A quasi-zero strain spinel LiMn2O4@Mn2O3 and its preparation method
By preparing quasi-zero strain spinel LiMn2O4@Mn2O3 materials and controlling the crystal structure through heteroatom doping, the mechanical fatigue problem caused by volume changes in lithium-ion battery cathode materials during charging and discharging was solved, achieving high cycle stability and performance improvement of the materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF SCI & TECH
- Filing Date
- 2026-01-15
- Publication Date
- 2026-05-29
AI Technical Summary
The existing lithium-ion battery cathode material, spinel lithium manganese oxide, suffers from mechanical fatigue and cycle stability problems due to crystal volume changes during charging and discharging, especially in aqueous electrolytes. Existing improvement strategies are insufficient to completely solve these problems from both the lattice scale and the overall electrode mechanics perspectives.
Quasi-zero strain spinel LiMn2O4@Mn2O3 material was prepared by employing a heteroatom doping strategy. By controlling the molar ratio of manganese salt and lithium salt and calcining at high temperature, a crystal structure with quasi-zero strain characteristics was formed, suppressing the crystal volume change during the charging and discharging process.
It significantly improves the cycling stability and rate performance of the material, avoids cracking of the electrode material, simplifies the process, and is easy to industrialize.
Smart Images
Figure CN122102215A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery cathode materials technology, specifically to a method for preparing spinel lithium manganese oxide material. Background Technology
[0002] Spinel-type lithium manganese oxide (LiMn2O4, LMO) is a low-cost and environmentally friendly cathode material that has found widespread application in both traditional organic electrolyte systems and the increasingly popular aqueous batteries. Its advantages lie in its abundant raw material resources, mature synthesis process, three-dimensional ion diffusion channels that facilitate rapid kinetics, and compatibility with various electrode systems, making it attractive for cost-sensitive large-scale energy storage and portable applications. Meanwhile, aqueous battery systems, with their non-flammability, simple preparation, and ecological safety, further highlight the potential of LMO in practical applications.
[0003] However, the complex interfacial interactions between the electrolyte and the LMO electrode have become a key issue limiting its long-term cycling stability. In organic electrolytes, the exposed active electrode interface reacts with the electrolyte, leading to surface passivation, the consumption of lithium ions in the electrolyte to form a CEI layer, and severely impairing the electrode's cycle life. In aqueous electrolytes, our work and other studies have shown that hydrated protons (in the form of H3O)... + (In its current form) it can be adsorbed or embedded in the electrode surface and lattice channels, leading to local blockage of ion transport channels and lattice distortion; at the same time, the inevitable cell expansion and contraction during charging and discharging causes volume changes, stress concentration and interface fatigue, which will promote the appearance of microcracks and pulverization of electrode particles, thus exposing more unpassivated active surfaces to direct contact with the electrolyte, amplifying the interaction between the electrolyte and the substrate, forming a failure cycle of electrochemical and mechanical coupling, and ultimately leading to capacity decay and battery failure.
[0004] To alleviate these problems, the industry has proposed various improvement strategies, including surface coatings and encapsulation to isolate direct contact, adjusting lattice rigidity and electronic structure through metal or non-metal doping, and optimizing electrolyte composition (such as high-concentration salt solutions or functional additives). These methods have, to some extent, delayed surface side reactions, improved conductivity, or reduced local stress, but they also have limitations: coatings may detach during cycling and affect conductivity, high-concentration electrolytes increase costs and affect viscosity and mass transfer, and most methods focus on counteracting or suppressing surface reactions rather than fundamentally eliminating mechanical failures caused by changes in lattice parameters. Therefore, existing solutions cannot completely solve the capacity decay problem of lithium manganese oxide electrodes from both the lattice scale and the overall electrode mechanics perspective. Summary of the Invention
[0005] To address the aforementioned problems in the existing technology, the present invention aims to provide a method for preparing quasi-zero strain LiMn2O4@Mn2O3 cathode materials. This invention employs a heteroatom doping strategy to suppress crystal volume changes during the charge-discharge process, achieving quasi-zero strain characteristics. The spinel LiMn2O4@Mn2O3 treated by the method of this invention exhibits significantly improved cycle stability.
[0006] In a first aspect, the present invention provides a method for preparing quasi-zero strain spinel LiMn2O4@Mn2O3, the method comprising the following steps:
[0007] Manganese salt and lithium salt are mixed evenly in a molar ratio of 2:0.7 to 2:0.9. The mixture is then placed in a box-type resistance furnace and calcined at high temperature. After cooling to room temperature with the furnace, quasi-zero strain spinel LiMn2O4@Mn2O3 can be obtained.
[0008] Preferably, the manganese salt is selected from at least one of manganese acetate, manganese sulfate, manganese nitrate, manganese chloride, manganese oxide, and manganese carbonate.
[0009] Preferably, the lithium salt is selected from at least one of lithium acetate, lithium sulfate, lithium nitrate, lithium chloride, lithium hydroxide, and lithium carbonate.
[0010] Preferably, the manganese salt and lithium salt are mixed evenly in a molar ratio of 2:0.7 to 2:0.9.
[0011] Preferably, the high-temperature calcination temperature is 600~1000℃, more preferably 700~900℃.
[0012] Preferably, the high-temperature calcination time is 12~24 h.
[0013] Preferably, manganese salt and lithium salt are placed in a mortar at a molar ratio of 2:0.7 to 2:0.9 and ground until uniform. During this process, a grinding aid can be added to assist grinding. The grinding aid is selected from at least one of ethanol, dimethyl carbonate, diethyl carbonate, propylene carbonate, acetonitrile, methyl formate, methyl acetate, and ethyl acetate.
[0014] Preferably, manganese salt and lithium salt can be dissolved in water at a molar ratio of 2:0.7 to 2:0.9 and a chelating agent can be added and mixed evenly. Then, the mixture is heated and stirred until the water is evaporated. The resulting solid is then ground evenly. The chelating agent is selected from at least one of acetylacetone, diethanolamine, triethanolamine, citric acid, and ethylenediaminetetraacetic acid.
[0015] Preferably, before high-temperature calcination, the sample can be pre-calcined at 200~500℃ for 3~5 hours, and the pre-calcined product can be ground evenly before high-temperature calcination to improve the uniformity of the sample.
[0016] In a second aspect, the present invention provides a quasi-zero strain spinel LiMn2O4@Mn2O3 prepared by the method described in the first aspect.
[0017] Thirdly, the present invention also provides a lithium battery, wherein the positive electrode material of the lithium battery adopts the quasi-zero strain spinel LiMn2O4@Mn2O3 described in the second aspect.
[0018] Preferably, its X-ray diffraction pattern shows that when it is used as a positive electrode material for charging and discharging, the shift value of its (111) characteristic peak is not greater than 0.2°.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0020] This invention innovatively utilizes atomic structure support to effectively suppress the volume change of crystal structure during the charging and discharging process of spinel lithium manganese oxide, thus achieving quasi-zero strain characteristics.
[0021] By suppressing material volume changes, mechanical fatigue caused by the expansion and contraction of electrode materials during charging and discharging is alleviated, thus preventing electrode material cracking.
[0022] The LiMn2O4@Mn2O3 material prepared by the method of this invention exhibits significantly enhanced cycle stability in an aqueous electrolyte environment. Simultaneously, the rate performance of the material is also improved.
[0023] This method requires no complex equipment, has a simple process flow, is easy to industrialize, and has high commercialization value. Attached Figure Description
[0024] Figure 1 These are high-resolution transmission electron microscopy (HRTEM) comparison images of the spinel lithium manganese oxide materials prepared in Example 1 and Comparative Example 1 of this invention.
[0025] Figure 2 These are XRD comparison images of the spinel lithium manganese oxide materials prepared in Example 1 and Comparative Example 1 of this invention before and after charge-discharge cycles. Detailed Implementation
[0026] The following examples further illustrate the content of this invention, but should not be construed as limiting the invention. Any modifications and substitutions made to the methods, steps, or conditions of this invention without departing from its essence are within the scope of this invention.
[0027] Unless otherwise stated, all raw materials and reagents used in the embodiments of this invention are commercially available.
[0028] Example 1
[0029] Step 1: Take 0.8 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0030] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0031] Step 3: Transfer the evenly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 700℃ at a rate of 10℃ / min and hold for 12 hours.
[0032] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain sample S1.
[0033] Example 2
[0034] Step 1: Take 0.7 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0035] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0036] Step 3: Transfer the evenly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 700℃ at a rate of 10℃ / min and hold for 12 hours.
[0037] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain sample S2.
[0038] Example 3
[0039] Step 1: Take 0.9 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0040] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0041] Step 3: Transfer the evenly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 700℃ at a rate of 10℃ / min and hold for 12 hours.
[0042] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain sample S3.
[0043] Example 4
[0044] Step 1: Take 0.8 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0045] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0046] Step 3: Transfer the uniformly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 900℃ at a rate of 10℃ / min and hold for 12 hours.
[0047] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain sample S4.
[0048] Example 5
[0049] Step 1: Take 0.8 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol and grind manually until it becomes a paste.
[0050] Step 2: Transfer the paste into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and keep it at that temperature for 4 hours. After cooling, grind the resulting solid back into a uniform paste.
[0051] Step 3: Transfer the evenly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 700℃ at a rate of 10℃ / min and hold for 24 hours.
[0052] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain sample S5.
[0053] Example 6
[0054] Step 1: Take 0.8 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, dissolve them in 10 mL of water, and add 1 g of citric acid.
[0055] Step 2: Heat and stir until the water evaporates, then remove the remaining solids and grind them evenly.
[0056] Step 3: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0057] Step 4: Transfer the uniformly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 700℃ at a rate of 10℃ / min and hold for 12 hours.
[0058] Step 5: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain sample S6.
[0059] Comparative Example 1
[0060] Step 1: Take 1 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0061] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0062] Step 3: Transfer the evenly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 700℃ at a rate of 10℃ / min and hold for 12 hours.
[0063] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain control sample D1.
[0064] Comparative Example 2
[0065] Step 1: Take 0.5 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0066] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0067] Step 3: Transfer the evenly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 700℃ at a rate of 10℃ / min and hold for 12 hours.
[0068] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain control sample D2.
[0069] Comparative Example 3
[0070] Step 1: Take 0.8 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0071] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0072] Step 3: Transfer the uniformly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 450℃ at a rate of 10℃ / min and hold for 12 hours.
[0073] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain control sample D3.
[0074] Comparative Example 4
[0075] Step 1: Take 0.8 mmol lithium acetate and 2 mmol manganese acetate as lithium and manganese sources, add ethanol, and manually grind and mix evenly.
[0076] Step 2: Transfer the mixed solid into a high-temperature resistant container, place it in a muffle furnace, heat it to 450℃ at 10℃ / min and hold it for 4 hours. After cooling, grind the resulting solid again until it is uniform.
[0077] Step 3: Transfer the uniformly ground solid into a high-temperature resistant container and place it in a muffle furnace to heat to 1000℃ at a rate of 10℃ / min and hold for 12 hours.
[0078] Step 4: Allow the sample to cool naturally to room temperature, then remove it, grind and sieve it to obtain control sample D4.
[0079] Performance Result Analysis
[0080] Half-cell assembly: Using the samples prepared in Examples 1-7 and Comparative Examples 1-3 as positive electrode materials, the positive electrode material, conductive agent (acetylene black), and binder (PVDF) were mixed at a mass ratio of 90:5:5, and a slurry was prepared using NMP as a solvent. This slurry was then uniformly coated onto titanium foil and dried in a vacuum oven to form a positive electrode sheet. An aqueous three-electrode half-cell system was assembled using activated carbon as the counter electrode, a saturated calomel electrode as the reference electrode, and a 1 M lithium sulfate solution as the electrolyte.
[0081] Table 1 shows the electrical performance statistics of the examples and comparative examples (test current density 1C = 148 mA / g, test voltage range 0.0~1.1 V).
[0082] Test sample Specific capacity at 1C discharge at 25℃ (mAh / g) Capacity retention rate (%) after 100 cycles at 25°C (1C) S1 101.3 95.2 S2 85.1 97.3 S3 111.4 90.8 S4 95.7 92.1 S5 100.2 96.2 S6 102.8 96.8 D1 123.1 87.1 D2 61.2 95.6 D3 94.2 76.4 D4 74.1 73.2
[0083] The information in the table above confirms that the quasi-zero strain lithium manganese oxide cathode material of the present invention exhibits significantly better cycle stability than the lithium manganese oxide control sample.
[0084] Comparing S1 to S6 with D1, it can be seen that although lithium manganese oxide has a higher capacity than lithium manganese oxide material synthesized directly without the addition of metal atoms for support, its cycle stability is significantly lower than that of quasi-zero strain lithium manganese oxide cathode material due to the influence of interfacial reactions and electrode cracking.
[0085] Comparing S1 to S6 with D2, it can be seen that excessive metal atom support introduces an excessive amount of inert phase, resulting in a significant decrease in the specific capacity of lithium manganese oxide. Simultaneously, because a large number of active sites are occupied by Mn, channel blockage occurs, leading to an actual capacity far lower than the actual Li / Mn ratio.
[0086] Compared with D3, S1~S6 shows that the lower reaction temperature prevents lithium manganese oxide material from growing and crystallizing normally, thus failing to form ordered ion channels, resulting in a severe decrease in its capacity. At the same time, the presence of a large number of impurities makes its structure unstable, causing its capacity to decay rapidly during charging and discharging.
[0087] Compared to D4, S1~S6 exhibits higher reaction temperatures that, while more favorable for lithium manganese oxide crystallization, also leads to excessively high temperatures causing small grains to "swallow" each other and grow into coarse grains. This grain growth drastically reduces the specific surface area of the material, decreasing the number of reaction interfaces accessible to lithium ions. Simultaneously, the diffusion path of ions within the large grains becomes longer, increasing migration resistance. Furthermore, the unstable surface structure of the material becomes passivated, leading to intensified electrode polarization, decreased capacity, and poorer stability.
[0088] Structural testing and analysis
[0089] The quasi-zero strain lithium manganese oxide cathode material obtained in Example 1 was tested, and the results are as follows:
[0090] Figure 1 These are high-resolution transmission electron microscopy (HRTEM) comparison images of the spinel lithium manganese oxide materials prepared in Example 1 and Comparative Example 1 of this invention. Comparative Example 1 exhibits well-organized and uniformly oriented lattice fringes, fully demonstrating its high crystallinity and structural integrity. In the sample of Example 1, although the overall lattice is still clearly discernible, showing good crystal structure characteristics, obvious anomalies can be observed. Specifically, in areas that originally belong to Li... + A bright spot signal appeared at the occupied location. Given Li + The low atomic number and mass of the lithium particles make them almost impossible to directly resolve in HRTEM. Therefore, these bright spots are more likely to originate from the substitution or partial occupation of lithium sites by high atomic number elements in multi-component doping. Meanwhile, the lattice fringes of Example 1 exhibit extensive bending and twisting characteristics, significantly different from the regularity of the undoped sample. This indicates that the heteroelement successfully embeds into the spinel lattice and interacts with lattice oxygen, thereby inducing structural distortion and stress perturbation in localized regions.
[0091] Figure 2 These are comparative X-ray diffraction (XRD) patterns of the spinel lithium manganese oxide materials prepared in Example 1 and Comparative Example 1 during the charge-discharge process. For Comparative Example 1, the interplanar distance of the (111) crystal plane before charging was 2.424 Å, and after charging it was 2.369 Å, a change of 0.055 Å. In Example 1, the interplanar distance of the (111) crystal plane before charging was 2.432 Å, and after charging it was 2.420 Å, a change of 0.012 Å. This indicates that the metal atom support imparts quasi-zero strain characteristics to the lithium manganese oxide material, resulting in a smaller volume change rate during charge-discharge, avoiding electrode cracking and exposure of active materials, and effectively improving material performance.
[0092] In summary, this invention proposes a "quasi-zero strain" electrode design concept, aiming to significantly reduce the changes in cell parameters during charge and discharge through lattice engineering and composition optimization. This maintains channel openness at the microscopic level and suppresses stress accumulation and particle crack propagation caused by volume changes at the macroscopic level. This strategy alleviates mechanical failure caused by volume changes, provides a feasible path for synergistic optimization to improve the cycle stability and rate performance of spinel-type manganese-based oxides in batteries, and lays a theoretical and practical foundation for the further development and process scale-up of quasi-zero strain electrodes through doping, interface engineering, or composite materials.
Claims
1. A method for preparing quasi-zero strain spinel LiMn2O4@Mn2O3, characterized in that, Includes the following steps: (1) Mix manganese salt and lithium salt evenly in an atomic molar ratio of 2:0.7 to 2:0.9; (2) The mixture obtained in step (1) is calcined at high temperature; (3) Quasi-zero strain spinel LiMn2O4@Mn2O3 can be obtained by cooling it to room temperature in the furnace.
2. The method according to claim 1, characterized in that, The manganese salt is selected from at least one of manganese acetate, manganese sulfate, manganese nitrate, manganese chloride, manganese oxide, and manganese carbonate.
3. The method according to claim 1, characterized in that, The lithium salt is selected from at least one of lithium acetate, lithium sulfate, lithium nitrate, lithium chloride, lithium hydroxide, and lithium carbonate.
4. The method according to claim 1, wherein the atomic molar ratio is characterized in that the molar ratio of manganese atoms in the manganese salt to lithium atoms in the lithium salt is 2:0.7 to 2:0.
9.
5. The method according to claim 1, characterized in that, The high-temperature calcination temperature is 600~1000℃, more preferably 700~900℃; the high-temperature calcination time is 12~24 h.
6. The method according to claim 1, characterized in that, Manganese salt and lithium salt are placed in a mortar at a molar ratio of 2:0.7 to 2:0.9 and ground until homogeneous. During the grinding process, a grinding aid is added to assist the grinding. The grinding aid is selected from at least one of ethanol, dimethyl carbonate, diethyl carbonate, propylene carbonate, acetonitrile, methyl formate, methyl acetate, and ethyl acetate.
7. The method according to claim 1, characterized in that, Manganese salt and lithium salt are dissolved in water at a molar ratio of 2:0.7 to 2:0.9, and a chelating agent is added. The mixture is then heated and stirred until the water is evaporated. The resulting solid is ground and mixed evenly. The chelating agent is at least one of acetylacetone, diethanolamine, triethanolamine, citric acid, and ethylenediaminetetraacetic acid.
8. The method according to claim 1, characterized in that, Before high-temperature calcination, the mixture is sintered at 200~500℃ for 3~5 hours.
9. A quasi-zero strain spinel LiMn2O4@Mn2O3 cathode material prepared by the method according to any one of claims 1-8.
10. A lithium battery, characterized in that, The positive electrode material of the lithium battery is the quasi-zero strain spinel LiMn2O4@Mn2O3 as described in claim 9.