The basic reaction chemistry only involves the lithium and oxygen in the conventional aprotic lithium-oxygen (Li-O
2) battery, which makes it extremely attractive for high-energy-density storage devices. However, it has proven difficult to achieve this reaction in the practical rechargeable Li-O
2 batteries. There are many factors such as the operating conditions or environment that can affect the reaction paths to the final Li
2O
2 discharge product, which results in some parasitic reactions and affects the cyclic stability and energy efficiency of Li-O
2 battery. In this study, we focus our attention on improving the energy density of Li-O
2 batteries from both the gravimetric and volumetric aspects by optimizing the cathode structure. It is widely accepted that graphene-based material is considered as a promising air-breathing cathode in Li-O
2 batteries because of its exceptional specific surface area, excellent conductivity, diverse morphologies and hierarchical porous structure. However, the relatively low density of graphene-based material is not beneficial for volumetric performance in practical application. To solve the problem, we develop a convenient strategy to prepare template-assisted, high density, porous graphene monolith (THPGM) cathodes with high densities for compact Li-O
2 batteries. Graphene oxide is used as the primary building block to construct condensed carbon electrodes by self-assembly followed by capillary drying. SiO
2 nanoparticles are incorporated onto the dense graphene monolith to function as sacrificial pore former. The bimodal pores of diameters ranging 1–6 and ∼40 nm created in the close-grained graphene monolith facilitate ion transport and oxygen diffusion, while providing sufficient space to accommodate the discharge products. The oxygen cathodes made from THPGM possess the advantageous features of high volumetric densities, a fully-developed porous structure and a robust architecture, resulting in unprecedented volumetric energy densities and excellent cyclic stability for Li-O
2 batteries. Note that the conventional Li-O
2 batteries using metallic lithium anodes also suffer from the serious safety issues arising from the possible formation of lithium dendrites. To overcome the obstacle, we report the synthesis of a long-life lithium ion O
2 battery (LIOB) consisting of an anode made from pre-lithiated aluminum (Al) foil and a Li
2O
2-preloaded oxygen cathode, which are both commercially available. The assembled LIOB delivers an excellent specific reversible capacity of 1000 mAh g
-1 for over 100 cycles at 100 mA g
-1 and a maximum specific energy density of 1178 Wh kg
-1. The pre-lithiated Al foil functions as both the anode and current collector, and the stable solid electrolyte interphase layer formed on anode during pre-lithiation greatly improves the cyclic stability. In view of abundance and availability of the cathode and anode materials, the assembly strategy developed here can offer a promising route to large-scale fabrication of LIOBs for real-world applications.
| Date of Award | 2018 |
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| Original language | English |
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| Awarding Institution | - The Hong Kong University of Science and Technology
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