Artificial Interfaces From In Situ Self-Polymerized Pyrazinoquinoxaline Tetraalkyne For Highly Stable Lithium Metal Anode

With the rapid development of science and technology,energy shortages and environmental pollution present a continuous demand for battery energy storage systems with higher energy density.As a secondary energy storage device,lithium ion batteries have broad application prospects in energy storage fields such as portable electronic equipment and electric vehicles.However,the energy density of developed lithium-ion batteries is close to its theoretical limit,and its inherent limitations still cannot meet the high expectations of energy density of cutting-edge electronic devices In order to further improve the energy and power density of next-generation lithium batteries,it is urgent to develop new battery systems beyond traditional lithium batteries.In the selection of anode materials for lithium batteries,lithium(Li)is considered to be one of the most promising anode materials due to its lowest mass density,ultra-high theoretical capacity and maximum negative reduction potential.However,there are still some serious scientific problems in the application of lithium metal as a negative electrode material inside the battery.The non-uniform deposition of lithium metal anodes during the cyclic charging and discharging process results in the growth of lithium dendrites,and there is a huge potential safety hazard in lithium metal batteries with volume expansion.Its low Coulomb efficiency and cycle stability make rechargeable lithium metal batteries not yet commercially available.Therefore,improving the performance of lithium metal anodes is important to achieve the high energy density of metal lithium.Aiming at a series of problems encountered in the lithium metal negative electrode during the cycling process,this paper proposes to suppress the formation and growth of lithium dendrites during the charge and discharge process by in situ polymerizing conjugated polymer materials as artificial SEI films.The main work includes:(1)a new type of nitrogen and oxygen doped polymer was designed and synthesized from a chemical point of view.Various synthetic methods were explored to obtain polymer materials with different morphologies,which werecharacterized using a range of physical and chemical methods;(2)the surface of the lithium anode was covered with a lithium-philic polymer layer using a spin coating method,which provided rich and uniform active sites for lithium nucleation.A series of tests such as SEM,TEM,and XPS have been used to confirm the role of alkynes polymer film in inhibiting the growth of lithium dendrites.In the Li/Li symmetrical battery test,it can be stably cycled for more than 1800 hours without internal short circuit,and the coulomb efficiency is still 99.8%after 300 cycles.The excellent rate and cycle stability test results in Li/NCM full cells have confirmed the excellent performance of artificial SEI films in lithium anode protection.