Rapid charging of Li-ion batteries is limited by lithium plating on graphite anodes, whereby Li + ions are reduced to Li metal on the graphite particle surface instead of inserting between graphitic layers. Plated Li metal not only poses a safety risk due to dendrite formation, but also contributes to capacity loss due to the low reversibility of the Li plating/stripping process. Understanding when Li plating occurs and how much Li has plated is therefore vital to remedying these issues. We demonstrate a titration technique with a minimum detection limit of 20 nmol (5×10-4 mAh) Li which is used to quantify inactive Li that remains on the graphite electrode after fast charging. Additionally, the titration is extended to quantify the total amount of solid carbonate species and lithium acetylide (Li2C2) within the solid electrolyte interphase (SEI). Finally, electrochemical modeling is combined with experimental data to determine the Li plating exchange current density (10 A/m 2) and stripping efficiency (65%) of plated Li metal on graphite. These techniques provide a highly accurate measure of Li plating onset and quantitative insight into graphite SEI evolution during fast charge.

An electrocatalytic method has been developed to oxidize primary alcohols and aldehydes to the corresponding carboxylic acids using 4-acetamido-2,2,6,6-tetramethylpiperidin-1-oxyl (ACT) as a mediator. The method successfully converts benzylic, aliphatic, heterocyclic, and other heteroatom-containing substrates to the corresponding carboxylic acids in aqueous solution at room temperature. The mild conditions enable retention of stereochemistry adjacent to the site of oxidation, as demonstrated in a 40 g-scale synthesis of a precursor to levetiracetam, a medication used to treat epilepsy.

A key challenge for energy storage and conversion technologies is finding simple, reliable methods that can identify device failure and prolong lifetime. Lithium plating is a well-known degradation process that prevents Li-ion battery fast charging, which is essential to reduce electric vehicle “range anxiety” and enable emerging technologies such as aerial drones and high-performance portable electronics. The ability to detect the initial onset of lithium plating from easily accessible voltage measurements would greatly improve battery safety and feedback controls modeling. In this work, we highlight the application of a differential open-circuit voltage analysis (dOCV) to detect when Li plating begins during a single charge for room-temperature fast charging. We also show that dOCV can identify the Li plating onset during cycling with sensitivity of 4 mAh plated Li per gram graphite, indicating that this method has commercial promise for online Li detection.