UC Riverside

Material Engineering at nanoscale as the practical application of nanoscience, makes useful materials, structures, devices, and systems. In the realm of electrochemical energy storage devices, nano-engineering enables novel active materials with enhanced capacity, conductivity, stability, scalability, and sustainability. In this thesis, synthesis of nano-engineered sulfur cathode, carbon nanotubes (CNTs), vanadium carbide (VC)-based MXene, and nanoporous silicon/MXene composite (Si/VC) have been developed. Potential applications in electrochemical energy storage devices including supercapacitors (SCs) and lithium-ion batteries (LIBs) have been demonstrated. To address the shuttle effect in sulfur batteries, a deposition of SnO2 thin films onto the cathodes of Li-S batteries was employed, which are made up of porous carbon and sulfur. This research demonstrates that the strong adsorption capacity of SnO2 for polysulfides can be harnessed to enhance battery performance. Consequently, the cathode coated with 5 nm of SnO2 (615.69 mAh/g) exhibited a specific capacity that was 45.19% greater than a control sample after 100 cycles at a 0.1C rate. When the charge and discharge rate was amplified by five times, the specific capacity of the 5 nm SnO2 coated cathode (604.93 mAh/g) was 157.32% greater than the uncoated one. A porous carbon foam infused with metal nanoparticles, synthesized from basic polysaccharides and metal salts, was utilized as a foundation for cultivating nano-structured carbons in multi-walled CNTs and multi-layer graphene. The products were employed to fabricate a hierarchical carbon foam that can serve as a SC and LIB active material. The SC showed a high specific capacity of 73.45 F/g when paired with K+ electrolyte. Stable cycling of 110 cycles were reached when the SC was paired with Li+ electrolyte. A scalable, environmentally friendly sol-gel synthesis method using renewable resources, such as saccharides and transition metal salts, is presented for the hydrothermal synthesis of vanadium carbides. Proof-of-concept SCs and LIBs were fabricated for both K+ and Li+. Furthermore, a composite consisting of nanoporous silicon and VC MXene was prepared. The composite anode with no other conductive additive showed a high initial capacity of 3000 mAh/g.