Preparation Of Nickel Oxide Composites With Adjustable Nitrogen And Carbon Doped Carbon Nanocene And Its Application In Negative Electrode Materials Of Lithium Ion Batteries

As an electrochemical energy storage device, lithium-ion batteries (LIBs), which show the high energy density of rechargeable batteries, long cycle life, high rate capability, and environment-friendly have been crucial for portable electronics, military industry, aerospace and other fields. Now the lithium-ion batteries (LIBs) can also be the power source for the most competitive system to supply power for future electric vehicles (EVs) and hybrid electric vehicle (HEV). However, the electrochemical performance of lithium-ion batteries, and the cycle safety cannot fully meet the current market demands. As an important part of the lithium-ion batteries, the anode material plays a key role to improve the performance of lithium batteries, address security issues of lithium-ion batteries. Nickel oxides (NiO) has attracted considerable attention for its good stability at high temperatures, low cost, and natural abundance and it has been widely used in catalysis, magnetic materials, and many other fields. NiO with higher theoretical capacities (718mAh g-1), easily to preparation and environmental friendliness have been widely studied as alternative anode materials for LIBs.This work reports the hydrothermal synthesis of the N-doped carbon-coated NiO nanocrystals (N-C-NiO NCs) with tunable N/C ratios using the nitrogen-containing ionic liquids (ILs) as new carbon precursor, and studies the N-doped carbon layer composition-dependent performances of N-C-NiO NCs anode for LIBs. The N-C-NiO NCs with the N/C ratio of21.2%in the N-doped carbon layer show a high specific capacity of～710mA h g-1at a current rate of0.3C (this value is almost the same as the theoretical capacity of NiO (718mA h g-1). Compare with the normally pristine NiO nanoparticles the N-doped carbon-coated NiO nanocrystals show a high rate capability, good capacity retention upon cycling, and high current density, after50cycles still remained～690mA h g-1reversible specific capacity.Moreover, the electrochemical performances of the N-C-NiO NCs depend on the N/C ratios in the N-doped carbon layer and are enhanced with increasing of the N/C ratios. The improved electrochemical properties of the N-C-NiO NCs are mainly due to that the N-doped carbon coating can significantly enhance the electronic conductivity, effectively avoid the problems of cracking or pulverization of the NiO, and prevent the aggregation of the active materials upon cycling. All of these properties make this synthesized material a promising anode material for LIBs. Our effective and convenient approach can provide general approach toward the synthesis of other metal oxides coated with N-doped carbon layer.