This paper presents the lithium insertion into carbon-rich polymer-derived silicon carbonitride (SiCN) ceramic synthesized by the thermal treatment of poly(diphenylsilylcarbodiimide) at three temperatures, namely 1100, 1300, and 1700°C under 0.1MPa Ar atmosphere. At lower synthesis temperatures, the material is X-ray amorphous, while at 1700°C, the SiCN ceramic partially crystallizes. Anode materials prepared from these carbon-rich SiCN ceramics without any fillers and conducting additives were characterized using cyclic voltammetry and chronopotentiometric charging/discharging. We found that the studied silicon carbonitride ceramics demonstrate a promising electrochemical behavior during lithium insertion/extraction in terms of capacity and cycling stability. The sample synthesized at 1300°C exhibits a reversible capacity of 392mAhg−1. Our study confirms that carbon-rich SiCN phases are electrochemically active materials in terms of Li inter- and deintercalation.