Energy storage is more important today than at any time in human history. Future generations of rechargeable lithium batteries are required to power portable electronic devices (cellphones, laptop computers etc.), store electricity from renewable sources, and as a vital component in new hybrid electric vehicles. To achieve the increase in energy and power density essential to meet the future challenges of energy storage, new materials chemistry, and especially new nanomaterials chemistry, is essential. We must find ways of synthesizing new nanomaterials with new properties or combinations of properties, for use as electrodes and electrolytes in lithium batteries. Herein we review some of the recent scientific advances in nanomaterials, and especially in nanostructured materials, for rechargeable lithium-ion batteries.

Nanomaterials for rechargeable lithium batteries

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Ageing mechanisms in lithium-ion batteries

Solid-state electrolytes are attracting increasing interest for electrochemical energy storage technologies. In this Review, we provide a background overview and discuss the state of the art, ion-transport mechanisms and fundamental properties of solid-state electrolyte materials of interest for energy storage applications. We focus on recent advances in various classes of battery chemistries and systems that are enabled by solid electrolytes, including all-solid-state lithium-ion batteries and emerging solid-electrolyte lithium batteries that feature cathodes with liquid or gaseous active materials (for example, lithium–air, lithium–sulfur and lithium–bromine systems). A low-cost, safe, aqueous electrochemical energy storage concept with a ‘mediator-ion’ solid electrolyte is also discussed. Advanced battery systems based on solid electrolytes would revitalize the rechargeable battery field because of their safety, excellent stability, long cycle lives and low cost. However, great effort will be needed to implement solid-electrolyte batteries as viable energy storage systems. In this context, we discuss the main issues that must be addressed, such as achieving acceptable ionic conductivity, electrochemical stability and mechanical properties of the solid electrolytes, as well as a compatible electrolyte/electrode interface. This Review details recent advances in battery chemistries and systems enabled by solid electrolytes, including all-solid-state lithium-ion, lithium–air, lithium–sulfur and lithium–bromine batteries, as well as an aqueous battery concept with a mediator-ion solid electrolyte.

Lithium battery chemistries enabled by solid-state electrolytes

Ionically conducting polymer membranes (polymer electrolytes) might enhance lithium-battery technology by replacing the liquid electrolyte currently in use and thereby enabling the fabrication of flexible, compact, laminated solid-state structures free from leaks and available in varied geometries1. Polymer electrolytes explored for these purposes are commonly complexes of a lithium salt (LiX) with a high-molecular-weight polymer such as polyethylene oxide (PEO). But PEO tends to crystallize below 60 °C, whereas fast ion transport is a characteristic of the amorphous phase. So the conductivity of PEO–LiX electrolytes reaches practically useful values (of about 10−4 S cm−1) only at temperatures of 60–80 °C. The most common approach for lowering the operational temperature has been to add liquid plasticizers, but this promotes deterioration of the electrolyte's mechanical properties and increases its reactivity towards the lithium metal anode. Here we show that nanometre-sized ceramic powders can perform as solid plasticizers for PEO, kinetically inhibiting crystallization on annealing from the amorphous state above 60 °C. We demonstrate conductivities of around 10−4 S cm−1 at 50 °C and 10−5 S cm−1 at 30 °C in a PEO–LiClO4 mixture containing powders of TiO2 and Al2O3 with particle sizes of 5.8–13 nm. Further optimization might lead to practical solid-state polymer electrolytes for lithium batteries.

Nanocomposite polymer electrolytes for lithium batteries

Electroactive phases of poly(vinylidene fluoride) : determination, processing and applications

The relative viscosity of NaCl solutions has been measured as a function of temperature and solvent composition in the formamide + water system. The resulting Jones–Dole B-coefficients are examined by considering each solvent mixture as an “averaged pure solvent” and applying transition state theory. B-coefficients and related parameters were found to be monotonic functions of solvent composition. Changes in viscosity are interpreted in terms of a reduction of structure breaking by the chloride ion and an increase in long-range ordering of solvent molecules by the ionic electric fields, as the solvent composition moves towards a higher proportion of formamide.

Study of ion-solvent interactions in formamide + water mixtures by the measurement of viscosity of sodium chloride solutions

A dc technique for measurement of solid electrolyte conductivity

Conductivity and n.m.r. measurements are reported for three poly(ethylene oxide)-inorganic salt complexes: PEO-LiCF3SO3-NaI ([EO]/[Li]/[Na] = 8/1/1), PEO-LiCF3SO3 ([EO]/[Li] = 4), and PEO-NaI ([EO]/[Na] = 4). The mixed-salt system was shown to have a larger amorphous phase content than either of the single-salt systems and more potential charge carriers. A dramatic effect upon the lithium motion and the microviscosity of the amorphous phase was noted upon the mixing of salts. It is proposed that some lithium ions are in environments of low symmetry, possibly of the ion-pair type, and do not contribute to the n.m.r. signal. The recrystallisation behaviour of the mixed-salt material was studied by the n.m.r. technique and an initial fast recrystallisation appears to be due to the formation of the high-melting temperature phase.

A mixed‐salt polyether electrolyte: PEOLiCF3SO3Nal

The electrical double layer at the interface between mercury and a polyether electrolyte: Part 1: Tetraethylene glycol dimethyl ether solutions

Lap-top computers, calculators, cameras, CD players, and remote controls rely on efficient, lightweight power sources In recognition of the economic impact of these power sources and their widespread everyday use, a brief description of these devices is often included in course curricula However, it is difficult to provide students with appropriate study material Fortunately a great variety of well-designed, cost- and performance-optimized commercial devices are available, which may provide the basis of simple experiments designed to stimulate the interest of students in the applied electrochemistry of galvanic cells We describe an experiment that complements electrochemical characterization and allows students to explore the structure of commercial cells and calculate the anode and cathode capacities from the stoichiometry of the cell reaction These values may be compared with the practical capacity obtained from the controlled discharge of the cells through a resistor

Colin A. Vincent

Papers

Study of ion-solvent interactions in formamide + water mixtures by the measurement of viscosity of sodium chloride solutions

A dc technique for measurement of solid electrolyte conductivity

A mixed‐salt polyether electrolyte: PEOLiCF3SO3Nal

The electrical double layer at the interface between mercury and a polyether electrolyte: Part 1: Tetraethylene glycol dimethyl ether solutions

Structure and Content of Some Primary Batteries