In situ visualization of Li/Ag 2 VP 2 O 8 batteries revealing rate-dependent discharge mechanism

Watching the silver lining inside Some types of batteries contain both a transition metal reducible metal, such as the cathode material Ag 2 VP 2 O 8 . During operation, both Ag and V ions are reduced, and the Ag atoms can form wires to enhance the internal conductivity. Kirshenbaum et al. probe the discharge of a battery at different rates and track the formation of Ag atoms using in situ energy-dispersive x-ray diffraction (see the Perspective by Dudney and Li). They show how the discharge rate affects whether the Ag or V is preferentially reduced and also the distribution of the Ag atoms, and then correlate this to the loss of battery capacity at higher discharge rates. Science , this issue p. 149 ; see also p. 131