Dae Yang Oh

Solution-Processable Glass LiI-Li4SnS4 Superionic Conductors for All-Solid-State Li-Ion Batteries

A new, highly conductive (4.1 × 10(-4) S cm(-1) at 30 °C), highly deformable, and dry-air-stable glass 0.4LiI-0.6Li4 SnS4 is prepared using a homogeneous methanol solution. The solution process enables the wetting of any exposed surface of the active materials with highly conductive solidified electrolytes (0.4LiI-0.6Li4 SnS4), resulting in considerable improvements in the electrochemical performance of these electrodes over conventional mixture electrodes.

Bendable and Thin Sulfide Solid Electrolyte Film: A New Electrolyte Opportunity for Free-Standing and Stackable High-Energy All-Solid-State Lithium-Ion Batteries

Bulk-type all-solid-state lithium batteries (ASLBs) are considered a promising candidate to outperform the conventional lithium-ion batteries. Unfortunately, the current technology level of ASLBs is in a stage of infancy in terms of cell-based (not electrode-material-based) energy densities and scalable fabrication. Here, we report on the first ever bendable and thin sulfide solid electrolyte films reinforced with a mechanically compliant poly(paraphenylene terephthalamide) nonwoven (NW) scaffold, which enables the fabrication of free-standing and stackable ASLBs with high energy density and high rate capabilities. The ASLB, using a thin (∼70 μm) NW-reinforced SE film, exhibits a 3-fold increase of the cell-energy-density compared to that of a conventional cell without the NW scaffold.

Infiltration of Solution-Processable Solid Electrolytes into Conventional Li-Ion-Battery Electrodes for All-Solid-State Li-Ion Batteries

Bulk-type all-solid-state lithium-ion batteries (ASLBs) have the potential to be superior to conventional lithium-ion batteries (LIBs) in terms of safety and energy density. Sulfide SE materials are key to the development of bulk-type ASLBs because of their high ionic conductivity (max of ∼10-2 S cm-1) and deformability. However, the severe reactivity of sulfide materials toward common polar solvents and the particulate nature of these electrolytes pose serious complications for the wet-slurry process used to fabricate ASLB electrodes, such as the availability of solvent and polymeric binders and the formation of ionic contacts and networks. In this work, we report a new scalable fabrication protocol for ASLB electrodes using conventional composite LIB electrodes and homogeneous SE solutions (Li6PS5Cl (LPSCl) in ethanol or 0.4LiI-0.6Li4SnS4 in methanol). The liquefied LPSCl is infiltrated into the tortuous porous structures of LIB electrodes and solidified, providing intimate ionic contacts and favorable ionic percolation. The LPSCl-infiltrated LiCoO2 and graphite electrodes show high reversible capacities (141 and 364 mA h g-1) at 0.14 mA cm-2 (0.1 C) and 30 °C, which are not only superior to those for conventional dry-mixed and slurry-mixed ASLB electrodes but also comparable to those for liquid electrolyte cells. Good electrochemical performance of ASLBs employing the LPSCl-infiltrated LiCoO2 and graphite electrodes at 100 °C is also presented, highlighting the excellent thermal stability and safety of ASLBs.

All-solid-state lithium-ion batteries with TiS2 nanosheets and sulphide solid electrolytes

Bulk-type all-solid-state lithium-ion batteries (ASLBs) using sulphide solid electrolytes (SEs) are considered as one of the promising alternative batteries because of their ultimate safety and scalable fabrication. However, they suffer from poor ionic contacts between active materials and SEs. Herein, we report, for the first time, the excellent electrochemical performances of sulphide-SE-based bulk-type ASLBs employing TiS2 nanosheets (TiS2-NSs) prepared by scalable mechanochemical lithiation, followed by exfoliation in water under ultrasonication. The TiS2-NS in all-solid-state cells exhibits an enhancement of reversible capacity which is attributed to the SE region in intimate contact with TiS2-NSs. Importantly, an exceptionally superior rate capability of the TiS2-NS compared to that of bulk TiS2 and even ball-milled TiS2, which is attributed to the ultrathin 2D structure (with short Li-ion diffusion length and intimate contacts between the TiS2-NS and SE) and high electronic conductivity, is highlighted.

Coatable Li4SnS4 solid electrolytes prepared from aqueous solutions for all-solid-state lithium-ion batteries

Bulk-type all-solid-state lithium-ion batteries (ASLBs) for large-scale energy-storage applications have emerged as a promising alternative to conventional lithium-ion batteries (LIBs) owing to their superior safety. However, the electrochemical performance of bulk-type ASLBs is critically limited by the low ionic conductivity of solid electrolytes (SEs) and poor ionic contact between the active materials and SEs. Herein, highly conductive (0.14 mS cm-1 ) and dry-air-stable SEs (Li4 SnS4 ) are reported, which are prepared using a scalable aqueous-solution process. An active material (LiCoO2 ) coated by solidified Li4 SnS4 from aqueous solutions results in a significant improvement in the electrochemical performance of ASLBs. Side-effects of the exposure of LiCoO2 to aqueous solutions are minimized by using predissolved Li4 SnS4 solution.

Diagnosis of failure modes for all-solid-state Li-ion batteries enabled by three-electrode cells

Bulk-type all-solid-state Li-ion batteries have emerged as the enabler to achieve better safety and to use Li metal negative electrodes for higher energy density. However, all-solid-state half-cells fabricated using In or Li–In counter electrodes (CEs) have been routinely tested to assess working electrodes (WEs) without any verification. Moreover, there have been few reports on the in-depth analysis of all-solid-state full-cells, which is imperative for practical applications. In this work, for the first time, we report novel bulk-type all-solid-state three-electrode cells that enable successful deconvolution and diagnosis of the voltages of positive and negative electrodes even for cells having thin solid electrolyte (SE) layers. In the first case study, that of Sn/Li–In half-cells, earlier termination of Li–In CEs than Sn WEs, which results in unexpectedly low capacity, is measured. This problem is solved by percolating Li–In with SEs. For the second case, namely, that of LiNi0.6Co0.2Mn0.2O2/graphite full-cells having only 50–60 μm-thick SE layers (which are fabricated by a scalable wet-slurry process), internal short circuits by penetrating growth of Li metal during charging at high C-rates are revealed for the first time. Further, a unique dischargeability to 0 V for LiNi0.6Co0.2Mn0.2O2/graphite or LiNi0.6Co0.2Mn0.2O2/Si–C full-cells is described.