Neurotechnologically inspired multilayered polymer electrolyte membranes to harness ion concentration gradient for energy restoration

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NON-TECHNICAL SUMMARY:The main concept of this project emerges from the neuronal circuits of the body as paradigms for novel types of solid-state batteries based on mechanisms operative in neurotransmission. The brain controls various functions of the body through the nervous system composed of neuronal networks. Neurons are excitable, individual cells making specific contacts with other surrounding neurons. Their signal-processing is empowered by ion osmosis, driven by ion concentration gradients across the cell membrane which regulates passage of selective ions via ionic channels. The concept of polymer-based solid lithium ion batteries to be explored in this project shares this common origin with neuronal networks, as it operates by harnessing ion concentration gradients across the proposed "multilayered polymer electrolyte membranes" (MLPEM) which contain different ion concentrations in each layer, thus generating an internal voltage. The proposed concentration-gradient approach to battery design is conceptually similar to the neuronal operation of an electric eel, whereby series of thousands of innervated and non-innervated cell membranes are capable of generating internal voltages of about 600 volts to fend off predators. Just as the neural network of the electric eel allows this voltage to be regenerated, the proposed MLPEM batteries could be rechargeable on their own. The working principle of the self-rechargeable battery in this project is that the mobile lithium cation will be transported to the cathode during discharging, but it will revert back to the anode during battery resting, thereby restoring the ion concentration gradient and hence a voltage. This project will explore these aspects by synthesizing and processing multilayered polymer electrolyte membranes allowing ionic concentration gradients, evaluate and attempt to optimize the ionic conductivity, the thermal and electrochemical stability, and the mechanical properties of the battery. If successful, this project may benefit society by leading to novel lightweight, shape-conformable, thermally and electrochemically stable, flame-retardant, self-rechargeable batteries. The project also includes integration of research and education through interdisciplinary training of students and outreach activities.TECHNICAL SUMMARY:This project is inspired by the neuronal circuits of the body as paradigms for novel types of solid-state batteries based on mechanisms operative in neurotransmission, e.g. the generation of high voltages by electric eels followed by internal recharging. It focuses on five thrust areas: (1) Development of all-solid-state multilayered polymer electrolyte membranes (MLPEM) having specific chemical and electrochemical compatibility with electrodes for enhancing energy-storage capacity. MLPEM will be fabricated by stacking individual polymer electrolyte (PEM) layers having different ion populations by photopolymerizing network-precursor (poly(ethylene glycol) diacrylate)/solid plasticizer (succinonitrile)/ionic salt (lithium bis-trifluorosulfonylimide). The ion concentration gradient thus produced in MLPEM will create potential differences across the membrane interfaces, thereby affording self-rechargeability of the battery. (2) Fabrication of directionally aligned phase-separated domains having various concentration gradients via holographic photopolymerization-induced phase separation in multicomponent solid electrolytes containing plasticizer and modifiers as a means of creating networks of micro-electrolyte cells. (3) Synthesis of PEM additives such as amido-carbonyl carbamate and amido-carbamate to prevent uncontrolled solid electrolyte interface formation on electrodes. (4) Grafting of poly(ethylene glycol) diamine to multiwall carbon nanotube (MWCNT) followed by end-capped reaction with carbamate derivatives to improve interface compatibility of MLPEM with carbonaceous anode and concurrently increase in ionic conductivity. (5) Modification of MWCNT surface by grafting of lithiated PEG-chains and/or arborescent PEG to raise lithium ion storage capacity and provide separate pathways for electron and ion conductions. The network of lithiated arborescent hyperbranched PEG resembles a neuronal network structurally and functionally. The ion conductivity and mobility will be determined by AC impedance, solid-state NMR, and Raman spectroscopy. Electrochemical stability will be evaluated by means of cyclic voltammetry and galvanostatic charge/discharge cycling in half-cell configurations. By virtue of the self-restored potential difference between the electrodes afforded by the ion concentration gradient of MLPEM, the battery would be rechargeable in the rest state, thereby prolonging the battery life. The project includes integration of research and education through interdisciplinary training of students and outreach activities.