Tin based anode material for a rechargeable battery and preparation method
A tin based anode material for a rechargeable battery comprises nanoparticles of composition SnM x O y wherein M is a further element selected from the group 5 consisting of Ni, Cu, In, Al, Ge, Pb, Bi, Sb, Fe, Co, Ga, with 0≤x≤0.5 and 0≤y≤2+2x. The nanoparticles form a substantially monodisperse ensemble with an average size not exceeding 30 nm and a size deviation not exceeding 15%, the nanoparticles optionally being coated with a capping species. A method for preparing the tin based anode material is carried out in situ in a non-aqueous solvent and starts by reacting a tin salt and an organometallic amide reactant and oleylamine.
1. A tin based anode material for a rechargeable battery, the anode material comprising nanocrystals of composition SnO y , wherein 0≤y≤2, the nanocrystals forming a substantially monodisperse ensemble with an average size not exceeding 20 nm and a size deviation not exceeding 15%, the nanocrystals consisting of a single-crystalline Sn core entirely surrounded by a shell of SnO 2 directly contacting a surface of the single-crystalline Sn core, the shell of SnO 2 having a thickness of not less than 10 nm.
2. The material according to claim 1 , wherein the average size of the nanocrystals does not exceed 15 nm.
3. The material according to claim 2 , wherein the average size of the nanocrystals does not exceed 10 nm.
4. The material according to claim 1 , wherein the nanocrystals are coated with a capping species, the capping species being a sulfur containing species selected from the group consisting of SH − , SO 4 2− or S 2− .
5. The material according to claim 1 , wherein the shell of SnO 2 is an amorphous oxide shell.
6. The material according to claim 1 , wherein the nanocrystals are all spherical or centrosymtnetric polyhedral in shape.
7. The material according to claim 1 , wherein the size deviation not exceeding 15% is defined by a formula for size deviation S:
S=FWHM/ 2 d× 100[%],
where FWHM is a full width at half maximum of a Gaussian fit of measured nanocrystals, and d is a diameter of the measured nanocrystals at a maximum of the Gaussian fit.
8. The material according to claim 1 , wherein the shell includes only the atoms Sn and O.
9. A method for preparing a tin based anode material for a rechargeable battery, the anode material comprising nanocrystals of composition SnO y wherein 0≤y≤2, the nanocrystals forming a substantially monodisperse ensemble with an average size not exceeding 20 nm and a size deviation not exceeding 15%, the nanocrystals consisting of a single-crystalline Sn core entirely surrounded by a shell of SnO 2 directly contacting a surface of the single-crystalline Sn core, the shell of SnO 2 having a thickness of not less than 10 nm, said method comprising:
a) in a non-aqueous solvent, reacting a tin salt and an organometallic amide reactant and oleylamine,
b) adding thereto a transform reactant selected from the group consisting of reducing agents, oxidizing agents and alloying agents,
c) adding thereto a precipitating agent, thereby forming a substantially monodisperse nanocrystalline material comprising the nanocrystals of composition SnO y coated with an initial capping layer, and
d) optionally carrying out a ligand exchange to provide an inorganically capped nanocrystalline material or an uncapped nanoctystalline material.
10. The method according to claim 9 , wherein said solvent is oleylamine.
11. The method according to claim 9 , wherein said tin salt is selected from the group consisting of tin chloride, tin acetate, tin triflate and tin silylamide.
12. The method according to claim 9 , wherein said organometallic amide reactant is selected from the group consisting of LiN(Si(CH 3 ) 3 ) 2 , LiN(CH 3 ) 2 , and lithium oleylamide.
13. The method according to claim 9 , wherein said reducing agents are selected from the group consisting of diisohutylaluminum hydride and lithium triethylborohydride.
14. The method according to claim 9 , wherein said oxidizing agents are selected from the group consisting of oxygen, an oxygen/nitrogen mixture and ozone.
15. The method according to claim 9 , wherein said alloying agents are selected from the group consisting of a chloride, bromide, acetate and triflate.
16. The method according to claim 9 , wherein said precipitating agent is selected from the group consisting of ethanol, methanol, acetone and acetonitrile.
17. A rechargeable battery comprising an anode and a cathode, wherein the anode comprises a tin based anode material comprising nanocrvstals of composition SnO y , wherein 0≤y≤2, the nanoctystals forming a substantially monodisperse ensemble with an average size not exceeding 20 nm and a size deviation not exceeding 15%, the nanocrystals consisting of a single-crystalline Sn core entirely surrounded by a shell of SnO 2 directly contacting a surface of the single-crystalline Sn core, the shell of SnO 2 , having a thickness of not less than 10 nm.
18. The rechargeable battery according to claim 17 , wherein said rechargeable battery is a sodium ion battery.
19. The rechargeable battery according to claim 17 , wherein said rechargeable battery is a lithium ion battery.