Antifreezing Hydrogel with High Zinc Reversibility for Flexible and Durable Aqueous Batteries by Cooperative Hydrated Cations

Abstract

Hydrogels are widely used in flexible aqueous batteries due to their liquid-like ion transportation abilities and solid-like mechanical properties. Their potential applications in flexible and wearable electronics introduce a fundamental challenge: how to lower the freezing point of hydrogels to preserve these merits without sacrificing hydrogels' basic advantages in low cost and high safety. Moreover, zinc as an ideal anode in aqueous batteries suffers from low reversibility because of the formation of insulative byproducts, which is mainly caused by hydrogen evolution via extensive hydration of zinc ions. This, in principle, requires the suppression of hydration, which induces an undesirable increase in the freezing point of hydrogels. Here, it is demonstrated that cooperatively hydrated cations, zinc and lithium ions in hydrogels, are very effective in addressing the above challenges. This simple but unique hydrogel not only enables a 98% capacity retention upon cooling down to −20 °C from room temperature but also allows a near 100% capacity retention with >99.5% Coulombic efficiency over 500 cycles at −20 °C. In addition, the strengthened mechanical properties of the hydrogel under subzero temperatures result in excellent durability under various harsh deformations after the freezing process.

Fully integrated design of a stretchable kirigami-inspired micro-sized zinc–sulfur battery

“…3(e–h) at 25 °C expectedly showed lower capacity and energy density at lower temperatures. As confirmed in our recent study 36 and reported by another research group, 49 the decelerations of ion diffusion and kinetics of the reactions caused at lower temperatures are the key reasons for lower electrochemical performance. As shown in Fig.…”

Bottom‐Up Design of a Green and Transient Zinc‐Ion Battery with Ultralong Lifespan

“…The polarization profiles correspond to 1 mA cm −2 -1 mAh cm −2 symmetric Zn plating-stripping with ). [57] As shown in inset ii) of Figure 3a, the voltage-time trace maintains a steady and flat shape over the whole time interval, in agreement with a stable and smooth zinc depositiondissolution process. The demonstrated lifespan is superior to previously reported works which mainly involve nontransient strategies such as the use of petroleum-based gel electrolytes, [58] the use of strongly oxidizing, flammable, and hazardous electrolyte additives such as Zn(ClO 4 ) 2 , [59] or anodes bearing complex materials such as Ti 3 C 2 T x MXene.…”

Polyacrylic Acid‐Modified Gel Electrolytes for Enhanced Electrochemical Performance in Aqueous Zinc Batteries

“…Raman spectrum of the gel electrolyte without PAA reveals characteristic peaks at 1034, 2929 and 3300 cm À 1 attributed to the stretching vibrations of ether (À OÀ ) bonds, methylene group (À CH 2 ), and hydroxyl (OÀ H) or amine (À NH 2 ) groups, respectively (Figure 1c-d). [17][18] Additionally, a bending vibration peak of CÀ H was observed at 764 cm À 1 , further confirming the presence of À CH 2 À groups. While the ether bond stretching vibration peak of the PAA gel electrolyte slightly shifts to 1037 cm À 1 , indicating enhanced intermolecular interactions, particularly through the formation of additional hydrogen bonds due to the addition of PAA.…”