JP2004513470A - Rechargeable dual cation electrochemical battery cell - Google Patents

Abstract

A rechargeable battery cell (10) having a high operating voltage and a greatly increased specific capacity is placed between a positive electrode member (13), a negative electrode member (17) and a non-aqueous polyvalent cation solute. A separator member (15) containing an electrolytic solution containing a solution dissolved in a solvent. The positive electrode member contains an active material that reversibly captures and releases reactive polyvalent cation species during battery operation, while the negative electrode active material simultaneously reversibly converts monovalent cation species into an electrolyte. Released into the solvent and taken up from the electrolyte solvent. Preferred cationic species are alkaline earth metals such as Y ³⁺ metal, an alkali metal cation such as Li ^+.

Description

[0001]
(Background of the Invention)
The present invention relates to a rechargeable, high-voltage, high-capacity electrochemical battery cell comprising a positive electrode, a negative electrode, and a separator interposed therebetween and containing an electrolyte. The electrolyte contains a pair of different mobile cationic species that are individually involved in redox activity at each electrode during battery operation. More particularly, the present invention relates to making and using rechargeable battery cells. The battery cell includes a multivalent electrode material mainly involved in an oxidation-reduction reaction with a first chemical species that is a polyvalent cation present in an electrolyte among a pair of cationic chemical species in the circulation of the battery. , The second cationic species react mainly at the counter electrode of the battery. In these simultaneous oxidation-reduction reactions, a plurality of electrons can move per ion during the operation of the battery, and as a result, the capacity of the battery is significantly increased without impairing the high voltage output.
[0002]
Lithium intercalation that provides a significant level of specific capacity, ie, the amount of energy per unit cell weight that can be stored in and transferred from the battery, thanks to the lightweight lithium electrode and electrolyte component materials Batteries, especially Li-ion batteries, make a significant contribution to the current market for lightweight and compact rechargeable batteries. The high reactivity of lithium has the additional advantage that the potential of the negative electrode containing lithium is very low. The negative electrode can include lithium metal or a lithium alloy, or a lithium intercalated material. As a further advantage, a variety of metal oxide, sulfide or fluoride materials are available that can react with lithium at high potentials and thereby be used as positive electrode components in the resulting high voltage battery cells.
[0003]
However, the advantageous combined effect of light weight and high voltage operation of Li-ion batteries on the specific energy density of these resulting rechargeable batteries is that the mobile lithium cation on which the battery operation depends is monovalent. Thus, it is impaired by the limitations that can cause only one electron to be effectively transferred per available Li ⁺ ion.
[0004]
Given that cell capacity depends on the valency of charge transfer ions, an alternative to increasing the capacity of an electrochemical cell would logically involve the use of multivalent reactive components. Although such an approach is being considered, such as in US Pat. No. 5,601,949, attempts to obtain higher capacity intercalation battery cells using polyvalent cations instead of monovalent lithium. Had little success in practice. The failure of such a battery is believed to be due to several causes, in particular, the size of the multiply charged ions is quite large, which is the negative electrode of graphite or other carbon materials proposed in the patent specification. It often hinders effective intercalation into the composition.
[0005]
Another factor that hinders the efficient operation of a multi-ion battery is a passivation layer of a reactive material called the solid / electrolyte interface (SEI). This is typically a reduction by-product formed on the surface of the negative electrode battery during the first cyclic charging period, such as oxides, fluorides, carbonates, etc. of electrolyte cations. The Li ⁺ ions of a typical Li ion intercalation cell can diffuse through the SEI layer and come into contact with the negative electrode and be reduced there, while the polyvalent cations can diffuse in this manner. In addition, participation in the essential oxidation-reduction reaction at the negative electrode is considerably hindered. Although some reduction of polyvalent cations also occurs, this reaction always occurs at a high potential of the passivation layer reaction product, thus reducing the potential difference between the electrodes and consequently lowering the operating voltage of the battery.
[0006]
Thus, in order to actually utilize multivalent electrochemical cell components to increase battery capacity, it is necessary to implement a mechanism other than simple transfer of mobile multivalent cationic species between battery electrodes. The present invention provides a new and effective mechanism that can increase capacity using multivalent battery components.
[0007]
(Summary of the Invention)
A rechargeable electrochemical cell made according to the present invention includes a positive electrode member, a negative electrode member, and an ion-permeable and electronically insulating separator member interposed therebetween. An electrolytic solution containing a polyvalent cation species is further included between the electrode members. The electrolytic solution is preferably a non-aqueous solution of a solute that supplies a multivalent cation such as Y ³⁺ , La ³⁺ , Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , and Sr ²⁺ . The positive electrode member is a transition metal oxide, sulfide and fluoride, capable of capturing and releasing polyvalent cations in a reversible oxidation reaction such as intercalation, alloying, or adsorption during battery operation. Contains active materials such as carbon. The negative electrode member includes an active material that provides a source of a highly reactive second cationic species that acts on the negative electrode. The second cationic species is reversibly released into the electrolyte solvent during operation of the battery and can be taken up from the electrolyte solvent, such as Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ . Preferably, it is an alkali metal cation species. Such a negative electrode active material may be an alkali metal, an alkali metal alloy, or a carbon material capable of intercalating an alkali metal cation, such as coke, hard carbon, or graphite.
[0008]
One embodiment of the battery of the present invention comprises a positive electrode member made of V ₂ O ₅ , a negative electrode member made of LiSi, and 0.5M dissolved in a 2: 1 mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). Y comprises a separator film (C1O _{4) 3} borosilicate glass fibers saturated with electrolyte. During the initial discharge of the battery, ^{Y3 +} ions from the electrolyte go to a reversible reaction at the positive electrode, and Li ⁺ ions from the negative electrode are released into the electrolyte EC: DMC solvent. These reactions are dominant at their respective electrodes, primarily due to the physical proximity of the higher concentration of Y3 ⁺ ions to the positive electrode and the higher overall intercalation potential.
[0009]
When the battery is recharged, the reaction tends to go in the opposite direction in the usual way. That is, deintercalation or other release of ^{Y3 +} ions from the positive electrode occurs, and both cationic species migrate toward reduction at the negative electrode. However, due to the rapid formation of passivation products at the surface of the negative electrode, only Li ⁺ ions can diffuse through the SEI layer and reach the LiSi negative electrode material, where they are theoretically at about -3.0 V vs. It is reduced at the potential of SHE. Despite the greater recharge voltage is applied, a passivation layer of the negative electrode, prevent the reduction of Y ³⁺ ions, Y ³⁺ ion remains in the electrolyte solution, thus a relatively low potential of the negative electrode, and as a result The high operating voltage of the battery is maintained.
[0010]
The procedure for fabricating a practically widely used laminated polymer electrolysis cell electrode member, such as that described in US Pat. No. 5,460,904, also suffices for the fabrication of the electrode member of the battery of the present invention. In this way, the positive electrode member is provided with an active material capable of intercalating polyvalent cations, preferably in the form of nanomaterials, for example 28 parts of any vanadium and cobalt oxides and 6 parts of conductive carbon, with poly ( In a matrix composition comprising an organic solution of about 15 parts of a binder polymer such as vinylidene fluoride-co-hexafluoropropylene) and a primary plasticizer of the polymer, for example 23 parts of dibutyl phthalate, for example in 28 parts of acetone. It can be easily prepared by dispersing.
[0011]
The composition is cast into layers, which are air-dried at room temperature into membranes, which are then cut to the desired size for manufacturing batteries. Next, the membrane sample is laminated on the conductive current collecting member, and then laminated on the counter electrode and the separator member. The plasticizer contained therein is then typically extracted from the laminated assembly using a polymer inert solvent such as diethyl ether, after which the electrolyte solution is added. Commercially available batteries are preferably manufactured as fully stacked electrode-separator assemblies, but laboratory laboratory models are more easily assembled for testing in Swagelok test cells. These models are very similar in nature to physical pressure style battery cells represented by the well-known "button" battery. The present invention can also be practiced using this latter style of battery structure.
[0012]
Next, the present invention will be described with reference to the accompanying drawings.
[0013]
(Description of the invention)
A battery cell structure 10 useful in the present invention, as shown in FIG. 1, comprises a positive electrode member 13, a negative electrode member 17, and a separator member 15 interposed therebetween and containing a battery electrolyte, preferably as described in the aforementioned U.S. Pat. No. 5,460,904, in the form of a laminated member assembly. Current collecting members 11, 19 associated with the respective positive and negative electrode members provide an electrical circuit connection to the battery, such as at the extension terminal tabs 12, 16, etc. For laboratory testing purposes, it is useful to place an intermediate electrode, such as a silver wire 14, in the separator member 15 to establish a quasi-reference potential for each of the positive and negative half cells.
[0014]
Positive electrode 13 is generally a nanosized active material capable of intercalating or adsorbing polyvalent electrolyte cations, for example cations such as alkaline earths, for example oxides of transition metals, for example V ₂ O ₅ , MnO. ₂ , a vinylidene copolymer matrix film containing a dispersion of Co ₃ O ₄ . The negative electrode 17 of the counter electrode can reversibly plate monovalent cations such as Li, Na and other alkalis, form alloys with them, intercalate them, or react with them in other ways. A similar copolymer matrix dispersion of nanomaterial compounds that can, and thus, provide these sources, or simply include metal foils. The separator 15 may also be a polymer membrane as described in the above-referenced specification, or may comprise a widely used microporous membrane or simply a glass fiber mat. All of these can absorb non-aqueous electrolytes, such as 0.5 to 2 M polyvalent cation compound solutions in a mixed solvent of cyclic and acyclic carbonates. Such electrolytes can further include small amounts of monovalent alkali salts that can increase the reaction rate of the negative electrode and allow for the production of a discharged battery.
[0015]
The data criteria established by the optional Ag electrode 14 provide a convenient means to individually determine the electrolysis activity at each electrode of the selected composition. In this way, effective electrode and electrolyte combinations can be identified. For example, the realization of such a reference electrode helps to confirm the electrolysis cell mechanism. In this mechanism, despite applying a voltage well above the theoretically required voltage, the polyvalent cation species, eg, Y ^3+, is denied access to the passivated alkali metal anode, thus The electrode cannot be plated or reduced and the battery cannot be charged. In this way, a very positive reduction reaction of the Y3 ⁺ cation that takes place at the accessible surface of the passivated negative electrode of the single cation cell in the half-cell, Has been found to be responsible for the essentially invalid combined voltage level indicated by one of the following:
[0016]
In making the working battery cells, the selected battery compositions and components were conveniently assembled in a standard Swagelok test cell apparatus. In this assembly, the positive electrode member and the negative electrode member sandwiching the separator member saturated with the electrolytic solution are compressed between the opposing current collecting block members to achieve indispensable inter-member contact. After assembly, each test cell was placed in a circuit containing a MacPile automatic cycling control / data recording system operating in a galvanostatic mode at a preselected circulating rate of about 7.6 mA / g of active material. The characteristic signature voltage / capacity profile of the test battery was obtained.
[0017]
In view of the above discussion, the following examples provide those skilled in the art with further guidance in selecting combinations of components and compositions useful for effective practice of the present invention.
[0018]
Example I
As a comparative example of the operating voltage level and capacity achieved with a single monovalent cation battery cell common in the prior art, a lithium intercalation test battery was fabricated. The positive electrode was composed of 28 parts by weight of nanosize V ₂ O _5, 6 parts by weight of conductive carbon black (MMM super P), 15 parts by weight of poly (vinylidene fluoride-co-hexafluoropropylene) (Elf Atochem, Kynar 2801) and phthalate. The composition was cast as a layer containing 23 parts by weight of dibutyl acid plasticizer in 28 parts by weight of acetone. This layer was dried at 22 ° C. for about 0.5 hour to form a free-standing film, and a 1 cm ² disk was cut from the film to obtain an electrode member containing about 4 to 10 mg of an active material, that is, V ₂ O ₅ . A plasticizer was extracted from the electrode disk member using diethyl ether in order to introduce an electrolytic solution into the battery by a conventional method of a stacked battery structure.
[0019]
Similarly, a negative electrode member of LiSi was prepared from a casting layer having the same composition as the positive electrode layer except that Si was used instead of V ₂ O ₅ . A layer of the dried and extracted piece was placed over a piece of lithium foil and an electrode member disk was cut from the composite material. At the position of the electrode disk member, a LiSi alloy having a surface area of more than about 0.5 m ² / g was spontaneously formed in a short time.
[0020]
These electrode members were assembled under substantially anhydrous conditions (dew point -80 ° C) in a Swagelok test cell. At this time, a disk-shaped borosilicate glass fiber mat saturated with a 1M LiClO ₄ electrolyte solution dissolved in a 2: 1 mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) was sandwiched. The battery is then cycled through the circuit containing the automatic test controller / recorder for several cycles, during which the Li ⁺ electrolyte cation reaction at the positive electrode during discharge and reduction at the negative electrode during recharge Was repeated in the usual manner. The recorded data, including the two-electrode output voltage of the battery and indicating a typical intrinsic capacity of about 125 mAh / g, was plotted to obtain the characteristic trace shown in FIG.
[0021]
Example II
The method of Example I utilizing a second comparative example of a battery cell containing a single multivalent cation utilizing the positive electrode member of Example I and the negative electrode member containing a nanosized YSi ₂ powdery active material. It was produced in. The electrolyte is a 0.5 M Y (ClO ₄ ) ₃ solution dissolved in a 2: 1 EC: DMC mixture.
[0022]
Examination of the Y ³⁺ cation half-cell reaction at each of the positive and negative electrodes using the quasi-reference electrode 14 reveals a clear intercalation or adsorption at the positive electrode and a reduction or alloying at the negative electrode, Reversible multivalent Y ³⁺ cation activity in this battery was confirmed. Unfortunately, however, the voltage of this single multivalent cation negative electrode material reaction is too high for the positive electrode reaction and the voltage difference between the electrodes required to provide the resulting resulting working voltage level useful in battery cells. Can not be established. This disadvantage is evident from the circulating voltage trace shown in FIG. In FIG. 3, the battery capacity is greatly increased, but the voltage output is of little use.
[0023]
Example III
A battery cell embodying the present invention, that is, a battery cell containing dual cations, at least one of which is a multivalent cation, was produced by the method of the above-described embodiments. The battery cell is capable of intercalating or adsorbing multivalent cations, such as yttrium, lanthanum, alkaline earth metal cations, during the discharge cycle, respectively, in the positive and negative electrodes, and during the charge cycle. In addition, it includes materials capable of reducing, plating, or alloying with smaller, more reactive second cations, generally monovalent alkali cations. With such a combination of electrode materials, the electrolyte can supply multivalent cations and easily receive the second cation species.
[0024]
Specifically, the positive electrode member of the dual cation battery includes the V ₂ O ₅ nanomaterial of Example I, and the negative electrode member includes LiSi of Example I. Thus, the battery electrode active material can function in the battery structure of the present invention in the same manner as in the prior art structure, but there are surprisingly effective differences in the electrolyte cations used. According to the present invention, the cation of the electrolyte solution is selected as a multivalent cation in a dual cation combination, and the complementary cation is generally the monovalent cation component of the negative electrode composition. In this embodiment, the electrolyte is a 0.5 MY (ClO ₄ ) ₃ solution. A trace of the circulating voltage of this cell is shown in FIG. 4, which shows a significant intrinsic capacity of up to about 250 mAh / g and the resulting working voltage is stable, in the range of about 3 to 3.5 V .
[0025]
The theorized mode of operation of the dual cation battery of the present invention appears to follow a generalized process. That is, during discharge of the battery, the polyvalent Y ³⁺ cations in the electrolyte solution are taken in by the positive electrode, Li ⁺ cations enter the solution from the negative electrode, and during recharge of the battery, the Y ³⁺ polyvalent cation species The solution is re-entered and the Li ⁺ cation is reduced, plated, or alloyed at the negative electrode to about -3 V vs. -3V. Maintain stable low voltage battery data for SHE.
[0026]
This mode of operation, in which the reaction of one cationic species is dominant at one electrode and the reaction of the complementary cationic species is dominant at the other electrode, is the mode of operation of the sample cell at various reversible circulation stages. Supporting evidence has been received from a series of energy dispersive spectroscopy (EDS) assays of the electrodes. From these EDS test results, the superiority of each of the electrodes in the cation reaction is confirmed by the fact that the Y / V ratio in the positive electrode matches the degree of battery discharge and recharge.
[0027]
Example IV
Another embodiment of the dual cation battery of the present invention, comprising a lithium metal negative electrode member on a nickel support, a positive electrode member containing a Co ₃ O ₄ active material, and a 0.5 MY (ClO ₄ ) ₃ electrolyte solution. Produced. This battery showed similar results as the battery of Example III.
[0028]
Example V
Another embodiment of the present invention comprising a metal sodium negative electrode member on a stainless steel support, a positive electrode member containing the same V ₂ O ₅ active material as in Example III, and a 0.33 MY (CF ₃ SO ₃ ) ₃ electrolyte solution Was further fabricated. The high voltage stability and improved capacity of this dual cation configuration battery can be confirmed from the cycling characteristics trace of the battery shown in FIG. A similar battery limited to the monovalent cation configuration, that is, a battery utilizing an electrolyte containing NaClO ₄ dissolved in propylene carbonate, provided only an active capacity of about 90 mAh / g.
[0029]
In view of the above description and examples, it is expected that other embodiments and modifications of the invention will be readily apparent to those skilled in the art. Such embodiments and modifications are intended to be included within the scope of the present invention as set forth in the appended claims.
[Brief description of the drawings]
FIG.
1 is a schematic sectional view of a laminated battery cell embodying the present invention.
FIG. 2
5 is a graph tracing the characteristic recycle voltage and the specific capacity of a prior art single monovalent cation battery.
FIG. 3
4 is a graph tracing the characteristic recycle voltage and specific capacity of a single multivalent cation battery.
FIG. 4
4 is a graph tracing the characteristic recycle voltage and the specific capacity of one embodiment of the dual cation battery of the present invention.
FIG. 5
5 is a graph tracing the characteristic recycle voltage and the specific capacity of another embodiment of the dual cation battery of the present invention.

Claims (11)

A rechargeable battery cell comprising a positive electrode member, a negative electrode member, and a separator member including an electrolyte disposed therebetween.
a) the electrolyte comprises a solution in which a solute supplying a polyvalent cation species is dissolved in a non-aqueous solvent;
b) the positive electrode member comprises an active material capable of reversibly capturing and releasing the polyvalent cation species during operation of the battery;
c) The battery cell, wherein the negative electrode member includes an active material capable of reversibly releasing a second cationic species into the solvent during operation of the battery and taking in the second cationic species from the solvent. a) said polyvalent cation species is selected from the group consisting of yttrium, lanthanum and alkaline earth metals;
2. The battery cell of claim 1, wherein b) said second cationic species is selected from the group consisting of alkali metals. The battery cell according to claim 2, wherein the positive electrode active material is selected from the group consisting of transition metal oxides, sulfides and fluorides, and fluorocarbons. The battery cell according to claim 3, wherein the positive electrode active material is selected from the group consisting of oxides of vanadium, manganese, and cobalt. The battery cell according to claim 2, wherein the negative electrode active material is selected from the group consisting of an alkali metal, an alkali metal alloy, and a carbon material capable of intercalating an alkali metal cation. The battery cell according to claim 5, wherein the negative electrode active material is selected from the group consisting of lithium, sodium, a lithium alloy, and a sodium alloy. The multivalent cationic species is selected from the group consisting of Y ³⁺ , La ³⁺ , Mg ²⁺ , Ca ²⁺ , Ba ²⁺ and Sr ^2+, and the second cationic species is Li ⁺ , Na ⁺ , K ⁺ , The battery cell according to claim 2, wherein the battery cell is selected from the group consisting of Rb ⁺ and Cs ⁺ . Positive electrode member, a negative electrode member, comprising a separator member containing an electrolytic solution disposed therebetween, a battery cell capable of reversible operation by charging and discharging,
During operation of the battery,
a) the electrolyte comprises a non-aqueous solvent comprising at least two reactive cationic species at various concentrations;
b) a first of the cationic species reacts primarily at the positive electrode member;
c) The other of the cationic species reacts mainly at the negative electrode member. a) said first species of said species is a multivalent cation selected from the group consisting of Y ³⁺ , La ³⁺ and alkaline earth metal cation;
9. The battery cell of claim 8, wherein b) the other species of the species is a monovalent cation selected from the group consisting of alkali metal cations. a) during the discharge of the battery, the first species of the cationic species is taken from the solvent in the positive electrode reaction, and the other species of the cationic species is the solvent in the negative electrode reaction. Released into the
b) during charging of the battery, the first species of the cationic species is released into the solvent in the positive electrode reaction, and the other species of the cationic species is released in the negative electrode reaction. The battery cell according to claim 8, wherein the battery cell is taken from a solvent. The first species of the cationic species is selected from the group consisting of Y ³⁺ , La ³⁺ , Mg ²⁺ , Ca ²⁺ , Ba ²⁺ and Sr ^2+, and the other cationic species is Li ⁺ , Na ⁺ , ^K +, battery cell according to claim 8, characterized in that it is selected from the group consisting of Rb ⁺ and Cs ^+.

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