JP2009081039A - Nickel-hydrogen secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nickel-hydrogen secondary battery excellent in continuous charging characteristics under high temperature, and excellent in discharge performance under very low temperature, in addition to excellent charging efficiency under high temperature. <P>SOLUTION: The nickel-hydrogen secondary battery is provided with a positive electrode (3), a negative electrode (4) and alkaline electrolyte solution in an outer package can (1). The negative electrode (4) contains negative electrode active material particles (20) containing hydrogen storage alloy, and negative electrode-use oxide particles (21) containing at least a kind of additive element selected from a group consisting of Y, Yb, Tm, Er, Gd and Lu, and carbon, the positive electrode (3) contains positive electrode active material particles (14) containing nickel hydroxide or high-order nickel hydroxide, and positive electrode-use oxide particles (15) containing at least the same kind of additive element as the one contained in the negative electrode-use oxide particles (21), with a mass concentration of carbon in the negative electrode-use oxide particles (21) larger than that in the positive electrode-use oxide particles (15). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nickel metal hydride secondary battery.

Nickel metal hydride secondary batteries are used for various applications, for example, batteries for electronic / electrical equipment and electric tools.
A nickel metal hydride secondary battery has a positive electrode, a negative electrode, and an alkaline electrolyte housed in a container. The positive electrode includes particles of nickel hydroxide or higher-order nickel hydroxide as a positive electrode active material, and the negative electrode includes particles of a hydrogen storage alloy capable of occluding and releasing hydrogen as the negative electrode active material.

It is known that rare earth oxide powder is added to the positive electrode in order to suppress a decrease in oxygen overvoltage and improve charging efficiency at high temperatures (see, for example, Patent Document 1). In addition, it is known that rare earth oxide powder is added to the negative electrode in order to improve the corrosion resistance of the hydrogen storage alloy particles and improve the cycle characteristics (see, for example, Patent Document 2).
JP 2001-185137 A JP 2000-285915 A

By the way, in recent years, a shift in demand from lead-acid batteries to nickel-metal hydride secondary batteries has progressed due to an increase in environmental awareness. Specifically, nickel metal hydride secondary batteries are also used for backup applications and disaster prevention related applications.
With application to backup and disaster prevention related applications, conventional nickel metal hydride secondary batteries not only have long-term reliability, especially good continuous charging characteristics at high temperatures, but also at extremely low temperatures. There is a need for improved discharge performance.

  The present invention has been made based on the above-mentioned circumstances, and the object thereof is to ensure good charging efficiency at high temperatures and good continuous charging characteristics at high temperatures, and at extremely low temperatures. The object is to provide a nickel metal hydride secondary battery having excellent discharge performance.

In order to achieve the above object, the present inventors have made various studies and found that the carbon concentration in the oxide particles added to the positive electrode and the negative electrode affects the discharge performance at extremely low temperatures. I came up with it.
That is, according to the present invention, in a nickel metal hydride secondary battery including a positive electrode, a negative electrode, and an alkaline electrolyte in a container, the negative electrode includes negative electrode active material particles containing a hydrogen storage alloy, Y, Yb, Tm, Er. Cathode active material containing at least one additive element selected from the group consisting of Gd and Lu and oxide particles for negative electrode containing carbon, wherein the positive electrode contains nickel hydroxide or higher-order nickel hydroxide Particles and positive electrode oxide particles containing at least the same type of additive element as the negative electrode oxide particles, and the mass concentration of carbon in the negative electrode oxide particles is A nickel-metal hydride secondary battery characterized by having a mass concentration higher than that of carbon in oxide particles is provided.

  Preferably, the positive electrode oxide particles and the negative electrode oxide particles contain Y as the additional element (Claim 2).

  In the nickel metal hydride secondary battery according to claim 1 of the present invention, the mass concentration of carbon in the oxide particles for negative electrode is larger than the mass concentration of carbon in the oxide particles for positive electrode. As a result, this nickel metal hydride secondary battery has excellent charge efficiency at high temperatures and good continuous charge characteristics at high temperatures, and is excellent in discharge rate at extremely low temperatures. Therefore, this nickel metal hydride secondary battery is suitable for backup applications and disaster prevention related applications.

  The nickel metal hydride secondary battery according to claim 2 is further excellent in continuous charge characteristics at a high temperature and discharge rate at a very low temperature because the oxide particles for positive electrode and the oxide particles for negative electrode contain Y. .

FIG. 1 shows a nickel metal hydride secondary battery according to an embodiment of the present invention.
The nickel metal hydride secondary battery includes a bottomed cylindrical outer can 1 as a container, and an electrode group 2 is accommodated in the outer can 1. The electrode group 2 is formed by winding a positive electrode 3 and a negative electrode 4 in a spiral shape with a separator 5 interposed therebetween, and a portion on the outer end side of the negative electrode 4 is disposed on the outermost periphery of the electrode group 2 when viewed in the spiral direction. The negative electrode 4 is electrically connected to the inner peripheral wall of the outer can 1. The outer can 1 contains an alkaline electrolyte (not shown). As the alkaline electrolyte, for example, a mixture of a potassium hydroxide aqueous solution and a sodium hydroxide aqueous solution or a lithium hydroxide aqueous solution is used. Can do.

  A circular lid plate 8 having a gas vent hole 7 in the center is disposed in the opening of the outer can 1 via a ring-shaped insulating gasket 6. The insulating gasket 6 and the cover plate 8 are fixed by the opening edge of the caulked outer can 1. Between the positive electrode 3 of the electrode group 2 and the inner surface of the cover plate 8, a positive electrode lead 9 that electrically connects them is disposed. On the other hand, a rubber valve body 10 is disposed on the outer surface of the cover plate 8 so as to close the gas vent hole 7, and a cylindrical positive electrode terminal 11 with a flange is attached so as to surround the valve body 10. ing.

An annular insulating plate 12 is disposed on the opening edge of the outer can 1, and the positive terminal 11 projects through the insulating plate 12. Reference numeral 13 is attached to the outer tube, and the outer tube 13 covers the periphery of the insulating plate 12, the outer peripheral surface of the outer can 1 and the periphery of the bottom wall.
The positive electrode 3 in the electrode group 2 is, for example, a non-sintered nickel electrode, and includes a conductive positive electrode substrate and a positive electrode mixture held on the positive electrode substrate. As the positive electrode substrate, for example, a net-like, sponge-like, fiber-like, or felt-like metal porous body plated with nickel can be used.

As schematically shown in one circle of FIG. 1, the positive electrode mixture includes at least positive electrode active material particles 14, positive electrode oxide particles 15 and a binder 16 as main components, and positive electrode active material particles 14 and the positive electrode oxide particles 15 are fixed to the positive electrode substrate by a binder 16.
As the binder 16, for example, carboxymethylcellulose, methylcellulose, PTFE dispersion, HPC dispersion and the like can be used.

  The positive electrode active material particles 14 contain a nickel hydroxide compound as an essential main component. As nickel hydroxide compounds, use nickel hydroxide, nickel hydroxide whose nickel average valence is higher than divalent (higher order nickel hydroxide), or a mixture of nickel hydroxide and higher order nickel hydroxide. Can do. In addition, the positive electrode active material particles 14 may contain, for example, zinc or cobalt as an optional additive component, and the nickel hydroxide compound and zinc or cobalt may form a solid solution.

The nickel hydroxide-based compound changes depending on the battery reaction, and becomes nickel hydroxide or higher-order nickel hydroxide when the battery is in a discharged state.
At least a part or all of the surface of the positive electrode active material particles 14 is preferably covered with a coating layer 17, and the coating layer 17 is mainly composed of a cobalt compound. The cobalt compound preferably has a disordered crystal structure and the average valence of cobalt is 2 or more.

In the positive electrode 3 described above, for example, a positive electrode slurry is prepared by kneading the powder of the positive electrode active material particles 14, the powder of the oxide particles 15 for the positive electrode, the binder 16, and pure water. It is possible to produce a positive electrode substrate with a slurry that has been deposited and filled by rolling and cutting the slurry after drying the slurry.
The negative electrode 4 (hydrogen storage alloy electrode) in the electrode group 2 is composed of a conductive negative electrode substrate and a negative electrode mixture held on the negative electrode substrate. As the negative electrode substrate, for example, punching metal can be used. .

As schematically shown in the other circle of FIG. 1, the negative electrode mixture includes at least hydrogen storage alloy particles 20, negative electrode oxide particles 21, and a binder 22, and a conductive agent as necessary. Including. Since the hydrogen storage alloy can store and release hydrogen, which is a negative electrode active material, in this specification, the hydrogen storage alloy particles 20 are also referred to as negative electrode active material particles.
As the hydrogen storage alloy particles 20, for example, it can be the crystal structure used or intended type ₅ AB, those superlattice as a combination of the ₅ type and AB ₂ type AB. As the binder 22, for example, carboxymethyl cellulose, methyl cellulose, PTFE dispersion, HPC, sodium polyacrylate and the like can be used alone or in combination. In addition, as the conductive agent, for example, carbon powder can be used.

The negative electrode 4 described above adjusts a slurry for negative electrode comprising a powder of hydrogen storage alloy particles 20, a powder of oxide particles 21 for negative electrode, a binder 22, pure water, and a conductive agent blended as necessary. The negative electrode substrate coated with the negative electrode slurry can be produced by rolling and cutting after drying.
Here, the negative electrode oxide particles 21 of the negative electrode 4 were selected from the group consisting of Y (yttrium), Yb (ytterbium), Tm (thulium), Er (erbium), Gd (gadolinium), and Lu (lutetium). An oxide containing at least one additive element as a main component and carbon as an impurity. For example, the mass concentration of carbon in the oxide particles 21 for negative electrode is in the range of more than 0.05 wt.% And not more than 0.4 wt.%.

  On the other hand, the positive electrode oxide particles 15 of the positive electrode 3 are oxides containing at least an additive element of the same type as the additive element contained in the negative electrode oxide particles 21 as a main component. That is, the positive electrode oxide particles 15 are also at least one selected from the group consisting of Y (yttrium), Yb (ytterbium), Tm (thulium), Er (erbium), Gd (gadolinium), and Lu (lutetium). Although the additive element is included, the positive electrode oxide particle 15 and the negative electrode oxide particle 21 include the same type of additive element. Preferably, the positive electrode oxide particles 15 and the negative electrode oxide particles 21 contain Y as an additive element.

  The positive electrode oxide particles 15 may contain carbon as an impurity in addition to the additive element, but the average mass of carbon in the negative electrode oxide particles 21 is The mass concentration of carbon in the positive electrode oxide particles 15 is limited to be larger than the mass concentration of carbon in. For example, the mass concentration of carbon in the positive electrode oxide particles 15 is in the range of 0.05 wt.% Or more and less than 0.4 wt.

The mass concentration of carbon in the positive electrode oxide particles 15 and the negative electrode oxide particles 21 is, for example, arbitrary temperature and arbitrary time when a rare earth-organic acid compound as a reaction intermediate is fired to obtain a rare earth oxide. It can be adjusted by firing. The mass concentration of carbon in the positive electrode oxide particles 15 and the negative electrode oxide particles 21 can be confirmed by wet analysis.
The average particle diameter of the positive electrode oxide particles 15 and the negative electrode oxide particles 21 is, for example, in the range of 1 μm to 5 μm. The amount of the positive electrode oxide particles 15 contained in the positive electrode 3 is, for example, in the range of 0.1 parts by mass to 2.0 parts by mass with respect to 100 parts by mass of the positive electrode active material particles 14. On the other hand, the amount of the negative electrode oxide particles 21 contained in the negative electrode 4 is, for example, in the range of 0.1 parts by mass to 2.0 parts by mass with respect to 100 parts by mass of the negative electrode active material particles 20.

In the nickel hydride secondary battery described above, the mass concentration of carbon in the anode oxide particles 21 is larger than the mass concentration of carbon in the anode oxide particles 15. As a result, this nickel metal hydride secondary battery has excellent charge efficiency at high temperatures and good continuous charge characteristics at high temperatures, and is excellent in discharge performance at extremely low temperatures.
In particular, the nickel metal hydride secondary battery in which the positive electrode oxide particles 15 and the negative electrode oxide particles 21 contain Y as an additive element is more excellent in continuous charge characteristics at high temperatures and discharge rates at extremely low temperatures. .

1. Production of Oxide Particles Using organic acid compounds of Y, Yb, Tm, Er, Gd, and Lu as raw materials, by firing these organic acid compounds at an arbitrary temperature for an arbitrary time, Y, Yb, Tm, Er, Gd and Lu oxides were produced, respectively. The obtained oxide contains Y ₂ O ₃ , Yb ₂ O ₃ , Tm ₂ O ₃ , Er ₂ O ₃ , Gd ₂ O ₃ and Lu ₂ O ₃ as main components, and contains carbon as an impurity. contains. The mass concentration of carbon in the oxide was adjusted to 0.4, 0.2, or 0.05 wt.% By adjusting the firing temperature and firing time.

2. Production of positive electrode Oxide particles produced, positive electrode active material particles of nickel hydroxide having a disordered crystal structure and a coating layer of a cobalt compound having an average cobalt valence of 2 or more, and a binder, and a binder PTFE dispersion and pure water as 1 part by weight of oxide particles, 100 parts by weight of nickel hydroxide in the positive electrode active material particles, 1 part by weight of PTFE dispersion (specific gravity 1.5, solid content 60% by weight) Solid content) and kneaded at a ratio of 30 parts by mass of pure water to prepare a positive electrode slurry. A nickel porous body (porosity 95, average pore diameter 300 μm) as a positive electrode substrate filled with the obtained positive electrode slurry with a predetermined filling amount, dried to a predetermined thickness after drying the positive electrode slurry, and then with predetermined dimensions A non-sintered positive electrode was produced.

3. Production of negative electrode Oxidized oxide particles, hydrogen storage alloy particles, sodium polyacrylate, carboxymethylcellulose and PTFE dispersion as binder, and pure water were oxidized to 100 parts by mass of hydrogen storage alloy particles. 1 part by weight of particles, 0.5 part by weight of sodium polyacrylate, 0.12 part by weight of carboxymethyl cellulose, 1.0 part by weight of PTFE disperse (specific gravity 1.5, solid content 60% by weight), 1.0 part by weight of carbon black, and A slurry for negative electrode was prepared by kneading at a ratio of 30 parts by mass of pure water. The punched metal coated with the prepared negative electrode slurry was roll-rolled and cut after the negative electrode slurry was dried to prepare a negative electrode.

4). Assembling of the nickel metal hydride secondary battery The obtained positive electrode and negative electrode were spirally wound through a separator made of a polyamide non-woven fabric to produce an electrode group. The obtained electrode group was housed in an outer can and subjected to a predetermined attachment process, and then an 8N alkaline electrolyte mainly composed of an aqueous potassium hydroxide solution was injected into the outer can. Then, the opening of the outer can was sealed with a cover plate or the like, and an AA-sized sealed cylindrical nickel-metal hydride secondary battery with a nominal capacity of 1200 mAh was assembled.

  At this time, by changing the oxide particles used for the positive electrode (positive oxide particles for positive electrode) and the oxide particles used for the negative electrode (oxide particles for negative electrode), the nickel hydrogen hydrides of Examples 1 to 8 and Comparative Examples 1 to 18 were used. The next battery was assembled. The types of the positive electrode oxide particles and the negative electrode oxide particles in Examples 1 to 8 and Comparative Examples 1 to 18 and the carbon concentration thereof are as shown in Table 1. Table 1 also shows the former ratio A / B as the carbon mass concentration ratio, where A is the carbon concentration in the positive electrode oxide particles and B is the carbon concentration in the negative electrode oxide particles. It was.

In Comparative Example 12, oxide particles were not used for the positive electrode and the negative electrode. In Comparative Examples 13 to 18, oxide particles were used for only one of the positive electrode and the negative electrode.
5). Battery characteristic evaluation The following evaluation was performed about each produced nickel hydride secondary battery of Examples 1-8 and Comparative Examples 1-18.

(1) High-temperature charging test Each battery was charged at 120mA (0.1It) at an ambient temperature of 25 ℃ for 16 hours and then 1200mA (1It) at an ambient temperature of 25 ℃. A discharge current was discharged until the final discharge voltage reached 1.0 V, and the discharge capacity at this time was measured. Then, after charging for 16 hours at a charging current of 120mA (0.1It) at an ambient temperature of 60 ° C, the end-of-discharge voltage is 1.0V at a discharging current of 1200mA (1It) at an ambient temperature of 25 ° C. It was made to discharge until it became, and the discharge capacity at this time was measured. The ratio of the subsequent discharge capacity to the previous discharge capacity is shown in Table 1 as 60 ° C. charging efficiency.

(2) Low temperature discharge test Each battery was charged at 120mA (0.1It) at an ambient temperature of 25 ℃ for 16 hours and then 1200mA (1It) at an ambient temperature of 25 ℃. A discharge current was discharged until the final discharge voltage reached 1.0 V, and the discharge capacity at this time was measured. Then, after charging for 16 hours at a charging current of 120mA (0.1It) at an ambient temperature of 25 ° C, the discharge end voltage is 1.0 at a discharging current of 1200mA (1It) at an ambient temperature of -30 ° C. The battery was discharged until V, and the discharge capacity at this time was measured. The ratio of the subsequent discharge capacity to the previous discharge capacity is shown in Table 1 as a -30 ° C discharge rate.

(3) Continuous charge durability characteristic test (JIS C 8705 JT)
Each battery was charged for 28 days at 55 ° C ambient temperature with 40mA (0.033It) charge current, then immediately discharged at 1200mA (1It) discharge current at 55 ° C ambient temperature. Ten charge / discharge cycles were performed until the voltage reached 1.1 V, and the discharge capacity was measured in the first and tenth cycles. In Table 1, when the discharge capacity of the first cycle is X and the discharge capacity of the 10th cycle is Y, together with the discharge capacity of the first cycle and the 10th cycle, the ratio Y / X of the latter to the former is the capacity. Shown as maintenance rate. The ratio of the discharge capacity Y at the 10th cycle to the nominal capacity (1200 mAh) is also shown in Table 1 as the nominal capacity ratio.

(4) Test results From Table 1, the following is clear.
(I) In Examples 1 to 8 and Comparative Examples 1 to 11 and 16 to 18 in which the positive electrode oxide particles were used for the positive electrode, compared with Comparative Examples 12 to 15 in which the positive electrode oxide particles were not used for the positive electrode. The charging efficiency at 60 ℃ was high. From this, in Examples 1-8, it turns out that the favorable charging efficiency under high temperature is ensured.

(Ii) Examples 1 to 8 in which the mass concentration ratio A / B of carbon is less than 1 are not as large as those in Comparative Examples 1 to 8, but one or both of the positive electrode oxide particles and the negative electrode oxide particles. Compared with Comparative Examples 12 to 18 in which no is used, the nominal capacity ratio is excellent. From this, in Examples 1-8, it turns out that the favorable continuous charge characteristic under high temperature is ensured.
(Iii) In Examples 1 to 8 in which the mass concentration ratio A / B of carbon is smaller than 1, compared to Comparative Examples 1 to 11 in which the mass concentration ratio A / B of carbon is 1 or more, the discharge rate is −30 ° C. Is expensive. From this, it can be seen that the discharge performance at extremely low temperatures is improved when the mass concentration of carbon in the oxide particles for negative electrode is larger than the mass concentration of carbon in the oxide particles for positive electrode.

(Iv) In particular, in Examples 1, 7 and 8 in which the main component of the positive electrode oxide particles and the negative electrode oxide particles is Y ₂ O ₃ , the capacity retention ratio is higher than those of other Examples 2 to 6. high. Also from this point, it is understood that the positive electrode oxide particles and the negative electrode oxide particles preferably contain Y as an additive element.
The present invention is not limited to the above-described embodiment and examples, and various modifications are possible. For example, the battery may be a rectangular battery, and the mechanical structure of the battery is particularly limited. There is no.

1 is a partially cutaway perspective view showing a nickel metal hydride secondary battery according to an embodiment of the present invention, and the inside of the circle is a cross-sectional view schematically showing an enlarged part of each of a positive electrode and a negative electrode.

Explanation of symbols

1 Exterior can (container)
2 Electrode group 3 Positive electrode 4 Negative electrode 5 Separator
14 Cathode active material particles
15 Oxide particles for positive electrode
20 Negative electrode active material particles
21 Negative electrode oxide particles

Claims (2)

In a nickel metal hydride secondary battery comprising a positive electrode, a negative electrode and an alkaline electrolyte in a container,
The negative electrode is
Negative electrode active material particles containing a hydrogen storage alloy;
Including at least one additive element selected from the group consisting of Y, Yb, Tm, Er, Gd, and Lu, and oxide particles for negative electrode containing carbon.
The positive electrode is
Positive electrode active material particles containing nickel hydroxide or higher order nickel hydroxide;
Including positive electrode oxide particles containing at least the same type of additive elements as the additive elements contained in the negative electrode oxide particles,
The nickel hydride secondary battery, wherein a mass concentration of carbon in the oxide particles for negative electrode is larger than a mass concentration of carbon in the oxide particles for positive electrode.   The nickel-hydrogen secondary battery according to claim 1, wherein the positive electrode oxide particles and the negative electrode oxide particles contain Y as the additive element.

Images