Structural Lithium-Ion Battery Cathodes and Anodes Based on Branched Aramid Nanofibers

High Electrochemical Capacity MnO2/Graphene Hybrid Fibers Based on Crystalline Regulatable MnO2 for Wearable Supercapacitors

Fiber-based supercapacitors (FSCs) exhibit desirable application potential and development prospects in wearable energy storage devices because of their flexibility and wearability. However, the low capacity in the unit volume and insufficient fiber strength hinder their further development in practical application. Herein, the MnO2 nanomaterials with regulatable crystalline structure were synthesized by one-step hydrothermal strategy. The formation of the MnO2 crystalline structure involved the "crimp-phase transition" process. Among them, the 2 × 2 tunnel type α-MnO2 nanowires exhibited excellent electrochemical capacitance (43.8 F g-1), high rate performance (61%, 0.25 to 6 A g-1), and remarkable cyclic stability (99%), which can be attributed to their good symmetry in space and high shared vertices proportion. On this basis, the α-MnO2 nanowires were coblended with GO to construct MnO2/rGO hybrid fibers by scalable continuous wet spinning and in situ acid reduction. Noteworthily, in MnO2/rGO hybrid fibers, the doping amount of MnO2 nanowires as high as 50 wt % could be achieved, while the strength reached 11.73 MPa, which can be ascribed to the superior surface morphology of MnO2 nanowires and the unique cement wall structure of hybrid fibers. Finally, the obtained hybrid fiber electrodes were assembled into symmetrical FSCs. Notably, the FSCs delivered remarkable volume specific capacitance (129.5 F cm-3) and impressive energy density (18 mWh cm-3) at 1.75 A cm-3. In addition, the assembled all-solid-state FSCs indicated excellent deformability and application potential. This work offers some insight for promoting the continuous preparation of fiber electrodes, the development of FSCs, and practical application in wearable energy textile.

Reducing volume expansion in micro silicon anodes via aramid nanofibers for stable lithium-ion batteries

The aramid nanofibers form networks on micro silicon particles (ANF-SMPs) by cryofixation and acid-induced protonation, whose zongzi-like wrapping structure reduces volume expansion during (de)lithiation. The obtained ANF-SMP electrode achieves a high capacity retention of 90.7% after 100 cycles at 0.5C, which maps a promising future for anodes with a long lifespan.

Fabrication of VO Nanorings on a Porous Carbon Architecture for High-Performance Li-Ion Batteries

Vanadium monoxide (VO) is a promising candidate as an anode for lithium-ion batteries due to its high theoretical capacity, low cost, and considerable electronic conductivity. Unfortunately, a large volume change during electrochemical processes obstructs its practical application. In this work, a composite of VO nanorings grown on a porous carbon architecture is prepared via a topochemical self-reduction approach. When used as an anode for lithium-ion batteries, improved redox kinetics from enhanced electronic conduction and the corresponding fast lithium-ion diffusion is observed to greatly promote the electrochemical performance of lithium-ion batteries. The resulting composite delivered a reversible capacity of 336 mA h g^-1 after 400 cycles at 10 A g^-1 with a capacity retention of 85%, owing to the synergistic effect of VO nanorings and porous carbon in alleviating volume changes that result in a long-term cycling ability at a high current density. At 20 A g^-1, the composite anode exhibited a rate capability of 235 mA h g^-1, superior to all VO-based electrodes reported in the literature. Furthermore, a full cell was first fabricated by employing VO@C-2 as the anode and LiFePO₄ as the cathode, which exhibited a capacity of 213 mA h g^-1 after 100 cycles at 0.1 A g^-1, indicating the potential of VO as an anode for practical application.