JP2020038756A - Lithium ion secondary battery and lithium ion secondary battery system - Google Patents

Abstract

To provide a lithium ion secondary battery capable of grasping a deterioration status in real time during use, and a lithium ion secondary battery system.SOLUTION: A lithium ion secondary battery is configured by including a cell case, an electrolyte, a cathode and an anode. The lithium ion secondary battery comprises: a porous hollow tube which is disposed inside of the cell case and constituted of a material through which infrared light is transmissive, and that only a gas can pass; and two optical windows which are disposed correspondently to both ends of the porous hollow tube and through which infrared light is transmissive. In one of the two optical windows, infrared light from an infrared light source outside of the cell case is incident and in the other optical window, the infrared light is emitted toward a detector outside of the cell case.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a lithium ion secondary battery and a lithium ion secondary battery system.

  2. Description of the Related Art In recent years, demand for high-capacity, high-output batteries has been rapidly expanding due to the spread of various sizes of electric and electronic devices such as automobiles, personal computers, and mobile phones. Among various types of batteries, lithium ion secondary batteries exhibiting high energy density and output are widely used for all kinds of electronic devices, and further higher performance is required. Currently, lithium ion secondary batteries that are widely used mainly use an organic solvent-based electrolyte.

  Incidentally, it is known that an organic solvent-based electrolytic solution causes a chemical reaction with an electrode with the use of a lithium ion battery. That is, by repeating charging and discharging, the form of the electrolytic solution and the electrodes changes due to this reaction, and the capacity of the battery gradually deteriorates (for example, see Patent Document 1).

  Conventionally, in order to grasp the state of deterioration of the battery, a map of the deterioration condition is created in advance, the usage history of the battery is recorded and applied to the map, and the capacity, resistance and impedance of the battery are measured. For example, a method of estimating a state has been proposed (for example, see Patent Document 2).

JP 2015-56308 A International Publication No. 2011/121692

  However, the production of the map requires a great deal of time, labor and a large number of batteries, and there is also a problem in its accuracy. Further, when the state is estimated from the actually measured values, the deterioration appears as a decrease in the full charge / discharge capacity, so that it is difficult to accurately estimate the state of deterioration of the battery without the opportunity of the full charge / discharge.

  The present invention has been made in view of the above, and by analyzing the gas generated due to the deterioration of a lithium ion secondary battery, the deterioration state of the battery can be grasped without performing full charge and discharge, and the full cell It is an object of the present invention to provide a lithium ion secondary battery and a lithium ion secondary battery system capable of determining a state.

  (1) The present invention provides a cell case (for example, a cell case 1 to be described later), an electrolytic solution (for example, an electrolytic solution 2 to be described later), a positive electrode (for example, a positive electrode 3 to be described later), and a negative electrode (for example, a And a negative electrode 4) (for example, a lithium ion secondary battery 100 to be described later), which is disposed inside the cell case and is made of a substance that can transmit infrared light. And a porous hollow tube (for example, a porous hollow tube 5 described later) through which only gas can pass, and are disposed corresponding to both ends of the porous hollow tube, and are capable of transmitting infrared light. Two optical windows (for example, an optical window 6 to be described later), and the two optical windows can receive infrared light from an infrared light source outside the cell case on the one hand, and on the other hand, receive the cell light on the other hand. Can emit infrared light to an external detector There, a lithium ion secondary battery.

The capacity of a lithium ion secondary battery deteriorates with use due to an oxidation-reduction reaction generated between an electrode and an electrolytic solution. At the time of such a reaction, gas such as CO ₂ and CH ₄ is generated. Therefore, by performing qualitative and quantitative analysis on the generated gas, the deterioration state of the battery can be grasped.
According to the lithium ion battery of the present invention, the qualitative / quantitative analysis of the gas in the cell case via the optical window is performed to determine the deterioration state of the battery in use in real time and determine the battery state. Can be. Further, it is possible to predict a future deterioration state of the battery and perform control to suppress the future deterioration.

  (2) In the invention of (1), the optical window may further be detachable with an optical fiber (for example, an optical fiber 7 described later).

  Thereby, the degree of freedom of arrangement of the infrared spectroscopy analyzer at the time of analysis is improved, and the handling becomes easy.

  (3) The present invention further provides a lithium ion secondary battery according to (1) or (2), and an infrared spectrometer for inputting and outputting infrared light to and from the porous hollow tube. A secondary battery system (for example, a lithium ion secondary battery system 200 described below) is provided.

  Thus, the capacity deterioration state of the electrode can be analyzed only by the battery system without using an analyzer separately. In addition, it becomes easy to analyze the battery state over time or at a high frequency. For example, in the case of a vehicle equipped with the present system, it is also possible to grasp the deterioration state on-board.

  (4) In the invention according to (3), the lithium ion secondary battery system further includes an analyzer for analyzing gas present in the battery cell case by infrared spectroscopy, and qualitative / quantitative information obtained by the analyzer. Based on the analysis result, an evaluation unit that acquires the capacity deterioration state of at least one of the positive and negative electrodes, and a determination unit that determines the battery state based on the capacity deterioration state of the positive and negative electrodes obtained by the evaluation unit, May be provided.

  Thereby, the battery state is determined by the battery system itself, and, for example, in the case of a vehicle equipped with the present system, the driver can accurately and immediately grasp the state of deterioration of the battery based on the determination result, and take timely action such as replacement. be able to.

  According to the present invention, the deterioration state of a battery in use can be grasped in real time without performing full charge and discharge, and the state of a full cell can be determined. Control can be implemented to suppress the above.

5 is a graph showing the relationship between the capacity and voltage of positive and negative electrodes and a full cell of a lithium ion secondary battery. 5 is a graph showing the magnitude of a capacity shift amount of each of the positive and negative electrodes due to deterioration due to reaction with an electrolytic solution. FIG. 3 is a front view (FIG. 3A) and a side view (FIG. 3B) illustrating the battery cell 10 of the lithium ion secondary battery 100 according to the embodiment of the present invention. It is a figure showing signs that an optical fiber was attached to battery cell 10 of lithium ion secondary battery 100 concerning an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating a lithium ion secondary battery system 200 according to the embodiment.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

<Lithium ion secondary battery>
The battery cell 10 of the lithium ion secondary battery 100 of the present invention includes a cell case 1, an electrolyte solution 2, a positive electrode 3, and a negative electrode 4. Inside the cell case 1, a positive electrode 3 and a negative electrode 4 are arranged to face each other with a separator interposed therebetween, and a porous hollow tube 6 through which only gas can pass is provided by an infrared light source outside the cell case 1. It is arranged so that infrared light can enter and exit. In the cell case 1, two optical windows 6 capable of transmitting infrared rays are arranged corresponding to both ends of the porous hollow tube.

  The cell case 1 is not particularly limited in shape, material, and the like, and a cell case 1 used for a general liquid lithium ion secondary battery can be used. However, in order to measure the amount of gas generated in the cell case 1, it is preferable that the cell case 1 is sealed.

  The electrolytic solution 2 is not particularly limited, and an organic electrolytic solution used for a general liquid lithium ion secondary battery can be used. In general, it is known that an organic electrolyte of a liquid lithium ion secondary battery reacts by transferring electrons to and from an electrode as it is used, and is decomposed to generate a gas.

The positive electrode 3 is not particularly limited, and an electrode material used for a general liquid lithium ion secondary battery can be used. The positive electrode 3 causes an oxidation reaction of the electrolytic solution 2 as the battery is used, and generates a gas such as CO ₂ .

The negative electrode 4 is not particularly limited, and an electrode material used for a general liquid lithium ion secondary battery can be used. The negative electrode 4 causes a reduction reaction of the electrolytic solution 2 with the use of the battery, and generates a gas such as a hydrocarbon represented by CH ₄ .

  The porous hollow tube 5 has a porous structure that allows only gas to pass through, and is made of, for example, ceramics or a polymer material. The porous hollow tube 6 is provided with an infrared light source outside the cell case 1 in a gas phase portion that does not come into contact with the liquid phase portion of the electrolyte solution 2 in the battery cell 10 in order to prevent the electrolyte solution 2 from entering from both ends. Is arranged so as to be able to enter and emit infrared light. Further, the porous hollow tube 5 is preferably arranged in the cell case 1 such that the entire length of the porous hollow tube 5 becomes long in order to secure an optical path length of infrared light transmitted during analysis.

  Since the gas can freely permeate through the tube wall, the hollow portion in the porous hollow tube 5 is filled with a gas having the same composition as the gas phase portion. That is, by performing qualitative / quantitative analysis on the gas in the hollow portion of the porous hollow tube 5, the total amount of gas generated by the reaction between the electrode and the electrolyte in the battery cell 10 can be obtained.

The optical window 6 only needs to be able to transmit infrared rays, and may be made of KBr, NaCl, CaF ₂ , BaF ₂ , Si, Ge, diamond, or the like. The optical windows 6 are disposed on the wall surface of the cell case 1 corresponding to both ends of the porous hollow tube 5, and can receive and emit infrared rays through the optical windows 6. Note that a detachable optical fiber 7 may be further provided on the optical window 6. This enables analysis without arranging the infrared light source and the detector on a straight line, and improves the degree of freedom in the arrangement of the spectroscopic analyzer, thereby facilitating the analysis.

<Battery capacity decrease>
As described above, the capacity of a lithium ion secondary battery decreases due to a reaction that occurs between an electrode and an electrolytic solution with use. This occurs because electrons emitted from the negative electrode at the time of discharge are consumed in a decomposition reaction of the electrolytic solution, and Li ions are deactivated without returning to the positive electrode. That is, since the capacity of each electrode is deteriorated, the capacity of the entire battery (full cell) is reduced.

FIG. 1 is a graph showing the relationship between capacity and voltage for positive and negative electrodes and full cells.
In the graph shown in FIG. 1, the discharge capacity of a full cell is determined by the size of the capacity region where the potential-capacity curves of the positive electrode and the negative electrode overlap. Then, the respective capacities of the positive electrode and the negative electrode are degraded by the above reaction, and the respective potential-capacity curves in FIG. 1 shift to the left.

FIG. 2 is a graph showing the magnitude of the capacity shift amount due to the deterioration of each of the positive and negative electrodes due to the reaction with the electrolytic solution.
The discharge capacity of the full cell after deterioration is determined by the size of the capacity area where the potential-capacity curves of the positive electrode and the negative electrode after the shift overlap. The shift amount of each of the positive and negative electrodes is represented as shown in FIG. Until a certain period thereafter, the shift amount of the negative electrode is larger. That is, until a certain period after the start of use, the capacity region where the potential-capacity curve of the positive electrode and the negative electrode in FIG. 1 overlaps is reduced, and the battery capacity is reduced.

  Based on the above findings, the progress of the above reaction was observed by analyzing the battery in use, and if the shift amount of each of the positive and negative electrodes could be grasped in real time, the capacity of the full cell at the time of observation was obtained, and further the tendency of deterioration was predicted. can do.

  In the lithium ion secondary battery 100 of the present invention, the degree of deterioration of each electrode is grasped and the capacity of the full cell is grasped by qualitatively and quantitatively analyzing the gas generated by the reaction between the electrode and the electrolyte solution 2 in the battery cell 10. can do. As an analysis method, an infrared spectroscopic analysis method can be used to perform analysis by changing / separating an infrared absorption spectrum. The infrared spectroscopy apparatus may be a commercially available general analysis instrument, which may be used as appropriate during the test, or may be provided as a part of the battery 100 in order to analyze and determine the battery state over time. , May be integrated with the battery cell 10.

In order to observe the reaction of the positive electrode 3, for example, it is sufficient to quantify mainly the generated CO ₂ . By quantifying the CO ₂ concentration in the gas in the cell case 1, the total amount of generated CO ₂ can be calculated, and the degree of progress of the reaction can be evaluated. By calculating the shift amount of the potential-capacity curve shown in FIG. 1 based on the evaluated degree of reaction progress, the potential-capacity curve after the shift due to the reaction deterioration in the positive electrode 3 can be estimated.

In order to observe the reaction of the negative electrode 4, for example, it is sufficient to quantify mainly the generated CH ₄ . By quantifying the CH ₄ concentration in the gas in the cell case 1, the total amount of generated CH ₄ can be calculated, and the degree of progress of the reaction can be evaluated. By calculating the shift amount of the potential-capacity curve shown in FIG. 1 based on the evaluated degree of reaction progress, the potential-capacity curve after the shift due to the reaction deterioration in the negative electrode 4 can be estimated.

Actually, the same gas may be generated from both electrodes. For example, CO ₂ may be generated not only from the positive electrode 3 but also from the negative electrode 4. In that case, it is preferable to calculate the degree of reaction progress for both electrodes, assuming a reaction that occurs with respect to the electrolyte solution 2 to be used in advance.

  If the potential-capacitance curve after the shift of both electrodes can be estimated, the capacity of the full cell can be calculated. Specifically, the size of the capacitance region where the potential-capacitance curves of both electrodes overlap is the capacity of the full cell. This is because the battery has an electromotive force only in a capacity region where the difference between the potentials of both electrodes can be calculated.

  Furthermore, by observing the above-mentioned reaction progress and capacity over time, the tendency of deterioration can be grasped. As a result, the battery life can be extended by predicting the future deterioration tendency and performing appropriate operation control according to the deterioration state. Alternatively, it is also possible to estimate an appropriate time to replace or inspect the battery in order to avoid trouble of the device.

  The determination of the state of the lithium-ion secondary battery 100 of the present invention may be performed by real-time infrared spectroscopy analysis on-board, or may be performed on the vehicle-mounted battery at any time during vehicle inspection or inspection. Good. In addition, an actual battery often has a plurality of cells, but all the cells may be the battery cells 10 having the above-described configuration, or only a representative cell may be the above-described cell in terms of cost. The battery cell 10 having the configuration may be used.

<Lithium ion secondary battery system>
The lithium ion secondary battery of the present invention further includes: an analysis unit that analyzes gas present in the battery cell case by infrared spectroscopy; and a qualitative / quantitative analysis result obtained by the analysis unit. An evaluation unit that acquires at least one of the capacity deterioration states, and a determination unit that determines the battery state based on the capacity deterioration states of the positive and negative electrodes obtained by the evaluation unit, It can be used as the battery system 200. Thus, the battery state is determined by the battery system itself, the user can immediately grasp the battery state, and can immediately take measures when the battery is deteriorated.

  The analysis unit in the lithium ion secondary battery system 200 of the present invention analyzes the gas present in the battery cell case by infrared spectroscopy. In the analysis, the absorption spectrum is analyzed by irradiating infrared rays to the gas in the porous hollow tube 5 arranged in the cell case 1 through the optical window 6 and detecting the emitted infrared rays. Perform qualitative and quantitative analysis.

  The evaluation unit in the lithium ion secondary battery system 200 of the present invention evaluates the capacity deterioration state of at least one of the positive and negative electrodes based on the qualitative / quantitative analysis results obtained by the analysis unit. By quantifying the gas generated by the reaction between the positive and negative electrodes and the electrolytic solution 2, the degree of reaction progress can be calculated, and the capacity deterioration state of the positive and negative electrodes can be evaluated.

  The determination unit in the lithium ion secondary battery system 200 of the present invention determines the battery state based on the capacity deterioration state of the positive and negative electrodes obtained by the evaluation unit. If the potential-capacitance curve after the shift of both electrodes can be estimated based on the capacity deterioration state of the positive and negative electrodes, the capacity of the full cell can be calculated.

  Further, the lithium ion secondary battery system 200 of the present invention may include a control unit that controls the operation of the lithium ion secondary battery 100 based on the determination result obtained by the determination unit. Thus, for example, by performing operation control in which output is adjusted so as to suppress deterioration, the life of the lithium ion secondary battery 100 can be extended.

  Furthermore, by observing the above-mentioned reaction progress and capacity over time, the tendency of deterioration can be grasped. As a result, the battery life can be extended by predicting the future deterioration tendency and performing appropriate operation control according to the deterioration state. Alternatively, it is also possible to estimate an appropriate time to replace or inspect the battery in order to avoid trouble of the device.

  In the lithium ion secondary battery system of the present invention, the infrared spectroscopy may be performed on-board in real time, or may be performed on the vehicle-mounted battery at any time during vehicle inspection or inspection. Further, although many actual batteries have a plurality of cells, the above analysis may be performed on all cells, or only representative cells may be extracted from the viewpoint of cost. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1st Embodiment)
FIG. 3 is a front view (FIG. 3A) and a side view (FIG. 3B) showing the battery cell 10 of the lithium ion secondary battery 100 according to the first embodiment of the present invention.
The battery cell 10 of the lithium ion secondary battery 100 has an electrolyte solution 2, a positive electrode 3, a negative electrode 4, and a separator 8 in a sealed cell case 1. Inside the cell case 1, a positive electrode 3 and a negative electrode 4 are arranged to face each other with a separator 8 interposed therebetween, and a porous hollow tube 6 through which only gas can pass is provided from an infrared light source outside the cell case 1. Are arranged so as to be able to enter and emit infrared light. Further, in the battery cell 10, two optical windows 6 that can transmit infrared rays are arranged corresponding to both ends of the porous hollow tube 5 or both ends of the porous hollow tube 6 in the cell case 1.

The electrolytic solution 2 reacts with the positive electrode 3 with the use of the battery to generate CO ₂ gas. Further, similarly, it reacts with the negative electrode 4 to generate CH ₄ gas.

  The porous hollow tube 5 has a porous structure that allows only gas to pass through, and is made of a polymer material. In order to prevent the electrolyte solution 2 from entering from both ends, the porous hollow tube 6 is placed in a gas phase portion that does not come into contact with the liquid phase portion of the electrolyte solution 2 in the battery cell 10 from an infrared light source outside the cell case 1. Are arranged so as to be able to enter and emit infrared light. Further, as shown in FIG. 3, the porous hollow tube 5 is arranged so as to extend along a long side of a rectangular shape in a horizontal cross section of the rectangular parallelepiped cell case 1 in order to secure an optical path length of infrared light transmitted at the time of analysis. .

Since the gas can freely permeate the tube wall of the porous hollow tube 5, the composition of the gas in the tube and in the gas phase is the same. That is, by performing qualitative / quantitative analysis on the gas in the porous hollow tube 5, the total amount of CO ₂ gas and CH ₄ gas generated by the reaction between the electrode and the electrolyte in the battery cell 10 can be obtained.

  The optical windows 6 are arranged in the cell case 1 corresponding to both ends of the porous hollow tube 5. Thereby, infrared rays can be input / output through the optical window 6 and the gas in the battery cell 10 can be analyzed.

FIG. 4 is a diagram illustrating a state where an optical fiber is attached to the battery cell 10 according to the present embodiment.
In the present embodiment, a detachable optical fiber 7 can be attached on the optical window 6 fixed to the cell case 1. Accordingly, analysis can be performed without disposing the infrared light source and the detector on a straight line, and the degree of freedom of arrangement of the spectroscopic analyzer is improved, so that handling during analysis is facilitated.

(2nd Embodiment)
FIG. 5 is a diagram schematically illustrating the lithium-ion secondary battery system 200 according to the present embodiment.
The lithium-ion secondary battery system 200 according to the second embodiment of the present invention includes the lithium-ion secondary battery 100 according to the first embodiment and an analysis that analyzes gas present in the battery cell case by infrared spectroscopy. Unit, based on the qualitative / quantitative analysis results obtained in the analysis unit, an evaluation unit that acquires the capacity deterioration state of at least one of the positive and negative electrodes, and the capacity deterioration state of the positive and negative electrodes obtained in the evaluation unit And a determination unit that determines the battery state based on the above. Thus, the battery state is determined by the battery system itself, the user can immediately grasp the battery state, and can immediately take measures when the battery is deteriorated.

  Further, the lithium ion secondary battery system 200 of the present invention includes a control unit that controls the operation of the lithium ion secondary battery 100 based on the determination result obtained by the determination unit. Accordingly, by performing the operation control in which the output is adjusted so as to suppress the deterioration, the life of the lithium ion secondary battery 100 can be extended.

According to the above battery cell 10, the degree of progress of the reaction between the electrode and the electrolytic solution is evaluated based on the results of the qualitative and quantitative analysis of the CO ₂ gas and the CH ₄ gas by infrared spectroscopy. The capacity of the full cell can be grasped. In the present embodiment, the infrared spectroscopy device is used as a part of the battery system 200 and integrated with the battery 100. This facilitates the continuous analysis and determination of the battery state.

  Further, according to the battery cell and the battery determination method of the present invention, the deterioration tendency can be grasped by observing the above-mentioned reaction progress and capacity over time. As a result, the battery life can be extended by predicting the future deterioration tendency and performing appropriate operation control according to the deterioration state. Alternatively, it is also possible to estimate an appropriate time to replace or inspect the battery in order to avoid trouble of the device.

  In order to extend the life of the battery 100, for example, a method of reducing the rate of deterioration by appropriately controlling operation such as suppressing a charge / discharge amount, a method of replenishing lithium ions from the outside and a method of recovering the capacity of the battery, and the like. May be used.

DESCRIPTION OF SYMBOLS 1 ... Cell case 2 ... Electrolyte solution 3 ... Positive electrode 4 ... Negative electrode 5 ... Porous hollow tube 6 ... Optical window 7 ... Optical fiber 8 ... Separator 10 ... Battery cell 100 ... Lithium ion secondary battery 200 ... Lithium ion secondary battery system

Claims (4)

In a lithium ion secondary battery including a cell case, an electrolytic solution, a positive electrode, and a negative electrode,
A porous hollow tube that is disposed inside the cell case and is made of a substance that can transmit infrared light and allows only gas to pass therethrough,
And two optical windows that are arranged corresponding to both ends of the porous hollow tube and can transmit infrared light,
The two optical windows, on the one hand, can receive infrared light from an infrared light source outside the cell case and, on the other hand, can emit infrared light toward a detector outside the cell case. Rechargeable battery.   The lithium ion secondary battery according to claim 1, wherein the optical window is detachable with an optical fiber. A lithium ion secondary battery according to claim 1 or 2,
A lithium-ion secondary battery system, comprising: an infrared spectroscopy device that inputs and outputs infrared light to and from the porous hollow tube. An analysis unit for qualitatively and quantitatively analyzing the gas present in the battery cell case by infrared spectroscopy;
Based on the qualitative / quantitative analysis results obtained in the analysis unit, an evaluation unit that acquires the capacity deterioration state of at least one of the positive and negative electrodes,
The lithium ion secondary battery system according to claim 3, further comprising: a determination unit that determines a battery state based on the capacity deterioration state of the positive and negative electrodes obtained by the evaluation unit.

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