Toward Durable Lithium–Selenium Batteries with Sustainable, Self-Healing Poly(acrylic acid)-Citric Acid Binders

The practical implementation of Li–Se batteries is hindered by critical challenges, particularly the considerable volume expansion of the selenium electrode during lithiation–delithiation cycling, which threatens structural stability and cycling performance. Among the key components of electrodes, the binder plays a pivotal role in maintaining electrochemical integrity as it directly influences the mechanical robustness and cohesion of the electrode structure. Herein, a physically cross-linked poly(acrylic acid)-citric acid (PAA-CA) binder is synthesized, and for the first time, its efficacy is explored in Li–Se batteries. The PAA-CA system utilizes dynamic, reversible hydrogen bonding interactions between citric acid and poly(acrylic acid), giving the binder intrinsic self-healing capability, superior structural integrity, and remarkable tensile properties. Experimental investigations, including ex situ AFM and SEM analyses, reveal that the PAA-CA binder effectively accommodates the volumetric fluctuations of the selenium electrode, mitigating pulverization and structural degradation over prolonged cycling. Consequently, Li–Se cells incorporating the PAA-CA binder exhibit a high specific capacity of approximately 551 mA h/g at 1C (1C = 675 mA/g) after 100 cycles as well as a high specific capacity of ∼433 mA h/g even at the high current density of 5 C after 400 cycles. This study underscores the potential of self-healing polymeric binders as a strategic approach to enhancing the electrochemical performance and structural resilience of Li–Se batteries. Computational analysis substantiates that PAA-CA significantly enhances adhesion, interfacial stability, and charge transfer on Se and Li2Se surfaces while maintaining conductivity and the intrinsic semiconducting properties of the material, further reinforcing its role in binder flexibility and self-healing.