Battery and EV manufacturers carry out extensive long-term tests to estimate the lifetime of the battery and base warranty durations on those tests. The long duration of these tests slows progress in the research and development required to improve the lifetime of Li-ion batteries. This paper shows that accurate measurements of coulombic efficiency (CE) and impedance spectra of Li-ion batteries, that take a few weeks to acquire, can be used to rank the resulting lifetime of Li-ion cells. Adding one or more electrolyte additives to Li-ion batteries that act synergistically can dramatically improve the CE and long-term tests show corresponding ten-fold improvements in lifetime.In a recent review of battery technologies for electric vehicle applications, Bruce et al. 1 argue that technologies with greater energy densities than those achievable by Li-ion batteries are required in order to reach driving ranges greater than 200 km. Bruce et al. picked the Nissan Leaf as their canonical example which has an approximate 160 km range. The view that Li-ion batteries cannot lead to electric vehicles with widely acceptable driving ranges is also held by others. 2,3 Recently, the Tesla Model S, a Li-ion battery powered electric vehicle, was named Motor Trend car of the year for 2013. 4 The Tesla S has a driving range of 425 km when equipped with an 85 kWhr Li-ion battery. The Tesla S demonstrates that Li-ion batteries can power EV's for distances over 200 km in an elegant design. However, the vehicle is expensive and the 85 kWh battery must contribute at least $25,000 to the price assuming the $300/kWh USDOE target for EV battery costs. 5 No one would argue that increased energy density would not be an advantage, but the real issues with Li-ion batteries are cost and lifetime, not energy density, as far as automotive applications are concerned.Recently, a class action lawsuit was brought against Nissan by Nissan Leaf owners alleging that the Li-ion batteries in the Leaf can lose as much as 27% of their energy storage capacity within one year of use. 6 The Nissan Leaf uses a different Li-ion battery technology than the Tesla Model S. Nevertheless, EV manufacturers and users are worried about battery lifetime since the cost of a replacement battery is large.Testing the lifetime of a Li-ion battery under realistic conditions for an EV application takes years. Research and development to improve the lifetime of Li-ion batteries cannot have iterative cycles of several years before the outcome of experiments are known. We recently proposed the use of high precision measurements of the coulombic efficiency (CE) of Li-ion cells as a rapid way to screen and rank new electrode materials, electrolytes, and electrolyte additives for their impact on Li-ion cell lifetime. 7-10 In this paper it is demonstrated that short-term CE measurements coupled with initial impedance measurements can serve as a good predictor for cell lifetime and also dramatically demonstrate the beneficial impact of multiple electrolyte additives on lifetime. Figure...

LiCoO2/graphite and Li[Ni1/3Mn1/3Co1/3]O2/graphite pouch cells and Li[Ni1-x-yMnxCoy]O2/graphite 18650 cells were made with varying concentrations of vinylene carbonate (VC) and studied using high precision coulometry, extended cycling as well as electrochemical impedance spectroscopy (EIS). As expected, adding increased concentrations of VC (up to 6 wt%) to the control electrolyte resulted in improved coulombic efficiency, decreased charge endpoint slippage and longer cycle life. However, high concentrations of VC led to larger charge transfer resistance, especially at the graphite negative electrode. Understanding how varying amounts of VC impact cell lifetime and impedance allows for optimized electrolyte formulations to be found for different applications that may balance lifetime and power demands.

The kinetics and equilibrium position of place exchange (alkylthiol-for-alkylthiol) reactions of gold nanoparticles are reported. These reactions were monitored via a gas chromatography analysis of structurally similar incoming and outgoing alkylthiols, as a function of time. The place exchange reactions described here proceed to an equilibrium position, where Keq approximately 1. The product-time data follow Langmuir diffusion kinetics.

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