JP5574115B2 - Status management method for lithium-ion batteries - Google Patents

Description

  The present invention relates to a state management method for a lithium ion battery.

  A lithium ion battery is one of non-aqueous electrolyte secondary batteries. In a lithium ion battery, for example, a lithium metal oxide is used as an active material for a positive electrode, and a carbon material such as graphite is used as an active material for a negative electrode. Lithium ions released from the active material of the positive electrode during charging are negative electrodes. In the discharge, lithium ions occluded in the active material of the negative electrode are released and occluded in the positive electrode. In this way, current flows between the electrodes as the lithium ions move between the electrodes. That is, in the lithium ion battery, lithium ions moving between the electrodes are responsible for electrical conduction. Since this lithium ion battery has a high energy density, it is used, for example, as a battery for electric vehicles.

  In such a lithium ion battery, lithium ions that move between the electrodes are deposited on the negative electrode surface by use and are fixed by forming a film, so that lithium ions that can move between the electrodes are reduced. Thereby, the capacity | capacitance of a battery may fall.

  In order to solve such a decrease in capacity, a non-aqueous electrolyte secondary battery having a third electrode provided with metallic lithium that does not come into contact with the electrolytic solution is known (for example, see Patent Document 1).

JP 2002-324585 A

  According to such a non-aqueous electrolyte secondary battery, the capacity of the battery is recovered by supplementing lithium ions from the third electrode for the capacity reduction. For example, when the initial discharge capacity is 50 Ah but the discharge capacity is reduced to 48 Ah, the third electrode is energized to release lithium ions into the battery corresponding to 2 Ah, which is the reduced amount, Thereby, the lithium ion which moves between electrodes is supplied and the discharge capacity is recovered.

  However, in such a case, lithium ion may be replenished too much to form lithium dendrite on the positive electrode, and the battery capacity may not be recovered.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and it is possible to calculate an appropriate addition amount of lithium ions that can suppress the formation of lithium dendrite, and by supplementing this addition amount, An object of the present invention is to provide a state management method for a lithium ion battery capable of recovering the capacity.

A lithium ion battery state management method according to the present invention includes a first active material, a positive electrode including a second active material having a lower electrode potential than the first active material, a negative electrode, and an electrolyte solution. A state management method for an ion battery, in which the initial charge / discharge state of the lithium ion battery and the charge / discharge state at the time of determination are compared to determine the cause of deterioration of the lithium ion battery. The initial charge / discharge capacity is the same as the charge / discharge capacity at the time of judgment , which is the charge / discharge capacity changed from the start of expansion / contraction of the first active material during the charge / discharge The charge / discharge capacity changed from the start of expansion / contraction of the second active material to the end of expansion / contraction at the time of charge / discharge of the lithium ion battery. If it has decreased than before The cause of deterioration is determined to be a decrease in lithium ions, and the lithium ion is determined from the difference between the charge / discharge capacities at the time of determination in the region where the voltage at charge / discharge holds the electrode potential corresponding to the second active material and the initial charge / discharge capacity. The amount of decrease is calculated.

In the present invention, the cause of deterioration is determined to be a decrease in lithium ions, and the difference in charge / discharge capacity between the determination time and the initial value in the region where the voltage during charge / discharge holds the electrode potential corresponding to the second active material. By calculating the amount of decrease in lithium ions, an appropriate amount of lithium ions with suppressed formation of lithium dendrite can be calculated. Here, charging / discharging means charging or discharging, and expansion / contraction means expansion or contraction. Furthermore, the initial state means a state before use or a time immediately after the start of use.
A lithium ion replenishing electrode that releases lithium ions; and when the cause of deterioration is determined to be a decrease in lithium ions, the lithium ion replenishing electrode and the positive electrode or the negative electrode are connected, It is preferable that lithium ions corresponding to the decrease amount be released from the replenishment electrode to replenish the lithium ion battery with lithium ions to recover the battery capacity. By comprising in this way, it is possible to replenish a lithium ion battery with the appropriate amount of lithium ions which suppressed the formation of thium dendrite.

  As a preferred embodiment of the present invention, the first active material is a spinel type lithium-containing metal oxide, the second active material is a ternary lithium-containing metal oxide, and the negative electrode active material is It is mentioned that it is a carbon type active material. By using these, it is possible to easily determine the cause of the decrease in lithium ions and replenish the reduced lithium ion amount.

As a preferred embodiment of the present invention, whether from the start of expansion / contraction of the first active material to the end of expansion / contraction, or from the start of expansion / contraction of the second active material to the end of expansion / contraction, the positive electrode and the Judging by the amount of expansion / contraction of the negative electrode, the expansion / contraction amount is estimated from the internal pressure of the lithium ion battery, or the expansion / contraction amount is estimated from the deformation amount of the battery case of the lithium ion battery. Can be mentioned. By these, it is possible to easily estimate the amount of expansion and contraction.

Further, the charge / discharge capacity at the initial stage, which is the charge / discharge capacity changed from the start of expansion / contraction of the first active material to the end of expansion / contraction at the time of charge / discharge of the lithium ion battery , is the charge / discharge capacity at the time of determination. If the discharge capacity is larger than the discharge capacity, it is preferable not to calculate the amount of decrease of the lithium ions and to connect the lithium ion supplementing electrode and the positive electrode or the negative electrode. In this case, since the battery is deteriorated due to a cause other than the decrease of lithium ions due to the deposition of lithium ions, replenishment of lithium ions up to such a case will accelerate the deterioration of the battery.

  As a preferred embodiment of the present invention, an amount of electrons for releasing lithium ions corresponding to the amount of decrease is calculated, and a current corresponding to the amount of electrons flows from the positive electrode or the negative electrode into the lithium ion replenishment electrode. If the current corresponding to the amount of electrons flows, the connection between the lithium ion replenishment electrode and the positive electrode or the negative electrode may be released.

  According to the state management method of the lithium ion battery of the present invention, it is possible to calculate an appropriate addition amount of lithium ions capable of suppressing the formation of lithium dendrite, and to restore the capacity by supplementing this addition amount. It is possible to achieve an excellent effect of being able to.

The schematic diagram which shows the structure of the lithium ion battery of this invention. The graph which shows the relationship between the discharge capacity at the time of discharge of a lithium ion battery, and a voltage. The figure which shows the electrode potential with respect to the negative electrode material of the positive electrode material of the lithium ion battery of this embodiment. The graph which shows the relationship between the discharge capacity at the time of discharge of a lithium ion battery at the time of partial peeling of an electrode, and a voltage. The schematic diagram of the vehicle carrying the lithium ion battery of this invention.

The lithium ion battery of the present invention will be described with reference to FIG.
The lithium ion battery 1 includes a battery case 2. The battery case 2 is filled with the electrolyte solution 3. A power generation element 4 is accommodated in the battery case 2. The power generation element 4 is formed by laminating a positive electrode plate and a negative electrode plate via a separator. In the present invention, this positive electrode plate is called a positive electrode, and the negative electrode plate is called a negative electrode. Moreover, these positive electrodes and negative electrodes are collectively referred to as electrodes.

  In the power generation element 4, the positive electrode terminal 5 is connected to the positive electrode plate of the power generation element 4, and the negative electrode terminal 6 is connected to the negative electrode plate of the power generation element 4. The positive electrode and the negative electrode are respectively held in a state in which the positive electrode and the negative electrode are sealed by a seal member or the like on a case lid 7 provided on the upper part of the battery case 2.

  The positive electrode and the negative electrode are configured by, for example, applying a positive electrode material and an negative electrode material containing an active material described below to a current collector made of aluminum on both surfaces.

  In the present embodiment, the positive electrode contains two or more active materials, and each active material may have different electrode potentials with respect to the electrolytic solution. Examples of the active material include metal oxides capable of inserting and extracting lithium, for example, layered structure type metal oxides, spinel type metal oxides and metal compounds, and oxide type metal oxides. Examples of the layered structure type metal oxide include lithium nickel composite oxide and lithium cobalt composite oxide. The lithium nickel-based composite oxide is an oxide having lithium (Li) and nickel (Ni) as constituent metal elements, and at least one other metal element in addition to lithium and nickel (that is, other than Li and Ni) Transition metal elements or typical metal elements, or transition metal elements and typical metal elements) are typically less than nickel (according to the number of atoms). If two or more metal elements other than Li and Ni are included, their It also includes oxides contained as constituent metal elements in a total amount less than Ni). Examples of the metal element other than Li and Ni include, for example, cobalt (Co), aluminum (Al), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), and titanium (Ti ), Zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La) And one or more metal elements selected from the group consisting of cerium (Ce). The same applies to the following lithium cobalt complex oxide and lithium manganese complex oxide described later.

  As such a lithium nickel composite oxide, lithium nickelate is preferably used. Moreover, as a lithium cobalt type complex oxide, Preferably lithium cobaltate is mentioned.

  Examples of the spinel metal oxide include lithium manganese complex oxides such as lithium manganate. Examples of the oxide metal oxide include lithium iron phosphate, lithium manganese phosphate, and lithium lithium phosphate.

  In the present embodiment, lithium cobaltate (second active material) and lithium manganate (first active material) are used as the active material of the positive electrode terminal 5.

  Examples of the active material for the negative electrode include metal materials such as lithium metal, lithium alloy, metal oxide, metal sulfide, metal nitride, and graphite. Examples of the metal oxide include those having irreversible capacity such as tin oxide and silicon oxide. The graphite as the carbon-based material may be artificial graphite or natural graphite. In this embodiment, graphite is used as the active material of the negative electrode terminal 6.

  In addition, the positive electrode material and the negative electrode material may contain other substances. For example, a binder such as polyvinylidene fluoride, a conductivity improver such as acetylene black, and an electrolyte (for example, a lithium salt (supporting electrolyte), an ion conductive polymer, etc.) may be included. When an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

  The electrolyte solution 3 includes a polar solvent. Examples of such polar solvents include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1 , 2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, methyl acetate and the like, or a mixture thereof may be used.

The polar solvent may be contained metal salts, _{e.g., LiPF 6, LiPF 3 (C} 2 F 5) 3, LiBF 4, LiAsF 6, LiClO 4, LiSCN, LiI, LiCF 3 SO 3, LiCl, LiBr , Lithium salts such as LiCF ₃ CO ₂ , or a mixture thereof.

In this embodiment, ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were used as the electrolyte solution 3, and LiPF ₆ was contained as a metal salt.

  A third electrode 11 is held on the case lid 7 of the battery case 2. The third electrode 11 is in contact with the electrolyte solution 3. Examples of the active material of the third electrode 11 include materials capable of releasing lithium ions, such as metal lithium, lithium titanate, and lithium siliconide. In the present embodiment, metallic lithium is used as the active material of the third electrode 11. The third electrode 11 may also include the above-described binder. The content in the case of containing this binder is 5% or less, preferably 1% or less, based on the weight of the entire third electrode 11, as long as the third electrode 11 can release lithium ions when the battery deteriorates. It is preferable. Further, since the third electrode 11 only needs to be able to release lithium ions when the battery deteriorates, the entire third electrode 11 of the conductive material (conductive material contained in the current collector and active material) contained in the third electrode 11 is used. It is preferable that it is 5% or less on the basis of the weight.

  The third electrode 11 and the positive electrode, that is, the positive electrode terminal 5 are connected via a switch element 12 installed outside the battery case 2. The controller 13 controls the opening / closing operation of the switch element 12 based on an expansion / contraction amount curve (details will be described later) of the electrode of the lithium ion battery 1 as described below. Since the active material of each electrode repeatedly expands and contracts as lithium ions are released and occluded, the electrode itself expands and contracts. In the present embodiment, the control unit 13 controls the opening / closing operation of the switch element 12 by determining the cause of deterioration from the amount of expansion / contraction of the electrode and estimating the amount of lithium ions insufficient due to deposition.

  As will be described in detail later, the control unit 13 determines the cause of deterioration of the lithium ion battery 1 based on the expansion / contraction amount curve of the electrode of the lithium ion battery 1, and the cause of the deterioration is that lithium ions are deposited. When it is determined that the lithium ions are insufficient in the battery, the amount of lithium ions lost due to deposition in the lithium ion battery 1 is obtained. And the control part 13 is controlled to make the switch element 12 into a closed state, in order to supplement lithium ion. As a result, the positive electrode and the third electrode 11 are connected, and lithium ions are supplied from the third electrode 11 to the positive electrode and occluded by the electrode potential difference between the positive electrode and the third electrode 11. As a result, the lithium ion battery 1 can be replenished with insufficient lithium ions, and the capacity of the lithium ion battery can be recovered.

  This will be specifically described. First, when a signal indicating control start is input from a battery control unit or the like that performs integrated control of a lithium ion battery (battery) (not shown), the control unit 13 starts control. When the control is started, the control unit 13 first determines the cause of deterioration from a curve (hereinafter referred to as an expansion / contraction curve) indicating the amount of expansion / contraction of the electrode with respect to the discharge capacity when the lithium ion battery 1 is discharged.

  Here, the expansion / contraction amount curve is a graph showing the internal pressure (internal pressure) with respect to the discharge capacity shown in FIG. 2 in this embodiment. Here, since the amount of expansion / contraction of the electrode cannot be directly measured, in this embodiment, the internal pressure in the battery case 2 that changes corresponding to the amount of expansion / contraction of the electrode is measured. That is, in the present embodiment, the internal pressure is detected from the internal pressure detection unit 15 that is a pressure gauge provided in the battery case 2, and the detection result is input to the control unit 13. As the amount of expansion / contraction of the electrode, if the battery case 2 can be deformed, a change in the size of the outer shape of the battery case 2 accompanying the amount of expansion / contraction of the electrode may be detected by, for example, a displacement meter. In the present embodiment, since the battery case 2 is formed so as to be difficult to be deformed by, for example, a vise, the internal pressure inside the battery case 2 is detected, and control is performed based on the detection result.

  FIG. 2 shows the expansion / contraction amount curve A of the current lithium ion battery 1 and the expansion / contraction amount curve B of the lithium ion battery 1 in the initial state. In FIG. 2, zero discharge means a substantially fully charged state. The expansion / contraction amount curve B is recorded in advance in a recording unit provided in the control unit 13. Both the expansion / contraction amount curve A and the expansion / contraction amount curve B in the initial state are substantially constant internal pressures with respect to the discharge capacity, but when the discharge capacity increases thereafter, the internal pressure is It goes down sharply.

  Such an expansion / contraction curve will be described with reference to FIG. FIG. 3 shows the state of the electrode potential of each electrode material in this embodiment.

  As shown in FIG. 3 (a), graphite used as the negative electrode active material is more base than lithium cobaltate and lithium manganate used as the positive electrode active material, so that lithium ions are easily released from the graphite. . The released lithium ions are initially stored in lithium manganate, which is nobler than lithium cobaltate. Thereafter, when lithium ions are occluded in the entire capacity of lithium manganate and no more lithium ions are occluded in lithium manganate, they are occluded in lithium cobaltate.

  In such a lithium ion battery, the amount of expansion / contraction of each active material is as shown in FIG. FIG. 3B schematically shows the volume of each active material with respect to the charge / discharge capacity, with the left end in the figure indicating a fully discharged state and the right end indicating a fully charged state. It is considered that the volume of graphite expands by about 10% during charging, the volume of lithium cobaltate expands by about 2.6% during charging, and the volume of lithium manganate contracts by about 6.4% during charging. When discharge is started (T0 in the figure), lithium ions are released from the graphite, so that the graphite contracts as the discharge amount increases. On the other hand, lithium ions are initially occluded in lithium manganate (LMO) as described above. In this case, lithium manganate expands when lithium ions are occluded. Although this expansion amount is smaller than that of graphite, the volume of the positive electrode is larger than the volume of the negative electrode, so that the contraction amount of graphite is negated. In addition, lithium cobaltate (LCO) does not swell because lithium ions are not occluded until occlusion with lithium manganate is completed.

  Then, until the occlusion of lithium ions into lithium manganate is completed (until T1 in the figure), the entire active material of the electrode is slightly contracted, and a large contraction amount change is not observed.

  When the discharge amount increases, the lithium ions are released from the graphite until the complete discharge state is reached (T2 in the figure), so that the graphite contracts. On the other hand, lithium ions are occluded by lithium cobaltate, but lithium cobaltate contracts even if lithium ions are occluded.

  Therefore, after the occlusion of lithium ions into lithium manganate is completed and until a complete discharge state is reached (between T1 and T2), occlusion of lithium ions into lithium manganate is completed for the entire electrode. It shrinks greatly compared to before.

  Since the volume of each active material changes in this way, the volume of the entire electrode, that is, the internal pressure of the lithium ion battery is as shown in FIG. In both of the expansion / contraction amount curves A and B, until the occlusion of lithium ions into the lithium manganate is completed, the amount of contraction of the electrode is very small as described above. It is constant. In this embodiment, the region where the internal pressure is constant is defined as a plateau portion. Thereafter, after the occlusion of lithium ions into lithium manganate is completed and the occlusion of lithium ions into lithium cobaltate is started, the internal pressure decreases with respect to the discharge capacity because the electrode contraction amount is large. A region from the start of the decrease to the end of the discharge is defined as a gradually decreasing portion.

  In this case, the expansion / contraction amount curve A stops earlier than the discharge capacity in the initial state of the expansion / contraction amount curve B, and the decrease in internal pressure stops. That is, the expansion / contraction amount curve A is shorter in the expansion / contraction amount curve B than in the expansion / contraction amount curve B. This is because lithium ions are deposited and the lithium ions in the battery are reduced, so that no lithium ions move between the electrodes and the occlusion / release in each active material is stopped.

  As described above, the difference between the expansion / contraction amount curve B in the initial state and the expansion / contraction amount curve A after use in FIG. 2 indicates a shortage of lithium ions due to precipitation of lithium ions. By the way, as another cause of deterioration of the lithium ion battery, partial peeling due to chipping of electrodes can be considered.

  When partial peeling due to such chipping of the electrode occurs, both the lithium manganate and the lithium cobaltate are chipped at the same time as shown in the expansion / contraction curve C shown in FIG. The expansion / contraction amount curve C is shorter in both the plateau portion and the gradually decreasing portion than the expansion / contraction amount curve B in the initial state.

  Thus, the expansion / contraction amount curves of the lithium ion battery are different depending on the cause of deterioration.

  Based on the difference in the expansion / contraction amount curve due to these causes of deterioration, the determination unit 13a of the control unit 13 shown in FIG. 2 determines the cause of deterioration. The determination unit 13a compares the expansion / contraction amount curve B and the expansion / contraction amount curve A in the initial state, and the plateau part of the expansion / contraction amount curve A is the plateau of the expansion / contraction amount curve B in the initial state. If it is shorter than the part, it is determined that the electrode is peeled off. Specifically, the control unit 13 determines an inclination of a straight line connecting the internal pressure when the discharge capacity of the expansion / contraction amount curve B in the initial state is 0 and the internal pressure when the discharge capacity is the maximum discharge capacity. When the reference slope is set, the area from the start of discharge until the slope of each discharge capacity of the expansion / contraction amount curve A becomes larger than the reference slope is defined as a plateau portion, and the discharge capacity of the plateau portion (that is, the plateau) (Discharge capacity corresponding to the part). The length of the plateau part below is also the same. If the plateau portion of the expansion / contraction amount curve A is less than 90% of the plateau portion of the expansion / contraction amount curve B in the initial state, it is determined that the electrode is peeled off.

  Further, the determination unit 13a compares the expansion / contraction amount curve A with the expansion / contraction amount curve B in the initial state, and the plateau length of the expansion / contraction amount curve A is the expansion / contraction amount in the initial state. If the discharge capacity in the gradually decreasing portion of the expansion / contraction amount curve A is substantially the same as the length of the plateau portion of the curve B and the discharge capacity in the gradually decreasing portion of the expansion / contraction amount curve B is smaller than the lithium ion It is judged that a decrease due to precipitation occurs. Specifically, the control unit 13 determines that the plateau length of the expansion / contraction amount curve A is 90% to 100% of the plateau length of the expansion / contraction amount curve B in the initial state, and the expansion / contraction amount curve A If the discharge capacity in the gradually decreasing portion of the contraction amount curve A is 0% to 90% of the discharge capacity in the gradually decreasing portion of the expansion / contraction amount curve B in the initial state, it is determined that a decrease due to lithium ion precipitation occurs. . In addition, the discharge capacity in the gradually decreasing portion refers to the discharge capacity from when the slope of each discharge capacity of the expansion / contraction amount curve A becomes larger than the reference slope until the end of discharge.

  When the control unit 13 determines that the cause of deterioration is peeling of the electrode by determining the cause of deterioration, the control unit 13 holds the switch element 12 in the open state.

  When the determination unit 13a determines that a decrease due to lithium ion precipitation occurs, a determination signal is input to the calculation unit 13b of the control unit 13, and the calculation unit 13b causes a decrease due to lithium ion precipitation. Only when it is determined, the difference in discharge capacity corresponding to the gradually decreasing portion of the expansion / contraction amount curve A and the expansion / contraction amount curve B is calculated. That is, the discharge capacity corresponding to the gradually decreasing portion of the expansion / contraction amount curve A in use is reduced from the discharge capacity corresponding to the gradually decreasing portion of the expansion / contraction amount curve B in the initial state. The calculation unit 13b calculates the amount of lithium ions that is insufficient due to precipitation from the difference in the obtained discharge capacities. The control unit obtains the amount of electrons corresponding to the insufficient amount of lithium ions based on the reduced discharge capacity with respect to the lithium ion battery in the initial state. In this way, in the present embodiment, the amount of lithium ions that is deficient can be appropriately calculated based on the reduced discharge capacity with respect to the lithium ion battery in the initial state, and the formation of lithium dendride can be suppressed. it can.

  When the calculation unit 13b calculates the amount of electrons corresponding to the insufficient amount of lithium ions in this way, the element control unit 13c of the control unit 13 inputs a signal for holding the switch element 12 in the closed state to the switch element 12. Then, the switch element 12 is closed, and the positive electrode terminal 5 and the third electrode are conducted to release lithium ions, thereby supplying lithium ions to the lithium ion battery 1.

  Then, the element control unit 13c conducts the current between the positive electrode terminal 5 and the third electrode 11 by causing the positive electrode terminal 5 and the third electrode 11 to conduct, and the current detection unit 14 (this embodiment). Then, it is detected by an ammeter), and it is determined from the detected current amount whether or not a desired amount of electrons has flowed. When the desired amount of electrons flows as a current, the switch element 12 is opened and the lithium ion battery 1 is opened. Control to stop the supply of lithium ions to the battery.

  The element control unit 13c holds the switch element 12 in the open state when it is determined by the determination unit 13a that the cause of deterioration is electrolyte separation or electrode separation.

  As described above, in the present embodiment, the first active material and the second active material are contained in the positive electrode, and the gradually decreasing portion of the second active material is detected, so that the shortage of lithium ions can be accurately detected. it can.

  In the present embodiment, the control unit 13 can supply an appropriate amount of lithium ions only when the lithium ion battery is deteriorated due to lack of lithium ions. Therefore, lithium ions are not supplied too much to form dendrites in the battery, and an appropriate amount of lithium can be supplied to recover the deterioration of the lithium ion battery.

  In this case, in the present embodiment, the first active material (lithium manganate in the present embodiment) and the second active material having a lower electrode potential than the first active material (lithium cobaltate in the present embodiment) The cause of deterioration as described above can be specified by forming a positive electrode by mixing a predetermined amount.

  Furthermore, when the electrode is formed only with lithium manganate, there may be a case where a desired battery potential cannot be obtained, but in this embodiment, lithium cobaltate having a higher standard electrode potential than lithium manganate is mixed. Therefore, a desired battery potential can be obtained.

  In order to obtain such an effect, the mixing ratio between the first active material and the second active material is preferably 10 to 40% of the second active material based on the weight of the positive electrode. Within this range, the cause of deterioration can be easily identified, and a desired battery potential can be obtained. If the second active material is contained in an amount of less than 10% based on the weight of the positive electrode, the gradually decreasing portion becomes too short, and it is difficult to specify the cause of deterioration, and the required amount of lithium ions cannot be calculated. Conceivable. On the other hand, if the second active material is contained in an amount of more than 40% based on the weight of the positive electrode, a desired battery potential cannot be obtained.

  In particular, when the electrode is formed only with lithium cobaltate as in the present embodiment, the cost becomes high, but the production cost of the electrode can be suppressed by mixing lithium manganate.

  Further, in the present embodiment, when lithium ions are released from the third electrode 11 as described above, the third electrode 11 and the positive electrode terminal 5 need only be connected, and no power is required. It is possible to replenish lithium ions by replenishing them.

  In the present embodiment, the positive electrode terminal 5 and the third electrode 11 are connected, but the present invention is not limited to this. The negative electrode terminal 6 and the third electrode 11 may be connected as long as lithium ions can be released from the third electrode. However, it is easier for lithium ions to be released when the positive electrode terminal 5 and the third electrode 11 are connected.

The above-described expansion / contraction amount curve shown in FIG. 2 is generated by a combination of the first active material, the second active material, and the active material of the negative electrode in the present embodiment. Therefore, the first active material, the second active material, Depending on the combination of the active material of the negative electrode and the negative electrode, the plateau portion and the gradually decreasing portion are not generated in the expansion / contraction amount curve. In the present embodiment, since the first active material and the active material of the negative electrode have a large expansion / contraction amount, and the second active material has a small expansion / contraction amount compared to these, the expansion / contraction amount curve as described above and It has become. Examples of such a combination of active materials having relatively large expansion / contraction amounts include a combination of a carbon-based active material (negative electrode) and lithium cobaltate (positive electrode) that both expand during charging. Examples of the combination of active materials having relatively small expansion / contraction amounts include a combination of a carbon-based active material (negative electrode) that expands during charging and lithium manganate (positive electrode) that contracts during charging. Examples of the active material that expands during charging include a carbon-based active material and a silicon alloy as the negative electrode material, and lithium cobalt oxide as the positive electrode material. Examples of the active material that contracts during charging include a ternary material (LiMO ₂ (M = 1 / 3Mn + 1 / 3Ni + 1 / 3Co)) and lithium manganate as the positive electrode material. An example of an active material that does not expand or contract even when charging and discharging is performed is lithium titanate.

  In the present embodiment, the cause of deterioration and the reduction amount of lithium ions are determined from the expansion / contraction amount curve indicating the relationship between the discharge capacity and the internal pressure during discharge, but the present invention is not limited to this. The cause of deterioration and the reduction amount of lithium ions may be determined from an expansion / contraction amount curve indicating the relationship between the charge amount during charging and the internal pressure. Further, the present invention is not limited to the internal pressure, and the amount of expansion / contraction of the battery case may be detected, and the cause of deterioration and the reduction amount of lithium ions may be determined based on this.

  In this embodiment, after managing the state of lithium ions, the third electrode is connected in accordance with the amount of decrease in lithium ions. However, the present invention is not limited to this. It suffices if lithium ions can be added according to the amount of decrease in lithium ions calculated by managing the state of lithium ions.

  In this embodiment, the positive electrode contains two active materials, but the present invention is not limited to this. For example, three or more active materials may be included.

  For example, as shown in FIG. 5, such a lithium ion battery can be configured as a battery pack in which a plurality of lithium ion batteries are mounted in a battery case 20 and can be mounted on a vehicle I.

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Battery case 3 Electrolyte liquid 4 Electric power generation element 5 Positive electrode terminal 6 Negative electrode terminal 7 Case cover 11 3rd electrode 12 Switch element 13 Control part

Claims (7)

A method for managing a state of a lithium ion battery comprising a first active material, a positive electrode including a second active material having a lower electrode potential than the first active material, a negative electrode, and an electrolyte solution,
In determining the cause of deterioration of the lithium ion battery by comparing the initial charge / discharge state of the lithium ion battery and the charge / discharge state at the time of determination,
The charge / discharge capacity changed from the start of expansion / contraction of the first active material to the end of expansion / contraction at the time of charge / discharge of the lithium ion battery, the initial charge / discharge capacity and the charge / discharge capacity at the time of determination Are equivalent,
The charge / discharge capacity changed from the start of expansion / contraction of the second active material to the end of expansion / contraction at the time of charge / discharge of the lithium ion battery. Is also reduced, it is determined that the cause of deterioration is a decrease in lithium ions,
A reduction amount of lithium ions is calculated from a difference between a charge / discharge capacity between a determination time in an area where an electrode potential corresponding to the second active material holds an electrode potential corresponding to the second active material and an initial charge / discharge capacity. A state management method for a lithium ion battery. It further comprises an electrode for replenishing lithium ions that releases lithium ions,
When it is determined that the cause of deterioration is a decrease in lithium ions,
Connecting the lithium ion replenishment electrode and the positive electrode or the negative electrode;
The state of the lithium ion battery according to claim 1 , wherein the lithium ion battery is replenished from the lithium ion replenishment electrode to replenish the lithium ion battery with lithium ion to restore the battery capacity. Management method. Calculate the amount of electrons for releasing lithium ions corresponding to the amount of decrease,
It is detected whether a current corresponding to the amount of electrons flows from the positive electrode or the negative electrode into the lithium ion replenishing electrode. If a current corresponding to the amount of electrons flows, the lithium ion replenishing electrode and the positive electrode or the The state management method for a lithium ion battery according to claim 2, wherein the connection with the negative electrode is released. The first active material is a spinel type lithium-containing metal oxide, the second active material is a ternary lithium-containing metal oxide,
The state management method for a lithium ion battery according to any one of claims 1 to 3, wherein the negative electrode active material is a carbon-based active material.   Whether the first active material expands or contracts from the start to the end of expansion or contraction or the second active material starts from the start of expansion or contraction to the end of expansion or contraction is determined by the amount of expansion or contraction of the positive electrode and the negative electrode. The state management method for a lithium ion battery according to claim 1, wherein the expansion / contraction amount is estimated from an internal pressure of the lithium ion battery.   Whether the first active material expands or contracts from the start to the end of expansion or contraction or the second active material starts from the expansion or contraction to the end of expansion or contraction is determined by the amount of expansion or contraction of the positive electrode and the negative electrode 5. The state management method for a lithium ion battery according to claim 1, wherein the expansion / contraction amount is estimated from a deformation amount of a battery case of the lithium ion battery. The charge / discharge capacity at the initial stage, which is the charge / discharge capacity changed from the start of expansion / contraction of the first active material to the end of expansion / contraction at the time of charge / discharge of the lithium ion battery, is determined at the time of determination. If more than capacity,
The state management of the lithium ion battery according to any one of claims 2 to 6, wherein the lithium ion replenishment electrode and the positive electrode or the negative electrode are not connected without calculating a decrease amount of the lithium ion. Method.

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