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Nanocomposite polymer electrolytes based on polyethylene glycol diacrylate and 1 M LiBF4 solution in γ-butyrolactone with addition of SiO2 nanoparticles were synthesized and studied. Resistance measurement at the Li/electrolyte and Li/nanocomposite electrolyte interface by the time-resolved electrochemical impedance showed its significant decrease in the presence of SiO2 nanoparticles. Charge-discharge cycling of prototypes of Li/LiFePO4 batteries for 50 cycles also showed the advantage of using nanocomposite polymer electrolytes over electrolytes without SiO2 additives.

One novel cage kind of polyhedral ligomeric silsesquioxane (POSS), for modification application of gel polymer electrolyte (GPE) in lithium ion batteries (LIBs), was successfully synthesized via a facile two-step reaction under simple conditions. In four kinds of GPE with different filling amount of POSS, GPE-8 with 8 wt.% POSS content expresses the highest ionic conductivity up to the level of 10−3 S cm−1 at 30 °C. The comprehensive investigation indicates that GPE-8 is thermally stable before 100 °C, electrochemical stability window (ESW) is identified as 5.0 V, and the compatibility of electrolyte with lithium electrode and the charging-discharging cycling property of the assembled cell is satisfying.

Lithium metal is known to form ramified structures during electrodeposition not only at high current densities (above diffusion limit) but also, unexpectedly, at low currents. In this issue of Joule, Bai and coworkers describe an analytical approach to explain structural evolution of lithium electrode at different current densities. They find three distinct regimes as a function of current rate, such that the morphology changes from whiskers to mossy to dendrites.

The properties of interfaces of water-stable lithium electrode have been investigated by EIS in Li–air batteries and four-electrode test-cells. The water-stable lithium electrode was prepared with the protection of NASICON-type glass–ceramic plate [0.8Li 2 O·0.25Al 2 O 3 ·1.5GeO 2 ·1.5P 2 O 5 glass–ceramic (LAGP)]. The glass–ceramic plates are water-stable and 200–500 μm thick with ion-conductivity of 4 × 10 −4 S cm −1 . In Li–air batteries, the AC impedance spectra of LAGP protected lithium electrode contained two semicircles and became three after one week. The composition of impedance of LAGP protected lithium electrode was analyzed, by comparison on the impedance spectra of LAGP protected lithium electrode and bare Li metal electrode in organic electrolyte. Furthermore, in four-electrode test-cell which excluded the LAGP|aqueous-solution interface, the interface impedance of LAGP plate was analyzed. And then by the analysis of impedance, the Li|organic-electrolyte interface caused the main impedance of the water-stable lithium electrode during the discharge. The impedance of water-stable lithium electrode should be decreased by the study of new electrolyte and interface modification.

Several key issues of aqueous lithium/air rechargeable batteries that consists of a water-stable lithium electrode, an aqueous electrolyte, and a bifunctional air electrode are reviewed. Based on r...

The solid-state lithium electrolytes Li5La3Ta2O12 and Li5La3Nb2O12 have been the focus of recent studies due to their chemically robust nature (against the lithium electrode; particularly the tantalate analogue) and high lithium conductivity. Structural characterization and Li-conductivity studies have shown that there are two populations of lithium cations, nominally called octahedral (less tightly bound) and tetrahedral sites (tightly bound), and the octahedrally coordinated lithium are considerably more mobile than the tetrahedrally coordinated lithium. In this study, we have documented two methods to preferentially vacate the tetrahedral or nonmobile lithium sites. This is accomplished by either Li2O volatility upon repeated mixing and heating solid-state processing steps or by aqueous H+ → Li+ exchange, followed by removal of the exchanged-in H+ by water vaporization. The aqueous treatment produces the largest change in the tetrahedral (nonmobile) lithium sites concentration. The ability to ion-excha...

This work considers the fundamental problems in the design of lithium-sulfur batteries (LSBs): low practical specific energy, rapid decrease in capacity during cycling, and high self-discharge rates. We demonstrate that these problems will be solved by the provision of an optimum combination of the rates of electrode and corrosion processes in lithium-sulfur batteries during cycling.

Three-volt lithium-ion batteries consisting of Li[Li1/3Ti5/3]O4 and Li[Ni1/2Mn3/2]O4 were constructed and examined in terms of their intermittent charge and discharge consisting of a 5 s current on and 15 s off at high rate (9.3 mA cm−2) together with the continuous charge and discharge at low rate (0.17 mA cm−2) for 100 cycles. To monitor the polarization voltages of the positive and negative electrodes, an auxiliary lithium electrode was placed around the electrodes in the battery. The auxiliary lithium electrode worked well for monitoring voltage balance in the battery. The continuous 100-cycle test of the battery operated in the voltage range of 1.5 to 3.5 V showed an excellent capacity retention, i.e., more than 97% of the initial capacity after 100 cycles. Based on these results, the polarization measurements of the lithium insertion electrodes are discussed, through which the electrode kinetics of the lithium insertion materials can be developed and the battery materials can also be improved for high-power applications.

Fluctuations of the potential of a lithium electrode in conditions of galvanostatic polarization in aprotic organic electrolytes are studied by a method of correlation functions. Computer-aided removal of heavy interference in the form of slow variation of the electrode potential proved to be possible to perform with use made of fifth-power polynomials. The time coordinate of the first zero in the correlation function weakly depends on the electrolyte type and lies within the limits 1.5–3 s. At the same time, the electrolyte type affects the dispersion of the electrode potential fluctuations in a substantial manner. In so doing, lithium systems that feature a high cycling efficiency possess a lower level of noise.

The ionic conductivities of all-solid polymer electrolytes prepared by UV irradiation crosslinkable oligo(oxyethylene) branched low molecular weight poly(organophosphazenes) macromonomers are reported. The dimensional stability of the poly(organophosphazes) electrolytes was improved by crosslinking. The temperature dependence of ionic conductivity of the all-solid polymer electrolytes followed the Vogel–Tamman–Fulcher equation. Furthermore, the effects of the length of the oligo(oxyethylene) chain and the degree of crosslinking on the ionic conductivity of the polymer electrolytes are discussed. The stability of the lithium electrode and the all-solid polymer electrolytes interface were evaluated by measuring the alternating current impedance on symmetric cells. The maximum ionic conductivity of the all-solid polymer electrolyte was obtained as high as 2.92 × 10−4 sec/cm at 25°C. Copyright © 2006 John Wiley & Sons, Ltd.

The processes occurring in aprotic electrolyte on a lithium electrode in the steady state conditions and under polarization are studied using the method of electrochemical noise characterization. The evidence of the electro-chemical noise measurements on polarized lithium electrodes indicates that the discharge of lithium ions under cathodic polarization, as well as lithium anodic dissolution, is localized under the passive film rather than on its surface. An increase in the polarizing current results in local breakdown of the film; in this case, the electrochemical process emerges on the electrode surface affecting the character of potential fluctuations. The intensity of electrochemical noise significantly increases in the course of cathodic polarization with high currents. The reason is that lithium metal crystals, which are formed under the passive film, perforate the film, and dendrites grow on its surface. The method shows the dependence of electrochemical noise intensity on the nature of the electrolyte and establishes the correlation between the stability of the lithium electrode in the course of cycling and the intensity of fluctuations. This offers an opportunity of using the method of electrochemical noise for screening organic electrolytes for lithium batteries.

Using impedance spectroscopy and in situ optical absorption experiments, we have studied the evolution of a lithium electrode/polymer electrolyte interface during aging and cycling. During a period of 3–5 days after assembling a cell, aging has a detrimental effect on the interface: this effect is observed both on the interface impedance and on the optical properties of the electrolyte. After this initial period, optical absorption measured during cycling a cell reveals a concentration evolution in the electrolyte in agreement with theoretical predictions.

The last major advance in portable electrochemical energy storage was the introduction of Li-ion chemistry by Sony in 1991. Since that time battery manufacturers have been relentless in pursuing incremental improvements to Li-ion technology. Still, there are fundamental limits to any battery chemistry and Li-ion technology is clearly maturing. In pursuit of the next battery breakthrough, a number of researchers are exploring the Li/O2 couple, due largely to its extremely high theoretical energy density and the low cost of the oxygen electrode. However, in order to realize those gains, the Li/O2 battery will need to utilize ambient air, and this presents a major technical hurdle as ambient moisture will attack and rapidly corrode the lithium metal electrode. Fortunately, the invention of the protected lithium electrode (PLE) by PolyPlus solves this problem and enables the practical construction of both primary and secondary lithium air batteries. In this chapter we highlight the advances and challenges in aqueous and nonaqueous lithium air battery technology. Notably, external testing of PolyPlus 10 Ah primary lithium air cells has confirmed specific energies in excess of 800 Wh/kg.

Several key issues of aqueous lithium/air rechargeable batteries that consists of a water-stable lithium electrode, an aqueous electrolyte, and a bifunctional air electrode are reviewed. Based on r...

The charge/discharge behavior of a lithium negative electrode is intensively affected by the structure of the lithium electrode/organic electrolyte interface and the composition of the electrolyte solution. Addition of some metal ions such as Mg2+, Zn2+, In3+, Ga3+, etc., to electrolyte solutions improves the coulombic efficiencies of the electrode during the charge/discharge cycles. Some organic additives, e.g., 2-methylthiophene, 2-methylfuran, benzene, etc., also improve the coulombic efficiencies for lithium cycling. The mechanisms of these additives are discussed in connection with the structure of the electrode/electrolyte interface.

The solid-state lithium electrolytes Li5La3Ta2O12 and Li5La3Nb2O12 have been the focus of recent studies due to their chemically robust nature (against the lithium electrode; particularly the tantalate analogue) and high lithium conductivity. Structural characterization and Li-conductivity studies have shown that there are two populations of lithium cations, nominally called octahedral (less tightly bound) and tetrahedral sites (tightly bound), and the octahedrally coordinated lithium are considerably more mobile than the tetrahedrally coordinated lithium. In this study, we have documented two methods to preferentially vacate the tetrahedral or nonmobile lithium sites. This is accomplished by either Li2O volatility upon repeated mixing and heating solid-state processing steps or by aqueous H+ → Li+ exchange, followed by removal of the exchanged-in H+ by water vaporization. The aqueous treatment produces the largest change in the tetrahedral (nonmobile) lithium sites concentration. The ability to ion-excha...

Zero-strain insertion material of lithium titanium oxide (Li[Li1/3Ti5/3]O4) is used as a negative electrode in lithium-ion batteries and as a positive electrode in lithium batteries. It is crystallized as a defect spinel structure having space group symmetry of Fd3¯m (a=8.36 A). The material is topotactically reduced to Li2[Li1/3Ti5/3]O4, and it is oxidized to Li[Li1/3Ti5/3]O4 at 1.55 V against a lithium electrode in nonaqueous lithium cells. The lattice dimension is virtually unchanged during the reaction, and therefore the material is ideal for long-life lithium-ion battery application. Some trials for modification of Li[Li1/3Ti5/3]O4 are also described, and recent application of the material to backup memory in solar cells for digital watches, solid-state batteries, asymmetric hybrid supercapacitors, and ‘lead-free’ accumulators is also highlighted.

The reversible storage capacity of lithium in a mesophase-derived semi-coke, heat-treated (HTT) below 700°C, was found by far exceeding the theoretical value corresponding to the LiC6 composition. A capacity as high as 1660 mAh/g was obtained in the case of carbon, heat-treated at ∼ 450 °C, when poly(ethylene oxide)-based electrolyte is used in lithium cells operated at 100 °C. This great capacity is discussed on the basis of a model where lithium forms multilayers on the external basal surfaces of the nanometric size mesocarbon domains.

Sodium—cesium alloy was permitted to react with tetrahydrofuran as a model for the lithium electrode. The products of this reaction were treated with methyl bromide. The NMR of the final products gives evidence that cleaved tetrahydrofuran reacts with more tetrahydrofuran to form derivatives of itself.

The growth of the passivating film on a lithium electrode in contact with sulfuryl chloride solutions has been examined by micropolarization and complex impedance measurements. The results tend to confirm the hypothesis of a two-layer film, where probably the first layer is thin and compact and the second layer is porous and defective.

Lithium electrode surface morphologies during cycling were measured in and electrolytes. Particulate and needle‐like Li were observed on the Li electrode after cycling. Although the particulate Li could be stripped during discharge, much of the needle‐like Li remained. It appears that the needle‐like Li tends to become "dead‐Li" and is responsible for the loss of cycling of lithium electrodes.

The cyclability of lithium in aprotic media at ambient temperature is discussed in terms of the properties of passivating films that are formed at the electrode surface by the reaction of the metal with the various electrolytes. Some models and experimental techniques are examined with the object of establishing guidelines in the search for successful operational systems and/or optimal cycling conditions.

V 6 O 13 has been utilized as the active material of the positive electrode in lithium batteries. Such batteries, using 1 M LiClO 4 in propylene carbonate as electrolyte, have been built and tested galvano-statically, the lithium electrode being periodically replaced when consumed by its reaction with the organic electrolyte during the charges. The nature and content of the carbon added as current collector have been optimized, leading to 5 wt.% of Ketjen black in the positive electrode. The contact between the V 6 O 13 grains and the electrolyte has been improved, leading to a substaintial increase in the initial capacity. However, a decrease in capacity is observed whatever the electrode technology during the first 200 cycles. Afterwards, a steady state seems to be reached.

The reversibility of the LixNbS2 electrode in organic electrolyte cells has been examined by polarization and cycling tests. The reversibility of the electrode appears to be influenced by lithium composition and diffusion, while the cycling life of complete Li/LixNbS2 cells is limited by the poor cyclability of the lithium electrode.

The state of the art of the secondary lithium electrode in organic solvent based electrolytes at ambient temperature is reviewed.

Lithium electrode surface morphologies during cycling were measured in and electrolytes. Particulate and needle‐like Li were observed on the Li electrode after cycling. Although the particulate Li could be stripped during discharge, much of the needle‐like Li remained. It appears that the needle‐like Li tends to become "dead‐Li" and is responsible for the loss of cycling of lithium electrodes.

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