Advanced Engineering for Cathode in Lithium–Oxygen Batteries: Flexible 3D Hierarchical Porous Architecture Design and Its Functional Modification

Abstract

Modern technology constantly requires smaller, more efficient lithium-oxygen batteries (LOBs). To meet this need, a chemical vapor deposition (CVD) method is used to create an innovative cathode design with both a hierarchical porous nanostructure and a 3D flexible macroscopical morphology. This method employs architectural optimization to further improve cathodic ORR and OER performance via heteroatom doping, surface-sprouted carbon nanofibers (CNFs) grafting, and boundary exposing. The cathode consists of a 3D hierarchical porous graphene foam (PGF), along with RuO 2 nanoparticles impregnated and nitrogen doped CNFs (RuO 2 @NCNFs), where the PGF serves as a structural support and cathodic current collector, and the RuO 2 @NCNFs work as a superior bi-functional catalyst. The cathode delivers an outstanding discharge capacity of 8440 mAh g cathode −1 while maintaining a recharge plateau at ≈4.0 V, and can cycle for over 700 rounds without obvious degeneration under a fixed capacity. Notably, this free-standing cathode can be directly used in LOBs without the need for additional substrates or current collectors. Therefore, the current densities and capacities herein are calculated based on the total weight of the cathodes. These results demonstrate the RuO 2 @NCNFs-PGF cathode's remarkable potential for LOB applications, and this rational cathodic structure may be extended to other highly efficient catalyst applications.

Co/Zn‐based bimetallic MOF ‐derived hierarchical porous Co/C composite as cathode material for high‐performance lithium‐air batteries

“…Consequently, the hierarchical porous structure of Co@C(700-1000) can be beneficial for improving the electrochemical performance by promoting the diffusion of the electrolyte into the air cathode and exposing more active sites for reaction with lithium ions. 48 To evaluate the applicability of the cells, lithium-air batteries were assembled using the C(700-1000), Co@C (700-1000), and super P. After lithium-air batteries were assembled, the EIS was utilized to indicate the resistive information of the air cathodes in Figure S9. The shape and value of the resistance in the impedance spectrum are strongly influenced by the electrode porosity.…”

“…The cylindrical pores can be explained to be originated from the rod‐shaped zinc oxides. Consequently, the hierarchical porous structure of Co@C(700‐1000) can be beneficial for improving the electrochemical performance by promoting the diffusion of the electrolyte into the air cathode and exposing more active sites for reaction with lithium ions 48 …”

Effect of singlet oxygen on redox mediators in lithium–oxygen batteries

“…[6][7][8] To decrease the charging overpotential, various approaches, e.g. embedding catalysts in the cathode, 9,10 structural design of porous air electrodes, 11,12 and solvent design 13,14 have been proposed. Among them, redox mediators (RMs) are one of the most promising methods.…”

Safe and Energy-Dense Flexible Solid-State Lithium–Oxygen Battery with a Structured Three-Dimensional Polymer Electrolyte

“…Rechargeable lithium–oxygen batteries (LOBs) have the highest theoretical energy density (about 3500 Wh kg –1 ) among existing metal-based chemical battery systems and are expected to be a candidate for green energy storage devices. − Nevertheless, there are still several issues limiting the practical application of LOBs. One major bottleneck relates to the use of organic liquid electrolytes, which leads to several safety issues such as volatility, flammability, and leakage of organic solvents. − In addition, the diffusion of oxygen in the liquid LOB system is limited by the dissolved oxygen gas in the air electrode filled with an organic liquid electrolyte, which results in large polarization, poor rate performance, and weak reversibility. − Safer and reliable electrolytes are urgently needed to substitute for the organic liquid electrolytes currently used.…”