Researchers must find a sustainable way of providing the power our modern lifestyles demand.

Building better batteries

The increasing interest in energy storage for the grid can be attributed to multiple factors, including the capital costs of managing peak demands, the investments needed for grid reliability, and the integration of renewable energy sources. Although existing energy storage is dominated by pumped hydroelectric, there is the recognition that battery systems can offer a number of high-value opportunities, provided that lower costs can be obtained. The battery systems reviewed here include sodium-sulfur batteries that are commercially available for grid applications, redox-flow batteries that offer low cost, and lithium-ion batteries whose development for commercial electronics and electric vehicles is being applied to grid storage.

Electrical Energy Storage for the Grid: A Battery of Choices

Li-ion batteries have transformed portable electronics and will play a key role in the electrification of transport. However, the highest energy storage possible for Li-ion batteries is insufficient for the long-term needs of society, for example, extended-range electric vehicles. To go beyond the horizon of Li-ion batteries is a formidable challenge; there are few options. Here we consider two: Li-air (O(2)) and Li-S. The energy that can be stored in Li-air (based on aqueous or non-aqueous electrolytes) and Li-S cells is compared with Li-ion; the operation of the cells is discussed, as are the significant hurdles that will have to be overcome if such batteries are to succeed. Fundamental scientific advances in understanding the reactions occurring in the cells as well as new materials are key to overcoming these obstacles. The potential benefits of Li-air and Li-S justify the continued research effort that will be needed.

Li-O2 and Li-S batteries with high energy storage.

Each cell of a battery stores electrical energy as chemical energy in two electrodes, a reductant (anode) and an oxidant (cathode), separated by an electrolyte that transfers the ionic component of the chemical reaction inside the cell and forces the electronic component outside the battery. The output on discharge is an external electronic current I at a voltage V for a time Δt. The chemical reaction of a rechargeable battery must be reversible on the application of a charging I and V. Critical parameters of a rechargeable battery are safety, density of energy that can be stored at a specific power input and retrieved at a specific power output, cycle and shelf life, storage efficiency, and cost of fabrication. Conventional ambient-temperature rechargeable batteries have solid electrodes and a liquid electrolyte. The positive electrode (cathode) consists of a host framework into which the mobile (working) cation is inserted reversibly over a finite solid–solution range. The solid–solution range, which is...

The Li-ion rechargeable battery: a perspective.

2.1. Solvents 4307 2.1.1. Propylene Carbonate (PC) 4308 2.1.2. Ethers 4308 2.1.3. Ethylene Carbonate (EC) 4309 2.1.4. Linear Dialkyl Carbonates 4310 2.2. Lithium Salts 4310 2.2.1. Lithium Perchlorate (LiClO4) 4311 2.2.2. Lithium Hexafluoroarsenate (LiAsF6) 4312 2.2.3. Lithium Tetrafluoroborate (LiBF4) 4312 2.2.4. Lithium Trifluoromethanesulfonate (LiTf) 4312 2.2.5. Lithium Bis(trifluoromethanesulfonyl)imide (LiIm) and Its Derivatives 4313

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Nonaqueous liquid electrolytes for lithium-based rechargeable batteries.

A novel rechargeable Li/O{sub 2} battery is reported. It comprises a Li{sup +} conductive organic polymer electrolyte membrane sandwiched by a thin Li metal foil anode, and a thin carbon composite electrode on which oxygen, the electroactive cathode material, accessed from the environment, is reduced during discharge to generate electric power. It features an all solid state design in which electrode and electrolyte layers are laminated to form a 200 to 300 {micro}m thick battery cell. The overall cell reaction during discharge appears to be 2Li + O{sub 2} {yields} Li{sub 2}O{sub 2}. It has an open-circuit voltage of about 3 V, and a load voltage that spans between 2 and 2.8 V depending upon the load resistance. The cell can be recharged with good coulombic efficiency using a cobalt phthalocyanine catalyzed carbon electrode.

https://iopscience.iop.org/article/10.1149/1.1836378/pdf

A Polymer Electrolyte‐Based Rechargeable Lithium/Oxygen Battery

A fundamental study of the influence of solvents on the oxygen reduction reaction (ORR) in nonaqueous electrolytes has been carried out for elucidating the mechanism of the oxygen electrode processes in the rechargeable Li−air battery. Using either tetrabutylammonium hexafluorophosphate (TBAPF6) or lithium hexafluorophosphate (LiPF6) electrolyte solutions in four different solvents, namely, dimethyl sulfoxide (DMSO), acetonitrile (MeCN), dimethoxyethane (DME), and tetraethylene glycol dimethyl ether (TEGDME), possessing a range of donor numbers (DN), we have determined that the solvent and the supporting electrolyte cations in the solution act in concert to influence the nature of reduction products and their rechargeability. In solutions containing TBA+, O2 reduction is a highly reversible one-electron process involving the O2/O2− couple. On the other hand, in Li+-containing electrolytes relevant to the Li−air battery, O2 reduction proceeds in a stepwise fashion to form O2−, O22−, and O2− as products. Th...

Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium−Air Battery

Unlocking the true energy capabilities of the lithium metal negative electrode in a lithium battery has until now been limited by the low capacity intercalation and conversion reactions at the positive electrodes. Abraham et al. (Abraham, K. M.; Jiang, Z. J. Electrochem. Soc. 1996, 143, 1−5) overcame this limitation by removing these electrodes and allowing lithium to react directly with oxygen in the atmosphere, forming the Li-air battery. The Li/O2 battery redox couple has a theoretical specific energy of 5200 W h/kg and represents the ultimate, environmentally friendly electrochemical power source. In this work, we report for the first time the intimate role of electrolyte, in particular the role of ion conducting salts, in determining the reversibility and kinetics of oxygen reduction in nonaqueous electrolytes designed for such applications. Such fundamental understanding of this high energy density battery is crucial to harnessing its full energy potential. The kinetics and mechanisms of O2 reductio...

Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications

Prototype cells of the configuration Li/~5M S as , THF, have been characterized with regard to capacity, rate, and rechargeability. Virtually 100% of the theoretical capacity could be realized at 50°C at rates below 1.0 mA/cm2. In high rate cell configurations, 75% cathode utilization is possible at ~4 mA/cm2 (C/3–C/4 rate). The capacities at high rate are enhanced by Lewis acids, although the ultimate cause of rate limitation is passivation of the current collector by discharge products. The self‐discharge rates of Li in contact with 4–5M S (as ) solutions reveal capacity losses of 0.5%/day at 25°C to 4.4%/day at 71°C. Based on the experimental results, a practical energy density of ~300 W‐hr kg−1 is possible using a standard cell design. Results on the battery's rechargeability are briefly reviewed.

A Lithium/Dissolved Sulfur Battery with an Organic Electrolyte

Polymer electrolyte membranes comprising poly(vinylidene fluoride)−hexafluoropropene (PVdF−HFP) copolymer plasticized with a solution of LiSO3CF3, LiN(SO2CF3)2, or LiPF6 in oligomeric poly(ethylene glycol) dimethyl ethers (PEGDME, Mw = 250, 400, and 500) were prepared by hot-melt-rolling or solvent-casting techniques. Since the electrolytes containing PEGDME400 and PEGDME500 are “dry” with essentially no volatile components up to 150 °C, we have dubbed them PEO-like. Their thermal stability, mechanical strength, conductivity, electrochemical stability window, and Li/electrolyte interface stability were characterized. Plasticizing PVdF−HFP with the PEGDME/LiX solutions disordered the polymer structure leading to polymer electrolytes having lower crystallinity than the polymer host itself. The mechanical strength of the electrolyte membranes varied depending on the PVdF content. Tensile strength (stress) as high as 420 psi at an elongation-at-break value (strain) of 75% was observed. The conductivities of t...

K. M. Abraham

Papers

A Polymer Electrolyte‐Based Rechargeable Lithium/Oxygen Battery

Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium−Air Battery

Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications

A Lithium/Dissolved Sulfur Battery with an Organic Electrolyte

Highly Conductive PEO-like Polymer Electrolytes