Solid-state Synthesis Of Graphite-like C₃N₄ And Its Reversible Li⁺ Intercalation

Lithium-ion battery, a pollution-free battery, was introduced into market in the 1990s. In recent years, it has gained more and more attention because of its high working voltage, low self-discharge rate, high power density and no memory effect. One of the key factors that restrict its performance is the properties of the anode materials. Generally, the lithium-ion batteries use carbon/graphite as its anode. A lot of researches have been carried out to improve modify the performance of carbon/graphite, but few achievements have been reached. To meet the increasing demands for energy conversion and storage, researchers have focused on searching for new materials to replace carbon/graphite.This paper firstly introduced basic principles and features of lithium-ion secondary battery, and summarized research progress of all kinds of anode materials as well as carbon nitride. We synthesized graphite-like carbon nitride (g-C₃N₄) under the protection of nitrogen using a solid state method. The composition and the structure of the product were characterised using XPS, FTIR, SEM, TEM and XRD. Its electrochemical performances have been evaluated by galvanostatic charge/discharge method and cyclic voltammetry (CV) using the carbon nitride as anode material of lithium-ion battery. It was found that g-C₃N₄ showed reversible intercalation capacity of Li⁺, but the capacity dropped sharply during the first few cycles.In order to improve the electrochemical performances of carbon nitride, it was modified by electrochemical intercalation and electroless copper plating. The microstructure characteristics were analyzed after modification. The electrochemical performances of the carbon nitride could be improved. Electrochemical intercalation of Mg²⁺ and Al³⁺ enhanced the binding force of carbon nitride layers. Electroless copper plating constrained decomposition of materials and enhanced conductivity of the carbon nitride. It showed the possibility to improve the electrochemical performances of carbon nitride.This research confirmed that graphite-like carbon nitride had reversible intercalation capacity of Li⁺. It could become the fifth member of the anode materials after graphite, nonmetal materials, alloy materials and metal oxide. This dissertation will create a new field and promote the development of lithium battery technology.