Irreversible capacity and rate-capability properties of lithium-ion negative electrode based on natural graphite

In this paper, the results of experimental work with doped natural graphite are presented and described. The graphite material plays major role within negative electrode materials used in lithium-ion batteries. Behavior of graphite used as an active material for negative electrodes in lithium-ion cell was widely investigated and published. The one key characteristic property of graphite is its irreversible capacity loss. The irreversible capacity represents losses which occur in the graphite negative electrode within initial charge-discharge cycles (process called cell formatting). This phenomenon is associated connected with lower negative electrode potential vs. lithium (Li/Li+) and the growth of the Solid Electrolyte Interphase (SEI) layer. The SEI layer is important and necessary for proper operation of the lithium-ion cell; on the other hand growth of the SEI layer limits and lowers the theoretical capacity of lithium-ion cell by up to 40%. A possible way how to offset these losses is to dope the graphite material by lithium atoms before its use in the lithium-ion cell. The lithiation process has been studied as a possible way how to dope the (pre-lithiated) natural graphite prior to its use as an active electrode material. Suppression of irreversible capacity losses at initial charge-discharge cycles is the main focus of our investigation.