Composite positive electrode material, preparation method and lithium-manganese battery

Abstract

The invention discloses a composite positive electrode material, a preparation method and a lithium-manganese battery. The composite positive electrode material comprises manganese dioxide and conductive carbon containing lithium sulfide. Conductive carbon containing lithium sulfide is introduced into the composite positive electrode material, and polarization of manganese dioxide is reduced by taking a charging product lithium polysulfide of lithium sulfide as a redox couple, so that the conductivity of the composite positive electrode material is improved, and the problem of poor high-rate discharge performance of a lithium-manganese primary battery is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of primary batteries, and particularly relates to a composite positive electrode material, a preparation method and a lithium-manganese battery. BACKGROUND

[0002] Lithium-manganese batteries are one of the most promising primary lithium battery technologies at present, and have been widely used in small electronic devices, small unmanned aerial vehicles, portable communication devices and the like. The lithium-manganese battery has the characteristics of high specific energy and long storage life, and in addition, has the advantages of low positive electrode cost and rich resources. Compared with lithium thionyl chloride batteries, lithium sulfur dioxide batteries and other lithium primary batteries, the lithium-manganese battery has higher safety and is more suitable for use in closed spaces and high safety requirement places.

[0003] However, the conductivity of manganese dioxide is relatively low, and even the typical electrolytic manganese dioxide with battery activity has a resistivity of only up to 50-100 Ω·cm. The low conductivity of the positive electrode material significantly increases the discharge polarization of the battery, which is the main obstacle to limiting its large rate discharge, especially the low-temperature large rate discharge performance. The electrolytic manganese dioxide obtained directly in the prior art does not fully meet the performance requirements of the lithium-manganese battery, so a large amount of research work has been carried out to modify it, including adding conductive carbon, or through metal modification (such as coating, modification or doping) to improve the conductivity of the electrolytic manganese dioxide material, thereby optimizing the overall electrochemical performance of the battery. However, excessive use of conductive carbon will reduce the active material content and reduce the specific energy of the battery.

[0004] Therefore, it is urgent to develop a lithium-manganese battery positive electrode material with high conductivity and large rate discharge performance. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the purpose of the present application is to provide a composite positive electrode material, a preparation method and a lithium-manganese battery, which solve the technical problems of poor conductivity and poor large rate discharge performance of the existing lithium-manganese battery positive electrode material.

[0006] To achieve the above-mentioned purpose, the present application realizes the following technical scheme: In a first aspect, the present application provides a composite positive electrode material, comprising manganese dioxide and lithium sulfide-containing conductive carbon.

[0007] Preferably, the mass percentage content of manganese dioxide in the composite positive electrode material is 80%-95%, and the mass percentage content of lithium sulfide in the composite positive electrode material is 1%-5%.

[0008] Preferably, in the lithium sulfide-containing conductive carbon, the average particle size of lithium sulfide is 5-150 nm.

[0009] Preferably, the lithium sulfide contained in the conductive carbon exists in at least one of the following forms: being loaded on the surface of the conductive carbon, being doped in the conductive carbon, and being coated in the conductive carbon.

[0010] Preferably, the conductive carbon is at least one of porous carbon, acetylene black, ketjen black, carbon fiber, carbon nanotube, and graphene.

[0011] Preferably, the manganese dioxide is electrolytic manganese dioxide.

[0012] In a second aspect, the present application provides a preparation method of the composite cathode material, comprising the following steps: providing the conductive carbon containing lithium sulfide; and mixing the manganese dioxide with the conductive carbon containing lithium sulfide and ball milling to obtain the composite cathode material.

[0013] Preferably, the preparation method of the conductive carbon containing lithium sulfide comprises the following steps: providing the conductive carbon; mixing the lithium sulfide solution with the conductive carbon, and drying to obtain the conductive carbon containing lithium sulfide.

[0014] Preferably, the preparation method of the conductive carbon containing lithium sulfide comprises the following steps: providing the conductive carbon precursor; mixing the lithium sulfate solution or the lithium sulfide solution with the conductive carbon precursor to obtain a mixed slurry; performing electrostatic spinning or spray drying on the mixed slurry, and then performing calcination to obtain the conductive carbon containing lithium sulfide; or, removing the solvent in the mixed slurry, and then performing calcination to obtain the conductive carbon containing lithium sulfide.

[0015] In a third aspect, the present application provides a lithium-manganese battery device, comprising a main battery and a starting battery, wherein the main battery comprises the composite cathode material as described in the first aspect.

[0016] The present application has the following beneficial effects: The present application introduces the conductive carbon containing lithium sulfide into the composite cathode material, and relies on the charging product of the lithium sulfide, i.e., lithium polysulfide, as the redox pair to reduce the polarization of the manganese dioxide, thereby improving the conductivity of the composite cathode material and solving the problem of poor high-rate discharge performance of the lithium-manganese primary battery. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced as follows.

[0018] Figure 1 is a schematic diagram of the principle of the present application.

[0019] Figure 2 is the discharge curve of the lithium-manganese primary battery after activation of Example 1 and Comparative Example 1 at room temperature.

[0020] Figure 3 is the discharge curve of the lithium-manganese primary battery after activation of Example 1 and Comparative Example 1 at -20℃. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0022] In a first aspect, the embodiments of the present application provide a composite positive electrode material, comprising manganese dioxide and lithium sulfide-containing conductive carbon. The mass percentage of the manganese dioxide in the composite positive electrode material is 80% to 95%, and the mass percentage of the lithium sulfide in the composite positive electrode material is 1% to 5%.

[0023] In some preferred embodiments, the average particle size of the lithium sulfide in the lithium sulfide-containing conductive carbon is 5 to 150 nm; the lithium sulfide in the lithium sulfide-containing conductive carbon exists in at least one of the following forms: being loaded on the surface of the conductive carbon, being doped in the conductive carbon, and being coated in the conductive carbon; the conductive carbon is at least one of porous carbon, acetylene black, ketjen black, carbon fiber, carbon nanotube, and graphene; and the manganese dioxide is electrolytic manganese dioxide.

[0024] In a second aspect, the embodiments of the present application provide a preparation method of a composite positive electrode material, comprising the following steps: (1) Preparing lithium sulfide-containing conductive carbon: providing conductive carbon; mixing a lithium sulfide solution with the conductive carbon, and obtaining the lithium sulfide-containing conductive carbon after drying. Alternatively, providing a conductive carbon precursor; mixing a lithium sulfate solution with the conductive carbon precursor to obtain a mixed slurry; performing electrostatic spinning or spray drying on the mixed slurry, and then performing calcination to obtain the lithium sulfide-containing conductive carbon. Alternatively, providing a conductive carbon precursor; mixing a lithium sulfide solution with the conductive carbon precursor to obtain a mixed slurry; removing the solvent in the mixed slurry, and then performing calcination to obtain the lithium sulfide-containing conductive carbon.

[0025] (2) Preparing a composite positive electrode material: mixing manganese dioxide with the lithium sulfide-containing conductive carbon, and performing ball milling to obtain the composite positive electrode material.

[0026] The present application solves the problem of poor conductivity of the positive electrode of lithium-manganese primary battery and poor high-rate discharge performance, without introducing too much carbon conductive agent or metal conductive agent, and the principle is as follows: by introducing lithium sulfide-containing conductive carbon into the composite positive electrode material, the charging product of lithium sulfide, polysulfide, is used as a redox couple to reduce the polarization of manganese dioxide. The ordinary primary battery does not need to be charged, and the lithium-manganese primary battery prepared by using the composite positive electrode material provided by the present application is first activated and charged for a short time by using a starting battery during discharge, and the lithium sulfide will be converted into polysulfide during the activation and charging process. Then the main battery is connected to the load for discharge, and in this process, the polysulfide transports electrons between the positive electrode conductive network and the un-discharged manganese dioxide, as shown in Figure 1 , thereby reducing the polarization of manganese dioxide and improving the high-rate performance of the battery. After the manganese dioxide is completely discharged, the polysulfide can continue to discharge to regenerate lithium sulfide, and the charge from the starting battery to the main battery is also discharged, so that the activation and charging of the starting battery to the main battery does not lose the total output energy of the system.

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be further described in detail below. Unless otherwise specified, all reagents and raw materials used in the present application are commercially available or can be prepared by known methods.

[0028] Example 1 A composite positive electrode material is prepared by the following method: 12 g of polyvinylpyrrolidone (PVP) is dissolved in 88 g of N,N-dimethylformamide (DMF), and 0.3 g of lithium sulfate is dissolved in 10 mL of water. The two solutions are mixed to obtain a spinning precursor solution. The spinning precursor solution is added to the syringe of the electrospinning device, and the power voltage is set to 15 kV, the injection speed is 1 mL / h, and the distance between the nozzle and the collection screen is 15 cm. After electrospinning, PVP fibers containing lithium sulfate are obtained. The PVP fibers containing lithium sulfate are heated to 700 °C under argon to obtain carbon fibers containing lithium sulfate. The lithium sulfate is then carbothermally reduced by further heating to 800 °C to obtain carbon fibers containing lithium sulfide. The size of the lithium sulfide particles is about 80 nm, and the content of lithium sulfide is 5% as measured by plasma emission spectroscopy. The carbon fibers containing lithium sulfide are mixed with electrolytic manganese dioxide (fineness of 200 mesh) and ball milled, and the content of manganese dioxide is 80% and the content of carbon fibers containing lithium sulfide is 20%, so that the content of lithium sulfide in the final composite positive electrode material is 1%.

[0029] Example 2 A composite positive electrode material is prepared by the following method: A solution of lithium sulfide in ethanol was dropped on the graphene aerogel sheet, and after drying, a graphene aerogel loaded with lithium sulfide was obtained, in which the content of lithium sulfide was 10%. The graphene aerogel loaded with lithium sulfide was mixed with manganese dioxide and ball-milled, the content of manganese dioxide was 80%, the content of graphene aerogel was 20%, and thus the content of lithium sulfide in the final composite positive electrode material was 2%.

[0030] Example 3 A composite positive electrode material was prepared by the following method: A solution of lithium sulfide in ethanol was dropped on the graphene aerogel sheet, and after drying, a graphene aerogel loaded with lithium sulfide was obtained, in which the content of lithium sulfide was 10%. The graphene aerogel loaded with lithium sulfide was mixed with manganese dioxide and ball-milled, the content of manganese dioxide was 80%, the content of graphene aerogel was 20%, and thus the content of lithium sulfide in the final composite positive electrode material was 2%.

[0031] Example 4 A composite positive electrode material was prepared by the following method: Polystyrene microspheres and carbon nanotubes were dispersed in an aqueous solution of lithium sulfate, and the dispersion was spray-dried to obtain lithium sulfate coated with carbon nanotubes. The lithium sulfate coated with carbon nanotubes was subjected to carbothermal reduction at 800°C to obtain carbon nanotubes loaded with lithium sulfide particles, in which the content of lithium sulfide was 45%. 10% of the carbon nanotubes loaded with lithium sulfide particles were mixed with 85% of manganese dioxide and 5% of LA-133 binder and ball-milled to obtain a composite positive electrode material, and the content of lithium sulfide in the final composite positive electrode material was 4.5%.

[0032] Example 5 A composite positive electrode material was prepared by the following method: Polystyrene microspheres and carbon nanotubes were dispersed in an aqueous solution of lithium sulfate, and the dispersion was spray-dried to obtain lithium sulfate coated with carbon nanotubes. The lithium sulfate coated with carbon nanotubes was subjected to carbothermal reduction at 800°C to obtain carbon nanotubes loaded with lithium sulfide particles, in which the content of lithium sulfide was 45%. 10% of the carbon nanotubes loaded with lithium sulfide particles were mixed with 85% of manganese dioxide and 5% of LA-133 binder and ball-milled to obtain a composite positive electrode material, and the content of lithium sulfide in the final composite positive electrode material was 4.5%.

[0033] Example 6 A composite positive electrode material was prepared by the following method: Polystyrene microspheres and Ketjen Black were dispersed in an aqueous solution of lithium sulfate. The dispersion was spray-dried to obtain lithium sulfate-loaded Ketjen Black. The lithium sulfate-loaded Ketjen Black was then carbothermally reduced at 800°C to obtain Ketjen Black loaded with lithium sulfide particles, containing 30% lithium sulfide. 10% of the lithium sulfide-loaded Ketjen Black was mixed with 85% electrolytic manganese dioxide and 5% PVDF binder and ball-milled to obtain a composite cathode material. The final composite cathode material had a lithium sulfide content of 3%.

[0034] Comparative Example 1 A composite positive electrode material, the preparation method of which is basically the same as that of Example 1, except that: the spinning precursor solution does not contain lithium sulfate, and the final composite positive electrode components are manganese dioxide and carbon fiber that does not contain lithium sulfide.

[0035] Performance Testing The positive electrode materials prepared in the examples and comparative examples were assembled with negative electrode materials and electrolytes to form the main cells of lithium-manganese primary batteries. The negative electrode material was metallic lithium, the electrolyte was a 1M LiClO4 solution in propylene carbonate (PC), the N / P ratio was 1.05:1, and the nominal capacity was 1.6Ah. Two conventional commercial lithium-manganese primary batteries were then connected in series as starter batteries. Before discharge, the starter battery and the main battery were connected in parallel for reverse discharge. The main battery was activated, and the performance of the lithium-manganese primary batteries before and after activation was tested. The test results are as follows: (1) Before activation, the 1 kHz AC impedance of the main batteries of Example 1 and Comparative Example 1 was 200 mΩ. After activation, the AC impedance of the battery of Comparative Example 1 was 200 mΩ, and the AC impedance of the battery of Example 1 was reduced to 145 mΩ, indicating that the composite positive electrode material provided by the present invention has good conductivity.

[0036] (2) The activated lithium manganese primary battery was discharged at 1A current density at room temperature. The discharge results are as follows: Figure 2 As shown, from Figure 2 It can be seen that Example 1 has a higher discharge voltage platform and discharge capacity under high current discharge. The discharge platform of Example 1 is 2.75V and the discharge capacity is 1.34Ah. The discharge platform of Comparative Example 1 is 2.4V and the discharge capacity is 1.28Ah, indicating that the lithium manganese primary battery prepared using the composite positive electrode material provided by the present invention has good high-rate discharge performance.

[0037] (3) The activated lithium manganese primary battery is discharged at a current density of 1A at -20℃. The discharge results are as follows: Figure 3 As shown, from Figure 3It can be seen that the example 1 has higher discharge capacity under low temperature discharge. The capacity of the example 1 is 0.54 Ah, and the capacity of the comparative example 1 is 0.14 Ah, which indicates that the lithium manganese primary battery prepared by using the composite cathode material provided by the application has higher rate performance at low temperature.

[0038] It should be noted that each of the above embodiments belongs to the same inventive concept, and the description of each embodiment has its own emphasis. If the description in an individual embodiment is not exhaustive, the description in other embodiments can be referred to.

[0039] The above-described embodiments only express the implementation of the present application, and the description is more specific and detailed, but it should not be construed as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the inventive concept, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A composite positive electrode material, characterized in that Includes manganese dioxide, and conductive carbon containing lithium sulfide.

2. The composite cathode material according to claim 1, characterized in that The mass percentage of the manganese dioxide in the composite positive electrode material is 80% to 95%, and the mass percentage of the lithium sulfide in the composite positive electrode material is 1% to 5%.

3. The composite cathode material according to claim 1, characterized in that In the conductive carbon containing lithium sulfide, the average particle size of the lithium sulfide is 5 to 150 nm.

4. The composite cathode material according to claim 1, characterized in that In the conductive carbon containing lithium sulfide, the lithium sulfide exists in at least one of the following forms: supported on the surface of the conductive carbon, doped in the conductive carbon, and coated in the conductive carbon.

5. The composite cathode material according to claim 1, characterized in that The conductive carbon is at least one of porous carbon, acetylene black, Ketjen black, carbon fiber, carbon nanotube, and graphene.

6. The composite cathode material according to claim 1, characterized in that The manganese dioxide is electrolytic manganese dioxide.

7. The method for preparing a composite cathode material according to any one of claims 1 to 6, wherein: The following steps are involved: Providing conductive carbon containing lithium sulfide; Manganese dioxide and the conductive carbon containing lithium sulfide are mixed and ball-milled to obtain the composite positive electrode material.

8. The method for preparing a composite positive electrode material according to claim 7, wherein: The method for preparing the conductive carbon containing lithium sulfide comprises the following steps: Provides conductive carbon; The lithium sulfide solution is mixed with the conductive carbon, and the mixture is dried to obtain the conductive carbon containing lithium sulfide.

9. The method for preparing a composite cathode material according to claim 7, wherein: The method for preparing the conductive carbon containing lithium sulfide comprises the following steps: providing a conductive carbon precursor; mixing a lithium sulfate solution or a lithium sulfide solution with the conductive carbon precursor to obtain a mixed slurry; The mixed slurry is subjected to electrostatic spinning or spray drying and then calcined to obtain the conductive carbon containing lithium sulfide; or The solvent in the mixed slurry is removed, and then a calcination treatment is performed to obtain the conductive carbon containing lithium sulfide.

10. A lithium manganese battery device, characterized in that: The invention comprises a main battery and a starting battery, wherein the main battery comprises the composite positive electrode material according to any one of claims 1 to 6.

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