Interfacing electrolytes with electrodes in Li ion batteries

-A poetic definition of a binary liquid/solid interface by Luis de Camoes (1572). Since its birth in early 1990s, Li ion battery technology has been powering the rapid digitization of our daily life and finally made its debut in 2010 into the large format application for electrified vehicles such as the Nissan Leaf and GM Chevrolet Volt; however, much of the chemistry and processes underneath this amazing energy storage device still remain to be understood, among which is the interphase between electrolyte and electrodes. Interphases are formed in situ on electrode surfaces from sacrificial decomposition of electrolytes. Their ad hoc chemistry supports the reversible Li+-intercalation in both anode and cathode materials at extreme potentials, while preventing parasitic reductions/oxidations on the reactive surfaces of those electrodes; but their existence places restrictions on energy and power densities of the device by impeding Li+-transport and setting operating voltage limits, respectively. It has been the dream of battery engineers to maximize the former and minimize the latter. This review summarizes the most recent knowledge about the chemistry and formation mechanism of this elusive battery component on both anode and cathode surfaces. The attempts to tailor a desired interphasial chemistry via diversified means were also discussed.