KR800000158B1 - Nonaqueous cell having an electrolyte containing crotonitrile - Google Patents

Abstract

A nonaq. cell uses a highly active metal anode such as Li, Na, K, Mg a solid cathode such as CuS graphite fluoride a liq. org. electrolyte consisting mainly of crotonitrile in combination with a protective cosolvent, preferably propylene carbonate and an ionizable solute such as LiClO4.

Description

Non-aqueous battery of electrolyte containing crotonitrile

The development of a high energy battery is compatible with a highly active positive electrode material, that is, lithium, calcium, sodium, and the like, and an electrolyte having desirable electrochemical properties, and a high energy density negative electrode material, ie Effective use of materials such as carbon fluoride, copper sulfide and the like is required. The use of aqueous electrolytes is excluded from this system because the anode material shows great activity in chemically reacting with water.

Therefore, in order to obtain a high energy density by using a highly reactive positive electrode and a high energy density negative electrode, research and development on a non-aqueous electrolyte system and in particular a non-aqueous organic electrolyte system was required.

The term "non-aqueous organic electrolyte", which has been used in the past, refers to an electrolyte in which complex salts belonging to groups I-A, II-A or III-A in the heat or periodic table are dissolved in a suitable non-aqueous organic solvent. Conventional solvents include propylene carbonate, ethylene carbonate, or γ-butyrolactone. As used herein, the term “periodic table” refers to the periodic table of elements listed on the eye cover of the 48th edition of the Handbook of Chemistry and Physics (1967-68), of Chemical Rubber, Ohio.

Many solvents have been known and recommended for use, but in practice it is particularly difficult to select a suitable solvent, because many solvents used to prepare an electrically conductive electrolyte sufficient to effectively transport ions through a solution are described above. This is because it causes a reaction with one highly active anode. Therefore, in the investigation of suitable solvents, many researchers have focused on the study of aliphatic and aromatic nitrogen- and oxygen-containing compositions, while also on organic sulfur, phosphoric acid and arsenic-containing compositions. . The results of this effort have not been satisfactory because many of the solvents studied so far have not yet been able to be effectively used with high energy density cathode materials such as carbon fluoride, and these solvents are extremely corrosive to lithium anodes. Because the action was so severe that after a certain time did not work effectively.

US Patent No. 3.547,703 to Blomgren et al. Discloses the use of a non-aqueous cell electrolyte in which a solute is dissolved in ethylene glycol sulfite. In addition, US Patent No. 3,536,332 3,700,502 discloses a non-aqueous battery using a solid fluorocarbon [(CF _x ) _n ] as an active cathode, using a light metal anode and a conventional non-aqueous electrolyte.

In addition, French invention 2,124,388 introduced an electrolyte using dioxolane as a solvent. And G.W. US application No. 509,820 to Mellors introduces a non-aqueous electrolyte consisting of sulfolane or a liquid alkyl substituted derivative thereof, combined with a low viscosity crude solvent and an ionic solute. And also M.L. U.S. Application No. 462,792 to Kronen berg introduces a non-aqueous electrolyte based on 3-methyl-2-oxazolidone, combined with a low viscosity common solvent and an ionic solute.

U.S. Patent No. 3,567,515 to Maricle et al., Also introduces a non-aqueous battery preparation, in which sulfur dioxide forms a so-called "passivating" film on a highly active metal such as lithium, which is either a metal-sulfur dioxide mixture or as a reaction product. Prevent further erosion of sulfur dioxide on the metal. In the same way, in the article entitled "Reaction Process of Solid Lithium Electrodes in Propylene Carbonate," published in J. Electrochemical Society Vol. 117, No. 3, March 1970, propylene carbonate is reacted with the reaction between it and lithium. It has been announced that it forms a film on lithium metal.

Also in the final report of 9 Will in 1967 under a contract with USAECOM in the United States (contract no. Turned out to be. On the other hand, crotonitrile is also a usable solvent, but it has been found that the corrosion rate of lithium becomes too excessive when it comes into contact with lithium. Therefore, crotonitrile is a solvent having properties comparable to propylene carbonate. It was determined that it was not good.

Ionic energy, such as the electrical energy produced potentially from the bond of the selected positive and negative poles, is relatively easy to measure, but for such bonds, the actual energy produced by the assembled cell approaches the theoretical energy. It is necessary to select a nonaqueous electrolyte. A common problem is that it is impossible to predict in advance how effectively the non-aqueous electrolyte will work with the chosen electrode bond. As such, the cell must be regarded as a unit with three parts of negative electrode, positive electrode and electrolyte, and it is also true that these parts of one cell cannot be interchanged with other parts of the cell to make an effective battery.

An object of the present invention is to provide a non-aqueous battery using a liquid organic electrolyte consisting essentially of crotonitrile, using a protective common solvent and a solute together. In addition, the present invention consists of a highly active metal anode such as lithium and (CF _x ) _n solid sulfide such as copper sulfide, nickel fluoride or silver chloride, and a protective common solvent and crotonitrile with a solute It is to provide a non-aqueous battery using a liquid organic electrolyte.

It is also an object of the present invention to provide an electrolyte solvent system for a non-aqueous solid cathode cell composed of a crotonnitrile using a protective common solvent, a low viscosity cosolvent and a solute together.

It is also an object of the present invention to provide a non-aqueous battery using a liquid organic electrolyte based on crotonitrile using a metal anode, a solid cathode grease propylene carbonate, and a solute such as LiClO ₄ .

The present invention relates to the manufacture of a high energy density non-aqueous, battery, which comprises three parts: a high active metal positive electrode, a solid negative electrode and a crotononitrile, a protective common solvent, and a liquid organic electrolyte composed of an ionic solute. If the viscosity of the common common solvent is such that the solution conductivity of the electrolyte is reduced to 10 ^-4 ohm ^-1 cm ^-1 or less, the conductivity of the electrolyte should be at least 10 ^-4 ohm ^-1 by mixing a common solvent having a low viscosity. It should be about cm ^-1 .

A protective common solvent, such as used herein, when the crotonitrile and the ionic solute are mixed to form a liquid electrolyte for use in a highly active positive electrode nonaqueous battery, the highly active metal positive electrode of the cell is subjected to excessive corrosion by crotonitrile. At least one such common solvent that effectively forms a protective barrier from This prevents chemical or physical interactions between the anode metal and the electrolyte solution.

A key element of the liquid electrolyte of the present invention is crotonitrile, the characteristics of which are shown in Table 1. Crotonitrile is also commonly known as Crotononitrile.

TABLE 1

The ionic solute of LiClO ₄ mixed in various concentrations in crotonitrile shows the characteristics shown in Table 2 measured in the laboratory.

TABLE 2

When a crotonitrile-LiClO ₄ electrolyte is used in a lithium cathode cell, a chemical reaction occurs between the crotonitrile and an unprotected highly active lithium anode. This undesirable reaction continues until the polymerization of crotonitrile occurs, which leads to gradual concentration of the electrolyte resulting in the formation of a solid. Thus, although the measured solution conductivity and viscosity indicated that crotonitrile mixed with the ionic solute would be a suitable electrolyte for non-aqueous cells using high active metal anodes, the observations were reversed.

Although it is not necessary to be bound by academic theory, it is believed that the following reaction occurs between a highly active surface such as lithium and a liquid crotonitrile solvent.

The crotonitrile group ion indicated as reacts with other crotonitrile molecules in the anionic polymerization process, gradually increasing the molecular weight of the polymer to finally form a solid. This process continues even after lithium is used up, unless there are additional crotonitrile molecules and there is no material in the system to stop the reaction.

According to the present invention, crotonitrile can be successfully used in non-aqueous batteries using a high active metal anode if a protective common solvent is added together with crotonitrile. One example of a good protective common solvent is propylene carbonate. When lithium is contacted with a protective common solvent propylene carbonate, the following reactions occur in a limited range, forming a thin protective film on the surface of lithium.

If propylene carbonate is mixed with crotonitrile and an ionic solute (metal salt such as LiClO ₄ ) is present, reaction (2) takes precedence and no crotonitrile polymerization occurs. At this time, it is considered that the solute must exist in order to increase the conductivity of the solution so that the reaction (2) (actually believed to be a corrosion reaction) proceeds at a sufficiently high rate to prevent the reaction (1) from occurring. If there is no solute, reaction (1) will occur despite the presence of propylene carbonate. The effective concentration range of these common protective solvents, such as propylene carbonate, is 1-50% by volume of the solvent mixture, in particular 4-30% by volume, in which concentration (2) takes place at a sufficient rate in the solution. To prevent the occurrence of).

If the concentration of the protective common solvent is less than 1% by volume of the solvent mixture, it is not effective in properly forming a protective coating on the metal, and may also cause undesirable chemical and physical reactions between the crotonitrile and the metal anode. It is believed that it cannot be prevented sufficiently. Mixing the protective common solvent at a concentration of more than 50% by volume of the solvent mixture counteracts the useful effects of crotonitrile, that is, allows for high efficiency cathode discharge at high discharge rates. In the case of propylene carbonate, since it is a relatively viscous material, concentrations above 30% by volume of the solvent mixture will rather lower the solution conductivity of the electrolyte and, due to the reduced conductivity, will degrade the performance of the battery itself. To overcome this, it is desirable to keep the viscosity of the solution at least about 5 centipoise by adding a low viscosity solvent.

Other such common protective solvents include ethylene carbonate, γ-butyrolactone, nitrobenzene, methyl acetate, methyl formate, dimethyl sulfoxide, pro-pylene glycol sulfite, Diethylsulfite, 3-methyl sulfolane and the like.

Suitable low viscosity common solvents in the present invention include tetrahydrofuran (THF), dioxolane, dimethoxyethane (DME), dimethyl isoxazole (DMI), dioxane Etc.

If necessary, the low-viscosity common solvent can be mixed to lower the viscosity of the electrolyte to a level suitable for use in the battery, and the viscosity decrease at this temperature is preferably 5 centipoise or less, particularly 3 centipoise or less. .

Also suitable as the high active metal anode of the present invention are lithium (Li), sodium (Na), cadmium (K), calcium (Ca), magnesium (Mg) and alloys thereof, of which lithium is particularly effective. The reason is that lithium is not only a flexible and soft metal that can be readily assembled in batteries, but also has the highest energy / mass ratio in the appropriate group of anode metals. If sulfolane or its alkyl substituted der-ivatives are used as the protective common solvent, the sodium anode is not suitable because it causes a reaction with the protective common solvent.

The negative electrode used in the present invention is a solid electrode containing fluorinated carbon represented by the structural formula (CF _x ) _{n wherein} X is a value between 0.5-1.2 and n is a monomer unit that can be widely varied. It represents the number of. Copper sulfide (CuS), nickel fluoride (NiF ₂ ), copper oxide (CuO), manganese dioxide (MnO ₂ ), lead dioxide (PbO ₂ ), ferric sulfide (FeS ₂ ), copper chloride (CuCl ₂ ), silver chloride ( AgCl), sulfur (S) and the like are also used as the cathode. The (CF _x ) _n electrode is a mixture of carbon and fluorine, where carbon refers to non-graphite forms such as graphite and coke, charcoal or activated carbon. As also disclosed in US Pat. Nos. 3,536,532 and 3,700,502, solid fluorocarbon electrodes are extremely stable and resistant to chemicals in the value of x in the 0-1 range.

It is most appropriate when the (CF _x ) _n cathode has an X value of 0.8-1.1, since the most useful energy density of the cathode material is obtained in this range of values.

Ionic solutes used in the present invention are suitable for simple salts (LiClO ₄ ) or double salts or mixtures thereof, which are ionically electrically conductive when they are dissolved in one or more solvents. It is because it becomes a whitish solution. Suitable solutes are the conformation of inorganic or organic Lewis acids with inorganic ionic salts. One requirement for practical use is that, whether the salt is a simple salt or a double salt, it may be present with crotonitrile and, using a common solvent, with the ionic conductivity of the solution at least 10 ⁻⁴ ohm ⁻¹ cm ⁻¹ . Is to have sufficient electrical conductivity. In general, at least about 0.5 M (moles / L) is an amount suitable for use in most cells.

According to Lewis and acid theory of acids and bases, many substances that do not have active hydrogen can act as acceptors of acids or electron pairs. Its fundamental concept is introduced in a chemistry paper (Journal of the Franklin Institute, Vol 226, pages 293-313, published by Lewis on December 7, 1938).

The proposed reaction mechanism for how these complexes (solutes) work in solvents is described in detail in US Pat. No. 3,542,602, and the double or double salts formed between Lewis acids and ionic salts are more stable than if each component alone. Suggests that.

Typical Lewis acids include aluminum fluoride, aluminum bromide, antimony pentachloride, zirconium tetr-achloride, phosphorus pentachloride, phosphorus pentafluoride, boron fluoride, boron chloride, boron bromide, and arsenic fluoride.

Ionic salts that can be used with Lewis acids include lithium fluoride, lithium chloride, lithium bromide, lithium sulfide, sodium fluoride, sodium chloride, sodium bromide, potassium fluoride, potassium chloride and potassium bromide.

The double salts formed by Lewis acid and inorganic ionic salts can be used for this purpose, and it is well known that the individual components are separately mixed with a solvent to form the double salts or the resulting ions. Suitable for such double salts are lithium tetrachlorides produced by the mixing of aluminum chloride and lithium chloride. Other good salts include tetrafluorolithium borate (LiBF ₄ ), hexafluorolithium phosphate (LiAsF ₆ ) 6fluorolithium phosphate (LiPF ₆ ), and fluoropotassium phosphate (KAsF ₆ ).

The main selection criterion for ionic salts is that it does not react with crotonitrile, the protective common solvent and the electrodes of the cell. As such, the non-aqueous electrolyte should be substantially non-reactive with respect to the highly active positive electrode metal, while at the same time the positive electrode should not be fully stabilized as the current flow is delayed when the battery is discharged.

All crotonitriles, protective common solvents, and solute combinations should not be considered as effective electrolytes in all positive / cathode cell systems, and once the positive and negative components of a nonaqueous cell are selected, they may be combined with the crotonitrile of the present invention. It is up to the skill of the technician to choose the appropriate protective common solvent and solute used to make the electrolyte work effectively in the nonaqueous battery system.

For example, propylene carbonate is a good protective common solvent and, when added in a 1M lysate of LiClO ₄ with different concentrations of crotonitrile, exhibits a conductivity change as shown in Table 3. This indicates that the conductivity decreases as the concentration of propylene carbonate increases.

TABLE 3

Recommended nonaqueous cell systems according to the present invention are shown in Table 4.

TABLE 4

Example 1

A nonaqueous button cell, 1.7 inches (4.32 cm) in diameter and 0.35 inches (0.91 cm) in height, contains a solid cathode of CuS or (CF _x ) _n , an electrolyte of 1M LiClO ₄ solution in crotonitrile, and lithium. Assembled using anode. In particular, each cell is assembled by placing a solid negative electrode in a nickel container and adding a separator containing 1 ml of electrolyte thereon, which consists of two layers of "Celgard 2400" material and fiberglass. A lithium electrode consisting of a lithium die pressed onto an expanded nickel screen is placed on top of the separator and fitted with a fibrous giass pad to contain extra electrolyte if necessary. These cells are covered with nickel lids at the top, which are placed on an annular polypropylene gasket with an L-shaped cross section, which in turn is mounted on the circumferential surface of the vessel. It seals between the cover, the gasket and the container, and seals the entire Iro seed cell.

For different current outflows for a specific short circuit voltage, the discharge capacity of the cathode, the cathode efficiency and the average discharge voltage with short circuit were obtained for each cell and are shown in Table 5. Because the cells are limited to the negative electrode, the negative electrode efficiency was calculated as a percentage based on the theoretical capacity of the negative electrode material useful for each cell.

For example, the efficacy of CF (X = 1) as a negative electrode material in a lithium anode battery discharged at 1 mA / cm 2 in a 1.5 volt short circuit is calculated as follows.

If you represent the scheme,

Therefore, using 1 gram of CF results in an equivalent weight ratio of 1/31.

Since one Faraday is obtained from one equivalent weight, AH for each equivalent weight is calculated as follows.

Therefore 1/31 equivalent weight × 26.8AH / Equivalent weight = 0.864AH

This 0.864AH or 864mAH is the theoretical capacity per gram of CF material when the CF material is used as a negative electrode in a lithium anode battery. And using this calculation, the negative electrode efficiency of (CF _x ) _n material and the negative electrode efficiency of other negative electrode material can be calculated when it is used as negative electrode in battery with different electrolyte.

The experimental data according to Table 5 show that as shown, the discharge capacity and negative electrode efficiency of the battery containing crotonitrile are extremely low, and if crotonitrile is used as the sole solvent, it is not suitable for non-aqueous cells.

TABLE 5

Example 2

Several similar types of button cells were made as described in Example 1. The difference is that each electrolyte is a 1 mole LiClO ₄ solution with different concentrations of crotonitrile and propylene carbonate. The negative electrode used in each of these cells is a solid (CF _x ) _n negative electrode, and X has a value between 0.85-1.0.

The average discharge voltage, cathode efficiency, discharge capacity, etc. in the discharge range of 0.1 mA / cm 2 -5.0 mA / cm 2 are shown in Table 6. The experimental data of Table 6 show that the negative electrode efficiency increases when using a crotonitrile-based electrolyte by mixing propylene carbonate and LiClO ₄ . The data also show that the concentration of propylene carbonate can vary between 10-30% by volume of the solvent mixture, providing a good electrolyte for non-aqueous lithium electricity.

TABLE 6

Example 3

Several similar types of button-type batteries were prepared in accordance with Example 1 except that different cathodes were used, with different concentrations of crotonitrile and propylene carbonate in the LiClO ₄ electrolyte solution.

Discharge capacities, average discharge voltages, and cathode efficiencies were obtained for each battery using a 1mA / cm2 emission current for a specific short-circuit voltage, shown in Table 7. As is well known in the art, CuS cells are discharged in two stages, so the data obtained for CuS cells represent two stage discharges.

As indicated in Table 7, crotonitrile mixed with propylene carbonate and an ionic solute produces an electrolyte suitable for use in nonaqueous cells.

It is believed that the negative electrode efficiency over 100% at night for the NiF ₂ negative electrode is within the range of the experimental error and is not important.

TABLE 7

1M LiCLO ₄ -Various Cathodes-Discharge Rate 1.0㎃ / ㎠

Although the present invention has been described in accordance with many embodiments, these examples do not limit the scope of the invention.

Claims (1)

It consists of a highly active metal anode, a solid cathode, and a non-aqueous electrolyte consisting of crotonitrile, cosolvent and ionizing solute, the cosolvent being propylene carbonate, ethylene carbonate, γ-butyrolactone, nitrobenzene, methyl Acetate, sulfolane, 3-methyl sulfolane, methyl formate, dimethyl sulfoxide, propylene glycol sulfite and diethyl sulfite, the metal anode consisting of lithium, sodium, potassium, calcium, magnesium and their alloys The solid cathode is selected from the group consisting of (CF _x ) _n , copper sulfate, nickel fluoride, copper oxide, manganese dioxide, lead dioxide, ferrous sulfide, copper chloride, silver chloride and sulfur and the electrolyte is tetrahydrofuran , Selected from the group consisting of dioxolane, dimethoxyethane, diethylisoxazole and dioxane A nonaqueous battery of an electrolyte containing crotonitrile, characterized in that it contains an auxiliary solvent.