LiI-Doped Sulfide Solid Electrolyte: Enabling a High-Capacity Slurry-Cast Electrode by Low-Temperature Post-Sintering for Practical All-Solid-State Lithium Batteries

Abstract

All-solid-state lithium batteries (ASSLBs) based on sulfide solid electrolytes (SEs) have received great attention because of the high ionic conductivity of the SEs, intrinsic thermal safety, and higher energy density achievable with a Li metal anode. However, studies on practical slurry-cast composite electrodes show an extremely limited battery performance than the binder-free pelletized electrodes because of the poor interfacial robustness between the active materials and SEs by the presence of a polymeric binder. Here, we employ a low-temperature post-sintering process for the slurry-cast composite electrodes in order to overcome the binder-induced detrimental effects on the electrochemical performance. The LiI-doped LiPS SEs are chosen because the addition of iodine not only improves the Li-ion conductivity and Li metal compatibility but also lowers the glass-transition and crystallization temperatures. Low-temperature post-sintering of composite cathodes consisting of a LiNiCoMnO-active material, LiI-doped LiPS SE, polymeric binder, and conducting agent shows a significantly improved electrochemical performance as compared to a conventional slurry-cast electrode containing pre-annealed SEs. Detailed analyses by electrochemical impedance spectroscopy and galvanostatic intermittent titration technique confirm that post-sintering effectively reduces the interfacial resistance and enhances the chemomechanical robustness at solid-solid interfaces, which enables the development of practical slurry-cast ASSLBs with sulfide SEs.

Li4SiO4 Doped-Li7P2S8I solid electrolytes with high lithium stability synthesised using liquid-phase shaking

“…In contrast, the x = 20 and 30 samples had similar results before and after the EIS measurement, showing no enhancement in their conductivities. This is compatible with the XRD pattern for the x = 10 sample after the EIS measurement, which indicates the presence of highly conductive thio-LISICON II analogue phase 11,15–17 as shown in Fig. S2 †.…”

“…In addition, diffraction peaks at 2 θ = 20°, 25°, and 30° in both samples were attributed to the highly conductive thio-LISICON analogue phase. 11,16,17 Next, the effect of Li 4 SiO 4 -doping on Li 7 P 2 S 8 I was considered. The peaks attributed to Li 4 SiO 4 were not identified and no peak shifts were observed in Li 7 P 2 S 8 I·10Li 4 SiO 4 .…”

Graphitic Hollow Nanocarbon as a Promising Conducting Agent for Solid‐State Lithium Batteries

“…Indium foil (thickness = 0.05 mm, diameter = 15 mm, Nilaco, Japan) and lithium foil (thickness = 0.02 mm, diameter = 11 mm, Honjo, Japan) with a Cu current collector (thickness = 0.02 mm, diameter = 16 mm) were attached to the other side of the LPSCl pellet. To identify the external pressure effect for electrochemical performance, the pressurized cell was also prepared following a previous report . All the steps were carried out in an Ar‐filled glove box and dry room at a dew point of ≈–100 °C.…”

Current Trends in Nanoscale Interfacial Electrode Engineering for Sulfide‐Based All‐Solid‐State Li‐Ion Batteries

“…The conventional slurry‐casting method applied to the commercial manufacturing of lithium‐ion cells has not been successful for the cells with SSEs primarily due to the detrimental effect of solvent and binder for the slurry formulation. The solvent‐free dry‐film approach for composite cathodes [ 57 ] and the low‐temperature post‐sintering of slurry‐cast composite electrodes [ 58 ] are some of the current techniques to tackle the electrode fabrication issue. In the following sections, the interfacial problems in cathode and anode associated with SSEs are summarized in detail, and the strategies to mitigate such problems are also discussed.…”

“…Where treating active material particles is one method of improving the interfacial characteristics of cathode toward SSEs, fabrication techniques can also be altered to get the characteristics deemed best for ASSLBs. In doing so, instead of modifying the material itself but by changing the sintering process, a novel low‐temperature post‐sintering method is also introduced by Choi et al [ 58 ] for slurry cast composite electrodes; instead of using a pre‐annealed solid electrolyte, they used amorphous LiI‐doped sulfide solid electrolyte and annealed at 160 °C. In this way, post‐annealing was able to manipulate the microstructure and reduced the number of grain boundaries in solid electrolyte, thus increasing the speed of Li mobility.…”