Changing Established Belief on Capacity Fade Mechanisms: Thorough Investigation of LiNi1/3Co1/3Mn1/3O2 (NCM111) under High Voltage Conditions

Abstract

The further development of lithium ion batteries operating at high voltages requires basic understanding of the occurring capacity fade mechanisms. In this work, the overall specific capacity loss with regard to reversible and irreversible processes for LiNi1/3Co1/3Mn1/3O2 (NCM111)/Li half cells, cycled at a charge cutoff potential of 4.6 V vs Li/Li+, has been investigated in detail. By means of total X-ray fluorescence (TXRF) technique it was shown that specific capacity losses associated with the amount of dissolved transition metals are negligible, implying a still intact NCM111 active material after 53 cycles. It was demonstrated that the specific capacity fade during cycling at constant specific currents can be mainly attributed to the increase of the delithiation (charge) hindrance, whereas lithiation (discharge) hindrance is only present after a specific current increase, leading to apparent specific capacity losses and to decreased Coulombic efficiencies. This could be proven by the determination ...