Insight into Accelerating Polysulfides Redox Kinetics by BN@MXene Heterostructure for Li-S Batteries.

Sluggish redox kinetics and shuttle effect of polysulfides hinder the extensive application of the lithium-sulfur batteries (LSBs). Herein a functional heterostructure of boron nitride (BN) and MXene with an alternately layered structure (BN@MXene) is designed as separator interlayer. High efficiency Li+ transmission, uniform lithium deposition, strong adsorption, and efficient catalytic conversion activities of lithium polysulfides (LiPSs) realized by this heterostructure are confirmed by experiments and theoretical calculations. The alternately layered structure provides unblocked ion transmission channels and abundant active sites to accelerate the polysulfides redox kinetics with reduced energy barriers of oxidation and reduction reactions. As a result, the LSBs deliver an initial discharge capacity of up to 1273.9 mAh g-1 at 0.2 °C and a low decay of 0.058% per cycle in long-term cycling up to 700 cycles at 1 °C. This work provides an effective designing strategy to accelerate the polysulfides redox kinetics for advanced Li-S electrochemical system.

2D-2D heterostructure of ionic liquid-exfoliated MoS2/MXene as lithium polysulfide barrier for Li-S batteries.

Suppressing the dissolution and shuttling of lithium polysulfides (LiPSs) in electrolytes in lithium-sulfur batteries (LSBs) is the focus of researchers. Herein, functional liquid phase exfoliated MoS2 and MXene (IL-MoS2/MX) interlayer is proposed as the separator of LSBs. The unique alternating intercalation structure of the IL-MoS2/MX interlayer provides a channel for ion transport while achieving uniform Li+ deposition on the anode side. Moreover, IL-MoS2 achieves physical and chemical anchoring to LiPSs and lowers the energy barrier for battery reactions. As a result, the separator in the coin cell delivers an initial capacity of 764.4 mAh·g-1 at 1C and high retention of 58.7 % after 700 cycles, with a decay only 0.059 % per cycle. Simultaneously, the excellent stability is also verified under varying current densities. Beyond that, ionic conductivity and lithium-ion migration number are adopted to confirm unique ion transport channels and uniform deposition of lithium. X-ray photoelectron spectroscopy, S8 and Li2S decomposition and nucleation energy barrier analysis are performed to verify the adsorption and catalytic conversion mechanisms. The convenient preparation and excellent performance of IL-MoS2/MX provide a design strategy for functionalized interlayers for LSBs, and the possibility for commercialization.

Plasma and magnetron sputtering constructed dual-functional polysulfides barrier separator for high-performance lithium-sulfur batteries.

In order to fundamentally suppress the shuttle effect, N2 Plasma & Al2O3 magnetron sputtered separators (Al2O3@N-PP) are proposed for lithium-sulfur batteries (LSBs). Such a dual-functional polysulfides (LiPSs) barrier separator greatly inhibits the shuttle effect from the perspective of physical and chemical interaction. Physically, the inherently electronegative amorphous Al2O3 first achieves the repulsion of LiPSs to the sulfur cathode through the electrostatic repulsive effect, effectively preventing a large amount of soluble LiPSs from accumulating at the separator. At the same time, the Al2O3 film seals the shuttle channel of LiPSs to a certain extent. Chemically, N2 plasma-doped N heteroatoms form a lithium bond with Li+ in LiPSs to achieve the first step chemical adsorption and anchoring of LiPSs. When the LiPSs reaches the amorphous Al2O3 film, more stable chemical bonds are formed between Al3+ and S2-, Li+ and O2- to achieve more effective adsorption and anchoring of LiPSs. At 1C with a high sulfur loading up to 3-5 mg cm-2 the LSB contributes a specific charge capacity of 717.4 mAh g-1, with high retention rate up to 75.49 % after 450 cycles. The U-shaped electrolytic cell experiment and ultraviolet-visible spectrum experiment confirmed the LiPSs barrier function of the functional separator.

Lead zirconate titanate aerogel piezoelectric composite designed with a biomimetic shell structure for underwater acoustic transducers.

In this study, we used lead zirconate titanate (PZT) aerogels prepared by a solvothermal assisted sol-gel method as raw materials to synthesize PZT aerogel/PVDF composite coatings and PZT aerogel sintered sheets through natural annealing and PVDF composite and hot pressing, respectively, and then combined them with the design principle of a biomimetic shell structure to prepare an alternate coating/sheet structured PZT aerogel piezoelectric composite with natural distinguished mechanical properties. It had excellent piezoelectric properties with a piezoelectric coefficient d33 of 435.15 pC N-1 and d31 of -144.55 pC N-1, excellent electromechanical coupling properties with a planar electromechanical coupling coefficient of 60.14%, low dielectric loss of 0.76% at 40 Hz and low density of 3.04 g cm-3. When used as the piezoelectric material in underwater acoustic transducers (UATs), compared with all kinds of piezoelectric ceramics, it achieved higher piezoelectric and comprehensive mechanical properties, lower dielectric loss, lower density, and electromechanical coupling properties similar to that of Pb-containing piezoelectric ceramics, thus showing extremely promising application prospects in UATs.

Bimetallic composite induced ultra-stable solid electrolyte interphase for dendrite-free lithium metal anode.

Lithium metal is the most promising anode materials for the next generation lithium ion battery. However, the electrode polarization leads to the formation of dendrites and "dead lithium", which degrades the performance of lithium metal batteries and induce a variety of security risk. The electrode polarization and lithium dendrites can be suppressed by lithium metal composite electrode. Herein, a simple and effective strategy is adopted to construct nickel and lithium bimetallic composite (NiLi-BC) electrode by a double roll process. The Ni framework inside the electrode can optimize the electric field and Li+ distribution at the electrode/electrolyte interface and induce the uniform lithium deposition. As a result, the NiLi-BC exhibits a lithium dendrite-free feature and stable cycling performance under a low overpotential (<15 mV throughout 2180 h at 1 mA cm-2 with a deposition capacity of 1 mAh cm-2). Moreover, the assembled NiLi-BC||LiFePO4 coin cell and pouch cell exhibit improved capability and stable cycling performance. Finally, the in-situ optical microscopy and in-situ Raman spectroscopy are employed to obtain a better understanding of the interfacial structure and chemical component during the Li plating and striping processes. The scheme of this study of the NiLi electrode has great practical application value.