We demonstrate here that hemoglobin, a biological oxygen binder/transporter, can be used as a performance-enhancing additive in nonaqueous lithium–oxygen batteries. In a fashion similar to the way hemoglobin binds and transports oxygen in the human blood, it can bind and transport oxygen in the electrolyte solution in a conventional lithium–oxygen battery. Binding and transport of oxygen into the soluble electrolyte phase enhance the efficiency of oxygen reduction reactions (ORRs) occurring at the air cathode by preventing the accumulation of solid insulating discharge products at the cathode site. We observe stable galvanostatic cycling, high specific capacity, and low polarization in the cell in the presence of hemoglobin. Electrochemical impedance spectroscopy indicates low interfacial resistance even after several rounds of galvanostatic charge–discharge cycles. We thus propose the use of oxygen-binding natural biomolecules as possible redox mediators for energy-harvesting systems utilizing oxygen electrochemistry in the future.

We discuss here a self-standing and flexible homogeneous amorphous gel polymer electrolyte (abbreviated as LiGPE) as an alternative electrolyte for lithium-metal batteries. The LiGPE, comprises of a large volume of liquid lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in tetra ethylene glycol dimethyl ether (TEGDME) electrolyte confined inside in situ synthesized network of acrylonitrile and acrylate, which is poly(ethylene glycol) methyl ether methacrylate or PEGME-MA. The glyme-based liquid electrolyte in the LiGPE discussed here, which is completely devoid of ionic liquids, essentially plays the role of a plasticizer. The LiGPE exhibits high room temperature ionic conductivity (2.3 mS cm À 1 ), high lithiumtransference number of approximately 0.6, good thermal stability (155 °C) and excellent electrochemical properties. At varying current densities, it facilitates a dendrite free plating and de-plating of lithium across its interface for long periods of time. The high oxidative stability against lithium (Li) up to 5.3 V strongly suggests that it will provide a safer operating Li-metal battery compared to conventional liquid electrolytes. The LiGPE, when assembled in Li-metal cell comprising of Li-metal anode and Li-ion insertion cathode material (LiFePO 4 , LFP), demonstrated excellent stability and delivered 90 % of theoretical capacity when cycled over 100 cycles. We discuss here a selfstanding and flexible homogeneous amorphous gel polymer electrolyte (abbreviated as LiGPE) as an alternative electrolyte for lithium-metal batteries. The gel shows superior interfacial properties with lithium (Li) metal, supressing dendritic growth and enhancing Li-ion transference number (0.64). The high oxidative stability against Li up to 5.3 V strongly suggests that it will provide a safer operating Li-metal battery. The LiGPE, comprises of a large volume of liquid lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in tetra ethylene glycol dimethyl ether (TEGDME) electrolyte confined inside insitu synthesized network of acrylonitrile and acrylate, which is poly(ethylene glycol) methyl ether methacrylate or PEGMEMA. The glyme-based liquid electrolyte in the LiGPE discussed here, which is completely devoid of ionic liquids, essentially plays the role of a plasticizer, enhancing the ionic conductivity (2.3 mS cm À 1 ) without compromising with the mechanical stability or thermal stability (155 °C) of GPE.

We present here a gel polymer electrolyte, where the Li+-ion transport is completely decoupled from the polymer host solvation and dynamics. A free-standing gel polymer electrolyte with a high volume content (nearly 60%) of xM LiTFSI in G4 (tetraglyme) ( x = 1–7; Li+:G4 = 0.2–1.5) liquid electrolyte confined inside the PAN (polyacrylonitrile)-PEGMEMA [poly (ethylene glycol) methyl ether methacrylate oligomer] based polymer matrix is synthesized using a one-pot free radical polymerization process. For LiTFSI concentrations, x = 1–7 (Li+:G4 = 0.2–1.5), Raman and vibrational spectroscopies reveal that like in the liquid electrolyte, the designed gel polymer electrolytes (GPEs) also show direct coordination of Li+-ions with the tetraglyme leading to the formation of [Li(G4)]+. Coupled with the spectroscopic studies, impedance and nuclear magnetic resonance investigations also show that the ion transport is independent of the polymer segmental motion and is governed by the solvated species {[Li(G4)]+}, very similar to the scenario in ionic liquids. As a result, the magnitude of ionic conductivity and activation energies of the gel polymer electrolyte are very similar to that of the liquid electrolyte. The Li+-ion transport number for the GPE varied from 0.44 ( x = 1) to 0.5 ( x = 7) with the maximum being 0.52 at x = 5.