Abstract
N-doped Li_4Ti_5O_(12) anode materials are successfully fabricated by a facile and green atmospheric pressure Ar/N_2 binary plasma irradiation. The atmospheric pressure plasma surface modification can play a multi-functions role on different anode materials. Sufficient oxygen vacancies have been evidenced by high resolution X-ray photoelectron spectroscopy analysis and Raman spectra after plasma treatment.Nitrogen doping has also been achieved simultaneously by the surface reaction between pristine Li_4Ti_5O_(12) particles, owing to chemically reactive plasma species, such as N~* and N_2~+. The variety of Li_4Ti_5O_(12) particles on the surface of electrodes after different plasma processing time has been examined by grazing incident X-Ray diffraction.Electrochemical impedance spectra(EIS) confirm that the Ar/N_2atmospheric plasma treatment facilitates Li~+ ions diffusion and reduces the internal charge-transfer resistance. The as-prepared Li_4Ti_5O_(12) anodes exhibit a superior capacity(132mAh g~(-1)) and excellent stability with almost no capacity decay over 100 cycles under a high C rate(10C). Furthermore, Nano-scale carbon overlayers, with and without Ar/N_2 binary APP surface modification,have been investigated as surface passivation layers to enhance the rate capability and cycling stability of Li_4Ti_5O_(12). As indicated by optical emission spectroscopy, Raman spectra and high resolution X-ray photoelectron spectroscopy analysis,the nitrogen successfully dopes into the carbon overlayer by Ar/N_2 binary plasma irradiation, owing to the interaction between the carbon overlayer and chemically reactive plasma species such as N_2~+and N. In addition, the results of SEM and XPS depth profiles also prove that the N-doped carbon overlayer can effectively suppress the formation of a resistive solid-electrolyte-interface(SEI) film. The excellent chemical performance of Li4Ti5O_(12)-based anodes can be demonstrated, based on the concept of designing a conducting passivation layer. These findings enhance the understanding of the atmospheric plasma treatment on the potential application of Li_4Ti_5O_(12) anode material in Li-ion battery.