Preparation method of manganese dioxide cathode material

Abstract

The invention discloses a preparation method of a manganese dioxide cathode material, belongs to the technical field of electrochemical materials, and relates to a preparation method of a battery cathode material. Manganese dioxide is prepared by reaction of organic acid bivalent manganese salt and permanganate; the chemical reaction speed is reduced by reducing the reaction temperature or adjusting the pH value of the system to be an alkaline condition to synthesize manganese dioxide; and then low-temperature hydrothermal treatment is carried out under an acidic condition, and then high-temperature thermal treatment is carried out at 380-700 DEG C, so that the obtained manganese dioxide positive electrode material has the characteristics of high capacity and high compaction density at thesame time under a high-current discharge condition. In the synthesis reaction process, the content of alkali metal ions can be regulated to ensure that the final product is high-purity alpha-MnO2. The manganese dioxide positive electrode material prepared by the method takes high capacity and high compaction density into consideration under the condition of high-current discharge, has low requirements on production equipment, and is lower in production cost.

Description

technical field [0001] The invention belongs to the technical field of electrochemical materials, and relates to a method for preparing a battery positive electrode material, in particular to a method for preparing a manganese dioxide positive electrode material with both high capacity and high compaction density under large current discharge conditions. Background technique [0002] Since petrochemical energy is a non-renewable resource and has serious pollution, most countries are vigorously developing new energy batteries to replace petrochemical energy. Lithium-ion batteries have made great progress in electric vehicles and energy storage. However, commercial lithium-ion batteries use organic electrolytes, and the assembly and production conditions are harsh. Coupled with the scarcity of lithium resources, the cost of lithium-ion batteries is high, and organic electrolytes are easy to use. The flammable characteristics of lithium-ion batteries lead to greater safety haza...

AI Technical Summary

Problems solved by technology

[0003] Manganese dioxide has various crystal forms such as α, δ, β, γ, etc., among which α-MnO 2 It has high capacity and has the best cycle performance when used as the positive electrode of secondary zinc-manganese batteries, but the high-current discharge performance of the manganese dioxide positive electrode is poor, resulting in low capacity utilization, which severely limits the development of secondary zinc-manganese batteries.

In the currently known technology, rod-shaped α-MnO with a diameter of about 40 nanometers synthesized by hydrothermal method 2 , used as the positive electrode of zinc-manganese secondary batteries, manganese dioxide can achieve a high capacity of more than 300mAh / g under the condition of 1C constant current discharge, but the positive electrode material made of nanorod-shaped manganese dioxide has a very low compaction density and low compaction There must be a lot of pores in the dense manganese dioxide, too many pores will absorb a lot of extra electrolyte, too much electrolyte in the battery will increase the extra weight of the battery, and the extra weight will lead to a decrease in the overall capacity of the battery

Both sol-gel method and solid-state reaction method can synthesize spherical α-MnO with particle size less than 60 nm 2 , the small-particle nano-spherical manganese dioxide synthesized by high-temperature heat treatment has better high-current discharge performance, and the compaction density of the spherical manganese dioxide material is lower than that of the nanorod-shaped α-MnO synthesized by the hydrothermal method. 2 The compaction density is much higher, but there is no report of high-capacity manganese dioxide materials with a capacity of more than 300mAh / g under 1C rate constant current discharge conditions after high-temperature heat treatment above 380°C

According to a large number of literature reports, when the heat treatment temperature of manganese dioxide exceeds 120°C, it begins to lose the adsorbed water in the structure, and when it exceeds 300°C, it begins to deoxidize and transform into low-priced manganese trioxide. There is a part of manganese trioxide, and the presence of low-valent manganese will lead to a decrease in the capacity of the manganese dioxide cathode after high-temperature heat treatment

At present, some manganese dioxide is synthesized by high-temperature hydrothermal method, and then high-temperature heat treatment is performed to synthesize granular α-MnO. 2 However, the manganese dioxide synthesized through high-temperature heat treatment still has not solved the problem of low capacity under high-current discharge conditions. Larger particles lead to insufficient capacity release under high current discharge conditions

[0004] At present, manganese dioxide is synthesized by hydrothermal method, sol-gel method, solid-state reaction method and high temperature hydrothermal method above 100 ℃, followed by high-temperature heat treatment, and the manganese dioxide cathode material with a diameter or particle size of less than 60 nanometers has good high-current discharge performance. , but the manganese dioxide synthesized by the above method is either due to the low compaction density of the manganese dioxide positive electrode due to the nanorod shape, which eventually leads to a low overall battery capacity, or because of the presence of low Manganese dioxide or manganese dioxide particles are relatively large, so that the large-capacity characteristics of manganese dioxide cathode materials cannot be fully utilized, and hydrothermal synthesis above 100°C needs to be carried out in a high-pressure vessel, requiring high preparation conditions and high costs

In short, the manganese dioxide prepared by the above methods failed to achieve both high capacity and high compaction density under high current discharge conditions.

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