CN1142323C

CN1142323C - Preparation method of cobaltous oxide used as positive pole of alkaline secondary cell

Info

Publication number: CN1142323C
Application number: CNB001062352A
Authority: CN
Inventors: 杰阎; 阎杰; 王登国; 周震; 许光惠; 庞国彬; 高峰; 林进
Original assignee: Nankai University
Current assignee: Nankai University
Priority date: 2000-04-28
Filing date: 2000-04-28
Publication date: 2004-03-17
Anticipated expiration: 2020-04-28
Also published as: CN1321795A

Abstract

The present invention relates to the manufacture of alkali secondary cells. A metal cobalt plate is used as an anode, and a metal nickel sheet or other metal sheets are used as a cathode. A neutral solution of inorganic acid salts of sodium and potassium, which is added with organic acid, is used as an electrolyte, and a pH value is kept to be from 7 to 14 by adding inorganic acid or filling acidic gas in an electrolytic process. Intermediate products are prepared by controlling an electrolytic temperature, a plate clearance, a tank voltage, a current density, etc. After being washed and dried, the intermediate products are roasted at the temperature of 300 to 800 DEG C and under the protection of an inert gas. Finally, CoO or CoO. Co<x> with high reactivity and good bonding performance is obtained. The present invention can greatly improve the utilization rate of the active substance, namely Ni(OH)2, and the CoO or CoO. Co<x> is the most suitable anode additive in the alkali secondary cells containing Ni/MH alkali secondary cells, Ni/Cd alkali secondary cells, etc.

Description

The preparation method of cobaltous oxide used as positive pole of alkaline secondary cell

Affiliated technical field

The present invention relates to the manufacturing of alkaline secondary cell.

Background technology

In recent years, since alkaline secondary cell performances such as Ni/MH, Ni/Cd improve constantly the particularly bonded anodal widespread use of nickel foam.For improving positive active material ball-type Ni (OH) ₂Utilization ratio, in that make must be to wherein adding a certain amount of CoO or CoOCo when anodal _xAdditive.CoO is the meeting slow oxidation in air, and CoOCo _xMore stable, even oxidized, also be that Co is earlier oxidized, and in making battery, use CoOCo _x, can make the required reserve capacity of the easier acquisition of straight envelope battery.CoO and CoOCo as the nickel electrode additive _x, general requirement has good reactive behavior, higher purity is arranged, and should avoid Co ₃O ₄Generation.

Usually the method for preparing CoO has: the 1. thermal decomposition method of cobaltous carbonate or cobaltous dihydroxycarbonate (O.Otetuo, JP08 88005,1996); 2. Co (OH) ₂Thermal decomposition method (Agency of Industrial Science and Technology, JP80,43,404,1980); 3. the high-temperature spray pyrolysis method of cobalt salt solution (K.Noriyuki, J.Mater.Process Manuf.Sci, 1994,2 (3): 315); 4. grey cobalt is deoxidation vacuum cooling (A.I.Vulikh, Zh.Prikl.Khim., 1967,40 (12): 2627 more than 1000 ℃; H.Kyoyuki, JP08,208,238,1996); 5. metal cobalt powder method such as logical rare gas element cooling after the oxidation more than 900 ℃ (G.Astrid, P.Katrin, O.Armin, et al, Ger.DE 195 04 320,1996); Also useful electrolytic process is promptly made electrolytic solution with hydrochloric acid, makes CoCl earlier ₂, and then make Co (OH) with NaOH solution neutralization ₂(Xie Ming, Zhai Yuchun, power technology, 1998,28 (3): 135; Liao Weilin, Huang Liyan, Cui Guodi etc., inorganic chemicals industry, 1995,3:4).This method shortcoming is will constantly replenish hydrochloric acid in the electrolytic process, and electrolysate also will neutralize with a large amount of NaOH, and operation steps is numerous and diverse, and cost is also higher.

4. 5. method requires high temperature or higher vacuum tightness, and it is bigger to consume energy, and industrial realization is difficulty comparatively.By 1. 2. 3. method set out, must use the very high cobalt salt of purity, and the preparation of cobalt salt must be with a large amount of soda acids, and product needs the crystallization several, can cause environmental pollution, the wasting of resources is bigger, and cost is higher.

Summary of the invention

The preparation method who the purpose of this invention is to provide a kind of new cobaltous oxide used as positive pole of alkaline secondary cell.It is to adopt electrolytic process, selects for use the electrolytic condition of optimization to obtain the cobaltous oxide product, and technology of the present invention is simple, and cost is low, the purity height, and product performance are stable, and chemical property is good.

The present invention is to be anode with the cobalt metal plate, in the inorganic salt solution of sodium, potassium, add a certain amount of organic reagent, by in electrolytic solution, feeding sour gas or adding the pH value that mineral acid is controlled electrolytic solution, by control electrolysis temperature, polar plate spacing, current density and bath voltage etc., make the suspension intermediate product, after filtration, step such as washing, oven dry, roasting, finally obtain the CoOCo of alkaline secondary cell special uses such as Ni/MH, Ni/Cd _x(0≤x＜0.2) qualified product.

The present invention is to be anode (putting into the titanium basket) with the cobalt metal plate at first, with a kind of in metallic nickel, cobalt, titanium or the stainless steel is negative electrode, electrolyte solution is inorganic acid salt (muriate, vitriol, carbonate or several mixing that contains sodium, potassium, concentration is 50-300g/l), and a certain amount of organic acid (one or more mixing in citric acid, oxalic acid, xitix, the Weibull, concentration 0-60g/l).Dropping inorganic acid (HCl, H in electrolytic solution at any time when electrolysis ₂SO ₄Or HAc) or feed sour gas, so that the pH value of electrolytic solution maintains certain scope interior (pH=7-14).Electrolysis is carried out in electrolyzer, electrolytic product constantly flows out from the below, filtrate behind fresh electrolyte and the filtration electrolysate enters electrolyzer from the top, will control electrolyte temperature (10-80 ℃), polar plate spacing (1-8cm), bath voltage (1-4V) and current density (200-2000A/m during electrolysis ²).The intermediate product that electrolysis obtains is the complex compound that contains inorganic acid radical and organic acid ionic alkalescence cobalt, and the filter cake through filter gained with deionized water wash (is washed till no Cl ^-Or SO ₄ ^2-), put into baking oven oven dry (30～90 ℃), at last at the roasting kiln roasting that protective gas (argon gas or nitrogen) is arranged, temperature 300-800 ℃, constant temperature 2-7 hour, cool off then, treat the furnace temperature cool to room temperature after, take out product, vacuum packaging.

Positively effect of the present invention is: 1. whole process of production technology is simple, and production cost is low, and environment is not produced pollution; 2. electrolytic solution can be recycled behind some materials that supplement consumed is fallen; 3. in electrolytic process by control organic acid content, can make the CoO product that contains a certain amount of Co, the stability of product is had good effect; 4. CoO or the CoOCo that makes with this method _xProduct electrochemical activity height can improve ball-type Ni (OH) significantly ₂Loading capacity; 5. CoO or the CoOCo that makes with this invention _xAdhesive property is good, with ball-type Ni (OH) ₂The electrode of making is difficult for dry linting, has improved the loading capacity of battery, sees Table 1; 6. can make the class ball-type CoO of different-grain diameter by the control reaction conditions, and the CoO that usual way makes is a thin slice shape, sees Fig. 1 (SEM of different CoO samples schemes, and a is that the present invention makes, and b is that usual way makes); 7. the product purity height that makes of this method.

Substantive distinguishing features that the present invention gives prominence to and marked improvement can be embodied from following embodiment, but they are not that the present invention is imposed any restrictions.

Description of drawings

The SEM figure of the different CoO samples of Fig. 1, a is that the present invention makes, b is that usual way makes; The XRD figure of the CoO sample that Fig. 2 the present invention makes; The XPS spectrum figure of the CoO sample that Fig. 3 the present invention makes; Fig. 4 is CoOCo _xXRD figure, wherein contain the peak of Co.

Embodiment

Embodiment 1

Get 5 kilograms of cobalt metal plates, be placed in the titanium basket of four placed in-line electrolyzers, make negative electrode with two nickel plates in each electrolyzer.Adding concentration in electrolyzer is the electrolyte solution (NaCl and KCl respectively account for 50%) of 160g/l, wherein contains citric acid, oxalic acid mixing acid 30g/l, pH=11,15 ℃ of temperature are put into electrolyzer with cathode and anode, and anode cathode separation is 6cm, bath voltage 3V, anodic current density is 1200A/m ²The product that electrolysis is obtained takes out, washing, 65 ℃ of oven dry (containing micro-moisture).Under nitrogen protection, will fill intermediates and put into stoving oven, 400 ℃ of following roastings 6 hours.After being cooled to room temperature, take out product, its structure is seen Fig. 2 (XRD figure of the CoO sample that the present invention makes).

Cobalt contents, foreign matter content and other physical property measurement data are as follows in the cobaltous oxide:

Elements C o Ni Fe Mn Ca Si Mg Cu Pb

Percentage contains 77.32 0.014 0.0009 0.0003 0.0022 0.002 0.0001 0.0001 0.0034 amount % moisture 0.19% median sizes (μ m), 0.87 loose density (g/cm ³) 0.52 tap density (g/cm ³) 0.86

The CoO product of above parameter indicating the inventive method preparation is better than the product performance of other method preparation, is more suitable for the manufacturing in alkaline secondary cell.

The activity of CoO is with the CoO of 5% weight and ball-type Ni (OH) ₂Make electrode, with Ni (OH) ₂Loading capacity characterize, the 0.1C charging, the 0.4C discharge, its result is as follows: table 1 is made ball-type Ni (OH) in the nickel electrode of additive with CoO ₂Loading capacity

Cycle	1	2	3	4	5
Cycle	1	2	3	4	5	Loading capacity (mAh/g)	235	255	268	280	281

With the CoO of this method preparation, make battery after, the charging voltage of battery is low, and the sparking voltage height, the loading capacity height of battery.

In roasting process, the roasting body of heater contains the suitable quantity of water steam, can obtain good CoO of adhesive property or CoOCo _x, electrode does not produce the dry linting phenomenon.The product of roasting gained under containing water vapor atmosphere not, when making electrode, discovery has active substance to fall down from electrode matrix, so the capacity of electrode and life-span all can be affected, and does not just have this phenomenon containing the product that a certain amount of steam atmosphere roasting obtains.From Fig. 3 (the XPS spectrum figure of the CoO sample that the present invention makes), as can be seen, containing the CoOCo that roasting obtains under the atmosphere of water vapour _xNear 529.78V, there is OH ^-The bound energy peak, the product of roasting gained does not then have this peak under not steam-laden atmosphere.Table 3 is made ball-type Ni (OH) in the nickel electrode of additive with the product of roasting under the different atmosphere ₂Loading capacity (0.1C charging, 0.4C discharge)

Atmosphere	Cycle
	Cycle						1	2	3	4	10	20
	N ₂+ water vapour	245	255	268	288	287	1	2	3	4	10	20	287
N ₂	N ₂+ water vapour	245	255	268	288	287	218	245	258	262	254	242	287

Embodiment 2

Test conditions is with embodiment 1, changes organic acid amount in the electrolytic solution, when the amount that particularly has the oxalic acid that reducing substances produces changes, content, product specific surface area, the electrochemical activity of Co in the product all had important effect.The performance of the product that the different oxalic acid add-ons of table 2 make

Numbering	Oxalic acid add-on %	Cobalt element content %	Specific surface area m ²/g	Ball-type Ni (OH) ₂Loading capacity m ²/g
Numbering	Oxalic acid add-on %	Cobalt element content %	Specific surface area m ²/g	Ball-type Ni (OH) ₂Loading capacity m ²/g	1	0	77.3	0.7	235
2	3.5	78.5	1.0	259	1	0	77.3	0.7	235
2	3.5	78.5	1.0	259	3	6.0	79.4	1.7	288
4	9.0	81.9	2.4	284	3	6.0	79.4	1.7	288

Fig. 4 is CoOCo _xXRD figure, wherein contain the peak of Co.

Claims

1, a kind of preparation method of cobaltous oxide used as positive pole of alkaline secondary cell, its composition is CoOCo _x, wherein 0≤x＜0.2 is characterized in that comprising the steps:

1) in electrolyzer, adds inorganic salt and the organic acid electrolyte solution that contains sodium or potassium, the cobalt metal plate is made anode, and nickel, cobalt, titanium or stainless steel plate are made negative electrode, carries out electrolysis continuously, filtrate behind fresh electrolyte and the filtration electrolysate enters electrolyzer from the top, wherein:

Electrolysis temperature 10-80 ℃

Polar plate spacing 1-8cm

Current density 200-2000A/m ²

Bath voltage 1-4V

pH＝7-14

2) take out electrolysate from the below of electrolyzer continuously, water washing is filtered the filter cake of gained to there not being Cl ^-Or SO ₄ ^2-Negative ion, dry down at 30-90 ℃;

3) with the said products 300-800 ℃ with protective gas protection under roasting kiln roasting 2-7 hour;

4) be cooled to room temperature after, take out product, vacuum-packed getting final product.

2, preparation method according to claim 1 is characterized in that the cobalt metal plate is placed in the metal titanium basket.

3, preparation method according to claim 1, the salt that it is characterized in that described ionogen sodium or potassium is muriate, vitriol or carbonate, or their mixing salt, concentration is 50-300g/l.

4, preparation method according to claim 1 is characterized in that described organic acid is citric acid, oxalic acid, xitix, Weibull or several mixing acid, and concentration is 0-60g/l.

5, preparation method according to claim 1, the pH value that it is characterized in that described electrolytic solution are by feeding sour gas or dropping inorganic acid HCl, H ₂SO ₄Or HAc controls.