A mild, configurable, flexible CoNi-LDH(v)/Zn battery based on H-vacancy-induced reversible Zn2+ intercalation

Flexible Zn-based batteries have attracted increasing research interest as essential components of wearable energy storage devices. However, the advancement of flexible aqueous Zn-based batteries based on Co-Ni layered double hydroxide (CoNi-LDH) as the cathode material is hampered by their poor cycling stability and the corrosiveness of alkaline electrolytes. Herein, CoNi-LDH nanosheets enriched with H vacancies (CoNi-LDH_(v)) were constructed on a flexible carbon cloth (CC) substrate via electrochemical deposition and activation. The Zn-based battery comprising CoNi-LDH_(v)@CC as the cathode exhibited highly reversible conversion reactions and stable operation in 3 M ZnSO₄ electrolyte (pH = 4). The battery delivered an excellent specific capacity (225 mA h g⁻¹, 0.26 mA h cm⁻²), acceptable cycling stability (53.9%, 900 cycles), and high discharging voltage. The abundant H vacancies served as active sites for the reversible intercalation of Zn²⁺ and the extravasation of NO₃⁻ generated channels and space for Zn²⁺ transport and storage, together enabling an excellent Zn²⁺ storage capacity. Furthermore, a sandwich-structured solid-state CoNi-LDH_(v)@CC//Zn@CC battery was fabricated and was found to exhibit a noteworthy electrochemical performance and mechanical durability. As a proof of concept, the unencapsulated battery powered a digital watch under various deformation conditions and operated stably for 80 h. Additionally, the flexible battery displayed outstanding customizability, maintaining an open-circuit voltage of 1.42 V even after being cut twice. The proposed engineering strategy contributes to the realization of textiles with truly wearable energy-storage devices.