High-performance artificial SEI layer with high elastic modulus and multiple Li-ion channels

Lithium metal batteries have a high energy density, can store more energy in a smaller volume, and have an extensive development prospect. However, several problems arising from dendrite growth have limited its practical application. Therefore, we designed a composite protective film that can inhibit the growth of dendrites and improve the energy density of batteries by adding hydroxylated multi-walled carbon nanotubes (MWCNT-OH) into poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP), which serves as an artificial SEI layer. We found that the introduction of MWCNT-OH played a role in improving the elastic modulus of the film and increasing the ion channels, which made the ion channels more uniform, optimised the lithium deposition morphology, and successfully suppressed the growth of lithium dendrites. The artificial protective film of MWCNT-OH/PVDF-HFP enabled the symmetric battery to be stably cycled for 1600 h, which substantially improved the cycling stability of the battery. Meanwhile, MWCNT-OH, as a carbon material, can accommodate lithium-ion. This strategy cleverly solves the problem of the conventional artificial SEI layer having no energy density, and the overall energy density of the battery is improved. This work presents a viable option for applying safe and stable lithium metal batteries.