Alkali-Ion Battery Based on Selected Allotropes of Sulphur, and Methods for the Production Thereof

Abstract

The invention relates to a new generation of alkali-ion-sulphur batteries in which specific sulphur allotropes, particularly the Psi allotrope of sulphur, are used as the active material of the cathode. Alkali metals or alkaline-earth metals are used as anodes. A preferred production method describes the production of the Psi-sulphur fibres by a special form of electrospinning. Another preferred production method describes the addition of the cation source in liquid form during the production of battery stacks. Finally, the invention relates to specific preferred novel forms of embodiment of alkali-ion-sulphur batteries, which are characterised by significant advantages in terms of capacity and service life.

Claims

1. An alkali metal ion-sulfur battery which contains sulfur allotropes having a chain-like arrangement, preferably mu, omega or psi allotropes, most preferably psi allotropes.

2. The alkali metal ion-sulfur battery as claimed in claim 1, wherein the proportion by mass of the individual or all selected allotropes in the cathode is from 5 to 95%, preferably from 60 to 90%, most preferably from 73 to 77%.

3. The alkali metal ion-sulfur battery as claimed in claim 1, wherein the sulfur material is present as a one-dimensional structure, preferably as fibers, hollow fibers, rods or tubes, most preferably as hollow fibers.

4. The alkali metal ion-sulfur battery containing phi allotropes of sulfur in the cathode.

5. The alkali metal ion-sulfur battery as claimed in claim 4, wherein the proportion by mass of the phi allotrope is from 5 to 30%, preferably from 10 to 15%.

6. The alkali metal ion-sulfur battery as claimed in claim 1, wherein the total proportion by Mass of sulfur in the cathode is more than 75%, preferably from 80 to 95%, more preferably from 83 to 85%.

7. The alkali metal ion-sulfur battery as claimed in claim 1, wherein the cathode contains a self-supporting structure formed by 1D sulfur structures such as fibers, rods or hollow fibers which form a 3D sulfur structure such as a mat, a woven fabric or the like.

8. The alkali metal ion-sulfur battery as claimed in claim 1, wherein the proportion by mass of sulfur per unit area of the active composition is at least 5 mg/cm.sup.2, more preferably at least 20 mg/cm.sup.2.

9. The alkali metal ion-sulfur battery as claimed in claim 1, wherein a plurality of electrodes are processed so as to be stacked in a bipolar design.

10. The alkali metal ion-sulfur battery as claimed in claim 1, wherein the cathode consists of a self-supporting 3D structure which is adhesively joined to a collector foil.

11. The alkali metal ion-sulfur battery as claimed in claim 1, wherein a metal oxide coating is provided in situ on the surface of the 1 D structures.

12. An alkali metal ion-sulfur battery, wherein the cathode or/and anode is free of alkali and alkaline earth metals during the stack and/or cell and/or battery production process.

13. The alkali metal ion-sulfur battery as claimed in claim 12, wherein a monovalent, divalent or trivalent cation source, preferably Li.sup.+ or Na.sup.+ as monovalent source, Mg.sup.2+ as divalent source or Al.sup.3+ as trivalent source, is injected as liquid A into the cells or the battery during the battery production process.

14. The alkali metal ion-sulfur battery as claimed in claim 13, wherein a precursor medium for a solid electrolyte is also injected as liquid B into the cells or the battery during the battery production process.

15. The alkali metal ion-sulfur battery as claimed in claim 14, wherein the main electrolyte is injected as liquid C into the cells or the battery during the battery production process.

16. The alkali metal ion-sulfur battery as claimed in claim 14, wherein two different electrolytes are injected as liquid C and liquid D into the cells or the battery during the battery production process, with liquid C being injected exclusively on the cathode side and liquid D being injected exclusively on the anode side.

17-27. (canceled)

Description

EXAMPLES

[0041] Sulfur fibers were produced using the materials and process parameters indicated below:

[0042] Sulfur: procured from Merck

[0043] Temperature: 200 C.

[0044] Transport device: transport cylinder

[0045] Outlet: perforated membrane or multi-nozzle

[0046] Volume flow: about 10 g/minute

[0047] Pressure: atmospheric pressurepure pushing along of the material

[0048] Voltage: 30 KV

[0049] Cooling medium/protective

[0050] gas: nitrogen at room temperature

[0051] The production apparatus consists of a metal cylinder 1 which has a perforated membrane as outlet at one end and at the other end is closed by a tightly sealing likewise cylindrical transport device. Heating elements are wound around the metal cylinder 1 so as to allow heating of the cylinder. At the end corresponding to the transport unit, the metal cylinder 1 can be opened in order to be filled with the production medium, in this case sulfur. The end with the perforated membrane is connected in an airtight manner to a further cylinder 2. The cylinder 2 is preferably made of metal and coated on the inside with polymer (e.g. PTFE) and has a diameter of from 10 to 20 cm. This cylinder 2 is closed in an airtight manner at the bottom and the top and can be flushed with protective gas or a cooling medium. For this purpose, the upper end of the cylinder is provided with an inlet and the lower end of the cylinder is provided with an outlet for the protective gas or cooling medium. The lower end/the outlet additionally contains a suitable trapping device for solids, e.g. a filter. A high voltage source is present at the end of the cylinder 2 opposite the outlet of the metal cylinder 1. This high voltage source is insulated from the cylinder wall.

[0052] The metal cylinder 1 is filled with pulverulent sulfur and heated to 200 C., resulting in the sulfur melting. After a temperature of 200 C. has been reached in the interior of the metal cylinder 1, a voltage of 30 kV is applied by means of the high voltage source in the cylinder 2. This voltage leads to the liquid sulfur being drawn out of the outlet opening into the cylinder 2. There, it is immediately cooled strongly by nitrogen flowing through, and the fiber falls as fragment to the outlet end or is conveyed to there by the cooling medium flowing past.

[0053] A yield of about 10 g/minute can be produced by means of the apparatus described. The sulfur material produced in this way is used as active cathode material in a battery cell according to the invention.

[0054] The following table gives an overview of the main differences between a battery cell according to the prior art and the battery cell according to the invention.

TABLE-US-00001 TABLE 1 Fiber-based sulfur- State of the art LiS lithium battery according battery/prior art to the invention (Part 14 of 2) Construction Monopolar pouch cell Bipolar octagonal cell Production method for Slurry coating - solvent- Self-supporting woven cathodes based fabric-solvent-free Drying method for IR drying No drying necessary - cathodes pick and place used for the woven fabric Average sulfur loading 5 mg/cm.sup.2 >20 mg/cm.sup.2 Method for sulfur Infiltration in porous No extra inclusion inclusion support structures (infiltration) necessary - (micro-meso-macro direct production of the porous) sulfur fibers Average porosity ca. 38% (v/v) <25% (v/v) (volume) of the cathode after pressing Method for compressing Rolling/pressing Only cutting-out/ the electrodes (calendaring) at 85 C. stamping. Optionally simple pressing at room temperature Type of collector foil Carbon-coated aluminum Aluminum foil pretreated (cathode) foil with adhesive Method for compensating Internal porosity and In the case of an intact for volume changes binder excess fiber according to the invention, only small volume change (<3% v/v) Binder content ca. 10% <=6% (Part 2 of 2) Total content of ca. 18% <=10% conductive additives Type of electron Particle-to-particle Entire fiber-based 3D conduction in the cathode interaction e.sup. conduction path (e.sup. transfer) through 1D fibers which project into another/are conductively connected Gravimetric capacity 940 mAh/g @ C/2 1420 mAh/g @ C/2 (80% (sulfur cathode) DoD) Life as a function of the 5 mg/cm.sup.2 of sulfur >18 mg/cm.sup.2 of sulfur sulfur concentration and 200 @ C/10 380 @ 1C (prototypes C rate in ongoing test on potentiostat) Production method for Lithium foil Carbon-based support anodes structure for lithium Lithium excess 120% 20% Method for loss Significant lithium Precise method for compensation excess adding the lithium source; additionally small lithium excess Method for reducing Thin layer on separator Use of (quasi) solid formation of polysulfites electrolyte in the cathode Degree of order of the Disordered, unoriented, 80% oriented 1D fiber electrode porosity high degree of structure, conductively entanglement connected fibers, low degree of entanglement, improved conduction paths for cations.sup.+

[0055] (All values +/ industrially normal productionand/or measurement-related standard deviations. All percentages are percent by mass (m/m) unless specifically indicated).