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.

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Argyrodites, with fast lithium-ion conduction, are promising for applications in rechargeable solid-state lithium-ion batteries. We report a new compositional space of argyrodite superionic conductors, Li 6−x PS 5−x ClBr x [0 ≤ x ≤ 0.8], with a remarkably high ionic conductivity of 24 mS/cm at 25 °C for Li 5.3 PS 4.3 ClBr 0.7 . In addition, the extremely low lithium migration barrier of 0.155 eV makes Li 5.3 PS 4.3 ClBr 0.7 highly promising for low-temperature operation. Average and local structure analyses reveal that bromination (x > 0) leads to (i) retention of the parent Li 6 PS 5 Cl structure for a wide range of x in Li 6−x PS 5−x ClBr x (0 ≤ x ≤ 0.7), (ii) co-occupancy of Cl − , Br − , and S 2− at 4a/4d sites, and (iii) gradually increased Li + -ion dynamics, eventually yielding a "liquid-like" Li-sublattice with a flattened energy landscape when x approaches 0.7. In addition, the diversity of anion species and Li-deficiency in halogen-rich Li 6−x PS 5−x ClBr x induce hypercoordination and coordination entropy for the Li-sublattice, also leading to enhanced Li + -ion transport in Li 6−x PS 5−x ClBr x . This study demonstrates that mixed-anion framework can help stabilize highly conductive structures in a compositional space otherwise unstable with lower anion diversity.

Organic−inorganic hybrid solid electrolytes are expected to integrate the merits of both moieties for addressing the challenges in achieving fast ion conduction and high stability for energy storage applications. Li 10 GeP 2 S 12 (LGPS)-poly-(ethylene oxide) (PEO) (bis(trifluoromethane)sulfonimide lithium (LiTFSI)) hybrid electrolytes have been prepared, which exhibit ionic conductivities up to 0.22 mS cm −1 and good longterm cycling stability against Li-metal. High-resolution solid-state 6 Li NMR is employed to examine the local structural environments of Li ions in the LGPS-PEO (LiTFSI) hybrids, which identifies Li ions from PEO (LiTFSI), in bulk LGPS, and at LGPS-PEO interfaces. Tracer-exchange Li NMR reveals that Li ions transport mainly through LGPS-PEO interfaces. The impact of LGPS and LiTFSI contents on the interface chemistry within LGPS-PEO hybrid electrolytes has been examined. The measured conductivities of LGPS-PEO hybrids positively correlate with the available Li ions at LGPS-PEO interfaces. This study provides insights for engineering interfaces in organic− inorganic hybrids to develop high-performance electrolytes for solid-state rechargeable batteries.

Carbon nanotube (CNT) forests were grown directly on a silicon substrate using a Fe/Al/Mo stacking layer which functioned as both the catalyst material and subsequently a conductive current collecting layer in pseudocapacitor applications. A vacuum-assisted, in situ electrodeposition process has been used to achieve the three-dimensional functionalization of CNT forests with inserted nickel nanoparticles as pseudocapacitor electrodes. Experimental results have shown the measured specific capacitance of 1.26 F/cm(3), which is 5.7 times higher than pure CNT forest samples, and the oxidized nickel nanoparticle/CNT supercapacitor retained 94.2% of its initial capacitance after 10,000 cyclic voltammetry tests.

High ionic conductivity of solid electrolytes is key to achieving high-power all-solid-state rechargeable batteries. The superionic argyrodite family is among the most conductive Li-ion conductors. However, their potential in ionic conductivity and stability is far from being reached, especially with Li 6 PS 5 Br. Here, we synthesized Li 6−x PS 5−x Br 1+x with increased site mixing of Br − /S 2− . An ionic conductivity of 11 mS cm −1 at 25 °C is achieved with a low activation energy of 0.18 eV for Li 5.3 PS 4.3 Br 1.7 . The influence of Br − /S 2− mixing on ion conduction is systematically investigated with multinuclear solid-state NMR coupled with X-ray diffraction and impedance spectroscopy. A statistically random distribution of Br − and S 2− at 4d sites is observed with 31 P NMR. The resulting local structures regulate the jump rates of their neighboring Li ions and Li redistribution. As a result, the increased Li + occupancy at 24g sites promotes fast ion conduction, and the role of Li (24g) in ion conduction has been elucidated with tracer-exchange NMR. Experimental evidence combined with density functional theory calculations has revealed that the particular arrangement of 1S3Br at 4d sites near Li maximizes overall Li + conduction. This insight applies to other argyrodites and will be useful to the design of new fast ion conductors.

All-solid-state rechargeable sodium (Na)-ion batteries are promising for inexpensive and high-energy-density large-scale energy storage. In this contribution, new Na solid electrolytes, Na 3−y PS 4−x Cl x , are synthesized with a strategic approach, which allows maximum substitution of Cl for S (x = 0.2) without significant compromise of structural integrity or Na deficiency. A maximum conductivity of 1.96 mS cm −1 at 25 °C is achieved for Na 3.0 PS 3.8 Cl 0.2 , which is two orders of magnitude higher compared with that of tetragonal Na 3 PS 4 (t-Na 3 PS 4 ). The activation energy (E a ) is determined to be 0.19 eV. Ab initio molecular dynamics simulations shed light on the merit of maximizing Cldoping while maintaining low Na deficiency in enhanced Na-ion conduction. Solid-state nuclear magnetic resonance (NMR) characterizations confirm the successful substitution of Cl for S and the resulting change of P oxidation state from 5+ to 4+, which is also verified by spin moment analysis. Ion transport pathways are determined with a tracer-exchange NMR method. The functional detects that promote Na -ion transport are maximized for further improvement in ionic conductivity. Full-cell performance is demonstrated using Na/Na 3.0 PS 3.8 Cl 0.2 /Na 3 V 2 (PO 4 ) 3 with a reversible capacity of ≈100 mAh g −1 at room temperature.

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