Gel polymer electrolyte with MXene to extend cycle lifespan of flexible and rechargeable Zinc–Air batteries

Zinc–Air Batteries with an Efficient and Stable MnCo2O4/Carbon Fiber Bifunctional Electrocatalyst and a Poly(acrylic Acid)-Based Gel Electrolyte

“…For example, the work by Wang et al 42 reported a maximum power output of 231 mW cm −2 for a ZAB with an aqueous alkaline electrolyte, however, this cell had a stable charge/discharge performance for only 25 h. The use of micron-scale CFs in this work generated a porous 3D design for the air electrode with a maximum power output of 240 mW cm −2 and stable cycling behavior. This power output is rare for ZABs and the cycling behavior of MnCo 2 O 4 / CF-Hydrogel-30-mM was the same or better than the batteries (with GPEs) reported by Roy et al, 31 Tang et al, 43 Miao et al, 30 Chen et al, 29 Ramakrishnan et al, 44 Muthurasu et al 45 and Chen et al, 46 even though those studies used lower current densities and/or shorter cycling durations for battery cycle testing. For example, the batteries reported by He et al 47 and Tran et al, 48 using PAA as the GPE, have relatively high maximum power densities of 158 and 146 mW cm −2 , respectively.…”

“…In 2015, Fu et al 27 and Xu et al 28 introduced flexible ZABs with PVA-based alkaline electrolytes, which suffered from poor cycling stability even at current densities as low as 0.01−0.1 mA cm −2 . Chen et al 29 investigated the extension of the cycle life of ZABs with PVA-based electrolytes. The best performing cell could be cycled for 160 h, but the current density utilized for cycling was only 2 mA cm −2 and the maximum power density delivered by the cell was ∼70 mW cm −2 .…”

Challenges for large scale applications of rechargeable Zn–air batteries

“…46 Compared with the traditional liquid-state electrolytes, their excellent mechanical properties and safety and exible characteristics lay a foundation for the research and development of exible batteries. [47][48][49] The mainstream trend is to use a solid gel or solid anhydrous membrane [50][51][52][53][54][55][56][57] as the carrier to absorb enough liquid electrolyte or adding ionic groups for cell reactions directly during synthesis to achieve the effect of solid-state electrolytes.…”

“…Karaman et al 52 produced a PVA-KOH-H 2 O gel doped with functionalized carbon nanotubes and graphene oxide, and the ionic conductivity was signicantly improved and reached 69 mS cm À1 , and a signicant enhancement in the gel mechanical properties was also observed such as the Young's modulus (E ¼ 2.3) and tensile strength (22.3 kPa). Chen et al 55 similarly functionalized a gel electrolyte with MXene and achieved an ionic conductivity of 77.6 mS cm À1 . Besides, some polymer anhydrous gels such as poly(vinylidene uoride) (PVDF), 59,60 propylene carbonate (PC), 61 and polydimethylsiloxane [62][63][64] are applied in Li-based batteries due to their special characteristics to work as a salt solvent and H 2 O could be isolated to avoid some related problems.…”

Current Understanding of the Wettability of MXenes

“…(The green/grey/yellow/red/ white balls represent Ti/C/F/O/H atoms.). Reproduced with permission [40]. Copyright 2022, Elsevier.…”