Preparation Of Phenazine-based Derivatives And Their Application In Organic Batteries

Electrical energy generated from renewable resources such as solar and wind energy puts forward the demand of developing electrical energy storage devices integrated into a smart electrical grid.Among the existing electrical energy storage devices,batteries,particularly the lithium/sodium ion batteries,appear to be one of the most effective energy storage technology for the integration of renewable energy resources.Although lithium ion batteries have been considered for electrical grid storage,the limited availability and unevenly distribution of lithium resources might hinder their practical applieation.Sodium is much cheaper than lithium,but the host materials commonly explored for lithium ion batteries are close-packed oxide-ion arrays connected by first-row transition metals,in which the sodium ion transport properties are restricted by limited interstitial space in the rigid matrix of host material.Redox-active organic compounds offer the opportunity for the design of alternative electrode materials,because of their structural diversity,molecular level controllability,and resource sustainability.Organic compounds also offer the possibility to build battery system with various types of cations/anions,there by broadening the freedom in the selection of charge carriers in the electrolyte.This work based on phenazine derivative carboxylates as the artificial bipolar organic electrode materials were designed and synthesized,which open a new direction for the development of organic symmetric batteries.1.4,4'-(phenazine-5,10-diyl)dibenzoate anion(denoted as PZDB)can be served as a bipolar active material for organic symmetric cell.PZDB can be simply regarded as a cathode-active phenazine moiety covalently sandwiched between two conjugated anode-active benzoate moieties.The PZDB-Li2 as an artificial bipolar molecule for organic symmetric batteries,this molecule exhibits an average discharge voltage of 2.7 V and an energy density of 127 Wh/kg at a current rate of 1 C with manifested stable capacity retention and cycling efficiency.The discharge capacity based on the total weight of the cathode and anode was stabilized at ca.53 mAh/g with corresponding Coulombic efficiency of ca.97%in the measured 200 cycles.When PZDB-Na2 were applied in the organic symmetric sodium ion batteries,the corresponding Coulombic efficiency was stabilized at ca.90%,the energy and power density at the current rate of 1C were up to 119.1 Wh/kg and 344.7 W/kg,respectively.This study highlights the prospect of using organic material as a competitive candidate to improve the voltage and energy density restrictions in sylmetric batteries.2.In order to further improve the specific capacity of the electrode materials,PPDB-Li2 and PPDB-Na2 were synthesized.When PPDB-Li2 was served as the cathode material of lithium ion battery,there were two voltage platforms with average potential of ca.3.16 V and 3.95 V vs.Li/Li+,the discharge specific capacity at the current rate of 0.5 C was stable at 108 mAh/g,and the Coulombic efficiency was 98%?99%,the energy density was 387.7 Wh/kg,and the power density was 274.9 W/kg.When PPDB-Na2 was served as the cathode material of sodium ion battery,there were two voltage platforms with average potential of ca.2.78 V and 3.55 V vs.Na/Na+,the discharge specific capacity at the current rate of 4C was stable at 99.5 mAh/g,and the Coulombic efficiency was 98%?99%,the energy density was 304.5 Wh/kg,and the power density was 471.0 W/kg.This demonstrates that higher capacity and batter cycle stability.