V2O5—LiBO2, V2O5—NiO—LiBO2 glasses and their composites obtained by nitrogen doping and reduced graphite oxide blending as cathode active materials

Abstract

An electronically active glass has the composition (T.sub.xO.sub.y).sub.z-(M.sub.uO.sub.v).sub.w(Na/LiBO.sub.2).sub.t wherein T is a transition metal selected from V and Mo, M is a metal selected from Ni, Co, Na, Al, Mn, Cr, Cu, Fe, Ti and mixtures thereof, x, y, u, and v are the stoichiometric coefficients resulting in a neutral compound, i.e. x=2y/(oxidation state of T) and u=2v/(oxidation state of M), z, w and t are weight-%, wherein z is 70-80, w is 0-20 t is 10-30, and the sum of z, w and t is 100 weight-%, in particular V.sub.2O.sub.5LiBO.sub.2 and V.sub.2O.sub.5NiOLiBO.sub.2.

Claims

1. A glass having a composition (V.sub.2O.sub.5).sub.z-(M.sub.uO.sub.v).sub.w(LiBO.sub.2).sub.t, wherein M.sub.uO.sub.v is selected from the group consisting of NiO, Co.sub.3O.sub.4, Na.sub.2O, Al.sub.2O.sub.3, MnO, MnO.sub.2, CrO.sub.3, CuO, Ni.sub.2O.sub.3, Fe.sub.2O.sub.3, TiO.sub.2, and mixtures thereof, where u and v are stoichiometric coefficients resulting in a neutral compound such that u=2v/(oxidation state of M), where z, w, and t are weight-% of (V.sub.2O.sub.5), (M.sub.uO.sub.v), and (LiBO.sub.2) in the composition, respectively, wherein: z is a number from 70-80, w is a number greater than zero and up to 20, t is a number from 10-30, and a sum of z, w, and t equal to 100 weight-%.

2. The glass of claim 1, wherein z is about 80, w is about 5, and t is about 15.

3. The glass of claim 1, wherein w is at least 1.

4. The glass of claim 3, wherein the composition is nitrogen-doped.

5. The glass of claim 1, wherein M.sub.uO.sub.v is NiO.

6. The glass of claim 2, wherein M.sub.uO.sub.v is NiO.

7. The glass of claim 3, wherein M.sub.uO.sub.v is NiO.

8. The glass of claim 1, wherein M.sub.uO.sub.v is Na.sub.2O and/or Al.sub.2O.sub.3.

9. The glass of claim 2, wherein M.sub.uO.sub.v is Na.sub.2O and/or Al.sub.2O.sub.3.

10. The glass of claim 3, wherein M.sub.uO.sub.v is Na.sub.2O and/or Al.sub.2O.sub.3.

11. The glass of claim 1, the glass being enriched with Li due to doping with Li.sub.3N.

12. A composite cathode material, comprising a glass of claim 1 together with carbon and/or graphite, the carbon and/or graphite obtained by reduction of graphite oxide.

13. A composite cathode material, comprising the glass of claim 5 together with carbon and/or graphite, the carbon and/or graphite obtained by reduction of graphite oxide.

14. A composite cathode material, comprising the glass of claim 8 together with carbon and/or graphite, the carbon and/or graphite obtained by reduction of graphite oxide.

15. A cathode, comprising the glass of claim 1 disposed on a current collector.

16. A cathode, comprising the composite cathode material of claim 12 disposed on a current collector.

17. A rechargeable battery, comprising the cathode of claim 15, an anode, a diaphragm, and an electrolyte.

18. A rechargeable battery, comprising the cathode of claim 16, an anode, a diaphragm, and an electrolyte.

19. A method for producing a glass of claim 1, comprising: providing a composition of (V.sub.2O.sub.5).sub.z-(M.sub.uO.sub.v).sub.w(LiBO.sub.2).sub.t by mixing and grinding of z wt-% of V.sub.2O.sub.5, w wt-% of (M.sub.uO.sub.v), and t wt-% LiBO.sub.2; heating the mixture to a temperature and for a time to form a homogenous melt, but not over 900 C.; and quenching the heated mixture.

20. A method for producing a glass of claim 5, comprising: providing a composition of (V.sub.2O.sub.5).sub.z-(M.sub.uO.sub.v).sub.w(LiBO.sub.2).sub.t by mixing and grinding of z wt-% of V.sub.2O.sub.5, w wt-% of M.sub.uO.sub.v, and t wt-% LiBO.sub.2; heating the mixture to a temperature and for a time to form a homogenous melt, but not over 900 C.; and quenching the heated mixture.

21. A method for producing a glass of claim 8, comprising: providing a composition of (V.sub.2O.sub.5).sub.z-(M.sub.uO.sub.v).sub.w(LiBO.sub.2).sub.t by mixing and grinding of z wt-% of V.sub.2O.sub.5, w wt-% M.sub.uO.sub.v, and t wt-% LiBO.sub.2; heating the mixture to a temperature and for a time to form a homogenous melt, but not over 900 C.; and quenching the heated mixture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein the Figures show:

(2) FIG. 1: XRD powder pattern of 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass.

(3) FIG. 2: Electron microscope images of pulverized 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass with

(4) FIG. 2.1: SEM images of pulverized 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass.

(5) FIG. 2.2: TEM images of 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass.

(6) FIG. 3: Galvanostatic (50 A/kg rate) cycling (0th to 10th) of 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass.

(7) FIG. 4: XRD powder pattern of the V.sub.2O.sub.5LiBO.sub.2 glass composite material.

(8) FIG. 5: Differential thermal analysis of 80-20 wt-% V2O5-LiBO2 glass.

(9) FIG. 6 Electron microscope images of V.sub.2O.sub.5LiBO.sub.2 glass composite material with

(10) FIG. 6.1: SEM images of the V.sub.2O.sub.5LiBO.sub.2 glass composite material.

(11) FIG. 6.2: TEM images of the V.sub.2O.sub.5LiBO.sub.2 glass composite material.

(12) FIG. 7: Galvanostatic measurements with

(13) FIG. 7.1: Galvanostatic (50 A/kg rate) cycling (0.sup.th to 90.sup.th) of the V.sub.2O.sub.5LiBO.sub.2 glass-redGO (reduced graphite oxide) composite. The first discharge capacity is 350 Ah/kg and reversible cycling around 300 Ah/kg (between 1.5-4.0 V) with decreases in subsequent cycles (ca. 250 Ah/kg at 90th cycle). The cycling properties and the initial discharge capacity is considerably improved compared to plain V.sub.2O.sub.5LiBO.sub.2 glass.

(14) FIG. 7.2: Galvanostatic (25 A/kg rate) cycling (0.sup.th to 42.sup.nd) of the V.sub.2O.sub.5LiBO.sub.2 glass-redGO composite. The battery was first charged to 4.5 V and a capacity of 20 Ah/kg was obtained (Lithium extraction in the 1.sup.st charge was not possible for the plain V.sub.2O.sub.5LiBO.sub.2 glass). The first discharge capacity was approx. 400 Ah/kg. Reversible cycling between 1.5-4.5 V resulted in decreases in subsequent cycles. The capacity and the voltage range dropped drastically through the 40.sup.th cycle.

(15) FIG. 8: XRD powder pattern of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material.

(16) FIG. 9: Electron microscope images of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material wherein

(17) FIG. 9.1: SEM images of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material.

(18) FIG. 9.2: TEM images of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material.

(19) FIG. 10: Galvanostatic cycling at a rate of 25 A/kg (0.sup.th to 24.sup.th) of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material. OCV=3.50 V, cycling 4.5-1.5 V, 8.5 Ah/kg capacity on the 1.sup.st charge to 4.5 V, and first discharge capacity was 435 Ah/kg. Then cycling between 1.5-4.5 V. At 20.sup.th cycle the charge capacity was 372 Ah/kg and the discharge capacity 376 Ah/kg.

(20) FIG. 11: Specific energy vs. cycle number plot for the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material (cycling between 4.5-1.5 V at 25 A/kg). High specific energy with polarization at 20th cycle 1100 Wh/kg for charge and 950 Wh/kg for discharge. The average voltage was 2.51V for discharge and 2.96V for charge. These are ca. 0.3 V higher than the V.sub.2O.sub.5LiBO.sub.2 glass system indicating the contribution of NiO addition.

(21) FIG. 12: Galvanostatic cycling at a rate of 50 A/kg (0.sup.th to 60.sup.th) of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material. OCV=3.51 V, in the first discharge to 1.5 V a specific capacity of 380 Ah/kg was obtained. Then cycling was performed between 1.5-4.0 V. At 60.sup.th cycle the charge capacity was 275 Ah/kg and the discharge capacity 265 Ah/kg.

(22) FIG. 13: XRD powder pattern of the nitrogen doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material.

(23) FIG. 14: TEM images of the nitrogen doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material.

(24) FIG. 15.1: Galvanostatic cycling at a rate of 25 A/kg (0th to 10th) of the nitrogen doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material. OCV=3.16 V, cycling between 4.5-1.5 V. 77 Ah/kg capacity was obtained on the 1.sup.st charge to 4.5 V proving the chemical lithiation achieved by the reaction with Li.sub.3N. The first discharge capacity was 362 Ah/kg. Further cycling was performed between 1.5-4.5 V. At 8.sup.th cycle the charge capacity was 378 Ah/kg and the discharge capacity 375 Ah/kg.

(25) FIG. 15.2: Galvanostatic cycling at a rate of 50 A/kg (0th to 20th) of the nitrogen doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material. OCV=3.16 V, the first discharge capacity was 291 Ah/kg. Further cycling was performed between 1.5-4.0 V. At 20.sup.th cycle the charge capacity was 277 Ah/kg and the discharge capacity 275 Ah/kg.

(26) FIG. 16: Specific energy vs. cycle number plot for different glass composite materials of the present invention (cycling between. 1.5-4.0 V at 50 A/kg).

MODES FOR CARRYING OUT THE INVENTION

(27) General Remark: Wherever capacities are mentioned these capacities are for the glass composite material and would be higher when calculated only for the comprised vanadium oxide.

Example 1: V2O5LiBO2 Glass

(28) The V.sub.2O.sub.5LiBO.sub.2 glass system is interesting because completely glassy material can be obtained with only 20 wt-% LiBO.sub.2, which was not possible with B.sub.2O.sub.3 as the glass former in earlier trials. A V.sub.2O.sub.5LiBO.sub.2 glass delivering high specific capacity is shown here for the first time as well as its use as cathode material for Li-ion batteries.

(29) Although glassy materials with more than 20 wt-% LiBO.sub.2 can easily be obtained and are also within the scope of the present invention, glasses with as low as possible LiBO.sub.2 content are preferred in view of maximized content of electronically active material.

(30) Synthesis:

(31) 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass was obtained with a glass synthesis procedure. V.sub.2O.sub.5 and LiBO.sub.2 analytical pure grade powders in corresponding amounts were thoroughly mixed and grinded in an agate mortar, and the mixtures were placed in a Pt crucible. The crucible with the material was put in a muffle furnace at 900 C., and the desired melt was obtained after 1 hour of heat treatment. The melt was quenched in air between Cu plates and V.sub.2O.sub.5LiBO.sub.2 glass was formed. Dependent on possible delays during quenching, it is also possible to obtain glass ceramics including crystallites of partially lithiated V.sub.2O.sub.5(LixV.sub.2O.sub.5) or LiV.sub.3O.sub.8.

(32) The V.sub.2O.sub.5LiBO.sub.2 glass was pulverized in an agate mortar in order to make analytical measurements. The powder had a green-brown color.

(33) Characterization:

(34) XRD Powder Diffraction:

(35) The XRD powder pattern of the V.sub.2O.sub.5LiBO.sub.2 glass is illustrated in FIG. 1. The product was glassy, but the diffraction peaks at 2 26.5 and 27.8 could be attributed to trace amounts of LixV.sub.2O.sub.5.

(36) SEM-TEM:

(37) SEM and TEM images of 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass are given in FIG. 2 with FIG. 2.1 being SEM images of pulverized 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass and FIG. 2.2 being respective TEM images. The electron microscopy images revealed that the material had mostly non-crystalline parts. But the particle sizes still were in the micron range. By milling methods, like ball milling, the particle sizes can be further reduced, preferably from the size obtained in Example 1 which is 1 to 20 microns for most particles with some large particles in the range of 40 to 50 m to about 200 nm to 3 m or smaller such as at most 2 m or 1 m. Crystalline particles that may be incorporated within the glass such as LixV.sub.2O.sub.5 usually are in the range of 20 to 30 nm.

(38) Magnetic Measurement:

(39) The magnetic measurements showed that 80-20 wt-% V.sub.2O.sub.5LiBO.sub.2 glass synthesized at 900 C. had paramagnetic behaviour. The paramagnetic behaviour could be attributed to the formation of lower oxidation states of vanadium at 900 C. by the loss of oxygen in the system. The glass synthesized at 700 C. had a yellowish color, whereas the one obtained at 900 C. was more greenish-brown, which is also an indication for the formation of lower oxidation state. Thus, the glass should be synthesized at temperatures below 900 C., preferably at 800 C. or less.

(40) Electrochemical Characterization:

(41) The working electrode was 7:2:1 (w/w/w) V.sub.2O.sub.5LiBO.sub.2 (80/20)glass/Super P conductive carbon/polyvinylidene fluoride (PVDF). The materials were mixed and grinded in an agate mortar and the mixture was added into a small amount of 4:1 THF:Toluene solvent mixture. With small amount an amount is meant that is sufficient to provide a slurry suitable to be applied onto a current collector, usually an amount of about 1 to 2 ml/g glassy material, at most about 5 ml/g. The slurry was spread on a titanium (Ti) current collector and dried at 85 C. for 3 hours under vacuum. The active material on the current collector was approx. 3-6 mg at the end of the process. The battery cell was constructed using lithium metal as an anode, 1 M solution of LiPF.sub.6 in 1:1 ethylene carbonate/dimethyl carbonate (EC/DMC) as an electrolyte, and polypropylene film as a separator. The cells were charged-discharged with a rate of 50 A/kg between 1.5V and 4V. The galvanostatic measurement for V.sub.2O.sub.5LiBO.sub.2 glass is depicted in FIG. 3.

Example 2: V2O5LiBO2 GlassReduced Graphite Oxide (redGO) Composite

(42) A composite electrode material of V.sub.2O.sub.5LiBO.sub.2 glass is obtained by the reduction of graphite oxide to graphite and amorphous carbon in a mixture of the glass and graphite oxide. The composite electrode material gives higher practical specific capacity, and the cycling is much improved compared to plain V.sub.2O.sub.5LiBO.sub.2 glass.

(43) Synthesis:

(44) 20 wt-% graphite oxide and 80 wt-% V.sub.2O.sub.5LiBO.sub.2 were ball-milled together and the resulting mixture was heated at 200 C. for 8 hours under N.sub.2 flow or in air to ensure the reduction of graphite oxide to graphite and amorphous carbon. The carbon content was found to be 10.9 wt-% at the end of the process.

(45) Characterization:

(46) XRD Powder Diffraction and DTA:

(47) After ball-milling and heat treatment, a black powder was obtained. No diffraction peak from graphite oxide or graphite was observed. The absence of a graphite peak was attributed to the thin layers formed. The crystallinity of the material was enhanced by heat treatment with the formation of LixV.sub.2O.sub.5 phases (see FIG. 4). The formation of these phases could also be tracked by differential thermal analysis with the exothermic peak at about 200 C. (see FIG. 5).

(48) SEM-TEM:

(49) SEM and TEM images of the composite material are given in FIG. 6, wherein FIG. 6.1 shows SEM images of the V.sub.2O.sub.5LiBO.sub.2 glass composite material and FIG. 6.2 respective TEM images. The graphite flakes and carbon on the surface of V.sub.2O.sub.5LiBO.sub.2 can be seen in the electron microscopy images.

(50) Electrochemical Characterization:

(51) The working electrode used was 9:1 (w/w) composite material/polyvinylidene fluoride (PVDF), which can be also given as approx. 81 wt-% active material (V.sub.2O.sub.5LiBO.sub.2 glass), 9 wt-% conductive carbon and 10 wt-% PVDF. The materials were mixed and grinded in an agate mortar and the mixture was added into a small amount of 4:1 THF:Toluene solvent mixture. The slurry was spread on a Ti current collector and dried at 85 C. for 3 hours under vacuum. The active material on the current collector was ca. 3-6 mg at the end of the process. The battery cell was constructed using lithium metal as an anode, 1 M solution of LiPF.sub.6 in 1:1 EC/DMC as an electrolyte, and polypropylene film as a separator. The cells were charged-discharged with a rate of 50 A/kg between 1.5V and 4V (or 4.5V). The galvanostatic measurement for the composite material is depicted in FIG. 7.

(52) FIG. 7.1 illustrates galvanostatic cycling at a rate of 50 A/kg (0.sup.th to 90.sup.th cycles) of the V.sub.2O.sub.5LiBO.sub.2 glass-redGO composite (redGO designates reduced graphene oxide). The first discharge capacity was approx. 350 Ah/kg and for reversible cycling (between 1.5-4.0 V) was around 300 Ah/kg with decreases in subsequent cycles (ca. 250 Ah/kg at 90.sup.th cycle). The cycling properties and the initial discharge capacity was considerably improved compared to plain V.sub.2O.sub.5LiBO.sub.2 glass.

(53) FIG. 7.2 illustrates galvanostatic cycling at a rate of 25 A/kg (0.sup.th to 42.sup.nd cycle) of the V.sub.2O.sub.5LiBO.sub.2 glass-redGO composite. The battery was first charged to 4.5 V and a capacity of 20 Ah/kg was obtained (Lithium extraction in the 1.sup.st charge was not possible for the plain V.sub.2O.sub.5LiBO.sub.2 glass). The first discharge capacity was about 400 Ah/kg and reversible cycling between 1.5-4.5 V resulted in decreases in subsequent cycles. The capacity and the voltage range dropped drastically through 40.sup.th cycle.

Example 3: V2O5-MnOvLiBO2 GlassReduced Graphite Oxide Composite, in Particular V2O5NiOLiBO2 GlassReduced Graphite Oxide Composite

(54) In order to improve the voltage range of the glass system ternary and quaternary glass systems of the inventive type, in particular V.sub.2O.sub.5 glass systems where LiBO.sub.2 is used as the glass former, can be synthesized with M in M.sub.uO.sub.v being high voltage redox couples, such as Co.sup.2+/Co.sup.3+ and Ni.sup.2+/Ni.sup.3+. As an alternative or in combination with the high voltage redox couples the structural integrity upon cycling can be improved by incorporating a compound like Na.sub.2O and/or Al.sub.2O.sub.3 as it was previously shown for NMC (nickel-mangan-cobaltoxide) materials.

(55) V.sub.2O.sub.5Na.sub.2OLiBO.sub.2, V.sub.2O.sub.5Co.sub.3O.sub.4LiBO.sub.2, V.sub.2O.sub.5Co.sub.3O.sub.4Al.sub.2O.sub.3LiBO.sub.2, and V.sub.2O.sub.5NiOLiBO.sub.2 glasses were successfully synthesized. Among these systems, the best results so far were obtained with V.sub.2O.sub.5NiOLiBO.sub.2. Therefore V.sub.2O.sub.5NiOLiBO.sub.2 is further described below.

(56) Synthesis:

(57) 80-5-15 wt-% V.sub.2O.sub.5NiOLiBO.sub.2 glass was obtained as described before. V.sub.2O.sub.5, NiO and LiBO.sub.2 analytical pure grade powders in corresponding amounts were thoroughly mixed and grinded in an agate mortar, and the mixtures were placed in a Pt crucible. The crucible with the material was put in a muffle furnace at 900 C. The melt was obtained after 1 hour of heat treatment. The melt was quenched in air between Cu plates and V.sub.2O.sub.5LiBO.sub.2 glass was formed.

(58) To obtain the composite material, 33.3 wt-% graphite oxide and 67.7 wt-% V.sub.2O.sub.5NiOLiBO.sub.2 glass were ball-milled together and the resulting mixture was heated at 200 C. for 8 hours in N.sub.2 flow or air flow to ensure the reduction of graphite oxide to graphite and amorphous carbon. The carbon content was found to be 18.5 wt-% at the end of the process.

(59) Characterization:

(60) XRD Powder Diffraction:

(61) The XRD powder pattern of the 80-5-15 wt-% V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material is illustrated in FIG. 8. Both the initial glass and the composite material obtained after treatment with graphite oxide were amorphous and differing from the V.sub.2O.sub.5LiBO.sub.2 system. No diffraction due to LixV.sub.2O.sub.5 phases was observed.

(62) SEM-TEM:

(63) SEM and TEM images of the composite material are given in FIG. 9, wherein FIG. 9.1 shows SEM images of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material, and FIG. 9.2 shows respective TEM images. The graphite flakes and carbon on the surface of V.sub.2O.sub.5NiOLiBO.sub.2 glass can be seen in the electron microscopy images. The presence of nickel and vanadium are confirmed by the EDX spectrum (not shown); though the boron was not detected in the EDX spectrum due to the background, the presence can be seen in the EELS spectrum at approx. 200 eV (not shown).

(64) Electrochemical Characterization:

(65) The working electrode used was 72.5 wt-% active material (V.sub.2O.sub.5NiOLiBO.sub.2 glass), 17.5 wt-% conductive carbon and 10 wt-% PVDF. The materials were mixed and grinded in an agate mortar and the mixture was added into a small amount of 4:1 THF:Toluene solvent mixture (e.g. 2 ml solvent per g glass). The slurry was spread on a Ti current collector and dried at 85 C. for 3 hours under vacuum. The active material on the current collector was approx. 3-6 mg at the end of the process. The battery cell was constructed using lithium metal as an anode, 1 M solution of LiPF.sub.6 in 1:1 EC/DMC as an electrolyte, and polypropylene film as a separator. The cells were charged-discharged with a rate of 50 or 25 A/kg between 1.5V and 4V (or 4.5V). The galvanostatic cycling for the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material at a rate of 25 A/kg (0.sup.th to 24.sup.th cycle) is shown in FIG. 10. OCV was 3.50 V, cycling was performed from 4.5-1.5 V, capacity on the 1.sup.st charge to 4.5 V was 8.5 Ah/kg, the first discharge capacity was 435 Ah/kg. Then cycling between 1.5-4.5 V was performed. At 20.sup.th cycle the charge capacity was 372 Ah/kg and the discharge capacity 376 Ah/kg.

(66) FIG. 11 is a plot of specific energy vs. cycle number for the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material (cycling between 4.5-1.5 V at 25 A/kg) showing high specific energy with polarization at 20.sup.th cycle 1100 Wh/kg for charge and 950 Wh/kg for discharge. The average voltage was 2.51V for discharge and 2.96V for charge. This is about 0.3 V higher than the V.sub.2O.sub.5LiBO.sub.2 glass system indicating the contribution of NiO addition.

(67) FIG. 12 shows galvanostatic cycling at a rate of 50 A/kg (0.sup.th to 60.sup.th cycle) of the V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material. OCV was 3.51 V, first discharge to 1.5 V resulted in a specific capacity of 380 Ah/kg. Then cycling was performed between 1.5-4.0 V. At 60.sup.th cycle the charge capacity was 275 Ah/kg and the discharge capacity 265 Ah/kg.

Example 4: N-Doped V2O5NiOLiBO2 GlassReduced Graphite Oxide Composite

(68) The performance of the V.sub.2O.sub.5LiBO.sub.2 glass systems has been improved step by step with (i) NiO doping and (ii) the composite electrode formation via graphite oxide treatment. However, the polarization and the cycling stability, though it could be considerably improved with these means, still was an object for further improvement. Nitrogen doping and chemical lithiation by the reaction of glass with Li.sub.3N was found to further decrease these problems by mainly increasing the conductivity of the system.

(69) Below, nitrogen doping and chemical lithiation with Li.sub.3N is shown for V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material, but it can be applied to other V.sub.2O.sub.5LiBO.sub.2 glass systems as well.

(70) Synthesis:

(71) 33.3 wt-% graphite oxide, 67.7 wt-% V.sub.2O.sub.5NiOLiBO.sub.2 glass, and 3.3 wt-% Li.sub.3N were ball-milled together under Ar atmosphere and the resulting mixture was heated at 200 C. for 8 hours under N.sub.2 flow to ensure the reduction of graphite oxide to graphite and amorphous carbon. The carbon and nitrogen content were found to be 18.9 wt-% and 0.45 wt-% at the end of the process by elemental analysis.

(72) Characterization:

(73) XRD Powder Diffraction:

(74) The XRD powder pattern of the nitrogen doped 80-5-15 wt-% V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material is shown in FIG. 13. The composite material obtained after treatment with graphite oxide and Li.sub.3N was amorphous, and no diffraction peaks due to graphite oxide and Li3N were observed.

(75) TEM:

(76) TEM images of the composite material are given in FIG. 14 showing graphite flakes and carbon on the surface of V.sub.2O.sub.5NiOLiBO.sub.2 glass particles.

(77) Electrochemical Characterization:

(78) The working electrode used was 73 wt-% active material (nitrogen doped and chemically lithiated V.sub.2O.sub.5NiOLiBO.sub.2 glass), 17 wt-% conductive carbon and 10 wt-% PVDF. The materials were mixed and grinded in an agate mortar and the mixture was added into a small amount of 4:1 THF:Toluene solvent mixture. A small amount of solvent mixture refers to an amount that makes the slurry spreadable onto the current collector and may be about 2 ml/g active material. The slurry was spread on a Ti current collector and dried at 85 C. for 3 hours under vacuum. The active material on the current collector was approx. 3-6 mg at the end of the process. The battery cell was constructed using lithium metal as an anode, 1 M solution of LiPF.sub.6 in 1:1 EC/DMC as an electrolyte, and polypropylene film as a separator. The cells were charged-discharged with a rate of 50 or 25 A/kg between 1.5V and 4V (or 4.5V). The galvanostatic measurement for the composite material is depicted in FIG. 15, wherein FIG. 15.1 shows galvanostatic cycling at a rate of 25 A/kg (0.sup.th to 10.sup.th cycle) of the nitrogen doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material and FIG. 15.2 shows galvanostatic cycling at a rate of 50 A/kg (0.sup.th to 20.sup.th cycle) of the same nitrogen doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material.

(79) From FIG. 15.1 the following features can be deduced: OCV=3.16 V, cycling 4.5-1.5 V, 77 Ah/kg capacity on the 1.sup.st charge to 4.5 V proving the chemical lithiation achieved by the reaction with Li.sub.3N. The first discharge capacity was 362 Ah/kg. Then further cycling between 1.5-4.5 V was performed. At 8.sup.th cycle the charge capacity was 378 Ah/kg and the discharge capacity 375 Ah/kg.

(80) From FIG. 15.2 the following features can be deduced: OCV=3.16 V, the first discharge capacity was 291 Ah/kg. Then cycling was performed between 1.5-4.0 V. At the 20.sup.th cycle the charge capacity was 277 Ah/kg and the discharge capacity 275 Ah/kg.

(81) Comparison with Different Systems:

(82) FIG. 16 shows a specific energy vs. cycle number plot for different materials of the present invention cycled between 1.5 V-4.0 V at 50 A/kg. For the nitrogen doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material, high specific energy was obtained with polarization at 10.sup.th cycle 800 Wh/kg for charge and 675 Wh/kg for discharge and the average voltage was about 2.4 V. For non N-doped V.sub.2O.sub.5NiOLiBO.sub.2 glass composite material, these values were 1005 Wh/kg for charge and 885 Wh/kg for discharge and the average voltage was about 2.4 V, so that there was a decrease in the specific capacity for the nitrogen doped sample. The values were 736 Wh/kg and 2.24V for redGO comprising V.sub.2O.sub.5LiBO.sub.2 glass, and 647 Wh/kg and 2.23V for plain V.sub.2O.sub.5LiBO.sub.2 glass.

(83) Advantages of the Glassy Composite Materials of the Present Invention:

(84) The inventive materials, wherein Li/NaBO.sub.2 acts as the glass former and T.sub.xO.sub.y, in particular V.sub.2O.sub.5 as the main electrochemically active part and that have high specific capacity and energy are suitable electronically active materials for Li-ion batteries. One of their advantages is that the synthesis method is very simple and cost efficient. Comparable cathode materials delivering close capacities and energies are only obtainable by laborious synthetic methods and using expensive techniques and educts. The specific advantages of important embodiments of the invention can be described as follows:

(85) V.sub.2O.sub.5LiBO.sub.2 Glass:

(86) The completely glassy material is obtained with only 20 wt-% LiBO.sub.2 meaning that the major part of the glass still is electrochemically active. Irreversible capacity loss that occurs for 3 lithium insertion in crystalline V.sub.2O.sub.5 phases is not found in this glass as the system cycles as a solid solution and there is no phase transformation in the first discharge.

(87) V.sub.2O.sub.5LiBO.sub.2 GlassReduced Graphite Oxide (redGO) Composite:

(88) The cycling properties and charge/discharge capacities of the V.sub.2O.sub.5LiBO.sub.2 glass is improved by a better conducting carbon network obtained via reduction of well distributed graphite oxide. Besides, excess Li in the initial glass could be partially extracted in the first charge, which was not possible using plain V.sub.2O.sub.5LiBO.sub.2 glass where Li remained therein as dead weight.

(89) V.sub.2O.sub.5NiOLiBO.sub.2 GlassReduced Graphite Oxide (redGO) Composite:

(90) NiO addition into the system increased the voltage range and so the specific energy of the system. In addition, the cycling in the broader voltage range, 4.5V-1.5V was advanced compared to the plain system (V.sub.2O.sub.5LiBO.sub.2 glass). Though it was not tested, the thermal stability of the system is also thought to be improved.

(91) N-Doped V.sub.2O.sub.5NiOLiBO.sub.2 GlassReduced Graphite Oxide (redGO) Composite:

(92) The cycling stability and the columbic efficiency (when cycled between 1.5-4.0 V) were increased by nitrogen doping via the reaction with Li.sub.3N. In addition, the glass can be lithiated by this method, which is advantageous or even necessary for the commercial use if the anode part of the battery is chosen from a non lithiated material, such as graphite.

(93) In order to specifically examine the features of the glassy material, the glass particles examined above were not provided with a coating. However, using special coatings on the surface of the glass particles, such as C, ZrO.sub.2, Al.sub.2O.sub.3, Li.sub.3PO.sub.4, LiFePO.sub.4, Li.sub.3BO.sub.3 etc. is within the scope of the present invention. Such coatings may e.g. further improve stability since a main reason for stability problems is assumed to be the dissolution of the transition metal centers into the electrolyte.

(94) Further improvement is obtainable through optimization of the particle sizes of the inventive glasses, since those examined above were still in the m range. Big particle size of materials with low ionic conductivity is assumed to be the main reason for the large hysteresis of approx. 100-150 Wh/kg, observed.

(95) While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

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