JPS59139556A - Manufacturing method of positive electrode black mix for solid electrolyte battery - Google Patents

Abstract

PURPOSE:To obtain a positive electrode black mix with good discharge characteristics by mixing lead iodide powder and carbonyl nickel powder within the specified time. CONSTITUTION:Lead iodide powder and carbonyl nickel powder are mixed within 10hr, i.e. for 0.5 to 10hr, desirably 2 to 5hr. For example, mixing is performed by using ball mills. It is desirable that the mixing ratio between lead iodide and carbonyl nickel should be 4:1 to 4:0.25 (4:0.75 to 4:0.25 is optimal) in the theoretical volume ratio. When carbonyl nickel is used as an electric conduction agent, discharge performance is more reduced if the mixing time is prolonged unlike normal metal powder. Since this tendency becomes more remarkable when the loadings of carbonyl is reduced, a positive electrode black mix with good discharge characteristics can be obtained by doing the said item.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a positive electrode mixture for solid electrolyte batteries using lead iocide as a positive electrode active material.

In general solid electrolyte batteries, metal powder is added to the positive electrode active material as an electron conductive agent in order to impart electronic conductivity to the positive electrode. The longer the time required to mix the positive electrode active material and the metal powder, the better the mixing state will be, so conventionally it has been adopted to mix the cathode active material and metal powder for about 20 hours. In reality, when lead powder is used as an electron conductive agent, discharge characteristics are often better when mixed for a long time than when mixed for a short time.

By the way, the inventors have developed a solid electrolyte battery using lead iodide as a positive electrode active material, in which carbonyl nickel has a well-developed structure, high electronic conductivity, greater oxidation resistance than lead, and uniform fine particles. Since carbonyl nickel is easily available, we plan to use it as an electron conductive agent.However, in the case of this carbonyl nickel, ordinary metal powder
1 is different, and it is observed that when the mixing time is lengthened, the discharge performance deteriorates on the contrary. This tendency becomes even more pronounced when the amount of carbonyl nickel added is reduced in order to improve discharge and capacity.

Therefore, the inventors of the present invention conducted various studies to find the appropriate mixing time for lead iodide and carbonyl nickel, and found that it is better to keep the mixing time within 10 hours rather than taking a long time to achieve better discharge characteristics. It was discovered that a positive electrode mixture could be obtained, and the present invention was completed.

In other words, lead iodide powder is a relatively smooth powder, and carbonyl nickel is extremely easy to mix with other substances, so it takes a long time to mix compared to when lead powder is used as an electron conductive agent. First, a well-mixed positive electrode mixture can be obtained from about 30 minutes. The phenomenon that a positive electrode mixture with better discharge characteristics can be obtained by mixing for a relatively short time than by mixing for a long time is due to the fact that carbonyl nickel is used to improve discharge capacity. This becomes more noticeable when the amount added is reduced. A particularly preferred mixing time is 2 to 5 hours.

In the present invention, mixing is usually carried out in a ball mill. However, it is not limited to this. The mixing ratio of lead iodide and carbonyl nickel is 4:1 to 4:0 in theoretical volume ratio.
25, a range of 4:0.75 to 4:0.25 is preferable because the discharge capacity is large and the necessary electronic conductivity is ensured.

Next, the present invention will be explained with reference to Examples.

EXAMPLE Lead iodide powder and carbonyl nickel powder were weighed so that the mixing ratios were 4:1 and 4:0.5 in terms of theoretical volume ratio, and each was 30y when mixed. After putting it in a ball mill and mixing it for a predetermined time, it was taken out.

In order to check the mixed state of the obtained positive electrode mixture,
09 was placed in a mold with an inner diameter of 10 ff and pressure-molded at 7 j /cM2, a model cell was installed, and its resistance was measured. The results are shown in FIG.

As shown in Figure 1, the mixing ratio of lead iodide and carbonyl nickel does not change much until the theoretical volume ratio of 4 = 1 and the amount of carbonyl nickel changes to about 20 hours n]. When the mixing time is reduced to 4:0.5, the mixing time remains almost constant until 4 hours, but after that, the resistance increases and
After a certain period of time, the resistance exceeds 10Ω, making it difficult to put it to practical use as a positive electrode for solid electrolyte batteries.

Next, a solid electrolyte battery as shown in FIG. 2 was prepared using the above positive electrode mixture, and the battery was discharged at a constant current of 130 μA at 20° C. to a final voltage of 1.4 V, and the utilization rate of the positive electrode was examined. The results are shown in FIG. The above battery is 0.8
8 Solid electrolyte 50 consisting of Li3N-0,12Li■
After temporarily forming a pellet with an inner diameter of 1 (in a mold of ltm) at t/as2, the above-mentioned positive electrode mixture 200 W was filled thereon and pressure-formed at 7t/CIIg2 to form the solid of this two-layer pellet. Thickness o, 2t MM, lI! diameter 8FI on electrolyte side
! N lithium foil was pressed and crimped, and the following was fabricated according to the usual method.

In FIG. 2, (1) is a lithium negative electrode, (2) is a positive electrode made of a press-molded body of the positive electrode mixture, (3) is a solid electrolyte layer,
(4) is a negative electrode plate, (5) is a positive electrode plate, and (6) is an insulator made of a ceramic ring, which is fixed to the negative electrode plate (4) and the positive electrode plate (5) by a locking material (7).

As shown in Figure 3, when the mixing ratio of lead iodide and carbonyl nickel is 4:1 in volume ratio, the discharge utilization rate of the positive electrode decreases by a factor of 10 after about 20 hours of mixing time. However, if the mixing time is 100 hours, about 40 sections will be 1 hour.
The discharge utilization rate of mold decreases.

When the mixing ratio of lead iodide and carbonyl nickel is a theoretical volume ratio of 4:0.5, the discharge utilization rate of the positive electrode decreases by about 30% when the mixing time is about 10 hours. Such a decrease in the discharge utilization rate is similar to early disconnection of the positive electrode resistance, suggesting a close relationship between the two. The reason why long-term ball mill mixing actually increases the resistance of the positive electrode and reduces the discharge utilization rate is thought to be because the well-developed structure of carbonyl nickel is destroyed by mixing. It is also noteworthy that partial aggregation of carbonyl nickel also occurs, which is considered to be one of the causes of the above.

Note that the resistance increases quickly when the mixing ratio is 4:0.5;
; The reason why it takes longer in case 1 is considered to be that even if some of the carbonyl nickel is destroyed and aggregated, the remaining carbonyl nickel still ensures electronic conductivity. Therefore, when the addition of carbonyl nickel -t is reduced, it is necessary to shorten the mixing time, and the mixing time is preferably within 10 hours at the longest. However, if the stirring time is too short, the mixing state may be insufficient, so the lower limit of the mixing time is preferably about 30 minutes, considering the stability of the mixing state, the internal resistance of the positive electrode, and the discharge utilization rate. A mixing time of 2 to 5 hours is considered particularly favorable.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the mixing time of lead iodide and carbonyl nickel and the internal resistance of the positive electrode, Fig. 2 is a cross-sectional view showing an example of a solid electrolyte battery according to the present invention, and Fig. It is a diagram showing the relationship between the mixing time of lead chloride and carbonyl nickel and the discharge utilization rate of the positive electrode. (2)...Positive electrode, (3)...Solid electrolyte layer Patent applicant Hitachi Maxell Co., Ltd. 72 Leefang 6 figure warm special +t+(h)

Claims (1)

[Claims] ■. 10 lead iocide powder and carbonyl nickel powder
A method for producing a positive electrode mixture for a solid electrolyte cell, which is characterized by being mixed within hours. 2. The method for producing a positive electrode mixture for a solid electrolyte battery according to claim 1, wherein the mixing time is 0.5 to 10 hours. 3. The method for producing a positive electrode mixture for a solid electrolyte battery according to claim 1, wherein the mixing time is 2 to 5 hours. 4. A method for producing a positive electrode mixture for a solid electrolyte battery according to claim 1, claim 2, or claim Ii, wherein the mixture is mixed in a ball mill. 5. The solid electrolyte battery according to claim 1, 2, 3, or 4, wherein the mixing ratio of lead iocide and carbonyl nickel is 4:1 to 4:0.25 in theoretical volume ratio. Method for producing positive electrode mixture for use. 6. The solid according to claim 1, 2, 3, or 4, wherein the mixing ratio of lead iodide and carbonyl nickel is 4: 0.75 to 4: 0.25 in theoretical volume ratio. A method for producing a positive electrode mixture for electrolyte batteries.