Method for the preparation of Li
The invention relates to a lithium vanadium oxide which corresponds to the formula Li 1+α V 3 O 8 (0.1≦α≦0.25). It is composed of agglomerates of small needles having a length l from 400 to 1000 nm, a width w such that 10<l/w<100 and a thickness t such that 10<l/t<100. It is obtained by a process consisting in preparing a precursor gel by bringing α-V 2 O 5 and a Li precursor into contact in amounts such that the ratio of the concentrations [V 2 O 5 ]/[Li] is between 1.15 and 1.5 and in subjecting the gel to a heat treatment comprising a first stage at 80° C.-150° C. for 3 h to 15 days and a second stage between 250° C. and 350° C. for 4 min to 1 hour, under a nitrogen or argon atmosphere. It is useful as an active material of a positive electrode.
1. A process for the preparation of an oxide Li 1+α V 3 O 8 (0≦α≦0.25) comprising preparing a precursor gel and subjecting said gel to a heat treatment, wherein:
the precursor gel is prepared by bringing α-V 2 O 5 and a Li precursor into contact in a reaction medium in amounts such that the ratio of the [V 2 O 5 ]/[Li] concentrations is between 1.15 and 1.5; and
the heat treatment is carried out in two stages: a first stage under air at a temperature of between 80° C. and 150° C. for a time of 3 hours to 15 days and a second stage under a nitrogen or argon atmosphere at a temperature of between 250° C. and 350° C. for a time of between 4 min and 1 hour.
2. The process as claimed in claim 1 , wherein the Li precursor is LiOH.H 2 O and α-V 2 O 5 and LiOH.H 2 O are introduced in water under a nitrogen atmosphere.
3. The process as claimed in claim 2 , wherein the concentration of α-V 2 O 5 is between 0.75 mol/l and 3 mol/l and the concentration of LiOH.H 2 O is between 0.55 mol/l and 2.2 mol/l.
4. The process as claimed in claim 1 , further comprising adding an aqueous solution comprising from 10 to 50% by volume of hydrogen peroxide to the reaction medium.
5. The process as claimed in claim 4 , wherein the concentrations are from 0.05 mol/l to 2 mol/l for α-V 2 O 5 and from 0.04 mol/l to 1.5 mol/l for the Li precursor.
6. The process as claimed in claim 4 , wherein the lithium precursor is LiOH.H 2 O, LiCl, LiNO 3 or a lithium salt of a carboxylic acid.
7. The process as claimed in claim 6 , wherein the lithium salt of carboxylic acid is lithium acetylacetonate, lithium acetate, lithium stearate, lithium formate, lithium oxalate, lithium citrate, lithium lactate, lithium tartrate or lithium pyruvate.
8. The process as claimed in claim 4 , wherein α-V 2 O 5 is brought into contact with an aqueous peroxide solution in the presence of a lithium precursor.
9. The process as claimed in claim 4 , wherein the respective amounts of Li precursor and of α-V 2 O 5 in the reaction medium are such that 0.08 mol/l<[Li]<0.7 mol/l and 0.1 mol/l<[V 2 O 5 ]<1 mol/l.