Dongyun Zhang

Thin-walled graphitic nanocages with nitrogen-doping as superior performance anodes for lithium-ion batteries

N-Doped nanocages with thin-walled graphitic shells (∼1.2 nm) were synthesized by removing the ferrous cores of Fe@C nanoparticles. The Fe@C nanopores were prepared by floating catalytic pyrolysis with the N atoms being in situ doped in their graphitic shells. Due to the thin-walled graphitic shells of the nanocages, the fast distribution of the electrolyte and ions was achieved and the prepared nanocage-based anode of lithium-ion batteries showed excellent performance: a high reversible specific capacity (after 50 cycles; 760 mA h g−1 at 0.5 A g−1) and a remarkable rate capability (after 40 cycles; 250 mA h g−1 at 10 A g−1).

Enhancing the rate performance of spherical LiFeBO3/C via Cr doping

Spherical LiFe1−xCrxBO3/C (x = 0, 0.005, 0.008) has been successfully synthesized by ball-milling and spray-drying assisted high-temperature solid-state reaction. The effect of Cr doping on LiFeBO3/C is characterized by XRD, energy-dispersive X-ray spectroscopy (EDS) and XPS. The results show that LiFe0.995Cr0.005BO3/C delivers the highest initial discharge specific capacity of 196.3 mA h g−1 at 0.1C and superior rate capability of 90 mA h g−1 at 5C. Moreover the material presents a cyclic retention of 95% after 50 cycles at 1C. Such improvement in the electrochemical performance can be attributed to the high electronic conductivities (4.75 × 10−5 S cm−1) and Li ion diffusion coefficients (9.20 × 10−13 cm2 s−1). The introduction of supervalent Cr3+ into the LiFeBO3 lattice produces Fe vacancies with accompanying conduction electrons, which lead to the enhanced electronic conductivity and Li ion diffusion coefficient.