Spontaneous Proton Chemistry Enables Ultralow‐temperature and Long‐life Aqueous Copper Metal Batteries

Abstract

Aqueous copper metal batteries with acidic electrolytes are regarded as promising candidates for low-temperature energy storage, benefiting from fast kinetics of protons and acid resistance of copper. Here, a Cu(BF 4 ) 2 electrolyte that spontaneously generates protons is developed for ultralow-temperature copper metal batteries. Systematic studies demonstrate that the hydrolysis of BF 4 À generates more protons, rendering the Cu(BF 4 ) 2 among the most effective aqueous electrolyte capable of breaking hydrogen bonds in water molecules. This electrolyte endows a polyaniline/Cu battery to deliver a short charging time of 21 s and a charge/discharge capability of up to 10 A g À 1 at À 30 °C, along with a high discharge specific capacity of 70 mAh g À 1 and a supercapacitor-comparable power density of 3000 W kg À 1 . Furthermore, it can exhibit a long and stable cycling lifespan over 10 000 cycles at À 50 °C and works well at À 70 °C. This work provides an opportunity for intrinsically acidic electrolytes.

Aqueous copper batteries for future energy storage

“…(c) 铜电极和锌电极的性能差别; (d) Cu-PANI电池示意图 [61] Figure 5 (Color online) Some typical copper anode batteries. (a) Schematic diagram of in situ generation of MnO2 on carbon cloth [58] ; (b) utilizing Fe 3+ /Fe 2+ to suppress the disproportionation reaction of Mn 3+ [59] ; (c) performance differences between copper and zinc electrodes; schematic diagram of a Cu-PANI battery [61] 除金属氧化物外，正极材料还可选用普鲁士蓝类似物 [62] ，该类似物具有空腔结构，可实现铜离子嵌入与 脱出，并且溶液中的大量铜离子可以缓解酸性电解液中普鲁士蓝类似物过渡金属离子的溶出，但是高成本对 大规模储能不利.…”

“…当然，一些导电聚合物也可以作为铜电池的正极材料. 如图5(c，d)所示，Cu-PANI(聚苯 胺)电池配合Cu(BF 4 ) 2 电解质的使用能够展现出卓越的低温表现，并拥有高功率密度、高能量密度等特点，能 在特殊环境下达到稳定工作 [61] . 也可通过铜电池与氢能源相结合来达到可再生能源充分利用的目的 [63] ，该设 计为电网能量存储与转化提供了一种新的思路，显示出铜电池应用于可再生能源中的潜能.…”

Electrolyte and Electrode–Electrolyte Interface for Proton Batteries: Insights and Challenges

“…The introduced hydrogen bond acceptor can compete with the oxygen in water molecules, disrupting the original hydrogen bonding network between water, and effectively lowering the freezing point of the aqueous solution. [55][56] The freezing point of 2 M HBF 4 + 2 M Mn(BF 4 ) 2 aqueous electrolyte is lower than À 160 °C, and the ionic conductivity reaches 0.21 mS cm À 1 at À 70 °C. The addition of Mn(BF 4 ) 2 is intended to suppress the precipitation of Mn 2 + in the electrode material.…”