The direct effect of nitrogen content and various nitrogen species on oxygen reduction reaction (ORR) activities in non-aqueous lithium-oxygen (Li-O 2 ) batteries are systematically investigated. Mesoporous carbon (MC) with various nitrogen species is prepared through heat treatment of N-containing precursor under different temperature. The effect of the heat treatment temperature on the performance of carbon materials in Li-O 2 battery is investigated. The bonding state of nitrogen atoms is found to have a significant effect on the ORR activity. The ORR activity in Li-O 2 battery is proved to be dependent on the quaternary N content while the total N content in the carbon material does not play a crucial role in the ORR process.
Hui Wang,Houzhen Chen,Hongjiao Wang,Lei Wu,Qixing Wu,Zhongkuan Luo,Fang Wang
The electrochemical performance of the lithium−oxygen (Li−O 2 ) batteries largely depends on the material and architecture of the catalytic cathode. In this paper, to avoid the parasitic reactions of carbon and binder with discharge products and reaction intermediates, we proposed an effective design of a free-standing catalytic cathode for Li−O 2 batteries. The FeCo 2 O 4 @Ni electrode consists of FeCo 2 O 4 nanosheets grown directly on nickel (Ni) foam. The resultant hierarchical macroporous/mesoporous structure provides sufficient space for the insoluble discharge product Li 2 O 2 and catalytically active sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Consequently, the carbon- and binder-free self-supporting electrode has demonstrated a high discharge capacity with relatively low charge overvoltage and a better cycle performance than the corresponding carbon-based electrodes.
Ranxi Liang,Chaozhu Shu,Anjun Hu,Minglu Li,Zhiqun Ran,Ruixin Zheng,Jianping Long
The sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics greatly limit the development of lithium-oxygen (Li-O 2 ) batteries. Therefore, developing efficient electrocatalysts with high stability to boost oxygen involved reactions is particularly important for promoting the application of Li-O 2 batteries. Here, CoSe 2 @NiSe 2 heterostructure with distinct heterogeneous interfaces was fabricated via deliberate interface engineering. The formation of heterogeneous interface promotes local fine atomic array distortion that can act as an additional active site of ORR/OER. In addition, CoSe 2 @NiSe 2 with a distinct heterogeneous interface is favorable for the formation of built-in electric field during charging/discharging to enable electrodes with fast electrical transfer rates and reaction kinetics. Synergistically, the additional active sites brought by the fine atomic array distortion are highly conducive to the reversible formation and decomposition of the product. Undoubtedly, batteries with CoSe 2 @NiSe 2 exhibit excellent discharge/charge capacity (3530.1 mA h g −1 and 3485.6 mA h g −1 ), low overpotential (1.21 V) and excellent electrochemical stability for over 1200 h.
Gel-polymer electrolytes are considered as a promising candidate for replacing the liquid electrolytes to address the safety concerns in Li–O 2 /air batteries. In this work, by taking advantage of the hydrogen bond between thermoplastic polyurethane and aerogel SiO 2 in gel polymer, a highly crosslinked quasi-solid electrolyte (FST-GPE) with multifeatures of high ionic conductivity, high mechanical flexibility, favorable flame resistance, and excellent Li dendrite impermeability is developed. The resulting gel-polymer Li–O 2 /air batteries possess high reaction kinetics and stabilities due to the unique electrode–electrolyte interface and fast O 2 diffusion in cathode, which can achieve up to 250 discharge–charge cycles (over 1000 h) in oxygen gas. Under ambient air atmosphere, excellent performances are observed for coin-type cells over 20 days and for prototype cells working under extreme bending conditions. Moreover, the FST-GPE electrolyte also exhibits durability to protect against fire, dendritic Li, and H 2 O attack, demonstrating great potential for the design of practical Li–O 2 /air batteries.
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