Synthesis of MoS2 and Nitrogen doped MoS2 nanostructures as anode materials for Lithium Ion Batteries (LIBs)

Abstract

Lithium-ion batteries (LIBs) have attracted lots of attention over last few years due to the high specific energy, high power density, longer life cycle and low self-discharge, making LIBs the advantageous over the conventional rechargeable lead-acid batteries. Electronic systems are being reduced so that the system can accommodate more components for increasing reliability of the electronic device and cheaper cost. The high power density batteries have an important role in this miniaturization process. Use of nanomaterials can reduce the size of LIBs by increasing the power and energy density. Therefore, efforts have done to decrease the particle size of anode materials to nanoscale level. Many efforts are in progress to find effective anodes for LIBs since the commercial anode for LIBs, graphite, has shown very limited capacity. In view of this, the project has been focused on the development of indigenous raw materials as well as design and fabrication of lithium ion battery using the same nanomaterials. Among many different types of materials, molybdenum disulphide holds a great deal in LIBs technology as their structural resemblance with graphite structure and more theoretical capacity than graphite. The nitrogen-doped graphene has shown the promising result for increasing the capacity and power density of LIBs. Hence, attempts have been made to synthesize the nitrogen-doped MoS2, as nitrogen-doped graphene has high processing cost. The work has been presented in the form of four chapters. The first chapter includes the introduction of Lithium-ion battery, literature survey, recent development in anode materials etc. The second chapter includes details of physicochemical and electrochemical characterization techniques, fabrication of LIBs, and detailed synthesis process for MoS2 and nitrogen doped MoS2 materials for the lithium-ion battery application. The third chapter includes the detailed discussion of results and characterization, and the last chapter concludes the thesis. The anode material was synthesized using the hydrothermal method to get the optimized morphology of the materials. The nitrogen doped MoS2 nanostructures have been prepared for the first time in lithium-ion battery applications. Different characterization techniques have been used to investigate the phase purity of active materials. A morphological study performed shows the flowerlike morphology of MoS2 nanosheets and the size of each petal is in the range of 20-80 nm depending on the amount of nitrogen doping in the material. The MoS2 electrode exhibits a high rate capability and structural stability even at very high Li-ion insertion−extraction current densities, which is comparable to other carbon materials.