JPS63274059A - Nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To increase charge-discharge performance by constituting a battery with a negative active material mainly comprising lithium, a positive active material mainly comprising LiMn2O4, and a nonaqueous electrolyte. CONSTITUTION:A battery consists of a negative active material 2 mainly comprising lithium, a positive active material 5 mainly comprising LiMn2O4, and a nonaqueous electrolyte. LiMn2O4 having a half width in a diffraction peak of 1.1-2.1 deg. in a diffraction angle of 46.1 deg. in X-ray diffraction using FeKalpha beam is used as the positive active material 5 of a nonaqueous electrolyte battery. High charge-discharge capacity corresponding to 90% of the theoretical charge- discharge capacity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a chargeable and dischargeable non-aqueous electrolyte battery that is expected to be used as a power source for various small electronic devices.

[Summary of the Invention] The present invention provides a non-aqueous electrolyte battery using a lithium-containing material as a cathode active material, and the half-width of the diffraction peak at a diffraction angle of 46.1° when X-ray diffraction is performed using FeKα rays. By selectively using LiMnzOa with an angle of 1.1 to 2.1° as an anode active material, it is possible to improve the charge/discharge characteristics of the non-aqueous electrolyte battery.

[Conventional technology]

So-called non-aqueous electrolyte batteries, which use lithium as the cathode active material and an organic electrolyte as the electrolyte, have advantages such as low self-discharge, high voltage, and excellent storage stability. As a battery with long-term reliability of IO years, it is widely used as a memory backup battery for electronic watches and other types of batteries.

However, these conventionally used non-aqueous electrolyte batteries are primary batteries, and their lifespan ends after one use, so there is room for improvement in economic efficiency.

Therefore, along with the dramatic advances in various electronic devices in recent years, the emergence of rechargeable non-aqueous electrolyte secondary batteries as a power source that can be conveniently and economically used for long periods of time has been awaited, and much research is being carried out. ing.

Generally, as the cathode active material of a non-aqueous electrolyte secondary battery, metallic lithium, lithium alloy (for example, Li-Al alloy) is used.
, conductive polymers doped with lithium ions (such as polyacetylene and polypyrrole), and even compounds with lithium ions mixed into their crystals are used, and the electrolyte is a non-aqueous solution in which the electrolyte is dissolved in an organic solvent. An electrolyte is used.

On the other hand, as a result of research, various materials have been proposed as anode active materials, and representative examples include, for example,
-Ti5z, Mo as described in Publication No. 54836
5t, NbSez, v, oS, etc.

The discharge reaction of batteries using these materials progresses by intercalation of lithium ions at the cathode between the eyebrows of these materials, which are the anode active materials, and conversely, when charging, lithium ions are intercalated between the eyebrows of the materials. is intercalated with the cathode. That is, charging and discharging can be repeated by repeating the reaction in which lithium ions at the cathode move in and out of the glabella of the anode active material.

However, in the above-mentioned anode materials, as the charge/discharge reaction is repeated, lithium ions become gradually less likely to be deintercalated, so that the discharge capacity gradually decreases and the cycle life is shortened. Furthermore, since these anode materials are expensive, manufacturing a large-capacity battery will result in high costs, making it economically disadvantageous compared to nickel-cadmium batteries, which are the mainstream of secondary batteries.

Therefore, as an anode material that has less deterioration in discharge capacity due to charge/discharge cycles, has excellent cycle life characteristics, and is also economical, the applicant of the present application has proposed, for example, Japanese Patent Application No. 61
In the specification of JP-257479, an anode material mainly composed of LiMnmOa was disclosed.

[The gap that the invention attempts to solve]

As mentioned above, the development of LiMn, O, as an anode material has resulted in a certain degree of improvement in discharge capacity, cycle life, and economic efficiency. By the way, this LiMn2
A battery reaction using O4 is expressed by the following equation.

This LiMnzOa is generally produced by mixing lithium carbonate and manganese dioxide at a molar ratio of 1=2, and
It is prepared by firing at 0''C. However, even if a battery is constructed using LiMn2O4 prepared in this way as an anode active material, its charge/discharge capacity is the same as that calculated theoretically from the above reaction formula. It only reaches about 30% of its capacity.

Therefore, the present invention proposes non-aqueous electrolysis using LiMnxOa, which has excellent charge and discharge characteristics, as an anode active material. & batteries.

[Means for solving problems]

The present inventors conducted various studies in order to bring the charge/discharge capacity of a non-aqueous electrolyte battery using LiMn, O, as an anode active material closer to the theoretical capacity, and as a result, conducted X-ray diffraction using FeKα rays. In particular, when LiMnm0a, which has a diffraction peak half-width of 1.1 to 2.1° at a diffraction angle of 46.1", is used as the anode active material of the above-mentioned non-aqueous electrolyte battery, excellent charge-discharge characteristics can be obtained. The inventors have discovered that the non-aqueous electrolyte battery of the present invention can be obtained using a negative electrode active material mainly composed of Ll, and a positive electrode active material mainly composed of LiMn, O, and the like. and a nonaqueous electrolyte, and in X-ray diffraction using FeKα rays, the half-width of the diffraction peak at a diffraction angle of 46.1 @ is 1.1 to 2.1.

It is characterized by:

LiMnmOa used as the anode active material of the nonaqueous electrolyte battery of the present invention is prepared, for example, by firing lithium carbonate and manganese dioxide in air. At this time, by adjusting the firing temperature, the half-width of the diffraction peak observed in X-ray diffraction changes.

In the present invention, when performing X-ray diffraction using FeKα rays, LiHn2O4 whose half-value width of the diffraction peak at a diffraction angle of 46.1° is 141 to 2.1 is selectively used. If the value range is smaller than the above range, the desired discharge capacity will not be achieved.

Furthermore, lithium iodide may be used instead of the lithium carbonate, and the calcination may be performed in an inert gas instead of in air.

On the other hand, materials used as cathode active materials include metallic lithium, lithium alloys (e.g. Li-A1, LiP
b, Li5nSLiBi, LiCd, etc.), intercalation compounds with lithium ions mixed into the crystal (for example, Ti
5z,? IoS, etc. with lithium sandwiched between layers)
etc. are available.

In addition, a non-aqueous electrolyte in which a lithium salt is used as an electrolyte and is dissolved in an organic solvent is used as the electrolyte.

Here, the organic solvents include 1,2-dimethoxyethane, 1,2-jethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1
．． Solvents such as 3-dioxolane and 4-methyl-1,3-dioxolane may be used alone or in combination of two or more.

As an electrolyte, LiCIO4, LiAsF6, Lit
It is possible to use one or a mixture of two or more of Fb, LiBFa, and LiB(CaHs)4.

[Effect]

When performing X-ray diffraction using FeKα radiation, the diffraction angle is 4.
By selectively using LiMntO, which has a peak half-width of 1.1 to 2.1 degrees at 6.1''', as an anode active material of a non-aqueous electrolyte battery, the theoretical charge/discharge capacity of 90 It is possible to secure a high charge/discharge capacity of % or more.

〔Example〕

Hereinafter, the present invention will be explained based on specific experimental examples and with reference to the drawings.

First Example In this example, LiMn2O4 was prepared at various firing temperatures, so-called button-type batteries were made using these, and their charge and discharge characteristics were investigated.

First, in order to obtain iMn=o=, which has good properties as an anode active material for non-aqueous electrolyte batteries, we varied the firing temperature of LiMnzOa and investigated the resulting changes in X-ray diffraction peaks and discharge capacity. Examined.

To prepare LiMntO4, 86.9 g (1 mol) of commercially available manganese dioxide and 18.5 g of lithium carbonate were used.
g (0.25 mol) were sufficiently mixed while being ground in a mortar, and the resulting mixture was calcined on an alumina boat in air for 1 hour. Firing temperature ranges from 430°C to 900°C
'C' room.

The product was then cooled and analyzed by X-ray diffraction. This x1 diffraction was performed using FeKα radiation, and the measurement conditions were a tube voltage of 30 kV, a tube current of 15 kV, and a measurement range of 2,000 m.
cps, scanning speed 1°/min, recording paper speed 5mm/min,
The divergence slit width is 1°, and the light receiving slit width is 0.6 m+n. Identification of substances is based on the American Society for Testing and Materials (ASTM)
) by comparing it with the card index of
The above product was confirmed to be LiMntO4.

As an example of this, L obtained at a calcination temperature of 460 °C
The X-ray diffraction spectrum of iMnzOa is shown in FIG. At this time, the half-width of the diffraction peak at a diffraction angle of 46.1@ is 2.08@, which is wider than that of LiMntO4 fired at 800-900'C in the conventional general manufacturing method. be. Note that data on half-widths of LiMnzOa fired at other temperatures are summarized in Table 1 below.

Next, LiM obtained at each firing temperature as described above
A non-aqueous electrolyte battery as shown in the cross-sectional view in FIG. 2 was prepared using No. 04. That is, the above LiMntO<
An anode composition was prepared by adding 86.4 parts by weight of graphite and 5 parts by weight of polytetrafluoroethylene (Teflon) as a binder. This anode composition was molded into an anode pellet (5) having a diameter of 15.511111, a thickness of 0.44 #ll, and a Tfl amount of 0.213 g.

On the other hand, a commercially available 0.3 mm thick aluminum plate was
5.5 vavs, adhered to the cathode can (2) by spont welding, and press-bonded a lithium foil with a thickness of 0.18 mm into a circular shape with a diameter of 15 mm on top of it to form a cathode pellet (1 ) was created to form a cathode.

Next, a separator (3) was placed on top of the cathode, a gasket (4) made of brass tink was fitted, and 1 mol/l of L
A mixed electrolyte of propylene carbonate and 1,2-dimethoxyethane in which iCl0a was dissolved was injected. The anode belen (5) prepared earlier was stacked on the separator (3), and the anode can (6) was covered, and the opening was caulked to seal. 1.6 mm
We created a so-called button-type non-aqueous electrolyte battery.

LiMn prepared at each calcination temperature by the above method
Nonaqueous electrolyte battery A uses 2O4.

B, C, D, E, F, G, H, I, J, and K were created.

The correspondence between the name of each of these batteries and the firing temperature is as shown in Table 1.

Nonaqueous electrolyte batteries A and B thus obtained.

The charging and discharging characteristics of C, D, E, F, G, H, I, and J were investigated.

Table 1 First, connect a resistor of Ω to 1 to these non-aqueous electrolyte batteries, and set the final voltage to 2. Figure 3 shows the results of measuring the discharge characteristics as Ov. In this figure, the vertical axis is the battery voltage (■
), the horizontal axis represents the discharge time (Hr), the average discharge voltage value is read from this Figure 3 and converted to the average discharge 'mi current value,
Furthermore, by multiplying the discharge duration until reaching the final voltage, the discharge capacity can be calculated as ampere-hour capacity (in this measurement system, a resistance of Ω is used for 1, so the unit is mAH). Table 1 also shows the discharge capacity determined in this manner.

Next, each battery that has undergone discharge as described above is given 4 + m
A current is applied and the final voltage is set to 3. The results of measuring the charging characteristics as IV are shown in Figure 4. In this figure, the vertical axis represents the battery voltage (■), and the horizontal axis represents the charging time (H''). In FIG. 3, as can be seen from the fact that the curves corresponding to each battery have many flat parts (parts that vary in constant voltage), the charge-discharge characteristics of the non-aqueous electrolyte battery according to the present invention are shown. is very stable.

This is evidence that intercalation and deintercalation of lithium ions between the LiMnz04 layers occurs very quickly, and LiMn1O, prepared as described above, is excellent as an anode active material. It can be seen that it has certain characteristics.

Further, the relationship between the discharge capacity and firing temperature listed in Table 1 is illustrated in FIG. 5. In this figure, the vertical axis is the discharge capacity! 1 (mAH), the horizontal axis represents the firing temperature ("C), 0 or more, from Table 1, Figures 3 and 5, 20 mAH
Batteries that have the above excellent discharge capacity and can withstand practical use are A.
B, C, D, E, and F batteries, and their anode active materials 1 and iMnzOm all have a diffraction peak half-width of 1.1 to 2.1 at an X-ray diffraction angle of 46.1°. It can be seen that it is in the range of °.

Moreover, this half-width can be controlled by the firing temperature of LiMngOa, and the appropriate temperature range is 430°C.
~520°. It has been found that when the firing temperature is higher than the above range, the discharge capacity tends to gradually decrease. Furthermore, even if the firing temperature is lower than the above range, the discharge capacity still decreases. For example, in a battery using LiMn1O4 prepared at a firing temperature of 400'C, the discharge capacity is 19.1 sAH (5th (see figure), on the contrary, it was decreasing. The X-ray diffraction spectrum of LiMn1O4 at this time is as shown in FIG. This figure shows that when the firing temperature is as low as 400"C, unreacted lithium carbonate and manganese dioxide remain, and the desired characteristics are not achieved.

Second Example In this example, when preparing LiMnzO, lithium iodide was used instead of lithium carbonate as described in the first example, and calcination was performed under a nitrogen atmosphere instead of in air. This is an example of what was done.

First, 50 g (0.57 mol) of commercially available manganese dioxide, 39 g (0.29 mol) of lithium iodide, and 5.2 g of graphite were thoroughly mixed while grinding in a mortar, and the resulting mixture was poured into a container weighing 3 tons of 7 cm. The pellets were placed on an alumina boat and fired at 300°C for 6 hours under a nitrogen atmosphere. After firing, the product was cooled and washed successively with ethylene glycol and dimethyl ether.

This product was analyzed by X-ray diffraction under the conditions described in the first example, and compared with the ASTM card index, it was confirmed that it was LiMnzOa.

This X-ray diffraction spectrum is shown in FIG.
The half width of the peak at P was 1.57°.

In this FIG. 7, in addition to the peak appearing in the first round, a graphite peak can be seen.

Next, 5 parts by weight of polytetrafluoroethylene (Teflon) as a binder was added to 95 parts by weight of this LiMnzO4 to prepare an anode composition. The following assembly of the non-aqueous electrolyte battery was carried out according to the method described in the first example, and a battery M was created. The discharge capacity of this battery M was 23.1 m as a result of the method described in the first example.
It was good as AH.

Third Example This example is an example in which LiMnzOa was prepared in a nitrogen atmosphere instead of in air as described in the first example.

First, 86.9 g (1 mol) of commercially available manganese dioxide and 18.5 g (0.25 mol) of lithium carbonate were ground and mixed thoroughly in a mortar, and the resulting mixture was placed on an alumina boat and heated under a nitrogen atmosphere. , 1 at 450°C
Baked for an hour. This product was analyzed by X-ray diffraction under the conditions described in the first example, and it was confirmed that it was LiMnzOm.The half width of the peak at 0 diffraction angle of 46.1'' was 1.60'. .

The following assembly of the non-aqueous electrolyte battery was performed according to the method described in the first example, and battery N was created. This battery N
The discharge capacity was as good as 22.9 +sAH as a result of conducting the test according to the method described in the first example.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
LiMn used as anode active material for non-aqueous electrolyte secondary batteries
The firing temperature of 2O4 was set lower than before to the extent that a practically suitable discharge capacity could be maintained, and in particular, the diffraction angle was 46.1'.
Since the half-value width of the diffraction peak is set to be wide, it is possible to significantly improve the charge/discharge characteristics of a battery made using this to 90% or more of the theoretical capacity.

In addition, since LiMnzO4 is a relatively inexpensive substance,
TiS, MoS, conventionally used as anode active materials
, , NbSe, , V203, and other expensive materials, it is not only more economical, but also allows for energy savings in the manufacturing process.

[Brief explanation of the drawing]

Figure 1 shows manganese dioxide and lithium carbonate at 460'
An X-ray diffraction spectrum diagram of LiMntOm obtained by firing with C, Figure 2 is a schematic cross-sectional view showing an example of the configuration of a non-aqueous electrolyte battery, and Figure 3 is the difference in half-width of the diffraction peaks of the LiMnzO4 used. Figure 4 is a characteristic diagram showing the difference in charging characteristics due to the difference in the half-width of the diffraction peak of the used LiMnzOa, and Figure 5 is the relationship between the discharge capacity of the non-aqueous electrolyte battery and LiMnxOa. A characteristic diagram showing the relationship with firing temperature, Figure 6' shows LiMn2 obtained by firing manganese dioxide and lithium carbonate at 400'C.
FIG. 7 is an X-ray diffraction spectrum diagram of LtMnJa obtained by firing manganese dioxide and lithium iodide at 300'C. 1... Cathode berent 2... Cathode can 3... Separator 4... Gasket 5... Anode pellet 6... Anode can Patent applicant Sony Corporation representative Patent attorney Koike Mitami Sakae Tamura - Masaru Sato 20 30 40 1$o 60
70 80 90 to. 53 Chocho 2E;) F@Ka Figure 1 Exit Figure 2 0 2 4 6 B
Io f2 late! Ginma (Hr) Fig. 3 Fig. 4 Kaibutsu

Claims (1)

[Claims] Consisting of a negative electrode active material mainly composed of Li, a positive electrode active material mainly composed of LiMn_2O_4, and a non-aqueous electrolyte, the LiMn_2O_4 has a diffraction angle in X-ray diffraction using FeKα rays. A nonaqueous electrolyte battery characterized in that the half width of the diffraction peak at 46.1° is 1.1 to 2.1°.