Size Controlled Carboxymethyl Cellulose Enhance Electrochemical Performance of Graphite/SiOx Composites Lithium Ion Battery

摘要

The use of silicon active materials for negative anode in lithium ion battery (LiB) could increase their energy density compared to carbon ones. But their massive volume change during charge/discharge cause damage to layer structure and decreasing capacity retention. In addition to this problem, their particle size is generally smaller than graphite and it makes difficult to disperse their particle homogeneously in the slurry. We found using highly size controlled carboxymethyl cellulose (MAC series CMC) as anode binder help disperse SiOx particles well in the graphite/SiOx composite slurry. We observed localization of SiOx in the anode layer with SEM. Then it seemed to be located homogeneously. We analyzed surface smoothness. The surface was very smooth and there seemed to be no pinhole which is from micro gel of CMC. We did electrochemical measurement test. Initial discharge capacity of SiOx-containing LiB was much higher than only carbon ones. Even containing 30% of SiOx, the capacity remained about 80% after 52 cycle high rate test. These results indicate size controlled CMC will help disperse SiOx and enhance capacity.