Excellent Deformable Oxide Glass Electrolytes and Oxide-Type All-Solid-State Li₂S–Si Batteries Employing These Electrolytes

Abstract

Oxide-type all-solid-state lithium-ion batteries have attracted great attention as a candidate for a next-generation battery with high safety performance. However, batteries based on oxide systems exhibit much lower energy densities and rate performances than liquid-type lithium-ion batteries, owing to the difficulty in preparing the ion-and electron-transfer path between particles. In this study, Li 2 SO 4 −Li 2 CO 3 −LiX (X = Cl, Br, and I) glass systems are investigated as highly deformable and high-ionic-conductive oxide electrolytes. These electrolytes show excellent deformable properties and better ionic conductivity. The LiI oxide glass system is a suitable electrolyte for the negative electrode because it shows a higher ionic conductivity and is stable up to 2.8 V. The LiCl or LiBr oxide glass systems are suitable electrolytes for the positive electrode and separation layer because they show high ionic conductivity and kinetic stability up to 3.2 V. The Li 2 S positive and Si negative composite electrodes employing LiBr and LiI oxide glass electrolytes, respectively, show high battery performances because of increased reaction points between active materials and the solid electrolyte and carbon via a mechanical milling process and are capable of forming good interparticle contact. Therefore, it suggests that the excellent deformable electrolytes are suitable for solid electrolytes in composite electrodes because their ionic conductivity does not change by the mechanical milling process. Furthermore, an oxide-type all-solid-state Li 2 S−Si full-battery cell employing these positive and negative composite electrodes and a LiBr oxide glass electrolyte separation layer is demonstrated. The full-battery cell indicates a relatively high discharge capacity of 740 mA h g −1 (Li 2 S) and an area capacity of 2.8 mA h cm −2 at 0.064 mA cm −2 and 45 °C despite using only safe oxide electrolytes.

Effective One-Step Preparation of High Performance Positive and Negative Composite Electrodes for All-Solid-State Li2S-Si Batteries

“…The XRD measurement was performed on a closed cell assembled in an Arfilled glove box for evaluation under an Ar atmosphere, as described in our previous studies. 28,30 X-ray photoelectron spectroscopy (XPS) analyses of the composite electrodes and raw materials were performed on a spectrometer (KRATOS Nova, KRATOS ANALYTICAL) using a monochromatic Al-Kα source. The measurement samples were prepared in an Ar-filled glove box and inserted into the spectrometer using an unexposed transporter under vacuum conditions, as described in our previous studies.…”

“…This battery provided an area capacity of 3.6 mAh cm −2 and an energy density of 270 Wh kg −1 (masses of the positive and negative composite electrodes) at 0.064 mA cm −2 and 45 °C. 28 However, its current density was below that of commercial lithium ion batteries using organic liquid electrolytes. This low performance was attributed to the low ionic conductivity of the oxide glass SEs.…”

A Rational Design of Silicon‐Based Anode for All‐Solid‐State Lithium‐Ion Batteries: A Review

“…[82] To prepare Si electrode with sulfide-or oxide-based electrolyte, a one-step preparation method via mechanical milling is suggested. [83][84][85][86] H. Nagata et al proposed the composite electrode via the one-step method, which consists of Si, activated carbon (AC), and Li 3 PS 4 -LiI in a weight percentage of 50:10:40, respectively. [83] This composite anode is integrated into Li 2 S-Si full cells, where high area capacity of 4.2 mAh cm À2 and energy density of 376 Wh kg À1 were achieved in a current density of 0.25 mA cm À2 at 25 °C.…”

Issues Concerning Interfaces with Inorganic Solid Electrolytes in All-Solid-State Lithium Metal Batteries

“…It has the characteristics of high thermal stability, wide chemical windows, excellent chemical stability against air, and electrochemical stability against lithium metal. The sulfide electrolyte is mainly composed of Li 2 S and sulfides (SiS 2 [28], P 2 S 5 [29], and GeS 2 [30]). Due to the larger radius of S 2− , the lithium-ion transmis-sion channel of the sulfide electrolyte is larger, so the ion conductivity can even reach 10 −2 S cm −1 at room temperature, higher than that of the oxide electrolyte [31].…”