Thin Free-Standing Sulfide/Halide Bilayer Electrolytes for Solid-State Batteries Using Slurry Processing and Lamination

Thin-film solid electrolytes with wide electrochemical stability windows are required to develop solid-state lithium (Li) metal batteries with high energy densities. In this work, free-standing Li3InCl6 (30 μm)|Li6PS5Cl (30 μm) bilayer thin films are prepared by slurry casting, drying, and lamination. This combination of solid electrolytes is stable at both the cathode interface (high voltages) and anode interface (low voltages). The bilayer thin films exhibit >10× lower area-specific resistance than thick (∼1 mm) pellets fabricated by traditional powder pressing. The free-standing bilayer electrolytes are laminated onto electrodeposited LiCoO2 cathodes. Subsequently a Li–In anode is laminated on top of the stack, and stable cycling of all-solid-state batteries is demonstrated. Because of reduced ohmic losses, cells fabricated with thin-film electrolytes exhibit lower cell polarization and improved rate capability compared with cells with a traditional pellet geometry. This study offers a general strategy to fabricate free-standing bilayer thin-film solid electrolytes for high-energy-density solid-state batteries

Anodes for Sodium Ion Batteries Based on Tin–Germanium–Antimony Alloys

Here we provide the first report on several compositions of ternary Sn–Ge–Sb thin film alloys for application as sodium ion battery (aka NIB, NaB or SIB) anodes, employing Sn50Ge50, Sb50Ge50, and pure Sn, Ge, Sb as baselines. Sn33Ge33Sb33, Sn50Ge25Sb25, Sn60Ge20Sb20, and Sn50Ge50 all demonstrate promising electrochemical behavior, with Sn50Ge25Sb25 being the best overall. This alloy has an initial reversible specific capacity of 833 mAhg^–1 (at 85 mAg^–1) and 662 mAhg^–1 after 50 charge–discharge cycles. Sn50Ge25Sb25 also shows excellent rate capability, displaying a stable capacity of 381 mAhg^–1 at a current density of 8500 mAg^–1 (∼10C). A survey of published literature indicates that 833 mAhg^–1 is among the highest reversible capacities reported for a Sn-based NIB anode, while 381 mAhg^–1 represents the optimum fast charge value. HRTEM shows that Sn50Ge25Sb25 is a composite of 10–15 nm Sn and Sn-alloyed Ge nanocrystallites that are densely dispersed within an amorphous matrix. Comparing the microstructures of alloys where the capacity significantly exceeds the rule of mixtures prediction to those where it does not leads us to hypothesize that this new phenomenon originates from the Ge(Sn) that is able to sodiate beyond the 1:1 Na:Ge ratio reported for the pure element. Combined TOF-SIMS, EELS TEM, and FIB analysis demonstrates substantial Na segregation within the film near the current collector interface that is present as early as the second discharge, followed by cycling-induced delamination from the current collector

Carbon Nanosheet Frameworks Derived from Peat Moss as High Performance Sodium Ion Battery Anodes

We demonstrate that peat moss, a wild plant that covers 3% of the earth’s surface, serves as an ideal precursor to create sodium ion battery (NIB) anodes with some of the most attractive electrochemical properties ever reported for carbonaceous materials. By inheriting the unique cellular structure of peat moss leaves, the resultant materials are composed of three-dimensional macroporous interconnected networks of carbon nanosheets (as thin as 60 nm). The peat moss tissue is highly cross-linked, being rich in lignin and hemicellulose, suppressing the nucleation of equilibrium graphite even at 1100 °C. Rather, the carbons form highly ordered pseudographitic arrays with substantially larger intergraphene spacing (0.388 nm) than graphite (<i>c</i>/2 = 0.3354 nm). XRD analysis demonstrates that this allows for significant Na intercalation to occur even below 0.2 V <i>vs</i> Na/Na⁺. By also incorporating a mild (300 °C) air activation step, we introduce hierarchical micro- and mesoporosity that tremendously improves the high rate performance through facile electrolyte access and further reduced Na ion diffusion distances. The optimized structures (carbonization at 1100 °C + activation) result in a stable cycling capacity of 298 mAh g^–1 (after 10 cycles, 50 mA g^–1), with ∼150 mAh g^–1 of charge accumulating between 0.1 and 0.001 V with negligible voltage hysteresis in that region, nearly 100% cycling Coulombic efficiency, and superb cycling retention and high rate capacity (255 mAh g^–1 at the 210th cycle, stable capacity of 203 mAh g^–1 at 500 mA g^–1)

Hybrid Device Employing Three-Dimensional Arrays of MnO in Carbon Nanosheets Bridges Battery–Supercapacitor Divide

It is a challenge to meld the energy of secondary batteries with the power of supercapacitors. Herein, we created electrodes finely tuned for this purpose, consisting of a monolayer of MnO nanocrystallites mechanically anchored by pore-surface terminations of 3D arrays of graphene-like carbon nanosheets (“3D-MnO/CNS”). The biomass-derived carbon nanosheets should offer a synthesis cost advantage over comparably performing designer nanocarbons, such as graphene or carbon nanotubes. High Li storage capacity is achieved by bulk conversion and intercalation reactions, while high rates are maintained through stable ∼20 nm scale diffusion distances. For example, 1332 mAh g^–1 is reached at 0.1 A g^–1, 567 mAh g^–1 at 5 A g^–1, and 285 mAh g^–1 at 20 A g^–1 with negligible degradation at 500 cycles. We employed 3D-MnO/CNS (anode) and carbon nanosheets (cathode) to create a hybrid capacitor displaying among the most promising performances reported: based on the active materials, it delivers 184 Wh kg^–1 at 83 W kg^–1 and 90 Wh kg^–1 at 15 000 W kg^–1 with 76% capacity retention after 5000 cycles