Positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of battery materials, and provides a positive electrode material and a preparation method and application thereof, and the positive electrode material comprises modified manganese dioxide formed by doping beta-Al2O3 in a manganese dioxide lattice. According to the invention, the beta-Al2O3 is doped with manganese dioxide, so that the high-temperature performance of the button cell can be improved, the expansion of the cell after high-temperature storage is effectively slowed down, and the low-temperature pulse load level after high-temperature storage is improved. The doping of Al < 3 + > can reduce the disproportionation reaction of Mn < 3 + > and Jahn-Teller distortion, so that the stability of the structure is improved, the side reaction with electrolyte can be reduced during high-temperature storage, gas production is reduced, and the expansion height of the battery is reduced.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and relates to a cathode material, a method for preparing it, and its uses. Background Technology

[0002] Manganese dioxide (MnO2), as an important electrochemical active material, has long held a key position in the field of lithium primary batteries due to its advantages such as high theoretical specific capacity, abundant resources, environmental friendliness, and low cost. Especially in lithium-manganese dioxide primary batteries (referred to as lithium-manganese primary batteries), which use metallic lithium as the negative electrode, organic electrolyte as the medium, and MnO2 as the positive electrode active material, it is widely used in scenarios requiring long lifespan and high reliability, such as smart meters, medical equipment, military equipment, and IoT terminals, thanks to its relatively high operating voltage (approximately 3.0V), good storage performance, and stable discharge characteristics.

[0003] Typically, during the discharge process of a lithium-manganese primary battery, lithium ions are extracted from the negative electrode, migrate through the electrolyte to the positive electrode, and intercalate into the MnO2 lattice tunnel structure. Simultaneously, electrons are transferred through the external circuit to achieve energy output. However, the crystal structure of manganese dioxide exhibits significant instability under deep discharge or high-rate discharge conditions, becoming a key bottleneck restricting battery capacity utilization, cycle life, and overall performance improvement. Specifically, during the lithium-ion intercalation process, Mn... 4+ Reduced to Mn 3 + This process triggers the Jahn-Teller effect, leading to severe distortion of the MnO6 octahedron, lattice parameter imbalance, and localized stress accumulation. Ultimately, this can result in surface cracks, particle pulverization, and even the collapse of the overall crystal structure. This structural degradation not only causes contact failure between the active material and the conductive network but can also block lithium-ion diffusion channels, preventing some MnO2 from participating in subsequent reactions. This results in problems such as lower actual specific capacity than theoretical values, a decreased discharge plateau, and voltage hysteresis during high-current discharge. Furthermore, the destruction of the crystal structure can exacerbate side reactions of the electrolyte on the positive electrode surface, consuming limited lithium sources and electrolyte, and further shortening the battery's lifespan.

[0004] To improve the electrochemical performance of manganese dioxide in lithium-ion primary batteries, current technologies primarily employ carbon material coating strategies. Carbon material coating involves combining manganese dioxide particles with carbon materials such as carbon nanotubes and graphene to form a conductive network, thereby enhancing the overall electronic conductivity of the material. This method helps reduce electrode polarization, improve the discharge voltage plateau and high-current discharge capability, while the carbon layer can buffer volume changes and inhibit particle agglomeration to some extent. However, the addition of carbon materials dilutes the mass proportion of active material in the cathode, reducing the overall energy density of the battery; moreover, some carbon materials (such as graphene or carbon nanotubes) may introduce impurities such as metal catalysts during the preparation process, which can easily affect the battery and its stability.

[0005] Therefore, there is still a need to develop a new optimization scheme that can stabilize and effectively maintain the MnO2 crystal structure, while also ensuring that manganese dioxide has good ion and electron transport properties, in order to overcome the core problem that current materials cannot achieve both structural stability and electrochemical performance. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a cathode material, a method for preparing the same, and its uses. The cathode material comprises modified manganese dioxide formed by doping β-Al₂O₃ within a manganese dioxide lattice. This invention improves the high-temperature performance of coin cells by doping manganese dioxide with β-Al₂O₃, effectively mitigating battery expansion after high-temperature storage and improving the low-temperature pulse load level after high-temperature storage. 3+ Doping can reduce Mn 3+ The disproportionation reaction and Jahn-Teller distortion are reduced, thereby improving the structural stability. During high-temperature storage, side reactions with the electrolyte are reduced, gas production is reduced, and the battery expansion height is lowered.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a positive electrode material, the positive electrode material comprising manganese dioxide, and further comprising β-Al2O3 doped in the manganese dioxide.

[0009] Compared to doping and / or coating with other metal oxides such as TiO2 or α-Al2O3, traditional TiO2 and α-Al2O3 materials are wide-bandgap semiconductors with dense lattice structures and extremely low ionic and electronic conductivity. In cathode systems, they are unlikely to promote rapid lithium-ion migration and may even hinder ion diffusion pathways within the active material, exacerbating concentration polarization, especially under high-rate discharge conditions. Furthermore, these oxides have poor crystal structure compatibility with MnO2, resulting in weak interfacial bonding. During charge and discharge, microcracks easily form due to differences in thermal expansion coefficients or volume changes, leading to interfacial debonding and weakening the structural support. This invention uses β-Al2O3 to dope manganese dioxide. β-Al2O3 has a hexagonal crystal structure, and its ion diffusion channels are more conducive to rapid lithium-ion transport. The doped β-Al2O3 can undergo a solid-state reaction with MnO2 to form a stable composite structure, which can further effectively suppress volume changes and crystal collapse of manganese dioxide during charge and discharge. Meanwhile, the high lithium conductivity of β-Al₂O₃ can also promote the uniform distribution of lithium ions on the surface of the cathode material, effectively reducing the occurrence of side reactions. Therefore, this invention improves the high-temperature performance of coin cells by doping β-Al₂O₃ with manganese dioxide, effectively mitigating battery expansion after high-temperature storage and improving the low-temperature pulse load level after high-temperature storage. 3+ Doping can reduce Mn 3+ The disproportionation reaction and Jahn-Teller distortion are reduced, thereby improving the structural stability. During high-temperature storage, side reactions with the electrolyte are reduced, gas production is reduced, and the battery expansion height is lowered.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0011] As a preferred embodiment of the present invention, the purity of the β-Al2O3 is ≥98%.

[0012] β-Al2O3 belongs to the hexagonal crystal system, but its lattice arrangement is different from that of α-Al2O3. In α-Al2O3, oxygen ions are hexagonally close-packed, and aluminum ions occupy octahedral voids; while in β-Al2O3, aluminum and oxygen ions are distributed differently, forming a unique hexagonal structure.

[0013] For example, the β-Al2O3 includes gas-phase nano-β-Al2O3 with a hexagonal crystal system.

[0014] Preferably, the particle size (D50) of the β-Al2O3 is 50 nm to 200 nm. Exemplarily, it can be 50 nm, 80 nm, 120 nm, 160 nm, or 200 nm, etc.

[0015] In this invention, β-Al2O3 is preferably selected with a narrow particle size distribution and a moderate D50 particle size, which is more conducive to uniform doping and sintering. Small particles have higher specific surface area and surface energy, and when used as dopants, they are also highly efficient sintering promoters. However, excessively small particle size can also affect the mixing effect, making it difficult to disperse, and agglomeration can also affect the sintering effect.

[0016] As a preferred embodiment of the present invention, the manganese dioxide comprises electrolytic manganese dioxide.

[0017] Preferably, the manganese dioxide particles have a D50 particle size of 20 μm to 30 μm. Exemplarily, the particle size can be 20 μm, 25 μm, 28 μm, or 30 μm, etc.

[0018] Preferably, the manganese dioxide has a γ-type crystal structure, and the modified manganese dioxide has a β+γ-type crystal structure.

[0019] In this invention, the manganese dioxide crystal form is γ-type, and the modified manganese dioxide obtained by sintering with β-Al2O3 has a β+γ-type crystal form. It can be characterized by XRD, and the success of sintering doping can be judged by the characteristic peaks and the transformation of the crystal form.

[0020] As a preferred technical solution of the present invention, based on the mass of the positive electrode material as 100%, the manganese dioxide accounts for 97% to 99.5%, and for example, it can be 97%, 98%, 99%, or 99.5%; the β-Al2O3 accounts for 0.5% to 3%, and for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%.

[0021] In a second aspect, the present invention provides a method for preparing the cathode material described in the first aspect, the method comprising: mixing manganese dioxide with β-Al2O3 and then sintering to obtain a cathode material for a lithium manganese battery.

[0022] The method for preparing cathode materials described in this invention is simple and convenient. Through the doping and sintering process, uniform doping and distribution of β-Al2O3 can be achieved, avoiding complex coating and other process steps, which helps to save time and costs.

[0023] As a preferred technical solution of the present invention, the mixing includes solid-phase mixing.

[0024] Preferably, the sintering temperature is 350℃~450℃. For example, it can be 350℃, 380℃, 400℃ or 450℃, etc.

[0025] Preferably, the sintering time is 6h to 10h. For example, it can be 6h, 7h, 8h, 9h, or 10h.

[0026] In this invention, a dehydration reaction of the water of crystallization and a crystal form transformation reaction occur during the sintering process. The chemically bound water in the original γ-type manganese dioxide is removed, and the γ-type manganese dioxide is transformed into a β+γ crystal form mixture. Furthermore, if the sintering temperature is too low, incomplete sintering will affect the electrical performance; if the temperature is too high, the γ-type manganese dioxide will excessively transform into the β-type, affecting the battery capacity and performance. Further, the preferred sintering temperature is 370℃~400℃.

[0027] In this invention, β-Al2O3 can be obtained by purchasing and using existing products or by synthesis.

[0028] As a further example, the method for synthesizing β-Al2O3 includes: mixing α-Al2O3 with an activator and carrying out a high-temperature solid-phase reaction to obtain β-Al2O3.

[0029] Preferably, the mixing includes solid-phase grinding.

[0030] Preferably, the activator includes at least one of KCl, LiCl, or NaCl.

[0031] Preferably, the temperature of the high-temperature solid-phase reaction is 800℃~1000℃. For example, it can be 800℃, 850℃, 900℃, 960℃ or 1000℃, etc.

[0032] β-Al₂O₃ is prone to crystal transformation at high temperatures, and its hexagonal crystal structure needs to be maintained by controlling the sintering temperature. Excessively high temperatures may cause the β phase to transform into the α phase (α-Al₂O₃), reducing its ionic conductivity.

[0033] Thirdly, the present invention provides a positive electrode sheet containing the positive electrode material described in the first aspect, or containing the positive electrode material obtained by the method described in the second aspect.

[0034] It should be noted that, by way of example, the positive electrode sheet, in addition to the positive electrode material, also includes a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector. The positive electrode active layer includes the positive electrode material and also includes a conductive agent and / or a binder.

[0035] Preferably, the conductive agent includes at least one of graphite, conductive carbon black, acetylene black, graphene, or carbon nanotubes.

[0036] Preferably, the adhesive comprises at least one of polytetrafluoroethylene, styrene-butadiene rubber, ethylene-acrylic acid copolymer, or polyvinylidene fluoride and its modifiers.

[0037] Preferably, based on the mass of the positive electrode active layer as 100%, the mass percentage of the positive electrode active material is 88%~92%, such as 88%, 89%, 90%, 91%, or 92%; the mass percentage of the conductive agent is 6%~8%, such as 6%, 6.6%, 7%, 7.5%, or 8%; and the mass percentage of the binder is 2%~4%, such as 2%, 2.6%, 3%, 3.4%, or 4%.

[0038] As a further example, the positive electrode sheet can be produced by the following process:

[0039] A semi-dry process is adopted. After mixing the raw materials, an appropriate amount of granulating agent is added to the mixture and mixed thoroughly. Then, the mixture is baked at 100℃~140℃ for 0.5h~2h to obtain the positive electrode mixture. The positive electrode is obtained by compression molding using a specified molding die.

[0040] Fourthly, the present invention provides a lithium manganese primary battery containing the positive electrode material described in the first aspect, or containing the positive electrode sheet described in the third aspect.

[0041] It should be noted that, by way of example, the lithium manganese primary battery, in addition to the positive electrode material and the positive electrode sheet, also includes a negative electrode sheet, a separator, and an electrolyte.

[0042] Preferably, the negative electrode comprises pure metallic lithium or a lithium alloy.

[0043] Preferably, the doped metal element in the lithium alloy includes at least one of aluminum, magnesium, or calcium; based on the total mass of the negative electrode sheet (100%), the mass percentage of the doped metal element is 0.05% to 3%, for example, 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, or 3%.

[0044] Preferably, the diaphragm comprises polypropylene (PP) and polyethylene (PE).

[0045] Preferably, the electrolyte comprises a lithium salt and a non-aqueous solvent; the lithium salt comprises at least one of LiClO4, LiFSI, LiBOB or LiTFSI; the non-aqueous solvent comprises at least one of ethylene carbonate, butyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane or 1,2-diethoxyethane.

[0046] Preferably, as a preferred technical solution of the present invention, the electrolyte injection volume is 1.2g / Ah to 1.5g / Ah, such as 1.2g / Ah, 1.23g / Ah, 1.26g / Ah, 1.3g / Ah, 1.33g / Ah, 1.35g / Ah, 1.38g / Ah, 1.4g / Ah, 1.42g / Ah, 1.44g / Ah, 1.46g / Ah, 1.48g / Ah, or 1.5g / Ah.

[0047] Preferably, the lithium manganese primary battery refers to any one of button cells, cylindrical cells, or pouch cells.

[0048] Fifthly, the present invention provides an electrical device comprising the lithium manganese primary battery described in the fourth aspect.

[0049] As a further example, the electrical devices include those applicable to smart meters and remote monitoring systems, such as water meters, electricity meters, gas meters, and heat meters; they can also be used in the field of medical electronic devices, such as implantable medical devices like pacemakers, nerve stimulators, implantable defibrillators, portable medical testing instruments, blood glucose meters, or electronic thermometers; and they can also be used as backup power for Internet of Things (IoT) and wireless sensor networks or computer motherboard CMOS memory, as well as in consumer electronics products such as cameras, electronic door locks, remote controls, electronic tags (RFID), and small electronic toys. Furthermore, when the lithium manganese primary battery is a button cell battery, it can be used as a power supply for computer motherboard BIOS / CMOS clock and configuration retention, a main power supply or clock battery for various small electronic devices (such as remote controls, electronic scales, timing / counting devices, wearable and portable electronics, etc.), and can also be used as a power supply for tire pressure monitoring systems (TPMS), a battery for smart meters, a power supply for small instruments, a power supply for health monitoring devices such as blood glucose meters, and a power supply for smoke / security detectors, etc.

[0050] It should be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0051] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0052] In the cathode material described in this invention, manganese dioxide is doped with β-Al₂O₃. β-Al₂O₃ has a hexagonal crystal structure, and its ion diffusion channels are more conducive to the rapid transport of lithium ions. The doped β-Al₂O₃ can undergo a solid-state reaction with MnO₂ to form a stable composite structure, which can further effectively suppress the volume change and crystal collapse of manganese dioxide during charge and discharge. Simultaneously, β-Al₂O₃ can also promote the uniform distribution of lithium ions on the surface of the cathode material, effectively reducing the occurrence of side reactions. The resulting modified manganese dioxide effectively mitigates battery expansion after high-temperature storage and reduces the low-temperature pulse load level after high-temperature storage. 3+ Doping can reduce Mn 3+ The disproportionation reaction and Jahn-Teller distortion are reduced, thereby improving the structural stability. During high-temperature storage, side reactions with the electrolyte are reduced, gas production is reduced, and the battery expansion height is lowered.

[0053] The method for preparing cathode materials described in this invention is simple and convenient. Through the doping and sintering process, uniform doping and distribution of β-Al2O3 can be achieved, avoiding complex coating and other process steps, which helps to save time and costs. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0055] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0056] Example 1

[0057] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide, i.e., modified manganese dioxide formed by doping β-Al2O3 inside the manganese dioxide lattice; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm; the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm; based on the mass of the cathode material being 100%, the manganese dioxide accounts for 99% and the β-Al2O3 accounts for 1%, and the mixture is mixed in a ball mill for 4 h and then sintered at 380 °C for 10 h.

[0058] Example 2

[0059] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 98.5% and the β-Al2O3 accounts for 1.5%; after mixing in a ball mill for 4 hours, it is sintered at 380°C for 10 hours; except for the above, other conditions are exactly the same as in Example 1.

[0060] Example 3

[0061] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 98% and the β-Al2O3 accounts for 2%, and the mixture is mixed in a ball mill for 4 h and then sintered at 380 °C for 10 h; except for the above, the other conditions are exactly the same as in Example 1.

[0062] Example 4

[0063] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 97% and the β-Al2O3 accounts for 3%, and the mixture is mixed in a ball mill for 4 h and then sintered at 380 °C for 10 h; except for the above, the other conditions are exactly the same as in Example 1.

[0064] Example 5

[0065] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 99% and the β-Al2O3 accounts for 1%; after mixing in a ball mill for 4 hours, it is sintered at 400°C for 10 hours; except for the above, other conditions are exactly the same as in Example 1.

[0066] Example 6

[0067] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 99% and the β-Al2O3 accounts for 1%, and the mixture is mixed in a ball mill for 4 h and then sintered at 450 °C for 10 h; except for the above, the other conditions are exactly the same as in Example 1.

[0068] Example 7

[0069] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 99% and the β-Al2O3 accounts for 1%, and the mixture is mixed in a ball mill for 4 hours and then sintered at 380°C for 6 hours; except for the above, the other conditions are exactly the same as in Example 1.

[0070] Example 8

[0071] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 99% and the β-Al2O3 accounts for 1%, and the mixture is mixed in a ball mill for 4 hours and then sintered at 380°C for 8 hours; except for the above, the other conditions are exactly the same as in Example 1.

[0072] Example 9

[0073] This embodiment provides a cathode material comprising manganese dioxide and β-Al2O3 doped in the manganese dioxide; the β-Al2O3 is a hexagonal fumed nano-β-Al2O3 with a particle size of 100 nm (D50); the manganese dioxide is γ-manganese dioxide with a particle size of 25 μm (D50); based on the mass of the cathode material being 100%, the manganese dioxide accounts for 99% and the β-Al2O3 accounts for 1%, and the mixture is mixed in a ball mill for 4 h and then sintered at 380 °C for 12 h; except for the above, the other conditions are exactly the same as in Example 1.

[0074] Comparative Example 1

[0075] This comparative example provides a positive electrode material, which is only the manganese dioxide of Example 1 and does not contain any other dopants. Except for the above, the other conditions are exactly the same as those of Example 1.

[0076] Characterization and testing:

[0077] The positive electrode material obtained in the examples and comparative examples was mixed with the binder polyvinylidene fluoride and the conductive agent graphite in a mass ratio of 91:7:2. An appropriate amount of granulating agent was added to the mixture and it was thoroughly mixed. The mixture was then baked at 120°C for 1 hour to obtain the positive electrode mixture. The positive electrode was obtained by compression molding using a specified molding die.

[0078] A negative electrode, a separator, and an electrolyte are provided; the negative electrode is a lithium metal sheet; the separator is a PE separator; the electrolyte includes a lithium salt and a non-aqueous solvent; the lithium salt is LiFSI, and the non-aqueous solvent is ethylene carbonate; the obtained positive electrode sheets are assembled with the above-mentioned negative electrode sheet, separator, electrolyte, and other components to form batteries, thereby obtaining various lithium-manganese primary batteries;

[0079] Electrochemical performance tests were conducted on all obtained lithium-manganese primary batteries. The basic performance of the batteries from Examples 1 to 9 and Comparative Example 1 was tested, including internal resistance, open-circuit voltage, and total height. Then, 10 cells each from Examples 1 to 9 and Comparative Example 1 were stored at 125°C for 300 hours. After storage, the batteries were removed and placed at room temperature for 6 hours before testing their basic performance, including internal resistance, open-circuit voltage, and total height. The expansion height of the batteries before and after storage was obtained. An 8mA 0.2s pulse was applied at -40°C to measure the pulse load (CCV). The results are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] As shown in Table 1, overall, modified manganese dioxide improved the low-temperature pulse load level at -40℃ after high-temperature storage. Compared with Comparative Example 1, Examples 1-6 showed a smaller battery expansion height after high-temperature storage, and the low-temperature pulse load was improved to varying degrees. Compared with Examples 1-4, the doping ratio of γ-manganese dioxide and β-Al2O3 between 99:1 and 97:3 significantly improved the load, and the load levels were not significantly different. Compared with Examples 5-6, different sintering temperatures also had a significant impact on the high-temperature performance. The higher the sintering temperature, the greater the battery expansion height after storage, and the lower the low-temperature load. It is speculated that the high sintering temperature caused a side reaction during sintering, producing inert Mn2O3. Compared with Examples 7-9, sintering time was also a key factor affecting high-temperature performance. A longer sintering time would generate more β-crystalline manganese dioxide. The higher the proportion of β-crystalline manganese dioxide, the worse the structural stability, and the easier it is to generate gas during high-temperature storage, affecting electrical performance.

[0083] In summary, the cathode material of this invention uses β-Al₂O₃ to dope manganese dioxide. The unique lattice structure of β-Al₂O₃ effectively suppresses the structural collapse of manganese dioxide during discharge, and β-Al₂O₃ has superior ion conductivity, which is beneficial to improving the overall electrochemical performance of the cathode material. The method for preparing the cathode material of this invention, through doping and sintering processes, can achieve a uniform doping distribution, avoid complex procedures, and save time and costs.

[0084] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0085] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0086] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A positive electrode material, characterized in that, The cathode material comprises modified manganese dioxide formed by doping β-Al2O3 inside the manganese dioxide lattice.

2. The cathode material according to claim 1, characterized in that, The purity of the β-Al2O3 is ≥98%; Preferably, the particle size (D50) of the β-Al2O3 is 50 nm to 200 nm.

3. The cathode material according to claim 1 or 2, characterized in that, The manganese dioxide includes electrolytic manganese dioxide; Preferably, the manganese dioxide particles have a D50 particle size of 20 μm to 30 μm; Preferably, the manganese dioxide has a γ-type crystal structure, and the modified manganese dioxide has a β+γ-type crystal structure.

4. The cathode material according to any one of claims 1-3, characterized in that, Based on the mass of the modified manganese dioxide being 100%, manganese dioxide accounts for 97% to 99.5%, and β-Al2O3 accounts for 0.5% to 3%.

5. A method for preparing the cathode material according to any one of claims 1-4, characterized in that, The method includes: mixing manganese dioxide with β-Al2O3 and then sintering to obtain the positive electrode material for lithium manganese batteries.

6. The method according to claim 5, characterized in that, The mixing includes solid-phase mixing.

7. The method according to claim 5 or 6, characterized in that, The sintering temperature is 350℃~450℃; Preferably, the sintering time is 6h to 10h.

8. A positive electrode sheet, characterized in that, The cathode material comprises any one of claims 1-4, or the cathode material prepared by the method described in any one of claims 5-7.

9. A lithium-manganese primary battery, characterized in that, It contains the positive electrode material according to any one of claims 1-4, or the positive electrode sheet according to claim 8.

10. An electrical device, characterized in that, It contains the lithium manganese primary battery as described in claim 9.

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