ALKALI AND/OR ALKALINE EARTH ION- SULFUR BATTERY

Abstract

An alkali- and/or alkaline earth-ion sulfur battery having at least one cathode containing a cathode current collector foil, optionally a conductive adhesive interlayer, a primary cathode mass layer containing a conductive dimensionally stable porous host structure, sulfur as an active material, preferably at least 20% of the sulfur present is monoclinic sulfur allotrope, and optionally conductive additives, binders and pore-forming additives; a secondary cathode mass layer containing sulfur and alkali-ion- and/or alkaline earth-ion-intercalating material, optionally a layer containing graphene oxide and/or reduced graphene oxide, heteroatom Group VIIa and/or Group Va elements co-doped graphene, and a Group VIIa and/or Group Va heteroatom-containing polymer; at least one anode and at least one separator. The resulting cells offer a wide range of economic and ecological advantages over the currently available cells, as well as allowing versatility of materials and production processes.

Claims

1: An alkali- and/or alkaline earth-ion-sulfur battery comprising at least one cathode containing: a cathode current collector foil; optionally a conductive adhesive interlayer placed between the cathode current collector foil and a primary cathode mass layer; a primary cathode mass layer, containing a conductive dimensionally stable porous host structure, sulfur as an active material, wherein preferably at least 20% of the sulfur present is monoclinic sulfur allotrope, and optionally conductive additives, binders and pore-forming additives; a secondary cathode mass layer, containing sulfur and alkali-ion- and/or alkaline earth-ion-intercalating material; optionally a layer containing graphene oxide and/or reduced graphene oxide, heteroatom Group VIIa and/or Group Va elements co-doped graphene, and a Group VIIa and/or Group Va heteroatom-containing polymer; at least one anode and at least one separator.

2: The alkali- and/or alkaline earth-ion-sulfur battery according to claim 1, wherein the at least one anode contains an anode current collector foil; optionally a conductive adhesive interlayer placed between the anode current collector foil and a primary anode mass layer; a primary anode mass layer, containing a conductive dimensionally stable porous host structure, a metal capable of forming intermetallic alloys with an alkali metal and/or an alkaline earth metal, and optionally conductive additives, binders and pore-forming additives; optionally a secondary anode mass layer, containing graphene oxide and/or reduced graphene oxide, heteroatom Group VIa elements co-doped graphene, and a polymer, preferably an elastomeric polymer; an alkali metal and/or an alkaline earth metal, preferably in the form of foil or powder.

3: The battery according to claim 1, wherein the dimensionally stable conductive porous host structure is selected from carbon foam, flexible porous carbon foam, carbonized organic and/or polymeric foam, electroless plated organic and/or polymeric foam, graphene coated carbon foam; MnO.sub.2 foam, and MnO.sub.2-coated carbon foam.

4: The battery according to claim 1, wherein the conductive porous host structure is self-supporting.

5: The battery according to claim 1, wherein sulfur is present in the cathode in at least one of the following forms: soft-case form configured to reversibly change its volume during charging and discharging; hard-case form comprising sulfur infiltrated into a second porous host material wherein the host material is configured to maintain its external dimensions together regardless of the change of volume of the sulfur during charging and discharging.

6: The battery according to claim 5, wherein sulfur in the cathode is present as a mixture of the soft-case form of sulfur in the amount of 50 to 90 wt. % of sulfur, relative to the total amount of sulfur, and of the hard-case form in the amount of 50 to 10 wt. % of sulfur, relative to the total amount of sulfur, and the separator optionally contains about up to 10 wt. % of sulfur.

7: The battery according to claim 1, wherein 60 to 100 wt. % of the sulfur present in the cathode is monoclinic sulfur allotrope.

8: The battery according to claim 1, wherein the binders are present in the primary mass layer, said binders including binary or ternary immiscible binder systems which are used in amounts from 3 to 20 wt. %, relative to the amount of the primary mass layer, wherein in the binary system, a first solid conductive binder insoluble in a solvent used for the preparation of the electrode and a second conductive binder soluble in the solvent used for the preparation of the electrode are used; in the ternary system, a first solid conductive binder insoluble in a solvent used for the preparation of the electrode, a second conductive binder soluble in the solvent used for the preparation of the electrode, and a third polymeric binder as a surfactant are used.

9: The battery according to claim 2, wherein the primary anode mass layer contains a conductive porous host structure coated by a metal capable of forming intermetallic alloys with alkali metal and/or alkaline earth metal, and said coated porous host structure hosts metallic-decorated carbon nanoparticles and/or metallic-decorated graphene and/or carbon-decorated metallic nanoparticles, nanorods, nanotubes and/or metallic nanoparticles, nanorods, nanotubes.

10: The battery according to claim 9, wherein the metal is Sn, optionally in combination with Cu, Ag, Sb.

11: The battery according to claim 1, wherein the electrode materials selected from sulfur, alkali metal, alkaline earth metal, conductive additives, pore-forming additives, binders, graphene oxide, graphene, polymers, comprise a combination of at least two different sizes of materials wherein the ratio of the sizes is from 3:1 to 18:1 and/or a combination of at least two different shapes selected from zero-dimensional shape, one-dimensional shapes, two-dimensional shapes and three-dimensional shapes.

12: The battery according to claim 1, wherein the layer containing graphene oxide and/or reduced graphene oxide, heteroatom co-doped graphene, and polymer contains regions containing more than 50% of a mixture of graphene oxide and/or reduced graphene oxide and polymer, and regions containing more than 50% of heteroatom co-doped graphene.

13: The battery according to claim 1, wherein the separator is selected from a spray deposited separator on the cathode, said separator is preferably soaked with liquid electrolyte and/or ionic liquid and/or said separator preferably contains sulfur as pore forming additive, or a separator inserted between the two electrodes, which is preferably selected from a solid separator soaked with liquid electrolyte and/or ionic liquid, a gel separator, a liquid electrolyte, ionic liquid, and a combination thereof.

14: A method for production of the cathode for the battery according to claim 1, comprising the following steps: a) milling and homogenizing sulfur, and optionally conductive additives, binders, and optionally pore-forming additives to form a soft-case sulfur composite; and/or b) milling and homogenizing sulfur and infiltrating it into a second porous host material, preferably by dip coating, spray coating or vacuum forced infiltration, to form hard-case sulfur composite, optionally adding conductive additives, binders and pore-forming additives, c) depositing alkali- and/or alkaline earth-ion-intercalating material on the top of a conductive porous host structure, preferably structure with a working potential window under 4.2 V, d) infiltrating the material prepared in step a) or b) or their mixture into the dimensionally stable conductive porous host structure from step c), e) attaching the resulting dimensionally stable conductive porous host structure with embedded sulfur, conductive additives, binders, alkali- and/or alkaline earth-ion-intercalating material, optionally pore-forming additives, to a current collector foil, preferably by means of a conductive adhesive, f) heating the resulting electrode precursor to the temperature from 95 to 135° C. for at least 5 minutes, and then maintaining it at 90 to 130° C. and subjecting it to calendering, then cooling it to 20 to 70° C. for at least 5 minutes to allow for re-crystallization and dissipation of internal material stress resulting from phase conversion, g) optionally applying graphene oxide and/or reduced graphene oxide/polymer mixture and subject it to reduction procedure, preferably using pulse light flash drying and/or reducing procedure, forming heteroatom co-doped graphene surface in the regions directly subjected to the reduction.

15: The method according to claim 14, wherein the hard-case sulfur is prepared by dry pre-mixing of sulfur with the second porous host material, heating this pre-mixed material with additional sulfur under inert atmosphere at 300 to 380° C., draining out non-encapsulated melted sulfur, cooling the mixture to room temperature and then optionally dry milling and/or impact, e.g. jet, milling the resulting material with polymer binders and conductive additives.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0073] FIGS. 1A and 1B show the result of electrochemical characterization of a cell produced by the process of Example 1 by galvanostatic cycling (comparative example).

[0074] FIGS. 2A and 2B show the result of electrochemical characterization of a cell produced by the process of Example 2 by galvanostatic cycling.

[0075] FIGS. 3A and 3B show the result of electrochemical characterization of a cell produced by the process of Example 3 by galvanostatic cycling.

[0076] FIG. 4 shows the result of electrochemical characterization of a cell produced by the process of Example 4 by galvanostatic cycling.

[0077] FIG. 5 shows the result of electrochemical characterization of a cell produced by the process of Example 5 by galvanostatic cycling.

EXAMPLES OF CARRYING OUT THE INVENTION

Example 1 (Comparative Example): Standard Li—S Cell

[0078] Example 1 describes a basic LiS cell where cathode is applied in the form of slurry coating with standard NMP/PVDF binder/solvent combination and sulfur present as orthorhombic allotrope. FIGS. 1A and 1B describe gravimetric capacity as mAh/g of sulfur after 1, 5, 20 and 50 cycles (charge/discharge curves). FIGS. 2A and 2B describe area capacity of cathode as mAh/cm.sup.2.

[0079] Experimental: The standard Li—S cathode was composed of 60% Sulphur (99.5%—Sigma Aldrich), 30% carbon Super P and 10% binder PVDF (Polyvinylidene difluoride—Sigma Aldrich). Sulphur was mixed with carbon Super P in a planetary mill (FRITSCH Pulverisette 7—premium line) in a ZrO.sub.2 bowl with 10 mm diameter balls. The weight ratio of mixed material and the balls was 1:20. Milling was done in ethyl alcohol for 30 min at 500 rpm. The sample was dried in an oven (BMT venticell) for 12 hours at 30° C. after milling. Then it was again milled in a ball mill (FRITSCH PULVERISETTE 0) for 10 minutes. The next step was dissolving 0.04 g of PVDF in 2.6 ml of NMP (N-methylpyrrolidone—Sigma Aldrich) and 0.36 g of previously created mixture of S and Super P was added subsequently. This was mixed for 24 hours by a magnetic stirrer (HEIDOLPH MR Hei-Standard). The material was then deposited on an Al foil using a coating bar and dried for 12 hours at 50° C. An electrode of 18 mm diameter was cut out of the foil after drying. This electrode was then stored in vacuum at room temperature for 12 hours. After this, it was dried at 60° C. in argon atmosphere in a glove box (Jacomex). An electrochemical cell El-Cell ECC-STD was then assembled in the glove box. A pure lithium disk was used as an anode and 0.25 M LiNO.sub.3+0.7 M LiTFSI in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) 2:1 (v:v) soaked in glass fiber separator (Whatman glass microfiber) was used as electrolyte. The assembled cell was connected to the VMP3 (Bio-logic) potentiostat and electrochemically characterized by galvanostatic cycling.

Example 2: Li—S Cell Containing the Cathode of the Invention

[0080] Example 2 describes self supported cathode structure where sulfur is present as monoclinic allotrope as both soft case and hard case form and where electrode mass is made independently from current collector foil in such a way that 3D carbonized skeleton is infiltrated by electrode materials and, after drying, it is placed onto Al current foil which was prior primed with conductive adhesives.

[0081] Experimental: Melamine foam as self supporting structure: was sintered at 800° C. for 30 min in nitrogen atmosphere. After sintering, foam was pre-treated with hydrochloric acid, neutralized and washed with ultra-pure water and then cleaned in ultrasonic bath (water/ethanol) and dried for 10 h in air. Meanwhile, mixture of KJ Ketjenblack EC-600JD (AkzoNobel) carbon and gelatine is dissolved in water at 60° C. Electrode prepared by sintered melamine foam was then dip coated by this gelatine KJ black mixture and dried at 105° C. for 1 hour. After drying, carbonized coated melamine electrode was again sintered 820° C. for 60 min. Foam was then cut to thin slice approximately 500 μm thick and finally electrodes with diameter of 18 mm were cut out. This electrode was infiltrated by slurry and dried at 50° C. for 12 hours. The composition of slurry: 75.0% Sulphur (99.5%—Sigma Aldrich), 2% NaCMC, 7% BP, 1% CNT, 5% KJ black and 10% of the mixture of binders PVP (Polyvinylpyrrolidone—Sigma Aldrich) and PEI (Poly(ethyleneimine) hyperbranched—Sigma Aldrich) in the ratio of 5:1. The first step was milling the mixture of Sulphur, Black Pearl BP2000 carbon (CABOT corporation BLACK PEARLS®), CNT and NaCMC in a planetary mill (FRITSCH Pulverisette 7—premium line) in ethyl alcohol for 30 min at 500 rpm. The sample was dried in an oven (BMT venticell) for 12 hours at 30° C. after milling. Then it was again milled in a ball mill (FRITSCH Pulverisette 0) for 10 minutes. Mixing of the electrode paste was done in three stages in the planetary mill KJ black infiltrated by sulfur, BP carbon and PEI were mixed in a given ratio in the first step. The solvent was a mixture of isopropyl alcohol and water. It was mixed for 15 minutes. KJ black was infiltrated by sulfur before slurry preparation. Infiltration was done in heated glass tube connected to the heating stage with sulfur. Sulfur was heated to 360° C. for 5 hours and evaporated. Evaporated sulfur was then infiltrated into KJ black in the glass tube. A mixture of S+Black Pearls+CNT+NaCMC and PVP was then created in the planetary mill A mixture of isopropyl alcohol and water was used as a solvent again. Mixing time was 15 minutes. Both these mixtures were then mixed together in the planetary mill. It was mixed for 30 minutes. Conductive adhesive slurry was prepared using magnetic stirrer; it contained P84 (polyimide HP Polymer GmbH) binder and carbon Super P in NMP solvent. Mixing time was 24 hours. The weight ratio between P84 binder and Super P was (90:10). This slurry was then coated on Al foil by 24 μm coating bar and after drying at 50° C. for 12 hours. A self supporting cathode was placed on primed Al foil and secured on place by adhesive primed Al foil. The final electrode (ø15 mm) was cut out from this electrode composite. This electrode was then stored in vacuum at room temperature for 12 hours. After this, it was dried at 60° C. in argon atmosphere in the Jacomex glove box. The electrode was subsequently dried again at 105° C. for 12 hours in argon atmosphere. After that, an electrochemical cell El-Cell ECC-STD was assembled in the glove box. A pure lithium disk was used as an anode and 0.25M LiNO.sub.3+0.7M LiTFSI in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) 2:1 (v:v) soaked in glass fiber separator was used as electrolyte. The assembled cell was connected to the VMP3 (Bio-logic) potentiostat and electrochemically characterized by galvanostatic cycling.

Example 3: Li—S Cell Containing the Cathode and the Anode of the Invention

[0082] Example 3 describes self supported cathode structure presented in Example 2 in combination with a dimensionally stable anode where a 3D current collector was used, which serves as a matrix for a lithium layer.

[0083] Experimental: Preparation process of the self supporting cathode used in this example was described in Example 2. Dimensionally stable lithium metal anode was prepared from carbonized melamine foam as a template agent which was sintered and cleaned as in the example 2. Meanwhile a mixture of SuperP and gelatine was dissolved in 60° C. water and it was then dip coated into carbonized melamine foam (3× with 15 min forced air drying intervals between steps). Finally, the dip coated anode was dried at 105° C. for 1 hour and subsequently sintered again at 900° C. for 60 min. A layer of metallic tin was sputtered onto carbonized foam/Super P carbon black anode by magnetron PVD method from one side and non-conductive Al.sub.2O.sub.3 layer from opposite side. The dimensionally stable anode is made by placing foam with Sn coated side onto the adhesive prime-coated Cu current collector foil while the Al.sub.2O.sub.3 coated side is on top. The electrode was then cut to thin slices approximately 300 μm thick and finally electrodes with diameter of 18 mm are made. After drying at 50° C. for 12 hours, the electrode was inserted into the electrochemical test cell El-Cell ECC-STD inside the glove box. A pure lithium disk was used as a counter electrode and a mixture of 1M LiPF.sub.6 in ethylene carbonate (EC) and dimethyl carbonate (DMC) 1:1 (v:v) soaked in glass fiber separator was used as electrolyte. Lithium was subsequently deposited on the tin layer on the surface of porous electrode at the potential of 0 V. The cell was then opened in the glove box and the lithium coated porous electrode was inserted into another electrochemical test cell El-Cell ECC-STD. The self supported cathode structure presented in example 2 was used as a cathode and a mixture of 0.25M LiNO.sub.3+0.7M LiTFSI in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) 2:1 (v:v) soaked in a glass fiber separator was used as electrolyte. The assembled cell was connected to the VMP3 (Bio-logic) potentiostat and electrochemically characterized by galvanostatic cycling.

Example 4: Mg—S Cell Containing the Cathode of the Invention

[0084] Example 4 describes self supported cathode structure where sulfur is present as monoclinic allotrope as both soft case and hard case form and where electrode mass is made independently from current collector foil in a way that 3D carbonized skeleton is infiltrated by electrode materials and after drying it is placed onto Al current foil which was prior primed with conductive adhesives.

[0085] Experimental: Melamine foam as self supporting structure was sintered at 800° C. for 30 min in nitrogen atmosphere. After sintering, foam was pre-treated with hydrochloric acid, neutralized and washed with ultra-pure water and then cleaned and in an ultrasonic bath (water/ethanol) and dried for 10 h in air. Meanwhile, a mixture of KJ Ketjenblack EC-600JD (AkzoNobel) carbon and gelatine was dissolved in 60° C. water. The electrode prepared by sintered melamine foam was then dip coated by this gelatine KJ black mixture and dried at 105° C. for 1 hour. After drying, the carbonized coated melamine electrode was again sintered at 820° C. for 60 min. Foam was then cut to thin slices approximately 500 μm thick and finally electrodes with diameter 18 mm were cut out. This electrode was infiltrated by slurry and dried at 50° C. for 12 hours. The composition of slurry: 75.0% Sulphur (99.5%—Sigma Aldrich), 2% NaCMC, 7% BP, 1% CNT, 5% KJ black and 10% mixture of binders PVP (Polyvinylpyrrolidone—Sigma Aldrich) and PEI (Poly(ethyleneimine)—Sigma Aldrich) in the ratio of 5:1. The first step was milling the mixture of Sulphur, Black Pearl BP2000 carbon (CABOT corporation BLACK PEARLS®), CNT and NaCMC in a planetary mill (FRITSCH Pulverisette 7—premium line) in ethyl alcohol for 30 min at 500 rpm. The sample was dried in an oven (BMT venticell) for 12 hours at 30° C. after milling. Then it was again milled in a ball mill (FRITSCH Pulverisette 0) for 10 minutes. Mixing of the electrode paste was done in three stages in the planetary mill KJ black infiltrated by sulfur, BP carbon and PEI were mixed in a given ratio in the first step. The solvent was a mixture of isopropyl alcohol and water. It was mixed for 15 minutes. KJ black was infiltrated by sulfur before slurry preparation. Infiltration was done in the heated glass tube connected to heating stage with sulfur. Sulfur was heated to 360° C. for 5 hours and evaporated. Evaporated sulfur was then infiltrated into KJ black in the glass tube. A mixture of S+Black Pearls+CNT+NaCMC and PVP was then created in the planetary mill A mixture of isopropyl alcohol and water was used as a solvent again. Mixing time was 15 minutes. Both these mixtures were then mixed together in the planetary mill. It was mixed for 30 minutes. Conductive adhesive slurry was prepared in the magnetic stirrer. It contained P84 (polyimide HP Polymer GmbH) binder and carbon Super P in NMP solvent. Mixing time was 24 hours. Weight ratio between P84 binder and Super P was (90:10). This slurry was then coated on Al foil by 24 μm coating bar and after drying at 50° C. for 12 hours, a self supporting cathode was placed on primed foil Al foil and secured on place by adhesive primed Al foil. The final 015 mm electrode was cut out from this electrode composite. This electrode was then stored in vacuum at room temperature for 12 hours. After this, it was dried at 60° C. in argon atmosphere in the Jacomex glove box. The electrode was subsequently dried again at 105° C. for 12 hours in the argon atmosphere. After that, an electrochemical cell El-Cell ECC-STD was assembled in the glove box. A Mg-carbon composite pellet containing magnesium powder and Carbon black (80:20) weight ratio was used as an anode and 0.25M Mg(HMDS).sub.2 (magnesium bis(hexamethyldisilazide))+0.75M LiTFSI (lithium bis(trifluoromethane)sulfonimide) salt in DEGDME (diethylene glycol dimethyl ether) soaked in glass fiber separator was used as electrolyte. The assembled cell was connected to the VMP3 (Bio-logic) potentiostat and electrochemically characterized by galvanostatic cycling.

Example 5: Mg—S Cell Containing the Cathode and the Anode of the Invention

[0086] Example 5 describes self-supported cathode structure presented in Example 4 in combination with a dimensionally stable anode where its 3D porous and conductive structure serves as a matrix for an efficient magnesium plating-stripping process without volume change.

[0087] Experimental: Preparation process of the self-supporting cathode used in this example was described in Example 2. The dimensionally stable magnesium metal self-supporting anode was prepared from carbonized melamine foam as matrix structure which was sintered and cleaned as in example 2. Meanwhile a mixture of SuperP and gelatine was dissolved in 60° C. water and carbonized melamine foam was then dip coated into this mixture (3× with 15 min forced air drying intervals between the steps). Finally, the dip coated anode was dried at 105° C. for 1 hour and subsequently sintered again at 900° C. for 60 min. A layer of metallic tin was sputtered onto carbonized foam/Super P carbon black anode by magnetron PVD. A dimensionally stable anode is made by placing foam with the Sn coated side onto adhesive prime-coated Cu current collector foil. The electrode was then cut to thin slices approximately 300 μm thick and finally electrodes with the diameter of 18 mm were made. After drying at 50° C. for 12 hours, the electrode was inserted into the electrochemical test cell El-Cell ECC-STD inside the glove box. A pure magnesium disk was placed onto the top of dimensionally stable anode and 0.25M Mg(HMDS).sub.2 (magnesium bis(hexamethyldisilazide))+0.75M LiTFSI (lithium bis(trifluoromethane)sulfonimide) salt in DEGDME (diethylene glycol dimethyl ether) soaked in the glass fiber separator was used as electrolyte. The cell is then fully discharged—activated at low currents, preferably C/20, when the magnesium chip is fully stripped and divalent Mg.sup.2+ cations subsequently react with sulfur cathode. During the first re-charging cycle, magnesium was deposited inside the tin coated carbonized porous electrode at the potential of −1.2 V vs Mg with limited areal capacity leaving 15% porosity on anode after fully stripping the Mg chip. The assembled cell was connected to the VMP3 (Bio-logic) potentiostat and electrochemically characterized by galvanostatic cycling.