Search

Abstract All-solid-state lithium–sulfur batteries exhibit high energy densities, operate safely, and suppress polysulfide shuttling. However, their electrochemical performance is restricted by the insulating nature of sulfur and Li2S, and by severe cathode-related volumetric changes during cycling. Here, we prepare a Li2S-based cathode composite with high mixed-conductivity and stability, by infiltrating a Li2S–LiI active material solution into a mesoporous carbon replica with ~10-nm-sized pores, followed by mixing with a liquid-phase-synthesized Li6PS5Br solid electrolyte and vapour-grown carbon fibres. Benefiting from a mechanically reinforced, three-dimensional ion/electron-conducting structure, the cathode exhibits high discharge capacity (1009 mAh g−1, 20 cycles, 298 K, 0.05 C) and high reversible capacity (650 mAh g−1, 100 cycles, 298 K, 0.1 C). These findings underscore the feasibility of developing high-performance all-solid-state lithium-sulfur batteries by designing three-dimensional mixed-conducting mechanically robust cathodes.

Abstract Information on the cathode/organic–electrolyte interface structure provides clues regarding the rate and reversibility of lithium intercalation reactions in lithium‐ion batteries. Herein, structural changes within the LiCoO2 electrode, throughout the interphase region, and in the LiPF6/propylene carbonate electrolyte are observed concurrently by in situ neutron reflectometry. The formation of an electrical double layer (EDL) during the early stages of charging and discharging is investigated and compared with that at an intercalation‐inactive Nb:SrTiO3 electrode. At the intercalation‐inactive interface between Nb:SrTiO3 and the electrolyte, a voltage‐dependent ionic distribution corresponding to the EDL forms on the electrolyte side without the formation of a cathode/electrolyte interphase (CEI) layer. In contrast, at the intercalation‐active LiCoO2/electrolyte interface, a CEI layer forms immediately after cell construction, and the ionic distribution in the electrolyte formed outside the CEI layer scarcely changes upon voltage application. The CEI/electrolyte interface is shielded from potential changes by the electronically insulating CEI; therefore, structural changes in the EDL are restricted. This supports the prevailing understanding that the CEI layer defines the rates of solvation/de‐solvation and adsorption/desorption reactions of lithium ions.

A thin-film battery composed of a LiFePO4 cathode/Li3PO4 electrolyte/Li anode was fabricated on a Pt/Ti/Si (PTS) substrate via RF magnetron sputtering. The amorphous Li3PO4 film was densely stacked on a 60 nm-thick LiFePO4 film, which provided a suitable reaction field for understanding the electrochemical properties of LiFePO4 at the interface with the solid electrolyte. The LiFePO4 cathode film exhibited highly reversible lithium desertion/insertion at the interface at room temperature and 60 °C, without any side reactions. An irreversible oxidation reaction occurred during the initial charging process at 100 °C, leading to an increase in the charge-transfer resistance of the LiFePO4/Li3PO4 interface with no significant decrease in the lithium desertion/insertion capacity of LiFePO4. This result suggests the formation of a resistive interphase via the decomposition of Li3PO4 at 100 °C. A severe decrease in capacity is observed at 125 °C, which indicates the LiFePO4-side interface contributed to the side reactions. The film battery exhibits a severe decrease in capacity at 125 °C.

Mechanical properties of Li10.35Ge1.35P1.65S12 (LGPS) solid electrolytes with different grain sizes were investigated via indentation tests. Hand-milled LGPS (HM LGPS, d50: 1.32 μm) and wet-milled LGPS (WM LGPS, d50: 0.46 μm) powders were uniaxially pressed to obtain pellet samples. The HM LGPS and WM LGPS pellets had a similar bulk density of 1.63 g cm-3. At the initial loading/unloading, the WM LPGS pellet showed a large deformation owing to a decrease in cavities compared with the HM LGPS. In the subsequent cycles, both pellets exhibited elastic deformation behavior in the pressure range up to 20 N. The elastic modulus and relative residual depth of HM LGPS and WM LGPS were 21.7 GPa and 15.0 GPa and 0.75 and 0.71, respectively. This result revealed that WM LGPS is more elastically deformable and less plastically deformable than HM LGPS, which could be associated with the grain boundary strengthening interpreted by the Hall-Petch relation. Based on these mechanical properties, the superior cycle stability at the In-Li electrode/WM LGPS electrolyte interface during charging/discharging was discussed. Controlling the mechanical properties of sulfide solid electrolytes by the grain size is important for suppressing physical degradation in all-solid-state batteries. [ABSTRACT FROM AUTHOR]