The resurgence of the lithium metal battery requires innovations in technology, including the use of non-conventional liquid electrolytes. The inherent electrochemical potential of lithium metal (-3.04 V vs. SHE) inevitably limits its use in many solvents, such as acetonitrile, which could provide electrolytes with increased conductivity. The aim of this work is to produce an artificial passivation layer at the lithium metal/electrolyte interface that is electrochemically stable in acetonitrile-based electrolytes. To produce such a stable interface, the lithium metal was immersed in fluoroethylene carbonate (FEC) to generate a passivation layer via the spontaneous decomposition of the solvent. With this passivation layer, the chemical stability of lithium metal is shown for the first time in 1 m LiPF in acetonitrile.

Summary The effects of solvent absorption on the electrochemical and mechanical properties of polymer electrolytes for use in solid-state batteries have been measured by researchers since the 1980s. These studies have shown that small amounts of absorbed solvent may increase ion mobility and decrease crystallinity in these materials. Even though many polymers and lithium salts are hygroscopic, the solvent content of these materials is rarely reported. As ppm-level solvent content may have important consequences for the lithium conductivity and crystallinity of these electrolytes, more widespread reporting is recommended. Here we illustrate that ppm-level solvent content can significantly increase ion mobility, and therefore the reported performance, in solid polymer electrolytes. Additionally, the impact of absorbed solvents on other battery components has not been widely investigated in all-solid-state battery systems. Therefore, comparisons will be made with systems that use liquid electrolytes to better understand the consequences of absorbed solvents on electrode performance.

Gel polymer electrolytes (GPEs) based on polyacrylonitrile elastomer (HNBR) are investigated for lithium-ion batteries application. This study examines the acrylonitrile content, as well as the solvent used to make the GPE, to understand their impact on lithium solvation. To do so, we propose a three-component system comprising HNBR:solvent:LiTFSI to pinpoint the correct ratio to provide the GPE with competitive conductivity. Infrared spectroscopy is used to shed light on the interactions between nitriles and lithium ions. Spin–lattice relaxation times (T 1) and diffusion coefficients of 7Li and 19F for various HNBR-based GPEs are obtained through PFG-NMR, enabling determination of the transport number of lithium cations (t +) and activation energy (E a). Among the GPEs tested, those composed of propylene carbonate with 2 M LiTFSI and HNBR with an acrylonitrile content of 50% are the most promising, with an ionic conductivity of 2.1 × 10–3 S/cm, D 7Li of 12.0 × 10–8 cm/s, and a t + of 0.42 at room temperature. When this GPE was tested in Li5Ti4O12/LiFePO4 coin cells, a capacity of 135 mAh/g was obtained at a discharge rate of D/5, showing promising results for its use in Li-ion batteries. This study highlights the benefits of high acrylonitrile content in the polymer and a solvent with a moderate donor number to promote interactions between nitriles and Li+.

With the ever-growing energy storage notably due to the electric vehicle market expansion and stationary applications, one of the challenges of lithium batteries lies in the cost and environmental impacts of their manufacture. The main process employed is the solvent-casting method, based on a slurry casted onto a current collector. The disadvantages of this technique include the use of toxic and costly solvents as well as significant quantity of energy required for solvent evaporation and recycling. A solvent-free manufacturing method would represent significant progress in the development of cost-effective and environmentally friendly lithium-ion and lithium metal batteries. This review provides an overview of solvent-free processes used to make solid polymer electrolytes and composite electrodes. Two methods can be described: heat-based (hot-pressing, melt processing, dissolution into melted polymer, the incorporation of melted polymer into particles) and spray-based (electrospray deposition or high-pressure deposition). Heat-based processes are used for solid electrolyte and electrode manufacturing, while spray-based processes are only used for electrode processing. Amongst these techniques, hot-pressing and melt processing were revealed to be the most used alternatives for both polymer-based electrolytes and electrodes. These two techniques are versatile and can be used in the processing of fillers with a wide range of morphologies and loadings.

We reproducibly quantify water content in different SPE systems through the various processing/drying conditions and we tie the residual amounts of water to heightened ionic conductivities. Moreover, we emphasise on...

In this paper, we will describe in detail the setting up of a Design of Experiments (DoE) applied to the formulation of electrodes for Li-ion batteries. We will show that, with software guidance, Designs of Experiments are simple yet extremely useful statistical tools to set up and embrace. An Optimal Combined Design was used to identify influential factors and pinpoint the optimal formulation, according to the projected use. Our methodology follows an eight-step workflow adapted from the literature. Once the study objectives are clearly identified, it is necessary to consider the time, cost, and complexity of an experiment before choosing the responses that best describe the system, as well as the factors to vary. By strategically selecting the mixtures to be characterized, it is possible to minimize the number of experiments, and obtain a statistically relevant empirical equation which links responses and design factors.

Substituting flammable liquid electrolytes with solid polymer electrolytes (SPEs) presents a serious challenge in improving the safety of lithium-ion batteries. Even though SPEs are a safer choice, their ionic transport properties are still lower than those of their liquid counterparts (<10 −4 S•cm −1 at room temperature). Here, we report the preparation of a blend of polymers used as SPEs in lithium-ion batteries. Composed of an elastomer, hydrogenated nitrile butadiene rubber (HNBR), and poly(ethylene oxide) (PEO), this blend combines the high conductivity of PEO and the stable properties of HNBR and shows better flexibility than a pristine PEO SPE. It is worth noting that the addition of HNBR, coupled with the intrinsic LiTFSI salt concentration, also reduces the crystallinity and melting temperature of typical PEO-LiTFSI SPEs; this also explains the higher ionic conductivity at low temperature (1.18 × 10 −4 S•cm −1 at 40 °C). Given these initial results, we may conclude that this polymer blend is a promising candidate as an SPE for all solid-state lithium-ion batteries.

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