RESUMEN
The practical implementation of aqueous zinc-ion batteries (AZIBs) encounters challenges such as dendrite growth, parasitic reactions, and severe decay in battery performance under harsh environments. Here, a novel hydrated eutectic electrolyte (HEE) composed of Zn(ClO4 )2 ·6H2 O, ethylene glycol (EG), and InCl3 solution is introduced to effectively extend the lifespan of AZIBs over a wide temperature range from -50 to 50 °C. Molecular dynamics simulations and spectroscopy analysis demonstrate that the H2 O molecules are confined within the liquid eutectic network through dual-interaction, involving coordination with Zn2+ and hydrogen bonding with EG, thus weakening the activity of free water and extending the electrochemical window. Importantly, cryo-transmission electron microscopy and spectroscopy techniques reveal that HEE in situ forms a zincophobic/zincophilic bilayer interphase by the dissociation-reduction of eutectic molecules. Specifically, the zincophilic interphase reduces the energy barrier for Zn nucleation, promoting uniform Zn deposition, while the zincophobic interphase prevents active water from contacting the Zn surface, thus inhibiting the side reactions. Furthermore, the relationships between the structural evolution of the liquid eutectic network and interfacial chemistry at electrode/electrolyte interphase are further discussed in this work. The scalability of this design strategy can bring benefits to AZIBs operating over a wide temperature range.
RESUMEN
Sustainable organic electrode materials, as promising alternatives to conventional inorganic electrode materials for sodium-ion batteries (SIBs), are still challenging to realize long-lifetime and high-rate batteries because of their poor conductivity, limited electroactivity, and severe dissolution. It is also urgent to deeply reveal their electrochemical mechanism and evolution processes. A porous organic polymer (POP) with a conjugated and hierarchical structure is designed and synthesized here. The unique molecule and structure endow the POP with electron delocalization, high ionic diffusivity, plentiful active sites, exceptional structure stability, and limited solubility in electrolytes. When evaluated as an anode for SIBs, the POP exhibits appealing electrochemical properties regarding reversible capacity, rate behaviors, and long-duration life. Importantly, using judiciously combined experiments and theoretical computation, including in situ transmission electron microscopy (TEM), and ex situ spectroscopy, we reveal the Na-storage mechanism and dynamic evolution processes of the POP, including 12-electron reaction process with Na, low volume expansion (125-106% vs the initial 100%), and stable composition and structure evolution during repeating sodiation/de-sodiation processes. This quantitative design for ultrafast and highly durable sodium storage in the POP could be of immediate benefit for the rational design of organic electrode materials with ideal electrochemical properties.
RESUMEN
Aqueous zinc-ion batteries (AZIBs) have attracted attention for their low cost and environmental friendliness. Unfortunately, commercialization has been hampered by several problems with dendrite growth and side reactions. Herein, we select sodium tartrate (TA-Na) as a dual-functional electrolyte additive to enhance the reversibility of AZIBs. The tartrate anions are preferentially adsorbed on the Zn surface, and then the highly nucleophilic carboxylate will coordinate with Zn2+ to promote the desolvation of [Zn(H2O)6]2+, leading to uniform Zn deposition on the beneficial (002) plane and inhibiting side reactions and dendrite growth. Consequently, the Zn|Zn cells show a long-term cycling stability of over 1500 cycles at 0.5 mA cm-2. Moreover, the Ta-Na additive improves the performance of Zn||MnO2 full cells, evidenced by a cycling life of 1000 cycles at 1 A g-1 under practical conditions with a limited Zn anode (negative/positive capacity ratio of 10/1) and controlled electrolyte (electrolyte/capacity ratio of 20 µL mAh-1).