Colloidal Hot‐Injection Synthesis of CuBSe₂ Nanocrystals: Tetragonal Chalcogenide Templates for Superionic Lithiation Pathways

Copper boron selenides represent a previously unexplored class of materials with tetragonal structural symmetries and bonding chemistries potentially relevant to lithium‐ion conduction. In this work, the first colloidal synthesis of nanocrystalline copper boron selenides is reported, enabling access to nanocrystals with reaction times shown as the synthetic knob to control composition and morphology. Copper boron selenide nanocrystals are synthetically designed as precursors for lithiation reactions aimed at probing structural evolution and ionic mobility pathways toward superionic conductors applicable as solid electrolytes in lithium‐ion batteries. Postsynthetic lithiation studies under ambient conditions reveal a series of phase transformations and morphological changes, which are characterized using a combination of X‐ray diffraction and high‐resolution transmission electron microscopy analysis. Thermometric and differential scanning calorimetry analyses on both copper boron selenide nanocrystals and their lithiated counterparts further uncover the associated signatures of superionic phase changes with lithium incorporation, suggesting dynamic structural rearrangements, and potential onset of fast ion transport. This study highlights colloidal synthesis as a powerful route to explore new composition spaces in complex chalcogenides and establishes copper boron selenides as a platform for investigating structure–transport relationships in emerging solid‐state electrolyte chemistries.