While solid-state batteries are tantalizing for achieving improved safety and higher energy density, solid ion conductors currently available fail to satisfy the rigorous requirements for battery electrolytes and electrodes. Inorganic ion conductors allow fast ion transport, but their rigid and brittle nature prevents good interfacial contact and impedes device integration and stability.Conversely, flexible polymeric ion conductors provide better interfacial compatibility and mechanical tolerance, but suffer from inferior ionic conductivity (< 10 −5 S cm −1 at room temperature) due to the coupling of ion transport with the polymer chain motion 1-3 . In this work, we report a general design strategy for achieving one-dimensional (1D), high-performance polymer solid-state ion conductors through molecular channel engineering, which we demonstrate via Cu 2+ -coordination of cellulose nanofibrils. The cellulose nanofibrils by themselves are not ionic conductive; however, by opening the molecular channels between the cellulose chains through Cu 2+ coordination we are able to achieve a Li-ion conductivity as high as 1.5×10 −3 S cm −1 at room temperature-a record among all known polymer ion conductors. This improved conductivity is enabled by a unique Li + hopping mechanism that is decoupled from the polymer segmental motion. Also benefitted from such decoupling, the cellulose-based ion conductor demonstrates multiple advantages, including a high transference number (0.78 vs. 0.2-0.5 in other polymers 2 ), low activation energy (0.19 eV), and a wide electrochemical stability window (4.5 V) that accommodate both Li metal anode and high-voltage cathodes. Furthermore, we demonstrate this 1D ion conductor not only as a thin, high-conductivity solid-state electrolyte but also as an effective ion-conducting additive for the solid cathode, providing continuous ion transport pathways with a low percolation threshold, which allowed us to utilize the thickest LiFePO4 solidstate cathode ever reported for high energy density. This approach has been validated with other 3 polymers and cations (e.g., Na + and Zn 2+ ) with record-high conductivities, offering a universal strategy for fast single-ion transport in polymer matrices, with significance that could go far beyond safe, high-performance solid-state batteries.

The energy used for regulating building temperatures accounts for 14% of the primary energy consumed in the U.S. One-quarter of this energy is leaked through inefficient glass windows in cold weather. The development of transparent composites could potentially provide affordable window materials with enhanced energy efficiency. Transparent wood as a promising material has presented desirable performances in thermal and light management. In this work, the performance of transparent wood is optimized toward an energy efficient window material that possesses the following attributes: 1) high optical transmittance (≈91%), comparable to that of glass; 2) high clarity with low haze (≈15%); 3) high toughness (3.03 MJ m −3 ) that is 3 orders of magnitude higher than standard glass (0.003 MJ m −3 ); 4) low thermal conductivity (0.19 W m −1 K −1 ) that is more than 5 times lower than that of glass. Additionally, the transparent wood is a sustainable material, with low carbon emissions and scaling capabilities due to its compatibility with industryadopted rotary cutting methods. The scalable, high clarity, transparent wood demonstrated in current work can potentially be employed as energy efficient and sustainable windows for significant environmental and economic benefits.

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