Unraveling the energy storage mechanism in graphene-based nonaqueous electrochemical capacitors by gap-enhanced Raman spectroscopy oleh Xiao-Ting Yin, En-Ming You, Ru-Yu Zhou, Li-Hong Zhu, Wei-Wei Wang, Kai-Xuan Li, De-Yin Wu, Yu Gu, Jian-Feng Li, Bing-Wei Mao, Jia-Wei Yan