JP7450978B2 - Evaluation device, evaluation method, and program for metal-air batteries - Google Patents

Description

The present invention relates to an evaluation device, an evaluation method, and a program for continuously and automatically evaluating battery characteristics of metal-air batteries.

In recent years, with the spread of renewable energy and the demand for electrification of automobiles, there has been a demand for the development of storage batteries that are lightweight and have large capacity, that is, higher energy density. Among the secondary batteries that can be expected to be realized, lithium-air batteries have the highest theoretical energy density, and can achieve an energy density that significantly exceeds the currently popular lithium-ion batteries.

Lithium-air batteries use lithium metal as the negative electrode active material and atmospheric oxygen as the positive electrode active material. During discharging, the lithium metal negative electrode is eluted (Li⇔Li ⁺ +e ⁻ ), reacts with oxygen absorbed from the atmosphere at the positive electrode, and precipitates lithium peroxide (2Li ⁺ +2e ⁻ +O ₂ ⇔Li ₂ O ₂ ). During charging, the opposite reaction occurs, and these reactions are repeated to perform charging and discharging. The positive electrode is also called an air electrode because it has the function of absorbing and exhausting atmospheric oxygen during charging and discharging.

In order to improve the charge/discharge cycle characteristics of a lithium-air battery cell, it is necessary to create a situation in which the above-mentioned electrochemical reaction at the air electrode proceeds reversibly with nearly 100% efficiency. Therefore, it is necessary to accurately measure and determine the "efficiency" of these battery reactions, but these methods are often limited and lack accuracy and reliability, and they do not reflect the actual environment in which cells are charged and discharged. In many cases, it is not something that can be done.

_At present, _there ^{are 1} _. 2. A method for quantifying Li ₂ O ₂ precipitated and decomposed on the air electrode by titration; Methods for quantifying oxygen gas absorbed and discharged into cells have been devised and widely studied.

However, 1. The amount of Li ₂ O ₂ detected by the above method is less than 90% of the amount estimated to be generated from the amount of discharge or charge, and the generated Li ₂ O ₂ may not be completely captured. Alternatively, it is unclear whether charging and discharging are actually proceeding with a battery reaction efficiency of 90% or less. Furthermore, since it is necessary to prepare a plurality of cells with different discharge/charge states and individually disassemble and titrate them, the workability is low and there is large variation due to individual differences (for example, see Non-Patent Document 1).

2. The method for quantifying the amount of oxygen absorbed and discharged into a cell is to discharge the cell in a sealed casing and measure the oxygen partial pressure that decreases. Charging is done by replacing the casing with inert gas, charging the cell, and collecting and measuring the entire amount of exhausted oxygen. Since the pressure varies depending on the discharge/charge state, there is a problem that the measurement does not reflect the actual cell environment, such as the atmospheric environment (for example, see Non-Patent Document 1). Furthermore, it is difficult to track reaction efficiency over multiple cycles because it is necessary to replace the gas and change the measurement method when switching between discharging and charging.

On the other hand, recent progress has been made in the development of electrolytes and electrode materials for lithium-air battery cells, and the capacity and number of cycles that can be discharged and charged are increasing. Accordingly, there is a need to establish a measurement method that can accurately and easily evaluate battery reaction efficiency during long-term, multi-cycle charging and discharging operation (see, for example, Non-Patent Document 2).

In addition, cells designed to handle larger currents and have larger electrode areas and laminated structures than those used for basic battery reaction testing have begun to be developed. There is a need to develop a method for measuring how much the electrolyte evaporates through the air holes in an atmospheric environment or an oxygen flow environment (for example, see Non-Patent Document 3). In addition, in an atmospheric environment, it is necessary to investigate how much impurity gases contained in the atmosphere, such as water and carbon dioxide, that are not involved in normal battery reactions are absorbed by the cell.

Among these, the mass of the cell is noteworthy. Lithium-air battery cells absorb and emit oxygen as they discharge and charge, which causes their weight to change little by little. The amount of oxygen fixed in the cell can be measured from the cell's discharge/charge capacity and weight change, and the battery reaction efficiency can be estimated. Further, the amount of volatilization of the electrolyte can be estimated from minute changes in cell weight when no current is applied (during rest). However, since it is not possible to continuously weigh a cell that has been left still for a long period of time, estimates can only be made by comparing cell weights before and after discharging and charging, or after a certain period of time.

Bryan D. McCloskey et al., J. Phys. Chem. Lett. ,2013,4,2989-2993 Akihiro Nomura et al., Sci. Rep. ,2017,7,45596 Yoshimi Kubo et al., ECS Transactions, 62, 1, 129-135, 2014

In view of the above, an object of the present invention is to provide an evaluation device, a method thereof, and a program thereof, which continuously and automatically evaluate the battery characteristics of a metal-air battery.

An evaluation device for evaluating battery characteristics of a metal-air battery according to the present invention includes a weight measuring section for measuring the weight of the metal-air battery, and a stage for placing the metal-air battery, and an elevator for raising and lowering the stage. a housing that accommodates at least the weight measuring section and the metal air battery; a charging and discharging characteristic measuring section that measures the charging and discharging characteristics of the metal air battery; the elevating section, the weight measuring section and the charging and discharging section; a control section that controls the operation with the discharge characteristic measurement section and evaluates the battery characteristics of the metal-air battery; the control section raises and lowers the stage of the elevating section; a measurement control unit that executes a measurement by a characteristic measurement unit and obtains the amount of weight change and charge/discharge characteristics of the metal-air battery; and based on the amount of weight change and the charge/discharge characteristics obtained by the measurement control unit, The present invention includes a calculation/evaluation section that calculates and evaluates battery characteristics of the metal-air battery, thereby solving the above problem.
The calculation/evaluation unit calculates a weight change amount difference Wt between a weight change amount Wt _r at time t _r and a weight change amount Wt _r0 at time t _r0 (where t _r >t _r0 ) during rest of the charge/discharge characteristics. The method may further include an electrolyte volatilization rate calculation unit that divides _r - Wt _r0 by the time difference t _r -t _r0 and calculates the electrolyte volatilization rate ((Wt _r - Wt _r0 )/(t _r -t _r0 )). good.
The calculation/evaluation unit calculates the electrolyte volatilization rate at the time _{t d} estimated from the weight change amount at the time t d during discharging of the charge/discharge characteristics using the electrolyte volatilization rate during rest immediately before the discharge. The discharge weight change amount calculation unit may further include a discharge weight change amount calculation unit that calculates a weight change amount due only to the discharge reaction.
The calculation/evaluation unit divides the amount of weight change due only to the discharge reaction at the time interval Δt _d during discharging of the charge/discharge characteristics calculated by the discharge weight change calculation unit by the time interval Δt _d . , Calculate the rate of weight change, divide the current value used to measure the charge/discharge characteristics by the rate of weight change, and calculate the number of electrons reacting with the air absorbed in the metal-air battery.The number of reaction electrons. It may further include a calculation unit.
The calculation/evaluation unit calculates the electrolyte volatilization rate at the time t _c estimated from the amount of weight change at the time t _c during charging of the charge/discharge characteristics using the electrolyte volatilization rate during rest immediately before the charging. The battery may further include a charged weight change amount calculation unit that calculates a weight change amount due only to the charging reaction.
The calculation/evaluation unit divides the amount of weight change due only to the charging reaction of the charging/discharging characteristic during the charging time interval Δt _c calculated by the charged weight change calculation unit by the time interval Δt _c . , a reaction of calculating the rate of weight change, dividing the current value used to measure the charge/discharge characteristics by the rate of weight change, and calculating the number of electrons required to discharge the air fixed in the metal-air battery. It may further include an electron number calculation section.
The calculation/operation section is a capacitance calculation section that calculates capacitance from the time ΔT required for weight change to occur after the start of discharging of the charge/discharge characteristics and the current value flowing during the time ΔT. It may further include.
The control section may further include a display section that displays the results of the calculation/evaluation section.
The housing may further include a temperature detection section.
The housing may further include an air pressure detection section.
The control unit may further include a weight value correction unit that corrects the weight value obtained by the weight measurement unit using a sensitivity drift value of the weight measurement unit.
The housing may include a gas supply port and a gas exhaust port.
The device may further include a temperature control device that maintains the temperature inside the housing.
The method for evaluating the battery characteristics of a metal-air battery according to the present invention includes repeating the steps of placing the metal-air battery at a measurement position of a weight measurement unit and separating the metal-air battery from the measurement position. repeatedly measuring the weight of the metal-air battery, simultaneously measuring the weight repeatedly, measuring the charge/discharge characteristics of the metal-air battery, the amount of weight change obtained by the repeated measurements, and the charge/discharge The method includes calculating and evaluating the battery characteristics of the metal-air battery based on the charge-discharge characteristics obtained by measuring the characteristics, thereby solving the above problem.
What is calculated and evaluated is the weight change amount difference between the weight change amount Wt _r at time t _r and the weight change amount Wt _r0 at time t _r0 (however, t _r > t _r0 ) during the rest of the charge/discharge characteristics. The method may further include dividing Wt _r -Wt _r0 by the time difference t _r -t _r0 to calculate the electrolyte volatilization rate ((Wt _r -Wt _r0 )/(t _r -t _r0 )).
The calculation/evaluation is based on the amount of weight change at time t _d during discharging of the charge/discharge characteristics, and the electrolyte solution at time t _d estimated using the electrolyte volatilization rate during rest immediately before the discharge. It may further include reducing the amount of volatilization and calculating the amount of weight change due only to the discharge reaction.
The calculation and evaluation includes dividing the weight change amount due only to the discharge reaction during the time interval Δt _d during discharging of the calculated charge/discharge characteristics by the time interval Δt _d to calculate the weight change rate. However, the method may further include dividing the current value used for measuring the charge/discharge characteristics by the weight change rate to calculate the number of electrons reacting with the air absorbed in the metal-air battery.
The calculation/evaluation is based on the amount of weight change at time t _c during charging of the charge/discharge characteristics, and the electrolyte solution at time t _c estimated using the electrolyte volatilization rate during rest immediately before the charging. It may further include subtracting the amount of volatilization and calculating the amount of weight change due only to the charging reaction.
The calculation and evaluation includes dividing the amount of weight change caused only by the charging reaction during the charging time interval Δt _c of the calculated charge/discharge characteristics by the time interval Δt _c to calculate the weight change rate. However, the method may further include calculating the number of electrons required for discharging the air fixed in the metal-air battery by dividing the current value used for measuring the charge-discharge characteristics by the weight change rate. good.
The calculating and evaluating further includes calculating the capacitance from the time ΔT required for the weight change to occur after the start of discharge of the charge/discharge characteristics and the current value flowing during the time ΔT. You may.
Prior to the repeated measurement, the weight of the constant weight item is repeatedly measured by repeatedly placing the constant weight item at the measurement position of the weight measurement unit and separating the constant weight item from the measurement position. Measuring the temperature change and/or pressure change in the measurement environment simultaneously with the repeated measurement of the weight of the constant weight item; and determining whether or not the weight has fluctuated due to a change in atmospheric pressure; and if it is determined in the determination that the weight has fluctuated, correcting the weighed value with a sensitivity drift value of the weight measuring section; It may further include not correcting the weighed value if it is determined that there is no variation.
The method may further include flowing an atmosphere control gas into the measurement environment prior to the repeated measurements.
The program for evaluating the battery characteristics of the metal-air battery of the present invention repeats placing the metal-air battery at the measurement position of the weight measurement unit and separating the metal-air battery from the measurement position, a function to repeatedly measure the weight of the metal-air battery, a function to simultaneously measure the charge/discharge characteristics of the metal-air battery at the same time as the repeated measurement of the weight, the amount of change in weight obtained by the repeated measurement, and the charge/discharge The above problem is solved by making a computer realize a function of calculating and evaluating the battery characteristics of the metal air battery based on the charge/discharge characteristics obtained by measuring the characteristics.
The function to calculate and evaluate is the weight change amount difference between the weight change amount Wt _r at time t _r and the weight change amount Wt _r0 at time t _r0 (however, t _r > t _r0 ) during the rest of the charge/discharge characteristics. It may further include a function of dividing Wt _r -Wt _r0 by the time difference t _r -t _r0 to calculate the electrolyte volatilization rate ((Wt _r - Wt _r0 )/(t _r -t _r0 )).
The function to calculate and evaluate the electrolytic solution at the time t _d estimated from the weight change amount at the time t _d during discharging of the charge/discharge characteristics using the electrolytic solution volatilization rate during the rest immediately before the discharging. It may further include a function of reducing the amount of volatilization and calculating the amount of weight change due only to the discharge reaction.
The calculation/evaluation function calculates the rate of weight change by dividing the amount of weight change caused only by the discharge reaction during the time interval Δt _d during discharging of the calculated charge/discharge characteristics by the time interval Δt _d . However, the method may further include a function of dividing the current value used for measuring the charge/discharge characteristics by the weight change rate to calculate the number of electrons reacting with the air absorbed in the metal-air battery.
The function to calculate and evaluate the electrolytic solution at the time t c estimated from the amount of weight change at the time t _c during charging of the charge/discharge characteristics using the electrolytic solution volatilization rate during the rest immediately before _the charging. It may further include a function of reducing the amount of volatilization and calculating the amount of weight change due only to the charging reaction.
The calculation/evaluation function calculates the rate of weight change by dividing the amount of weight change caused only by the charging reaction of the calculated charge/discharge characteristics during the charging time interval _Δtc by the time interval _Δtc . However, the method may further include a function of dividing the current value used for measuring the charge/discharge characteristics by the rate of weight change to calculate the number of electrons required to discharge the air fixed in the metal-air battery.
The calculation/evaluation function further includes a function of calculating the capacitance from the time ΔT required for the weight change to occur after the start of discharging of the charge/discharge characteristics and the current value flowing during the time ΔT. But that's fine.

As described above, the evaluation device for evaluating the battery characteristics of a metal-air battery of the present invention includes an elevating section and performs zero point correction of the weight measuring section every time a measurement is made. This allows the weight change of the metal-air battery to be continuously and accurately measured over a long period of time. In addition, since the measurement of weight change by the weight measurement section and the charge/discharge measurement by the charge/discharge characteristic measurement section are carried out simultaneously, it is possible to determine the It is possible to calculate the electrolyte volatilization rate, the amount of weight change due to discharge or charge reactions, the number of electrons required to absorb or discharge air (oxygen), the capacitance, etc., and the performance evaluation of metal-air batteries can be continuously improved over a long period of time. Can be executed with precision.

The metal-air battery evaluation method of the present invention involves repeatedly measuring the weight of the metal-air battery, measuring the charge-discharge characteristics at the same time, and evaluating the battery characteristics of the metal-air battery based on the obtained weight change and charge-discharge characteristics. evaluate. Various battery characteristics are evaluated based on the amount of weight change over time, which is zero-point corrected each time the weight is measured, and the associated charging/discharging characteristics over time, making it possible to evaluate the performance of metal-air batteries over a long period of time. It can be performed continuously and with high accuracy over a period of time. Further, the present invention provides a program for a computer to execute such functions.

Schematic diagram showing an evaluation device of the present invention Block diagram showing the configuration of the control unit of the evaluation device of the present invention Diagram showing an example graphical user interface (GUI) screen Diagram showing an exemplary weight measurement condition settings screen Diagram showing exemplary weight measurement results Diagram showing another exemplary weight measurement condition settings screen Diagram showing another exemplary weight measurement result Diagram showing an exemplary charge/discharge characteristic measurement condition setting screen Diagram showing an exemplary evaluation item setting screen Showing exemplary results Diagram showing another exemplary result Flowchart showing a method for evaluating battery characteristics of the metal-air battery of the present invention Flowchart showing a method for evaluating battery characteristics of another metal-air battery of the present invention Diagram showing the charge/discharge characteristic measurement condition setting screen of Example 1 Diagram showing the amount of weight change and charge/discharge characteristics of the lithium ion battery of Example 1 Diagram showing the amount of weight change and temperature change of the lithium ion battery of Example 1 Diagram showing the amount of weight change and temperature change of the lithium ion battery of Example 2 Diagram showing the charge/discharge characteristic measurement condition setting screen of Example 3 Diagram showing the results of battery characteristics of the lithium-air battery of Example 3 A diagram showing another result of the battery characteristics of the lithium-air battery of Example 3 Diagram showing the weight measurement condition setting screen of Example 4 Diagram showing the results of battery characteristics of the lithium-air battery of Example 4 A diagram showing another result of the battery characteristics of the lithium-air battery of Example 4 A diagram showing another result of the battery characteristics of the lithium-air battery of Example 4 A diagram showing another result of the battery characteristics of the lithium-air battery of Example 4

Embodiments of the present invention will be described below with reference to the drawings. Note that similar elements are given similar numbers and their explanations will be omitted.

FIG. 1 is a schematic diagram showing an evaluation device of the present invention.

The evaluation device 100 of the present invention measures battery characteristics of a metal-air battery. Here, the metal-air batteries in question are metal batteries that interact with external gas, such as lithium-air batteries, lithium-carbon dioxide batteries, sodium-air batteries, zinc-air batteries, iron-air batteries, aluminum-air batteries, and magnesium-air batteries. be. In the following description, for simplicity, a lithium-air battery is used as the metal-air battery and the external gas is oxygen. Note that in this specification, external gas may be collectively referred to simply as air.

The evaluation device 100 of the present invention includes a weight measurement unit 110 that measures the weight of a metal-air battery (shown as a cell in FIG. 1), and a stage 120 on which the metal-air battery is placed, and that raises and lowers the stage 120. an elevating section 130, a casing 140 that accommodates at least the weight measuring section 110 and the metal-air battery, a charge-discharge characteristic measuring section 150 that measures the charge-discharge characteristics of the metal-air battery, the elevating section 130 and the weight measuring section 110. It includes a control section 160 that controls the operation with the charge/discharge characteristic measurement section 150 and evaluates the battery characteristics of the metal-air battery.

With such a configuration, the evaluation device 100 of the present invention can accurately measure the weight change of the metal-air battery over a long period of time, simultaneously measure the weight and charge/discharge measurement of the metal-air battery, and compare the results. Since they are stored in association with each other, it is possible to calculate the electrolyte volatilization rate, weight change due to charging and discharging, number of electrons due to reaction and discharge of air, capacitance, etc. associated with the charge/discharge reaction of the metal-air battery. performance evaluation can be performed with high accuracy over a long period of time. Hereinafter, each component will be explained in detail.

The weight measurement unit 110 is not particularly limited as long as it can measure the weight of the metal-air battery, but an example is an electronic balance. Although the weight measurement unit 110 is connected to the control unit 160 by wire in FIG. 1, it may be connected to the control unit 160 by wireless communication such as Wi-Fi (registered trademark) and Bluetooth.

The elevating section 130 includes a stage 120 on which the metal-air battery is placed, and the stage 120 is placed at the measurement position of the weight measurement section 110 (left diagram in FIG. 1) and the position where the stage 120 is separated from the weight measurement section 110 (see (Figure on the right) is equipped with a drive mechanism such as a motor that repeatedly moves up and down. In this way, the weight of the metal-air battery is measured by the lifting unit 130 at intervals set by the user. As a result, when measuring the weight of the metal-air battery, zero point correction is performed for each measurement, and the weight of the metal-air battery is accurately measured. Although the elevator unit 130 is connected to the control unit 160 by wire in FIG. 1, it may be connected to the control unit 160 by wireless communication such as Wi-Fi (registered trademark) and Bluetooth.

The housing 140 houses at least the weighing pan and the metal air battery of the weight measuring section 110, and functions to control the environment such as temperature and atmosphere during measurement. The housing 140 preferably includes a gas inlet 170 and a gas outlet 180, and the gas inlet 170 may be connected to an atmosphere control gas so that the atmosphere within the housing 140 can be controlled. Oxygen gas, carbon dioxide gas, and rare gases such as nitrogen, argon, helium, and xenon can be used as such atmosphere control gases. In addition, in FIG. 1, the housing 140 is shown to include the elevating section 130 in addition to the weight measuring section 110 and the metal-air battery, but it is not essential to include the elevating section 130.

The charge/discharge characteristic measuring section 150 may be a charge/discharge tester that measures the discharge/charge/discharge characteristics of the metal-air battery during rest (rest or no current), charging, and discharging. The charge/discharge characteristic measuring section 150 is connected to the metal-air battery via a conductive wire. Although there is no particular restriction on such a conductive wire, a copper wire, a carbon nanotube wire, a gold wire, or the like having a diameter of 10 μm or more and 250 μm or less can be used in consideration of the influence on the amount of weight change of the weight measurement unit 110. Among these, a gold wire having a diameter of 10 μm or more and 50 μm or less is preferable because it has a small influence on the amount of weight change.

Although the charging/discharging characteristic measuring section 150 is connected to the control section 160 by wire in FIG. 1, it may be connected to the control section 160 by wireless communication such as Wi-Fi (registered trademark) and Bluetooth. . Further, the charge/discharge characteristic measuring section 150 does not need to be housed in the casing 140, but may be housed depending on the capacity of the casing 140.

The evaluation device 100 of the present invention may further include a temperature detection section 190 within the housing 140. Thereby, the temperature inside the housing 140 can be measured. Such temperature detection unit 190 may be a thermocouple, for example. Although the temperature detection unit 190 is connected to the control unit 160 by wire in FIG. 1, it may be connected to the control unit 160 by wireless communication such as Wi-Fi (registered trademark) and Bluetooth.

The evaluation device 100 of the present invention may further include an air pressure detection section (not shown) within the housing 140. Thereby, the atmospheric pressure inside the housing 140 can be measured. Such an atmospheric pressure detection unit may be a barometer, for example. Similar to the temperature detection section 190, the atmospheric pressure detection section may also be connected to the control section 160 by wire or wirelessly. The evaluation device 100 may include both the temperature detection section 190 and the atmospheric pressure detection section, or either one, but by including both, the influence of temperature and atmospheric pressure on the amount of weight change of the metal-air battery can be reduced. Since measurements can be taken with this in mind, highly accurate evaluations are possible.

The evaluation device 100 of the present invention may further include a temperature control device (not shown) that maintains the temperature inside the housing 140. Thereby, the temperature inside the housing 140 can be kept constant. Such a temperature control device is capable of heating and/or cooling, and may be a constant temperature tester, a constant temperature bath, or the like. The temperature control device may also be connected to the control unit 160 by wire or wirelessly.

The control unit 160 controls the operations of the lifting unit 130, the weight measuring unit 110, and the charge/discharge characteristic measuring unit 150, and determines the temperature of the metal-air battery based on the information acquired by the weight measuring unit 110 and the charge/discharge characteristic measuring unit 150. Evaluate battery characteristics. Such a control unit 160 may be a general-purpose personal computer or a dedicated terminal device. In FIG. 1, as an example, the control unit 160 is a personal computer equipped with an input device such as a keyboard and a mouse, and a display device such as a display.

FIG. 2 is a block diagram showing the configuration of the control section of the evaluation device of the present invention.

The control unit 160, as a functional block, raises and lowers the stage 120 of the elevating unit 130, performs measurements by the weight measuring unit 110 and the charging/discharging characteristics measuring unit 150, and obtains the amount of weight change and charging/discharging characteristics of the metal-air battery. It includes a measurement control section 210 and a calculation/evaluation section 220 that calculates and evaluates the battery characteristics of the metal-air battery based on the amount of weight change and charge/discharge characteristics acquired by the measurement control section 210.

In the evaluation device 100 of the present invention, the elevating section 130 repeatedly moves the stage 120 to and from the measurement position while measuring the amount of weight change of the metal-air battery. can be done. Thereby, the amount of weight change of the metal-air battery can be accurately measured over a long period of time. Furthermore, since the charge/discharge characteristics are measured simultaneously with the amount of weight change, the charge/discharge reaction efficiency of the metal-air battery can be calculated and evaluated with high precision. From this point of view, in the present specification, evaluation of battery characteristics is intended to evaluate a metal-air battery based on its charging and discharging characteristics.

The control unit 160 may include a display unit 230 that displays the results of the calculation/evaluation unit 220. The display unit 230 is, for example, a liquid crystal display. In addition to the results, the display section 230 may display a setting screen for measurement conditions of the weight measurement section 110 and the charge/discharge characteristic measurement section 150 performed by the measurement control section 210.

The control unit 160 may include an input unit 240 that accepts input operations from the user. The input unit 240 is, for example, a keyboard, a mouse, a button, a touch panel, a touch sensor, a touch pen, a voice input, or the like.

The control unit 160 includes a storage unit 250 that records various programs (evaluation programs) executed by the measurement control unit 210, calculation/evaluation unit 220, etc., an OS program, an application program, and various data read out when these programs are executed. It's okay to stay. The storage unit 250 stores the weight change amount measured by the weight measurement unit 110 and the charge/discharge characteristics measured by the charge/discharge characteristic measurement unit 150 in association with each other. The storage unit 250 is a nonvolatile storage device such as a hard disk or flash memory.

The control unit 160 may include a weighed value correction unit 260 that corrects the amount of weight change caused by the weight measurement unit 110. The weighed value correction section 260 corrects the weight measurement section 110 when the weighed value changes due to temperature fluctuations and/or atmospheric pressure fluctuations measured by the temperature detecting section 190 and/or the atmospheric pressure detecting section (not shown). Correct the weighing value using the sensitivity drift value. The sensitivity drift value may be provided in advance in the weight measuring section 110, or it may be determined immediately before measurement whether there is a dependence on temperature fluctuations/pressure fluctuations of weight value changes of constant weight items such as weights and cell holders, and the You may set it accordingly. From this point of view, the measurement control unit 210 may obtain the amount of weight change (weighed value) of a constant weight item other than the metal-air battery.

With reference to FIG. 2, the calculation/evaluation unit 220 will be described in further detail.
The control unit 160 further includes an electrolyte volatilization rate calculation unit 221, a discharge weight change calculation unit 222, a reaction electron number calculation unit 223, a charged weight change calculation unit 224, and a capacitance calculation unit 225 as functional blocks. You can prepare.

The calculation/evaluation unit 220 preferably includes an electrolyte volatilization rate calculation unit 221 that calculates the rate at which the electrolyte in the metal-air battery naturally volatilizes over time. The electrolyte volatilization rate calculation unit 221 calculates the amount of weight change W _tr at time t _r and the amount of weight change at time t _r0 (where t _r > t _r0 ) during the rest of the charge/discharge characteristics measured by the charge/discharge characteristic measurement unit 150. The weight change difference Wt _r -Wt _r0 with respect to Wt _r0 is divided by the time difference t _r -t _r0 to calculate the electrolyte volatilization rate ((Wt _r -Wt _r0 )/(t _r -t _r0 )). An exemplary time difference is a time difference of 30 minutes or more and 50 hours or less. By using this time difference, the electrolyte volatilization rate can be calculated. Here, the electrolyte volatilization rate calculation unit 221 reads the amount of weight change between times t _r and t _r0 from the storage unit 250 . Hereinafter, the electrolyte volatilization rate will be referred to as r _vol .

The calculation/evaluation section 220 preferably includes a discharge weight change amount calculation section 222 that calculates the weight change amount of the metal-air battery due only to the discharge reaction. The discharge weight change amount calculation unit 222 subtracts the amount of electrolyte volatilization that has spontaneously volatilized up to that time t _d from the amount of weight change at time t _d during discharging of the charge/discharge characteristics determined by the charge/discharge characteristic measurement unit 150 . Let be the discharge weight change amount.

Specifically, the discharge weight change amount calculation unit 222 calculates the weight change amount Wt _d at time t _d during discharging of the charge/discharge characteristics, the weight change amount Wt d0 at time t _d0 (however, t _d >t _d0 ), _and From _the difference _in weight change ₍ Wt _d - _{Wt d0} ), calculate the amount of electrolyte (r _vol The discharge weight change amount ((Wt _d - Wt _d0 ) - (r _vol x (t _d - t _d0 ))) is obtained by subtracting the equation. Here, r _vol is the electrolyte volatilization rate determined previously.

In this way, the discharge weight change amount calculation unit 222 reads the weight change amount Wt _d at time t _d from the storage unit 250, and calculates the time t _d from this value using the electrolyte volatilization rate at the time of rest immediately before discharge. Reduces the amount of electrolyte volatilization in The electrolyte volatilization rate is a value calculated by the electrolyte volatilization rate calculation unit 221. In addition, "rest just before discharging" means rest before discharging in the case of charge-discharge characteristics in the order of rest, discharge, rest, and charge, and in the case of charge-discharge characteristics in the order of rest, discharge, and charge. Intend to rest before discharge.

The discharge weight change amount calculation unit 222 may calculate the amount at predetermined time intervals according to the user's settings, or may calculate it every time the amount of weight change of the metal-air battery is measured.

The calculation/evaluation section 220 preferably includes a reaction electron number calculation section 223 that calculates the number of electrons reacting with oxygen in the metal-air battery during the discharge reaction. The reaction electron number calculation unit 223 divides the amount of weight change due only to the discharge reaction during the time interval Δt _d during discharging of the charge/discharge characteristics calculated by the discharge weight change amount calculation unit 222 by the time interval Δt _d , The rate of weight change is calculated, and the current value used to measure the charge/discharge characteristics is divided by this rate of weight change, and this is taken as the number of reaction electrons. An exemplary time interval Δt _d ranges from 1 second to 60 seconds.

For example, when the metal-air battery is a lithium-air battery, an electrochemical reaction expressed by the following formula occurs during discharge.
2Li ⁺ +2e ^- + O ₂ →Li ₂ O ₂
Therefore, the closer the number of reactive electrons is to +2, the more excellent the lithium-air battery can be evaluated to be in terms of discharge efficiency.

The calculation/evaluation section 220 preferably includes a charged weight change amount calculation section 224 that calculates the amount of weight change of the electrolyte in the metal-air battery caused only by the charging reaction. The charged weight change amount calculation unit 224 subtracts the amount of electrolyte volatilization that has spontaneously evaporated up to that time t _c from the amount of weight change at time t _c during charging of the charge/discharge characteristics measured by the charge/discharge characteristic measurement unit 150 , Let be the charge weight conversion amount.

Specifically, the charged weight change amount calculation unit 224 calculates the amount of weight change Wt c at time t _c during charging and the amount of weight change Wt _c0 at time t _c0 (where _{t c} >t _c0 ) in charge/discharge characteristics. From _the difference _in weight change ₍ Wt _c - _{Wt c0} ), calculate the amount of electrolyte (r _vol The charge weight change amount ((Wt _c - Wt _c0 ) - (r _vol x (t _c - t _c0 ))) is obtained. Here, r _vol is the electrolyte volatilization rate determined previously.

In this way, the charged weight change amount calculating unit 224 reads the weight change amount at time _tc from the storage unit 250, and calculates the electrolysis rate at time _tc calculated from this value using the electrolyte volatilization rate at the time of rest immediately before charging. Reduces liquid volatilization. The electrolyte volatilization rate is a value calculated by the electrolyte volatilization rate calculation unit 221.

The charged weight change amount calculation unit 224 may calculate the amount at predetermined time intervals according to the user's settings, or may calculate it every time the amount of weight change of the metal-air battery is measured.

The reaction electron number calculation unit 223 may calculate the number of electrons required to discharge oxygen from the metal-air battery during the charging reaction. In this case, the reaction electron number calculation unit 223 calculates the amount of weight change due only to the charging reaction during charging of the charging/discharging characteristics calculated by the charging weight change amount calculation unit ₂₂₄ at the time interval Δt _c . The weight change rate is calculated, and the current value used to measure the charge/discharge characteristics is divided by this weight change rate, and this is taken as the number of reaction electrons. An exemplary time interval Δt _c ranges from 1 second to 60 seconds.

For example, when the metal-air battery is a lithium-air battery, an electrochemical reaction expressed by the following formula occurs during charging.
2Li ⁺ +2e ^- + O ₂ ←Li ₂ O ₂
Therefore, the closer the number of reaction electrons is to -2, the more excellent the charging efficiency of the lithium-air battery can be evaluated.

As described above, the reaction electron number calculation unit 223 may calculate the number of electrons required for absorbing/emitting oxygen only during discharging, only during charging, or both during discharging and charging.

The calculation/evaluation section 220 preferably includes a capacitance calculation section 225 that calculates capacitance. The capacitance calculation unit 225 calculates the charge/discharge characteristics from the time ΔT required after the start of discharging and until the weight change occurs, and the current value (mA) passed during the time ΔT. In detail, the capacitance (mAh) is based on the following formula. It can be seen that discharge is progressing by the calculated capacitance.
Capacitance (mAh) = Current (mA) x Time ΔT

Next, the operation of the evaluation device 100 of the present invention will be explained.
When the metal-air battery to be evaluated is placed on the stage 120 of the lifting section 130 and the atmospheric gas and temperature inside the housing 140 are controlled as necessary, the measurement control section 210 of the control section 160 The measurement conditions of the weight measuring section 110 and the charging/discharging characteristic measuring section 150 are received from , the stage 120 of the lifting section 130 is raised and lowered, the weight measuring section 110 and the charging/discharging characteristic measuring section 150 are simultaneously measured, and the amount of weight change is determined. and charge/discharge characteristics are acquired continuously. The acquired data regarding the amount of weight change and charge/discharge characteristics may be temporarily stored in the measurement control unit 210 or may be stored in the storage unit 250 in association with each other based on elapsed time, for example. Here, it is assumed that the acquired data is stored in the storage unit 250.

Next, the calculation/evaluation section 220 of the control section 160 reads out the acquired weight change amount and charge/discharge characteristic data from the storage section 250, and calculates and evaluates the battery characteristics of the metal-air battery. Specifically, the calculation/evaluation unit 220 receives evaluation conditions from the user, and the electrolyte volatilization rate calculation unit 221 calculates the electrolyte volatilization rate, and the discharge weight change amount calculation unit 222 calculates the weight change during the discharge reaction. The charged weight change amount calculating section 224 calculates the amount of weight change during the charging reaction, and the reaction electron number calculating section 223 calculates the amount of air absorbed and discharged during the discharging reaction and/or the charging reaction. The required number of electrons is calculated, and the capacitance calculation unit 225 calculates the capacitance. These evaluations may be performed simultaneously or by selecting one of them. The control unit 160 may display these results on the display unit 230.

The calculation/evaluation unit 220 can evaluate the performance of the metal-air battery over a long period of time using data on the amount of weight change and charge/discharge characteristics that are associated with each other. Furthermore, since the weight change of the metal-air battery is zero-point corrected each time it is measured, the resulting performance evaluation is highly accurate and reliable.

FIG. 3 is an illustration of an exemplary graphical user interface (GUI) screen.

FIG. 3 shows an exemplary GUI screen as an operation screen for the user to operate the evaluation device 100. The operation screen may be displayed on the display unit 230 of the control unit 160. Such screen operations are performed using the input unit 240 described above.

The top page 300 includes a weight measurement condition setting button 310, a charge/discharge characteristic measurement condition setting button 320, an evaluation item setting button 330, a measurement execution button 340, a result button 350, and an end button 360.

FIG. 4 is a diagram showing an exemplary weight measurement condition setting screen.

When the user selects the weight measurement condition setting button 310, the screen moves to a weight measurement condition setting screen 400. The user appropriately sets conditions for measuring the weight of a metal-air battery or a constant weight item. For example, in FIG. 4, the lifting speed of the stage 120 included in the lifting section 130, the measurement period, the number of measurements, the waiting time until weight measurement, and the waiting time until Tare can be set. In FIG. 4, weighed value correction is turned off. Further, the weight measurement condition setting screen 400 may display the weight at the time of measurement, the current number of measurements, elapsed time, etc. in real time.

After inputting the weight measurement condition settings, selecting the setting button, and confirming the measurement conditions, the screen returns to the top page 300. When the measurement execution button 340 is selected, the measurement control section 210 sends the measurement conditions set in the weight measurement conditions to the elevating section 130 and the weight measuring section 110, and the elevating section 130 raises and lowers the stage 120 while moving the metal air battery. Perform a weight measurement. Here, since no charge/discharge characteristic measurement conditions are input, only the weight measurement of the metal-air battery is performed. When the measurement is completed and the results button 350 is selected, the results are displayed.

FIG. 5 is a diagram showing exemplary weight measurement results.

When the evaluation device 100 includes the temperature detection unit 190, the measurement result 500 shows a temporal change in the temperature within the housing 140 and a temporal change in the amount of weight change of the metal-air battery. FIG. 5 shows how the weighed value of a load, which is a constant weight item, changes (drifts) in response to increases and decreases in temperature.

FIG. 6 is a diagram showing another exemplary weight measurement condition setting screen.

FIG. 6 shows a weight measurement condition setting screen 600, which differs from FIG. 4 in that weighing value correction is turned on. The weighed value correction section 260 of the control section 160 corrects the weighed value using the sensitivity drift value. After the settings, the results of measurement are shown in FIG.

FIG. 7 is a diagram illustrating another exemplary weight measurement result.

When the weighed value correction is turned on, the measured value 700 shows that the weighed value of the load remains constant regardless of changes in temperature. In this way, by turning on the weight value correction, the weight value correction section 260 automatically corrects the weight value using the sensitivity drift value. Such a corrected weight change amount remains constant regardless of changes in temperature or atmospheric pressure. The sensitivity drift value may be a sensitivity drift value that the weight measuring section 110 has in advance, or may be set using the drift value shown in FIG. 5.

FIG. 8 is a diagram showing an exemplary charge/discharge characteristic measurement condition setting screen.

Returning to FIG. 3 again, when the user selects the charge/discharge characteristic measurement condition setting button 320, the screen moves to a charge/discharge characteristic measurement condition setting screen 800. Here, the user selects a sequence regarding the number of repeated measurements (cycle number) of charging and discharging, and selects a pattern for setting the amount of charge electricity during charging, the rest, and the discharge capacity during discharging.

In FIG. 8, the user selects the sequence number on the sequence tab. 1 is selected, and sequence No. 1 is selected. 1 is pattern No. 2, it can be seen that the number of cycles consists of a sequence of 20 times. Furthermore, the user can select the sequence number on the sequence tab. Pattern No. 1 cited in 1. 2 details (mode, control time, recording time interval, cutoff (target) voltage, current). It can be seen that the target voltage is 2V to 4.5V.

If various sequences and various patterns are stored in the storage unit 250 in advance, it is only necessary to read them out.

FIG. 9 is a diagram showing an exemplary evaluation item setting screen.

After inputting the weight measurement condition settings and the charge/discharge characteristic measurement condition settings, and selecting the setting button to confirm the measurement conditions, the screen returns to the top page 300. When the evaluation item setting button 330 is selected, an evaluation item setting screen 900 for setting various evaluations of the metal-air battery shown in FIG. 9 is displayed. Here, various evaluation items such as electrolyte volatilization rate, amount of weight change due to discharge reaction, calculation of number of electrons due to discharge reaction, amount of change in weight due to charge reaction, calculation of number of electrons due to charge reaction, and calculation of capacitance were evaluated. You can choose. The user can select a desired evaluation item and input calculation intervals and the like.

In this way, when the settings for weight measurement conditions, the settings for charge/discharge characteristic measurement conditions, and the settings for evaluation items are entered, the display returns to the top page 300, and the measurement execution button 340 is selected, the measurement control unit 210 performs the weight measurement. The measurement conditions set in the conditions and charge/discharge characteristic measurement conditions are sent to the lifting section 130, the weight measuring section 110, and the charging/discharging characteristic measuring section 150, and while the lifting section 130 raises and lowers the stage 120, the weight of the metal-air battery is measured. and conduct charge/discharge characteristic measurements.

FIG. 10 is a diagram showing exemplary results.
FIG. 11 shows another exemplary result.

When the measurement is completed and the result button 350 on the top page 300 is selected, result screens 1000 and 1100 shown in FIGS. 10 and 11 are displayed. The result screen 1000 shows the change in the amount of electrolyte volatilization based on the electrolyte volatilization rate selected on the evaluation item setting screen 900, in addition to the net weight change and charge/discharge characteristics of the metal-air battery.

When proceeding to the next page is selected on the result screen 1000, a result screen 1100 is displayed. The result screen 1100 shows the amount of weight change associated with the charge/discharge reaction selected on the evaluation item setting screen 900, the rate of weight change associated with the charge/discharge reaction, and the change in the number of reaction electrons in the charge/discharge reaction. Here, since the case of a lithium air battery is shown as a metal air battery, the number of electrons is displayed as "e ^- /O ₂ " since the air exchanged with the outside is oxygen. If we pay attention to the number of reaction electrons during the charging reaction on the result screen 1100, it shows a tendency to deviate from -2 as time elapses, suggesting that the normal charging reaction no longer progresses.

When the user returns to the top page 300 from the result screens 1000 and 1100 and selects the end button 360, the application ends. In this way, the evaluation device 100 of the present invention can evaluate a metal-air battery over time based on accurate weight changes.

In addition to the result screens shown in FIGS. 10 and 11, measurement results of the weight change and charge/discharge characteristics of the metal-air battery before characteristic evaluation may be displayed.

Next, a method for evaluating the metal-air battery of the present invention will be explained. Although the evaluation method of the present invention will be described as being implemented using the evaluation apparatus shown in FIG. 1, it is not limited to the evaluation apparatus of the present invention. Any device capable of performing each step may be employed to implement the evaluation method of the present invention.
FIG. 12 is a flowchart showing a method for evaluating battery characteristics of the metal-air battery of the present invention.

Step S1210: Flow the atmosphere control gas into the measurement environment such as the housing 140. This controls the atmosphere of the measurement environment of the metal-air battery. The atmosphere control gas may be oxygen gas, carbon dioxide gas, and rare gases such as nitrogen, argon, helium, xenon, and the like. Although step S1210 is not essential, more accurate battery evaluation can be performed by controlling the measurement environment.

Step S1220: Repeating the arrangement of the metal-air battery at the measurement position of the weight measurement unit 110 (left figure in FIG. 1) and the separation of the metal-air battery from the measurement position (right figure in FIG. 1). Measure the weight repeatedly. As a result, zero point correction is performed every time the weight of the metal-air battery is measured, and an accurate amount of weight change can be obtained.

Such repeated measurements of the weight of the metal-air battery are performed by the elevating unit 130 raising and lowering the stage 120 on which the metal-air battery is placed at regular intervals. When the metal-air battery moves away from the measurement position, the weight measurement section 110 performs zero point correction, and when the metal-air battery comes to the measurement position, the weight measurement section 110 measures the weight of the metal-air battery. The measured weight change amount is stored, for example, in the storage unit 250 of the control unit 160 of the evaluation device 100.

Step S1230: Simultaneously with step S1220, the charge/discharge characteristics of the metal-air battery are measured. Because they are measured simultaneously, the charge/discharge characteristics can be associated with the amount of change in weight over time that is zero-point corrected each time the weight is measured. The charge/discharge characteristics are tested using a charge/discharge tester or the like. The measured charge/discharge characteristics are stored in the storage unit 250 of the control unit 160 of the evaluation device 100, and are stored in association with the weight change amount, for example, by time.

Step S1240: The metal-air battery is calculated and evaluated based on the amount of weight change obtained in step S1220 and the charge/discharge characteristic data obtained in step S1230. In this way, the rate of electrolyte volatilization, the amount of weight change due to charging and discharging, and the number of reactive electrons associated with charging and discharging of the metal-air battery are determined based on the accurate amount of weight change and charge/discharge characteristics that are correlated with each other. In order to calculate and evaluate battery characteristics such as capacitance, performance evaluation of metal-air batteries can be performed continuously and with high precision over a long period of time. The calculation and evaluation are performed by the control unit 160 of the evaluation device 100.

The calculation and evaluation in step S1240 will be explained in further detail.
In the calculation and evaluation, preferably, the rate at which the electrolytic solution in the metal-air battery naturally evaporates over time is calculated. The weight change amount difference Wt _{r −Wt r0} between the weight change amount W _tr at time t r and the weight change amount Wt _r0 at time t _r0 (however, t _r > t _r0 ) during the rest of charge/discharge characteristics is defined as _the time _difference t The electrolyte volatilization rate ((Wt _r -Wt _r0 )/(t _r -t _r0 )) is calculated by dividing by _{r -} t r0 . An exemplary time difference is a time difference of 30 minutes or more and 50 hours or less. By using this time difference, the electrolyte volatilization rate can be calculated accurately. Here, the amount of weight change between times t _r and t _r0 is read from the storage unit 250 and used for calculation. The electrolyte volatilization rate is called r _vol .

In the calculation and evaluation, preferably, the amount of change in the weight of the metal air due only to the discharge reaction is calculated. The discharged weight change amount is calculated by subtracting the amount of electrolyte volatilization that spontaneously volatilized up to that time t _d from the weight change amount at time t _d during discharging of the charge/discharge characteristics.

Specifically _, the _{weight change} amount _difference ( _{Wt d - From} Wt _d0 ), calculate _and subtract the amount _of electrolyte ₍ r _{vol d} −Wt _d0 )−(r _vol x(t _d −t _d0 ))). r _vol is the electrolyte volatilization rate determined previously.

Specifically, the amount of weight change Wt _d at time t _d is read from the storage unit 250, and the amount of electrolyte volatilization at time t _d calculated using the electrolyte volatilization rate at the time of rest immediately before discharge is subtracted from this value. "Rest immediately before discharging" means a rest before discharging in the case of charge/discharge characteristics in the order of rest, discharge, rest, charge, and in the case of charge/discharge characteristics in the order of rest, discharge, charge , intended for rest before discharge.

The amount of change in discharged weight may be calculated at predetermined time intervals according to user settings, or may be calculated each time the amount of weight change of the metal-air battery is measured.

In the calculation and evaluation, preferably, the number of electrons reacting with the air of the metal-air battery during the discharge reaction is calculated. The amount of weight change due only to the discharge reaction during the time interval Δt _d during discharging of the charge-discharge characteristics is divided by the time interval Δt _d to calculate the weight change rate, and the current value used to measure the charge-discharge characteristics is Divide by the rate of weight change to calculate the number of air reaction electrons. An exemplary time interval Δt _d ranges from 1 second to 60 seconds.

In the calculation and evaluation, preferably, the amount of weight change of the electrolyte in the metal-air battery caused only by the charging reaction is calculated. From the amount of weight change at time t _c during charging of the charge/discharge characteristics, the amount of electrolyte volatilization that spontaneously volatilized up to that time t _c is subtracted to calculate the charged weight conversion amount.

_In detail, _the weight _change amount _difference ( _{Wt c − From} Wt _c0 ), calculate _and subtract the amount _of electrolyte ₍ r _{vol c} −Wt _c0 )−(r _vol x(t _c −t _c0 ))). r _vol is the electrolyte volatilization rate determined previously.

In this way, the amount of weight change at time t _c is read from the storage unit 250, and from this value, the amount of electrolyte volatilization at time t _c calculated using the electrolyte volatilization rate at the time of rest immediately before charging is subtracted. The previously calculated value is used for the electrolyte volatilization rate.

The charged weight change amount may be calculated at predetermined time intervals according to user settings, or may be calculated every time the weight change amount of the metal-air battery is measured.

In the calculation and evaluation, preferably, the number of electrons required to discharge oxygen from the metal-air battery during the charging reaction is calculated. The amount of weight change caused only by the charging reaction during the time interval Δt _c during charging of the charge/discharge characteristics is divided by the time interval Δt _c to calculate the weight change rate, and the current value used to measure the charge/discharge characteristics is calculated by dividing this amount by the time interval Δt c. Divide by the rate of weight change to calculate the number of reaction electrons. An exemplary time interval Δt _c ranges from 1 second to 60 seconds.

In the calculation and evaluation, preferably, capacitance is calculated. The capacitance is calculated from the time ΔT required for the charge/discharge characteristic after the start of discharge and until a weight change occurs, and the current value (mA) flowing during the time ΔT. In detail, the capacitance (mAh) is based on the following formula.
Capacitance (mAh) = Current (mA) x Time ΔT

FIG. 13 is a flowchart showing a method for evaluating battery characteristics of another metal-air battery of the present invention.

Step S1310: Prior to step S1210 in FIG. 12, the placement of unchangeable heavy items such as weights and cell holders at the measurement position of the weight measuring section 110 (left figure in FIG. 1), and the separation of unchangeable heavy items from the measurement position ( (right figure in Figure 1) is repeated, and the weight of the item with the same weight is repeatedly measured. This step is the same as step S1220, so the explanation will be omitted.

Step S1320: Simultaneously with step S1310, temperature changes in the measurement environment such as inside the casing 140 and/or changes in air pressure inside the casing 140 are measured. Because they are measured simultaneously, temperature changes and/or pressure changes can be correlated to weight changes. The measured temperature change and/or pressure change data is stored, for example, in the storage unit 250 of the control unit 160 of the evaluation device 100 in association with the weight change amount value over time.

Step S1330: Determine whether the weighed value of the constant weight item is changing due to temperature change and/or atmospheric pressure change. Normally, even in a limited space like the housing 140, it is known that temperature changes of about ±1°C and pressure changes of about ±20 Pa occur, and with such slight changes, If the amount of weight change increases or decreases within the range of ±5 ppm (±0.0005%), it is determined that the weighed value has fluctuated. If the range of increase/decrease in weight change is within the above range, the influence on battery evaluation is small and can be ignored. Such a determination may be made by the control unit 160 by comparing the values of the amount of weight change, temperature change, and atmospheric pressure change.

If it is determined that the weighed value of the unchanging weight item is changing due to temperature change and/or atmospheric pressure change, the process advances to step S1330. If it is not determined that the weighed value of the unchangeable heavy item is fluctuating due to temperature change and/or atmospheric pressure change (that is, it is determined that it is not fluctuating), the process proceeds to step S1210 without correcting the weighed value. Next, we will conduct a battery evaluation of metal-air batteries.

Step S1340: If it is determined in step S1330 that the weight value of the unchanging weight item is fluctuating due to temperature change and/or atmospheric pressure change, the weight value is corrected by the sensitivity drift value of the weight measurement unit 110. . The sensitivity drift value may be a value provided in the weight measuring section 110 in advance, or may be set according to the amount of change obtained in step S1320. This makes it possible to take into account the effects of temperature and atmospheric pressure on the amount of weight change of the metal-air battery, making highly accurate evaluation possible. Next, the process advances to step S1210, and a battery evaluation of the metal-air battery is performed. The subsequent steps have been described with reference to FIG. 12, and will therefore be omitted.

Each functional block in the control unit 160 of the evaluation device 100 of the present invention described with reference to FIG. 2 may be configured by hardware logic, or may be realized by software using a CPU (Central Processing Unit). good.

The evaluation device 100 of the present invention includes a CPU (not shown) that executes instructions of a program that implements each function, a ROM (Read Only Memory, not shown) that stores the program, and a RAM (Random Access) that expands the program. (Memory (not shown)), a storage medium such as a memory that stores programs and various data. A computer or a CPU may read and execute the program code recorded on the recording medium using a recording medium in which a computer-readable program code of a program, which is software that implements the above-mentioned functions, is recorded. In this way, a method for evaluating battery characteristics of a metal-air battery using the evaluation device 100 can be realized.

Examples of such recording media include disks such as CD-ROMs, cards such as IC cards, and semiconductor memories such as flash ROMs.

The evaluation device 100 of the present invention may be connected to a communication network, and the program code may be supplied via the communication network. Such a communication network is not particularly limited, and may be, for example, the Internet, an intranet, a LAN, an ISDN, a CATV communication network, a telephone line network, a satellite communication network, or the like. The program code may be embodied in an electronic transmission and may be in the form of a computer data signal embedded in a carrier wave.

Next, the present invention will be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

[Example 1]
In Example 1, the evaluation apparatus shown in FIG. 1 was constructed, and the battery characteristics of a lithium ion battery were evaluated. In addition, since the weight of the lithium ion battery does not change, it was used as a constant weight product.

An electronic balance (manufactured by A&D Co., Ltd., AD-4212B-23) is used as the weight measuring section 110 in FIG. A thermocouple was used as the temperature detection section 190, and a personal computer was used as the control section 160. The lithium ion battery was a CR-2032 coin cell battery with Li metal foil/LFP (LiFePO ₄ : lithium iron phosphate) positive electrodes (φ16 mm) facing each other.

A lithium ion battery was placed on stage 120, which is a battery holder. The battery holder could be raised and lowered by the lifting section 130. The weight measuring section 150 and the elevating section 130 were housed in a casing 140 (internal volume: 5 L) having a gas supply port and a gas exhaust port. The lithium ion battery was brought into electrical contact with the charge/discharge tester by a gold wire with a diameter of 30 μm. Cables and conductors necessary to control the electronic balance, lifting section, and charge/discharge tester were routed through the gas exhaust port and connected to a personal computer, etc.

FIG. 14 is a diagram showing a charging/discharging characteristic measurement condition setting screen of Example 1.

The battery characteristics of the lithium ion battery were evaluated under the same weight measurement conditions as in FIG. 4 and the charging/discharging characteristics measurement conditions shown in FIG. The results are shown in FIG.

FIG. 15 is a diagram showing the amount of weight change and charge/discharge characteristics of the lithium ion battery of Example 1.

According to FIG. 15, the weight of the lithium ion battery hardly changed over 7 days (168 hours), and it was found that charging and discharging of the lithium ion battery could be normally controlled.

[Example 2]
In Example 2, the battery characteristics of a lithium ion battery were evaluated in the same manner as in Example 1 under the same weight measurement conditions as in FIG. 4 (i.e., the same weight measurement conditions as in FIG. 6) except that weighing value correction was turned on. The results are shown in FIGS. 16 and 17. The sensitivity drift value of the electronic balance was 2.8 ppm/°C.

FIG. 16 is a diagram showing the amount of weight change and temperature change of the lithium ion battery of Example 1.
FIG. 17 is a diagram showing the amount of weight change and temperature change of the lithium ion battery of Example 2.

Note that the temperature changes in FIGS. 16 and 17 are temperature changes within the housing. FIG. 16 is an enlarged view of the amount of weight change in FIG. 15 in Example 1, together with the temperature change. According to FIG. 16, even within the housing, the temperature fluctuated by ±1° C., and following this temperature fluctuation, it was found that the weight value of the lithium ion battery also fluctuated by ±40 μg.

On the other hand, according to FIG. 17, the weighed value of the lithium ion battery of Example 2 was constant without following temperature changes, and was continuously weighed with a standard deviation of 8 μg. This standard deviation of the weighed values was also appropriate based on the accuracy specifications of the electronic balance. This indicates that weight correction using the sensitivity drift value of the weight measurement unit is effective. In all of the following examples, measurements were performed with weighing value correction turned on.

[Example 3]
In Example 3, using the evaluation apparatus constructed in Example 1, the battery characteristics (one cycle of rest, discharge, and charge) of a lithium-air battery cell were evaluated while flowing pure oxygen into the housing (flow rate 150 mL/min). The lithium-air battery cell is a CR-2032 coin cell with Li metal foil/CNT carbon nanotube air electrodes (φ16 mm) facing each other, and the air electrode side has many air holes (φ0.7 mm) for oxygen absorption and discharge. It had

FIG. 18 is a diagram showing a charging/discharging characteristic measurement condition setting screen of Example 3.

The battery characteristics of the lithium-air battery were evaluated under the weight measurement conditions shown in FIG. 6 and the charge/discharge characteristics measurement conditions shown in FIG. As the evaluation items for the battery characteristics, the calculation of the electrolyte volatilization rate shown in FIG. 9, the calculation of the amount of weight change accompanying the charging reaction/discharging reaction, and the calculation of the number of electrons accompanying the charging reaction/discharging reaction were selected. The time interval for electrolyte volatilization rate was 50 hours, the amount of weight change due to charging/discharging reaction was measured every time the weight was measured, and the time interval for calculating the number of electrons due to charging/discharging reaction was every 30 seconds. Ta. The results are shown in FIGS. 19 and 20.

FIG. 19 is a diagram showing the results of the battery characteristics of the lithium-air battery of Example 3.
FIG. 20 is a diagram showing another result of the battery characteristics of the lithium-air battery of Example 3.

According to Figure 19, the electrolyte volatilization rate during rest is -5.63 (±0.06) μg/h, indicating that the electrolyte contained in the lithium-air battery evaporates naturally. Do you get it.

The upper part of FIG. 20 shows the amount of weight change associated with the charging reaction/discharging reaction calculated from the electrolyte volatilization rate of FIG. 19. In the middle part of FIG. 20, the weight change rate is shown in the charging reaction/discharging reaction calculated from the amount of weight change accompanying the charging reaction/discharging reaction. The lower part of FIG. 20 shows the air reaction/number of discharged electrons calculated from the weight change rate and the current value in the charging reaction/discharging reaction.

The weight change rate during the discharge reaction excluding the electrolyte volatilization loss is +122.11 (±0.08) μg/h, and +1.955±0.005 electrons per oxygen molecule react, It turns out that oxygen is fixed. This value was one to two orders of magnitude higher in accuracy than the method described in Non-Patent Document 1. This indicates that the battery characteristics of metal-air batteries can be evaluated with high accuracy by using the evaluation apparatus of the present invention.

Similarly, the weight change rate during the charging reaction (at the beginning of charging, excluding the electrolyte volatilization loss) is -114.50 (±0.08) μg/h, which is -2.0 μg/h per oxygen molecule. It was found that 109±0.006 electrons reacted and oxygen was released. Looking at FIG. 20, in the early stage of charging, the weight of the lithium ion battery decreased linearly due to oxygen release, but in the latter half of charging, the weight decreased significantly, indicating a weight loss greater than the amount of oxygen fixed. This suggests that gas was released due to decomposition and deterioration of the electrolyte and electrode materials of the lithium-air battery.

[Example 4]
In Example 4, the evaluation device constructed in Example 1 was used to evaluate the battery characteristics (multiple cycles of rest, discharge, rest, and charge) of a lithium-air battery while flowing pure oxygen into the casing.

FIG. 21 is a diagram showing the weight measurement condition setting screen of Example 4.

The battery characteristics of the lithium-air battery were evaluated under the weight measurement conditions shown in FIG. 6 and the charge/discharge characteristics measurement conditions shown in FIG. As evaluation items for battery characteristics, select the calculation of the electrolyte volatilization rate shown in Figure 9, the calculation of the amount of weight change due to charge reaction/discharge reaction, the calculation of the number of electrons due to charge reaction/discharge reaction, and the calculation of capacitance. did. The time interval for electrolyte volatilization rate was 50 hours, the amount of weight change due to charging/discharging reaction was measured every time the weight was measured, and the time interval for calculating the number of electrons due to charging/discharging reaction was every 30 seconds. Ta. The results are shown in FIGS. 22 to 25.

FIG. 22 is a diagram showing the results of the battery characteristics of the lithium-air battery of Example 4.
FIG. 23 is a diagram showing another result of the battery characteristics of the lithium-air battery of Example 4.

According to FIG. 22, the electrolyte volatilization rate at the first rest is -5.36 (±0.07) μg/h, and by performing multiple cycles of rest, discharge, rest, and charge, the It was found that the overall weight of lithium-ion batteries decreases by repeating weight increases and weight decreases due to charging reactions. This suggests that in addition to the weight loss due to volatilization of the electrolytic solution, gas release due to decomposition and deterioration of the electrolytic solution and electrode materials has a large influence. Although FIG. 22 shows only the electrolyte volatilization rate during the first rest, in reality, the electrolyte volatilization rates at all rest times are calculated.

The upper part of FIG. 23 shows the amount of weight change associated with the charging reaction/discharging reaction calculated from the electrolyte volatilization rate of FIG. 22. In the middle part of FIG. 23, the rate of weight change in the charging reaction/discharging reaction calculated from the amount of weight change accompanying the charging reaction/discharging reaction is shown. In the lower part of FIG. 23, the number of reaction electrons calculated from the weight change rate and the current value in the charging reaction/discharging reaction is shown.

Focusing on the number of reaction electrons during the charging reaction, the number of electrons deviates significantly from the ideal value (-2) in the latter half of the cycle, suggesting that gas was released due to decomposition and deterioration of the electrolyte and electrode material.

FIG. 24 is a diagram showing another result of the battery characteristics of the lithium-air battery of Example 4.
FIG. 25 is a diagram showing another result of the battery characteristics of the lithium-air battery of Example 4.

FIG. 24 is an enlarged view of a part of FIG. 23. According to FIG. 24, it can be seen that the weight is changed according to the start and stop of charging and discharging, and the charging and discharging reactions are accurately tracked.

However, according to FIG. 25, there was a difference of about ten minutes between the start of discharge and the start of weight change. A capacitance of 0.2 mAh was calculated from the current value and time during this shift period. It was found that the lithium air battery used in Example 4 was discharged by this capacitance. Note that this capacitance matched well with the capacitance (0.2 mAh) estimated from the voltage drop rate, and was a reliable value.

Using the metal-air battery evaluation device of the present invention, it is possible to continuously measure minute changes in the weight of the metal-air battery over a long period of time. This makes it possible to accurately measure over a long period of time over multiple charge/discharge cycles. It also makes it possible to measure and evaluate the volatilization rate of the electrolyte from the change in weight of the cell during no current (rest). In addition to metal-air batteries, such an evaluation device can also evaluate the absorption and emission characteristics of materials that interact with external gases.

100 Evaluation device 110 Weight measuring section 120 Stage 130 Lifting section 140 Housing 150 Charge/discharge characteristic measuring section 160 Control section 170 Gas intake port 180 Gas exhaust port 190 Temperature detection section

Claims (26)

An evaluation device for evaluating battery characteristics of a metal-air battery,
a weight measuring unit that measures the weight of the metal air battery;
an elevating section that includes a stage for placing the metal-air battery and that raises and lowers the stage;
a casing that houses at least the weight measuring section and the metal air battery;
a charge-discharge characteristic measurement unit that measures charge-discharge characteristics of the metal-air battery;
a control unit that controls the operations of the lifting unit, the weight measuring unit, and the charging/discharging characteristic measuring unit and evaluates the battery characteristics of the metal-air battery;
The control unit includes:
a measurement control unit that raises and lowers the stage of the elevating unit, performs measurements by the weight measuring unit and the charging/discharging characteristic measuring unit, and obtains a weight change amount and charging/discharging characteristics of the metal-air battery;
a calculation/evaluation unit that calculates and evaluates battery characteristics of the metal-air battery based on the weight change amount and the charge/discharge characteristics obtained by the measurement control unit;
The calculation/evaluation unit calculates a weight change amount difference Wt between a weight change amount Wt _r at time t _r and a weight change amount Wt _r0 at time t _r0 (where t _r >t _r0 ) during rest of the charge/discharge characteristics. Evaluation further comprising an electrolyte volatilization rate calculation unit that divides _r - Wt _r0 by the time difference t _r -t _r0 and calculates an electrolyte volatilization rate ((Wt _r - Wt _r0 )/(t _r -t _r0 )) Device. The calculation/evaluation unit calculates the electrolyte volatilization rate at the time _{t d} estimated from the weight change amount at the time t d during discharging of the charge/discharge characteristics using the electrolyte volatilization rate during rest immediately before the discharge. The evaluation device according to claim 1, further comprising a discharge weight change amount calculation unit that calculates a weight change amount due only to the discharge reaction. The calculation/evaluation unit divides the amount of weight change due only to the discharge reaction at the time interval Δt _d during discharging of the charge/discharge characteristics calculated by the discharge weight change calculation unit by the time interval Δt _d . , Calculate the rate of weight change, divide the current value used to measure the charge/discharge characteristics by the rate of weight change, and calculate the number of electrons reacting with the air absorbed in the metal-air battery.The number of reaction electrons. The evaluation device according to claim 2, further comprising a calculation section. The calculation/evaluation unit calculates the electrolyte volatilization rate at the time t _c estimated from the amount of weight change at the time t _c during charging of the charge/discharge characteristics using the electrolyte volatilization rate during rest immediately before the charging. The evaluation device according to any one of claims 1 to 3, further comprising a charged weight change amount calculation unit that calculates a weight change amount due only to the charging reaction. The calculation/evaluation unit divides the amount of weight change caused only by the charging reaction of the charging/discharging characteristic during the charging time interval Δt _c calculated by the charged weight change calculation unit by the time interval Δt _c . , a reaction of calculating the rate of weight change, dividing the current value used to measure the charge/discharge characteristics by the rate of weight change, and calculating the number of electrons required to discharge the air fixed in the metal-air battery. The evaluation device according to claim 4, further comprising an electron number calculation section. The calculation/evaluation section is a capacitance calculation section that calculates capacitance from the time ΔT required for weight change to occur after the start of discharging of the charge/discharge characteristics and the current value flowing during the time ΔT. The evaluation device according to any one of claims 1 to 5, further comprising: The evaluation device according to any one of claims 1 to 6, wherein the control section further includes a display section that displays the results of the calculation/evaluation section. The evaluation device according to claim 1, further comprising a temperature detection section within the housing. The evaluation device according to any one of claims 1 to 8, further comprising an air pressure detection section within the housing. The evaluation device according to claim 8 or 9, wherein the control section further includes a weighed value correction section that corrects the weighed value obtained by the weight measuring section using a sensitivity drift value of the weight measuring section. The evaluation device according to any one of claims 1 to 10, wherein the casing includes a gas supply port and a gas exhaust port. The evaluation device according to any one of claims 1 to 11, further comprising a temperature control device that maintains the temperature inside the housing. A method for evaluating battery characteristics of a metal-air battery, the method comprising:
repeating placement of the metal air battery at a measurement position of a weight measurement unit and separation of the metal air battery from the measurement position, and repeatedly measuring the weight of the metal air battery;
Measuring the charge/discharge characteristics of the metal air battery simultaneously with the repeated measurement of the weight;
Calculating and evaluating battery characteristics of the metal-air battery based on the weight change amount obtained by the repeated measurements and the charge-discharge characteristics obtained by measuring the charge-discharge characteristics. and,
What is calculated and evaluated is the weight change amount difference between the weight change amount Wt _r at time t _r and the weight change amount Wt _r0 at time t _r0 (however, t _r > t _r0 ) during the rest of the charge/discharge characteristics. The method further comprises dividing Wt _r -Wt _r0 by a time difference t _r -t _r0 to calculate an electrolyte volatilization rate ((Wt _r - Wt _r0 )/(t _r -t _r0 )). The calculation/evaluation is based on the amount of weight change at time t _d during discharging of the charge/discharge characteristics, and the electrolyte solution at time t _d estimated using the electrolyte volatilization rate during rest immediately before the discharge. 14. The method according to claim 13, further comprising subtracting the amount of volatilization and calculating the amount of weight change due only to the discharge reaction. The calculation and evaluation includes dividing the weight change amount due only to the discharge reaction during the time interval Δt _d during discharging of the calculated charge/discharge characteristics by the time interval Δt _d to calculate the weight change rate. Claim 14, further comprising dividing the current value used for measuring the charge/discharge characteristics by the rate of weight change to calculate the number of electrons reacting with the air absorbed in the metal-air battery. The method described in. The calculation/evaluation is based on the amount of weight change at time t _c during charging of the charge/discharge characteristics, and the electrolyte solution at time t _c estimated using the electrolyte volatilization rate during rest immediately before the charging. The method according to any one of claims 13 to 15, further comprising reducing the amount of volatilization and calculating the amount of weight change due only to the charging reaction. The calculation and evaluation includes dividing the amount of weight change caused only by the charging reaction during the charging time interval Δt _c of the calculated charge/discharge characteristics by the time interval Δt _c to calculate the weight change rate. and further comprising dividing the current value used to measure the charge/discharge characteristics by the rate of weight change to calculate the number of electrons required for discharging the air fixed in the metal-air battery. The method according to item 16. The calculating and evaluating further includes calculating the capacitance from the time ΔT required for the weight change to occur after the start of discharge of the charge/discharge characteristics and the current value flowing during the time ΔT. The method according to any one of claims 13 to 17. Prior to the repeated measurements,
repeating the arrangement of the constant weight item at the measurement position of the weight measurement unit and the separation of the constant weight item from the measurement position, and repeatedly measuring the weight of the constant weight item;
Measuring temperature changes and/or pressure changes in the measurement environment at the same time as repeatedly measuring the weight of the constant weight item;
Determining whether the weighed value of the constant weight item changes due to the temperature change and/or the atmospheric pressure change;
If it is determined in the above-mentioned determination that there is a fluctuation, the weighed value is corrected by the sensitivity drift value of the weight measuring section, and if it is determined that there is no fluctuation in the said determination, the weighed value is not corrected. 19. The method according to any of claims 13 to 18, further comprising: 20. The method of any of claims 13 to 19, further comprising flowing an atmosphere control gas into the measurement environment prior to said repeated measurements. A program for evaluating battery characteristics of metal-air batteries,
a function of repeatedly placing the metal-air battery at a measurement position of a weight measurement unit and separating the metal-air battery from the measurement position, and repeatedly measuring the weight of the metal-air battery;
A function of measuring the charge/discharge characteristics of the metal air battery simultaneously with the repeated measurement of the weight;
a function of calculating and evaluating battery characteristics of the metal-air battery based on the weight change amount obtained by the repeated measurements and the charge-discharge characteristics obtained by measuring the charge-discharge characteristics; to be realized by a computer,
The function to calculate and evaluate is the weight change amount difference between the weight change amount Wt _r at time t _r and the weight change amount Wt _r0 at time t _r0 (however, t _r > t _r0 ) during the rest of the charge/discharge characteristics. The program further includes a function of dividing Wt _r -Wt _r0 by a time difference t _r -t _r0 to calculate an electrolyte volatilization rate ((Wt _r - Wt _r0 )/(t _r -t _r0 )). The function to calculate and evaluate the electrolytic solution at the time t _d estimated from the weight change amount at the time t _d during discharging of the charge/discharge characteristics using the electrolytic solution volatilization rate during the rest immediately before the discharging. 22. The program according to claim 21, further comprising a function of reducing the amount of volatilization and calculating the amount of weight change due only to the discharge reaction. The calculation/evaluation function calculates the rate of weight change by dividing the amount of weight change caused only by the discharge reaction during the time interval Δt _d during discharging of the calculated charge/discharge characteristics by the time interval Δt _d . 23. The method according to claim 22, further comprising a function of calculating the number of electrons reacting with air absorbed in the metal-air battery by dividing the current value used for measuring the charge-discharge characteristics by the weight change rate. Programs listed. The function to calculate and evaluate the electrolytic solution at the time t c estimated from the amount of weight change at the time t _c during charging of the charge/discharge characteristics using the electrolytic solution volatilization rate during the rest immediately before _the charging. The program according to any one of claims 21 to 23, further comprising a function of reducing the amount of volatilization and calculating the amount of weight change due only to the charging reaction. The calculation/evaluation function calculates the rate of weight change by dividing the amount of weight change caused only by the charging reaction of the calculated charge/discharge characteristics during the charging time interval _Δtc by the time interval _Δtc . Claim: further comprising a function of dividing the current value used for measuring the charge/discharge characteristics by the weight change rate to calculate the number of electrons required to discharge the air fixed in the metal-air battery. The program described in 24. The calculation/evaluation function further includes a function of calculating capacitance from the time ΔT required for the weight change to occur after the start of discharging of the charge/discharge characteristics and the current value flowing during the time ΔT. , the program according to any one of claims 21 to 25.

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