Crystalline ion-conducting nanomaterial and method for the production thereof
View Patent ↗The invention relates to a crystalline ion-conducting material made of LiMPO 4 nanoparticles, wherein M is selected from Cr, Mn, Co, Fe and Ni, in addition to mixtures thereof and the nanoparticles have an essentially flat prismatic shape. The invention also relates to a method for producing said type of crystalline ion-conducting material which consists of the following steps: a precursor component is produced in a solution front a lithium compound of a component containing metal ions M and a phosphate compound, the precursor compound is subsequently precipitated from the solution and, optionally, a suspension of the precursor compound is formed, the precursor compound and/or the suspension is dispersed and/or ground, and the precursor compound and/or the suspension is converted under hydrothermal conditions and subsequently, the crystalline material is extracted.
1. A crystalline ion-conducting material consisting of LiMPO 4 nanoparticles, wherein M is Cr, Mn, Co, Fe or Ni or a mixture thereof, and the nanoparticles have a substantially flat prismatic form and a monomodal size distribution.
2. The crystalline material as claimed in claim 1 , wherein a family of successive lattice planes run parallel to the basal face of the prism.
3. The crystalline material as claimed in claim 2 , wherein the family of lattice planes are the 0k0 lattice planes, in which k is an integer ≧1.
4. The crystalline material as claimed in claim 3 , wherein the family of lattice planes contain the 020 lattice plane.
5. The crystalline material as claimed in claim 1 , wherein the ratio of the intensities of two selected reflections in an X-ray powder diffraction pattern of the crystalline material are greater than 2.6:1, the reflections representing lattice planes are arranged perpendicular to one another, and a lattice plane is the 0k0 lattice plane.
6. The crystalline material as claimed in claim 5 , wherein the intensity ratio of the reflections I(020+211):I(301) is greater than 2.6:1.
7. The crystalline material as claimed in claim 1 , wherein the prism is an n-sided prism where n is 4.
8. The crystalline material as claimed in claim 7 , wherein the ratio of the length l of the basal face of the prism to its height h is ≧4.
9. The crystalline material as claimed in claim 6 , wherein the length l of the basal face of the prism is in the range from 1 to 15 μm.
10. The crystalline material as claimed in claim 9 , wherein the height h of the prism is from 10 to 100 nm.
11. A method for preparing a crystalline material as claimed in claim 1 , which comprises
a) preparing a precursor compound in solution from a lithium compound, a compound containing metal ions M and a phosphate compound,
b) precipitating the precursor compound from the solution and optionally forming a suspension of the precursor compound,
c) dispersing and/or milling the precursor compound and/or the suspension,
d) reacting the precursor compound and/or the suspension under hydrothermal conditions,
e) isolating the resultant crystalline material.
12. The method as claimed in claim 11 , wherein the metal ions M are selected from the group consisting of Cr, Mn, Co, Fe, Ni and mixtures thereof.
13. The method as claimed in claim 11 , wherein the dispersing or milling in c) begins before or during the precipitation of the precursor compound.
14. The method as claimed in claim 13 , wherein the reaction product is dried after d).
15. The method as claimed in claim 14 , wherein d) is carried out at a temperature in the range from 100 to 250° C.
16. The method as claimed in claim 11 , wherein d) is carried out at a pressure of from 1 bar to 40 bar vapor pressure.
17. The method as claimed in claim 11 , wherein a template compound is furthermore added in a).
18. The method as claimed in claim 11 , wherein the lithium compound, the compound containing metal ions M and the phosphate compound in a) are mixed with one another.
19. The method as claimed in claim 11 , wherein the lithium compound is LiOH or Li 2 CO 3 .
20. The method as claimed in claim 11 , wherein the compound containing metal ions is selected from the group consisting of metal sulfates, halides, nitrates, phosphates, carboxylates and acetylacetonates.
21. The method as claimed in claim 11 , wherein the phosphate compound is a phosphoric acid, a phosphate, a hydrogen phosphate or a dihydrogen phosphate.
22. The method as claimed in claim 11 , wherein the precursor compound is prepared in water.
23. The method as claimed in claim 11 , wherein the lithium compound, the compound containing metal ions M and the phosphate compound in a) are mixed with one another in the concentration ratio of 1:1:1 or with an Li excess of 1:1:3.
24. The crystalline material as claimed in claim 5 , wherein the intensity ratio of the reflections I(020+211):I(301) is greater than 3:1.
25. The crystalline material as claimed in claim 6 , wherein the length l of the basal face of the prism is in the range from 1 to 5 μm.