JPS58206061A - Nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To increase the field of practical use and reliability in graphite fluoride famIly batteries by mixing titanium dioxide which is rechargeable active mass to a positive electrode. CONSTITUTION:A negative electrode using lithium as an active mass, an electrolyte prepared by dissolving an inorganic salt in organic solvent, and a positive electrode having an active mass prepared by mixing graphite fluoride and titanium dioxide are provided. TiO2 having almost same potential as graphite fluoride was selected as an additional active mass from the reason that it gives no adverse effect to basic discharge performance of graphite fluoride family batteries, and reacts prior to or in parallel with graphite fluoride in initial discharge stage, and rechargeable TiO2.Li can exist as much as possible in the positive electrode to give rechargeability.

Description

Detailed Description of the Invention The present invention uses lithium as a negative electrode active material, and uses lithium borofluoride, lithium perchlorate, etc. in an aprotic organic solvent such as tetranohydrofuran, dimethoxyethane, dioxolane, propylene carbonate, and γ-butyrolactone. Fluorinated graphite ((CFx), nQ (z 41 , in other words, (O
F) Addition of auxiliary active material to the positive electrode of a non-aqueous electrolyte battery in which the main active material of the positive electrode is n + (02F)n, either alone or as a mixture, and including those containing unreacted carbon. It is about addition.

Non-aqueous electrolyte batteries using the above-mentioned fluorinated graphite as the positive electrode active material have high energy density and good voltage flatness, and have already been widely put into practical use as primary batteries with excellent storability, and their applications continue to expand. It's progressing. Among these new applications, although the current is extremely small on the order of nanoampere and microampere, as typified by the power supply for back-up amplifiers of IC memory, it leaks in the direction of charging over a long period of time to the primary battery as a backup power supply. current flows,
For this level of charging, even though it is a primary battery, it is required to be able to function normally as a secondary battery without any problems such as battery characteristics, external shape, abnormality in appearance, bursting, etc. many. The minute current as mentioned above is also an electronic resistor, -7
As the reliability and service life of applied equipment such as computers has been extended, the service life required for backup batteries has also increased to 10%.
Since it is common for a long period of 20 years, let alone a year, the amount of electricity accumulated during that time ranges from several mAh to several tens of mAh.
In some cases, it reaches mAh.

In the fluorinated graphite-based non-aqueous electrolyte battery, it is essentially impossible to charge the positive electrode, and although the discharge reaction proceeds as described below, the reverse electrochemical reaction does not proceed. this is,(
CF) zl + nLx + no→C+LiF [supposedly to produce more inactive LiF.

Therefore, when the above-mentioned charging current flows through the battery, gas generation and deterioration of the electrolytic liquid occur due to electrochemical reactions mainly consisting of solvent decomposition and polymerization reactions, and in severe cases, battery expansion and There is a concern that it may cause rupture and deterioration of battery performance.

In that sense, in order to provide longer-term durability,
Improvements are required to withstand the amount of charging electricity that corresponds to at least a portion of the discharge capacity.

The present invention maintains the original excellent performance of a fluorinated graphite-based non-aqueous electrolyte battery as a primary battery, and also adds the characteristic of at least partial charging and discharging, expanding the range of application as a power source for equipment. This is intended to increase compatibility.

The present invention is characterized in that titanium dioxide (Ti02), which is a chargeable and dischargeable active material, is mixed into the positive electrode of the battery.

There are two types of Tioz, rutile type and anatase type, and research on the latter is mainly underway as it has better charge and discharge characteristics as a positive electrode active material for non-aqueous electrolyte batteries. However, the discharge characteristics themselves are inferior in terms of energy density, voltage stability, etc. compared to the positive electrode of primary non-aqueous electrolyte batteries such as fluorinated graphite. Although it is not very attractive, it is worthy of attention as a material that can be charged and discharged.

When a lithium negative electrode is used as a counter electrode, the charge/discharge reaction of Ti0z is expressed by the following formula, and is a reversible topochemical reaction due to the incorporation and extraction of Ll into Ti0z, which is similar to the discharge reaction of fluorinated graphite described above. The mechanism is different.

TiO+Li''-+ e d TiO2・LiThe present invention focuses on the fact that TiO2 is chargeable and dischargeable and has a positive electrode potential close to that of fluorinated graphite, and considers it to be an extremely excellent active material for all-power batteries. By mixing a certain fluorinated graphite as an auxiliary active material, the battery has all the resistance to charging during practical use as described above without impairing the characteristics of a fluorinated graphite-based secondary battery.Also, the present invention In order to further enhance this effect, it is preferable to include chargeable TiO2.Li in the positive electrode, which uses fluorinated graphite gold as the main active material.

This Q, TiO2.Li, can be achieved, for example, by configuring a battery containing TiO2 in the positive electrode and then discharging a part of the discharge capacity. It is possible to put it into practical use after
As a result, even if a current is passed in the charging direction from the beginning of use, TiO2 is generated by a reversible reaction, and the above-mentioned problems caused by decomposition and polymerization of the electrolytic solution can be solved. The important significance of selecting TiO2, which has a potential similar to that of fluorinated graphite, as the auxiliary active material added to the positive electrode is that
First, it does not have a negative effect on the basic discharge performance of fluorinated graphite batteries, and TiO2, which is a discharge product that reacts preferentially or in parallel to fluorinated graphite at the initial stage of discharge and can be charged.・It is possible to have as much Li as possible in the positive electrode during use to prepare for charging. Furthermore, the well-known chemical stability of TiO2 in a non-aqueous electrolyte is also one of the requirements that made the configuration of the present invention possible.

FIG. 1 is a cross-sectional view of a battery experimentally manufactured to confirm the effects of the present invention. In Figure 1, 1 is a sealing plate made of stainless steel, 2 is a negative electrode current collector net made of a homogeneous net welded to 1, 3 is a lithium negative electrode crimped to 2, 4 is a separator made of polypropylene nonwoven fabric, and 5 is a separator made of polypropylene nonwoven fabric. The positive electrode is mainly composed of fluorinated graphite ((ci')n), and is formed by mixing carbon powder, fluororesin, and TiO2 in various formulations as described below. 6 is a positive electrode current collection net made of titanium; 6 is press-fitted. Number 8 is a stainless steel battery case, number 8 is a polypropylene gasket, and the seal [
1 is accomplished by folding the opening of the battery case 7 inward. An electrolytic solution in which lithium fluoroborate is dissolved in a solvent mixed with propylene carbonate and dimethoxyethane at a volume ratio of 1=1 is injected into the battery.

Batteries having a diameter of 20mm and a thickness of 1.6mm were fabricated according to the above configuration using positive electrodes having various compositions as shown in Table 1, and tested. For the positive electrode, the sum of the weights of fluorinated graphite and titanium dioxide was 1100, and acetylene black was added to this by 100.
, fluororesin powder was uniformly added at a ratio of 5 parts, mixed, and molded. Table 1 shows only the active material formulations.

(The following is a blank space.) Table 1 Next, the results of evaluating the discharge characteristics and charging resistance of these prototype batteries are shown.

The test method is to repeat a partial discharge and then charge it to a partial capacity.The device discharges mainly for memory backup, and then charges due to leakage current when running on an AC power source. The simulation experiment conditions were set according to practical conditions. The conditions and order of charging and discharging are as follows.

Primary discharge: Discharge for 36 hours at a temperature of 20°C with a constant resistance load of 30Ω (approx. 6 ↓ of total capacity...approximately 3.5mAh) Primary charge: Temperature of 20°C, 10μm Charge for 200 hours at constant current (2mAh) Secondary discharge = 20℃, discharge for 350 hours at 30Ω constant resistance load (approx. 2
Charging for 700↓ hours at 10μm constant current at o℃ (7m
Ah) Tertiary discharge = 20℃, 30Ω constant resistance load, terminal voltage 2. Discharge until it drops to OV ↓ Third charge: 20°Cs 10 pm constant current 500 ↓
Time charge (s mjh) Final discharge: 20°C, 30Ω constant resistance load, terminal voltage 2. Discharge until it drops to OV Of the test results, Figures 2 and 3 show the complete discharge characteristics, Figure 2 shows the difference in the addition of anatase type Tie2, and Figure 3 shows the difference in the addition of TiO2. It shows the difference when changing the type. Table 2 shows the degree of expansion of the battery after charging as a value obtained by subtracting the thickness of the undischarged battery from the thickness of the battery after charging, and also shows the discharge duration in the final discharge.

(The following is a blank space) From FIG. 2 and Table 2, it is clear that the greater the amount of anatase-type TiO2 added, the less expanded dust is generated after charging, and the charging progresses smoothly. This is also supported by the difference in duration of final discharge. However, the weight ratio of Ti to the total active material is 45 or more.
When 02f is included, the voltage drop in the latter half of the discharge is large. This is thought to be because the discharge characteristics due to the remaining TlO2 are dominant, and on the other hand, the amount of TiO2 added at 5% is slightly insufficient to sufficiently accept charge, and during the tertiary discharge, the battery There is a slight drop in voltage due to poor contact due to expansion. These tests are only mock tests, and the appropriate formulation should be selected each time depending on the charge resistance required for the battery, but common sense suggests that T
It seems appropriate to add iO2 in an amount of 10 to 30% by weight of the total active material.

On the other hand, in the case of no additives, the discharge after the first charge is performed without any abnormality as in the case of normal intermittent discharge, but
Discharge after the second charge shows a decrease in electrical IE and instability. This is because regas is generated during charging, and during the first charge, the amount of gas generated was small so there was no problem with the battery's function, but on the second charge, the gas pressure increased, causing the battery to expand and cause gaps between the electrodes. It is thought that the internal resistance increased due to lack of contact within the battery due to the presence of gas, etc., and the voltage characteristics deteriorated.

Further, FIG. 3 and Table 2 show that although rutile type TiO2 is also effective, the effect is greater when anatase type TiO2 is mixed.

From the results shown below, the charge resistance is significantly improved by mixing TiO2 into the positive electrode of a fluorinated graphite battery, and it is particularly preferable to mix 10 to 30 inches of TiO2 based on the total active material in terms of weight ratio. We also use anatase type TiO
It was confirmed that the effect of mixing 2 was large.

In addition, although the following explanation has been made only regarding the charging and discharging characteristics of the positive electrode, in the case of the present invention, the reversibility of charging and discharging of the negative electrode can be partially and Because the charge is small, there is no need to worry about internal short circuits or falling off due to resinous lithium crystals deposited on the negative electrode, and ordinary lithium is sufficient for practical use as a negative electrode. An alloy may also be used.

As described above, the present invention is extremely effective in improving the practical range and reliability of fluorinated graphite batteries.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a battery according to an example of the present invention, and FIGS. 2 and 3 show discharge characteristics of a battery in which the effects of the present invention were studied. DESCRIPTION OF SYMBOLS 1... Sealing plate, 2... Negative electrode current collection net, 3... Lithium negative electrode, 4... Separator, 5... iEIIM, 6...Positive electrode current collection net, 7...Battery case, 8...
·gasket.

Claims (1)

[Scope of Claims] 0) A non-aqueous product comprising a negative electrode containing lithium as an active material, an electrolytic solution containing an inorganic salt dissolved in an organic solvent, and a positive electrode containing a mixture of fluorinated graphite and titanium dioxide as active materials. electrolyte battery. (2) The non-aqueous electrolyte battery according to claim 1, wherein the titanium dioxide is anatase type. (3) The non-aqueous electrolyte battery according to claim 1, wherein the mixing ratio of fluorinated graphite and titanium dioxide is from 90:10 to 70:30 by weight. (4) Equipped with a negative electrode using lithium as an active material, an electrolytic solution containing an inorganic salt dissolved in an organic solvent, and a positive electrode using fluorinated graphite as the main active material, and the positive electrode contains a rechargeable TiO2.Li
f non-aqueous electrolyte battery.