Franck GASCOIN, SYLVERE SARCIAUX, DOMINIQUE GUYOMARD and YVES PIFFARD
IMN - 2, rue de la Houssinière - BP 32229 - 44322 Nantes Cedex 3 - France

The usual preparation route of lithiated Rancieite-type Manganese Oxide (Li-RMO) includes three steps: reduction of KMnO4 in acidic medium (1), followed by a further acidic treatment which ensures a complete K+/H+ exchange (2) and subsequent Li+/H+ ion-exchange reaction (3). The surface area of the as prepared Li-RMO is always several tens of m2g-1. Its initial capacity with respect to electrochemical Li intercalation is 220 mAh/g with an average voltage of 2.85V (vs Li). However, a rapid capacity fading is observed upon cycling, due to a dissolution of the material likely related to its large surface area. A new synthetic route is proposed leading to a material with a surface area less than 10 m2g-1. As expected, the cycling behavior of this new material is greatly improved.

Keywords: phyllomanganate; surface area; Li intercalation; cycling behavior