A graphene-like nanomaterial, carbon nano-fragments (CNFs), is obtained using the graphite anodes of spent lithium-ion batteries (LIBs) as carbon source, and its morphology, structure, functional groups, and reactivity are characterized to evaluate the properties and potential applications. The interlayer space increase, layer distortion, and remnant lithium of the waste lithium-intercalated graphite are utilized to prepare the oxidized CNFs (ox-CNFs) through a chemical oxidation and ultrasonic crushing process. These ox-CNFs exhibit a size distribution of 15nm to 2μm and excellent hydrophilicity, and disperse well in an aqueous suspension. Under the hydrothermal condition at 180°C for 12h, the ox-CNFs are converted into a suspension of reduced CNFs (re-CNFs), or a cylindrical aggregate when the concentration exceeds 2 mg·mL−1. The spectroscopic results demonstrate that there are abundant edges, defects, and functional groups existing on the CNFs, which affect their reactive, electronic, and electrochemical properties. Thereinto, the vacuum-dried ox-CNFs film can be converted from an insulator to a conductor after a chemical reduction by hydroiodic acid. And the re-CNFs modified glass carbon electrode (re-CNFs/GCE) exhibits enhanced electrocatalytic activity of about 8 times than the GCE to the oxidation reaction of dopamine. Furthermore, with the addition of the carboxylic ox-CNFs in aniline, the CNFs/polyaniline composite discharges a capacitance of 356.4 F·g−1 at 2 mV·s−1, an increase of 80.5% compared to the polyaniline. This preparation entails not only novel carbon nanomaterials but also an excellent disposal method of spent graphite, showing special significance in materials innovation and environmental science.