Self-healing liquid metal confined in carbon nanofibers/carbon nanotubes paper as a free-standing anode for flexible lithium-ion batteries

Abstract

• Variation of Young's modulus of Ga in the process of discharge (lithiation) was measured. • Self-healing ability of EGaIn to automatic repair the cracks resulted from charge/discharge. • The CNF/CNT@EGaIn NPs anode is free-standing, flexible and binder-free. Gallium-based liquid metals are considered as potential anode materials for lithium-ion batteries owing to their self-healing, non-poisonous advantages, as well as high theoretical capacity. However, due to the alloying/dealloying reaction mechanism to store lithium, Gallium-based alloys face huge volume change resulted in poor cycle life. Furthermore, the poor wettability of liquid metals on many kinds of substrates (carbon materials, stainless steel, etc.) and their strong ability to form alloys with many metallic current collectors (Cu, Al foil) make them hard to be designed into electrode with excellent electrochemical performance. One objective of this paper is to investigate Young's modulus of Ga discharged to different cut-off potentials, in order to gain a further understanding of mechanical property attenuation of Ga in the process of lithiation. Moreover, a three-dimensional (3D) free-standing electrode is fabricated by confining Ga-based liquid metal, EGaIn, in the matrix of carbon nanofibers/carbon nanotubes paper (CNF/CNT@EGaIn NPs). The network structure provides effective pathways for electrons and ions, as well as enough space to contain the volume expansion of EGaIn. The dense CNT layer plays a further role on preventing EGaIn from shedding of the conductive substrates. Obtained CNF/CNT@EGaIn NPs exhibits a good ionic/electronic conductivity and mechanical stability, delivers capacity of 351 mAh g −1 at 1.6 A g −1 and remains a reversible capacity of ∼420 mAh g −1 after 100 cycles at 800 mA g −1 . This work could provide valuable insights into the development of Ga-based liquid metal anodes.