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By virtue of high theoretical sodium storage capacities and low cost, FeP is a prospective anode material for sodium-ion batteries (SIBs). Nevertheless, poor cycling and rate performance greatly limit the application of FeP in practice. Herein, a facile template-engaged method is employed to synthesize copper and carbon-incorporated yolk-shelled FeP (denoted as YS-Cu-FeP@C) spheres. The copper is doped into FeP, while the carbon layer with N-doping is coated on the surface of yolk-shelled FeP spheres. Aided by the unique compositional and structural advantages, the as-synthesized YS-Cu-FeP@C spheres exhibit enhanced electrochemical performance for SIBs, including excellent rate capability (145 mAh g−1 at 10 A g−1) and remarkable long-term cycle performance (up to 900 cycles at 1 A g−1). This work provides a rational design and synthetic strategy to boost the sodium storage properties of metal phosphide-based electrode materials. • A template method is developed to synthesize copper and carbon-incorporated yolk-shelled FeP spheres. • The copper is doped into FeP, while the carbon layer with N-doping is coated on the surface. • Excellent rate capability (145 mAh g−1 at 10 A g−1) and remarkable long-term cycle performance is demonstrated. [ABSTRACT FROM AUTHOR]

By virtue of high theoretical sodium storage capacities and low cost, FeP is a prospective anode material for sodium-ion batteries (SIBs). Nevertheless, poor cycling and rate performance greatly limit the application of FeP in practice. Herein, a facile template-engaged method is employed to synthesize copper and carbon-incorporated yolk-shelled FeP (denoted as YS-Cu-FeP@C) spheres. The copper is doped into FeP, while the carbon layer with N-doping is coated on the surface of yolk-shelled FeP spheres. Aided by the unique compositional and structural advantages, the as-synthesized YS-Cu-FeP@C spheres exhibit enhanced electrochemical performance for SIBs, including excellent rate capability (145 mAh g−1 at 10 A g−1) and remarkable long-term cycle performance (up to 900 cycles at 1 A g−1). This work provides a rational design and synthetic strategy to boost the sodium storage properties of metal phosphide-based electrode materials. • A template method is developed to synthesize copper and carbon-incorporated yolk-shelled FeP spheres. • The copper is doped into FeP, while the carbon layer with N-doping is coated on the surface. • Excellent rate capability (145 mAh g−1 at 10 A g−1) and remarkable long-term cycle performance is demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • The few-layer defective δ-MnO 2 was developed by hydrothermal with CTAB and KMnO 4. • As the current increases by 50-fold, δ-MnO 2 -CTAB shows ultra-high rate-capability. • The kinetics diffusion mechanism of the sample was analyzed by DFT calculations. δ-MnO 2 nanosheets are promising cathode candidates for supercapacitors because of their cost-effective, environmental protection, and high theoretical capacity. Unfortunately, the commercial application of δ-MnO 2 is hindered by the challenging issues of sluggish diffusion kinetic and poor rate-capability. It is urgent to optimize its kinetics behavior to improve the ion diffusion ability and electronic conductivity. Herein, one-step and one-phase synthesis of few-layer defective δ-MnO 2 nanosheets (named δ-MnO 2 -CTAB) has been developed via a redox reaction between cetyltrimethylammonium bromide (CTAB) and KMnO 4 , and the kinetics storage mechanisms are investigated by DFT calculations. The migration barrier energies of Na in the surface or interlayer of δ-MnO 2 (0 0 1) are reduced significantly with the reduction of layer-number (0.32 eV of 3 layers and 0.04 eV of 2 layers), which is conducive to the Na ion diffusion. Moreover, the generation of defects increases the density of states at the Fermi level of δ-MnO 2 , indicating the improvement of electronic conductivity. Therefore, when the current density is increased 50-fold (1 A g−1 to 50 A g−1), the rate-capability of δ-MnO 2 -CTAB is as high as 77%, exhibiting ultra-high rate-capability. This work unveils the kinetics storage mechanisms in few-layer δ-MnO 2 with defects nanosheets for ultra-high rate-capability supercapacitors. [ABSTRACT FROM AUTHOR]