Constructing durable ultra-high loading and areal capacity lithium/sodium-selenium batteries via a robust aqueous network binder

Selenium is a considerable energy storage material, with presenting a one-step electrochemical reaction in a cheap carbonate-based electrolyte and providing a considerable capacity as a cathode. However, capacity loss and safety issues caused by volume changes during charge and discharge processes, as well as low mass loading, still hinder the practical development of selenium cathodes. Binder is one of the indispensable constitutions of the electrode and crucial for improving the electrochemical performance of the battery. Herein, we design an aqueous robust network binder by doping a trace amount of Fe 3+ ions into sodium alginate for durable lithium/sodium-selenium batteries for the first time. With the modified binder, the capacity of the battery is increased by more than 17% at a current of 0.2C. Furthermore, it can achieve the highest Se loading made by blade coating of up to 12 mg cm −2 , which brings ultra-high reversible areal capacity of 4.9 mAh cm −2 for lithium-selenium battery, and currently the highest reported reversible areal capacity currently of up to 5.6 mAh cm −2 for sodium-selenium battery. Such a well-designed binder can improve the electrochemical performance and areal capacity of selenium cathodes, thereby boosting the practical application of selenium cathodes for energy storage.