Dendrite growth and side reactions of Zn metal anodes remain unresolved obstacles for practical application of aqueous Zn ion batteries. Herein, a two-dimensional (2D) organic−inorganic heterostructure with controlled thickness was constructed as a protective layer for a Zn metal anode. The reduction of uniformly distributed polyoxometalate in the layer causes a negative charge density gradient, which can accelerate zinc ion transfer, homogenize zinc deposition, and shield sulfates at the electrode interface, while the exposed hydrophobic alkyl chain of the layer can isolate the direct contact of water with the Zn anode. As a result of the synergetic effect, this 2D organic−inorganic heterostructure enables high Zn plating/stripping reversibility, with high average Coulombic efficiencies of 99.97% for 3700 cycles at 2 mA cm −2 . Under high Zn utilization conditions, a high arealcapacity full cell with hundreds of cycles was demonstrated.
The shuttling effect of soluble polysulfides and the
inadequate
conductivity of sulfur and lithium sulfide impede the practical utilization
of lithium–sulfur batteries. To address this issue, the polar
δ-MnO2 nanosheets with a 2D morphology can provide
abundant anchor and catalytic sites for polysulfides. However, the
poor intrinsic conductivity restricts the transformation ability.
Herein, we introduce mixed Mn4+/Mn3+ valence
states in δ-MnO2 nanosheets by a facile annealing
method to promote the redox kinetics of polysulfides. This treated
MnO2 maintains its 2D morphology, providing abundant absorption
sites for polysulfides, while the introduction of mixed valence states
enhances charge transfer and facilitates reaction kinetics. As a result,
the lithium–sulfur battery achieves high areal capacities of
7.0 mAh cm–2 at 0.56 mA cm–2 and
4.0 mAh cm–2 at 1 mA cm–2 after
100 cycles with a sulfur loading of 10.91 mg cm–2 and an E/S ratio of 6.46 μL mg–1.
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