Na2Ti3O7 has attracted much attention in the field of anode materials for Na-ion batteries thanks to its non-toxicity and very low working potential of 0.3 V vs Na0/Na+.Building a clearer picture of its forma-tion from cheap Na2CO3 and TiO2 starting materials is therefore of obvious interest.Here,we report new insights from an in-situ high temperature X-ray diffraction study conducted from room temperature to 800 ℃,complemented by ex-situ characterizations.We were thereby able to position the previously reported Na4Ti5O12 and Na2Ti6O13 intermediate phases in a reaction scheme involving three successive steps and temperature ranges.Shifts and/or broadening of a subset of the Na2Ti6O13 reflections suggested a combination of intra-layer disorder with the well-established ordering of successive layers.This in-situ study was carried out on reproducible mixtures of Na2CO3 and TiO2 in 1∶3 molar ratio prepared by spray-drying of mixed aqueous suspensions.Single-phase Na2Ti3O7 was obtained after only 8 h at 800 ℃ in air,instead of a minimum of 20 h for a conventional solid-state route using the same precursors.Microstructure analysis revealed ～ 15 μm diameter granules made up from rectangular rods of a few-μm length presenting electrochemical properties in line with expectations.In the absence of grinding or formation of intimate composites with conductive carbon,the specific capacity of 137 mAh/g at C/5 decreased at higher rates.

Caroline Piffet;Bénédicte Vertruyen;Frédéric Hatert;Rudi Cloots;Frédéric Boschini;Abdelfattah Mahmoud

GREENMAT,CESAM Research Unit,Chemistry Department,University of Liège,4000 Liège,Belgium;Laboratory of Mineralogy,Geology Research Unit,University of Liège,4000 Liège,Belgium

能源化学

[1]Caroline Piffet;Bénédicte Vertruyen;Frédéric Hatert;Rudi Cloots;Frédéric Boschini;Abdelfattah Mahmoud-.High temperature X-ray diffraction study of the formation of Na2Ti3O7 from a mixture of sodium carbonate and titanium oxide)[J].能源化学,2022(02):210-218

Na4Ti5O12,Na2Ti6O13

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