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Solid-state electrolytes (SSEs) are challenged by complex interfacial chemistry and poor ion transport through the interfaces they form with battery electrodes. Here, we investigate a class of SSE composed of micrometer-sized lithium oxide (Li₂O) particles dispersed in a polymerizable 1,3-dioxolane (DOL) liquid. Ring-opening polymerization (ROP) of the DOL by Lewis acid salts inside a battery cell produces polymer-inorganic hybrid electrolytes with gradient properties on both the particle and battery cell length scales. These electrolytes sustain stable charge-discharge behavior in Li||NCM811 and anode-free Cu||NCM811 electrochemical cells. On the particle length scale, Li₂O retards ROP, facilitating efficient ion transport in a fluid-like region near the particle surface. On battery cell length scales, gravity-assisted settling creates physical and electrochemical gradients in the hybrid electrolytes. By means of electrochemical and spectroscopic analyses, we find that Li₂O particles participate in a reversible redox reaction that increases the effective CE in anode-free cells to values approaching 100%, enhancing battery cycle life. 

Abstract A full cell chemistry of aqueous dual‐ion battery (DIB) was reported, comprising the graphite cathode and 3,4,9,10‐perylenetetracarboxylic diimide (PTCDI) as the anode. This DIB employed a mixture aqueous electrolyte: 5 mtributylmethylammonium (TBMA) chloride plus 5 mMgCl₂, where [MgCl₃]⁻and TBMA⁺serve as the charge carriers for cathode and anode of the DIB, respectively. This novel full cell exhibited a specific capacity of around 41 mAh g⁻¹based on the total active mass of both electrodes with an average operation voltage of 1.45 V and stable cycling for 400 cycles. 

Abstract New acceptor‐type graphite intercalation compounds (GICs) offer candidates of cathode materials for dual‐ion batteries (DIBs), where superhalides represent the emerging anion charge carriers for such batteries. Here, the reversible insertion of [LiCl₂]⁻into graphite from an aqueous deep eutectic solvent electrolyte of 20mLiCl+20mcholine chloride is reported. [LiCl₂]⁻is the primary anion species in this electrolyte as revealed by the femtosecond stimulated Raman spectroscopy results, particularly through the rarely observed H–O–H bending mode. The insertion of Li–Cl anionic species is suggested by⁷Li magic angle spinning nuclear magnetic resonance results that describe a unique chemical environment of Li⁺ions with electron donors around.²H nuclear magnetic resonance results suggest that water molecules are co‐inserted into graphite. Density functional theory calculations reveal that the anionic insertion of hydrated [LiCl₂]⁻takes place at a lower potential, being more favorable. X‐ray diffraction and the Raman results show that the insertion of [LiCl₂]⁻creates turbostratic structure in graphite instead of forming long‐range ordered GICs. The storage of [LiCl₂]⁻in graphite as a cathode for DIBs offers a capacity of 114 mAh g⁻¹that is stable over 440 cycles. 

Abstract Oxidative anion insertion into graphite in an aqueous environment represents a significant challenge in the construction of aqueous dual‐ion batteries. In dilute aqueous electrolytes, the oxygen evolution reaction (OER) dominates the anodic current before anions can be inserted into the graphite gallery. Herein, we report that the reversible insertion of Mg‐Cl superhalides in graphite delivers a record‐high reversible capacity of 150 mAh g⁻¹from an aqueous deep eutectic solvent comprising magnesium chloride and choline chloride. The insertion of Mg‐Cl superhalides in graphite does not form staged graphite intercalation compounds; instead, the insertion of Mg‐Cl superhalides makes the graphite partially turbostratic.