(A) study on the electrochemical performance of organic cathodes for rechargeable Li-ion batteries

Abstract

Lithium-ion batteries (LIBs) are representative energy storage technologies and are applied to various application fields, and there is a growing demand to develop new materials to improve performance and reduce costs. As an alternative, an organic-based active material with high price competitiveness and energy density is attracting attention as a material for the next generation LIBs with lightweight. However, an organic electrode material excluding a conductive polymer has low electrical conductivity and low electrochemical characteristics for using a secondary battery due to factors such as dissolution in an electrolyte. In addition, there is a problem of easily deteriorating during the reforming process due to the vulnerability to humidity and heat of the organic material. In this study, 5-10 dihydro 5-10 diemethylphenzene (DMPZ) was used as an organic cathode material for high-performance secondary batteries by surface modification and electrode structural engineering. The specific capacity and rate performance of the DMPZ cathode were enhanced by increased specific surface area through surface modification. In order to overcome the low cyclic performance of the organic active material, a study on separator modification and electrode structural modification is conducted to suppress the elution and diffusion of the organic electrode materials, causing the shuttle effect. The surface modification on separators improved the selective permeability of Li ions and suppressed the diffusion of eluted active materials to improve cyclic performance. Moreover, a charge-transfer model of organic pairs was developed for suppressing the elution of organic materials through the hybridization of two types of organic active materials. The effect and mechanism of the charge-transfer reaction between various organic-organic pairs and organic-metal hybrid pairs were confirmed by various electrochemical and ex-situ analyses. As a result, high specific capacity and excellent cyclic performance of organic-based cathode were ensured for 600 cycles.