Amorphous zinc–molybdenum–sulfide chalcogel as a long-cycle, high-capacity electrode for lithium-ion batteries

Abstract

The inherent limitations of intercalation-based electrodes in lithium-ion batteries have prompted the search for alternative materials with higher specific capacities and robust electrochemical stability. Sulfur-based electrodes, despite their high theoretical capacities (1672 mAh g⁻¹), typically suffer from poor cycling performance. In this work, zinc molybdenum polysulfide (Zn_xMo₃S₁₃, 0.5 ≤ x), an amorphous semiconductor chalcogel, exhibits high specific capacity and excellent cycling stability. Synchrotron X-ray pair distribution function and extended X-ray absorption fine structure analyses reveal a short-range atomic structure comprising Mo–Mo, M–S (M = Mo, Zn), and S–S bonding motifs. The coordination environment of Mo and S closely resembles that of Mo₃S₁₃ clusters, interconnected via S–S bridges and Zn²⁺ cations. The Li/Zn_xMo₃S₁₃ cell delivers an initial discharge capacity of 844 mAh g⁻¹ at C/3, and retains 386.2 mAh g⁻¹ after 1000 cycles with an average coulombic efficiency of 99.99%. The distribution of relaxation times analysis confirms the formation of a stable solid electrolyte interphase, which underpins the cell's long-term stability. This outstanding performance is attributed to the synergistic effects of the chalcogel's unique amorphous framework, semiconductive character, Zn-mediated polysulfide anchoring, and structural resilience, positioning Zn_xMo₃S₁₃ chalcogel among the most durable pure metal sulfide cathodes reported for next-generation LIBs.