JP2021170464A - Manufacturing method of all-solid-state battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an all-solid-state battery capable of appropriately evaluating the performance of the all-solid-state battery without executing charging / discharging. A method for manufacturing an all-solid-state battery includes a voltage behavior acquisition step (S2) and a resistance prediction step (S14). In the voltage behavior acquisition step (S2), the voltage behavior of the all-solid-state battery when the all-solid-state battery that has not been charged after being assembled is heated and maintained at the target temperature is acquired. When the temperature of the all-solid-state battery reaches the target temperature, the voltage of the all-solid-state battery when the target temperature is reached is V0, and the maximum voltage of the all-solid-state battery when the voltage rise and fall after the target temperature is reached, or once stagnant. Let V1 be the voltage at the time of re-rise when the voltage rises again, and T1 be the elapsed time from the time when the target temperature is reached until the voltage becomes V1. In the resistance prediction step (S14), the resistance of the all-solid-state battery is predicted at least based on the difference between V1 and V0 and T1. [Selection diagram] Fig. 1

Description

The present invention relates to a method for manufacturing an all-solid-state battery.

Secondary batteries are widely used as a power source for driving vehicles such as EVs (electric vehicles), HVs (hybrid vehicles), and PHVs (plug-in hybrid vehicles). In the process of manufacturing a secondary battery, various methods for evaluating the performance of the manufactured secondary battery have been proposed. For example, the state of charge measuring device described in Patent Document 1 uses the voltage and current of the secondary battery detected at the start of charging or discharging of the secondary battery after a lapse of a predetermined time, and uses the voltage and current of the secondary battery to resist the secondary battery. Is calculated. The state of charge of the secondary battery is measured using the calculated resistance.

Japanese Unexamined Patent Publication No. 2013-142649

Conventional methods for evaluating the performance of manufactured secondary batteries require charging and discharging the secondary batteries. It would be very useful if the performance of the manufactured secondary battery could be evaluated without charging and discharging the secondary battery.

A typical object of the present invention is to provide a method for manufacturing an all-solid-state battery, which can appropriately evaluate the performance of the all-solid-state battery without performing charge / discharge.

In order to achieve such an object, one aspect of the method for manufacturing an all-solid-state battery disclosed herein is to heat an all-solid-state battery that has not yet been charged after being assembled and maintain it at a target temperature. The resistance includes a voltage behavior acquisition step of acquiring the voltage behavior of the all-solid-state battery and a resistance prediction step of predicting the resistance of the all-solid-state battery based on the voltage behavior acquired in the voltage behavior acquisition step. In the prediction step, the voltage of the all-solid-state battery when the temperature of the all-solid-state battery reaches the target temperature reaches V0, and the increase in the voltage after reaching the target temperature is once all the above-mentioned decrease. The maximum voltage of the solid-state battery, or the voltage at which the all-solid-state battery rises again when it stagnates and rises again is V1, and the elapsed time from when the target temperature is reached until the voltage of the all-solid-state battery reaches V1. Is T1, and the resistance of the all-solid-state battery is predicted based on at least the difference between V1 and V0 and T1.

In a secondary battery using an electrolytic solution, unlike an all-solid-state battery, a positive electrode and a negative electrode are separated from each other. Therefore, even if the secondary battery using the electrolytic solution is heated after being assembled, the charge carrier (for example, lithium ion or the like) is difficult to move, so that the voltage of the secondary battery does not increase. Further, in a secondary battery using an electrolytic solution, if the battery is left uncharged after assembly, the substance used for the electrode (for example, copper used for the negative electrode current collecting foil) is eluted into the electrolytic solution, and the battery Problems such as deterioration of performance may occur. On the other hand, when the all-solid-state battery is assembled and then heated, the voltage of the all-solid-state battery rises. In an all-solid-state battery, since the positive electrode, the negative electrode, and the solid electrolyte are adhered to each other, it is considered that the voltage rises by diffusing the charge carrier from the higher concentration to the lower concentration by heating. Further, in the all-solid-state battery, the problem of substance elution does not occur even if the battery is left uncharged after assembly.

Here, the inventor of the present application has a correlation between the resistance of the voltage behavior of the all-solid-state battery when heating the all-solid-state battery that has not been charged since it was assembled and maintaining it at the target temperature. I found that there is. Specifically, when the temperature of the all-solid-state battery reaches the target temperature (when the target temperature is reached), the voltage of the all-solid-state battery is set to V0. When the voltage rise after reaching the target temperature drops once, the maximum voltage of the all-solid-state battery, or when the voltage rise after reaching the target temperature stagnates and rises again, the all-solid-state battery reappears. Let the rising voltage be V1. Let T1 be the elapsed time from the time when the target temperature is reached until the voltage of the all-solid-state battery becomes V1. The inventor of the present invention has found that there is at least a correlation between the difference between V1 and V0 (ΔV1) and between T1 and the resistance of the all-solid-state battery.

In the method for manufacturing an all-solid-state battery according to the present disclosure, the resistance of the all-solid-state battery that correlates with these values is predicted based on at least the difference between V1 and V0 (ΔV1) and T1. Therefore, the resistance of the all-solid-state battery can be appropriately predicted without performing charging and discharging of the all-solid-state battery after assembly. When evaluating the resistance of an assembled secondary battery, in the conventional method, it is necessary to charge and discharge the secondary battery with a large current (for example, a current of 1C to 3C or more). On the other hand, according to the method for manufacturing an all-solid-state battery according to the present disclosure, the resistance of the all-solid-state battery can be appropriately predicted at a low cost.

The case where the voltage of the all-solid-state battery which has risen after reaching the target temperature falls once after reaching V1 and rises again will be described. In this case, the minimum voltage of the all-solid-state battery after reaching V1 is V2. Further, the voltage of the all-solid-state battery when the fluctuation of the amount of increase per unit time becomes equal to or less than the threshold value while the voltage is increasing after reaching V2 is defined as V3. In the resistance prediction step, the resistance of the all-solid-state battery may be predicted based on the difference between V1 and V0 (ΔV1), the difference between V3 and V2 (ΔV2), and T1. By considering ΔV2 in addition to ΔV1 and T1, the correlation between the voltage behavior and resistance of the all-solid-state battery becomes high. It is considered that this is because ΔV2 is caused by the diffusion resistance of the all-solid-state battery. Therefore, by predicting the resistance of the all-solid-state battery based on ΔV1, ΔV2, and T1, the prediction accuracy is further improved.

The case where the voltage of the all-solid-state battery which once stagnated after reaching the target temperature and became V1 then rises again will be described. In this case, the voltage of the all-solid-state battery when the fluctuation of the amount of increase per unit time becomes equal to or less than the threshold value while the voltage is increasing after reaching V2 is defined as V4. In the resistance prediction step, the resistance of the all-solid-state battery may be predicted based on the difference between V1 and V0 (ΔV1), the difference between V4 and V1 (ΔV2), and T1. By considering ΔV2 in addition to ΔV1 and T1, the correlation between the voltage behavior and resistance of the all-solid-state battery becomes high. It is considered that this is because ΔV2 is caused by the diffusion resistance of the all-solid-state battery. Therefore, by predicting the resistance of the all-solid-state battery based on ΔV1, ΔV2, and T1, the prediction accuracy is further improved.

However, even if only ΔV1 and T1 are used, there is a correlation with the resistance of the all-solid-state battery. Therefore, the resistance of the all-solid-state battery may be predicted based only on ΔV1 and T1 without referring to ΔV2.

Prediction algorithm for determining the predicted value of resistance from the voltage behavior based on the voltage behavior when maintaining the temperature at the target temperature and the measured value of resistance obtained for each of multiple all-solid-state batteries of the same type. (For example, a calculation formula or a table, etc.) may be constructed. In the resistance prediction step, the predicted value of the resistance of the all-solid-state battery may be obtained by applying the voltage behavior acquired in the voltage behavior acquisition step to the prediction algorithm. In this case, the resistance of the all-solid-state battery is appropriately predicted according to the algorithm constructed according to the type of the all-solid-state battery.

The method of constructing the prediction algorithm can be appropriately selected. For example, the voltage behavior (for example, ΔV1 ・ T1 or ΔV1 ・ ΔV2 ・ T1) obtained for each of a plurality of all-solid-state batteries when maintaining the temperature at the target temperature and the measured resistance value are large. By performing a multivariate analysis, a correlation equation may be constructed to determine the predicted value of the resistance.

It is a flowchart of the manufacturing method of an all-solid-state battery. It is a graph which shows an example of the relationship between the elapsed time and the voltage of an all-solid-state battery when a plurality of all-solid-state batteries are heated to a target temperature and left uncharged. It is a graph which shows an example of the relationship between the elapsed time and the voltage of an all-solid-state battery when the voltage takes a maximum value and a minimum value during heating. It is a graph which shows an example of the relationship between the elapsed time and the voltage of an all-solid-state battery when the voltage does not take the maximum value and the minimum value during heating. It is a graph which plotted the measured value of the resistance and the calculated value (predicted value) of the resistance predicted by the method shown in this embodiment for each of a plurality of all-solid-state batteries. It is a graph which plotted the measured value of the resistance and the calculated value (predicted value) of the resistance predicted based on ΔV1 and T1 for each of a plurality of all-solid-state batteries.

Hereinafter, one of the typical embodiments in the present disclosure will be described in detail with reference to the drawings. Matters other than those specifically mentioned in the present specification and necessary for implementation (for example, the configuration of an all-solid-state battery) can be grasped as design matters of a person skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art.

First, a schematic configuration of an all-solid-state lithium-ion secondary battery (hereinafter, may be simply referred to as an “all-solid-state battery”), which is an example of an all-solid-state battery manufactured by the manufacturing method exemplified in the present disclosure, will be described. However, the all-solid-state battery to which the manufacturing method in the present disclosure is applied is not limited to the all-solid-state lithium ion secondary battery. That is, the all-solid-state battery may be a battery using a metal ion other than lithium ion as an electric carrier, for example, a sodium ion secondary battery, a magnesium ion secondary battery, or the like.

The all-solid-state battery includes a positive electrode, a solid electrolyte layer (separator layer), and a negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer. The negative electrode includes a negative electrode current collector and a negative electrode active material layer. The solid electrolyte layer is arranged between the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode. The solid electrolyte layer also functions as a separator that insulates between the positive electrode and the negative electrode.

The solid electrolyte layer contains at least a solid electrolyte. Examples of the solid electrolyte include a sulfide-based solid electrolyte and an oxide-based solid electrolyte. Examples of the sulfide-based solid _electrolyte, Li ₂ S-SiS 2 _{system, Li 2 S-P 2 S} 3 _{system, Li 2 S-P 2 S} 5 _based, Li ₂ S-GeS 2 system, _Li 2 S- Examples include glass or glass ceramics such as B ₂ S _{3 series.} Examples of oxide-based electrolytes include various oxides having a NASICON structure, a garnet-type structure, or a perovskite-type structure. The solid electrolyte is, for example, in the form of particles.

The positive electrode active material layer contains at least the positive electrode active material. The positive electrode active material layer preferably further contains a solid electrolyte, and may further contain a conductive material, a binder (binding material), and the like. As the positive electrode active material, various compounds conventionally used in this type of battery can be used. Examples of positive electrode active materials include _{layered composite oxides such as LiCoO 2} and LiNiO ₂ , spinel-structured composite oxides such as Li ₂ Nimn ₃ O ₈ and LiMn ₂ O ₄ , and olivine-structured composite compounds such as _{LiFePO 4.} , Etc. can be mentioned. As the solid electrolyte in the positive electrode active material layer, the same kind of material as the solid electrolyte contained in the solid electrolyte layer can be used. The positive electrode active material is, for example, in the form of particles.

The negative electrode active material layer contains at least the negative electrode active material. The negative electrode active material layer preferably further contains a solid electrolyte, and may further contain a conductive material, a binder, and the like. As the negative electrode active material, various compounds conventionally used in this type of battery can be used. Examples of the negative electrode active material include carbon-based negative electrode active materials such as graphite, mesocarbon microbeads, and carbon black. Further, as an example of the negative electrode active material, a negative electrode active material containing silicon (Si) or tin (Sn) as a constituent element can be mentioned. As the solid electrolyte in the negative electrode active material layer, the same kind of material as the solid electrolyte contained in the solid electrolyte layer can be used. The negative electrode active material is, for example, in the form of particles.

As the positive electrode current collector, those used as the positive electrode current collector of this type of battery can be used without particular limitation. Typically, the positive electrode current collector is preferably made of a metal having good conductivity. The positive electrode current collector may be made of a metal material such as aluminum, nickel, titanium, or stainless steel. As the negative electrode current collector, those used as the negative electrode current collector of this type of battery can be used without particular limitation. Typically, the negative electrode current collector is preferably made of a metal having good conductivity. As the negative electrode current collector, for example, copper (copper foil) or an alloy mainly composed of copper can be used.

The manufacturing method (resistance prediction method) of the all-solid-state battery in the present embodiment will be described with reference to FIGS. 1 to 5. First, an all-solid-state battery (for example, the all-solid-state lithium-ion secondary battery described above in the present embodiment) is assembled (S1). That is, the manufacturer of the all-solid-state battery assembles the all-solid-state battery by accommodating the power generation element including the positive electrode, the solid electrolyte layer (separator layer), and the negative electrode inside the battery case.

Next, the manufacturer acquires the voltage behavior of the all-solid-state battery when the all-solid-state battery that has not been charged after being assembled in S1 is heated and maintained at the target temperature (S2). For example, the manufacturer arranges an all-solid-state battery to which a voltage logger or the like for measuring and recording a voltage is connected in a temperature-adjustable constant temperature bath or the like, and heats the all-solid-state battery to a target temperature. When the temperature of the all-solid-state battery reaches the target temperature, the temperature is maintained at the target temperature. The voltage of the all-solid-state battery during this period is recorded for each elapsed time. When the step of acquiring the voltage behavior (S2) is completed, the heated all-solid-state battery is cooled (S3).

The target temperature for heating the all-solid-state battery is preferably set to 60 ° C to 80 ° C. The target temperature set in this embodiment is 80 ° C. However, the target temperature may be appropriately changed according to the type of the all-solid-state battery and the like.

FIG. 2 is a graph showing an example of the relationship between the elapsed time and the voltage when a plurality of all-solid-state batteries are heated and left uncharged. As shown in FIG. 2, when the assembled all-solid-state battery is heated in an uncharged state, the voltage of each all-solid-state battery first rises significantly, then falls or stagnates, and then gradually rises again. It turns out that there is a tendency. The inventor of the present invention has found that there is a correlation between the voltage behavior of the all-solid-state battery illustrated in FIG. 2 and the resistance of the all-solid-state battery. Since there is a correlation between the voltage behavior and resistance of the all-solid-state battery during heating, the resistance of the all-solid-state battery can be predicted based on the voltage behavior without performing charging / discharging of the all-solid-state battery.

Specifically, the voltage of the all-solid-state battery during heating rises and then falls once and then gradually rises again (see FIG. 3), and rises and then stagnates once and then gradually rises again (see FIG. 3). (See FIG. 4). In the graphs of FIGS. 3 and 4, the time at which the temperature of the all-solid-state battery rises and reaches the target temperature (when the target temperature is reached) is set to “0”.

As shown in FIG. 3, when the voltage rises and then falls once, the voltage of the all-solid-state battery rises after reaching the target temperature to reach the maximum voltage V1, and then drops once to reach the minimum voltage V2. After that, it gradually rises again. After the voltage becomes the minimum voltage V2, the voltage when the fluctuation of the amount of increase in voltage per unit time becomes equal to or less than the threshold value (that is, the amount of increase in voltage is substantially constant) is defined as the constant increase voltage V3.

When there are a maximum voltage and a minimum voltage in the transition of the voltage of the all-solid-state battery acquired in S2 (in the case illustrated in FIG. 3) (S5: YES), the voltage V0, the maximum voltage V1, and the minimum when the target temperature is reached. The voltage V2, the constant rising voltage V3, and the elapsed time T1 from the voltage V0 when the target temperature is reached to the maximum voltage V1 are acquired as the voltage behavior of the all-solid-state battery (S6). Next, the difference between V1 and V0 is acquired as ΔV1, and the difference between V3 and V2 is acquired as ΔV2 (S7).

Further, as shown in FIG. 4, the voltage of the all-solid-state battery may rise after reaching the target temperature, and then temporarily stagnate and rise again without taking the maximum value and the minimum value. In this case, the voltage at the time when the voltage rise once stagnates and then rises again (that is, the voltage at the inflection point in the graph of FIG. 4) is defined as the voltage at the time of the rise again V1. After the voltage becomes the voltage V1 when rising again, the voltage when the fluctuation of the amount of voltage rise per unit time becomes less than the threshold value (that is, the amount of voltage rise is substantially constant) is defined as the constant rising voltage V4. do.

When there is no maximum voltage and minimum voltage in the voltage transition of the all-solid-state battery acquired in S2 (in the case illustrated in FIG. 4) (S5: NO), the voltage V0 when the target temperature is reached and the voltage V1 when the voltage rises again. , The constant rising voltage V4 and the elapsed time T1 from the voltage V0 at the time of reaching the target temperature to the voltage V1 at the time of re-rising are acquired as the voltage behavior of the all-solid-state battery (S8). Next, the difference between V1 and V0 is acquired as ΔV1, and the difference between V4 and V1 is acquired as ΔV2 (S9).

Next, it is determined whether or not the correlation between the voltage behavior and the resistance is known for the type of all-solid-state battery for which the resistance is predicted (S11). That is, in S11, it is determined whether or not a prediction algorithm for determining the predicted value of the resistance is constructed from the voltage behavior.

If the correlation between voltage behavior and resistance is unknown (S11: NO), a step for building a prediction algorithm is performed (S12, S13). Specifically, first, the resistance R of the all-solid-state battery from which the voltage behavior has been acquired is measured (S12). As an example, in the present embodiment, the relationship between the voltage and the current when the all-solid-state battery is charged and then discharged until the SOC (State Of Charge) reaches 100%, and the battery is discharged at 3C for 10 seconds from the state where the SOC is 30%. Then, the discharge resistance is measured for 10 seconds. Next, a prediction algorithm is constructed based on the voltage behavior (ΔV1, ΔV2, T1) and the measured value R of the resistor (S13). As an example, in the present embodiment, a correlation equation for determining the predicted value of resistance is obtained by performing multivariate analysis on the measured values of voltage behavior and resistance acquired for each of a plurality of all-solid-state batteries. , Build as a prediction algorithm. An example of the correlation equation constructed (Equation 1) is shown below. In the following (Equation 1), Rp is a predicted value of resistance, and a, b, c, and d are coefficients and intercepts determined according to the type of all-solid-state battery.
Rp = a × ΔV1 + b × T1 + c × ΔV2 + d ... (Equation 1)

It is also possible to change the method of constructing the prediction algorithm. For example, a table or the like for determining the predicted value of the resistance based on the voltage behavior may be constructed as the prediction algorithm.

When the correlation between the voltage behavior and the resistance is known (when the prediction algorithm is constructed) (S11: YES), the resistance of the all-solid-state battery is based on the voltage behavior (ΔV1, ΔV2, T1). Predicted (S14). Specifically, in the present embodiment, the predicted value of the resistance of the all-solid-state battery is obtained by applying the voltage behavior (ΔV1, ΔV2, T1) to the above-mentioned (Equation 1).

Here, for each of a plurality of all-solid-state batteries of the same type, a graph plotting the calculated resistance value (predicted value) predicted by the method shown in S14 and the measured value measured by the method shown in S12 is shown. It is shown in FIG. As shown in FIG. 5, both the measured value and the calculated value (predicted value) are close to each other, and there is a correlation of R ^ 2 = 0.7338 between the two. As described above, it can be seen that the resistance of the all-solid-state battery can be predicted with high accuracy by the method shown in the present embodiment without executing charging / discharging.

Next, the quality of the all-solid-state battery is determined based on the resistance measured in S12 or the resistance predicted in S14 (S16). For example, an all-solid-state battery whose measured or predicted resistance is equal to or less than a threshold value may be judged as a non-defective product. All-solid-state batteries judged to be non-defective are charged and shipped after their capacity is inspected.

Although the detailed description has been given with reference to specific embodiments, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the above-described embodiments. For example, in the above embodiment, the resistance of the all-solid-state battery is predicted with high accuracy after considering ΔV2 (V3-V2 or V4-V1) in addition to ΔV1 (V1-V0) and the elapsed time T1. NS. It is considered that this is because ΔV2 is caused by the diffusion resistance of the all-solid-state battery. However, it is also possible to predict the resistance of an all-solid-state battery based only on ΔV1 and T1 without considering ΔV2.

FIG. 6 is a graph in which the calculated resistance value (predicted value) predicted based only on V1 and T1 and the measured value measured by the method shown in S12 are plotted for each of a plurality of all-solid-state batteries of the same type. Shown in. The prediction algorithm (correlation formula) for calculating the predicted value shown in FIG. 6 is constructed based on the voltage behaviors ΔV1 and T1 and the measured value R of the resistance. As shown in FIG. 6, the calculated value (predicted value) of the resistance predicted based only on V1 and T1 is also close to the measured value. There was a correlation of R ^ 2 = 0.5231 between the calculated value and the measured value. As described above, even when only ΔV1 and T1 are used as the voltage behavior, the accuracy is slightly lower than when ΔV2 is also used, but it can be seen that the resistance of the all-solid-state battery can be appropriately predicted. In other words, in the above embodiment in which ΔV2 is also used as the voltage behavior, it can be said that the resistance of the all-solid-state battery can be predicted with higher accuracy.

Claims (1)

It is a manufacturing method of all-solid-state batteries.
A voltage behavior acquisition step for acquiring the voltage behavior of the all-solid-state battery when heating the all-solid-state battery that has not been charged since it was assembled and maintaining it at the target temperature.
A resistance prediction step for predicting the resistance of the all-solid-state battery based on the voltage behavior acquired in the voltage behavior acquisition step, and a resistance prediction step.
Including
In the resistance prediction step,
When the temperature of the all-solid-state battery reaches the target temperature, the voltage of the all-solid-state battery when the target temperature is reached is set to V0.
The voltage rise after reaching the target temperature is the maximum voltage of the all-solid-state battery when it falls once, or the voltage when the all-solid-state battery rises again when it stagnates and rises again.
When the elapsed time from the time when the target temperature is reached until the voltage of the all-solid-state battery reaches V1 is T1.
A method for manufacturing an all-solid-state battery, which comprises predicting the resistance of the all-solid-state battery based on at least the difference between V1 and V0 and T1.

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