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Layered double hydroxides (LDH) have shown to improve the zinc electrodeposition efficiency at the negative electrode of aqueous zinc‐ion batteries. In this work, a copper‐doped Zn−Al−CO3 layered double hydroxide (LDH) has been synthesized by co‐precipitation method under constant pH, and investigated as suitable solid‐state additive in zinc‐based negative electrodes. X‐ray diffraction patterns in combination with scanning electron microscope images show that the as‐synthesized LDHs are well crystalline and hexagonal platelet‐like. LDH was mixed with zinc powder in different ratios and the electrochemical performances of the mixtures were characterized by galvanostatic cycling with potential limitation (GCPL) at different current rates. The results show that an appropriate combination of zinc and LDH can be used to reach electrodeposition efficiency equal to 98 %. Thereafter, the performance of this electrode in a full cell is studied. In such configuration, the electrode shows that the electrodeposition efficiency remains high even at high current rates, which is an important characteristic for grid‐scale energy storage.

The structural changes of copper hexacyanoferrate (CuHCF), a Prussian blue analogue, which occur when used as a cathode in an aqueous Zn‐ion battery, are investigated using electron microscopy techniques. The evolution of ZnxCu1−xHCF phases possessing wire and cubic morphologies from initial CuHCF nanoparticles are monitored after hundreds of cycles. Irreversible introduction of Zn ions to CuHCF is revealed locally using scanning transmission electron microscopy. A substitution mechanism is proposed to explain the increasing Zn content within the cathode material while simultaneously the Cu content is lowered during Zn‐ion battery cycling. The present study demonstrates that the irreversible introduction of Zn ions is responsible for the decreasing Zn ion capacity of the CuHCF cathode in high electrolyte concentration.

The reversible electrochemical insertion of zinc into host materials has been shown to be very promising for large‐scale energy storage applications. In particular, copper hexacyanoferrate (CuHCF) and its derivatives from the Prussian Blue family enable a fast and reversible (de‐)insertion of zinc ions when operated in a zinc‐based aqueous electrolyte. In this work, the effect of the concentration of a zinc sulfate‐containing aqueous neutral solution on the aging of CuHCF and copper‐zinc hexacyanoferrate mixture (CuZnHCF) was studied. The electrochemical and morphological analysis revealed the occurrence of a phase change during the materials aging. Such phase transformation induced morphological changes, different from the ones formed when the materials were cycled in lower electrolyte concentration. In the case of CuZnHCF, the occurrence of a spike‐shaped morphology upon cycling, which appears to be electrochemically inactive, caused a faster capacity fading.

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