A positive electrode material for primary lithium-manganese batteries, its preparation and use

Abstract

This invention relates to the field of battery cathode materials technology, and particularly to a primary lithium-manganese battery cathode material, its preparation method, and its application. The cathode material comprises core-shell structured particles and a three-dimensional conductive network. The core-shell structured particles consist of a modified manganese dioxide core and a fast-ion conductor shell sequentially coated with a modified manganese dioxide core, wherein the modified manganese dioxide core is pre-lithium-intercalated γ-MnO2. The preparation method includes the following steps: mixing highly crystalline manganese dioxide with lithium nitrate to obtain a pre-lithium-intercalated modified manganese dioxide core; dispersing the manganese dioxide core in a lithium titanium aluminum phosphate precursor sol to form a complete fast-ion conductor shell, obtaining a core-shell structured powder; and co-dispersing the core-shell structured powder, multi-walled carbon nanotubes, and graphene oxide to introduce a three-dimensional conductive network, thereby obtaining the primary lithium-manganese battery cathode material. This invention improves the electrochemical performance of the electrode by constructing a synergistic structure of a pre-lithium-intercalated modified manganese dioxide core, a fast-ion conductor shell, and a three-dimensional conductive network.

Description

Technical Field

[0001] This invention relates to the field of battery cathode material technology, and in particular to a primary lithium manganese battery cathode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of technologies such as the Internet of Things, portable medical electronic devices, smart meters, and radio frequency identification (RFID), the market demand for high-performance, long-life, and highly reliable miniaturized primary power supplies is becoming increasingly urgent. Primary lithium-manganese batteries, with their advantages of high open-circuit voltage, high energy density, long storage life, wide operating temperature range, and good safety, have secured their dominant position in these fields. The electrochemical performance of primary lithium-manganese batteries depends on the efficiency of their cathode material.

[0003] Currently, primary lithium-manganese batteries commonly use electrolytic manganese dioxide (EMD) or chemically modified manganese dioxide (CMD) as the positive electrode active material. While manganese dioxide has a theoretical specific capacity of up to 308 mAh / g, in practical battery systems, its effective utilization is only 220–280 mAh / g. Furthermore, it suffers from low intrinsic electronic conductivity, slow solid-phase ion diffusion kinetics, and poor electrode / electrolyte interface stability. Existing solutions typically involve simple carbon coating or physically mixed three-dimensional conductive networks. These improvements often sacrifice other properties while enhancing one, resulting in suboptimal quality for primary lithium-manganese batteries.

[0004] Therefore, there is a need for a method for preparing primary lithium-manganese battery cathode materials that simultaneously addresses the problems of slow electron conduction, sluggish ion diffusion, and interfacial instability in manganese dioxide cathodes, as well as their applications. Summary of the Invention

[0005] The main objective of this invention is to provide a primary lithium manganese battery cathode material, its preparation method, and its application, aiming to solve the problems of slow electron conduction, sluggish ion diffusion, and interface instability in existing technologies for manganese dioxide cathodes.

[0006] To achieve the above objectives, the present invention proposes a primary lithium manganese battery cathode material, wherein the lithium manganese battery cathode material comprises core-shell structured particles and a three-dimensional conductive network, wherein the core-shell structured particles comprise a modified manganese dioxide core and a fast ion conductor shell sequentially coated thereon, and the modified manganese dioxide core is γ-MnO2 pre-intercalated with lithium.

[0007] The fast-ion conductor shell is lithium aluminum titanium phosphate, and the chemical formula of the pre-lithium-intercalated γ-MnO2 is Li. x MnO2, x=0.1~0.2, the three-dimensional conductive network is composed of one-dimensional multi-walled carbon nanotubes interwoven with two-dimensional graphene.

[0008] Furthermore, the chemical formula of the lithium titanium aluminum phosphate is Li.1.3 Al 0.3 Ti 1.7 (PO4)3.

[0009] This invention also proposes a method for preparing a primary lithium manganese battery cathode material, comprising the following steps:

[0010] Core preparation involves heat-treating electrolytic manganese dioxide powder at 380℃~420℃ for 5~8 hours in air atmosphere to obtain highly crystalline manganese dioxide. The highly crystalline manganese dioxide is then mixed with lithium nitrate at a lithium-manganese molar ratio of (0.1~0.2):1, and reacted at 350℃~400℃ for 4~6 hours to obtain a pre-lithiated modified manganese dioxide core.

[0011] The manganese dioxide core is dispersed in lithium titanium aluminum phosphate precursor sol, and after ultrasonic impregnation and drying, it is heat-treated at 680℃~720℃ for 4~6h under argon atmosphere to form a complete fast ion conductor shell, thus obtaining core-shell structured powder.

[0012] A three-dimensional conductive network was constructed by dispersing the core-shell structure powder, multi-walled carbon nanotubes, and graphene oxide together at a mass ratio of 90:(3~5):(3~5). After high-speed shear emulsification and freeze-drying, the mixture was annealed in a hydrogen-containing inert atmosphere at 400℃~500℃ for 1~2 hours to introduce the three-dimensional conductive network, thus obtaining a primary lithium manganese battery cathode material.

[0013] Further, the shell coating process involves dispersing the manganese dioxide core in a lithium aluminum titanium phosphate precursor sol, followed by ultrasonic impregnation and drying, and then heat-treating at 680℃~720℃ for 4~6 hours under an argon atmosphere to form a complete fast ion conductor shell, thus obtaining a core-shell structured powder. The steps also include:

[0014] According to Li 1.3 Al 0.3 Ti 1.7 Weigh out lithium acetate, aluminum isopropoxide, tetrabutyl titanate and triethyl phosphate in the stoichiometric ratio of (PO4)3.

[0015] Tetrabutyl titanate was mixed with anhydrous ethanol, and a mixture of glacial acetic acid and water was slowly added while stirring under ice-water bath conditions to form a homogeneous titanium precursor.

[0016] Add aluminum isopropoxide in ethanol, lithium acetate in aqueous solution, and triethyl phosphate in sequence;

[0017] After adjusting the pH of the mixture to 3-4, the mixture was stirred continuously at 60-80℃ for 4-6 hours to obtain the lithium titanium aluminum phosphate precursor sol.

[0018] The molar ratio of lithium acetate, aluminum isopropoxide, tetrabutyl titanate and triethyl phosphate is 1.3:0.3:1.7:3.

[0019] Further, the step of constructing a three-dimensional conductive network, which involves co-dispersing the core-shell structure powder, multi-walled carbon nanotubes, and graphene oxide at a mass ratio of 90:(3~5):(3~5), followed by high-speed shear emulsification and freeze-drying, and then annealing in a hydrogen-containing inert atmosphere at 400℃~500℃ for 1~2 hours to introduce the three-dimensional conductive network and obtain the primary lithium manganese battery cathode material, also includes the following steps:

[0020] Multi-walled carbon nanotubes and graphene oxide were dispersed together in deionized water at a mass ratio of 1:(1-1.5), and the mass of the deionized water was 200 to 500 times the total mass of the carbon materials.

[0021] Perform ultrasonic dispersion for 30-60 minutes, then process with a high-speed shear disperser at a speed of 8000-12000 r / min for 15-30 minutes to obtain a uniform conductive network dispersion.

[0022] Furthermore, the step of introducing the three-dimensional conductive network further includes:

[0023] The core-shell structure powder is slowly added to the conductive network dispersion, and the mixture is continuously stirred at 40℃~60℃ to ensure that the core-shell structure powder is fully wetted and adsorbed by the conductive network dispersion.

[0024] Spray drying is performed with an inlet temperature of 180℃~220℃ and an outlet temperature of 80℃~100℃ to obtain a preliminary composite powder.

[0025] The pre-composite powder was heat-treated at 400℃~500℃ for 1~2h in an inert atmosphere containing hydrogen, so that the graphene oxide was partially reduced and synergistically formed with carbon nanotubes to construct a three-dimensional conductive network covering the core-shell structure powder, thus obtaining a primary lithium manganese battery cathode material.

[0026] Furthermore, the feed rate for the spray drying is 5~10 ml / min.

[0027] Furthermore, the hydrogen-containing inert atmosphere is a mixture of hydrogen and argon, wherein the volume content of hydrogen is 5-10%.

[0028] The present invention also proposes a primary lithium manganese battery cathode sheet, comprising core-shell structured particles and a three-dimensional conductive network as described in any of the above technical solutions, as well as a conductive agent and a binder.

[0029] The present invention also proposes a primary lithium manganese battery, comprising a positive electrode, a lithium metal negative electrode, and a non-aqueous organic electrolyte as described in the above technical solutions.

[0030] The present invention provides a primary lithium-manganese battery cathode material, its preparation method, and its application. By constructing a synergistic structure of "pre-lithium-intercalated modified manganese dioxide core - lithium aluminum titanium phosphate (LATP) fast ion conductor shell - carbon nanotube / graphene three-dimensional conductive network", the invention solves the problems of low electronic conductivity, slow ion diffusion kinetics, and unstable electrode-electrolyte interface of existing manganese dioxide cathode materials. This greatly improves the mixed conductivity of the electrode and enhances the environmental adaptability and long-term reliability of the battery. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the processes shown in these drawings without creative effort.

[0032] Figure 1 This is a schematic flowchart illustrating a method for preparing a primary lithium-manganese battery cathode material according to an embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0035] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0036] Understandably, manganese dioxide is a semiconductor material, and its inherently low electronic conductivity leads to severe ohmic polarization within the electrodes. Under high current or pulse discharge conditions, the voltage plateau drops sharply, resulting in a significant decrease in effective capacity, limiting the battery's application in high-power devices. Simultaneously, during battery discharge, lithium ions must diffuse in solid-state tunnels within the manganese dioxide lattice; this process is slow and becomes the rate-determining step for capacity release, especially at low temperatures where ion diffusion is significantly hindered, leading to deterioration in low-temperature performance. Furthermore, during prolonged contact between the cathode material and the organic electrolyte, slow interfacial side reactions occur, including electrolyte decomposition and manganese ion dissolution. This not only causes self-discharge and capacity loss during storage but also affects the battery's long-term reliability.

[0037] Existing improvement methods include, but are not limited to: heat-treating manganese dioxide to improve its crystallinity and structural stability; surface carbon coating of manganese dioxide to enhance interparticle electronic contact; or simple physical mixing with highly conductive materials to construct conductive pathways. In addition, some studies have attempted to modify the surface of electrode materials with ion-conducting materials in order to improve interfacial ion transport.

[0038] However, existing technical solutions mostly focus on solving single problems. For example, carbon coating can improve electron conduction, but this method has limited effect on suppressing interfacial side reactions and promoting bulk ion diffusion. Mixing conductive networks can be used to construct conductive pathways, but simple physical mixing is difficult to form a stable and efficient three-dimensional continuous conductive network, and it cannot solve the problem of direct contact between active materials and electrolyte.

[0039] Based on this, this application provides a primary lithium-manganese battery cathode material. This lithium-manganese battery cathode material includes core-shell structured particles and a three-dimensional conductive network. The core-shell structured particles include a modified manganese dioxide core and a fast-ion conductor shell sequentially coated with each other. The modified manganese dioxide core is pre-lithium-intercalated γ-MnO2. The fast-ion conductor shell is lithium aluminum titanium phosphate, and the chemical formula of the pre-lithium-intercalated γ-MnO2 is Li. x MnO2, x=0.1~0.2, a three-dimensional conductive network is composed of one-dimensional multi-walled carbon nanotubes interwoven with two-dimensional graphene.

[0040] Furthermore, the chemical formula of lithium titanium aluminum phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0041] This invention also proposes a method for preparing a primary lithium manganese battery cathode material, comprising the following steps:

[0042] Step S1, Core preparation: Electrolytic manganese dioxide powder is heat-treated at 380℃~420℃ for 5~8h in air atmosphere to obtain highly crystalline manganese dioxide. Then, the highly crystalline manganese dioxide is mixed with lithium nitrate at a lithium-manganese molar ratio of (0.1~0.2):1 and reacted at 350℃~400℃ for 4~6h to obtain a pre-lithiated modified manganese dioxide core.

[0043] Step S2, shell coating: Manganese dioxide cores are dispersed in lithium titanium aluminum phosphate precursor sol, and after ultrasonic impregnation and drying, they are heat-treated at 680℃~720℃ for 4~6h under argon atmosphere to form a complete fast ion conductor shell and obtain core-shell structure powder.

[0044] Step S3: Construct a three-dimensional conductive network. Core-shell structure powder, multi-walled carbon nanotubes and graphene oxide are dispersed together in a mass ratio of 90:(3~5):(3~5). After high-speed shear emulsification and freeze-drying, the mixture is annealed in a hydrogen-containing inert atmosphere at 400℃~500℃ for 1~2h to introduce the three-dimensional conductive network and obtain a primary lithium manganese battery cathode material.

[0045] Furthermore, step S2, the step of dispersing manganese dioxide nuclei in the lithium titanium aluminum phosphate precursor sol, further includes:

[0046] Step S2, press Li 1.3 Al 0.3 Ti 1.7 Weigh out lithium acetate, aluminum isopropoxide, tetrabutyl titanate and triethyl phosphate in the stoichiometric ratio of (PO4)3.

[0047] Step S201: Tetrabutyl titanate is mixed with anhydrous ethanol, and a mixed solution of glacial acetic acid and water is slowly added while stirring under ice-water bath conditions to form a homogeneous titanium precursor.

[0048] In step S202, an ethanol solution of aluminum isopropoxide, an aqueous solution of lithium acetate, and triethyl phosphate are added sequentially.

[0049] Step S203: After adjusting the pH of the mixed system to 3-4, the mixture is stirred continuously at 60-80℃ for 4-6 hours to obtain lithium titanium aluminum phosphate precursor sol.

[0050] The molar ratio of lithium acetate, aluminum isopropoxide, tetrabutyl titanate and triethyl phosphate is 1.3:0.3:1.7:3.

[0051] Furthermore, a three-dimensional conductive network is constructed by co-dispersing core-shell structured powder, multi-walled carbon nanotubes, and graphene oxide at a mass ratio of 90:(3~5):(3~5). After high-speed shear emulsification and freeze-drying, the mixture is annealed at 400℃~500℃ in a hydrogen-containing inert atmosphere for 1~2 hours to introduce the three-dimensional conductive network, thus obtaining the primary lithium-manganese battery cathode material. The steps also include the following:

[0052] Multi-walled carbon nanotubes and graphene oxide were dispersed together in deionized water at a mass ratio of 1:(1-1.5), and the mass of the deionized water was 200 to 500 times the total mass of the carbon materials.

[0053] Perform ultrasonic dispersion for 30-60 minutes, then process with a high-speed shear disperser at a speed of 8000-12000 r / min for 15-30 minutes to obtain a uniform conductive network dispersion.

[0054] Furthermore, step S3, the step of constructing the three-dimensional conductive network, also includes:

[0055] Step S301: The core-shell structure powder is slowly added to the conductive network dispersion and stirred continuously at 40℃~60℃ to ensure that the core-shell structure powder and the conductive network dispersion are fully wetted and adsorbed.

[0056] Step S302: Spray drying is performed with an inlet temperature of 180℃~220℃ and an outlet temperature of 80℃~100℃ to obtain a preliminary composite powder.

[0057] In step S303, the pre-composite powder is heat-treated at 400℃~500℃ for 1~2h in an inert atmosphere containing hydrogen, so that the graphene oxide is partially reduced and synergistically forms a three-dimensional conductive network that coats the core-shell structure powder with carbon nanotubes, thus obtaining a primary lithium manganese battery cathode material.

[0058] Furthermore, the feed rate for spray drying is 5~10 ml / min.

[0059] Furthermore, the hydrogen-containing inert atmosphere is a mixture of hydrogen and argon, wherein the volume content of hydrogen is 5-10%.

[0060] The present invention also discloses the following three sets of embodiments and two sets of comparative embodiments, and the specific implementation of each embodiment is as follows:

[0061] Example 1

[0062] Step S10: Weigh 100g of electrolytic manganese dioxide (EMD) powder and place it in a muffle furnace. Heat the powder to 400℃ at a rate of 5℃ / min under air atmosphere, and maintain this temperature for 6 hours. After natural cooling, obtain highly crystalline manganese dioxide. Grind 80g of highly crystalline manganese dioxide and 8.4g of lithium nitrate (LiNO3) thoroughly and mix them uniformly, with a lithium-manganese molar ratio of 0.15:1. Transfer the uniformly mixed powder to a tube furnace and heat it to 375℃ at a rate of 5℃ / min under air atmosphere. Maintain the temperature for 5 hours. After natural cooling, obtain pre-lithium-intercalated modified manganese dioxide cores (LiNO3). 0.15 MnO2).

[0063] Step S20, press Li 1.3 Al 0.3 Ti 1.7 Weigh out 19.6 g of lithium acetate, 6.12 g of aluminum isopropoxide, 57.8 g of tetrabutyl titanate, and 46.4 g of triethyl phosphate in the stoichiometric ratio of (PO4)3. Mix the tetrabutyl titanate with 50 ml of anhydrous ethanol, and then slowly add a mixture of glacial acetic acid and deionized water in a volume ratio of 2:1. After the addition is complete, stir continuously for 30 min to form a homogeneous titanium precursor. Slowly add the aluminum isopropoxide solution dissolved in 20 ml of anhydrous ethanol and the lithium acetate solution dissolved in 20 ml of deionized water, and then slowly add the triethyl phosphate. Adjust the pH of the entire mixture to 3.5 using an ammonia solution and transfer it to an 80°C oil bath. Stir and reflux continuously for 5 h to obtain a clear and stable lithium aluminum titanium phosphate (LATP) precursor sol.

[0064] Step S30: Add all the modified manganese dioxide cores (90g) prepared in step S10 to the lithium aluminum titanium phosphate precursor sol prepared in step S20 and ultrasonically impregnate for 60 min; dry the ultrasonically impregnated mixture in an 80℃ drying oven to obtain dried precursor powder; place the precursor powder in a tube furnace, introduce argon gas, heat to 700℃ at a heating rate of 5℃ / min and hold for 5 h for crystallization treatment, and obtain core-shell structure powder after natural cooling;

[0065] Step S40: Weigh 0.4 g of multi-walled carbon nanotubes (CNTs, diameter 10-20 nm, length 10-30 μm) and 0.4 g of graphene oxide (GO, sheet diameter 0.5-5 μm), disperse them together in 200 ml of deionized water, and then ultrasonically disperse for 40 min; process with a high-speed shear grinder (speed 10000 r / min) for 20 min to obtain a uniform conductive network dispersion; slowly add all the core-shell structure powder prepared in step S30 to the conductive network dispersion, and continuously stir at 50 °C for 2 h to allow the dispersion to settle. The core-shell structured powder and the conductive network dispersion were fully impregnated and adsorbed. The slurry was dried using a spray dryer with an inlet temperature of 200℃, an outlet temperature of 90℃, and a feed rate of 8ml / min to obtain a preliminary composite powder. The preliminary composite powder was placed in a tube furnace, and an argon-hydrogen mixture containing 8% hydrogen was introduced. The temperature was increased to 450℃ at a rate of 5℃ / min and held for 1.5h to partially reduce the graphene oxide and synergistically construct a three-dimensional conductive network that coats the core-shell structured powder with carbon nanotubes. After cooling, a primary lithium manganese battery cathode material was obtained.

[0066] Example 2:

[0067] Step S10: Weigh 100g of electrolytic manganese dioxide (EMD) powder and place it in a muffle furnace. Heat the powder to 400℃ at a rate of 5℃ / min under air atmosphere, and maintain this temperature for 6 hours. After natural cooling, obtain highly crystalline manganese dioxide. Grind 80g of highly crystalline manganese dioxide and 5.6g of lithium nitrate (LiNO3) thoroughly and mix them uniformly, with a lithium-manganese molar ratio of 0.1:1. Transfer the uniformly mixed powder to a tube furnace and heat it to 375℃ at a rate of 5℃ / min under air atmosphere. Maintain this temperature for 5 hours. After natural cooling, obtain pre-lithium-intercalated modified manganese dioxide cores (LiNO3). 0.1 MnO2).

[0068] Step S20, press Li 1.3 Al 0.3 Ti 1.7 Weigh out 19.6 g of lithium acetate, 6.12 g of aluminum isopropoxide, 57.8 g of tetrabutyl titanate, and 46.4 g of triethyl phosphate in the stoichiometric ratio of (PO4)3. Mix the tetrabutyl titanate with 50 ml of anhydrous ethanol, and then slowly add a mixture of glacial acetic acid and deionized water in a volume ratio of 2:1. After the addition is complete, stir continuously for 30 min to form a homogeneous titanium precursor. Slowly add the aluminum isopropoxide solution dissolved in 20 ml of anhydrous ethanol and the lithium acetate solution dissolved in 20 ml of deionized water, and then slowly add the triethyl phosphate. Adjust the pH of the entire mixture to 3.5 using an ammonia solution and transfer it to an 80°C oil bath. Stir and reflux continuously for 5 h to obtain a clear and stable lithium aluminum titanium phosphate (LATP) precursor sol.

[0069] Step S30: Add all the modified manganese dioxide cores prepared in step S10 to the lithium aluminum titanium phosphate precursor sol prepared in step S20 and ultrasonically impregnate for 60 min; dry the ultrasonically impregnated mixture in an 80℃ drying oven to obtain dried precursor powder; place the precursor powder in a tube furnace, introduce argon gas, heat to 700℃ at a heating rate of 5℃ / min and hold for 5 h for crystallization treatment, and obtain core-shell structure powder after natural cooling;

[0070] Step S40: Weigh 0.4 g of multi-walled carbon nanotubes (CNTs, diameter 10-20 nm, length 10-30 μm) and 0.4 g of graphene oxide (GO, sheet diameter 0.5-5 μm), disperse them together in 200 ml of deionized water, and then ultrasonically disperse for 40 min; process with a high-speed shear grinder (speed 10000 r / min) for 20 min to obtain a uniform conductive network dispersion; slowly add all the core-shell structure powder prepared in step S30 to the conductive network dispersion, and continuously stir at 50 °C for 2 h to allow the dispersion to settle. The core-shell structured powder and the conductive network dispersion were fully impregnated and adsorbed. The slurry was dried using a spray dryer with an inlet temperature of 200℃, an outlet temperature of 90℃, and a feed rate of 8ml / min to obtain a preliminary composite powder. The preliminary composite powder was placed in a tube furnace, and an argon-hydrogen mixture containing 8% hydrogen was introduced. The temperature was increased to 450℃ at a rate of 5℃ / min and held for 1.5h to partially reduce the graphene oxide and synergistically construct a three-dimensional conductive network that coats the core-shell structured powder with carbon nanotubes. After cooling, a primary lithium manganese battery cathode material was obtained.

[0071] As can be seen, compared with Example 1, Example 2 adjusts the amount of lithium nitrate to 5.6g, so that the lithium-manganese molar ratio is 0.10:1, in order to investigate the effect of different pre-lithiation degrees on material properties.

[0072] Example 3:

[0073] Step S10: Weigh 100g of electrolytic manganese dioxide (EMD) powder and place it in a muffle furnace. Heat the powder to 400℃ at a rate of 5℃ / min under air atmosphere, and maintain this temperature for 6 hours. After natural cooling, obtain highly crystalline manganese dioxide. Grind 80g of highly crystalline manganese dioxide and 8.4g of lithium nitrate (LiNO3) thoroughly and mix them uniformly, with a lithium-manganese molar ratio of 0.15:1. Transfer the uniformly mixed powder to a tube furnace and heat it to 375℃ at a rate of 5℃ / min under air atmosphere. Maintain the temperature for 5 hours. After natural cooling, obtain pre-lithium-intercalated modified manganese dioxide cores (LiNO3). 0.15 MnO2).

[0074] Step S20, press Li1.3 Al 0.3 Ti 1.7 Weigh out 19.6 g of lithium acetate, 6.12 g of aluminum isopropoxide, 57.8 g of tetrabutyl titanate, and 46.4 g of triethyl phosphate in the stoichiometric ratio of (PO4)3. Mix the tetrabutyl titanate with 50 ml of anhydrous ethanol, and then slowly add a mixture of glacial acetic acid and deionized water in a volume ratio of 2:1. After the addition is complete, stir continuously for 30 min to form a homogeneous titanium precursor. Slowly add the aluminum isopropoxide solution dissolved in 20 ml of anhydrous ethanol and the lithium acetate solution dissolved in 20 ml of deionized water, and then slowly add the triethyl phosphate. Adjust the pH of the entire mixture to 3.5 using an ammonia solution and transfer it to an 80°C oil bath. Stir and reflux continuously for 5 h to obtain a clear and stable lithium aluminum titanium phosphate (LATP) precursor sol.

[0075] Step S30: Add all the modified manganese dioxide cores prepared in step S10 to the lithium aluminum titanium phosphate precursor sol prepared in step S20 and ultrasonically impregnate for 60 min; dry the ultrasonically impregnated mixture in an 80℃ drying oven to obtain dried precursor powder; place the precursor powder in a tube furnace, introduce argon gas, heat to 700℃ at a heating rate of 5℃ / min and hold for 5 h for crystallization treatment, and obtain core-shell structure powder after natural cooling;

[0076] In step S40, 90g of the core-shell structure powder, 5g of conductive carbon black (Super P), and 5g of polyvinylidene fluoride (PVDF) binder are added to N-methylpyrrolidone (NMP) solvent and ball-milled at 300r / min for 4 hours to form a uniform positive electrode slurry. The slurry is then coated onto aluminum foil and vacuum-dried at 120°C for 12 hours. After rolling, a primary lithium manganese battery positive electrode material is obtained.

[0077] It can be seen that Example 3 uses a traditional mechanical mixing method to construct the conductive pathway, without introducing a three-dimensional conductive network composed of interwoven carbon nanotubes and graphene.

[0078] Comparative Example 1:

[0079] Step S10: Weigh 90g of unmodified electrolytic manganese dioxide (EDM) powder, 5g of conductive carbon black (Super P), and 5g of polyvinylidene fluoride (PVDF) adhesive.

[0080] Step S20: Place the weighed 90.0 g EMD powder, 5.0 g Super P conductive carbon black, and 5.0 g PVDF powder together in a 500 ml zirconium oxide ball mill jar; add 200 g zirconium oxide grinding balls (ball diameter ratio: Φ5 mm: Φ10 mm = 1:1) and 150 ml NMP solvent to the jar; seal the ball mill jar and place it on a planetary ball mill, set the revolution speed to 300 rpm and the rotation speed to 600 rpm, and continue ball milling and mixing for 6 hours until a uniform, stable, black positive electrode slurry without obvious particle texture is formed.

[0081] Step S30: Use a coating machine to uniformly coat the above slurry onto a clean aluminum foil current collector with a thickness of 20 μm; set the gap of the coating blade to 200 μm and the coating speed to 0.5 m / min; immediately transfer the coated wet electrode to a forced-air drying oven and pre-dry at 120°C for 30 minutes to remove most of the solvent; transfer the electrode to a vacuum drying oven and continue drying at 120°C and -0.095 MPa vacuum for 12 hours to completely remove residual solvent and moisture.

[0082] In step S04, the completely dried electrode sheet is rolled using a roller press with a roller gap of 100 μm and a rolling speed of 0.2 m / min. The electrode sheet is then subjected to a single cold pressing. After rolling, the electrode sheet is punched into a circular piece with a diameter of 14 mm using a cutting machine. This circular piece is the primary lithium manganese battery positive electrode sheet prepared in this comparative example for subsequent battery assembly and testing.

[0083] As can be seen, compared with Example 1, Comparative Example 1 represents the most basic prior art, using unmodified manganese dioxide and conventional conductive agents.

[0084] Comparative Example 2:

[0085] Step S10: Weigh 100g of electrolytic manganese dioxide (EMD) powder and place it in a muffle furnace. Heat the powder to 400℃ at a rate of 5℃ / min under air atmosphere, and maintain this temperature for 6 hours. After natural cooling, obtain highly crystalline manganese dioxide. Grind 80g of highly crystalline manganese dioxide and 8.4g of lithium nitrate (LiNO3) thoroughly and mix them uniformly, with a lithium-manganese molar ratio of 0.15:1. Transfer the uniformly mixed powder to a tube furnace and heat it to 375℃ at a rate of 5℃ / min under air atmosphere. Maintain the temperature for 5 hours. After natural cooling, obtain pre-lithium-intercalated modified manganese dioxide cores (LiNO3). 0.15 MnO2).

[0086] Step S20: Weigh 90g of the modified manganese dioxide prepared in step S10 and disperse it in 200ml of deionized water to obtain a modified manganese dioxide solution; weigh 7.5g of ammonium dihydrogen phosphate (NH4H2PO4) and lithium carbonate (L... i2 3.7 g of CO3 was dissolved in 50 ml of deionized water to obtain a lithium phosphate source solution. The lithium phosphate source solution was slowly added dropwise to the modified manganese dioxide solution under stirring and mixed. After the addition was completed, the mixture was stirred for 2 h to obtain a mixture. The mixture was dried at 80 °C to obtain a powder coated with the precursor. The powder was heated to 600 °C at a heating rate of 5 °C / min under argon protection and held for 3 h to convert the precursor into a Li3PO4 coating layer.

[0087] In step S30, 90g of Li3PO4 coated core-shell powder, 5g of conductive carbon black (Super P), and 5g of polyvinylidene fluoride (PVDF) binder are added to N-methylpyrrolidone (NMP) solvent and ball-milled at 300r / min for 4 hours to form a uniform positive electrode slurry. The slurry is then coated onto aluminum foil and vacuum dried at 120℃ for 12 hours. After rolling, a primary lithium manganese battery positive electrode material is obtained.

[0088] As can be seen, in contrast to Example 1, Comparative Example 2 uses a technical solution that coats other fast ion conductors but does not have a three-dimensional network.

[0089] This invention also discloses performance tests, as detailed below:

[0090] In this invention, the positive electrode materials obtained in the above embodiments and comparative embodiments were assembled into CR2032 type coin cells for testing according to the same standards. Specifically, lithium metal sheets were used as the negative electrode, Celgard 2400 was used as the separator, and the electrolyte was a 1 mol / L LiClO4 solution of propylene carbonate (PC) / 1,2-dimethoxyethane (DME) (volume ratio 1:1). All cells were tested after standing at 25±1℃ for 24 hours.

[0091] The specific results are shown in the table below:

[0092] Table 1. Electrochemical performance of the cathode materials prepared in each embodiment and comparative embodiment.

[0093]

[0094] Table 2. High and low temperature electrochemical performance of the cathode materials prepared in each embodiment and comparative embodiment.

[0095]

[0096] The discharge cutoff voltage is 2.0 V; the capacity retention rate is a percentage of the baseline performance (0.2C or capacity before storage) under the same group and conditions (such as temperature); the pulse discharge test method is: charge to 3.5V at 0.2C, let stand for 5 minutes, and then discharge to 2.0V at a constant current of 5C.

[0097] In detail, a comparison of the electrochemical performance test results of Examples 1-3 and Comparative Examples 1-2 shows that Example 1 of the present invention has high capacity, high rate performance and low temperature / storage performance. Example 3 has a significant gap with Example 1 in high rate (1C, 5C) and low temperature performance, indicating that the three-dimensional conductive network is crucial for achieving rapid electron transport.

[0098] It can be seen that the present invention combines high capacity, excellent rate performance, and low-temperature / storage performance. Comparing the electrochemical performance of Examples 1-3 with that of Control Examples 1-2, the pre-lithiated modified manganese dioxide core, LATP fast ion conductor shell, and three-dimensional conductive network disclosed in this invention work synergistically. The fast ion conductor shell lowers the lithium-ion interface migration barrier, and the three-dimensional conductive network provides an ultra-high-speed electron transport channel, greatly improving the mixed conductivity and high-rate performance of the electrode. Simultaneously, the low-temperature and high-temperature storage performance is also improved because the fast ion conductor shell isolates the electrolyte from corrosion, suppressing interfacial side reactions and manganese ion dissolution. From the technical solution of Example 3 using conventional conductive carbon black, it can be seen that although it has a complete fast ion conductor shell and is superior to the control examples in terms of storage and low-temperature performance, its 1C capacity retention rate and 5C pulse retention rate are still lower than those of Example 1. This indicates that the simple physical mixed conductive agent in the prior art cannot obtain a continuous electronic pathway, making electron transport a bottleneck at high-rate discharge, leading to increased polarization, a lower voltage plateau, and a sharp reduction in usable capacity.

[0099] The present invention also proposes a primary lithium manganese battery cathode sheet, comprising core-shell structured particles and a three-dimensional conductive network as described in any of the above technical solutions, as well as a conductive agent and a binder.

[0100] The present invention also proposes a primary lithium-manganese battery, comprising a positive electrode, a lithium metal negative electrode, and a non-aqueous organic electrolyte as described in the above technical solution.

[0101] This invention provides a primary lithium-manganese battery cathode material, its preparation method, and its application. By constructing a multi-level synergistic structure of "pre-lithiated modified manganese dioxide core—lithium aluminum titanium phosphate (LATP) fast ion conductor shell—carbon nanotube / graphene three-dimensional conductive network," it solves the problems of low electronic conductivity, slow ion diffusion kinetics, and unstable electrode-electrolyte interface in existing manganese dioxide cathode materials. Pre-lithiation treatment introduces lithium ions into the manganese dioxide lattice, reducing the activation barrier during the first discharge. Simultaneously, the LATP shell promotes lithium ion intercalation and provides a low-resistance lithium ion interface conduction channel. Synergistically, the LATP shell, along with the three-dimensional conductive network composed of carbon nanotubes and graphene, significantly improves the mixed conductivity of the electrode, enhancing the battery's environmental adaptability and long-term reliability.

[0102] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A primary lithium-manganese battery cathode material, characterized in that, The lithium manganese battery cathode material includes core-shell structured particles and a three-dimensional conductive network. The core-shell structured particles include a modified manganese dioxide core and a fast ion conductor shell that are sequentially coated. The modified manganese dioxide core is γ-MnO2 with pre-intercalated lithium. The fast-ion conductor shell is lithium aluminum titanium phosphate, and the chemical formula of the pre-lithium-intercalated γ-MnO2 is Li. x MnO2, x=0.1~0.2, the three-dimensional conductive network is composed of one-dimensional multi-walled carbon nanotubes interwoven with two-dimensional graphene.

2. A primary lithium-manganese battery cathode material as described in claim 1, characterized in that, The chemical formula of the lithium titanium aluminum phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3.

3. A method for preparing a primary lithium manganese battery cathode material, characterized in that, Includes the following steps: Core preparation involves heat-treating electrolytic manganese dioxide powder at 380℃~420℃ for 5~8 hours in air atmosphere to obtain highly crystalline manganese dioxide. The highly crystalline manganese dioxide is then mixed with lithium nitrate at a lithium-manganese molar ratio of (0.1~0.2):1, and reacted at 350℃~400℃ for 4~6 hours to obtain a pre-lithiated modified manganese dioxide core. The manganese dioxide core is dispersed in lithium titanium aluminum phosphate precursor sol, and after ultrasonic impregnation and drying, it is heat-treated at 680℃~720℃ for 4~6h under argon atmosphere to form a complete fast ion conductor shell, thus obtaining core-shell structured powder. A three-dimensional conductive network was constructed by dispersing the core-shell structure powder, multi-walled carbon nanotubes, and graphene oxide together at a mass ratio of 90:(3~5):(3~5). After high-speed shear emulsification and freeze-drying, the mixture was annealed in a hydrogen-containing inert atmosphere at 400℃~500℃ for 1~2 hours to introduce the three-dimensional conductive network, thus obtaining a primary lithium manganese battery cathode material.

4. The method for preparing the primary lithium manganese battery cathode material as described in claim 3, characterized in that, The shell coating process, which involves dispersing the manganese dioxide core in a lithium aluminum titanium phosphate precursor sol, followed by ultrasonic impregnation and drying, and then heat treatment at 680℃~720℃ for 4~6 hours under an argon atmosphere to form a complete fast ion conductor shell, further includes the following steps to obtain the core-shell structured powder: According to Li 1.3 Al 0.3 Ti 1.7 Weigh out lithium acetate, aluminum isopropoxide, tetrabutyl titanate and triethyl phosphate in the stoichiometric ratio of (PO4)3. Tetrabutyl titanate was mixed with anhydrous ethanol, and a mixture of glacial acetic acid and water was slowly added while stirring under ice-water bath conditions to form a homogeneous titanium precursor. Add aluminum isopropoxide in ethanol, lithium acetate in aqueous solution, and triethyl phosphate in sequence; After adjusting the pH of the mixture to 3-4, the mixture was stirred continuously at 60-80℃ for 4-6 hours to obtain the lithium titanium aluminum phosphate precursor sol. The molar ratio of lithium acetate, aluminum isopropoxide, tetrabutyl titanate and triethyl phosphate is 1.3:0.3:1.7:

3.

5. The method for preparing the primary lithium manganese battery cathode material as described in claim 4, characterized in that, The step of constructing a three-dimensional conductive network, which involves co-dispersing the core-shell structure powder, multi-walled carbon nanotubes, and graphene oxide at a mass ratio of 90:(3~5):(3~5), followed by high-speed shear emulsification and freeze-drying, and then annealing in a hydrogen-containing inert atmosphere at 400℃~500℃ for 1~2 hours to introduce the three-dimensional conductive network and obtain a primary lithium manganese battery cathode material, also includes the following steps: Multi-walled carbon nanotubes and graphene oxide were dispersed together in deionized water at a mass ratio of 1:(1-1.5), and the mass of the deionized water was 200 to 500 times the total mass of the carbon materials. Perform ultrasonic dispersion for 30-60 minutes, then process with a high-speed shear disperser at a speed of 8000-12000 r / min for 15-30 minutes to obtain a uniform conductive network dispersion.

6. The method for preparing the primary lithium manganese battery cathode material as described in claim 5, characterized in that, The step of introducing the three-dimensional conductive network further includes: The core-shell structure powder is slowly added to the conductive network dispersion, and the mixture is continuously stirred at 40℃~60℃ to ensure that the core-shell structure powder is fully wetted and adsorbed by the conductive network dispersion. Spray drying is performed with an inlet temperature of 180℃~220℃ and an outlet temperature of 80℃~100℃ to obtain a preliminary composite powder. The pre-composite powder was heat-treated at 400℃~500℃ for 1~2h in an inert atmosphere containing hydrogen, so that the graphene oxide was partially reduced and synergistically formed with carbon nanotubes to construct a three-dimensional conductive network covering the core-shell structure powder, thus obtaining a primary lithium manganese battery cathode material.

7. The method for preparing the primary lithium manganese battery cathode material as described in claim 6, characterized in that, The feed rate for spray drying is 5~10 ml / min.

8. The method for preparing the primary lithium manganese battery cathode material as described in claim 3, characterized in that, The hydrogen-containing inert atmosphere is a mixture of hydrogen and argon, wherein the volume content of hydrogen is 5-10%.

9. A primary lithium-manganese battery positive electrode sheet, characterized in that, It comprises core-shell structured particles and a three-dimensional conductive network as described in any one of claims 1-2, as well as a conductive agent and a binder.

10. A primary lithium-manganese battery, characterized in that, It comprises the positive electrode sheet, the lithium metal negative electrode, and the non-aqueous organic electrolyte as described in claim 9.

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