Square-Scheme Electrochemistry in Battery Electrodes

CONSPECTUS:Sustainable development cannot be achieved without substantial technological advancements.For instance,flexible electricity management requires smart power sourcing with advanced energy storage/conversion technologies.Remedies for abrupt power spikes/drops observed in renewable energy sources such as solar and wind require rapid load-leveling using high-power energy storage systems when they are integrated into a microgrid.Electrochemical energy storage devices efficiently convert electrical and chemical energy,which can potentially function as distributed power sources.Among these,lithium-ion batteries are a present de facto standard with their relatively high energy density and energy efficiencies that are based on topochemical intercalation chemistry,whereby guest lithium ions are(de)intercalated reversibly with simultaneous redox reactions and minimal structural changes.However,their energy density,power density,life-cycle cost,calendar life,and safety remain unsatisfactory for widespread use.When the storage capacity is maximized,as a result of which a labile deep charge/discharge state is generated,to develop batteries with high energy density,subsequent irreversible phase transformations or chemical reactions occur in many cases.The combination of the reversible electrode reactions and the subsequent irreversible phase transformations sometimes causes a charge/discharge curve characterized by a large voltage hysteresis with 100%Coulombic efficiency.Because a large voltage hysteresis significantly degrades the energy efficiency,unveiling the reaction mechanism is of primary importance in mitigating energy loss.