Potassium-ion batteries (KIB) are a promising complementary technology to lithium-ion batteries because of the comparative abundance and affordability of potassium. Currently, the most promising KIB chemistry consists of a potassium manganese hexacyanoferrate (KMF) cathode, a Prussian blue analog, and a graphite anode (723 W h l^–1 and 359 W h kg^–1 at 3.6 V). No electrolyte has yet been formulated that is concurrently stable at the high operating potential of KMF (4.02 V vs K⁺/K) and compatible with K⁺ intercalation into graphite, currently the most critical hurdle to adoption. Here, we combine a KMF cathode and a graphite anode with a KFSI in Pyr_1,3FSI ionic liquid electrolyte for the first time and show unprecedented performance. We use high-throughput techniques to optimize the KMF morphology for operation in this electrolyte system, achieving 119 mA h g^–1 at 4 V vs K⁺/K and a Coulombic efficiency of >99.3%. In the same ionic liquid electrolyte, graphite shows excellent electrochemical performance and we demonstrate reversible cycling by operando X-ray diffraction. These results are a significant and essential step forward toward viable potassium-ion batteries.

中文翻译：

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利用离子液体电解质为高效，高能钾离子电池铺平道路

钾离子电池（KIB）是锂离子电池的有前途的补充技术，因为钾的含量相对较高且价格适中。当前，最有前途的KIB化学由六氰合铁酸钾锰（KMF）阴极，普鲁士蓝类似物和石墨阳极（在3.6 V下为723 W hl ^–1和359 W h kg ^–1）组成。目前还没有一种电解质能够在KMF的高工作电压下（4.02 V vs K ⁺ / K）同时稳定并且与K ⁺嵌入石墨中兼容，这是目前采用的最关键的障碍。在这里，我们在Pyr _1,3中结合了KMF阴极和石墨阳极以及KFSIFSI离子液体电解质首次展现出前所未有的性能。我们使用高通量技术优化了在该电解质系统中运行的KMF形态，在4 V vs K ⁺ / K时达到119 mA hg ^–1，库仑效率> 99.3％。在相同的离子液体电解质中，石墨显示出优异的电化学性能，并且我们通过操作X射线衍射证明了可逆循环。这些结果是朝着可行的钾离子电池迈出的重要而重要的一步。