JP2018190565A - Activation method of nickel metal hydride battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent method for activating a nickel metal hydride battery.SOLUTION: In the method for activating a nickel metal hydride battery which performs charging and discharging in a plurality of cycles, charging and discharging is carried out under a temperature range of 30 to 50°C and a constant temperature in the whole cycles of the plurality of cycles.SELECTED DRAWING: None

Description

  The present invention relates to a method for activating a nickel metal hydride battery.

  A nickel metal hydride battery includes a positive electrode having a nickel oxide compound such as nickel hydroxide as a positive electrode active material, a negative electrode having a hydrogen storage alloy as a negative electrode active material, and an electrolyte comprising a strongly basic alkali metal aqueous solution. Secondary battery.

  In order to activate the nickel metal hydride battery, a technique for charging and discharging the nickel metal hydride battery in a plurality of cycles is known.

  For example, in paragraphs 0063 and 0064 of Patent Document 1, a nickel metal hydride battery having a specific binder is charged at a constant current of 0.1 C and discharged at a constant current of 0.1 C. It is specifically described that the nickel metal hydride battery is activated by performing 10 cycles of charging and discharging.

  In paragraph 0071 of Patent Document 2, a nickel metal hydride battery equipped with a specific separator is charged at 0.1 C for 12 hours, and discharged after 0.5 hours of rest at 0.1 C. It is specifically described that the nickel metal hydride battery is activated by performing 10 cycles of charging and discharging.

In paragraph 0039 of Patent Document 3, a nickel metal hydride battery having an AB ₂ type hydrogen storage alloy is charged and discharged at a charge / discharge rate of 0.1 C for 10 cycles under a 25 ° C. condition. It is specifically described that the metal hydride battery was initially activated.

JP 2010-177071 A JP 2011-198632 A JP2015-113522A

  As described in Patent Document 1 to Patent Document 3, as a method for activating a nickel metal hydride battery, it was common to repeat charge and discharge at a low rate of about 0.1 C. The reason for this is that, when charging at a high rate, polarization occurs in the positive electrode and the potential partially increases, so that water contained in the electrolytic solution may be decomposed to generate oxygen. Furthermore, since the power at the time of charging is consumed for oxygen generation, the power is wasted and it may be difficult to perform sufficient charging.

  However, the present inventor considered that there is room for further improvement in the conventional activation method.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an excellent method for activating a nickel metal hydride battery.

  In the first place, the activation of the nickel metal hydride battery is performed for the purpose of reducing the resistance of the nickel metal hydride battery. From the viewpoint of resistance, the present inventor has activated nickel metal hydride batteries by varying various parameters, and found that the temperature during charging and discharging is an important parameter that affects the resistance. . Based on this finding, the present inventor has completed the present invention.

The activation method of the nickel metal hydride battery of the present invention is as follows.
A method for activating a nickel metal hydride battery that performs charge and discharge in a plurality of cycles,
Charging / discharging is performed in a temperature range of 30 to 50 ° C. and at a constant temperature in all of the plurality of cycles.

  In addition, the activation method of the nickel metal hydride battery of this invention can also be understood as the adjustment method, manufacturing method, or initial stage activation method of the nickel metal hydride battery of this invention.

  The nickel metal hydride battery activation method of the present invention can provide a low resistance nickel metal hydride battery.

  Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from these numerical ranges can be used as new upper and lower numerical values.

  An activation method for a nickel metal hydride battery according to the present invention (hereinafter sometimes simply referred to as “activation method according to the present invention”) is a method for activating a nickel metal hydride battery in which charging and discharging are performed in a plurality of cycles. In all of the plurality of cycles, charging / discharging is performed under a temperature range of 30 to 50 ° C. and a constant temperature. Hereinafter, the nickel metal hydride battery that has undergone the method for activating the nickel metal hydride battery of the present invention may be referred to as the “nickel metal hydride battery of the present invention”.

  In the present invention, the cycle means a set of charging / discharging for charging and discharging the nickel metal hydride battery. One cycle means one set of charging / discharging, and the first cycle means one set of first charging / discharging. The charge cycle means a charged state in the cycle, and the discharge cycle means a discharged state in the cycle.

  The number of cycles in the activation method of the present invention is determined by whether or not a nickel metal hydride battery that satisfies the required characteristics is manufactured. Since the required characteristics differ depending on the specifications of the nickel metal hydride battery, it is generally difficult to determine the number of cycles in the activation method of the nickel metal hydride battery of the present invention. If the number of cycles in the activation method of the nickel metal hydride battery of the present invention is exemplified, 3 to 30, 4 to 25, 5 to 20, 5 to 15 and 5 to 10 can be exemplified.

  The activation method of the present invention is characterized in that charge and discharge are performed under a temperature range of 30 to 50 ° C. and a constant temperature. If the temperature is too low or too high, the resistance of the nickel metal hydride battery is not suitably reduced. As temperature range of charging / discharging, 35-45 degreeC is more preferable, and 37-43 degreeC is further more preferable.

  In the activation method of the present invention, it is preferable to perform the charge in the first cycle and the charge in each cycle other than the first cycle with a capacity exceeding 80% of the theoretical charge capacity, and further to a capacity greater than the theoretical charge capacity. More preferred. In particular, in the first cycle, it is preferable to charge to a capacity exceeding the theoretical charge capacity. By charging with a sufficient capacity, the hydrogen storage alloy as the negative electrode active material sufficiently stores hydrogen. When the hydrogen storage alloy sufficiently stores hydrogen, the volume expands and the number of contact points between the hydrogen storage alloy and the strongly basic electrolyte increases. Then, a part of the metal having high solubility in the strongly basic electrolyte solution is eluted from the surface of the hydrogen storage alloy, and a metal such as Ni having low solubility in the strongly basic electrolyte solution is present on the surface of the hydrogen storage alloy. stay. As a result, it is considered that a Ni enriched layer that is convenient for charge and discharge and has a high ability to dissociate hydrogen to the atomic level is formed on the surface of the hydrogen storage alloy.

  The theoretical charge capacity means so-called SOC (State of Charge) 100%. In the present specification, SOC 100% means a value calculated by multiplying the mass (g) of the positive electrode active material in the nickel metal hydride battery by its theoretical capacity (Ah / g).

  Charging in the first cycle is preferably performed from SOC 105% to 120%, more preferably from 105% to 115%. Charging in each cycle other than the first time is preferably performed up to SOC 90% to 110%, more preferably up to SOC 95% to 105%. If a remarkably excessive capacity is charged, the electrolytic solution may be decomposed to generate a large amount of oxygen. In addition, if the first cycle or each cycle other than the first cycle is charged with a capacity of 80% or less of the theoretical charge capacity, the resistance of the nickel metal hydride battery may not be suitably reduced.

Of the charge / discharge cycles, the charge rate of the first cycle is preferably low. The range of the charge rate in the first cycle is preferably less than 0.5C, more preferably 0.01C or more and less than 0.5C, further preferably 0.02C or more and 0.4C or less, and 0.03C or more and 0.3C or less. Particularly preferred. If the charge rate of the first cycle is too high, the electrolyte may decompose and oxygen may be generated, and the resistance of the nickel metal hydride battery may increase excessively. If the charge rate of the first cycle is too low, charging will take a long time.
Note that 1C means a current value required to charge the nickel metal hydride battery from SOC 0% to SOC 100% at a constant current.

  When the nickel metal hydride battery is a nickel metal hydride battery containing cobalt in the positive electrode, the first charge rate is less than 0.1 C and the second charge rate exceeds the first charge rate. It is preferable that the battery is charged at a plurality of charging rates including a charging rate. Due to charging at the first charge rate, cobalt in contact with the strongly basic electrolyte is oxidized to change to cobalt oxyhydroxide having excellent conductivity, and the cobalt oxyhydroxide is the surface of the positive electrode active material. Is expected to be suitably coated. The first charging rate is preferably 0.01 C or more and less than 0.1 C, more preferably 0.02 C or more and 0.08 C or less, and further preferably 0.03 C or more and 0.07 C or less. Charging at the first charging rate is preferably performed up to SOC 10 to 50%, more preferably up to SOC 20% to 40%.

  The second charging rate exceeding the first charging rate is preferably 0.02C or more and less than 0.5C, more preferably 0.05C or more and 0.4C or less, and further preferably 0.07C or more and 0.3C or less.

  The charge rate of each cycle is preferably less than 3C, more preferably 2C or less. If the charge rate is excessively high, the resistance of the nickel metal hydride battery may not be suitably reduced. The charge rate of each cycle is preferably 0.1 C or more and 2 C or less, more preferably 0.2 C or more and 1.5 C or less, further preferably 0.3 C or more and 1 C or less, and particularly preferably 0.4 C or more and 0.7 C or less. .

  The activation method of the present invention preferably includes an increased rate charging cycle in which charging is performed at a charging rate larger than the charging rate of the previous cycle. The activation method of the present invention may be a method in which an increased rate charging cycle is included in one cycle among charging / discharging in a plurality of cycles, but the increased rate charging cycle is 2 cycles, 3 cycles or more. The method included in the cycle is preferred. The increased rate charging cycle may be performed over all cycles other than the first cycle performed in the activation method of the nickel metal hydride battery of the present invention.

  The charging rate in the increased rate charging cycle (hereinafter, sometimes referred to as an increased charging rate) is larger than the charging rate of the previous cycle. However, if the increased charge rate is excessively high, there is a risk that the electrolyte solution decomposes and oxygen is generated. Therefore, 2C, 1.5C, and 1C can be exemplified as the upper limit value of the increased charging rate. Further, the range of the ratio R of the increased charge rate to the charge rate of the previous cycle (R = (increase charge rate) / (charge rate of the previous cycle)) is 1 <R ≦ 3, 1 <R ≦ 2.5, Examples are 1 <R ≦ 2, 1 <R ≦ 1.5.

  The increased charge rate may be determined from the result of monitoring the characteristics of the nickel metal hydride battery in the previous cycle. For example, if the characteristics of the nickel metal hydride battery in the previous cycle are good, the ratio R of the increased charge rate may be set to a high value. On the other hand, if the characteristics of the nickel metal hydride battery in the previous cycle are poor, it is preferable to charge at the same or lower charge rate as the charge rate of the previous cycle without adopting the increase rate charge cycle in this cycle.

  In the activation method of the present invention, each cycle is preferably discharged to an appropriate voltage, for example, 0.8V, 0.9V or 1V. Further, the discharge rate in the activation method of the present invention is preferably 0.1 C or more and 3 C or less, more preferably 0.2 C or more and 2 C or less, and further preferably 0.3 C or more and 1.5 C or less. The discharge rate may be gradually increased as the number of cycles is increased.

  In the activation method of the present invention, it is preferable that the charge rate of each cycle other than the first cycle is constant within the same cycle in terms of process management, and similarly, the discharge rate of each cycle is within the same cycle. And constant.

  In the activation method of the present invention, a pause period or a voltage holding period may be provided between charging and discharging without departing from the spirit of the present invention.

  Next, the structure of the nickel metal hydride battery used in the activation method of the present invention and the nickel metal hydride battery of the present invention will be described. Specifically, the nickel metal hydride battery includes a positive electrode, a negative electrode, an electrolytic solution, and a separator.

  The positive electrode includes a current collector and a positive electrode active material layer formed on the surface of the current collector. The negative electrode includes a current collector and a negative electrode active material layer formed on the surface of the current collector. Hereinafter, although it demonstrates from the structure of a positive electrode, about the thing which overlaps with the structure of a negative electrode, it demonstrates without attaching | limiting with a positive electrode.

  The current collector refers to a chemically inert electronic conductor that keeps current flowing through the electrodes during the discharge or charging of the nickel metal hydride battery. The material of the current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. The current collector material is at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Examples of such a metal material can be given. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector. As a material for the current collector, nickel or a metal material plated with nickel is preferable.

  The current collector can take the form of a foil, a sheet, a film, a line, a rod, a mesh, a sponge, and the like. In the case where the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm. What is called an expanded metal shape which spread | stretched the metal plate and made it mesh shape is preferable.

  The positive electrode active material layer includes a positive electrode active material, and includes a positive electrode additive, a binder, and a conductive additive as necessary.

  The positive electrode active material is not limited as long as it is used as a positive electrode active material for a nickel metal hydride battery. Specific examples of the positive electrode active material include nickel hydroxide and nickel hydroxide doped with metal. Examples of the metal doped into nickel hydroxide include Group 2 elements such as magnesium and calcium, Group 9 elements such as cobalt, rhodium and iridium, and Group 12 elements such as zinc and cadmium.

The surface of the positive electrode active material may be treated by a known method. The positive electrode active material is preferably in a powder state, and the average particle size thereof is preferably in the range of 1 to 100 μm, more preferably in the range of 3 to 50 μm, and still more preferably in the range of 5 to 30 μm. In the present specification, the average particle diameter means a value of D ₅₀ in the measurement using a conventional laser diffraction particle size distribution meter.

  The positive electrode active material layer preferably contains 75 to 99% by mass, more preferably 80 to 97% by mass, and more preferably 85 to 95% by mass of the positive electrode active material with respect to the total mass of the positive electrode active material layer. More preferably, it is contained in mass%.

The positive electrode additive is added to the positive electrode in order to improve the battery characteristics of the nickel metal hydride battery. The positive electrode additive is not limited as long as it is used as a positive electrode additive for nickel metal hydride batteries. Specific positive electrode additives include niobium compounds such as Nb ₂ O ₅ , tungsten compounds such as WO ₂ , WO ₃ , Li ₂ WO ₄ , Na ₂ WO ₄ and K ₂ WO _4, and ytterbium compounds such as Yb ₂ O ₃ . And titanium compounds such as TiO ₂ , yttrium compounds such as Y ₂ O ₃ , zinc compounds such as ZnO, calcium compounds such as CaO, Ca (OH) ₂ and CaF ₂ , and other rare earth oxides.

  The positive electrode active material layer preferably contains the positive electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the total mass of the positive electrode active material layer. .

  The binder plays a role of binding an active material or the like to the surface of the current collector. The binder is not limited as long as it is used as a binder for electrodes of nickel metal hydride batteries. Specific binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, polyolefin resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, carboxymethylcellulose, methylcellulose and hydroxypropyl. Cellulose derivatives such as cellulose, copolymers such as styrene butadiene rubber, and polyacrylic acid, polyacrylic acid ester, polymethacrylic acid and polymethacrylic acid ester containing (meth) acrylic acid derivatives as monomer units ( An example is a (meth) acrylic resin.

  The active material layer preferably contains 0.1 to 15% by mass, more preferably 1 to 10% by mass, and more preferably 2 to 7% by mass of the binder based on the total mass of the active material layer. More preferably, it is contained in mass%. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be added to the active material layer in a powder state, or may be used in a state where the surfaces of the active material particles are coated. The conductive auxiliary agent may be an electronic conductor that is chemically inert. Specific conductive materials include metals such as cobalt, nickel, copper, metal oxides such as cobalt oxide, metal hydroxides such as cobalt hydroxide, carbon materials such as carbon black, graphite, and carbon fiber. Illustrated.

  It is preferable that the active material layer contains 0.1 to 10% by mass of the conductive additive with respect to the mass of the entire active material layer. In the positive electrode active material layer, the conductive additive is preferably contained in an amount of 0.5 to 10% by mass, more preferably 1 to 7% by mass with respect to the mass of the entire positive electrode active material layer. More preferably, it is contained at ˜5% by mass. The negative electrode active material layer preferably contains 0.1 to 5% by mass, more preferably 0.2 to 3% by mass of the conductive additive with respect to the total mass of the negative electrode active material layer. More preferably, the content is 0.3 to 1% by mass. This is because if the amount of the conductive auxiliary is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary is too large, the moldability of the active material layer is deteriorated and the energy density of the electrode is lowered.

  The negative electrode active material layer includes a negative electrode active material, and includes a negative electrode additive, a binder, and a conductive additive as necessary. The binder and the conductive aid are as described above.

  The negative electrode active material is not limited as long as it is used as a negative electrode active material of a nickel metal hydride battery, that is, a hydrogen storage alloy. The hydrogen storage alloy is basically an alloy of metal A, which easily reacts with hydrogen, but is inferior in hydrogen releasing ability, and metal B, which does not easily react with hydrogen but has excellent hydrogen releasing ability. A includes a group 2 element such as Mg, a group 3 element such as Sc and a lanthanoid, a group 4 element such as Ti and Zr, a group 5 element such as V and Ta, and a misch containing a plurality of rare earth elements. Examples thereof include metal (hereinafter sometimes abbreviated as Mm), Pd, and the like. Examples of B include Fe, Co, Ni, Cr, Pt, Cu, Ag, Mn, Zn, and Al.

Specific hydrogen-absorbing alloy, AB ₅ type showing a hexagonal CaCu ₅ type crystal structure, hexagonal MgZn ₂ type or AB ₂ type showing a cubic MgCu ₂ type crystal structure, AB type indicating the cubic CsCl-type crystal structure , A ₂ B type showing hexagonal Mg ₂ Ni type crystal structure, solid solution type showing body-centered cubic crystal structure, and AB ₃ type and A ₂ B _{7 in which} AB ₅ type and AB ₂ type crystal structures are combined Examples include molds and A ₅ B ₁₉ types. The hydrogen storage alloy may have one of the above crystal structures, or may have a plurality of the above crystal structures.

Examples of the AB ₅ type hydrogen storage alloy include LaNi ₅ , CaCu ₅ , and MmNi ₅ . Examples of the AB ₂ type hydrogen storage alloy include MgZn ₂ , ZrNi ₂ , and ZrCr ₂ . Examples of the AB type hydrogen storage alloy include TiFe and TiCo. Examples of the A ₂ B type hydrogen storage alloy include Mg ₂ Ni and Mg ₂ Cu. Examples of the solid solution type hydrogen storage alloy include Ti-V, V-Nb, and Ti-Cr. An example of the AB ₃ type hydrogen storage alloy is CeNi ₃ . Ce ₂ Ni ₇ can be exemplified as the A ₂ B ₇ type hydrogen storage alloy. Examples of the A ₅ B ₁₉ type hydrogen storage alloy include Ce ₅ Co ₁₉ and Pr ₅ Co ₁₉ . In each of the above crystal structures, some of the metals may be replaced with one or more other types of metals or elements.

  The surface of the negative electrode active material may be treated by a known method. The negative electrode active material is preferably in a powder state, and the average particle diameter is preferably in the range of 1 to 100 μm, more preferably in the range of 3 to 50 μm, and still more preferably in the range of 5 to 30 μm.

  The negative electrode active material layer preferably contains the negative electrode active material in an amount of 85 to 99% by mass, more preferably 90 to 98% by mass with respect to the mass of the entire negative electrode active material layer.

The negative electrode additive is added to the negative electrode in order to improve the battery characteristics of the nickel metal hydride battery. The negative electrode additive is not limited as long as it is used as a negative electrode additive for nickel metal hydride batteries. Specific negative electrode additives include rare earth fluorides such as CeF ₃ and YF ₃ , bismuth compounds such as Bi ₂ O ₃ and BiF ₃ , indium compounds such as In ₂ O ₃ and InF ₃ , and positive electrode additives Can be mentioned as examples.

  The negative electrode active material layer preferably contains the negative electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the mass of the entire negative electrode active material layer. .

  In order to form an active material layer on the surface of the current collector, a current collecting method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method can be used. An active material may be applied to the surface of the body. Specifically, an active material, a solvent, and if necessary, a binder, a conductive additive and an additive are mixed to form a slurry, and the slurry is applied to the surface of the current collector and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

  The electrolytic solution is an aqueous solution in which an alkali metal hydroxide is dissolved. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. The electrolytic solution may contain one kind of alkali metal hydroxide or may contain a plurality of kinds of alkali metal hydroxides. As a density | concentration of the alkali metal hydroxide in electrolyte solution, 2-10 mol / L is preferable, 3-9 mol / L is more preferable, and 4-8 mol / L is further more preferable.

  When only lithium hydroxide is used as the alkali metal hydroxide in the electrolytic solution, the concentration of lithium hydroxide is preferably 1.5 to 5 mol / L, more preferably 2 to 5 mol / L, and more preferably 3 to 5 mol / L. L is more preferable. When only sodium hydroxide is used as the alkali metal hydroxide in the electrolytic solution, the concentration of sodium hydroxide is preferably 1.5 to 15 mol / L, more preferably 3 to 10 mol / L, and more preferably 4 to 8 mol / L. L is more preferable. When only potassium hydroxide is used as the alkali metal hydroxide in the electrolytic solution, the concentration of potassium hydroxide is preferably 1.5 to 15 mol / L, more preferably 3 to 10 mol / L, and 4 to 8 mol / L. L is more preferable.

  The electrolytic solution may contain an alkali metal halide. The alkali metal halide is considered to be ionized into an alkali metal cation and a halogen anion in the electrolytic solution. Then, the halogen anion having a negative charge is electrically adsorbed on the positive electrode, so that the positive electrode is covered with the halogen anion. In the positive electrode coated with the halogen anion, since the direct contact of water molecules with the positive electrode body is suppressed, it is considered that the generation of oxygen in the positive electrode is suppressed.

  The alkali metal cation is considered to be coordinated with water molecules in the electrolytic solution in the electrolytic solution. Here, it can be expected that the water molecule is strongly coordinated with the alkali metal cation, thereby improving the oxidation resistance and increasing the oxygen generation potential.

It can be said that the smaller the ionic radius of the alkali metal cations, the easier it is to coordinate with water molecules. It is known that the ionic radius of the alkali metal cation is in the order of Li ⁺ <Na ⁺ <K ⁺ <Rb ⁺ <Cs ⁺ <Fr ⁺ . Accordingly, lithium halide is most preferred as the alkali metal halide, sodium halide is the next most preferred, and potassium halide is the second most preferred.

In addition, it is not preferable that the halogen anion adsorbed on the positive electrode is oxidized to form a halogen simple substance. Oxidation resistance of the halogen ^{anions, F -> Cl -> Br} -> it - is known to be in the order of. Therefore, from the viewpoint of oxidation resistance, the alkali metal halide is most preferred as the alkali metal halide, the alkali metal chloride is the next most preferred, and the alkali metal bromide is the second most preferred.

  Examples of the alkali metal halide include LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, and KI. From the viewpoint of coordination with water molecules and oxidation resistance, it can be said that LiF, LiCl, NaF and NaCl are preferable as the alkali metal halide. From the viewpoint of solubility, it can be said that LiCl and NaCl are preferable as the alkali metal halide.

  The concentration of the alkali metal halide in the electrolytic solution is preferably 0.01 to 3 mol / L, more preferably 0.03 to 2 mol / L, still more preferably 0.05 to 1.5 mol / L, -1.0 mol / L is particularly preferred.

  The electrolyte may be added with known additives that are employed in electrolytes for nickel metal hydride batteries.

  The separator separates the positive electrode and the negative electrode, and provides a storage space and a passage for the electrolyte while preventing a short circuit due to contact between the two electrodes. A known separator may be employed, such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, polyacrylonitrile or other synthetic resin, cellulose, amylose or other polysaccharide, fibroin. And porous materials, nonwoven fabrics, woven fabrics, and the like using one or more electrical insulating materials such as natural polymers such as keratin, lignin, and suberin, and ceramics. The separator may have a multilayer structure.

  The separator is preferably subjected to a hydrophilic treatment on the surface. Examples of the hydrophilic treatment include sulfonation treatment, corona treatment, fluorine gas treatment, and plasma treatment.

A specific method for producing the nickel metal hydride battery of the present invention will be described.
If necessary, a separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using current collecting leads, etc., an electrolyte is added to the electrode body to form a nickel metal hydride battery. . A nickel metal hydride battery showing suitable characteristics is manufactured by charging / discharging the nickel metal hydride battery thus manufactured in a plurality of cycles defined by the activation method of the present invention. be able to.

  The following charge / discharge control apparatus of the present invention can be grasped by the activation method of the nickel metal hydride battery of the present invention.

  The charge / discharge control apparatus of the present invention includes a control unit that instructs the activation method of the present invention to a nickel metal hydride battery. The charge / discharge control device of the present invention may be disposed in a nickel metal hydride battery manufacturing facility, or may be disposed in a charging system that charges a nickel metal hydride battery before or after shipment of the nickel metal hydride battery. . It is preferable that the charge / discharge control apparatus of the present invention, the manufacturing facility, or the charging system includes a temperature control unit that controls the temperature of the nickel metal hydride battery.

  The shape of the nickel metal hydride battery of the present invention is not particularly limited, and various shapes such as a square shape, a cylindrical shape, a coin shape, and a laminate shape can be adopted.

  The nickel metal hydride battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy generated by a nickel metal hydride battery for all or a part of its power source. For example, the vehicle may be an electric vehicle or a hybrid vehicle. When a nickel metal hydride battery is mounted on a vehicle, a plurality of nickel metal hydride batteries may be connected in series to form an assembled battery. Examples of the device on which the nickel metal hydride battery is mounted include various home electric appliances, office devices, industrial devices, and the like driven by batteries, such as personal computers and portable communication devices, in addition to vehicles. Furthermore, the nickel metal hydride battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power for power sources such as ships, and / or power supply sources for auxiliary equipment, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited by these Examples.

(Production Example 1)
92 parts by mass of nickel hydroxide powder as a positive electrode active material, 3 parts by mass of cobalt powder as a conductive additive, a total of 4 parts by mass of acrylic resin emulsion and carboxymethyl cellulose as solids as a binder, and Y ₂ O as an additive ₃ was mixed with 1 part by mass and an appropriate amount of ion-exchanged water to prepare a slurry. A nickel foil having a thickness of 10 μm was prepared as a positive electrode current collector. The slurry was applied in a film form on the surface of the nickel foil using a doctor blade. The nickel foil coated with the slurry was dried to remove water, and then pressed to produce a positive electrode having a positive electrode active material layer formed on a current collector.

98 parts by mass of an A ₂ B ₇ type hydrogen storage alloy as a negative electrode active material, a total of 2 parts by mass of an acrylic resin emulsion and carboxymethyl cellulose as a solid content as a binder, and an appropriate amount of ion-exchanged water are mixed, Manufactured. A nickel foil having a thickness of 10 μm was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the nickel foil using a doctor blade. The nickel foil coated with the slurry was dried to remove water, and then pressed to produce a negative electrode having a negative electrode active material layer formed on a current collector. In addition, the used A ₂ B ₇ type hydrogen storage alloy contains a misch metal such as La as the metal A and Ni as a part of the metal B.

  An aqueous solution having a total concentration of potassium hydroxide, sodium hydroxide and lithium hydroxide of 7 mol / L was prepared as an electrolytic solution.

  As a separator, a non-woven fabric made of polyolefin fiber having a thickness of 70 μm and subjected to sulfonation treatment was prepared. A separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. A nickel metal hydride battery according to Production Example 1 before activation was manufactured by arranging an electrode plate group in a resin casing, injecting the electrolyte, and sealing the casing.

(Example 1)
The activation treatment shown in Table 1 was performed on the nickel metal hydride battery of Production Example 1 under the condition of 40 ° C., and the nickel metal hydride battery of Example 1 was produced. In addition, after discharge of each cycle, after providing a rest time for 1 hour, discharge to voltage 1V was performed at 0.1C.

(Comparative Example 1)
The activation treatment shown in Table 1 was performed on the nickel metal hydride battery of Production Example 1 under the condition of 25 ° C., and the nickel metal hydride battery of Comparative Example 1 was produced. In addition, after discharge of each cycle, after providing a rest time for 1 hour, discharge to voltage 1V was performed at 0.1C.

(Comparative Example 2)
The nickel metal hydride battery of Production Example 1 was subjected to the activation treatment shown in Table 1 under the condition of 60 ° C., and the nickel metal hydride battery of Comparative Example 2 was produced. In addition, after discharge of each cycle, after providing a rest time for 1 hour, discharge to voltage 1V was performed at 0.1C.

(Evaluation example 1)
The nickel metal hydride batteries of Example 1, Comparative Example 1, and Comparative Example 2 adjusted to SOC 60% were discharged at 10 C for 10 seconds. From the current value and the amount of voltage change before and after the discharge, the resistance at the time of discharge was calculated as a DC resistance according to Ohm's law. The results are shown in Table 2.

(Evaluation example 2)
For the nickel metal hydride batteries of Example 1, Comparative Example 1 and Comparative Example 2 adjusted to SOC 60%, the AC impedance was measured under the conditions of 25 ° C., AC frequency of 0.05 to 1000000 Hz, and AC voltage of 10 mV. The obtained results were plotted on the complex plane, and the intercept between the obtained curve and the real axis in the complex plane was defined as the pure resistance of each battery. The value obtained by subtracting the pure resistance from the impedance | Z | at the inflection point of the curve on the complex plane (the inflection point here means the point at which the curve changes to a straight line) was defined as the reaction resistance. Note that inflection points in the curve on the complex plane in this test were all observed at a frequency of 0.1 Hz. The results are shown in Table 2.

  From Table 2, it can be seen that the values of DC resistance and reaction resistance change depending on the temperature of activation. In both DC resistance and reaction resistance, the value of Example 1 with an activation temperature of 40 ° C. was the lowest. From these results, it can be said that the activation temperature of the nickel metal hydride battery is preferably around 40 ° C. Further, if the activation temperature is too low, the activation of the nickel metal hydride battery is insufficient, and if the activation temperature is too high, it is considered that some side reaction occurs in the nickel metal hydride battery.

(Reference Example 1 (Comparative Example 1) to Reference Example 4)
The nickel metal hydride battery of Reference Example 1 (Comparative Example 1) to Reference Example 4 was subjected to the activation treatment shown in Tables 3 and 4 on the nickel metal hydride battery of Production Example 1 at 25 ° C. Manufactured. In addition, after discharge of each cycle, after providing a rest time for 1 hour, discharge to voltage 1V was performed at 0.1C.

(Reference Evaluation Example 1)
The nickel metal hydride batteries of Reference Examples 1 to 4 adjusted to SOC 60% were discharged at 10 C for 10 seconds. From the current value and the amount of voltage change before and after the discharge, the resistance at the time of discharge was calculated as a DC resistance according to Ohm's law. The results are shown in Table 5.

  From the results of Reference Example 1 and Reference Example 2, it can be said that when the charge rate in the first cycle is 0.5 C or more, the battery resistance is adversely affected. From the results of Reference Example 1 and Reference Example 3, it can be said that the battery resistance is adversely affected when the charge rate is 3C or higher. From the results of Reference Example 1 and Reference Example 4, it can be said that the battery resistance is adversely affected if the charge capacity of each cycle is low. From the above results, in the activation of the nickel metal hydride battery, the charge rate in the first cycle is less than 0.5C, the charge rate in each cycle is less than 3C, and the charge capacity in each cycle is more than 80% SOC. It can be said that it is preferable.

Claims (8)

A method for activating a nickel metal hydride battery that performs charge and discharge in a plurality of cycles,
A method for activating a nickel metal hydride battery, wherein charging and discharging are performed in a temperature range of 30 to 50 ° C. and under a constant temperature in all of the plurality of cycles.   The activation method according to claim 1, wherein the charge rate of the first cycle is less than 0.5C.   The activation method according to claim 1, wherein the first cycle charging is performed up to a capacity exceeding 80% of the theoretical charging capacity.   The activation method according to claim 1, wherein the charge rate is less than 3C.   The activation method according to any one of claims 1 to 4, including an increased rate charging cycle in which charging is performed at a charging rate larger than a charging rate of a previous cycle.   The activation method according to claim 5, wherein the increase rate charging cycle is included in two or more cycles. The nickel metal hydride battery is a nickel metal hydride battery containing cobalt in the positive electrode;
The first cycle is charged at a plurality of charge rates, including a first charge rate that is less than 0.1 C and a second charge rate that exceeds the first charge rate. The activation method according to 1.   The activation method according to claim 1, wherein the plurality of times is within a range of 3 to 30 times.