Manipulation of Nitrogen-Heteroatom Configuration for Enhanced Charge-Storage Performance and Reliability of Nanoporous Carbon Electrodes

Abstract

In this study, various nitrogen-containing functional groups, namely, pyridine (N-6), pyrrole (N-5), oxidized N (N–O), and quaternary N (N-Q), are created on activated carbon (AC) surface via melamine, ammonia, and nitric oxide doping methods. N-5 and N-6 groups markedly alter the specific surface area and pore size of AC. N–O is found to affect electrolyte wettability, and the N-Q content is closely associated with AC electronic conductivity. The nitrogen-containing groups do not contribute to pseudocapacitance in propylene carbonate and acetonitrile electrolytes. However, the nitric-oxide-treated carbon (AC-NO) exhibits the best high-rate charge–discharge performance among the investigated materials. The N-Q-enriched and N-5/N-6-depleted AC-NO most effectively suppresses the leakage current and gas evolution of supercapacitors. Online gas chromatography is used to analyze the gaseous species produced from AC electrodes. With an appropriate surface functionality on carbon, the cell voltage can be increased to ∼3 V, increasing the energy and power densities. The aging behavior of the carbon electrodes with and without nitrogen modification after being floated at 2.5 V and 70 °C for 3 days is investigated. An effective strategy for enhancing supercapacitor performance and reliability is proposed.

Recent research advances of self-discharge in supercapacitors: Mechanisms and suppressing strategies

“…Sutarsis and coworkers treated commercial activated carbon with melamine, ammonia gas/argon and nitric oxide (NO) to finely tune the content of N-containing functional groups of activated carbon [70]. Subsequently, the leakage current for supercapacitor electrodes with different N-containing levels was evaluated in the propylene carbonate electrolyte.…”

Development of Novel Carbon Electrode for Electrochemical Energy Storage. Nano-sized Carbon and Classic Carbon Electrodes for Capacitors

“…Recently, another research group also reported that the surface modification with NO is effective for the improvement of the durability and the rate performance. 42 The electrochemical stability is the key to finding the effective surface modification for the improvement of the operating voltage of the nanoporous carbon electrode.…”

Hierarchical Carbon Composites for High‐Energy/Power‐Density and High‐Reliability Supercapacitors with Low Aging Rate

“…The evolved gas can block the pores of the electrode material and separator and thus increase the capacitor internal resistance and pressure, leading to performance degradation, cell rupture, and even safety risks. [10,11] The self-discharge rate of SCs should also be considered. Self-discharge, which involves voltage depression when SCs are disconnected from a power supply, can result in coulombic efficiency loss and energy dissipation.…”

“…[12] Moreover, the aging behavior at high voltage is of a great concern because long-term durability is an essential characteristic of SCs. [11] However, due to the emphasis (sometimes overemphasis) on high capacitance, few studies have focused on improving these crucial properties of carbon-based EDLCs. These properties are thus investigated in this work.…”

“…However, the capacitor leakage current, which is mainly associated with parasitic side reactions and can lead to cell heating and gas evolution, [9,10] is usually overlooked. The evolved gas can block the pores of the electrode material and separator and thus increase the capacitor internal resistance and pressure, leading to performance degradation, cell rupture, and even safety risks [10,11] . The self‐discharge rate of SCs should also be considered.…”