In situ construction of graded porous carbon matrix to strengthen structural stability of NiFe2O4 nanoparticles as high-capacity anodes of Li-ion batteries

Transition metal oxides are considered as promising anode materials of high-performance lithium-ion batteries because of their higher specific capacities than that of commercial graphite. However, they still suffer from huge volume expansion/contraction during cycling, leading to fast decay of the reversible capacity and poor cycle stability. In this work, a graded porous carbon matrix has been in situ constructed successfully to strengthen structural stability of NiFe 2 O 4 nanoparticles via a facile and green low-temperature combustion method. The calcination temperature has a significant effect on the purity and electrochemical performances of the final NiFe 2 O 4 /C composites. NiFe 2 O 4 /C prepared at 350 °C shows a high first discharge capacity of 1385.8 mAh g −1 at 200 mA g −1 , excellent cycle stability, and good rate capability. This excellent electrochemical performance may be attributed to its favorable graded porous structure. The carbon matrix can effectively protect the NiFe 2 O 4 nanoparticles, buffer the surface stress caused by volume expansion/contraction, and facilitate the transmission of electrons and Li + ions. The symbiotic relationship between NiFe 2 O 4 active nanoparticles and graded porous carbon matrix strengthens the structural stability of the electrode, which expands the way of designing high-performance electrode materials for secondary rechargeable batteries.