Speaker
Description
The utilisation of organic electrode materials (OEMs) as versatile redox-active hosts for lithium- and sodium-ion batteries is a recent development. The popularity of these materials is driven by their tunability, sustainability, and capacity to store both cations and anions within one framework. The structural flexibility inherent to these substances renders them far less sensitive to the ionic radius of the charge carrier in comparison to conventional inorganic intercalation hosts. This quality positions them as a particularly attractive proposition for use in sodium-ion batteries, where the larger size of Na⁺ frequently limits both diffusion and structural stability.
Here, we investigate the mechanism of bipolar redox reactions in naphthalimide (NI) derivatives when used as cathodes in lithium and sodium half-cells with ionic liquid electrolytes. To improve the low electronic conductivity, NI was composited with rGO.
Electrochemical tests were conducted in potentiostatic and galvanostatic modes within a range of potential windows spanning between 1.0-4.6 V. The results of the CV experiments demonstrate the bipolar nature of the studied NIs. The objective of the cyclic stability experiments is to ascertain the influence of the incorporated groups at the imide nitrogen and the halogen substituent in the naphthalimide core. The results demonstrate that the specific capacity of lithium cells stabilises after the 20th cycle, whereas that of sodium cells stabilises after the 5th cycle, irrespective of the halogen substituent. Furthermore, long-term cycling tests were conducted under conditions of high current loads. The investigation revealed that the specific capacity of the sodium electrolyte at a current load of 500 mA/g decreased marginally from 45 mAh/g to 35 mAh/g. This finding suggests that the cathode material exhibited consistent high-rate performance.