KR0137006B1 - Cell for making secondary batteries - Google Patents

Abstract

The present invention is a full solid-state lithium and sodium battery operated in an approximate temperature range (limited by melting point or electrode / electrolyte) from ambient temperature to 145 ° C. with excess energy and power density over state-of-the-art high-temperature cell systems. It is about. This preferred cell comprises a solid lithium or sodium electrode, a polymer electrolyte 15 such as polyethylene oxide doped with lithium triflate (PEO ₈ LiCF ₃ SO ₃ ), and a polymer organic sulfur electrode, (SRS) m, and a polymer electrolyte. It consists of a solid-state synthetic anode 14 comprising dispersed carbon black.

Description

[Name of invention]

Secondary Battery Manufacturing Cell

FIELD OF THE INVENTION

The present invention relates to a metal-sulfur type cell for the manufacture of secondary batteries and in particular to a cell which operates in the solid state of all components.

Secondary batteries are widely used in modern society, especially in applications where large amounts of energy are not needed. However, it is desirable to use batteries in applications that require significant power, and much effort has been made to develop batteries suitable for high power applications such as electric vehicles. Of course, such batteries are also suitable for use in low power applications such as cameras or portable recording devices.

At present, the most common secondary batteries are preferably lead-acid batteries used in automobiles. This cell has the advantage that it can be operated for many charge cycles without significant loss of performance. However, this battery has a low power to weight ratio.

Lithium batteries have been studied closely to always keep the weight ratio. Although improved, it would be desirable to be able to use it for a wider range of applications.

Typically, lithium polyethylene oxide cells have improved minimum reduction (FOM), which is about 50 to multiply the average cycle capacity by the number of cycles and divide by the excess plant lithium capacity. Typical examples of such cells are described in US Pat. No. 4,589,197, which describes lithium / polyethylene battery systems in which the electroactive material is an internal addition compound. It is also known that this type of battery can be proportionally increased in large sizes with little loss of performance.

Another lithium type cell is described in US Pat. No. 4,833,048 which uses an organic sulfur anode, which has a sulfur-sulfur bond in the charged state and decomposes in the discharged state to form an organometallic salt. This patent states that although the cells have an excellent weight ratio, the described electrodes are used in the liquid state and solvents are needed to provide the intended current transport. The present invention provides improved performance over these patented systems. In particular, the present invention provides a cell having a minimum sensitivity of about 120 with the ability to operate at room or skirmish temperatures.

Summary of the Invention

It is therefore an object of the present invention to provide a metal-sulfur type cell which has a high minimum sensitivity and operates at ambient temperature.

Another object of the present invention is to provide a cell in which all components are solid and may be reliably produced in units with reproducible performance values.

It is a further object of the present invention to provide a battery having a weight ratio far exceeding the level required for load balancing and / or electric vehicle applications.

These and other objects will become apparent upon observing the specification.

According to the present invention, a battery system composed of a composite positive electrode and a composite positive electrode system is provided. In the fully charged state, the anode comprises a one-dimensional, two-dimensional, or three-dimensional polymer electroactive component. In this one-dimensional linear form, this component can be defined as (SRS) n, where R is the organic moiety defined later, n is greater than 2, preferably greater than 20 in the charged state. . The half-cell reaction can be described as follows:

^{(SRS) n + 2n e -} = n SRS

And the whole cell reaction can be described as follows:

(SRS) n + 2nLi = nLi ₂ SRS

In the most general sense, the electroactive component of the solid-state organosulfur electrode can be represented as (RSy) n in the charged state, where y is 2 to 6, n is greater than 2, preferably greater than 20, R may include one or more oxygen, phosphorus, silicon, sulfur or nitrogen heteroatoms when R comprises one or more aromatic rings, or one or more oxygen, phosphorus, silicon bonded to the chain when R consists of aliphatic chains , One or more other aliphatic or aromatic moieties having 1 to 20 carbon atoms, which may include sulfur, nitrogen or fluorine atoms, which aliphatic groups may be linear or branched, saturated or unsaturated, and may be aliphatic chains or aromatic rings May have a substituted group, and the organosulfur anode is characterized by a number of sulfur-sulfur bonds when in a charged state, It is decomposed when it is discharged to form an organic metal salt and metal ions in the cell.

This charge / discharge process at the anode can be seen as a reversible redox polymerization reaction (or redox dimerization reaction / decomposition in the case of monomeric RSSR compounds). An example of a two-dimensional (crosslinked polymer) electrode is the following disulfide, which is polyethylene as follows:

While these polymer electrode materials carry alkali metal ions, in most cases it is necessary to include a suitable polymer electrolyte such as polyethylene oxide for rapid ion transport, as is done for electrodes based on internal addition. Or would be desirable. Furthermore, since this organosulfur electrode is not electrically conductive, it is important that a small amount of carbon black (typically 7% by weight), or the same amount of conductor particles, is dispersed in the composite electrode. The range of materials in the polymer anode is about 30-80% by weight of active organic sulfur, about 20-70% by weight polymer electrolyte, and about 1-20% by weight of conductor particles.

This preferred mixture is achieved by dissolving or dispersing (SRS) n polymer, polyethylene oxide and carbon black powder in acetonitrile and then evaporating the solvent to cast a thin (ie, 10-20 micron) film of the solid composite electrode. do. In a preferred case, this anode is a composite electrode consisting of an organosulfur redox polymer, polyethylene oxide and carbon black.

In a sufficiently charged state, the organosulfur anode is of formula (SRS) n, an important characteristic of which is that sulfur-sulfur bonds are formed during the oxidation reaction of alkali metal thio salts. Preferred electrodes are polymeric disulfides, but monomeric disulfides (RSSR) as described in US Pat. No. 4,833,048 are also believed to operate in solid state cells. In a sufficiently discharged state, the organosulfur electrode contains polythio and / or dithio anions (-SRS-) dispersed in a polymer electrolyte matrix. The final discharge product, of course, depends on the type of R group in the polymer chain and on the dimensionality of the polymer anode sufficiently oxidized.

Another advantage of the present invention lies in the ability of the solid state electrode to be reversible with various metals. Lithium has the lowest equivalent weight and corresponding weight advantage, but is more expensive than sodium. In addition, the conductivity of preferred polyether electrolytes such as polyethylene oxide is higher for sodium transport than for lithium transport. Accordingly, the internal addition type cell requires lithium as a practical material, but the cathode of the present electrode may be made of many different metals. Accordingly, mixtures comprising any alkali or alkaline earth metal or transition metal (polyether electrolytes are known to carry divalent cations such as Zn ⁺⁺ ), in particular lithium and / or sodium, are within the scope of the present invention. .

The electrolytes used in the cells of the present invention serve as separators for electrodes and as carrier media for metal ions. Thus, any solid material capable of carrying metal ions can be used. For example, sodium beta alumina is known to be usable. However, preferably this solid electrolyte separator is a suitable polymeric electrolyte such as polyether, polyimine, polythioether, polyphosphazene, polymer mixture and suitable electrolyte salts are added.

[Brief Description of Drawings]

1 is a cross-sectional view of the main parts of a cell constructed in accordance with the present invention.

Figure 2 illustrates the operation of one aspect of the present invention and shows data in graphical form compared to the data of aspects of the prior art.

Detailed Description of the Invention

The metal-sulfur type cell shown in FIG. 1 is inserted between the current collector 11 in parallel with the negative electrode 12, the current collector 13 in parallel with the positive electrode 14, and between the negative electrode 12 and the positive electrode 14. Electrolyte 15 is included. In a typical cell, all these parts would be enclosed in a suitable case of plastic or similar material (not shown), with only the current collector extending out of the enclosure. In this way, reactive metals such as sodium or lithium in the cathode are protected. Other parts of the cell can be similarly protected.

Suitable battery structures can be prepared according to known techniques for assembling cell components and cells as desired, and any known form can be made using the present invention. The exact structure will depend primarily on the intended use for the cell unit. However, it should be understood that these cell units all exist in a virtually solid state at ambient temperature and during operation.

Referring back to FIG. 1, current collectors 11 and 13 are virtually unchanged during discharge and charging of the cell and are sheets of conductive material such as stainless steel that provide current connections to the cathode and anode of the cell. The cathode 12 is preferably an alkali metal such as lithium or sodium, with sodium being more preferred than lithium. The organosulfur cathode or anode 14 is coated on the current collector 13 as described above, and the whole unit is pressed together with the electrolyte 15 inserted between the electrodes as shown.

The thickness of all cell parts in the figures is exaggerated for illustrative purposes, and all these parts are typically many thin sheets. For example, a typical lithium or sodium solid anode 12 is about 10 to 50 microns thick, a typical solid composite polymeric cathode 14 is about 50 to 100 microns thick, and a typical PEO electrolyte 15 Silver is about 10 to 100 microns thick.

Preferred electrolytes are polyalkylene oxides such as polyethylene oxide to which a plasticizing electrolyte salt such as LiN (CF ₃ SO ₂ ) 2 is added. The effect of plasticizing electrolyte salts allows the cell to operate at low temperatures by keeping the polyethers amorphous (conductive) at low temperatures.

According to the present invention, the organosulfur compound comprising the novel anode of the present invention forms a first bond with the organic moiety and, when the material is in a charged state, with the other sulfur atoms which are also bonded to the organic moiety. It is characterized by an organosulfur material having at least one sulfur atom forming a double bond. When the compound is in the discharged state, the sulfur-sulfur bond is broken down, and metal ions such as sodium form salts with the respective formed organic sulfur anions.

As such, the anode material consists of an organosulfur material comprising a basic or pivotal general formula R-S-. In the charged state, this sulfur atom (or an atom as described below) forms -S-S-R with another R-S- group of sulfur atoms to form R-S-S-R. Upon discharge, the S-S bonds decompose, and each R-S- group forms a salt with a metal ion, for example sodium, that is, R-S-Na.

The R group representing the organic moiety described below may also have sulfur atoms bonded to it by double bonds, ie R = S, as well as the sulfur atoms just described. In addition, the R group has one or more sulfur atoms bonded to it by a single bond, thereby enabling a polymerization reaction, for example in the case of -S-R-S-. Branching may occur when this R group has three or more sulfur atoms single bonded to it.

Thus, the general formula for the organosulfur material comprising the novel anode of the present invention can be represented by (R (S) y) n in the charged state, where y is 2 to 6 and n is greater than 20; R may include one or more oxygen, sulfur, phosphorus, silicon or nitrogen heteroatoms when R comprises one or more aromatic rings, and one or more oxygen, phosphorus, silicon bonded to the chain when R comprises an aliphatic chain , At least one identical or different aliphatic or aromatic organic moiety having 1 to 20 carbon atoms, which may include sulfur, nitrogen or fluorine atoms, wherein the aliphatic groups may be linear or branched, saturated or unsaturated, and aliphatic chains Or the aromatic ring may have a substituted group.

When n in formula (R (S) y) n is greater than 2, at least some organic sulfur anode materials may form sulfur and sulfur-sulfur bonds bonded to the same organic moiety and bonded to another organic moiety. Organic portions having one or more sulfur atoms present. Thus, the polymer-like material in which the length of the polymer in the charged state depends on the presence of an impurity or a chain stopper, such as a mono sulfide organic moiety, ie CH ₃ -CH ₂ -S-Na, to terminate the polymerization reaction Can be formed. For example, such a polymer may comprise a linear aliphatic chain having such a sulfur atom at each end of its chain, for example -S-CH ₂ CH ₂ -S, so that general formula (R (S) ₂ ) such as dimers, oligomers, such as _{-S-CH 2 -CH 2 -SS-} CH 2 -CH 2 -SS-CH 2 -CH 2 -S corresponding to ₃ so that they can be formed.

Similarly, this organosulfur compound may comprise a branched polysulfide material having more than two sulfur capable of forming sulfur-sulfur bonds with adjacent sulfur atoms of other organosulfur materials. For example, when each R group contains three sulfur atoms capable of forming a sulfur-sulfur bond, this general formula can be represented by (R (S) ₃ ) n.

Thus, y recognizes the presence of one or more sulfur atoms capable of forming sulfur-sulfur bonds with similar sulfur atoms on other molecules, as well as the possibility of the presence of double bonded sulfur atoms on the R group, giving a value of 2 to 6 in the general formula. Given by In this general formula, the value of n is preferably greater than 20, but since the possibility of a lower stage of the polymerization reaction, for example, ring formation, is acknowledged, and the solid state battery has the advantage that the organosulfur compound does not polymerize. It is given in the range of 20 to 20. There is no upper limit for n because the degree of polymerization is limited to the charging conditions by the properties of the organosulfur compound used.

The oxidation-reduction chemistry of this organosulfur electrode is described in detail in US Pat. No. 4,833,048, which is incorporated by reference as appropriate. The invention uses similar organosulfur electrodes, but differs in that they operate at lower temperatures in the solid state. Therefore, organosulfur polymers having 20, preferably more than 50 monomer units in the present invention are preferred. In addition, the anode of the invention differs from the anode of the cited patent in that it uses a specific current carrying additive.

The operating temperature of this solid state cell is from -40 to 145 ° C, with the upper limit being limited by the melting point of the electrode or electrolyte. Preferred temperature ranges are from ambient temperature to 100 ° C. Sodium cathodes are limited to temperatures below 98 ° C, but sodium alloy electrodes such as Na ₄ Pb can be used in solid form at temperatures well above 100 ° C.

The use of solid polymeric electrolytes and solid redox polymerization cathodes allows the production of a fully solid state without the difficulties associated with the use of solid or liquid electrolytes. The adhesion and elasticity of the solid polymeric electrolyte and the solid redox polymerization cathode prevent the loss or severe reduction of electrical contact between the solid electrolyte and the electrode during cell circulation. In addition, the present invention provides improved techniques by replacing certain liquid and corrosive materials with solid and safer compositions. By doing so, the cells using the present invention can be more easily manufactured and packaged in a highly automated process and provide a cell that is not corrosive to the encapsulation material.

The following examples tested in the laboratory further illustrate the present invention.

The experimental cell was assembled from a sodium anode, sodium beta alumina electrolyte, and a positive electrode made of (SRS) n, polyethylene oxide and carbon particles. The (SRS) n polymer used was a polymer of 2,5 dimercapto 1,3,4 thiadiazole, with three units of the polymer exhibiting the following structure:

The composite anode was cast to an electrode surface area of approximately 100 microns thick, that is, about 0.015 g / cm 2. The available capacity of the 100 micron polymer film is about 6.4 coulombs / cm 2 or 1.8 mAh / cm 2. The assembled cell was cycled at the end of 6 coulombs (defined at 100% of capacity). These cells were charged and discharged at various temperatures and current densities over the entire 80 cycles with no evidence of any performance degradation. At an operating temperature of 130 ° C., the cell can discharge at 100% of the available capacity at a current density of 4 mA / cm 2 and fully recharge without adversely affecting the chain circulation at a current density of 3 mA / cm 2. Furthermore, the cell can discharge at 50% of the available capacity at a high rate of 10 mA / cm 2, and charge at a high rate of 60 mA / cm 2 for 65% of the available capacity. In addition, extremely high charge / discharge current densities do not harm the integrity of the solid polymer electrode. This study demonstrated the reversibility and reliability of solid redox polymerization electrodes even under undesirable electrochemical conditions.

A cell composed of a lithium anode, a polyethylene oxide electrolyte, and a cathode made of (SRS) n polymer, polyethylene oxide and carbon particles was fabricated to test the actual performance of the thin film battery fabricated according to the present invention. The solid electrolyte used in this cell was polyethylene trioxide doped with lithium triflate (LiCF ₃ SO ₃ ) lithium perchlorate (LiClO ₄ ), or other suitable electrolyte salt. The concentration of the electrolyte salt is ₈ PEO monomer units (CH ₂ CH ₂ O) per molecule of salt (abbreviated as PEO ₈ LiX when X is salt negative). The organosulfur polymers used are the same as described above for sodium cells.

The composite anode is based on sodium, except for casting two thicknesses of the electrode, a high capacity 6 coulomb / cm 2 film (100 microns) and a low capacity 3 coulomb / cm 2 film (50 microns) for high power density cells. Prepared as described above for the cell. This Li / PEO / [(SRS) n / PEO / C] cell has a theoretical energy density of 1000 Wh / kg, and the assembled cell contains a real electrode, a PEO film, and a 4: 1 lithium (actual cell contains more excess lithium). The practical energy density is 338 Wh / kg (zero current drain) for high capacity films, and 304 Wh / kg for low capacity films. These cells were charged and discharged at two different discharge levels for a total of 350 cycles. The first 100 cycles discharged to 80% of capacity and the remaining 250 cycles discharged to 50% of capacity. As can be seen from the table below, the power and energy densities shown are extremely high, surpassing the cells based on all known solid state internal additives. In addition, these cells perform better than cells operating at higher temperatures, such as Na / beta-alumina / S cells (350 ° C.), Li / LiCs / KCs / FeS ₂ cells (450 ° C.).

In FIG. ₂ the comparative data between Li / PEO / X and Li / PEO / TiS ₂ is shown graphically. In this graphic, Jc represents a cell under charge and JD represents a cell under discharge. This test was computer controlled, and peaks were printed for a short off-time. Thus, true data lines are obtained by removing these peaks. As shown in the graph, the cell of the present invention maintained the voltage well through the discharge period, while the comparison cell dropped sharply. In addition, the cell of the present invention can be recharged close to the level at which the cathode can be used 100%.

In the above description, the present invention provides highly specific energy and power cells that go beyond the highly advanced systems known and used so far. At the same time, this high energy and power is available for room temperature or ambient operation.

Claims (20)

a) solid metal anode; b) in the charged state, a polymer of the general formula (SRSy) n wherein y is 2 to 6, n is greater than 20, and R is at least one oxygen, sulfur or nitrogen hetero atom when it comprises at least one aromatic ring One or more identical or different aliphatic or aromatic groups having from 1 to 20 carbon atoms, which may include one or more oxygen, sulfur, nitrogen, or fluorine atoms bonded to the chain when R consists of an aliphatic chain Where the aliphatic group is linear or branched, saturated or unsaturated, the aliphatic chain or aromatic ring may have substituted groups, and the organosulfur anode material features sulfur-sulfur bonds when in the charged state So that when the cell is discharged, the sulfur-sulfur bond decomposes to form an organosulfur metal salt with metal ions in the cell). DE; And (c) a solid-state metal-sulfur cell comprising an electrolyte separator and positioned between the cathode and the anode, the organic polymer and the electrolyte salt being capable of ion transport between the cathode and the anode. The cell of claim 1, wherein the solid metal anode comprises a metal selected from the group consisting of alkali metals and alkaline earth metals. The cell of claim 1, wherein the solid metal anode comprises a metal selected from the group consisting of lithium and sodium. The cell of claim 1, wherein the solid metal anode comprises lithium. The cell of claim 1, wherein the solid metal anode comprises sodium. The cell of claim 1, wherein the solid organosulfur cathode further comprises 0 to 20% by weight of conductor particles. The cell of claim 6, wherein the solid organosulfur cathode comprises 0 to 10% by weight of carbon particles. The cell of claim 6, wherein the solid organosulfur cathode comprises 0-70 wt% polymer electrolyte. 9. A cell according to claim 8, wherein the solid organosulfur cathode comprises 0 to 70 weight percent polyalkylene oxide polymer. The method of claim 1, wherein the solid organic sulfur cathode comprises: a) 1 to 20% by weight of conductor particles; b) 20 to 70% by weight of a polymer electrolyte; And (c) a remainder consisting essentially of an organosulfur polymer of the general formula (R (S) y) n in the charged state. The cell of claim 1, wherein the organic polymer in the electrolyte separator between the anode and the cathode is selected from the group consisting of polyethers, polyimines, polythioethers, poly phosphazenes, and mixtures thereof. The cell of claim 1, wherein the organic polymer in the electrolyte separator between the anode and the cathode comprises polyalkylene oxide. The cell of claim 12, wherein the organic polymer comprises polyethylene oxide. The cell of claim 1, wherein the electrolyte salt in the electrolyte separator between the anode and the cathode comprises lithium triflate. a) solid lithium anode; b) in the charged state, a polymer of the general formula (SRSy) n wherein y is 2 to 6, n is greater than 20, and R is at least one oxygen, sulfur or nitrogen hetero atom when it comprises at least one aromatic ring One or more identical or different aliphatic or aromatic groups having from 1 to 20 carbon atoms, which may include one or more oxygen, sulfur, nitrogen, or fluorine atoms bonded to the chain when R consists of an aliphatic chain Where the aliphatic group is linear or branched, saturated or unsaturated, the aliphatic chain or aromatic ring may have substituted groups, and the organosulfur anode material features sulfur-sulfur bonds when in the charged state A solid organo-sulfur casso comprising a sulfur-sulfur bond decomposing to form an organosulfur metal salt with a metal ion in the cell when the cell is discharged. DE; And (c) an electrolyte separator located between the cathode and the anode, the electrolyte separator comprising an organic polymer and an electrolyte salt and capable of ion transport between the cathode and the anode. a) solid metal anode; (b) in the charged state, a polymer of the general formula (SRSy) n wherein y is 2 to 6, n is greater than 20 and R is at least one oxygen, sulfur or nitrogen hetero atom when containing at least one aromatic ring At least one same or different aliphatic having from 1 to 20 carbon atoms, which may include, when R is composed of an aliphatic chain, which may include one or more oxygen, sulfur, nitrogen, or fluorine atoms bonded to the chain; Or an aromatic moiety wherein the aliphatic group is linear or branched, can be saturated or distributed, the aliphatic chain or aromatic ring can have a substituted group, and the organosulfur anode material is sulfur-sulfur when in the charged state A solid organo-sulfur casso comprising a bond, wherein when the cell is discharged the sulfur-sulfur bond decomposes to form an organosulfur metal salt with metal ions in the cell). wood ; And (c) an organic salt selected from the group consisting of electrolyte salts and polyethers, polyimines, polythioethers, polyphosphazenes and mixtures thereof and capable of transporting between the anode and the cathode; A solid metal sulfur cell comprising an electrolyte separator positioned between the cathodes. a) solid lithium anode; (b) in the charged state, a polymer of the general formula (SRSy) n wherein y is 2 to 6, n is greater than 20 and R is at least one oxygen, sulfur or nitrogen hetero atom when containing at least one aromatic ring At least one same or different aliphatic having 1 to 20 carbon atoms, which may include and when R is composed of an aliphatic chain, which may include one or more oxygen, sulfur, nitrogen, or fluorine atoms bonded to the chain; Aromatic moiety wherein the aliphatic group is linear or branched, may be saturated or unsaturated, the aliphatic chain or aromatic ring may have a substituted group, and the organosulfur anode material may be sulphur-sulfur bond when in a charged state. A solid organo-sulfur casso comprising a sulfur-sulfur bond that breaks down to form an organosulfur metal salt with metal ions in the cell when the cell is discharged. wood ; And (c) one or more polyether polymers and an electrolyte salt and comprising an electrolyte separator positioned between the anode and the cathode, capable of ion transport between the anode and the cathode. Cell. 18. The cell of claim 17, wherein the polyether polymer in the electrolyte separator between the anode and the cathode comprises polyethylene oxide. 18. The cell of claim 17 wherein the electrolyte salt in the electrolyte separator between the anode and the cathode comprises lithium triflate. 18. The method of claim 17, wherein the solid organosulfur cathode comprises: a) 1 to 20% conductive particles; b) 20 to 70 weight percent polymer electrolyte; And c) a remainder consisting essentially of an organosulfur polymer of the general formula (R (S) y) n in the charged state.