You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Self-assembly of mesoporous CuO nanosheets-CNT 3D-network composites for lithium-ion batteries. A facile, flexible and large-scale technique was proposed to prepare a CuO-CNT 3D-network composite with the aid of electrostatic interactions in aqueous solution. The composite greatly improves the electrochemical performance. At a rate of 0.1 C, the cycling discharge capacity of the optimal composite is more than 2.3 times of that of unmodified mesoporous CuO nanosheets as the active material in an anode after 40 cycles.
{"Chemical": ["CuO", "lithium"]}