JP3550228B2 - Negative electrode active material for secondary battery, electrode using the same, and secondary battery - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a negative electrode active material for a secondary battery comprising metal tin or a mixture of metal tin and tin oxide, an electrode for a secondary battery using the same, and a secondary battery.
[0002]
[Prior art]
Conventionally, studies have been made using various materials alone or in combination as a negative electrode active material for a secondary battery. Pb, nickel for a lead storage battery, -Cd for cadmium batteries, hydrogen storage alloys for hydrogen batteries, and other substances containing Zn, Li, etc. as main components thereof.
[0003]
For this reason, the types of negative electrode active materials that affect the basic performance of batteries were limited, so there are few types of secondary batteries that can be used practically, and these batteries alone cannot sufficiently compensate for the disadvantages of each other's batteries. I couldn't say it.
[0004]
[Problems to be solved by the invention]
From the above, conventional secondary batteries have (1) low voltage that can be taken out, (2) difficult handling due to being a chemically active substance, and (3) toxicity that poses environmental problems. There is a drawback that there is a problem, and the development of a new active material has been desired because there are few types of the negative electrode active material used for the secondary battery.
[0005]
Accordingly, it is an object of the present invention to provide a novel negative electrode active material that can compensate for the drawbacks of the conventional secondary battery, a negative electrode electrode using the same, and a secondary battery.
[0006]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that Sn, which is the 50th element of the periodic table, has a function as a negative electrode active material that can compensate for the above-mentioned disadvantages. It has been found that by forming the body into a sheet, it can be used also as an electrode for a battery, enabling the manufacture of a secondary battery, and achieving the present invention.
[0007]
That is, the present invention firstly provides an anode active material for an alkaline secondary battery, which is an active material comprising metal tin or a mixture of metal tin and tin oxide; secondly, metal tin or metal tin and oxide A negative electrode for an alkaline secondary battery, comprising a sheet body containing an active material composed of a mixture of tin; third, a sheet containing an active material composed of metallic tin or a mixture of metallic tin and tin oxide A negative electrode for an alkaline secondary battery, wherein the negative electrode for an alkaline secondary battery has a structure in which a pressed body obtained by pressing the body to a metal plate surface is covered with a resin body having micropores; An object of the present invention is to provide an alkaline secondary battery using a negative electrode.
[0008]
[Action]
Tin used in the negative electrode active material of the present invention is the 50th element in the periodic table, and the valence changes accompanying the electrochemical reaction are divalent and tetravalent, and the following reaction proceeds in an alkaline aqueous solution.
[0009]
^{_{Sn + 4OH - = SnO 2 +}} 2H 2 O + 4e - (1)
Sn + 2OH ⁻ = Sn (OH) ₂ + 2e ⁻ (2)
_{^{Sn + 4OH - = Sn (OH}} ) 4 + 4e - (3)
^{_{Sn + 3OH - = HSnO 2 -}} + H 2 O + 2e - (4)
^{_{Sn + 6OH - = SnO 3 2-}} + 3H 2 O + 4e - (5)
During these reactions, particularly in a high-concentration alkaline aqueous solution, the reactions (4) and (5) predominantly occur, and Sn in the solution finally exists as SnO ₃ ^2- ions. The electrochemical equivalent of tin is 59.35 (divalent) and 29.67 (tetravalent), which indicates that the material can theoretically be a high-capacity battery material.
[0010]
The electrode potential using tin in a highly alkaline region having a pH of 14 or more is about -1.0 V (vs NHE). When a battery is formed using a nickel hydroxide electrode as a counter electrode, the battery has a voltage of about 1.5 V. Since it is assumed that a high potential of about 25% is obtained from the battery voltage of the Ni-Cd battery of 1.2 V, a battery having a high energy capacity can be obtained, and the hydrogen overvoltage of tin itself is 0.53 V. Since it is high, it also has an effect that hydrogen gas generation due to charge and discharge is small.
[0011]
In addition, since the maximum discharge current density is supposed to be high when the tin electrode is used as a negative electrode for a battery by the measurement of the polarization of the tin electrode, in the present invention, metal tin or metal tin is oxidized. As shown in FIG. 2, a sheet body made of a negative electrode active material made of a mixture with tin is brought into contact with a copper plate (expanded copper) so as to cover the copper plate (expanded copper). An electrode having a structure to be covered with a body was produced.
[0012]
The negative electrode active material used in the present invention is metal tin or a mixture of metal tin and tin oxide as described above, and a metal plate can also be used. It has been confirmed that the method of forming an electrode obtained by compression bonding to a current collector contributes to improvement of charge and discharge characteristics.
[0013]
For the above reasons, the present inventors consider that tin is a very advantageous element as a negative electrode active material for a battery, and as shown in the following examples, prepared an electrode using tin as a negative electrode active material, By combining such a positive electrode and an electrolytic solution, it was possible to manufacture a desired secondary battery having excellent high current density characteristics.
[0014]
Embodiment 1
FIG. 1 is a schematic sectional view showing a cell used in the present embodiment, and FIG. 3 is a graph showing a charge / discharge curve obtained in the present embodiment, which will be described below with reference to these.
[0015]
The cell 1 shown in FIG. 1 has a metal tin plate having a purity of 3N, an area of 1 cm × 1 cm and a thickness of 0.8 mm as a negative electrode plate 3, a nickel hydroxide plate as a positive electrode plate 4, and a 30 wt% KOH aqueous solution in an electrolyte 2. And a charge / discharge test was performed using this cell.
[0016]
The conditions of the charge / discharge test were a charge current of 5 mA, a charge time of 5 hr, a discharge current of 5 mA, and a discharge end voltage of 1.0 V. A cycle test was performed under these conditions. In this case, in the initial battery configuration, the negative electrode is in a charged state, but the positive electrode is not in a charged state, so that the positive electrode is charged as initial charge (at this time, hydrogen gas is generated in the negative electrode). The cycle test is regarded as the main test from the second charge / discharge cycle.
[0017]
FIG. 3 shows a charge / discharge curve of the fourth cycle. A flat portion is observed around 1.5 V and 2 V at the time of charging, and no gas generation accompanying charging is observed at a potential of 1.5 V during charging. When the potential becomes 2 V, gas generation from the negative electrode surface is observed. On the other hand, the discharge potential shows a relatively flat potential behavior at 1.5 to 1.4V.
[0018]
When metal tin is used as the electrode as described above, charging and discharging are possible, but tin, which is an active material, precipitates in the form of dendrites (dendrites) on the surface of the negative electrode during charging. This short-circuited the positive electrode, making subsequent charging and discharging impossible.
[0019]
Embodiment 2
FIG. 4 is a graph showing the current-voltage curve obtained in the present embodiment and the third embodiment, which will be described below with reference to FIG.
[0020]
Among the cells used in Example 1, the cell having the area of the nickel hydroxide electrode of the positive electrode increased by 50 times was used, and the relationship between the discharge current and the electric voltage was obtained with the influence of the positive electrode being eliminated.
[0021]
In this case, as a measuring method, a voltage was measured 30 seconds after applying a certain current to the battery, and the results are shown in FIG. From this graph, it was found that the tin electrode in the present example can extract a current having a current density of 380 mA / cm ² .
[0022]
Embodiment 3
FIG. 4 is a graph showing a current-voltage curve obtained in this embodiment, which will be described below with reference to FIG.
[0023]
As a cathode active material, 10 g of Sn powder with 100 mesh under (purity 3N, manufactured by Kojundo Chemical Laboratory) was used, and PTFE (ethylene tetrafluoride resin) dispersion liquid (solid concentration: 60%) was added to the powder. c. And an appropriate amount of ethanol were added, kneaded to form a lump of appropriate size, dried, and then rolled to a thickness of 0.4 mm to obtain a sheet.
[0024]
Two sheets of 1 cm x 1 cm in size were cut out from this sheet and pressed on expanded copper as a current collector to form an electrode. This electrode was used as a negative electrode and filled in the cell shown in Example 1. A discharge test was performed.
[0025]
As a result, the same charge / discharge curve as in Example 1 was obtained, and dendrite deposition was also observed during charging. However, the dendrite precipitation of Sn was smaller than that of the electrode of Example 1, and the number of charge / discharge cycles was 20 to 25, and the number of cycles could be improved to 2 to 3 times as compared with Example 1.
[0026]
Subsequently, the relationship between the discharge current and the battery voltage is shown in FIG. 4 by the measurement method shown in Example 2. The discharge current was about 480 mA, which was improved by about 20 to 30% as compared with Example 2.
[0027]
Embodiment 4
FIG. 2 is a perspective view showing the electrodes used in the present embodiment, which will be described below with reference to FIG.
[0028]
As shown in FIG. 2, an electrode was obtained by attaching cellophane (# 500) having fine pores through which water could move to the surface of the electrode used in Example 3, and using this electrode as a negative electrode in the cell shown in Example 1. When the battery was assembled and subjected to a charge / discharge test under the discharge conditions shown in Example 1, the charge / discharge cycle characteristics were improved to about 100 cycles.
[0029]
From this, cellophane attached to the electrode,
(1) Separator to prevent short circuit with positive electrode (2) Physically push back tin-like moss dendrite, which has a large volume deposited during charging and is relatively soft, to the negative electrode surface to prevent loss and inactivation of active material It was found to have a great function.
[0030]
Embodiment 5
The Sn powder 100 mesh under as a negative electrode active material (purity 3N), SnO ₂ powder (manufactured by Kojundo Chemical Laboratory) 20 wt%, mixed powder obtained by mixing SnO powder (manufactured by Kojundo Chemical Laboratory) 5 wt% Then, two 1 cm × 1 cm plate bodies were cut out from a sheet obtained by adding the PTEF dispersion liquid and ethanol shown in Example 3 to produce an electrode shown in FIG.
[0031]
When this electrode was assembled into the cell shown in Example 1 and subjected to a charge / discharge test, the content of metallic tin in the electrode was reduced as compared with Examples 3 and 4, so that the battery capacity value and the discharge current value were slightly Although decreasing, charging and discharging of about 100 cycles were possible.
[0032]
【The invention's effect】
As described above, according to the present invention, by using metal tin or a mixture of metal tin and tin oxide as a new negative electrode active material for an alkaline secondary battery, a battery characteristic of high voltage can be obtained, It has a great practical advantage because it has no toxicity like conventional batteries. Also, if the copper plate surface is covered with a sheet containing the above-mentioned negative electrode active material, and a cellophane having fine pores through which water can move is attached to the sheet to form a negative electrode, the negative electrode is deposited on the negative electrode with charge and discharge. Since a short circuit with the positive electrode due to dendrite can be prevented, a secondary battery having excellent charge / discharge cycle characteristics is provided.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a cell used in an example of the present invention.
FIG. 2 is a perspective view showing a structure of an electrode used in Example 4.
FIG. 3 is a graph showing a charge / discharge curve obtained in Example 1.
FIG. 4 is a graph showing current-voltage curves obtained in Examples 2 and 3.
[Explanation of symbols]
Reference Signs List 1 cell 2 electrolytic solution 3 negative electrode plate 4 positive electrode plate 5 expanded copper 6 negative electrode active material sheet 7 cellophane

Claims (4)

An anode active material for an alkaline secondary battery, which is an active material comprising metal tin or a mixture of metal tin and tin oxide. A negative electrode for an alkaline secondary battery, comprising a sheet containing an active material comprising metal tin or a mixture of metal tin and tin oxide. A sheet body containing an active material composed of metal tin or a mixture of metal tin and tin oxide is pressure-bonded to a metal plate surface, and the pressure-bonded body is covered with a resin body having micropores. Negative electrode for alkaline secondary batteries. An alkaline secondary battery using the negative electrode according to claim 2 or 3.

Images