JP2007328981A - Lead acid battery - Google Patents

Abstract

An object of the present invention is to improve life characteristics when a lead-acid battery is used in a low SOC region.
A lead acid battery including platinum in a negative electrode active material and 0.00001 to 0.003 parts by mass of platinum per 100 parts by mass of Pb as a negative electrode active material is shown. Platinum in the negative electrode active material improves the charge acceptability of the negative electrode, and improves the charge / discharge life characteristics in the low SOC region. In addition, platinum does not promote corrosion of the current collecting ears of the negative electrode grid body, and does not deteriorate the self-discharge characteristics in the above-mentioned addition amount range, and thus provides a long-life lead storage battery with excellent reliability. be able to.
[Selection figure] None

Description

  The present invention relates to a lead-acid battery.

  Lead-acid batteries are mainly used as automobile engine starting batteries. Various attempts have been made to suppress maintenance and inspection of lead-acid batteries and improve maintenance-free performance.

  In particular, when Sb is contained in a lattice alloy or an active material to a certain extent, self-discharge tends to proceed in the negative electrode, and the amount of water decrease in the electrolytic solution increases, resulting in a decrease in maintenance-free properties. For example, the amount is limited to about 50 ppm or less.

  In recent years, from the environmental aspect, the trend toward vehicle HEV and idle stop vehicle acceleration for the purpose of improving fuel efficiency has been accelerated. In such a vehicle, the use mode of the lead storage battery is greatly different from that of a conventional vehicle.

  In a lead-acid battery used in a conventional vehicle, since the state of charge (SOC) is frequently used in a high region of 95 to 100%, the lead-acid battery has been required to have high overcharge resistance. On the other hand, in the HEV or idle stop vehicle, the SOC is controlled in a region lower than that of the conventional vehicle in order to give the rechargeable charge function to the lead storage battery. Moreover, in such a lead storage battery, compared with the conventional vehicle, the amount of discharge tends to increase due to various electronic devices and frequent engine start.

  That is, while the conventional vehicle is used with an overcharge tendency in the high SOC region, the new type vehicle as described above is in a use mode in which deep discharge frequently enters in the low SOC region.

  In order to secure the battery life in such a use mode in which deep discharge frequently enters in such a low SOC region, it is necessary to further improve the charge acceptability of the lead storage battery.

  In order to improve the charge acceptability of lead-acid batteries, it has been studied to add carbon to the negative electrode active material or to examine the composition and amount of lignin added as a shrinkage preventing agent. However, in any case, these additives are eluted or decomposed in the lead-acid battery, so that there is a drawback that the effect gradually decreases.

In Patent Document 1, as a representative of Sb, by adding a substance that lowers the hydrogen overvoltage of the negative electrode to the negative electrode, the potential of the negative electrode at the time of charging is transferred preciously, and the charging voltage is decreased, and As a result, it is shown that the charge acceptability is improved and the life characteristics at low SOC-deep discharge are improved.
JP 2003-346888 A

  However, the addition of Sb naturally increases the self-discharge of the lead acid battery. Therefore, the addition amount is limited to a very small amount, but Sb becomes a cause of corrosion of the negative electrode lattice, particularly in a use mode in which deep discharge occurs in a low SOC region. In particular, the corrosion of the negative electrode ears and the lattice bones reduces the current collection efficiency, and there is a problem that the discharge capacity of the battery is drastically reduced when disconnection occurs in these parts.

  In order to solve the above-described problem, the invention according to claim 1 of the present invention includes platinum in the negative electrode active material, and 0.00001 to 0.003 parts by mass of platinum per 100 parts by mass of Pb as the negative electrode active material. The lead acid battery which contains is shown.

  According to a second aspect of the present invention, in the lead storage battery according to the first aspect, the distance between the positive and negative electrode plate surfaces is 1.50 mm or less.

  The above-described lead-acid battery of the present invention has excellent charge acceptance and significantly improves the life characteristics in low SOC-deep discharge. Moreover, the remarkable effect of suppressing the deterioration of the self-discharge characteristic and the corrosion of the negative electrode lattice part as seen with the addition of Sb is exhibited.

  The lead acid battery by embodiment of this invention contains platinum in a negative electrode active material. As a platinum content, 0.00001 mass part to 0.003 mass part of platinum are included with respect to 100 mass parts of Pb as a negative electrode active material.

  By including platinum in such a content range in the negative electrode active material, the charge acceptability of the negative electrode is improved, and the charge / discharge cycle life at low SOC-deep discharge can be remarkably improved. Moreover, since platinum exists stably in the negative electrode active material, the effect can be obtained stably.

  Moreover, even if platinum is added to the negative electrode active material, corrosion of the negative electrode lattice does not occur. For example, although antimony has the effect of improving the charge acceptability of the negative electrode by reducing the hydrogen overvoltage of the negative electrode, antimony in the negative electrode active material is once eluted into the electrolyte and re-deposited on the negative electrode lattice. In particular, when antimony is deposited on the current collecting ear portion of the negative electrode grid body, when the current collecting ear portion is exposed from the electrolyte surface, the current collecting ear portion is disconnected due to corrosion, and the battery capacity is rapidly reduced.

  The platinum added to the negative electrode active material does not re-deposit on the negative electrode grid, unlike antimony, and does not particularly promote corrosion breakage of the current collecting ear portion of the negative electrode grid. Therefore, since the effect of improving the charge acceptability of the negative electrode and the effect of suppressing the corrosion of the current collecting ear portion of the negative electrode grid body can be obtained at the same time, a lead storage battery that is extremely excellent in terms of reliability can be obtained.

As a method for adding platinum, a method of adding platinum or a platinum compound such as platinum powder (platinum black, Pt) or platinum oxide (PtO ₂ ) to the negative electrode active material paste can be used. However, platinum containing halogen or nitro group such as chloroplatinic acid (H ₂ PtCl ₆ ), dinitrodiammine platinum (Pt (NH ₃ ) ₂ (NO ₂ ) ₂ , dichlorotetraammine platinum (Pt (NH ₃ ) ₄ Cl ₂ )) Compounds are not preferred because they may corrode lead.

  A predetermined amount of platinum powder or platinum oxide as described above may be added to the raw material lead powder of the negative electrode active material and kneaded with water and dilute sulfuric acid to form a negative electrode active material paste. And the lead acid battery of this invention can be obtained by filling this negative electrode active material paste in a negative electrode grid body, and using the negative electrode plate obtained by carrying out aging drying.

  When the platinum content is less than 0.00001 parts by mass with respect to 100 parts by mass of Pb as the negative electrode active material, the effect of improving the charge acceptability is hardly observed. It is essential to contain at least 00001 parts by mass.

  Further, platinum in an amount exceeding 0.003 parts by mass with respect to 100 parts by mass of Pb as the negative electrode active material is not preferable because it reduces the self-discharge characteristics. Further, since platinum is a noble metal and is relatively expensive, it is preferable that the addition amount be as small as possible within the above range.

  In addition, in the conventional lead-acid battery in which antimony is added to the negative electrode active material for the purpose of improving the charge acceptability of the negative electrode active material, the self-electrode surface is particularly less than 1.50 mm. Although the discharge characteristics tend to decrease, in the configuration in which a predetermined amount of platinum is added to the negative electrode active material as in the present invention, even when the distance between the electrode plates is 1.50 mm, the self-discharge characteristics are reduced. There is no downward trend.

  Therefore, in order to improve the output characteristics of the lead storage battery, it is more preferable to apply the configuration of the present invention to a lead storage battery in which the distance between the electrode plates is set to 1.50 mm or less.

  The lead storage battery according to the above-described embodiment of the present invention and the lead storage battery according to the comparative example (55D23 start lead storage battery (12V48Ah) respectively defined in JIS D5301) are prepared, self-discharge characteristics, low SOC-deep discharge life test, And the corrosion degree of the negative electrode grid in this life test was evaluated.

(1) Battery A group (Batteries A1 to A7)
The battery group A is a lead-acid battery containing various contents of platinum in the negative electrode active material. Platinum is added to the negative electrode active material by adding 200 mesh platinum powder to the raw material lead powder having a degree of oxidation of 70%, and carbon and lignin corresponding to 0.1 parts by mass with respect to 100 parts by mass of the raw material lead powder. And after adding and mixing barium sulfate, it knead | mixed with water and dilute sulfuric acid, and was set as the negative electrode active material paste.

  The negative electrode active material paste was filled into an expanded lattice having a composition of Pb-0.06 mass% Ca-0.25 mass% Sn, and aged and dried to prepare a negative electrode plate. A battery in which this negative electrode plate and a positive electrode plate obtained by a conventional method were combined was designated as a battery group A. The above negative electrode lattice alloy does not contain platinum.

  Further, the positive electrode plate has a Pb-0.06 mass% Ca-1.60 mass% Sn composition obtained by kneading raw material lead powder having a degree of oxidation of 70% similar to the above with water and sulfuric acid. It is obtained by filling an expanded lattice and aging and drying.

As shown in Table 1, the amount of platinum in the negative electrode active material in the battery A group was changed in the range of 0 to 0.01 parts by mass with respect to 100 parts by mass of Pb as the negative electrode active material. Furthermore, the negative electrode plate was covered with a microporous polyethylene bag-like separator, and the distance between the positive electrode plate surface and the negative electrode plate surface was 1.20 mm. Further, the electrolytic solution was diluted sulfuric acid having a density of 1.280 g / cm ^{3 in} terms of 20 ° C.

(2) Battery B
Battery B is obtained by adding antimony instead of platinum added to the negative electrode active material in battery A group. The amount of antimony added was 0.005 parts by mass with respect to 100 parts by mass of Pb of the negative electrode active material, and antimony oxide (Sb ₂ O ₃ ) was added to the raw material lead powder having an oxidation degree of 70%. There is no difference from the battery A group except that platinum is not contained and antimony is contained instead of platinum. Further, the distance between the positive and negative electrode plate surfaces is 1.20 mm, which is the same as in the battery A group.

  For each of the batteries A1 to A7 and the battery B shown in Table 1, the self-discharge characteristics, the life test in the low SOC region, and the thickness reduction rate of the negative electrode grid ear in this life test were evaluated.

  As the self-discharge characteristics, the 5-hour rate capacity before and after being left at 60 ° C. for one month was measured for the test battery in the initial state, and the percentage of the capacity after being left to stand before being left as a capacity remaining rate was evaluated.

  As a life test method, the following procedure was used. In a 25 ° C. atmosphere, the test battery is discharged at a constant current of 10 A until the battery voltage reaches 10.5V. Thereafter, a 12 W light bulb was connected between the battery terminals and left for 48 hours to overdischarge the test battery. Then, the test battery was charged with 14.5V constant voltage (maximum current 25A) for 8 hours, and the following charge / discharge cycle was performed.

As charge / discharge cycle conditions, 25A discharge 20 seconds and 14V constant voltage charge (maximum charge current 25A) 40 seconds are repeated 7200 cycles in a 25 ° C. atmosphere, and then the mass loss (W _L ) due to this cycle is measured. Thereafter, the battery is discharged at 300 A for 30 seconds, and the discharge voltage (V ₃₀ ) at 30 seconds is measured. Thereafter, the lead storage battery is replenished with water corresponding to the mass loss (W _L ).

The number of charge / discharge cycles until V ₃₀ is decreased to 7.2 V for every 7200 cycles of charge / discharge is defined as the life cycle number. Normally, a light load life test defined in JIS D5301 for a starter lead-acid battery is composed of a cycle of 25 A discharge for 4 minutes and a constant current charge of 10 minutes with a maximum current of 25 A. The test conditions were such that charging and discharging were frequently performed in a state where the SOC was lower than in the load life test.

The calculation method of the life cycle number was as follows. n-th on the measured V ₃₀ voltage (number of charge and discharge cycles 7200 × n), the first time V ₃₀ is equal to or less than 7.2V, that the V ₃₀ and Vn. Then, last of V ₃₀ voltage of (n-1 time) is taken as Vn-1, the vertical axis V _30, the horizontal axis in the graph of the number of charge and discharge cycles, the coordinates (7200 (n-1), Vn- 1) and coordinates (7200n, Vn) are connected by a straight line L, and the value on the horizontal axis at the intersection of this straight line L and V ₃₀ = 7.2 is defined as the number of life cycles.

Moreover, about each battery which the lifetime test was complete | finished, the decomposition | disassembly investigation of the battery was conducted and the ear corrosion rate of the negative electrode was calculated | required. In addition, the negative electrode lattice ear cross-sectional area in the initial state before the test is S, the negative electrode lattice ear cross-sectional area after the life test is SE, and the reduction rate of the ear cross-sectional area obtained as {100 × (S−SE) / S} is Ear corrosion rate. The cross-sectional area of the negative electrode grid ear in the initial state before the test was (width) 13.0 mm × (thickness) 0.7 mm = 9.1 mm ² , and when the ear corrosion rate was 50%, the cross-sectional area was 4. This corresponds to a reduction of 55 mm ² .

  Table 2 shows the results of the negative electrode grid edge corrosion rate and the life cycle number in the above life test, and the results of the capacity remaining rate after standing. The life cycle number is shown as a percentage of the life cycle number in the battery A1.

  From the results shown in Table 2, it can be seen that according to the present invention, excellent lifetime characteristics can be obtained while suppressing the decrease in the capacity remaining rate after being left and the corrosion of the negative electrode lattice ear. The life test in this example is a test performed in a low SOC region. By including an appropriate amount of platinum in the negative electrode active material, the negative electrode lattice body or the electrolytic solution, the charge acceptability is improved and good. Lifetime characteristics could be obtained.

  When antimony is added instead of platinum, the life characteristics can be improved, but the remaining capacity retention rate, that is, the self-discharge performance is lowered, and the corrosion of the negative electrode lattice also proceeds by the charge / discharge cycle in the example, which is not preferable.

  Next, for battery A3, battery A5, and battery B, as shown in Table 3, batteries were prepared by changing the distance between the positive electrode plate surface and the negative electrode plate surface from 1.20 mm to 1.0 to 2.0 mm, respectively. did. For each battery shown in Table 3, the results of measuring the capacity remaining rate after standing, the life test, and the negative electrode grid ear corrosion rate after the life test are also shown in Table 3. The life cycle number is shown as a percentage of the life cycle number of the battery A1 as shown in Table 2.

  From the results shown in Table 3, in the battery of the present invention containing platinum in the negative electrode active material, the change in the distance between the electrode plates does not significantly affect the remaining capacity after standing, the life characteristics and the negative electrode ear corrosion rate. In the battery of the comparative example containing the antimony in the negative electrode active material, when the distance between the electrode plates is 1.5 mm or less, the remaining capacity and the life characteristics after being left are lowered, and the negative electrode grid edge corrosion rate is also increased. Recognize.

  In general, the distance between the electrode plates is set shorter for the purpose of improving the high rate discharge characteristics, but in the battery of the comparative example containing antimony, when the distance between the electrode plates is 1.5 mm or less, the trouble due to the addition of antimony, That is, there is a drawback that the self-discharge characteristics are deteriorated and the negative electrode ear corrosion easily proceeds.

  In the structure of the present invention in which platinum is added to the negative electrode active material instead of antimony, even if the distance between the electrode plates is 1.5 mm or less, excellent self-discharge characteristics and life characteristics are realized, Moreover, corrosion of the negative electrode lattice ear can be suppressed.

  According to the present invention, it is possible to provide a long-life lead storage battery while suppressing the deterioration of the self-discharge characteristics of the lead storage battery and the corrosion of the negative electrode ear. It is.

Claims (2)

The lead acid battery which contains platinum in a negative electrode active material, and contains 0.00001-0.003 mass part of platinum per 100 mass parts of Pb as a negative electrode active material. The lead acid battery according to claim 1, wherein a distance between electrode plates of the positive electrode and the negative electrode is 1.50 mm or less.