Thin Solid Electrolyte Layers Enabled by Nanoscopic Polymer Binding

To achieve high-energy all-solid-state batteries (ASSBs), solid-state electrolytes (SE) must be thin, mechanically robust, and possess the ability to form low resistance interfaces with electrode materials. Embedding an inorganic SE into an organic polymer combines the merits of high conductivity and flexibility. However, the performance of such an SE-in-polymer matrix (SEPM) is highly dependent on the microstructure and interactions between the organic and inorganic components. We report on the synthesis of a free-standing, ultrathin (60 μm) SEPM from a solution of lithium polysulfide, phosphorus sulfide, and ethylene sulfide (ES), where the polysulfide triggers the in situ polymerization of ES and the formation of Li3PS4. Reactant ratios were optimized to achieve a room-temperature conductivity of 2 × 10-5 S cm-1. Cryogenic electron microscopy confirmed a uniform nanoscopic distribution of β-Li3PS4 and PES (polyethylene sulfide). This work presents a facile route to the scalable fabrication of ASSBs with promising cycling performance and low electrolyte loading

Electrochemically primed functional redox mediator generator from the decomposition of solid state electrolyte.

Recent works into sulfide-type solid electrolyte materials have attracted much attention among the battery community. Specifically, the oxidative decomposition of phosphorus and sulfur based solid state electrolyte has been considered one of the main hurdles towards practical application. Here we demonstrate that this phenomenon can be leveraged when lithium thiophosphate is applied as an electrochemically "switched-on" functional redox mediator-generator for the activation of commercial bulk lithium sulfide at up to 70 wt.% lithium sulfide electrode content. X-ray adsorption near-edge spectroscopy coupled with electrochemical impedance spectroscopy and Raman indicate a catalytic effect of generated redox mediators on the first charge of lithium sulfide. In contrast to pre-solvated redox mediator species, this design decouples the lithium sulfide activation process from the constraints of low electrolyte content cell operation stemming from pre-solvated redox mediators. Reasonable performance is demonstrated at strict testing conditions

Tuning mobility and stability of lithium ion conductors based on lattice dynamics

Lithium ion conductivity in many structural families can be tuned by many orders of magnitude, with some rivaling that of liquid electrolytes at room temperature. Unfortunately, fast lithium conductors exhibit poor stability against lithium battery electrodes. In this article, we report a fundamentally new approach to alter ion mobility and stability against oxidation of lithium ion conductors using lattice dynamics. By combining inelastic neutron scattering measurements with density functional theory, fast lithium conductors were shown to have low lithium vibration frequency or low center of lithium phonon density of states. On the other hand, lowering anion phonon densities of states reduces the stability against electrochemical oxidation. Olivines with low lithium band centers but high anion band centers are promising lithium ion conductors with high ion conductivity and stability. Such findings highlight new strategies in controlling lattice dynamics to discover new lithium ion conductors with enhanced conductivity and stability.United States. National Science Foundation. Graduate Research Fellowship Program (Grant 1122374)Taiwan. Ministry of Science and Technology (Grant 102-2917-I-564-006-A1)United States. National Science Foundation (Award DMR-0819762)United States. National Energy Research Scientific Computing Center (Contract DE-AC02-05CH11231)Extreme Science and Engineering Discovery Environment (Grant ACI-1548562

Improvements to the Overpotential of All-Solid-State Lithium-Ion Batteries during the Past Ten Years

After the research that shows that Li10GeP2S12 (LGPS)-type sulfide solid electrolytes can reach the high ionic conductivity at the room temperature, sulfide solid electrolytes have been intensively developed with regard to ionic conductivity and mechanical properties. As a result, an increasing volume of research has been conducted to employ all-solid-state lithium batteries in electric automobiles within the next five years. To achieve this goal, it is important to review the research over the past decade, and understand the requirements for future research necessary to realize the practical applications of all-solid-state lithium batteries. To date, research on all-solid-state lithium batteries has focused on achieving overpotential properties similar to those of conventional liquid-lithium-ion batteries by increasing the ionic conductivity of the solid electrolytes. However, the increase in the ionic conductivity should be accompanied by improvements of the electronic conductivity within the electrode to enable practical applications. This essay provides a critical overview of the recent progress and future research directions of the all-solid-state lithium batteries for practical applications

Interfacial architecture for extra Li+ storage in all-solid-state lithium batteries

The performance of nanocomposite electrodes prepared by controlled ball-milling of TiS2 and a Li2S-P2S5 solid electrolyte (SE) for all-solid-state lithium batteries is investigated, focusing on the evolution of the microstructure. Compared to the manually mixed electrodes, the ball-milled electrodes exhibit abnormally increased first-charge capacities of 416 mA h g-1and 837 mA h g-1 in the voltage ranges 1.5-3.0 V and 1.0-3.0 V, respectively, at 50 mA g-1 and 30??C. The ball-milled electrodes also show excellent capacity retention of 95% in the 1.5-3.0 V range after 60 cycles as compared to the manually mixed electrodes. More importantly, a variety of characterization techniques show that the origin of the extra Li+ storage is associated with an amorphous Li-Ti-P-S phase formed during the controlled ball-milling process.open1

硫化物系無機固体電解質を用いた高エネルギー密度型全固体リチウム－硫黄電池の構築

リチウム－硫黄電池は、活物質として用いる硫黄が1675 mAhg-1の非常に大きな理論電気化学容量を有することから、次世代型の高エネルギー密度蓄電デバイスとなり得る可能性があるため、注目を集めている。しかしながら、従来の電解質溶液を用いた電池系では、電気化学的な反応が生じた際に生成するリチウムポリサルファイドが電解質溶液に溶解してしまうため、硫黄をリチウム二次電池の正極活物質として用いることが困難とされてきた。そこで、従来の電池系で用いられてきた電解質溶液を硫化物系固体電解質に置き換えた全固体電池とすることで、放電時に生成するリチウムポリサルファイドが溶解することなく、硫黄が可逆な電極材料として機能し得るとの観点から、硫黄を正極活物質とした全固体型リチウム－硫黄電池の検討を行った。正極活物質としての硫黄の利用効率を向上させる試みとして、1）電子伝導性と触媒機能の付与、2）機械的加工力を利用した均一な電極複合体の作製、3）液体成分の添加による電極複合体の均一性の向上について検討した。これらの検討により、全固体電池における硫黄の利用効率が、理論電気化学容量の約80%にあたる1270 mAhg-1まで向上することを見出した。さらに、100回程度の充放電を繰り返した場合においても、電気化学容量がほとんど劣化することなく、高容量、かつ安定した二次電池として動作することを見出している。また、このような全固体型リチウム－硫黄電池を構築するための材料として、硫化物系固体電解質のイオン伝導特性の向上についても取り組み、1）75Li2S･5P2S3･20P2S5(mol%)ガラスにホットプレスを用いることで、稠密であり、かつ10-3 Scm-1以上の高いイオン導電率を有する固体電解質を構築できること、2）75Li2S･5P2S3･20P2S5(mol%)組成のガラスを523 Kで熱処理したガラスセラミックスにおいて、新しい結晶相が析出していること、また、この新しい結晶相が10-3Scm-1以上の高いイオン導電率を示すことを見出した。さらに、全固体電池用の負極材料についても検討を進め、従来の電解質溶液を用いたリチウムイオン二次電池で用いられている人造黒鉛材料であるMCMB（メソカーボンマイクロビーズ）が、硫化物系固体電解質を用いた電池系においても優れた負極材料特性を示すことを明らかにした。甲南大学平成26年(2014年度

Enabling Thin and Flexible Solid-State Composite Electrolytes by the Scalable Solution Process

All solid-state batteries (ASSBs) have the potential to deliver higher energy densities, wider operating temperature range, and improved safety compared with today's liquid-electrolyte-based batteries. However, of the various solid-state electrolyte (SSE) classes - polymers, sulfides, or oxides - none alone can deliver the combined properties of ionic conductivity, mechanical, and chemical stability needed to address scalability and commercialization challenges. While promising strategies to overcome these include the use of polymer/oxide or sulfide composites, there is still a lack of fundamental understanding between different SSE-polymer-solvent systems and its selection criteria. Here, we isolate various SSE-polymer-solvent systems and study their molecular level interactions by combining various characterization tools. With these findings, we introduce a suitable Li7P3S11SSE-SEBS polymer-xylene solvent combination that significantly reduces SSE thickness (∼50 μm). The SSE-polymer composite displays high room temperature conductivity (0.7 mS cm-1) and good stability with lithium metal by plating and stripping over 2000 h at 1.1 mAh cm-2. This study suggests the importance of understanding fundamental SSE-polymer-solvent interactions and provides a design strategy for scalable production of ASSBs