Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium-ion batteries are the systems of choice, offering high energy density, flexible and lightweight design, and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based rechargeable batteries, highlight ongoing research strategies, and discuss the challenges that remain regarding the synthesis, characterization, electrochemical performance and safety of these systems.

Issues and challenges facing rechargeable lithium batteries

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.

Energy storage using batteries offers a solution to the intermittent nature of energy production from renewable sources; however, such technology must be sustainable. This Review discusses battery development from a sustainability perspective, considering the energy and environmental costs of state-of-the-art Li-ion batteries and the design of new systems beyond Li-ion. Images: batteries, car, globe: © iStock/Thinkstock.

Towards greener and more sustainable batteries for electrical energy storage

Research Development on Sodium-Ion Batteries

The status of ambient temperature sodium ion batteries is reviewed in light of recent developments in anode, electrolyte and cathode materials. These devices, although early in their stage of development, are promising for large-scale grid storage applications due to the abundance and very low cost of sodium-containing precursors used to make the components. The engineering knowledge developed recently for highly successful Li ion batteries can be leveraged to ensure rapid progress in this area, although different electrode materials and electrolytes will be required for dual intercalation systems based on sodium. In particular, new anode materials need to be identified, since the graphite anode, commonly used in lithium systems, does not intercalate sodium to any appreciable extent. A wider array of choices is available for cathodes, including high performance layered transition metal oxides and polyanionic compounds. Recent developments in electrodes are encouraging, but a great deal of research is necessary, particularly in new electrolytes, and the understanding of the SEI films. The engineering modeling calculations of Na-ion battery energy density indicate that 210 Wh kg−1 in gravimetric energy is possible for Na-ion batteries compared to existing Li-ion technology if a cathode capacity of 200 mAh g−1 and a 500 mAh g−1 anode can be discovered with an average cell potential of 3.3 V.

Sodium‐Ion Batteries

Electrochemical insertion of sodium ions into carbon using solid polymer electrolytes or organic liquid electrolytes is described. Cells with the configuration Na/P(EO)sNaCF3SOJCP(EO) = polyethylene oxide) or Na/liquid electrolyte/C were galvanostatically discharged, charged, and cycled. The extent of insertion into C (Le., x in Na§ was found to be a strong function of the type and particle size of the carbon used, and the reversibility of the process was highly dependent upon the type of electrolyte used. The possibility of designing a sodium ion rocking chair cell is discussed, and a first-generation example, using a petroleum coke anode, polymer electrolyte, and sodium cobalt bronze cathode is described. Rocking chair batteries, in which both the anode and cathode are intercalation materials, have recently been commercialized. Because the anodes are commonly inexpensive carbons such as petroleum coke or graphite, reductive intercalation of lithium into these materials is now the subject of intense scrutiny] Similar sodium insertion reactions into carbons have been observed, 2 but have not yet been exploited for use in batteries. We now describe a preliminary study of these insertion reactions and discuss the possibility of developing a sodium ion cell analogous to the wellknown lithium ion systems. Experimental Conoco petroleum coke, Shawinigan black, and JohnsonMatthey microcrystalline graphite were either ground in an attritor mill or used as received after heat-treatment. Polymer electrolytes of composition P(EO)sNaCF3SO3 (PEO = polyethylene oxide) and composite cathodes containing the carbon of interest, PEO, and NaCF3SO3 were made as described previously. 3 Electrodes for use in cells with liquid electrolytes consisted of carbon and ethylene propylene diene monomer (EPDM) binder (2% by weight) and were vacuum dried prior to use. Battery-grade solvents from Mitsubishi Petrochemical Company were stored in an inert atmosphere glove box (02 < 1 ppm) and used as supplied. Sodium was purified as described previously?

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Electrochemical Insertion of Sodium into Carbon

https://escholarship.org/content/qt5pc2b46r/qt5pc2b46r.pdf

Protective coating on stainless steel interconnect for SOFCs: oxidation kinetics and electrical properties

Polymer electrolytes based on alkali metal salts in poly(ethylene oxides) are important for possible use in rechargeable batteries for both electric vehicle and consumer electronics applications. The authors measure a complete set of transport properties for one particular binary salt solution: sodium trifluoromethanesulfonate in poly(ethylene oxide), over a wide range of salt concentrations (0.1 to 2.6M) at 85 C. The properties measured include the conductivity, the salt diffusion coefficient, and the Na ion transference number. The mean molar activity coefficient of the salt is also determined. The conductivity and diffusion coefficients of NaCF{sub 3}SO{sub 3} are similar in magnitude to those of LiCF{sub 3}SO{sub 3} in (polyethylene oxide). The transference number and thermodynamic factor are found by combining concentration cell data with the results of galvanostatic polarization experiments. A theoretical analysis of the experimental method based on concentrated-solution theory is given. The study verifies that the transference numbers derived from the experiments retain fundamental significance in applications involving both steady and transient processes and in systems coupling the polymer electrolyte with electrodes of all types (stoichiometries). The relevant transference numbers can be determined independently of any knowledge of speciation of the polymer electrolyte. The transference numbers found here for themore » sodium ion are much lower than those reported for the lithium ion, especially in the concentrated solutions. The transference number of the sodium ion is negative in the more concentrated solutions and levels off at its maximum value of 0.31 in the dilute concentration range. The transference number results are interpreted in terms of complexation of the sodium ion with the anionic species.« less

The Measurement of a Complete Set of Transport Properties for a Concentrated Solid Polymer Electrolyte Solution

A method for forming lithium electrodes having protective layers involves plating lithium between a lithium ion conductive protective layer and a current collector of an “electrode precursor.” The electrode precursor is formed by depositing the protective layer on a very smooth surface of a current collector. The protective layer is a glass such as lithium phosphorus oxynitride and the current collector is a conductive sheet such as a copper sheet. During plating, lithium ions move through the protective layer and a lithium metal layer plates onto the surface of the current collector. The resulting structure is a protected lithium electrode. To facilitate uniform lithium plating, the electrode precursor may include a “wetting layer” which coats the current collector.

Plating metal negative electrodes under protective coatings

Protected anode architectures have ionically conductive protective membrane architectures that, in conjunction with compliant seal structures and anode backplanes, effectively enclose an active metal anode inside the interior of an anode compartment. This enclosure prevents the active metal from deleterious reaction with the environment external to the anode compartment, which may include aqueous, ambient moisture, and/or other materials corrosive to the active metal. The compliant seal structures are substantially impervious to anolytes, catholyes, dissolved species in electrolytes, and moisture and compliant to changes in anode volume such that physical continuity between the anode protective architecture and backplane are maintained. The protected anode architectures can be used in arrays of protected anode architectures and battery cells of various configurations incorporating the protected anode architectures or arrays.

Lutgard C. De Jonghe

Papers

Electrochemical Insertion of Sodium into Carbon

Protective coating on stainless steel interconnect for SOFCs: oxidation kinetics and electrical properties

The Measurement of a Complete Set of Transport Properties for a Concentrated Solid Polymer Electrolyte Solution

Plating metal negative electrodes under protective coatings

Compliant seal structures for protected active metal anodes