ARC Centre of Excellence for Electromaterials Science, Institute for Frontier Materials, Deakin University, Geelong, Victoria, 3200, Australia.
CIC EnergiGUNE, Alava Technology Park, C/Albert Einstein 48, 01510, Miñano, Álava, Spain.
ChemSusChem. 2019 Sep 6;12(17):4054-4063. doi: 10.1002/cssc.201901351. Epub 2019 Aug 9.
A series of electrospun binder-free carbon nanofiber (CNF) mats have been studied as air cathodes for Na-oxygen batteries using a pyrrolidinium-based electrolyte and compared with the commercial air cathode Toray 090. A tenfold increase in the discharge capacity is attained when using CNFs in comparison with Toray 090, affording a discharge capacity of 1.53 mAh cm at a high discharge rate of 0.63 mA cm . The good specific discharge and charge capacities of these CNFs are determined by the void space and the highly accessible surface of the carbon fiber. Furthermore, a threefold increase has been attained in terms of specific capacity by controlling the flooding of the air cathode and hence the location of the three-phase boundary within the CNF mat. The enhancement in performance has been correlated to the morphology, composition, distribution, and location of the discharge products. Sodium superoxide and peroxide were identified as the discharge products and, more importantly, the common side reaction discharge products, which are known to be detrimental to battery performance (including sodium fluoride, sodium hydroxide, and formate), were not observed, exemplifying the stability of the pyrrolidinium-based electrolyte and these binder-free CNF air cathodes.
已经研究了一系列无粘结剂的电纺碳纳米纤维（CNF）垫作为基于吡咯烷的电解质的钠离子 - 氧气电池的空气阴极，并与商业空气阴极 Toray 090 进行了比较。与 Toray 090 相比，使用 CNF 时可获得十倍的放电容量，在高放电率 0.63 mA cm 时可提供 1.53 mAh cm 的放电容量。这些 CNF 的良好的比放电和充电容量是由碳纤维的空隙空间和高可及表面决定的。此外，通过控制空气阴极的淹没程度，从而控制三相界在 CNF 垫内的位置，可以获得三倍的比容量增加。性能的提高与放电产物的形态、组成、分布和位置有关。鉴定出超氧化物和过氧化物是放电产物，更重要的是，常见的副反应放电产物（已知对电池性能有害，包括氟化钠、氢氧化钠和甲酸盐）没有被观察到，这证明了基于吡咯烷的电解质和这些无粘结剂的 CNF 空气阴极的稳定性。
