Search

Silicon (Si) is one of the most promising materials for the next-generation anode of lithium-ion batteries (LIBs). It not only has the highest theoretical capacity but also is rich in natural resources and related mature technologies. However, its large volume fluctuation and poor electrical conduction must be overcome by compositing it with guest materials. Different from complicated methods that run counter to industrialized applications, herein, a facile and efficient strategy has been applied to prepare an editable Si composite precursor within 30 seconds with rapid biomineralization. After simple post-processing, a high-performance carbon-coated Si composite electrode was obtained, which exhibited good electrical contact, structural stability, and favorable diffusion paths and space for electrolytes. Specifically, this biomineralization strategy improves the capability of lithium storage in the Si electrode with a high-reversible specific capacity. The electrode shows an excellent rate capability at large current density (4 A g−1) and excellent capacity retention in long-term cycling (600 cycles). This approach also provides a new choice to synthesize rapidly diverse electrodes for high-performance lithium-ion batteries.

The high-performance silicon (Si) composite electrodes are being widely developed due to their considerable theoretical capacity. Coating with carbon-based materials is an efficient way to solve the common issues of Si-based materials. Currently, most of the reported strategies are complicated, pollutive, or uneconomic, which hamper their practical applications. Herein, a honeycomb-like Si-based composite was prepared to address these issues via a facile and green reduction approach at room temperature. The pre-anchored Si nanoparticles could be packed and interconnected through a three-dimensional graphene network to further enhance the electrochemical properties of the active materials. As an electrode, this composite shows good rate capabilities upon lithium storage and cycling stability. The continued cycling measurement delivers a -0.049% capacity decay rate per cycle within 600 cycles. A direct comparison further exhibits the obviously improved performance between the as-designed Si-based composite and naked Si, suggesting a potential application of this convenient strategy for other high-performance electrode materials.

A facile two-step strategy to prepare flexible graphene electrodes has been developed for supercapacitors using thermal reduction of graphene oxide (GO) and thermally reduced graphene oxide (TRGO) composite films. The tunable porous structure of the GO/TRGO film provided channels to release the high pressure generated by CO

Polysulfides shuttling and lithium dendrite growth are two challenges confronting lithium–sulfur batteries (LSBs). Herein, edge engineering of 2D transition metal dichalcogenides (TMDs) is proposed to simultaneously address these two issues. First, utilizing MoS2 as a model material, theoretical calculations demonstrate the strong binding affinity of polysulfides to molybdenum edges and the robust electrovalent bonds between Li+ and sulfur edges, thus predicting the multifunctional regulation capability of edge‐rich MoS2. Holey atomically thin MoS2‐constructed nanobrushes (HATM‐NBs) are then prepared by a polar functionality‐assisted anchoring strategy. The functionality anchoring effectively inhibits longitudinal growth of 2D MoS2 and more impressively facilitates formation of plentiful in‐plane nanopores due to the fast nucleation and growth. Spectroscopy and electrochemical techniques verify the superior adsorption/catalytic conversion of polysulfides by Mo edges and therefore accelerated redox reactions. The sulfur edge‐rich nanobrush structure promotes good contact with the lithium metal anode, homogenized Li+ flux, and thus uniform lithium plating/stripping. A fabricated laminate cell with ultrathin HATM‐NBs‐coated separator demonstrates superior electrochemical performances even under harsh test conditions (high sulfur loading of 7.43 mg cm−2 and low E/S ratio of 5 mL g−1). The rational design of multifunctional edge‐rich 2D TMDs provides fresh insights for developing stable LSBs.

The structure fracture of silicon electrodes due to the volume change during Si-Li alloying reactions greatly hinders their practical applications. Herein a layered Si material (LSM) was prepared by a simple one-step topological reaction and used as an effective LIBs anode. The layered structure has abundant gaps and pores to accelerate ion transportation. Microstructure measurements demonstrate the formation of an amorphous lithiation product but not Si-Li alloys. As a result, the LSM anode shows higher specific capacity and a much better cycling performance than common bulk Si anode. Thus, the LSM could be alternative high-performance Si anode in LIBs.

The design and development of durable and high efficient supercapacitors is highly desired in electronic and energy storage devices. Traditional carbon based capacitors suffer from low specific capacitance and energy density. Recently transition metal sulfides are attractive alternatives for crystal electrode materials. Herein we demonstrate a facial design and synthetic method to grow novel metal sulfide double-shelled polyhedral nanocages consisting of mesoporous amorphous Ni x S y @CoS via a metal-organic-framework engaged strategy for use in supercapacitors. The Ni x S y @CoS polyhedrons with the inner and outer-shells respectively consisting of CoS and Ni x S y are obtained at mild room temperature without further thermal-treatment. The outer-shell is easily adjustable to suit various combinations according to the requirement. The morphological and structural evolution of the Ni x S y @CoS nanocages was studied systematically. Further electrochemical performance shows that the Ni x S y @CoS exhibits remarkably high capacitance of 2291 F g −1 at 1.0 A g −1 in 6 M KOH aqueous solution.

Polymer mesoporous membranes are widely employed in many membrane processes including ultrafiltration and dialysis, and become more crucial with increasing demand in chemical and life fields. Here we report a highly-efficient polymer membrane with sub-5 nm pores and high flux from polyacrylonitrile (PAN) nanoparticles produced from dilute PAN solution via fast freeze-extraction process. The ∼25 nm-size PAN nanoparticles forming brad-like chains are dispersed in ethanol solution and used to prepare the membrane by filtration-assisted assembly method across a macroporous support. Effects of solvents and usage of PAN on membrane formation is studied in detail. The resultant membranes comprise of the nanoparticles stacked on the support to form a mesoporous separation layer with a controllable thickness and a cut-off of below 5 nm. They exhibit excellent separation performances in ultrafiltration of protein and nanoparticle solutions. Typically, the membrane with 94.6% rejection of 5 nm gold nanoparticles has a pure water flux of 823 L m−1 h−1 bar−1 and perfect rejection for ferritin molecules and 10 nm gold nanoparticles. The newly developed membranes should have wide application in chemical, environment and life fields.

Highly-permeable nanofiltration membranes are highly desired in water production and dissolved solutes removal due to environmental and energy concerns. Here a facile approach is presented to prepare ultrathin polymeric nanofiltration membrane using surface modification of ultrafine cellulose nanofiber (UCN) membrane via interfacial polymerization. The hydrophilic UCN membrane endows an interconnected nanoporous microstructure containing free spaces for the growth of the crosslinked-PEI layer creating narrow permeation channels that are responsible for the transport of water moleucles. The resultant membranes comprising an ultrathin selective layer intertwined with cellulose nanofiber matrix are smooth and allow fast permeation of water. Typically, the 77.4 nm-thick membrane with a mean pore size of about 0.45 nm and molecular weight cut-off of 824 g mol −1 has a high pure water flux of 32.7 L m −2 h −1 bar −1 that is an order of magnitude higher than those of previously reported similar nanofiltration membranes. The membranes are also positively charged and display high permeation flux and sufficient rejections for inorganic salts and organic dyes in the water purification. Further performance evaluation using model synthetic wastewater demonstrates the membranes have a great potential in the wastewater treatment. This approach presents a promising strategy for the development of highly-permeable nanofiltration membranes for fast water purification and high-efficient separation of small molecules.

Novel polymer–MOF nanocomposite membranes are prepared via the incorporation of ZIF-8 nanocrystals into cardo polyetherketone (PEK-c) for pervaporation separation of water/methanol/MTBE ternary mixtures. The ZIF-8 nanocrystals with 20–40 nm size are synthesized for preparing membranes. The resulting membranes have ZIF-8 nanocrystals dispersed homogeneously and embedded in the membrane matrix with adjustable ZIF-8 loading of up to 20 wt%. Moreover, the membranes have homogeneous microstructure, good thermal and mechanical stabilities. They show favorable pervaporation performances for separation of the water/methanol/MTBE mixtures. The incorporation of ZIF-8 greatly enhances the permeation flux. At the low ZIF-8 loading, the water selectivity increases and the total separation factor is very high and greater than 1.97 × 104. Typically, the membrane with 4 wt% ZIF-8 has the total flux of 1.48 kg μm m−2 h−1, water and total separation factor of 181 and 1.97 × 104 respectively. The newly developed nanocomposite membranes have a great potential in high-efficient purification of MTBE.

The development of inorganic functionalized membranes with the capacity to effectively separate molecules or ions in solutions based on the size or electrostatic interactions is pivotal to purification and separation applications. Herein, we demonstrate a novel green strategy utilizing a completely aqueous process to construct an asymmetrically structured metal surface functionalized polymer–matrix nanocomposite nanofiltration membrane. Crosslinked polyethyleneimine (PEI) is grafted on a carboxylated carbon nanotube intermediate layer incorporated into the macroporous cellulose acetate substrate to form the composite membrane. The resulting membrane is subsequently inorganically modified via an in situ surface reaction of zinc nitrate with excess ammonium hydroxide to produce the hydrophilic and positively charged membrane. Crosslinking enhances the polymer interaction with the carbon nanotube interlayer which in turn endows it with mechanical strength and sustains the membrane pore structure during pressure driven filtration. The functionalized membrane displays outstanding pure water flux of 16.5 ± 1.3 L m−2 h−1 bar−1 while exhibiting good nanofiltration performance of bivalent cations, which is ascribed to the electrostatic repulsion via the Donnan exclusion effect. Meanwhile the membranes exhibit excellent separation of organic molecules and long-term filtration stability. This newly developed approach presents a promising route for the construction of highly permeable nanofiltration membranes for fast purification and separation applications.

Polymer mesoporous materials have attracted increasing concerns in various fields especially in membrane separation process. Here we report a versatile approach to fabricate novel highly-permeable polymer mesoporous membrane for size-exclusion separation. This approach employs copper hydroxide nanowire thin films as the soluble templates to form a polymer mesoporous separation layer. The membrane formation mechanism is revealed by varying the polymer concentration, the thickness of template films and the size of nanowires. The resultant membranes have a three-layer sandwich structure, allow fast permeation of water, and exhibit excellent size-exclusion separation performances. Typically, the 1.39 µm-thick membrane has a high water flux of 1.17 103 L m−2 h−1 bar−1 and rejections of 94.1 % for ferritin molecules. The developed approach have a great potential in the fabrication of polymer mesoporous materials, and produce the membranes have a wide range of applications including in environmental fields.

Silicon-based materials are showing appealing potentials for electrical energy storage because of their unparalleled theoretical energy density. In this work, a rapid and efficient surface-polymerization processing has been developed to obtain a sandwich-like silicon-carbon composite structure for fast lithium storage. The anchored silicon particles are connected with a low diffusion tortuosity in the designed structure that facilitates the electron transport throughout the electrode and enhances the response rate under high current density. Electrochemical measurements demonstrate that the silicon-carbon composite electrode exhibits a high capacity for lithium storage. It shows a reversible capacity of 1990 mA h g−1 at 0.5 C after 100 cycles and also has an excellent capacity retention property (only −0.062% capacity reduction per cycle) in long-term cycling at 1 C. Furthermore, it can deliver a high reversible specific capacity of 1170 mA h g−1 even at 4 C.

Silicon-based materials with high specific capacities have attracted great attentions as an alternative to graphite anode in lithium-ion batteries. However, the low electrical conductivity and inefficient suppression of volume expansion make it somewhat unsuitable for practical applications. Thence, a rapid self-encapsulating approach was first adopted to construct a conductive and effective carbon protective shell on the surface of layered SiOx-based nanosheets by compositing polyelectrolyte (polyethyleneimine, PEI) with graphene oxide (GO). This designed composite electrode has a compact and robust interfacial structure attributed to chemical integration and electrostatic interactions, which also greatly increased the tap density of the electrode. As an anode material, it delivered a high reversible capacity of 867 mAh g−1 and excellent rate capability. The cycling stability is also retained even after rate performance test, which resulted a −0.033% capacity decay rate for each cycle in 500 cycles.

Silicon (Si) has been broadly investigated as a promising anode in lithium-ion batteries (LIBs). However, there is still a problem that the alloying reactions of Si and Li often cause structural failures and rapid degradation in capacity of the electrode. Herein, an in-situ encapsulation of Si nanoparticles forming metal-organic-framework (MOF) derived carbon shells has been developed to improve the performance and retain the structural integrity of the electrode. Using this strategy, a compact and robust interface was ensured between the Si nanoparticles and carbon shell while also reducing the unnecessary exposing areas simultaneously. Moreover, the pores in the MOF-derived carbon shells offered good channels for Li-ion penetration and diffusion. The resulted composite electrode exhibited excellent electrochemical performance and delivered a capacity of 3714 mAh g−1 at 200 mA g−1, and an outstanding reversible capacity of 820 mAh g−1 at 5000 mA g−1 even after 1000 cycles, Direct comparison between the encapsulated Si and naked Si revealed the significance of the MOF-derived carbon shells and its great potential for the next-generation high capacity LIBs.

Graphene materials have attracted significant research interest as anodes in lithium-ion batteries (LIBs). However, their low volumetric capacity and high working voltage limit the energy density and thus hinder their practical applications. In this research, monolayer graphene and MoS2 were prepared by controlled CVD growth processes. Graphene/MoS2 alternately stacked structure (GMASS) was subsequently fabricated by alternately stacking graphene and MoS2 monolayers layer by layer. When evaluated as an anode for LIB, GMASS demonstrates an obviously reduced working voltage compared to monolayer graphene electrodes (1.31 V vs. 1.46 V). And its volumetric capacity is much higher than that of an average graphite anode (1260 mAh cm−3 vs. 461 mAh cm−3). This fundamental research could promote the development of graphene/MoS2 heterostructures for high-energy LIBs.