Method of producing high performance lithium titanate anode material for lithium ion battery applications

Abstract

The method of producing lithium titanate anode material for lithium ion battery applications is comprising of: a) mixing of mixed phase having 60-80% anatase and 20-40% rutile of TiO.sub.2 as titanium precursor with Li.sub.2CO.sub.3 as lithium precursor in a stoichiometric ratio of 5:4 and adding with 2 to 5% stearic acid as process control agent as well as carbon precursor; b) milling in horizontal attrition milling unit maintained with the ball to powder ratio of 10:1-12:1 at 250-500 rpm for 0.5 to 2 hrs c) repeating the milling for 40 to 48 times; d) palletisation of the milled powder to a diameter of 30-35 mm under a pressure of 0.5-1 ton; e) annealing under inert atmosphere at a temperature of 700-900° C. for a period of 2-12 hrs; and f) grinding the resultant annealed composite powder to a fine powder. Resultant powder has shown excellent electrochemical properties in terms of charge-discharge, cyclic-stability and rate capability.

Claims

1. A method of producing nano sized lithium titanate powders for making an anode for a lithium ion battery, using horizontal attrition milling comprising the steps of: a) mixing 60-80% anatase and 20-40% rutile TiO.sub.2 with Li.sub.2CO.sub.3 in a stoichiometric ratio of 5:4 with 5 wt % of extra lithium carbonate to provide a mixture; b) adding 2 to 5% stearic acid to the mixture; c) milling the mixture and the stearic acid in a horizontal attrition milling unit with a ball to powder ratio of 10:1-12:1 at a speed of 100-250 rpm for 0.5-2 hrs to provide a blended product; d) milling the blended product in a horizontal attrition milling unit with a ball to powder ratio of 10:1-12:1 at a speed of 250-500 rpm for 0.5-2 hrs for 40 to 48 times in a pattern including increasing and decreasing the speed for a period of 0.5 to 2 hrs to provide a milled powder; e) discharging the milled powder from the horizontal attrition milling unit on completion of milling and storing them for annealing in dry form; f) pelletizing the milled powder using a 30-35 mm die at a pressure of 0.5-1 ton using a hydraulic press to provide a pelletized powder; g) annealing the pelletized powder under an inert atmosphere of argon in a tubular furnace maintained at a temperature ranging from 700-900° C. with a heating rate of 10° C./min for a period of 2-12 hrs to provide annealed pellets; and h) grinding the annealed pellets to provide the nano sized lithium titanate powder.

2. The method of claim 1, further comprising forming Ti.sup.3+ ions and oxygen vacancies during the annealing.

3. The method of claim 1, wherein an average particle size of the lithium titanate from 200-750 nm.

4. The method of claim 1, wherein a carbon layer on the lithium titanate has a thickness in a range of 2.0-8 nm, when analyzed by HR-TEM analysis.

5. The method of claim 1, wherein the lithium titanate has an electrochemical efficiency in range of 150-156 mAh.Math.g.sup.−1, when determined at a 1 C rate.

6. The method claim 1, wherein the lithium titanate powder has a coulombic efficiency of 99%, when tested in a full cell configuration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention should become apparent from the following description of the preferred process and read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

(2) FIG. 1: Flow chart showing the synthesis of lithium titanate by horizontal attrition milling.

(3) FIG. 2A: X-ray diffraction pattern of A-LTO synthesized from anatase TiO.sub.2 as TiO.sub.2 precursor.

(4) FIG. 2B: X-ray diffraction pattern of R-LTO synthesized from rutile TiO.sub.2 as TiO.sub.2 precursor.

(5) FIG. 2C: X-ray diffraction pattern of M1-LTO synthesized from mixed phases of anatase (60%) and rutile TiO.sub.2 (40%) as TiO.sub.2 precursor.

(6) FIG. 2D: X-ray diffraction pattern of M2-LTO synthesized from mixed phases of anatase (80%) and rutile TiO.sub.2 (20%) as TiO.sub.2 precursor.

(7) FIG. 3A: FE-SEM image of A-LTO.

(8) FIG. 3B: FE-SEM image of R-LTO.

(9) FIG. 3C: FE-SEM image of M1-LTO.

(10) FIG. 3D: FE-SEM image of M2-LTO.

(11) FIG. 4A: Average particle size distribution of A-LTO calculated using histogram.

(12) FIG. 4B: Average particle size distribution of R-LTO calculated using histogram.

(13) FIG. 4C: Average particle size distribution of M1-LTO calculated using histogram.

(14) FIG. 4D: Average particle size distribution of M2-LTO calculated using histogram.

(15) FIG. 5: XPS spectra of M2-LTO.

(16) FIG. 6A: HR-TEM image of M2-LTO.

(17) FIG. 6B-6D: HR-TEM image of M2-LTO showing the crystallinity along with carbon coating thickness.

(18) FIG. 7A: Charge-Discharge profile of A-LTO (a), R-LTO (b), M1-LTO (c) and M2-LTO (d).

(19) FIG. 7B: Cyclic stability of A-LTO (a), R-LTO (b), M1-LTO (c) and M2-LTO(d).

(20) FIG. 8A: Electrochemical performance-charge discharge profile of M2-LTO annealed in Argon (a), Nitrogen (b) and Air (c).

(21) FIG. 8B: Electrochemical performance-cyclic stability of M2-LTO annealed in Argon (a), Nitrogen (b) and Air (c).

(22) FIG. 8C: Electrochemical performance-charge discharge profile of M2-LTO annealed for 1 h (a) and 12 h (b).

(23) FIG. 8D: Electrochemical performance-cyclic stability of M2-LTO annealed for 1 h (a) and 12 h (b).

(24) FIG. 9A: Electrochemical performance-charge discharge profile of M2-LTO carried out at different current rate of 1 C to 10 C.

(25) FIG. 9B: Electrochemical performance-rate capability of M2-LTO carried out at different current rate of 1 C to 10 C.

(26) FIG. 10A: Benchmark studies-comparison of charge-discharge profile of M2-LTO (a) and commercial LTO (b) at 1 C rate.

(27) FIG. 10B: Benchmark studies-Comparison of rate capability of M2-LTO (a) and commercial LTO (b) at 1 C rate.

(28) FIG. 11 A: Full cell studies-Formation cycle at C/10.

(29) FIG. 11 B: Full cell studies-charge-discharge profiles at C/5 rate.

(30) FIG. 11 C: Full cell studies-capacity retention at C/5 rate.

(31) FIG. 11 D: Full cell studies-charge-discharge profiles at 1 C rate, and

(32) FIG. 11 E: Full cell studies-long term stability at 1 C rate of LFP-LTO 2032 coin cell.

DETAILED DESCRIPTION OF THE INVENTION

(33) In accordance with the invention, high performance lithium titanate anode having excellent electrochemical characteristics are developed using TiO.sub.2 and Li.sub.2CO.sub.3 precursors by a simple, economical and scalable Horizontal attrition milling technique to achieve highly conducting lithium titanate. The preferred embodiments of the process under the invention with particular reference to the drawings are as follows.

(34) Lithium titanate as an efficient anode for high energy density lithium ion battery application, according to the invention is synthesized by a simple, facile, fast, and economical and energy efficient Horizontal attrition milling technique. According to the invention, suitable Ti precursor is used without further purification or treatment. For synthesis of LTO, TiO.sub.2 and Li.sub.2CO.sub.3 in the stoichiometry ratio of 5:4 with 5 wt % of extra Lithium carbonate to compensate the lithium loss during heat treatment are transferred to the stainless steel horizontal vial of attrition milling unit. Stainless steel ball used as grinding media and with the ball to powder ratio of 10:1-12:1 was used for milling. Milling was carried out for a period of 0.5-2 hrs with appropriate acceleration and deceleration. Speed of milling was controlled between 250-500 rpm, which will avoid raise in temperature and thereby damage of the instrument. The capacity of milling vials is about 500-2500 g per run, which makes it attractive for large-scale production. Stearic acid was added as the process control agent to avoid stacking and the powders after milling were collected in the form of dry powders and stored properly.

(35) The milled powders were then annealed to produce single-phase lithium titanate anode. Prior literatures have reported that temperatures above 750° C. results in the formation of crystalline lithium titanate. In the prior works argon atmosphere with mixed phases of hydrogen, nitrogen and air was used for annealing of lithium titanate. Mixed gas atmosphere is reported to create oxygen vacancies in the lithium titanate anode producing Ti.sup.3+ concentration. Ti.sup.3+ vacancies due to its more electron concentration improve the intrinsic electronic conductivity of lithium titanate.

(36) According to the instant invention, LTO was synthesized using non-toxic, eco-friendly, cheap TiO.sub.2 precursors which were available commercially and was used without further purification. Horizontal attrition milling technique used in this embodiment of the invention enables proper blending and uniform particle size reduction of TiO.sub.2. Due to its high energy produced, it ensures less milling time compared to conventional planetary ball milling technique. The process control agent, which becomes a default additive for milling process here acts as a carbon source and helps to create oxygen vacancies and therefore improves the electronic conductivity of the material. This technique thus enables us to produce an efficient anode material lithium titanate, which can be very much suitable for high energy density lithium ion battery application.

(37) Another embodiment of the invention is the presence of Ti.sup.3+ ions and oxygen vacancies created during annealing process under argon atmosphere. Milled lithium titanate precursors are pelletized using 30-35 mm die at a pressure of 0.5-1 ton and this ensures proper inter-particle contact. This makes proper crystallization of the bulk powders. The PCA present along with argon gas creates oxygen vacancies and therefore for charge compensation, Ti.sup.4+ ions are converted to Ti.sup.3+ ions.

(38) The above embodiment of the present investigation facilitates formation of Ti.sup.3+ ion rich lithium titanate by a simple and economical Horizontal attrition milling technique. Lithium titanate synthesized under optimized condition of Ti precursors and annealing condition exhibit excellent electrochemical performance in terms of rate capability and cyclic stability showing its better role as a promising material in lithium ion batteries.

(39) Having described the process of the invention in a general way, now we will further illustrate the mode of execution and demonstrate the characteristics/properties of LTO according to the process under the invention and also its electrochemical properties with the help of the following examples. The present invention is, however, not limited to these examples and various embodiments are possible within the scope thereof.

Example 1

Effect of Different Crystalline Phases of TiO.SUB.2

(40) Li.sub.4Ti.sub.5O.sub.12 was synthesised using horizontal attrition milling process. The invention produces LTO using four different phases of TiO.sub.2. It uses pure anatase phase, rutile phase, Mixed phase 1 (60% Anatase and 40% Rutile) and Mixed phase two (80% Anatase and 20% Rutile) accordingly the respective LTO phases are labelled as A-LTO, R-LTO, M1-LTO and M2-LTO. The technique makes use of milling the raw TiO.sub.2 powders with Li.sub.2CO.sub.3 in a stochiometric ratio of 5:4 with 5 wt % of extra Lithium carbonate to compensate the lithium loss during heat treatment. For horizontal attrition milling powder ratio was maintained to be 10:1-12:1 with stainless steel as milling medium and stainless steel balls of 0.5 mm diameter. Process control agent (PCA) was used to prevent stacking of the powders to the walls of the vials. Here stearic acid was used as PCA. It was used to 2-5 wt % as it may contribute to the carbon content as well. The powders were initially blended at 250 rpm followed by milling at a speed between 250-500 rpm. This process was continued for 48 repetitions after which the powders were discharge and then stored for annealing and characterization. The schematic illustration for the synthesis of lithium titanate in the present invention is shown in FIG. 1.

Example 2

Influence of Annealing Atmosphere and Time

(41) The product of example 1 is calcined to produce highly crystalline single phase LTO. Annealing was carried out under argon, nitrogen and air atmosphere. The powders were pelletized using a 30-35 mm die under 0.5-1 ton pressure using a hydraulic press. When in pellet form it is expected to exert uniform heat distribution by improved inter-particle contact. In inert gas atmosphere, purging was carried out using the respective gas to ensure oxygen is completely expelled. Heat treatment was carried out at 700-900° C. with a heating rate of 10° C./min. In the presence of inert atmosphere, carbon from PCA creates a reductive atmosphere to produce oxygen vacancies. When these oxygen-vacancies are created, the charge compensation is done by titanium ion in oxidation state of four. To find the influence of annealing time, annealing was carried out for different time lapses like 2-12 h. All the anatase TiO.sub.2 will be converted to rutile above 650° C. and then lithium diffusion into the lattice takes place. Lithium titanate formation takes place above 750° C. In the presence of inert atmosphere, carbon from stearic acid aids as carbon source creating uniform carbon layer to improve the electronic conductivity and also restricts the grain growth. X-ray diffraction studies were carried out to find the phase formation and crystallinity of the material developed using the invented method and is shown in FIG. 2(A-D). The XRD pattern of sample synthesized from A-LTO (FIG. 2A) did not result in single phase lithium titanate. The conversion was found to be incomplete where 111 plane of LTO was produced with high intensity but with traces of anatase and rutile forming the major contributors. It is seen that for R-LTO (FIG. 2B) there exists some traces of anatase and rutile TiO.sub.2 (in agreement with ICDD=00-021-1272 {Anatase} and #00-021-1276 {Rutile}) which otherwise matches with LTO in all means. LTO from mixed phases of TiO.sub.2 is found to match with LTO (in agreement with ICDD: #00-049-0207) and show high crystallinity however, the intensity count varies which may vary the degree of crystallinity within each samples. LTO synthesized using mixed phase precursors (FIG. 2C and FIG. 2D) shows diffraction peaks at =18.39, 35.57, 43.24, 57.21, 62.83, 66.07 which can be indexed to phase of pure lithium titanate respectively, (in agreement with ICDD #00-049-0207). The sharp peaks indicate that the LTO formed is crystalline. Such a pure phase with high order crystallinity may help to improve the battery properties of the developed anode material. The size and morphology of the materials were evaluated by field emission scanning electron microscopy and the results are depicted in FIG. 3(A-C). Smaller the particle size shorter is the lithium ion diffusion length. A-LTO (FIG. 3A) showed larger irregular particle size distribution with non-uniform particles. Whereas, R-LTO in FIG. 3B showing particles without high agglomeration, and particles with more or less uniform size distribution. M1-LTO (FIG. 3C) showed agglomerated particles with tetragonal morphology with smaller particle size compared to A-LTO. Finally, M2-LTO (FIG. 3D) shows moderate particle size with particles distributed evenly throughout without any agglomeration. Particle size always influences the electrochemical properties. Hence, the particle size analyses were done using Image J software and then average particle size is plotted using a histogram {FIG. 4(A-D)}. The average particle sizes were calculated to be 200-500, 200-450, 190-360 and 200-750 nm for A-LTO (FIG. 4A), R-LTO (FIG. 4B), M1-LTO (FIG. 4C) and M2-LTO (FIG. 4D) respectively. M2-LTO (FIG. 4D) though has larger particle size than LTO from other three conditions, it is expected that the moderate particle size may avoid unwanted side reactions with electrolyte which may result in capacity fading and therefore is expected to perform better in terms of electrochemical studies. XPS analysis was carried out to find the oxidation state and the corresponding wide scan spectrum of Ti is shown in FIG. 5. The wide scan spectrum of titanium shows Ti.sup.3+ peaks. M2-LTO show the presence of Ti.sup.3+ and Ti.sup.4+ oxidation states of Ti comprising 70% of Ti.sup.4+ ions and 30% of Ti.sup.3+ ions. The presence of Ti.sup.3+ ions were also physically interpreted from the colour change observed after annealing. Generally, LTO has the physical characteristic showing white in colour. However, in the present inventions the powders changed to bluish-ash after annealing showing the presence of Ti.sup.3+ ions. Ti.sup.3+ ions due to its smaller ionic radii and higher electron affinity, improves the electron population to improve the electronic conductivity of the material developed using the invented synthesis technique. HR-TEM images (FIG. 6A) showed that M2-LTO with higher degree of Ti.sup.3+ ion concentration contained cubic particles which are the characteristics of spinel LTO. It showed traces of carbon finely distributed around the edges uniformly in the form a thin layer which is from the stearic acid with thickness of around 2.5 to 8 nm {FIG. 6(B-D)}, which is expected to improve the conductivity of the anode material developed.

Example 3

Electrochemical Performance in Half Cell Configuration

(42) The electrochemical properties are the final target of the invented technique. The property of anode developed was tested in half-cell configuration using lithium metal as counter electrode. The crystalline anode material prepared was used for electrode fabrication to test the efficiency for electrochemical properties. For electrode fabrication, the electrode active material synthesized using horizontal attrition milling is taken along with conductive carbon and binder in a ratio of 80:10:10. They are grinded together and dissolved in NMP solvent to form homogenous slurry, which can be used for electrode fabrication. This slurry was coated over a current collector (in the present case copper foil acts as current collector) using doctor blade in a thickness of 15 micrometer. The resulting electrode is then dried at 60° C. for 12 h to evaporate the moisture and ensure the proper adherence of active material to the current collector. Then to ensure proper drying this is then dried at 120° C. for another 6 h. The efficiency of the horizontal attrition mill synthesized lithium titanate anode is tested using coin-cell to find the electrochemical performance using the electrodes fabricated using the above-mentioned process. An electrode was punched around 12 mm diameter and was weighed to find the active material weight. Lithium metal was used as the counter electrode and LiPF.sub.6 as electrolyte (EC:DEC:EMC in 1:1:1 vol %). The cells were assembled in argon-filled glove box to avoid the oxidation of electrolyte and to ensure the safety of lithium metal. The cells were then kept aside for a period of 6 h for wettability and stabilization of the open circuit voltage. The as fabricated cells were then tested using MTS pro 2000 Arbin instruments to find the electrochemical properties. FIG. 7 (A-B) shows the electrochemical performance of LTO synthesized using different TiO.sub.2 for optimization to find the appropriate Ti precursor. When tested at 1 C rate A-LTO (FIG. 7A-a), R-LTO (FIG. 7A-b), M1-LTO (FIG. 7A-c) and M2-LTO (FIG. 7A-d) delivered a capacity of 35 mA hg.sup.−1, 142 mA hg.sup.−1, 154 mA hg.sup.−1 and 156 mA hg.sup.−1 respectively. The cyclic stability data's of A-LTO (FIG. 7B-a), R-LTO (FIG. 7B-b), M1-LTO (FIG. 7C-c) and M2-LTO (FIG. 7D-d) also in good agreement with the results of charge-discharge profile. Here the active material loading of M2-LTO on electrode disk was around 2.3 mg/cm.sup.2. Particle size distribution is correlated to the specific capacity of the anode materials mentioned above. Since the phase formation in the case of A-LTO being incomplete, it leads to the poor electrochemical performance. Even the charge discharge profile does not even resemble the signature curve of lithium titanate. Polarization resistance was very high and delivered very low electrochemical performance. R-LTO showed some impurities like anatase and rutile phases of TiO.sub.2 which may degrade the electrochemical performance and then particle size were also higher increasing the lithium ion diffusion length. Increases path length with semiconducting TiO.sub.2 phases may be attributed as the reasons for poor electrochemical performance. M1-LTO showed 145 mA hg.sup.−1 which is considered to be reasonable however it was less convincing when compared to the performance of M2-LTO. M1-LTO consisted for 60% anatase TiO.sub.2 and 40% rutile TiO.sub.2 whereas M2-LTO consisted to 80% of anatase TiO.sub.2 and 20% rutile TiO.sub.2. Anatase TiO.sub.2 has smaller particle size than rutile, which may increase the activity of lithium diffusion into its crystal lattice and decreases the particle size. Therefore it produced a capacity of 156 mA hg.sup.−1 at 1 C which is close to the theoretical capacity i.e. 175 mA hg.sup.−1. The average particle size of M1 and M2-LTO were 243 and 342 nm showing that M2 LTO with high crystallinity and moderate particle size perform better due to shorted lithium ion diffusion length and structural stability. XPS also showed an increased concentration of Ti.sup.3+ ions in M2-LTO compared to other samples. Ti.sup.3+ ions due to its smaller ionic radii and increased electron density improve the electronic conductivity of M2-LTO. M2 LTO was found to be efficient among all the synthesis conditions the annealing conditions were optimized using different time periods and different atmospheric conditions. When annealed under argon (FIG. 8A-a), nitrogen (FIG. 8A-b) and air (FIG. 8A-c) they delivered a capacity of 156, 154 and 147 mA hg.sup.−1 respectively. The cyclic stability of lithium titanate which annealed under argon (FIG. 8B-a), nitrogen (FIG. 8B-b) and air (FIG. 8B-c) also reveal that argon annealed lithium titanate exhibit stable electrochemical performance. It is seen that argon being heavier than nitrogen aided in avoiding complete oxidation and helped to improve the electronic conductivity. When annealing in air, carbon which may improve the conductivity was removed with air and it is expected that there does not exists Ti.sup.3+ ions as the samples annealed in air looked pure white in color which indicates the absence of oxygen vacancies. Charge discharge profile (FIG. 8C) annealed for 1 h (FIG. 8C-a) & 12 h (FIG. 8C-b) and cyclic stability (FIG. 8D) of M2-LTO annealed for 1 h (FIG. 8D-a) & 12 h (FIG. 8D-b) results reveal that 12 h annealed lithium titanate exhibit better electrochemical performance than 1 h annealed lithium titanate, indicating that short time annealing may not be enough for lithium titanate phase formation. A fresh half cell with LTO loading of around 3 mg/cm.sup.2 was fabricated and stabilized with 6 h rest period to analyze the rate capability. Charge-discharge profile (FIG. 9A) and rate capability (FIG. 9B) results at different current rate revealed that M2-LTO delivered a capacity of 156, 134, 121, 110 and 98 mA hg.sup.−1 at 1 C, 3 C, 5 C, 7 C and 10 C respectively. This was higher than the values reported without Ti.sup.3+ ions and was comparable to that of other reports (Yuan et al, J. Phys. Chem. C, 15, (2011), 4943-4952) where only with the help of conductive additives they were able to achieve high capacities. Improved rate capability proves the efficiency to be used in high energy density applications. Polarization resistance as well as the stability was found to be supporting to make it suitable for high energy density application. This shows the material developed is highly suitable for commercial applications as it performed better in terms of rate capability and cyclic stability. The better electrochemical performance delivered by M2-LTO developed in the present study can be attributed to the presence of oxygen vacancy, carbon layer and the pure phase of lithium titanate.

Example 4

Benchmarks Studies of M2 LTO with Commercial LTO

(43) As M2-LTO developed in the present invention is found to be efficient in terms of electrochemical performance, benchmark studies were carried out to find the efficiency of the material for practical applications. Commercial lithium titanate powders were fabricated as thin film electrodes on copper foil using same procedure mentioned in example 3. Then it was cut to 12 mm discs to fabricate half-cell for electrochemical studies. Bench mark studies (FIG. 10A) revealed that the specific capacity of LTO (156 mAh/g) synthesized by horizontal attrition milling process (FIG. 10A-a) is higher than the specific capacity (113 mAh/g) of commercial LTO (FIG. 10A-b). The commercial lithium titanate was tested between 1 C and 10 C (FIG. 10B) to find out the rate capability and the results were compared with the performance of M2-LTO. It was seen that M2-LTO delivered a capacity of 156, 134, 121, 110 and 97 mA hg.sup.−1 at 1 C, 3 C, 5 C, 7 C and 10 C respectively whereas commercial lithium titanate anode delivered capacity of 115, 70, 58, 35 and 30 mA hg.sup.−1 at 1 C, 3 C, 5 C, 7 C and 10 C respectively, indicating that the electrochemical performance of lithium titanate developed in the present invention is superior than commercial lithium titanate.

Example 5

Electrochemical Performance in Full Cell Configuration

(44) The LTO material synthesized by solid state milling method as mentioned in Example 1 was tested for electrochemical efficiency in full cell configuration with combination of LiFePO.sub.4 as cathode. The composite cathode consists of 88:8:4 (LFP:CB:PVDF) in the weight ratio. The cathode laminate thickness was 60 μm and the active materials loading was 3 mg/cm.sup.2. The anode consists of 80:10:10 (LTO:CB:PVDF) in the weight ratio. The anode laminate thickness was 50 μm and the active materials loading was 2.6 mg/cm.sup.2. The capacities were matched based on the half cell performance of LTO and LFP vs. Li metal. The anode to cathode active material weight ratio was maintained to be 0.88:1. The electrochemical performance of LFP-LTO full cell was tested using borosilicate glass fibre separator in 2032 type coin cell with 1M LiPF.sub.6 in EC:DEC:DMC (Geylon, PR China) as electrolyte. The initial charge process was carried out at C/10 rate, which is known as the formation step. The full cell delivered a capacity of 0.65 mAh during the formation step as shown in FIG. 11A. The electrochemical cycling test was carried out at C/5 rate. The full cell exhibited a capacity of 0.5 mAh after the formation step which corresponds to an irreversible loss (IRL) of 23% (FIG. 11B). The capacity retention at C/5 rate is shown in FIG. 11C, which is 100% up to 15 cycles. The long term cycling of the full cell is tested at 1 C current rate. The charge-discharge profiles of the LFP-LTO full cell for the 1st cycle at 1 C is shown in FIG. 11D. The capacity obtained at 1 C rate was 0.47 mAh. The long term stability of the full cell is shown in FIG. 11E with 98.5% retention after 650 charge-discharge cycles.

(45) Present embodiment explained the method of producing the lithium titanate anode with in-situ carbon coating, smaller particle size with Ti.sup.3+ ions and oxygen vacancies. The invention highlights a reliable method for up-scaling of nano materials using a simple, cost effective technique. It used titanium dioxide and lithium carbonate as titanium and lithium precursors along with process control agent to improve the efficiency of milling process. The parameters like ratios of different phases of titanium dioxide precursor suitable for producing single phase, crystalline lithium titanate powders with oxygen vacancies, annealing atmosphere, annealing time are optimized and corresponding physico-chemical and electrochemical studies were carried out as explained in above mentioned examples. It is identified that mixed phases of titanium dioxide milled with lithium carbonate in horizontal attrition mill was efficient in creating highly performing anode material with desirable characteristics for lithium ion battery applications.

(46) We have bought out the novel features of the invention by explaining some of its preferred embodiments thereby enabling any person skilled in the art to understand and visualize our invention. It is also to be understood that the above invention is not limited in its application to the details set forth in the above description or illustrated in the drawings. The phraseology and terminology employed herein are for the purpose of description only and should not be regarded as limiting. Although the invention has been preferred embodiments thereof, variations and modifications can be affected within the spirit and scope of the invention as described herein above and as defined in the appended claims.