Liquid-phase exfoliation of 2D transition metal dichalcogenides (TMDs) nanosheets in water is critical for their practical applications towards advanced thin-film electronics and ionotronics. We here report a versatile strategy for liquid-phase exfoliation of clay-like water-swollen TMD multilayers into delaminated 2D TMD nanosheets (including MoS2, WS2, MoSe2, etc.) with thin thicknesses of < 2 nm (e.g., 1.4 nm of MoS2) and high nanosheet concentrations. The delaminated TMD nanosheets can form stable colloidal dispersions in water with low Zeta potentials of <–32 mV over a month, and undergo phase transformation upon annealing from metallic 1 T phase to semiconducting 2H phase. These nanosheets can be coated on various circuit substrates as thin-film ionotronics; for example, an ionotronic device with an as-delaminated MoS2 channel achieves a high transconductance of 23 µS at a low operating voltage of −0.2 V. The delaminated TMDs dispersions are capable of co-dispersing other nanomaterials including 2D MXene and graphene, and 1D carbon nanotube and cellulose nanofibrils, forming stable colloidal co-dispersions in water offering a platform to fabricate multifunctional TMD-based nanocomposite films with high electromechanical integrity. Examples of MoS2/MXene films show an electronic conductivity of 1.66 × 105 S m−1 and a tensile strength of 70 MPa, higher than pure MoS2 films of 1.08 × 104 S m−1 and 55 MPa, and MoS2/CNF films with a higher tensile strength of 178 MPa and their hydrogel films presenting a mixed electronic/ionic conductivity of 18.2/0.16 S m−1. These outcomes promise potentially scalable applications in neuromorphic ionotronics, flexible electronics, energy storage, etc.

Herein, we report on scalable, environmentally benign, and additive-free, high-performance anodes for alkali-metal-ion batteries (MIBs, where M = Li+, Na+, K+). The intercalators in these anodes are the red phosphorus (RP) nanoparticles of uniform size (~40 nm), which are dispersible and blend with water-dispersed Ti3C2Tx MXene, forming a highly viscous aqueous slurry to fabricate additive-free nanocomposite electrodes. We further enhanced their performance using a very low weight percentage of various carbonaceous nanomaterials. Our RP-MWCNT/MXene nanocomposite anodes exhibited enhanced ion transport and low charge transfer resistance, delivering specific capacities of 1293.7 mA h g-1 at 500 mA g-1 and 263.3 mA h g-1 at 2600 mA g-1 for 10 000 cycles in Li+ cells, 371.6 mA h g-1 at 500 mA g-1 in Na+ cells, and 732.8 mA h g-1 at 50 mA g-1 in K+ cells. Our work shows a path towards fabricating nanoarchitectured electrodes using sustainable materials to eliminate inert polymer binders, toxic processing solvents, and rare earth elements from the battery fabrication process for next-generation alkali-metal-ion batteries.

The drawbacks of amorphous hard carbon are its low conductivity and structural instability, due to its large volume change and the occurrence of side reactions with the electrolyte during cycling. Here, we propose a simple and rapid method to address these disadvantages; we used an emulsion solvent-evaporation method to create hierarchically structured microparticles of hard carbon nanoparticles, derived from soot, and multi-walled-carbon-nanotubes at a very low threshold of 2.8 wt%. These shrub-ball like microparticles have well-defined void spaces between different nanostructures of carbon, leading to an increased surface area, lower charge-resistance and side reactions, and higher electronic conductivity for Na+ insertion and de-insertion. They can be slurry cast to assemble Na+ anodes, exhibiting an initial discharge capacity of 713.3 mA h g(-1) and showing long-term stability with 120.8 mA h g(-1) at 500 mA g(-1) after 500 cycles, thus outperforming neat hard carbon nanoparticles by an order of magnitude. Our work shows that hierarchical self-assembly is attractive for increasing the performance of microparticles used for battery production.

Synaptic devices with linear high-speed switching can accelerate learning in artificial neural networks (ANNs) embodied in hardware. Conventional resistive memories however suffer from high write noise and asymmetric conductance tuning, preventing parallel programming of ANN arrays. Electrochemical random-access memories (ECRAMs), where resistive switching occurs by ion insertion into a redox-active channel, aim to address these challenges due to their linear switching and low noise. ECRAMs using 2D materials and metal oxides however suffer from slow ion kinetics, whereas organic ECRAMs enable high-speed operation but face challenges toward on-chip integration due to poor temperature stability of polymers. Here, ECRAMs using 2D titanium carbide (Ti3C2Tx) MXene that combine the high speed of organics and the integration compatibility of inorganic materials in a single high-performance device are demonstrated. These ECRAMs combine the speed, linearity, write noise, switching energy, and endurance metrics essential for parallel acceleration of ANNs, and importantly, they are stable after heat treatment needed for back-end-of-line integration with Si electronics. The high speed and performance of these ECRAMs introduces MXenes, a large family of 2D carbides and nitrides with more than 30 stoichiometric compositions synthesized to date, as promising candidates for devices operating at the nexus of electrochemistry and electronics.