Positive electrode material for lithium-sulfur secondary battery and preparation method of positive electrode material

Abstract

The invention relates to a positive electrode material for a lithium-sulfur secondary battery and a preparation method of the positive electrode material. Particularly, an activated carbon material with ultra-high specific surface area and large pore volume is prepared by adopting biomass waste mangosteen peel as a raw material through pre-carbonization and potassium hydroxide activation methods;and a carbon / sulfur composite material is further prepared by adopting the activated carbon material as a carrier through a melting diffusion method. A test result shows that the initial discharge specific capacity of a positive electrode prepared from the carbon / sulfur composite material with the sulfur bearing capacity of 65% under the current of 0.5C is 870.5mAhg<->, the discharge specific capacity of the positive electrode after 100 cycles is 599.6mAhg<-1> and the discharge capacity after 100 cycles under the current of 2C is 569.2mAhg<->. The carbon / sulfur composite positive electrode material prepared by adopting the biomass waste mangosteen peel as the raw material is high in sulfur bearing capacity, good in chemical stability, high in specific capacity, good in rate capability, simple in preparation method and suitable for the lithium-sulfur secondary battery.

Description

Technical field [0001] The invention relates to the technical field of battery materials, in particular to a positive electrode material for lithium-sulfur secondary batteries and a preparation method thereof. Background technique [0002] With the rapid development of new energy vehicles and portable electronic equipment, the demand for rechargeable secondary batteries with high energy density has increased sharply, and the effective use of renewable and clean energy such as wind, solar, and hydropower is also in urgent need of development. Performance energy storage battery. Among the two most widely used traditional secondary batteries, the development of lithium-ion batteries has approached its theoretical energy density (about 500Wh kg -1 ), and its positive electrode material often contains a large amount of precious metal cobalt, which makes the cost of the battery high. Although the price of lead-acid battery is cheap, its energy density is too low and often cannot be ful...

AI Technical Summary

Problems solved by technology

[0003] However, lithium-sulfur batteries also have some shortcomings that restrict their commercialization process. Among them, the three main shortcomings derived from the positive active material sulfur are: (1) The electronic conductivity of sulfur is extremely low, which is only about 5×10 at room temperature. -30 S cm -1 ), which seriously affects the electrochemical activity of sulfur; (2) sulfur and its discharge product lithium sulfide (Li 2 S) have very different densities (2.07 and 1.66 g cm -3 ), resulting in the destruction of the structure of the positive electrode and the shedding of the active material due to repeated volume changes during the charge and discharge process, thereby affecting the cycle performance of the battery; (3) the electrochemical reaction of sulfur and lithium will generate a series of lithium polysulfides ( Li 2 S x , 1≤x≤8) intermediate products, these intermediate products will be dissolved in the electrolyte, resulting in a "shuttle effect", which is equivalent to the self-discharge of the battery, which will seriously reduce the utilization rate of the positive active material and the Coulomb of the battery cycle efficiency

Images