JP6977988B2 - Secondary battery - Google Patents

Description

The present invention relates to a secondary battery.

Although nickel-zinc secondary batteries have been developed and studied for a long time, it is known that there are large barriers to practical use. This is because zinc constituting the negative electrode forms dendritic crystals called dendrites during charging, and the dendrites break through the separator and cause a short circuit with the positive electrode. On the other hand, nickel-cadmium batteries and nickel-metal hydride batteries have already been commercialized. However, the nickel-zinc secondary battery has an extremely high theoretical capacity density of about 5 times that of the nickel-cadmium secondary battery, 2.5 times that of the nickel-hydrogen secondary battery, and 1.3 times that of the lithium-ion battery. It also has the advantage that the raw material price is low. Therefore, in a nickel-zinc secondary battery, a technique for preventing a short circuit due to zinc dendrite is strongly desired.

In order to deal with such problems or demands, a layered double hydroxide (LDH) separator having ^{hydroxide ion (OH −) conductivity has been proposed.} For example, Patent Document 1 (International Publication No. 2013/118561) discloses that an LDH separator is provided between a positive electrode and a negative electrode in a nickel-zinc secondary battery for the purpose of preventing a short circuit due to zinc dendrite. Further, Patent Document 2 (International Publication No. 2016/076047) discloses a separator structure including an LDH separator compounded with a porous substrate, and the LDH separator is gas impermeable and / or. It is disclosed that it has a high degree of density enough to have water impermeableness.

On the other hand, Patent Document 3 (Japanese Unexamined Patent Publication No. 61-285661) describes the general formula [M ²⁺ _(1-x) Fe ³⁺ _x (OH) ₂ ] ^{X +} [(x / n) in an alkaline storage battery in a non-charged state. ) X ^n- , yH ₂ O] ^X- (In the formula, x is 0.05 to 0.4, M ²⁺ represents oxidative and reducing cations, and X ^n- is at least complex double hydroxide. It is disclosed to use a positive storage battery electrode which is a double hydroxide (representing any anion that guarantees the charge of a cation of an object).

International Publication No. 2013/118561 International Publication No. 2016/076047 Japanese Unexamined Patent Publication No. 61-285661

The positive electrode of a nickel-zinc battery generally contains nickel hydroxide and / or nickel oxyhydroxide. For example, when the nickel-zinc battery is configured in the discharge end state, the positive electrode contains nickel hydroxide, while when the nickel-zinc battery is configured in the fully charged state, the positive electrode contains nickel oxyhydroxide. Nickel hydroxide, which is a typical positive electrode active material, is β-Ni (OH) ₂ (theoretical capacity 289 mAh / g, density 4.1 g / cm ³ ) having a stable structure even under strong alkali, which is filled. The discharge reaction reversibly changes to β-Ni (OH) ₂ ⇔ β-NiOOH (average valence 3, density 4.7 g / cm ^3). By the way, when a nickel-zinc battery provided with such a positive electrode is overcharged, ^{a compound of γ-NiOOH (average valence 3.6 to 3.7, density 3.79 g / cm 3} ) is produced on the positive electrode. This γ-NiOOH has a larger number of reaction electrons than the β type, and an increase in capacity can be expected. Specifically, γ-NiOOH can be expected to improve the capacity of nickel hydroxide (β type), which is a current material that can only be oxidized by one electron, by 1.5 times. However, α-Ni (OH) ₂ generated by reduction due to discharge is unstable and easily returns to β-Ni (OH) _2, which causes volume shrinkage, which causes a problem of deterioration of the electrode. be. Therefore, a positive electrode active material that has the above-mentioned advantages of γ-NiOOH and can avoid the above-mentioned problems is desired. On the other hand, a negative electrode active material that replaces the zinc negative electrode without causing the problem of short circuit due to zinc dendrite is also desired.

The present inventors have now been able to reversibly change the interlayer distance of a layered double hydroxide (LDH) containing a predetermined constituent element such as Ni with charge and discharge, and therefore for a secondary battery. It was found that it can be used as a positive electrode active material. Further, it is considered that the layered double hydroxide (LDH) containing a predetermined constituent element such as Cu and Al also changes the interlayer distance reversibly with charge and discharge, and therefore, a negative electrode active material for a secondary battery. It was also found that it can be adopted as. It was found that by adopting the LDH positive electrode and the LDH negative electrode in this way, it is possible to provide a secondary battery that is expected to increase in capacity, has high stability due to charging and discharging, and does not cause the problem of short circuit due to zinc dendrite. ..

Therefore, an object of the present invention is to provide a secondary battery which is expected to have an increase in capacity, has high stability due to charge / discharge, and does not cause a short circuit problem due to zinc dendrite.

According to one aspect of the present invention, as the positive electrode active material, a positive electrode containing a layered double hydroxide (LDH) containing at least one selected from the group consisting of Ni, Fe and Mn as a constituent element.
As the negative electrode active material, a negative electrode containing a layered double hydroxide (LDH) containing at least one selected from the group consisting of Cu, Al and Zn as a constituent element, and a negative electrode.
Alkaline electrolyte and / or hydroxide ion conductive solid electrolyte,
A secondary battery is provided.

It is a figure which conceptually shows the secondary battery by this invention. It is a figure which shows the charge / discharge characteristic of the Ni-V-LDH positive electrode (Ni: V = 4: 1) measured in Example A1. It is a figure which shows the charge / discharge characteristic of the Ni-Fe-LDH positive electrode (Ni: Fe = 4: 1) measured in Example A2. The Ni-V-LDH (Ni: V = 4: 1) measured in Example A1 is fully charged before charge / discharge (as pre), after 10 charge / discharge cycles (after 10 cycle Cha), and charge / discharge. The XRD profile in the discharge end state (after 30 cycle Dis) after 30 cycles is shown. Discharge of β-Ni (OH) ₂ measured for comparison, before charge / discharge (as pre), fully charged after 10 charge / discharge cycles (after 10 cycle Cha), and after 10 charge / discharge cycles. The XRD profile in the terminal state (after 10 cycle Dis) is shown. The Fourier transform diagram of EXAFS before reaction, after charge, and after discharge of Ni-V-LDH (Ni: V = 4: 1) measured in Example A1 is shown. The Fourier transform diagram of EXAFS before reaction, after charge, and after discharge of Ni-Fe-LDH (Ni: Fe = 4: 1) measured in Example A2 is shown. The Fourier transform diagram of EXAFS before the reaction, after charging, and after discharging of Ni (OH) _{2 measured for comparison is shown.} 6 is an SEM image of the Ni-Fe-LDH powder produced in Example B1 taken at 40,000 times. 6 is a charge / discharge curve measured for a nickel-zinc secondary battery using the Ni-Fe-LDH powder produced in Example B1 as a positive electrode. 6 is an SEM image of the Ni-V-LDH powder produced in Example B4 taken at 40,000 times. 6 is a charge / discharge curve measured for a nickel-zinc secondary battery using the Ni-V-LDH powder produced in Example B4 as a positive electrode.

FIG. 1 conceptually shows a secondary battery according to the present invention. As shown in FIG. 1, the secondary battery 10 includes a positive electrode 12, a negative electrode 14, and an electrolytic solution and / or a solid electrolyte 16. The positive electrode 12 contains a layered double hydroxide (LDH) containing at least one selected from the group consisting of Ni, Fe and Mn as a constituent element as the positive electrode active material. The negative electrode 14 contains a layered double hydroxide (LDH) containing at least one selected from the group consisting of Cu, Al and Zn as a constituent element as the negative electrode active material. The electrolytic solution and / or the solid electrolyte 16 (hereinafter, both may be collectively referred to as an electrolyte 16) is an alkaline electrolytic solution and / or a hydroxide ion conductive solid electrolyte. As described above, by adopting the layered double hydroxide (LDH) containing a predetermined constituent element such as Ni as the positive electrode active material for the secondary battery 10, the interlayer distance is reversibly changed with charge and discharge. be able to. Further, by adopting a layered double hydroxide (LDH) containing a predetermined constituent element such as Cu and Al as a negative electrode active material for the secondary battery 10, the interlayer distance is reversibly changed with charge and discharge. be able to. Therefore, by adopting the LDH positive electrode and the LDH negative electrode, it is possible to provide a secondary battery in which an increase in capacity can be expected, stability due to charging and discharging is high, and the problem of short circuit due to zinc dendrite does not occur.

LDH is known as a compound in which divalent and trivalent (sometimes tetravalent) ions form a layered hydroxide, and anions such as carbonate ions are inserted between layers in order to balance charges between them. .. Here, since divalent and trivalent (sometimes tetravalent) ions can be selected from a wide range of candidates, inexpensive metals such as manganese and iron can be used. This LDH has a structure similar to α-Ni (OH) _2, and can reversibly change the interlayer distance with charge and discharge. As mentioned above, charging from β-Ni (OH) ₂ to γ-NiOOH can be expected to improve the capacity by 1.5 times compared to charging from β-Ni (OH) _{2 to β-NiOOH.} There is a problem that α-Ni (OH) ₂ generated by reduction accompanying electric discharge is unstable and easily returns to β-Ni (OH) ₂ , and at that time, volume shrinkage occurs and the electrode deteriorates. Therefore, a positive electrode active material that has the above-mentioned advantages of γ-NiOOH and can avoid the above-mentioned problems is desired. On the other hand, a negative electrode active material that replaces the zinc negative electrode without causing the problem of short circuit due to zinc dendrite is also desired. In this respect, according to the LDH secondary battery of the present invention, it can be expected that these requirements are conveniently satisfied.

The positive electrode 12 contains LDH as the positive electrode active material. That is, in the secondary battery 10 of the present invention, LDH itself is involved in the charge / discharge reaction of the positive electrode 12. LDH contained in the positive electrode 12 contains at least one selected from Ni, Fe and Mn as a constituent element. That is, as is generally known, LDH is composed of a plurality of hydroxide basic layers and an intermediate layer interposed between the plurality of hydroxide basic layers. The basic hydroxide layer is mainly composed of metal elements (typically metal ions) and OH groups. Intermediate layer of LDH is composed of anionic and _{H 2} O. The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, the anions in LDH contain OH ⁻ and / or CO ₃ ^2- . Therefore, LDH contained in the positive electrode 12 contains at least one selected from Ni, Fe and Mn as a part of the metal element constituting the hydroxide basic layer. Of these, Ni-based LDH containing at least Ni is preferable.

More preferably, LDH contained in the positive electrode 12 contains a combination of Ni and V, a combination of Ni and Fe, or a combination of Ni and Mn as constituent elements. That is, LDH contained in the positive electrode 12 preferably contains Ni and V, Ni and Fe, or Ni and Mn as the metal elements constituting the hydroxide basic layer. In other words, preferred examples of LDH contained in the positive electrode 12 include Ni-V-LDH, Ni-Fe-LDH, and Ni-Mn-LDH. Particularly preferred is Ni-V-LDH or Ni-Fe-LDH. In the case of Ni-V-LDH, the molar ratio of V / (Ni + V) is preferably 0.15 to 0.50, more preferably 0.20 to 0.40, and even more preferably 0.20 to 0.20. It is 0.35. On the other hand, in the case of Ni-Fe-LDH, the molar ratio of Fe / (Ni + Fe) is preferably 0.15 to 0.50, more preferably 0.20 to 0.40, and even more preferably 0. It is 20 to 0.35. Within these ranges, the charge / discharge capacity can be further improved when used for the positive electrode 12.

The negative electrode 14 contains LDH as a negative electrode active material. That is, in the secondary battery 10 of the present invention, LDH itself is involved in the charge / discharge reaction of the negative electrode 14. LDH contained in the negative electrode 14 contains at least one selected from Cu, Al and Zn as a constituent element. Again, as is generally known, LDH is composed of a plurality of hydroxide basic layers and an intermediate layer interposed between the plurality of hydroxide basic layers. The basic hydroxide layer is mainly composed of metal elements (typically metal ions) and OH groups. Intermediate layer of LDH is composed of anionic and _{H 2} O. The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, the anions in LDH contain OH ⁻ and / or CO ₃ ^2- . Therefore, LDH contained in the negative electrode 14 contains at least one selected from Cu, Al and Zn as a part of the metal element constituting the hydroxide basic layer. Of these, Al-based LDH containing Al is preferable.

More preferably, LDH contained in the negative electrode 14 contains a combination of Cu and Al or a combination of Zn and Al as a constituent element. That is, the LDH contained in the positive electrode 12 preferably contains Cu and Al, or Zn and Al as the metal elements constituting the hydroxide basic layer. In other words, Cu-Al-LDH and Zn-Al-LDH are preferred examples of LDH contained in the negative electrode 14.

The electrolyte 16 is an alkaline electrolyte and / or a hydroxide ion conductive solid electrolyte. That is, the secondary battery 10 of the present invention may be configured as a liquid-based battery, an all-solid-state battery, or a battery having both elements. A typical alkaline electrolyte is an aqueous alkali metal hydroxide solution. Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide and the like, but potassium hydroxide is more preferable. On the other hand, the hydroxide ion conductive solid electrolyte is in the form of a film-like, layered or plate-shaped member that separates the positive electrode 12 and the negative electrode 14 so that the positive electrode 12 and the negative electrode 14 can conduct hydroxide ions and do not allow electron conduction. It is preferable to have (that is, in the form of a separator). This solid electrolyte may be dense or porous, and its structure is not limited as long as it does not contain an electron conductive substance. For example, it may be a green compact layer in which hydroxide ion conductive solid electrolyte particles are deposited in a thin layer and pressurized, or it may be integrated by a method such as heating or hydrothermal treatment. May be good. In particular, since the secondary battery 10 of the present invention does not need to use an electrolytic solution, no particular problem (for example, deterioration or collapse due to permeation of the electrolytic solution) occurs even if the green compact layer is used. Further, a hydroxide ion conductive solid electrolyte molded into a film may be arranged as a separator. The hydroxide ion conductive solid electrolyte is not particularly limited as long as it is a solid electrolyte having hydroxide ion conductivity, but an inorganic solid electrolyte is preferable. Examples of the hydroxide ion conductive inorganic solid electrolyte include layered double hydroxide (LDH), layered perovskite oxide and the like. LDH is most preferable because it is inexpensive and exhibits high hydroxide ion conductivity. In particular, as described above, LDH separators are known in the fields of nickel-zinc secondary batteries and zinc-air secondary batteries (see Patent Documents 1 and 2), and the LDH separator can be used as the secondary battery 10 of the present invention. Can also be preferably used. This LDH separator may be composited with a porous substrate as disclosed in Patent Documents 1 and 2, but in that case, pores are formed throughout the thickness direction in the porous substrate. It is desirable that LDH is filled inside. By doing so, smooth transfer of hydroxide ions to the positive electrode 12 and the negative electrode 14 in contact with the LDH separator becomes possible. Therefore, if there is a portion of the porous substrate that is not filled with LDH, it is desirable to remove such portion by cutting, polishing, or the like and use it as a separator.

According to a preferred embodiment of the present invention, the secondary battery 10 contains an alkaline electrolytic solution. That is, the secondary battery 10 can be configured as a liquid-based battery. The preferable alkaline electrolytic solution is an aqueous alkali metal hydroxide solution as described above, and more preferably an aqueous solution of potassium hydroxide. It is preferable that the secondary battery 10 further includes a separator that separately separates the positive electrode 12 and the negative electrode 14 so that hydroxide ions can be conducted. As the separator, a known separator material such as a non-woven fabric that allows the passage of an electrolytic solution or hydroxide ions may be used. The advantages of the secondary battery 10 in the case of a liquid battery are that (i) zinc dissolution precipitation and shape deterioration, which are problems with the zinc negative electrode, do not occur, and (ii) the volume change of the positive electrode and the negative electrode is small. , And (iii) no short circuit due to zinc dendrite occurs. In addition, the advantages of (i) and (ii) above lead to good cycle characteristics.

According to another preferred embodiment of the invention, the secondary battery 10 comprises a hydroxide ion conductive solid electrolyte, thereby forming an all-solid secondary battery. The preferred hydroxide ion conductive solid electrolyte in this embodiment is a layered double hydroxide (Mg-Al-LDH) containing Mg and Al as components. Again, as is generally known, LDH is composed of a plurality of hydroxide basic layers and an intermediate layer interposed between the plurality of hydroxide basic layers. The basic hydroxide layer is mainly composed of metal elements (typically metal ions) and OH groups. Intermediate layer of LDH is composed of anionic and _{H 2} O. The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, the anions in LDH contain OH ⁻ and / or CO ₃ ^2- . Therefore, Mg-Al-LDH contains Mg and Al as metal elements constituting the hydroxide basic layer. Particularly preferably, the hydroxide ion conductive solid electrolyte is a green compact of Mg-Al-LDH. The advantages of the secondary battery 10 in the case of an all-solid-state battery are (i) high energy density, (ii) no liquid leakage, and (iii) no gas generation that causes deterioration of the liquid battery. It is safer than water-based batteries.

According to yet another preferred embodiment of the present invention, the secondary battery 10 contains both an alkaline electrolyte and a hydroxide ion conductive solid electrolyte. That is, the secondary battery 10 may be a battery having both elements of a liquid-based battery and an all-solid-state battery. The preferred hydroxide ion conductive solid electrolyte in this embodiment is a layered double hydroxide (Mg-Al-LDH) containing Mg and Al as components, and Mg-Al-LDH is as described above. .. Specifically, the hydroxide ion conductive solid electrolyte is an Mg-Al-LDH green compact, and it is preferable that the green compact is impregnated with an alkaline electrolytic solution. The advantages of the secondary battery 10 in the case of a battery having the elements of a liquid-based battery and an all-solid-state battery are (i) high energy density, (ii) less likely to cause liquid leakage, and (iii) liquid. Gas generation that causes deterioration of the system battery is less likely to occur, it is safer than the water system battery, and (iv) the interface resistance is lower than that of the all-solid-state battery.

The present invention will be described in more detail with reference to the following examples.

Examples A1 and A2
(1) Measurement of charge / discharge characteristics A 6M KOH aqueous solution was used as the electrolytic solution, and Ni-V-LDH (molar ratio Ni: V = 4: 1) (eg A1) or Ni-Fe-LDH (molar ratio Ni:) was used for the positive electrode. An electrochemical cell was prepared using Fe = 4: 1) (Example A2), using a platinum plate as the counter electrode and HgO as the reference electrode. When a charge / discharge test was performed using this electrochemical cell at a current density of 50 mA / g, a capacity exceeding that of nickel hydroxide was obtained. FIG. 2 shows the charge / discharge characteristics of Ni-V-LDH (Example A1), and FIG. 3 shows the charge / discharge characteristics of Ni-Fe-LDH (Example A2). When the change in the valence of Ni in the Ni-V-LDH positive electrode and the Ni-Fe-LDH positive electrode charged using X-ray absorption fine structure analysis (XAFS) was investigated, it changed from divalent to 3.5 valence due to charging. It was confirmed that

(2) XRD analysis of structural changes due to charge / discharge In Example A1, ex-situ XRD analysis is performed to investigate the detailed mechanism of the charge / discharge reaction in the Ni-V-LDH positive electrode (Ni: V = 4: 1). Was done. Specifically, an X-ray diffractometer (Ultima IV, manufactured by Rigaku Co., Ltd.) was used to obtain an XRD profile of the above powder under measurement conditions of a voltage of 40 kV and a current value of 40 mA. FIG. 4 shows the Ni-V-LDH in a fully charged state before charging / discharging (as pre), in a fully charged state after 10 charge / discharge cycles (after 10 cycle Cha), and in a discharge end state after 30 charge / discharge cycles (after 30). The XRD profile in the cycle Dis) is shown. As can be seen from FIG. 4, the peaks caused by the (003) and (006) planes of Ni-V-LDH are shifted to the high angle side by charging, which means that the interlayer distance is narrowed by charging. .. Further, in the discharge after 30 charge / discharge cycles, the peaks caused by the (003) plane and the (006) plane have returned to the same positions as before the charge / discharge, that is, have returned to the original structure. From this, it can be seen that Ni-V-LDH exhibits extremely high reversibility in the charge / discharge cycle. For comparison, the same measurement was performed for β-Ni (OH) ₂ , and the XRD profile shown in FIG. 5 was obtained. As a result, as shown in FIG. 5, _{a part of β-Ni (OH) 2} undergoes a large structural change to γ-NiOOH due to overcharging (caused by the (001) and (002) planes of γ-NiOOH. It was found that the structure did not return to the original structure even when discharged, and the structure collapsed. It was also found that the crystals became amorphous by repeated charging and discharging. No phase of α-Ni (OH) ₂ was observed. On the other hand, the Ni-V-LDH positive electrode of Example A1 can be said to be a stable positive electrode material even under strong alkali because it maintains its structure even after discharge, in contrast to _{β-Ni (OH) 2.} ..

(3) Estimation of structural change during charge / discharge from EXAFS spectrum Charge / discharge reaction in Ni-V-LDH (Ni: V = 4: 1) or Ni-Fe-LDH (molar ratio Ni: Fe = 4: 1) In order to investigate the detailed mechanism of, wide area X-ray absorption fine structure (EXAFS) measurement was performed. Specifically, the measurement was performed on the BL11S2 line of the Aichi Science and Technology Foundation Aichi Synchrotron Optical Center. FIG. 6 shows a Fourier transform diagram of EXAFS before reaction, after charging, and after discharging Ni-V-LDH (eg A1), and FIG. 7 shows a Fourier transform diagram of Ni-Fe-LDH (eg A2) before reaction. The Fourier transform diagram of EXAFS after charging and discharging is shown. For comparison, FIG. 8 shows a Fourier transform diagram of EXAFS before the reaction of _{Ni (OH) 2, after charging, and after discharging.} The peak of the Fourier transform diagram of EXAFS indicates an ion located at a distance on the horizontal axis from the nickel ion existing in the center. In this regard, in Ni-V-LDH and Ni-Fe-LDH shown in FIGS. 6 and 7, the distance between the oxygen ion existing in the first coordination sphere and the adjacent nickel ion existing in the second coordination sphere will be any longer. Has shrunk and returned to its original position after discharge. On the other hand, in Ni (OH) ₂ shown in FIG. 8, it can be seen that the positions of adjacent nickel ions have changed significantly due to charging and have not returned to their original positions even after discharging. Therefore, it was found that LDH, in contrast to Ni (OH) ₂ , reversibly repeats expansion and contraction and expansion both in layers and in-plane with charge and discharge.

(4) Consideration of reaction mechanism associated with charge / discharge Nickel hydroxide desorbs protons with charge and recombines with protons with discharge, but LDH and nickel hydroxide are significantly different from each other in terms of structural changes. Therefore, the reaction mechanism of LDH is considered to be different from the desorption / recombination of protons, which is the main mechanism of nickel hydroxide. In particular, the volume change during charging and discharging of LDH is about 9%, which is significantly different from 66% of nickel hydroxide, which is rather close to 4% of _{LiCoO 2, which is a typical positive electrode material of lithium ion batteries.} From this, it is considered that the charging / discharging mechanism of LDH is not the desorption / recombination of protons but the insertion / desorption of ions as in a lithium ion battery. More specifically, it seems that anions are inserted between the layers in order to balance the charges with charging (oxidation), and the inserted anions are desorbed with discharging (reduction). Based on this knowledge, a lithium-ion battery type secondary battery can be designed. For example, a nickel-based LDH is used for the positive electrode, and a material (for example, Cu-Al-LDH) from which anions are eliminated by reduction is used for the negative electrode. The electrode reaction is
- the positive electrode: Ni-V-LDH + A -
⇔ Ni-V-LDH · A + e -
・ Negative electrode: Negative electrode ・ A + e ⁻ ⇔ Negative electrode + A ⁻
(A ^- is an anion, Ni-V-LDH · A is a Ni-V-LDH has an anion inserted)
Etc. are conceivable. An example of a typical A ^{− is OH −} . LDH (for example, Cu-Al-LDH) can be used for the negative electrode ^{as a material from which OH − is desorbed by reduction.} Then, if an LDH sheet (for example, Mg-Al-LDH sheet) known as a hydroxide ion conductive solid electrolyte is used as the solid electrolyte, an all-solid-state LDH battery can be constructed. Since the all-solid-state LDH battery can be easily stacked, the voltage can be increased, and the volume of the electrolytic solution and the packaging material can be saved, so that the energy density also increases. Therefore, this type of battery is expected to be most suitable for battery applications that require high energy density, such as stationary type and car-mounted type.

Examples B1 to B7
Examples B1 to B7 described below are reference examples or comparative examples in which a Zn-ZnO electrode is used as the negative electrode instead of the LDH electrode, but Ni-Fe-LDH or Ni-V-LDH is used as the positive electrode active material of the secondary battery. It shall be added to demonstrate that it can be preferably adopted.

Example B1 (reference)
(1) Preparation of Ni-Fe-LDH powder Ni-Fe-LDH (Ni ₈ Fe ₂ (OH) ₂₀ (CO ₃ ) · mH ₂ O with a molar ratio of Ni: Fe of 4: 1 but m is 0 or more. ) Was prepared by the following procedure. 20 ml of ethylene glycol, 15 ml of aqueous ammonia and 5 ml of sodium carbonate were mixed. To the resulting mixture, nickel nitrate (II) 6 hydrate _{(Ni (NO 3) 2 ·} 6H 2 O, manufactured by Kishida Chemical Co., Ltd., special grade) and iron nitrate (III) 9 hydrate (Fe (NO _{3) 3} · _9H 2 O, Kishida chemical Co., Ltd., special grade) and Ni: Fe (molar ratio) = 4: stirred with aqueous metal ion solution 10ml in a proportion of 1. The obtained aqueous solution of raw materials was placed in an autoclave and crystal-grown by hydrothermal synthesis at 170 ° C. for 18 hours to precipitate an LDH precipitate. The precipitate-containing solution thus obtained was suction-filtered to collect the precipitate. The recovered LDH precipitate was washed with water, further washed with ethanol, and then dried in vacuum at 80 ° C. to obtain Ni-Fe-LDH powder.

(2) SEM observation and particle size measurement The obtained Ni-Fe-LDH powder was observed with a scanning electron microscope (SEM) (JSM-6610LV, manufactured by JEOL). FIG. 9 shows an SEM image of LDH powder taken at a magnification (40,000 times) suitable for observing primary particles. As shown in FIG. 9, the primary particle size of the Ni-Fe-LDH powder was 0.1 to 0.6 μm. The average primary particle size of the Ni-Fe-LDH powder was 0.24 μm. The average primary particle size was measured by measuring the longest distance of the diameter of the plate-like particles in the SEM image. The magnification of the SEM image used for this measurement is 40,000 times, and the primary particle size is measured for 10 primary particles per field, and the primary particle size for 2 fields (that is, a total of 20 primary particles). The average value was calculated and used as the average primary particle size. The length measurement function of the SEM software was used for the length measurement.

(3) Evaluation by X-ray diffraction X-ray diffraction measurement was performed on the obtained Ni-Fe-LDH powder. Specifically, using an X-ray diffractometer (Rigaku Co., Ltd., RINT TTR III), an XRD profile of the above powder is obtained under measurement conditions of voltage: 50 kV, current value: 300 mA, and measurement range: 10 to 70 °. rice field. From the obtained XRD profile, it was confirmed that the powder was LDH.

(4) Fabrication and evaluation of nickel-zinc secondary battery (4a) Electrode fabrication Ni-Fe-LDH powder and acetylene black (AB) are mixed at a weight ratio of 20:80, and polytetrafluoroethylene (PTFE) is added. After kneading, it was formed into a sheet. The obtained sheet was pressed on nickel foam to prepare an LDH electrode.

(4b) Preparation of Nickel-Zinc Secondary Battery An LDH electrode as a positive electrode, a Zn-ZnO electrode (including a mixture of zinc metal and zinc oxide) as a negative electrode, and a 6M KOH aqueous solution saturated with zinc oxide as an electrolytic solution. It was used to construct a nickel-zinc secondary battery.

(4c) Charge / discharge test A charge / discharge test was performed on the obtained nickel-zinc secondary battery. The charge / discharge test was performed at a 10-hour rate using a 580-inch Battery Test System manufactured by Toyo Corporation. The obtained charge / discharge curve is shown in FIG. The measured discharge capacity is shown in Table 1 as a relative value with respect to the case where _{a Ni (OH) 2 positive electrode is used (Example B7 described later).}

Examples B2 and B3 (reference)
The same as in Example B1 except that the Ni—Fe-LDH composition was changed so that the molar ratio of Ni: Fe shown in Table 1 was 3: 1 (Example B2) or 2: 1 (Example B3). Nickel-zinc secondary batteries were manufactured and evaluated. The results are as shown in Table 1. The average primary particle size of the Ni-Fe-LDH powder was in the range of 0.1 to 3 μm.

Example B4 (reference)
(1) Preparation of Ni-V-LDH powder Ni-V-LDH (Ni ₄ V-LDH (Ni ₈ V ₂ (OH) ₂₀ (CO ₃ ) ・ mH ₂ O) with a molar ratio of Ni: V of 4: 1 However, m is 0 or more) was prepared by the following procedure. 20 ml of ethylene glycol, 15 ml of aqueous ammonia and 5 ml of sodium carbonate were mixed. Nickel (II) chloride hexahydrate (NiCl _2. 6H ₂ O, manufactured by Kishida Chemical Co., Ltd., special grade) and vanadium chloride (III) (VCl ₃ , manufactured by Kishida Chemical Co., Ltd., special grade) at a ratio of Ni: V (molar ratio) = 4: 1 10 ml of metal ion aqueous solution Was added and stirred. The obtained raw material aqueous solution was placed in an autoclave, and crystals were grown by hydrothermal synthesis at 170 ° C. for 18 hours to precipitate an LDH precipitate. The precipitate-containing solution thus obtained was suction-filtered. The precipitate was recovered. The recovered LDH precipitate was washed with water, further washed with ethanol, and then dried in vacuum at 80 ° C. to obtain a Ni-V-LDH powder.

(2) SEM observation and particle size measurement The obtained Ni-V-LDH powder was SEM observed in the same manner as in Example B1. FIG. 11 shows an SEM image of LDH powder taken at a magnification (40,000 times) suitable for observing primary particles. As shown in FIG. 11, the primary particle size of the Ni-V-LDH powder was 0.05 to 0.5 μm. The average primary particle size of the Ni-V-LDH powder was 0.15 μm.

(3) Evaluation by X-ray Diffraction The obtained Ni-V-LDH powder was subjected to X-ray diffraction measurement in the same manner as in Example B1 to obtain an XRD profile of the powder. From the obtained XRD profile, it was confirmed that the powder was LDH.

(4) Preparation and Evaluation of Nickel-Zinc Secondary Battery A nickel-zinc secondary battery was prepared and evaluated in the same manner as in Example B1 except that the obtained Ni-V-LDH powder was used. The obtained charge / discharge curve is shown in FIG. The measured discharge capacity is shown in Table 1 as a relative value with respect to the case where _{a Ni (OH) 2 positive electrode is used (Example B7 described later).}

Examples B5 and B6 (reference)
In the same manner as in Example B4, except that the Ni—V-LDH composition was changed so that the molar ratio of Ni: V shown in Table 1 was 3: 1 (Example B5) or 2: 1 (Example B6). Nickel-zinc secondary batteries were manufactured and evaluated. The results are as shown in Table 1. The average primary particle size of the Ni-V-LDH powder was in the range of 0.05 to 3 μm.

Example B7 (comparison)
A nickel-zinc secondary battery was prepared and evaluated in the same manner as in Example B1 except _{that Ni (OH) 2} powder was used instead of Ni-Fe-LDH powder. The results are as shown in Table 1.

Claims (8)

As the positive electrode active material, a positive electrode containing a layered double hydroxide (LDH) containing a combination of Ni and V or a combination of Ni and Fe as a constituent element,
As the negative electrode active material, a negative electrode containing a layered double hydroxide (LDH) containing at least one selected from the group consisting of Cu, Al and Zn as a constituent element, and a negative electrode.
Alkaline electrolyte and / or hydroxide ion conductive solid electrolyte,
A rechargeable battery equipped with. The secondary battery according to claim 1 , wherein the LDH contained in the negative electrode contains a combination of Cu and Al or a combination of Zn and Al as a constituent element. The secondary battery according to claim 1 or 2 , wherein the secondary battery contains the alkaline electrolytic solution. The secondary battery according to claim 3 , wherein the secondary battery further includes a separator that separately separates the positive electrode and the negative electrode so that hydroxide ions can be conducted. The secondary battery contains both the alkaline electrolyte and the hydroxide ion conductive solid electrolyte, and the hydroxide ion conductive solid electrolyte contains Mg and Al as constituent elements of the layered compound hydroxide. The secondary battery according to claim 1 or 2 , which is (Mg-Al-LDH). The secondary battery according to claim 5 , wherein the hydroxide ion conductive solid electrolyte is a green compact of Mg-Al-LDH, and the green compact is impregnated with the alkaline electrolytic solution. A layered compound hydroxide (Mg-Al-LDH) in which the secondary battery contains the hydroxide ion conductive solid electrolyte, and the hydroxide ion conductive solid electrolyte contains Mg and Al as components. The secondary battery according to claim 1 or 2 , wherein the secondary battery forms an all-solid-state secondary battery. The secondary battery according to claim 7 , wherein the hydroxide ion conductive solid electrolyte is a green compact of Mg-Al-LDH.

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