Alexander Kraytsberg

A critical review-promises and barriers of conversion electrodes for Li-ion batteries

Conversion-type electrode materials are discussed in this critical review. Most of the conversion materials are significantly less expensive than modern intercalation-type materials, and the materials involved are appreciably abundant in the nature. However, up to now, no practically viable battery with conversion material-based electrodes was reported, as there are several major barriers to a practical employment of these materials. First, material utilization and cell energy performance are seriously compromised by a low conductivity of the most conversion materials and by a substantial electrolyte involvement in the electrochemical process. Second, the conversion reactions usually demonstrate a severe volume effect, and also conversion electrodes interact with electrolyte developing thick and resistant solid electrolyte interphase films; both of these features result in impractically low electrode cyclability. Third, a large lithiation/de-lithiation voltage hysteresis results in impractically low charge/discharge energy efficiency and suggests a severe battery heating in the course of the battery operation. All these problems present serious challenges for the researchers in the field; the approaches for handling these issues are discussed in the review. For the foreseeable future, there are grounds to expect progress in tackling some of these issues. The issue of high voltage hysteresis is a bottleneck, though, and it actually precludes conversion materials from any practical application.

Comment on Oxygen Solubility Measurements in Non-Aqueous Electrolytes

In this comment, we would like to highlight errors in recently published papers in Journal of Electrochemical Society, which contain the results on O 2 solubility in a series of non-aqueous electrolytes; the articles address the influence of this electrolyte property on the performance of Li/air batteries. The effect of O 2 partition between the investigated electrolytes and the aqueous in-probe media had been neglected, though. This may be a source of substantial errors in determining O 2 solubility, and also may explain contradictions between reported works presenting data and values on O 2 solubility in non-aqueous electrolytes.

This electrode is best served cold—a reversible electrochemical lithiation of a gray cubic tin

AbstractThe behavior of a cubic allotropic modification of tin (α-Sn) towards lithium electrochemical alloying/de-alloying is reported for the first time. The cycling stability of the α-Sn electrode is superior compared with the cycling stability of the tetragonal white tin (β-Sn). Scanning electron microscopy studies reveal that unlike β-Sn, the α-Sn crystal grains preserve their integrity during the lithiation/delithiation cycles. The shift in the charge/discharge potential stages in the α-Sn electrode with reference to the β-Sn electrode is demonstrated. The potential shift is discussed in terms of differences in the elastic stress—the related component of Gibbs energy of β- and α-Sn lithiation/delithiation processes. Graphical abstractA cubic allotropic modification of tin (α-Sn) towards lithium electrochemical alloying/de-alloying represents a superior cycling stability compared with a tetragonal white tin (β-Sn)