oa Effect of Surface Oxidation on Performance of Ti3C2Tx/MO Composite as Anode Materials for Lithium Ion Batteries

Recently, a new group of 2D material showed a great promise in supercapacitors and batteries application due to their good conductivity as well as hydrophilic nature [1]. It has general formula Mn+1Xn, where n = 1, 2 or 3, M is an early transitional metal and X is C and/or N [2]. According to X-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectrometry (EDS) studies, MXenes can be terminated with a mixture of O, OH, and/or F groups depending on the chemical etching method and post-treatment. The as-synthesized MXenes are electronically conducting and hydrophilic, which is a unique combination. Ultrasonication can be used to delaminate the 2D layers and produce single-layer and few-layered flake [3].

As MXenes are hydrophilic, once delaminated, they form stable, surfactant-free colloidal solutions in water. The possibility of intercalating MXenes with various organic molecules plays a critical role for utilizing MXene in a range of applications, from polymer reinforcements to energy storage systems. The MXenes’ 2D morphology, together with to their good electronic conductivities, render them strong candidates for many applications that range from sensors and electronic device materials to catalysts in the chemical industry, conductive reinforcement additives to polymers, and electrochemical energy storage materials, among many others [4].

We have used hydrothermal route to synthesize nanocomposite material i.e. Ti3C2Tx/MO (MO = Fe2O3, Co3O4). After hydrothermal treatment, nanocomposite was calcinated at 400°C for 4 hours to get rid of entrapped moisture. Nano-composite was characterized using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. After synthesis, nanocomposite was applied as anode in lithium ion battery. Anode was fabricated as thin film using doctor blade on copper foil.

Ti3C2Tx/Fe2O3 composite as anode material exhibited discharge and charge capacities of 190 and 120 mAh/g, respectively. Characterization shows that the MO nanoparticles are not uniformly distributed and also X-ray diffraction analysis has confirmed that Ti3C2Tx has oxidized during hydrothermal treatment. Due to oxidation, the surface of Ti3C2Tx was decomposed to TiO2 and leaving carbon sheets behind which played a big role in decreasing conductivity of the anode. In turn, it has greatly affected its performance as anode material in the lithium ion batteries. To enhance its performance as anode material in Lithium ion batteries, it is extremely important to protect it from oxidizing. For this purpose, it should be exfoliated in a medium other than water. Besides this, metal oxide should be uniformly distributed.