WO2012150062A1

WO2012150062A1 - Polyacrylonitrile-sulfur composite material

Info

Publication number: WO2012150062A1
Application number: PCT/EP2012/053857
Authority: WO
Inventors: Jens Grimminger; Jean Fanous; Martin Tenzer; Marcus Wegner
Original assignee: Robert Bosch Gmbh
Priority date: 2011-05-02
Filing date: 2012-03-07
Publication date: 2012-11-08
Also published as: DE102011075053A1

Abstract

The invention relates to a method for producing a polyacrylonitrile-sulfur composite material. In order to provide a polyacrylonitrile-sulfur composite material having a high content of covalently bonded sulfur and thus to increase the capacity or energy density of an alkaline sulfur cell, in particular a lithium sulfur cell, having the polyacrylonitrile-sulfur composite material as a cathode material, according to the method polyacrylonitrile is reacted with sulfur at least for a time in the presence of a catalyst to form a polyacrylonitrile-sulfur composite material. The invention further relates to a polyacrylonitrile-sulfur composite material, to a cathode material, to an alkaline sulfur cell or battery, and to an energy store.

Description

description

title

Polyacrylonitrile-sulfur composite

The present invention relates to a process for the preparation of a polyacrylonitrile-sulfur composite material, a polyacrylonitrile-sulfur

Composite material, a cathode material, an alkali-sulfur cell - or battery and an energy storage.

State of the art

In order to produce batteries with a much higher energy density, research is currently being conducted on lithium-sulfur battery technology (Li / S for short). Inasmuch as the cathode of a lithium-sulfur cell would consist entirely of elemental sulfur, theoretically an energy content above 1,000 Wh / kg could be achieved. However, elemental sulfur is neither ionic nor electrically conductive, so additives must be added to the cathode that significantly lower the theoretical value. Additionally, elemental sulfur is conventionally reduced to soluble polysulfides S _x ^{2 "} upon discharge of a lithium-sulfur cell, which may diffuse into regions, such as the anode region, where they can no longer participate in the electrochemical reaction of the subsequent charge / discharge cycles In addition, polysulfides which can not be further reduced can be dissolved in the electrolyte, and in practice the sulfur utilization and thus the energy density of lithium-sulfur cells is currently significantly lower and is currently estimated to be between 400 Wh / kg and 600 Wh / kg ,

There are different concepts for increasing the sulfur utilization. Nazar et al. describe in Nature Materials, Vol. 8, June 2009, 500-506 that Carbon tubes favor retention of polysulfides in the cathode compartment and at the same time ensure sufficient electrical conductivity.

Wang et al. describe in Advanced Materials, 14, 2002, No. 13-14, pp. 963-965 and Advanced Functional Materials, 13, 2003, No. 6, pp. 487-492 and Yu et al. Describe in Journal of Electroanalytical Chemistry, 573, 2004, 121-128 and Journal of Power Sources 146, 2005, 335-339 another technology in which polyacrylonitrile (PAN) is heated with an excess of elemental sulfur, wherein the sulfur to One is cyclized to form H ₂ S polyacrylonitrile to a polymer with conjugated ττ system and on the other hand bound in the cyclized matrix.

Disclosure of the invention

The present invention provides a process for producing a polyacrylonitrile-sulfur composite material, wherein polyacrylonitrile is reacted with sulfur at least temporarily in the presence of a catalyst to form a polyacrylonitrile-sulfur composite material.

By adding a catalyst, advantageously, the reaction temperature and the reaction time can be reduced. By lowering the reaction temperature, moreover, the chain length of polysulfides covalently bonded to the cyclized polyacrylonitrile can be increased. This is due to the fact that elemental sulfur is present at room temperature in the form of S ₈ rings. At temperatures above room temperature, sulfur is present in the form of medium chain Sx chains, for example from 6 to 26 sulfur atoms, or long chain length, for example from 10 ³ to 10 ⁶ sulfur atoms. Above 187 ° C, a thermal cracking process begins and the chain length decreases again. From 444, 6 ° C (boiling point) is gaseous sulfur with a

Chain length of 1-8 atoms before. The use of a vulcanization catalyst has the advantage that at a lower temperature longer inter- and / or intramolecular, covalently bonded, in particular cyclized, polyacrylonitrile bound sulfur bridges can be introduced into the polyacrylonitrile-sulfur composite material. In particular, by the inventive

Process Polysulfide chains with a chain length of> 3 sulfur atoms, in particular particular> 4 or> 5 or> 6 or> 7 or> 8 or> 9 or> 10 sulfur atoms, are covalently bonded to the polyacrylonitrile skeleton of the polyacrylonitrile-sulfur composite. Thus, in turn, advantageously, a higher sulfur content of the polyacrylonitrile-sulfur composite material can be achieved. Although this can lead to a reduction in the cycle stability, but this can be compensated for example by the choice of a suitable electrolyte.

The polyacrylonitrile-sulfur composite material which can be produced by the process according to the invention can be used particularly advantageously as cathode material for alkali metal compounds.

Sulfur cells, in particular lithium-sulfur cells, are used. In this case, cathodes or alkali-sulfur cells, in particular lithium-sulfur cells, which comprise the polyacrylonitrile-sulfur composite material produced according to the invention can advantageously - with respect to known polyacrylonitrile-sulfur composite materials, have improved electrochemical properties. In particular, due to the high sulfur content, such alkali-sulfur cells may advantageously have a high capacity and energy density. Suitable catalysts for the process according to the invention are known from the technical field of rubber vulcanization.

Within the scope of one embodiment, the reaction is carried out, at least temporarily, in the presence of a vulcanization catalyst or vulcanization accelerator.

In a further embodiment, the vulcanization catalyst or vulcanization accelerator comprises at least one sulfidic radical initiator. If appropriate, the vulcanization catalyst or vulcanization accelerator may consist of at least one sulfidic radical initiator. Sulfidic radical initiators are particularly suitable for the process according to the invention.

In a further embodiment, the sulfidic radical initiator is selected from the group consisting of sulfidic metal complexes, obtainable, for example, by reaction of zinc oxide (ZnO) and tetramethylthiurea. midisulfide or Ν, Ν-dimethylthiocarbamate, sulfenamides, for example, 2-mercaptobenzothiazoylamine derivatives, and combinations thereof. For example, the reaction mixture may comprise> 3 wt% to <5 wt% zinc oxide and optionally> 0.5 wt% to <1 wt% tetramethylthiuramidisulfide. Such catalysts are particularly suitable for the process according to the invention.

In order to reduce the reaction rate or terminate a reaction phase with, for example, by the catalyst, increased reaction rate, at least one vulcanization inhibitor may be added.

Within the scope of a further embodiment, the reaction is therefore carried out, at least temporarily, in the presence of a vulcanization inhibitor. Through the use and duration of the use of the catalyst, in particular of the vulcanization catalyst or vulcanization accelerator and / or vulcanization inhibitor, the properties of the polyacrylonitrile-sulfur composite material can be adjusted in a targeted manner. Vulcanization inhibitors suitable for this purpose are likewise known from the technical field of rubber vulcanization. For example, N- (cyclohexylthio) phthalamide may be used as

Vulkanisationsinhibitor be used.

In the context of a further embodiment, elemental sulfur, for example sublimed elemental sulfur, is used. Elemental sulfur, in particular sublimated elemental sulfur, is advantageously inexpensive and comparatively easy to handle. In principle, however, it is also possible to use sulfur compounds, especially those which react with the cyclized polyacrylonitrile to form a covalent sulfur-carbon bond.

In particular, the sulfur can be used in excess.

Within the scope of a further embodiment, the weight ratio of sulfur to cyclized polyacrylonitrile is> 1: 1, in particular> 1.5: 1, for example> 2: 1, for example> 3: 1, and / or <20: 1, in particular <15: 1 or <10: 1, for example <5: 1 or <3: 1 or <2.5: 1 or <2: 1. These proportions They have proved to be suitable for carrying out the process according to the invention.

In a further embodiment, the reaction is carried out temporarily or completely at a temperature in a range of> 120 ° C to

<380 ° C, in particular from> 150 ° C to <350 ° C, for example from> 180 ° C to <330 ° C.

In the context of a further embodiment, a first temperature is first during the reaction, for example in a range of> 250 ° C to

<600 ° C, in particular from> 300 ° C to <500 ° C, for example from> 330 ° C to <450 ° C, and then a second temperature which is lower than the first temperature, for example in a range of> 120 ° C to <250 ° C, in particular from> 150 ° C to <250 ° C, for example from> 180 ° C to <200 ° C, adjusted. In this case, the phase within which the second temperature is adjusted, in particular, be longer than the phase in which the first temperature is set. By the first temperature phase, a cyclization of the polyacrylonitrile can be effected. During the second temperature phase, essentially the formation of covalent sulfur-carbon bonds can take place. As a result of the fact that a lower temperature is set in this case, as already explained, longer polysulfide chains can be linked to the cyclized polyacrylonitrile skeleton.

Preferably, the reaction takes place at a temperature of <300 ° C.

The reaction can be carried out temporarily or completely in an inert gas atmosphere, for example in an argon or nitrogen atmosphere.

Preferably, the reaction is carried out in less than 12 hours, in particular less than 8 hours, for example 5 hours to 7 hours, for example in about 6 hours.

Within the scope of an embodiment, the method further comprises the method step:

Removing, for example, extracting, excess or unbound sulfur. When using the polyacrylonitrile-sulfur composite material as the cathode material of an alkali-sulfur cell, unbound or elemental sulfur can react with the reduction with some electrolyte systems, which is why the choice of the electrolyte system is limited in the presence of unbound or elemental sulfur. By removing excess or unbound sulfur, further or different electrolyte systems can advantageously be used and / or properties of the alkali-sulfur cell, in particular the cycle stability, can be improved.

Optionally, the catalyst and optionally the inhibitor are also partially or completely removed in the same removal step or in a further removal step. In particular, elemental sulfur can be carried out by means of a Soxhlet extraction, in particular with an apolar solvent or solvent mixture, for example toluene.

However, it is also possible to leave the unreacted or excess sulfur in the reaction mixture.

Thus, when the reaction mixture is used as the cathode material for an alkali-sulfur cell, in particular a lithium-sulfur cell, an even higher voltage and capacity of the cell can advantageously be achieved.

This is due to the fact that the sulfur utilization can be improved by the excess or unreacted or unbound, in particular elemental, sulfur, in particular in combination with the polyacrylonitrile-sulfur composite material according to the invention. On the one hand, the polyacrylonitrile-sulfur composite material offers a conductive surface that can be used to reduce elemental sulfur. On the other hand, the polyacrylonitrile-sulfur composite material can inhibit a migration of polysulfides formed during a reduction of the elemental sulfur, for example into the anode region, by virtue of the covalently bonded sulfur of the polyacrylonitrile

Sulfur composite reacts with the polysulfides and these covalently binds. In this case, the polysulfide anions can open sulfur bridges in the polyacrylonitrile-sulfur composite material, wherein, for example, in each case two polysulfide monoanions are formed which are covalently bound to the cyclized polyacrylonitrile skeleton at one chain end. In the following reduction, such polysulfide chains can be built up successively. Since these polysulfide chains are covalently bonded to the cyclized polyacrylonitrile skeleton, they can no longer be dissolved by the electrolyte. Thus, in this way advantageously the sulfur utilization and thus the voltage and capacity increased.

In principle, the reaction can be a one-step synthesis, for example analogous to that described by Wang et al. and Yu et al. act.

However, a two-step synthesis is also possible.

For example, the method may include the method steps:

a) reacting polyacrylonitrile to cyclized polyacrylonitrile,

b) reacting the cyclized polyacrylonitrile with sulfur to form a polyacrylonitrile triisocyanate material,

include.

In process step a), for example, an electrically conductive base in the form of the electrically conductive, cyclized polyacrylonitrile (cPAN) can be formed first of all. In process step b), the reaction with the electrochemically active sulfur can then take place, in particular wherein it is covalently bonded to the electrically conductive skeleton of cyclized polyacrylonitrile to form a polyacrylonitrile-sulfur composite material (ScPAN).

By separating into two partial reactions, the reaction conditions can advantageously be optimized for the respective reaction. Process step a) here resembles a dehydrogenation reaction known from carbon fiber production, process step b) being similar to a reaction from another entirely different technical field, namely the vulcanization reaction of rubber. This has the advantage that it can be made possible the production of a polyacrylonitrile-sulfur composite material with a defined structure.

In particular, such a produced polyacrylonitrile-sulfur composite material - in contrast to those according to Yu et al. For example, the proportion of sulfur atoms bound in a thioamido unit may be referred to as having less or essentially no thioamide unit (S = CR (NR'R "), in particular S = CR (NHR ')) on the total number of sulfur atoms in the polyacrylonitrile-sulfur composite, while <25 atomic percent, in particular

<20 atomic percent or <15 atomic percent, for example, <10 atomic percent. In thioamide units, the sulfur already has an oxidation number of -2 and, when used in a cathode of an alkali-sulfur cell, in particular a lithium-sulfur cell, theoretically can not be further reduced. The sulfur of thioamide units thus reduces the theoretical sulfur utilization of the cathode material. By virtue of the fact that the formation of thioamide units can be reduced or even prevented by the process according to the invention, the polyacrylonitrile-sulfur composite material produced by the process according to the invention advantageously has a better utilization of sulfur.

Process step a) can be carried out in particular in an oxygen-containing atmosphere, for example an air or oxygen atmosphere. In this case, process step a), for example, at a temperature in a range of> 150 ° C to <500 ° C, in particular from> 150 ° C to <330 ° C or <300 ° C or <280 ° C, for example of> 230 ° C to <270 ° C, take place. Advantageously, the reaction time of process step a) can be less than 3 h, in particular less than 2 h, for example less than 1 h. In particular, process step a) can take place in the presence of a cyclization catalyst. As cyclization catalysts known catalysts can be used, for example, from the production of carbon fiber. By adding a cyclization catalyst, advantageously the reaction temperature and / or the reaction time in process step a) can be reduced. Preferably, the reaction mixture is mixed occasionally or continuously in process step a). In process step b), it is possible in particular to use a previously explained vulcanization catalyst or vulcanization accelerator.

Process step b) can be carried out in particular in an inert gas atmosphere, for example in an argon or nitrogen atmosphere. Advantageously, the reaction time of process step b) may be less than 8 hours, for example 1 hour to 7 hours, for example less than 3 hours.

Another object of the present invention is a polyacrylonitrile-sulfur composite material, for example, for use as a cathode material for an alkali-sulfur cell, in particular for a lithium-sulfur cell. In particular, the inventive polyacrylonitrile-sulfur composite material can be produced by a method according to the invention. As already explained, polysulfide chains having a chain length of> 3 sulfur atoms, in particular> 4 or> 5 or> 6 or> 7 or> 8 or> 9 or> 10 sulfur atoms, may be covalently bonded to the polyacrylonitrile skeleton of the polyacrylonitrile skeleton by the process according to the invention. Sulfur composite material are bound.

Within the scope of a further embodiment, polysulfide chains having a chain length of> 3 sulfur atoms, in particular> 4 or> 5 or> 6 or> 7 or> 8 or> 9 or> 10 sulfur atoms, are therefore covalent in the polyacrylonitrile-sulfur composite material according to the invention bonded to one or the polyacrylonitrile skeleton of the polyacrylonitrile-sulfur composite material. Thus, advantageously, a particularly high covalently bound sulfur content and thus a high capacity and energy density of the alkali-sulfur cell can be achieved. In this case, at least a part of the sulfur atoms, for example in the form of

Polysulfide chains, intramolecularly on one or both sides with a cyclized polyacrylonitrile strand, in particular with formation of an annelated at the cyclized polyacrylonitrile strand S-heterocycle, and / or on both sides intermolecularly covalently bonded with two cyclized polyacrylonitrile strands, in particular forming a bridge, especially Polysulfidbrücke, between the cyclized polyacrylonitrile strands be. The sulfur atoms can thereby probably directly by covalent sulfur-carbon bonds, as well as indirectly by one or more covalent sulfur-sulfur bonds, in particular polysulfide chains, and one or more sulfur-carbon bonds to the cyclized polyacrylonitrile skeleton.

A further subject of the present invention is a cathode material for an alkali-sulfur cell, in particular for a lithium-sulfur cell, which surrounds a polyacrylonitrile-sulfur composite material according to the invention.

Furthermore, the cathode material may comprise at least one electrically conductive additive, in particular selected from the group consisting of carbon black, graphite, carbon fibers, carbon nanotubes and mixtures thereof.

In addition, the cathode material may further comprise at least one binder, for example polyvinylidene fluoride (PVDF) and / or polytetrafluoroethylene (PTFE).

For example, the cathode material

> 10% by weight to <95% by weight, for example> 70% by weight to <85% by weight, of polyacrylonitrile-sulfur composite material,

> 0, 1 wt .-% to <30 wt .-%, for example> 5 wt .-% to <20 wt .-%, of electrically conductive additives, and

25 -> 0, 1 wt .-% to <30 wt .-%, for example> 5 wt .-% to <20 wt .-%, of binders

include.

The sum of the percentages by weight of polyacrylonitrile-sulfur

30 Composite material, electrically conductive additives and binders in particular total of 100 percent by weight result.

Within the scope of an embodiment, the cathode material may further comprise additional elemental sulfur. As already related to the

35 explains excess or unreacted sulfur can Advantageously, the presence of unbound elemental sulfur increases the voltage and capacity of the cell.

For example, the cathode material can thereby

> 10% by weight to <90% by weight, for example> 10% by weight to <30% by weight, of polyacrylonitrile-sulfur composite material,

> 5% by weight to <60% by weight, for example> 30% by weight to <60% by weight, of elemental sulfur,

> 0, 1 wt .-% to <30 wt .-%, for example> 5 wt .-% to <20 wt .-%, of binders

include.

In this case, the sum of the percentages by weight of polyacrylonitrile-sulfur composite material, elemental sulfur, electrically conductive additives and binders can yield in particular a total of 100 percent by weight.

Furthermore, the cathode material, in particular in the form of a cathode material slip for producing a cathode, may comprise at least one solvent, for example N-methyl-2-pyrrolidone. Such a cathode material slurry can be applied, for example by knife coating, to a carrier material, for example an aluminum plate or foil.

The solvents of the cathode material slip are preferably removed again after the application of the cathode material slip and before the assembly of the lithium sulfur cell, preferably completely, in particular by a drying process.

The cathode material-carrier material arrangement can then be divided into several cathode material-carrier material units, for example by punching or cutting.

The cathode material-carrier material arrangement or units can be installed with a lithium metal anode, for example in the form of a plate or foil of metallic lithium, to form a lithium-sulfur cell. In this case, in particular, an electrolyte can be added. The electrolyte may comprise, for example, at least one electrolyte solvent and at least one conductive salt. For example, the electrolyte solvent may be selected from the group consisting of carbonic acid esters, especially cyclic or acyclic carbonates, lactones, ethers, especially cyclic or acyclic ethers, and combinations thereof. For example, the electrolyte solvent may include diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), or a combination thereof consist of it. The salt can for example be selected from the group consisting of Lithiumhe- hexafluorophosphate (LiPF _6), lithium bis (trifluormethylsulphonyl) imide (LiTFSI), lithium thiumtetrafluoroborat (LiBF _4), lithium trifluoromethanesulfonate (LiCF ₃ S0 _3), Li thiumchlorat (LiCI0 ₄ ), Lithium bis (oxalato) borate (LiBOB), lithium fluoride (LiF), lithium nitrate (LiNO ₃ ), lithium hexafluoroarsenate (LiAsF ₆ ), and combinations thereof.

Inasmuch as the cathode material comprises little or no untethered or elemental sulfur, the electrolyte solvent is preferably selected from the group consisting of cyclic carbonates, acyclic carbonates, and combinations thereof. Lithium hexafluorophosphate (LiPF ₆ ) is preferably used as conductive salt.

Insofar as the cathode material comprises unbound or elemental sulfur, in particular additional elemental sulfur, the electrolyte solvent is preferably selected from the group consisting of cyclic ethers, acyclic ethers and combinations thereof. Lithium bis (trifluoromethylsulphonyl) imide (LiTFSI) is preferably used as conductive salt.

Another object of the present invention is an alkali-sulfur cell or battery, in particular lithium-sulfur cell or battery, with an alkali-containing, in particular lithium-containing, anode and a cathode, wherein the cathode comprises a cathode material according to the invention. The anode may in particular be an alkali metal anode, in particular a lithium metal anode, for example in the form of a plate or foil, for example of metallic lithium. Furthermore, the alkali-sulfur cell may comprise an electrolyte, in particular described above.

In another embodiment, the alkali-sulfur cell comprises an electrolyte of at least one electrolyte solvent and at least one conducting salt.

In the context of one embodiment of this embodiment, the electrolyte solvent is selected from the group consisting of cyclic carbonates, acyclic carbonates and combinations thereof, and / or the conductive salt lithium hexafluorophosphate (LiPF ₆ ). This embodiment has proved to be particularly advantageous insofar as the cathode material contains no unbound sulfur.

In another embodiment of this embodiment of this embodiment, the electrolyte solvent is selected from the group consisting of cyclic ethers, acyclic ethers and combinations thereof, and / or the conductive salt lithium bis (trifluoromethylsulphonyl) imide (LiTFSI). This embodiment has proven to be particularly advantageous insofar as the cathode material contains unbound sulfur.

Another object of the present invention is an energy storage, in particular mobile or stationary energy storage, which comprises an inventive alkali-sulfur cell or battery, in particular lithium-sulfur cell or battery. For example, the energy store may be an energy store for a vehicle, such as an electric or hybrid vehicle, or a power tool or device, such as a screwdriver or gardening tool, or an electronic device, such as a portable computer and / or a telecommunications device as a cellphone, PDA, or a high energy storage system for a home or facility. Since the alkali-sulfur cells according to the invention or Batteries have a very high energy density, these are particularly suitable for vehicles and stationary storage systems, such as high energy storage systems for houses or facilities.

Examples

Further advantages and advantageous embodiments of the objects according to the invention are illustrated by the examples. It should be noted that the examples are only descriptive and are not intended to limit the invention in any way.

Examples 1

Sulfur and polyacrylonitrile were mixed in a weight ratio of 3: 1 and reacted in an argon atmosphere at 300 ° C to form a polyacrylonitrile-sulfur composite.

Example 2:

Sulfur and polyacrylonitrile were mixed in a weight ratio of 3: 1. To this was added 4% by weight of zinc oxide (ZnO). The mixture was reacted by heating for six hours at 250 ° C to a polyacrylonitrile-sulfur composite.

Example 3:

Sulfur and polyacrylonitrile were mixed in a weight ratio of 3: 1. To this was added 4% by weight of zinc oxide (ZnO) and 0.75% by weight of tetramethylthiuram disulfide. The mixture was reacted by heating for 6 hours at 250 ° C to a polyacrylonitrile-sulfur composite. Example 4:

Sulfur and polyacrylonitrile were mixed in a weight ratio of 3: 1. To this was added 4% by weight of zinc oxide (ZnO). The mixture was first heated to 330 ° C for 30 minutes and then to 200 ° C for 5.5 hours, converting to a polyacrylonitrile-sulfur composite.

Example 5:

Sulfur and polyacrylonitrile were mixed in a weight ratio of 3: 1. To this was added 4% by weight of zinc oxide (ZnO) and 0.75% by weight of tetramethylthiuram disulfide. The mixture was first heated to 330 ° C for 30 minutes and then to 200 ° C for 5.5 hours, converting to a polyacrylonitrile-sulfur composite.

Example 6:

Sulfur and polyacrylonitrile were mixed in a weight ratio of 3: 1 and reacted in an argon atmosphere at 300 ° C to form a polyacrylonitrile-sulfur composite. The product obtained was mixed in a weight ratio of 1: 2 with sulfur and 4 wt .-% zinc oxide (ZnO). The mixture was converted to a polyacrylonitrile-sulfur composite by heating for six hours at 150 ° C.

Example 7:

Sulfur and polyacrylonitrile were mixed in a weight ratio of 3: 1 and reacted in an argon atmosphere at 300 ° C to form a polyacrylonitrile-sulfur composite. The product obtained in a weight ratio of 1: 2 with sulfur and 4 wt .-% zinc oxide (ZnO) and

0.75 wt .-% Tetramethylthiuramdisulfid mixed. The mixture was passed through heating for six hours at 150 ° C to a polyacrylonitrile-sulfur composite.

The reaction products of Examples 1 to 7 were freed from excess or non-covalently bound sulfur by Soxhiet extraction with toluene. The elemental analysis showed that the purified products according to Example 2 to 7 had a higher sulfur content than the product according to Example 1.

Claims

A process for producing a polyacrylonitrile-sulfur composite material, wherein polyacrylonitrile is reacted with sulfur at least temporarily in the presence of a catalyst to form a polyacrylonitrile-sulfur composite material.

The method of claim 1, wherein the reaction is carried out at least temporarily in the presence of a vulcanization catalyst or vulcanization accelerator.

The method of claim 2, wherein the vulcanization catalyst comprises at least one sulfidic radical initiator.

A process according to claim 2 or 3, wherein the vulcanization catalyst comprises at least one sulfidic radical initiator selected from the group consisting of sulfidic metal complexes, for example obtainable by reaction of zinc oxide and tetramethylthiuramidisulfide or N, N-dimethylthiocarbamate, sulfenamides, for example 2- Mercaptobenzothiazoylamine derivatives, and combinations thereof.

Method according to one of claims 1 to 4, wherein the reaction is carried out at least temporarily in the presence of a vulcanization inhibitor.

Method according to one of claims 1 to 5, wherein elemental sulfur, for example, sublimated elemental sulfur, is used.

7. The method according to any one of claims 1 to 6, wherein the weight ratio of sulfur to cyclized polyacrylonitrile> 1: 1, in particular> 1, 5: 1, at- for example> 2: 1, for example> 3: 1, and / or <20: 1, in particular <15: 1 or <10: 1, for example <3: 1 or <2.5: 1 or <2: 1, is.

Method according to one of claims 1 to 7, wherein the reaction temporarily or completely at a temperature in a range of> 120 ° C to <380 ° C, in particular from> 150 ° C to <350 ° C, for example

> 180 ° C to <330 ° C, take place.

Method according to one of claims 1 to 8, wherein during the reaction first a first temperature, for example in a range of

> 250 ° C to <600 ° C, in particular from> 300 ° C to <500 ° C, for example from> 330 ° C to <450 ° C, and then a second temperature which is lower than the first temperature, for example in a range of

> 120 ° C to <250 ° C, in particular from> 150 ° C to <250 ° C, for example from> 180 ° C to <200 ° C, is set.

Polyacrylonitrile-sulfur composite material, for example for use as cathode material for an alkali-sulfur cell, in particular for a lithium-sulfur cell, produced by a method according to one of claims 1 to 9.

A polyacrylonitrile-sulfur composite material, for example, for use as a cathode material for an alkali-sulfur cell, in particular for a lithium-sulfur cell, wherein polysulfide chains having a chain length of

> 3 sulfur atoms, in particular> 4 or> 5 or> 6 or> 7 or> 8 or> 9 or> 10 sulfur atoms, are covalently bonded to the polyacrylonitrile skeleton of the polyacrylonitrile-sulfur composite material.

Cathode material for an alkali-sulfur cell, in particular for a lithium-sulfur cell, comprising a polyacrylonitrile-sulfur composite material according to claim 10 or 11.

Alkali-sulfur cell or battery, in particular a lithium-sulfur cell or battery, having an alkali-containing, in particular lithium-containing, anode and a cathode, wherein the cathode comprises a cathode material according to claim 12. An alkali-sulfur cell according to claim 13, wherein the alkali-sulfur cell comprises an electrolyte of at least one electrolyte solvent and at least one conducting salt,

wherein the electrolyte solvent is selected from the group consisting of cyclic carbonates, acyclic carbonates and combinations thereof, and / or the conductive salt is lithium hexafluorophosphate, or

wherein the electrolyte solvent is selected from the group consisting of cyclic ethers, acyclic ethers and combinations thereof, and / or the conductive salt is lithium bis (trifluoromethylsulphonyl) imide.

15. Energy storage, in particular mobile or stationary energy storage, for example for a vehicle, for example an electric or hybrid vehicle, a power tool or device, such as a screwdriver or gardening tool, an electronic device, such as a portable computer and / or a Telecommunication device, such as a mobile telephone, PDA, or a high energy storage system for a home or a facility, comprising an alkali-sulfur cell or battery, in particular lithium-sulfur cell or battery, according to claim 13 or 14.