JP2017103896A - Method for controlling secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a secondary battery capable of preventing a short circuit caused by a precipitate.SOLUTION: The control method of a secondary battery, which can be charged and discharged, includes; identifying the amount of precipitate ΔM and a shape at a negative electrode of the secondary battery; calculating the height of the precipitate based on the identified amount of precipitate ΔM and shape; and making an allowable input power to the secondary battery smaller than when the height of the precipitate is less than a reference height when the height of the deposited precipitate is equal to or higher than the predefined reference height.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for controlling a chargeable / dischargeable secondary battery.

  2. Description of the Related Art Conventionally, secondary batteries containing a reaction-participating substance that can be deposited on the surface of a negative electrode in an electrolytic solution are known. For example, the lithium ion secondary battery electrolyte contains lithium ions. During charging, depending on the input power, the lithium ions dissolved in the electrolyte are deposited as metallic lithium on the negative electrode surface. To do.

  Patent Document 1 discloses a technique for calculating the deposition amount of lithium ions and calculating the SOC of the secondary battery based on the calculated deposition amount. Patent Document 1 further discloses that the limit value of the input / output power to the secondary battery is changed in accordance with the SOC of the secondary battery.

JP 2014-126411 A

  By the way, a separator that insulates the two is usually interposed between the negative electrode and the positive electrode. The precipitate deposited on the negative electrode surface gradually grows toward the positive electrode side as the deposition proceeds and proceeds in the separator. If such deposition continues to proceed, the deposit may completely penetrate the separator, contact the positive electrode, and a short circuit may occur.

  In the prior art such as Patent Document 1, attention is paid to the amount of precipitates, but no consideration is given to the height of the precipitates. Therefore, in the prior art, a short circuit due to the precipitate as described above could not be prevented.

  Therefore, an object of the present embodiment is to provide a secondary battery control method that can prevent a short circuit due to precipitates.

  The secondary battery control method of the present invention is a chargeable / dischargeable secondary battery control method, wherein the amount and shape of precipitates in the negative electrode of the secondary battery are specified, and the specified precipitation amount and From the shape, the height of the precipitate is calculated, and when the calculated height of the precipitate is equal to or higher than a predetermined reference height, the allowable input power value to the secondary battery is determined. It is characterized in that the height of the object is smaller than the case where the height is less than the reference height.

  According to the present invention, the allowable input power value is determined according to the height of the precipitate. As a result, when there is a possibility of a short circuit, the allowable input power value is reduced, so that a short circuit due to precipitates can be prevented. Further, in the present invention, not only the amount of precipitates but also the shape is taken into account, so that the height of the precipitates can be calculated more accurately, and as a result, a short circuit can be prevented more reliably.

1 is an overall configuration diagram of a vehicle on which a secondary battery control device according to an embodiment of the present invention is mounted. It is a schematic diagram which shows the structure of a lithium ion secondary battery. It is a schematic diagram which shows the mode of the growth of metallic lithium It is a figure which shows an example of a conversion map. It is a flowchart which shows the flow of determination of the input power allowable value Win at the time of charge. It is a flowchart which shows the flow of determination of the input power allowable value Win at the time of charge. It is a flowchart which shows the flow of determination of the input power allowable value Win at the time of discharge.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a vehicle on which a secondary battery control device 10 according to an embodiment of the present invention is mounted. The vehicle includes an engine 106, two rotating electric machines 108 and 109, a power split device 110, a PCU (Power Control Unit) 104, a battery 100, and a control device 10. The vehicle is a hybrid vehicle that travels by power output from at least one of the engine 106 and the second rotating electrical machine 109. However, the vehicle may have another configuration as long as it is an electric vehicle that travels using energy supplied from battery 100. For example, the vehicle may be a hybrid vehicle having a configuration different from that in FIG. 1 or an electric vehicle that does not include the engine 106 and is driven only by power from the rotating electrical machines 108 and 109.

  The power of the engine 106 is divided into a path transmitted to the drive wheels 112 and a path transmitted to the first rotating electrical machine 108 by the power split device 110. First rotating electrical machine 108 generates power using the power of engine 106 divided by power split device 110. Second rotating electrical machine 109 generates power using at least one of the electric power stored in battery 100 and the electric power generated by first rotating electric machine 108. The power of the second rotating electrical machine 109 is transmitted to the drive wheels 112. During braking of the vehicle, the second rotating electrical machine 109 is driven by the drive wheels 112, and the second rotating electrical machine 109 operates as a generator. At this time, the second rotating electrical machine 109 functions as a regenerative brake that converts the kinetic energy of the vehicle into electric power. The regenerative power generated by the second rotating electrical machine 109 is stored in the battery 100.

  The PCU 104 performs power conversion between the battery 100 and the first and second rotating electrical machines 108 and 109. By operating the PCU 104, the first and second rotating electric machines 108 and 109 are driven by the electric power stored in the battery 100, or the battery 100 is generated by the electric power generated by the first and second rotating electric machines 108 and 109. It is charged.

  The battery 100 includes a plurality of single cells 102 connected in series. The unit cell 102 is a lithium ion secondary battery. The number of single cells 102 constituting the battery 100 can be appropriately set in consideration of the required output of the battery 100 and the like. A plurality of single cells 102 may be connected in series or in parallel to constitute one battery block, and a plurality of battery blocks may be connected in series to constitute one battery 100.

  A lithium metal oxide such as lithium cobaltate is used as the positive electrode active material of the unit cell 102 (lithium ion secondary battery), and a carbon material such as graphite is used as the negative electrode active material. Moreover, the ion conductor which conducts ionized lithium (reaction participating substance) between a positive electrode and a negative electrode can be comprised with resin which osmose | permeated electrolyte solution, for example. Further, for example, a so-called nonaqueous electrolytic solution may be used as the electrolytic solution.

  In a lithium ion secondary battery, during discharge, a chemical reaction that releases lithium ions and electrons occurs on the interface of the active material of the negative electrode, and a chemical reaction that absorbs lithium ions and electrons occurs on the interface of the active material of the positive electrode. Conversely, during charging, a chemical reaction that absorbs lithium ions and electrons occurs on the negative electrode active material interface, and a chemical reaction that releases lithium ions and electrons occurs on the positive electrode active material interface.

  In addition, although this embodiment demonstrates the case where the battery 100 is used as a lithium ion secondary battery, the battery 100 is not limited to a lithium ion battery, The reaction participation which deposits on the negative electrode surface in electrolyte solution is demonstrated. Other secondary batteries may be used as long as the secondary battery contains a substance.

  The control device 10 that controls charging / discharging of the battery 100 includes a plurality of sensors 12, 14, and 16 for detecting the state of the battery 100, and a controller 20. As the sensors, a voltage sensor 12 that detects a voltage value of the battery 100, a current sensor 14 that detects a current value of the battery 100, and a temperature sensor 16 that detects the temperature of the battery 100 are provided. The voltage sensor 12 detects a voltage between terminals of the battery 100 (hereinafter referred to as “battery voltage VB”) and outputs a detection result to the controller 20. The current sensor 14 detects the current flowing through the battery 100 as the battery current IB and outputs the detection result to the controller 20.

  The temperature sensor 16 detects the temperature of the battery 100 (hereinafter referred to as “battery temperature TB”). The temperature sensor 16 outputs the detection result to the controller 20. The temperature sensor 16 can be provided at one place of the battery 100 or can be provided at a plurality of places. When a plurality of temperature sensors 16 are provided, a statistical value of a plurality of temperature detection values, for example, a minimum value, a maximum value, an average value, or the like can be used as the battery temperature TB.

  The controller 20 includes a CPU 22 that performs various calculations, a memory 24, and the like. The memory 24 stores various programs, control parameter values used for control, and the like. The memory 24 temporarily stores detection values from various sensors, calculation results from the CPU 22, and the like. The CPU 22 performs necessary calculations based on various parameters, detection values, and calculation results stored in the memory 24, and controls the driving of the battery 100 according to the calculation results. For example, the controller 20 calculates an allowable value of input / output power to the battery 100, that is, an allowable input power value Win and an allowable output power value Wout based on various parameters. Then, the controller 20 controls charging / discharging of the battery 100 such that the actual input / output power to the battery 100 does not exceed the calculated input / output power allowable values Win, Wout.

  Next, the setting of the input power allowable value Win by the control device 10 will be described. First, the characteristics of the lithium ion secondary battery 50 will be briefly described. FIG. 2 is a schematic diagram showing the configuration of the lithium ion secondary battery 50. FIG. 3 is a schematic diagram showing how the metallic lithium 58 grows.

  As is well known, in the lithium ion secondary battery 50, a positive electrode 52 and a negative electrode 54 are disposed to face each other with a separator 56 interposed therebetween. The positive electrode 52 includes a base material 52a and a positive electrode active material 52b laminated on the base material 52a. The negative electrode 54 includes a base material 54a and a negative electrode active material 54b stacked on the base material 54a.

  When the lithium ion secondary battery 50 is charged, lithium ions in the electrolytic solution are deposited as metallic lithium 58 depending on the magnitude of the power (input power). In the following, lithium deposited as a solid is referred to as “metallic lithium 58” and is distinguished from lithium dissolved in the electrolytic solution. The metal lithium 58 is deposited on the surface of the negative electrode 54 as shown in FIG. Further, as shown in FIG. 3, the metal lithium 58 is always deposited on the surface of the negative electrode 54, and the metal lithium 58 deposited in the past is pushed toward the positive electrode 52 side. In other words, in the lithium ion secondary battery 50, the metal lithium 58 gradually grows toward the positive electrode 52 side. Here, the deposited metal lithium 58 contains active lithium and inactive lithium. The active lithium can be dissolved in the electrolytic solution in accordance with the potential of the negative electrode 54, and can contribute to the electrochemical reaction again by being dissolved. As shown in FIG. 3, the active lithium is dissolved by discharging the battery. This dissolution proceeds in order from the most recently deposited active lithium, that is, active lithium close to the negative electrode 54 surface. In addition, active lithium reacts with the surrounding electrolyte and gradually inactivates to be transformed into inactive lithium. Inactive lithium cannot be dissolved in the electrolyte and does not contribute to the electrochemical reaction.

  By the way, when the metallic lithium 58 is deposited, the capacity of the secondary battery is reduced. Therefore, conventionally, in order to prevent the deposition of the metallic lithium 58, the allowable input power value Win is set to a relatively small value so that the input power to the battery 100 is reduced. However, if the input power allowable value Win is excessively small, another problem of deterioration of fuel consumption is caused.

  Therefore, in the present embodiment, the allowable input power value Win is increased in order to allow the deposition of the metallic lithium 58 in a state where the short circuit of the lithium ion secondary battery 50 (unit cell 102) can be prevented. Here, the state where the short circuit of the lithium ion secondary battery 50 can be prevented means a state where the height of the metal lithium 58 deposited on the surface of the negative electrode 54 is less than the thickness of the separator 56. That is, the metallic lithium 58 deposited on the surface of the negative electrode 54 gradually grows toward the positive electrode 52 in the separator 56. When the height of the metal lithium 58 is equal to or greater than the thickness of the separator 56 and the metal lithium 58 penetrates the separator 56, a short circuit is established in which the positive electrode 52 and the negative electrode 54 are conducted. Therefore, in the present embodiment, the amount M and the shape of the metal lithium 58 deposited or dissolved during charge / discharge are estimated, and the height of the metal lithium 58 deposited on the surface of the negative electrode 54 from the estimated amount and shape ( (Hereinafter referred to as “residual height Hc”). Then, the obtained remaining height Hc is compared with the reference height Hdef, and when the remaining height Hc is equal to or higher than the reference height Hdef, it is possible to prevent the deposition of the metal lithium 58 as the input power allowable value Win. The initial value Win_i to be obtained is set. On the other hand, when the remaining height Hc is less than the reference height Hdef, a relaxation value Win_w larger than the initial value Win_i is set as the input power allowable value Win. The reference height Hdef is a value determined based on the thickness of the separator 56, and is a value obtained by subtracting a certain amount of margin from the thickness of the separator 56. Hereinafter, each process will be described in detail.

[Calculation of metal lithium precipitation / dissolution amount ΔM]
First, calculation of the precipitation dissolution amount ΔM of the metallic lithium 58 accompanying charge / discharge will be described. The metal lithium 58 deposited on the surface of the negative electrode 54 can be divided into active lithium and inactive lithium. Active lithium can be dissolved in an electrolytic solution in accordance with the negative electrode potential. By dissolving, active lithium can contribute to the electrochemical reaction again. Inactive lithium cannot be dissolved in the electrolyte and does not contribute to the electrochemical reaction. This inactive lithium is generated when active lithium reacts with the surrounding electrolyte.

The amount M of metallic lithium 58 deposited on the negative electrode 54 is the sum of the amount of active lithium m ₃ and the amount of inert lithium m ₄ . Here, as described above, the inactive lithium is generated when the active lithium reacts with the surrounding electrolyte. Therefore, even if the amount M of the metallic lithium 58 does not change, the active lithium amount m ₃ decreases or the inactive lithium amount m ₄ increases. The amount of metal lithium 58 deposited or dissolved with charging / discharging (hereinafter referred to as “precipitation dissolution amount ΔM”) is an increase / decrease amount of the amount M of metal lithium 58 after the start of charging or discharging. That is, when the amount of metallic lithium 58 at the start of charging or discharging is the initial lithium amount Ms, and the amount of metallic lithium 58 calculated per unit time thereafter is M, the precipitation dissolution amount ΔM is , ΔM = M−Ms. The precipitation dissolution amount ΔM is positive when the metal lithium 58 is deposited, and is negative when the metal lithium 58 is dissolved.

The amount M of metallic lithium 58 is constantly calculated. The amount M of the metallic lithium 58 is a total value of the active lithium amount m ₃ and the inactive lithium amount m ₄ . The active lithium amount m ₃ and the inactive lithium amount m ₄ are calculated from the battery temperature TB, the battery current IB, the battery voltage VB, and the like. More specifically, the amount of active lithium m ₃ is determined by the following formula 1.
m ₃ = k ₃ × ∫ (V ₃ ) dt Equation 1
V ₃ = i ₃ × s ₃ Formula 2

In Equation 1, V ₃ is the precipitation dissolution rate of active lithium, and ∫ (V ₃ ) dt indicates the amount of charge corresponding to the amount of active lithium. The coefficient k ₃ is a coefficient for converting 予 め (V ₃ ) dt into the amount of active lithium m ₃ with a fixed value determined in advance based on experimental results and the like. The active lithium deposition rate V ₃ is calculated by the equation shown in Equation 2. In Equation 2, s ₃ is a contact area between active lithium and the negative electrode 54. This contact area s ₃ is a fixed value determined in advance by an experimental result or the like. i ₃ is the current density of the active lithium precipitation dissolution reaction in the negative electrode 54. The current density i _3, for example, based on the relational expression Butler Volmer showing the relationship between overvoltage and the current value in the anode 54 can be calculated using Equation 3 below.

In Equation 3, i ₀₃ is the exchange current density of the lithium precipitation dissolution reaction, α is the transfer coefficient of the oxidation reaction (subscript a) and the reduction reaction (subscript c), and F is the Faraday constant. Yes, R is the gas constant, T is the temperature of the active lithium, and η ₃ is the overvoltage of the active lithium precipitation dissolution reaction. The exchange current density i ₀₃ corresponds to the reaction rate coefficient and can be determined in advance based on experimental results and the like. The movement coefficients α _a , α _c , Faraday constant F, and gas constant R are all fixed values. The temperature T of active lithium and the overvoltage η ₃ of the precipitation dissolution reaction can be calculated using the battery voltage VB, the battery current IB, and the battery temperature TB as parameters.

On the other hand, the inactive lithium amount m ₄ is obtained by the following formula 4.
m ₄ = k ₄ × ∫ (V ₄ ) dt Equation 4
V ₄ = i ₄ × s ₄ Formula 5

In Equation 4, V ₄ is the inactivation rate of lithium, and ∫ (V ₄ ) dt indicates the amount of charge corresponding to the amount of inactive lithium. The coefficient k ₄ is a coefficient for converting 実 験 (V ₄ ) dt into the inactive lithium amount m ₄ , which is a fixed value determined in advance based on experimental results and the like. The lithium deactivation rate V ₄ is calculated by the equation shown in Equation 5. In Equation 5, s ₄ is a contact area between the active lithium and the electrolytic solution. This contact area s ₄ is a fixed value determined in advance by an experimental result or the like. i ₄ is the current density of the deactivation reaction of active lithium in the negative electrode 54. The current density i ₄ can be calculated using the following equation 6 based on the Butler-Volmer relational expression indicating the relation between the overvoltage and the current value in the negative electrode 54, for example.

In Equation 6, i ₀₄ is the exchange current density of the lithium deactivation reaction, and η ₄ is the overvoltage of the lithium deactivation reaction. Others are the same as those used in Equation 3 above. The exchange current density i ₀₄ corresponds to the reaction rate coefficient, and can be determined in advance based on experimental results and the like. The overvoltage η ₄ of the inactivation reaction can be calculated using the battery voltage VB, the battery current IB, and the battery temperature TB as parameters.

The calculation method described here is an example, and the active / inactive lithium amounts m ₃ and m ₄ may be obtained by other methods. For example, the battery voltage VB, battery current IB, and active / inactive lithium amounts m ₃ and m ₄ corresponding to the battery temperature TB are stored in advance as a map, and the measured battery voltage VB, battery current IB, and battery temperature TB are stored. The amount of active / inactive lithium m ₃ and m ₄ may be obtained by comparing with the map.

By adding the calculated active / inactive lithium amounts m ₃ and m ₄ , the amount M of the metallic lithium 58 at that time is obtained. The difference value between this amount M and the amount at the start of charging or discharging (starting lithium amount Ms) is the precipitation dissolution amount ΔM. If the precipitation dissolution amount ΔM is positive, the remaining height Hc increases. If it is negative, the remaining height Hc decreases.

[Identification of lithium shape]
Next, specification of the shape of the newly deposited metallic lithium 58 will be described. The shape of the metallic lithium 58 deposited on the surface of the negative electrode 54 is not uniform, and the ratio of the height to the diameter (or width) is relatively small, and the ratio of the height to the diameter (or width) is relatively large. It is known that there are needles. In general, acicular metal lithium 58 is likely to be deposited when one charge duration tc is long, and bulk metal lithium 58 is likely to be deposited when the charge time is short. Even if the precipitation amount ΔM is the same, the height of the metallic lithium 58 is higher in acicular lithium than in bulk lithium. Therefore, in order to accurately estimate the height of the metallic lithium 58, it is necessary to specify whether the deposited metallic lithium 58 is needle-like or massive.

  Therefore, in the present embodiment, the elapsed time from the start of charging, that is, the charging duration time tc is counted, and if the charging duration time tc is equal to or greater than a predetermined reference time tdef, a new one is generated during the charging. It is determined that all the deposited metal lithium 58 has a needle shape. On the other hand, when the charging is completed before the charging duration tc reaches the reference time tdef, it is determined that all the metal lithium 58 newly deposited by the charging is in a lump shape.

  At the time of discharging, the active lithium close to the surface of the negative electrode 54 is dissolved in order. It is very difficult to distinguish whether the active lithium that is dissolved is in the form of lumps or needles. Therefore, in the present embodiment, at the time of discharging, it is considered that all the active lithium dissolved is in a lump shape. By considering it as a lump, the height reduction amount ΔH accompanying the discharge can be estimated smaller than the actual reduction amount. As a result, the remaining height Hc is prevented from being estimated lower than the actual height. And it can prevent more reliably that the metallic lithium 58 penetrates the separator 56, and by extension, a battery short circuit by this.

[Calculation method of remaining height Hc]
If the precipitation dissolution amount ΔM and the shape of the metal lithium 58 can be specified, the controller 20 calculates the height of the remaining metal lithium 58 (residual height Hc). The remaining height Hc is obtained by adding the height increase / decrease amount ΔH generated by charging / discharging to the height of the metal lithium 58 at the start of charging / discharging (hereinafter referred to as “starting height Hs”). That is, Hc = Hs + ΔH. The height increase / decrease amount ΔH is positive at the time of deposition (charge) and negative at the time of dissolution (discharge).

  In order to calculate the height increase / decrease amount ΔH, the memory 24 of the controller 20 stores in advance a conversion map 60 indicating the correlation between the precipitation dissolution amount ΔM of the metallic lithium 58 and the height increase / decrease amount ΔH. FIG. 4 is a diagram illustrating an example of the conversion map 60. The conversion map 60 includes a lump line 62 indicating a correlation between the precipitation dissolution amount ΔM of the bulk lithium and the height increase / decrease amount ΔH, and a needle indicating a correlation between the precipitation dissolution amount ΔM of the needle lithium and the height increase / decrease amount ΔH. A line 64 for the shape. In both the lump line 62 and the needle line 64, the height increase / decrease amount ΔH increases as the precipitation dissolution amount ΔM increases, but the inclination of the needle line 64 is larger. Further, when the precipitation dissolution amount ΔM is positive (at the time of precipitation), the height increase / decrease amount ΔH is also positive, and when the precipitation dissolution amount ΔM is negative (at the time of dissolution), the height increase / decrease amount ΔH is also negative.

  At the time of charging / discharging, the controller 20 selects a reference line according to the shape of the deposited lithium metal 58, and compares the calculated precipitation dissolution amount ΔM with the selected line to increase or decrease the height. ΔH is calculated. For example, when it is determined that ΔM = m_a is deposited as a result of charging, the controller 20 increases the height of the metallic lithium 58 by a height h_a corresponding to m_a in light of the needle line 64. Judge that Then, a value obtained by adding the increase / decrease amount ΔH = h_a to the starting height Hs is calculated as the remaining height Hc (Hc = Hs + h_a). In addition, when it is determined that the massive lithium has dissolved m_b due to the discharge (that is, ΔM = −m_b), the controller 20 compares the metallic lithium with the height −h_b corresponding to −m_b in light of the massive line 62. It is determined that the height of 58 has decreased. Then, a value obtained by adding the increase / decrease amount ΔH = −h_b to the starting height Hs is calculated as the remaining height Hc (Hc = Hs−h_b).

[Flow of determination of allowable input power value Win]
Next, the flow of determining the allowable input power value Win will be described with reference to FIGS. 5 and 6 are flowcharts showing the flow of determining the allowable input power value Win during charging. Although not shown in FIGS. 5 to 7, the controller 20 always calculates the amount M = m ₃ + m ₄ of the metallic lithium 58 for each unit time regardless of whether or not charging / discharging is performed. This calculation is performed based on the above-described equations 1 to 6.

  As shown in FIG. 5, when charging is started (Yes in S10), the controller 20 sets the remaining height Hc stored in the memory 24 as the starting height Hs (S12). Further, the amount M of the metallic lithium 58 at the start of charging is set as the starting lithium amount Ms (S12). Furthermore, a timer is started and measurement of the charge duration time tc is started (S14).

  Next, the controller 20 calculates the difference between the amount M calculated per unit time and the starting lithium amount Ms as the precipitation dissolution amount ΔM (S16). Next, the controller 20 compares the charging duration tc with the reference time tdef (S18). As a result of the comparison, if the charge duration time tc is less than the reference time tdef, it is estimated that the metal lithium 58 deposited during the charge is all in a lump shape (S24). Then, the amount of metal lithium 58 deposited so far ΔM is compared with the lump line 62 to calculate the height increase / decrease amount ΔH of the metal lithium 58 (S26). On the other hand, when the charging duration tc is equal to or longer than the reference time tdef, it is estimated that the metal lithium 58 deposited during the charging is all needle-shaped (S20). Then, the amount of metal lithium 58 deposited so far ΔM is compared with the needle-like line 64 to calculate the height increase / decrease amount ΔH of the metal lithium 58 (S22).

  If the height increase / decrease amount ΔH can be calculated, the controller 20 adds the increase / decrease amount ΔH to the start height Hs set at the start of charging to calculate the remaining height Hc (S28, see FIG. 6). Subsequently, the controller 20 compares the remaining height Hc with the reference height Hdef (S30). As a result of the comparison, if the remaining height Hc is less than the reference height Hdef, it is determined that further deposition of the metal lithium 58 is possible, and the relaxation value at which the metal lithium 58 can be deposited as the input power allowable value Win. Win_w is set (S34). On the other hand, if the remaining height Hc is equal to or higher than the reference height Hdef, it is determined that the deposition of the metallic lithium 58 needs to be stopped, and the input power allowable value Win is a low value that does not deposit the metallic lithium 58, that is, the initial value. Win_i is set (S32).

  Thereafter, the controller 20 checks whether or not the charging is finished (S36). When the charging is finished, the last calculated residual height Hc is stored in the memory 24 (S38). The value of the remaining height Hc does not change thereafter until charging or discharging is performed. On the other hand, when charging does not end and continues, the controller 20 returns to step S16 (see FIG. 5). Thereafter, steps S16 to S36 are repeated until the charging is completed.

  Next, with reference to FIG. 7, the flow of determination of the allowable input power value Win during discharging will be described. If the discharge is started (Yes in S40), the controller 20 sets the remaining height Hc stored in the memory 24 as the starting height Hs (S42). Further, the amount M of metallic lithium 58 at the start of discharge is set as the starting lithium amount Ms (S42).

  Subsequently, the controller 20 calculates a difference between the amount M of the metallic lithium 58 calculated per unit time and the starting lithium amount Ms as the precipitation dissolution amount ΔM (S44). Next, the height increase / decrease amount ΔH of the metallic lithium 58 is calculated based on the precipitation dissolution amount ΔM (S46). Here, as described above, in the present embodiment, all of the dissolved metal lithium 58 is regarded as bulk lithium. This is because it is difficult to specify the shape of active lithium to be dissolved. The remaining height Hc is not estimated to be lower than the actual height by regarding all the active lithium to be dissolved as a lump having a relatively low height. As a result, a short circuit can be prevented more reliably. If the precipitation dissolution amount ΔM can be calculated, the controller 20 refers to the block line 62 and calculates the height increase / decrease amount ΔH of the metallic lithium 58.

  If the height increase / decrease amount ΔH can be calculated, the controller 20 calculates the remaining height Hc by adding the increase / decrease amount ΔH to the start height Hs set at the start of discharge (S48). Subsequently, the controller 20 compares the remaining height Hc with the reference height Hdef (S50). As a result of the comparison, if the remaining height Hc is less than the reference height Hdef, it is determined that further deposition of the metal lithium 58 is possible, and the relaxation value at which the metal lithium 58 can be deposited as the input power allowable value Win. Win_w is set (S54). On the other hand, if the remaining height Hc is equal to or higher than the reference height, it is determined that the deposition of the metal lithium 58 needs to be stopped, and the input power allowable value Win is a low value at which the metal lithium 58 does not deposit, that is, the initial value Win_i. Is set (S52).

  Thereafter, the controller 20 confirms whether or not the discharge has ended (S56). When the discharge is completed, the last calculated remaining height Hc is stored in the memory 24 (S58). The value of the remaining height Hc does not change thereafter until charging or discharging is performed. On the other hand, when the discharge does not end and continues, the controller 20 returns to step S44. Thereafter, steps S44 to S56 are repeated until the discharge is completed.

  As is clear from the above description, in the present embodiment, the allowable input power value Win is set to a relatively large relaxation value Win_w until the remaining height Hc reaches the reference height Hdef. Further, the fuel consumption can be further improved by relaxing the input power allowable value Win.

  In the present embodiment, the shape of the deposited metal lithium 58 is specified, and the conversion ratio from the precipitation dissolution amount ΔM to the height increase / decrease amount ΔH is changed according to the shape. With this configuration, the height of the deposited metal lithium 58 can be estimated more accurately. As a result, the input power allowable value Win can be more relaxed while preventing the secondary battery from being short-circuited, and the fuel consumption can be further improved.

  In addition, the structure demonstrated so far is an example, the deposit amount and the deposit form of the deposit of the secondary battery are identified, and the height of the deposit is calculated from the identified deposit amount and the deposit form. If the allowable input power value is determined according to the height of the precipitate, other configurations may be changed as appropriate. For example, in the present embodiment, as the shape of the metal lithium 58, only two types of needle shape and lump shape are listed, but the shape may be classified into a larger number of types. In this embodiment, the shape of the metallic lithium 58 is determined according to the charging duration tc. However, the shape may be determined in consideration of other conditions such as temperature and current value. Good. Moreover, the calculation method of the precipitation dissolution amount ΔM of the metal lithium 58 described above is an example, and may be changed as appropriate.

  DESCRIPTION OF SYMBOLS 10 Control apparatus, 12 Voltage sensor, 14 Current sensor, 16 Temperature sensor, 20 Controller, 22 CPU, 24 Memory, 50 Lithium ion secondary battery, 52 Positive electrode, 52a base material, 52b Positive electrode active material, 54 Negative electrode, 54a base material , 54b Negative electrode active material, 56 Separator, 58 Metal lithium, 60 conversion map, 62 lump line, 64 needle line, 100 battery, 102 cell, 106 engine, 108 first rotating electric machine, 109 second rotating electric machine, 110 Power split device, 112 Drive wheels.

Claims (1)

A control method of a chargeable / dischargeable secondary battery,
The precipitation amount and shape of the precipitate in the negative electrode of the secondary battery are specified, the height of the precipitate is calculated from the specified precipitation amount and shape, and the calculated height of the precipitate is In the case of a specified reference height or more, the input power allowable value to the secondary battery is made smaller than the case where the height of the deposit is less than the reference height.
A control method for a secondary battery.