One of the major challenges in advancing polymer-inorganic hybrid solid electrolytes (HSEs) lies in comprehending and controlling their internal structure. In addition, the intricate interplay between multiple phases further complicates efforts to establish the structure-property relationships. In this study, by introducing a multifunctional LiI additive to an HSE compromising of polyethylene oxide (PEO) polymeric electrolyte and the fast lithium-ion conductor Li₆PS₅Cl, the relationship between the bulk and interface structure and ascertaining their impact on lithium-ion dynamics within the HSE is disentangled. Using multidimensional solid-state nuclear magnetic resonance, we find that the addition of LiI stabilizes the internal interfaces and enhances lithium-ion mobility. A kinetically stable solid-electrolyte interphase is formed at the lithium-metal anode, increasing the critical current density to 1.3 mA cm⁻², and enabling long-term stable cycling of lithium symmetric cells (>1200 h). This work sheds light on tailoring the structure of HSEs to improve their conductivity and stability for enabling all-solid-state lithium-metal batteries.

Hybrid solid electrolytes (HSEs) leverage the benefits of their organic and inorganic components, yet optimizing ion transport and component compatibility requires a deeper understanding of their intricate ion transport mechanisms. Here, macroscopic charge transport is correlated with local lithium (Li)-ion diffusivity in HSEs, using poly(ethylene oxide) (PEO) as matrix and Li6PS5Cl as filler. Solvent- and dry-processing methods were evaluated for their morphological impact on Li-ion transport. Through multiscale solid-state nuclear magnetic resonance analysis, we reveal that the filler enhances local Li-ion diffusivity within the slow polymer segmental dynamics. Phase transitions indicate inhibited crystallization in HSEs, with reduced Li-ion diffusion barriers attributed to enhanced segmental motion and conductive polymer conformations. Relaxometry measurements identify a mobile component unique to the hybrid system at low temperatures, indicating Li-ion transport along polymer-filler interfaces. Comparative analysis shows solvent-processed HSEs exhibit better morphological uniformity and enhanced compatibility with Li-metal anodes via an inorganic-rich solid electrolyte interphase.

Lithium argyrodites with high ionic conductivities are favorable solid electrolytes (SEs) for all-solid-state batteries (ASSBs). However, their low preparation efficiency and poor cycling performance hinder their large-scale applications. In this work, we demonstrate successful large-scale production (over 1 kg per batch for the first time) of Li_5.5PS_4.5Cl_0.75Br_0.75 (LPSCB) by fast dry mixing followed by annealing, which presents high room temperature ionic conductivities of 13 mS cm⁻¹ for cold-pressed and 25 mS cm⁻¹ for sintered pellets. Combining neutron powder diffraction and ⁶Li → ⁷Li tracer-exchange nuclear magnetic resonance (NMR) spectroscopy measurements, we show that intercage jumps frequently occur through the 48h-16e-48h pathway in LPSCB, promoting the overall lithium conduction. The assembled ASSBs using LPSCB and a LiNi_0.83Co_0.11Mn_0.06O₂ electrode can be cycled for over 2,500 cycles at a 0.5 C rate and 1,800 cycles at a 2 C rate without any capacity degradation. Our results will accelerate the commercialization of sulfide SE for ASSBs.

Rechargeable lithium (Li)-metal batteries (LMBs) stand out as a top contender for nextgeneration high-energy-density storage solutions, originating from the high theoretical specific capacity and low redox potential of metallic Li. However, developing LMBs is hindered by safety issues arising from dendrite growth as well as electrolyte decomposition reactions during Li plating/stripping. These dendrites can cause short-circuits that may start thermal runaway, greatly amplifying fire hazards. The rapid reaction between the electrolyte and Li-metal leads to the formation of the solid electrolyte interphase (SEI), whose structure and Li-ion conduction properties are crucial for the uniformity of Li deposition. This affects dendrite formation and cycling efficiency, which in turn influences battery life. Yet very little is known about the Li-ion kinetics through the SEI and how these correlate with the structure and composition of the SEI...

Formation cycling is a critical process aimed at improving the performance of lithium ion (Li-ion) batteries during subsequent use. Achieving highly reversible Li-metal anodes, which would boost battery energy density, is a formidable challenge. Here, formation cycling and its impact on the subsequent cycling are largely unexplored. Through solid-state nuclear magnetic resonance (ssNMR) spectroscopy experiments, we reveal the critical role of the Li-ion diffusion dynamics between the electrodeposited Li-metal (ED-Li) and the as-formed solid electrolyte interphase (SEI). The most stable cycling performance is realized after formation cycling at a relatively high current density, causing an optimum in Li-ion diffusion over the Li-metal-SEI interface. We can relate this to a specific balance in the SEI chemistry, explaining the lasting impact of formation cycling. Thereby, this work highlights the importance and opportunities of regulating initial electrochemical conditions for improving the stability and life cycle of lithium metal batteries.

The development of commercial solid-state batteries has to date been hindered by the individual limitations of inorganic and organic solid electrolytes, motivating hybrid concepts. However, the room-temperature conductivity of hybrid solid electrolytes is still insufficient to support the required battery performance. A key challenge is to assess the Li-ion transport over the inorganic and organic interfaces and relate this to surface chemistry. Here we study the interphase structure and the Li-ion transport across the interface of hybrid solid electrolytes using solid-state nuclear magnetic resonance spectroscopy. In a hybrid solid polyethylene oxide polymer–inorganic electrolyte, we introduce two representative types of ionic liquid that have different miscibilities with the polymer. The poorly miscible ionic liquid wets the polymer–inorganic interface and increases the local polarizability. This lowers the diffusional barrier, resulting in an overall room-temperature conductivity of 2.47 × 10⁻⁴ S cm⁻¹. A critical current density of 0.25 mA cm⁻² versus a Li-metal anode shows improved stability, allowing cycling of a LiFePO₄–Li-metal solid-state cell at room temperature with a Coulombic efficiency of 99.9%. Tailoring the local interface environment between the inorganic and organic solid electrolyte components in hybrid solid electrolytes seems to be a viable route towards designing highly conducting hybrid solid electrolytes.