Phase Stabilization of In₂Se₃ by Disordered Ni Intercalation and its Enhanced Thermoelectrical Performance

Van der Waals (vdW) layered materials have gained significant attention owing to their distinctive structure and unique properties. The weak interlayer bonding in vdW layered materials enables guest atom intercalation, allowing precise tuning of their physical and chemical properties. In this work, a ternary compound, Ni_xIn₂Se₃ (x = 0-0.3), with Ni randomly occupying the interlayers of In₂Se₃, is synthesized via an intercalation route driven by electron injection. The intercalated Ni atoms act as "anchor points" within the interlayer of In₂Se₃, which effectively suppresses the phase transition of In₂Se₃ at elevated temperatures. Furthermore, the disordered Ni intercalation significantly enhanced the electrical conductivity of In₂Se₃ through electron injection, while reducing the thermal conductivity due to the interlayer phonon scattering, leading to an improved thermoelectric performance. For instance, the thermoelectric figure of merit (ZT) of Ni_0.3In₂Se₃ increased by 86% (in-plane) and 222% (out-of-plane) compared to In₂Se₃ at 500 °C. These findings not only provide an effective strategy to enhance the performance of layered thermoelectric materials but also demonstrate the potential of intercalation chemistry for expanding the application scope of van der Waals (vdW) layered materials.