Using the organic ionic plastic crystal N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ([Cmpyr][FSI]) with electrospun nanofibers, LiFSI doped [Cmpyr][FSI]-PVdF composites were developed as solid state, self-standing electrolyte membranes. Different lithium salt concentration were investigated, with 10 mol% LiFSI found to be optimal amongst those assessed. Composites with different weight ratios of plastic crystal and polymer were prepared and 10 wt% polymer gave the highest conductivity. In addition, the effects of PVdF incorporation on the morphological, thermal, and structural properties of the organic ionic plastic crystal were investigated. Ion mobilities were also studied using solid-state nuclear magnetic resonance techniques. The electrolytes were then assembled into lithium symmetric cells and cycled galvanostatically at 0.13 mA cm at both ambient temperature and at 50 °C, for more than 500 cycles.

Organic ionic plastic crystals (OIPCs) are a class of solid-state electrolytes with good thermal stability, non-flammability, non-volatility, and good electrochemical stability. When prepared in a composite with electrospun polyvinylidene fluoride (PVdF) nanofibers, a 1:1 mixture of the OIPC N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ([C mpyr][FSI]) and lithium bis(fluorosulfonyl)imide (LiFSI) produced a free-standing, robust solid-state electrolyte. These high-concentration Li-containing electrolyte membranes had a transference number of 0.37(±0.02) and supported stable lithium symmetric-cell cycling at a current density of 0.13 mA cm . The effect of incorporating PVdF in the Li-containing plastic crystal was investigated for different ratios of PVdF and [Li][FSI]/[C mpyr][FSI]. In addition, Li|LiNi Co Mn O cells were prepared and cycled at ambient temperature and displayed a good rate performance and stability.

Li-ion batteries have revolutionized the portable electronics industry and empowered the electric vehicle (EV) revolution. Unfortunately, traditional Li-ion chemistry is approaching its physicochemical limit. The demand for higher density (longer range), high power (fast charging), and safer EVs has recently created a resurgence of interest in solid state batteries (SSB). Historically, research has focused on improving the ionic conductivity of solid electrolytes, yet ceramic solids now deliver sufficient ionic conductivity. The barriers lie within the interfaces between the electrolyte and the two electrodes, in the mechanical properties throughout the device, and in processing scalability. In 2017 the Faraday Institution, the UK’s independent institute for electrochemical energy storage research, launched the SOLBAT (solid-state lithium metal anode battery) project, aimed at understanding the fundamental science underpinning the problems of SSBs, and recognising that the paucity of such understanding is the major barrier to progress. The purpose of this Roadmap is to present an overview of the fundamental challenges impeding the development of SSBs, the advances in science and technology necessary to understand the underlying science, and the multidisciplinary approach being taken by SOLBAT researchers in facing these challenges. It is our hope that this Roadmap will guide academia, industry, and funding agencies towards the further development of these batteries in the future.

Sulfide‐based Li+ conducting solid electrolytes, such as argyrodite, Li6PS5Cl, for all‐solid‐state batteries can have comparable ionic conductivities with liquid electrolytes. However, the interface between sulfide containing solid electrolytes and Li metal and Li‐ion positive electrodes has been found to be unstable, leading to poor cell performance and cycling. Understanding the in situ evolution of interfacial layers between the electrolyte and both electrodes is of paramount importance for designing stable and long‐life solid‐state batteries. Here, in situ Raman microscopy was used to study the interface between Li6PS5Cl electrolyte and metallic Li and LiCoO2. Under potential control, Raman microscopy identified the appearance of degradation products (Li2S, P2Sx and polysulfides) at the electrode/solid electrolyte interface.