Carbon-based cobalt phosphide for high performance lithium ion battery

• Main Author: Liu, Hongzheng
• Other Authors: Yan Qingyu Alex
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/66340
• Institution: Nanyang Technological University

As the development of power providing equipment, Lithium Ion Batteries (LIBs) was one of the most popular techniques being applied in mobile electronic machines such as cell phones, and laptops. It has been even used for future electric devices such as hybrid electronic devices and other smart devices. However, as energy demands increase, it’s necessary to raise the energy density of batteries to ensure the power sufficiency. Recently, transition metal phosphides have drawn great attention on LIBs of anodes due to higher electronic capacity, more efficient cycling behavior and good rate capaability in comparison with conventional graphite material. In this report, pure CoP nanowire and carbon-based CoP composites (CoP/RGO, CoP/CNT) have been successfully synthesized as anode material in LIBs via hydrothermal method followed by an annealing treatment. After that, by using scanning electrode microscope (SEM), Transmission Electrode Microscope (TEM), X-ray Diffraction (XRD), and characteristics of the structure and morphology could be identified. Surface area and porosity were measured by accelerated surface area and porosimetry system (ASAP). Cyclic voltammetry (CV), Charge/discharge performance, and rate capability studies were used for analyzing the electrochemical behavior of the anode material of the LIBs. The outcome indicated that the electrochemical results are greatly relying on the structures. Based on a density of 0.2 A g-1, pure CoP nanowire has invertible capability of around 429 mAh g-1. The CoP/CNT composite has relatively big invertible capability of around 810 mAh g-1 bigger than 100 cycles. CoP/RGO composite has better invertible capability and cycling outcomes of around 1100 mAh g-1 with more than 200 cycles with 0.2 A g-1 density. Moreover, CoP/RGO composite demonstrated a great rate ability of around 424 mAh g-1 at 10 A g-1 density. The great Li ions storage outcome and stable cyclibity of CoP/RGO due to the enhanced conductivity facilitates the charge transport and big particular surface area tools accommodate amount changes during lithiation/de-lithiation process. Besides, the framework of CoP/RGO provides much more active sites for the electrochemical reactions and also shortened diffusion path of Li ions and electrons. All in all, CoP/RGO composite shows a promising potential to be utilized since the anode sources with excellent outcomes lithium-ion batteries.