Abstract
High-voltage cathodes such as LiNi0.5Mn1.5O4 (LNMO) with an operating voltage of 4.7 V vs. Li/Li+ are potential candidates for enhancing the energy density limitations of the existing lithium-ion batteries.1 However, to be operational, electrolytes under these high voltages need to be electrochemically stable or enable the formation of a stable passivation layer for long cycle-life.2 Although linear sweep voltammetry (LSV) is a very well-established and most commonly used technique to find the electrochemical stability window (ESW) of an electrolyte, the stability limits are often assigned arbitrarily with no evident cut-off which often leads researchers to over-estimate the electrolyte stability.
Herein, we demonstrate a method to evaluate anodic stability of electrolytes termed as Potential-profile Sweep Voltammetry (PSV), where the potential is controlled to follow the electrode potential profile of LNMO, to mimic the operating conditions and passivation kinetics in a real battery rather than applying a constant voltage scan rate. Electrolytes with different functionalities such as ether, carbonate, sulfone and a carbonate-sulfone mixture with lithium hexafluorophosphate (LiPF6) salt were assessed with the LNMO electrode potential profile as a base in this technique. Coulombic efficiencies of the LNMO half-cells using these different electrolytes were monitored to validate this method.
Figure 1. dQ/dV vs. V for the first anodic sweep of all the four electrolytes using the PSV method
References:
J Ma, P Hu, G Cui, L Chen, Mater. 2016, 28, 3578−3606
Z Li, Y Zhao, W Tenhaeff, Mater.2021, 33, 6, 1927–1934
Figure 1