Ultrastable Bioderived Organic Anode Induced by Synergistic Coupling of Binder/Carbon-Network for Advanced Potassium-Ion Storage.

Bioderived molecules have been identified as viable anodes for organic potassium-ion batteries (OPIBs) due to the abundance of the necessary natural resources, their high capacity, and their sustainability. However, the high solubility and the inherent nonconductivity cause serious capacity decay and large voltage hysteresis. Here, the biomass molecule juglone was cross-linked with a carbon nanotube network, coupling and cooperating with sodium alginate binder (J@CNT-SA), and was proposed to inhibit small molecule dissolution via weak intermolecular interactions. The synergistic effect of hydrogen bonding and π-π stacking is proven for its outstanding reversible high capacities (262 mA h g-1 at 0.05 A g-1), and a remarkable long life span with capacity retention of 77% over 5000 cycles. Further in situ Fourier transform infrared spectroscopy (FTIR) was performed to reveal the electrochemical mechanism. The feasibility of juglone as an anode for PIBs paves the way for other natural organic small molecules to be investigated as potential energy storage materials.

Understanding the Effect of Interplanar Space and Preintercalated Cations of Vanadate Cathode Materials on Potassium-Ion Battery Performance.

Nonaqueous potassium-ion batteries (KIBs) have been regarded as a promising alternative energy system to lithium-ion batteries, due to the abundance of the K resource and unique electrochemical properties. However, exploring suitable KIB cathode materials remains a great challenge, owing to the much larger size of the K ion than that of the Li ion. Here, a series of layered vanadates have been developed as cathodes for KIBs to elucidate the key factors that determine the electrochemical performance of KIBs, including the interlayer distance between adjacent (100) planes (d100) and preintercalated cations. Compared to NH4V3O8 nanowires with a d100 of 7.80 Å, (NH4)0.5V2O5 nanowires with a wider d100 of 9.52 Å show a faster K+ diffusion and much higher reversible capacity. The preintercalation of potassium ions into V-O slabs is also crucial to the stability of the structure of vanadates, which leads to better electrochemical cycling stability in K0.5V2O5 than that in (NH4)0.5V2O5 and NH4V3O8 nanowires. These findings reveal the great potential of the vanadate cathode in future KIBs and provide a new direction to rationally design a stable layered intercalation compound for practical KIBs.