JPH10149812A - Positive electrode plate for lithium battery and lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode plate for a lithium battery of high performance, in which electrodes can be reacted uniformly, and a lithium battery with an excellent contact between a current collector and an active substance or between active substances. SOLUTION: A positive electrode plate for a lithium battery holds nickel oxyhydroxide in a sintered type nickel substrate, and a lithium battery uses the positive electrode plate. Use of the three-dimensional porous body achieves excellent electric contact between an active substance and a current collector, improves the contact between particles of oxynickel hydroxide as the active substance, reduces contact resistance between the particles, and facilitates diffusion of lithium ions even among the particles during a reaction rate determining process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode plate for a lithium battery and a lithium battery using the same.

[0002]

2. Description of the Related Art Conventionally, a manganese dioxide zinc battery as a primary battery and a nickel-cadmium battery, a nickel zinc battery,
Nickel-based and lead batteries of nickel-hydride batteries have been used. An alkaline aqueous solution such as potassium hydroxide or an aqueous solution such as sulfuric acid is used as an electrolyte for these batteries.

In recent years, with the development of electronic equipment, a new high-performance battery is expected to appear. Instead of the above-mentioned aqueous battery, a battery having a higher energy density using a non-aqueous electrolyte has been developed. Is underway. A typical example is a lithium battery using lithium or a carbon material for the negative electrode.

As lithium batteries, primary batteries include manganese dioxide-lithium batteries and carbon fluoride-lithium batteries, and secondary batteries include manganese dioxide-lithium batteries and vanadium oxide-lithium batteries.

[0005] Secondary batteries using lithium metal for the negative electrode are disadvantageous in that short-circuits are apt to occur due to dendrites of lithium metal deposited during charging, the life is short, and safety is high due to the high reactivity of lithium metal. Is difficult to secure. Therefore, a so-called lithium ion battery has been devised in which graphite or carbon is used for the negative electrode to prevent dendrite precipitation by forming an interlayer compound between lithium and these, and lithium cobaltate is used for the positive electrode. And is used as a high energy-density battery.

However, since lithium cobaltate is expensive, a lithium-containing manganese composite oxide or lithium nickelate has been proposed as an alternative. In the case of this lithium-containing manganese composite oxide, there is a problem that the theoretical capacity density is low and the capacity decrease becomes large as the charge / discharge cycle proceeds.

[0007] On the other hand, lithium nickelate has the same crystal structure as lithium cobaltate, but has the disadvantage that the capacity is reduced when charge and discharge are repeated. Recently, as proposed in Japanese Patent Application No. 7-129663, an attempt has been made to synthesize lithium nickelate exhibiting a uniform charge / discharge reaction by reacting lithium nitrate with nickel oxyhydroxide containing cobalt. However, in any case, in order to form a positive electrode plate using lithium nickelate, the synthesized coarse particles are pulverized into fine particles and then mixed with a conductive agent such as carbon to form a binder such as polyvinylidene fluoride. A step of applying to a metal current collector such as aluminum or nickel together with the adhesive is required. Therefore, the manufacturing process is complicated,
There is a problem that the performance is greatly affected by the amounts of the carbon powder and the binder.

Further, there has been an attempt to make a positive electrode plate for a lithium battery using nickel oxyhydroxide, which is an active material completely different from the above-mentioned active material. For example, JP-A-63-197
No. 60 proposes to use nickel oxyhydroxide containing 20 to 75% of cobalt.
No. 61 proposes to use nickel hydroxide charged in an aqueous lithium hydroxide solution as an active material, but none of them has sufficient performance and has not been put to practical use until now.

[0009]

As described above, nickel oxyhydroxide has the same layered structure as lithium cobalt oxide which has been put to practical use, but it has been proposed in Japanese Patent Application Laid-Open No. 63-19760. Nevertheless, it has not been put to practical use until now. From the viewpoint of the electrode reaction, the cause is that the diffusion of lithium ions into the positive electrode active material due to the charge / discharge reaction, that is, the intercalation of lithium ions into nickel oxyhydroxide does not occur uniformly. It is considered something. It is also considered that one of the causes is that an optimal electrode structure between the active material and the current collector has not been established.

At present, the material of the current collector used for the positive electrode plate of the lithium battery is mainly aluminum. Nickel cadmium batteries and nickel hydride batteries use a nickel hydroxide positive electrode plate with a sintered nickel base that also serves as a current collector as the active material holder. It has hardly been considered to use it as a material for a positive electrode plate for use. This is because nickel is not only dissolved in the electrolytic solution, but also may be deposited on the negative electrode to cause a short circuit of the battery.
Further, LiCoO ₂ , LiNiO ₂ , V ₂ O ₅ , Li as general positive electrode active materials used for lithium batteries
Since Mn ₂ O _{4 and the} like are particles of about 20 μm called a solid phase method and usually produced by firing at 500 ° C. or more,
This is because it was practically impossible to apply the method to a sintered nickel substrate having an average pore diameter of about 0 μm.

According to the present invention, it has been found that when nickel oxyhydroxide, which is a new active material of a lithium battery which has not been put into practical use, is filled in a sintered nickel substrate, the performance is remarkably improved. This is based on the finding that nickel dissolution was prevented and no short circuit occurred. ADVANTAGE OF THE INVENTION According to this invention, the contact state of nickel which is a collector and an active material or active materials is made favorable, and the high-performance positive electrode plate for lithium batteries and a battery in which an electrode reaction occurs uniformly can be provided.

[0012]

The first invention according to the present invention is characterized in that nickel oxyhydroxide is held on a sintered nickel substrate. A second invention according to the first invention is characterized in that nickel oxide or nickel oxyhydroxide is formed on the surface of a sintered nickel substrate.
Further, a third invention according to the first or second invention is characterized in that the battery is provided with the positive electrode plate obtained in the first or second invention.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to Japanese Patent Application Laid-Open No. 63-1976.
The invention is characterized in that nickel oxyhydroxide is not held on a nickel mesh as disclosed in No. 0, but is held on a sintered nickel substrate. In that case,
When an oxide film or a nickel oxyhydroxide film is formed on the surface of the nickel substrate, the life is extended and the reliability is improved.

Thus, the active material is filled in a state in which the current collecting structure is firmly formed, so that the current collector and the active material or the active material are in good contact with each other, and the new active material, oxywater Diffusion due to intercalation of lithium ions, which is an electromotive reaction of nickel oxide, occurs uniformly, thereby improving charge / discharge characteristics and charge / discharge cycle performance.

At present, the charge / discharge reaction is not always clear, but it is presumed to be the following formula in which lithium ions are intercalated and deintercalated in nickel oxyhydroxide.

[0016] ^{(discharge) NiOOH + Li + + e -} → L
iHNiO ₂ ^{(charging) NiOOH + Li + + e -} ← L
iHNiO ₂

【Example】

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described.

Example 1 A sintered nickel substrate (100 mesh) having a porosity of about 85% obtained by sintering carbonyl nickel powder used as an active material holder of a sintered nickel-cadmium battery. Heat treated at 200 ° C. for 30 minutes in an air atmosphere.
A nickel oxide thin film was formed on the surface.

Next, a substrate containing nickel hydroxide was manufactured by applying a so-called reduced pressure impregnation method widely used as a method for manufacturing a nickel hydroxide positive electrode plate of a nickel-cadmium battery. That is, 3 mol% [｛Co / (N
i + Co)｝ × 100] was impregnated with a 4M aqueous solution of nickel nitrate under reduced pressure to 5 mmHg under reduced pressure.
Subsequently, a known operation of neutralizing in a 5 M aqueous sodium hydroxide solution, washing with hot water and drying at 100 ° C. was repeated six times to produce an electrode plate filled with nickel hydroxide.

Subsequently, it was immersed in a 4.5 M aqueous potassium hydroxide solution, and two nickel plates were used as counter electrodes.
Anode energization is performed at a current density of mA / cm ² for 3 hours. After that, the remaining alkali is washed with hot water and removed, and then dried at 120 ° C. to have a size of 30 mm × 40 mm.
A nickel oxyhydroxide positive electrode plate A according to the present invention having a size of 0.8 mm mm and a nominal capacity of 300 mAh was manufactured.

[Example 2] A sintered nickel substrate (100 mesh nickel) having a porosity of about 85% obtained by sintering carbonyl nickel powder used as an active material holder of a sintered nickel-cadmium battery. (The net was used as the core material.)
Was prepared.

Next, a substrate containing nickel hydroxide was manufactured by applying a so-called reduced pressure impregnation method widely used as a method for manufacturing a nickel hydroxide positive electrode plate of a nickel-cadmium battery. That is, 3 mol% [｛Co / (N
i + Co)｝ × 100] was impregnated with a 4M aqueous solution of nickel nitrate under reduced pressure to 5 mmHg under reduced pressure.
Subsequently, a known operation of neutralizing in a 5 M aqueous sodium hydroxide solution, washing with hot water and drying at 100 ° C. was repeated six times to produce an electrode plate filled with nickel hydroxide.

Subsequently, the sheet was immersed in a 4.5 M aqueous solution of potassium hydroxide, and two nickel plates were used as counter electrodes.
Anode energization is performed at a current density of mA / cm ² for 3 hours.

Thereafter, the remaining alkali content is removed by washing with hot water, dried with hot air at 100 ° C., and further heat-treated at 135 ° C. for 2 hours in an air atmosphere to form nickel oxide on the surface of the nickel substrate. With a size of 30 mm x 40 mm x 0.8 mm and a nominal capacity of 300
A nickel oxyhydroxide positive electrode plate B according to the present invention having a mAh was produced.

Example 3 A sintered nickel substrate having a porosity of about 85% obtained by sintering carbonyl nickel powder (a nickel mesh of 100 mesh was used as a core material) was 2 m long.
ol% [{Co / (Ni + Co)} × 100], a 4M aqueous solution of nickel nitrate containing 5% Hg was impregnated under reduced pressure, then neutralized in a 5M aqueous solution of sodium hydroxide and washed with hot water. A known operation of drying at 100 ° C. was repeated six times to produce an electrode plate filled with nickel hydroxide.

Subsequently, the sample was immersed in 5 M sodium hydroxide, and two nickel plates were used as counter electrodes to obtain 5 mA / c.
Anode current was applied for 3 hours at a current density of m ² to convert nickel hydroxide to nickel oxyhydroxide.
By drying at ℃ for 1 hour, the size is 30mm × 4
A positive electrode plate C according to the present invention having a size of 0 mm × 0.8 mm and a nominal capacity of 300 mAh was manufactured. A thin film of nickel oxyhydroxide was formed on the substrate surface of this positive electrode plate.

Example 4 A sintered nickel substrate having a porosity of about 85% obtained by sintering carbonyl nickel powder (a nickel mesh of 100 mesh was used as a core material) was 2 m long.
ol% [{Co / (Ni + Co)} × 100], a 4M aqueous solution of nickel nitrate containing 5% Hg was impregnated under reduced pressure, then neutralized in a 5M aqueous solution of sodium hydroxide and washed with hot water. A known operation of drying at 100 ° C. was repeated six times to produce an electrode plate filled with nickel hydroxide.

Then, the nickel hydroxide was immersed in 1M sodium hydroxide in which potassium peroxodisulfate was dissolved to form nickel oxyhydroxide, washed with water, and then dried at 100 ° C. for 1 hour. Size 3
0mm x 40mm x 0.8mm with a nominal capacity of 300mA
h of the positive electrode plate D according to the present invention. X-ray diffraction analysis confirmed that a thin film of nickel oxyhydroxide was formed on the substrate surface of the positive electrode plate.

Comparative Example For comparison, 10 parts of graphite was used as a conductive material and 2 mol% of 20 μm [｛Co /
(Ni + Co)｝ × 100] and 50 parts of cobalt-containing nickel oxyhydroxide powder containing cobalt, further mixed with a solution of n-methyl-2-pyrrolidene containing 1% of polyvinylidene difluoride, and then mixed with aluminum. Of the current collector. After that, by washing at 100 ° C. and then drying at 100 ° C. for 1 hour, the size is 50 mm × 60 mm ×
Comparative Example Positive Electrode E with 0.8 mm and Nominal Capacity of 300 mAh
Was made.

Each of the positive electrode plates was prepared by using two lithium metal plates having the same size as one positive electrode plate and 300 ml of a mixed solution of ethylene carbonate and diethyl carbonate containing 1 M lithium perchlorate as an electrolyte. Batteries A, B, C, and D according to the present invention using a plate and a comparative example battery E were produced. These batteries were charged at 20 ° C. and 30 mA to a terminal voltage of 4.1 V, and then charged at 150 mA to 1.5 V.
FIG. 1 shows the discharge characteristics when discharging to V. FIG. 2 shows the change of the discharge capacity with the charge / discharge cycle, where the initial capacity is 100. The first cycle was started from the discharge.

From the figure, it can be seen that the discharge performance of the batteries A, B, C and D according to the present invention is clearly superior to the comparative battery. It can also be seen that the batteries A, B, C, and D according to the present invention also have a better life performance than the E battery.

In this case, no short circuit occurred in the battery using the positive electrode plate according to the present invention in which an oxide film or a nickel oxyhydroxide film was formed on a nickel substrate, and good characteristics were exhibited up to 500 cycles. This is presumably because the nickel oxide or nickel oxyhydroxide film formed on the surface of the sintered nickel substrate prevented the base nickel from dissolving in the electrolyte. In the embodiment, nickel oxyhydroxide containing cobalt (Ni _1-x Co _x
00H), but the cobalt content was 2 mol%
[{Co / (Ni + Co)} × 100] or more was good. It has been found that the addition of cobalt is effective even when a substrate having good current collecting properties is used as in the present invention. The content of this cobalt is 2 to 90 mol%, but if it exceeds 50 mol%, the cost becomes high, so it is not preferable. The effect of this cobalt is presumed to be that diffusion of the active material becomes easier and that the active material works homogeneously, resulting in improved performance. In that case, it is advantageous to form a solid solution with nickel oxyhydroxide and cobalt oxyhydroxide.

As described above, the performance of the positive electrode plate according to the present invention and the battery using the same are excellent because the use of a sintered nickel substrate having both an active material holding member and a current collector makes it possible to reduce the oxygen content. It is presumed that this is due to good electrical contact between the nickel hydroxide active material and the current collector, and good bonding between the nickel oxyhydroxide particles as the active material. Further, it is presumed that the contact resistance between the particles is small, and the diffusion of lithium ions, which is the process of controlling the reaction, is facilitated even between the particles.

The nickel oxyhydroxide may be either β-form or γ-form, or a mixture thereof. Particularly, in the case of a three-dimensional aluminum porous body, a hydroxide containing water is formed, so that γ-NiOOH Is low, desirably β-NiOOH without crystallization water.

In this embodiment, lithium metal is used as the negative electrode. However, if a carbon material such as graphite is used as the negative electrode active material after the nickel oxyhydroxide is discharged, a lithium ion battery is obtained. Furthermore, even if LiC6 is used as the negative electrode active material and nickel oxyhydroxide is used as the positive electrode, a lithium ion battery is obtained. In the present invention, these are collectively referred to as lithium batteries, and according to the present invention, such excellent lithium batteries can be provided.

[0035]

The first invention according to the present invention is characterized in that nickel oxyhydroxide is held on a sintered nickel substrate. A second invention according to the first invention is characterized in that nickel oxide or nickel oxyhydroxide is formed on the surface of a sintered nickel substrate. A third invention according to the first or second invention is characterized in that the battery is provided with the positive electrode plate obtained in the first or second invention.

According to the present invention, when an oxide film or a nickel oxyhydroxide film is formed on a nickel substrate, the film acts as a protective film to prevent the base nickel from being dissolved in the electrolytic solution. It is estimated to be. In addition, the electrical contact between the active material and the current collector is good, the bonding state between the nickel oxyhydroxide particles as the active material is good, and the contact resistance between the particles is small. It is presumed that diffusion of certain lithium ions is facilitated even between particles. Thereby, a high-performance lithium battery can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram comparing the discharge characteristics of a battery using a positive electrode plate according to the present invention and a battery using a conventional positive electrode plate.

FIG. 2 is a diagram comparing a change in capacity of a battery using a positive electrode plate according to the present invention and a battery using a conventional positive electrode plate with a charge / discharge cycle.

Claims (3)

[Claims] 1. A positive electrode plate for a lithium battery, wherein nickel oxyhydroxide is held on a sintered nickel substrate. 2. The positive electrode plate according to claim 1, wherein a surface film of nickel oxide or nickel oxyhydroxide is formed on the sintered nickel substrate. 3. A lithium battery provided with the positive electrode plate according to claim 1.