The lack of appropriate cathodes is restraining the advances of Mg batteries. Crystalline cathode materials suffer from sluggish reaction kinetics and low-capacity delivery. The finite type of crystalline structure further confines the rational design of cathode materials. Herein, we proposed amorphization and anion enrichment as a brand-new strategy to not only enhance the solid-state ion diffusion and provide more ion-storage sites in amorphous structure but also contribute to the local transfer of multiple electrons through the additional anionic redox centers. Accordingly, a series of amorphous titanium polysulfides (a-TiS_x, x = 2, 3, and 4) were designed, which significantly outperformed their crystalline counterparts and achieved a highly competitive energy density of ∼260 Wh/kg. The unique Mg²⁺ storage mechanism involves the dissociation/formation of S–S bonds and changes in the coordination number of Ti, namely, a mixture of conversion and intercalation reaction, accompanied by the joint cationic (Ti) and anionic (S) redox-rich chemistry. Our proposed amorphous and redox-rich design philosophy might provide an innovative direction for developing high-performance cathode materials for multivalent-ion batteries.

中文翻译：

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用于镁阴极的无定形富氧化还原多硫化物

缺乏合适的正极限制了镁电池的发展。结晶正极材料的反应动力学缓慢且传输容量低。有限类型的晶体结构进一步限制了正极材料的合理设计。在此，我们提出了非晶化和阴离子富集作为一种全新的策略，不仅可以增强固态离子扩散并在非晶结构中提供更多的离子存储位点，还可以通过额外的阴离子氧化还原中心促进多个电子的局部转移. 因此，一系列非晶多硫化钛（a-TiS _x , x= 2、3 和 4) 的设计，其性能明显优于晶体对应物，并实现了极具竞争力的能量密度，约为 260 Wh/kg。独特的 Mg ²⁺存储机制涉及 S-S 键的解离/形成和 Ti 配位数的变化，即转化和嵌入反应的混合，伴随着联合的阳离子 (Ti) 和阴离子 (S) 氧化还原- 丰富的化学。我们提出的无定形和富含氧化还原的设计理念可能为开发用于多价离子电池的高性能正极材料提供创新方向。