Preparation of Lithium Titanate/Reduced Graphene Oxide Composites with Three-Dimensional "Fishnet-Like" Conductive Structure via a Gas-Foaming Method for High-Rate Lithium-Ion Batteries

Zinc-Bismuth Binary Alloy Enabling High-Performance Aqueous Zinc Ion Batteries

Reconfiguration of zinc anodes efficiently mitigates dendrite formation and undesirable side reactions, thus favoring the long-term cycling performance of aqueous zinc ion batteries (AZIBs). This study synthesizes a Zn@Bi alloy anode (Zn@Bi) using the fusion method, and find that the anode surfaces synthesized using this method have an extremely high percentage of Zn(002) crystalline surfaces. Experimental results indicate that the addition of bismuth inhibits the hydrogen evolution reaction and corrosion of zinc anodes. The finite-element simulation results indicate that Zn@Bi can effectively achieve a uniform anodic electric field, thereby regulating the homogeneous depositions of zinc ions and reducing the production of Zn dendrite. Theoretical calculations reveal that the incorporation of Bi favors the anode structure stabilization and higher adsorption energy of Zn@Bi corresponds to better Zn deposition kinetics. The Zn@Bi//Zn@Bi symmetric cell demonstrates an extended cycle life of 1000 h. Furthermore, when pairing Zn@Bi with an α-MnO2 cathode to construct a Zn@Bi//MnO2 cell, a specific capacity of 119.3 mAh g-1 is maintained even after 1700 cycles at 1.2 A g-1 . This study sheds light on the development of dendrite-free anodes for advanced AZIBs.

K2Ti6O13 Nanoparticle-Loaded Porous rGO Crumples for Supercapacitors

One-dimensional alkali metal titanates containing potassium, sodium, and lithium are of great concern owing to their high ion mobility and high specific surface area. When those titanates are combined with conductive materials such as graphene, carbon nanotube, and carbon nanofiber, they are able to be employed as efficient electrode materials for supercapacitors. Potassium hexa-titanate (K₂Ti₆O₁₃, KTO), in particular, has shown superior electrochemical properties compared to other alkali metal titanates because of their large lattice parameters induced by the large radius of potassium ions. Here, we present porous rGO crumples (PGC) decorated with KTO nanoparticles (NPs) for application to supercapacitors. The KTO NP/PGC composites were synthesized by aerosol spray pyrolysis and post-heat treatment. KTO NPs less than 10 nm in diameter were loaded onto PGCs ranging from 3 to 5 µm. Enhanced porous structure of the composites was obtained by the activation of rGO by adding an excessive amount of KOH to the composites. The KTO NP/PGC composite electrodes fabricated at the GO/KOH/TiO₂ ratio of 1:3:0.25 showed the highest performance (275 F g^-1) in capacitance with different KOH concentrations and cycling stability (83%) after 2000 cycles at a current density of 1 A g^-1.

Three-Dimensional and Mesopore-Oriented Graphene Conductive Framework Anchored with Nano-Li4Ti5O12 Particles as an Ultrahigh Rate Anode for Lithium-Ion Batteries

Because of the disadvantages of commercial graphite anodes for high-power lithium-ion batteries, a kind of spinel nanolithium titanate (Li₄Ti₅O₁₂)/graphene microsphere composite [denoted as LTO/reduced graphene oxide (rGO)] is successfully synthesized. The as-prepared composite is made up of curled graphene sheets which are anchored with nano-Li₄Ti₅O₁₂ particles. These nano-Li₄Ti₅O₁₂ particles are uniformly decorated on the conductive graphene framework and their sizes range from just 15 to 20 nm. In the as-prepared composite, the curled graphene sheets form a unique mesopore-oriented structure which provides plenty of three-dimensional channels for ion transportation. These structure characters greatly improve both the electron conductivity and Li⁺ diffusion ability. The ratio of pseudocapacitive capacity dramatically increases in the obtained LTO/rGO composite and generates excellent ultrahigh rate performances. The as-prepared LTO/rGO composite delivers a reversible capacity of 70.3 mA h g^-1 at 200 C and a capacity retention of 84.7% after 1000 cycles at 50 C. As the current density varies from 30 to 100 C, the special capacity remains unchanged (about 112 mA h g^-1). These results show that the graphene framework-supported nano-Li₄Ti₅O₁₂ composite has potential application in high-power lithium-ion batteries.