Triboelectrification can occur between any two materials with different charge affinities. This phenomenon represents the fundamental physics of triboelectric nanogenerators (TENGs). Organic materials such as polymers have been widely used in TENGs because of their dielectric properties. Inorganic materials are, however, not widely studied despite the increasing attention paid to perovskite materials. In this paper, a new type of TENG has been fabricated based only on inorganic materials such as Mo6S3I6 and indium tin oxide (ITO). The output power density of the TENG operating in contact-separation mode reaches 18 W m−2. Mechanisms of the high output involve the unique semiconducting property of Mo6S3I6 and the unique chemical composition of ITO. The findings in this study indicate that inorganic materials can be used for fabricating high-output TENGs for energy harvesting.