FIELD OF INVENTION:
This invention relates to a process for preparing nanostructured Li4Ti5O12 and
carbon coated Li4Ti5O12.
BACKGROUND OF THE INVENTION:
Lithium ion battery technology has become increasingly important in recent years
because it provides lightweight, compact, high energy density batteries for
powering appliances in the rapidly growing electronic industries. These batteries
are also considered as power sources for future electric vehicles (Evs) and
hybrid electric vehicles (HEVs). A typical commercial lithium-ion cell consists of a
layered LiCoO2 as cathode, LiPF6 in EC/DMC as electrolyte and graphite anode.
However, the capacity and rate performance of today's lithium-ion batteries are
limited which hinders its application in green vehicles technology. Therefore, all
battery scientists are focused on overcoming the technical barriers associated
with future battery technology, namely cost, performance, safety, and life.
Initially, metallic lithium has been used as anode but when the cell is subjected to
repeated charge-discharge cycles, the dendrite growth causes the lithium to be
deformed resulting in a short cycle life. In order to overcome this problem, use of
carbonaceous materials, alloys and metal oxides as anode have been
investigated.
Carbonaceous anodes are the most utilized anodic material due to their low cost
and availability. However, the theoretical capacity (372 mAh/g) is poor compared
to that of lithium (3,862 mAh/g). Again, Lithium ions are intercalated into the
carbonaceous materials at potential as low as the lithium deposition potential.
Therefore, most common electrolytes are not stable at this potential value and a
passivation film is formed during charging which consumes lithium from the
cathode inducing decomposition of the electrolyte. Furthermore, there is no clear
end-of-charge indicator in the voltage profile that can signal the release of
oxygen from the cathode (LiCoO2) counterpart. This can result in the structural
damage to the positive electrode.
Alloy anodes and intermetallic compounds have high capacities but also show a
dramatic volume change, resulting in poor cycling behavior. Efforts have been
made to overcome the volume change by using nanocrystalline materials and by
having the alloy phase (with Al, Bi, Mg, Sb, Sn, Zn, and others) in a nonalloying
stabilization matrix (with Co, Cu, Fe, or Ni). Silicon has an extremely high
capacity of 4,199 mAh/g, corresponding with a composition of Si5Li22. However,
cycling behavior is poor, and capacity fading not yet understood.
In this background, lithium titanium oxide, Li4Ti5O12 is considered as one of most
promising anode for lithium-ion battery application, especially for EV applications.
Insertion/extraction of Li into/from Li4Ti5O12 anode is known to proceed with no
significant volume change in the lattice and thus, it is considered as a zero-strain
insertion compound. Particularly this 'zero strain' property results in excellent
cycling performance and long cycle life. Recently, nanostructured materials are
being considered to improve the rate performance of lithium-ion batteries. This is
due to the fact that in nano regime, the Li-ion diffusion path is small leading to a
fast charge transfer process, that increase the rate performance of the cell during
cycling.
There are number of techniques such as co-precipitation, combustion, sol-gel etc
that are found in various literatures for making nanostructured LTO. However,
most of them are laboratory based methods that are either unsuitable or having
lots of complications for process up-scaling and executing in bulk. The material
produced using conventional industrial solid state process has several
disadvantages such as inhomogeneity, irregular and inconsistent particle
morphology, larger particle size, poor control of stoichiometry etc while working in
range of particles of submicron sized. Therefore, an advanced solid state
process has been invented in this work to counter all the disadvantages related
to conventional solid state process of preparing particularly nano-structured LTO
and LTO-C.
OBJECTS OF THE INVENTION:
An object of the present invention is to provide a process to prepare nano
structured Li4Ti5O12 and carbon coated Li4Ti5O12 using low cost starting raw
materials e.g. micron sized TiO2 and salts of lithium together with the agents like
glycol, sugars, inorganic acids, hydrocarbons, etc. taken individually or in a
mixture;
Another object of the present invention is to use agents like glycol, sugars,
inorganic acids, hydrocarbons etc, to produce LTO and LTO-C composite by in
situ methodology;
Yet another object of the present invention is to produce nano structured LTO
and LTO-C by using the exothermic heat produced during combustion of the
agents like glycol, sugars, inorganic acids, hydrocarbons etc. during synthesis;
Still another object of the present invention is to have a process of making LTO,
LTO-C and its derivatives through continuous process to produce nano
structured materials in large quantity;
Further, object of the present invention is to have a consistent and repeatable
process of producing LTO, LTO-C and its derivatives using simple and
inexpensive equipments and utilities;
Still further object of the present invention is to have an environment friendly
process of producing LTO-C and its derivatives.
BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a process for preparing
nanostructured Li4Ti5O12 and carbon coating Li4Ti5O12 comprising the steps of:
preparing a homogeneous mixture of stoichiometric amount of Lithium and
Titanium Salts;
preparing a stoichiometric solution of polyethylene glycol (PEG);
mixing both the solutions in a high speed mixing vessel for 2-5 hours;
subjecting the mixture to the step of drying at a temperature range of 80-140°C;
calcining the dried mass at a temperature range of 700-800°C for 8-12 hours in
air and in inert atmosphere to get LTO and LTO-c and;
pulverizing the final calcined powder to get the final product.
DETAILED DESCRIPTION OF THE INVENTION:
Solution A: preparing a homogeneous mixture of stoichiometric amount of
Lithium and Titanium Salts in an aqueous medium.
Solution B: Preparing a stoichiometric aqueous solution of poly ethylene glycol
(PEG).
Mixing of Solution A & Solution B in a high speed mixing vessel for two to five
hours.

Drying the mixture solution at a temperature in the range of 80 to 140°C.
Calcining the dried mass at a temperature between 70-800°C for 8-12 hours in
air and in inert atmosphere to get LTO and LTO-C respectively.
Pulverizing the final calcined powder to get the product.
EXAMPLES:
EXAMPLE 1:
LiOH and micron sized TiO2 were taken in an stoichometric proportion and
dissolved in distilled water to make a homogeneous mixture. A stoichimetric
aqueous solution of PEG-400 was mixed with the previous solution. Both the
solution is kept in HSM (High speed mixture machine) for 3 hours. The mixture
solution was dried in an oven at 120°C to evaporate the solvent. The dries mass
is then calcined at 800°C for 10 hours in air. The calcined mass was then
pulverized to get a highly flowable Li4Ti5O12 anode powder. The powder thus
obtained was single phase as determined by XRD. The primary particle size was
found to be 100-200nm. To get a carbon coated Li4Ti5O12, the phase pure
Li4Ti5O12 was mixed with PEG-400 in an HSM. The solvent used was water. The
aqueous solution of LTO and PEG was then dried and calcined at 650°C for 5
hours. The final powder crushed and the carbon percentage inside the powder
was measured to be 2 Wt%. The carbon coated powder was phase pure as
determined by XRD.
EXAMPLE 2:
LiOH and micron sized TiO2 were taken in an stoichometric proportion and
dissolved in distilled water to make a homogeneous mixture. A stoichimetnc
aqueous solution of PEG-400 was mixed with the previous solution. Both the
solution is kept in HSM (High speed mixture machine) for 3 hours. The mixture
solution was dried in an oven at 140°C to evaporate the solvent. The dries mass
is then calcined at 800°C for 10 hours in air. The calcined mass was then
pulverized to get a highly flowable Li4Ti5O12 anode powder. The powder thus
obtained was single phase as determined by XRD. The primary particle size was
found to be 150-200 nm. To get a carbon coated Li4Ti5O12, the phase pure
Li4Ti5O12 was mixed with PEG-400 in an HSM. The solvent used was water. The
aqueous solution of LTO and PEG was then dried and calcined at 650°C for 5
hours. The final powder crushed and the carbon percentage inside the powder
was measured to be 2.3 wt%. The carbon coated powder was phase pure as
determined by XRD.
EXAMPLE 3:
LiOH and micron sized TiO2 were taken in an stoichometric proportion and
dissolved in distilled water to make a homogeneous mixture. A stoichimetric
aqueous solution of PEG-400 was mixed with the previous solution. Both the
solution is kept in HSM (High Speed mixture machine) for 3 hours. The mixture
solution was dried in an oven at 120°C to evaporate the solvent. The dries mass
is then calcined at 700°C for 10 hours in air. The calcined mass was then
pulverized to get a highly flowable Li4Ti5O12 anode powder. The powder thus
obtained was single phase as determined by XRD. The primary particle size was

found to be 180-200nm. To get a carbon coated Li4Ti5O12, the phase pure
Li4Ti5O12 was mixed with PEG-400 in an HSM. The solvent used was water. The
aqueous solution of LTO and PEG was then dried and calcined at 650°C for 5
hours. The final powder crushed and the carbon percentage inside the powder
was measured to be 2.8 wt%. The carbon coated powder was phase pure as
determined by XRD.
EXAMPLE 4:
LiOH and micron sized TiO2 were taken in an stoichometric proportion and
dissolved in distilled water to make a homogeneous mixture. A stoichimetnc
aqueous solution of PEG-400 was mixed with the previous solution. Both the
solution is kept in HSM (High speed mixture machine) for 2-3 hours. The mixture
solution was dried in an oven at 120°C to evaporate the solvent. The dries mass
is then calcined at 750°C for 10 hours in air. The calcined mass was then
pulverized to get a highly flowable Li4Ti5O12 anode powder. The powder thus
obtained was single phase as determined by XRD. The primary particle size was
found to be 100-180nm. To get a carbon coated Li4Ti5O12, the phase pure
Li4Ti5O12 was mixed with PEG-400 in an HSM. The solvent used was water. The
aqueous solution of LTO and PEG was then dried and calcined at 650°C for 5
hours. The final powder crushed and the carbon percentage inside the powder
was measured to be 1.98 wt%. The carbon coated powder was phase pure as
determined by XRD.

EXAMPLE 5:
LiOH and micron sized TiO2 were taken in an stoichometric proportion and
dissolved in distilled water to make a homogeneous mixture. A stoichimetric
aqueous solution of PEG-400 was mixed with the previous solution. Both the
solution is kept in HSM (High speed mixture machine) for 2-3 hours. The mixture
solution was dried in an oven at 120°C to evaporate the solvent. The dries mass
is then calcined at 800°C for 8 hours in air. The calcined mass was then
pulverized to get a highly flowable Li4Ti5O12 anode powder. The powder thus
obtained was single phase as determined by XRD. The primary particle size was
found to be 80-180 nm. To get a carbon coated Li4Ti5O12, the phase pure
Li4Ti5O12 was mixed with PEG-400 in an HSM. The solvent used was water. The
aqueous solution of LTO and PEG was then dried and calcined at 650°C for 5
hours. The final powder crushed and the carbon percentage inside the powder
was measured to be 2.5 wt%. The carbon coated powder was phase pure as
determined by XRD.
EXAMPLE 6:
LiOH and micron sized TiO2 were taken in an stoichometric proportion and
dissolved in distilled water to make a homogeneous mixture. A stoichimetric
aqueous solution of PEG-400 was mixed with the previous solution. Both the
solution is kept in HSM (High speed mixture machine) for 2-3 hours. The mixture
solution was dried in an oven at 120°C to evaporate the solvent. The dries mass
is then calcined at 800°C for 10 hours in air. The calcined mass was then
pulverized to get a highly flowable Li4Ti5O12 anode powder. The powder thus
obtained was single phase as determined by XRD. The primary particle size was
found to be 100-200 nm. To get a carbon coated Li4Ti5O12, the phase pure

Li4Ti5O12 was mixed with PEG-400 in an HSM. The solvent used was water. The
aqueous solution of LTO and PEG was then dried and calcined at 600°C for 5
hours. The final powder crushed and the carbon percentage inside the powder
was measured to be 2.0 wt%. The carbon coated powder was phase pure as
determined by XRD.
LiOH and micron sized TiO2 were taken in an stoichometric proportion and
dissolved in distilled water to make a homogeneous mixture. A stoichimetric
aqueous solution of PEG-400 was mixed with the previous solution. Both the
solution is kept in HSM (High speed mixture machine) for 2-3 hours. The mixture
solution was dried in an oven at 140°C to evaporate the solvent. The dries mass
is then calcined at 800°C for 10 hours in air. The calcined mass was then
pulverized to get a highly flowable Li4Ti5O12 anode powder. The powder thus
obtained was single phase as determined by XRD. The primary particle size was
found to be 100-200 nm. To get a carbon coated Li4Ti5O12, the phase pure
Li4Ti5O12 was mixed with PEG-400 in an HSM. The solvent used was water. The
aqueous solution of LTO and PEG was then dried and calcined at 600°C for 3
hours. The final powder crushed and the carbon percentage inside the powder
was measured to be 2.5 wt%. The carbon coated powder was phase pure as
determined by XRD.

WE CLAIM:
1. A process for preparing nanostructured Li4Ti5O12 and carbon coating Li4Ti5O12
comprising the steps of:
preparing a homogeneous mixture of stoichiometric amount of Lithium and
Titanium Salts;
preparing a stoichiometric solution of hydrocarbon;
mixing both the solutions in a high speed mixing vessel for 2-5 hours;
subjecting the mixture to the step of drying at a temperature range of 80-140°C;
calcining the dried mass at a temperature range of 700-800°C for 8-12 hours in
air and in inert atmosphere to get LTO and LTO-c and;
pulverizing the final calcined powder to get the final product.
2. The method as claimed in claim 1, wherein the time required for mixing is
preferably 2-5 hours.
3. The method as claimed in claim 1-2, wherein the solution is prepared in
aqueous medium. Any other volatile solvent like acetone, alcohol may be used
4. The method as claimed in claim 1-3, wherein the metal ion such as lithium
may be obtained from lithium oxides, lithium carbonate, lithium hydroxide, lithium
acetates, lithium chlorides, lithium nitrates etc
5. The method as claimed in claim 1-4, wherein the metal ion such as titanium
may be obtained from any other titanium salts like titanium chloride, titanium
oxides, titanium alcoxides etc.

6. The method as claimed in claim 1-5, wherein the said hydrocarbon is selected
from polyethylene glycol, by any other glycols like high and low molecular weight
glycols, sugars like glucose, fructose etc, inorganic oxides like citric acids, acetic
acids and various forms of other hydrocarbons.
7. The method as claimed in claim 1-6, wherein the preferred temperature for
drying is 120-140°C.
8. The method as claimed in claim 1-7, wherein the temperature for calcinations
is in the range of 700-800°C and the time for calcination is in the range of 8-10
hours.
9. The method as claimed in claim 1-8, wherein the calcination may be carried
out in presence of air, oxygen, nitrogen, argon for LTO and nitrogen and argon
for LTO-C
10. The method as claimed in claim 1-9, wherein the carbon sources for
preparing carbon coated LTO may be any other glycols like high and low
molecular weight glycols, sugars like glucose, fructose etc, inorganic oxides like
citric acids, acetic acids and various forms of other hydrocarbons.
11. The method as claimed in claim 1-10, wherein the calcinations temperature
for preparing LTO-C is in the range of 600-650°C for 3-5 hours in inert
atmosphere.

12. The method as claimed in claim 1-11, wherein the carbon percentage in the
product is in the range of 1-4 wt%.

A process for preparing nanostructured Li4Ti5O12 and carbon coating Li4Ti5O12
comprising the steps of: preparing a homogeneous mixture of stoichiometric
amount of Lithium and Titanium Salts; preparing a stoichiometric solution of
hydrocarbon; mixing both the solutions in a high speed mixing vessel for 2-5
hours; subjecting the mixture to the step of drying at a temperature range of 80-
140°C; calcining the dried mass at a temperature range of 700-800°C for 8-12
hours in air and in inert atmosphere to get LTO and LTO-c and; pulverizing the
final calcined powder to get the final product.