Title of Invention	“SUBMICRON SIZED DOPED LITHIUM MANGANESE OXYSULPHIDE CATHODE AND A PROCESS OF PREPARATION THEREOF”
Abstract	The present invention provides a submicron sized doped lithium manganese oxysulphide cathode for Lithium-ion battery applications having high retention capacity and structural integrity and a low temperature combustion process for the synthesis of doped lithium manganese oxysulphide cathode. The invention provides an economic process for the preparation of doped lithium manganese oxysulphide cathode material at a low synthesis temperature (150-200°C) using aqueous solutions of the precursor salts. The single phase submicron sized doped lithium manganese oxysulphide product powder is obtained that can be used as a cathode in lithium ion batteries.

Title of Invention

“SUBMICRON SIZED DOPED LITHIUM MANGANESE OXYSULPHIDE CATHODE AND A PROCESS OF PREPARATION THEREOF”

Abstract

The present invention provides a submicron sized doped lithium manganese oxysulphide cathode for Lithium-ion battery applications having high retention capacity and structural integrity and a low temperature combustion process for the synthesis of doped lithium manganese oxysulphide cathode. The invention provides an economic process for the preparation of doped lithium manganese oxysulphide cathode material at a low synthesis temperature (150-200°C) using aqueous solutions of the precursor salts. The single phase submicron sized doped lithium manganese oxysulphide product powder is obtained that can be used as a cathode in lithium ion batteries.

Full Text	SUBMICRON SIZED DOPED LITHIUM MANGANESE OXYSULPHIDE CATHODE AND A PROCESS OF PREPARATION THEREOF FIELD OF THE INVENTION The present invention relates to the field of rechargeable lithium ion battery technology. The present invention particularly provide submicron sized doped lithium manganese oxysulphide cathodes for lithium ion battery applications and process of synthesis thereof. BACKGROUND OF THE INVENTION Rechargeable 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 of interest for their possible application as power sources for zero emission vehicles (ZEV). State-of-the-art rechargeable lithium batteries are known as ‘lithium ion’ batteries because during the charge-discharge process lithium ions are shuttled between two host structures with a concomitant reduction and oxidation of host electrodes. The typical commercial lithium-ion cell is a 3.7 V LixC6/Li1-xCoO2 cell, in which lithium ion is extracted from a layered LiCoO2 structure (cathode) during charge and inserted into a carbonaceous structure, typically graphite or a pyrolyzed carbon (anode). In recent years, LiMn2O4 intercalation compounds have shown exceptional promise as positive electrode materials on the basis of their economy, electrochemical efficacy and environmental adequacy. However, LiMn2O4 shows disadvantages related to poor cycling behavior caused by a fast capacity fading in the 3V range (due to Jahn Teller distortion of [MnO6] octahedral) and also in the 4V range (due to Mn3+ dissolution during intercalation/de-intercalation of the lithium ions). Attempts have been made to partially substitute manganese by other metal elements for overcoming these problems. Such doping improves both 3V (due to reduction of Jahn-Teller (JT) distortion) and 4V (lesser dissolution of Mn) capacity retention. However, doping causes a reduction in cell capacity due to limited Li ion extraction. In case of a small amount of substitution in Mn site, the dopant reduces the initial capacity at the 4V plateau only slightly, but improves the cycle-life of the cell considerably. On the other hand, an extensive amount of substitution shows a significant decrease in capacity at the 4V plateau. Over the past decade, a number of techniques have been developed for the production of Li-Mn-O based cathode powders - they are mainly divided into two categories: (1) dry methods (like solid state synthesis) and (2) wet chemistry methods (like Sol-gel, Co-precipitation, hydrothermal etc.). The conventional solid state process is tedious, requires prolonged heat treatment and has several disadvantages such as in homogeneity, irregular morphology, larger particle size, poor control of stoichiometry etc. On the other hand, synthesis of Li-Mn-O based cathode powders by wet chemistry methods such as sol-gel, micro-emulsion, co-precipitation etc. necessitates a non- aqueous medium, complex multi-step processes and long time duration. Therefore, there is a need to provide a lithium ion cathode that do not suffer capacity fading during cycling and have better structural integrity. Further, a process for synthesis of lithium manganese oxide cathode is required that does not suffer from drawbacks such as multi-step procedures, longer processing time, high reaction temperature, inhomogeneity, irregular morphology, larger particle size, poor control of stochiometry. OBJECTS OF THE INVENTION The object of the present invention is to develop a novel submicron sized doped lithium ion cathode that do not suffer capacity fading during cycling and have structural integrity. Another object of the present invention is to provide a low temperature combustion process for the synthesis of a submicron sized doped lithium manganese oxysulphide cathode. STATEMENT OF THE INVENTION The present invention provides a submicron sized doped lithium manganese oxysulphide cathode of formula LiMxMn2-xO4-dSd, wherein M is a metal dopant; 0 = x = 0.5; and 0 = d = 0.1. SUMMARY OF THE INVENTION Submicron sized doped lithium manganese oxysulphide cathode that do not suffer capacity fading and have structural integrity have been developed. The low temperature combustion synthesis process for the synthesis of submicron sized doped lithium manganese oxysulphide cathode involves codoping simultaneously at cation and anion site in the spinel LiMn2O4. A BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1: X-ray diffractogram of pristine LiMn2O4 Fig. 2: X-ray diffraction patterns of different Ni doped oxysulphide powders showing single phase spinel compound having Fd3m symmetry Fig. 3: FESEM micrograph showing submicron sized particles in different oxysulphide systems synthesized by alanine assisted combustion process Fig. 4: Initial charge discharge cycle of Ni-doped lithium manganese oxysulphide cathodes using Li-metal as an anode in a 2032 coin cell in the voltage range of 3.4 to 5.0 V Fig. 5: Cycle number vs Capacity plot of Ni-doped lithium manganese oxysulfides. The oxysulfide cathodes shows better performance that the pristine compound Fig. 6: Excellent capacity retention on cycling by indium oxysulphide cathodes Fig.7: Charge and discharge capacities vs cycle number plot of indium oxysulphide cathodes DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a submicron sized doped lithium manganese oxysulphide cathode of formula LiMxMn2-xO4-dSd , wherein M is a metal dopant; 0 = x = 0.5; and 0 = d = 0.1. The metal dopant is chosen from a transitional metal and a non-transitional metal. The transitional metal is selected from Titanium, Vanadium, Chromium, Nickel, Copper, Iron and Zinc and the non-transitional metal is selected from Boron, Aluminium, Magnesium, Gallium, Indium, Antimony and Tin. This cathode is different from LiMn2O4 or cation doped LiMn2O4 and do not suffer from severe capacity fading and have structural integrity. In contrast to the prior art, the present invention utilizes low temperature combustion synthesis process involving codoping at both cation and anion site of the LiMn2O4 spinel. Codoping at manganese and oxygen sites improves capacity by reducing JT distortion at 3 V and enhances its structural integrity which in turn retards Mn dissolution at 4 V region. The combustion synthesis is of particular interest because it offers several attractive advantages over the other wet-chemical/soft chemical routes-like sol-gel, co-precipitation, inner-gel etc. The major advantages of combustion synthesis are: ultra fine homogeneous phase pure product powder, simplicity of experimental set up, relatively short processing time and cost effectiveness. However, the entire prior art reports on the synthesis of LiMn2O4 spinel either by sol-gel or by solid-state synthesis process. On the contrary, use of an aqueous soft chemical method to synthesize transition and non-transition metal doped lithium manganese oxysulphides will solve the drawbacks of the prior art processes. Accordingly, the present invention provides a low temperature combustion synthesis process for making submicron sized doped lithium manganese oxysulphide cathode for Lithium battery applications in aqueous medium which comprises preparing a saturated mixed salt solution of stochiometric lithium, metal dopant, manganese and lithium sulfide in distilled water; adding 70-80 Volume % nitric acid and a saturated aqueous solution of combustion fuel ie. a polycarboxylic acid to the mixed salt solution, molar proportion of combustion fuel to nitrate being in the range of (1-2):1; placing the beaker containing the mixed salt solution on a hot plate at 150oC- 200oC with constant stirring till a clear viscous gel is formed; further, heating the viscous gel to spontaneous burning of the same resulting in blackish/brownish solid mass and calcining the solid mass in the temperature range of 700oC-800oC for 10 hours to obtain the doped lithium manganese oxysulphide cathode (powder). Combustion fuel, polycarboxylic acid is selected from alanine, glycine, valine, leucine and iso-leucine. The synthesis of submicron sized doped lithium manganese oxysulphide cathode is carried out in an aqueous medium where alanine acts both as a a combustion fuel as well as complexing agent which helps in producing nanostructured powders at a low combustion temperature in the range of 150 oC to 200oC, which is significantly lower than those described in the prior-art processes. A controlled exothermic and self igniting oxidation reduction reaction takes place within the individual components. A self-propagating auto ignition takes place, which utilizes a part of the heat evolved during combustion process to synthesize a number of transition and non-transition metal doped lithium manganese oxysulfides. As the electrochemical reactivity of ceramic powders used for battery materials depends largely on its particle size and surface area, a low combustion temperature is needed for greater reactivity. In this regard, the present invention has great advantage as it produces particles in the submicron range with a comparatively high surface area at a low temperature of 150oC to 200oC by a cost effective aqueous combustion process. The low temperature aqueous combustion synthesis of submicron sized doped lithium manganese oxysulphide is an economic process rather than solid state or sol-gel process. The introduction of alanine in aqua- combustion process has a great advantage. Alanine having an extra methyl group in branch chain accelerates the combustion process. The branch-chain methyl groups present in alanine evolutes more gaseous species during combustion making the product highly porous. More carbon in the chain enhances the reaction temperature instantaneously up to 800oC. Another specialty of alanine is that it can chelate with multivalent cationic species. Presence of alanine as fuel results in a low combustion temperature as well as a high flame temperature forming 80-90% phase even in the ash form. Thereby, the required calcination (firing) temperature is also lowered. The following examples are illustrative only and not limitative of the invention. EXAMPLES Example 1 Ni-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Ni, 0 Example 2 Cr-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Cr, 0 Example 3 Cu-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Cu, 0 Example 4 Fe-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Fe, 0 Example 5 In-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M=In, 0 Example 6 B-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M=B, 0 Example 7 Ga-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M=Ga, 0 Example 8 X-ray diffraction pattern of LiMn2O4 (pristine) available in the prior art and LiNixMn2-xO4-dSd of the present invention show the structural differences between the two cathodes [Figure 1 and 2]. Further, figure 5 shows better performance of Ni doped Lithium manganese oxysulphides when compared with LiMn2O4 (pristine) available in prior art. Figure 5 provides cell cycle vs capacity plot of LiMxMn2-xO4-dSd where M= Ni, 0 WE CLAIM: 1. A submicron sized doped lithium manganese oxysulphide cathode of formula LiMxMn2-xO4-dSd , wherein M is a metal dopant; 0 = x = 0.5; and 0 = d = 0.1. 2. A low temperature combustion synthesis process for making submicron sized doped lithium manganese oxysulphide cathode comprising: a) Preparing saturated aqueous mixed salt solution of lithium, metal dopant, manganese and lithium sulfide; b) adding nitric acid and a saturated aqueous solution of combustion fuel to the mixed salt solution; c) heating the solution obtained in step (b) to obtain a clear viscous gel; d) heating the viscous gel obtained in step (c) to obtain a solid mass; and e) calcining the solid mass obtained in step (d) to obtain the doped lithium manganese oxysulfide cathode. 3. The cathode as claimed in claim 1 and 2, wherein metal dopant is selected from a transitional metal and a non-transitional metal. 4. The cathode as claimed in claim 3, wherein the transitional metal comprises Titanium, Vanadium, Chromium, Nickel, Copper, Iron and Zinc. 5. The cathode as claimed in claim 3, wherein the non-transitional metal comprises Boron, Aluminium, Magnesium, Gallium, Indium, Antimony and Tin. 6. The process as claimed in claim 2, wherein said process is carried out in an aqueous medium. 7. The process as claimed in claim 2, wherein lithium salt is selected from oxide, carbonate, hydroxide, chloride, acetate and nitrate salts. 8. The process as claimed in claim 2, wherein the metal dopant and manganese salt is selected from oxide, acetate and nitrate salts. 9. The process as claimed in claim 2, wherein nitric acid is in the range from 70%-80%. 10. The process as claimed in claim 2, wherein the combustion fuel is a polycarboxylic acid. 11. The process as claimed in claims 10, wherein the polycarboxylic acid is selected from alanine, glycine, valine, leucine and iso-leucine. 12. The process as claimed in claims 10 and 11, wherein the polycarboxylic acid is preferably alanine. 13. The process as claimed in claim 2, wherein the molar proportion of combustion fuel to nitrate is in the range of (1-2):1. 14. The process as claimed in claim 2, wherein the heating in step (c) is carried out at temperature in the range of 150-200oC. 15. The process as claimed in claim 2, wherein the heating of viscous gel in step (d) is carried out at temperature in the range of 150-200oC. 16. The process as claimed in claim 2, wherein the calcination of solid mass in step (e) is carried out at temperature in the range of 700-800oC. 17. The cathode as claimed in claim 1, wherein said cathode do not suffer capacity fading during cycling. 18. The doped lithium manganese oxysulphide cathode and a process of preparation thereof substantially as herein described with reference to the foregoing examples and accompanying drawings.

Full Text

SUBMICRON SIZED DOPED LITHIUM MANGANESE OXYSULPHIDE CATHODE AND A PROCESS OF PREPARATION THEREOF

FIELD OF THE INVENTION
The present invention relates to the field of rechargeable lithium ion battery technology. The present invention particularly provide submicron sized doped lithium manganese oxysulphide cathodes for lithium ion battery applications and process of synthesis thereof.
BACKGROUND OF THE INVENTION
Rechargeable 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 of interest for their possible application as power sources for zero emission vehicles (ZEV). State-of-the-art rechargeable lithium batteries are known as ‘lithium ion’ batteries because during the charge-discharge process lithium ions are shuttled between two host structures with a concomitant reduction and oxidation of host electrodes. The typical commercial lithium-ion cell is a 3.7 V LixC6/Li1-xCoO2 cell, in which lithium ion is extracted from a layered LiCoO2 structure (cathode) during charge and inserted into a carbonaceous structure, typically graphite or a pyrolyzed carbon (anode). In recent years, LiMn2O4 intercalation compounds have shown exceptional promise as positive electrode materials on the basis of their economy, electrochemical efficacy and environmental adequacy. However, LiMn2O4 shows disadvantages related to poor cycling behavior caused by a fast capacity fading in the 3V range (due to Jahn Teller distortion of [MnO6] octahedral) and also in the 4V range (due to Mn3+ dissolution during intercalation/de-intercalation of the lithium ions). Attempts have been made to partially substitute manganese by other metal elements for overcoming these problems. Such doping improves both 3V (due to reduction of Jahn-Teller (JT) distortion) and 4V (lesser dissolution of Mn) capacity retention. However, doping causes a reduction in cell capacity due to limited Li ion extraction. In case of a small amount of substitution in Mn site, the dopant reduces the initial capacity at the 4V plateau only slightly, but improves the cycle-life of the cell considerably. On the other hand, an extensive amount of substitution shows a significant decrease in capacity at the 4V plateau.

Over the past decade, a number of techniques have been developed for the production of Li-Mn-O based cathode powders - they are mainly divided into two categories: (1) dry methods (like solid state synthesis) and (2) wet chemistry methods (like Sol-gel, Co-precipitation, hydrothermal etc.). The conventional solid state process is tedious, requires prolonged heat treatment and has several disadvantages such as in homogeneity, irregular morphology, larger particle size, poor control of stoichiometry etc. On the other hand, synthesis of Li-Mn-O based cathode powders by wet chemistry methods such as sol-gel, micro-emulsion, co-precipitation etc. necessitates a non- aqueous medium, complex multi-step processes and long time duration.

Therefore, there is a need to provide a lithium ion cathode that do not suffer capacity fading during cycling and have better structural integrity. Further, a process for synthesis of lithium manganese oxide cathode is required that does not suffer from drawbacks such as multi-step procedures, longer processing time, high reaction temperature, inhomogeneity, irregular morphology, larger particle size, poor control of stochiometry.

OBJECTS OF THE INVENTION
The object of the present invention is to develop a novel submicron sized doped lithium ion cathode that do not suffer capacity fading during cycling and have structural integrity.
Another object of the present invention is to provide a low temperature combustion process for the synthesis of a submicron sized doped lithium manganese oxysulphide cathode.
STATEMENT OF THE INVENTION
The present invention provides a submicron sized doped lithium manganese oxysulphide cathode of formula LiMxMn2-xO4-dSd, wherein M is a metal dopant; 0 = x = 0.5; and 0 = d = 0.1.
SUMMARY OF THE INVENTION
Submicron sized doped lithium manganese oxysulphide cathode that do not suffer capacity fading and have structural integrity have been developed. The low temperature combustion synthesis process for the synthesis of submicron sized doped lithium manganese oxysulphide cathode involves codoping simultaneously at cation and anion site in the spinel LiMn2O4.
A BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1: X-ray diffractogram of pristine LiMn2O4
Fig. 2: X-ray diffraction patterns of different Ni doped oxysulphide powders showing single phase spinel compound having Fd3m symmetry
Fig. 3: FESEM micrograph showing submicron sized particles in different oxysulphide systems synthesized by alanine assisted combustion process

Fig. 4: Initial charge discharge cycle of Ni-doped lithium manganese oxysulphide cathodes using Li-metal as an anode in a 2032 coin cell in the voltage range of 3.4 to 5.0 V

Fig. 5: Cycle number vs Capacity plot of Ni-doped lithium manganese oxysulfides. The oxysulfide cathodes shows better performance that the pristine compound

Fig. 6: Excellent capacity retention on cycling by indium oxysulphide cathodes

Fig.7: Charge and discharge capacities vs cycle number plot of indium oxysulphide cathodes

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a submicron sized doped lithium manganese oxysulphide cathode of formula LiMxMn2-xO4-dSd , wherein M is a metal dopant; 0 = x = 0.5; and 0 = d = 0.1. The metal dopant is chosen from a transitional metal and a non-transitional metal. The transitional metal is selected from Titanium, Vanadium, Chromium, Nickel, Copper, Iron and Zinc and the non-transitional metal is selected from Boron, Aluminium, Magnesium, Gallium, Indium, Antimony and Tin. This cathode is different from LiMn2O4 or cation doped LiMn2O4 and do not suffer from severe capacity fading and have structural integrity. In contrast to the prior art, the present invention utilizes low temperature combustion synthesis process involving codoping at both cation and anion site of the LiMn2O4 spinel. Codoping at manganese and oxygen sites improves capacity by reducing JT distortion at 3 V and enhances its structural integrity which in turn retards Mn dissolution at 4 V region. The combustion synthesis is of particular interest because it offers several attractive advantages over the other wet-chemical/soft chemical routes-like sol-gel, co-precipitation, inner-gel etc. The major advantages of combustion synthesis are: ultra fine homogeneous phase pure product powder, simplicity of experimental set up, relatively short processing time and cost effectiveness. However, the entire prior art reports on the synthesis of LiMn2O4 spinel either by sol-gel or by solid-state synthesis process. On the contrary, use of an aqueous soft chemical method to synthesize transition and non-transition metal doped lithium manganese oxysulphides will solve the drawbacks of the prior art processes.

Accordingly, the present invention provides a low temperature combustion synthesis process for making submicron sized doped lithium manganese oxysulphide cathode for Lithium battery applications in aqueous medium which comprises preparing a saturated mixed salt solution of stochiometric lithium, metal dopant, manganese and lithium sulfide in distilled water; adding 70-80 Volume % nitric acid and a saturated aqueous solution of combustion fuel ie. a polycarboxylic acid to the mixed salt solution, molar proportion of combustion fuel to nitrate being in the range of (1-2):1; placing the beaker containing the mixed salt solution on a hot plate at 150oC- 200oC with constant stirring till a clear viscous gel is formed; further, heating the viscous gel to spontaneous burning of the same resulting in blackish/brownish solid mass and calcining the solid mass in the temperature range of 700oC-800oC for 10 hours to obtain the doped lithium manganese oxysulphide cathode (powder). Combustion fuel, polycarboxylic acid is selected from alanine, glycine, valine, leucine and iso-leucine.

The synthesis of submicron sized doped lithium manganese oxysulphide cathode is carried out in an aqueous medium where alanine acts both as a a combustion fuel as well as complexing agent which helps in producing nanostructured powders at a low combustion temperature in the range of 150 oC to 200oC, which is significantly lower than those described in the prior-art processes. A controlled exothermic and self igniting oxidation reduction reaction takes place within the individual components. A self-propagating auto ignition takes place, which utilizes a part of the heat evolved during combustion process to synthesize a number of transition and non-transition metal doped lithium manganese oxysulfides. As the electrochemical reactivity of ceramic powders used for battery materials depends largely on its particle size and surface area, a low combustion temperature is needed for greater reactivity. In this regard, the present invention has great advantage as it produces particles in the submicron range with a comparatively high surface area at a low temperature of 150oC to 200oC by a cost effective aqueous combustion process.

The low temperature aqueous combustion synthesis of submicron sized doped lithium manganese oxysulphide is an economic process rather than solid state or sol-gel process. The introduction of alanine in aqua- combustion process has a great advantage. Alanine having an extra methyl group in branch chain accelerates the combustion process. The branch-chain methyl groups present in alanine evolutes more gaseous species during combustion making the product highly porous. More carbon in the chain enhances the reaction temperature instantaneously up to 800oC. Another specialty of alanine is that it can chelate with multivalent cationic species. Presence of alanine as fuel results in a low combustion temperature as well as a high flame temperature forming 80-90% phase even in the ash form. Thereby, the required calcination (firing) temperature is also lowered.

The following examples are illustrative only and not limitative of the invention.
EXAMPLES
Example 1
Ni-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Ni, 0
Example 2
Cr-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Cr, 0
Example 3
Cu-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Cu, 0
Example 4
Fe-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M= Fe, 0
Example 5
In-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M=In, 0
Example 6
B-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M=B, 0

Example 7
Ga-doped Lithium manganese oxysulphides (LiMxMn2-xO4-dSd where M=Ga, 0
Example 8
X-ray diffraction pattern of LiMn2O4 (pristine) available in the prior art and LiNixMn2-xO4-dSd of the present invention show the structural differences between the two cathodes [Figure 1 and 2]. Further, figure 5 shows better performance of Ni doped Lithium manganese oxysulphides when compared with LiMn2O4 (pristine) available in prior art. Figure 5 provides cell cycle vs capacity plot of LiMxMn2-xO4-dSd where M= Ni, 0

WE CLAIM:

1. A submicron sized doped lithium manganese oxysulphide cathode of formula LiMxMn2-xO4-dSd , wherein M is a metal dopant;
0 = x = 0.5; and
0 = d = 0.1.

2. A low temperature combustion synthesis process for making submicron sized doped lithium manganese oxysulphide cathode comprising:
a) Preparing saturated aqueous mixed salt solution of lithium, metal dopant, manganese and lithium sulfide;
b) adding nitric acid and a saturated aqueous solution of combustion fuel to the mixed salt solution;
c) heating the solution obtained in step (b) to obtain a clear viscous gel;
d) heating the viscous gel obtained in step (c) to obtain a solid mass; and
e) calcining the solid mass obtained in step (d) to obtain the doped lithium manganese oxysulfide cathode.

3. The cathode as claimed in claim 1 and 2, wherein metal dopant is selected from a transitional metal and a non-transitional metal.

4. The cathode as claimed in claim 3, wherein the transitional metal comprises Titanium, Vanadium, Chromium, Nickel, Copper, Iron and Zinc.

5. The cathode as claimed in claim 3, wherein the non-transitional metal comprises Boron, Aluminium, Magnesium, Gallium, Indium, Antimony and Tin.

6. The process as claimed in claim 2, wherein said process is carried out in an aqueous medium.

7. The process as claimed in claim 2, wherein lithium salt is selected from oxide, carbonate, hydroxide, chloride, acetate and nitrate salts.

8. The process as claimed in claim 2, wherein the metal dopant and manganese salt is selected from oxide, acetate and nitrate salts.

9. The process as claimed in claim 2, wherein nitric acid is in the range from 70%-80%.

10. The process as claimed in claim 2, wherein the combustion fuel is a polycarboxylic acid.

11. The process as claimed in claims 10, wherein the polycarboxylic acid is selected from alanine, glycine, valine, leucine and iso-leucine.

12. The process as claimed in claims 10 and 11, wherein the polycarboxylic acid is preferably alanine.

13. The process as claimed in claim 2, wherein the molar proportion of combustion fuel to nitrate is in the range of (1-2):1.

14. The process as claimed in claim 2, wherein the heating in step (c) is carried out at temperature in the range of 150-200oC.

15. The process as claimed in claim 2, wherein the heating of viscous gel in step (d) is carried out at temperature in the range of 150-200oC.

16. The process as claimed in claim 2, wherein the calcination of solid mass in step (e) is carried out at temperature in the range of 700-800oC.

17. The cathode as claimed in claim 1, wherein said cathode do not suffer capacity fading during cycling.

18. The doped lithium manganese oxysulphide cathode and a process of preparation thereof substantially as herein described with reference to the foregoing examples and accompanying drawings.

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Patent Number

278393

Indian Patent Application Number

784/DEL/2009

PG Journal Number

53/2016

Publication Date

23-Dec-2016

Grant Date

21-Dec-2016

Date of Filing

16-Apr-2009

Name of Patentee

DIRECTOR GENERAL DEFENCE RESEARCH & DEVELOPMENT ORGANISATION

Applicant Address

Ministry of Defence Government of India Room No. 348 B-Wing DRDO Bhawan Rajaji Marg New Delhi-110011 India

Inventors:

#	Inventor's Name	Inventor's Address
1	MIR WASIM RAJA	Central Glass and Ceramic Research Institute 196 Raja S.C.. Mullick Road Kolkata -700 032 West Bengal India
2	SOURINDRA MAHANTY	Central Glass and Ceramic Research Institute 196 Raja S.C.. Mullick Road Kolkata -700 032 West Bengal India.
3	RAJENDRA NATH BASU	Central Glass and Ceramic Research Institute 196 Raja S.C.. Mullick Road Kolkata -700 032 West Bengal India
4	HIMADRI SEKHAR MAITI	Central Glass and Ceramic Research Institute 196 Raja S.C.. Mullick Road Kolkata -700 032 West Bengal India

PCT International Classification Number

C01G 45/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA