Nanotexturing TiO2 over carbon nanotubes for high-energy and high-power density pseudocapacitors in organic electrolytes

Abstract

Titanium oxides have been considered potential electrode materials for pseudocapacitors because of their exceptional properties, such as high thermal and chemical stabilities, ready availability and low cost. However, they are not ideal for practical applications due to their poor ionic and electrical conductivity. The electrochemical performance of TiO2 can be greatly improved if the material is nanotextured by reducing the particle size in optimizing the synthesis pathway. Actually, for metallic oxides, the electrochemical performance significantly depends on the particle size/morphology. At relatively low current densities the higher capacity values are exhibited by noncrystalline TiO2 having 2 nm particle size, with values reaching 704 C g−1. However, only thin electrodes are able to operate at a high charge density, limiting the energy density of the final device. Here, we propose a solution to circumvent such a drawback by further nanotexturing TiO2 over multiwalled carbon nanotubes (CNTs). For that purpose, CNTs were introduced during oxide preparation. The synthesis protocol has been optimized for obtaining a uniform coverage of small TiO2 particles on the surface of the CNTs. At low current densities, high mass loading TiO2/CNT composites electrodes are able to deliver capacitances as high as 480 F g−1 and the presence of CNTs allows keeping 70% of the capacitance at high current densities while only 27% is retained when using a regular conductivity agent as carbon black. The results demonstrate that uniform nanotexturation of TiO2 over CNTs allows good rate capabilities to be obtained for thick electrodes having sufficient active material loading to achieve high specific energy and power densities.

Sustainable Approach for the Development of TiO2-Based 3D Electrodes for Microsupercapacitors

“…charge-discharge profiles presented in Figure 3b at a moderately high charge density o 0.1 mA cm −1 show a typical capacitive behavior, confirming the pseudocapacitive char acter of the nanosized TiO2 comprising the thin films where diffusion-controlled lith um-ion intercalation processes are replaced by surface reactions [48,49].…”

“…The CVs shown in Figure 3a present the typical signature of a nanosized TiO 2 film in organic electrolytes exhibiting a capacitive contribution and Ti 4+ /Ti 3+ redox peaks, which may originate from multiple lithium sites in the TiO 2 structure [57]. The galvanostatic charge-discharge profiles presented in Figure 3b at a moderately high charge density of 0.1 mA cm −1 show a typical capacitive behavior, confirming the pseudocapacitive character of the nanosized TiO 2 comprising the thin films where diffusion-controlled lithium-ion intercalation processes are replaced by surface reactions [48,49].…”

“…An organic solvent will be more advantageous in terms of electrochemical stability window allowing the system to operate up to higher voltages. In fact, the nanotexturation of TiO 2 particles at the nanoscale affords the oxide in Li-based organic electrolytes with a pseudocapacitive character since the charge exchange can be almost continuous as a function of the potential [48,49]. This pseudocapacitive character affords fast charge-discharge kinetics, which is compatible with the power demand of a supercapacitor.…”

10 years of frontiers in carbon-based materials: carbon, the “newest and oldest” material. The story so far

“…However, generally, synthesis methods use solvents to favor the interaction between both compounds. Poirot et al (2022) reported the synthesis of the TiO 2 /CNTs composite by mixing them with solvents together with a combination of sonication and reflux processes to produce CNTs with a thin layer of TiO 2 . Geng et al (2023) designed the synthesis of SiO 2 /CNFs composite by a coating method using a SiO 2 sol with carbon nanofibers.…”

“…Concerning metal oxides, the review article of Wu et al (2020) reported the use of MnO2 to form diverse MnO2/carbon composites with carbon materials like CNT, graphene, CNF, and activated carbon as promising electrodes for supercapacitors. Meanwhile, Poirot et al (2022) reported the TiO2/CNTs as an interesting electrode for supercapacitors due to the high pseudocapacitance provided by the metal oxide. In the case of doping, Han et al (2021) designed a B,N dual doped coral-like carbon framework (BN-CCF) which offered an excellent performance as an electrode in supercapacitor.…”