JPS636496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an improved process for producing manganese dioxide from manganous salts (ie, Mn ⁺² ). The method includes the step of intimately contacting at least one manganous salt with at least one compound selected from the group consisting of alkali metal permanganates and ammonium permanganate. The materials brought into intimate contact undergo a two-step heating schedule to produce electrochemically active manganese dioxide.

BACKGROUND OF THE INVENTION The use of manganese dioxide as a positive electrode active material (depolarizer) in non-aqueous batteries is known. Easily available manganese compounds that have been used as raw materials for manganese dioxide include manganese chloride, manganous sulfate, and manganous carbonate. Typically, these manganous salts are thermally decomposed to yield manganese dioxide. For example, Advanced Inorganic Chemistry, F. A. Cotton and G. Wilkinson, Interscience, published by John Wylie and Saiz (3rd edition, 1972), p. states that it is produced by heating at a temperature of approximately 530°C. However, such processes lead to the production of highly crystalline beta form of manganese dioxide, or pyroluthite. This material is used in aqueous batteries of the Lecrancier type, but generally does not produce satisfactory results, as do other types of manganese dioxide.

European Patent No. 27076 discloses a process for the pyrolysis of manganous tetrahydrate nitrate to form fully beta manganese dioxide. More specifically, this method involves heating Mn(NO ₃ ) ₂ 4H ₂ O at 150°C.
The product thus obtained is washed first with hot distilled water and then with a 1% ammonium hydroxide solution, and the material is then dried at a temperature of the order of 400°C to 450°C. including the step of However, when the moisture-resistant manganese dioxide made using the method of this patent is used in lithium/non-aqueous batteries,
This type of cell does not produce commercially useful efficiency at temperatures between 21°C and 35°C. The inventor believes that the reason for the poor performance of the thus thermally decomposed manganese nitrate at these temperatures is that the beta-manganese dioxide produced has a highly crystalline form.

Other approaches have also been adopted to produce electrochemically effective manganese dioxide from manganous salts. Among the most effective of these approaches is the method described in US Pat. No. 4,048,027. It consists in producing amorphous electrolytic manganese dioxide ("EMD") by electrolysis of hexahydrated manganese nitrate. Generally, EMD is
It can be heat treated to reduce its moisture content as described in UK Patent No. 1,199,426 and US Pat. No. 4,133,856 and has desirable electrochemical properties for non-aqueous batteries. However, heat treated
Even EMD, when exposed to ambient humidity,
Even in a dry room with a relative humidity of 3%, it absorbs moisture, making it difficult to assemble a lithium battery that uses EMD as a cathode material and retains its capacity. As is known in the industry, the water in _MnO2 reacts with the lithium and/or non-aqueous electrolyte, resulting in bulging from the initial height of the cell.

U.S. Patent Application No. 451,877, dated December 31, 1981, and a continuation in part of U.S. Patent Application No. 451,877, dated March 24, 1983.
No. 476,639 (which patent application is incorporated herein by reference) discloses a novel form of manganese dioxide and a process for its production. This new manganese dioxide is
It has a low area combined with a high degree of amorphousness. More specifically, this type of manganese dioxide has a surface area of about 15 m ² /g or less and a d value of about 30% or less when compared to crystalline beta-type manganese dioxide (IC sample No. 6). , d value
It has an X-ray diffraction pattern showing a relative intensity of about 80% or less at 2.41 Å, about 65% or less at d value of 1.63 Å, and about 65% or less at d value of 1.31 Å. Such properties are believed to be the reason why this type of manganese dioxide has high water absorption resistance and high electrochemical activity. Crystalline Beta Manganese Dioxide (IC
No. 6) is the minutes of the 1st Manganese Dioxide Conference,
Refers to IC sample No. 6 described by A. Kozawa and RA Power in P.4, V1, Cleveland, published by the Electrochemical Society. This type of manganese dioxide produces an x-ray diffraction pattern essentially identical to that reported in ASTM Card No. 24-735.

However, although the manganese dioxide of this patent has desirable properties, the described method for producing such manganese dioxide is limited to the use of raw materials containing manganous hexahydrate nitrate. Hexahydrated manganous nitrate can be prepared by means known in the art (e.g., "Hydrated Nitrates of Divalent Metals", D. Weigel, B. Imelik and M. Prettre,
Bull. Soc. Chemi. It is desirable to provide a method that allows this. Also,
The process described in Japanese Patent Application No. 476,639 tends to produce manganese dioxide with a very low surface area of about 1.2 square meters per gram or less unless carefully monitored. This low surface area is
It appears that the pulsing performance of this manganese dioxide at ambient and lower temperatures, ie, 21° C. and below, is adversely affected. By slightly increasing the surface area of the manganese dioxide produced, i.e., to more than about 3.0 square meters per gram, the pulse performance can be improved to an acceptable level without significantly adversely affecting the water absorption resistance of the manganese dioxide. It seems likely that this will be possible.

It is therefore an object of the present invention to provide a process for the production of manganese dioxide which has a relatively low surface area combined with a high degree of amorphism, in which a wide variety of raw materials can be used.

Another object of the invention is to provide a method for producing manganese dioxide having a relatively low surface area combined with a high degree of amorphism, which manganese dioxide exhibits desirable pulsing properties in non-aqueous batteries at room temperature. It is in.

The above objects and additional objects will become apparent from the examples below.

SUMMARY OF THE INVENTION The present invention provides the following features: (a) at least one manganic salt selected from the group consisting of ammonium permanganate and alkali metal permanganate;
(b) placing the manganous salts/permanganates brought into contact with each other in step (a) above in an oxygen-containing gas at a temperature of 120°C to 180°C; , preferably about
(c) heating the material produced in step (b) above to about 210°C in an oxygen-containing gas until substantially complete conversion of the manganous salt to the manganese dioxide-containing material occurs; heating at a temperature of up to about 300<0>C, preferably about 250<0>C, until at least about 85% of the manganese present as oxide is present as _MnO2 .

The water absorption rate of a particular form of manganese dioxide appears to be related to the surface area of this manganese dioxide. However, in order to obtain the desired pulse performance at room temperature (i.e., approximately 21°C) or below,
A certain minimum surface area appears to be desirable. Although some embodiments of the present invention may yield manganese dioxide with a slightly higher surface area (e.g., up to about 50 m ² /g), preferred embodiments of the process of the present invention have a surface area of about 3 m ² /g to 15 m ² The objective is to produce manganese dioxide having a surface area of /g. Manganese dioxide made by the process of the present invention therefore appears to have desirable water absorption resistance with acceptable pulsing performance.

Furthermore, it is theorized that manganese dioxide, which has a more disordered structure, has higher electrochemical properties compared to manganese dioxide, which has a highly crystalline structure. It is therefore believed that manganese dioxide produced by the method of the present invention has a relatively amorphous structure and is therefore highly suitable for use in electrochemical cells.

The term "manganous salt" as used herein refers to a compound containing manganese in the +2 valent state. Representative examples of manganous salts used in the method of the present invention are:
manganous nitrate, manganous chloride, manganous sulfate, manganous carbonate, and mixtures thereof. However, care must be taken when manganous chloride is used since chlorine gas is released during the formation of manganese dioxide. The manganous salt raw material can be in a hydrated or anhydrous state. The preferred manganous salt source is a 50% aqueous solution of manganous nitrate because of its commercial availability and desirability of the resulting product properties.

Typical examples of alkali metal permanganates used are potassium permanganate, lithium permanganate and sodium permanganate. Ammonium permanganate may also be used, but the use of this compound is undesirable due to its explosive properties.

The alkali metal permanganate and/or ammonium permanganate is about 1 to 20% by weight based on the weight ratio of anhydrous alkali metal permanganate and/or ammonium permanganate to anhydrous manganous salt, preferably about It is added in an amount of 5 to about 10% by weight, based on the manganous salt raw material.

The method of the invention is typically carried out as follows. The manganous salt raw material is prepared by any means known to those skilled in the art, such as grinding, rolling, mixing, etc.
Close contact with alkali metal permanganate. (Due to its explosive nature, ammonium permanganate is not included in the description of this representative embodiment of the invention. However, if it is desired to use this compound, it is an alkali metal permanganate. ). A preferred method of achieving such intimate contact when manganous hexahydrate nitrate is used as a raw material is to provide a temperature sufficient to melt the manganous hexahydrate nitrate, i.e., at a temperature of about 100°C; A mixture of this compound and an alkali metal permanganate is heated. The mixture is then cooled to form a solid mass and the mass is ground to form a manganous nitrate/alkali metal permanganate material in intimate contact. This melting must be carried out in an oxygen-containing gas.

The heating step of the process of the invention is typically carried out in a closed reactor to control the moisture in the reactor. The reactor is equipped with an inlet for pumping oxygen or oxygen-containing gas. The reactor must also have a degassing port through which gases released by the reaction can escape. The degassing means must also include oil-filled traps to prevent back diffusion of air or water vapor.

Place the manganous salt/alkali metal permanganate material in intimate contact into the reactor and begin a continuous flow of dry or wet oxygen-containing gas. In this case, the term "dry oxygen-containing gas" means a gas that has not been bubbled into water before entering the reactor. Conversely, the term "wet oxygen-containing gas" means a gas that is bubbled through water before entering the reactor. Next, the reactor is heated to about 120℃~approx.
Heat to 180°C, preferably about 150°C, preferably slowly. Such heating step occurs for about 15-30 minutes, although longer or shorter times can be used.

When the desired temperature is reached, the reaction system is maintained within this temperature range until substantially complete conversion of the manganous salt to the manganese dioxide-containing compound is achieved. This conversion is typically indicated by the formation of a black mass. Typically, such temperature is maintained for about 1 to 4 hours, preferably about 2 hours. As will be apparent to those skilled in the art, this period will depend on the temperature selected, reaction batch size, composition of the raw materials, and other similar factors. The oxygen-containing gas introduced into the reactor during this isothermal period can be a wet gas or a dry gas.

After the first heating stage described above is completed, the reaction product of this stage is further heated to about 210<0>C to about 300<0>C, preferably about 250<0>C. This second temperature increase is
When carried out as a single step, preferably about 15
It is carried out for a time period of from about 60 minutes to about 60 minutes, most preferably about 20 minutes. This second heating step can occur in the presence of wet or dry oxygen-containing gas.

When the desired temperature of this second heating stage is reached, at least about 85% of the manganese present as an oxide in the manganese dioxide-containing material produced in the first heating stage is
The reaction is held at said temperature for a sufficient time to change the properties of this material such that % _MnO2 is present. Typically, this time will be about 1 hour to about 4 hours.
time, preferably about 2 hours. Care must be taken to ensure that this high temperature holding period is not too long. Otherwise, the product will be too crystalline and have undesirable electrochemical properties. The crystallinity of the manganese dioxide during this second heating stage is monitored by periodically performing X-ray diffraction analysis on a sample of the produced manganese dioxide. The product is then allowed to cool to room temperature. This cooling is preferably carried out in dry oxygen-containing gas.

The produced crude manganese dioxide is preferably washed with an acidic solution to remove alkali metal ions. Most preferably, in many cases of the manganous salts of the present invention, the acid used for such washing corresponds to the anion of the manganous salt used. That is, when manganous chloride is used as a raw material, preferably hydrochloric acid is used, when manganese sulfate is used, sulfuric acid is preferred, and when manganous nitrate is used, nitric acid is preferred. In the case of manganous carbonate, hydrochloric acid, nitric acid or sulfuric acid can be used. This pickling is preferably carried out at an elevated temperature of about 60°C to about 70°C. The pickled manganese dioxide is washed with water and then heated to about 125℃~
Dry by heating at a temperature of approximately 150°C.

Manganese dioxide produced by the method of the present invention exhibits desirable electrochemical properties, including desirable pulsability at ambient temperatures. Many embodiments of the invention also produce manganese dioxide with a surface area of 15 m ² /g or less. Therefore, the manganese dioxide is not operated in a dry box (with a moisture content of about 50 ppm to about 100 ppm) but in a dry room (about
% to about 3% relative humidity).

EXAMPLES The following examples are intended to further illustrate the invention and are not intended to limit the scope of the invention in any way.

Example 1 A quantity of intimately combined hexahydrate manganous nitrate/potassium permanganate was made as follows. 80% by weight (19.24g) of Mn( _NO3 ) ₂ .
6H ₂ O and 20% by weight (3 g) KMnO ₄ were placed in a 500 ml conical flask equipped with a two-necked rubber stopper. One neck of the flask is connected to an oxygen tank and the other neck serves as a gas outlet (these weight percentages are based on the anhydrous Mn( _NO3 ) ₂ : _KMnO4 ratio). Until the manganous hexahydrate nitrate melts,
Heat the mixture at 100°C. KMnO ₄ hardly dissolves in melted manganous hexahydrate nitrate;
The solidified mass was then cooled, removed from the flask and ground.

This milled mixed material was placed into the same flask assembly as above. The temperature of this flask is about 20
Raise the temperature from room temperature to 150℃ in minutes. During this period, dry oxygen is pumped directly from the tank into the flask at a flow rate of about 1 cubic foot per hour.

When the temperature reached 150°C, the system was held at this temperature for approximately 2 hours. The temperature was then increased to approximately 250°C for half an hour. During this entire period (i.e.
Dry oxygen continued to flow directly from the tank into the flask at a flow rate of approximately 1 cubic foot per hour (during the 2 hour hold at 150°C and subsequent temperature ramp to 250°C).

The temperature of the flask was maintained at 250°C for 2 hours.
Next, it was cooled to room temperature. During this period, dry oxygen was continuously pumped into the reactor.

The crude manganese dioxide obtained in this way was
℃, washed with 10% aqueous nitric acid, filtered, and washed several times with water. The final product was heated to about 125°C to about 150°C for 16 hours.
Dry by heating at a temperature of °C.

Elemental analysis showed that the product was 98.63% by weight of manganese dioxide based on the total weight of the product, and the manganese dioxide had the molecular formula MnO _2.00.
It had In the formula MnOx, “x” is [1
+% peroxide/100], where "peroxide" is defined as the total manganese content in the tetravalent form. The surface area of this product was determined by the BET method and was 10.7 m ² /
It was quantified as g. This method is described in J.Am.Chem.
Soc., Vol. 60, pp. 309-316 (1938) by S. Brunauer, P. Emmett and E. Teller.

Example 2 The apparatus used in Example 1 was used, except that manganous hexahydrate nitrate was used as the manganous salt, and the weight ratio of manganese nitrate and potassium permanganate was 90:10. produced several grams of manganese dioxide using a method similar to Example 1. The product was determined to be 94.92% by weight of manganese dioxide based on its total weight, and the manganese dioxide had MnO _1.99 . Its surface area is 6.70
It was determined as square meter/gram.

Example 3 Several grams of manganese dioxide were produced in the same manner as in Example 2, using the equipment used in Example 1, but using trihydrated lithium permanganate instead of potassium permanganate. . The ratio of hexahydrated manganous nitrate to trihydrated lithium permanganate is 90: based on Mn( _NO3 ) ₂ : _LiMnO4 .
It was 10. This product is based on its total weight
It was determined to contain 88.85% by weight manganese dioxide. Said manganese dioxide has the formula MnO _1.99 . The surface area was determined to be 3.15 square meters/gram.

Example 4 Using the apparatus of Example 1, the ratio of hexahydrated manganous nitrate to trihydrated lithium permanganate was 95:
A few grams of manganous hexahydrate nitrate were treated using a method similar to Example 3 _, except that 5 (Mn(NO ₃ ) 2 :LiMnO ₄ based) was used. The product was determined to contain 93.36% by weight of manganese dioxide, based on its total weight, which had the formula MnO _1.99 .

Example 5 8.25 g of KMnO ₄ and 150 ml of 50% Mn(NO ₃ ) ₂ were heated in air in an evaporating dish at about 130° C. until oxidation occurred. It was then heated in air at 150°C for 2 hours, followed by 250°C for 2 hours.

_MnO2 containing 3.06% potassium was obtained, which was treated with 10% nitric acid solution, washed with distilled water, and then dried at 110 °C overnight. Analysis showed a product containing 97.38% manganese dioxide based on the total weight. This manganese dioxide has the formula MnO _1.98 . The surface area was 5.1 square meters/gram.
X-ray analysis showed a pyroluthite pattern with amorphousness as defined in US Pat. No. 4,766,39.

Example 6 About 40% by volume of 1,3-dioxolane, about 30% by volume of 1,2-dimethoxyethane, and about 30% by volume
of 3-methyl-2-oxazolidone and about 0.2
The material of Example 1 was introduced into a cell filled with a non-aqueous electrolyte consisting of % dimethyl isoxazole and 1 mol/liter of the solvent LiCF ₃ SO ₃ . The contents of the battery were 40 milligrams of lithium as a negative electrode, about 1.5 ml of the electrolyte described above, a nonwoven polypropylene separator with a portion of the electrolyte adsorbed, and 86.2% by weight of MnO ₂ (produced in the same manner as in Example 1). and 0.35 g of a positive electrode mix consisting of 8.5% by weight graphite, 2.1% by weight acetylene black, and 3.2% by weight polytetrafluoroethylene binder.

Tests were conducted at 21°C and 35°C until a 2-volt cutoff was reached. A load resistance of 30000 ohms (0.1 mA/cm ² positive electrode current density) was used for continuous discharge, and 2 times every 3 days for pulsed discharge.
A weight load of 250 ohms for 2 seconds was used. this
_MnO2 is 83.7% up to 2 volt cut-off at 21℃
The efficiency was 94.0% at 35°C (based on one electron decrease). The pulsing behavior of manganese dioxide produced by the method of the invention was approximately equivalent to that exhibited by heat treated Tetsukosia EMD at these temperatures.

Claims (1)

[Claims] 1 (a) at least one manganous salt in intimate contact with at least one compound selected from the group consisting of alkali metal permanganates and ammonium permanganate; (b) introducing the intimately contacted manganous salt/permanganate material made in step (a) for about 120 min until substantially complete conversion of the manganous salt to the manganese dioxide-containing material; (c) heating the material produced in step (b) to a temperature between about 180°C and about 180° _C ; heating at a temperature ranging from about 210° C. to about 300° C. until the amount of manganese dioxide is present. 2 The alkali metal permanganate and/or ammonium permanganate is about 1% by weight to about 20% by weight based on the weight ratio of anhydrous alkali metal permanganate and/or ammonium permanganate to anhydrous manganous salt. 2. The method of claim 1, wherein the manganese salt is contacted in an amount in the range of % by weight. 3. The alkali metal permanganate and/or ammonium permanganate is about 5% by weight to about 10% by weight based on the weight ratio of anhydrous alkali metal permanganate and/or ammonium permanganate to anhydrous manganous salt. 3. The method of claim 2, wherein an amount of % by weight is contacted with the manganous salt. 4. The method of claim 1, wherein the temperature of step (b) is maintained for about 1 hour to about 4 hours. 5. The method of claim 4, wherein the temperature of step (c) is maintained for about 1 hour to about 4 hours. 6. The method of claim 1, wherein the temperature in step (b) is about 150°C and this temperature is maintained for about 2 hours. 7. Claim 6, wherein in step (c) the temperature is raised to 250°C and held at this temperature for about 2 hours.
Section method. 8. The method of claim 1, wherein the manganous salt is selected from the group consisting of manganous nitrate, manganous chloride, manganous sulfate, manganous carbonate, and mixtures thereof. 9. The method of claim 8, wherein the manganous salt is a 50% aqueous solution of manganese nitrate. 10. The method of claim 1, wherein the alkali metal permanganate is selected from the group consisting of sodium permanganate, lithium permanganate, potassium permanganate and mixtures thereof. 11 The manganese salt is manganous nitrate hexahydrate, and step a involves heating this compound and the permanganate at a temperature sufficient to melt the manganous nitrate hexahydrate. , a patent for bringing said manganous hexahydrate nitrate into intimate contact with an alkali metal permanganate and/or ammonium permanganate by cooling the molten manganese material into a mass and crushing the mass. The method according to claim 1.