Finding my Cherokee Heritage

I am seeking information related to my great great grandfather Ezekiel Ellison. He had a wife Caroline ., two daughters, Sarah Elizabeth and Frances Rachel. He died at Andersonville Prison during the Civil War of pneumonia and possibly starvation. I am told he was of direct Cherokee descent but can find no information about the Englands other than they lived in Claiborne Co., TN around 1834. My grandmother Mary said that she was half cherokee and I’d like to find proof.