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Mo6S8 is regarded as a promising cathodematerial in rechargeable Mg batteries. Despite extensive studies,some fundamental questions are still unclarified, including the originationof the chemical stability, key factors inducing the structural evolution,and the factors determining the electrochemical reversibility. HereinMo L2,3 and S K-edge X-ray absorption spectroscopy areutilized to uncover the underlying mechanism. Two kinds of S withdifferent effective charge are found, indicating the nonuniform chargedistribution. With one cation inserted, the charge distribution becomeshomogeneous, relevant to the chemical stability and electrochemicalreversibility. The structural evolution is attributed to the changeof bond length induced by the delocalization of inserted cations.Moreover, the evolution of intercluster Mo–Mo bond length canbe revealed by the drastic change of the S K pre-edge and is closelyrelated to the electrochemical reversibility. This study can shedlight on the aforementioned questions and guide the development ofMg cathode material.
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