Spinel-like structure oxide electrode active material and preparation and application thereof

Abstract

The invention belongs to the technical field of ion battery materials, and particularly relates to a spinel-like structure oxide electrode active material and preparation and application thereof. Aiming at the problems of poor intrinsic conductivity, high electrode / electrolyte interface impedance and the like of the existing spinel structure oxide, the invention provides a spinel-like structure oxide electrode active material Mg3FexGa2-xGeO8, the spinel-like structure oxide electrode active material has a Mg3Fe2GeO8 spinel structure, x is greater than or equal to 0 and less than or equal to 2, and the ionic conductivity can reach 10 <-5 > S / cm; the buckle type lithium ion electrode assembled by the Mg3FexGa2-xGeO8 / C composite material formed after carbon coating and a Li metal sheet shows an abnormal specific capacity increase phenomenon, after 320 cycles, the specific capacity reaches more than 700mAh / g, the discharge capacity retention rate is 143%, the specific capacity is increased by about 43%, and the buckle type lithium ion electrode shows excellent rate capability and cycling stability.

Description

Technical Field

[0001] This invention belongs to the field of ion battery materials technology, specifically relating to a spinel-like structure oxide electrode active material and its preparation and application. Background Technology

[0002] Lithium-ion batteries, as the current mainstream energy storage technology, rely heavily on electrode materials for their core performance. Traditional graphite anodes have a limited theoretical capacity (372 mAh / g), making it difficult to meet the ever-increasing demand for high energy density. While silicon-based materials offer high capacity, they suffer from significant volume expansion (>300%) and cycle stability issues. Therefore, developing novel anode materials that combine high capacity, excellent cycle stability, and good rate performance has become a research hotspot. Spinel-type and layered structures, with their complex and ordered transition metal oxides, exhibit higher theoretical capacities than graphite due to their multi-electron reaction mechanisms and relatively smaller volume changes, making them potential alternatives. However, these materials generally suffer from two major bottlenecks: firstly, poor intrinsic conductivity, including low ionic and electronic conductivity, leading to poor rate performance and cycle stability; secondly, high electrode / electrolyte interface impedance, where interfacial side reactions and unstable solid electrolyte interfacial films exacerbate capacity decay and affect cycle life.

[0003] To address these issues, researchers often employ strategies such as nanostructuring, doping modification, and carbon composites. Among these, constructing carbon-coated composite materials is an effective way to improve overall performance: the carbon layer can provide a continuous electronic conductivity network, improving electron transport, suppressing active particle aggregation, buffering volume changes, and potentially reducing direct contact with the electrolyte, thus stabilizing the interface. However, the key to success lies in finding an intrinsically stable, highly mobile, and synergistic active matrix material with carbon. Spinel-like structures, due to their open three-dimensional ion diffusion channels, theoretically have the potential to achieve high ionic conductivity; however, there has been no prior research on the application of such structures in anodes, and how to precisely control their composition to optimize ion transport capabilities and achieve low impedance and strong bonding with carbon materials remains a technical challenge. Furthermore, controllable preparation methods and the cost-effectiveness of the final composite electrode are also factors that must be considered for industrialization. Therefore, there is an urgent need to design a novel spinel-like active material based on specific ion transport optimization, and to synergistically solve the problems of conductivity, interface stability and cycle life through effective composite with carbon, so as to provide a feasible anode solution for the next generation of high-performance, low-cost lithium-ion batteries. Summary of the Invention

[0004] This invention designs a coated Mg3Fe x Ga 2-xThe GeO8 / C composite electrode combines a complex, ordered spinel-like conductive oxide active material with a stable carbon phase to achieve high ionic conductivity, electronic conductivity, and high specific capacity, providing a solution for high-performance ion battery composite electrode materials.

[0005] The active material of the spinel-like oxide electrode of this invention is Mg3Fe x Ga 2-x GeO8 has a spinel-like structure similar to Mg3Fe2GeO8, with 0≤x≤2 and an ionic conductivity up to 10. -5 S / cm, Mg3Fe after carbon coating x Ga 2-x The GeO8 / C composite material and Li metal sheet are assembled into a button electrode, and after 320 cycles, the specific capacity can reach 712 mAh / g.

[0006] The method for preparing the spinel-like structured oxide electrode active material of the present invention includes the following:

[0007] Magnesium oxide, iron oxide, gallium oxide, and germanium oxide powders were mixed to obtain a precursor powder. The precursor powder was then mixed with binder 1 and a solvent, ground, dried, and pressed into tablets. After pressing, the tablets were sintered in air at 1200℃~1400℃ for 5~10 hours. After air-cooling and quenching, a one-time sintered ceramic sheet was obtained. The one-time sintered ceramic sheet was crushed and ground into ceramic powder, and after 2~3 pressing-sintering-cooling cycles, Mg3Fe was obtained. x Ga 2-x GeO8-type spinel structure conductive oxide electrode active material.

[0008] Magnesium oxide, iron oxide, gallium oxide, and germanium oxide were weighed according to a stoichiometric molar ratio of 3:(0~2):(0~2):1, dissolved in a solvent, ball-milled, and dried to obtain precursor powder. The solvent included one of deionized water, anhydrous ethanol, isopropanol, and acetone. The ball milling was wet ball milling, with a milling time of 3h~5h and a milling speed of 250rpm~600rpm. The particle size of the precursor powder obtained after ball milling was 500nm~5μm.

[0009] Binder 1 includes one of polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyethylene glycol, and is used at a rate of 0.5 wt.% to 5 wt.% of the precursor powder. The tableting pressure is 5 MPa to 30 MPa. The tableting-sintering-cooling method is the same as the method for processing ceramic sheets sintered in one step; the particle size of the ceramic powder after each crushing and grinding is 2 μm to 15 μm.

[0010] The spinel-like structure oxide electrode active material Mg3Fe of the present invention x Ga 2-xGeO8 can be used to prepare carbon-coated spinel oxide composites Mg3Fe. x Ga 2-x The electronic conductivity of GeO8 / C composite materials can reach 10. -4 S / cm. Carbon coating methods include the following: Mg3Fe... x Ga 2-x GeO8 electrode active material powder, carbon powder, binder 2, and N-methylpyrrolidone were mixed to form a composite slurry, which was then vacuum dried to obtain a carbon-coated spinel-like oxide composite material Mg3Fe. x Ga 2-x GeO8 / C.

[0011] The spinel-like structure oxide electrode active material of the present invention can be used to prepare lithium-ion batteries. The preparation method includes the following: Mg3Fe... x Ga 2-x GeO8 electrode active material powder, carbon powder, binder 2, and N-methylpyrrolidone were mixed to form a composite slurry, which was then uniformly coated onto copper foil to a thickness of 100 μm to 300 μm. After vacuum drying and pressing, a Mg3Fe3+-containing composite material was obtained. x Ga 2-x Electrode sheets made of GeO8 / C composite material; the electrode sheets and Li metal sheets are used as the two electrodes of the lithium-ion battery, respectively, and assembled in the order of negative electrode shell-pad-Li metal sheet-electrolyte-separator-electrode sheet-pad-positive electrode shell to obtain a coin cell lithium-ion battery.

[0012] Electrode active materials used in the preparation of carbon-coated composite materials or lithium-ion batteries must meet the following conditions:

[0013] Electrode active material powder consists of Mg3Fe x Ga 2-x GeO8 electrode active material was prepared by ball milling and drying with an appropriate amount of anhydrous ethanol for 0.5 h to 2 h at a speed of 600 rpm to 800 rpm. The raw materials were then mixed and magnetically stirred to obtain a composite material slurry for 10 h to 24 h at a speed of 200 rpm to 600 rpm.

[0014] The mass ratio of electrode active material powder, carbon powder, and binder 2 is (6~8):(2~4):(1~2). The carbon powder includes one or more of the following: graphite, soft carbon, hard carbon, super carbon powder, graphene, carbon nanotubes, porous carbon, activated carbon, etc.; the binder 2 includes one or more of the following: polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polytetrafluoroethylene.

[0015] The prepared lithium-ion battery exhibited an initial discharge specific capacity as high as 500 mAh / g at a current density of 300 mA / g, demonstrating an unusual increase in specific capacity. After 320 cycles, it reached over 700 mAh / g, retaining a discharge capacity of 143% and showing an increase in specific capacity of approximately 43%. It also exhibited excellent rate performance and cycle stability. The battery performance also demonstrates the superior performance of Mg3Fe x Ga 2-x GeO8 / C composites exhibit the same specific capacity increase phenomenon.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) Excellent overall conductivity: By designing a spinel-like Fe-based Mg3Fe with high ionic conductivity x Ga 2- x By combining GeO8 electrode active material with carbon materials, both high ionic conductivity and high electronic conductivity are achieved, significantly improving the ion and electron transport efficiency of the battery and laying the foundation for high-performance batteries.

[0018] (2) Significantly improved battery performance: When this composite electrode is applied to lithium-ion batteries, it exhibits a specific capacity of up to 500 mAh / g, which is much higher than many traditional electrode materials, providing an effective solution for the development of high energy density batteries.

[0019] (3) Excellent cycle stability and capacity growth characteristics: After 300 cycles, the specific capacity of this electrode material not only did not decrease significantly, but increased by about 43%. This unique “capacity growth” phenomenon, combined with excellent cycle stability, greatly extends the battery’s lifespan and reliability.

[0020] (4) Excellent rate performance: The composite electrode material exhibits very good rate performance, which means that the battery can maintain good capacity output at different charge and discharge rates, meeting the requirements of different power demand scenarios in practical applications.

[0021] (5) Low interfacial impedance and low cost potential: The coating structure design combining active oxides and carbon materials effectively reduces the interfacial impedance inside the electrode and improves the reaction kinetics. At the same time, low-cost materials such as iron-based and carbon-based materials help to achieve low-cost and controllable benefits.

[0022] (6) The preparation methods involved include ball milling, coating, drying, and tableting. The process is simple and mature, requires no complex equipment, and is suitable for industrial production. Combined with common materials such as carbon powder, it has the potential to achieve low-cost and large-scale production. Attached Figure Description

[0023] Figure 1 XRD patterns of the active materials prepared in each embodiment;

[0024] Figure 2 Impedance spectra of the active materials prepared in each embodiment;

[0025] Figure 3 The charge-discharge curve of the composite electrode prepared in Example 1 is shown.

[0026] Figure 4 The images show SEM images of the composite electrode material prepared in Example 1 before and after cycling; where (a) and (b) are before cycling, and (c) and (d) are after cycling.

[0027] Figure 5 This is a rate performance curve of the composite electrode material prepared in Example 1;

[0028] Figure 6 The graph shows the charge-discharge cycle stability of the composite electrode material prepared in Example 1. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The scope of protection of the present invention is not limited to the specific implementation methods in the embodiments.

[0030] S1 Preparation of Mg3Fe x Ga 2-x GeO8 active material:

[0031] (1) Weigh dry magnesium oxide, iron oxide, gallium oxide, germanium oxide and other oxides according to the stoichiometric molar ratio of 3:(0~2):(0~2):1. The purity of the raw materials is ≥99.99%. Add an appropriate amount of anhydrous ethanol, ball mill for 3h~5h and then dry at a speed of 250rpm~600rpm to obtain precursor powder with a particle size of about 500nm~5μm.

[0032] (2) Take 1g of precursor powder, add 0.5wt.%~5wt.% of the precursor powder and an appropriate amount of anhydrous ethanol, grind for 0.5h~1h and dry, put it into a mold with a diameter of 13mm and press the powder into a ceramic sheet green body, the molding pressure is 5Mpa~30Mpa. The obtained ceramic sheet green body is subjected to solid-state sintering in air at a sintering temperature of 1200℃~1400℃ and a holding time of 5h~10h. After air quenching and cooling, a one-time sintered ceramic sheet is obtained.

[0033] (3) The sintered ceramic sheets are crushed and ground into ceramic powder with a particle size of approximately 2μm to 15μm. The pressing-sintering-quenching process is repeated, using the same method as in step (2). After three sintering processes, Mg3Fe is obtained. x Ga 2-x GeO8 active material, 0≤x≤2.

[0034] S2 carbon coating and assembly of lithium-ion batteries:

[0035] (4) Mg3Fe x Ga 2-x GeO8 active material and an appropriate amount of anhydrous ethanol were ball-milled for 0.5 h to 2 h at a speed of 600 rpm to 800 rpm. After drying, the active material powder was obtained.

[0036] (5) Weigh the active material powder, super carbon powder and polyvinylidene fluoride in a mass ratio of (6~8):(2~4):(1~2), add an appropriate amount of N-methylpyrrolidone, and stir magnetically for 10h~24h at 200rpm~600rpm to obtain a composite material slurry; coat the slurry on copper foil with a thickness of 100μm~300μm, and dry and press it under vacuum to obtain a composite material electrode sheet.

[0037] (6) The composite material electrode sheet and the Li metal sheet are used as the two electrodes of the coin cell lithium-ion battery, respectively. The half-cell is assembled in the following order: negative electrode shell - gasket - Li metal sheet - electrolyte - separator - composite material electrode sheet - gasket - positive electrode shell. After the assembled battery is left overnight, its electrochemical performance is tested.

[0038] Example 1

[0039] Preparation of Mg3Fe2GeO8 active material by S1:

[0040] (1) When x is 2, dry magnesium oxide, iron oxide, germanium oxide and other oxides are weighed according to the stoichiometric molar ratio of 3:2:1, an appropriate amount of anhydrous ethanol is added, and the mixture is ball-milled for 5 hours and then dried at a speed of 500 rpm to obtain precursor powder with a particle size of 2 μm.

[0041] (2) Take 1g of precursor powder, add 1.5wt.% polyvinyl butyral and an appropriate amount of anhydrous ethanol, grind for 1h and dry, put into a mold with a diameter of 13mm to press the powder into ceramic green sheet, the molding pressure is 15Mpa. The obtained ceramic green sheet is subjected to solid-state sintering in air at a temperature of 1250℃ and a holding time of 8h. After air cooling and quenching, a single-sintered ceramic sheet is obtained.

[0042] (3) The sintered ceramic sheet is crushed and ground into ceramic powder, and the pressing-sintering-quenching process is repeated, which is the same as the treatment method in step (2). After three sintering processes, Mg3Fe2GeO8 active material is obtained.

[0043] S2 carbon coating and assembly of lithium-ion batteries:

[0044] (4) The Mg3Fe2GeO8 active material and an appropriate amount of anhydrous ethanol were ball-milled for 1 hour at 800 rpm and then dried to obtain active material powder.

[0045] (5) Weigh the active material powder, super carbon powder and polyvinylidene fluoride in a mass ratio of 7:2:1, add an appropriate amount of N-methylpyrrolidone, and stir magnetically at 500 rpm for 15 h to obtain a composite material slurry; coat the slurry on copper foil, dry it under vacuum and press it into a sheet to obtain a composite material electrode sheet.

[0046] (6) Use the composite material electrode sheet and the Li metal sheet as the two electrodes of the button lithium-ion battery respectively. Assemble the half cell in the order of negative electrode shell-pad-Li metal sheet-electrolyte-separator-composite material electrode sheet-pad-positive electrode shell and leave the assembled battery overnight.

[0047] Electrochemical performance tests on the battery demonstrated its excellent structural stability and electrochemical reversibility, indicating its potential as a highly stable anode material. (See details...) Figures 3-6 .

[0048] Example 2

[0049] Preparation of Mg3FeGaGeO8 active material by S1:

[0050] (1) When x is 1, dry magnesium oxide, iron oxide, gallium oxide, germanium oxide and other oxides are weighed according to the stoichiometric molar ratio of 3:1:1:1, an appropriate amount of anhydrous ethanol is added, and the mixture is ball-milled for 3 hours and then dried at a speed of 600 rpm to obtain precursor powder with a particle size of 1 μm to 2 μm.

[0051] (2) Take 1g of precursor powder, add 1wt.% polyvinyl butyral and an appropriate amount of anhydrous ethanol, grind for 1h and dry, put into a mold with a diameter of 13mm to press the powder into ceramic green sheet, the molding pressure is 20Mpa. The obtained ceramic green sheet is subjected to solid-state sintering in air at a temperature of 1300℃ and a holding time of 10h. After air cooling and quenching, a single-sintered ceramic sheet is obtained.

[0052] (3) The sintered ceramic sheet is crushed and ground into ceramic powder, and the pressing-sintering-quenching process is repeated, which is the same as the treatment method in step (2). After three sintering processes, Mg3FeGaGeO8 active material is obtained.

[0053] S2 carbon coating and assembly of lithium-ion batteries:

[0054] (4) The Mg3FeGaGeO8 active material and an appropriate amount of anhydrous ethanol were ball-milled for 30 min at a speed of 600 rpm and then dried to obtain the active material powder.

[0055] (5) Weigh the active material powder, super carbon powder and polyvinylidene fluoride in a mass ratio of 6.5:2.5:1, add an appropriate amount of N-methylpyrrolidone, and stir magnetically at 400 rpm for 15 h to obtain a composite material slurry; coat the slurry on copper foil, dry it under vacuum and press it into a sheet to obtain a Mg3FeGaGeO8 / C composite material electrode sheet.

[0056] (6) Use the composite material electrode sheet and the Li metal sheet as the two electrodes of the button lithium-ion battery respectively. Assemble the half cell in the order of negative electrode shell-pad-Li metal sheet-electrolyte-separator-composite material electrode sheet-pad-positive electrode shell and leave the assembled battery overnight.

[0057] Electrochemical performance tests were conducted on the above-mentioned battery. Its charge-discharge specific capacity was lower than that of Example 1, but its rate performance and cycle stability were excellent, proving that the Mg3FeGaGeO8 / C composite electrode has excellent structural stability and electrochemical reversibility.

[0058] Example 3

[0059] S1 Preparation of Mg3Fe 0.5 Ga 1.5 GeO8 active material:

[0060] (1) When x is 0.5, dry magnesium oxide, iron oxide, gallium oxide, germanium oxide and other oxides are weighed according to the stoichiometric molar ratio of 3:0.5:1.5:1, an appropriate amount of anhydrous ethanol is added, and the mixture is ball-milled for 4 hours and then dried at a speed of 600 rpm to obtain a precursor powder of 1.7 μm.

[0061] (2) Take 1g of precursor powder, add 2wt.% polyvinyl butyral and an appropriate amount of anhydrous ethanol, grind for 0.5h and dry, put into a mold with a diameter of 13mm to press the powder into ceramic green sheet, the molding pressure is 10Mpa. The obtained ceramic green sheet is subjected to solid-state sintering in air at a temperature of 1400℃ and a holding time of 6h. After air cooling and quenching, a single-sintered ceramic sheet is obtained.

[0062] (3) The sintered ceramic sheet is crushed and ground into ceramic powder, and the pressing-sintering-quenching process is repeated, in the same way as in step (2). After three sintering processes, Mg3Fe is obtained. 0.5 Ga 1.5GeO8 active material.

[0063] S2 carbon coating and assembly of lithium-ion batteries:

[0064] (4) Mg3Fe 0.5 Ga 1.5 GeO8 active material and an appropriate amount of anhydrous ethanol were ball-milled for 0.5 hours at a speed of 800 rpm, and then dried to obtain active material powder.

[0065] (5) Weigh the active material powder, super carbon powder and polyvinylidene fluoride in a mass ratio of 6:3:1, add an appropriate amount of N-methylpyrrolidone, and stir magnetically at 400 rpm for 20 h to obtain a composite material slurry; coat the slurry onto copper foil, dry it under vacuum and press it into tablets to obtain Mg3Fe 0.5 Ga 1.5 GeO8 / C composite electrode sheet.

[0066] (6) Use the composite material electrode sheet and the Li metal sheet as the two electrodes of the button lithium-ion battery respectively. Assemble the half cell in the order of negative electrode shell-pad-Li metal sheet-electrolyte-separator-composite material electrode sheet-pad-positive electrode shell and leave the assembled battery overnight.

[0067] Electrochemical performance tests were conducted on the above-mentioned batteries. While their charge-discharge specific capacity was lower than that of Examples 1 and 2, they still exhibited better rate performance and cycle stability, demonstrating that Mg3Fe 0.5 Ga 1.5 The GeO8 / C composite electrode also exhibits good structural stability and electrochemical reversibility.

[0068] Example 4

[0069] S1 Preparation of Mg3Fe 0.25 Ga 1.75 GeO8 active material:

[0070] (1) When x is 0.25, dry magnesium oxide, iron oxide, gallium oxide, germanium oxide and other oxides are weighed according to the stoichiometric molar ratio of 3:0.25:1.75:1, an appropriate amount of anhydrous ethanol is added, and the mixture is ball-milled for 5 hours and then dried at a speed of 500 rpm to obtain a precursor powder of 2.3 μm.

[0071] (2) Take 1g of precursor powder, add 5wt.% of polyvinyl alcohol and an appropriate amount of anhydrous ethanol to the precursor powder, grind for 1h and dry, put it into a mold with a diameter of 13mm to press the powder into ceramic green sheet, the molding pressure is 10Mpa. The obtained ceramic green sheet is subjected to solid-state sintering in air at a temperature of 1300℃ and a holding time of 8h. After air cooling and quenching, a single-sintered ceramic sheet is obtained.

[0072] (3) The sintered ceramic sheet is crushed and ground into ceramic powder, and the pressing-sintering-quenching process is repeated, in the same way as in step (2). After three sintering processes, Mg3Fe is obtained. 0.25 Ga 1.75 GeO8 active material.

[0073] S2 carbon coating and assembly of lithium-ion batteries:

[0074] (4) Mg3Fe 0.25 Ga 1.75 GeO8 active material and an appropriate amount of anhydrous ethanol were ball-milled for 1 hour at a speed of 700 rpm, and then dried to obtain active material powder.

[0075] (5) Weigh the active material powder, super carbon powder and polyvinylidene fluoride in a mass ratio of 7:2:1, add an appropriate amount of N-methylpyrrolidone, and stir magnetically at 500 rpm for 15 h to obtain a composite material slurry; coat the slurry onto copper foil, dry it under vacuum and press it into tablets to obtain Mg3Fe 0.25 Ga 1.75 GeO8 / C composite electrode sheet.

[0076] (6) Use the composite material electrode sheet and the Li metal sheet as the two electrodes of the button lithium-ion battery respectively. Assemble the half cell in the order of negative electrode shell-pad-Li metal sheet-electrolyte-separator-composite material electrode sheet-pad-positive electrode shell and leave the assembled battery overnight.

[0077] Electrochemical performance tests were conducted on the above-mentioned batteries. Their charge-discharge specific capacity was lower than that of Example 1, but slightly higher than that of Examples 2 and 3. This is consistent with their impedance performance. At the same time, the composite electrode also showed good structural stability and electrochemical reversibility.

[0078] Example 5

[0079] S1 Preparation of Mg3Fe 0.1 Ga 1.9 GeO8 active material:

[0080] (1) When x is 0.1, dry magnesium oxide, iron oxide, gallium oxide, germanium oxide and other oxides are weighed according to the stoichiometric molar ratio of 3:0.1:1.9:1, an appropriate amount of anhydrous ethanol is added, and the mixture is ball-milled for 5 hours and then dried at a speed of 600 rpm to obtain a precursor powder of 1 μm.

[0081] (2) Take 1g of precursor powder, add 5wt.% of polyvinyl alcohol and an appropriate amount of anhydrous ethanol to the precursor powder, grind for 0.5h and dry, put it into a mold with a diameter of 13mm to press the powder into a ceramic sheet green body, and the molding pressure is 15Mpa. The obtained ceramic sheet green body is subjected to solid-state sintering in air at a temperature of 1300℃ and a holding time of 7h. After air cooling and quenching, a one-time sintered ceramic sheet is obtained.

[0082] (3) The sintered ceramic sheet is crushed and ground into ceramic powder, and the pressing-sintering-quenching process is repeated, in the same way as in step (2). After three sintering processes, Mg3Fe is obtained. 0.1 Ga 1.9 GeO8 active material.

[0083] S2 carbon coating and assembly of lithium-ion batteries:

[0084] (4) Mg3Fe 0.1 Ga 1.9 GeO8 active material and an appropriate amount of anhydrous ethanol were ball-milled for 1 hour at a speed of 800 rpm, and then dried to obtain active material powder.

[0085] (5) Weigh the active material powder, super carbon powder and polyvinylidene fluoride in a mass ratio of 6:3:1, add an appropriate amount of N-methylpyrrolidone, and stir magnetically at 450 rpm for 15 h to obtain a composite material slurry; coat the slurry on copper foil, dry it under vacuum and press it into a sheet to obtain a composite material electrode sheet.

[0086] (6) Use the composite material electrode sheet and the Li metal sheet as the two electrodes of the button lithium-ion battery respectively. Assemble the half cell in the order of negative electrode shell-pad-Li metal sheet-electrolyte-separator-composite material electrode sheet-pad-positive electrode shell and leave the assembled battery overnight.

[0087] Electrochemical performance tests were conducted on the above-mentioned batteries. Their charge-discharge specific capacity was lower than that of Example 1, but comparable to that of Examples 2, 3, and 4. They also exhibited good structural stability and electrochemical reversibility.

[0088] The active materials and lithium-ion batteries prepared in the above embodiments were tested, and the test results are as follows:

[0089] Figure 1 Mg3Fe was prepared for each example x Ga 2-x The XRD patterns of the GeO8 active materials show that the diffraction peak positions of all samples are basically consistent, indicating that Fe successfully replaced some Ga into the crystal lattice without changing the main crystal structure framework of the material. This confirms that Ga... 3+ with Fe 3+With similar ionic radii, isomorphous substitution was achieved. The absence of obvious impurity peaks in the spectra indicates high purity of the synthesized material. While the diffraction peak intensities changed slightly with increasing Fe doping concentration, the peak positions remained stable, further demonstrating that doping did not induce significant lattice distortion or phase separation. This structural stability provides a crucial microstructural basis for the material's excellent capacity retention and anomalous capacity activation with increasing cycling during electrochemical cycling.

[0090] Figure 2 Mg3Fe prepared for each example x Ga 2-x Impedance spectra of GeO8 active materials show that the Nyquist curves of all samples consist of a semicircle in the high-frequency region and a sloping line in the low-frequency region, corresponding to the charge transfer process and ion diffusion behavior, respectively. The diameter of the semicircle fluctuates with changing x values, indicating that the ratio of Fe to Ga affects the reaction kinetics at the electrode interface. Fitting and calculation of the curves yielded good ionic conductivity values. With x values ​​increasing from 0.1 to 2, the ionic conductivity values ​​were 1.26 × 10⁻⁶. -5 S / cm, 1.43×10 -5 S / cm, 1.07×10 -5 S / cm, 1.25×10 -5 S / cm, 3.87×10 -5 S / cm. When x is 2, the ionic conductivity is the highest, indicating that a moderate Fe content is beneficial for maintaining a high ionic conductivity. This result is consistent with the rate performance and cycle stability described later, demonstrating that the material composition has a significant regulatory effect on its electrochemical performance.

[0091] Figure 3 The charge-discharge curves of the Mg3Fe2GeO8 / C composite electrode prepared in Example 1 with x = 2 are shown. The electrode material exhibits typical high-capacity characteristics. At a current density of 20 mA / g, the initial charge-discharge capacities are 1661 mAh / g and 834 mAh / g, respectively. The extremely high charge capacity and relatively low initial coulombic efficiency (approximately 50%) are mainly due to the irreversible formation of the SEI film and material activation side reactions. The fifth charge-discharge capacities are 802 mAh / g and 783 mAh / g, respectively, indicating a stable charge-discharge process. The coulombic efficiency significantly increases to over 97%, demonstrating excellent structural stability and electrochemical reversibility after activation.

[0092] Figure 4 The images shown are SEM images of the Mg3Fe2GeO8 / C composite electrode prepared in Example 1 before and after cycling. Figure 4 (a) It can be seen that before the cycle, the surface of the active material particles and the super carbon powder are bonded together by the binder, and the gaps are relatively large; Figure 4(b) is a cross-sectional view of the active material particles before cycling, showing that the interface between the toner and the active material is in good contact, with no obvious gaps in the interlayer contact; from Figure 4 (c) It can be seen that no obvious breakage of the active material particles was observed after cycling. Figure 4 (d) It can be seen that there is an obvious film structure on the surface of the particles after cycling, with a thickness of about 42 nm, which is the SEI film generated during the electrode reaction.

[0093] Figure 5 The rate performance curves for the Mg3Fe2GeO8 / C composite electrode prepared in Example 1 show that as the current density increases from 30 mA / g, 50 mA / g to 100 mA / g, the charge-discharge specific capacity of the electrode exhibits a stepwise decrease. This is due to the increased electrode polarization and the limitation of ion diffusion kinetics at high rates. When the current density is adjusted back to 30 mA / g, the specific capacity rapidly recovers to near its initial level, indicating that the electrode material possesses excellent structural stability and kinetic reversibility, without significant structural damage or loss of active material even after high current surges. This excellent rate performance is attributed to the good conductivity of the carbon network in the composite material and the potential optimization of ion transport paths due to Fe doping, giving it the potential for application in high-power lithium-ion batteries.

[0094] Figure 6 The charge-discharge cycle stability curves of the Mg3Fe2GeO8 / C composite electrode prepared in Example 1 are shown. At a test current density of 300 mA / g, the initial discharge capacity was approximately 500 mAh / g. After 320 cycles, the discharge capacity increased to 712 mAh / g, with a capacity retention rate of 143%. The composite electrode exhibits an unusual capacity increase, indicating that the material may have undergone continuous activation during cycling, such as structural optimization, gradual exposure of active sites, or improvement of the electrode interface, thereby enhancing lithium-ion storage performance. This highlights the material's excellent cycle stability and structural adaptability, demonstrating its potential as a highly stable anode material.

[0095] The above description of the embodiments is provided to enable those skilled in the art to understand and use the present invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A spinel-like oxide electrode active material, characterized in that, The electrode active material is Mg3Fe x Ga 2-x GeO8 has a spinel-like structure similar to Mg3Fe2GeO8, and 0≤x≤2.

2. The method for preparing a spinel-like structure oxide electrode active material according to claim 1, characterized in that, The process includes the following steps: Magnesium oxide, iron oxide, gallium oxide, and germanium oxide are weighed and dissolved in a solvent, then ball-milled and dried to obtain a precursor powder. The precursor powder is mixed with binder 1 and the solvent, then ground, dried, and pressed into tablets. A first-time sintering is performed, followed by cooling to obtain a first-time sintered ceramic sheet. The first-time sintered ceramic sheet is crushed and ground into ceramic powder, and after 2-3 cycles of pressing, sintering, and cooling, Mg3Fe is obtained. x Ga 2-x GeO8-type spinel structure oxide electrode active materials.

3. The method for preparing a spinel-like structure oxide electrode active material according to claim 2, characterized in that, The molar ratio of magnesium oxide, iron oxide, gallium oxide, and germanium oxide is 3:(0~2):(0~2):1; the primary sintering temperature is 1200℃~1400℃, and the holding time is 5h~10h.

4. The method for preparing a spinel-like structure oxide electrode active material according to claim 2, characterized in that, The solvent includes one of deionized water, anhydrous ethanol, isopropanol, and acetone; wet ball milling is used, with a milling time of 3-5 hours and a milling speed of 250-600 rpm; the particle size of the precursor powder is 500 nm-5 μm.

5. The method for preparing a spinel-like structure oxide electrode active material according to claim 2, characterized in that, The binder 1 includes one of polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyethylene glycol, and is used in an amount of 0.5 wt.% to 5 wt.% of the precursor powder; the pressing pressure is 5 MPa to 30 MPa; the pressing-sintering-cooling method is the same as the processing method of the single-sintering ceramic sheet; the particle size of the ceramic powder after each crushing and grinding is 2 μm to 15 μm.

6. The application of the spinel-like structure oxide electrode active material according to claim 1, characterized in that, Electrode active material Mg3Fe x Ga 2-x GeO8 was used to prepare carbon-coated Mg3Fe. x Ga 2-x The preparation method of GeO8 / C composite material includes the following: Mg3Fe... x Ga 2-x GeO8 electrode active material powder, carbon powder, binder 2, and N-methylpyrrolidone were mixed to form a composite slurry, which was then vacuum dried to obtain the Mg3Fe2+. x Ga 2-x GeO8 / C composite material.

7. The application of the spinel-like structure oxide electrode active material according to claim 1, characterized in that, Electrode active material Mg3Fe x Ga 2-x GeO8 is used to prepare lithium-ion batteries. The preparation method includes the following: [The text abruptly ends here, likely due to an incomplete sentence or a missing section.] x Ga 2-x GeO8 electrode active material powder, carbon powder, binder 2, and N-methylpyrrolidone are mixed to form a composite slurry, which is then uniformly coated onto copper foil. After vacuum drying and pressing, a Mg3Fe3+-containing composite material is obtained. x Ga 2-x The electrode sheet is made of GeO8 / C composite material. The electrode sheet and the Li metal sheet are used as the two electrodes of the lithium-ion battery, respectively. They are assembled in the order of negative electrode shell-pad-Li metal sheet-electrolyte-separator-electrode sheet-pad-positive electrode shell to obtain the lithium-ion battery.

8. The application of a spinel-like structure oxide electrode active material according to claim 6 or 7, characterized in that, The electrode active material and anhydrous ethanol are ball-milled and dried to obtain the electrode active material powder; the ball milling time is 0.5h~2h and the rotation speed is 600rpm~800rpm; the raw materials are mixed and then magnetically stirred to obtain the composite material slurry; the magnetic stirring time is 10h~24h and the rotation speed is 200rpm~600rpm.

9. The application of a spinel-like structure oxide electrode active material according to claim 6 or 7, characterized in that, The mass ratio of the electrode active material powder, carbon powder and binder 2 is (6~8):(2~4):(1~2); the carbon powder includes one or more of graphite, soft carbon, hard carbon, super carbon powder, graphene, carbon nanotubes, porous carbon and activated carbon; the binder 2 includes one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber and polytetrafluoroethylene.

10. The application of a spinel-like oxide electrode active material according to claim 6 or 7, characterized in that, The composite material exhibits a specific capacity increase phenomenon.

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