  Due to the hydrolytic instability of $LiPF_6$ in carbonate-based solvents, HF
is a typical impurity in Li-ion battery electrolytes. HF significantly
influences the performance of Li-ion batteries, for example by impacting the
formation of the solid electrolyte interphase at the anode and by affecting
transition metal dissolution at the cathode. Additionally, HF complicates
studying fundamental interfacial electrochemistry of Li-ion battery
electrolytes, such as direct anion reduction, because it is
electrocatalytically relatively unstable, resulting in LiF passivation layers.
Methods to selectively remove ppm levels of HF from $LiPF_6$-containing
carbonate-based electrolytes are limited. We introduce and benchmark a simple
yet efficient electrochemical in situ method to selectively remove ppm amounts
of HF from $LiPF_6$-containing carbonate-based electrolytes. The basic idea is
the application of a suitable potential to a high surface-area metallic
electrode upon which only HF reacts (electrocatalytically) while all other
electrolyte components are unaffected under the respective conditions.
