JP2014116251A - Lithium ion secondary battery, and lithium ion secondary battery control method, state detection method of lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that a larger available capacity of cells is wasted due to variation of individual cells, when controlling a large number of cells simultaneously in a system.SOLUTION: In a lithium ion secondary battery and its control system, state of charge (SOC) of an active material is obtained by detecting the color (=reflection light obtained when irradiating light of visible light wavelength region) of an active material contained in a positive electrode or a negative electrode, and then charge and discharge are controlled depending on the state thus controlling a battery.

Description

  The present invention relates to a battery control system having high capacity and excellent safety, and an assembled battery such as a battery, a module, and a pack provided with the system.

  Lithium ion secondary batteries are being rapidly developed as batteries for use in portable electronic devices and hybrid vehicles. In such a lithium ion secondary battery, a positive electrode having a positive electrode mixture layer containing a positive electrode active material on one side or both sides of the current collector and a negative electrode mixture layer containing a negative electrode active material are usually provided on the current collector. A negative electrode having one or both sides is used. In addition, lithium-containing composite oxides such as lithium cobaltate, lithium nickelate, and lithium manganate are generally used for the positive electrode active material of the lithium ion secondary battery, and a carbon material or the like is generally used for the negative electrode active material.

  Moreover, high safety | security is calculated | required by the lithium ion secondary battery with the high capacity | capacitance accompanying various functions, etc. of use apparatus, and improvement of various battery characteristics.

  In Patent Document 1, as a means for directly measuring the remaining capacity of the battery, an optical fiber is disposed in the battery, irradiated with infrared light, and the reflected light intensity from the negative electrode is measured, whereby the residual graphite is obtained. A means of predicting capacity is used. As a result, it is described that the remaining capacity can be measured more accurately and the life can be predicted as compared with the remaining capacity determination using electrical measurement.

JP 2000-131405 A

  Conventionally, when controlling and controlling the battery voltage range in a battery system, even if the internal electrode state has deteriorated after long-term use, it will be used at the same voltage range and the same rate. The risk to the battery such as generation increases. At the same time, when a large number of cells are controlled simultaneously in the system, due to variations in individual cells, etc., only a voltage range narrower than the actual specified range can be practically used, and there is still a margin. Even if there is a cell that can use more capacity, there is a problem that this is wasted.

  On the other hand, there is a description that by using the method described in Patent Document 1, it is possible to more accurately measure the remaining capacity and predict the life. By using this method, it is possible to measure the remaining capacity, but on the other hand, when used at a high rate, or after long-term use, with negative electrode deterioration, the remaining capacity is large, It cannot be predicted and measured that the polarization on the negative electrode surface increases and the risk of dendrite generation increases. Therefore, when used as a system, the effect of increasing the available capacity safely and effectively cannot be expected.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a battery control system having a high capacity and excellent safety, and an assembled battery such as a battery, a module, and a pack provided with the system. Is.

  The battery control system according to the present invention that has achieved the above object can detect the color of the active material contained in the positive electrode or the negative electrode (= reflected light obtained when irradiated with light in the visible light wavelength region). The battery is controlled by grasping the state of charge (SOC) of the substance and controlling charging and discharging according to the state.

  According to the present invention, it is possible to provide a battery control system having a high capacity and excellent safety and a long battery life, and an assembled battery such as a battery, a module, and a pack provided with the system.

It is a schematic diagram which shows the structure of the optical charge control battery in this invention. It is the figure which showed typically arrangement | positioning on the electrode surface of the optical fiber in this invention. It is the figure which showed typically arrangement | positioning on the electrode surface of the other optical fiber in this invention. It is the figure which showed typically arrangement | positioning on the electrode surface of the other optical fiber in this invention. It is the figure which represented typically the characteristic of the optical fiber for signal lights in this invention, and a detection part. It is the figure which represented typically the characteristic of the optical fiber for other signal lights in this invention, and a detection part. It is a flowchart of the process concerning the inspection of the optical system in the present invention. It is a flowchart of the process process concerning the battery control in this invention.

  In the present invention, the state of charge (SOC) of the active material is grasped by detecting the color of the active material contained in the positive electrode or the negative electrode (= reflected light obtained when irradiated with light in the visible light wavelength region). Control the battery by triggering charging and discharging.

  As mentioned earlier, there is an example of measuring the reflected light intensity using infrared light and measuring the remaining capacity, but in the present invention, it is possible to grasp the state of charge more directly. Measure the “color” of the active material. Furthermore, not only the color is measured, but when the color indicating the most dangerous state is detected, the battery is controlled by a method of stopping charging and switching to discharging.

  For example, it is known that graphite used for the negative electrode active material changes in hue due to change in interlayer distance with insertion of lithium. When lithium is inserted between the graphite phases, a regular laminated structure is formed by separating several graphite layers. At this time, a state in which lithium is inserted for each n layer is called an nth stage. In addition, it is known that the stage 1 which is the most filled state has a LiC6 structure, in which lithium is inserted between all the layers, and the stage 2 has a LiC12 structure. In the inserted state, lithium is inserted every three layers in stage 3, and every four layers in stage 4. It is considered that the hue changes due to the change in the interlayer distance of the graphite with these stage changes, and each of the following colors is exhibited.

Stage 1; yellow to gold Stage 2; red to reddish brown Stage 3; blue to dark blue Stage 4; black to gray Of these, graphite into which lithium has been inserted up to Stage 1 is when the battery is disassembled in a charged state From the fact that the negative electrode surface is gold, it is well known by those skilled in the art that the LiC6 of the stage 1 exhibits yellow to gold.

  As shown above, the color of the graphite changes as lithium is inserted into the graphite. However, if lithium is further inserted into the graphite in the stage 1 = yellow to gold state, Lithium that cannot enter between the layers is deposited as dendrites on the graphite surface. Therefore, even in an actual battery, after graphite exhibits a yellow to gold color, it must be avoided to try to insert lithium into the same graphite. Accordingly, the present inventors have observed the color of the active material used for the electrode, and have studied to control charging / discharging using this as a trigger when the “color” indicating the most dangerous state is detected.

  Specifically, an optical fiber is built in the battery, and thereby, light having a wavelength of 400 to 650 nm is irradiated from the outside, and the wavelength and intensity of the light reflected by the active material are measured. The wavelength of 400 to 650 nm is a wavelength including visible light that roughly shows blue, green, yellow, and orange. Among the colors that change depending on the graphite stage, the wavelength that includes yellow light has the highest risk of dendrite generation. It is an area. Since the reflected light is detected by changing the intensity of light in the same wavelength range as the irradiated light, it is only necessary to select which wavelength range of light is used as the irradiated light. Here, among the color changes of graphite, the most dangerous state before the occurrence of dendrite is the case of exhibiting yellow to gold color, but on the other hand, if it is a slight dendrite, it will disappear upon discharge even if it is generated. There may be no problem. In such a case, a slight dendrite may be allowed to be generated if it can be confirmed that it can completely disappear during discharge. In such a case, it is necessary to detect not only the color change of graphite but also the generation of dendrite, and it is necessary to irradiate a wide range of visible light from blue to orange. Since dendrite is a lithium metal, reflection occurs over a wide range of visible light. Therefore, when yellow light is irradiated to detect only the risk of graphite, it is difficult to determine whether the reflection is close to graphite or close to dendrite, and visible light in a wide wavelength range is irradiated. Therefore, if the reflected light intensity of yellow only is measured, the color of the graphite will be detected. Is possible. Further, by irradiating light in such a wavelength region, it is possible to detect the generation of dendrites even when an active material that does not cause a color change other than graphite is used. In this sense, the wavelength range of the irradiation light is preferably a wide range of 400 to 650 nm. When such control is performed, a white light source having a wide wavelength band such as a halogen lamp can be used as the light source. In addition, when using a light source with a limited wavelength range, such as an LED or various laser lights, each of the above-mentioned charging is performed by irradiating with a plurality of light sources having different wavelengths and measuring a change in reflected light intensity at each wavelength. It is also possible to detect the stage state and the occurrence of dendrite and control charging and discharging accordingly.

  Thus, when using light of a plurality of wavelengths, an independent detection system for each light of each wavelength, that is, (light source-illumination optical fiber-detection point-detection optical fiber-detector) is installed and It is also possible to comprehensively determine the obtained detection signal and provide feedback to control such as charging and discharging. A single path, that is, (light including a plurality of wavelengths-illumination optical fiber-detection point-detection optical fiber-light separation unit-detector) is also possible. In the case of this configuration, a mechanism for separating the light emitted from the detection optical fiber into components of respective wavelengths is necessary. It is convenient to use a color filter as the separation mechanism. It is also possible to separate the light using a spectroscope.

  On the other hand, when dendrite is generated even once, fine seed crystals remain on the surface of the graphite, and there is a problem that dendrite easily grows at the same location during the next charge. From such a viewpoint, the color immediately before the dendrite is generated on the graphite is yellow to gold, and only the yellow light of 550 to 600 nm is selectively irradiated in the charging process, and there is the intensity of the reflected light with respect to the irradiated light. It is also possible to stop charging when a certain level or more is reached. When performing such control, since the reflected light intensity also depends on the graphite content contained in the negative electrode mixture layer, depending on the composition and type of various negative electrode mixture layers, there is a risk in advance. It is necessary to measure the high reflected light intensity. If charging is stopped by detecting only a slight amount of yellow light, charging will stop even if there is still a margin in the negative electrode utilization rate, and the usable capacity will be reduced more than necessary. This is because there is a danger. Thus, when selectively irradiating only yellow light, charging can be stopped before dendrite is generated, and higher safety can be ensured. In this sense, the wavelength range of the irradiation light is more preferably 550 to 600 nm yellow light. When performing such control, it is possible to use a light source with a limited wavelength range, and it is preferable to use a lamp, a light emitting diode (LED), or various lasers that emit light of the wavelength as the light source. is there. As the yellow light source, for example, an AlGaInP-based LED having a light emitting layer can be used.

  Arbitrary forms can be adopted for the coupling between the light source and the illumination optical fiber. For example, a condensing lens may be combined with a bullet-type LED, and the emitted light may be condensed on the end face of the illumination optical fiber. At this time, it is desirable to match the NA (numerical aperture) of the condensing optical system with the NA of the illumination fiber. Further, the LED chip can be arranged near the end face of the illumination fiber and can directly enter the illumination optical fiber without passing through the air layer. The end surfaces of the LED chip and the illumination optical fiber are sealed with a transparent resin or the like. At this time, it is desirable to design the shape of the transparent resin so that most of the light emitted from the LED is totally reflected in the sealing transparent resin and efficiently transmitted into the illumination optical fiber. This form has no loss of light due to the interface with air, and is effective in miniaturization.

  In the present invention, an optical fiber is arranged at a position in contact with the electrode surface in order to measure the entire electrode surface in a wider range and to obtain a more reliable measurement method that is less affected by location dependence. That is, an optical fiber is disposed between the electrode surface and the separator and used, and it is necessary to prevent the battery reaction as much as possible. Therefore, from such a viewpoint, the diameter is preferably as small as possible. However, if it is too small, there are problems that it is difficult to manufacture and obtain, is expensive, and it is difficult to ensure that the intensity of light incident light and reflected light is measurable. For this reason, it is better that the diameter of the fiber is small if the diameter is small in a range where the irradiation light can be introduced and the reflected light can be transmitted with a measurable intensity.

  The open core of the optical fiber may be coated with a fluororesin or may be treated with a silane coupling agent containing a fluorine element. The control system of the present invention can be applied to a lithium ion battery using a non-aqueous electrolyte, and is within the range that does not impair the optical performance of the optical fiber such as illumination and detection in terms of preventing the deterioration of the optical fiber itself. May be used.

  In the present invention, the optical fiber is incorporated in the battery without roughening the electrodes such as the positive electrode and the negative electrode. As described above, the optical fiber is disposed at a position in contact with the electrode surface. Therefore, the range in which the light incident through the optical fiber can be measured is the active material present on the outermost surface of the electrode. In addition to this, it is possible to obtain information on the side surface by arranging an optical fiber on the side surface of the electrode, but in this case as well, the active material existing on the outermost surface of the side surface is measured.

  Next, in the method of the present invention, the arrangement of the optical fiber inside the battery can be any arrangement as long as the entire electrode surface can be measured in a wider range and measurement with less influence due to location dependence can be performed. You can match by method.

  FIG. 1 schematically shows a configuration of an optical charge control battery according to the present invention. Lithium ion battery, optical system for detecting the state of charge, optical state determination system for optically determining the state of charge of the battery by receiving the detection signal, and charge / discharge control by receiving the determination signal It consists of a charge / discharge control system. The optical system includes a light source system, a reference light optical fiber, a signal light optical fiber, a reference light detector, and a signal light detector.

  The light source system includes a light source that is a member that emits light and an optical material member such as a condensing lens for coupling the light source to each optical fiber. The optical fiber preferably has two systems for reference light and signal light.

  By dividing the light reception signal of both, the influence of changes in the brightness of the light source and detector sensitivity due to individual differences in the light source and detector, power supply fluctuations, temperature changes, or changes over time is canceled, and only the internal state change of the battery Can be detected more accurately. For this purpose, the reference light and the illumination light are preferably received from the same light source, and the light receiving positions are preferably close to each other and fixed to the light source system.

  The optical fiber for reference light is for transmitting the light source light quantity. Therefore, it is possible to go outside the battery. Further, the inside of the battery can be routed in the same manner as the signal light fiber. In the present invention, since the transmission distance by the optical fiber is short, there is almost no influence even if the lengths of both the reference light and the signal light are different, and the lengths can be designed differently. Furthermore, if the reference light is designed so that it can be directly detected by the reference light detector, the reference light can be detected without going through the optical fiber.

  The optical fiber for signal light is preferably introduced into the lithium ion battery, and the optical fiber is preferably disposed at a position in contact with the electrode active material. The signal optical fiber has a detection unit for detecting the state of the active material. In the signal light optical fiber, the light source system to the detection unit is referred to as illumination light optical fiber, and the detection unit to the signal detector is referred to as detection light optical fiber. It is also possible to install a plurality of signal light optical fibers for the detection unit. A place where the optical fiber for signal light is embedded can be set so that each detection unit is arranged at a predetermined position on the electrode. In this configuration, an optical fiber for signal light is arranged in parallel with one end of the electrode surface, and three detection units are installed at equal intervals.

It is preferable to install a detector for reference light and a signal light, respectively. In order to reduce the difference between the two, it is preferable to use two independent detectors configured on the same chip.
The light emitted from each optical fiber is condensed on each detector using a condensing lens if necessary. The detected light reception signal is subjected to signal processing in accordance with a light control algorithm described later, and is used for charge control of the lithium ion battery.

  Further, as a method for efficiently obtaining information on the entire surface of the electrode while using as little optical fiber as possible, for example, an optical fiber arrangement as shown in FIG. 2 can be used. As shown in FIG. 2, the optical fiber for signal light is arranged on the diagonal line of the electrode surface, and the distance from the optical fiber insertion port is set by narrowing the interval according to the distance from the light source and setting four positions. All of the left and right sides of the electrode can be observed.

  FIG. 3 shows a configuration example in which a signal optical fiber is arranged in a loop on an electrode and can be detected by a plurality of detectors arranged in a plane. The introduction / extraction point of the optical fiber into the battery is close, and the distance between the light source system and the detector can be close.

  FIG. 4 shows an example in which an optical fiber for detection light and an optical fiber for illumination light are separately installed in the optical fiber for signal light. This configuration has an advantage that the angles of the illumination light and the detection light can be arbitrarily set, and an efficient arrangement can be selected.

  Furthermore, as an arrangement for obtaining information on the entire surface of the electrode more reliably, optical fibers may be arranged radially or in a mesh form. Furthermore, the material of the separator itself may be used as a waveguide, or the waveguide may be arranged in a mesh shape on the separator surface.

  FIG. 5 shows an example of the structure of the detection unit. In this detection part, the core of the fiber was exposed in a concave shape by removing the fiber cladding, and the core opening part was gradually narrowed at the center part. With this configuration, the propagated irradiation light diffuses out of the core and irradiates the electrode active material. A part of the light reflected / scattered by the active material returns to the core, propagates again in the optical fiber, and reaches the detector. The structure of the detection unit is established if the total reflection condition is violated, and a structure for effectively irradiating illumination light and collecting reflected light / scattered light can be appropriately incorporated.

  FIG. 6 shows a derivative example, in which a lens is arranged between cut optical fibers. In this configuration, the angle of the illumination light and the detection light with respect to the axial direction of the optical fiber can be increased, and there is an advantage that a wide range can be illuminated and reflected / scattered light from a wide range can be collected. .

  The intensity of incident light inside the battery is strongest immediately after the optical fiber is inserted into the battery from the outside of the battery, and as the distance from the insertion port increases, the intensity decreases as the optical fiber is transmitted. Go. Accordingly, the intensity of the reflected light also decreases accordingly, and when these are corrected and finally measured, it is necessary to measure evenly at any location. From such a viewpoint, it is possible to apply a method in which the detection unit is made smaller in the vicinity of the insertion opening where the light intensity is strongest, and the detection unit is gradually enlarged as the distance increases.

  In the present invention, it is also possible to detect a Raman scattering spectrum by irradiating excitation light using an optical fiber waveguide incorporated in the battery. The precipitate on the negative electrode surface can be measured by Raman scattering measurement, and the cycle life can be determined by the kind, element ratio, amount, etc. of the precipitate. Moreover, the Raman scattering spectrum changes depending on the amount of Li extraction (that is, the state of charge) of the positive electrode, and it is possible to detect the overcharge and overdischarge states of the positive electrode by capturing this.

  Next, in the present invention, the optical fiber for signal light and the optical fiber for reference light that are incorporated in the battery and transmit the irradiation light and the detection light, and any optical fiber for reference light can be used as long as they can transmit visible light. It may be used. Since the optical fiber used in the present invention does not require long-distance / large-capacity transmission as compared with an optical communication application, there is a margin in propagation loss and bandwidth. Since the optical fiber is surrounded by an electrolytic solution and an active material in the battery, it is preferable to use a fiber with a clad in consideration of light transmission stability. The thickness of the cladding in the transmission line is preferably at least one of the transmission wavelengths. As for the fiber mode, since the multimode fiber has a larger aperture and can secure the detection signal strength, it is preferable to use the multimode fiber rather than the single mode fiber. For the refractive index profile of the core and the clad, either a step index or a graded index can be used. Specifically, it is possible to use optical fibers such as glass fiber, plastic clad silica (PCS) fiber, and plastic fiber. As the glass-based material of the optical fiber, a material made of high-purity silicon dioxide for both the core and the clad can be used. The core material is mainly made of quartz glass and has a refractive index higher by about 0.3 to 6% than that of the clad. In order to adjust the refractive index, quartz to which an element such as fluorine is added is used as the cladding material. As a plastic material, polystyrene, polymethyl methacrylate, or the like can be used as the core material, and silicone, polytetrafluoroethylene (PTFE), or the like can be used as the cladding material.

  The optical fiber is preferably designed with a core diameter of 5 μm or more and 600 μm or less, and an optical fiber including a cladding having a diameter of 10 μm or more and 750 μm or less. From the viewpoint of being incorporated in the battery, the core diameter of the optical fiber is 20 μm or more and 200 μm or less, without impairing the charge / discharge performance and capacity of the battery, and sufficient detection signal strength. The diameter is preferably 30 μm or more and 300 μm or less. If it is thin, there is an advantage that it can be mounted without reducing the battery volume, but the opening becomes small and the detection signal becomes weak. When the thickness is thick, the opposite is true, and it is desirable to design the detection signal quality in conformity with the battery capacity and structure.

  As shown in FIGS. 1 to 4, as the optical fiber for signal light, separate optical fibers for illumination light and optical fibers for detection light can be used. The same fiber can also be used.

  As shown in FIG. 4, when different optical fibers for illumination light and optical fibers for detection light are used, the respective front ends in the batteries are opened. The illumination light emitted from the irradiation fiber is reflected and scattered by the electrode active material in the battery. Since the reflectance varies depending on the stage of the active material, the scattered light intensity also changes accordingly. Of the reflected / scattered light, the light incident on the aperture cone of the detection fiber propagates through the detection fiber and exits to the detector side. It is desirable to design the shape and position of the tip of each fiber for irradiation and detection so that this irradiation, scattering and detection can be performed efficiently. As for the position, relatively strong scattered light can be detected when close to each other. On the other hand, the area to be detected becomes smaller. When isolated, the reverse is true, and it is preferable to design an appropriate position. As the shape of the tip of the fiber, it is possible to form a curved surface in addition to a plane perpendicular to the longitudinal direction of the fiber and a plane having an angle. A curved surface is formed, and the illumination fiber has a wide-angle diffused light, and the detection fiber has a configuration capable of collecting a wide angle. As in the case of the position, the tip shape can be illuminated over a wide area by wide-angle illumination, while the illuminance decreases, so it is preferable to design an appropriate shape. When forming a plane with an angle as the end face, the end face of the irradiation fiber and the end face of the detection fiber are configured to face each other, and the scattered light of the irradiated light efficiently enters the aperture cone of the detection fiber. As such, it is preferred to design the angle and position. The surface in that case may be a curved surface.

  In the signal light optical fiber, as a first method of using the same fiber for the illumination light optical fiber and the detection light optical fiber, an illumination light source is disposed at one end of one optical fiber, A detector is placed at the other end. The intermediate portion of the optical fiber is disposed inside the battery so as to be in contact with the electrode active material. And in a detection part, the state which does not become a total reflection condition of an optical fiber is comprised. As a typical structure, the core opening is formed by removing the cladding of the detection point fiber and exposing the core. In such a case, a configuration in which the refractive indexes of the core and the surrounding electrolyte are close to each other is desirable. With this configuration, the propagated irradiation light diffuses out of the core and irradiates the electrode active material. A part of the light scattered by the active material returns to the core, propagates again in the optical fiber, and reaches the detector. The structure of the detection unit is established if the total reflection condition is violated, and a structure for effectively irradiating illumination light and collecting scattered light can be appropriately incorporated. For example, (I) The exposed core is gradually thinned at the exposed central portion. (FIG. 5) (II) A lens is disposed between the cut optical fibers. (FIG. 6) (III) It is possible to adopt a shape for increasing the irradiation / condensing efficiency, such as cutting the optical fiber obliquely and facing the end faces. Further, in this configuration, it is easy to provide the detection units at a plurality of locations on the fiber, and it is also possible to detect the stage state of the active material as state information at a plurality of locations on the electrode.

  In the second method using the same optical fiber for illumination light and optical fiber for detection light, the reflected / scattered light is returned through the optical fiber through which the illumination light has propagated, and the light is detected. Is the method. In this case, a mechanism for separating the returned detection light is provided outside the battery.

  As the detector, any optical sensor device that can be detected as an electrical signal by receiving light irradiation can be used. Photoelectron emission effect type photosensors, photoelectron emission effect type photosensors such as photomultipliers, and the like can be used.

  As a constituent material such as a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing an electrolyte that can be applied to the battery control system of the present invention, any material that can be used for a lithium ion battery can be used. However, since an observation means for capturing a color change is used, it is preferable to use an active material exhibiting a color change in the visible light region, and among them, a material containing graphite as the negative electrode active material. Hereinafter, although a specific example is given, the application scope of the present invention is not limited to the following.

Specific examples of the positive electrode active material that can be used for the positive electrode according to the present invention include, for example, Li _{1 + c} M ¹ O ₂ (−0.1 <c <0.1, M ¹ : Co, Ni, Mn, Al, Mg (1-x) Li ₂ MnO ₃ —xLiMO ₂ (0.2 <x <0.7, M: Co, Ni, Mn, Al, Mg) layered oxide comprising a solid solution represented by like), LiMn ₂ O ₄ and lithium manganese oxides substituted spinel structure part with another element of the ^{_{element, LiM 2 PO 4 (M 2}} : Co, Ni, Mn , Fe, etc.) can be used. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO ₂ and LiNi _1-d Co _{d e} Al _e O ₂ (0.1 ≦ d ≦ 0.3, 0.01 ≦ e ≦ 0. 2) and other oxides containing at least Co, Ni and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , LiMn _{3 / 5} Ni _1/5 Co _1/5 O ₂ etc.). Only 1 type may be used for a positive electrode active material among the said illustrations, and 2 or more types may be used together.

  The positive electrode mixture layer usually contains a conductive additive and a binder together with the positive electrode active material. Specific examples of the conductive additive related to the positive electrode mixture layer include, for example, graphite such as natural graphite (flaky graphite, etc.), artificial graphite, etc .; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black And carbon black; and carbon fiber. Examples of the binder related to the positive electrode mixture layer include polyvinylidene fluoride, polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like.

  The positive electrode comprises a positive electrode mixture-containing composition in which a positive electrode mixture containing a positive electrode active material, a conductive additive and a binder is dispersed in an organic solvent such as N-methyl-2-pyrrolidone (NMP) and a solvent such as water ( Paste, slurry, etc.) can be prepared, and this positive electrode mixture-containing composition can be applied to one side or both sides of the current collector, dried, and subjected to a press treatment as necessary. However, the positive electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.

  As a composition of a positive mix layer, it is preferable that a positive electrode active material shall be 80-99.8 mass%, for example, it is preferable that a conductive support agent will be 0.1-10 mass%, and a binder is 0.1. It is preferable to set it as -10 mass%.

  As the positive electrode current collector, an aluminum foil, a punching metal, a net, an expanded metal, or the like can be used, but an aluminum foil is usually used. The thickness of the positive electrode current collector is preferably 10 to 30 μm.

  The negative electrode according to the lithium ion secondary battery of the present invention has a negative electrode mixture layer containing a negative electrode active material on at least one surface of a current collector.

  Specific examples of the negative electrode active material that can be used in the negative electrode according to the present invention include, for example, graphite [natural graphite: pyrolytic carbons, mesophase carbon microbeads (MCMB), carbon fiber and other graphitizable carbon at 2800 ° C. or higher. Artificial graphite graphitized with, etc.], pyrolytic carbons, cokes, glassy carbons, sintered materials of organic polymer compounds, MCMB, carbon fibers, activated carbon and other carbon materials; metals that can be alloyed with lithium (Si, Sn, etc.), materials containing these metals (alloys, oxides, etc.); LTO (titanium compounds), and the like. As the negative electrode active material, only one type may be used or two or more types may be used in combination.

  The negative electrode mixture layer usually contains a binder together with the negative electrode active material. As a binder which concerns on a negative mix layer, the same thing as the various binders illustrated previously as a binder which concerns on a positive mix layer can be used, for example.

  Moreover, a conductive support agent can also be contained in the negative mix layer as needed. As a conductive support agent which concerns on a negative mix layer, the same thing as the various conductive support agents illustrated previously as a conductive support agent which concerns on a positive mix layer can be used, for example.

  The negative electrode is prepared by dispersing a negative electrode mixture containing a negative electrode active material, a binder, and a conductive auxiliary agent used as necessary in an organic solvent such as NMP or a solvent such as water. Paste, slurry, etc.) can be prepared, and this negative electrode mixture-containing composition can be applied to one side or both sides of the current collector, dried, and subjected to a press treatment as necessary. However, the negative electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.

  As a composition of a negative mix layer, it is preferable that a negative electrode active material shall be 80-99.8 mass%, for example, and it is preferable that a binder shall be 0.1-10 mass%. Moreover, when making a negative mix layer contain a conductive support agent, it is preferable that the quantity of the conductive support agent in a negative mix layer shall be 0.1-10 mass%.

For the negative electrode current collector, a copper or nickel foil, punching metal, net, expanded metal, or the like can be used for the current collector, but a copper foil is usually used. The thickness of the negative electrode current collector is preferably 5 to 30 μm. The separator is the same separator as that used in ordinary lithium ion secondary batteries, such as polyethylene (PE) or polypropylene (PP). A microporous membrane made of polyolefin such as ethylene-propylene copolymer can be used, but it may be selected so as to fall within the scope of the present invention according to the combination of the positive electrode and the negative electrode. The microporous film constituting the separator may be, for example, one using only PE or one using PP, or a laminate of a PE microporous film and a PP microporous film. There may be.

  The separator preferably has a property (that is, a shutdown function) that the pores are blocked at 80 ° C. or higher (more preferably 100 ° C. or higher) and 170 ° C. or lower (more preferably 150 ° C. or lower).

  The microporous membrane made of polyolefin is composed of the polyolefin as described above. For example, a film or sheet formed by a stretching method, that is, a polyolefin mixed with an inorganic filler is uniaxially or biaxially stretched to form a fine film. After forming the pores, those produced by removing the inorganic filler as required can be used. In addition, the pore formation method using a solvent, that is, the polyolefin illustrated above and another resin or paraffin are mixed to form a film or sheet, and then, in a solvent that dissolves only the other resin or paraffin, What is manufactured by immersing a film or sheet and dissolving only the other resin or paraffin to form pores can be used as a polyolefin microporous film. Furthermore, a polyolefin microporous membrane produced by a method combining the stretching method and the pore formation method using the solvent can also be used.

  As the nonaqueous electrolytic solution according to the lithium ion secondary battery of the present invention, a solution in which an electrolyte salt is dissolved in an organic solvent can be used. Examples of the solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone, 1, 2 -Dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, Sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3-propane sultone, etc. Aprotic organic solvents, and the like, may be used these alone, or in combination of two or more of these. Also, amine imide organic solvents, sulfur-containing or fluorine-containing organic solvents, and the like can be used. Among these, a mixed solvent of EC, MEC, and DEC is preferable. In this case, it is more preferable to include DEC in an amount of 15% by volume to 80% by volume with respect to the total volume of the mixed solvent. This is because such a mixed solvent can enhance the stability of the solvent during high-voltage charging while maintaining the low temperature characteristics and charge / discharge cycle characteristics of the battery high.

As the electrolyte salt related to the non-aqueous electrolyte, a salt of a fluorine-containing compound such as lithium perchlorate, lithium organic boron, trifluoromethanesulfonate, imide salt, or the like is preferably used. Specific examples of the electrolyte salt, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiCF 3 CO 2, Li 2 C 2 F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (Rf ₃ OSO ₂ ) ₂ [where Rf is Represents a fluoroalkyl group. These may be used alone or in combination of two or more thereof. Among these, LiPF ₆ and LiBF ₄ are more preferable because of good charge / discharge characteristics. This is because these fluorine-containing organic lithium salts have a large anionic property and are easily ion-separated, so that they are easily dissolved in the solvent. The concentration of the electrolyte salt in the solvent is not particularly limited, but is usually 0.5 to 1.7 mol / L.

  In addition, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexyl benzene, biphenyl, and fluorobenzene are used for the purpose of improving the safety, charge / discharge cycleability, and high-temperature storage properties of the non-aqueous electrolyte. An additive such as t-butylbenzene may be added as appropriate. In the present invention, the lithium-containing composite oxide (A) containing Mn is used. However, since the surface activity can be stabilized, it is particularly preferable to add an additive containing sulfur element.

  Further, in the lithium ion secondary battery of the present invention, the above non-aqueous electrolyte is gelated by adding a known gelling agent such as a polymer (gel electrolyte), or replaced by a non-aqueous electrolyte. A solid electrolyte or the like can also be used.

As the solid electrolyte, a material that can exist stably under the operating voltage of the battery, and glass, oxide, sulfide, or the like having lithium ion conductivity can be used. For _{example, Li 3.25 Ge 0.25 P 0.75 S} , or sulfides such as _{Li 2 S-GeS 2, Li} 1 + x Al x Ti 2-x (PO 4) 3; (0 ≦ x ≦ 1), Li _{1 + y} M _y Zr _2-y (PO ₄ ) ₃ ; (M = Cr, La, In, 0 ≦ y ≦ 1) and other compounds having a NASICON structure, and Li _{1 + z} Al _z Ti _{2− z (P 1-s Si s} O 4) 3; (0 ≦ z ≦ 1,0 ≦ s ≦ 0.5), Li 1 + t Al t M u Ti 2-t-u (PO 4) 3; (M = Ga, In) (0 ≦ t ≦ 1, 0 ≦ u ≦ 0.5).

  The battery control system of the present invention is not limited to the above example, and any known lithium ion can be used as long as an active material that exhibits a color change with lithium insertion / extraction in the visible light region is used. It can also be preferably used for a secondary battery.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

  An example of the process concerning the battery control of this invention is shown.

  FIG. 7 is a flowchart for checking the optical system. First, this control is started in response to an instruction to start a charging operation, and an optical system inspection operation is performed as a first stage. In the inspection operation, the power source of the light source and the detector is turned on, and the light reception signal of the reference light is received from the detector that receives the reference light. If this signal cannot be received, it is determined that either the light source or the detector has failed, and the flow proceeds to another flow. When the light reception signal is received, the light reception signal of the signal light that receives the internal information of the battery is received. Even when this signal cannot be received, it is determined that either the light source or the detector is out of order, and the flow proceeds to another flow. When the light reception signal is received, it is determined that the optical system is operating normally, and the inspection operation of the optical system is terminated. Note that the light source and detector are turned off as necessary. It is preferable to perform this inspection operation frequently, such as when the light source / detector is ON.

  Next, the operation proceeds to an optical measurement operation in a charged state. The flow is shown in FIG. First, the power source and the detector are turned on. Then, the light reception signal of the reference light is received. This is data A. Next, a light reception signal of signal light is received. This is data B. These data are stored in a memory and division is performed. The result is stored in memory as data X.

X = B / A
This division operation cancels the effects of changes in light source brightness and detector sensitivity due to differences in individual light sources and detectors, power supply fluctuations, temperature changes, and changes over time, and only changes in the internal state of the battery are more accurate. To detect. In a state where the same amount of light is incident on the reference light optical fiber and the signal light optical fiber, the data X corresponds to the transmittance of the signal light optical fiber.

  Next, an operation for determining the state of charge is performed. Data of a level used as a reference for the determination is stored in a memory, and the state is determined by comparing with data X. FIG. 8 shows, as an example, a case where charge / discharge control for performing constant current / constant voltage charge / constant current discharge is performed, where a is a level indicating the discharge state, c is a level indicating the charge state, and a level is used for switching the charging method. Three stages of b were set. When these levels a, b, and c are compared with data X and a <X <b, no active material has reached the fully charged / discharged state, and either charging or discharging is performed. Also good. When B ≦ X <c, the active material in a fully charged state and the active material that does not reach full charge are mixed in the electrode, and it is preferable to charge using a relatively small current during charging. Then, the case where c ≦ X is determined as a fully charged state (SOC = 100), and the case where X ≦ a is determined as a discharged state (SOC = 0).

  Then, a signal corresponding to each determination is output and transmitted to the charge / discharge control system. The charge / discharge control system that has received the optical state determination signal for charge / discharge performs charge / discharge control in accordance with each determination signal. When the determination signal corresponds to a <X <b, it is preferable to perform charging with the charging method as constant current control. When b ≦ X <c, charging is preferably performed by switching the charging method to constant voltage control. When c ≦ X, charging is stopped, and when X ≦ a, discharging is stopped.

Of the above levels, only level a indicating the discharge state and level c indicating the full charge state may be set, and charge / discharge control for performing constant current charge-constant current discharge may be performed. In this case, when a <X <c, either charging or discharging may be performed. When c ≦ X, the charging is stopped by determining that the battery is fully charged, and corresponding to X ≦ a. If so, stop the discharge.
It is also possible to store a fixed specified value as the level data used as a criterion for determining the state of charge. It is also preferable to measure in the initial stage of battery production and store it in a memory. In this way, it is possible to hold appropriate judgment reference values in each battery, that is, control including individual differences of the batteries becomes possible.

  During the charging operation, it is also preferable to appropriately turn off the light source and the detector to reduce power consumption. Then, after a predetermined time interval, the light source and the detector are turned on again to return to a loop process in which the state of charge is optically measured. And charging control is performed according to the determination signal corresponding to the data X which changes as charging progresses.

  Note that there are cases where the state change of the active material proceeds non-uniformly depending on the position on the electrode, such as when rapid charging or pulse charging is performed. After that, the leveling occurs, and the detection level of the optical state may vary accordingly. For example, even if c ≦ X once, it may return to X ≦ c if measured again after a while. If such a phenomenon occurs due to the battery and the charge control method, return to the optical measurement loop a predetermined number of times before recharging, and re-measure and return to X ≦ c again. It is also preferable to perform a charging operation.

  Moreover, it is preferable to perform the charging control by the optical measurement described above in parallel with the electric control by measuring the voltage and current of the battery.

Example 1
<Production of test cell>
As the positive electrode active material, LiMn _1/3 Ni _1/3 Co _1/3 O ₂ : 93.5 parts by mass with an average particle diameter of 6 μm was used. In addition, acetylene black: 4 parts by mass, polyvinylidene fluoride: 2 parts by mass And polyvinylpyrrolidone (PVP): 0.5 part by mass is dispersed in NMP to prepare a positive electrode mixture-containing composition, which is applied to one side of an aluminum foil having a thickness of 15 μm to be a current collector using an applicator. Then, after drying and pressing, it was cut into a size of 100 × 100 mm to produce a positive electrode. The thickness of the positive electrode mixture layer of the obtained positive electrode was 76.5 μm.

  Scale-like graphite (manufactured by Hitachi Chemical Co., Ltd.): 97.8 parts by mass, CMC: 1.2 parts by mass and SBR: 1 part by mass are dispersed in water: 100 parts by mass to prepare a negative electrode mixture-containing composition. This was applied to one side of a copper foil having a thickness of 8 μm serving as a current collector using an applicator, dried, pressed, and then cut into a size of 105 × 105 mm to prepare a negative electrode. The thickness of the negative electrode mixture layer of the obtained negative electrode was 92.8 μm.

  As the reference light optical fiber and the signal light optical fiber, an optical fiber having a diameter including the cladding of 80 μm, a core diameter of 50 μm, a refractive index value of the core of 1.47, and a cladding of 1.46 was used. In the present embodiment, the above-described configuration in which the light source for illumination is disposed at one end portion of one optical fiber and the detector is disposed at the other end portion as the above-described configuration of the signal light optical fiber is installed. . The middle part of the optical fiber was placed inside the battery so as to be in contact with the electrode active material. The portion where the optical fiber and the electrode active material are in contact with each other was arranged on the diagonal of the electrode surface. And detection points were installed at three places on the incident side, center, and emission side. As shown in FIG. 5, the optical fiber cladding was removed and the core was exposed as shown in FIG. 5 to form an open core portion. Each detector was configured to break the total reflection condition of the optical fiber. With this configuration, the radiated light that has propagated diffuses out of the optical fiber from the open core and irradiates the electrode active material. A part of the light reflected / scattered by the active material returns to the core from the core opening again, and propagates again in the optical fiber to reach the detector. Furthermore, the core diameter is made thinner at the center of the open core so that the irradiated light can effectively irradiate the electrode active material, and the scattered light can be efficiently collected on the optical fiber on the detection side. In the core opening part, the light source side serves as an irradiation part, and the detector side serves as a light collecting part. In this example, the length of the core opening part was 200 μm and the core diameter at the center of the core opening part was 40 μm in all three detection parts.

On the positive electrode, the air permeability is 90 sec. / 100cc. After laminating the separator (PE microporous film with a thickness of 18 μm), the optical fiber was placed diagonally, and the negative electrode was laminated so as to face the positive electrode and inserted into the laminate film outer package. . Then, after injecting a non-aqueous electrolyte (solution in which LiPF ₆ was dissolved at a concentration of 1.2 M in a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 2: 8), the laminate film outer package was sealed. A test cell was prepared.

<Wavelength 591 nm; Measurement and control using yellow light>
In the test cell incorporating the above optical fiber, an optical fiber for signal light was installed on the electrode surface. A light source was placed at one end and a detector at the other end. An AlGaInP-based bullet-type yellow light-emitting diode having a peak wavelength of 591 nm was used as a light source, and the light was condensed on an optical fiber for illumination light through an imaging lens. The light emitting diode was made to emit light at a driving voltage of 2.1 V and a maximum driving current of 20 mA. A silicon photodiode was used as the detector, and the light emitted from the optical fiber for detection light was directly received, and the intensity was converted into a voltage.

  A reference light measurement system was also constructed. In the above light source system, an optical fiber for reference light is disposed in parallel with the optical fiber for signal light so that a part of the light source light is received. The reference light optical fiber is not provided with a detector. A detector was placed at the opposite end of the light source system to measure the output signal voltage. The measurement value of the emitted light of the optical fiber for signal light in the test cell is normalized by setting the detection signal of the reference light as 100%. This numerical value corresponds to the data X described above. This optical fiber for reference light was installed outside the battery.

  The measurement was started from the discharge state of the test cell. In the discharge state, about 7% of light was detected as data X. This state indicates that the battery is in a discharged state. From this, charging was started at a 1C rate. Then, the detected light intensity started to increase at the stage of 3.95V. This indicates that the active material in the stage 1 state has started to be generated on the negative electrode surface. Further, constant current charging was continued, and when the battery voltage reached 4.28 V and the detected signal intensity reached approximately 55%, the increase in signal intensity slowed down. This state indicates that all active materials on the negative electrode surface have reached stage 1, that is, are fully charged. This ended the charging operation.

  As a result, rapid charging using only constant current charging is possible, and the maximum capacity can be charged, and further charging is continued after all active materials on the negative electrode surface have reached stage 1. By doing so, it is possible to prevent lithium ions that have not been occluded in the active material from being deposited as dendrites.

Claims (12)

In a lithium ion secondary battery comprising a positive electrode that stores and releases lithium ions, a negative electrode that stores and releases lithium ions, and an electrolyte having lithium ion conductivity,
An illumination light guide that guides visible light emitted from a light source into the battery;
A detector that irradiates the light inside the battery and receives the light reflected inside the battery; and
A detection light guide for guiding the received light beam to a detector outside the battery;
A lithium ion secondary battery provided.   The lithium ion secondary battery according to claim 1, wherein the illumination light guide unit and the detection light guide unit are optical fibers. 3. The lithium ion secondary battery according to claim 2, wherein a diameter of the optical fiber is 10 μm or more and 750 μm or less. The illumination light guide and the detection light guide are formed as an integral light guide,
3. The lithium ion secondary battery according to claim 1, wherein the detection unit is formed by forming a part of the light guide unit out of a condition where light is guided. The light guide is composed of an optical fiber;
The lithium ion secondary battery according to claim 4, wherein the detection unit is formed by opening a part of the core of the optical fiber. 6. The lithium ion secondary battery according to claim 5, wherein the open core of the optical fiber is coated with a fluororesin. 6. The lithium ion secondary battery according to claim 5, wherein the opened core of the optical fiber is treated with a silane coupling agent containing a fluorine atom. The lithium ion secondary battery according to claim 2, wherein the optical fiber is inserted between the negative electrode and the separator. 9. The lithium ion secondary battery according to claim 2, wherein the optical fibers are arranged on a diagonal line of the negative electrode and / or radially and / or in a mesh shape. In a control method of a lithium ion secondary battery comprising a positive electrode that occludes and releases lithium ions, a negative electrode that occludes and releases lithium ions, and an electrolyte having lithium ion conductivity,
An illumination light guide that guides visible light emitted from the light source to the inside of the battery;
A detector that irradiates the light inside the battery and receives the light reflected inside the battery; and
A detection light guide that guides the received light beam to a detector outside the battery, and
Irradiating the visible light to the positive electrode and / or negative electrode of the battery,
Detecting change information of reflected light intensity at the visible light wavelength of the active material of the positive electrode and / or the negative electrode,
A method for controlling a lithium ion secondary battery, comprising: controlling charge / discharge of the lithium-on secondary battery according to change information of the reflected light intensity. The method for controlling a lithium ion secondary battery according to claim 10, wherein the visible light wavelength is visible light having a blue to orange color of 400 to 650 nm. In the method for detecting the state of a lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte,
A light guide for irradiating and detecting light on the negative electrode;
The light guide part is an optical fiber, the pumping light is irradiated using the optical fiber, and the Raman scattering spectrum is detected as reflected light, thereby detecting deposits on the negative electrode surface and determining the cycle life. A method for detecting a state of a lithium ion secondary battery.

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