Compared with lithium, sodium resource is abundant and the price is low, so sodium ion battery has a broad application prospect in the field of large-scale electric energy storage. The radius of sodium ion is larger than that of lithium ion, which puts forward new requirements for the structure and performance of commonly used carbon based anode materials. In order to improve the performance of sodium ion batteries, it is necessary to improve the conductivity and stability of carbon based anode materials, and improve their ion surface and bulk diffusion ability. For this reason, in recent years, heteroatom doping, defect engineering, active pore making and other methods have been widely used to control the structure and properties of carbon materials and improve their sodium storage performance. However, it is still a challenge to optimize the properties of carbon materials such as layer spacing, conductivity, pore structure and wettability. In addition, binder is often used in the preparation of carbon based anode materials, which will increase the weight and volume of the electrode, resulting in the decrease of energy density. Therefore, it is very important for improving the performance of sodium ion batteries to develop the synergistic optimization method of carbon based anode materials and to build a macro electrode structure without binder.
Recently, Professor Ma Yanwen of Nanjing University of Posts and Telecommunications and Professor Husam N. Alshareef of Saudi Arabia Abdullah University proposed a selective etching method for constructing nitrogen and Oxygen Co doped porous graphene aerogels. The synergistic optimization of nitrogen and oxygen doping and material crystallinity was achieved by controlling the etching conditions by using the difference of crystallinity of carbon materials. The nitrogen and Oxygen Co doped porous graphene aerogel exhibits excellent electrochemical performance as an integrated negative electrode material for sodium ion batteries. The results were published on advanced energy materials (DOI: 10.1002/aenm.202000099). Dr. Zhao Jin and Dr. Zhang Yizhou are co authors of the paper.
Firstly, the graphene / PU sponge derived carbon composite structure was constructed with polyurethane (PU) sponge and graphene oxide as precursors. The low crystallinity Pu sponge derived carbon and part of the low crystallinity area in graphene were selectively etched by air mild oxidation to obtain nitrogen oxygen Co doped porous stone Graphene aerogels. In this process, Pu sponge is used as self sacrificing template and nitrogen source. In addition, by adjusting the etching time, the co optimization of the nitrogen and oxygen dopants and the crystallinity of the material was realized. The nitrogen and Oxygen Co doped porous graphene aerogels have well-developed porous structure, optimized crystallinity and large interlayer spacing, which are conducive to the rapid transmission of ions and electrons and the storage of ions. The doped nitrogen atom can provide more sodium adsorption sites, and the oxygen-containing functional group can increase the pseudo capacitance contribution through redox reaction. In addition, the integrated aerogel elastic structure can avoid the use of additives and can be directly applied to the negative electrode of sodium ion batteries. The nitrogen and Oxygen Co doped porous graphene aerogel has excellent sodium storage properties, showing high specific capacity (0.1 A G? 1 under current density of 446 mAh G? 1), high rate performance (10 A G 1 current density of 189 mAh G? 1), and long cycle performance (5 A G? 1 current density under cyclic 2000 ring capacity retention rate of 2000). The selective etching method based on the different crystallinity of carbon materials developed in this work not only provides a new strategy for the development of high-performance graphene sodium ion battery anode materials, but also provides a reference for the construction of other high-performance carbon based electrode materials. Guess you love it.
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