Rechargeable Lithium Battery with a Composite Anode

Abstract

The invention relates to a rechargeable lithium battery comprising a composite anode (negative electrode) containing a metal nitrogen compound as the electrochemically active component in the composite anode, according to the general formulas (I) and/or (II)

Li.sub.xM.sup.2.sub.z(NH).sub.0.5x+z  (I)

Li.sub.mM.sup.2.sub.n(NH.sub.2).sub.1+n  (II),

wherein (I) and (II) are present in any mixing ratio and M.sup.2=an alkaline earth element selected from the group consisting of Mg, Ca, Sr, Ba, or any mixture thereof, with x=0-4; z=0-2; m=1 or 0; n=1 or 0, where (m+n)=1, and wherein they correspond to the fully discharged, lithium-poorest state of charge of the nitrogen-containing compounds, a cathode (positive electrode), separated therefrom by a separator, containing lithium-insertable compounds selected from metal oxides, lithium metal oxides, lithium oxides and lithium hydroxide and an aprotic lithium electrolyte, wherein the electrochemically active metal nitrogen compounds of the composite anode are embedded in a transition metal-containing electronically or—mixed-conductive network consisting of finely divided transition metals and/or electronically or mixed-conductive interstitial transition metal compounds, and the weight ratio between the components forming the network and the nitrogen-containing compounds I and/or II is in the range of 1:100 to 1:2.

Claims

1. A rechargeable lithium battery with a composite anode containing a metal nitrogen compound as the electrochemically active component in the composite anode, according to the general formula (I) and/or (II)
Li.sub.xM.sup.2.sub.z(NH).sub.0.5x+z  (I)
Li.sub.mM.sup.2.sub.n(NH.sub.2).sub.1+n  (II), wherein (I) and (II) are present in any mixing ratio and M.sup.2 is an alkaline earth element selected from the group consisting of Mg, Ca, Sr, Ba, and any mixture thereof, with x=0-4; z=0-2; m=1 or 0; n=1 or 0, wherein (m+n)=1, wherein they correspond to the fully discharged, lithium-poorest state of charge of the metallic nitrogen compounds; a cathode separated from the anode by a separator, wherein the cathode contains lithium-insertable compounds selected from the group consisting of metal oxides, lithium metal oxides, lithium oxides and lithium hydroxide; and an aprotic lithium electrolyte; characterized in that the electrochemically active metal nitrogen compounds of the composite anode are embedded in a transition metal-containing electronically or mixed-conductive network consisting of transition metals and/or electronically or mixed-conductive interstitial transition metal compounds, and the weight ratio between the components forming the network and the metal nitrogen compounds is in the range of 1:100 to 1:2.

2. A lithium battery according to claim 1, characterized in that the transition metal-containing electronically or mixed-conductive network contains finely divided, nanoparticulate transition metal powders M or interstitial transition metal compounds with an electrochemical potential of <2.5 V against Li/Li.sup.+.

3. A lithium battery according to claim 1, characterized in that the composite anode contains as transition metal powder the elements of the 3rd to 12th group of the periodic table of the elements.

4. A lithium battery according to claim 1 characterized in that the composite anode contains electronically or mixed-conductive interstitial transition metal compounds selected from the group consisting of transition metal nitrides, transition metal carbides of at least one element of groups 3 to 12 of the periodic table of the elements, transition metal hydrides of at least one element of groups 3 to 10 of the periodic table of the elements, and any combination of two or more of the foregoing.

5. A lithium battery according to claim 1, characterized in that the transition metal powders and/or the mixed-conductive interstitial transition metal compounds and the electrochemically active metal nitrogen compounds are present homogeneously mixed in finely divided, amorphous or nanoparticulate form with particle sizes in the range from 0.1 to 100 nm.

6. A lithium battery according to claim 1, characterized in that the weight ratio between the transition metals and/or the electronically or mixed-conductive interstitial transition metal compounds and the nitrogen-containing active materials in the composite anode is in the range from 1:50 to 1:5.

7. A lithium battery according to claim 3, characterized in that the composite anode contains, as an electronically or mixed-conductive network containing transition metals, finely divided transition metal powders M wherein is selected from the group consisting of Sc, Ti, Zr, Hf, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, Yb, Lu and any combination of two or more of the foregoing.

8. A lithium battery according to claim 4, characterized in that the composite anode contains at least one finely divided interstitial compound selected from the group consisting of (a) TiN.sub.n, ZrN.sub.n, HfN.sub.n, VN.sub.n, NbN.sub.n, TaN.sub.n, CrN.sub.n, MoN.sub.n, WN.sub.n, MnN.sub.n, FeN.sub.n, CoN.sub.n, NiN.sub.n, ZnN.sub.n; Cr.sub.1-nFe.sub.nN with n=0.3 to 1; (b) Li.sub.7MnN.sub.4, LiMoN.sub.2; Li.sub.2.6Co.sub.0.2Cu.sub.0.15Fe.sub.0.05N; Li.sub.27Fe.sub.0.3; Li.sub.3FeN.sub.2; Li.sub.25Co.sub.0.2Cu.sub.0.1N; Li.sub.2.6Co.sub.0.2Cu.sub.0.2N; Li.sub.2.6Co.sub.0.4N; (c) TiC, WC; ZrC.sub.1-m, HfC.sub.1-m, VC.sub.1-m, NbC.sub.1-m, TaC.sub.1-m, Cr.sub.3C.sub.2, Mo.sub.2C, Fe.sub.3C with m=0 to 0.5; and (d) ScH.sub.2, YH.sub.o, LaH.sub.o, CeH.sub.2, PrH.sub.o, NdH.sub.o, SmH.sub.n, EuH.sub.o, GdH.sub.o, TbH.sub.o, DyH.sub.o, HoH.sub.o, ErH.sub.o, TmH.sub.o, YbH.sub.o, LuH.sub.o, TiH.sub.2, ZrH.sub.2, HfH.sub.2, VH, VH.sub.2, TaH.sub.0.5, MnH with o=2 or 3.

9. A lithium battery according to claim 1, characterized in that the composite anode contains at least one electrochemically active material embedded in a matrix consisting of an electronically or mixed-conductive transition metal-containing material, wherein the at least one electrochemically active material is selected from the group consisting of Li.sub.2NH, MgNH, CaNH, Li.sub.2Mg(NH).sub.2, Li.sub.2Ca(NH).sub.2, MgCa(NH).sub.2, Li.sub.4Mg(NH).sub.3, Li.sub.2Mg.sub.2(NH).sub.3, and LiNH.

10. A lithium battery according to claim 1, characterized in that the composite anode contains non-metal-based conductivity improvers, lithium-donating additives and binders.

11. A lithium battery according to claim 1, characterized in that the composite anode is pressed or calendered.

12. A lithium battery according to claim 1, characterized in that the cathode comprises at least one anion redox active material in the form of a lithium oxygen compound selected from the group consisting of lithium hydroxide, lithium oxide, lithium peroxide and lithium superoxide, and lithium hydride.

13. A lithium battery according to claim 1, characterized in that the cathode is a layered structured material selected from the group consisting of LiCoO.sub.2, LiNiO.sub.2, Li(Ni,Mn,Co)O.sub.2, LiNi.sub.0.80Co.sub.0.15Al.sub.0.05O.sub.2, a spinel structured material selected from the group consisting of LiMn.sub.2O.sub.4 and LiNi.sub.0.5Mn.sub.1.5O.sub.4, an olivine structured material selected from the group consisting of LiFePO.sub.4 and LiMnPO.sub.4, a non-lithiated metal insertion compound selected from the group consisting of electrolytic manganese dioxide or vanadium oxides, metal fluorides, and metalloxy fluorides.

14. A lithium battery according to claim 1, characterized in that the proportion by weight of the transition metal and/or interstitial transition metal compound in the anode is in the range of from 1 wt % to 33 wt %.

15. A lithium battery according to claim 1, characterized in that the transition metal powders and/or the mixed-conductive interstitial transition metal compounds and the electrochemically active metal nitrogen compounds are present homogeneously mixed in finely divided, amorphous or nanoparticulate form with particle sizes in the range from 1 to 30 nm.

Description

COMPARATIVE EXAMPLE

[0065] The lithium nitrogen containing microcrystalline powdery anode materials LiNH.sub.2 and Li.sub.2NH, respectively, were mixed in an Ar-filled glove box with a transition metal free conductivity improver (carbon black AB 100) and PTFE powder (supplier Aldrich) and briefly homogenized by means of an agate mortar. The weight ratios were 60 wt % active material; 25 wt % carbon black; 15 wt % PTFE. The electrode material was then applied to a nickel net current collector with a surface area of 1 cm.sup.2 and isostatically pressed for one minute at a pressure of 10 t.

[0066] The anode produced in this way was tested in a glass cell with a three-electrode arrangement. In addition to the lithium nitrogen containing electrode, two electrodes consisting of lithium sheets were used as counter and reference electrodes. The electrolyte used was an 11% LiPF.sub.6 solution in EC/DMC (1:1).

[0067] The cell with LiNH.sub.2 had a rest potential of 1300 mV, the cell with Li.sub.2NH had one of 700 mV. In both cases polarization was performed with very low feed voltages up to a potential of 5 mV. The amount of charge consumed in each case was just under 0.1 eq lithium. The polarity was then reversed and lithium was removed. In the case of LiNH.sub.2 only about 0.3 Li could be extracted, in the case of Li.sub.2NH about 0.55 Li.

Example 1: Production of a Nitrogen and Transition Metal Containing Composite Anode Material by Grinding (Hydride Based Conductivity Improver)

[0068] In an Ar-filled glove box, 4.2 g lithium imide (Li.sub.2NH) with a X-ray purity of 100%, 2.1 g zirconium hydride (grade S from Albemarle Germany, H content at least 1.9%) and 0.7 g carbon black (AB 100) were premixed in a beaker. The homogenized mixture was filled into a 50 mL zirconia ceramic grinding beaker together with about. 27 g 3 mm zirconia ceramic balls and sealed. The mixture was then ground in a planetary ball mill (Pulverisette P7 from Fritsch) for 90 minutes at 800 rpm.

[0069] The grinding bowl was put back into the Ar-filled glove box and opened there. The ground product was separated from the grinding media by sieving.

[0070] Yield: 6.3 g grey-black, fine powder

Example 2: Production of a Nitrogen and Transition Metal Containing Composite Anode Material by Grinding (Nitride-Based Conductivity Improver)

[0071] In an Ar-filled glove box, 4.0 g lithium imide (Li.sub.2NH) (X-ray purity 100%), 0.75 g titanium nitride (<3 μm from Sigma-Aldrich) and 0.25 g carbon black (AB 100) were mixed in a beaker. The prehomogenized mixture was filled into a 50 mL zirconia ceramic grinding beaker together with about 27 g 3 mm zirconia ceramic balls and sealed. The mixture was then ground in a planetary ball mill (Pulverisette P7 from Fritsch) for 240 minutes at 800 rpm in reverse operation mode.

[0072] The grinding bowl was put back into the Ar-filled glove box and opened there. The ground product was separated from the grinding media by sieving.

[0073] Yield: 4.1 g grey-black, fine powder