Method of Making Silver Vanadium Oxide Material Useful as a Battery Cathode
INVENTION: Ag2V4O11 (SVO) and Ag4V2O6F2, (SVOF) are important cathode materials for medical battery applications such as defibrillators. A one-step process has been developed affording crystalline SVO and SVOF by reaction under ambient conditions, eliminating the need for superambient pressure and temperatures.
ADVANTAGES: Superior performing medical battery cathode materials can be produced with significant cost and environmental advantages.
SUMMARY: The current standard cathode material in medical batteries is silver vanadium oxide Ag2V4O11 (SVO). Recently Northwestern researchers reported Ag4V2O6F2, (SVOF) provides cathodes with more accessible silver content above 3 V than SVO and achieves 50% greater capacity than maximum SVO performance (NU24067). SVOF is made by a hydrothermal process that involves subjecting silver oxide, vanadium oxide, and concentrated HF solution to superambient temperature and pressure in a pressure vessel. The synthesis produces large particle sizes resulting from the hydrothermal procedure (> 1 mm single crystals and > 10 µm particle size after manually grinding), which can hinder high discharge rate capability. The present invention provides a one-step process for making crystalline silver vanadium oxide materials by reaction of oxide precursors in an aqueous HF solution under ambient temperature and pressure eliminating the autoclave process. The silver vanadium oxide material can comprise Ag2V4O11 (SVO); Ag2V4O11F2 (SVOF), and/or Ag2VO2F4 depending on the reaction parameters employed. The process generates silver vanadium oxide or silver vanadium oxide fluoride particles whose shape and size are advantageously platelets of 1 to 2 µm diameter and 50 to100 nm thickness or acicular particles of 10 to 20 nm width and 100 to 300 nm length, depending on the preparation conditions. The resultant nano-size particles afford superior reactivity versus lithium, exhibiting higher discharge rate capability and surprisingly high reversibility of the lithium insertion/de-insertion, even under severe cycling conditions (Figure 1). The tailored particles can be useful for commercial production of medical defibrillator batteries, rechargeable Li-ion batteries requiring high-rate charge/discharge capability such as H.E.V., and other applications.
The direct and economical synthetic process promises significant higher electrochemical performance favorable for commercial production of crystalline silver vanadium oxide or silver vanadium oxide fluoride particle materials.
STATUS: A patent application has been filed.
Kenneth R. Poeppelmeier, Thomas Albrecht, Frederic Sauvage
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