WE CLAIM:
1. A modified-solvothermal method (100) of preparing lithium titanate (LTO)
nanoparticles having self-assembled disordered surface layer, comprising the steps of:
adding titanium isopropoxide precursor to a first solution comprising lithium
hydroxide and a solvent to form a first mixture, wherein the ratio of lithium
hydroxide to titanium isopropoxide is in the range of 3.5:5 to 4.5:5;
adding ammonia to the first mixture to form a second solution;
heating the second solution at a temperature between 150 and 250°C in an
autoclave reactor for 36 hours or more to obtain a nanocomposite material of LTO
and titania (TiC^) nanoparticles;
cooling to room temperature and retaining the nanocomposite material in the
autoclave for 24 hours or more; and
removing the nanoparticles from the autoclave and annealing at a temperature between 400 and 600°C for 6 hours or more to obtain LTO nanoparticles having self-assembled disordered surface layer.
2. The method as claimed in claim 1, wherein the solvent is selected from ethylene glycol, diethylene glycol, deionized water or ethanol.
3. A nanoparticle composition (200) for use in an electrode, having a crystalline lithium titanate (LTO) core (210) and self-assembled disordered surface layer (220), wherein the composition is characterized by the absence of a peak corresponding to [101] of Ti02 at 2 theta value of 25° in the X-Ray diffraction spectra..
4. The nanoparticle composition as claimed in claim 3, characterized by the absence of Eg peak at 144 cm"1 in Raman shift.
5. The nanoparticle composition as claimed in claim 3, wherein the LTO nanoparticles (200) have a diffusion coëfficiënt of Li ions in the range of 10"9 cm2/s.
6. An electrode (300) comprising:
70-80 wt.% of the nanoparticle composition of claim 3;
10-20 wt.% of a carbon additive selected from carbon nanotubes (CNT)
(230), graphene nanoplatelets (GNP), carbon black (CB), or a combination
thereof; and
10-20 wt.% of a binder selected from polyvinylidene fluoride (PVDF),
polyvinylpyrrolidone (PVP), polyacrylic acid (PAA) or a combination
thereof.
7. The electrode as claimed in claim 6, wherein a first cycle specific charge capacity of the electrode is greater than 155 mAh/g at 50C discharge rate.
8. The electrode as claimed in claim 6, wherein charge retention at the end of 2000 cycles is 70% at 100C discharge rate, to 82.6% at 50C discharge rate of the first cycle specific capacity for 2000 cycles.
9. The electrode as claimed in claim 6, wherein specific charge capacity ranges from 149 mAh/g for 100C discharge rate to 60 mAh/g for 1200C discharge rate to.
10. An electrochemical cell (400) comprising:
i. a lithium based cathode (420);
ii. an anode (410) comprising LTO nanoparticles having a self-assembled disordered surface wherein the nanoparticles are
characterized by the absence of a peak corresponding to [101] of
ÜO2 at 2 theta value of 25° in the X-Ray diffraction spectra or Eg
peak at 144 cm"1 in Raman shift; iii. a separator (430) comprising commercial glass fiber or polymeric
placed between the anode and the cathode; and iv. a liquid electrolyte (440) in contact with the cathode, the anode and
the separator.
11. The electrochemical cell as claimed in claim 10, wherein the lithium based cathode is selected from spinel LiMn204 or LiCoC>2 or LiNio.5Mn1.5O4 or LiFePC>4 or other lithium containing layered oxides and phosphates
12. The electrochemical cell as claimed in claim 10, wherein the separator (430) is commercial glass or a polymer selected from polypropylene or polyethylene.
13. The electrochemical cell as claimed in claim 10, wherein the liquid electrolyte (440) comprises LiPF6 salt dissolved in a carbonate solvent selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate or combinations thereof.
14. The electrochemical cell as claimed in claim 11, wherein discharge capacity of the full cell ranges from 170 mAh/g for 25 C discharge rate to 115 for 200C discharge rate.
15. The electrochemical cell as claimed in claim 11, wherein power density is at least 76 kW/kg and energy density is 249 or more Wh/kg at 200C discharge rate based on active material weight of the anode.
16. The electrochemical cell as claimed in claim 11, wherein discharge capacity retention at 100C discharge rate is
150 to 160 mAh/g at elevated temperatures of 55°C; or 75 to 85 mAh/g at low temperatures of -10°C.
17. The electrochemical cell as claimed in claim 11, wherein specific capacity of a
half cell is 100 mAh/g or above at 300C discharge rate.