The cross-linked design facilitates the suitability of nitrogen-containing gel electrolyte for high-performance gel semi-solid batteries

Abstract

Nitrogen-containing gel electrolyte has the advantages of high safety and strong compatibility, which can improve the electrochemical performance of lithium-ion batteries (LIBs). However, its inherent issues of oxidation stability and insufficient conductivity limit its large-scale application. Here, Pentaerythritol acrylate (PETEA) is used as a cross-linking agent to build a cross-linking framework with nitrogen-containing N,N-dimethylacrylamide (PNDA) gel monomer to improve the electrochemical performance of gel electrolyte (PNDET). The three-dimensional cross-linked PNDET electrolyte has a continuous Li-ion fast conduction network (7.02 mS cm⁻¹), and its self-supporting structure improves its mechanical strength (220.0 MPa). Meanwhile, through calculation, PNDET has a lower HOMO energy level, which increases its oxidation voltage from 4.3 to 4.5 V. In addition, the cross-linked PNDET enhances the overall thermal stability of the electrolyte, and the flame retardant properties of the nitrogen-containing skeleton are significantly improved. When the PNDET matched with Ah-class NCM811/Gr pouch cells, the capacity retention rate still remains 93.5% after 600 cycles at the temperature of 60 ℃. However, due to its extremely poor oxidation stability and thermal stability, the capacity of pouch cells with PNDA electrolyte rapidly decreases at high voltage of 4.35 V and high temperature of 60 ℃. The cross linking strategy provides a direction for the practical application of gel electrolyte and promotes the development of gel semi-solid battery.