JPH0644970A - Nonaqueous electrolyte lithium battery - Google Patents

Abstract

PURPOSE:To improve capacity by constituting a nonaqueous electrolyte lithium secondary battery through using a positive electrode having a main body of composite oxide of lithium and nickel, obtained by a specific method. CONSTITUTION:A water soluble nickel salt aqueous solution is selected from the halide, sulfate, phosphate, and oxalate of the chloride or iodide, etc., of nickel. The aqueous solution of a water soluble basic lithium compound, selected from the hydroxide, carbonate, and hydrogencarbonate of equimolar lithium, is injectionally mixed in the water soluble nickel salt aqueous solution. A cake- state substance, obtained by dry-hardening this mixture, is baked at 600-800 deg.C. The composite oxide of lithium and nickel, obtained in this way, is used for the active material of an positive electrode 4 opposed via a negative electrode 2 and a separator 5. This can improve capacity to level equivalent to capacity level owned by a battery, having positive electrode active material of a composite oxide of lithium and cobalt, considered to have the largest capacity at present.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a relatively inexpensive composite oxide of lithium and nickel, which is expected as a high energy density storage battery for portable devices, electric vehicles, etc. because of its high voltage and high capacity. TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte lithium secondary battery using a material as a positive electrode active material.

[0002]

2. Description of the Related Art In order to achieve miniaturization and weight reduction of various portable devices and high performance such as mileage per charge of electric vehicles, research and development of high energy density storage batteries have been actively pursued all over the world. ing. In recent years, as a part thereof, metal such as metallic lithium or aluminum, an aluminum alloy of some kind, a wood alloy (Wood's metal) represented by lead-tin-bismuth-cadmium system, etc., which is easily alloyed with lithium at room temperature, An active material holder capable of reversibly occluding and releasing lithium reversibly by charge and discharge such as carbon materials such as certain graphite, oxides, sulfides, and conductive polymers such as polyacetylene and polyaniline Research and development and practical application of non-aqueous electrolyte lithium secondary batteries using a negative electrode mainly composed of are active.

MnO is used as the positive electrode active material.₂，
TiS₂, MoS₂, V₂O_Five, Cr₂O _Five, Nb₂O_Five, Li
CoO₂, LiNiO₂, LiFeO₂, LiMnO₂, L
iMn₂O_FourOxides of transition metals, such as chalcogen compounds
Materials, complex oxides with lithium, and the like are well known. This
These are layered or tunnel-like crystals like intercalation compounds.
The structure is such that lithium ions are reversibly charged and discharged.
It is possible to repeat release and occlusion. In particular, LiC
oO₂And LiNiO₂And LiMn₂O_FourHigh voltage of 4V class
Pressure positive electrode active material of non-aqueous electrolyte lithium secondary battery
Of these, LiCoO₂Represented by
The composite oxide of lithium and cobalt
Are better. But the idiot that cobalt is relatively expensive
Rural areas are unevenly distributed in specific areas,
Concerns about supply uncertainties and rising prices due to changes in tide have become a problem
Has been.

On the other hand, LiMn₂O_FourAnd LiNiO₂Represented by
Oxidation of Lithium with Manganese or Nickel
In the case of products, the manganese and nickel compounds that are the raw materials are
Relatively cheap and stable supply is possible.
There is no such concern, but in terms of characteristics, especially discharge capacity, Li
CoO₂There was a lesser drawback. Therefore, these
By examining the synthesis and processing conditions of complex oxides
Modifications are beginning to take place. Especially, LiNiO₂Is LiC
oO₂0.2V lower than LiCoO ₂same as
Because of its unique structure, it can be used as a positive electrode active material for high-capacity lithium secondary batteries.
It has been highly anticipated and attracted attention.

As a method for synthesizing a composite oxide of lithium and nickel represented by LiNiO ₂ , the conventional Journal of American Chemical Society (J.A.
american Chemical Soc. ) 76th
Vol., P. 1499 (1954),
It was synthesized by heating anhydrous lithium hydroxide and metallic nickel in an oxygen atmosphere to react with each other, but as a positive electrode active material of a lithium secondary battery, the discharge capacity was small and it was not satisfactory.

In addition, Chemistry Express (C
hemisphere Express) Volume 6, No. 3,
On page 161, (1991), an equimolar amount of 4.5 mol / 1
A LiOH aqueous solution and a 1.0 mol / 1 Ni (NO ₃ ) ₂ aqueous solution are mixed while being maintained at 60 ° C., and the mixture is stirred at the same liquid temperature for a long time and dried under reduced pressure to obtain a solidified precursor.

Next, the powder obtained by crushing this precursor is mixed with 3
It is described that a black composite oxide powder of lithium and nickel is obtained by pre-baking at 00 ° C. and then main baking at 800 ° C. It has been reported that this composite oxide can serve as a positive electrode active material for a lithium secondary battery having a relatively high capacity.

[0008]

However, the composite oxide of lithium and nickel produced by the conventional synthesis method described above is
Those produced by a simple synthesis method have a small capacity without sufficiently functioning as a positive electrode active material for a non-aqueous electrolyte lithium secondary battery, or have a relatively high capacity as a battery material. Regardless of the laboratory, industrially, the condition management was very delicate and complicated, and required a long time, poor reproducibility, and large variations in charge / discharge characteristics.

In the present invention, the composite oxide of lithium and nickel, which can be produced under relatively simple conditions, is used as the positive electrode active material, so that it has the highest voltage and capacity in the past, but the raw material cobalt is expensive. An object of the present invention is to provide a high-capacity non-aqueous electrolyte lithium secondary battery comparable to a battery using a composite oxide of lithium and cobalt, which has been unstable in supply, as a positive electrode active material.

[0010]

In order to achieve the above-mentioned object, the present invention is made of nickel chloride, halide such as iodide, sulfate, phosphate, acetate and oxalate. An aqueous solution of at least one water-soluble basic lithium compound selected from hydroxides, carbonates and hydrogen carbonates of equimolar amounts of the nickel salt in at least one water-soluble nickel salt aqueous solution selected. The cake-like substance obtained by drying and solidifying the reaction product obtained by pouring and mixing
A high-capacity non-aqueous electrolyte lithium secondary battery was realized by using a positive electrode mainly composed of a composite oxide of lithium and nickel obtained by firing in a temperature range of 0 to 800 ° C.

[0011]

By constructing a non-aqueous electrolyte lithium secondary battery using a positive electrode mainly composed of a composite oxide of lithium and nickel obtained by such means, it is relatively inexpensive and there is no fear of supplying raw materials. In addition, a compact, lightweight, high energy density storage battery with high capacity and high voltage can be achieved.

[0012]

EXAMPLES Examples of the present invention will be described in more detail below.

(Example 1) Nickel chloride NiCl₂Yayo
Nickel Carbide NiI₂Nickel halides such as
Axel NiSO_Four, Nickel phosphate Ni₃(PO_Four)₂,vinegar
Nickel acid Ni (C ₂H₃O₂)₂, Nickel oxalate Ni
C₂O_Four1 mol of saturated aqueous solution at 20 ° C
Collect and then add to them one mole of hydroxylation
Lithium LiOH, Lithium carbonate Li₂CO₃, Hydrogen carbonate
Lithium LiHCO₃The saturated aqueous solution at 20 ° C.
Pour little by little with stirring, then add each mixture.
Continue stirring for about 3 hours. The above pouring and mixing should be performed at about 30 ° C.
U Then, dry at 80-100 ° C with continuous stirring.
It If the drying process is performed under reduced pressure, it can be completed in a short time.
You can Lightly remove each cake-like solid substance produced.
After crushing, heat in air at 750 ° C for 12 hours to black
A colored fired powder is obtained. The firing is a rotary kiln type firing furnace
If you use, continuous firing becomes possible, high productivity,
Exhaust treatment is also easy. The obtained black fired powder
Are all made of LiNiO by X-ray diffraction.₂Indicated by
Was identified as a complex oxide of titanium and nickel.
It was

The charge and discharge characteristics of each of the above-mentioned composite oxides of lithium and nickel were measured according to the R2320 size (outer diameter 2
A coin-shaped battery having a size of 3.0 mm and a height of 2.0 mm) was manufactured and confirmed. The structure of the prototype battery is shown in FIG. In FIG. 1, 1 is a lid that also serves as a negative electrode terminal, 2 is a negative electrode made of lithium foil having a capacity of at least three times the capacity of the positive electrode pressed onto the lid 1, 3 is a case that also serves as a positive electrode terminal, and 4 is a positive electrode active material. A mixture of a complex oxide, acetylene black as a conductive agent, and a fluororesin as a binder in a weight ratio of 7: 2: 1.
A positive electrode was obtained by molding 15 g into a disk shape having a diameter of 17.5 mm at a pressure of ² t / cm ² and then sufficiently dried, 5 a microporous polypropylene film separator, 6 a polypropylene gasket, and 1 mol / mol as a non-aqueous electrolyte. A solution of 1 of lithium perchlorate in propylene carbonate was used. In the same manner, a battery B made of the above-mentioned composite oxide of tylium and nickel according to the above-mentioned literature as a conventional example and a battery C made of LiCoO ₂ as a reference example of a composite oxide of lithium and cobalt were similarly manufactured. Was used as a comparative sample. The capacity of each cell is regulated by the positive electrode, and the charge / discharge test is 20 ° C.
At a constant current of 0.5 mA to 4.3 V and discharged at 3.
It stopped at 0V. The prototype battery under each condition was 10 cells, and the performance of each cell was compared by the average value of the specific capacities (mAh / g) of the positive electrode active material at the time of discharging at the 5th cycle. The specific capacity of Battery B is 88 mAh / g, and that of Battery C is 129 mAh / g.
The values for each positive electrode active material according to the present invention are shown in (Table 1).

[0015]

[Table 1]

Further, the discharge characteristic curves of the battery A used as the positive electrode active material according to the present invention starting from nickel oxalate and lithium carbonate in (Table 1), the battery B of the conventional example and the battery C of the reference example. 2 are shown in comparison. Each of the batteries using the positive electrode active material according to the present invention has a larger specific capacity than the battery B according to the conventional example and a discharge voltage of about 0.2 V lower than that of the battery C of the reference example, but the specific capacity is almost the same level. There are many. In other words, the battery according to the invention is
The discharge voltage is the same as the conventional example, but all the specific capacities are large, and it is possible to realize a high capacity battery that is comparable to the case where the composite oxide of lithium and cobalt, which has the highest capacity in the past, is used for the positive electrode active material value. Is.

(Example 2) In Example 1, the case where the firing temperature was 750 ° C. was shown, but an appropriate firing temperature range was examined.

To a saturated aqueous solution of nickel oxalate at 20 ° C., a saturated aqueous solution of equimolar lithium carbonate at 20 ° C. was added little by little and stirred, and the mixture was stirred at 80 to 10%.
Dry at 0 ° C. to obtain a cake-like solid material. A coin-type battery was manufactured in the same manner as in Example 1, using a sample obtained by firing the solid substance at a temperature of 550 to 900 ° C. by 50 ° C. for 12 hours as a positive electrode active material. The specific capacity obtained by the charge / discharge test under the same conditions as in Example 1 is shown in FIG. From the result of FIG. 3, it can be understood that the firing temperature is appropriately in the range of 600 to 800 ° C. In Example 2, nickel oxalate was used as the nickel source and lithium carbonate was used as the lithium source. However, the temperature range of 600 to 800 ° C. is suitable over all combinations of the nickel source and the lithium source of the present invention. Have confirmed that.

Example 3 Using the positive electrode active materials of the batteries A, B and C shown in FIG. 2 of Example 1, an AA type (R6) battery shown in FIG. In FIG. 4, 1
Reference numeral 1 is a positive electrode plate, which was formed on both sides of the core material of the aluminum foil, and
A positive electrode mixture paste having the same composition as the above was applied, dried, and then pressed with a roller to prepare. The fluororesin used as the binder was a dispersion type. 12 is a negative electrode plate,
Prepared by applying a graphite powder, which is an active material holder for lithium, and polyvinyl chloride (cyclohexanone solution) as a binder in a weight ratio of 9: 1 on both sides of a copper foil as a core material, and drying and pressing. . Each of the positive electrode plate 11 and the negative electrode plate 12 is wound in a tight spiral through a separator 13 made of a microporous polypropylene film to form an electrode plate group. Positive plate 1
A positive electrode lead 11a and a negative electrode lead 12a made of the same material as the core material are attached to the 1 and the negative electrode plate 12, respectively. The insulation plates 14 and 15 made of polyethylene are arranged above and below the electrode plate group and housed in a case 16, and the negative electrode lead 12a is electrically connected to the inner bottom surface of the case 16 which also serves as a negative electrode terminal. Reference numeral 17 denotes a lid, and the lid 17 is a polypropylene lid main body 17a, a lower washer 17C and an upper washer 17d made of aluminum is caulked and sealed by caulking a rebed 17e, and a nickel plated steel cap 17b and an upper washer 17d are welded together. It was created. After the positive electrode lead 11a was electrically connected to the lower washer 17C of the lid, a non-aqueous electrolyte was injected in an amount enough to hold the electrode plate group, and then the upper edge of the case 16 was curved to form a sealing opening. The non-aqueous electrolyte having the same composition as in Example 1 was used.

As a positive electrode active material, nickel oxalate was used as a nickel source and lithium carbonate was used as a lithium source, and a prototype battery R6A using a composite oxide of lithium and nickel according to the present invention, the same conventional example as in Example 1 was used. FIG. 5 shows an average discharge characteristic curve of each of 10 cells in the 5th cycle, where R6B and R6C are prototype batteries using the positive electrode active material of Reference Example.
Shown in. The capacity of R6A according to the present invention is larger than that of the conventional example R6B and the voltage thereof is lower than that of the reference example R6C by about 0.2V.
It can be seen that the capacities are comparable. Although only one example of the discharge characteristic of the positive electrode active material according to the present invention is shown, a battery made of the positive electrode active material obtained by the combination of each plain or mixed nickel source and each plain or mixed lithium source according to the present invention. All had higher capacities than the conventional example, and performance comparable to that of a battery using a composite oxide of lithium and cobalt, which is currently the most excellent positive electrode active material, was obtained.

In Examples 1, 2 and 3, the case where lithium or graphite was used for the negative electrode was exemplified. However, a metal which is easily alloyed with lithium, some oxides, sulfides,
A high-capacity lithium secondary battery can be formed also when an active material holder capable of repeatedly occluding and releasing lithium by charging and discharging a conductive polymer is used for the negative electrode. Further, although the organic solvent solution of a lithium salt has been described as the non-aqueous electrolyte, the present invention is not limited to this, and a solid electrolyte made of polyethylene oxide in which lithium iodide or a certain lithium salt is dispersed. It is also applicable to.

[0022]

As described above, the present invention provides at least one water-soluble nickel selected from nickel halides such as nickel chloride and nickel iodide, nickel sulfate, nickel phosphate, nickel acetate and nickel oxalate. Lithium hydroxide in an equimolar amount to the nickel salt,
A cake-like substance obtained by drying and solidifying a reaction product obtained by pouring and mixing at least one water-soluble basic aqueous solution selected from lithium carbonate and lithium hydrogen carbonate to 600 to 8
By using a positive electrode mainly composed of a composite oxide of lithium and nickel, which is produced by a simple method of firing at a temperature of 00 ° C., it has been difficult to achieve a high capacity in the past although it has a high voltage. The problem of non-aqueous electrolyte thirium secondary battery using lithium-nickel composite oxide as the positive electrode active material is now considered to be the battery with the highest capacity lithium-cobalt composite oxide as the positive electrode active material. The capacity can be increased to a comparable level.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a coin type non-aqueous electrolyte lithium secondary battery according to an embodiment of the present invention.

FIG. 2 is a discharge characteristic curve diagram of a coin-type battery according to the present invention compared with a conventional example and a reference example.

FIG. 3 is a diagram showing the relationship between the firing temperature and the specific capacity of a prototype battery during the production of the positive electrode active material according to the present invention.

FIG. 4 is a sectional view of a cylindrical non-aqueous electrolyte lithium secondary battery according to another embodiment of the present invention.

FIG. 5 is a discharge characteristic curve diagram of the cylindrical battery according to the present invention in comparison with the conventional example and the reference example.

[Explanation of symbols]

 1 Lid 2 Negative electrode 3 Case 4 Positive electrode 5 Separator 6 Gasket

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Ito 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An aqueous solution of at least one water-soluble nickel salt selected from nickel halides such as nickel chloride and nickel iodide, nickel sulfate, nickel phosphate, nickel acetate, nickel oxalate and the nickel salt A cake-like substance obtained by drying and solidifying a reaction product obtained by pouring and mixing an aqueous solution of at least one water-soluble basic lithium compound selected from equimolar lithium hydroxide, lithium carbonate, and lithium hydrogen carbonate is 600 to A non-aqueous electrolyte lithium secondary battery using a positive electrode mainly composed of a composite oxide of tylium and nickel obtained by firing in a temperature range of 800 ° C. 2. An aqueous solution of at least one water-soluble nickel salt selected from nickel halides such as nickel chloride and nickel iodide, nickel sulfate, nickel phosphate, nickel acetate, nickel oxalate and the nickel salt In drying the reaction product obtained by pouring and mixing an equimolar solution of at least one water-soluble basic lithium compound selected from lithium hydroxide, lithium carbonate and lithium hydrogen carbonate, in air or under reduced pressure. The non-aqueous electrolyte lithium secondary battery according to claim 1, wherein the non-aqueous electrolyte lithium secondary battery is evaporated to dryness under stirring and mixing under the conditions below. 3. The non-aqueous electrolyte lithium secondary battery according to claim 1, wherein metallic lithium is used as the negative electrode. 4. An active material holder which is capable of repeating occlusion and release of lithium by charge and discharge of a metal which is easily alloyed with lithium, a certain kind of carbon material, oxide, sulfide, conductive polymer or the like. The non-aqueous electrolyte lithium secondary battery according to claim 1 or 2, wherein the negative electrode is used.