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Solid-state batteries (SSBs) promise better safety and potentially higher energy density than the conventional liquid- or gel-based ones. In practice, the implementation of SSBs often necessitates 3D porous scaffolds made by ceramic solid-state electrolytes (SSEs). Herein, a general and facile method to sinter 3D porous scaffolds with a range of ceramic SSEs on various substrates at high temperature in seconds is reported. The high temperature enables rapid reactive sintering toward the desired crystalline phase and expedites the surface diffusion of grains for neck growth; meanwhile, the short sintering duration limits the coarsening, thus accurately controlling the degree of densification to preserve desired porous structures, as well as reducing the loss of volatile elements. As a proof-of-concept, a composite SSE with a good ionic conductivity (i.e., ≈1.9 × 10-4 S cm-1 at room temperature) is demonstrated by integrating poly(ethylene oxide) with the 3D porous Li6.5 La3 Zr1.5 Ta0.5 O12 scaffold sintered by this method. This method opens a new door toward sintering a variety of ceramic-SSE-based 3D scaffolds for all-solid-state battery applications.

A bilayer actuator made of carbon nanotubes (CNTs) and boron nitride (BN) is developed that can withstand high temperatures. The bilayer actuator can be powered quickly to a temperature up to 2000 K within 100 ms and can operate at frequencies from sub-Hertz to about 30 Hz due to the low heat capacity of the thin CNT layer.

Lithium-metal batteries are considered one of the most promising energy-storage systems owing to their high energy density, but their practical applications have long been hindered by significant safety concerns and poor cycle stability. Solid-state electrolytes (SSEs) are expected to improve not only the safety but also the energy density of Li-metal batteries. The key challenge for solid-state Li-metal batteries lies in the low ionic conductivity of the SSEs and moreover the interface contact between the electrode and SSE. To achieve feasible solid-state Li-metal batteries, it is imperative that the ionic conductivity is improved, especially at the electrode-SSE interface. Herein, recent advances in interface engineering for solid-state Li-metal batteries are reported, mainly focusing on garnet-type SSEs. Various materials to modify the cathode-garnet and Li-garnet interfaces by intermediate layers, alloys, and polymer electrolytes are analyzed. Structural innovations for SSEs including composite electrolytes and multilayer SSE frameworks are reviewed, along with advanced characterization approaches to probe the interfaces, which will provide further insights for garnet-based solid-state batteries. Future challenges and the great promise of garnet-based Li-metal batteries are discussed to close.

Biological tissues generally exhibit excellent anisotropic mechanical properties owing to their well-developed microstructures. Inspired by the aligned structure in muscles, a highly anisotropic, strong, and conductive wood hydrogel is developed by fully utilizing the high-tensile strength of natural wood, and the flexibility and high-water content of hydrogels. The wood hydrogel exhibits a high-tensile strength of 36 MPa along the longitudinal direction due to the strong bonding and cross-linking between the aligned cellulose nanofibers (CNFs) in wood and the polyacrylamide (PAM) polymer. The wood hydrogel is 5 times and 500 times stronger than the bacterial cellulose hydrogels (7.2 MPa) and the unmodified PAM hydrogel (0.072 MPa), respectively, representing one of the strongest hydrogels ever reported. Due to the negatively charged aligned CNF, the wood hydrogel is also an excellent nanofluidic conduit with an ionic conductivity of up to 5 × 10-4 S cm-1 at low concentrations for highly selective ion transport, akin to biological muscle tissue. The work offers a promising strategy to fabricate a wide variety of strong, anisotropic, flexible, and ionically conductive wood-based hydrogels for potential biomaterials and nanofluidic applications.