Abstract
Maximizing the fixing ability of polyselenides to reduce the shuttle effect in Li-Se batteries remains highly challenging. Single crystal metal-organic framework (MOF)-derived N-doped ordered hierarchically porous carbon (S-NOHPC) synthesized by a confined crystal growth and template-assisted method demonstrates excellent electrochemical performance as a host material for Li-Se battery. The large number of micropores inherited from the MOF structure provides large space and surface for Se loading and reaction sites, ensuring the high energy density of the battery. The in-situ X-ray diffraction (XRD) technique is used to understand the reaction mechanism. The synergy of the interconnected three-scale-level micro-meso-macroporous structure and N-doped polar sites can buffer the volume expansion, shorten the ion transportation with a very high diffusion coefficient of 4.44 × 10−10 cm2 s−1 and accelerate the lithiation/delithiation reaction. Selenium is sufficiently reactive and the polyselenide intermediates are tightly fixed inside the carbon host material, thereby achieving excellent specific capacity, stability, and rate capability. Such a cathode exhibits a very high 2nd discharge/charge capacity of 658 and 683 mA h g−1, respectively, and retains a very high capacity of 367 mA h g−1 after 200 cycles at the current of 0.2 C. Even at the high current of 5 C, a very high discharge capacity of 230 mA h g−1 is obtained. This work provides a new kind of high-performance porous materials with rational pore arrangement applicable for highly efficient energy storage.
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