Cui Xinhang, Luo Yani, Zhou Yin, Dong Wenhao, Chen Wei
Department of Physics, National University of Singapore, 2 Science Drive 3, 117543, Singapore.
National University of Singapore (Suzhou) Research Institute, Suzhou, People's Republic of China.
Nanotechnology. 2021 Mar 26;32(13):132003. doi: 10.1088/1361-6528/abd1a7.
Li-O batteries (LOB) are considered as one of the most promising energy storage devices using renewable electricity to power electric vehicles because of its exceptionally high energy density. Carbon materials have been widely employed in LOB for its light weight and facile availability. In particular, graphene is a suitable candidate due to its unique two-dimensional structure, high conductivities, large specific surface areas, and good stability at high charge potential. However, the intrinsic catalytic activity of graphene is insufficient for the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in LOB. Therefore, various surface functionalization schemes for graphene have been developed to tailor the surface chemistry of graphene. In this review, the properties and performances of functionalized graphene cathodes are discussed from theoretical and experimental aspects, including heteroatomic doping, oxygen functional group modifications, and catalyst decoration. Heteroatomic doping breaks electric neutrality of sp carbon of graphene, which forms electron-deficient or electron-rich sites. Oxygen functional groups mainly create defective edges on graphene oxides with C-O, C=O, and -COO-. Catalyst decoration is widely attempted by various transition and precious metal and metal oxides. These induced reactive sites usually improve the ORR and/or OER in LOB by manipulating the adsorption energies of O, LiO, LiO, and promoting electron transportation of cathode. In addition, functionalized graphene is used in anode and separators to prevent shuttle effect of redox mediators and suppress growth of Li dendrite.
锂-氧电池（LOB）因其极高的能量密度，被认为是利用可再生电力为电动汽车供电的最具前景的储能装置之一。碳材料因其重量轻且易于获取，已在锂-氧电池中得到广泛应用。特别是石墨烯，由于其独特的二维结构、高导电性、大比表面积以及在高充电电位下的良好稳定性，是一种合适的候选材料。然而，石墨烯的固有催化活性不足以应对锂-氧电池中氧还原反应（ORR）和析氧反应（OER）缓慢的动力学过程。因此，人们开发了各种石墨烯表面功能化方案来调整石墨烯的表面化学性质。在这篇综述中，从理论和实验方面讨论了功能化石墨烯阴极的性质和性能,包括杂原子掺杂、氧官能团修饰和催化剂修饰。杂原子掺杂破坏了石墨烯sp碳的电中性，形成缺电子或富电子位点。氧官能团主要在氧化石墨烯上形成带有C-O、C=O和-COO-的缺陷边缘。人们广泛尝试用各种过渡金属、贵金属和金属氧化物进行催化剂修饰。这些诱导的活性位点通常通过控制O、LiO、LiO的吸附能以及促进阴极的电子传输来改善锂-氧电池中的ORR和/或OER。此外，功能化石墨烯还用于阳极和隔膜，以防止氧化还原介质的穿梭效应并抑制锂枝晶的生长。
