Modification of lithium titanate electrode particles to eliminate gas formation in cell operation

Patent metadata

Field	Value
Publication number	US-10601046-B2
Application number	US-201515761877-A
Country	US
Kind code	B2
Filing date	Oct 7, 2015
Priority date	Oct 7, 2015
Publication date	Mar 24, 2020
Grant date	Mar 24, 2020

Abstract

Lithium titanate, Li4Ti5O12, particles containing surface hydroxyl groups are susceptible to unwanted gas generation (such as hydrogen) in the presence of water contamination when the particles are used as active anode electrode material in lithium-ion cells operating with an anhydrous liquid electrolyte. In accordance with this disclosure, the hydroxyl groups on the surfaces of the particles are reacted with one of a group of selected agents containing organic alkoxy groups to form hydrophobic moieties on the surfaces of the particles which effectively block water molecules from the surfaces of lithium titanate particles in the anode of the cell.

First claim

The invention claimed is:

1. A method of preparing lithium titanate (Li 4 Ti 5 O 12 ) particles, characterized by the presence of hydroxyl groups on the surfaces of the particles, for use as anode material particles in an electrochemical cell with an anhydrous electrolyte, the preparation of the lithium titanate particles being performed to replace the hydroxyl groups on the surfaces of the particles with hydrophobic groups for isolating the lithium titanate particles from water molecules produced as a contaminant in the operation of the electrochemical cell; the method comprising:
reacting the hydroxyl groups on the surfaces of the lithium titanate particles with molecules of a compound selected from the group consisting of an alkanol, a sulfur-containing acid, a tetravalent silicon-containing compound, and a tetravalent titanium-containing compound, the selected compound containing hydroxyl groups or alkoxy groups or both alkyl groups and alkoxy groups, such that
the reaction of the molecules of the selected compound with the hydroxyl groups on the lithium titanate particles produces water or an alcohol as a product removable from the lithium titanate particles, and
molecular moieties of the remainder of the molecules of the selected compound are attached to the surfaces of the lithium titanate particles in place of the hydroxyl groups, the attached molecular moieties containing alkoxy groups or a combination of alkoxy groups and alkyl groups such that the remaining molecular moieties attached to the surfaces of the lithium titanate particles serve as barriers to water contamination when the lithium titanate particles are subsequently placed and used in an electrochemical cell, and
removing any residual selected compound and any residual water from the surface of the lithium titanate particles.

2. The method of claim 1 wherein the selected compound is an alkanol having one to four carbon atoms such that the molecules of alkanol react with the hydroxyl groups on the surfaces of the lithium titanate particles to form water as a by-product and to replace the hydroxyl groups with alkoxy groups to serve as barriers to water contamination.

3. The method of claim 2 wherein the alkanol is applied as a liquid to contact the surfaces of the lithium titanate particles to replace the hydroxyl groups with alkoxy groups, and excess liquid alcohol and by-product water are then removed from the alkoxy-coated lithium titanate particles.

4. The method of claim 2 wherein the alkanol is applied as a vapor to contact the surfaces of the lithium titanate particles to replace the hydroxyl groups with alkoxy groups, and the alcohol vapor and by-product water are then removed from the alkoxy-coated lithium titanate particles.

5. The method of claim 1 wherein the selected compound is a sulfur-containing acid selected from the group consisting of a sulfinic acid, a sulfenic acid, and a sulfonic acid, the sulfur-containing acid having a hydroxyl group, such that the sulfur-containing acid reacts with the hydroxyl groups on the surfaces of the lithium titanate particles to form water as a by-product and to replace the hydroxyl groups with a sulfur-containing moiety with at least one of alkyl groups, aromatic groups, and alkyl amino groups to serve as barriers to water contamination.

6. The method of claim 5 wherein the sulfur containing acid compound is dissolved in a non-aqueous solvent and the solution is applied to the surfaces of the lithium titanate particles to replace the hydroxyl groups with the sulfur-containing moiety, and any residual solution and any residual water are removed from the lithium titanate particles.

7. The method of claim 1 where the selected compound is a tetravalent silicon-containing compound with one to four alkoxy groups and the remainder alkane groups, such that an alkoxy group of the silicon-containing compound reacts with the hydroxyl groups on the surfaces of the lithium titanate particles to form an alcohol as a by-product and to replace the hydroxyl groups with a tetravalent silicon-containing moiety with alkoxy groups or a combination of alkoxy groups and alkyl groups to serve as barriers to water contamination.

8. The method of claim 7 wherein the tetravalent silicon-containing compound is a silane selected from the group consisting of hexadecyltrimethoxysilane, methyltrimethoxysilane, dimethyl dimethoxysilane, and methoxytrimethylsilane.

9. The method of claim 7 wherein the silicon-containing compound is dissolved in a non-aqueous solvent and the solution is applied to the surfaces of the lithium titanate particles to replace the hydroxyl groups with the tetravalent silicon-containing moiety, and any residual solution and any residual water are removed from the lithium titanate particles.

10. The method of claim 1 where the selected compound is a tetravalent titanium-containing compound with one to four alkoxy groups and the remainder alkane groups, such that alkoxy groups of the titanium-containing compound react with the hydroxyl groups on the surfaces of the lithium titanate particles to form an alcohol as a by-product and to replace the hydroxyl groups with a tetravalent titanium-containing moiety with alkoxy groups or a combination of alkoxy groups and alkyl groups to serve as barriers to water contamination.

11. The method of claim 10 wherein the tetravalent titanium-containing compound is a compound represented by one of Ti(OX) 4 , Ti(OX) 3 Y, Ti(OX) 2 YR 1 , Ti(OX)YR 1 R 2 , where X and Y are alkyl groups and R 1 is an alkyl group and R 2 is an alkyl group containing 1-6 carbon atoms.

12. The method of claim 10 wherein the tetravalent titanium-containing compound is dissolved in a non-aqueous solvent and the solution is applied to the surfaces of the lithium titanate particles to replace the hydroxyl groups with the tetravalent titanium-containing moiety, and any residual solution and any residual water are removed from the lithium titanate particles.

13. A method of preparing lithium titanate (Li 4 Ti 5 O 12 ) particles, characterized by the presence of hydroxyl groups on the surfaces of the particles, for use as anode material particles in an electrochemical cell with an anhydrous electrolyte, the preparation of the lithium titanate particles being performed to replace the hydroxyl groups on the surfaces of the particles with hydrophobic groups for isolating the lithium titanate from water molecules produced as a contaminant in the operation of the electrochemical cell; the method comprising:
reacting the hydroxyl groups on the surfaces of the particles with an aliphatic alkanol having one to four carbon atoms, the reaction of the aliphatic alkanol with the hydroxyl groups on the lithium titanate particles producing water as a product removable from the particles, and alkoxy groups attached to the surfaces of the lithium titanate particles in place of the hydroxyl groups, the attached alkoxy groups attached to the surfaces of the lithium titanate particles being selected to serve as barriers to water reaction with the lithium titanate particles when they are subsequently placed as an anodic electrode and used in an electrochemical cell employing an anhydrous electrolyte and in which the lithium titanate particles are to be used to repeatedly intercalate and de-intercalate lithium ions in the charging and discharging of the cell, and
removing any residual aliphatic alkanol and any residual water from the surface of the lithium titanate particles.

14. The method of claim 13 wherein the aliphatic alkanol is applied as a liquid to contact the surfaces of the lithium titanate particles to replace the hydroxyl groups with a

Assignees

• Gm Global Tech Operations Llc

Inventors

• Yu Zhiqiang
• Liu Haijing

Classifications

• C01G23/005

  Alkali titanates · CPC title

• H01M2220/20

  Batteries in motive systems, e.g. vehicle, ship, plane · CPC title

• H01M4/485 Primary

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• C09C1/36

  Compounds of titanium {(C09C1/0009, C09C1/0015, C09C1/0078 take precedence)} · CPC title