期刊
ADVANCED FUNCTIONAL MATERIALS
卷 29, 期 34, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.201902822
关键词
alkali-ion batteries; finite element simulation; high gravimetric; volumetric capacity; hollow bowls; mesoporous
Hollow structures are often used to relieve the intrinsic strain on metal oxide electrodes in alkali-ion batteries. Nevertheless, one common drawback is that the large interior space leads to low volumetric energy density and inferior electric conductivity. Here, the von Mises stress distribution on a mesoporous hollow bowl (HB) is simulated via the finite element method, and the vital role of the porous HB structure on strain-relaxation behavior is confirmed. Then, N-doped-C coated mesoporous alpha-Fe2O3 HBs are designed and synthesized using a multistep soft/hard-templating strategy. The material has several advantages: (i) there is space to accommodate strains without sacrificing volumetric energy density, unlike with hollow spheres; (ii) the mesoporous hollow structure shortens ion diffusion lengths and allows for high-rate induced lithiation reactivation; and (iii) the N-doped carbon nanolayer can enhance conductivity. As an anode in lithium-ion batteries, the material exhibits a very high reversible capacity of 1452 mAh g(-1) at 0.1 A g(-1), excellent cycling stability of 1600 cycles (964 mAh g(-1) at 2 A g(-1)), and outstanding rate performance (609 mAh g(-1) at 8 A g(-1)). Notably, the volumetric specific capacity of composite electrode is 42% greater than that of hollow spheres. When used in potassium-ion batteries, the material also shows high capacity and cycle stability.
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