Carbonyl‐Based π‐Conjugated Materials: From Synthesis to Applications in Lithium‐Ion Batteries

Abstract

The constant growth in the global energy demand together with the increasing awareness of clean and sustainable development has strongly pushed scientists to search for metal‐free, low‐cost, environmentally friendly functional energy‐storage systems (ESSs). Among the reported organic electrode materials, carbonyl‐based π‐conjugated compounds show excellent rate capabilities and cycling stabilities and are powerful candidates for the next generation of rechargeable lithium‐ion batteries (LIBs). Benefiting from the molecular structure versatility and design feasibility, the electrochemical properties of organic and polymeric materials can be easily tuned. This Review summarizes recent efforts in the search for carbonyl‐based π‐conjugated electrode materials in LIBs with a focus on the synthetic strategies developed to improve their electrochemical performance. The use of these materials in flexible, all‐organic LIBs is highlighted as a unique direction towards widespread applications of LIBs.

Tailored Redox Kinetics, Electronic Structures and Electrode/Electrolyte Interfaces for Fast and High Energy‐Density Potassium‐Organic Battery

“…The LUMO, HOMO and E g of the prepared PTCDA‐based cathode materials analyzed with density functional tight theory (DFTB) method can therefore be utilized for a quantitative comparison . Thus far, many studies have focused on the smart design of electroactive monomers with controlled electronic structures (namely preparation of different monomers), while we demonstrate here the improved electronic conductivity of prepared polymeric cathodes and electronic structure of PTCDA segments via simply engineering the length of interconnected alkyl chains.…”

“…Unlike the uniform LUMO distribution on the whole segment of PTCDA (Figure b), the LUMO orbitals are mainly concentrated on the four carbonyl groups for PTCDA‐0C (Figure c). This phenomenon could be attributed to the symmetrical introduction of strong electron‐donating group of ‐NH‐ segments on both sides . Upon further introduction of an weak electron‐donating group of ‐(CH 2 ) k ‐ segment (Figure d; Figure S8, Supporting Information), the LUMO orbitals of PTCDA‐2C, PTCDA‐3C, and PTCDA‐4C samples are further concentrated on the carbonyl groups near the ‐(CH 2 ) k ‐ segment.…”

“…For PTCDA and PTCDA‐0C, the main mass loss is concentrated over a narrow temperature range, confirming their crystalline character (Figure S2a, Supporting Information). Furthermore, all the polymers demonstrate a broad endothermic band from 80 to 450 °C (T 1 region) (Figure S2b, Supporting Information), indicating that all the polymers show better structural flexibility compared to pristine PTCDA …”

“…Enormous achievements have been obtained in LIBs and sodium‐ion batteries (SIBs) by using organic cathode materials. However, researches on organic electrodes for PIBs are sluggish, due to their inferior electrical conductivity, high solubility in electrolyte and more importantly low capacity at high rates and poor cycling stability …”

“…3) Understanding of the influences of macromolecular structure modifications on the redox kinetics. Previous works are mainly focused on designing new monomer molecules for enhancing performance of the polymer cathode . Much less attention has been put on the studies of their redox kinetics which have major influences on the rate performance and stability …”