JP2010205479A - All-solid battery employing power compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an all-solid secondary battery employing powder compact, capable of stabilizing voltage at discharge of the battery without being affected by temperature and noise. <P>SOLUTION: The all-solid battery employing powder compact includes a laminate equipped with a positive electrode layer, a negative electrode layer, and a solid electrolytic layer arranged between the positive electrode layer and the negative electrode layer, a voltage detection means detecting battery voltage, and a pressure control means controlling a restrictive pressure added on the laminate based on voltage detected by the voltage detection means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a compacted all solid state battery.

  In recent years, the demand for secondary batteries as a power source has expanded from small devices such as mobile phones to large devices such as automobiles, and the performance has been improved.

  The secondary battery used for the above application includes a positive electrode, a negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode. Among these, the electrolyte is a medium that conducts ions between the positive electrode and the negative electrode, and a liquid electrolyte or a solid electrolyte is used.

  When a liquid electrolyte (electrolyte) is used as the electrolyte of a secondary battery, there is a risk that gas will be generated inside the battery during charging and discharging, and the battery performance may be deteriorated. There is a fear. Therefore, a means for suppressing the generation of gas or allowing the gas to be removed, a means for preventing liquid leakage, and the like are required (for example, Patent Documents 1 and 2). On the other hand, when a solid electrolyte is used as the electrolyte of the secondary battery, there is no risk of the liquid leakage. In addition, it is not necessary to install a safety device that suppresses the temperature rise at the time of a short circuit, and to improve the structure and material for preventing a short circuit, which are necessary when a liquid electrolyte is used. As a technique related to an all-solid battery, for example, Patent Document 3 discloses a powder all-solid lithium battery obtained by pressure-molding a powdered solid electrolyte and a powdered active material.

  On the other hand, the battery can be used more stably as the voltage change is smaller. However, it is known that the voltage of the battery gradually decreases with discharge. Conventionally, a constant voltage circuit is installed in the circuit using a Zener diode or the like to make the voltage constant.

Japanese Patent No. 3735585 JP 2004-213902 A Japanese Patent Laid-Open No. 9-35724

  In the powder all solid lithium battery described in Patent Document 3, the positive electrode potential decreases with discharge, the contact area between the solid and the solid decreases due to deformation of the active material, the interface resistance increases, and the voltage increases. There was a problem of causing a drop.

  In addition, when a conventional Zener diode is used as a constant voltage circuit for a secondary battery, due to its semiconductor characteristics, the constant voltage range (breakdown voltage) fluctuates depending on the temperature, and the voltage drops when a current flows in the forward direction. Further, there is a problem that noise is generated and the voltage is changed.

  This invention is made | formed in view of the said problem, and makes it a subject to provide the powder all-solid-state secondary battery which can stabilize the voltage at the time of battery discharge, without receiving the influence of temperature or noise.

In order to solve the above problems, the present invention has the following configuration. That is,
The present invention provides a laminate having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a voltage detection means for detecting battery voltage, and the voltage detection means. And a pressure control means for controlling the constraining pressure applied to the laminate based on the measured voltage.

  Here, the “voltage detection means” is not particularly limited as long as it can detect a voltage, and may be, for example, a voltmeter. The “pressure control means” in the present invention is a means for controlling the restraining pressure applied to the laminate based on the voltage detected by the voltage detection means, and includes, for example, a piston device capable of motor control. The “compact all-solid battery” referred to in the present invention means an all-solid battery in which at least one of the positive electrode layer, the solid electrolyte layer, or the negative electrode layer contains a powdered battery material.

  In the present invention, the material used for the laminate preferably includes a material that causes volume shrinkage during battery discharge. When volume contraction occurs during battery discharge, for example, it is considered that the contact area between the active materials inside the battery and the contact area between the active material and the solid electrolyte decrease, but by increasing the restraint pressure by the pressure control means, This is because the contact area can be increased again, the battery reaction can be maintained, and the effect of the present invention becomes more remarkable.

  About the material which causes volume shrinkage at the time of battery discharge in this invention, it can be set as the active material contained in a positive electrode layer or a negative electrode layer.

  In this invention, it is preferable that the restraint pressure controlled by a pressure control means is a pressure with respect to the direction substantially the same as the lamination direction of a laminated body. This is because the voltage can be effectively controlled by adjusting the adhesion at the interface between the positive electrode layer and the electrolyte layer or between the electrolyte layer and the negative electrode layer.

  According to the present invention, the contact area between the active materials and the contact area between the active material and the solid electrolyte are intended by controlling the restraint pressure of the laminate according to the voltage value by the voltage detection means and the pressure control means. Can be increased or decreased. By appropriately increasing or decreasing the solid-solid contact area, the battery reaction can be controlled and the voltage during discharge can be stabilized. On the other hand, when the detection voltage value decreases, the pressure control means increases the restraint pressure, and the contact area between the active materials and the contact area between the active material and the solid electrolyte can be increased, thereby suppressing the voltage drop. . Further, the control of the restraint pressure is not affected by temperature or noise. That is, according to the present invention, it is possible to provide a powder all-solid secondary battery that can stabilize the voltage during discharge without being affected by temperature and noise, and has a sufficient discharge capacity.

It is a figure which shows roughly one form of the compacting all-solid-state battery concerning this invention. It is a figure which shows the voltage stabilization method of the compacting all-solid-state battery concerning this invention. It is a figure which shows the performance and effect of the compacting all-solid-state battery concerning this invention.

  Hereinafter, the case where the present invention is applied to a powdered all solid lithium ion secondary battery in which a positive electrode layer, an electrolyte layer, and a negative electrode layer are laminated in this order will be described. However, the present invention is not limited to this form, and can be applied to other compacted all solid secondary batteries.

1. Powdered all solid lithium ion secondary battery 100
FIG. 1 is a diagram schematically illustrating an entire compact all solid lithium ion secondary battery 100 (hereinafter referred to as “secondary battery 100”) according to the embodiment. As shown in FIG. 1, a secondary battery 100 includes a laminate 40 having a positive electrode layer 10, a solid electrolyte layer 20, and a negative electrode layer 30 in this order, current collectors 50 and 60, and a piston device as pressure control means. 80, a battery case 90 for housing them, a voltmeter 70 connected between terminals extending from the current collectors 50, 60, and a control unit 75 connected between the voltmeter 70 and the piston device 80. ing.

(Positive electrode layer 10)
The positive electrode layer 10 is a layer containing a positive electrode active material and a solid electrolyte. As a positive electrode active material, what can be used as a positive electrode active material of an all-solid-state lithium ion secondary battery can be used without being specifically limited, For example, a lithium transition metal oxide and a chalcogenide can be used. . In the secondary battery 100, it is particularly preferable to use a positive electrode active material that causes volume shrinkage during battery discharge. Examples of positive electrode active materials that cause volume shrinkage during battery discharge include LiCoO ₂ , LiNi _0.5 Co _0.5 O ₂ , LiTiS ₂ , LiNi _0.6 Co _0.3 Mn _0.1 O ₂ , and LiNi _0.6 Co. Mention may be made of _0.4 O ₂ , LiMn ₂ O ₄ and LiMn ₅ O ₁₂ . The solid electrolyte, those which can be used as the solid electrolyte of the all-solid-state lithium-ion secondary battery, in particular can be used without limitation, for example, can be used _{Li 2 S-P 2 S 5} . Li ₂ but S is not particularly limited ratio of the _P 2 _{O 5,} for _example, Li 2 _S: the P 2 _{O 5} 50: 50~100: it is 0 to be. In addition to these, the positive electrode 10 may contain a conductive material. As the conductive material, a material that can be used as a conductive material of an all-solid lithium ion secondary battery can be used without particular limitation. In the secondary battery 100, powdered materials are used as the positive electrode active material and the solid electrolyte, and after these are uniformly mixed, the positive electrode layer 10 is formed by pressure molding using a press machine or the like. . The form of the powder such as the powder particle diameter is not particularly limited. Moreover, a well-known means can be used about the mixing method and shaping | molding method of powder. The molding pressure is not particularly limited as long as it is a pressure that can provide a moldability that can function as the positive electrode layer 10 of the secondary battery 100.

(Solid electrolyte layer 20)
The solid electrolyte layer 20 is a layer formed by molding a powder solid electrolyte. As the solid electrolyte, the same solid electrolyte as that used for the positive electrode layer 10 can be used. After the solid electrolyte of the powder is uniformly mixed, it is pressure-formed using a press machine or the like to form the solid electrolyte layer 20. Known methods can be used for the powder mixing method and molding method. The molding pressure is not particularly limited as long as the molding pressure is such that the moldability to the extent that it can function as the solid electrolyte layer 20 of the secondary battery 100 is obtained.

(Negative electrode layer 30)
The negative electrode layer 30 is a layer containing a negative electrode active material and a solid electrolyte. As a negative electrode active material, what can be used as a negative electrode active material of an all-solid-state lithium ion secondary battery can be used without being specifically limited, For example, carbon, a lithium transition metal oxide, and a metal alloy are used. Can do. In the secondary battery 100, it is particularly preferable to use a negative electrode active material that causes volume shrinkage during battery discharge. Examples of the negative electrode active material that causes volume shrinkage during battery discharge include carbon. As the solid electrolyte, the same solid electrolyte as that used for the positive electrode layer 10 can be used. In addition to these, the negative electrode 30 may contain a conductive material. As the conductive material, those that can be used as the conductive material of the all-solid-state lithium ion secondary battery can be used without any particular limitation. In the secondary battery 100, powdery materials are used as the negative electrode active material and the solid electrolyte, and after these are uniformly mixed, the negative electrode layer 30 is formed by pressure molding using a press or the like. The form of the powder such as the powder particle diameter is not particularly limited. Moreover, a well-known means can be used about the mixing method and shaping | molding method of powder. The molding pressure is not particularly limited as long as the molding pressure is such that the moldability can function as the negative electrode layer 30 of the secondary battery 100.

(Laminated body 40)
The laminate 40 is formed by laminating the positive electrode layer 10, the electrolyte layer 20, and the negative electrode layer 30 in this order. In the secondary battery 100, a plurality of stacked bodies 40 are accommodated. The current collector 50 is on the positive side end surface (upper side of FIG. 1) of the laminates 40, 40,... And the current collector 60 is on the negative side end surface (lower side of FIG. 1) of the laminates 40, 40,. The current collectors 50 and 60 function as a positive electrode current collector and a negative electrode current collector, respectively. As the current collectors 50 and 60, those that can function as a positive electrode current collector and a negative electrode current collector of an all-solid-state lithium ion secondary battery can be used without particular limitation. The current collectors 50 and 60 extend to the outside of the battery case 90 so that the electric energy generated by the battery reaction can be taken out through the electrode terminals. Although not shown in FIG. 1, it is also collected between the stacked bodies 40, 40,... (Between the positive electrode layer 10 of one adjacent stacked body 40 and the negative electrode layer 30 of another stacked body 40). Electric body is provided.

(Voltmeter 70)
The voltmeter 70 is a means that is provided outside the secondary battery 100 and detects the voltage of the secondary battery 100. Based on the voltage value detected by the voltmeter 70, the operation of the piston device 80 described below is controlled.

(Piston device 80)
The piston device 80 is a device that controls the restraining pressure applied to the stacked bodies 40, 40,... In the battery case 90. 1, the piston device 80 is disposed between the upper wall surface of the battery case 90 and the current collector 50 of the stacked bodies 40, 40,..., And extends in the stacking direction of the stacked body 40 from the current collector 50 side. The pressure is applied toward. The piston device 80 is a device that controls the pressure applied to the stacked body 40 based on the voltage detected by the voltmeter 70. For this, for example, a piston device that operates by motor control can be used. As shown in the figure, the discharge voltage value information obtained from the voltmeter 70 at the time of battery discharge is sent to the control unit 75, and the operation of the piston device 80 is determined in the control unit 75, and the operation of the piston device 80 is fed back. Be controlled. Thereby, the pressure concerning the laminated body 40 is controlled. The control unit may be a known feedback control device. For restraining pressure on the stack 40 is not particularly limited, 30 N / cm ² or more 10000 N / cm ² or less, preferably be controlled at 100 N / cm ² or more 2000N / cm ² or less in the range preferable.

(Battery case 90)
The stacked bodies 40, 40,..., Current collectors 50, 60, and the piston device 80 are accommodated in a battery case 90, and the secondary battery 100 is formed. The material and shape of the battery case 90 are not particularly limited as long as the battery reaction of the all-solid-state lithium ion secondary battery can be performed without any problem and the battery case 90 is not deformed by a pressure change in the battery case. It is not something.

  The secondary battery 100 operates with the above configuration. During the operation of the secondary battery 100 (for example, at the time of discharging), the voltage of the secondary battery 100 is detected continuously or at predetermined intervals by the voltmeter 70, and voltage value information is fed back to the piston device 80 sequentially. The piston device 80 controls the pressure applied to the stacked body 40 based on the detected voltage value information. Hereinafter, the voltage control method of the secondary battery 100 will be described in detail with reference to an operation of the secondary battery 100 during discharging.

2. FIG. 2 is a diagram illustrating a voltage control method during discharging in the secondary battery 100. FIG. The voltage control method during discharging of the secondary battery 100 includes a discharge voltage detecting step S1, a determining step S2, and a pressurizing step S3 or a depressurizing step S4. Hereinafter, each process will be described with reference to FIGS.

(Discharge voltage detection step S1)
Step S <b> 1 is a step in which the voltage at the time of discharging the secondary battery 100 is detected by the voltmeter 70. A voltmeter 70 is provided between the electrode terminals of the current collectors 50 and 60 to detect the discharge voltage of the secondary battery 100. Whether or not the obtained discharge voltage is within a predetermined range is determined in the next step S2.

(Judgment process S2)
Step S2 is a step of determining whether or not the discharge voltage of the secondary battery 100 obtained in step S1 is within a preset voltage range. For example, consider a case where a battery is desired to be used at a battery voltage of 3.8V. In this case, considering the allowable range, for example, 3.75 V to 3.85 V is set as the set voltage, and it is determined whether or not the detected discharge voltage is within the set voltage range. If the discharge voltage is within the set voltage, the battery is discharged as it is. On the other hand, when the discharge voltage deviates from the set voltage, it is determined whether the discharge voltage is larger or smaller than the set voltage, and the operation of the piston device 70 is feedback controlled based on the determination.

(Pressurizing step S3)
Step S <b> 3 is a step of increasing the binding pressure of the stacked body 40 by pressurizing the stacked body 40 with the piston device 70. That is, in step S <b> 2, when it is determined that the discharge voltage is smaller than the set voltage, an operation instruction is given to the piston device 70, and feedback control is performed so that the piston device 70 pressurizes the stacked body 40. When the restraint pressure of the stacked body 40 is increased by the operation of the piston device 70, the contact area between the active materials in the stacked body 40 or between the active material and the solid electrolyte increases, and the interface resistance between the solid and the solid decreases. As a result, the discharge voltage that has become smaller than the set voltage is restored to the set voltage again. Therefore, through the pressurizing step S3, the discharge voltage can be stabilized within the set voltage, and a decrease in the discharge voltage can be suppressed.

(Decompression step S4)
Step S4 is a step in which the piston device 70 is operated to reduce (depressurize) the restraint pressure of the stacked body 40. That is, when it is determined in step S2 that the discharge voltage is higher than the set voltage, an operation instruction is given to the piston device 70, and the piston device 70 is feedback-controlled so as to depressurize the stacked body 40. When the restraint pressure of the laminated body 40 is lowered by the operation of the piston device 70, the contact area between the active materials in the laminated body 40 or between the active material and the solid electrolyte is reduced. As a result, the discharge voltage that has become larger than the set voltage settles again within the set voltage. Therefore, the discharge voltage can be stabilized within the set voltage through the decompression step S4.

  By repeating the above steps S1 to S4 and operating the secondary battery 100, the secondary battery 100 can be stably discharged within the set voltage, the battery reaction can be performed without waste, and a secondary battery having a high discharge capacity can be obtained. Can do.

  In particular, in the case where the material of the laminate 40 includes an active material that causes volume shrinkage during discharge, in the conventional battery structure, the contact area between the active materials or between the active material and the solid electrolyte accompanying discharge It is considered that the voltage decreases as the interface resistance increases. On the other hand, in the secondary battery 100, since the restraint pressure of the stacked body 40 is controlled by the steps S1 to S4 at the time of discharging, the contact area between the active materials or between the active material and the solid electrolyte can be appropriately controlled, and the voltage It can be maintained stably.

  In contrast to the conventional configuration in which the voltage is made constant using a Zener diode, the secondary battery 100 can stabilize the voltage without being affected by temperature, noise, or the like.

A compacted all-solid-state lithium ion secondary battery 100 was produced, and voltage behavior during discharge was confirmed. The restraining pressure applied to the laminate 40 in the battery before discharging was 500 N / cm ² . Moreover, the set voltage at the time of battery discharge was set to 3.75 to 3.85V. The results are shown in FIG.

As shown in FIG. 3, the discharge voltage of the secondary battery 100 decreased with time, and the discharge voltage that was higher than the set voltage was within the set voltage at 7.5 mAh / g. Thereafter, the discharge voltage further decreased and became the lower limit of the set voltage at 12.8 mAh / g. Therefore, the operation of the piston device 70 is controlled by feedback control, and the restraining pressure applied to the stacked body 40 is increased to 1270 N / cm ² . Then, the discharge voltage of the secondary battery 100 rose again and settled within the set voltage. Thereafter, the discharge voltage decreased again and reached the lower limit of the set voltage at 21.8 mAh / g. In this way, the use range in the set voltage range can be expanded to about 2.7 times by feedback control of the restraint pressure applied to the stacked body 40 based on the discharge voltage value of the secondary battery 100. did it.

  In the above description, in the secondary battery 100, the form in which the pressure applied in the stacking direction of the stacked body 40 is controlled is illustrated, but the present invention is not limited to this. For example, the pressure applied in the direction substantially perpendicular to the stacking direction of the stacked body 40 may be controlled as long as the restraint pressure of the stacked body 40 can be adjusted. However, from the viewpoint of suppressing an increase in the interface resistance between the active material and the solid electrolyte by appropriately controlling the contact pressure between the positive electrode layer 10 and the solid electrolyte layer 20 and the contact pressure between the solid electrolyte layer 20 and the negative electrode layer 30. Is preferably configured to control the pressure applied in the stacking direction of the stacked body 40.

  Further, in the above description, the configuration in which the stacked body 40 in which the positive electrode layer 10, the solid electrolyte layer 20, and the negative electrode 30 are stacked in this order and the end surface is substantially flat is accommodated in the battery case 90 is illustrated. However, the present invention is not limited to this. For example, the wound laminate 40 may be accommodated in the battery case 90.

  Further, in the above description, the embodiment in which the piston device 70 by motor control is provided as the pressure control means has been described. However, the present invention is applicable as long as the restraint pressure of the stacked body 40 can be appropriately controlled by changing the discharge voltage. Is not limited to this. For example, a device for controlling the fluid pressure in the battery case 90 may be used.

  Moreover, in the said description, although the pressure reduction process S4 was demonstrated in the voltage control method at the time of battery discharge, this invention is not limited to this. For example, even when the discharge voltage becomes too higher than the set voltage, the voltage gradually decreases due to the discharge and settles within the set voltage without intentionally performing the decompression step S4. However, it can be said that the embodiment including the pressure reducing step S4 is preferable from the viewpoint of appropriately maintaining the pressure in the battery, the viewpoint of preventing excessive discharge, and the like when excessive pressure is mistakenly applied in the pressing step S3.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the invention is not limited to the embodiments disclosed herein. The invention can be changed as appropriate without departing from the scope or spirit of the invention that can be read from the claims and the entire specification, and a compact all-solid battery with such changes is also included in the technical scope of the present invention. Must be understood as.

DESCRIPTION OF SYMBOLS 10 Positive electrode layer 20 Solid electrolyte layer 30 Negative electrode layer 40 Laminate body 50 Current collector 60 Current collector 70 Voltmeter 75 Control part 80 Piston apparatus 90 Battery case 100 Compaction all-solid-state secondary battery

Claims (4)

A positive electrode layer, a negative electrode layer, and a laminate having a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a voltage detection means for detecting a battery voltage, and a voltage detected by the voltage detection means And a pressure control means for controlling a restraining pressure applied to the laminate. The powder all-solid secondary battery according to claim 1, wherein the material used for the laminate includes a material that causes volume shrinkage during battery discharge. The powder all-solid battery according to claim 2, wherein the material that causes volume shrinkage during battery discharge is an active material contained in the positive electrode layer or the negative electrode layer. The powder all-solid battery according to any one of claims 1 to 3, wherein the restraining pressure controlled by the pressure control means is a pressure in a direction substantially the same as a stacking direction of the stacked body.

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