Designing high-performance asymmetric and hybrid energy devices via merging supercapacitive/pseudopcapacitive and Li-ion battery type electrodes

We report a strategic development of asymmetric (supercapacitive-pseudocapacitive) and hybrid (supercapacitive/pseudocapacitive-battery) energy device architectures as generation-II electrochemical energy systems. We derived performance-potential estimation regarding the specific power, specific energy, and fast charge-discharge cyclic capability. Among the conceived group, pseudocapacitor-battery hybrid device is constructed with a high-rate intrinsic asymmetric pseudocapacitive (α - MnO₂/rGO) and a high-capacity Li-ion intercalation battery type (po-nSi/rGO) electrodes. The experimental setup was developed to measure the current sharing between the two different active materials in a single device allowing us to distinguish the contribution of each active electrode material. The combined potentiostatic cyclic voltammograms and galvanostatic charge-discharge cycling profiles provided gravimetric capacity exceeding 600 F/g (or 180.5 mAh g^-1 and ≥ 35mC/cm²) resulting in higher specific power and specific energy densities of 6.5 kW kg^-1 and 33.5 Wh kg^-1 with Coulombic efficiency (CE) and capacitance retention exceeding ≥ 85-90%, reported to date for full cell configuration, compared with symmetric or half-cell configurations (ca. 0.1 kW kg^-1 and 13.7 Wh kg^-1). Other systems studied provided specific energy ranged between 28 Wh kg^-1 and 50 Wh kg^-1 and specific power between 6.5 kW kg^-1and 1.3 kW kg^-1. Moreover, the behavior of such asymmetric hybrid devices represented a linear combination of the two active electrode material systems. The use of aqueous (and organic) electrolytes for asymmetric electrodes dramatically improved device performance and stability depending upon the electrode combination forming hybrid energy devices. We attribute the observed efficient performance of these hybrid devices induced by hybridized and emergent redox chemistries of merged electrode materials and dynamical processes at the electrode-electrolyte interfaces (intrinsic electroactivity, optimized double-layer and quantum capacitance) which play multiple roles. These energy devices are commercially relevant due to their potential viability in future hybrid electric vehicles, smart electric grids, electrocatalytic fuel production, space (micro-satellites), and miniaturized flexible electronic and wearable biomedical devices.