JP6638939B2 - Zinc electrode and storage battery provided with the zinc electrode - Google Patents

Description

  The present invention relates to a zinc electrode and a storage battery provided with the zinc electrode.

In recent years, demands for higher energy density and lower cost as storage batteries for electronic devices and vehicles have been increasing. A storage battery including an electrode containing a zinc species as a negative electrode active material (hereinafter, referred to as a “zinc negative electrode”) is an attractive battery system having an advantage of high energy density per unit mass and high output density. Short life is an issue. This is because the zincate ion (Zn (OH) ₄ ²⁻ ), which is the discharge product of the zinc negative electrode, has high solubility in the electrolytic solution, and the zinc is deposited unevenly on the negative electrode during charging, so the cycle is repeated. And the shape change of the negative electrode (shape change) progresses, and further, dendrites grow from seeds formed in the negative electrode portion facing the pore portion of the separator, penetrate the separator and reach the positive electrode, causing an internal short circuit. It is the cause.

Various means for suppressing the shape change of the zinc negative electrode have been studied.
Patent Literature 1 discloses a battery electrode composition including active material particles containing a zinc species and a compound having an isoelectric point of greater than 7 (claims 1 and 8). Positively charged and attracts anions eluted during discharge, the anions become supersaturated near the negative electrode, and the active material can be controlled to reprecipitate near the negative electrode.As a result, the effect of suppressing the shape change of the zinc negative electrode is remarkable. Can be exerted on the subject "(paragraph [0009]).
As an example of the zinc negative electrode, "As the negative electrode active material, zinc oxide as an active material, manganese oxide (MgO) as positively charged particles, and polytetrafluoroethylene are kneaded at a ratio of 93: 3: 4. Rolled into a copper mesh and dried to prepare a zinc negative electrode. "(Paragraph [0076]), and" Same as in Example 1 except that yttrium oxide (Y ₂ O ₃ ) was used as positively charged particles. " [0078]) and "Same as Example 1 except that nickel hydroxide (Ni (OH) ₂ ) was used as the positively charged particles" (paragraph [0079]).

Patent Literature 2 has a structure made of an electrically insulating material in and / or on an active material layer containing active material particles containing a zinc species. Regarding a battery electrode having a structure in which ions derived from the active material are prevented from desorbing from the active material layer (claims 1 and 7), "the structure physically inhibits the desorption of the ions from the active material layer. Or the ions become supersaturated in the vicinity of the electrode, and the active material can be controlled to re-deposit in the vicinity of the electrode.As a result, the effect of suppressing the shape change of the electrode can be remarkably exerted. '' ing.
As an example of a battery electrode, “a polyolefin aqueous dispersion (Mitsui Chemicals Chemipearl S100), polytetrafluoroethylene, and zinc oxide (average particle diameter 1 μm) in a mass ratio (solid content ratio) of 1: 3: 96. The kneaded and pasted material was rolled and pasted on a copper mesh, and then dried to form a negative electrode. ”(Paragraph [0085]),“ Polytetrafluoroethylene and zinc oxide (average particle diameter 1 μm): A nonwoven fabric of 100 μm thick made of polyamide is attached to one surface of a paste (200 μm thick) kneaded at a mass ratio of 96 (solid content ratio) to form a negative electrode active material layer and a structure on the layer {In the initial state, the active material layer / nonwoven fabric layer / current collector were separated, but the positions of the active material-containing nonwoven fabric layer / electrode and active material shift as the battery is charged / discharged.] (Paragraph [008] ], It has been shown [0087]) is.

JP 2015-170390 A JP 2015-185260 A

The techniques described in Patent Literatures 1 and 2 disclose zinc, which is a discharge product of a zinc negative electrode, due to a compound kneaded in the negative electrode active material layer or a structure in the negative electrode active material layer and / or on the negative electrode active material layer. The acid ions are electrically or structurally captured in the vicinity of the negative electrode and are reprecipitated during charging, thereby suppressing a change in shape of the negative electrode.
However, in the above-described prior art, the suppression of shape change is not always sufficient, and the compound or structure as described above needs to be present in the zinc anode in a quantitative ratio of a certain value or more. The battery capacity per unit or mass was affected.

  In view of the above problems, the present inventors have sought a substance capable of suppressing a change in the shape of the negative electrode by adding an amount that does not affect the battery capacity, and by selecting a metal adsorbent having zinc adsorption ability. It has been found that the above problem can be solved. Metal adsorbents are commercially available, and are used mainly for adsorption and removal of metal components of metal catalysts required for chemical synthesis, and are known to dramatically improve the yield of compounds. However, by including a metal adsorbent in the zinc electrode as in the present invention, the form in which free ions are reprecipitated due to the battery reaction can be controlled, and the effect that the shape change of the electrode can be suppressed can be achieved by the present invention. The inventors have found it for the first time.

The present invention, which is means for solving the above problems, is as follows.
(1) The present first invention, the active material consisting of zinc species, a zinc electrode comprising a metal adsorbent, the metal adsorbent have a zinc adsorption capacity, bonding the functional groups containing N on the carrier all SANYO was an average particle size (D50) is at 150μm or less, and wherein that you have uniformly dispersed in the zinc electrode.
(2) The second invention is characterized in that in (1), the carrier is silica gel.
(3) The third invention is characterized in that in (1), the carrier is a polymer.
(4) The fourth invention is characterized in that in (3), the polymer is polyolefin or polystyrene .
(5 ) The fifth invention is characterized in that, in any one of the above (1) to ( 4 ), the metal adsorbent is contained in an amount of less than 5% by mass based on a zinc metal equivalent of the active material. to.
(6 ) The sixth invention provides a negative electrode comprising the zinc electrode according to any one of (1) to ( 5 ), a positive electrode, a separator for separating the negative electrode side region and the positive electrode side region, and an electrolyte. , Is characterized by having.

  According to the present invention, it is possible to provide a zinc electrode capable of suppressing a shape change and a storage battery having a negative electrode composed of the zinc electrode.

SEM photograph and conceptual diagram of a zinc electrode according to the present invention The graph which shows the cycle test result of the zinc electrode which concerns on this invention. Graph showing the AC resistance of the zinc electrode according to the present invention

(Zinc electrode)
The zinc electrode according to the present invention includes an active material containing an active material composed of a zinc species, and a metal adsorbent, wherein the metal adsorbent has a functional group having zinc adsorption ability bonded to a carrier. Features. In addition, in this specification, a "zinc electrode" points out the part except the collector.
FIG. 1 shows an SEM photograph of a zinc electrode supported on a foamed base material as a current collector, and an enlarged conceptual diagram. A metal adsorbent is present in the vicinity of the active material made of zinc species, and suppresses a change in shape of the zinc electrode due to a charge / discharge cycle.
The active material composed of zinc species may be any compound containing zinc and capable of repeating oxidation and reduction (alloys, metals), such as zinc, zinc oxide, zinc hydroxide, zinc sulfide, and tetrahydroxy zinc alkali. Examples thereof include metal salts, zinc alloys, and zinc solid solutions.

  The carrier of the metal adsorbent is preferably a silica gel having a silica skeleton or a polymer. In particular, when the electrode of the present invention is used for a storage battery in which the electrolyte is alkaline, it is more preferable to use, as the carrier, a polyolefin resin or a polystyrene resin that is a polymer unnecessary for an alkaline solution.

The functional group having the ability to adsorb zinc is preferably a functional group that forms a complex with zinc, and particularly preferably a functional group containing N. Examples of N-containing functional groups include amino group (aminopropyl (AP), ethylenediamine (EDA), triamine (TA)), tetrasodium triaminetetraacetate group (TAAcONa), thiourea group (TU), iminodiacetate group (IDA), An aminomethyl phosphate group (AMPA) and the like are exemplified.
These metal adsorbents include, for example, QuadraPure (trademark) of Sigma-Aldrich, R-Cat-Sil of Kanto Chemical Co., Ltd., scavenger silica gel of Fuji Silysia Chemical Ltd., SiliaMetS (trademark) of SILICYCLE, and It can be appropriately selected and obtained from a metal scavenger manufactured by Biotage, but is not limited thereto.

  The metal adsorbent according to the present invention is preferably contained in an amount of 0.05% by mass or more, more preferably 0.1% by mass or more, based on the mass of the active material in terms of zinc metal. Further, when the content is not too large, it is preferable that the content does not exceed 5% by mass, because a decrease in adsorption ability and a decrease in conductivity due to aggregation or the like can be suppressed. More preferably, it is 3% by mass or less.

Further, the average particle diameter (D50) is preferably 500 μm or less, more preferably 150 μm or less, so that the particle diameter can be uniformly dispersed in the zinc electrode and the electrode can be easily manufactured.
It is considered that if the distribution of the metal adsorbent is uniform, the distribution of the functional groups bonded to the carrier is also uniform, so that zinc deposition during charging will occur uniformly throughout the zinc electrode. The change in shape of zinc occurs when zinc is unevenly distributed due to charge and discharge, and the unevenly distributed portion is thicker than the original state. In the thick portion, the zinc particles become large lumps and the central portion cannot be used for charge / discharge, or fall off from the base material to deteriorate the conductivity, thereby deteriorating the cycle characteristics.
In the present invention, since the metal adsorbent is uniformly distributed in the zinc electrode, the zinc easily precipitates uniformly from the functional group bonded to the carrier as a starting point. It is assumed that the change can be suppressed. When the particle size of the metal adsorbent is large, it is preferable to pulverize the metal adsorbent to a desired particle size.

  The zinc electrode, the above zinc species and the metal adsorbent, for example, acetylene black, powder such as PbO, water, and a binder such as polytetrafluoroethylene, styrene butadiene rubber is added to make a paste, this paste Can be produced by filling or perforating a steel sheet with a base material such as foamed copper or foamed nickel, and then drying it sufficiently, followed by roll processing and cutting.

  A storage battery according to the present invention includes a negative electrode composed of the zinc electrode described above, a positive electrode, a separator that divides the region on the negative electrode side from the region on the positive electrode side, and an electrolyte.

(Positive electrode)
The positive electrode of the storage battery according to the present invention is preferably made of nickel, silver oxide, manganese dioxide, air, or the like, and the maximum operating voltage is preferably 0.4 V or more with respect to the potential of the Hg / HgO electrode. For example, a nickel electrode composed of a metal hydroxide containing nickel oxyhydroxide as a main component and a current collector such as foamed nickel, and an air electrode composed of a carbon material, an oxygen reduction catalyst, and a binder are used. be able to.

(Separator)
The separator according to the present invention is, for example, a polyolefin base film such as polyethylene, polypropylene, etc., irradiated with an electron beam accelerated by an electron beam accelerator under a nitrogen atmosphere to generate radicals, and then deoxygenated acrylic. It is preferable to obtain a semipermeable membrane obtained by immersing in an acid solution and performing graft polymerization, but is not limited thereto.
By using a polyolefin as a base material, a separator having high oxidation resistance and alkali resistance can be obtained. Further, in order to adjust the water permeability and the air permeability, a separator in which a nonwoven fabric, a microporous film, or the like is laminated on this film may be used.

(Electrolytes)
As the electrolyte according to the present invention, for example, a solution obtained by dissolving an alkali metal hydroxide in water can be used.Examples of the alkali metal hydroxide include KOH, NaOH, and LiOH. One type or a combination of two or more types can be used. The lower limit of the hydroxide concentration is preferably 3M or more, more preferably 4M or more. The upper limit is preferably 9M or less, more preferably 6M or less. By setting it to 3M or more, self-discharge can be suppressed, and by setting it to 9M or less, an increase in the viscosity of the electrolyte can be suppressed.

  The electrolyte preferably contains zinc oxide at a saturated concentration. By containing zinc oxide, elution of zinc contained in the negative electrode can be suppressed.

(Assembly of storage battery)
The storage battery according to the present invention can be assembled by separating the inside of the battery container with a separator, inserting the negative electrode into one region and inserting the positive electrode into the other region, and injecting the electrolytic solution into the container. The separator may be formed in a bag shape and one electrode, preferably the negative electrode, may be housed in the bag.

(Example 1)
<Preparation of alkaline electrolyte>
KOH powder was dissolved in pure water to prepare an alkaline solution to a concentration of 4M. Further, an excessive amount of ZnO powder was charged and the mixture was stirred at 25 ° C. for 24 hours. Then, it filtered and removed the surplus ZnO, and was set as the zinc saturated alkaline electrolyte.

<Preparation of zinc anode>
As a metal adsorbent, QuadraPure (trademark) IDA manufactured by Sigma-Aldrich (iminodiacetate group bonded to a polystyrene carrier) was ground in a mortar to obtain a powder having an average particle diameter of 118 µm. The average particle size is measured using a particle size distribution analyzer (trade name: Microtrac MT3000, manufactured by Nikkiso Co., Ltd.), and D50 (when the powder is divided into two from a certain particle size, the large side and the small side are equal). Value).
A predetermined amount of ZnO powder, acetylene black (AB), PbO powder, and the metal adsorbent were weighed and stirred. Thereafter, water and a polytetrafluoroethylene (PTFE) dispersion were added, and the mixture was further stirred to produce a paste. The solid content is set to ZnO: AB: PTFE: PbO: metal adsorbent = 87: 5: 5: 2: 1 (mass%), and the water content is set to about 65% by mass of the whole paste. Was adjusted. The paste was filled into a foamed copper base material having a thickness of 1 mm and a density per area of 0.45 g / cm ² , dried sufficiently, and then rolled. Thus, an electrode sheet base material having a thickness of 0.35 mm was obtained. This substrate was cut into 2 cm × 2 cm to obtain a zinc negative electrode. The paste filling amount was adjusted so that the theoretical capacity of the zinc negative electrode (electrode plate) was 100 mAh.

<Preparation of counter electrode>
In order to reduce the influence of the counter electrode on the zinc negative electrode, the counter electrode was prepared by adding Zn powder to the raw material of the zinc negative electrode containing no metal adsorbent and adjusting the mixing ratio of the paste solids to Zn: ZnO: AB: PTFE: PbO was set to be 54: 34: 5: 5: 2 (% by mass). The electrode was manufactured in the same manner as the zinc negative electrode, except that the electrode area was 2.5 cm × 3.0 cm and the paste was filled so that the electrode capacity was excessive with respect to the zinc negative electrode.

<Preparation of cell>
A microporous polypropylene separator made of polypropylene was placed on both sides of the zinc negative electrode and the counter electrode produced as described above, and a nonwoven fabric separator made of polypropylene and fibers using polypropylene was further placed thereon. Counter electrodes were arranged on both sides of the zinc negative electrode and set in a container. An Hg / HgO electrode was provided as a reference electrode. The alkaline electrolyte prepared as described above was poured to the extent that the electrode was sufficiently filled (2.5 mL). Thereafter, the sample was allowed to stand until the electrolyte sufficiently permeated the electrodes. In this way, the fabricated open cell was used as the battery according to Example 1.

(Example 2)
The same procedure as in Example 1 was carried out except that a ground product (D50 = 118 μm) of QuadraPure ™ EDA (ethylenediamine bonded to a polystyrene carrier) was used in place of QuadraPure ™ IDA as the metal adsorbent. Battery 2 was produced.

(Example 3)
The same procedure as in Example 1 was carried out except that R-Cat-Sil-AP of Kanto Chemical Co., Ltd. (aminopropyl bonded to a silica gel carrier, D50 = 48 μm) was used as a metal adsorbent without pulverization. Example battery 3 was produced.

(Example 4)
Example battery 4 was produced in the same manner as in Example 1 except that R-Cat-Sil-TA (triamine bonded to a silica gel carrier, D50 = 51 μm) was used as a metal adsorbent as it was.

(Comparative Example 1)
Comparative Example Battery 1 was produced in the same manner as in Example 1 except that the metal adsorbent was not used and ZnO: AB: PTFE: PbO was 88: 5: 5: 2 (% by mass).

(Comparative Example 2)
Comparative Example Battery 2 was produced in the same manner as in Example 1, except that silica powder (D50 = 70 nm) manufactured by Wako Pure Chemical Industries, Ltd. was used instead of the metal adsorbent.

(Comparative Example 3)
Comparative Example Battery 3 was produced in the same manner as in Example 1, except that polyvinyl alcohol (PVA) (average molecular weight: 5800, manufactured by Nippon Vinegar Vivovar) was used instead of the metal adsorbent.

(Comparative Example 4)
Comparative Example Battery 4 was produced in the same manner as in Example 1 except that polyethylene glycol (PEG) (manufactured by Aldrich (445858, average molecular weight 250)) was used instead of the metal adsorbent.

(Comparative Example 5)
Comparative Example Battery In the same manner as in Example 1, except that styrene-butadiene rubber (SBR) (manufactured by Nippon A & L Co., Ltd.) was used in an amount of 1% by mass relative to the zinc metal equivalent mass of the active material instead of the metal adsorbent. 5 was produced.

(Comparative Example 6)
Comparative Example Battery 6 was produced in the same manner as in Example 1 except that R-Cat-Sil-MP (thiol bonded to a silica gel carrier, D50 = 50 μm) was used as a metal adsorbent as it was.

<Measurement of zinc adsorption capacity of metal adsorbent>
The zinc adsorbing ability of the metal adsorbent used in Examples 1 to 4 and Comparative Examples 1 to 6 described above was prepared by preparing a 0.0005 M aqueous solution of zinc nitrate hexahydrate, and adding each metal adsorbent thereto. After diffusion for an additional 30 minutes, each liquid was taken out and subjected to ICP analysis.

<Cycle characteristics evaluation>
A cycle test was performed on the batteries of Examples 1 to 4 and the batteries of Comparative Examples 1 to 6 under the following conditions in an environment of 25 ° C.
In the first cycle, charging and discharging were performed under the following conditions.
The current was set to 0.25 CmA (25 mA), the battery was charged for 1 hour, paused for 5 minutes, and then discharged to −0.8 V with respect to the reference electrode.
The following conditions were repeated after the second cycle.
The current was set to 0.5 CmA (50 mA), the battery was charged for 1 hour, paused for 5 minutes, and then discharged to −0.8 V with respect to the reference electrode.
A cycle test was performed under the above conditions, and the number of cycles at which the discharge capacity began to rapidly decrease was defined as the cycle life. In addition, even when a short circuit occurred due to dendride generation, the cycle life was taken as the cycle life.
Table 1 shows the above results. FIG. 2 shows the results of the cycle tests of Example 4 and Comparative Example 1.

It can be seen that the batteries of Examples 1 to 4 all use a metal adsorbent having a zinc adsorption ability for a zinc electrode, and have excellent cycle life.
The batteries of Comparative Examples 1 to 5 do not use a metal adsorbent for the zinc electrode, and have a short cycle life.
Comparative Example Battery 6 is an example in which a metal adsorbent having no zinc adsorption ability is used, and does not contribute to an improvement in cycle life.

(Examples 5 to 7, Comparative Example 7)
Cycles similar to the above for Examples 5 to 7 and Comparative Example 7 when the amount of the metal adsorbent added in Examples 1, 2, 4, and Comparative Example 6 was 0.5% by mass in the paste mixing ratio. Characteristic evaluation was performed. The results are shown in Table 2 together with Examples 1, 2, 4, and Comparative Example 6.

  From the results in Table 2, it can be seen that when the metal adsorbent is contained in the paste solid content at 0.5% by mass, the metal adsorbent is sufficiently effective in improving the cycle life.

(Examples 8 and 9)
Regarding the relationship between the content of the metal adsorbent and the conductivity of the zinc electrode, the alkaline storage batteries produced in the same manner as in Example 1 except for the content of the metal adsorbent were referred to as Examples 8 and 9, and the charge / discharge test and the AC resistance were evaluated. The measurement was performed using a charge / discharge evaluation device (TOSCAT-3000) manufactured by Toyo System Co., Ltd., and the AC resistance after three cycles was measured at 1 kHz (measurement range: 1 to 1500 mΩ). The results are shown in FIG.
FIG. 3 shows that the AC resistance increased when the content of the metal adsorbent was 5% by mass. When the content is 3% by mass or less, the increase in resistance due to the metal adsorbent is small, and it can be seen that the conductive path is sufficiently secured by the effect of adding the conductive additive (AB).

  ADVANTAGE OF THE INVENTION Since the zinc electrode which concerns on this invention can suppress the shape change accompanying a charge / discharge cycle, the charge / discharge cycle characteristic of the storage battery which uses this for a negative electrode can be improved. Therefore, it is expected that a storage battery having a high energy density with a zinc electrode as a negative electrode can be put to practical use, and its use as a power source for electronic devices, electric vehicles, and the like is promoted.

Claims (6)

An active material comprising a zinc species and a zinc electrode containing a metal adsorbent,
The metal adsorbent have a zinc adsorption capacity state, and are not linked to a functional group containing N to the carrier, an average particle diameter (D50) is at 150μm or less, it is uniformly dispersed in the zinc electrode A zinc electrode.   The zinc electrode according to claim 1, wherein the carrier is silica gel.   The zinc electrode according to claim 1, wherein the carrier is a polymer.   The zinc electrode according to claim 3, wherein the polymer is polyolefin or polystyrene. The zinc electrode according to any one of claims 1 to 4 , wherein the metal adsorbent is contained in an amount of less than 5% by mass with respect to a zinc metal equivalent of the active material. A negative electrode comprising the zinc electrode according to any one of claims 1 to 5 ,
A positive electrode,
An electrolyte,
A storage battery comprising: