Stabilized, Pure Lithium Metal Powder And Method For Producing The Same

Abstract

The invention relates to a stabilized lithium metal powder and to a method for producing the same, the stabilized, pure lithium metal powder having been passivated in an organic inert solvent under dispersal conditions with fatty acids or fatty acid esters according to the general formula (I) R—COOR′, in which R stands for C.sub.10-C.sub.29 groups and R′ for H or C.sub.1-C.sub.8 groups.

Claims

1. (canceled)

2. A method for preparing a stabilized lithium metal powder which does not show any run-away phenomenon when in contact with N-methyl-2-pyrrolidone having a water content of less than about 200 ppm at a minimum of 15 hours storage at 50° C., the method comprising: reacting lithium metal having less than 200 ppm of metallic contamination above 180° C. in an organic, inert solvent under dispersal conditions with a passivation agent containing one or a plurality of fatty acids and/or one or a plurality of fatty acid esters according to formula I
R—COOR′  (I), wherein R denotes C.sub.10-C.sub.29 moieties and R′ stands for H or C.sub.1-C.sub.8 moieties.

3. The method for preparing a stabilized lithium metal powder according to claim 2, wherein the passivation agent is an unsaturated fatty acid selected from the group consisting of oleic acid, stearic acid, palmitic acid, lauric acid, myristinic acid, margaric acid, palmitoleic acid, linolic acid and linolenic acid.

4. The method for preparing a stabilized lithium metal powder according to claim 2, wherein the passivation agent is an ester of an unsaturated fatty acid selected from the group consisting of oleic acid, stearic acid, palmitic acid, lauric acid, myristinic acid, margaric acid, palmitoleic acid, linolic acid and linolenic acid.

5. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises at least two unsaturated fatty acids selected from the group consisting of oleic acid, stearic acid, palmitic acid, lauric acid, myristinic acid, margaric acid, palmitoleic acid, linolic acid and linolenic acid.

6. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises an ester of at least one unsaturated fatty acid selected from the group consisting of oleic acid, stearic acid, palmitic acid, lauric acid, myristinic acid, margaric acid, palmitoleic acid, linolic acid and linolenic acid.

7. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises an ethylate.

8. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises a triglyceride.

9. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises a propanolate.

10. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises a butylate.

11. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises a natural oil.

12. The method for preparing a stabilized lithium powder according to claim 2, wherein the passivation agent comprises a natural oil selected from the group consisting of rapeseed oil, olive oil, sunflower oil and linseed oil.

13. The method according to claim 2, wherein the passivation agent is used in quantities of 0.1 g to 50 g per kg lithium metal.

14. The method according to claim 2, wherein the organic, inert solvent is one or more hydrocarbons, selected from the group consisting of hexane, heptane, octane, decane, undecane, dodecane, toluene, ethyl benzene, cumene, and mixtures thereof.

15. The method according to claim 2, further comprising coating the stabilized lithium metal powder at temperatures <180.5° C.

16. A method as in claim 2 further comprising prelithiating an electrochemically active material with the stabilized lithium metal powder.

17. A method according to claim 16, wherein the electro-chemically active material is selected from the group consisting of graphite, alloy and a conversion anode for a lithium battery.

18. A method as in claim 2 wherein 0.1 g to 50 g of passivation agent is used per kg of lithium metal.

19. A method as in claim 2 further comprising applying a coating to the stabilized lithium metal powder.

Description

[0027] Shown are in:

[0028] FIG. 1: the thermal behavior during storage of the metal powder according to Example 1 in NMP at 80° C. and 100° C. furnace temperature (−) and sample temperature (+, Δ);

[0029] FIG. 2: the thermal behavior during storage of the metal powder according to comparison example 1 in NMP at 50° C. furnace temperature (−) and sample temperature (+);

[0030] FIG. 3: the thermal behavior during storage of a metal powder (Na content 17 ppm) obtained according to Example 1 in NMP with a water content of 1%, furnace temperature (−) and sample temperature (+, Δ);

[0031] FIG. 4: the thermal behavior during storage of a metal powder having an Na content of 55 ppm obtain according to Example 1 at 50° C. and 100° C. furnace temperature (−) and sample temperature (+, x) in NMP (148 ppm water content);

[0032] FIG. 5: the thermal behavior during storage of a metal powder having an Na content of 55 ppm obtained according to Example 1 at 80° C. furnace temperature (−) and sample temperature (+) in NMP (200 ppm water content).

EXAMPLE 1

[0033] Preparation of a lithium metal powder poor in sodium and passivated with linseed oil 399 g Shellsol D 100 and 19.4 g lithium metal bar sections are filled into a dry 2 L noble metal double-jacket reactor that was rendered inert. The lithium has a sodium content of 17 ppm. Stirring very slowly (ca. 50 rpm), the jacket heater raises the inside temperature to 205° C. Using a syringe, 0.05 g linseed oil is then added. The agitation frequency is raised to 3600 rpm and maintained for 6 minutes. The agitator is then brought to a halt and the suspension cooled to room temperature.

[0034] The suspension is drained onto a vacuum filter, the filter residue is washed multiple times with hexane until it is free of oil, then vacuum-dried.

[0035] Yield: 15.6 g (80% of the theory)

[0036] Mean particle size: ca. 50 μm (image evaluation under SEM)

Comparison Example 1

[0037] Preparation of lithium metal powder passivated with linseed oil 525 g Shellsol D 100 and 32.3 g lithium metal bar sections and 0.11 g sodium are filled into a dry 2 L noble metal double jacket reactor that was rendered inert and is equipped with a dispersion agitation system. The lithium has a sodium content of 17 ppm. Stirring very slowly (ca. 50 rpm), the jacket heater raises the inside temperature to 205° C. Using a syringe, 0.09 g linseed oil is then added. The agitation frequency is raised to 3600 rpm and maintained for 6 minutes. The agitator is then brought to a halt and the suspension cooled to room temperature.

[0038] The suspension is drained onto a vacuum filter, the filter residue is washed multiple times with hexane until it is free of oil, then vacuum-dried.

[0039] Yield: 27.3 g (84% of the theory)

[0040] Mean particle size: ca. 50 μm (image evaluation under SEM)

[0041] Na content (FES): 0.3%

EXAMPLE 2

[0042] Storage of a metal powder according to the invention from Example 1 in NMP at 80° C. and 100° C. (DSC test) Instrumentation by the company Systag, Switzerland (the Redex system) was used for the differential scanning calorimetry (DSC) testing. Under a protective gas atmosphere, approximately 2 g NMP and 0.1 g lithium metal powder were weighed into the sample vessels. Samples were stored at certain temperatures tor 15 hours.

Comparison Example 2

[0043] Storage of the meta 1 powder that is not according to the invention from Comparison Example 1 in NMP at 50° C. (DSC test) Example 2 and Comparison Example 2 demonstrate the substantially improved stability of the lithium 7 metal powder according to the invention in contact with NMP: while the product according to the invention did not cause any significant exothermal effects at storage at 80° C., nor at 100° C. (the sample temperature remains visibly below the furnace temperature throughout the entire observation period), the metal powder that is not according to the invention shows already at storage at 50° C. a visible exothermal reaction. This can be recognized in that the sample temperature clearly exceeds the furnace temperature.

EXAMPLE 3

[0044] Storage of the metal powder according to the invention (Na content 17 ppm) from Example 1 in NMP having a water content of 1% (DSC test).

[0045] The especially preferred Li metal powder having an Na content of 17 ppm proves kinetically stable even in water-rich NMP.

EXAMPLE 4

[0046] Storage of a lithium metal power prepared according to the invention having an Na content of 55 ppm at 50° C. and 100° C. in NMP (148 ppm water content) (DSC test)

EXAMPLE 5

[0047] Storage of a lithium metal power prepared according to the invention having an Na content of 55 ppm at 80° C. in NMP (200 ppm water content) (DSC test).

[0048] The metal powder having a sodium content of 55 ppm is stable at storage temperatures of 50° C. and 80° C.; at 100° C., however, it shows an exothermal, but not a run-away effect. According to the DSC experiment at 100° C., 73% of the used lithium is still present in metallic form.