ABSTRACT
The biomineralization process endows biominerals with unique hierarchically porous structures and physical-chemical properties by filling the restricted microreaction space with amorphous phases before the growth of inorganic crystals. In this paper, a confined-space fabrication method inspired by biomineralization for preparing hierarchically porous polyimide (PI) aerogels and PI-derived carbon aerogels is introduced. The confined structure is established through a self-assembly method of vacuum impregnation and ultrasound-assisted freeze-drying. The hierarchically porous structure is controlled by adjusting the structure characteristics of the confined space and secondary aerogels. Subsequently, a variety of performance demonstrations are conducted to demonstrate the mechanical properties and application prospects in the fields of thermal insulation and electromagnetic shielding of the prepared aerogel.
ABSTRACT
Designing an anchoring layer on the sulfur electrode has been considered one of the effective approaches to promoting the real application of room-temperature sodium-sulfur (RT-Na-S) batteries. In this work, based on the first-principles calculation method, the potential of pristine and doped borophosphene (BP) as anchoring materials for Na-S batteries has been investigated. The calculated adsorption energies of sodium polysulfides (NaPSs) adsorbed on pristine and doped substrates are higher than those of NaPSs adsorbed with the electrolytes (DOL&DME), indicating that the shuttle effect could be well alleviated. Meanwhile, the projected density of states (PDOS) suggests that the metallic characteristics of the adsorption systems are still well preserved, which is in favor of improving the electronic conductivity. More importantly, excellent electrocatalytic properties of the substrates are exhibited by reducing the catalytic decomposition energy barriers of Na2S, in which 0.27/0.79/1.02 eV is found on the pristine/N-doped/C-doped BP, indicating that the electrochemical processes could be improved smoothly. Therefore, it could be expected that pristine and doped BP are excellent anchoring materials for sodium-sulfur batteries.
ABSTRACT
Constructing heterostructures via the van der Waals coupling effect has provided an effective method for developing novel electrode materials. In this work, based on the first-principles calculation method, we proposed to construct a hexagonal SiC2/C3B heterostructure and confirmed its stability by analyzing its structural properties. Meanwhile, the electrochemical performances of the SiC2/C3B heterostructure as a new platform for lithium-ion batteries were evaluated. The calculated results illustrate that the pristine SiC2/C3B heterostructure is a semiconductor with a small bandgap of 0.15 eV and the lithiated heterostructure exhibits metallic properties which ensure superior electrical conductivity for fast electron transfer. Moreover, the low diffusion barriers of the heterostructure are acceptable to guarantee a high-rate performance for the batteries. Compared with the anode properties of isolated SiC2 and C3B monolayers, an enhancement of the storage capacity of Li ions on the SiC2/C3B heterostructure is observed, which could reach up to 1489.72 mA h g-1. In addition, the ab initio molecular dynamics simulations reveal that the SiC2/C3B heterostructure could maintain excellent structural stability during the lithiation processes even at a temperature of 350 K. All these encouraging results show that the SiC2/C3B heterostructure has fascinating potential to be an advanced platform for lithium-ion batteries.
ABSTRACT
With the increasing demand for sustainable and clean energies, seeking high-capacity density electrode materials applied in rechargeable metal-ion batteries is urgent. In this work, using first-principles calculations, we evaluate the ternary pentagonal BCN monolayer as a compelling anode material for metal ion batteries. Calculations show that the penta-BCN monolayer has favorable metallic behaviors after adsorbing Li (Na) atoms. More interestingly, the saturated adsorption systems provide a large storage capacity of 2183.12 (1455.41) mA h g-1 for Li (Na) ions. A low energy barrier of 0.14 (0.16) eV for Li (Na) diffusion is observed, being smaller than the reported other two-dimensional anode materials. Also, the wrinkled structure of penta-BCN has been demonstrated to be very beneficial to improve the energy density and cycle life of batteries. The calculated low open-circuit voltage and peculiar surface area expansion together with the thermal stability of saturated intercalation structures, further indicate that the penta-BCN monolayer has great potential as the anode material for Li (Na) ion batteries.
