2D Electrode Materials for Energy Storage

Abstract

Li ion/Na batteries has shown great promises in various energy related applications. The performance of these energy storage devices can improved with strategized design and preparation of the electrode materials. We carried out works on growth of 2D structured cathode/anode material, including LiMPO4 (M=Fe, Ni, Co, Mn) and MPO4, and few layered black phosphorus by wet chemical processes. This type of materials is typical thin sheet structure with thickness of 2-5 nm and show promising Li/Na storage properties. For Olivine-type LiMPO4 (M = Fe, Mn, Co, Ni), we develop a liquid-phase exfoliation approach combined with solvothermal lithiation process in high-pressure high-temperature (HPHT) supercritical fluids for the fabrication of ultrathin LiMPO4 nanosheets (thickness: 3.7-4.6 nm) with exposed (010) surface facets. The diffusion of Li along [010] direction is particularly tuned through the thickness of the nanosheet due to the crystal orientation, which fasten the diffusion process. [1] For MPO4, we prepared ultra-thin two-dimensional (2D) nanoflakes, including FePO4, Mn3(PO4)2 and Co3(PO4)2, with highly ordered mesoporous structures in non-polar solvent. It is found that the as-obtained nanoflakes with thickness of ~3.7 nm are constructed from a single layer of parallel-packed pore channels. When tested as cathodes for lithium ion battery, they exhibits excellent stability and high rate capabilities. [2]. We also synthesis of few layered black phosphorus nanosheets through diferent methods and study their Li/Na storage properties. Especially, we try to improve their chemical stability by forming composite structures with the aid of spark plasma sintering (SPS) process. It shows that excellent air stabilityof SPS-processed black phosphorus can be achieved over the 60 days observation in maintaining its high Li storage properties. [3]