One-step and efficient preparation of few-layer hydroxylated boron nitride nanosheets (OH-BNNSs) in electrochemical methods is still challenging. Here, we developed an electrolyte composed of a mixture of deep eutectic solvent (DES, choline chloride–urea) and water for electrochemical methods to enhance the exfoliation and oxidation processes, enabling the one–step preparation of OH-BNNSs. It was found that the obtained OH-BNNSs were an average lateral size of 625 nm and thickness of six layers. Furthermore, the OH-BNNSs and DES were added to the poly(vinyl alcohol) (PVA) substrate to prepare composite gel polymer electrolyte (PVA/DES/OH-BNNSs GPE) for solid–state flexible supercapacitor. The OH-BNNSs can effectively shorten the ionic transport distance and enhance ion conductivity. In addition, their excellent mechanical properties can significantly prevent the electrolyte structure from collapsing during reuse. In the meantime, DES was introduced to improve ionic conductivity and broaden the operating voltage window of supercapacitor. As a result, the symmetric solid–state flexible supercapacitor consisting of activated carbon electrodes and PVA/DES/OH-BNNSs GPE appeared a wide voltage window of 2.3 V, high specific capacitance of 151.22 F g^–1 at 0.1 A g^–1 and remained 98% capacitance after 1500 charge–discharge cycles. This study not only opened a new pathway to efficient exfoliation of insulating layered materials but also found a novel gel polymer electrolyte for solid–state flexible supercapacitors.

中文翻译：

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使用深共晶溶剂和水混合物作为电解质电化学制备用于固态柔性超级电容器的羟基化氮化硼纳米片

在电化学方法中一步有效地制备少层羟基化氮化硼纳米片（OH-BNNSs）仍然具有挑战性。在这里，我们开发了一种由深共晶溶剂（DES，氯化胆碱-尿素）和水的混合物组成的电解质，用于电化学方法以增强剥离和氧化过程，从而能够一步制备 OH-BNNS。发现所获得的 OH-BNNSs 的平均横向尺寸为 625 nm，厚度为 6 层。此外，将OH-BNNSs和DES添加到聚（乙烯醇）（PVA）基板中，制备用于固态柔性超级电容器的复合凝胶聚合物电解质（PVA/DES/OH-BNNSs GPE）。OH-BNNSs可以有效缩短离子传输距离，提高离子电导率。此外，它们优异的机械性能可以显着防止电解质结构在重复使用过程中坍塌。同时，引入DES以提高离子电导率并拓宽超级电容器的工作电压窗口。结果，由活性炭电极和 PVA/DES/OH-BNNSs GPE 组成的对称固态柔性超级电容器出现了 2.3 V 的宽电压窗口，151.22 F g 的高比电容^–1在 0.1 A g ^–1下，在 1500 次充放电循环后仍保持 98% 的电容。该研究不仅为绝缘层状材料的有效剥离开辟了一条新途径，而且还发现了一种用于固态柔性超级电容器的新型凝胶聚合物电解质。