Synthesis Of The Polyimides And Their Electrochemical Energy Storage Applications

With the development of industrial informatization, energy crisis and environmental pollution are prominent increasingly. New energy technologies are critical to address global concerns regarding energy shortages and environmental issues. However, renewable energy such us sunlight, wind and tidal are suffering from intermittent and randomness, making it difficult to integrate into electric grid directly. Therefore, it is of great importance to develop efficient electrochemical energy storage technologies. As a novel kind of energy storage technology, sodium ion batteries have attracted aroused attention due to its abundant resources, low cost and environmental friendliness. similar to LIBs, an overwhelming majority of the host materials developed so far for SIBs are based on transition-metal compounds, which have serious cost and negative environmental impacts on battery applications. In contrast, redox-active organic materials have competitive advantages of low cost,resource sustainability and structural diversity, being an ideal candidate for promising candidates for large-scale energy storage applications. In addition, compared to the rigid inorganic lattices, the flexible frameworks of organic materials are particularly favorable for the reversible insertion and extraction of the larger Na+ ions. In contrast, organic materials not only have abundant sources and environmental friendliness, but also have a flexible skeleton, which have less restrictions on cations. Based on above issues, we synthesized four different polyimide materials and investigated them as novel Na storage materials both in organic and aqueous electrolytes. The main results are summarized as follows:1. Four kinds of polyimides were prepared via a facile dehydration condensation reaction and investigated as a novel Na-storage. Different polyimides were prepared via a facile dehydration condensation reaction and investigated as a novel Na-storage cathode. PNP（based on NTCDA and PPD） exhibits excellent electrochemical performances. The PNP electrode delivers a reversible capacity of 109 m Ahg^-1 after 100 cycles; Even at a very high current density of 800 m Ag^-1, a capacity of 40 m A h g^-1 is still delivered. In addition, we preliminarily explored the multi-active center polyimide PTA（based on PTCDA and DDAQ）, compared with the previous material, the reversible capacity is up to 140 m Ah g^-1, with no capacity fading over 150 cycles, showing great promise in sodium ion applications.2. Constructing NIBs in aqueous electrolytes is promising in the field of large-scale energy storage for the intrinsic safety, low cost and high ionic conductivity of the aqueous electrolyte. A Polyimide-MWCNTs composite（PNP@CNTs） synthesized from 1, 4, 5, 8-naphthalenetetracarboxylic-dianhydride（NTCDA） and phenylene diamine（PDA） was investigated as a novel anode for aqueous Na-ion batteries. Benefiting from the highly conjugated structure and robust conducting network, this composite demonstrates a high reversible capacity of 149 m Ah g^-1 at quite a low potential of- 0.65 V（vs SCE）, superior rate capability and long-term cycling stability. The feasibility of PNP@CNTs in aqueous Na-ion full batteries is also confirmed in conjunction with the Na0.44 Mn O2 cathode, possibly serving as a high performance aqueous Na host anode for large-scale electric energy storage applications.