JP3379331B2 - Lead storage battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead-acid battery having improved conductivity at the interface between an active material and a lattice. 2. Description of the Related Art Lead-acid batteries are relatively inexpensive and have stable performance as secondary batteries. Therefore, they are used as power sources for portable devices and electric vehicles, and are used as backup power sources for cycle-use mobile computers and computers. It has been widely used as a stationary power supply for use in mobile phones. [0003] In recent years, as a part of global environmental measures, it has also been spotlighted as a power source for electric vehicles. Also, with the rapid progress of cordless portable devices, there is an increasing demand for high performance of low-cost lead storage batteries as power sources. In order to improve the performance of the lead storage battery, it is particularly important to increase the energy density and extend the life. [0004] In particular, the problem of prolonging the life greatly depends on the conductivity at the interface between the active material and the electrode plate. The lead-acid battery uses lead dioxide (PbO ₂ ) for the positive electrode, lead (Pb) for the negative electrode, and an aqueous solution of sulfuric acid (H ₂ O ₄ ) for the electrolyte, and the battery reaction is as follows. Positive electrode: PbO ₂ + 2H +++ H ₂ SO ₄ + 2e = PbSO ₄ + 2H ₂ O Negative electrode: Pb + SO ₄ ²⁻ = PbSO ₄ + 2e As is clear from the above reaction formula, in the discharge reaction, the active material is lead sulfate (PbSO 4) for both the positive and negative electrodes. ₄ ) On the contrary, in the charging reaction, lead sulfate is oxidized to lead dioxide in the positive electrode, and lead sulfate is reduced to lead in the negative electrode. However, not only the change of the active material during charge and discharge, but also the grid, which is the current collector of the electrode plate, is partially affected by oxidation and reduction due to the permeation of the electrolytic solution. That is, the lattice surface made of lead or lead alloy, which should originally maintain metal conduction, is placed in an oxidized state due to the oxidation-reduction reaction of the active material at the interface with the active material, and the electron conductivity is reduced. When the electron conductivity at the interface between the active material and the lattice is reduced in this manner, the capacity density is reduced due to resistance polarization, or the cycle characteristics are deteriorated, and it is difficult to supply a battery having high performance and long life. . In order to solve these problems, it has been studied to form various conductive materials at the interface between the lattice and the active material. Among them, in recent years, a material called barium plumbate (BaPbO ₃ ) having good chemical stability in sulfuric acid and oxidation resistance has been proposed as a conductive material having good electron conductivity. This material is provided at the interface between the active material and the lattice surface, and an attempt is made to eliminate a factor that lowers the electron conductivity due to partial oxidation of the lattice surface that occurs during charge / discharge reaction. However, the electrical resistance of barium plumbate (BaPbO ₃ ) is 1000 μΩ · c.
m, 20 μΩ · cm of metallic lead and 20 μΩ of lead oxide.
Compared with 0 μΩ · cm, the electron conductivity is remarkably low, and it cannot be said that the material has sufficient conditions to be used as a conductive material, and a material having further higher electron conductivity has been desired. The present invention has been made to solve the above problems, and
Using a material with high electron conductivity at the interface between the lattice and the active material,
It is an object of the present invention to provide a lead storage battery that does not cause a decrease in capacity density or deterioration in cycle characteristics. [0008] In order to achieve the above object, the present invention provides a lead-acid battery in which the negative electrode active material is lead and the positive electrode active material is lead dioxide, having the general formula (M1 + M2) _{1- y} M3 _x
Pb _1-x O _3-y (M1 is at least one member selected from the group consisting of K, Rb and Cs; M2 is at least one member selected from the group consisting of Ca, Sr and Ba; M3 is Sn and Sb , Bi
At least one selected from the group consisting of 0 <x
≦ 0.15, 0 ≦ y ≦ 0.05, abundance ratio R of M2 (M2
/ (M1 + M2) ) is formed at the interface between the active material and the lattice, where a conductive composite oxide satisfying 0.95 ≦ R <1.0) is formed. This novel conductive composite oxide has good chemical stability and oxidation resistance in sulfuric acid, and has the above-mentioned B
It is a material having much higher electron conductivity than aPbO ₃ , and by using this as a conductive material, the interface resistance between the lattice and the active material can be reduced. Since this state can be maintained even during discharging, it is possible to increase the capacity of the battery and improve the charge / discharge cycle characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a conductive composite oxide featured in the present invention will be described in relation to the previously proposed BaPbO ₃ . Since BaPbO ₃ contains an alkaline earth metal element having a low ionization potential in the A site of a perovskite-type oxide generally represented as ABO ₃ , the electronic state of the lead ion is determined by the barium s orbital and the formal value. It is in a state where electron conduction is easily imparted by donating some electrons to the 6s free orbit of lead ions which should be several valences. However, if the A site is replaced by an element having a lower ionization potential such as an alkali metal, a further increase in the electron density can be expected in the 6s orbital of the lead ion, which is preferable from the viewpoint of electron conductivity. Conceivable. However, the perovskite-type oxide has a property of site preference, and the A-site tends to preferentially contain those having an appropriate ionic radius such as an alkaline earth metal. It is impossible to cover all the A sites with an alkali metal. Thus, the present inventors have considered a model in which the main component of the A site is occupied by an alkaline earth metal (M2), and a part of the A site is replaced by an alkali metal (M1) having a low ionization potential. In this case, as the occupancy of the alkaline earth metal element (M2) decreases, oxygen deficiency occurs for charge compensation. Therefore, a new material was studied taking this into consideration. As a result, the electric resistance is 150 μΩ · c
About m composite oxides were obtained. A plurality of different alkali metals (M1) or different alkali earth metals (M1)
The same effect was obtained in the composite oxide system in which the element 2) was mixed. From these examination results, the general formula (M1 + M
2) _1-y PbO _3-y (M1 is one of K, Rb, Cs
M2 is one or more of Ca, Sr, and Ba, and 0 ≦ y ≦ 0.05;
The abundance ratio R of M2 (M2 / (M1 + M2) ) is 0.95 ≦
It has been found that the novel composite oxide represented by R <1.0) is a material having high conductivity that can be used as a conductive material. Furthermore, in order to improve the electron conductivity of the above materials, it has almost the same ionization potential as P-site as a B-site substitution element. Aiming at introducing Sb and Bi which are highly likely to donate electrons, or aiming at an electron correlation effect via oxygen 2p orbitals which are homologous to lead but caused by a difference in ionic radius, lead is introduced into Sn 6s by introducing Sn.
Attempt to donate electrons to orbit. By partially substituting these different elements at the A and B sites, the electric resistance could be reduced to about 120 μΩ · cm. In consideration of the above results, the highly conductive composite oxide for a conductive material according to the present invention can be expressed by the general formula: (M
1 + M2) _1-y PbO _3-y (M1 is one or more of K, Rb, Cs, M2 is one or more of Ca, Sr, Ba, and 0 ≦ y ≦ 0.
05, the abundance ratio R (M2 / (M1 + M2) ) of M2 is 0.
95 ≦ R <1.0). The present invention enables the construction of a battery having high capacity and excellent charge / discharge cycle characteristics by forming such a novel highly conductive composite oxide at the interface between the lattice and the active material. Examples Various conductive composite oxides studied as a conductive material for a lead-acid battery in this embodiment were prepared by using a lead oxide and a replacement element in an amount corresponding to the stoichiometric amount of the composite oxide. They were mixed and fired under an oxidizing atmosphere at 600 to 750 ° C. to synthesize. As the compounds containing the substitution element, hydroxides and carbonates were used for M1 and M2, and oxides and hydroxides were used for M3. PbO, Pb
An oxide such as ₃ O ₄ was used as a raw material. The conductive composite oxide thus obtained was added to a methylpyrrolidone-based volatile solvent and kneaded to prepare a conductive material paste. This conductive material paste was applied on a lead alloy casting grid for a sealed battery, dried at 80 ° C. for 1 hour, and the solvent was volatilized. The casting grid covered with the conductive material layer thus created was filled with the active material paste, and this electrode plate was formed into a positive electrode plate.
The active material paste is a lead powder 6 having an oxidation degree of 70% to 80%.
The mixture was kneaded while gradually adding 1.4 l of dilute sulfuric acid (specific gravity: 1.20 at 20 ° C.) to the kg. The size of the electrode plate is 40 mm long x 13 mm wide and 1.3 mm thick.
The weight of the paste filled in this electrode plate was about 2.3 g. The amount of electricity charged was calculated by calculating the number of moles of lead atoms contained in each paste, and assuming that all of them changed to lead dioxide by chemical conversion. The batteries of the examples were configured with a positive electrode capacity regulation using a negative electrode plate for a sealed battery having a filling capacity about twice as large as the filling capacity of the positive electrode, and the characteristics of the positive electrode were evaluated. The discharge capacity was examined by the constant current discharge of 0.2 C, and the discharge utilization rate of the active material was calculated based on the charged amount of the positive electrode. The cycle characteristics were evaluated by the number of cycles until the discharge capacity after the charge / discharge cycle test was reduced to half of the initial capacity. Tables 1 to 3 show that in the above general formula, y = 0,
M1: K, M2: Ba, M2 / (M1 + M2) = 0.9
The evaluation result of a battery using various conductive composite oxides in which the substitution amount of M3 (Bi, Sb, Sn) is changed to 8 is shown. Table 1 shows the case where M3 = Bi (y = M1: K, M2: B
a M2 / (M1 + M2) = 0.98), and Table 2 shows that M3 =
In the case of Sb (y = 0; M1: K, M2: Ba M2 /
(M1 + M2) = 0.98, Table 3 shows the case where M3 = Sn (y = 0; M1: K, M2: Ba M2 / (M1 + M
2) = 0.98). [Table 1] [Table 2] [Table 3] As can be seen from Tables 1 to 3, y = 0, M
1: K, M2: Ba, M2 / (M1 + M2) = 0.98
Under the condition of any one of Sn, Sb and Bi, 0 <x ≦
When the conductive composite oxide in the range of 0.15 was used as the conductive material, both of the utilization factor and the cycle characteristics were lower than those of Comparative Example B.
This is improved over the case where aPbO ₃ is used. X =
At 0.00, there was no effect of displacing the B site with the dissimilar metal, and thus the same characteristics as those of the comparative example were shown. But,
At X = 0.01, the effect of trace amounts of different elements was observed. On the other hand, when X is 0.2 or more, it is considered that the characteristics are deteriorated because a single-phase perovskite oxide cannot be synthesized. Next, the results of the battery characteristic tests when the conductive composite oxide used as the conductive material is M3; Bi, X = 0.1 and the element occupied by the A site is changed are shown in Tables 4 to 12.
Shown in Table 4 shows that M1 = K, M2 = Ba, M2 / (M1 +
M2) = 0.98 (X = 0.1 M3: Bi),
Table 5 shows that M1 = K, M2 = Ca, M2 / (M1 + M2) =
In the case of 0.98 (x = 0.1 M3: Bi), Table 6 shows M
1 = K , M2 = Sr, M2 / (M1 + M2) = 0.98
In the case of (x = 0.1 M3: Bi), Table 7 shows that M1 = R
b, M2 = Ba M2 / (M1 + M2) = 0.98 (x = 0.1 M3: Bi), Table 8 shows that M1 = Rb, M2
= Ca , M2 / (M1 + M2) = 0.98 (x
= 0.1 M3: Bi), Table 9 shows M1 = Rb, M2 = S
r, M2 / (M1 + M2) = 0.98 (x =
0.1 M3: Bi), Table 10 shows that M1 = Cs and M2 = C
a , M2 / (M1 + M2) = 0.98 (x =
0.1M3: Bi), Table 11 shows that M1 = Cs, M2 = S
r , M2 / (M1 + M2) = 0.98 (x =
0.1 M3: Bi), Table 12 shows that M1 = Cs, M2 = B
a , M2 / (M1 + M2) = 0.98 (x = 0.
1 M3: Bi). [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] [Table 9] [Table 10] [Table 11] [Table 12] As can be seen from Tables 4 to 12, x = 0.
1, M3: Under the condition of Bi, even if M1 is K, Rb, Cs and M2 is any combination of Ca, Sr, and Ba, it is 0 under the condition of M2 / (M1 + M2) = 0.98.
When a conductive composite oxide having a composition range of ≦ y ≦ 0.05 is used, a better utilization factor and cycle characteristics than in the comparative example can be obtained. When y = 0, all of the A site is occupied, and a part of the site is replaced by M1, so that the effect of improving the electron conductivity due to the non-stoichiometric stoichiometry in the A site can be obtained. . On the other hand, when y exceeds 0.05, the properties tend to decrease, but this is thought to be due to an increase in the amount of deficiency of the A site, making it essentially difficult to maintain the perovskite structure, and causing a decrease in properties. Can be The ratio R of M2 / (M1 + M2) is 9
If more than 5% is not in the group of M2 (alkaline earth metal),
Perovskite having a single-phase crystal structure is not generated due to the site preference effect. In addition, 10
When 0% is occupied by M2 (alkaline earth metal), the contribution of the alkali metal, which can be expected to have an electron-donating effect, disappears, and in order to obtain a composite oxide having high electron conductivity according to the present invention. Is preferably 0.95 ≦ R <1.0. In addition, Tables 1 to 12 show the results in the case of using a composite oxide in which a single element of M1, M2, and M3 is substituted. It was confirmed that a similar effect was obtained when a composite oxide introduced in a state where elements were mixed was used. As described above, the present invention provides a novel highly conductive composite oxide represented by the general formula described in the present text at the interface between the lattice and the active material as a conductive material. It is possible to provide a high-performance lead-acid battery that can significantly increase the utilization rate of the active material, and has a high capacity and excellent charge / discharge cycle characteristics as compared with the case of using barium lead oxide that has been conventionally proposed.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-45511 (JP, A) JP-A-2-299154 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/62 H01M 4/66-4/68

Claims (1)

(57) [Claims 1] A lead-acid battery in which the negative electrode active material is lead and the positive electrode active material is lead dioxide, and these active materials are held on a grid. Formula (M1 + M2) _1-y M
3 _x Pb _1-x O _3-y (M1 is at least one member selected from the group consisting of K, Rb and Cs, M2 is at least one member selected from the group consisting of Ca, Sr and Ba, and M3 is Sn , Sb,
At least one member selected from the group consisting of Bi,
<X ≦ 0.15, 0 ≦ y ≦ 0.05, M2 abundance R
A lead-acid battery characterized in that a conductive composite oxide (M2 / (M1 + M2) ) represented by 0.95 ≦ R <1.0 is present at an interface between the active material and the lattice.