhibits a high reversible charge-discharge specific capacity (110.69 mAh g). -1 After 350 cycles, the charge / discharge specific capacity remained at 102.64 mAh g. -1 It has significant application prospects.

[0031] 2. The preparation process of this invention is simple to operate, has few steps, high production efficiency, and uses inexpensive and readily available raw materials, which is conducive to industrial production. Attached Figure Description

[0032] Figure 1This is the XRD pattern of the Sn-doped high-voltage lithium nickel manganese oxide cathode material of Embodiment 1 of the present invention.

[0033] Figure 2 This is the Raman diagram of the Sn-doped high-voltage lithium nickel manganese oxide cathode material of Embodiment 1 of the present invention.

[0034] Figure 3 This is a SEM image of the Sn-doped high-voltage lithium nickel manganese oxide cathode material of Embodiment 1 of the present invention.

[0035] Figure 4 This is a CV diagram of the Sn-doped high-voltage lithium nickel manganese oxide cathode material of Embodiment 1 of the present invention.

[0036] Figure 5 This is a voltage distribution diagram of the Sn-doped high-voltage lithium nickel manganese oxide cathode material of Embodiment 1 of the present invention.

[0037] Figure 6 This is a cycle performance diagram of the Sn-doped high-voltage nickel-manganese lithium cathode material of Embodiment 1 of the present invention.

[0038] Figure 7 This is the EIS impedance diagram of the Sn-doped high-voltage lithium nickel manganese oxide cathode material of Embodiment 1 of the present invention. Detailed Implementation

[0039] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0040] Example 1:

[0041] The preparation method of Sn-doped high-voltage lithium nickel manganese oxide cathode material includes the following steps:

[0042] 1) Mix 0.0105 mol CH3COOLi, 0.005 mol (CH3COO)2Ni·4H2O, 0.0146 mol (CH3COO)2Mn·4H2O and 0.0004 mol (CH3COO)2Sn and dissolve them completely in 150 mL of deionized water. Then add 0.02 mol citric acid dissolved in deionized water as a complexing agent and stir magnetically for 12 h.

[0043] 2) Set the outlet temperature to 190℃, atomize the solution stirred in step 1), and dry it in a spray dryer under hot air conditions;

[0044] 3) Place the powder obtained in step 2) in a muffle furnace and heat at 5°C for 5 minutes. -1 The temperature was increased to 500℃ and pre-sintered for 4 hours.

[0045] 4) Take out the powder from step 3) after pre-sintering and grind it in a mortar for 1 hour;

[0046] 5) Place the powder ground in step 4) in a muffle furnace and heat at 5°C for 5 minutes. -1 The temperature was increased to 800℃ and calcined for 10 hours.

[0047] 6) After natural cooling, take out the sample obtained in step 5) and grind it for 1 hour to finally obtain a Sn-doped high-voltage nickel manganese oxide cathode material sample.

[0048] The Sn-doped high-voltage lithium nickel manganese oxide cathode material sample obtained in this embodiment was tested in the following details:

[0049] like Figure 1 As shown, the X-ray diffraction (XRD) pattern of the Sn-doped high-voltage lithium nickel manganese oxide cathode material, as determined by X-ray diffraction, indicates that the material has a spinel-type structure with Fd-3m space group symmetry after high-temperature calcination. The characteristic peaks of the Sn-doped high-voltage lithium nickel manganese oxide cathode material are obvious, and there are trace amounts of SnO diffraction peaks in the XRD pattern, which do not affect the integrity of the LNMO crystal structure.

[0050] like Figure 2 As shown, Raman spectroscopy analysis of Sn-doped high-voltage lithium nickel manganese oxide cathode material reveals that commercial red phosphorus exhibits high polarity at 400 cm⁻¹. -1 -700cm -1 There are three characteristic peaks within the range, located at 493 cm⁻¹. -1 599cm -1 and 633cm -1 The results at this location are consistent with the standard Raman spectrum of LNMO with disordered Fd-3m space group, indicating that the synthesized Sn-doped high-voltage lithium nickel manganese oxide cathode material has a spinel-type structure with Fd-3m space group symmetry.

[0051] like Figure 3 As shown in the image, scanning electron microscopy (SEM) imaging reveals that after high-temperature sintering, the Sn-4 sample exhibits a truncated octahedral morphology with an uneven surface. Clear particle coatings are visible on the surface, resulting from the enrichment of SnO on the surface. The truncated LNMO octahedron significantly suppresses side reactions at the electrode / electrolyte interface under high cutoff voltages, improving the cycle stability of the LNMO high-voltage cathode material.

[0052] The Sn-doped high-voltage nickel-manganese lithium oxide material prepared in this invention is used as the positive electrode active material for lithium-ion batteries. The Sn-doped high-voltage nickel-manganese lithium oxide material prepared in Example 1 is used as the positive electrode, metallic lithium as the counter electrode, a 1M EC:DEC = 1:1 (vol%) electrolyte is selected, Celgard 2400 polypropylene membrane is used as the separator, and CR2016 stainless steel is used as the battery casing to assemble a coin cell. Figure 5 As shown, the Sn-doped high-voltage lithium nickel manganese oxide electrode was tested at a scan rate of 0.1 mV / s. -1 The CV test showed three reversible peaks during charging, located at 4.05V, 4.76V, and 4.83V, representing Mn, respectively. 3+ To Mn 4+、 Ni 2+ / Ni 3+ and Ni 3+ / Ni 4+ The conversion corresponds to the stepwise lithiation of the cathode. During the discharge phase, three peaks at 4.65 V, 4.6 V, and 4.0 V indicate a stepwise delithiation process. The almost overlapping cathode CV curves demonstrate the good cycle stability of the Sn-doped cathode.

[0053] like Figure 5 As shown, Sn-doped high-voltage lithium nickel manganese oxide electrode material at 100 mA g -1 The charge-discharge voltage distribution under current density and a voltage window of 3.5–4.9 V indicates that the voltage plateau observed during charge-discharge is consistent with the redox behavior scanned during CV. The initial charge capacity of the Sn-doped high-voltage nickel-manganese oxide electrode material is 133.52 mA hg. -1 The discharge specific capacity is 110.69 mA hg -1 The coulombic efficiency was 82.91%. During subsequent cycles, voltage plateaus overlapped, indicating that Li... + Good reversibility of insertion / extraction.

[0054] like Figure 6 As shown, Sn-doped high-voltage lithium nickel manganese oxide electrode material at 100 mA g -1 At the current density, the initial charging specific capacity is 110.69 mA hg. -1 After 350 cycles, the charge / discharge specific capacity remained at 102.64 mA hg. -1 The LNMO material exhibits good cycling stability. Sn doping can alleviate the two-phase phase transition during high-voltage cycling, effectively reduce Mn dissolution, prevent unfavorable two-phase reactions that generate rock salt phase, block lithium-ion diffusion channels, suppress severe side reactions between the electrode and electrolyte under high voltage, and improve the cycling performance of the electrode material.

[0055] like Figure 7 As shown, the EIS impedance diagram of the Sn-doped high-voltage lithium nickel manganese oxide electrode material indicates that the Sn-doped high-voltage lithium nickel manganese oxide electrode material has excellent lithium-ion conduction and electronic conduction properties, exhibiting good conductivity.

[0056] The above test results show that Sn-doped high-voltage lithium nickel manganese oxide electrode material has excellent electrochemical performance and is a potential high-performance lithium-ion battery cathode material.

[0057] Comparative Example 1:

[0058] 1) Mix 0.0105 mol CH3COOLi, 0.005 mol (CH3COO)2Ni·4H2O and 0.015 mol (CH3COO)2Mn·4H2O and dissolve them completely in 150 mL of deionized water. Then add 0.02 mol citric acid dissolved in deionized water as a complexing agent and stir magnetically for 12 h.

[0059] 2) Set the outlet temperature to 190℃, atomize the well-stirred solution, and dry it in a spray dryer under hot air conditions;

[0060] 3) Place the obtained powder in a muffle furnace and heat at 5°C for 5 minutes. -1 The temperature was increased to 500℃ and pre-sintered for 4 hours.

[0061] 4) Take out the calcined powder and grind it in a mortar for 1 hour;

[0062] 5) Place the ground powder in a muffle furnace and heat at 5°C for 5 minutes. -1 The temperature was increased to 800℃ and calcined for 10 hours.

[0063] 6) After the sample has cooled naturally, it is taken out and ground for 1 hour to finally obtain the lithium nickel manganese oxide cathode material sample.

[0064] Taking the lithium nickel manganese oxide cathode material obtained in this embodiment as an example, at 100mA g -1 At the specified current density, the initial charge specific capacity reached 131.51 mAh / g, the discharge specific capacity was 106.75 mAh / g, and after 350 cycles, the discharge specific capacity was 86.91 mAh / g, with a capacity retention rate of 81.4%. Analysis suggests that the undoped pristine LNMO material experienced phase transitions and Mn dissolution during charge and discharge, leading to the collapse of the spinel-type structure of the LNMO electrode and an increase in charge transfer impedance, resulting in capacity decay and reduced cycle performance.

[0065] Comparative Example 2:

[0066] 1) Mix 0.0105 mol CH3COOLi, 0.005 mol (CH3COO)2Ni·4H2O, 0.0148 mol (CH3COO)2Mn·4H2O and 0.0002 mol (CH3COO)2Sn and dissolve them completely in 150 mL of deionized water. Then add 0.02 mol citric acid dissolved in deionized water as a complexing agent and stir magnetically for 12 h.

[0067] 2) Set the outlet temperature to 190℃, atomize the well-stirred solution, and dry it in a spray dryer under hot air conditions;

[0068] 3) Place the obtained powder in a muffle furnace and heat at 5°C for 5 minutes. -1 The temperature was increased to 500℃ and pre-sintered for 4 hours.

[0069] 4) Take out the calcined powder and grind it in a mortar for 1 hour;

[0070] 5) Place the ground powder in a muffle furnace and heat at 5°C for 5 minutes. -1 The temperature was increased to 800℃ and calcined for 10 hours.

[0071] 6) After natural cooling, the sample was taken out and ground for 1 hour to finally obtain a Sn-doped high-voltage lithium nickel manganese oxide cathode material sample.

[0072] Taking the lithium nickel manganese oxide cathode material obtained in this embodiment as an example, at 100 mAg -1 At the specified current density, the initial charge specific capacity reaches 132.95 mAh / g, the discharge specific capacity is 102.26 mAh / g, and after 350 cycles, the discharge specific capacity is 92.03 mAh / g, with a capacity retention of 90.1%. Analysis suggests that the 2 mol% Sn-doped LNMO material, due to insufficient tin content, provides limited support and has a limited effect on preventing phase transitions and Mn dissolution during charge and discharge, leading to a decline in electrochemical performance.

[0073] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing Sn-doped high-voltage lithium nickel manganese oxide cathode material, characterized in that, Includes the following steps: 1) Dissolve lithium, nickel, manganese, and tin sources in water, wherein the lithium, nickel, manganese, and tin sources are all acetates, according to the chemical formula LiNi 0.5 Mn 1.5-x Sn x The stoichiometric ratio of O4 is used, with x being 0.035~0.045, and the molar volume ratio of nickel source to water is 0.005 mol: 150~200 mL; then the complexing agent citric acid is added, and the reaction is stirred. 2) The mixture obtained in step 1) is dried by spray drying to obtain a solid powder; 3) Pre-sinter the solid powder obtained in step 2), grind it for 1~1.5h, then sinter it again, grinding it for 1~1.5h. The heating rate during pre-sintering is 3~5℃ / min. -1 The heating rate for resintering is 3~5℃ / min. -1 Thus, the Sn-doped high-voltage lithium nickel manganese oxide cathode material is obtained, which has a spinel-type structure with Fd-3m space group symmetry and exhibits a truncated octahedral crystal morphology.

2. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of citric acid to transition metal ions is 0.8 to 1:1, wherein the transition metals are Ni, Mn and Sn.

3. The preparation method according to claim 1, characterized in that, In step 1), the stirring reaction time is 12-18 hours.

4. The preparation method according to claim 1, characterized in that, In step 3), the pre-sintering process is: pre-sintering at 500℃~600℃ for 4h~6h; the sintering process is: sintering at 800~900℃ for 8~10h.

5. A Sn-doped high-voltage lithium nickel manganese oxide cathode material prepared by the preparation method according to any one of claims 1-4.

6. The application of the Sn-doped high-voltage nickel-manganese oxide cathode material as described in claim 5 in lithium-ion batteries.

7. A lithium-ion battery, characterized in that, Including the Sn-doped high-voltage lithium nickel manganese oxide cathode material as described in claim 5.

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