![]() ![]() So far, mainly hybridization between EDLCs and LIBs has been explored 18. The most intuitive approach to combine high energy and high power density within a single device is to combine the different types of energy storage sources. Moreover, especially in the case of electroactive polymer based supercapacitors, excess electrolyte has to be used to compensate the electrolyte depletion, diminishing the gravimetric capacity. Although excellent capacity retention for extended cycling can be obtained even at high charge - discharge rates 14, 17, specific capacity of RECs is typically lower than for LIBs. Here, charge is stored through surface or bulk (pseudocapacitive) redox reactions, similar to LIB materials, yet, with a very fast charge transfer response, similar to EDLCs. On the other extreme, electrochemical double-layer supercapacitors (EDLCs), which store energy through accumulation of ions on the electrode surface, have low energy storage capacity but very high power density 14.Ī special category of electrochemical capacitors is provided by redox capacitors (REC), which usually make use of electroactive polymers or transition metal oxides 15, 16, 17. Since both diffusion and charge transfer are slow processes, power delivery as well as the recharging time of the LIBs are kinetically limited. LIBs have the highest energy density but typically suffer from low power by virtue of reversible Coulombic reactions occurring at both electrodes, involving charge transfer and ion diffusion in bulk electrode materials 13. Rapid charging causes accelerated degradation of the battery constituents as well as a potential fire hazard due to local over-potential build-up and increased heat generation 9, 10, 11, 12. A key bottleneck in achieving this goal is the limited fast charging ability of LIBs. Li-ion batteries (LIBs) with high specific energy, high power density, long cycle life, low cost and high margin of safety are critical for widespread adoption of electric vehicles (EVs) 1, 2, 3, 4, 5, 6, 7, 8. As a result of hybrid's components synergy, enhanced power and energy density as well as superior cycling stability are obtained, otherwise difficult to achieve from separate constituents. A rate capability equivalent to full battery recharge in less than 5 minutes is demonstrated. We detail on a unique sequential charging mechanism in the hybrid electrode: PTMA undergoes oxidation to form high-potential redox species, which subsequently relax and charge the LiFePO 4 by an internal charge transfer process. ![]() ![]() The PTMA constituent dominates the hybrid battery charge process and postpones the LiFePO 4 voltage rise by virtue of its ultra-fast electrochemical response and higher working potential. Here, we provide a solution to this issue and present an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a Li-ion battery material (LiFePO 4). Meeting both characteristics within a single or a pair of materials has been under intense investigations yet, severely hindered by intrinsic materials limitations. surface ion diffusion and electron conduction. High energy and high power electrochemical energy storage devices rely on different fundamental working principles - bulk vs.
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