Hierarchical Micron-Sized Mesoporous/Macroporous Graphene with Well-Tuned Surface Oxygen Chemistry for High Capacity and Cycling Stability Li–O₂ Battery

Abstract

Nonaqueous Li-O2 battery is recognized as one of the most promising energy storage devices for electric vehicles due to its super-high energy density. At present, carbon or catalyst-supporting carbon materials are widely used for cathode materials of Li-O2 battery. However, the unique electrode reaction and complex side reactions lead to numerous hurdles that have to be overcome. The pore blocking caused by the solid products and the byproducts generated from the side reactions severely limit the capacity performance and cycling stability. Thus, there is a great need to develop carbon materials with optimized pore structure and tunable surface chemistry to meet the special requirement of Li-O2 battery. Here, we propose a strategy of vacuum-promoted thermal expansion to fabricate one micron-sized graphene matrix with a hierarchical meso-/macroporous structure, combining with a following deoxygenation treatment to adjust the surface chemistry by reducing the amount of oxygen and selectively removing partial unstable groups. The as-made graphene demonstrates dramatically tailored pore characteristics and a well-tuned surface chemical environment. When applied in Li-O2 battery as cathode, it exhibits an outstanding capacity up to 19 800 mA h g(-1) and is capable of enduring over 50 cycles with a curtaining capacity of 1000 mA h g(-1) at a current density of 1000 mA g(-1). This will provide a novel pathway for the design of cathodes for Li-O2 battery.

New Electrode and Electrolyte Configurations for Lithium‐Oxygen Battery

“…Carbon is one of the most suitable, low‐cost materials for employment in the positive electrode of Li/O 2 battery. Many different carbon morphologies and structures, that is, 1D, 2D, and 3D structured materials, have been studied, and revealed promising performance and cycle life. The chemical nature of the polymeric additive binding the Li/O 2 battery positive electrodes, as well as the traces of the solvent used for slurry preparation, may also have a significant impact on the nature of the final discharge product and the reversibility of the electrochemical process, as recently evidenced by research works .…”

“…Indeed, essential characteristics promoting the ORR/OER are electron conductivity,s tabilityi nt he reactive environmento ft he Li/O 2 battery,h igh surface area and porosity,a nd low tortuosity, [38] which favor the reactionk inetics, accommodatet he reactionp roducts,a nd improvet heir retention on the cathode surface. [38][39][40][41] Carbon is one of the most suitable, low-cost materials for employment in the positive electrode of Li/O 2 battery.M any different carbon morphologies and structures, that is, 1D, [42,43] 2D, [44,45] and 3D [46,47] structured materials, have been studied, and revealed promising performance and cycle life. The chemical nature of the polymeric additive bindingt he Li/O 2 battery positive electrodes, as well as the traces of the solventu sed for slurry preparation, may also have as ignificant impact on the natureo ft he final discharge product and the reversibility of the electrochemical process,a sr ecently evidencedb yr esearchw orks.…”

Carbon-Based Metal-Free Electrocatalysis for Energy Conversion, Energy Storage, and Environmental Protection

“…Because discharge products, such as Li 2 O 2 , continuously accumulate on the surface of cathode catalysts during cycling processes, it can clog electrodes and cause electrodes to electrically disconnected. Therefore, porous carbon materials with rationally designed architectures are highly desirable as cathode materials [177], with the capacity of Li-O 2 batteries using carbon cathodes being mainly determined by the surface area, pore volume and pore size available for the deposition of discharge products [177,178]. Hierarchically porous graphene materials consisting of microporous channels and highly connected nanoscale pores were demonstrated to deliver an exceptionally high capacity of 15,000 mAh g −1 in Li-O 2 batteries [20].…”

Recent Progress on Stability Enhancement for Cathode in Rechargeable Non‐Aqueous Lithium‐Oxygen Battery

“…As a consequence, the round-trip effi ciency of the Li-O 2 battery is lowered and the cycling performances are decayed. [65][66][67] Together, the enhancement of carbon cathode stability will undoubtedly increase the performance of Li-O 2 batteries. Encouragingly, many protective strategies adopted in the past several years have endowed the carbon cathode with increased stability, thus improving the Li-O 2 performances remarkably; this should be a benefi t for the applications of Li-O 2 batteries.…”