No carbon added: Using the intrinsic oxidative power of LiFePO4/FePO4 combined with the reinsertion of lithium ions, the formation of the conducting polymer poly(3,4‐ethylenedioxythiophene) (PEDOT) at the solid surface is demonstrated (see picture). The resulting composites have very promising electrochemical properties in rechargeable lithium batteries; in particular, they allow for the elimination of carbon additives.

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.

No abstract

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+.