Composite positive electrode of lithium sulfur battery, preparation method of composite positive electrode and lithium sulfur battery

Abstract

A composite positive electrode of a lithium sulfur battery is formed by combining a diaphragm layer, a porous carbon layer and a carbon sulfur compound, wherein the porous carbon layer is arranged on one side of the diaphragm layer, and the carbon sulfur compound is arranged on the porous carbon layer. The preparation method comprises the following steps of adding the porous carbon, a conductive agent and an adhesive into an organic solvent to prepare paste, applying the paste onto one side of a diaphragm, and forming a porous carbon layer compound on one surface of the diaphragm layer; and adding the carbon sulfur compound, the conductive agent and the adhesive into the organic solvent to prepare paste, and applying the paste onto the porous carbon layer in the compound to obtain the composite positive electrode of the lithium sulfur battery. The lithium sulfur battery disclosed by the invention comprises the composite positive electrode of the lithium sulfur battery, a negative electrode and an electrolyte. By the lithium sulfur battery, the interface resistance can be reduced, the ionic conductivity and electron conductivity are improved, and the energy density, the cycle performance and the rate performance of the lithium sulfur battery are effectively improved.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to a lithium-sulfur battery composite positive electrode, a preparation method thereof, and a lithium-sulfur battery. Background technique [0002] With the rapid development of electric vehicles and portable electronic products, there is an urgent need to develop lithium-ion batteries with higher energy density. However, limited by the specific capacity of traditional cathode materials such as lithium cobaltate and lithium manganate, it is difficult to increase the specific energy, so it is imperative to develop new cathode materials. Lithium-sulfur (Li-S) battery is a new type of electrochemical energy storage system with lithium as the negative electrode (theoretical specific capacity 3860mAh / g) and sulfur as the positive electrode (theoretical specific capacity 1675mAh / g). The theoretical specific energy can reach 2600Wh / kg, which is much larger than the current ...

AI Technical Summary

Problems solved by technology

But sulfur still has some problems in practical application. First, its electrical conductivity is very low, about 5×10 at room temperature -30 S / cm, when used as an electrode material, a conductive agent must be added, which will reduce the energy density of the positive electrode material; secondly, lithium polysulfide, an intermediate product of the electrochemical reaction, is easily soluble in the electrolyte and produces a "shuttle effect", which reduces the utilization of sulfur rate and cycle performance, increasing the ion migration resistance, while the discharge product Li 2 S 2 and Li 2 S will deposit on the surface of the sulfur electrode to form a solid electrolyte phase interface film (SEI), resulting in a decrease in sulfur utilization and cycle performance; thirdly, the repeated and drastic volume changes of the sulfur cathode during charge and discharge will cause the battery structure to be unstable, resulting in Cycle Life and Specific Capacity Fading

[0003] In recent years, the academic and commercial circles have mainly improved the conductivity and utilization of sulfur and inhibited the diffusion of polysulfides by studying related positive electrode materials and electrolytes. The overall energy density of the

Chinese patent CN103490027A proposes to use a porous barrier layer loaded on a common diaphragm as an adsorption layer for polysulfides to further inhibit the diffusion of polysulfides, but this method increases the mass and volume of the diaphragm in lithium-sulfur batteries, and it is actually possible Reduce the volumetric energy density of lithium-sulfur batteries, and the bonding interface between the porous barrier layer and the positive electrode is not tight, which easily increases the interface resistance and reduces the ionic conductance and electronic conductance

However, on the one hand, the use cost of graphene is still relatively high, which is not conducive to large-scale popularization and application; The graphene current collector and the graphene current collector are still two separate parts, and a certain interface resistance will be generated after being assembled into a battery

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