JPH06236756A - Electrode for nonaqueous electrolytic battery - Google Patents

Abstract

PURPOSE:To suppress the pulverization at an electrode active material and collapse of crystal structure accompanying charge and discharge, and provide an electrode for nonaqueous electrolytic battery having a long charge and discharge cycle life. CONSTITUTION:An electrode for nonaqueous electrolytic battery uses a metal compound powder 9 capable of storing and releasing lithium as an electrode active material. The metal compound powder 9 consists of the aggregate of polycrystal particles 3 and contains a superfine powder 1. The superfine powder 1 is present in the particle or grain boundary of the polycrystal particle 3, or in the both. The superfine powder 1 is never reacted with the polycrystal particle 3. The particle size of the superfine powder 1 is preferably less than 3mum. The metal compound capable of storing and releasing lithium is preferably a metal compound containing lithium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a non-aqueous electrolyte battery which has a long charge / discharge cycle life by suppressing pulverization of the electrode active material and collapse of the crystal structure due to charge / discharge.

[0002]

2. Description of the Related Art In a non-aqueous electrolyte secondary battery using lithium or a lithium alloy as an electrode, the electrode active material is
Conventionally, metallic compounds such as MnO ₂ and V ₂ O ₅ have been studied. However, the energy capacity of these metal oxides is significantly reduced due to the destruction of the crystal structure due to charge and discharge.
As a countermeasure, LiMn containing lithium ions in advance
It has been proposed to use a lithium composite oxide such as ₂ O ₄ as a metal compound (Material Res
search Bulletin 18 (1983) 46
1-472).

As shown in FIG. 3, a powder 9 of a metal compound composed of LiMn ₂ O ₄ is an aggregate of polycrystalline particles 3. The polycrystalline particles 3 have a cubic crystal structure having a spinel structure. The particle size of the powder 9 of the metal compound is generally several μm to several tens μm. The metal compound powder is obtained, for example, by mixing a lithium salt powder and a manganese oxide powder, and then firing these.

[0004]

By the way, when a non-aqueous electrolyte battery electrode using the metal compound as an electrode active material is charged and discharged, lithium ions enter and leave the electrode active material. And along with this, LiMn
Polycrystalline particles 3 in the ₂ O ₄ powder expand and contract.

Therefore, crystal defects occur in the above-mentioned powder 9 of the metal compound. In addition, strain accumulates at the grain boundaries, resulting in pulverization and collapse of the crystal structure. Therefore, the charge / discharge life of the nonaqueous electrolyte battery electrode is shortened. In view of such conventional problems, the present invention is intended to provide an electrode for a non-aqueous electrolyte battery that suppresses pulverization of the electrode active material and collapse of the crystal structure due to charge / discharge, and has a long charge / discharge cycle life. .

[0006]

The present invention relates to an electrode for a non-aqueous electrolyte battery using a powder of a metal compound capable of inserting and extracting lithium as an electrode active material, wherein the powder of the metal compound is an aggregate of polycrystalline particles. An electrode for a non-aqueous electrolyte battery, which is characterized in that it is composed of a body and contains ultrafine powder, and the ultrafine powder is present in the particles of the above-mentioned polycrystalline particles or at grain boundaries or both. .

What is most noticeable in the present invention is that the ultrafine powder is present in the grains of the polycrystalline particles of the metal compound or at the grain boundaries or both (FIGS. 1 and 2). 2). Here, the ultrafine powder has a particle size of 3
It is preferably μm or less. Further, in order to make the dispersion of the ultrafine powder uniform, it is preferably 0.5 μm, more preferably 0.2 μm or less. If the particle size exceeds 3 μm, it becomes difficult to incorporate the ultrafine powder into the metal compound. As the ultrafine powder, one that does not react with the above polycrystalline particles is used. As such ultrafine powder, for example, Si
There are powders of ₃ N ₄ , SiC, Al ₂ O _3, etc.

The metal compound capable of occluding or releasing lithium is preferably a metal compound containing lithium. As such a metal compound, LiMn ₂
O ₄ , Li _x MnO ₂ , LiCoO ₂ , LiNiO ₂ ,
Examples include LiFeO ₂ and LiV ₃ O ₈ .

Another metal compound capable of inserting or extracting lithium is V ₂ Mo containing no lithium.
_{O 8, Cu 2 V 2 O} 7, MoO 3, V 2 O 5, Cr 2 O
₅ , MnO ₂ , TiS ₂ , MoS _{2 and the} like. The ultrafine powder is preferably contained in the metal compound powder in an amount of 0.1 to 40% (volume ratio, the same applies hereinafter). 0.1
If it is less than 40%, it is difficult to obtain the effect of the present invention. On the other hand, if it exceeds 40%, by-products may be produced.

In producing the powder of the metal compound containing the above ultrafine powder, there is a method of adding and mixing the above ultrafine powder to the raw material of the metal compound and heating and firing. Alternatively, there is a method in which ultrafine powder is added and mixed in a solution containing metal ions of a metal compound to form a precipitate, and then heated and baked.

When the above heating and firing is carried out, it may be fired at normal pressure, but a pressure sintering method for applying pressure, for example, a hot pressing method, a hot isostatic pressing method (HIP) or the like is used. You can also The heating and firing temperature is preferably 300 to 1200 ° C. Thereby, the sintering reaction can be promoted.

The non-aqueous electrolyte battery electrode comprises a current collector,
And an electrode active material covering the current collector. As the current collector, a carbon thin film, carbon fiber, graphite fiber, metal, conductive polymer or the like having good conductivity is used. The electrode active material is obtained by kneading the metal compound with a conductive agent, a binder and the like. Carbon, metal or the like is used as the conductive agent. Further, Teflon or the like is used as the binder.

[0013]

In the electrode for a non-aqueous electrolyte battery of the present invention, in the powder of the metal compound used as the electrode active material, in the particles of the polycrystalline particles of the metal compound or at the grain boundaries or both, The ultrafine powder is present. Also, the ultrafine powder is smaller than the polycrystalline particles.

Therefore, when this electrode active material is incorporated into a battery and charging / discharging is performed, the expansion and contraction of the polycrystalline particles due to the ingress / egress of lithium ions are suppressed by the ultrafine powder. That is, the ultrafine powder plays a role as a cushion that moderates the expansion and contraction of the polycrystalline particles.

Therefore, the crystal structure of the polycrystalline particles is not collapsed, and the powder of the metal compound, which is an aggregate of the polycrystalline particles, is not pulverized. Therefore, the cycle life of the electrode for non-aqueous electrolyte battery is extended. As described above, according to the present invention, it is possible to provide an electrode for a non-aqueous electrolyte battery, which suppresses pulverization of the electrode active material and collapse of the crystal structure due to charge / discharge, and has a long charge / discharge cycle life.

[0016]

【Example】

Example 1 The electrode for a non-aqueous electrolyte battery of this example will be described with reference to FIG. In the non-aqueous electrolyte battery electrode of this example, powder 9 of a metal compound capable of inserting and extracting lithium was used as an electrode active material. The powder 9 of the metal compound is the polycrystalline particle 3
And an ultrafine powder 1 is contained. The ultrafine powder 1 exists in the particles of the polycrystalline particles 3.

In producing the powder 9 of the metal compound, LiI (lithium iodide) and MnO ₂ (manganese dioxide) were weighed at a molar ratio of Li / Mn = 1/2,
Mixed. Si ₃ N ₄ ultrafine powder was added to this mixture so that the amount of Si ₃ N ₄ in the metal compound was 3 vol%, and mixed. The added ultrafine powder does not react with the mixture of LiI and MnO ₂ . Then,
This was hot-pressed at 900 ° C, 30 MPa,
It was fired for 60 minutes in an N ₂ atmosphere. Thereby, powder 9 of the metal compound was obtained.

Next, when the fine structure of the above metal compound was observed, as shown in FIG. 1, the grain size was about 0.5 μm.
It was confirmed that the ultrafine powder 1 of m was present in the grains of the polycrystalline particles 3 having a grain size of about 5 μm. Further, when X-ray diffraction was performed on the above metal compound, polycrystalline particles 3 of LiMn ₂ O ₄ and ultrafine powder 1 of Si ₃ N ₄ were identified. Then, the powder 9 of the metal compound was kneaded with a conductive agent and a binder to prepare an electrode active material. Carbon was used as the conductive agent and Teflon was used as the binder.
This was attached to the periphery of the current collector to prepare a nonaqueous electrolyte battery electrode.

Example 2 In this example, as shown in FIG. 2, in the powder 9 of the metal compound, the ultrafine powders 1 and 2 exist within the grains of the polycrystalline grains 3 and at the grain boundaries. In producing the powder of the above metal compound, LiI and MnO ₂ are mixed with Li / M.
Weighed and mixed at a molar ratio of n = 1/2. Si ₃ N ₄ ultrafine powder was added to this mixture so that the amount of Si ₃ N ₄ in the metal compound was 20 vol%, and mixed. Then,
This was heated and calcined in the same manner as in Example 1 to obtain a metal compound powder 9.

Next, the fine structure of the powder 9 of the metal compound was observed. As a result, as shown in FIG. 2, the ultrafine powder 1 having a particle diameter of 0.5 μm was present in the particles of the polycrystalline particles 3. It was also confirmed that the ultrafine powder 2 having a particle size of 1 μm or more was present at the crystal grain boundaries of the polycrystalline particles 3. Then, in the same manner as in Example 1, a nonaqueous electrolyte battery electrode was produced using the powder 9 of the metal compound according to this example. Others are the same as in the first embodiment.

Example 3 In this example, manganese dioxide was first deposited around ultrafine powder in an MnSO ₄ aqueous solution, and then LiMn ₂ O ₄ was grown in the Li ₂ SO ₄ aqueous solution to form a metal compound. Obtained. That is, first, 75 g of MnSO ₄ was dissolved in 500 ml of water, and 1.5 μm of Si ₃ N ₄ ultrafine powder having a particle size of 0.5 μm was dissolved.
g was added. Then, 1N-Annimore water was gradually added to this solution with stirring to form a precipitate.

Next, oxygen was blown into the solution at a flow rate of 100 ml / min for 5 hours for oxidation treatment. Next, the precipitate was filtered and dried, and heat treated in air at 300 ° C. for 10 hours to obtain manganese dioxide. Next, 40 g of the manganese dioxide thus obtained was added to a 4N-LiOH solution 500
The mixture was added to ml, reacted with stirring at 70 ° C. for 5 hours, then filtered and dried, and this powder was heat treated at 900 ° C. for 24 hours.

As a result of X-ray diffraction of the obtained powder, LiM
Polycrystalline particles of n ₂ O ₄ and ultrafine powder of Si ₃ N ₄ were identified. The fine structure of the powder was similar to that of the metal compound of Example 1 (see FIG. 1). Then, in the same manner as in Example 1, a nonaqueous electrolyte battery electrode was produced using the powder 9 of the metal compound according to this example. Others are the same as in the first embodiment.

Example 4 In this example, LiMn ₂ O ₄ was deposited and grown around the ultrafine powder in an aqueous solution in which MnSO ₄ and Li ₂ SO ₄ were dissolved to obtain a metal compound. That is, first, 75 g of Mn
SO ₄ and 30 g of Li ₂ SO ₄ were dissolved in 500 ml of water, and 1.5 g of Si ₃ N ₄ ultrafine powder having a particle size of 0.5 μm was added. Then, 1N-ammonia water was gradually added to this solution with stirring to form a precipitate. Next, oxygen was blown into this solution at a flow rate of 100 ml / min for 5 hours for oxidation treatment. The precipitate is then filtered, dried and dried in air 90
Heat treatment was performed at 0 ° C. for 24 hours.

X-ray diffraction of the obtained powder revealed that LiM
Polycrystalline particles of n ₂ O ₄ and ultrafine powder of Si ₃ N ₄ were identified. The fine structure of the powder was similar to that of the metal compound of Example 1 (see FIG. 1). Then, in the same manner as in Example 1, a nonaqueous electrolyte battery electrode was produced using the powder 9 of the metal compound according to this example. Others are the same as in the first embodiment.

Comparative Example In this example, unlike the above-mentioned Examples 1 to 4, powders of the above metal compounds in which no ultrafine powder was present were prepared. The metal compound is composed of an aggregate of polycrystalline particles. The particle size of the polycrystalline particles was about 5 μm. Then, the above-mentioned Example 1
The electrode for non-aqueous electrolyte battery was produced in the same manner as in Steps 4 to 4.
Others are the same as that of Examples 1-4.

Experimental Example In this example, a non-aqueous electrolyte secondary battery was assembled using the electrodes for non-aqueous electrolyte batteries according to Examples 1 to 4 and the comparative example, and the charge / discharge cycle of each electrode for non-aqueous electrolyte batteries was assembled. The change in the energy capacity retention rate with respect to the number was measured. The non-aqueous electrolyte secondary battery is a button type battery having a diameter of 20 mm and a thickness of 3.2 mm. Metal lithium was used for the negative electrode.
The electrolyte used was a solution of lithium perchlorate dissolved in propylene carbonate.

In the above measurement, the button type battery was subjected to a charge / discharge cycle test in which it was charged for 5 hours under the conditions of a constant current of ² mA / cm ² and an upper limit voltage of 4.1 V, and then discharged to 2 V. The result is shown in FIG. As is known from FIG. 4, the energy capacity retention ratios of the nonaqueous electrolyte battery electrodes according to Examples 1 to 4 did not decrease up to 100 charge / discharge cycles. On the other hand, the non-aqueous electrolyte battery electrode according to the comparative example has a charge / discharge cycle number of 10
It decreased to 60% at the 0th time. The above shows that the electrode for a non-aqueous electrolyte battery of the present invention has a long charge / discharge cycle life because pulverization of the electrode active material and collapse of the crystal structure due to charge / discharge are suppressed.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a fine structure of a metal compound according to Example 1.

FIG. 2 is an explanatory view showing a fine structure of a metal compound according to Example 2.

FIG. 3 is an explanatory view showing a fine structure of a metal compound according to a conventional example.

FIG. 4 is a graph showing the relationship between the number of charge / discharge cycles and the energy capacity retention rate of the nonaqueous electrolyte battery electrode in the experimental example.

[Explanation of symbols]

 1,2. ． ． Ultrafine powder, 3. ． ． Polycrystalline particles, 9. ． ． Metal compound powder,

Claims (2)

[Claims] 1. An electrode for a non-aqueous electrolyte battery using a powder of a metal compound capable of occluding and releasing lithium as an electrode active material, wherein the powder of the metal compound is composed of an aggregate of polycrystalline particles and is An electrode for a non-aqueous electrolyte battery, which contains fine powder, and the ultrafine powder is present in the grains of the above-mentioned polycrystalline particles, or at grain boundaries or both. 2. The electrode for a non-aqueous electrolyte battery according to claim 1, wherein the metal compound capable of inserting and extracting lithium is a metal compound containing lithium.