Polyoxometalates Templated Metal Ag–Carbene Frameworks Anodic Material for Lithium-Ion Batteries

A POMs templated 3D Ag–carbene framework with <i>lvt-a</i> topology was hydrothermally synthesized. The POMs templated MCF combining the advantages of POMs, MOFs, and carbene not only shows excellent thermal and chemical stabilities but also possesses a good discharge capacity of 481 mAh·g^–1 after 100 cycles applied as anode material in LIBs

Single Cobalt Ion-Immobilized Covalent Organic Framework for Lithium–Sulfur Batteries with Enhanced Rate Capabilities

Covalent organic frameworks (COFs) are notable for their remarkable structure, function designability, and tailorability, as well as stability, and the introduction of “open metal sites” ensures the efficient binding of small molecules and activation of substrates for heterogeneous catalysis and energy storage. Herein, we use the postsynthetic metal sites to catalyze polysulfide conversion and to boost the binding affinity to active matter for lithium–sulfur batteries (LSBs). A dual-pore COF, USTB-27, with hxl topology has been successfully assembled from the imine chemical reaction between 2,3,8,9,14,15-hexa(4-formylphenyl)diquinoxalino [2,3-a:2′,3′-c]phenazine and [2,2′-bipyridine]-5,5′-diamine. The chelating nitrogen sites of both modules are able to postsynthetically functionalize with single cobalt sites to generate USTB-27-Co. The discharge capacity of the sulfur-loaded S@USTB-27-Co composite in a LSB is 1063, 945, 836, 765, 696, and 644 mA h g–1 at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 C, respectively, much superior to that of non-cobalt-functionalized species S@USTB-27. Following the increased current densities, the rate performance of S@USTB-27-Co is much better than that of S@USTB-27. In particular, the capacity retention at 5.0 C has a magnificent increase from 19% for the latter species to 61% for the former one. Moreover, S@USTB-27-Co exhibits a higher specific capacity of 543 mA h g–1 than that of S@USTB-27 (402 mA h g–1) at a current density of 1.0 C after electrochemical cycling for 500 runs. This work illustrates the “open metal sites” strategy to engineer the active chemical component conversion in COF channels as well as their binding strength for specific applications

Monolayer Thiol Engineered Covalent Interface toward Stable Zinc Metal Anode

Interface engineering of zinc metal anodes is a promising remedy to relieve their inferior stability caused by dendrite growth and side reactions. Nevertheless, the low affinity and additional weight of the protective coating remain obstacles to their further implementation. Here, aroused by DFT simulation, self-assembled monolayers (SAMs) are selectively constructed to enhance the stability of zinc metal anodes in dilute aqueous electrolytes. It is found that the monolayer thiol molecules relatively prefer to selectively graft onto the unstable zinc crystal facets through strong Zn–S chemical interactions to engineer a covalent interface, enabling the uniform deposition of Zn2+ onto (002) crystal facets. Therefore, dendrite-free anodes with suppressed side reactions can be achieved, proven by in situ optical visualization and differential electrochemical mass spectrometry (DEMS). In particular, the thiol endows the symmetric cells with a 4000 h ultrastable plating/stripping at a specific current density of 1.0 mA cm–2, much superior to those of bare zinc anodes. Additionally, the full battery of modified anodes enables stable cycling of 87.2% capacity retention after 3300 cycles. By selectively capping unstable crystal facets with inert molecules, this work provides a promising design strategy at the molecular level for stable metal anodes