ABSTRACT
Phosphates featuring a 3D framework offer a promising alternative to aqueous sodium-ion batteries, known for their safety, cost-effectiveness, scalability, high power density, and tolerance to mishandling. Nevertheless, they often suffer from poor reversible capacity stemming from limited redox couples. Herein, N-containing Na2VTi(PO4)3 is synthesized for aqueous sodium-ion storage through multi-electron redox reactions. It demonstrates a capacity of 155.2 mAh g-1 at 1 A g-1 (≈ 5.3 C) and delivers an ultrahigh specific energy of 55.9 Wh kg-1 in a symmetric aqueous sodium-ion battery. The results from in situ X-ray diffraction analysis, ex situ X-ray photoelectron spectroscopy analysis, and first-principle calculations provide insights into the local chemical environment of sodium ions, the mechanisms underlying capacity decay during cycling, and the dynamics of ion and electron transfer at various states of charge. This understanding will contribute to the advancement of electrode materials for aqueous sodium-ion batteries.
ABSTRACT
Adsorbents, especially those with high removal efficiency, long life, and multi-purpose capabilities, are the most crucial components in an adsorption system. By taking advantage of the liquid-like mobility and crystal-like ordering of liquid crystal materials, a liquid crystal induction method is developed and applied to construct three-dimensional graphene-based adsorbents featuring excellent shape adaptability, a distinctive pore structure, and abundant surface functional groups. When the monoliths are used for water restoration, the large amount of residual oxygen-containing groups is more susceptible to electrophilic attack, thus contributing to cation adsorption (up to 705.4 mg g-1 for methylene blue), while the connected microvoids between the aligned graphene oxide sheets facilitate mass transfer, e.g., the high adsorption capacity for organic pollutants (196.2 g g-1 for ethylene glycol) and the high evaporation rate for water (4.01 kg m-2 h-1). This work gives a practical method for producing high-performance graphene-based functional materials for those applications that are sensitive to surface and mass transfer properties.
