Development of Negative Electrode for Calcium Ion Battery Using Marimo Nano Carbon

Abstract

Lithium-ion batteries (LIBs) are used in various fields due to their high energy density and high cycle characteristics. In general, graphite materials are used for the negative electrode materials for lithium-ion batteries (LIBs). However, since the amount of Li ion that can be stored in the graphite material of the negative electrode is approaching the theoretical value for LIBs, a significant increase in capacity cannot be expected. Calcium ion batteries (CIBs) use Ca ion as charge carriers. Therefore, they can be expected to have twice the capacity of LIBs. In LIBs, charge and discharge mechanism occurs by intercalation and deintercalation of Li ion into graphite layers. However, Ca ion are poor in reactivity, intercalation and deintercalation of Ca ion do not occur in the graphite negative electrode, and charge and discharge capacity cannot be obtained. For this reason, we used Marimo Nano Carbon (MNC) as a new negative electrode material. MNC is an aggregate of carbon nano filaments (CNF). CNF has a layered structure similar to graphite and also has amazing electronic properties and many other unique properties. This CNF has coin-stacked structure in which graphene layers are stacked, and the edge surface is exposed. Hence, we expected that MNC negative electrode would react with less reactive Ca ions and indicated larger charge / discharge capacity than that of the graphite negative electrode. In this study, we evaluated MNC negative electrode performance. For MNC synthesis, nano metal particles carried on oxidized diamond were used. Oxidized diamond has oxygen-containing functional groups arranged regularly. Thus, nano metal particles are a highly dispersed on it. Pd metal was used for carried metal. Pd metal could synthesized CNF having coin-stacked structures. Pd metal was carried on oxidized diamond by metal nano-colloidal method. C2H4 as a feedstock for CNF was used, and MNC was synthesized by the chemical vapor deposition (CVD) method. When MNC was used as the negative electrode material, the charge and discharge capacity was larger than that of the graphite negative electrode. In addition, the intercalation of Ca ions between the graphene layers was confirmed.