Creatinine: A Muscle Metabolite as a Multifunctional Electrolyte Additive for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have demonstrated considerable potential for utilization in large-scale energy storage applications, driven by their environmental sustainability, inherent safety and cost-effectiveness. Nonetheless, the growth of Zn dendrites and side reactions, resulting in degraded cycling stability, poses a substantial obstacle to the practical implementation of AZIBs. Herein, it is demonstrated that creatinine (Cre), a metabolite derived from muscle, serves as a multifunctional electrolyte additive that enhances the performance of AZIBs. Both experimental and theoretical analyses reveal that Cre, when used as an electrolyte additive, fulfills three key roles: it disrupts the solvation structure of Zn²⁺ by carbonyl group; it forms a water-deficient electric double layer, thereby reducing the likelihood of interfacial water decomposition; and it promotes the deposition of Zn²⁺ on the (002) planes, facilitating the uniform deposition. The Zn||Zn symmetric cell utilizing a 1 M ZnSO₄ electrolyte with the addition of 0.3 M Cre exhibits stable cycling for 900 h under the condition of 1 mA cm^-2 and 1 mAh cm^-2, representing an over 11-fold increase in lifespan. Furthermore, the Zn||VO₂ full cell demonstrates a capacity retention of ≈105 mAh g^-1 after 300 cycles at a rate of 10 C.