Manufacturing method for long-life lithium sulfur battery positive electrode

Abstract

The invention discloses a new method for on-site synthesis of a lithium ion conductive protection film for preventing poly-sulfide-ions diffusion on a surface of a lithium sulfur battery positive electrode, and an application therefor. The method is carried out by the steps of reducing the initial discharge voltage lower limit of a lithium sulfur battery taking a carbon sulfur composite as the positive electrode material to be lower than the normal working voltage 1.5V to generate the lithium ion conductive protection film; the film is quite high in the lithium ion conductivity and capable of preventing the poly-sulfide-ions from being dissolved in an electrolyte to enable the lithium sulfur battery to realize and maintain higher cycle performance, rate capability, coulombic efficiency and lower self discharge performance, so that the service life of the lithium sulfur battery is prolonged, and the use cost of the lithium sulfur battery is reduced; meanwhile, porous carbon with hierarchical pores used as the supporting material can accommodate the poly-sulfide-ions and lithium sulfide generated in charging and discharging processes of sulphur and the lithium sulfur battery; and the sulphur content in the carbon-sulfur composite material made from the porous carbon with the hierarchical pores is high, so that the comprehensive specific capacity of the carbon-sulfur composite product can be improved so as to further increase the overall energy density of the battery.

Description

technical field [0001] The invention relates to the field of lithium battery positive electrode materials, in particular to a preparation method of lithium sulfur battery positive electrode materials. Background technique [0002] With the extensive use of fossil fuels, environmental pollution and energy crisis are becoming more and more serious, which have become the main obstacles to the sustainable development of the economy. Therefore, it is imperative to develop renewable clean energy. Renewable clean energy includes new energy sources such as solar energy, wind energy, and lithium-ion batteries. Among them, lithium-ion batteries are a device that can directly convert chemical energy into electrical energy and can be recycled. It can be used in combination with other secondary energy sources. A good energy storage system. [0003] Lithium-ion batteries have rapidly become the main power source of portable electronic products such as mobile phones, digital cameras, and ...

AI Technical Summary

Problems solved by technology

For example, Chinese patent CN101986443A discloses a lithium-sulfur battery positive electrode material and its preparation method. In this method, nano-sulfur particles are heated and melted and then filled in hollow carbon nanotubes of nano-mesoporous carbon materials, and the nano-mesoporous carbon materials are Using sucrose as the carbon source, concentrated sulfuric acid as the carbonizing agent, and silica as the template agent, after the sucrose is carbonized, use sodium hydroxide solution or hydrofluoric acid to remove the template silica. The reagents used in this method are concentrated sulfuric acid, sodium hydroxide or Hydrofluoric acid is very corrosive, especially concentrated sulfuric acid and hydrofluoric acid are dangerous chemicals, improper use can easily cause personal injury and environmental pollution, and the industrial applicability is poor. In addition, the nanometer mesoporous carbon material prepared by it The pore size is single, and the ions of different particle sizes formed by sulfur during the charging and discharging process cannot be adaptively attached and accommodated, so that the problem of the shuttle effect formed by the dissolution of polysulfide ions in the electrolyte cannot be solved.

[0007] Another example is the Chinese patent CN103219501A, which discloses a lithium-sulfur battery cathode material that limits the dissolution of polysulfides. It is composed of porous carbon and sulfur, wherein the porous carbon is composed of an inner core of a mesoporous carbon structure and an outer shell of a microporous structure. Although the porous carbon has different pore structures, it has weak chemical adsorption to sulfur and polysulfide ions generated during charging and discharging. Therefore, polysulfide ions can still form lithium sulfide on the negative electrode side after being dissolved in the electrolyte. deposition, resulting in poor cycle performance of the lithium-sulfur battery prepared from the positive electrode material, its initial discharge capacity is only 460-830mAh/g, after 50 cycles, the discharge capacity dropped sharply to 402-682mAh/g, the capacity retention rate Only 79-87%, can not meet the needs of practical applications

[0008] Another example is that Chinese patent CN102891292A discloses a preparation method of a lithium-sulfur battery cathode

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