Ultrafast Charge/Discharge by a 99.9% Conventional Lithium Iron Phosphate Electrode Containing 0.1% Redox-Active Fluoflavin Polymer
Kan Hatakeyama‐Sato, Tomoki Akahane, Choitsu Go, Takahiro Kaseyama, Takuji Yoshimoto, Kenichi Oyaizu
Abstract
Exceptionally large output (current density over 20 mA/cm2) is achieved by a 99.9 wt % conventional LiFePO4 cathode for lithium ion batteries. Adding just 0.1 wt % redox-active fluoflavin polymer to the electrode improves the electrochemical performance dramatically. The polymer’s redox potentials of 3.3 and 3.7 V vs Li/Li+, sandwiching that of LiFePO4 (3.4 V), are critical in accelerating the charge and discharge processes by electrochemical mediation. The lower overvoltage also helps to suppress electrode degradation and improve the cycle life of the cell (over 1000 cycles). The DC pulse technique reveals the transient, dynamic electrochemical mediation, which cannot be observed by conventional steady-state impedance spectroscopy. These dramatic improvements in material properties achieved by the catalytic amount of the organic additive (0.1 wt %) give new insights into organic/inorganic hybrid chemistry and may lead to the development of energy-related materials with improved properties.