Manganese dioxide, also known as "manganese peroxide", "black manganese oxide", is a black orthorhombic crystal or brown-black powder, and there are many variants. Insoluble in water, nitric acid, cold sulfuric acid and acetic acid, soluble in cold and concentrated hydrochloric acid to generate unstable light brown-green MnCl4, which is heated and reacted with concentrated hydrochloric acid to release chlorine gas. It reacts with concentrated sulfuric acid and releases oxygen slowly, and can be dissolved in dilute sulfuric acid or nitric acid in the presence of H2O2 or H2C2O4. When heated to 600℃ in air, it releases oxygen and transforms into Mn2O3, and when it is white hot, it transforms into Mn3O4. It is a strong oxidant and cannot be heated or rubbed together with organic substances or other oxidizable substances, such as sulfur, sulfide, phosphide, etc. It exists in nature as pyrolusite. Preparation method: It can be prepared by heating manganese nitrate crystals in the air at 150-190 ℃ for a long time.

1. Method for preparing electrolytic manganese dioxide with high compaction density
Since electrolytic manganese dioxide is an inexpensive and abundant material, and it has excellent discharge and long-term storage properties, it is commonly used as an active material for dry battery cells. For example, electrolytic manganese dioxide is used as a material for positive electrodes in alkaline primary batteries. Electrolytic manganese dioxide is typically prepared by passing a direct current through an electroplating bath containing an acidic solution of manganese sulfate and sulfuric acid.

The positive electrode of the electroplating cell may comprise a titanium plate with electrolytic manganese dioxide deposited thereon. The negative electrode can be made of graphite or copper or similar materials. When the deposited electrolytic manganese dioxide reaches a thickness of about 1 mm to about 75 mm, it is removed from the titanium plate with an external force, and it can be pulverized to a maximum size of 25-100 mm to obtain electrolytic manganese dioxide for further processing Manganese fragments. The size of the electrolytic manganese dioxide fragments is further reduced using a grinding or pulverizing process to meet battery manufacturer requirements. Since electrolytic manganese dioxide is prepared in an acid bath, the preparation of electrolytic manganese dioxide usually requires washing or caustic treatment of electrolytic manganese dioxide to neutralize the residual acidity of the acid bath.

This treatment can be performed before or after pulverizing the electrolytic manganese dioxide. If the neutralization step is performed after the pulverization step, the electrolytic manganese dioxide particles are usually suspended in an aqueous solution to which sodium hydroxide has been added, and once the acidity is neutralized, dehydration is then performed to separate the aqueous solution from the solid electrolytic manganese dioxide particles . The material obtained after the neutralization step is called neutralized electrolytic manganese dioxide. In the final step, the electrolytic manganese dioxide is dried to a certain size.

For example, for alkaline galvanic cell applications, the drying step is generally mild, leaving physisorbed water, which may comprise from about 1% to about 3% by weight of the product. The resulting material is an active material for alkaline primary batteries. Battery manufacturers use electrolytic manganese dioxide as the active material for the positive electrode in alkaline batteries against the zinc anode. The electrolytic manganese dioxide is combined with other materials that make up the positive electrode precursor and compacted by means of a tool. The amount of electrolytic manganese dioxide encapsulated in a predetermined volume of battery is an important factor in determining battery performance. The electrolytic manganese dioxide compaction density is a parameter used to predict the amount of electrolytic manganese dioxide that can be loaded into a battery. High compaction densities are preferred for battery manufacturers because batteries with a predetermined volume will have better performance when electrolytic manganese dioxide is more densely compacted.

2. Ultrasonic cleaning method of manganese dioxide
Electrolytic manganese dioxide is the best depolarizer material for zinc-manganese batteries. With the development of the battery industry, battery manufacturers have higher and higher requirements for electrolytic manganese dioxide materials, among which the discharge performance of electrolytic manganese dioxide is the top priority. Heavy. To this end, electrolysis manufacturers and many scientific research departments have invested a lot of effort to find more reasonable processes from the electrolysis process and post-treatment process to produce electrolytic manganese dioxide with higher quality. Especially the washing process of the product.

In the past, the industrial production method was to use hot water, stir and soak for a long time, wash repeatedly for many times, and then filter. Moreover, the cleaning effect of impurities is not good. In the article "Production Process of Electrolytic Manganese Dioxide for Mercury-Free Alkaline Manganese Batteries" ("Battery" publication, 2003, 33(2), p. 102, written by Xiao Zheng), it is suggested that the high-pressure steam washing method can be used. Involving high pressure, it is difficult to realize a large number of manganese dioxide processing equipment, and the process is complicated. The purpose of the present invention is to provide a method for ultrasonic cleaning of manganese dioxide, which has good effect of removing impurities, short production time, high efficiency, and can greatly improve the discharge performance of manganese dioxide.

To achieve the above purpose, CN03156025.3 adopts the following technical scheme: a method for ultrasonic cleaning of manganese dioxide, the method comprises the following steps:

(1), mix industrial manganese dioxide and water to be mixed with manganese dioxide and water, place in the container that is provided with heater and agitator; Or, in the container that is provided with heater and agitator , Mix industrial manganese dioxide and water to prepare a mixture of manganese dioxide and water;

(2), put the container into the ultrasonic tank in the ultrasonic equipment again, and put water in the ultrasonic tank;

(3), use heater to heat up, and stir, and carry out ultrasonic treatment at the condition that frequency is 25-40KHz;

(4) After ultrasonic treatment, take out the mixed solution of manganese dioxide and water, after filtration, drying manganese dioxide is completed.

The invention adopts the ultrasonic treatment method and uses ultrasonic cavitation to generate strong impact, destroying the gas film and liquid film on the surface of the micro-particles, so that the lotion can fully contact the surface of the micro-particles of manganese dioxide and impact the particles entering the manganese dioxide. The inside of the pores is then separated from the surface and micropores of the manganese dioxide particles to achieve the purpose of washing the surface and the interior of the manganese dioxide microparticles.

3. A controllable method for preparing nanometer manganese dioxide
The methods for preparing MnO2 mainly include liquid phase coprecipitation method, low temperature solid phase method, thermal decomposition method, hydrothermal synthesis method and sol-gel method. Among them, the liquid-phase precipitation method has the characteristics of simple, rapid, complete and low-cost reaction, but the disadvantage is that the morphology of the reaction product cannot be controlled during the reaction process, and the obtained particle size is large.

CN201711140262.8 proposes a method for preparing MnO2 by adding dodecyl ammonia bromide (CTAB) as a surfactant. The technical scheme of CN201711140262.8 is: a controllable preparation method of nano manganese dioxide, which adopts the following steps:

Step 1: Preparation of manganese dioxide active material: add surfactant to 200moL of 0.1mol/L KMn04 solution, dropwise add 300moL of 0.2mol/L Mn(CH3COO)2 solution within 2h, stir for 8h, The precipitated product is washed with deionized water and ethanol and filtered, and the filtrate is dried and ground to obtain a brown-black manganese dioxide active substance;

Step 2: Preparation of manganese dioxide electrode sheet: Mix manganese dioxide active material, conductive carbon black and binder polytetrafluoroethylene (PTFE), stir with N-methylpyrrolidone to form plasticine, press down on Ti A manganese dioxide electrode sheet is prepared on the chip.

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