JPH04248256A - Solid electrode composition - Google Patents

Abstract

PURPOSE:To provide electrode compositions which can be used as a negative electrode for a lithium secondary cell which is uniform and less in polarization. CONSTITUTION:Electrode compositions are composed of carbon powder, aluminium or aluminium alloy powder, polyether compound in which ethylene oxide chain and/or propylene oxide chain are added to polyamine compound, ion exchanging layer compound, and of ionic material represented by a formula MX, wherein M represents metal ion, proton, and ammonium ion which travel within solid electrolyte compositions by the action of electric fields, and X represents anion strong in acid. The carbon powder and the aluminium or aluminium alloy powder are uniformly dispersed by the action of the polyether compound, so that large reactive areas can thereby be obtained, and ionic conductive paths preferable to cell reaction are concurrently formed within the electrode compositions by the ether compound combined with the ionic material and the ion exchanging layer compound. The electrode compositions thus formed can effectively use as a negative electrode for a lithium cell less in polarization.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to batteries, capacitors,
The present invention relates to solid electrode compositions used in electrochemical devices such as sensors, display devices, and recording devices, and particularly to solid electrode compositions used in combination with lithium ion conductive electrolytes as negative electrodes of solid lithium batteries.

0002

2. Description of the Related Art By using a solid electrolyte, it is possible to obtain solid electrochemical devices such as small and thin batteries and electric double layer capacitors that do not leak.

[0003] However, since the conventional solid state electrochemical device is constructed of a solid material lacking in elasticity, it has the disadvantage that it is extremely brittle and easily damaged by mechanical impact. To solve these problems, polymer solid electrolytes made of polyethylene oxide (PEO) and alkali metal salts have been proposed (for example, "Fast").
IonTransport in Solid” P.
Vanishstate. al. , Eds. P.
131 (1979) North HollandPub
lishing Co. ). Polymer solid electrolytes are lighter and have superior flexibility and moldability compared to inorganic solid electrolytes. Since then, research and development has been actively conducted on materials that exhibit high ionic conductivity comparable to inorganic solid electrolytes while maintaining excellent flexibility and moldability. In particular, active research and development is being carried out because it is expected that by combining it with a metallic lithium negative electrode, a high energy density solid-state secondary battery with a voltage of 3 volts or more will be produced.

0004

[Problems to be Solved by the Invention] However, in conventional lithium secondary batteries that use metal lithium or lithium alloys such as lithium-aluminum as the negative electrode, there is a low polarizability and reversibility between the negative electrode and the polymer electrolyte. It is not always possible to obtain a uniform bonding interface with good properties, for example, 0.1 mA/
When charging and discharging at a current density exceeding cm2, there is a problem in that polarization increases rapidly even at the beginning of 50 or less charge/discharge cycles. In addition, there was a problem in that the electrolyte layer was broken and metallic lithium was deposited, leading to a short circuit in the battery.

[0005] The present invention solves these problems, and aims to obtain a solid electrode composition having excellent ionic conductivity and electronic conductivity as a negative electrode for solid-state lithium secondary batteries. It is something.

[0006]

[Means for Solving the Problem] In order to solve this problem, the present invention provides carbon powder, metal aluminum or its alloy powder, and polyamine compound with ethylene oxide (
Polyether compounds with added ethylene oxide (EO) or propylene oxide (PO), or polyamine compounds with ethylene oxide (EO) and propylene oxide (PO) added.
PO), an ion-exchange layered compound, and an ionic substance represented by the formula MX (where M is a metal ion, proton, or ammonium that moves within the solid electrode composition under the action of an electric field). ion, and X is an anion of a strong acid). Furthermore, ion conductive particles are included for the purpose of increasing the ion conductivity within the electrode composition.

[0007]

[Function] In the solid electrode composition thus obtained, the ionic compound MX forms a complex with the polyether compound and the ion-exchangeable layered compound, and the ionic compound MX forms a complex between the crystals of the layered compound. It is retained at a high concentration on the surface and forms an advantageous path for ion conduction. In addition, the carbon powder and the metallic aluminum or aluminum alloy powder are uniformly mixed with the solvent and the ion-exchangeable layered compound due to the surface active effect of the polyether compound. Furthermore, when adding and mixing ion conductive powder, the polyether compound prevents agglomeration of the metal powder and ensures uniform mixing and dispersion of the solvent and the ion exchange layered compound, carbon powder, metal aluminum powder, or their alloy powder. enable. In this way, high electronic and ionic conductivity and homogeneity are achieved. As a result, an electrode composition with low polarization is obtained. That is, as the battery reaction progresses, the negative electrode metal repeatedly precipitates and dissolves on the carbon powder, metal aluminum, or its alloy powder, but the electrode composition of the present invention is homogeneous and has a large electrode area, so that the current is localized. It's hard to concentrate. Furthermore, the presence of the ion-exchange layered compound makes it difficult for the negative electrode metal to precipitate in one direction, so that the negative electrode metal does not break through the electrolyte layer and precipitate, thereby preventing short-circuiting between the two electrodes. In addition, polyethylene oxide chains of polyether compounds and/or
Alternatively, the propylene oxide chain, or the polyethylene oxide chain and polypropylene oxide chain of the polyether compound are entangled with the microporous structure of the ion exchange layered compound, giving good moldability and sufficient mechanical strength. .

[0008]

[Example] An example of the present invention will be described below, but the present invention is not limited to the following example. Further, in the following examples, parts, percentages, and ratios represent parts by weight, percentages by weight, and weight ratios unless otherwise specified.

The carbon materials used in this example include natural graphite,
Any of artificial graphite, amorphous carbon, fibrous, powdered, petroleum pitch-based, and coal-coke-based materials can be used. The size of particles or fibers is 0.0 in diameter or fiber diameter.
It is desirable that the fiber length is 1 to 10 μm, and the fiber length is from several μm to several mm. As metal aluminum or its alloy powder, A
l, Al-Fe, Al-Si, Al-Zn, A
Spherical or amorphous powder obtained by mechanically pulverizing flakes obtained by ultra-quenching l-Li, Al-Zn-Si, etc. in air or an inert gas such as nitrogen is used. The particle size is from 1 μm in diameter
100 μm is desirable. The mixing ratio of the carbon material and the aluminum or aluminum alloy powder is 1 part of the aluminum or aluminum alloy powder to 0.0 parts of the carbon material powder.
01 to 5.0 parts, preferably 0.05 to 0.5 parts. If the carbon material is less than 0.01 part, it will be difficult to uniformly disperse the aluminum or aluminum alloy powder, the carbon powder will aggregate, the conductivity between aluminum or aluminum alloy particles will be poor, and the material will not work effectively as an electrode. . If the amount exceeds 5.0 parts, the aluminum or aluminum alloy powder particles will be thickly covered with carbon particles, and contact with the electrolyte will be cut off, resulting in unstable electrode potential and increased polarization.

The polyether compound of the present invention is obtained by adding ethylene oxide or propylene oxide to a polyamine compound, or the polyamine compound is obtained by adding ethylene oxide and propylene oxide to a polyamine compound.
It can be obtained by addition reaction of ethylene oxide or propylene oxide or ethylene oxide and propylene oxide at 00-180°C and 1-10 atm. As the polyamine compound, polyethyleneimine, polyalkylene polyamine, or derivatives thereof can be used. Examples of polyalkylene polyamines include diethylenetriamine, triethylenetetramine, hexamethylenetetramine, and dipropylenetriamine.

The number of moles of ethylene oxide and propylene oxide added is preferably 2 to 500 moles per active hydrogen of the polyamine compound. The ratio of ethylene oxide (EO) and propylene oxide (PO) to be added is:
The ratio is 80/20 to 10/90 (=EO/PO). The average molecular weight of the polyether thus obtained is 1.0
00 to 5 million. The amount of this polyether compound added is preferably 0.5 to 20% based on the total amount of the solid electrode composition.

[0012] There are no particular restrictions on the ionic substance, but LiI, LiClO4, LiCF3SO3, LiPF
6. Soluble lithium salts such as LiBF4, LiSCN, LiAsF6 are used.

Examples of ion exchange layered compounds include clay minerals containing silicates such as montmorillonite, hectorite, saponite, and smectite, phosphate esters such as zirconium phosphate and titanium phosphate, vanadate, antimonic acid, and tungsten. Examples include acids, or those modified with organic cations such as quaternary ammonium salts, or organic polar compounds such as ethylene oxide and propylene oxide.

Furthermore, as the ion conductive powder, Li
I, LiI・H2O, Li-β-Al2O3, LiI-
Lithium ion conductive solid electrolytes such as Li2S-B2S3 and PEO-LiCF3SO3 are preferably used. There is no limit to the amount of ion conductive powder added as long as the moldability of the solid electrode composition is not impaired.

The solid electrode composition of the present invention can be obtained as follows. Add 1 to 50% ion exchange layered compound powder to a solvent in which 1 to 50% of an ionic compound is dissolved, and then add a polyether compound having an EO chain or a PO chain, or a polyether compound having an EO chain or a PO chain. 0.1 to 20 of the polyether compound with respect to the entire slurry
%, and then pulverized and mixed using a mixer such as a disperser to prepare an electrolyte slurry having a solid content of 5 to 95%.

[0016] In addition, a polyether compound having an EO chain or a PO chain, or a polyether compound containing 0.1 to 20% of a polyether compound having an EO chain and a PO chain in a solvent in which an ionic compound is dissolved from 1 to 50%. A pre-mixed powder of carbon powder and aluminum or aluminum alloy powder is added to the solution to form an electrode slurry. Next, the electrolyte slurry and the electrode slurry are mixed to obtain an electrode composition slurry. Mixing is preferably carried out in an alumina ball mill with alumina balls having a diameter of 3 to 10 mm. The electrode composition slurry thus obtained is
A solid electrolyte composition can be obtained by casting or coating on a support such as a Teflon plate or a nylon mesh sheet, and then dissipating some or all of the solvent. If the support is in the form of a mesh, it is possible to use it as a solid electrode composition with the support integrated. If necessary, these steps are performed in a dry atmosphere with a relative humidity of 40% or less.

Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, saturated hydrocarbon solvents such as n-hexane, n-heptane, n-octane, and cyclohexane, and benzene, toluene, and xylene. Aromatic solvents, ester solvents such as ethyl acetate, butyl acetate, propylene carbonate, methanol, ethanol, isopropyl alcohol,
Alcohol solvents such as ethylene glycol, glycerin, and polyethylene glycol, nitriles such as acetonitrile, or water are used.

(Example 1) Ethylene oxide (EO) was added to polyethyleneimine containing 10 N atoms in the molecule.
) and propylene oxide (PO) so that the ratio of EO to PO is 30/70, the average molecular weight obtained is 18
A 20% polyether solution was prepared by dissolving 0,000% polyether compound in acetonitrile.

Furthermore, LiCF3S is used as an ionic substance.
γ-zirconium phosphate powder with an average particle size of 15 μm was added to a polyether solution in which 10% O3 was dissolved so that the solid content was 30%, and the mixture was stirred and mixed at 40°C for 24 hours to obtain an electrolyte slurry. Ta. Next, a mixed powder of 1 part of 99.8% pure metal aluminum powder with an average particle size of 18 μm and 0.1 part of artificial graphite powder with a graphitization degree of 48% and an average particle size of 2 μm was solidified in a polyether solution. The mixture was added so that the content was 50% and mixed at 40° C. for 24 hours to obtain an electrode slurry. The solid content ratio of the electrolyte slurry and electrode slurry is 1.
:2 in an alumina ball mill for 24 hours to obtain an electrode composition slurry. After applying the electrode composition slurry on a smooth Teflon plate using a doctor blade, it was dried in a dry argon stream at 130°C for 1 hour, and then vacuum dried for 5 hours to reduce the size to 80.
A sheet-like solid electrode composition having a size of 80 mm and a thickness of 210 μm was obtained. Further, for the construction of an electrolytic cell for evaluating the electrochemical properties of the electrode composition, an electrolyte sheet having a size of 80 x 80 mm and a thickness of 90 microns was prepared by applying and drying only the electrolyte slurry in the same manner.

(Example 2) One part of spherical Al-Si alloy (Si content: 25 atomic %) powder with an average particle size of 40 μm crushed in a nitrogen gas atmosphere and an average particle size of 7 μm with a purity of 99
．． A polyester with an average molecular weight of 65,000 obtained by mixing 0.1 part of 99% high-purity natural graphite with ethanol as a dispersion medium and drying it was used as an electrode powder and adding EO to triethylenetetramine. A 10% polyether solution in which an ether compound was dissolved in acetonitrile, montmorillonite powder with an average particle size of 25 μm, and lithium trifluorosulfonate (LiCF) as an ionic substance.
A sheet-like electrode composition with a thickness of 300 μm and a sheet-like electrode composition with a thickness of 110 μm were prepared in the same manner as in Example 1 except that 3SO3) was used.
A sheet-like electrolyte of m was prepared.

(Example 3) 1 part of amorphous Al-Cu alloy (Cu content: 25 atomic %) powder with an average particle size of 12 μm pulverized in air and furnace black 0 with an average particle size of primary particles of 0.01 μm 05 parts of EO and PO were mixed in acetonitrile as a dispersion medium, dried and used as an electrode powder, and EO and PO were mixed in hexamethylenetetramine at EO/PO=4.
The average molecular weight obtained by adding at a ratio of 0/60 is 15,00
0 polyether compound dissolved in acetonitrile 1
Using a 0% polyether solution, γ-zirconium phosphate powder with an average particle size of 8 μm, lithium perchlorate (LiClO4) as an ionic substance, and Li3N, LiI, and B2O3 as an ion-conductive solid electrolyte. A sheet-like electrode composition with a size of 80 x 80 mm and a thickness of 135 μm and a sheet-like electrode composition with a thickness of 65 μm were prepared in the same manner as in Example 1 except that 5% of the lithium compound was mixed as a solid content weight.
A sheet-like electrolyte was prepared.

(Comparative example) The average molecular weight of one-eighth of LiCF3SO3 dissolved per molecule of ethylene oxide is 4.
A polymer solid electrolyte made of 800,000% polyethylene oxide and the same electrode powder as in Example 2 were mixed and dried to prepare a sheet-like electrode composition with a thickness of 305 μm. Further, a sheet-like electrolyte having a thickness of 115 μm was produced. Characteristic Evaluation of Electrode Compositions The electrode compositions obtained in Examples 1 to 3 and Comparative Examples were
A disk of mm was punched out and used as a sample for characteristic testing. In addition, the sheet-shaped electrolyte produced in each example was 10 m in diameter.
It was punched out and used for constructing an electrolytic cell. Two electrolyte discs are stacked with a silver wire with a wire diameter of 50 μm for a reference electrode sandwiched between them to form an electrolyte layer, and a diameter of 10 mm is placed on one side of the electrolyte layer.
, a metal lithium disk with a thickness of 1 mm was placed, an electrode disk was placed on the other side, and platinum disks were placed above and below it, and the whole was pressurized from above and below at a pressure of 50 kg/cm2. The test cell A (Example 1), test cell B (Example 2), test cell C (Example 3), test cell D ( Comparative example) was assembled. Using the electrode disk as the working electrode, the metal lithium electrode as the counter electrode, and the silver wire as the reference electrode, the potential of the test cell was changed from 0 → 1.5 → in the range of ±1.5 V around zero V.
Sweep speed 5mV linearly from 0 → -1.5 → 0 → 1.5V
/s to change repeatedly. A current peak appears around ±0.6 to ±1.1 V, and the peak current value changes as the charge/discharge cycle progresses. The peak potential and current value of the reduction current after 20, 50, 100, and 200 cycles are shown in (Table 1).

[0023]

[Table 1]

As is clear from the results shown in Table 1, the electrode composition of the present invention provides a larger peak current value and smaller polarization than the electrode composition of the comparative example. Further, the decrease in peak current value due to progress of charge/discharge cycles is also small. In addition, in order to evaluate the mechanical strength of the electrode composition, a molded body with a length of 40 mm and a width of 5 mm was bent repeatedly along a curved surface with a radius of 50 mm at a rate of 2 times per second, and the number of times until it broke was evaluated. However, even after 800 bending tests, it maintained its original shape without breaking. It can be seen that it has excellent mechanical strength.

[0025]

Effects of the Invention As is clear from the description of the examples above, according to the present invention, a specific polyether compound having an ethylene oxide chain or a propylene oxide chain, or a specific polyether compound having an ethylene oxide chain and a propylene oxide chain, Due to the action of the polyether compound, it is possible to provide a homogeneous electrode composition with a large electrode area in which the electrode material powder is uniformly dispersed. This polyether compound forms a complex with the ion-exchangeable layered compound, is held at a high concentration between the layers or on the surface of the layered compound's crystals, forms an advantageous path for ion conduction, and is present in the electrode composition. Provides the ionic conduction path necessary for the smooth progression of battery reactions. According to the electrode composition of the present invention, electron and ion conduction paths are uniformly formed, and as a result, an electrode composition with low polarization can be obtained.

Claims (1)

[Claims] Claim 1: Carbon powder, metallic aluminum or its alloy powder, and a polyether compound obtained by adding either ethylene oxide or propylene oxide to a polyamine compound, or a polyether compound obtained by adding ethylene oxide and propylene oxide to a polyamine compound. , an ion exchange layered compound, and a formula MX
An ionic substance represented by
A solid electrode composition containing at least