Method for adjusting power storage device and power storage device

Abstract

To provide a method for adjusting a power storage device capable of suppressing a reduction in the usable amount of electricity of the power storage device and the power storage device capable of suppressing a reduction in the usable amount of electricity.SOLUTION: There is provided a method for adjusting a power storage device according to one aspect of the present invention, the power storage device including: a non-aqueous electrolyte power storage element having a negative electrode that contains a negative electrode active material that occludes and releases charge-transporting ions; and a control unit that controls charging / discharging of the non-aqueous electrolyte power storage element within a range equal to or less than a usage upper limit SOC. The method includes: detecting a parameter that indicates a degradation state of the non-aqueous electrolyte power storage element; and setting a new usage upper limit SOC being a value higher than the currently set usage upper limit SOC according to the parameter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for adjusting an electricity storage device and to an electricity storage device. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries, such as lithium ion secondary batteries, are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc., due to their high energy density. Non-aqueous electrolyte secondary batteries generally have a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring charge-transporting ions between the electrodes. In addition, as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries, capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used. Carbon materials such as graphite, silicon materials such as silicon oxide, etc. are widely used as negative electrode active materials for non-aqueous electrolyte storage elements (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-222933 A [Patent Document 2] JP 2011-113863 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a nonaqueous electrolyte electricity storage element and an electricity storage device including the nonaqueous electrolyte electricity storage element, the negative electrode active material and the like usually deteriorate due to repeated charging and discharging, etc., and the charge and discharge performance deteriorates. For example, when the electricity storage device is used for a long period of time, the amount of usable electricity decreases.

[0005] An object of the present invention is to provide a method for adjusting a power storage device that can suppress a decrease in the amount of usable electricity in the power storage device, and a power storage device that can suppress a decrease in the amount of usable electricity. [Means for solving the problem]

[0006] A method for adjusting an electricity storage device according to one aspect of the present invention is a method for adjusting an electricity storage device including a nonaqueous electrolyte storage element having a negative electrode including a negative electrode active material that absorbs and releases charge transport ions, and a control unit that controls charging and discharging of the nonaqueous electrolyte storage element within a range not exceeding an upper usage limit SOC, and includes detecting a parameter that indicates a deterioration state of the nonaqueous electrolyte storage element, and setting a new upper usage limit SOC that is a value higher than the set upper usage limit SOC in accordance with the parameter.

[0007] An electricity storage device according to another aspect of the present invention comprises a nonaqueous electrolyte storage element having a negative electrode including a negative electrode active material that absorbs and releases charge transport ions, and a control unit that controls charging and discharging of the nonaqueous electrolyte storage element within a range not exceeding an upper usage limit SOC and controls the upper usage limit SOC, wherein the control unit is configured to control the upper usage limit SOC by performing a detection process that detects a parameter indicative of a deterioration state of the nonaqueous electrolyte storage element, and a setting process that sets a new upper usage limit SOC that is a value higher than the currently set upper usage limit SOC in accordance with the parameter. Effect of the Invention

[0008] According to one aspect of the present invention, it is possible to provide a method for adjusting a power storage device that can suppress a decrease in the amount of usable electricity in the power storage device. According to another aspect of the present invention, it is possible to provide an electricity storage device capable of suppressing a decrease in the amount of usable electricity. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a graph that shows a schematic representation of a positive electrode potential curve and a negative electrode potential curve in a nonaqueous electrolyte electricity storage element in which the upper usage limit SOC is initially set to 80%. [Diagram 2] FIG. 2 is a graph that typically shows a positive electrode potential curve and a negative electrode potential curve when the nonaqueous electrolyte electricity storage element of FIG. 1 is in a deteriorated state. [Diagram 3] FIG. 3 is a schematic diagram showing an embodiment of the power storage device. [Figure 4] FIG. 4 is a flowchart showing one embodiment of a method for adjusting a power storage device. [Diagram 5] FIG. 5 is a diagram showing a schematic representation of a dV / dQ curve on the high SOC side of the power storage device in the initial stage. [Figure 6] FIG. 6 is a diagram showing a schematic representation of a dV / dQ curve on the low SOC side in the initial stage of a power storage device. [Figure 7] FIG. 7 is a diagram showing a schematic representation of a dV / dQ curve on the high SOC side of the power storage device in the intermediate stage. [Figure 8] FIG. 8 is a diagram showing a schematic representation of a dV / dQ curve on the low SOC side of the power storage device in the intermediate stage. [Figure 9] FIG. 9 is a diagram showing a schematic representation of a dV / dQ curve on the high SOC side of a power storage device in a later stage. [Figure 10] FIG. 10 is a diagram showing a schematic representation of a dV / dQ curve on the low SOC side of a power storage device in a later stage. [Figure 11] FIG. 11 is a first graph that illustrates the relationship between the voltage and SOC of a nonaqueous electrolyte electricity storage element. [Figure 12] FIG. 12 is a second graph that illustrates the relationship between the voltage and SOC of a nonaqueous electrolyte electricity storage element. [Figure 13] FIG. 13 is a transparent perspective view showing one embodiment of a nonaqueous electrolyte electricity storage element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First, an overview of the power storage device and the power storage device disclosed in this specification will be described.

[0011] (1) A method for adjusting an energy storage device according to one aspect of the present invention is a method for adjusting an energy storage device including a nonaqueous electrolyte storage element having a negative electrode including a negative electrode active material that absorbs and releases charge transport ions, and a control unit that controls charging and discharging of the nonaqueous electrolyte storage element within a range not exceeding an upper usage limit SOC, the method including detecting a parameter indicative of a deterioration state of the nonaqueous electrolyte storage element, and setting a new upper usage limit SOC that is a value higher than the currently set upper usage limit SOC in accordance with the parameter.

[0012] The method for adjusting the storage device described in (1) above can suppress the decrease in the amount of electricity that can be used by the storage device. The reason for this will be described with reference to Figs. 1 and 2. Fig. 1 shows a schematic diagram of a positive electrode potential curve and a negative electrode potential curve of a nonaqueous electrolyte storage element in which the upper limit SOC for use is set to 80% at the beginning. Usually, as the deterioration of the nonaqueous electrolyte storage element progresses, charge transport ions such as lithium ions are captured by the negative electrode, so that the negative electrode potential curve shifts (see Fig. 2). Therefore, if the upper limit SOC for use from the beginning is not changed, the amount of electricity that can be used decreases significantly as the nonaqueous electrolyte storage element deteriorates. In contrast, in the method for adjusting the storage device, the upper limit SOC for use is set to a higher value according to a parameter that indicates the deterioration state of the nonaqueous electrolyte storage element, and the range of the usable SOC is expanded. Fig. 2 shows a state in which the upper limit SOC for use is changed from 80% to 90% as the nonaqueous electrolyte storage element deteriorates. In this way, the range of the usable SOC can be expanded according to the deterioration state of the nonaqueous electrolyte storage element, thereby suppressing the decrease in the amount of electricity that can be used. In addition, in Figures 1 and 2, graphite is used as the negative electrode active material as an example, and a negative electrode potential curve is shown in which a structural change occurs in the graphite from the second stage (Stage 2) to the first stage (Stage 1). However, the negative electrode active material of the nonaqueous electrolyte storage element used in the method for adjusting a storage device described in (1) above is not limited to graphite.

[0013] "SOC (State of Charge)" refers to the state of charge of a nonaqueous electrolyte storage element, expressed as the ratio of the remaining capacity (amount of electricity) at that time to the capacity (amount of electricity) at that time when fully charged. In other words, SOC 100% refers to the fully charged state at that time.

[0014] (2) In the method for adjusting an energy storage device described in (1) above, the negative electrode active material contains graphite, and the set upper usage limit SOC is within a range in which the graphite does not undergo a structural change to the first stage, and in the setting, the new upper usage limit SOC may also be set within a range in which the graphite does not undergo a structural change to the first stage.

[0015] According to the method for adjusting the power storage device described in (2) above, it is possible to suppress a decrease in the output maintenance rate associated with the deterioration of graphite, which is the negative electrode active material, while suppressing a decrease in the amount of usable electricity. The reason for this is unclear, but is as follows. In a non-aqueous electrolyte power storage element using graphite as the negative electrode active material, when the element is deeply charged until the graphite reaches the first stage, the output maintenance rate decreases. The reasons for this are presumed to be as follows (i) and (ii). (i) When the element is deeply charged to the first stage, the graphite expands significantly, and the load on the negative electrode itself and the positive electrode increases. (ii) When the negative electrode potential reaches a low potential, a reaction between the negative electrode and the non-aqueous electrolyte is more likely to occur, and film formation on the negative electrode is promoted. In contrast, in the method for adjusting an energy storage device described in (2) above, the upper usage limit SOC is set within a range in which the graphite does not undergo a structural change to the first stage, and when a new upper usage limit SOC is set (i.e., when increasing the value of the upper usage limit SOC), the new upper usage limit SOC is also set within a range in which the graphite does not undergo a structural change to the first stage, thereby making it possible to suppress a decrease in the output maintenance rate due to deterioration of the graphite while suppressing a decrease in the amount of usable electricity. 1 and 2, when a structural change from the second stage to the first stage occurs in graphite, the slope of the negative electrode potential curve usually becomes steeper (as described later, dV (voltage) / dQ (residual capacity) shows a peak). Therefore, for example, by setting the upper limit SOC for use in a range where the negative electrode potential curve is relatively flat, or by setting the upper limit SOC for use in a range where dV / dQ does not show a peak on the high SOC side as described later, it is possible to set the upper limit SOC for use in a range where the structural change to the first stage does not occur in graphite.

[0016] "Graphite" refers to a material that has an average lattice spacing (d 002 ) is 0.33 nm or more and less than 0.34 nm. Here, the "discharged state" of the carbon material means a state in which the carbon material, which is a negative electrode active material, is discharged so that charge transport ions (e.g., lithium ions) that can be absorbed and released during charging and discharging are sufficiently released. For example, in a half cell using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and metallic Li as a counter electrode, it is a state in which the open circuit voltage is 0.6 V or more. The "first stage" of graphite is a structure in which charge-carrying ions are absorbed between all layers of graphite. When the charge-carrying ions are lithium ions, the first stage is the most deeply charged state, represented by LiC6. The amount of lithium atoms absorbed in graphite, i.e., the depth of charge of graphite, is Li x It can be expressed by the value of x in C6. x When C6 is deeply charged to a value where x is greater than 0.5, the average lattice spacing (d 002 Therefore, when the charge-transporting ion is lithium ion, the "range in which the graphite does not undergo a structural change to the first stage" is the range in which the charge depth of graphite is Li x This means the range in which x in C6 is 0.5 or less.

[0017] (3) In the method for adjusting an electricity storage device described in (2) above, the parameter correlates with the voltage of the nonaqueous electrolyte electricity storage element when a structural change to the first stage occurs in the graphite, and in setting an upper limit, the new upper limit use SOC may be set within a range in which an upper limit use voltage of the nonaqueous electrolyte electricity storage element corresponding to the new upper limit use SOC is equal to or lower than the voltage of the nonaqueous electrolyte electricity storage element when a structural change to the first stage occurs in the graphite.

[0018] In the method for adjusting an electricity storage device described in (3) above, the upper limit voltage for use of the nonaqueous electrolyte electricity storage element is set in a range in which the graphite does not undergo a structural change to the first stage according to the detected parameters. Therefore, according to the method for adjusting an electricity storage device described in (3) above, the graphite can be used with high reliability in a range in which the graphite does not undergo a structural change to the first stage, and the decrease in the output maintenance rate due to the deterioration of the graphite can be further suppressed while the decrease in the amount of usable electricity can be suppressed.

[0019] (4) In the method for adjusting an electricity storage device described in (3) above, the parameter may be a peak position of dV (voltage) / dQ (remaining capacity) that appears when the nonaqueous electrolyte electricity storage element is charged within a predetermined voltage range.

[0020] As described above, when the graphite undergoes a structural change from the second stage to the first stage, the slope of the negative electrode potential generally becomes large, and dV (voltage) / dQ (remaining capacity) shows a peak. That is, the peak position of dV (voltage) / dQ (remaining capacity) is an example of a parameter that correlates with the voltage of the nonaqueous electrolyte storage element when the graphite undergoes a structural change to the first stage. According to the method for adjusting the storage device described in (4) above, by detecting the peak position of dV (voltage) / dQ (remaining capacity) as a parameter that represents the deterioration state of the nonaqueous electrolyte storage element, it is possible to grasp the degree of the deterioration state of the nonaqueous electrolyte storage element relatively easily and reliably, and it is possible to easily set a new upper limit SOC for use within a range in which the graphite does not undergo a structural change to the first stage.

[0021] (5) An energy storage device according to another aspect of the present invention includes a nonaqueous electrolyte storage element having a negative electrode including a negative electrode active material that absorbs and releases charge transport ions, and a control unit that controls charging and discharging of the nonaqueous electrolyte storage element within a range not exceeding an upper usage limit SOC and controls the upper usage limit SOC, wherein the control unit is configured to control the upper usage limit SOC by performing a detection process that detects a parameter indicative of a deterioration state of the nonaqueous electrolyte storage element, and a setting process that sets a new upper usage limit SOC that is a value higher than the currently set upper usage limit SOC in accordance with the parameter.

[0022] The power storage device described in (5) above has a configuration in which the control unit implements the method for adjusting a power storage device described in (1) above. Thus, like the method for adjusting a power storage device described in (1) above, the power storage device described in (5) above can suppress a decrease in the amount of usable electricity by setting the upper usage limit SOC to a higher value in accordance with a parameter representing the deterioration state of the nonaqueous electrolyte power storage element.

[0023] (6) In the energy storage device described in (5) above, the control unit may have a memory in which information regarding a relationship between the parameter and the usage upper limit SOC is stored, and the control unit may set the new usage upper limit SOC based on the detected parameter and the information stored in the memory in the setting process.

[0024] According to the power storage device described in (6) above, a new usage upper limit SOC can be set based on the detected parameters and the information stored in the memory, so that a decrease in the amount of usable electricity can be suppressed with high reliability.

[0025] (7) In the energy storage device described in (5) or (6) above, the negative electrode active material contains graphite, the set upper usage limit SOC is within a range in which the graphite does not undergo a structural change to the first stage, and the control unit may set the new upper usage limit SOC in the setting process within a range in which the graphite does not undergo a structural change to the first stage.

[0026] The power storage device described in (7) above has a configuration for implementing the method for adjusting a power storage device described in (2) above. Therefore, like the method for adjusting a power storage device described in (2) above, the power storage device described in (7) above can suppress a decrease in the amount of usable electricity while suppressing a decrease in the output maintenance rate that is caused by deterioration of graphite, which is the negative electrode active material.

[0027] (8) In the energy storage device described in (7) above, the parameter correlates with a voltage of the nonaqueous electrolyte storage element when a structural change to the first stage occurs in the graphite, and the upper limit control unit, in the setting process, may set the new upper limit use SOC within a range in which an upper limit use voltage of the nonaqueous electrolyte storage element corresponding to the new upper limit use SOC is equal to or lower than a voltage of the nonaqueous electrolyte storage element when a structural change to the first stage occurs in the graphite.

[0028] The electric storage device described in (8) above has a configuration for implementing the method for adjusting an electric storage device described in (3) above. Therefore, like the method for adjusting an electric storage device described in (3) above, the electric storage device described in (8) above can use graphite with high reliability within a range in which a structural change to the first stage does not occur, and can suppress a decrease in the amount of usable electricity while further suppressing a decrease in the output maintenance rate due to deterioration of graphite.

[0029] A method for adjusting a power storage device according to an embodiment of the present invention, a power storage device, and other embodiments will be described in detail. Note that the names of the components (components) used in each embodiment may differ from the names of the components (components) used in the background art.

[0030] <Method of adjusting the power storage device> First, a power storage device used in a method for adjusting a power storage device according to one embodiment of the present invention will be described with reference to FIG.

[0031] (Electricity storage device) The electricity storage device 10 in FIG. 3 includes an electricity storage unit 11 and a nonaqueous electrolyte electricity storage element management device 12 (hereinafter also referred to as "management device 12").

[0032] The electricity storage unit 11 has a configuration in which a plurality of nonaqueous electrolyte electricity storage elements 1 are connected in series. The nonaqueous electrolyte electricity storage element 1 has a positive electrode including a positive electrode active material that absorbs and releases charge transport ions, and a negative electrode including a negative electrode active material that absorbs and releases charge transport ions. A specific form of the nonaqueous electrolyte electricity storage element 1 will be described later. The electricity storage unit 11 is electrically connected to a charging device 13 or a load (not shown) via wiring 14.

[0033] The management device 12 includes a control unit 15, an analog-digital converter (hereinafter also referred to as "ADC") 16, a current sensor 17, and a voltage sensor 18. The control unit 15 has a central processing unit (hereinafter also referred to as "CPU") 19, and a memory 20 such as a ROM, a RAM, etc. Various programs and the like for controlling the operation of the management device 12 are stored in the memory 20. The CPU 19 performs control such as executing various processes according to the programs read from the memory 20.

[0034] The current sensor 17 detects the value of the charging current or discharging current flowing through the power storage unit 11 via the wiring 14, and transmits an analog detection signal SG1 corresponding to the detected current value to the ADC 16. The voltage sensor 18 is connected to both ends of the power storage unit 11, detects the value of a voltage that is a voltage across both ends of the power storage unit 11, and transmits an analog detection signal SG2 corresponding to the detected voltage value to the ADC 16.

[0035] The ADC 16 converts the detection signals SG1, SG2 transmitted from the current sensor 17 and the voltage sensor 18 from analog signals to digital signals, and stores the digital data indicating the current value and voltage value in the memory 20. As will be described later, the remaining capacity, SOC, etc. of the electricity storage unit 11 (nonaqueous electrolyte electricity storage element 1) can be determined from the data stored in the memory 20.

[0036] The control unit 15 provided in the management device 12 controls the charging and discharging of the electricity storage unit 11 (the nonaqueous electrolyte electricity storage element 1) within a range equal to or less than the upper limit SOC of use. Specifically, the memory 20 of the control unit 15 stores the upper limit SOC of use and data for grasping the SOC. For example, the SOC can be grasped from a voltage. Therefore, the data for grasping the SOC stored in the memory 20 may be data relating to a correlation between the voltage and the SOC. Alternatively, the SOC can be grasped from an integrated value of the current or the like, and the necessary data according to each method is stored in the memory 20. For example, when the SOC reaches the upper limit SOC during charging, the control unit 15 controls the electricity storage device 10 to end charging. The upper limit SOC of use stored in the memory 20 is set to be updateable.

[0037] Hereinafter, an embodiment of the method for adjusting a power storage device of the present invention will be described. The method for adjusting a power storage device includes detecting a parameter representing a degradation state of a non-aqueous electrolyte storage element, and setting a new upper limit SOC for use that is higher than the set upper limit SOC in accordance with the parameter. The method for adjusting a power storage device may further include determining a degradation state of the non-aqueous electrolyte storage element based on the detected parameter. When the method for adjusting a power storage device includes determining such a degradation state, a new upper limit SOC for use may be set or a new upper limit SOC may not be set depending on the degradation state.

[0038] In this embodiment, the nonaqueous electrolyte storage element has a negative electrode containing graphite as a negative electrode active material, and the peak position of dV (voltage) / dQ (residual capacity) is used as a parameter representing the deterioration state of the nonaqueous electrolyte storage element, and the present embodiment will be specifically described with reference to FIG. 4 to FIG. 12 as an example. The initial upper limit SOC set in the nonaqueous electrolyte storage element is set as the upper limit SOC1. The upper limit SOC1 is set in a range in which the graphite, which is the negative electrode active material, does not undergo a structural change to the first stage. That is, in the initial nonaqueous electrolyte storage element, the SOC is set so that charging and discharging are performed in a range below the upper limit SOC1. The upper limit SOC1 may be controlled by a corresponding upper limit voltage V1. In other words, the initial upper limit voltage may be set below the voltage at which the graphite undergoes a structural change to the first stage.

[0039] (Detection of parameter (dV / dQ peak position)) FIG. 4 is a flow chart showing an embodiment of a method for adjusting a power storage device. In the method for adjusting a power storage device, first, a nonaqueous electrolyte power storage element is charged with a predetermined current within a predetermined voltage range, and dV / dQ corresponding to each SOC is calculated (S10, S20). In one embodiment of the present invention, charging (S10) for detecting the peak position of this dV / dQ is performed in a range exceeding the upper limit of use SOC1. When only the peak position of dV / dQ on the low SOC side described later is detected, charging may be performed within a range below the upper limit of use SOC at that time. Note that dV / dQ is the ratio of the change in voltage (dV) to the change in remaining capacity (amount of electricity charged in the nonaqueous electrolyte power storage element) (dQ). Then, for example, the peak position of dV / dQ is detected from a dV / dQ curve with SOC on the horizontal axis and dV / dQ on the vertical axis. The horizontal axis of the dV / dQ curve may be Q (remaining capacity), V (voltage), or the like, in addition to SOC. The peak position of dV / dQ correlates with the SOC and voltage of the nonaqueous electrolyte storage element when the graphite undergoes a structural change to the first stage. The horizontal axis values ​​(SOC, Q (remaining capacity), V (voltage), etc.) at the peak position of dV / dQ in the dV / dQ curve are used as parameters representing the deterioration state of the nonaqueous electrolyte storage element.

[0040] When the power storage device is in the initial stage, that is, when the nonaqueous electrolyte power storage element is hardly deteriorated, the dV / dQ peak usually appears on both the high SOC side (for example, in the range of SOC over 50%) and the low SOC side (for example, in the range of SOC below 50%) in the dV / dQ curve (see Fig. 5 and Fig. 6). Fig. 5 is a diagram that shows a schematic representation of the dV / dQ curve on the high SOC side of the power storage device in the initial stage, and Fig. 6 is a diagram that shows a schematic representation of the dV / dQ curve on the low SOC side of the power storage device in the initial stage. The dV / dQ peak position (SOC) that appears on the high SOC side corresponds to the position (SOC) at which the graphite undergoes a structural change to the first stage. When the dV / dQ peak position on the high SOC side can be detected, a new upper limit SOC for use can be set according to this peak position. When the deterioration of the nonaqueous electrolyte power storage element progresses, the dV / dQ peak on the high SOC side cannot be detected (see Fig. 9). In this case, a new upper usage limit SOC can be set according to the peak position of dV / dQ that appears on the low SOC side (for example, in the range of SOC 50% or less) (see FIG. 10). A specific description will be given below. Note that only the peak position of dV / dQ that appears on the low SOC side may be detected from the initial stage (a stage when the nonaqueous electrolyte storage element has hardly deteriorated).

[0041] In the dV / dQ curve, the high SOC side is the high voltage side, and the low SOC side is the low voltage side. For example, when a nonaqueous electrolyte storage element has a positive electrode containing a lithium nickel manganese cobalt composite oxide as a positive electrode active material and a negative electrode containing graphite as a negative electrode active material, the high voltage side may be in the range of 3.8 V or more, and the low voltage side may be in the range of less than 3.8 V.

[0042] (New upper SOC limit setting 1: Setting based on dV / dQ peak position on high SOC side) When a dV / dQ peak is detected on the high SOC side (S30), the position of this dV / dQ peak is determined as the threshold SOC. n It is determined whether the peak position of dV / dQ on the high SOC side reaches the threshold SOC (S40). nIf the threshold SOC is not reached, a new upper limit SOC is not set. In other words, the deterioration is almost not progressing, and the initial upper limit SOC1 is maintained. Specifically, for example, if the initial upper limit SOC1 is 80% and the threshold SOC n As shown in FIG. 5, when the peak position of dV / dQ that appears on the high SOC side is SOC 83%, the threshold SOC n Since the SOC usage limit has not been reached, a new SOC usage limit is not set and the SOC usage limit remains at 80%.

[0043] The peak position of dV / dQ on the high SOC side is the threshold SOC n If it has reached the threshold SOC, a new usage upper limit SOC2 is set (S50). n 8 is a diagram showing a dV / dQ curve on the high SOC side of the power storage device in the middle stage. FIG. 7 is a diagram showing a dV / dQ curve on the low SOC side of the power storage device in the middle stage. As shown in FIG. 7, when the peak position that appears in the dV / dQ on the high SOC side is SOC 88%, the threshold SOC n Since the threshold SOC has been reached, a new usage upper limit SOC2 is set. The new usage upper limit SOC2 is set in a range that is greater than the usage upper limit SOC1 and is less than or equal to the peak position of dV / dQ on the high SOC side that has been detected. In the above example, it is set in a range of more than 80% and less than or equal to 88%. The new usage upper limit SOC2 is set in a range that is greater than the threshold SOC n (In the above example, it may be a value equal to or greater than 85%). The new upper limit SOC2 is the threshold SOC n(85% in the above example) or an SOC corresponding to the peak position of dV / dQ on the detected high SOC side (88% in the above example). When the battery is charged to a range exceeding the peak position of dV / dQ on the detected high SOC side, a structural change to the first stage may occur in the graphite. That is, the new upper limit of use SOC2 is also set in a range in which a structural change to the first stage does not occur in the graphite. By setting the new upper limit of use SOC2 in a range that is higher than the upper limit of use SOC1 and lower than the peak position of dV / dQ on the detected high SOC side, it is possible to suppress a decrease in the output maintenance rate due to deterioration of the graphite, which is the negative electrode active material, while suppressing a decrease in the amount of usable electricity.

[0044] The new upper limit SOC2 may be set as the corresponding upper limit voltage. In this case, the upper limit voltage of the nonaqueous electrolyte storage element corresponding to the new upper limit SOC2 is equal to or lower than the voltage at which the graphite undergoes a structural change to the first stage. In other words, the new upper limit voltage is set to be equal to or lower than the voltage at which the graphite undergoes a structural change to the first stage.

[0045] 11 is a schematic example showing the relationship between the voltage and SOC of a nonaqueous electrolyte storage element. An initial upper limit voltage corresponding to an initial upper limit SOC1 can be set to V1. A new upper limit voltage corresponding to a new upper limit SOC2 can be set to V2. The upper limit voltage V2 may be set by preparing a database showing the correspondence between the upper limit SOC2 and the corresponding upper limit voltage V2.

[0046] Threshold SOC n In another embodiment, the threshold SOC n (that is, without determining the deterioration state of the nonaqueous electrolyte electricity storage element), the position of the detected dV / dQ peak on the high SOC side may be set as the usable upper limit SOC.

[0047] (New upper SOC limit setting 2: Setting based on dV / dQ peak position on low SOC side) As described above, when the power storage device is in the later stage, that is, when the deterioration of the nonaqueous electrolyte power storage element has progressed to a certain extent, the dV / dQ peak on the high SOC side cannot be detected (see FIG. 9). FIG. 9 is a diagram that shows a schematic representation of the dV / dQ curve on the high SOC side of the power storage device in the later stage, and FIG. 10 is a diagram that shows a schematic representation of the dV / dQ curve on the low SOC side of the power storage device in the later stage. As shown in FIG. 9, when the dV / dQ peak is not detected on the high SOC side (S30), a new upper limit SOC for use is set based on the dV / dQ peak position on the low SOC side shown in FIG. 10. Also, if the adjustment method for the power storage device has already been performed and a dV / dQ peak was detected on the high SOC side last time, and the position of this dV / dQ peak is lower than the threshold SOC, the adjustment method for the power storage device is performed. n (Multiple Threshold SOC n If you set the maximum threshold SOC n ) and the upper SOC limit has been changed, a new upper SOC limit is set based on the peak position of dV / dQ on the low SOC side. The peak position of dV / dQ on the low SOC side also shifts to the high SOC side as degradation progresses. In addition, the SOC and voltage at which the graphite undergoes a structural change to the first stage can be estimated from the peak position of dV / dQ on the low SOC side.

[0048] When a dV / dQ peak is detected on the low SOC side (S60), the position of this dV / dQ peak is determined as the threshold SOC m It is determined whether the peak position of dV / dQ on the low SOC side reaches the threshold SOC (S70). m If the current SOC limit (SOC limit 2) is 85%, the new SOC limit is not set. m If the peak position of dV / dQ that appears on the low SOC side is SOC 34%, the threshold SOC m Since the upper limit SOC has not been reached, a new upper limit SOC is not set and the upper limit SOC remains at 85%.

[0049] The peak position of dV / dQ on the low SOC side is the threshold SOC mIf the peak position reaches the final threshold SOC Fin It is determined whether the peak position of dV / dQ on the low SOC side reaches the threshold SOC (S70). m has been reached and the final threshold SOC Fin If it has not reached the final threshold SOC, a new upper limit SOC3 is set (S90). Fin corresponds to the final upper limit voltage (limit voltage) of the nonaqueous electrolyte storage element, and is set from a practical point of view. Specifically, as in the above, for example, the upper limit SOC (upper limit SOC2) currently set at 85%, the threshold SOC of dV / dQ on the low SOC side m 35%, final threshold SOC Fin If the peak position of dV / dQ that appears on the low SOC side is SOC 38%, the threshold SOC m and the final threshold SOC Fin Since this limit has not been reached, a new usage limit of SOC3 is set (see Figure 10).

[0050] The new upper limit of use SOC3 is set in a range that is greater than the upper limit of use SOC2 and is equal to or less than the SOC at which a structural change to the first stage occurs in graphite, which is estimated from the peak position of dV / dQ on the detected low SOC side (see Figure 12). The peak position of dV / dQ on the low SOC side is not the "SOC at which a structural change to the first stage occurs in graphite," itself, but it is correlated with the "SOC at which a structural change to the first stage occurs in graphite," and the "peak position of dV / dQ on the high SOC side" can be estimated from the peak position of dV / dQ on the low SOC side. The relationship between the peak position of dV / dQ on the low SOC side and the SOC (estimated value) at which a structural change to the first stage occurs in graphite can be compiled into a database based on past results, etc. For example, if the peak position of dV / dQ on the low SOC side is SOC 38%, and the SOC at which the graphite undergoes a structural change to the first stage is estimated to be 90%, then in the above example, the new upper limit of use SOC3 is set in the range of more than 85% and less than or equal to 90%. The new upper limit of use SOC3 is set when the peak position of dV / dQ on the detected low SOC side is below the threshold SOC mIn this case, the new upper limit of use SOC3 may be the SOC at which the estimated graphite undergoes a structural change to the first stage, which is estimated from the peak position of dV / dQ on the low SOC side detected. The new upper limit of use SOC3 may be the SOC at which the estimated graphite undergoes a structural change to the first stage, which is estimated from the peak position of dV / dQ on the low SOC side detected (90% in the above example). In this way, the new upper limit of use SOC3 is also set within a range in which the graphite does not undergo a structural change to the first stage. By setting the new upper limit of use SOC3 within a range that is greater than the upper limit of use SOC2 and less than the SOC at which the estimated graphite undergoes a structural change to the first stage, which is estimated from the peak position of dV / dQ on the low SOC side detected, it is possible to suppress a decrease in the amount of usable electricity while suppressing a decrease in the output maintenance rate due to deterioration of graphite, which is the negative electrode active material.

[0051] The new upper limit of use SOC3 may be set as the corresponding upper limit of use voltage V3 (see FIG. 12). In this case, the upper limit of use voltage V3 of the nonaqueous electrolyte storage element corresponding to the new upper limit of use SOC3 is equal to or lower than the voltage at which a structural change to the first stage occurs in the graphite. In other words, the new upper limit of use voltage is set to be equal to or lower than the voltage at which a structural change to the first stage occurs in the graphite. The upper limit of use voltage V3 may be set by preparing a database indicating the correspondence between the upper limit of use SOC3 and the corresponding upper limit of use voltage V3.

[0052] Threshold SOC m In another embodiment, the threshold SOC m The upper limit SOC may be set to the SOC at which a structural change to the first stage occurs in graphite, as estimated from the detected dV / dQ peak position on the low SOC side, without setting a limit (i.e., without determining the deterioration state of the nonaqueous electrolyte storage element).

[0053] When a dV / dQ peak is detected on the low SOC side (S60), the position of this dV / dQ peak is the final threshold SOC Fin If the SOC limit has been reached, a new upper limit SOC will not be set. Fin is the threshold SOC m The final threshold SOC is greater thanFin For example, it can be set to correspond to the deterioration state that occurs when the structural change to the first stage of graphite occurs at SOC 100% (see Figure 12). Also, if no dV / dQ peak is detected on the low SOC side, a new upper limit SOC is not set.

[0054] The method for adjusting the power storage device according to one embodiment of the present invention can be performed, for example, when the power storage device is inspected periodically. For example, if the power storage device is a power source for an automobile such as an electric vehicle (EV), a hybrid vehicle (HEV), or a plug-in hybrid vehicle (PHEV), the method for adjusting the power storage device according to one embodiment of the present invention can be performed when inspecting the automobile to set a new upper limit SOC. Also, if the power storage device is an industrial power storage device such as a power storage power source, the method for adjusting the power storage device according to one embodiment of the present invention can be performed when inspecting the power source to set a new upper limit SOC.

[0055] In addition, the method for adjusting the power storage device according to one embodiment of the present invention may be implemented by the power storage device itself detecting a parameter representing a deterioration state of the nonaqueous electrolyte power storage element, and setting a new upper limit SOC for use that is higher than the set upper limit SOC for use according to the parameter. Such a power storage device will be described below.

[0056] <Electricity storage device> The energy storage device according to one embodiment of the present invention has a configuration similar to that of the energy storage device 10 shown in Fig. 3 described above. That is, the energy storage device 10 includes an energy storage unit 11 and a management device 12. The specific configurations of the energy storage unit 11 and the management device 12 may also be similar to those described above.

[0057] In the power storage device according to one embodiment of the present invention, the control unit also controls the charging and discharging of the nonaqueous electrolyte power storage element (power storage unit) within a range equal to or lower than the upper limit SOC. The control unit is further configured to execute a detection process for detecting a parameter representing a degradation state of the nonaqueous electrolyte power storage element, and a setting process for setting a new upper limit SOC that is higher than the set upper limit SOC according to the parameter, thereby controlling the upper limit SOC. The control unit may be configured to execute a determination process for determining the degradation state of the nonaqueous electrolyte power storage element based on the detected parameter. When the control unit is configured to execute such a determination process, the control unit may set a new upper limit SOC or may not set a new upper limit SOC depending on the degradation state.

[0058] In one embodiment of the present invention, the memory of the control unit stores information on the relationship between a parameter representing the degradation state of the nonaqueous electrolyte storage element and the upper limit SOC for use. Specifically, when the parameter representing the degradation state of the nonaqueous electrolyte storage element is a peak position of dV (voltage) / dQ (residual capacity) that appears when the nonaqueous electrolyte storage element is charged within a predetermined voltage range, data showing the relationship between the peak position of this dV / dQ and the upper limit SOC for use is stored.

[0059] For example, in the power storage device according to one embodiment of the present invention, charging for setting a new upper limit SOC can be performed as necessary, in addition to normal charging and discharging. This charging may be performed up to an SOC higher than the set upper limit SOC. When performing this charging, the control unit detects the peak position of dV / dQ (one example of a parameter representing the deterioration state of the nonaqueous electrolyte power storage element) as a detection process. This detection can be performed based on, for example, the values ​​of current and voltage detected by a current sensor and a voltage sensor. The control unit may perform the detection process during normal charging and discharging.

[0060] Next, the control unit sets a new upper limit SOC for use, which is higher than the set upper limit SOC, according to the peak position of the detected dV / dQ, as a setting process. As described above, the control unit may determine the degradation state of the nonaqueous electrolyte storage element based on the peak position of the detected dV / dQ before the setting process. When the control unit determines that the element has reached a predetermined degradation state, it sets a new upper limit SOC for use.

[0061] In the determination process and setting process, the control unit sets a new use upper limit SOC based on the detected dV / dQ peak position and information stored in the memory (such as a threshold SOC for determining the degradation state, and data showing the relationship between the dV / dQ peak position and the use upper limit SOC). Specifically, similar to the method for adjusting the power storage device according to one embodiment of the present invention described above, a new use upper limit SOC can be set according to the flowchart shown in Fig. 4. That is, the memory of the control unit stores programs for the above-mentioned detection process, determination process, and setting process, and the CPU can execute the above-mentioned detection process, determination process, and setting process in accordance with the programs read from the memory.

[0062] A preferred embodiment of the power storage device according to the embodiment of the present invention is the same as the method for adjusting the power storage device according to the embodiment of the present invention described above. That is, it is preferred that the negative electrode active material contains graphite, the set upper use limit SOC is within a range in which the graphite does not undergo a structural change to the first stage, and the control unit 15 is configured to set a new upper use limit SOC within a range in which the graphite does not undergo a structural change to the first stage in the setting process.

[0063] Furthermore, in the electricity storage device according to one embodiment of the present invention, the parameter representing the deterioration state of the nonaqueous electrolyte electricity storage element is preferably one that correlates with the voltage of the nonaqueous electrolyte electricity storage element when the graphite undergoes a structural change to the first stage, such as the peak position of dV / dQ described above.The control unit is preferably configured to set a new upper limit SOC in the setting process within a range in which the upper limit voltage of the nonaqueous electrolyte electricity storage element corresponding to the new upper limit SOC is equal to or lower than the voltage of the nonaqueous electrolyte electricity storage element when the graphite undergoes a structural change to the first stage.

[0064] According to the power storage device of one embodiment of the present invention, a new use upper limit SOC can be set by the control unit to expand the range of the usable SOC, thereby suppressing a decrease in the amount of usable electricity. In the power storage device, for example, charging for setting a new use upper limit SOC may be performed as periodic maintenance, and the new use upper limit SOC may be automatically set. Also, charging for setting a new use upper limit SOC may be performed at a desired timing (irregularly), and the new use upper limit SOC may be set.

[0065] (Non-aqueous electrolyte storage element) Hereinafter, the configuration of a nonaqueous electrolyte storage element (hereinafter, also simply referred to as "storage element") provided in an electricity storage device according to one embodiment of the present invention will be described in detail. The nonaqueous electrolyte storage element includes an electrode assembly having a positive electrode, a negative electrode, and a separator, a nonaqueous electrolyte, and a container that contains the electrode assembly and the nonaqueous electrolyte. The electrode assembly is usually a stacked type in which a plurality of positive electrodes and a plurality of negative electrodes are stacked with a separator interposed therebetween, or a wound type in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween and wound. The nonaqueous electrolyte exists in a state that it is contained in the positive electrode, the negative electrode, and the separator. As an example of a nonaqueous electrolyte storage element, a nonaqueous electrolyte secondary battery (hereinafter, also simply referred to as "secondary battery") will be described.

[0066] (positive electrode) The positive electrode has a positive electrode substrate and a positive electrode active material layer disposed on the positive electrode substrate directly or via an intermediate layer.

[0067] The positive electrode substrate is conductive. Whether or not it has "conductivity" is determined by whether the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 -2 The threshold value is Ω·cm. The material of the positive electrode substrate is a metal such as aluminum, titanium, tantalum, stainless steel, or an alloy thereof. Among these, aluminum or an aluminum alloy is preferred from the viewpoints of potential resistance, high conductivity, and cost. The positive electrode substrate may be a foil, a vapor deposition film, a mesh, a porous material, etc., and a foil is preferred from the viewpoint of cost. Therefore, aluminum foil or an aluminum alloy foil is preferred as the positive electrode substrate. Examples of aluminum or an aluminum alloy include A1085, A3003, A1N30, etc., as specified in JIS-H-4000 (2014) or JIS-H-4160 (2006).

[0068] The average thickness of the positive electrode substrate is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, further preferably 8 μm to 30 μm, and particularly preferably 10 μm to 25 μm. By setting the average thickness of the positive electrode substrate within the above range, it is possible to increase the strength of the positive electrode substrate and to increase the energy density per volume of the nonaqueous electrolyte storage element.

[0069] The intermediate layer is a layer disposed between the positive electrode substrate and the positive electrode active material layer. The intermediate layer contains a conductive agent such as carbon particles to reduce the contact resistance between the positive electrode substrate and the positive electrode active material layer. The configuration of the intermediate layer is not particularly limited, and may contain, for example, a binder and a conductive agent.

[0070] The positive electrode active material layer contains a positive electrode active material and, as necessary, optional components such as a conductive agent, a binder, a thickener, and a filler.

[0071] The positive electrode active material can be appropriately selected from known positive electrode active materials. A material capable of absorbing and releasing lithium ions is usually used as the positive electrode active material for a lithium ion secondary battery. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2 type crystal structure, lithium transition metal composite oxides having a spinel type crystal structure, polyanion compounds, chalcogen compounds, and sulfur. Examples of the lithium transition metal composite oxides having an α-NaFeO2 type crystal structure include Li[Li x Ni (1-x) ]O2(0≦x<0.5), Li[Li x Ni γ Co (1-x-γ) ]O2(0≦x<0.5, 0<γ<1, 0<1-x-γ), Li[Li x Co (1-x) ]O2(0≦x<0.5), Li[Li x Ni γ Mn (1-x-γ) ]O2(0≦x<0.5, 0<γ<1, 0<1-x-γ), Li[Li x Ni γ Mn β Co (1-x-γ-β) ]O2(0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1, 0<1-x-γ-β), Li[Li x Ni γ Co β Al (1-x-γ-β) ]O2(0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1, 0<1-x-γ-β). Lithium transition metal composite oxides with spinel crystal structure include Li x Mn2O4, Li x Ni γ Mn (2-γ)O4, etc. Examples of polyanion compounds include LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, Li2CoPO4F, etc. Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, molybdenum dioxide, etc. Examples of the positive electrode active material include a material having a slope (small flat area) in the positive electrode potential curve, such as a lithium transition metal composite oxide (for example, lithium nickel manganese cobalt composite oxide) having an α-NaFeO2 type crystal structure, or a material having a relatively large flat area in the positive electrode potential curve, such as a polyanion compound. Atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements. The surfaces of these materials may be coated with other materials. In the positive electrode active material layer, one of these materials may be used alone, or two or more of them may be mixed and used.

[0072] The positive electrode active material is usually a particle (powder). The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material to the above lower limit or more, the positive electrode active material can be easily manufactured or handled. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electronic conductivity of the positive electrode active material layer is improved. In addition, when a composite of the positive electrode active material and another material is used, the average particle size of the composite is taken as the average particle size of the positive electrode active material. The "average particle size" means a value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50% based on the particle size distribution measured by a laser diffraction / scattering method for a diluted solution obtained by diluting particles with a solvent in accordance with JIS-Z-8825 (2013).

[0073] In order to obtain powder with a predetermined particle size, a pulverizer, a classifier, etc. are used. Examples of the pulverization method include a method using a mortar, a ball mill, a sand mill, a vibration ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, or a sieve. During pulverization, wet pulverization in the presence of water or an organic solvent such as hexane can also be used. As a classification method, a sieve, an air classifier, etc. are used as necessary for both dry and wet methods.

[0074] The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass to 99% by mass, more preferably 70% by mass to 98% by mass, and even more preferably 80% by mass to 95% by mass. By setting the content of the positive electrode active material in the above range, both high energy density and manufacturability of the positive electrode active material layer can be achieved.

[0075] The conductive agent is not particularly limited as long as it is a material having electrical conductivity. Examples of such conductive agents include carbonaceous materials, metals, conductive ceramics, and the like. Examples of carbonaceous materials include graphite, non-graphitic carbon, graphene-based carbon, and the like. Examples of non-graphitic carbon include carbon nanofibers, pitch-based carbon fibers, carbon black, and the like. Examples of carbon black include furnace black, acetylene black, ketjen black, and the like. Examples of graphene-based carbon include graphene, carbon nanotubes (CNT), fullerene, and the like. Examples of the conductive agent include powder and fiber. As the conductive agent, one of these materials may be used alone, or two or more of them may be mixed and used. These materials may also be used in combination. For example, a material in which carbon black and CNT are combined may be used. Among these, carbon black is preferred from the viewpoint of electronic conductivity and coatability, and acetylene black or furnace black is preferred.

[0076] The content of the conductive agent in the positive electrode active material layer is preferably from 1 mass % to 10 mass %, more preferably from 3 mass % to 9 mass %. By setting the content of the conductive agent in the above range, the energy density of the nonaqueous electrolyte storage element can be increased.

[0077] Examples of binders include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, polyimide, etc.; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, etc.; polysaccharide polymers, etc.

[0078] The content of the binder in the positive electrode active material layer is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 9% by mass. By setting the binder content within the above range, the positive electrode active material can be stably maintained.

[0079] Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC), methyl cellulose, etc. When the thickener has a functional group that reacts with lithium or the like, this functional group may be deactivated in advance by methylation or the like.

[0080] The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, carbonates such as calcium carbonate, poorly soluble ion crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, and mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof.

[0081] The positive electrode active material layer may contain typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metallic elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, and Nb as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

[0082] (Negative electrode) The negative electrode has a negative electrode substrate and a negative electrode active material layer disposed on the negative electrode substrate directly or via an intermediate layer. The configuration of the intermediate layer is not particularly limited and can be selected from the configurations exemplified for the positive electrode.

[0083] The negative electrode substrate has electrical conductivity. Metals such as copper, nickel, stainless steel, and nickel-plated steel, or alloys thereof, and carbonaceous materials are used as the material of the negative electrode substrate. Among these, copper or copper alloys are preferred. Examples of the negative electrode substrate include foils, vapor deposition films, meshes, and porous materials, and foils are preferred from the viewpoint of cost. Therefore, copper foil or copper alloy foil is preferred as the negative electrode substrate. Examples of copper foil include rolled copper foil and electrolytic copper foil.

[0084] The average thickness of the negative electrode substrate is preferably 2 μm to 35 μm, more preferably 3 μm to 30 μm, further preferably 4 μm to 25 μm, and particularly preferably 5 μm to 20 μm. By setting the average thickness of the negative electrode substrate within the above range, it is possible to increase the strength of the negative electrode substrate and to increase the energy density per volume of the secondary battery.

[0085] The negative electrode active material layer contains a negative electrode active material and, if necessary, any optional components such as a conductive agent, a binder, a thickener, and a filler.

[0086] The negative electrode active material layer may contain typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metallic elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W as components other than the negative electrode active material, conductive agent, binder, thickener, and filler.

[0087] The negative electrode active material can be appropriately selected from known negative electrode active materials that absorb and release charge transport ions. Materials that can absorb and release lithium ions are usually used as negative electrode active materials for lithium ion secondary batteries. Examples of negative electrode active materials include metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide; Li4Ti5O 12 , LiTiO 2、 Examples of the material include titanium-containing oxides such as TiNb2O7, polyphosphate compounds, silicon carbide, and carbon materials such as graphite and non-graphitic carbon (easily graphitized carbon or non-graphitizable carbon). Among these materials, graphite and non-graphitic carbon are preferred, and graphite is more preferred. In the negative electrode active material layer, one of these materials may be used alone, or two or more of them may be used in combination.

[0088] Examples of graphite include natural graphite and artificial graphite.

[0089] "Non-graphitic carbon" refers to carbon that has an average lattice spacing (d 002 ) is 0.34 nm or more and 0.42 nm or less. Examples of non-graphitizable carbon include non-graphitizable carbon and graphitizable carbon. Examples of non-graphitizable carbon include resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, and alcohol-derived materials.

[0090] "Non-graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.36 nm or more and 0.42 nm or less.

[0091] "Graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.34 nm or more and less than 0.36 nm.

[0092] The negative electrode active material is usually a particle (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide, or a polyphosphate compound, the average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to the above lower limit or more, the negative electrode active material can be easily manufactured or handled. By setting the average particle size of the negative electrode active material to the above upper limit or less, the electronic conductivity of the negative electrode active material layer is improved. In order to obtain powder with a predetermined particle size, a pulverizer, a classifier, or the like is used. The pulverizing method and the classifying method can be selected from, for example, the methods exemplified for the positive electrode. When the negative electrode active material is a metal, the negative electrode active material layer may be in the form of a foil.

[0093] The content of the negative electrode active material in the negative electrode active material layer is preferably 60% by mass or more and 99.5% by mass or less, and more preferably 90% by mass or more and 99% by mass or less. By setting the content of the negative electrode active material in the above range, both high energy density and manufacturability of the negative electrode active material layer can be achieved.

[0094] (Separator) The separator can be appropriately selected from known separators. For example, a separator consisting of only a substrate layer, a separator in which a heat-resistant layer containing heat-resistant particles and a binder is formed on one or both surfaces of the substrate layer, etc. can be used as the separator. Examples of the shape of the substrate layer of the separator include woven fabric, nonwoven fabric, and porous resin film. Among these shapes, a porous resin film is preferred from the viewpoint of strength, and a nonwoven fabric is preferred from the viewpoint of non-aqueous electrolyte retention. As the material of the substrate layer of the separator, polyolefins such as polyethylene and polypropylene are preferred from the viewpoint of shutdown function, and polyimide and aramid are preferred from the viewpoint of oxidation decomposition resistance. A material obtained by combining these resins may be used as the substrate layer of the separator.

[0095] The heat-resistant particles contained in the heat-resistant layer preferably have a mass loss of 5% or less when heated from room temperature to 500°C under an air atmosphere at 1 atmosphere, and more preferably have a mass loss of 5% or less when heated from room temperature to 800°C. Examples of materials with a mass loss of a predetermined amount or less include inorganic compounds. Examples of inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ion crystals such as calcium fluoride, barium fluoride, and barium titanate; covalent crystals such as silicon and diamond; mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof. As the inorganic compound, these substances may be used alone or in the form of a complex, or two or more of them may be mixed and used. Among these inorganic compounds, silicon oxide, aluminum oxide, or aluminosilicate is preferred from the viewpoint of the safety of the energy storage element.

[0096] The porosity of the separator is preferably 80% by volume or less from the viewpoint of strength, and is preferably 20% by volume or more from the viewpoint of discharge performance. Here, "porosity" refers to a volume-based value measured with a mercury porosimeter.

[0097] As the separator, a polymer gel composed of a polymer and a non-aqueous electrolyte may be used. Examples of the polymer include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, and polyvinylidene fluoride. The use of the polymer gel has an effect of suppressing leakage. As the separator, the above-mentioned porous resin film or nonwoven fabric may be used in combination with the polymer gel.

[0098] (Non-aqueous electrolyte) The nonaqueous electrolyte may be appropriately selected from known nonaqueous electrolytes. The nonaqueous electrolyte may be a nonaqueous electrolyte solution. The nonaqueous electrolyte solution includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent.

[0099] The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylates, phosphates, sulfonates, ethers, amides, and nitriles. As the non-aqueous solvent, those in which some of the hydrogen atoms contained in these compounds are substituted with halogens may be used.

[0100] Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinylethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, etc. Among these, EC is preferred.

[0101] Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, trifluoroethyl methyl carbonate, bis(trifluoroethyl) carbonate, etc. Among these, EMC is preferable.

[0102] As the non-aqueous solvent, it is preferable to use a cyclic carbonate or a chain carbonate, and it is more preferable to use a combination of a cyclic carbonate and a chain carbonate. By using a cyclic carbonate, it is possible to promote dissociation of the electrolyte salt and improve the ionic conductivity of the non-aqueous electrolyte. By using a chain carbonate, it is possible to keep the viscosity of the non-aqueous electrolyte low. When using a cyclic carbonate and a chain carbonate in combination, it is preferable that the volume ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate:chain carbonate) is, for example, in the range of 5:95 to 50:50.

[0103] The electrolyte salt can be appropriately selected from known electrolyte salts. Examples of the electrolyte salt include lithium salts, sodium salts, potassium salts, magnesium salts, onium salts, etc. Among these, lithium salts are preferred.

[0104] Examples of the lithium salt include inorganic lithium salts such as LiPF6, LiPO2F2, LiBF4, LiClO4, and LiN(SO2F)2, lithium oxalate salts such as lithium bis(oxalate)borate (LiBOB), lithium difluorooxalateborate (LiFOB), and lithium bis(oxalate)difluorophosphate (LiFOP), and lithium salts having a halogenated hydrocarbon group such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, and LiC(SO2C2F5)3. Among these, inorganic lithium salts are preferred, and LiPF6 is more preferred.

[0105] The electrolyte salt content in the non-aqueous electrolyte is 0.1 mol / dm at 20°C and 1 atmosphere. 3More than 2.5mol / dm 3 It is preferable that the value is 0.3 mol / dm or less. 3 More than 2.0mol / dm 3 More preferably, it is 0.5 mol / dm or less. 3 More than 1.7mol / dm 3 More preferably, it is 0.7 mol / dm or less. 3 More than 1.5mol / dm 3 By setting the content of the electrolyte salt within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

[0106] The nonaqueous electrolyte may contain additives in addition to the nonaqueous solvent and the electrolyte salt. Examples of additives include halogenated carbonates such as fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC); oxalates such as lithium bis(oxalate)borate (LiBOB), lithium difluorooxalateborate (LiFOB), and lithium bis(oxalate)difluorophosphate (LiFOP); imide salts such as lithium bis(fluorosulfonyl)imide (LiFSI); aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; partial halides of the aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; halogenated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole; vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, and the like. Carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, methyl methanesulfonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis(2,2-dioxo-1 ,3,2-dioxathiolane), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyl disulfide, dipyridinium disulfide, 1,3-propene sultone, 1,3-propane sultone, 1,4-butane sultone, 1,4-butene sultone, perfluorooctane, tristrimethylsilyl borate, tristrimethylsilyl phosphate, tetrakistrimethylsilyl titanate, lithium monofluorophosphate, lithium difluorophosphate, etc. These additives may be used alone or in combination of two or more.

[0107] The content of the additive contained in the non-aqueous electrolyte is preferably 0.01% by mass to 10% by mass, more preferably 0.1% by mass to 7% by mass, even more preferably 0.2% by mass to 5% by mass, and particularly preferably 0.3% by mass to 3% by mass. By setting the content of the additive within the above range, it is possible to improve the capacity retention performance or cycle performance after high-temperature storage, and to further improve safety.

[0108] The non-aqueous electrolyte may be a solid electrolyte, or a non-aqueous electrolyte solution and a solid electrolyte may be used in combination.

[0109] The solid electrolyte can be selected from any material that has ionic conductivity such as lithium, sodium, calcium, etc., and is solid at room temperature (e.g., 15° C. to 25° C.). Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and polymer solid electrolytes.

[0110] As the sulfide solid electrolyte, in the case of a lithium ion secondary battery, for example, Li2S-P2S5, LiI-Li2S-P2S5, Li 10 Ge-P2S 12 etc.

[0111] The shape of the nonaqueous electrolyte storage element of this embodiment is not particularly limited, and examples thereof include a cylindrical battery, a prismatic battery, a flat battery, a coin battery, and a button battery.

[0112] FIG. 13 shows a nonaqueous electrolyte storage element 1 as an example of a prismatic battery. Note that this figure is a see-through view of the inside of the container. An electrode body 2 having a positive electrode and a negative electrode wound with a separator sandwiched therebetween is housed in a prismatic container 3. The positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 41. The negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 51.

[0113] (Method of manufacturing non-aqueous electrolyte storage element) The method for producing the nonaqueous electrolyte storage element can be appropriately selected from known methods. The method for producing the nonaqueous electrolyte storage element can include, for example, preparing an electrode body, preparing a nonaqueous electrolyte, and housing the electrode body and the nonaqueous electrolyte in a container. The preparation of the electrode body includes preparing a positive electrode and a negative electrode, and forming the electrode body by stacking or winding the positive electrode and the negative electrode with a separator interposed therebetween.

[0114] The method of housing the non-aqueous electrolyte in the container can be appropriately selected from known methods. For example, when a non-aqueous electrolyte solution is used as the non-aqueous electrolyte, the non-aqueous electrolyte solution may be injected through an injection port formed in the container, and then the injection port may be sealed.

[0115] <Other embodiments> The method for adjusting a power storage device and the power storage device of the present invention are not limited to the above-mentioned embodiment, and various modifications may be made without departing from the scope of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a well-known technique. Furthermore, a part of the configuration of one embodiment can be deleted. Also, a well-known technique can be added to the configuration of one embodiment.

[0116] In the above embodiment, the negative electrode active material of the nonaqueous electrolyte storage element is mainly described as being graphite. However, any of various conventionally known negative electrode active materials that absorb and release charge transport ions can be used as the negative electrode active material.

[0117] In the above embodiment, the parameter representing the degradation state of the nonaqueous electrolyte storage element is mainly described as the peak position of dV / dQ that appears when the nonaqueous electrolyte storage element is charged at a predetermined current within a predetermined voltage range. However, the parameter may also be the peak position of dV / dQ that appears when the nonaqueous electrolyte storage element is discharged at a predetermined current within a predetermined voltage range.

[0118] In addition, parameters other than the peak position of dV / dQ can also be used. Other parameters that indicate the deterioration state of the nonaqueous electrolyte storage element include peak positions such as dQ (remaining capacity) / dV (voltage), dV (voltage) / dt (time), and dt (time) / dV (voltage) that appear when the nonaqueous electrolyte storage element is charged or discharged. These peak positions may appear on the high SOC side, for example. These peak positions, like the peak positions of dV / dQ, are correlated with the SOC and voltage of the nonaqueous electrolyte storage element when the graphite undergoes a structural change to the first stage, and by using these as parameters, it becomes easy to set a new upper limit SOC for use within a range in which the graphite does not undergo a structural change to the first stage. In addition, values ​​such as dV / dQ, dQ / dV, dV / dt, and dt / dV at a predetermined position (for example, the SOC or voltage of the nonaqueous electrolyte storage element when the graphite undergoes a structural change to the first stage) can also be used as parameters.

[0119] Further, other parameters include the discharge capacity (deterioration of the discharge capacity) of the nonaqueous electrolyte storage element, the resistance, the open circuit voltage at a given capacity, the closed circuit voltage at a given capacity, the repulsive force, etc. The repulsive force of the nonaqueous electrolyte storage element is, for example, the repulsive force when the outer surface of the container of the nonaqueous electrolyte storage element is pressurized to a given thickness. In order to detect such a repulsive force, the storage device may be equipped with a pressure measuring device such as a load cell.

[0120] In the above embodiment, the nonaqueous electrolyte storage element is used as a chargeable and dischargeable nonaqueous electrolyte secondary battery (lithium ion secondary battery), but the type, shape, size, capacity, etc. of the nonaqueous electrolyte storage element are arbitrary. The present invention can also be applied to various secondary batteries, electric double layer capacitors, lithium ion capacitors, and other capacitors.

[0121] In the above embodiment, the electrode assembly in which the positive electrode and the negative electrode are stacked with a separator interposed therebetween has been described, but the electrode assembly may not include a separator. For example, the positive electrode and the negative electrode may be in direct contact with each other in a state in which a non-conductive layer is formed on the active material layer of the positive electrode or the negative electrode. [Industrial Applicability]

[0122] The present invention can be applied to electronic devices such as personal computers and communication terminals, and power storage devices used as power sources for automobiles and the like. [Explanation of symbols]

[0123] 10. Energy storage device 11 Energy storage unit 12. Non-aqueous electrolyte storage element management device (management device) 13 Charging device 14 Wiring 15 Control section 16 Analog-to-Digital Converter (ADC) 17 Current Sensor 18 Voltage Sensor 19 Central Processing Unit (CPU) 20 Memory SG1, SG2 detection signal 1. Non-aqueous electrolyte storage element 2 Electrode body 3 containers 4 Positive terminal 41 Positive lead 5 Negative terminal 51 Negative lead

Claims

1. A method for adjusting an electricity storage device including a nonaqueous electrolyte electricity storage element having a negative electrode including a negative electrode active material that absorbs and releases charge transport ions, and a control unit that controls charging and discharging of the nonaqueous electrolyte electricity storage element within a range equal to or lower than an upper usage limit SOC, Detecting a parameter indicative of a deterioration state of the nonaqueous electrolyte storage element; and A new upper limit SOC for use is set according to the above parameters, the new upper limit SOC for use being a value higher than the currently set upper limit SOC for use. A method for adjusting a power storage device comprising:

2. The negative electrode active material contains graphite, The set upper limit SOC is a range in which the graphite does not undergo a structural change to the first stage, The method for adjusting a power storage device according to claim 1 , wherein the new upper limit SOC is set within a range in which a structural change to the first stage does not occur in the graphite.

3. the parameter correlates with the voltage of the nonaqueous electrolyte electricity storage element when the graphite undergoes a structural change to the first stage; 3. The method for adjusting an electricity storage device according to claim 2, wherein in setting an upper limit, the new upper limit SOC is set within a range in which an upper limit voltage of the nonaqueous electrolyte storage element corresponding to the new upper limit SOC is equal to or lower than a voltage of the nonaqueous electrolyte storage element when a structural change to the first stage occurs in the graphite.

4. 4. The method for adjusting a charging device according to claim 3, wherein the parameter is a peak position of dV (voltage) / dQ (residual capacity) that appears when the nonaqueous electrolyte electricity storage element is charged within a predetermined voltage range.

5. A non-aqueous electrolyte storage element having a negative electrode containing a negative electrode active material that absorbs and releases charge transport ions, and A control unit that controls charging and discharging of the nonaqueous electrolyte electricity storage element within a range equal to or less than an upper limit SOC of use and controls the upper limit SOC of use. Equipped with The control unit controls the use upper limit SOC by: A detection process for detecting a parameter indicative of a deterioration state of the nonaqueous electrolyte storage element; and A setting process for setting a new upper limit SOC for use that is higher than the currently set upper limit SOC for use according to the above parameters. The power storage device has a configuration for executing the above.

6. The control unit has a memory in which information regarding a relationship between the parameter and the upper limit SOC is stored, 6. The power storage device according to claim 5, wherein the control unit, in the setting process, sets the new usage upper limit SOC based on the detected parameter and the information stored in the memory.

7. The negative electrode active material contains graphite, The set upper limit SOC is a range in which the graphite does not undergo a structural change to the first stage, 7. The power storage device according to claim 5, wherein the control unit, in the setting process, sets the new use upper limit SOC within a range in which a structural change to the first stage does not occur in the graphite.

8. the parameter correlates with the voltage of the nonaqueous electrolyte electricity storage element when the graphite undergoes a structural change to the first stage; 8. The power storage device according to claim 7, wherein, in the setting process, the control unit sets the new use upper limit SOC within a range in which a use upper limit voltage of the nonaqueous electrolyte storage element corresponding to the new use upper limit SOC is equal to or lower than a voltage of the nonaqueous electrolyte storage element when a structural change to a first stage occurs in the graphite.

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