Advanced Carbon Materials for Sodium‐Ion Capacitors

Abstract

Nonaqueous sodium‐ion capacitors (SICs), as a new type of energy storage cell, can potentially achieve high energy‐power densities, long cycling lifespan, and low cost in one device. Given this, developing suitable carbonaceous electrode materials for carbon‐based SICs is of great significance. Unlike lithium‐ion batteries (LIBs) and lithium‐ion capacitors (LICs) that have been successfully commercialized, SICs are still at an early stage. As a result, rational electrode material design for SICs is needed to meet the requirements of electrochemical energy‐storage systems. Carbon materials with a wide range of sources and low toxicity deliver significant potential applications in high‐performance SICs, whether as positive or negative parts. Various carbonaceous electrode materials have been explored and investigated for developing SICs over the past years. This Review firstly introduces the classical and widely used configurations and corresponding energy‐storage mechanism in detail for SICs. Then, recent progress on carbonaceous electrode materials, including cathode and anode materials, are summarized. Finally, the challenges and some suggestions on the future development of carbon‐based SICs are proposed.

Sodium‐Ion Capacitors: Recent Development in Electrode Materials

“…where E , I and Δ t represent energy density, current density and discharging time, respectively, and V min and V max are the minimum and maximum voltages of the SIC [28,29] …”

“…where P , E and Δ t are power density, energy density and discharging time of the SIC, respectively [16,28,29] …”

“…Since the study of SICs, a lot of studies have demonstrated that the electrochemical performance of SICs largely depends on the choice of anode materials. To achieve both high energy density and power density as well as long cycling stability in SICs, the anode materials should possess the following merits: 1) low working voltage, resulting in a higher V max of SIC and higher energy/power densities; 2) good rate capability, which allow for high current density and matching with high power cathode; 3) high specific capacity, leading to a long discharge duration (Δ t ); 4) long lifespan, which is beneficial for the cycling stability [24,28,57–59] . Herein, several important types of anode materials are described in detail, including carbonaceous anode materials, MXene‐based anode materials, titanium and niobium‐based anode materials, and conversion‐type anode materials.…”

“…At present, activated carbon, porous carbon and graphene are popular cathode materials for SICs. Generally, the capacitive‐type electrode materials of SICs should have three properties: high specific surface area to obtain large capacitance; excellent intra‐ and interparticle conductivity and good electrolyte accessibility [28,29,128] . Herein, the latest progress on cathode materials is summarized, especially focusing on the design of carbonaceous microstructure, regulation of specific surface area/pore size/heteroatom doping and corresponding electrochemical performances.…”

“…Due to the large volume expansion and electrochemical instability of the metal‐based electrodes as well as the mismatch on dynamics between anode/cathode, the charge/discharge rate, cycling stability and reliability of the hybrid device will be affected [142] . In this regard, many researchers recently have turned their attention to the fabrication of all‐carbon based SICs [28] . Besides, the “homologous strategy” has been widely employed to construct suitable carbonaceous anode and cathode materials for high‐performance SICs [66] .…”