Currently, the application of supercapacitors (SCs) in portable electronic devices and vehicles is limited by their low energy density. Developing high-energy density SCs without sacrificing their advantages, such as their long-term stability and high power density, has thus become an increasing demand but a major challenge. This demand has motivated tremendous efforts, especially towards discovering and optimizing the architecture of novel electrode materials. To this end, we herein report the design, synthesis, and SC application of a new family of two-dimensional (2D) nanoplatelets, i.e., a transition-metal hydroxymethylate complex (Ni_xCo_1–x(OH)(OCH₃)). Bimetallic nanoplatelets were synthesized via a cost-effective approach involving a one-step solvothermal procedure. We for the first time tuned the metal composition of these 2D nanoplatelets over the entire molar-fraction range (0–1.0). Tuning the molar ratio of Ni/Co allowed us to optimize the structures and physicochemical properties of the nanoplatelets for SC applications. When tested in a half cell, SC electrodes using the nanoplatelets exhibited high electrochemical performance with a specific capacitance as high as 1,415 F·g^–1 and a 96.1% retention of the initial capacitance over 5,000 cycles. We exploited the novel 2D nanoplatelets as cathode materials to assemble a hybrid SC for full-cell tests. The resulting SCs operated in a wide potential window of 0–1.7 V, exhibited a high energy density over 50 Wh·kg^–1, and sustained their performance over 10,000 charge–discharge cycles. The results suggest that the novel 2D nanoplatelets are promising alternative materials for the development of high-energy density SCs.

中文翻译：

---

新型的二维双金属纳米小片，用于高能量密度和电化学稳定的混合超级电容器

当前，超级电容器（SC）在便携式电子设备和车辆中的应用受到其低能量密度的限制。因此，在不牺牲其长期稳定性和高功率密度等优势的情况下开发高能量密度的SC成为了日益增长的需求，但也是一项重大挑战。这种需求激发了巨大的努力，特别是在发现和优化新型电极材料的结构方面。为此，我们在此报告了二维（2D）纳米片新家族的设计，合成和SC应用，即过渡金属羟甲基复合物（Ni _x Co _{1- x}（OH）（OCH ₃））。通过一种涉及一步溶剂热法的经济有效方法合成了双金属纳米片。我们首次在整个摩尔分数范围（0–1.0）范围内调整了这些2D纳米片的金属成分。调整Ni / Co的摩尔比可以使我们优化用于SC应用的纳米片的结构和理化性质。在半电池中测试时，使用纳米片的SC电极表现出高电化学性能，比电容高达1,415 F·g ^–1并在5,000个循环中保留了96.1％的初始电容。我们利用新型的2D纳米血小板作为阴极材料来组装用于全细胞测试的混合SC。所得的SC在0–1.7 V的宽电位窗口中工作，在50 Wh·kg ^–1的范围内表现出高能量密度，并在10,000次充放电循环中保持了其性能。结果表明，新型2D纳米血小板是开发高能量密度SC的有前途的替代材料。