A kind of manufacturing method of long-life lithium-sulfur battery positive electrode

Abstract

A new method of synthesizing on the anode surface of a lithium-sulfur battery the lithium ion conductive protective film used for preventing diffusion of polysulfide ions and application of the method, to decrease the first discharge voltage lower limit of the lithium-sulfur battery using a carbon-sulfur compound as the anode material below the normal working voltage 1.5 V to produce the lithium ion conductive protective film; in addition, porous carbon with multi-level pores used as a support material can accommodate polysulfide ions and lithium sulfide produced in the charging / discharging process of sulfur and lithium-sulfur batteries.

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 composite material, which uses glucose as a carbon source, concentrated nitric acid as a carbonization agent, and silicon dioxide as a template agent. It is obtained by mixing iron powder, nano-lithium salt and nano-vanadium salt, drying and sintering and doping with rare earth materials. It not only uses strong corrosive and environmentally polluting reagents concentrated nitric acid and hydrofluoric acid in the process of preparing carbon nanofiber tubes, but also requires Carbon nanofiber tubes are doped with rare earth materials. These materials are expensive and not easy to obtain. Not only the operation is complicated but also the production cost is increased, which is not industrially practical. At the same time, the sulfur in the positive electrode material is coated on the surface of the nanofiber tubes without Embedded in carbon nanofiber tubes, therefore, it cannot intercept the dissolution and shuttling of various forms of polysulfide ions produced by sulfur in the electrolyte during charge and discharge

[0009] In addition, at present, lithium-sulfur batteries generally have problems such as low coulombic efficiency, small specific capacity, and a significant drop in specific capacity at the initial stage of use. In the prior art, there is a method of segmenting lithium-ion batteries to improve the lithium ion The service capacity and cycle performance of batteries, such as Chinese patent CN102185166B, discloses a battery formation and repair method, which adopts segmented formation for lithium-ion batteries, and first performs 1 to 3 cycles of charging and discharging in the low-current and low-voltage section, and then Carry out 1 to 5 rapid charge-discharge cycles in the high-current and medium-voltage section of the lithium-ion battery, so that the internal temperature of the battery reaches 30-45°C; The battery is subjected to high-current deep charge and discharge cycles for 1 to 3 times. This method is cumbersome and takes a lot of time, and the operating conditions are not easy to control and inconvenient to use. Moreover, the charging and discharging mechanism of lithium-sulfur batteries is different from that of ordinary lithium batteries. The method for improving the performance of lithium-ion batteries cannot be applied to the improvement of the performance of lithium-sulfur batteries

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