Pore structure of electrochemically pretreated glassy carbon and uptake of lithium ions into micropores

Abstract

Lithium ions were taken up into electrochemically pretreated glassy carbon fibres at negative electrode potentials, and the uptake amount of Li⁺ could be related to the porosity of the fibres. The B.E.T. area and pore volume of the fibres increased linearly with an increase in the time of oxidative pretreatment, and the uptake amount also increased linearly with the B.E.T. area and pores volume. It was found that the pores of the fibres consisted of the ‘old’ pores that had probably been created during the pyrolysis of material fibres and the ‘new’ ones created by electrochemical treatment. The plots of the uptake amount vs., the B.E.T. area and the amount vs. the pore volume indicated that only the new pores could take up Li⁺. Two models for ion uptake are discussed. (1) Ions are taken up into the pores, leaving their solvation sheaths held as in solution. In this model, the ions are dissolved even in the pores. (2) The ions taken up are adsorbed on the new pore surfaces. Analysis of uptake equilibrium indicated that the latter model was more likely.