Enhanced Ionic/Electronic Transport in Nano‐TiO2/Sheared CNT Composite Electrode for Na+ Insertion‐based Hybrid Ion‐Capacitors

• Published in: Advanced functional materials Vol. 30; no. 5
• Main Authors: Luo, Sainan, Yuan, Tao, Soule, Luke, Ruan, Jiafeng, Zhao, Yahui, Sun, Dalin, Yang, Junhe, Liu, Meilin, Zheng, Shiyou
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.01.2020
• Subjects: Activated carbon; Anodes; Architecture; Capacitors; Carbon; Carbon nanotubes; Electrode materials; Electrodes; Electron transport; Flux density; Graphene; hybrid Na+ capacitors; Insertion; Materials science; Nanoparticles; sheared CNT frameworks; Sodium; TiO2 nanoparticles; Titanium dioxide
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201908309

Ion‐insertion capacitors show promise to bridge the gap between supercapacitors of high power densities and batteries of high energy densities. While research efforts have primarily focused on Li+‐based capacitors (LICs), Na+‐based capacitors (SICs) are theoretically cheaper and more sustainable. Owing to the larger size of Na+ compared to Li+, finding high‐rate anode materials for SICs has been challenging. Herein, an SIC anode architecture is reported consisting of TiO2 nanoparticles anchored on a sheared‐carbon nanotubes backbone (TiO2/SCNT). The SCNT architecture provides advantages over other carbon architectures commonly used, such as reduced graphene oxide and CNT. In a half‐cell, the TiO2/SCNT electrode shows a capacity of 267 mAh g−1 at a 1 C charge/discharge rate and a capacity of 136 mAh g−1 at 10 C while maintaining 87% of initial capacity over 1000 cycles. When combined with activated carbon (AC) in a full cell, an energy density and power density of 54.9 Wh kg−1 and 1410 W kg−1, respectively, are achieved while retaining a 90% capacity retention over 5000 cycles. The favorable rate capability, energy and power density, and durability of the electrode is attributed to the enhanced electronic and Na+ conductivity of the TiO2/SCNT architecture. This work presents a high‐performance 3D TiO2/sheared‐carbon nanotube (SCNT) anodic material for Na+‐based capacitors (SICs) using a framework that combines the benefits of reduced graphene oxide and CNTs to enable high rate capability and stability. The TiO2/SCNT composite anode is used in a SIC and exhibits gravimetric and volumetric power densities of 54.9 Wh kg–1 and 1410 W kg–1, respectively.