JPS6138584B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to batteries. More particularly, the present invention relates to lithium or lithium alloy negative electrodes (hereinafter referred to as anodes), thionyl chloride active positive electrode depolarizer cells, and the use of certain films to enhance their performance. Recent developments in portable electronic products that require power batteries for energy have highlighted the shortcomings of existing power batteries for the required applications. In an effort to improve battery technology, much attention has been devoted to perfecting what are commonly referred to as lithium batteries. More specifically, this refers to batteries that use highly reactive anodes, such as lithium, in combination with various positive electrodes (hereinafter referred to as cathodes) and electrolytes. In fact, the literature describes numerous examples of lithium anode batteries with various cathodes and electrolytes. Interest in this type of battery technology stems from the recognition that such batteries theoretically offer higher energy density, higher voltage, wider temperature operating range, longer shelf life, and lower cost. Of all the known combinations of lithium anodes and various cathodes and electrolytes, those considered to have the highest energy density and current emission capabilities use certain inorganic liquids as active cathode depolarizers. In battery chemistry, this type is usually called a liquid cathode. The use of liquids as active cathode depolarizers
This is a fundamental departure from conventional battery technology. Until recently, it was generally believed that active cathode depolarizers could never come into direct contact with the anode. However, it has recently been discovered that some active cathode materials do not chemically react with the active anode metal to any appreciable extent at the interface between the active anode metal and the cathode material, allowing the cathode material to be contacted directly with the anode. Ta. Early liquid cathode batteries used liquid sulfur dioxide-activated cathode depolarizers, as described in Maricle et al., U.S. Pat. No. 367,515 (March 2, 1971); It turned out that it was difficult to treat because it was not a liquid at normal pressure. The discovery of a set of inorganic materials that are liquid at room temperature and commonly referred to as oxyhalides was a major advance in the development of liquid cathode batteries. These materials act as active cathode depolarizers. Furthermore, these materials can also be used as electrolyte solvents. Liquid cathode batteries using oxyhalides are described in U.S. Pat. No. 392,669 to Auborn (December 16, 1975) and British Pat. ing. At least one of the oxyhalides mentioned above, thionyl chloride ( _SOC2 ), besides having the general properties mentioned above, also has substantial additional energy density and current emitting capability. However, liquid cathode systems have involved two significant problems that have hindered their widespread use.
First, liquid cathode systems are dangerous under certain circumstances, and second, it has not been possible to produce high current rate cells with good long-term storage characteristics. This first issue arises from a pending application filed in the name of Lubuis R. Giattino and assigned to the same assignee as this application.
No. 828493. The second problem is the subject of this application. This problem appears in two formations. First, there is a voltage lag after storage at high temperatures. That is, after a battery is stored at a temperature above room temperature, it takes some time, from several seconds to several hours, for the battery voltage under a moderate discharge load to approach the level that it reached instantaneously before storage. operation is required. Second, it is difficult to obtain batteries that can reliably deliver current densities of 7 mA/cm ² or higher. These two problems are collectively called the passivation phenomenon. Studies have shown that passivation results from the deposition of compounds on the lithium anode surface. This compound is currently poorly understood, but is generally believed to be a reaction product between lithium and one or more of the following: electrolyte solvents, electrolyte solutes, or impurities, particularly iron. When assembling the battery carefully, a new battery will
Passivation can be minimized. However, storage, especially at high temperatures, rapidly causes passivation. In addition to this, various methods have been attempted to solve the passivation problem. One solution has been to partially discharge the battery before storage. A second solution was to increase the roughness factor of the anode by etching before assembly. A third solution was to pre-treat the cathode current collector to remove impurities. Other solutions have been tried including the introduction of water and certain minerals such as sulfur dioxide. However, to date all known solutions have had little impact on the passivation problem. It is therefore an object of the present invention to reduce the passivation phenomenon in lithium or lithium alloy anode, thionyl chloride liquid cathode cells. Another object of the present invention is to improve the voltage delay of lithium or lithium alloy anode, thionyl chloride liquid cathode cells. Another object of the present invention is to provide improved current density delivery capability for lithium or lithium alloy anode, thionyl oxide liquid cathode cells. Finally, it is an object of the present invention to provide improved storage properties for lithium or lithium alloy anode, thionyl chloride liquid cathode cells. The basis of the invention is the discovery that the passivation problem is significantly alleviated by applying an organic film consisting of a polymer of lower alkyl esters of cyanoacrylic acid to the anode or separator material. According to the invention, a cell chemistry (CeII chemistry) that suppresses the formation of compounds on the anode, while allowing lithium ions to pass through.
Passivation is reduced by a coating placed in contact with the anode that interacts with the anode. In particular, an organic compound that hardens from a liquid to an adhesive film can be applied to the anode and/or separator prior to assembly. In lithium anode, thionyl chloride cathode depolarizer cells, a class of organic compounds known as cyanoacrylics are very effective. The anode is lithium or lithium alloy. The electrolyte solvent, which is also the cathode depolarizer, is thionyl chloride. The electrolyte solute can be a simple or double salt that forms an ionically conductive solution when dissolved in a solvent. Preferred solutes are complexes of inorganic or organic Lewis acids and inorganic ionizable salts. A prerequisite to being useful is that the salt, whether a simple or double salt, be compatible with the solvent used and produce an ionically conductive solution. According to the Lewis or electronic concept of acids and bases, many substances that do not contain any active hydrogen have an acid or acceptor or electron doublet.
doublets). US Patent No. 3542602
The issue suggests that complexes or double salts formed between Lewis acids and ionizable salts produce entities that are more stable than either component alone. Representative Lewis acids suitable for use in the present invention are aluminum chloride, antimony pentachloride, zirconium tetrachloride, phosphorus pentachloride, boron fluoride, boron chloride, and boron bromide. Ionizable salts useful in combination with Lewis acids include lithium fluoride, lithium chloride, lithium bromide, lithium sulfide, sodium fluoride, sodium chloride, sodium bromide, potassium fluoride, potassium chloride,
Contains potassium bromide. The double salt formed by a Lewis acid and an inorganic ionizable salt can be used as the double salt itself, or the individual components can be added separately to a solvent to form the salt. For example, one of the double salts is lithium aluminum tetrachloride, which is formed by combining aluminum chloride and lithium chloride. In addition to the anode, active cathode depolarizer, and ionically conductive electrolyte, the cell requires a cathode current collector. Generally, any compatible solid that is substantially electrically conductive and inert within the cell can be used as the cathode current collector. This is because the function of the current collector is to bring the active cathode material into external electrical contact. It is desirable to have as wide a surface contact as possible between the liquid cathode and the current collector. Porous materials are therefore preferred because they provide a high surface area interface with the liquid cathode material. The current collector can be metal and can be in physical form such as a metal film, screen, or pressed powder. Examples of some suitable metal current collectors are shown in Table 2 of the Orborn patent. The current collector can also be made partially or entirely from carbon. Electrical isolation of the current collector and anode is required to ensure that no cathode or anode reaction occurs unless current flows through the external circuit. A mechanical separator can be used since the current collector is insoluble in the electrolyte and the anode does not react spontaneously with the electrolyte. Materials useful for this function are described in the Orborn patent. Although a variety of cells described in the Blomgung and Orborn patents are possible and to which the present invention can be applied, much of the current interest is in cells that use thionyl chloride as the active cathode depolarizer and electrolyte solvent. This is a result of thionyl chloride's apparent greater energy density and current emitting ability than other liquid cathode systems. Although thionyl chloride cells have been found to have the best performance of liquid cathode systems, their performance is still subject to passivation. The following examples and tables demonstrate the improvements the present invention has made to cells that use thionyl chloride as the active cathode depolarizer. This example and data are given by way of example only and are not intended to limit the invention in any way. Other than the specificity of the particular chemical coating that is the subject of this invention and the method of applying this coating to the battery component, all of the following examples were manufactured by the same method and are nearly identical in nature. Example has an outer diameter of 2.24 cm (0.880 inch) and a maximum height
0.381cm (0.150 inch) with a nominal internal volume of 0.574
It was a button cell with a stainless steel can having a diameter of ^0.035 cubic inches. Anode is 1.73 cm (0.680 inch) in diameter × 0.508 cm thick
(0.20 inch) lithium single disk. The separator was commercially available 95% A ₂ O ₃ ceramic paper baked at 500°C.
The current collector is acetylene black compacted into pellets. The electrolyte is a 1.4 molar solution of lithium aluminum tetrachloride in thionyl chloride. The battery is sealed with a high grade ceramic-metal seal. Various coatings were introduced into the basic cell described above. The basic manufacturing method involves simply assembling the parts by conventional methods. It is most convenient to apply the coating to a particular member prior to assembly. Immediately after assembly, a battery with a coating can exhibit a higher internal impedance than a battery without a coating. This phenomenon can be eliminated by a "burn in" operation, which consists of exposing the cell with the coating to high temperatures for a period of time. Exposure temperature and time are interrelated and must be determined experimentally for each coating. This can be accomplished simply by monitoring the internal impedance of the sample cell over time at some suitable temperature. Generally speaking, there is an inverse relationship between the exposure time and the temperature to which the battery is exposed.
The recommended temperature is 71°C. Each of the following examples describes a particular coating, its method of application, and heat treatment operations. Example 1 A thin layer of methyl cyanoacrylate was placed on both sides of a lithium disk and allowed to cure before assembly. The chemical is a thin liquid before curing and can be applied by any method to form a thin, uniform coating. This material can be diluted with methyl ethyl ketone to aid in applying a thin, uniform coating. After assembly, the battery was heat treated at 71°C for approximately 12 hours. Example 2 In this example, methyl cyanoacrylate was placed only on the separator material and allowed to dry prior to assembly. The preferred method of application is the dipping method. After assembly, the battery was heat treated at 71°C for approximately 12 hours. Example 3 In this example, methyl cyanoacrylate was applied to both the lithium anode and separator material and cured prior to assembly. After assembly, heat the battery to 71℃
It was heat treated for about 12 hours. Example 4 In this example, ethyl cyanoacrylate was applied to the lithium and cured prior to assembly. After assembly,
The storage battery was heat treated at 71°C for about 48 hours. Example 5 In this example, ethyl cyanoacrylate was applied to the separator only and cured prior to assembly.
After assembly, the battery was heat treated at 71°C for approximately 48 hours. Example 6 In this example, ethyl cyanoacrylate was applied to both the anode and separator materials and cured prior to assembly. After assembly, store the battery at 71℃ for approx.
Heat treated for hours. A number of cells of each example were made and tested.
Test procedures were the same for all cells in all examples. Immediately after the heat treatment, the battery was discharged and its initial lifespan was measured. The discharge rate is 10mA, the test temperature is 25
°C, cut-off voltage for practical life measurement is 2.4
It was hot with bolts. After heat treatment, the cells were stored in a furnace at a controlled temperature of 71°C. The batteries were removed periodically and their service life was measured as described above. Additionally, the voltage delay was measured. The test results are shown in Table 1.

[Table] Example 7 Voltage delay and capacity after high temperature storage of Li/SOcl ₂ battery anode coating with vinyl polymer and anode coating with polymer of cyanoethyl acrylate of the present invention (hereinafter referred to as Z coating) compared and evaluated. The evaluation was based on the electrical performance of the D-battery manufactured by AItus. For this comparison, two groups of batteries were made: a battery group of the present invention and a battery group for comparison. The battery group of the present invention is a standard D battery manufactured by Altus with a Z-coated anode, and the comparative group batteries are those described in Japanese Patent Publication No. 119936/1983.
This is a battery whose anode is coated with VYHH (Union Carbide product: a copolymer of vinyl chloride and vinyl acetate). Voltage delay and capacity measurements were made at room temperature for both new cells and cells after high temperature storage.
There were three storage conditions. That is, one week at 71°C and 29 days at 55°C. (See Table 2) With one exception, the batteries were tested for voltage delay capacity with a 2 ohm load at room temperature.
Capacity of cells stored for two weeks at 71° C. was tested at a load of 2.5 ohms. Next, the experimental method and results will be described in more detail. (A) Battery Fabrication Methods All anode assemblies for both groups of batteries were fabricated according to Altus' standard fabrication guidelines. The assemblies of the present invention were Z-coated, again following Altus' standard fabrication guidelines. The assembly of the comparison group battery is shown in the published publication
PVC as described in No. 51-119936
-It was removed from the manufacturing process and placed in a drying room for coating with PVA (VYHH) copolymer. VYHH (white powder) was dissolved in distilled thionyl chloride to make a 3.1 weight percent solution, approximately in the middle of the range specified in the above publication (0.5-6.0 w/o). The anode assembly was immersed in the solution for 1 minute, removed and dried. To determine whether the immersion was successful, take an IR spectrum of the solution.
confirmed. The battery group of the present invention and the comparative battery group were then final assembled as a single unit lot. (B) Test Results-1 (See Table 2) The data in Table 2 demonstrate that the Z coating of the present invention exhibits excellent performance even in new cells.

【table】

[Table] That is, for new batteries, the voltage delay of the battery group of the present invention was 1.1 seconds on average to reach 2.5V, while the average of the comparison group was 5.8 seconds. Also, the average delay for the batteries after one week of storage at 71°C was 30 seconds for the inventive battery group, but the delays for the comparison groups varied. In other words, the shortest time measured was 67 seconds, but some batteries showed more than 210 seconds. Further, in the case of the batteries after two weeks of storage at 71° C., the average voltage delay of the battery group of the present invention was 61 seconds, while the shortest time measured in the comparison group was a large value of 228 seconds. Furthermore, for the batteries after storage for 4 weeks at 55°C, the average delay for the inventive battery group was 30 seconds, compared to 36 seconds for the comparison group.
It was in the range of ~63 seconds. Next, it was also found that there was a large difference in capacity (Ah) data between the two batteries. That is,
The battery of the present invention has an average capacity when new.
The average capacity after storage for 1 week at 10.3Ah and 71℃ is
It was 9.4Ah. On the other hand, in the comparison group after one week of storage at 71°C, only one of the three test cells had a measurable capacity of 2.5V or more. This battery is a new comparison group battery.
It only had a capacity of 4.99Ah compared to 10.2Ah. Further, after two weeks of storage at 71° C., the batteries of the present invention had an average of 7.9 Ah, while all of the comparative batteries showed no capacity above 2.5V. Furthermore, after 4 weeks of storage at 55°C, the batteries of the invention average (at 3.15V)
It was 9.3Ah, but the comparison group battery (at 2.64V)
It was 5.42Ah. (C) Test results - (See Figures 1 and 2) As is clear from Figure 1, the new battery of the present invention reached 2.5V in about 1 second and reached 2.5V in about 12 seconds.
It has reached 3.0V. On the other hand, the comparison battery is 2.5V
It took about 6 seconds to reach 3.0V, and even when a load was applied, it did not reach 3.0V within 18 seconds. The cells of the invention showed their superiority more clearly even in batches stored at high temperatures. That is, in FIG. 2, the battery of the present invention reached 2.5V in 33 seconds, but the comparative battery did not even reach 1V even after 1 minute. Please note that these batteries are heated to 71°C.
It had been stored for one week. (D) Test results - (See Figures 3 and 4) The discharge performance of the batteries was compared. Figure 3 compares batteries stored at 71°C for one week. The batteries of the invention retained 91% of the capacity of a new battery at an average voltage equal to that of a new battery. Note that even after two weeks of storage at 71° C., the cells of the invention retained 77% of their nominal average voltage (not shown). Figure 4 shows the discharge characteristics after storage at 55°C for 4 weeks. As shown in the figure, the comparison battery showed a sharp drop in capacity and operating voltage. On the other hand, the battery of the present invention retained 90% of the capacity of a new battery at standard voltage.

[Brief explanation of the drawing]

FIG. 1 shows the voltage delay curves of a new battery of the present invention and a new battery of a comparative example, respectively. (Room temperature: 2 ohm load) FIG. 2 shows a battery of the present invention and a battery of a comparative example, respectively.
(Room temperature: 2 ohm load) FIG. 3 shows the discharge curves of the battery of the present invention and the battery of the comparative example after storage for one week at 71°C. FIG. 4 shows the discharge curves of the battery of the present invention and the battery of the comparative example after storage at 55° C. for 4 weeks.

Claims (1)

Claims: 1. (a) a cathode current collector; (b) a thionyl chloride active cathode depolarizer; and (c) a lithium or an anode comprising a lithium alloy; (d) an ionically conductive electrolyte comprising a solution of an ionically conductive solute in thionyl chloride in physical contact with the anode and the cathode current collector; ) a passivation limiting film made of a polymer of a lower alkyl ester of cyanoacrylic acid, in contact with at least one of the anode or the separator. 2. A method for producing a battery comprising an anode made of lithium or a lithium alloy, a cathode current collector spaced from the anode, and an ionically conductive electrolyte consisting of a solution of an ionically conductive solute dissolved in thionyl chloride. (a) prior to assembly, coating the anode with a liquid lower alkyl ester of cyanoacrylic acid that cures into an adhesive film; (b) curing it; and (c) coating the coated anode with a liquid lower alkyl ester of cyanoacrylic acid. The above manufacturing method includes various steps of incorporating it into a battery and then (d) heat-treating it. 3. An ion system consisting of a lithium or lithium alloy anode, a cathode current collector, a separator spaced between the anode and the cathode current collector, and a solution of an ionically conductive solute in thionyl chloride. A method of manufacturing a battery comprising a conductive electrolyte includes: (a) coating the separator before assembly with a liquid lower alkyl ester of cyanoacrylic acid that cures into an adhesive film; (c) incorporating the separator into a battery; and (d) heat-treating the separator.