Cation Additive Enabled Rechargeable LiOH‐Based Lithium–Oxygen Batteries

Recent Progress in Developing a LiOH-Based Reversible Nonaqueous Lithium-Air Battery

The realization of practical nonaqueous lithium-air batteries (LABs) calls for novel strategies to address their numerous theoretical and technical challenges. LiOH formation/decomposition has recently been proposed as a promising alternative route to cycling LABs via Li₂ O₂ . Herein, the progress in developing LiOH-based nonaqueous LABs is reviewed. Various catalytic systems, either soluble or solid-state, that can activate a LiOH-based electrochemistry are compared in detail, with emphasis in providing an updated understanding of the oxygen reduction and evolution reactions in nonaqueous media. We identify the key factors that can switch the cell chemistry between Li₂ O₂  and LiOH and highlight the debate around these routes, as well as rationalize potential causes for these opposing opinions. The identities of the reaction intermediates, activity of redox mediators and additives, location of reaction interfaces, causes of parasitic reactions, as well as the effect of CO₂  on the LiOH electrochemistry, all play a critical role in altering the relative rates of a series of interconnected reactions and all warrant further investigation.

An Ionic Liquid Electrolyte with Enhanced Li+ Transport Ability Enables Stable Li Deposition for High-Performance Li-O2 Batteries

Bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte could endow Li-O₂ batteries with low charging overpotential. However, their weak Li⁺ transport ability (LTA) leads to non-uniform Li deposition. Herein, guided by Sand formula, the LTA of TFSI-IL electrolyte is greatly enhanced to realize robust Li deposition through introducing hydrofluoroether (HFE) and optimizing electrolyte component ratios to regulate solvation environment. The solvation environment changes from Li(TFSI)₂ ^- ion pair into ionic aggregate clusters in the optimal electrolyte thanks to the slicing function of HFE toward ionic aggregate network. The transport parameters of Sand formula are synchronously enhanced, resulting in highly robust Li deposition behavior with greatly improved Coulombic efficiency (ca. 97.5 %) and cycling rate (1 mA cm^-2 ). Cycling stability of Li-O₂ batteries was greatly improved (a tiny overpotential rise of 64 mV after 75 cycles).

The Electrolysis of Anti-Perovskite Li2 OHCl for Prelithiation of High-Energy-Density Batteries

Anti-perovskite type Li₂ OHCl was previously studied as a solid-state Li⁺ conductor. Here, we report that the Li₂ OHCl can be electrolyzed at 3.3 V or 4.0 V, with the creation of O₂ /HCl gases and the release of 2 equiv. Li⁺ via two different decomposition routes, depending on the acidity of electrolyte. In the electrolyte with trace acid, the Li₂ OHCl is oxidized at a constant voltage of 3.3 V. In neutral electrolyte, the oxidization of Li₂ OHCl starts at 4.0 V, but the produced HCl will increase the acidity of electrolyte and lead to a voltage drop to 3.3 V for the electrolysis of Li₂ OHCl. The electrolysis of Li₂ OHCl delivers a lithium releasing capacity as high as 810 mAh g^-1 , with an equivalent Li-deposition or Li-intercalation on anode, making it a promising candidate as a Li reservoir for prelithiation of anode. Using Li₂ OHCl as the lithium source, silicon-carbon (Si@C) composite anode can be effectively prelithiated. The full cells composed of LiNi_0.8 Mn_0.1 Co_0.1 O₂ (NMC811) cathode and prelithiated Si@C anode exhibited increased capacities with the increment of prelithiation dosages.