Rechargeable magnesium batteries (rMBs) are regarded as an alternative to lithium-ion batteries but are hindered by low cycling stability and sluggish kinetics at present. Herein, we report a sandwich-structured CuS/hNCNC@rGO cathode for rMBs by immobilizing CuS nanoparticles on the hierarchical nitrogen-doped carbon nanocages (hNCNCs) followed by wrapping the reduced graphene oxide (rGO). The charge/discharge mechanism is established based on the unique mixed-valence CuS double-salt structure, i.e., Cu²⁺S₂²⁻⋅Cu⁺₂S²⁻, which was neglected in the previous studies of CuS-based rMBs. The cathode achieves a high reversible specific capacity of 285 mAh g⁻¹ at 100 mA g⁻¹, an outstanding rate capability of 158 mAh g⁻¹ at 1,000 mA g⁻¹, and ultralong cycling stability at room temperature, superior to most reported cathode materials to date. This study provides a fundamental understanding on the Mg storage mechanism of CuS and suggests a promising strategy for constructing high-performance conversion-type cathodes for rMBs.

可充电镁电池（rMB）被认为是锂离子电池的替代品，但目前受到循环稳定性低和动力学缓慢的阻碍。在此，我们通过将 CuS 纳米颗粒固定在分层氮掺杂碳纳米笼（hNCNC）上，然后包裹还原氧化石墨烯（rGO），报道了用于 rMB 的夹层结构 CuS/hNCNC@rGO 阴极。充放电机制是基于独特的混合价CuS双盐结构，即Cu ²⁺ S ₂ ^{2 −} ⋅Cu ⁺ ₂ S ²⁻建立的，该结构在之前的CuS基rMBs研究中被忽略。该正极在100 mA g ^{-1下实现了285 mAh g -1}的高可逆比容量，在1,000 mA g ^{-1下具有158 mAh g -1}的出色倍率性能，以及室温下的超长循环稳定性，优于大多数报道的迄今为止的正极材料。这项研究提供了对 CuS 的镁储存机制的基本了解，并提出了构建高性能 rMB 转换型阴极的有前景的策略。