JPS58206062A - Nonaqeuous electrolyte battery - Google Patents

Abstract

PURPOSE:To increase the field of practical use and reliability in graphite fluoride family batteries by mixing vanadium oxide 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 vanadium oxide (VOX, 2<=X<=2.5) are provided. Vanadium oxide was selected from the reason that it gives no adverse effect to basic discharge performance of graphite fluoride family batteries, reacts prior to or in parallel with graphite fluoride in initial discharge stage, and rechargeable LiaVOx 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 and lithium perchlorate in an aprotic organic solvent such as tetrahydrofuran, dimethoxyethane, dioxyfuran, propylene carbonate, and γ-butyrolactone. Fluorinated graphite ((CFx)n, Q (z l:1, in other words, (O
Addition of an auxiliary active material to the positive electrode in a non-aqueous electrolyte battery using F)n, (02F)n alone or a mixture thereof, and those containing unreacted carbon) as a positive electrode living material. It is related to.

Non-aqueous electrolyte batteries using the above-mentioned fluorinated graphite as a positive electrode active material have high energy density, good voltage flatness, and are already widely used as primary batteries with excellent storage properties, and their applications are expected to continue to expand. It's progressing. Among these new applications, although it is an extremely small current on the order of nanoamperes to microamperes, as typified by backup power supplies for IC memory, leakage current in the charging direction for a long period of time is generated in primary batteries as backup power supplies. Although it is a primary battery, there are no problems with battery characteristics, external shape, abnormality in appearance, bursting, etc. for this level of charge.
In many cases, it is required to be able to properly function as a secondary battery. Even with the small currents mentioned above, the reliability and service life of applied equipment such as electronic registers and computers has been extended, and 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 charged electricity accumulated during that time ranges from several mAh to several tens of mAh.
In some cases, it reaches mih.

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 )n-)-nLl -1-ne-+ O-1-L
This is believed to be because iF produces inactive LiF.

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

In this sense, in order to provide long-term Ω: durability characteristics, 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 adds the characteristic of at least partial charging/discharging, thereby expanding the scope of its application as a power source for equipment. This is intended to increase compatibility.

The present invention is characterized in that vanadium oxide, which is a chargeable and dischargeable active material, is mixed into the positive electrode of the battery.

Among vanadium oxides, V205 is a typical material that has long been considered as an active material for primary batteries, and although it has a high energy density, there is a voltage difference between the first half and the second half of discharge, so it can be used effectively. The energy often stops in the first half, resulting in a narrow practical range. However, in addition to V205, vanadium oxide is being considered as an active material for secondary batteries as it is capable of charging and discharging reactions, and there are many types of vanadium oxides, including VO2 and intermediate oxides between VO2 and V205. There are intermediate oxides such as te v6o, 3, v5o7, v4o9, etc. These intermediate oxides are produced by thermal decomposition of NH4VO3 at a relatively low temperature, which is commonly used as the method for producing v205. There are various methods, such as a method of reacting v205 and metal vanadium at high temperature in a non-stoichiometric manner.By appropriately adjusting the reaction conditions, any oxide (v
oz, 2rx≦2.5) is obtained. For example v205
When the reaction temperature between and metal vanadium is 650°C,
An intermediate oxide having a composition ratio of VO2,+ 7 to VO2,20 was obtained, which approximately corresponds to that previously indicated as v6o 13. These charge/discharge reactions are expressed by the following formula when a lithium negative electrode is used as a counter electrode, and Ll is taken into and taken out of the oxide. This is a so-called reversible topochemical reaction, and its basic mechanism is different from the above-mentioned discharge reaction of fluorinated graphite.

VOX-4-at+1+ae 4; LiavoxThe present invention focuses on the fact that such vanadium oxide is capable of charge-discharge reactions and has a positive electrode potential close to that of fluorinated graphite, and has made it extremely suitable for use in secondary batteries. By mixing with fluorinated graphite, which is an excellent active material, fluorinated graphite-based
The battery has added resistance to charging during practical use as described above without impairing its characteristics as a secondary battery.

In order to further enhance the effect of the present invention, it is also possible to use fluorinated graphite in daily life.
It is preferable to have a rechargeable LiaVO) present in a quality positive electrode. This LiaVO2 can be achieved, for example, by discharging a part of the discharge capacity after constructing a battery containing vanadium oxide in the positive electrode, and the reaction It is possible to put it into practical use after it is present in the positive electrode as a product, and even if current is passed in the charging direction from the beginning of use, vOx is generated by a reversible reaction, causing decomposition of the electrolyte and
The above-mentioned problems caused by misalignment can be solved. The important reason for selecting vanadium oxide, which has a potential slightly higher than or similar to that of fluorinated graphite, as the auxiliary active material to be added is that it does not have a negative impact on the basic discharge performance of fluorinated graphite batteries. and LiaV, which can be charged by reacting in priority to or in parallel with fluorinated graphite at the initial stage of discharge.
The purpose is to allow as much Ox as possible to exist in the positive electrode during use in preparation for charging. Furthermore, the well-known chemical stability of vanadium oxide 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 FIG. 1, 21 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, 6 is a positive electrode made of fluorinated graphite (CF)n, which is formed by mixing carbon powder, fluororesin, and vanadium oxide in various formulations as described below, and 6 is made of titanium. The positive electrode current collecting net is press-fitted into the positive electrode 5. 7 is a stainless steel battery case, 8 is a polypropylene gasket, and the sealing 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 20 mm and a thickness of 1.6 mm were manufactured 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 vanadium oxide was 100, to which acetylene black was uniformly added in a ratio of 10 parts and fluororesin powder was added in a uniform ratio of 6 parts, mixed, and molded. Table 1 shows only the active material formulations.

Table 1 shows the results of evaluating the discharge characteristics and charge resistance VC of these prototype batteries.

The test method is to repeat a partial discharge and then charge it to an amount equivalent to a portion of its weight.The device is then discharged mainly for memory backup, and then charged for a period of time due to leakage current when driven by a muC power source. The simulation experiment conditions were set according to the actual situation. The conditions and order of charging and discharging are as follows.

Primary discharge: Temperature [20T;, soKΩ constant resistance load Primary charging: Temperature 20°C, 10 μm constant current Secondary discharge: Temperature 20°C, 30Ω constant resistance load Secondary charging: Temperature 20 'C
Charging for 1700 hours at 110 μm constant current ↓ (7 mAh) 3rd discharge: Temperature 20'C 15oKΩ constant resistance load 3rd charge: Temperature 20°C, 10 μm constant current Final discharge: Temperature 2
0'C130 with Ω constant resistance load and terminal voltage is 2. Of the test results, Figures 2 and 3 show the discharge characteristics; Figure 2 shows the difference when changing the amount of v205 added; Figure 3 shows the difference when changing the amount of V205; 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.

As is clear from FIG. 2, the greater the amount h1 of the auxiliary active material added, the higher the initial voltage of discharge. This shows that v205, which has a higher potential than fluorinated graphite, reacts preferentially, and the same tendency is generally observed even after charging, indicating that charging of V2O5 was carried out smoothly. On the other hand, in the case of no additives, the discharge after the first charge is carried out without any abnormality as in the case of normal intermittent discharge, but the discharge after the second charge causes voltage drop and instability. It shows.

This is because gas is generated during charging, and during the first charge, the amount of gas generated was small and did not affect the battery's function, but on the second charge, the gas pressure increased, causing the battery to expand and cause damage to the electrodes. It is thought that due to the presence of gas, insufficient contact occurred within the battery, increasing internal resistance and deteriorating the voltage characteristics.

In addition, with F containing a large amount of V2O5, V2O5tp! j
The two-stage discharge curve is relatively remarkable, and from the viewpoint of voltage stability, it is better to use fluorinated graphite as a living material.In particular, the amount of auxiliary active material blended is about 100% of the total shielding material in terms of weight ratio. 10 to 46% is good in terms of discharge capacity.

In addition, from Figure 3, the effect of adding various vanadium oxides is uniformly recognized, and among them, the intermediate oxide has a slightly larger capacity than V2O5, which is also due to the lower degree of expansion of the battery, which will be shown later. It is presumed that this is because the charging reaction occurs more smoothly than with V20s and VO2.

In addition, as shown in Table 2, the degree of expansion of the battery is 1
The larger the amount of vanadium added, the smaller the amount of vanadium added, the smaller the amount of intermediate oxide, especially V6O13, and the longer the final discharge duration is generally the lower the degree of expansion, resulting in excellent charging ability. On the other hand, in the case of no additive, it was shown that there was a lot of expansion and no charging reaction took place, and the effects of the present invention are clearly demonstrated when taken together with FIGS. 2 and 3 above. In addition, although the above 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 is partially explained in order to supplement the function of the negative electrode and with a small number of cycles. Since it is a charging method, there is no need to worry about internal short circuits or falling off of the lithium dendrites deposited on the negative electrode, and the practicality of the negative electrode is sufficient for ordinary lithium. May be used.

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

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 examined.

1... Sealing plate, 3... Lithium negative electrode,
4...Separator, 6...Positive electrode mainly composed of fluorinated graphite, 7...Battery case, 8...
···gasket.

Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Illustration furnace 1st generation Hijo ◇ 1st fan R

Claims (1)

[Claims] (1) A negative electrode containing lithium as an active material, an electrolytic solution containing an inorganic salt dissolved in an organic solvent, and a mixture of fluorinated graphite and vanadium oxide (vOx, 24z-2.6). A non-aqueous electrolyte battery with a positive electrode that uses water as an active material. @) The non-aqueous electrolyte battery according to claim 1, wherein the mixing ratio of fluorinated graphite and vanadium oxide is from 90:10 to 55:46 by weight. (3) A negative electrode made of lithium as an active material, an electrolyte containing an inorganic salt dissolved in an organic solvent, and a positive electrode made of fluorinated graphite as a living material, with a rechargeable LiaVOx present in the positive electrode. Water electrolyte battery.