Lithium-abundant electrides, characterized by the presence of interstitial anionic electrons, have attracted considerable attention owing to their extraordinary properties, including superconductivity. Here, we conduct comprehensive first-principles structure-prediction simulations to investigate the phase stability of lithium-platinum (Li-Pt) compounds under high-pressure conditions. Our calculations identify several hitherto unknown electride phases in the Li-Pt system, namely, $\mathrm{L}{\mathrm{i}}_4\mathrm{Pt}, \mathrm{L}{\mathrm{i}}_5\mathrm{Pt}, {\mathrm{Li}}_6\mathrm{Pt}, {\mathrm{Li}}_{11}\mathrm{Pt}$, and $\mathrm{L}{\mathrm{i}}_{12}\mathrm{Pt}$. Among the metallic phases uncovered, ${\mathrm{Li}}_6\mathrm{Pt}$ exhibits the highest superconducting critical temperature ($T_{\mathrm{c}}$), reaching 18 K at 120 GPa. Strikingly, $\mathrm{L}{\mathrm{i}}_{12}\mathrm{Pt}$, the phase with the highest lithium content, is unexpectedly predicted to be a semiconductor. We further clarify the fundamental criteria governing interstitial electron localization and establish systematic correlations between superconductivity and key electronic and vibrational descriptors, including the electronic density of states, electron-phonon coupling strength, and phonon softening across all predicted phases. These results substantially broaden the structural diversity of the Li-Pt system and underscore the intriguing coexistence of superconductivity and semiconducting behavior in lithium-based electride materials.

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• Chemical bonding
• Composition
• Density of states
• Electronic structure
• Electronic structure of atoms & molecules
• Phase transitions
• Pressure effects
• Structural properties
• Superconductivity
• First-principles calculations