The zinc bromine flow battery (ZBFB) is regarded as one of the most promising candidates for large-scale energy storage attributed to its high energy density and low cost. However, it suffers from low power density, primarily due to large internal resistances caused by the low conductivity of electrolyte and high polarization in the positive electrode. In this work, chloride based salts including KCl and NH₄Cl are investigated as supporting electrolyte to enhance electrolyte conductivity, while graphite-felt electrodes are thermally treated to improve electrocatalytic activity. It is found that the use of 4 M NH₄Cl as a supporting electrolyte enables the battery to be operated at a current density of 40 mA cm⁻² with an energy efficiency of 74.3%, whereas without the addition of a supporting electrolyte the battery only outputs an energy efficiency of 60.4%. In combination with a thermally treated graphite-felt electrode, efficiency further reaches up to 81.8% at the same current density. More impressively, we demonstrate that even at a high current density of up to 80 mA cm⁻², the battery is capable of delivering an energy efficiency of 70%, representing one of the highest performances of ZBFBs in the open literature.

中文翻译：

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通过改进电解质和电极设计的高性能溴化锌液流电池

溴化锌液流电池（ZBFB）因其高能量密度和低成本而被认为是最有希望用于大规模储能的电池之一。然而，其遭受低功率密度的困扰，这主要归因于由电解质的低电导率和正电极中的高极化引起的大内阻。在这项工作中，包括KCl和NH ₄ Cl在内的氯化物盐被研究用作支持电解质以增强电解质的导电性，同时对石墨毡电极进行热处理以提高电催化活性。发现使用4 M NH ₄ Cl作为支持电解质可以使电池在40 mA cm ^-2的电流密度下运行电池的能量效率为74.3％，而没有添加支持电解质，则电池的能量效率仅为60.4％。与经过热处理的石墨毡电极相结合，在相同的电流密度下，效率可进一步达到81.8％。更令人印象深刻的是，我们证明，即使在高达80 mA cm ^-2的高电流密度下，该电池也能够提供70％的能量效率，这是公开文献中ZBFB的最高性能之一。