Two-dimensional (2D) materials offer numerous advantages for electrochemical energy storage and conversion due to fast charge transfer kinetics, highly accessible surface area, and tunable electronic and optical properties. Stacking of 2D materials generates heterogeneous interfaces that can modify native chemical and physical material properties. Here, we demonstrate that local strain at a carbon-MoS2 interface in a vertically stacked 2D material directs the pathway for chemical storage in MoS2 on lithium metal insertion. With average measured MoS2 strain of ∼0.1% due to lattice mismatch between the carbon and MoS2 layers, lithium insertion is facilitated by an energy-efficient cation-exchange transformation. This is compared with low-voltage lithium intercalation for unstrained MoS2. This observation implies that mechanical properties of interfaces in heterogeneous 2D materials can be leveraged to direct energetics of chemical processes relevant to a wide range of applications such as electrochemical energy storage and conversion, catalysis and sensing.

A key limitation to the practical incorporation of nanostructured materials into emerging applications is the challenge of achieving low-cost, high throughput, and highly replicable scalable nanomanufacturing techniques to produce functional materials. Here, we report a benchtop roll-to-roll technique that builds upon the use of binary solutions of nanomaterials and liquid electrophoretic assembly to rapidly construct hybrid materials for battery design applications. We demonstrate surfactant-free hybrid mixtures of carbon nanotubes, silicon nanoparticles, MoS2 nanosheets, carbon nanohorns, and graphene nanoplatelets. Roll-to-roll electrophoretic assembly from these solutions enables the controlled fabrication of homogeneous coatings of these nanostructures that maintain chemical and physical properties defined by the synergistic combination of nanomaterials utilized without adverse effects of surfactants or impurities that typically limit liquid nanomanufacturing routes. To demonstrate the utility of this nanomanufacturing approach, we employed roll-to-roll electrophoretic processing to fabricate both positive and negative electrodes for lithium ion batteries in less than 30 s. The optimized full-cell battery, containing active materials of prelithiated silicon nanoparticles and MoS2 nanosheets, was assessed to exhibit energy densities of 167 Wh/kgcell(-1) and power densities of 9.6 kW/kgcell(-1).

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Two-dimensional (2-D) transition metal dichalcogenides (TMDs) are a family of nanostructures possessing exciting physical properties relevant toward applications often requiring fabrication of macroscopic films and networks. Here, we demonstrate electrophoretic deposition (EPD) for assembly of a broad range of 2-D TMDs, including molybdenum disulfide (MoS 2 ), molybdenum diselenide (MoSe 2 ), and tungsten disulfide (WS 2 ), into uniform coatings that can be universally applied on both planar and porous three-dimensional foam electrodes. This assembly process can be directly coupled with solvent exfoliation to yield one-batch processing capable of transforming bulk TMD powders into functional films and coatings of 2-D TMD nanostructures. EPD from common exfoliating solvents 1-methyl-2-pyrollidone (NMP) and acetonitrile (ACN) indicates assembly kinetics governed by the inherent solution properties of the solvents, with poorer exfoliation in ACN compared to NMP, but more rapid deposition kinetics in ACN compared to NMP. In-situ absorbance monitoring indicates the capability to completely deposit all dispersed mass of highly purified 2-D TMDs onto a solid substrate. Overall, our work demonstrates EPD as a versatile and efficient route to assemble 2-D TMD nanostructures directly from exfoliated dispersions into planar and 3-D substrates for use in diverse applications.The heightened interest in two-dimensional (2-D) materials in recent years has led to tremendous interest in the novel electronic, optical, chemical, and electrochemical properties of these materials that can strongly differ from that observed in bulk materials. 1-3 Specifically, the transition metal dichalcogenides (TMDs) have received widespread attention due to the versatile chemical and electronic properties that arise from the available compositions, structures, and dimensionalities. 4-6 Unlike 2-D carbon sheets, TMDs represent a group of elements exhibiting a variable bandgap dependent on the number of layers in the sample, the elemental composition, and the presence of doping atoms which make them ideal for electronic and electrochemical devices. 7 TMDs are represented by the general formula MX 2 , and are composed of both a transition metal element (M) and a chalcogen species (X). Materials with this general formula characteristically possess a unique layered structure in which covalently bonded planes of M and X atoms are held together through weak van der Waals interaction. This unique atomic architecture enables facile exfoliation of the material to ultra-thin structures as small as one layer thick when starting with bulk materials. 8 Despite this straightforward route for liquid processing, current methods to produce high quality TMD materials for applications pivot around high cost, energy intensive, and low-yield techniques such as chemical vapor deposition or mechanical cleavage. 9 These routes are not suited for producing vast quantities of material, and this is a significant challenge for many applications, such as in electrochemical (e....