Ion intercalation is an effective strategy for improving the cycle stability and rate performance of δ-MnO₂ as a cathode material for aqueous zinc-ion batteries. However, in practice, ion selection appears rather arbitrary. In this work, Cu²⁺ was chosen for δ-MnO₂ intercalation because although Cu²⁺ and Zn²⁺ have similar diameters, Cu²⁺ has a slightly higher electronegativity (1.359) than Zn²⁺ (1.347). Therefore, Cu²⁺ has a stronger interaction with the MnO₂ lattice than Zn²⁺ and can be stable during the intercalation/deintercalation of Zn²⁺ and H⁺. Results showed that the performance of Cu-doped δ-MnO₂ (CMO) was greatly improved. Moreover, at the high current density of 2 A g⁻¹, CMO achieved excellent cycle stability with 100% capacity retention after 600 cycles, whereas pristine δ-MnO₂ exhibited only 23% capacity retention. When the current density was increased from 0.2 to 2.0 A g⁻¹, the CMO electrode also delivered remarkable rate performance with 72% capacity retention, which was considerably higher than the 32% capacity retention demonstrated by pristine δ-MnO₂. Given that Cu²⁺ has a greater electronegativity than Zn²⁺, the Cu-O bond formed in CMO acted as a stable structural column and greatly improved the stability of CMO. Cu²⁺ doping also increased the electronic conductivity and ionic conductivity of CMO and reduced the charge transfer resistance of H⁺ and Zn²⁺ at the electrode/electrolyte interface, which improved the rate performance of CMO greatly. This work provides new insights into intercalation strategies to improve the electrochemical performance of batteries.

离子嵌入是提高δ-MnO ₂作为水系锌离子电池正极材料循环稳定性和倍率性能的有效策略。然而，在实践中，离子选择显得相当随意。在这项工作中，选择 Cu ²⁺用于 δ-MnO ₂插层，因为尽管 Cu ²⁺和 Zn ²⁺具有相似的直径，但 Cu ²⁺的电负性 (1.359) 略高于 Zn ²⁺ (1.347)。因此，Cu ²⁺与MnO ₂晶格的相互作用比Zn ^{2+强，在Zn 2+}和H的嵌入/脱嵌过程中可以保持稳定⁺。结果表明，Cu掺杂的δ-MnO ₂ (CMO)的性能得到了极大的改善。此外，在 2 A g ^-1的高电流密度下，CMO 在 600 次循环后实现了出色的循环稳定性和 100% 的容量保持率，而原始的 δ-MnO ₂仅表现出 23% 的容量保持率。当电流密度从 0.2 增加到 2.0 A g ^-1时，CMO 电极还提供了显着的倍率性能和 72% 的容量保持率，这远高于原始 δ-MnO ₂所展示的 32% 的容量保持率。假设 Cu ^{2+比 Zn 2+}具有更大的电负性，CMO中形成的Cu-O键作为稳定的结构柱，大大提高了CMO的稳定性。Cu ²⁺掺杂还提高了CMO的电子电导率和离子电导率，降低了H ⁺和Zn ²⁺在电极/电解质界面的电荷转移电阻，大大提高了CMO的倍率性能。这项工作为提高电池电化学性能的插层策略提供了新的见解。