An example of a negative electrode includes silicon nanoparticles having a carbon coating thereon. The carbon coating has an oxygen-free structure including pentagon rings. The negative electrode with the silicon nanoparticles having the carbon coating thereon may be incorporated into a lithium-based battery. In an example of a method, silicon nanoparticles are provided. A carbon precursor is applied on the silicon nanoparticles. The carbon precursor is an oxygen-free, fluorene-based polymer. Then the silicon nanoparticles are heated in an inert gas atmosphere to form the carbon coating on the silicon nanoparticles. The carbon coating formed on the silicon nanoparticles has an oxygen-free structure including pentagon rings.