Reaching the full capacity of the electrode material Li3FeF6 by decreasing the particle size to nanoscale

An easy scalable reaction is used to prepare nanometric particles of the cryolite Li3FeF6 by precipitation below room temperature. Precipitation of Li3FeF6 in water:2-propanol ratio of 1:3 at 0 degrees C from a solution of Fe(NO3)(3)center dot 9H(2)O, 6HF((aq)) and Li2CO3, produces the smallest particles (ca. 20 nm). These particles are agglomerated building up spherical "raspberry-shaped" motifs having ca. 200 nm diameter. Interestingly, processing of as prepared Li3FeF6 using mechanical milling with carbon affects the size of agglomerates and its morphology, while the size of elemental nanometric particles is kept. Furthermore, mechanical milling has a beneficial effect on the electrochemical Li insertion and Li cells bearing Li3FeF6 as cathode deliver the theoretical full capacity (140 mAh g(-1)). The improvement of electrochemical performances is related to the more intimate mixing of Li3FeF6 and carbon black in the electrode due to the breakage of the "raspberry-shaped" agglomerates upon ball milling. A different result is obtained when Li3FeF6 is prepared from pure aqueous solution without addition of alcohol. Isolated submicrometric prismatic particles having an average size of 300 nm are obtained. These release only a 70% of theoretical electrochemical capacity in Li cells after mechanical milling. (C) 2011 Elsevier B.V. All rights reserved.