WO2022196114A1 - Secondary battery system and program - Google Patents
Secondary battery system and program Download PDFInfo
- Publication number
- WO2022196114A1 WO2022196114A1 PCT/JP2022/002717 JP2022002717W WO2022196114A1 WO 2022196114 A1 WO2022196114 A1 WO 2022196114A1 JP 2022002717 W JP2022002717 W JP 2022002717W WO 2022196114 A1 WO2022196114 A1 WO 2022196114A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- secondary battery
- battery
- negative electrode
- charging
- discharging
- Prior art date
Links
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- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a secondary battery system and program.
- An object of the present invention is to provide a method for recovering the performance of a deteriorated lithium-ion battery and a power supply system provided with means for recovering the battery performance.
- a battery in which a step of increasing the potential of a negative electrode of a deteriorated lithium-ion battery to a level higher than that of a positive electrode and then lowering the potential of the negative electrode to a level lower than that of the positive electrode is performed for at least one cycle.
- a power supply system comprising means for increasing the potential of the negative electrode of a lithium-ion battery above the potential of the positive electrode and then lowering the potential of the negative electrode below the potential of the positive electrode.” ing.
- Patent Document 3 states, "[Problem] To provide a technology for controlling charging and discharging of a lithium ion secondary battery in consideration of recoverable deteriorated components.
- the controller (40) controls the charging and discharging of the lithium ion secondary battery (10), the controller performs recovery processing for recovering the capacity of the lithium ion secondary battery (10) due to overdischarge, and after performing the recovery processing, The charging and discharging of the lithium ion secondary battery is controlled according to the deterioration state specified from the capacity of the lithium ion secondary battery.”
- Non-Patent Document 1 ⁇ Analysis of the differentiated discharge curve, which divides the discharge curve of the battery cell into that of the positive electrode and the negative electrode, is useful for investigating the deterioration mechanism (The differential dischargecurveanalysisthat separatesthedischargecurveofbatterycellsintothoseofthepositiveandnegativeelectrodesisusefulforinvestigatingdeteriorationmechanisms.)...”.
- the descriptions of these documents are incorporated as part of the present specification.
- JP 2012-169094 A Japanese Patent Application Laid-Open No. 2014-187002 JP 2011-159545 A
- the secondary battery system of the present invention provides a secondary battery having one or more battery cells that are lithium ion battery cells, and charging or discharging the secondary battery.
- a charge/discharge processing unit that performs charging processing for the secondary battery or discharging processing from the secondary battery based on control parameters that define control conditions for the current or voltage at the time, and for the secondary battery, the a capacity recovery processing unit that performs capacity recovery processing including processing for maintaining the terminal voltage of the battery cell at 2.0 V or less; and a parameter update unit that updates the control parameter according to the status of the capacity recovery processing. It is characterized by
- the life of the secondary battery can be extended.
- FIG. 1 is a diagram conceptually showing an example of a cross section of a battery cell
- FIG. FIG. 2 is a side view of the storage element shown in FIG. 1
- 1 is a block diagram of a secondary battery system according to an embodiment
- FIG. FIG. 4 is a schematic diagram of a presumed mechanism regarding capacity recovery by overdischarge treatment. 4 is a flow chart of a control program executed by a control unit; It is an example of a charge/discharge curve of a battery cell.
- FIG. 7 is a diagram showing the rate of change in the charge/discharge curve of FIG. 6;
- Lithium ion batteries are one type of non-aqueous electrolyte secondary batteries, and because of their high energy density, they are also used as batteries for mobile devices and, in recent years, as batteries for electric vehicles. However, it is known that the lithium ion battery deteriorates with use and the battery capacity decreases.
- Lithium ion batteries generally use a lithium metal oxide as a positive electrode active material and a carbon material such as graphite as a negative electrode active material.
- a positive electrode and a negative electrode of a lithium ion battery are formed by adding a binder (binder), a conductive agent, etc. to minute active material particles to form a slurry (mixture), and then applying the slurry (mixture) to a metal foil.
- lithium ions are taken into the film component (SEI; Solid Electrolyte Interphase) formed at the interface between the negative electrode and the electrolyte, resulting in loss of mobility.
- SEI Solid Electrolyte Interphase
- the lithium ions cannot be used for the battery reaction during discharging, resulting in a decrease in capacity. It is also possible that it will decrease.
- the capacity decrease due to (3) above, it is possible to recover the capacity or battery output by electrochemically oxidizing and decomposing and removing the above SEI.
- the capacity can be recovered by raising the negative electrode potential to the extent that the lithium ions taken into the non-facing surface are forcibly released during the discharge reaction, and using the released lithium ions as battery capacity again.
- Patent Document 3 does not clarify the specific revision policy.
- the measurement parameter for determining the charging/discharging operation conditions obtained in the technique applying Patent Document 3 is not the direct information about the negative electrode that deteriorates, but the deterioration rate of the entire battery. Therefore, there arises a problem that many steps are required to correct the charging/discharging operation conditions. Therefore, in the embodiments described below, a secondary battery system using a lithium ion battery that recovers the capacity by releasing the lithium ions immobilized in the negative electrode by performing overdischarge between the positive electrode and the negative electrode , the negative electrode information after recovery is detected. Then, based on the detection result, the charging/discharging operation control for suppressing further capacity deterioration is executed to extend the life of the secondary battery system.
- FIG. 1 is a diagram conceptually showing an example of a cross section of a bipolar battery cell 100 (secondary battery).
- a battery cell 100 includes a power storage element 1 , a positive electrode terminal 2 , a negative electrode terminal 3 and an exterior material 6 .
- a separator 5 is included in the storage element 1 .
- the exterior material 6 is constructed using a laminate film or a similar material.
- FIG. 2 is a side view of the storage element 1 shown in FIG.
- a plurality of positive electrodes 12 and a plurality of negative electrodes 13 are alternately stacked with separators 5 interposed therebetween.
- the storage element 1 shown in FIG. 1 corresponds to the region where the positive electrode 12 and the negative electrode 13 appear to overlap.
- the storage element 1 further contains an electrolytic solution (not shown), and the electrolytic solution impregnates micropores of the positive electrode 12, the negative electrode 13, the separator 5, and the like.
- the separator 5 for example, polypropylene can be applied.
- a microporous film made of polyolefin such as polyethylene or a non-woven fabric can be applied in addition to polypropylene.
- the positive electrode 12 includes a positive electrode collector foil 122 and a positive electrode mixture layer 121 applied thereto.
- the negative electrode 13 includes a negative electrode collector foil 132 and a negative electrode mixture layer 131 applied thereto.
- the positive electrode current collector foil 122 and the negative electrode current collector foil 132 are suitable metal current collector foils.
- the positive electrode mixture layer 121 and the negative electrode mixture layer 131 are mixtures of suitable electrode active materials, conductive agents, binders, and the like.
- Metal tabs serving as terminals are connected to the positive current collector foil 122 and the negative current collector foil 132, respectively. These tabs become the positive terminal 2 and the negative terminal 3 shown in FIG. In FIG.
- the exterior material 6 is sealed with the positive electrode terminal 2 and the negative electrode terminal 3 exposed to the outside of the exterior material 6 .
- the battery cell 100 can be connected to the outside through the positive terminal 2 and the negative terminal 3 .
- the potentials of the positive electrode 12 and the negative electrode 13 are hereinafter referred to as a positive electrode potential Ep and a negative electrode potential En.
- Ep-En The difference between the two, ie, "Ep-En" is the voltage between the positive terminal 2 and the negative terminal 3, and is called the battery voltage Epn.
- the battery cell 100 of the lithium ion battery of the present embodiment is not limited to materials, shapes, manufacturing methods, and the like. , any material, shape, manufacturing method, etc. can be applied.
- the positive current collector foil 122 (see FIG. 2) is made of an aluminum foil with a thickness of 10 to 100 ⁇ m, a perforated aluminum foil with a thickness of 10 to 100 ⁇ m and a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like. can be applied. In addition to aluminum, stainless steel, titanium, and the like can also be used for the material of the positive electrode current collector foil 122 .
- the positive electrode mixture layer 121 preferably contains a reactive species therein.
- the reactive species in lithium ion batteries is lithium ions.
- the electrode active material contains a lithium-containing compound capable of reversibly intercalating and deintercalating lithium ions.
- Examples of the electrode active material of the positive electrode 12 include lithium cobaltate, manganese-substituted lithium cobaltate, lithium manganate, lithium nickelate, lithium transition metal phosphate such as olivine-type lithium iron phosphate, or Li w Ni x . Co y Mn z O 2 (here, w, x, y, and z are 0 or positive values). Further, as the electrode active material of the positive electrode 12, the materials described above may be contained singly or in combination of two or more.
- the negative electrode current collector foil 132 As the negative electrode current collector foil 132, a copper foil with a thickness of 10 to 100 ⁇ m, a perforated copper foil with a thickness of 10 to 100 ⁇ m and a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like can be applied. Further, as the material of the negative electrode current collector foil 132, other than copper, stainless steel, titanium, or the like can be applied.
- the electrode active material in the negative electrode 13 contains a material capable of reversibly intercalating and deintercalating lithium ions.
- Examples of the type of electrode active material for the negative electrode 13 include natural graphite, a composite carbonaceous material obtained by forming a film on natural graphite by a dry CVD method or a wet spray method, a resin material such as epoxy or phenol, or a material made from petroleum or coal. Artificial graphite produced by firing the obtained pitch-based material as a raw material, silicon (Si), graphite mixed with silicon, non-graphitizable carbon material, lithium titanate, and Li 4 Ti 5 O 12 . Further, as the negative electrode active material of the negative electrode 13, the materials described above may be contained singly or in combination of two or more.
- the electrolyte is, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl Aprotic organic solvents such as propyl carbonate (MPC) and ethyl propyl carbonate (EPC) can be applied.
- ethylene carbonate EC
- propylene carbonate PC
- butylene carbonate BC
- EMC ethyl methyl carbonate
- EMC diethyl carbonate
- methyl Aprotic organic solvents such as propyl carbonate (MPC) and ethyl propyl carbonate (EPC)
- lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium iodide, lithium chloride, lithium bromide, LiB[OCOCF 3 ] is added to the solvent of the mixed organic compound of two
- LiB[ OCOCF2CF3 ] 4 LiPF4 ( CF3 ) 2 , LiN ( SO2CF3 ) 2 , LiN( SO2CF2CF3 ) 2 and other lithium salt - dissolved electrolytes.
- an electrolytic solution in which two or more kinds of mixed lithium salts described above are dissolved can be used.
- the constituent solvents of the aforementioned electrolytic solution are generally highly volatile, and the volatilization temperature of the electrolytic solution is often less than 25°C. Additionally, in one of the preferred embodiments, a lithium ion conductive liquid with an elevated volatilization temperature may be used.
- ionic liquids and solvated ionic liquids can be mentioned. Ionic liquids contain cations and anions. Ionic liquids are classified into imidazolium-based, ammonium-based, pyrrolidinium-based, piperidinium-based, pyridinium-based, morpholinium-based, phosphonium-based, sulfonium-based, and the like, depending on the cation species. Examples of cations constituting imidazolium-based ionic liquids include alkylimidazolium cations such as 1-etyl-3-methylimidazolium and 1-butyl-3-methylimidazolium (BMI).
- Examples of cations that make up ammonium-based ionic liquids include N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium (DEME) and tetraamylammonium, as well as N,N,N-trimethyl-N There are alkylammonium cations such as -propylammonium.
- Examples of cations constituting pyrrolidinium-based ionic liquids include alkylpyrrolidinium cations such as N-methyl-N-propylpyrrolidinium (Py13) and 1-butyl-1-methylpyrrolidinium.
- Examples of cations constituting piperidinium-based ionic liquids include alkylpiperidinium cations such as N-methyl-N-propylpiperidinium (PP13) and 1-butyl-1-methylpiperidinium.
- Examples of cations constituting pyridinium-based ionic liquids include alkylpyridinium cations such as 1-butylpyridinium and 1-butyl-4-methylpyridinium.
- Examples of cations constituting morpholinium-based ionic liquids include alkylmorpholinium such as 4-ethyl-4-methylmorpholinium.
- Examples of cations constituting phosphonium-based ionic liquids include alkylphosphonium cations such as tetrabutylphosphonium and tributylmethylphosphonium.
- Examples of cations constituting sulfonium-based ionic liquids include alkylsulfonium cations such as trimethylsulfonium and tributhylsulfonium.
- Examples of anions paired with these cations include bis (trifluoromethanesulfonyl) imide (TFSI), bis (fluorosulfonyl) imide, tetrafluoroborate (BF4), hexafluorophosphate (PF6), bis (pentafluoroethanesulfonyl) imide (BETI), trifluoromethanesulfonate (triflate). , acetate, dimethyl phosphate, dicyanamide, trifluoro (trifluoromethyl) borate, etc. These ionic liquids may be used singly or in combination.
- the ionic liquid may contain an electrolyte salt.
- the electrolyte salt one that can be uniformly dispersed in the solvent can be used.
- a lithium salt containing lithium as a cation and the above anion can be used.
- LiFSI lithium bis(fluorosulfonyl)imide
- LiTFSI lithium bis(trifluoromethanesulfonyl)imide
- LiBETI lithium bis(pentafluoroethanesulfonyl)imide
- the ether solvent constitutes the solvated electrolyte salt and the solvated ionic liquid.
- Known glyme (a general term for symmetrical glycol diethers represented by R-O(CH2CH2O)n-R' (R, R' are saturated hydrocarbons and n is an integer)) that exhibits similar properties to ionic liquids as an ether solvent. available.
- tetraglyme tetraethylene glycol dimethyl ether, G4
- triglyme triethylene glycol dimethyl ether, G3
- pentaglyme pentaglyme
- pentaglyme pentaglyme
- pentaglyme pentaglyme
- crown ethers (generic term for macrocyclic ethers represented by (-CH2-CH2-O)n (n is an integer)) can be used as ether-based solvents.
- 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6 and the like can be preferably used, but are not limited thereto.
- These ether solvents may be used singly or in combination.
- Tetraglyme and triglyme are preferably used because they can form a complex structure with the solvated electrolyte salt. In the present embodiment, tetraglyme is preferred because it has a coordination structure with excellent reduction stability with respect to lithium ions.
- Lithium salts such as LiFSI, LiTFSI, and LiBETI can be used as solvated electrolyte salts, but are not limited to these.
- Ether-based solvents and mixtures of solvated electrolyte salts may be used singly or in combination as semi-solid electrolyte solvents.
- the reduction potential of the semi-solid electrolyte solvent is desirably lower than the reduction potential of the negative electrode active material by 0.5 V or more, preferably 0.2 V or more.
- the weight ratio of the main solvent in the semi-solid electrolyte is not particularly limited, but from the viewpoint of battery stability and high-speed charging and discharging, the weight ratio of the main solvent in the total solvent in the semi-solid electrolyte is 30% to 70%. In particular, it is desirable to be 40% to 60%, more preferably 45% to 55%.
- a low-viscosity organic solvent lowers the viscosity of the semi-solid electrolyte solvent and improves the ionic conductivity. Since the internal resistance of a semi-solid electrolyte solution containing a semi-solid electrolyte solvent is high, the internal resistance of the semi-solid electrolyte solution can be lowered by adding a low-viscosity organic solvent to increase the ionic conductivity of the semi-solid electrolyte solvent. .
- the low-viscosity organic solvent is desirably a solvent having a viscosity lower than 140 Pa ⁇ s at 25° C. of a mixture of, for example, an ether solvent and a solvated electrolyte salt.
- Low-viscosity organic solvents include propylene carbonate (PC), trimethyl phosphate (TMP), gamma-butyl lactone (GBL), ethylene carbonate (EC), triethyl phosphate (TEP), tris(2,2,2- trifluoroethyl) (TFP), dimethyl methylphosphonate (DMMP), and the like. These low-viscosity organic solvents may be used singly or in combination. The electrolyte salt may be dissolved in a low-viscosity organic solvent.
- the reason why propylene carbonate is preferable is that the viscosity of the lithium glyme complex salt is lowered to increase the ionic conductivity, and the lithium glyme complex structure, which has excellent reduction stability, is not disturbed, so that the internal resistance of the battery is lowered and the A high-capacity battery can be produced.
- sulfolane and/or its derivatives can be used as solvents for forming solvated ionic liquids.
- solvated ionic liquid containing sulfolane and/or a derivative thereof When a solvated ionic liquid containing sulfolane and/or a derivative thereof is used, sulfolane and/or a derivative thereof and lithium ions take a unique coordination structure, so that the transport rate of lithium ions in the semi-solid electrolyte layer is increased. Become. Therefore, unlike the solvated ionic liquid having an ether solvent and an electrolyte salt, in which the input/output characteristics of the secondary battery deteriorate as the viscosity increases, the solvated ionic liquid can be used even if the viscosity of the solvated ionic liquid is increased. It is possible to suppress deterioration in input/output characteristics of the secondary battery.
- sulfolane derivatives include those in which hydrogen atoms bonded to carbon atoms constituting the sulfolane ring are substituted with fluorine atoms, alkyl groups, or the like. As a specific example, it can be used by appropriately selecting from a group of materials such as fluorosulfolane, difluorosulfolane, and methylsulfolane.
- an electrolytic solution in which two or more of the above mixed lithium salts are dissolved can be used.
- FIG. 3 is a block diagram of a secondary battery system 500 according to a preferred embodiment.
- a secondary battery system 500 includes a battery pack 510 and a current control device 550 .
- the battery pack 510 includes a battery cell module 512 (secondary battery) and a battery heating section 514 .
- the battery cell module 512 may be a single battery cell 100 (see FIG. 1), or multiple battery cells 100 connected in series and/or in parallel.
- the term "secondary battery” is a concept that includes lithium-ion battery cells, battery modules, and battery packs.
- Battery heating unit 514 heats battery cell module 512 based on a command from current control device 550 . However, the battery heating unit 514 is not essential and may be omitted.
- the battery pack 510 has a positive terminal 502 and a negative terminal 503 . If the battery cell module 512 comprises only one battery cell 100, the positive terminal 502 and the negative terminal 503 correspond to the positive terminal 2 and the negative terminal 3 of the battery cell 100 (see FIG. 1), respectively. On the other hand, when a plurality of battery cells 100 are connected in series in the battery cell module 512, the positive terminal 502 corresponds to the positive terminal 2 of the battery cell 100 with the highest voltage, and the negative terminal 503 has the lowest voltage. It corresponds to the negative electrode terminal 3 of the battery cell 100 . In FIG. 3, positive terminal 502 and negative terminal 503 of battery pack 510 are each connected to current controller 550 . Note that the power source 554 is mainly for charging, and the resistor 553 is for discharging.
- the current control device 550 includes an ammeter 551, a voltmeter 552, a resistor 553, a power supply 554, switches 560, 562, 564, and a controller 570 (computer). Current control device 550 also serves as a measuring instrument for grasping the state of battery pack 510 .
- the ammeter 551 measures the current flowing through the positive terminal 502 and the negative terminal 503 of the battery pack 510 and outputs the result to the control section 570 .
- the voltmeter 552 measures the voltage Ev between the positive electrode and the negative electrode and outputs the result to the control section 570 .
- Control unit 570 switches and controls switches 560 , 562 and 564 based on information from ammeter 551 and voltmeter 552 . As a result, control unit 570 sets positive terminal 502 and negative terminal 503 of battery pack 510 to an open state, a state in which resistor 553 is connected, or a state in which power source 554 is connected.
- the control unit 570 includes general computer hardware such as a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). Programs, various data, etc. are stored. In FIG. 3, the inside of the control unit 570 shows functions realized by control programs and the like as blocks.
- CPU Central Processing Unit
- RAM Random Access Memory
- ROM Read Only Memory
- control unit 570 includes a charge/discharge processing unit 572 (charge/discharge processing means), a capacity recovery processing unit 574 (capacity recovery processing means), and a parameter update unit 580 (parameter update means).
- Parameter updater 580 also includes a charge/discharge curve acquirer 582 , a correlation acquirer 584 , a discharge amount acquirer 586 , and a parameter determiner 588 .
- the charging/discharging processing unit 572 performs charging/discharging operation of the battery pack 510 according to normal applications based on predetermined control parameters. For example, if the battery pack 510 is used for driving the vehicle, the charging/discharging processing unit 572 performs charging/discharging operation for driving the vehicle.
- the control parameters described above include the "discharge stop voltage". When the voltage Ev becomes equal to or lower than the discharge stop voltage while the battery pack 510 is being discharged, the charge/discharge processing unit 572 stops the discharge of the battery pack 510 .
- the discharge stop voltage is a voltage at which the terminal voltage per battery cell 100 becomes 2.5 V or less, for example.
- the capacity recovery processing unit 574 executes capacity recovery processing.
- the capacity recovery process includes a process of connecting the power supply 554 or the resistor 553 between the positive electrode terminal 502 and the negative electrode terminal 503 to bring the battery pack 510 into an over-discharged state.
- "Overdischarge state” means that the voltage Ev is made less than the discharge stop voltage.
- the capacity recovery process includes a process of maintaining the terminal voltage per battery cell 100 at 2.0 V or less.
- the parameter update unit 580 After the capacity recovery processing of the battery pack 510, the parameter update unit 580 non-destructively analyzes the battery performance, and based on the negative electrode performance data etc. obtained at that time, Determine and update control parameters.
- Charge-discharge curve acquisition unit 582 acquires the charge-discharge curve of battery pack 510 in order to determine control parameters.
- the charge/discharge curve is a charge curve or a discharge curve.
- the correlation acquisition unit 584 acquires the correlation between the discharge amount (or charging rate) of the battery pack 510 and the negative electrode potential En (see FIG. 1) based on this charge/discharge curve.
- the lithium ion battery has a region where the negative electrode potential En becomes flat with respect to changes in the discharge amount Q (see FIG. 6). These are called flat portions PT1 (first flat portion) and PT2 (second flat portion). call.
- the discharge amount acquisition unit 586 acquires the discharge amount Q or the charge rate range corresponding to the flat portions PT1 and PT2.
- the parameter determination unit 588 charges and discharges the battery pack 510 within the above-described range of the flat portion PT1 or more, that is, the charging rate range where the negative electrode potential En is equal to or greater than En1.
- Determine and update the control parameters as follows.
- the parameter updating unit 580 acquires the charge/discharge curve and analyzes its shape as a non-destructive analysis method for battery performance. Henceforth, this analysis method may be called "charge-discharge curve analysis.”
- FIG. 4 is a schematic diagram of a presumed mechanism regarding capacity recovery by overdischarge treatment.
- state STA is a state in which capacity recovery processing is being performed on the battery cell 100 whose capacity has decreased
- state STB is a state after the capacity recovery processing is completed.
- a portion of the negative electrode 13 of the battery cell 100 that faces the positive electrode 12 is called a facing portion 13A, and the other portion is called a non-facing portion 13B.
- charging and discharging proceeds as the transfer of lithium ions 22 between the positive electrode 12 and the facing portion 13A of the negative electrode 13 progresses.
- the lithium ions 22 are taken into the non-facing portion 13B that does not face the positive electrode in the charging/discharging process, they become metal lithium 24 (hatched in the figure) that does not contribute to the charging/discharging, which is a factor in the decrease in capacity. becomes.
- the discharge reaction in the facing portion 13A proceeds, and the lithium ions 22 are released from the facing portion 13A.
- Metal lithium 24 is also released as lithium ions 22 from the non-facing portion 13B.
- the DC power supply 30 is connected to the battery cell 100 in the direction opposite to the state STA.
- the negative electrode potential En drops, the lithium ions 22 are taken into the non-facing portion 13B again, and there is concern that the capacity of the battery cell 100 may drop.
- State STB is a state in which the negative electrode potential En is kept high to some extent after the end of the capacity recovery process.
- the negative electrode potential En increases, a potential difference occurs inside the negative electrode 13, and the potential of the opposing portion 13A becomes slightly higher than the potential of the non-facing portion 13B.
- the electrons 26 move from the metallic lithium 24 adsorbed to the non-opposed portion 13B to the opposed portion 13A.
- the metallic lithium 24 becomes the lithium ion 22 and leaves the non-facing portion 13B, thereby contributing to charging and discharging again.
- FIG. 6 is an example of a charge/discharge curve of the battery cell 100.
- FIG. FIG. 6 shows an example of a lithium ion battery using LiwNixCoyMnzO2 (where w , x , y , and z are 0 or positive values) for the positive electrode 12 and graphite for the negative electrode.
- the vertical axis on the left side of FIG. 6 is the potential or voltage (V)
- the vertical axis on the right side is the potential with respect to the lithium electrode
- the horizontal axis is the discharge amount Q (Ah).
- the lithium electrode reference is a potential based on the standard electrode potential of lithium
- the standard electrode potential of lithium is the standard electrode potential in the chemical reaction represented by “Li + + e ⁇ ⁇ Li”.
- a large number of small circles (unsigned) along the curve of the battery voltage Epn in FIG. 6 are the measured values of the battery voltage Epn, and the curve of the battery voltage Epn is the interpolation result of the measured values.
- the charging/discharging curve may be formed by any method, but for example, there is a method of discharging from a fully charged state to a fully discharged state or charging from a fully discharged state to a fully charged state with a minute and constant current. Alternatively, the cycle of discharging at a constant current for a certain period of time and then resting for a certain period of time is repeated from a fully charged state to a fully discharged state, or the cycle of charging at a constant current for a certain period of time and then resting for a certain period of time is repeated from a fully discharged state to a fully charged state.
- the positive electrode potential Ep is normally set sufficiently higher than the negative electrode potential En.
- the battery voltage Epn is less than the lower limit voltage of 2.5 V, that is, when the battery is in an overdischarged state, the negative electrode potential En is relatively increased.
- the decomposition described above tends to proceed.
- the reaction proceeds more easily by setting ⁇ 2 ⁇ Epn ⁇ 0.1 [V].
- Epn ⁇ -2 [V] the active material structures of the positive electrode and the negative electrode are likely to be destroyed, resulting in a shorter life.
- the current control device 550 can cause the overdischarge current to flow through the battery pack 510 in pulses.
- the application time is not particularly limited, but may be 0.1 to 30 seconds. If the time is shorter than 0.1 seconds, the effect is weak, and if it is longer than 30 seconds, the positive electrode and negative electrode active material structures are likely to be destroyed, resulting in a shorter life.
- the negative electrode potential En changes stepwise as the discharge amount Q shifts from the low capacity side (the side where the discharge amount Q is large) to the high capacity side (the side where the discharge amount Q is small). do.
- a flat portion appearing when the amount of discharge Q in the drawing is near 0 to near 0.1 Ah is called PT1.
- a flat portion appearing in a region where the discharge amount Q is less than 0 is called PT2.
- FIG. 7 is a diagram showing the rate of change in the charge/discharge curve of FIG.
- the vertical axis of FIG. 7 represents the rate of change of the voltage or potential with respect to the amount Q of discharge.
- , Ep'
- , and En'
- the rate of change Epn' of the battery voltage Epn has a plurality of extreme values. These extreme values are caused by the extreme values of the change rate Ep' of the positive electrode potential Ep or the extreme values of the change rate En' of the negative electrode potential En.
- the flat portions PT1 and PT2 of the negative electrode potential En shown in FIG. 6 appear more clearly in FIG. That is, the flat portions PT1 and PT2 include a range in which the rate of change En' is "0", and a range in which the rate of change En' is greater than 0 is included between the flat portions PT1 and PT2. Note that the names of the flat portions PT1 and PT2 are given for convenience in describing the present embodiment, and the names may be different.
- the battery voltage Epn and its change rate Epn' shown in FIGS. 6 and 7 correspond to the positive electrode potential Ep, the negative electrode potential En, and the difference between these change rates Ep' and En'. Therefore, the deterioration state of the positive electrode 12 and the negative electrode 13 can be grasped by obtaining the correlation between the discharge amount Q and these values in advance and fitting the measured value to this correlation.
- the parameter updating unit 580 determines the charge/discharge conditions after the capacity recovery process, particularly by using the curve showing the relationship between the negative electrode potential En and the discharge amount Q.
- the negative electrode potential En in the flat portions PT1 and PT2 changes greatly at the boundary point (near 0Ah in FIG. 6), and the negative electrode potential En in the flat portion PT2 is considerably lower than that in the flat portion PT1. . Therefore, when charging and discharging are performed under the condition that the negative electrode potential En becomes the flat portion PT2, many lithium ions 22 are taken into the non-facing portion 13B of the negative electrode 13 (see state STA in FIG. 4), and the recovered capacity immediately decreases. Resulting in.
- the state of charge and the battery voltage Epn are managed so that the negative electrode potential En does not fall below the flat portion PT1, thereby reducing the capacity decrease after the capacity recovery.
- the boundaries between the flat portions PT1 and PT2 can be easily determined from the characteristics of the change rates Epn' and En' shown in FIG. That is, it is desirable to charge and discharge at a lower charging rate side (larger discharge amount Q side) than the discharge amount Q at which a large extreme value is obtained in the change rates Epn' and En'.
- the negative electrode potential En at the flat portion PT1 is preferably in the range of 0.1 V to 0.2 V based on the lithium electrode.
- the negative electrode potential En is lower than 0.1 V based on the lithium electrode, lithium deactivation at the negative electrode 13 proceeds.
- the negative electrode potential En is higher than 0.2 V based on the lithium electrode, a sufficient battery capacity may not be obtained.
- the parameter updating unit 580 determines the optimum battery charging/discharging conditions after the capacity recovery process by the method described above.
- FIG. 5 is a flow chart of a control program executed by the control unit 570. As shown in FIG. When the process proceeds to step S2 in FIG. 5, the charging/discharging processing unit 572 performs charging/discharging operation of the battery pack 510 according to the normal application. At that time, the charge/discharge processing unit 572 records the voltage Ev (see FIG. 3) or the battery voltage Epn (see FIG. 1) and the discharge amount Q for each predetermined sampling period.
- step S4 the charge/discharge curve acquisition unit 582 grasps the state of deterioration of the battery pack 510, that is, the state of decrease in the capacity of the battery pack 510, by the charge/discharge curve analysis described above.
- step S ⁇ b>6 capacity recovery processing unit 574 determines the capacity recovery amount of battery pack 510 according to the state of deterioration of battery pack 510 . Furthermore, in step S6, capacity recovery processing unit 574 determines an overdischarge condition for battery pack 510 based on the determined capacity recovery amount.
- the capacity recovery processing section 574 performs capacity recovery processing. That is, battery pack 510 is over-discharged based on the determined over-discharge condition. Also, the charge/discharge processing unit 572 records the voltage Ev (see FIG. 3) or the battery voltage Epn (see FIG. 1) and the discharge amount Q for each predetermined sampling period.
- parameter updating unit 580 acquires the negative electrode charge/discharge curve of battery pack 510 after overdischarge and analyzes it. More specifically, the charge/discharge curve acquisition unit 582 acquires the charge/discharge curve of the battery voltage Epn in FIG. A charge/discharge curve of the negative electrode potential En in FIG. 6 is obtained. Then, the discharged amount acquisition unit 586 acquires the discharged amount Q or the range of the charging rate corresponding to the flat portion PT1.
- the parameter determining unit 588 of the parameter updating unit 580 controls the negative electrode potential En to be within an appropriate range in the charge/discharge operation (step S2) according to the normal application.
- Update parameters Preferably, parameter updating section 580 updates the control parameters so that negative potential En does not become higher than negative potential En1 in flat portion PT1.
- step S12 ends, the process returns to step S2, and the control unit 570 performs charge/discharge operation of the battery pack 510 according to normal applications. At that time, control unit 570 charges and discharges battery pack 510 based on the updated control parameters.
- the battery heating unit 514 may temporarily heat the battery cell module 512 to increase the capacity recovery reaction speed.
- a heater such as a PT heater that converts electric energy by energization into thermal energy can be applied. More specifically, the battery temperature when not heated is set to the ambient temperature T amb (not shown), and the battery heating unit 514 is used to heat the battery to a heating temperature T R (not shown) suitable for promoting recovery processing. It is advisable to raise the temperature. Then, it is preferable to advance the recovery process by supplying a pulsed current from the current control device 550 to the battery pack 510 .
- the temperature can be lowered by forced cooling using refrigerant or air in addition to natural cooling.
- the optimum environmental temperature T amb is not particularly limited, but from the viewpoint of suppressing deterioration inside the battery, it is preferably less than 40°C, and more preferably less than 25°C.
- the environmental temperature T amb may be less than 10° C. due to the influence of the outside air temperature in which the battery is used, which may cause the output performance of the battery itself to decrease, but does not particularly affect the recovery process of the present invention.
- the optimum heating temperature T R is also not particularly limited. From the viewpoint of promoting the Li diffusibility and film decomposition reaction rate, the temperature is preferably 40° C. or higher, and is preferably 60° C. or higher because the temperature is further accelerated. If the temperature is 80° C. or higher, the reaction rate increases, but there is concern about adverse effects on the members themselves that constitute the battery.
- the electrolyte when the heat resistance of the electrolyte is low, increasing the heating temperature T R makes the electrolyte volatilize or easily decompose electrochemically. Therefore, by using an electrolyte material with high heat resistance, the effect of the secondary battery system of the present embodiment can be easily obtained. If the electrolyte volatilizes at the heating temperature T R and the battery swells, the recovery process does not proceed properly, so a high volatilization temperature of the electrolyte is desired. Specifically, it desirably exhibits a volatilization temperature higher than the heating temperature T R , and more desirably has a volatilization temperature exceeding 100°C. As a specific material, the electrolyte using the above-described ionic liquid or solvated ionic liquid can be used.
- a lithium-ion battery was experimentally produced as a battery pack 510 (see FIG. 3) with the battery cell configuration shown in FIG.
- an organic electrolyte with a carbonate solvent having a volatilization temperature of 20° C. was used.
- a solution obtained by dissolving LiPF6 at a concentration of 1M in a carbonate-based solvent was used.
- a laminate cell was fabricated using LiNi1/3Co1/3Mn1/3O2 for the positive electrode and graphite for the negative electrode.
- a positive electrode material was applied to both sides of the Al current collecting foil, and a negative electrode material was applied to both sides of the Cu current collecting foil, so that the opposing negative electrode/positive electrode capacity ratio was 1.3.
- the porous base material of polyolefin material, the positive electrode, and the negative electrode were laminated.
- the capacity of the positive electrode was designed to be about 80 mAh on one side, and the capacity of the negative electrode was designed to be about 90 mAh on one side.
- the capacity of battery pack 510 after initialization was about 280 mAh.
- the secondary battery system 500 includes a secondary battery (512) having one or more battery cells 100, and a charge or secondary battery (512) for the secondary battery (512).
- the charge/discharge processing unit 572 performs charge processing for the secondary battery (512) or discharge processing from the secondary battery (512) based on control parameters that define current or voltage control conditions when discharging from the secondary battery (512).
- a capacity recovery processing unit 574 that performs capacity recovery processing for the secondary battery (512)
- a parameter update unit 580 that updates control parameters according to the status of the capacity recovery processing. In this way, by updating the control parameters in accordance with the state of the capacity recovery process, it is possible to extend the life of the secondary battery system 500 .
- the battery cell 100 is a lithium ion battery and the capacity recovery process includes a process of maintaining the terminal voltage of the battery cell 100 at 2.0 V or less. By maintaining the terminal voltage of the battery cell 100 at 2.0 V or less in this manner, the film on the surface of the negative electrode can be decomposed, and the performance of the battery cell 100 can be recovered.
- the battery cell 100 has a first flat portion (PT1), which is a charging rate region including a range in which the negative electrode potential En is constant at the first potential (En1) with respect to changes in the charging rate, and a charging rate a second flat portion (PT2), which is a charging rate region including a range in which the negative electrode potential En is constant at a second potential (En2) lower than the first potential (En1) with respect to changes in
- the control parameters include an upper limit voltage designation parameter that designates the upper limit voltage of the secondary battery (512), and the parameter updating unit 580 updates the negative electrode potential En is more than the first potential (En1), it is more preferable to have a function to update the upper limit voltage designation parameter.
- the negative electrode potential En can be kept high, and favorable performance can be maintained for a long period of time.
- the battery cell 100 is a lithium ion battery and the first potential (En1) is a potential of 0.1 V or more and 0.2 V or less based on the lithium electrode.
- the battery cell 100 which is a lithium ion battery, can maintain favorable performance over a long period of time.
- the parameter updating unit 580 acquires the charge/discharge curve of the secondary battery (512) based on the current flowing through the secondary battery (512) or the voltage appearing in the secondary battery (512) during the charging process or discharging process.
- a charge/discharge curve acquisition unit 582 a correlation acquisition unit 584 that acquires the correlation between the charging rate and the negative electrode potential En based on the charge/discharge curve; 2, and based on the obtained charging rate, the negative electrode potential En is the first potential (En1) or higher in the charging rate range where the secondary
- a parameter determination unit 588 that determines control parameters for charging and discharging the battery (512). This makes it possible to determine appropriate control parameters based on the charge/discharge curve.
- the charge/discharge processing unit 572 stops discharging when the terminal voltage of the secondary battery (512) drops below a predetermined discharge stop voltage during discharge of the secondary battery (512). It is more preferable to include a process for maintaining the terminal voltage of the battery cell 100 at a voltage lower than the discharge stop voltage. By maintaining the terminal voltage of the battery cell 100 at a voltage lower than the discharge stop voltage in this manner, the film on the surface of the negative electrode can be appropriately decomposed.
- the battery cell 100 is not limited to a lithium ion battery, and various secondary batteries can be applied.
- battery cell 500 secondary battery system 512 battery cell module (secondary battery) 572 charge/discharge processing unit 574 capacity recovery processing unit 580 parameter update unit 582 charge/discharge curve acquisition unit 584 correlation acquisition unit 586 discharge amount acquisition unit 588 parameter determination unit En negative electrode potential En1 negative electrode potential (first potential) En2 negative electrode potential (second potential) PT1 flat part (first flat part) PT2 flat part (second flat part)
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Abstract
In this secondary battery system, the lifetime of a secondary battery is extended. To this end, the secondary battery system (500) comprises: a secondary battery (512) having one or more battery cells (100) that are lithium ion battery cells; a charging/discharging unit (572) that performs charging or discharging of the secondary battery (512) on the basis of a control parameter that specifies conditions for controlling current or voltage when charging or discharging the secondary battery (512); a capacity restoration unit (574) that performs, on the secondary battery (512), a capacity restoration process including a process for maintaining the terminal voltage of the battery cell (100) at or below 2.0 V; and a parameter updating unit (580) that updates the control parameter according to the status of the capacity restoration process.
Description
本発明は、二次電池システムおよびプログラムに関する。
The present invention relates to a secondary battery system and program.
本技術分野の背景技術として、下記特許文献1の要約には、「[課題]本発明の目的は、劣化したリチウムイオン電池の性能を回復させる方法、及び電池性能の回復手段を備える電源システムを提供することにある。[解決手段]劣化したリチウムイオン電池の負極の電位を正極の電位よりも上昇させた後、負極の電位を正極の電位よりも低下させる工程を少なくとも1サイクル以上実施する電池の再生方法にある。また、リチウムイオン電池の負極の電位を正極の電位よりも上昇させた後、負極の電位を正極の電位よりも低下させる手段を備えた電源システムにある。」と記載されている。
As a background art of this technical field, the abstract of Patent Document 1 below states, "[Problem] An object of the present invention is to provide a method for recovering the performance of a deteriorated lithium-ion battery and a power supply system provided with means for recovering the battery performance. [Solution] A battery in which a step of increasing the potential of a negative electrode of a deteriorated lithium-ion battery to a level higher than that of a positive electrode and then lowering the potential of the negative electrode to a level lower than that of the positive electrode is performed for at least one cycle. and a power supply system comprising means for increasing the potential of the negative electrode of a lithium-ion battery above the potential of the positive electrode and then lowering the potential of the negative electrode below the potential of the positive electrode.” ing.
また、下記特許文献2の要約には、「[課題]バッテリーの劣化を防止、または劣化を回復させるとともに、バッテリーの充放電性能を最大限に引き出し、バッテリーの充放電性能を長時間維持する。[解決手段]リチウムイオン二次電池などのバッテリーにおいて、様々な異常の発生や、劣化の原因は電極表面に生成される反応生成物である。具体的には、反応生成物が形成される電流とは逆方向に電流が流れるような信号(逆パルス電流)を加えて、その反応生成物を溶解する。」と記載されている。
In addition, in the abstract of Patent Document 2 below, it is stated that "[Problem] To prevent deterioration of a battery or recover the deterioration, to maximize the charging and discharging performance of the battery, and to maintain the charging and discharging performance of the battery for a long period of time. [Solution] In batteries such as lithium-ion secondary batteries, the cause of various abnormalities and deterioration is the reaction product generated on the surface of the electrode.Specifically, the current that forms the reaction product A signal (reverse pulse current) is applied such that the current flows in the opposite direction to dissolve the reaction product."
また、下記特許文献3の要約には、「[課題]回復できる劣化成分を考慮した上で、リチウムイオン二次電池の充放電を制御する技術を提供する。[解決手段]リチウムイオン二次電池の充放電を制御するコントローラ(40)を有する。コントローラは、リチウムイオン二次電池(10)の過放電によってリチウムイオン二次電池の容量を回復させる回復処理を行い、回復処理を行った後におけるリチウムイオン二次電池の容量から特定される劣化状態に応じて、リチウムイオン二次電池の充放電を制御する。」と記載されている。
In addition, the abstract of Patent Document 3 below states, "[Problem] To provide a technology for controlling charging and discharging of a lithium ion secondary battery in consideration of recoverable deteriorated components. [Solution] Lithium ion secondary battery. The controller (40) controls the charging and discharging of the lithium ion secondary battery (10), the controller performs recovery processing for recovering the capacity of the lithium ion secondary battery (10) due to overdischarge, and after performing the recovery processing, The charging and discharging of the lithium ion secondary battery is controlled according to the deterioration state specified from the capacity of the lithium ion secondary battery."
また、下記非特許文献1の要約(Abstract)には、「バッテリーセルの放電カーブを正極および負極のものに分割する、微分した放電カーブの解析は、劣化メカニズムの調査に有用である(The differential discharge curve analysis that separates the discharge curve of battery cells into those of the positive and negative electrodes is useful for investigating deterioration mechanisms.)…」と記載されている。これら文献の記述は本願明細書の一部として包含される。
In addition, in the abstract of Non-Patent Document 1 below, ``Analysis of the differentiated discharge curve, which divides the discharge curve of the battery cell into that of the positive electrode and the negative electrode, is useful for investigating the deterioration mechanism (The differential dischargecurveanalysisthat separatesthedischargecurveofbatterycellsintothoseofthepositiveandnegativeelectrodesisusefulforinvestigatingdeteriorationmechanisms.)…”. The descriptions of these documents are incorporated as part of the present specification.
ところで、上述した技術において、二次電池を一層長寿命化できれば好ましい。
この発明は上述した事情に鑑みてなされたものであり、二次電池を長寿命化できる二次電池システムおよびプログラムを提供することを目的とする。 By the way, in the technology described above, it is preferable if the life of the secondary battery can be further extended.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a secondary battery system and program capable of extending the life of a secondary battery.
この発明は上述した事情に鑑みてなされたものであり、二次電池を長寿命化できる二次電池システムおよびプログラムを提供することを目的とする。 By the way, in the technology described above, it is preferable if the life of the secondary battery can be further extended.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a secondary battery system and program capable of extending the life of a secondary battery.
上記課題を解決するため本発明の二次電池システムは、リチウムイオン電池セルである一または複数の電池セルを有する二次電池と、前記二次電池に対する充電または前記二次電池からの放電を行う際の電流または電圧の制御条件を規定する制御パラメータに基づいて、前記二次電池に対する充電処理または前記二次電池からの放電処理を行う充放電処理部と、前記二次電池に対して、前記電池セルの端子電圧を2.0V以下に維持する処理を含む容量回復処理を行う容量回復処理部と、前記容量回復処理の状況に応じて、前記制御パラメータを更新するパラメータ更新部と、を備えることを特徴とする。
In order to solve the above problems, the secondary battery system of the present invention provides a secondary battery having one or more battery cells that are lithium ion battery cells, and charging or discharging the secondary battery. A charge/discharge processing unit that performs charging processing for the secondary battery or discharging processing from the secondary battery based on control parameters that define control conditions for the current or voltage at the time, and for the secondary battery, the a capacity recovery processing unit that performs capacity recovery processing including processing for maintaining the terminal voltage of the battery cell at 2.0 V or less; and a parameter update unit that updates the control parameter according to the status of the capacity recovery processing. It is characterized by
本発明によれば、二次電池を長寿命化できる。
According to the present invention, the life of the secondary battery can be extended.
[実施形態の前提]
リチウムイオン電池は、非水電解質二次電池の一つであり、エネルギー密度が高いため、携帯機器のバッテリーや、近年では電気自動車のバッテリーとしても用いられている。但し、リチウムイオン電池は、使用に伴い劣化し、電池容量が減少することが知られている。リチウムイオン電池では、正極の活物質としてリチウム金属酸化物、負極の活物質とし黒鉛などの炭素材が用いられるのが一般的である。リチウムイオン電池の正極および負極は、微小な活物質粒子群にバインダ(結着剤)や導電剤等を加えてスラリー(混合体)化した後、金属箔に塗布して形成する。 [Premise of the embodiment]
Lithium ion batteries are one type of non-aqueous electrolyte secondary batteries, and because of their high energy density, they are also used as batteries for mobile devices and, in recent years, as batteries for electric vehicles. However, it is known that the lithium ion battery deteriorates with use and the battery capacity decreases. Lithium ion batteries generally use a lithium metal oxide as a positive electrode active material and a carbon material such as graphite as a negative electrode active material. A positive electrode and a negative electrode of a lithium ion battery are formed by adding a binder (binder), a conductive agent, etc. to minute active material particles to form a slurry (mixture), and then applying the slurry (mixture) to a metal foil.
リチウムイオン電池は、非水電解質二次電池の一つであり、エネルギー密度が高いため、携帯機器のバッテリーや、近年では電気自動車のバッテリーとしても用いられている。但し、リチウムイオン電池は、使用に伴い劣化し、電池容量が減少することが知られている。リチウムイオン電池では、正極の活物質としてリチウム金属酸化物、負極の活物質とし黒鉛などの炭素材が用いられるのが一般的である。リチウムイオン電池の正極および負極は、微小な活物質粒子群にバインダ(結着剤)や導電剤等を加えてスラリー(混合体)化した後、金属箔に塗布して形成する。 [Premise of the embodiment]
Lithium ion batteries are one type of non-aqueous electrolyte secondary batteries, and because of their high energy density, they are also used as batteries for mobile devices and, in recent years, as batteries for electric vehicles. However, it is known that the lithium ion battery deteriorates with use and the battery capacity decreases. Lithium ion batteries generally use a lithium metal oxide as a positive electrode active material and a carbon material such as graphite as a negative electrode active material. A positive electrode and a negative electrode of a lithium ion battery are formed by adding a binder (binder), a conductive agent, etc. to minute active material particles to form a slurry (mixture), and then applying the slurry (mixture) to a metal foil.
充電時には、正極の活物質から放出されたリチウムイオンが負極の活物質に吸蔵され、放電時には負極の活物質に吸蔵されたリチウムイオンが放出され正極の活物質に吸蔵される。このように、リチウムイオンが電極間を移動することで電極間に電流が流れる。
このようなリチウムイオン電池では、
(1)正極活物質の電気的な孤立、
(2)負極活物質の電気的な孤立、および
(3)電極間を往来するリチウムイオンの固定化、
によって容量が減少する。 During charging, the lithium ions released from the positive electrode active material are absorbed by the negative electrode active material, and during discharging, the lithium ions absorbed by the negative electrode active material are released and absorbed by the positive electrode active material. Thus, current flows between the electrodes as lithium ions move between the electrodes.
In such lithium-ion batteries,
(1) electrical isolation of the positive electrode active material,
(2) electrical isolation of the negative electrode active material, and (3) immobilization of lithium ions traveling between the electrodes,
capacity is reduced by
このようなリチウムイオン電池では、
(1)正極活物質の電気的な孤立、
(2)負極活物質の電気的な孤立、および
(3)電極間を往来するリチウムイオンの固定化、
によって容量が減少する。 During charging, the lithium ions released from the positive electrode active material are absorbed by the negative electrode active material, and during discharging, the lithium ions absorbed by the negative electrode active material are released and absorbed by the positive electrode active material. Thus, current flows between the electrodes as lithium ions move between the electrodes.
In such lithium-ion batteries,
(1) electrical isolation of the positive electrode active material,
(2) electrical isolation of the negative electrode active material, and (3) immobilization of lithium ions traveling between the electrodes,
capacity is reduced by
(3)については、負極と電解液の間の界面で形成される皮膜成分(SEI;Solid Electrolyte Interphase)にリチウムイオンが取り込まれ、移動度を失うことで生じると考えられる。また、充電時に正極と対向していない負極面(非対向面)に存在する負極活物質にリチウムイオンが取り込まれると、放電時にそのリチウムイオンを電池反応に使用することができず、結果として容量低下となることも考えられる。
Regarding (3), it is thought that lithium ions are taken into the film component (SEI; Solid Electrolyte Interphase) formed at the interface between the negative electrode and the electrolyte, resulting in loss of mobility. In addition, if lithium ions are taken into the negative electrode active material present on the negative electrode surface (non-facing surface) that does not face the positive electrode during charging, the lithium ions cannot be used for the battery reaction during discharging, resulting in a decrease in capacity. It is also possible that it will decrease.
これらの要因のうち、上記(3)による容量減少分については、上述のSEIを電気化学的に酸化し、分解除去することで容量ないし電池出力を回復させることが可能である。また、放電反応時に、非対向面に取り込まれたリチウムイオンを強制的に放出させる程度に負極電位を高くし、放出されたリチウムイオンを再び電池容量として使用することで容量を回復可能である。
Among these factors, for the capacity decrease due to (3) above, it is possible to recover the capacity or battery output by electrochemically oxidizing and decomposing and removing the above SEI. In addition, the capacity can be recovered by raising the negative electrode potential to the extent that the lithium ions taken into the non-facing surface are forcibly released during the discharge reaction, and using the released lithium ions as battery capacity again.
劣化電池の過放電処理により、負極表面の皮膜を分解・除去したり、非対向部の負極に取り込まれたリチウムイオンを開放することで、一時的に電池容量が回復するものの、その後の電池充放電で再び容量が劣化すると電池寿命は向上しない。そのため、過放電処理により電池容量を回復させた後に、急激な容量劣化を防ぐための制御を行うことが好ましい。前述の特許文献3を応用すれば、容量回復後の電池劣化状態を診断し、その後の充放電条件を制御することが可能であると考えられる。また、容量低下率が所定の閾値を上回る場合にその充放電運用を取りやめ、容量低下率が閾値内に収まるまで充放電運用条件を修正することも可能であると考えられる。
Due to overdischarge treatment of deteriorated batteries, the film on the surface of the negative electrode is decomposed and removed, and the lithium ions captured in the negative electrode in the non-facing part are released. If the capacity deteriorates again due to discharge, the battery life will not improve. Therefore, it is preferable to perform control to prevent rapid capacity deterioration after recovering the battery capacity by overdischarge treatment. By applying the above-mentioned Patent Document 3, it is considered possible to diagnose the state of deterioration of the battery after recovery of the capacity, and to control the subsequent charge/discharge conditions. It is also conceivable that when the capacity decrease rate exceeds a predetermined threshold, the charge/discharge operation is stopped and the charge/discharge operation conditions are corrected until the capacity decrease rate falls within the threshold.
しかし、特許文献3においては、具体的な修正方針については明確になっていない。また、特許文献3を応用した技術において得られる、充放電運用条件判断のための計測パラメータは、劣化が進行する負極に関する直接情報でなく、電池全体の劣化速度である。このため、充放電運用条件の修正に多くの工程を有するという問題が生じる。そこで、以下述べる実施形態においては、正極と負極の間で過放電を実行することで負極内に固定化されたリチウムイオンを放出させ、その容量を回復させるリチウムイオン電池を用いた二次電池システムにおいて、回復後の負極情報を検知する。そして、その検知結果に基づいて、更なる容量劣化を抑制するための充放電運用制御を実行することで、二次電池システムの長寿命化を実現する。
However, Patent Document 3 does not clarify the specific revision policy. In addition, the measurement parameter for determining the charging/discharging operation conditions obtained in the technique applying Patent Document 3 is not the direct information about the negative electrode that deteriorates, but the deterioration rate of the entire battery. Therefore, there arises a problem that many steps are required to correct the charging/discharging operation conditions. Therefore, in the embodiments described below, a secondary battery system using a lithium ion battery that recovers the capacity by releasing the lithium ions immobilized in the negative electrode by performing overdischarge between the positive electrode and the negative electrode , the negative electrode information after recovery is detected. Then, based on the detection result, the charging/discharging operation control for suppressing further capacity deterioration is executed to extend the life of the secondary battery system.
[リチウムイオン電池の電池セルの構造]
まず、図1および図2を参照して、好適な実施形態に適用可能な二極式の電池セルの構造例について説明する。
図1は、二極式の電池セル100(二次電池)の断面の一例を、概念的に示す図である。
図1において、電池セル100は、蓄電要素1と、正極端子2と、負極端子3と、外装材6とを備えている。セパレータ5は、蓄電要素1に含まれている。外装材6は、ラミネートフィルム、もしくは、それに類する素材を用いて構成されている。 [Structure of battery cell of lithium ion battery]
First, a structural example of a bipolar battery cell applicable to a preferred embodiment will be described with reference to FIGS. 1 and 2. FIG.
FIG. 1 is a diagram conceptually showing an example of a cross section of a bipolar battery cell 100 (secondary battery).
In FIG. 1 , abattery cell 100 includes a power storage element 1 , a positive electrode terminal 2 , a negative electrode terminal 3 and an exterior material 6 . A separator 5 is included in the storage element 1 . The exterior material 6 is constructed using a laminate film or a similar material.
まず、図1および図2を参照して、好適な実施形態に適用可能な二極式の電池セルの構造例について説明する。
図1は、二極式の電池セル100(二次電池)の断面の一例を、概念的に示す図である。
図1において、電池セル100は、蓄電要素1と、正極端子2と、負極端子3と、外装材6とを備えている。セパレータ5は、蓄電要素1に含まれている。外装材6は、ラミネートフィルム、もしくは、それに類する素材を用いて構成されている。 [Structure of battery cell of lithium ion battery]
First, a structural example of a bipolar battery cell applicable to a preferred embodiment will be described with reference to FIGS. 1 and 2. FIG.
FIG. 1 is a diagram conceptually showing an example of a cross section of a bipolar battery cell 100 (secondary battery).
In FIG. 1 , a
図2は、図1に示した蓄電要素1の側面図である。
図2に示すように、蓄電要素1においては、セパレータ5を介して複数の正極12と複数の負極13とが交互に積層されている。図1に示した蓄電要素1は、これら正極12および負極13が重なって見える領域に対応する。また、蓄電要素1は、さらに電解液(図示せず)を含んでおり、電解液は、正極12、負極13、セパレータ5等の微孔に含侵されている。セパレータ5としては、例えば、ポリプロピレンを適用することができる。但し、セパレータ5としては、ポリプロピレン以外にも、ポリエチレンなどのポリオレフィン製の微孔性フィルムや不織布などを適用することもできる。 FIG. 2 is a side view of thestorage element 1 shown in FIG.
As shown in FIG. 2 , in thestorage element 1 , a plurality of positive electrodes 12 and a plurality of negative electrodes 13 are alternately stacked with separators 5 interposed therebetween. The storage element 1 shown in FIG. 1 corresponds to the region where the positive electrode 12 and the negative electrode 13 appear to overlap. The storage element 1 further contains an electrolytic solution (not shown), and the electrolytic solution impregnates micropores of the positive electrode 12, the negative electrode 13, the separator 5, and the like. As the separator 5, for example, polypropylene can be applied. However, as the separator 5, a microporous film made of polyolefin such as polyethylene or a non-woven fabric can be applied in addition to polypropylene.
図2に示すように、蓄電要素1においては、セパレータ5を介して複数の正極12と複数の負極13とが交互に積層されている。図1に示した蓄電要素1は、これら正極12および負極13が重なって見える領域に対応する。また、蓄電要素1は、さらに電解液(図示せず)を含んでおり、電解液は、正極12、負極13、セパレータ5等の微孔に含侵されている。セパレータ5としては、例えば、ポリプロピレンを適用することができる。但し、セパレータ5としては、ポリプロピレン以外にも、ポリエチレンなどのポリオレフィン製の微孔性フィルムや不織布などを適用することもできる。 FIG. 2 is a side view of the
As shown in FIG. 2 , in the
正極12は、正極集電箔122と、これに塗布された正極合剤層121と、を備えている。また、負極13は、負極集電箔132と、これに塗布された負極合剤層131と、を備えている。正極集電箔122および負極集電箔132は、適切な金属の集電箔である。また、正極合剤層121および負極合剤層131は、適切な電極活物質、導電剤、結着剤などの混合体である。正極集電箔122および負極集電箔132には、それぞれ端子としての金属のタブが接続されている。これらのタブが、図1に示した正極端子2および負極端子3になる。図1において、これら正極端子2および負極端子3を外装材6の外部に露出させた状態で外装材6を封止する。これにより、正極端子2および負極端子3を介して、電池セル100を外部に接続することができる。以下、正極12および負極13の電位を正極電位Epおよび負極電位Enと呼ぶ。また、両者の差、すなわち「Ep-En」が、正極端子2および負極端子3の間の電圧であり、これを電池電圧Epnと呼ぶ。
The positive electrode 12 includes a positive electrode collector foil 122 and a positive electrode mixture layer 121 applied thereto. Further, the negative electrode 13 includes a negative electrode collector foil 132 and a negative electrode mixture layer 131 applied thereto. The positive electrode current collector foil 122 and the negative electrode current collector foil 132 are suitable metal current collector foils. Also, the positive electrode mixture layer 121 and the negative electrode mixture layer 131 are mixtures of suitable electrode active materials, conductive agents, binders, and the like. Metal tabs serving as terminals are connected to the positive current collector foil 122 and the negative current collector foil 132, respectively. These tabs become the positive terminal 2 and the negative terminal 3 shown in FIG. In FIG. 1, the exterior material 6 is sealed with the positive electrode terminal 2 and the negative electrode terminal 3 exposed to the outside of the exterior material 6 . Thereby, the battery cell 100 can be connected to the outside through the positive terminal 2 and the negative terminal 3 . The potentials of the positive electrode 12 and the negative electrode 13 are hereinafter referred to as a positive electrode potential Ep and a negative electrode potential En. The difference between the two, ie, "Ep-En", is the voltage between the positive terminal 2 and the negative terminal 3, and is called the battery voltage Epn.
以下、電池セル100の各部の材質等の例を説明するが、これらは一例であり、本実施形態のリチウムイオン電池の電池セル100は、材質、形状、製造方法などに制限されるものではなく、任意の材質、形状、製造方法など適用することができる。
Examples of materials and the like of each part of the battery cell 100 will be described below, but these are only examples, and the battery cell 100 of the lithium ion battery of the present embodiment is not limited to materials, shapes, manufacturing methods, and the like. , any material, shape, manufacturing method, etc. can be applied.
(正極12)
正極集電箔122(図2参照)には、厚さが10~100μmのアルミニウム箔、厚さが10~100μm、孔径0.1~10mmのアルミニウム製穿孔箔、エキスパンドメタル、発泡金属板などを適用することができる。また、正極集電箔122の材質も、アルミニウムの他に、ステンレス鋼、チタンなども適用可能である。正極合剤層121は、反応種を内部に含むものが望ましい。リチウムイオン電池の反応種は、リチウムイオンである。この場合、電極活物質は、リチウムイオンを可逆的に挿入脱離可能なリチウム含有化合物を含んでいる。 (Positive electrode 12)
The positive current collector foil 122 (see FIG. 2) is made of an aluminum foil with a thickness of 10 to 100 μm, a perforated aluminum foil with a thickness of 10 to 100 μm and a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like. can be applied. In addition to aluminum, stainless steel, titanium, and the like can also be used for the material of the positive electrodecurrent collector foil 122 . The positive electrode mixture layer 121 preferably contains a reactive species therein. The reactive species in lithium ion batteries is lithium ions. In this case, the electrode active material contains a lithium-containing compound capable of reversibly intercalating and deintercalating lithium ions.
正極集電箔122(図2参照)には、厚さが10~100μmのアルミニウム箔、厚さが10~100μm、孔径0.1~10mmのアルミニウム製穿孔箔、エキスパンドメタル、発泡金属板などを適用することができる。また、正極集電箔122の材質も、アルミニウムの他に、ステンレス鋼、チタンなども適用可能である。正極合剤層121は、反応種を内部に含むものが望ましい。リチウムイオン電池の反応種は、リチウムイオンである。この場合、電極活物質は、リチウムイオンを可逆的に挿入脱離可能なリチウム含有化合物を含んでいる。 (Positive electrode 12)
The positive current collector foil 122 (see FIG. 2) is made of an aluminum foil with a thickness of 10 to 100 μm, a perforated aluminum foil with a thickness of 10 to 100 μm and a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like. can be applied. In addition to aluminum, stainless steel, titanium, and the like can also be used for the material of the positive electrode
正極12の電極活物質の種類としては、例えば、コバルト酸リチウム、マンガン置換コバルト酸リチウム、マンガン酸リチウム、ニッケル酸リチウム、オリビン型リン酸鉄リチウムなどのリン酸遷移金属リチウム、またはLiwNixCoyMnzO2(ここで、w、x、y、zは0または正の値)が挙げられる。また、正極12の電極活物質として、上述した材料が一種単独、または、二種以上含まれていてもよい。
Examples of the electrode active material of the positive electrode 12 include lithium cobaltate, manganese-substituted lithium cobaltate, lithium manganate, lithium nickelate, lithium transition metal phosphate such as olivine-type lithium iron phosphate, or Li w Ni x . Co y Mn z O 2 (here, w, x, y, and z are 0 or positive values). Further, as the electrode active material of the positive electrode 12, the materials described above may be contained singly or in combination of two or more.
(負極13)
負極集電箔132には、厚さが10~100μmの銅箔、厚さが10~100μm、孔径0.1~10mmの銅製穿孔箔、エキスパンドメタル、発泡金属板などを適用することができる。また、負極集電箔132の材質も、銅の他に、ステンレス鋼、チタンなども適用可能である。負極13における電極活物質は、リチウムイオンを可逆的に挿入脱離可能な物質を含んでいる。 (Negative electrode 13)
As the negative electrodecurrent collector foil 132, a copper foil with a thickness of 10 to 100 μm, a perforated copper foil with a thickness of 10 to 100 μm and a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like can be applied. Further, as the material of the negative electrode current collector foil 132, other than copper, stainless steel, titanium, or the like can be applied. The electrode active material in the negative electrode 13 contains a material capable of reversibly intercalating and deintercalating lithium ions.
負極集電箔132には、厚さが10~100μmの銅箔、厚さが10~100μm、孔径0.1~10mmの銅製穿孔箔、エキスパンドメタル、発泡金属板などを適用することができる。また、負極集電箔132の材質も、銅の他に、ステンレス鋼、チタンなども適用可能である。負極13における電極活物質は、リチウムイオンを可逆的に挿入脱離可能な物質を含んでいる。 (Negative electrode 13)
As the negative electrode
負極13の電極活物質の種類としては、例えば、天然黒鉛、天然黒鉛に乾式のCVD法もしくは湿式のスプレー法によって被膜を形成した複合炭素質材料、エポキシやフェノール等の樹脂材料もしくは石油や石炭から得られるピッチ系材料を原料として焼成により製造される人造黒鉛、シリコン(Si)、シリコンを混合した黒鉛、難黒鉛化炭素材、チタン酸リチウム、Li4Ti5O12が挙げられる。また、負極13の負極活物質として、上述した材料が、一種単独、または、二種以上含まれていてもよい。
Examples of the type of electrode active material for the negative electrode 13 include natural graphite, a composite carbonaceous material obtained by forming a film on natural graphite by a dry CVD method or a wet spray method, a resin material such as epoxy or phenol, or a material made from petroleum or coal. Artificial graphite produced by firing the obtained pitch-based material as a raw material, silicon (Si), graphite mixed with silicon, non-graphitizable carbon material, lithium titanate, and Li 4 Ti 5 O 12 . Further, as the negative electrode active material of the negative electrode 13, the materials described above may be contained singly or in combination of two or more.
(電解液)
リチウムイオン電池の場合、電解液は、例えば、エチレンカーボネート(EC)、プロピレンカーボネート(PC)、ブチレンカーボネート(BC)、ジメチルカーボネート(DMC)、エチルメチルカーボネート(EMC)、ジエチルカーボネート(DEC)、メチルプロピルカーボネート(MPC)、エチルプロピルカーボネート(EPC)等の非プロトン性有機系溶媒などを適用することができる。
あるいは、上述した2種以上の混合有機化合物の溶媒に、六フッ化リン酸リチウム、四フッ化ホウ酸リチウム、過塩素酸リチウム、ヨウ化リチウム、塩化リチウム、臭化リチウム、LiB[OCOCF3]4、LiB[OCOCF2CF3]4、LiPF4(CF3)2、LiN(SO2CF3)2、LiN(SO2CF2CF3)2等のリチウム塩を溶解した電解液が挙げられる。
あるいは、上述した2種以上の混合リチウム塩を溶解した電解液が挙げられる。 (Electrolyte)
In the case of lithium-ion batteries, the electrolyte is, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl Aprotic organic solvents such as propyl carbonate (MPC) and ethyl propyl carbonate (EPC) can be applied.
Alternatively, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium iodide, lithium chloride, lithium bromide, LiB[OCOCF 3 ] is added to the solvent of the mixed organic compound of two or more kinds described above. 4 , LiB[ OCOCF2CF3 ] 4 , LiPF4 ( CF3 ) 2 , LiN ( SO2CF3 ) 2 , LiN( SO2CF2CF3 ) 2 and other lithium salt - dissolved electrolytes. .
Alternatively, an electrolytic solution in which two or more kinds of mixed lithium salts described above are dissolved can be used.
リチウムイオン電池の場合、電解液は、例えば、エチレンカーボネート(EC)、プロピレンカーボネート(PC)、ブチレンカーボネート(BC)、ジメチルカーボネート(DMC)、エチルメチルカーボネート(EMC)、ジエチルカーボネート(DEC)、メチルプロピルカーボネート(MPC)、エチルプロピルカーボネート(EPC)等の非プロトン性有機系溶媒などを適用することができる。
あるいは、上述した2種以上の混合有機化合物の溶媒に、六フッ化リン酸リチウム、四フッ化ホウ酸リチウム、過塩素酸リチウム、ヨウ化リチウム、塩化リチウム、臭化リチウム、LiB[OCOCF3]4、LiB[OCOCF2CF3]4、LiPF4(CF3)2、LiN(SO2CF3)2、LiN(SO2CF2CF3)2等のリチウム塩を溶解した電解液が挙げられる。
あるいは、上述した2種以上の混合リチウム塩を溶解した電解液が挙げられる。 (Electrolyte)
In the case of lithium-ion batteries, the electrolyte is, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl Aprotic organic solvents such as propyl carbonate (MPC) and ethyl propyl carbonate (EPC) can be applied.
Alternatively, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium iodide, lithium chloride, lithium bromide, LiB[OCOCF 3 ] is added to the solvent of the mixed organic compound of two or more kinds described above. 4 , LiB[ OCOCF2CF3 ] 4 , LiPF4 ( CF3 ) 2 , LiN ( SO2CF3 ) 2 , LiN( SO2CF2CF3 ) 2 and other lithium salt - dissolved electrolytes. .
Alternatively, an electrolytic solution in which two or more kinds of mixed lithium salts described above are dissolved can be used.
前述の電解液の構成溶媒は一般的に揮発性が高く、電解液の揮発温度は25℃未満であることが多い。これに加え、好適な実施形態の一つでは、揮発温度を高めたリチウムイオン伝導性の液体を用いることもできる。具体的には、イオン液体、および、溶媒和イオン液体を挙げることができる。イオン液体はカチオンおよびアニオンを含んでいる。イオン液体としては、カチオン種に応じ、イミダゾリウム系、アンモニウム系、ピロリジニウム系、ピペリジニウム系、ピリジニウム系、モルホリニウム系、ホスホニウム系、スルホニウム系などに分類される。イミダゾリウム系イオン液体を構成するカチオンには、例えば、1-etyl-3-methylimidazoriumや1-butyl-3-methylimidazorium(BMI)などのアルキルイミダゾリウムカチオンなどがある。
The constituent solvents of the aforementioned electrolytic solution are generally highly volatile, and the volatilization temperature of the electrolytic solution is often less than 25°C. Additionally, in one of the preferred embodiments, a lithium ion conductive liquid with an elevated volatilization temperature may be used. Specifically, ionic liquids and solvated ionic liquids can be mentioned. Ionic liquids contain cations and anions. Ionic liquids are classified into imidazolium-based, ammonium-based, pyrrolidinium-based, piperidinium-based, pyridinium-based, morpholinium-based, phosphonium-based, sulfonium-based, and the like, depending on the cation species. Examples of cations constituting imidazolium-based ionic liquids include alkylimidazolium cations such as 1-etyl-3-methylimidazolium and 1-butyl-3-methylimidazolium (BMI).
アンモニウム系イオン液体を構成するカチオンには、例えば、N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium(DEME)やtetraamylammoniumなどのほかに、N,N,N-trimethyl-N-propylammoniumなどのアルキルアンモニウムカチオンがある。ピロリジニウム系イオン液体を構成するカチオンには、例えば、N-methyl-N-propylpyrrolidinium(Py13)や1-butyl-1-methylpyrrolidiniumなどのアルキルピロリジニウムカチオンなどがある。ピペリジニウム系イオン液体を構成するカチオンには、例えば、N-methyl-N-propylpiperidinium(PP13)や1-butyl-1-methylpiperidiniumなどのアルキルピペリジニウムカチオンなどがある。
Examples of cations that make up ammonium-based ionic liquids include N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium (DEME) and tetraamylammonium, as well as N,N,N-trimethyl-N There are alkylammonium cations such as -propylammonium. Examples of cations constituting pyrrolidinium-based ionic liquids include alkylpyrrolidinium cations such as N-methyl-N-propylpyrrolidinium (Py13) and 1-butyl-1-methylpyrrolidinium. Examples of cations constituting piperidinium-based ionic liquids include alkylpiperidinium cations such as N-methyl-N-propylpiperidinium (PP13) and 1-butyl-1-methylpiperidinium.
ピリジニウム系イオン液体を構成するカチオンには、例えば、1-butylpyridiniumや1-butyl-4-methylpyridiniumなどのアルキルピリジニウムカチオンなどがある。モルホリニウム系イオン液体を構成するカチオンには、例えば、4-ethyl-4-methylmorpholiniumなどのアルキルモルホリニウムなどがある。ホスホニウム系イオン液体を構成するカチオンには、例えば、tetrabutylphosphoniumやtributylmethylphosphoniumなどのアルキルホスホニウムカチオンなどがある。スルホニウム系イオン液体を構成するカチオンには、例えば、trimethylsulfoniumやtributhylsulfoniumなどのアルキルスルホニウムカチオンなどがある。これらカチオンと対になるアニオンとしては、例えば、bis(trifluoromethanesulfonyl)imide(TFSI)、bis(fluorosulfonyl)imide、tetrafluoroborate(BF4)、hexafluorophosphate(PF6)、bis(pentafluoroethanesulfonyl)imide(BETI)、trifluoromethanesulfonate(トリフラート)、acetate、dimethyl phosphate、dicyanamide、trifluoro(trifluoromethyl)borateなどがある。これらのイオン液体を単独または複数組み合わせて使用してもよい。
Examples of cations constituting pyridinium-based ionic liquids include alkylpyridinium cations such as 1-butylpyridinium and 1-butyl-4-methylpyridinium. Examples of cations constituting morpholinium-based ionic liquids include alkylmorpholinium such as 4-ethyl-4-methylmorpholinium. Examples of cations constituting phosphonium-based ionic liquids include alkylphosphonium cations such as tetrabutylphosphonium and tributylmethylphosphonium. Examples of cations constituting sulfonium-based ionic liquids include alkylsulfonium cations such as trimethylsulfonium and tributhylsulfonium. Examples of anions paired with these cations include bis (trifluoromethanesulfonyl) imide (TFSI), bis (fluorosulfonyl) imide, tetrafluoroborate (BF4), hexafluorophosphate (PF6), bis (pentafluoroethanesulfonyl) imide (BETI), trifluoromethanesulfonate (triflate). , acetate, dimethyl phosphate, dicyanamide, trifluoro (trifluoromethyl) borate, etc. These ionic liquids may be used singly or in combination.
また、イオン液体に電解質塩を含めてもよい。電解質塩としては、溶媒に均一に分散できるものを使用できる。カチオンがリチウム、上記アニオンからなるものをリチウム塩として使用することができる。例えば、リチウムビス(フルオロスルホニル)イミド(LiFSI)、リチウムビス(トリフルオロメタンスルホニル)イミド(LiTFSI)、リチウムビス(ペンタフルオロエタンスルホニル)イミド(LiBETI)、リチウムテトラフルオロボレート(LiBF4)、リチウムヘキサフルオロフォスファート(LiPF6)、リチウムトリフラートなどが挙げられるが、これに限られない。これらの電解質塩を単独または複数組み合わせて使用してもよい。
Also, the ionic liquid may contain an electrolyte salt. As the electrolyte salt, one that can be uniformly dispersed in the solvent can be used. A lithium salt containing lithium as a cation and the above anion can be used. For example, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate Fart (LiPF6), lithium triflate, etc., but not limited to these. These electrolyte salts may be used singly or in combination.
エーテル系溶媒は、溶媒和電解質塩と溶媒和イオン液体を構成する。エーテル系溶媒として、イオン液体に類似の性質を示す公知のグライム(R-O(CH2CH2O)n-R’(R、R’は飽和炭化水素、nは整数)で表される対称グリコールジエーテルの総称)を利用できる。イオン伝導性の観点から、テトラグライム(テトラエチレンジメチルグリコール、G4)、トリグライム(トリエチレングリコールジメチルエーテル、G3)、ペンタグライム(ペンタエチレングリコールジメチルエーテル、G5)、ヘキサグライム(ヘキサエチレングリコールジメチルエーテル、G6)を好ましく用いることができる。
The ether solvent constitutes the solvated electrolyte salt and the solvated ionic liquid. Known glyme (a general term for symmetrical glycol diethers represented by R-O(CH2CH2O)n-R' (R, R' are saturated hydrocarbons and n is an integer)) that exhibits similar properties to ionic liquids as an ether solvent. available. In terms of ionic conductivity, tetraglyme (tetraethylene glycol dimethyl ether, G4), triglyme (triethylene glycol dimethyl ether, G3), pentaglyme (pentaethylene glycol dimethyl ether, G5), hexaglyme (hexaethylene glycol dimethyl ether, G6) It can be preferably used.
また、エーテル系溶媒として、クラウンエーテル((-CH2-CH2-O)n(nは整数)で表わされる大環状エーテルの総称)を利用できる。具体的には、12-クラウン-4、15-クラウン-5、18-クラウン-6、ジベンゾ-18-クラウン-6などを好ましく用いることができるが、これに限らない。これらのエーテル系溶媒を単独または複数組み合わせて使用してもよい。溶媒和電解質塩と錯体構造を形成できる点で、テトラグライム、トリグライムを用いることが好ましい。本実施形態において、テトラグライムが好ましい理由は、リチウムイオンに対し、還元安定性に優れる配位構造をとるためである。
In addition, crown ethers (generic term for macrocyclic ethers represented by (-CH2-CH2-O)n (n is an integer)) can be used as ether-based solvents. Specifically, 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6 and the like can be preferably used, but are not limited thereto. These ether solvents may be used singly or in combination. Tetraglyme and triglyme are preferably used because they can form a complex structure with the solvated electrolyte salt. In the present embodiment, tetraglyme is preferred because it has a coordination structure with excellent reduction stability with respect to lithium ions.
溶媒和電解質塩としては、LiFSI、LiTFSI、LiBETI等のリチウム塩を利用できるが、これに限らない。半固体電解質溶媒として、エーテル系溶媒および溶媒和電解質塩の混合物を単独または複数組み合わせて使用してもよい。半固体電解質溶媒の還元電位は、上述した負極活物質の還元電位よりも0.5V以上、好ましくは0.2V以上低いことが望ましい。半固体電解液における主溶媒の重量比率は特には限定されないが、電池安定性および高速充放電の観点から半固体電解液中の溶媒の総和に占める主溶媒の重量比率は30%~70%、特に40%~60%、さらには45%~55%であることが望ましい。
Lithium salts such as LiFSI, LiTFSI, and LiBETI can be used as solvated electrolyte salts, but are not limited to these. Ether-based solvents and mixtures of solvated electrolyte salts may be used singly or in combination as semi-solid electrolyte solvents. The reduction potential of the semi-solid electrolyte solvent is desirably lower than the reduction potential of the negative electrode active material by 0.5 V or more, preferably 0.2 V or more. The weight ratio of the main solvent in the semi-solid electrolyte is not particularly limited, but from the viewpoint of battery stability and high-speed charging and discharging, the weight ratio of the main solvent in the total solvent in the semi-solid electrolyte is 30% to 70%. In particular, it is desirable to be 40% to 60%, more preferably 45% to 55%.
(低粘度有機溶媒)
低粘度有機溶媒は、半固体電解質溶媒の粘度を下げ、イオン伝導率を向上させる。半固体電解質溶媒を含む半固体電解液の内部抵抗は大きいため、低粘度有機溶媒を添加して半固体電解質溶媒のイオン伝導率を上げることにより、半固体電解液の内部抵抗を下げることができる。低粘度有機溶媒は、例えばエーテル系溶媒および溶媒和電解質塩の混合物の25℃における粘度140Pa・sより粘度の小さい溶媒であることが望ましい。低粘度有機溶媒として、炭酸プロピレン(PC)、リン酸トリメチル(TMP)、ガンマブチルラクトン(GBL)、炭酸エチレン(EC)、リン酸トリエチル(TEP)、亜リン酸トリス(2,2,2-トリフルオロエチル)(TFP)、メチルホスホン酸ジメチル(DMMP)等が挙げられる。これらの低粘度有機溶媒を単独または複数組み合わせて使用してもよい。低粘度有機溶媒に上記の電解質塩を溶解させてもよい。 (low viscosity organic solvent)
A low-viscosity organic solvent lowers the viscosity of the semi-solid electrolyte solvent and improves the ionic conductivity. Since the internal resistance of a semi-solid electrolyte solution containing a semi-solid electrolyte solvent is high, the internal resistance of the semi-solid electrolyte solution can be lowered by adding a low-viscosity organic solvent to increase the ionic conductivity of the semi-solid electrolyte solvent. . The low-viscosity organic solvent is desirably a solvent having a viscosity lower than 140 Pa·s at 25° C. of a mixture of, for example, an ether solvent and a solvated electrolyte salt. Low-viscosity organic solvents include propylene carbonate (PC), trimethyl phosphate (TMP), gamma-butyl lactone (GBL), ethylene carbonate (EC), triethyl phosphate (TEP), tris(2,2,2- trifluoroethyl) (TFP), dimethyl methylphosphonate (DMMP), and the like. These low-viscosity organic solvents may be used singly or in combination. The electrolyte salt may be dissolved in a low-viscosity organic solvent.
低粘度有機溶媒は、半固体電解質溶媒の粘度を下げ、イオン伝導率を向上させる。半固体電解質溶媒を含む半固体電解液の内部抵抗は大きいため、低粘度有機溶媒を添加して半固体電解質溶媒のイオン伝導率を上げることにより、半固体電解液の内部抵抗を下げることができる。低粘度有機溶媒は、例えばエーテル系溶媒および溶媒和電解質塩の混合物の25℃における粘度140Pa・sより粘度の小さい溶媒であることが望ましい。低粘度有機溶媒として、炭酸プロピレン(PC)、リン酸トリメチル(TMP)、ガンマブチルラクトン(GBL)、炭酸エチレン(EC)、リン酸トリエチル(TEP)、亜リン酸トリス(2,2,2-トリフルオロエチル)(TFP)、メチルホスホン酸ジメチル(DMMP)等が挙げられる。これらの低粘度有機溶媒を単独または複数組み合わせて使用してもよい。低粘度有機溶媒に上記の電解質塩を溶解させてもよい。 (low viscosity organic solvent)
A low-viscosity organic solvent lowers the viscosity of the semi-solid electrolyte solvent and improves the ionic conductivity. Since the internal resistance of a semi-solid electrolyte solution containing a semi-solid electrolyte solvent is high, the internal resistance of the semi-solid electrolyte solution can be lowered by adding a low-viscosity organic solvent to increase the ionic conductivity of the semi-solid electrolyte solvent. . The low-viscosity organic solvent is desirably a solvent having a viscosity lower than 140 Pa·s at 25° C. of a mixture of, for example, an ether solvent and a solvated electrolyte salt. Low-viscosity organic solvents include propylene carbonate (PC), trimethyl phosphate (TMP), gamma-butyl lactone (GBL), ethylene carbonate (EC), triethyl phosphate (TEP), tris(2,2,2- trifluoroethyl) (TFP), dimethyl methylphosphonate (DMMP), and the like. These low-viscosity organic solvents may be used singly or in combination. The electrolyte salt may be dissolved in a low-viscosity organic solvent.
本実施形態において、炭酸プロピレンが好ましい理由は、リチウムグライム錯体塩の粘度を下げて高イオン伝導度化し、還元安定性に優れるリチウムグライム錯体構造を乱さないために、電池の内部抵抗を下げ、高容量な電池を作製することができる。また、エーテル系化合物以外に、溶媒和イオン液体を形成する溶媒としてスルホランおよび/またはその誘導体を挙げることができる。スルホランおよび/またはその誘導体を含む溶媒和イオン液体を用いると、スルホランおよび/またはその誘導体とリチウムイオンとで固有の配位構造をとるため、半固体電解質層中でのリチウムイオンの輸送速度が速くなる。従って、粘度を高くするにつれて二次電池の入出力特性が低下するエーテル系溶媒および電解質塩を有する溶媒和イオン液体とは異なり、溶媒和イオン液体の粘度を高くしても、溶媒和イオン液体を有する二次電池の入出力特性の低下を抑制することができる。
In the present embodiment, the reason why propylene carbonate is preferable is that the viscosity of the lithium glyme complex salt is lowered to increase the ionic conductivity, and the lithium glyme complex structure, which has excellent reduction stability, is not disturbed, so that the internal resistance of the battery is lowered and the A high-capacity battery can be produced. In addition to ether-based compounds, sulfolane and/or its derivatives can be used as solvents for forming solvated ionic liquids. When a solvated ionic liquid containing sulfolane and/or a derivative thereof is used, sulfolane and/or a derivative thereof and lithium ions take a unique coordination structure, so that the transport rate of lithium ions in the semi-solid electrolyte layer is increased. Become. Therefore, unlike the solvated ionic liquid having an ether solvent and an electrolyte salt, in which the input/output characteristics of the secondary battery deteriorate as the viscosity increases, the solvated ionic liquid can be used even if the viscosity of the solvated ionic liquid is increased. It is possible to suppress deterioration in input/output characteristics of the secondary battery.
スルホランの誘導体としては、スルホラン環を構成する炭素原子に結合する水素原子がフッ素原子やアルキル基等により置換されたものが挙げられる。具体例として、フルオロスルホラン、ジフルオロスルホラン、メチルスルホラン等の材料群から適宜選択して用いることができる。これら溶媒に対して、六フッ化リン酸リチウム、四フッ化ホウ酸リチウム、過塩素酸リチウム、ヨウ化リチウム、塩化リチウム、臭化リチウム、LiB[OCOCF3]4、LiB[OCOCF2CF3]4、LiPF4(CF3)2、LiN(SO2CF3)2、LiN(SO2CF2CF3)2等のリチウム塩を溶解した電解液が挙げられる。あるいは、前記の2種以上の混合リチウム塩を溶解した電解液が挙げられる。
Examples of sulfolane derivatives include those in which hydrogen atoms bonded to carbon atoms constituting the sulfolane ring are substituted with fluorine atoms, alkyl groups, or the like. As a specific example, it can be used by appropriately selecting from a group of materials such as fluorosulfolane, difluorosulfolane, and methylsulfolane. For these solvents, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium iodide, lithium chloride, lithium bromide, LiB[ OCOCF3 ] 4 , LiB[ OCOCF2CF3 ] 4 , LiPF 4 (CF 3 ) 2 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 CF 2 CF 3 ) 2 and other lithium salts dissolved therein. Alternatively, an electrolytic solution in which two or more of the above mixed lithium salts are dissolved can be used.
[二次電池システム]
図3は、好適な実施形態による二次電池システム500のブロック図である。
二次電池システム500は、電池パック510と、電流制御装置550と、を備えている。電池パック510は、電池セル・モジュール512(二次電池)と、電池加熱部514と、を備えている。電池セル・モジュール512は、1個の電池セル100(図1参照)であってもよく、複数の電池セル100を直列および/または並列に接続したものであってもよい。本明細書において、「二次電池」は、リチウムイオン電池のセル、電池モジュール、または電池パックを含む概念である。電池加熱部514は、電流制御装置550からの指令に基づいて電池セル・モジュール512を加熱する。但し、電池加熱部514は必須のものではなく、省略してもよい。 [Secondary battery system]
FIG. 3 is a block diagram of asecondary battery system 500 according to a preferred embodiment.
Asecondary battery system 500 includes a battery pack 510 and a current control device 550 . The battery pack 510 includes a battery cell module 512 (secondary battery) and a battery heating section 514 . The battery cell module 512 may be a single battery cell 100 (see FIG. 1), or multiple battery cells 100 connected in series and/or in parallel. As used herein, the term "secondary battery" is a concept that includes lithium-ion battery cells, battery modules, and battery packs. Battery heating unit 514 heats battery cell module 512 based on a command from current control device 550 . However, the battery heating unit 514 is not essential and may be omitted.
図3は、好適な実施形態による二次電池システム500のブロック図である。
二次電池システム500は、電池パック510と、電流制御装置550と、を備えている。電池パック510は、電池セル・モジュール512(二次電池)と、電池加熱部514と、を備えている。電池セル・モジュール512は、1個の電池セル100(図1参照)であってもよく、複数の電池セル100を直列および/または並列に接続したものであってもよい。本明細書において、「二次電池」は、リチウムイオン電池のセル、電池モジュール、または電池パックを含む概念である。電池加熱部514は、電流制御装置550からの指令に基づいて電池セル・モジュール512を加熱する。但し、電池加熱部514は必須のものではなく、省略してもよい。 [Secondary battery system]
FIG. 3 is a block diagram of a
A
電池パック510は、正極端子502と、負極端子503と、を備えている。電池セル・モジュール512が1個の電池セル100のみを備える場合、正極端子502および負極端子503は、それぞれ電池セル100の正極端子2および負極端子3(図1参照)に対応する。一方、電池セル・モジュール512において複数の電池セル100が直列接続されている場合、正極端子502は最も高電圧である電池セル100の正極端子2に対応し、負極端子503は最も低電圧である電池セル100の負極端子3に対応する。図3において、電池パック510の正極端子502および負極端子503は、それぞれ電流制御装置550に接続されている。なお、電源554は主として充電用であり、抵抗553は放電用である。
The battery pack 510 has a positive terminal 502 and a negative terminal 503 . If the battery cell module 512 comprises only one battery cell 100, the positive terminal 502 and the negative terminal 503 correspond to the positive terminal 2 and the negative terminal 3 of the battery cell 100 (see FIG. 1), respectively. On the other hand, when a plurality of battery cells 100 are connected in series in the battery cell module 512, the positive terminal 502 corresponds to the positive terminal 2 of the battery cell 100 with the highest voltage, and the negative terminal 503 has the lowest voltage. It corresponds to the negative electrode terminal 3 of the battery cell 100 . In FIG. 3, positive terminal 502 and negative terminal 503 of battery pack 510 are each connected to current controller 550 . Note that the power source 554 is mainly for charging, and the resistor 553 is for discharging.
電流制御装置550は、電流計551と、電圧計552と、抵抗553と、電源554と、スイッチ560,562,564と、制御部570(コンピュータ)と、を備えている。電流制御装置550は、電池パック510の状態を把握する計測器を兼ねている。
The current control device 550 includes an ammeter 551, a voltmeter 552, a resistor 553, a power supply 554, switches 560, 562, 564, and a controller 570 (computer). Current control device 550 also serves as a measuring instrument for grasping the state of battery pack 510 .
電流計551は、電池パック510の正極端子502および負極端子503に流れる電流を測定し、その結果を制御部570に出力する。電圧計552は、正極・負極間の電圧Evを測定し、その結果を制御部570に出力する。制御部570は、電流計551および電圧計552の情報に基づいて、スイッチ560,562,564を切替制御する。これにより、制御部570は、電池パック510の正極端子502および負極端子503を、開放状態、抵抗553を接続した状態、または電源554を接続した状態に設定する。
The ammeter 551 measures the current flowing through the positive terminal 502 and the negative terminal 503 of the battery pack 510 and outputs the result to the control section 570 . The voltmeter 552 measures the voltage Ev between the positive electrode and the negative electrode and outputs the result to the control section 570 . Control unit 570 switches and controls switches 560 , 562 and 564 based on information from ammeter 551 and voltmeter 552 . As a result, control unit 570 sets positive terminal 502 and negative terminal 503 of battery pack 510 to an open state, a state in which resistor 553 is connected, or a state in which power source 554 is connected.
制御部570は、CPU(Central Processing Unit)、RAM(Random Access Memory)、ROM(Read Only Memory)等、一般的なコンピュータとしてのハードウエアを備えており、ROMには、CPUによって実行される制御プログラムや、各種データ等が格納されている。図3において、制御部570の内部は、制御プログラム等によって実現される機能を、ブロックとして示している。
The control unit 570 includes general computer hardware such as a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). Programs, various data, etc. are stored. In FIG. 3, the inside of the control unit 570 shows functions realized by control programs and the like as blocks.
すなわち、制御部570は、充放電処理部572(充放電処理手段)と、容量回復処理部574(容量回復処理手段)と、パラメータ更新部580(パラメータ更新手段)と、を備えている。また、パラメータ更新部580は、充放電曲線取得部582と、相関関係取得部584と、放電量取得部586と、パラメータ決定部588と、を含んでいる。
That is, the control unit 570 includes a charge/discharge processing unit 572 (charge/discharge processing means), a capacity recovery processing unit 574 (capacity recovery processing means), and a parameter update unit 580 (parameter update means). Parameter updater 580 also includes a charge/discharge curve acquirer 582 , a correlation acquirer 584 , a discharge amount acquirer 586 , and a parameter determiner 588 .
充放電処理部572は、予め定められた制御パラメータに基づいて、通常のアプリケーションに応じた電池パック510の充放電運転を行う。例えば、電池パック510が車両の駆動用に用いられるのであれば、充放電処理部572は、車両の走行のための充放電運転を行う。上述した制御パラメータには、「放電停止電圧」が含まれる。充放電処理部572は、電池パック510が放電されている際、電圧Evがこの放電停止電圧以下になると、電池パック510の放電を停止させる。ここで、放電停止電圧は、1個の電池セル100あたりの端子電圧が例えば2.5V以下になる電圧である。
The charging/discharging processing unit 572 performs charging/discharging operation of the battery pack 510 according to normal applications based on predetermined control parameters. For example, if the battery pack 510 is used for driving the vehicle, the charging/discharging processing unit 572 performs charging/discharging operation for driving the vehicle. The control parameters described above include the "discharge stop voltage". When the voltage Ev becomes equal to or lower than the discharge stop voltage while the battery pack 510 is being discharged, the charge/discharge processing unit 572 stops the discharge of the battery pack 510 . Here, the discharge stop voltage is a voltage at which the terminal voltage per battery cell 100 becomes 2.5 V or less, for example.
容量回復処理部574は、容量回復処理を実行する。ここで、容量回復処理とは、正極端子502と負極端子503との間に電源554または抵抗553を接続し、電池パック510を過放電状態にする処理を含む。「過放電状態」とは、電圧Evを放電停止電圧未満にすることを意味する。例えば、容量回復処理は、1個の電池セル100あたりの端子電圧が2.0V以下に維持する処理を含む。詳細は後述するが、これにより、負極13の内部にて不活性化したリチウムイオンを再活性化することができ、その容量を回復させることができる。
The capacity recovery processing unit 574 executes capacity recovery processing. Here, the capacity recovery process includes a process of connecting the power supply 554 or the resistor 553 between the positive electrode terminal 502 and the negative electrode terminal 503 to bring the battery pack 510 into an over-discharged state. "Overdischarge state" means that the voltage Ev is made less than the discharge stop voltage. For example, the capacity recovery process includes a process of maintaining the terminal voltage per battery cell 100 at 2.0 V or less. Although the details will be described later, this makes it possible to reactivate lithium ions that have been inactivated inside the negative electrode 13 and restore the capacity thereof.
パラメータ更新部580は、電池パック510の容量回復処理後に、電池性能を非破壊で解析し、その際に得られる負極性能データ等に基づいて、その後に充放電処理部572が行う充放電制御における制御パラメータを決定し、更新する。
充放電曲線取得部582は、制御パラメータを決定するために、電池パック510の充放電曲線を取得する。ここで、充放電曲線とは、充電曲線または放電曲線である。 After the capacity recovery processing of thebattery pack 510, the parameter update unit 580 non-destructively analyzes the battery performance, and based on the negative electrode performance data etc. obtained at that time, Determine and update control parameters.
Charge-dischargecurve acquisition unit 582 acquires the charge-discharge curve of battery pack 510 in order to determine control parameters. Here, the charge/discharge curve is a charge curve or a discharge curve.
充放電曲線取得部582は、制御パラメータを決定するために、電池パック510の充放電曲線を取得する。ここで、充放電曲線とは、充電曲線または放電曲線である。 After the capacity recovery processing of the
Charge-discharge
相関関係取得部584は、この充放電曲線に基づいて、電池パック510の放電量(または充電率)と、負極電位En(図1参照)との相関関係を取得する。なお、「放電量=0」の状態は「充電率=100%」の状態であり、放電量が最大値になる状態は「充電率=0%」の状態になる。
The correlation acquisition unit 584 acquires the correlation between the discharge amount (or charging rate) of the battery pack 510 and the negative electrode potential En (see FIG. 1) based on this charge/discharge curve. The state of "discharged amount = 0" is the state of "charge rate = 100%", and the state where the discharged amount reaches the maximum value is the state of "charge rate = 0%".
詳細は後述するが、リチウムイオン電池には、放電量Q(図6参照)の変化に対して、負極電位Enが平坦になる領域が存在する。これらを平坦部PT1(第1の平坦部),PT2(第2の平坦部)と呼び、平坦部PT1,PT2における負極電位EnをそれぞれEn1(第1の電位),En2(第2の電位)と呼ぶ。放電量取得部586は、平坦部PT1,PT2に対応する放電量Qまたは充電率の範囲を取得する。
Although the details will be described later, the lithium ion battery has a region where the negative electrode potential En becomes flat with respect to changes in the discharge amount Q (see FIG. 6). These are called flat portions PT1 (first flat portion) and PT2 (second flat portion). call. The discharge amount acquisition unit 586 acquires the discharge amount Q or the charge rate range corresponding to the flat portions PT1 and PT2.
パラメータ決定部588は、上述の充放電処理部572が行う充放電制御において、上述した平坦部PT1以上の範囲、すなわち負極電位EnがEn1以上になる充電率の範囲で電池パック510を充放電させるように、制御パラメータを決定し、更新する。このように、パラメータ更新部580は、電池性能の非破壊解析手法として、充放電曲線を取得し、その形状を解析する。以降、この解析方法を「充放電曲線解析」と称することがある。
In the charging/discharging control performed by the charging/discharging processing unit 572, the parameter determination unit 588 charges and discharges the battery pack 510 within the above-described range of the flat portion PT1 or more, that is, the charging rate range where the negative electrode potential En is equal to or greater than En1. Determine and update the control parameters as follows. In this way, the parameter updating unit 580 acquires the charge/discharge curve and analyzes its shape as a non-destructive analysis method for battery performance. Henceforth, this analysis method may be called "charge-discharge curve analysis."
[過放電による電池容量回復の推定メカニズムと課題]
図4は、過放電処理による容量回復に関する推定メカニズムの模式図である。
図4において、状態STAは、容量が低下した電池セル100に対して、容量回復処理を行っている状態であり、状態STBは容量回復処理が完了した後の状態である。電池セル100の負極13のうち正極12に対向する部分を対向部13Aと呼び、それ以外の部分を非対向部13Bと呼ぶ。 [Estimation mechanism and problem of battery capacity recovery due to overdischarge]
FIG. 4 is a schematic diagram of a presumed mechanism regarding capacity recovery by overdischarge treatment.
In FIG. 4, state STA is a state in which capacity recovery processing is being performed on thebattery cell 100 whose capacity has decreased, and state STB is a state after the capacity recovery processing is completed. A portion of the negative electrode 13 of the battery cell 100 that faces the positive electrode 12 is called a facing portion 13A, and the other portion is called a non-facing portion 13B.
図4は、過放電処理による容量回復に関する推定メカニズムの模式図である。
図4において、状態STAは、容量が低下した電池セル100に対して、容量回復処理を行っている状態であり、状態STBは容量回復処理が完了した後の状態である。電池セル100の負極13のうち正極12に対向する部分を対向部13Aと呼び、それ以外の部分を非対向部13Bと呼ぶ。 [Estimation mechanism and problem of battery capacity recovery due to overdischarge]
FIG. 4 is a schematic diagram of a presumed mechanism regarding capacity recovery by overdischarge treatment.
In FIG. 4, state STA is a state in which capacity recovery processing is being performed on the
電池セル100等のリチウムイオン二次電池では、正極12と、負極13の対向部13Aとの間でリチウムイオン22の授受が進行することで充放電が進行する。しかし、充放電過程において、正極と対向していない非対向部13Bにリチウムイオン22が取り込まれると、充放電に寄与しない(図中ではハッチを付した)金属リチウム24となり、これが容量低下の要因となる。
In a lithium-ion secondary battery such as the battery cell 100, charging and discharging proceeds as the transfer of lithium ions 22 between the positive electrode 12 and the facing portion 13A of the negative electrode 13 progresses. However, when the lithium ions 22 are taken into the non-facing portion 13B that does not face the positive electrode in the charging/discharging process, they become metal lithium 24 (hatched in the figure) that does not contribute to the charging/discharging, which is a factor in the decrease in capacity. becomes.
ここで、容量回復処理を行う場合は、例えば状態STAに示すように、電池セル100に対して直流電源30を逆極性に接続する。すなわち、直流電源30の正極を負極13に接続し、直流電源30の負極を正極12に接続すると、電池セル100が過放電状態になる。但し、電池電圧Epn=Ep-Enを、2.5V未満にすれば、直流電源30は必ずしも逆極性でなくてもよい。
Here, when the capacity recovery process is performed, the DC power supply 30 is connected to the battery cell 100 in reverse polarity, for example, as shown in the state STA. That is, when the positive electrode of the DC power source 30 is connected to the negative electrode 13 and the negative electrode of the DC power source 30 is connected to the positive electrode 12, the battery cell 100 is over-discharged. However, if the battery voltage Epn=Ep-En is less than 2.5V, the DC power supply 30 does not necessarily have the reverse polarity.
このように、負極電位Enが高くなると、対向部13Aにおける放電反応が進行し、リチウムイオン22が対向部13Aから放出される。また、非対向部13Bからも金属リチウム24がリチウムイオン22となって放出される。但し、その後に電池セル100を充電する場合には、電池セル100に対して、状態STAとは逆方向に直流電源30が接続される。これにより、負極電位Enが低下すると、非対向部13Bに再びリチウムイオン22が取り込まれ、電池セル100の容量が低下することが懸念される。
As described above, when the negative electrode potential En increases, the discharge reaction in the facing portion 13A proceeds, and the lithium ions 22 are released from the facing portion 13A. Metal lithium 24 is also released as lithium ions 22 from the non-facing portion 13B. However, when charging the battery cell 100 after that, the DC power supply 30 is connected to the battery cell 100 in the direction opposite to the state STA. As a result, when the negative electrode potential En drops, the lithium ions 22 are taken into the non-facing portion 13B again, and there is concern that the capacity of the battery cell 100 may drop.
そこで、容量回復処理が終了した後、負極電位Enをある程度高くしておくと好ましい。状態STBは、容量回復処理の終了後に、負極電位Enをある程度高く保っている状態である。負極電位Enが高くなると、負極13の内部に電位差が生じ、対向部13Aの電位が非対向部13Bの電位よりも若干高くなる。すると、非対向部13Bに吸着されている金属リチウム24から電子26が対向部13Aに移動する。これにより、金属リチウム24はリチウムイオン22となって非対向部13Bから離脱し、これによって再び充放電に寄与するようになる。
Therefore, it is preferable to increase the negative electrode potential En to some extent after the capacity recovery process is completed. State STB is a state in which the negative electrode potential En is kept high to some extent after the end of the capacity recovery process. When the negative electrode potential En increases, a potential difference occurs inside the negative electrode 13, and the potential of the opposing portion 13A becomes slightly higher than the potential of the non-facing portion 13B. Then, the electrons 26 move from the metallic lithium 24 adsorbed to the non-opposed portion 13B to the opposed portion 13A. As a result, the metallic lithium 24 becomes the lithium ion 22 and leaves the non-facing portion 13B, thereby contributing to charging and discharging again.
[電池セル100の充放電曲線]
図6は電池セル100の充放電曲線の一例である。
図6では、正極12にLiwNixCoyMnzO2(ここで、w、x、y、zは0または正の値)、負極に黒鉛を用いたリチウムイオン電池の例を示した。図6の左側の縦軸は電位はまた電圧(V)であり、右側の縦軸はリチウム電極基準の電位であり、横軸は放電量Q(Ah)である。ここで、リチウム電極基準とは、リチウムの標準電極電位を基準とした電位であり、リチウムの標準電極電位とは、「Li++e-←→Li」で表される化学反応における標準電極電位を意味する。図6において電池電圧Epnの曲線に沿った多数の小円(符号なし)は、電池電圧Epnの計測値であり、電池電圧Epnの曲線は、該計測値の補間結果である。また、図示の正極電位Epおよび負極電位Enの曲線も、各々の計測値(図示略)の補間結果である。上述のように、放電量Q=0の状態が満充電状態に相当する。 [Charging and discharging curve of battery cell 100]
FIG. 6 is an example of a charge/discharge curve of thebattery cell 100. FIG.
FIG. 6 shows an example of a lithium ion battery using LiwNixCoyMnzO2 ( where w , x , y , and z are 0 or positive values) for thepositive electrode 12 and graphite for the negative electrode. . The vertical axis on the left side of FIG. 6 is the potential or voltage (V), the vertical axis on the right side is the potential with respect to the lithium electrode, and the horizontal axis is the discharge amount Q (Ah). Here, the lithium electrode reference is a potential based on the standard electrode potential of lithium, and the standard electrode potential of lithium is the standard electrode potential in the chemical reaction represented by “Li + + e − ←→ Li”. means. A large number of small circles (unsigned) along the curve of the battery voltage Epn in FIG. 6 are the measured values of the battery voltage Epn, and the curve of the battery voltage Epn is the interpolation result of the measured values. The curves of the positive electrode potential Ep and the negative electrode potential En shown in the figure are also interpolation results of the respective measured values (not shown). As described above, the state of the discharged amount Q=0 corresponds to the fully charged state.
図6は電池セル100の充放電曲線の一例である。
図6では、正極12にLiwNixCoyMnzO2(ここで、w、x、y、zは0または正の値)、負極に黒鉛を用いたリチウムイオン電池の例を示した。図6の左側の縦軸は電位はまた電圧(V)であり、右側の縦軸はリチウム電極基準の電位であり、横軸は放電量Q(Ah)である。ここで、リチウム電極基準とは、リチウムの標準電極電位を基準とした電位であり、リチウムの標準電極電位とは、「Li++e-←→Li」で表される化学反応における標準電極電位を意味する。図6において電池電圧Epnの曲線に沿った多数の小円(符号なし)は、電池電圧Epnの計測値であり、電池電圧Epnの曲線は、該計測値の補間結果である。また、図示の正極電位Epおよび負極電位Enの曲線も、各々の計測値(図示略)の補間結果である。上述のように、放電量Q=0の状態が満充電状態に相当する。 [Charging and discharging curve of battery cell 100]
FIG. 6 is an example of a charge/discharge curve of the
FIG. 6 shows an example of a lithium ion battery using LiwNixCoyMnzO2 ( where w , x , y , and z are 0 or positive values) for the
充放電曲線における電池電圧Epnは、開回路電圧に近い値であることが望ましい。充放電曲線の構成方法は任意でよいが、例えば微小かつ一定の電流で満充電状態から全放電状態まで放電し、もしくは全放電状態から満充電状態まで充電する方法がある。または、一定の電流で一定時間放電した後に一定時間休止するサイクルを満充電状態から全放電状態まで繰り返し、もしくは一定の電流で一定時間充電した後に一定時間休止するサイクルを全放電状態から満充電状態まで繰り返すことにより、充放電量と開回路電圧の関係を測定する方法がある。または、運転中の電流波形および電圧波形を統計的に処理し、もしくは等価回路に基づき回帰計算して開回路電圧を推定し、充放電量と開回路電圧の関係を推定する方法もある。
It is desirable that the battery voltage Epn in the charge/discharge curve is a value close to the open circuit voltage. The charging/discharging curve may be formed by any method, but for example, there is a method of discharging from a fully charged state to a fully discharged state or charging from a fully discharged state to a fully charged state with a minute and constant current. Alternatively, the cycle of discharging at a constant current for a certain period of time and then resting for a certain period of time is repeated from a fully charged state to a fully discharged state, or the cycle of charging at a constant current for a certain period of time and then resting for a certain period of time is repeated from a fully discharged state to a fully charged state. There is a method of measuring the relationship between the charge/discharge amount and the open circuit voltage by repeating up to. Alternatively, there is a method of estimating the open circuit voltage by statistically processing current waveforms and voltage waveforms during operation, or performing regression calculations based on an equivalent circuit, and estimating the relationship between the charge/discharge amount and the open circuit voltage.
通常、正極電位Epは負極電位Enに対して十分高く設定されている。負極13に黒鉛を用いた二極式電池セルでは、負極電位Enに対する正極電位Epの値、すなわち電池電圧Epn(=Ep-En)は2.5~4.5Vの範囲となり、寿命や安全性の観点で、例えば2.5~4.2Vの範囲をとることが多い。ここで、電池電圧Epnが下限電圧の2.5V未満、すなわち過放電状態となると、負極電位Enが相対的に高まる。そして、負極電位Enが負極表面の皮膜を分解する電位まで高まると、皮膜分解によって電池性能回復が生じる。また、負極電位Enの低下により非対向部13B(図4参照)に取り込まれたリチウムイオンが負極活物質から放出されることで容量が回復する。
The positive electrode potential Ep is normally set sufficiently higher than the negative electrode potential En. In a bipolar battery cell using graphite for the negative electrode 13, the value of the positive electrode potential Ep with respect to the negative electrode potential En, that is, the battery voltage Epn (=Ep-En) is in the range of 2.5 to 4.5 V, and the life and safety are improved. from the point of view, it is often in the range of, for example, 2.5 to 4.2V. Here, when the battery voltage Epn is less than the lower limit voltage of 2.5 V, that is, when the battery is in an overdischarged state, the negative electrode potential En is relatively increased. Then, when the negative electrode potential En rises to a potential that decomposes the film on the surface of the negative electrode, battery performance recovery occurs due to film decomposition. In addition, the lithium ions taken into the non-facing portion 13B (see FIG. 4) are released from the negative electrode active material due to the decrease in the negative electrode potential En, thereby recovering the capacity.
上述の過放電状態のうち、電池電圧Epn<0以下、すなわち正極電位Epに対して負極電位Enが高まると上述の分解が進行しやすくなる。特に、-2<Epn<0.1[V]とすることで反応が進行しやすくなる。しかし、Epn<-2[V]になると、正極および負極の活物質構造が破壊されやすくなり、かえって寿命が低下する。また、電流制御装置550は、電池パック510に対して、過放電電流をパルス状に通流させることができる。その印加時間は特に限定されないが、0.1~30秒を挙げることができる。0.1秒よりも短いと効果が弱く、30秒より長いと、正極および負極活物質構造が破壊されやすくなり、かえって寿命が低下するためである。
In the overdischarged state described above, when the battery voltage Epn<0 or less, that is, when the negative electrode potential En increases with respect to the positive electrode potential Ep, the decomposition described above tends to proceed. In particular, the reaction proceeds more easily by setting −2<Epn<0.1 [V]. However, when Epn<-2 [V], the active material structures of the positive electrode and the negative electrode are likely to be destroyed, resulting in a shorter life. In addition, the current control device 550 can cause the overdischarge current to flow through the battery pack 510 in pulses. The application time is not particularly limited, but may be 0.1 to 30 seconds. If the time is shorter than 0.1 seconds, the effect is weak, and if it is longer than 30 seconds, the positive electrode and negative electrode active material structures are likely to be destroyed, resulting in a shorter life.
図6の負極電位Enの特性において、負極電位Enは、放電量Qが低容量側(放電量Qが大きい側)から高容量側(放電量Qが小さい側)に推移すると、階段状に変化する。ここで図中の放電量Qが0近傍から0.1Ah近傍で現れる平坦部をPT1と呼ぶ。また、放電量Qが0未満の領域に現れる平坦部をPT2と呼ぶ。
In the characteristics of the negative electrode potential En in FIG. 6, the negative electrode potential En changes stepwise as the discharge amount Q shifts from the low capacity side (the side where the discharge amount Q is large) to the high capacity side (the side where the discharge amount Q is small). do. Here, a flat portion appearing when the amount of discharge Q in the drawing is near 0 to near 0.1 Ah is called PT1. A flat portion appearing in a region where the discharge amount Q is less than 0 is called PT2.
図7は、図6の充放電曲線における変化率を示す図である。
図7の縦軸は、電圧または電位の放電量Qに対する変化率である。ここで、Epn、Ep、Enに対応する変化率は、それぞれEpn’=|dEpn/dQ|、Ep’=|dEp/dQ|、およびEn’=|dEn/dQ|となる値である。図7に示したように、電池電圧Epnの変化率Epn’には複数の極値が存在する。これら極値は正極電位Epの変化率Ep’の極値、または負極電位Enの変化率En’の極値に起因する。 FIG. 7 is a diagram showing the rate of change in the charge/discharge curve of FIG.
The vertical axis of FIG. 7 represents the rate of change of the voltage or potential with respect to the amount Q of discharge. Here, the rates of change corresponding to Epn, Ep, and En are values such that Epn'=|dEpn/dQ|, Ep'=|dEp/dQ|, and En'=|dEn/dQ|, respectively. As shown in FIG. 7, the rate of change Epn' of the battery voltage Epn has a plurality of extreme values. These extreme values are caused by the extreme values of the change rate Ep' of the positive electrode potential Ep or the extreme values of the change rate En' of the negative electrode potential En.
図7の縦軸は、電圧または電位の放電量Qに対する変化率である。ここで、Epn、Ep、Enに対応する変化率は、それぞれEpn’=|dEpn/dQ|、Ep’=|dEp/dQ|、およびEn’=|dEn/dQ|となる値である。図7に示したように、電池電圧Epnの変化率Epn’には複数の極値が存在する。これら極値は正極電位Epの変化率Ep’の極値、または負極電位Enの変化率En’の極値に起因する。 FIG. 7 is a diagram showing the rate of change in the charge/discharge curve of FIG.
The vertical axis of FIG. 7 represents the rate of change of the voltage or potential with respect to the amount Q of discharge. Here, the rates of change corresponding to Epn, Ep, and En are values such that Epn'=|dEpn/dQ|, Ep'=|dEp/dQ|, and En'=|dEn/dQ|, respectively. As shown in FIG. 7, the rate of change Epn' of the battery voltage Epn has a plurality of extreme values. These extreme values are caused by the extreme values of the change rate Ep' of the positive electrode potential Ep or the extreme values of the change rate En' of the negative electrode potential En.
図6に示した負極電位Enの平坦部PT1,PT2は、図7においては一層明確に表れている。すなわち、平坦部PT1,PT2は、変化率En’が「0」になる範囲を含んでおり、平坦部PT1,PT2の間には、変化率En’が0より大きくなる範囲を含んでいる。なお、平坦部PT1,PT2の名称は、本実施形態を説明するうえで便宜的につけたものであり、その名称が異なっていてもよい。
The flat portions PT1 and PT2 of the negative electrode potential En shown in FIG. 6 appear more clearly in FIG. That is, the flat portions PT1 and PT2 include a range in which the rate of change En' is "0", and a range in which the rate of change En' is greater than 0 is included between the flat portions PT1 and PT2. Note that the names of the flat portions PT1 and PT2 are given for convenience in describing the present embodiment, and the names may be different.
図6および図7に示した電池電圧Epnおよびその変化率Epn’は、正極電位Ep、負極電位En、およびこれらの変化率Ep’,En’の差分に相当する。そのため、予め放電量Qと、これらの値との相関関係を取得しておき、この相関関係に対して実測値をフィッティングすることで、正極12および負極13の劣化状態を把握することができる。上述したように、パラメータ更新部580(図3参照)は、特に負極電位Enと放電量Qとの関係性を示した曲線を用いることで、容量回復処理後の充放電条件を決定する。
The battery voltage Epn and its change rate Epn' shown in FIGS. 6 and 7 correspond to the positive electrode potential Ep, the negative electrode potential En, and the difference between these change rates Ep' and En'. Therefore, the deterioration state of the positive electrode 12 and the negative electrode 13 can be grasped by obtaining the correlation between the discharge amount Q and these values in advance and fitting the measured value to this correlation. As described above, the parameter updating unit 580 (see FIG. 3) determines the charge/discharge conditions after the capacity recovery process, particularly by using the curve showing the relationship between the negative electrode potential En and the discharge amount Q.
図6において、平坦部PT1,PT2における負極電位Enは、その境界点(図6では0Ah近傍)で大きく変化しており、平坦部PT2では、負極電位Enが平坦部PT1よりも相当に低くなる。従って、負極電位Enが平坦部PT2になる条件で充放電を行うと、負極13の非対向部13B(図4の状態STA参照)にリチウムイオン22が多く取り込まれ、回復した容量が即座に低下してしまう。
In FIG. 6, the negative electrode potential En in the flat portions PT1 and PT2 changes greatly at the boundary point (near 0Ah in FIG. 6), and the negative electrode potential En in the flat portion PT2 is considerably lower than that in the flat portion PT1. . Therefore, when charging and discharging are performed under the condition that the negative electrode potential En becomes the flat portion PT2, many lithium ions 22 are taken into the non-facing portion 13B of the negative electrode 13 (see state STA in FIG. 4), and the recovered capacity immediately decreases. Resulting in.
そこで、本実施形態においては、負極電位Enが平坦部PT1を下回らないように、充電状態および電池電圧Epnを管理し、これによって容量回復後の容量低下を軽減することができる。上述のように、平坦部PT1,PT2の境界は、図7に示した変化率Epn’,En’の特性において、容易に判別できる。すなわち、変化率Epn’,En’において、大きな極値が得られる放電量Qよりも低充電率側(放電量Qが大きい側)で充放電運用することが望ましい。
Therefore, in the present embodiment, the state of charge and the battery voltage Epn are managed so that the negative electrode potential En does not fall below the flat portion PT1, thereby reducing the capacity decrease after the capacity recovery. As described above, the boundaries between the flat portions PT1 and PT2 can be easily determined from the characteristics of the change rates Epn' and En' shown in FIG. That is, it is desirable to charge and discharge at a lower charging rate side (larger discharge amount Q side) than the discharge amount Q at which a large extreme value is obtained in the change rates Epn' and En'.
この際、平坦部PT1での負極電位Enとしては、リチウム電極基準で0.1Vから0.2Vの範囲であることが望ましい。負極電位Enがリチウム電極基準で0.1Vよりも低いと、負極13でのリチウム不活性化が進行する。一方、負極電位Enがリチウム電極基準で0.2Vよりも高いと、十分な電池容量が得られないことがある。パラメータ更新部580は、上記の方法で、容量回復処理後の最適な電池充放電条件を決定する。
At this time, the negative electrode potential En at the flat portion PT1 is preferably in the range of 0.1 V to 0.2 V based on the lithium electrode. When the negative electrode potential En is lower than 0.1 V based on the lithium electrode, lithium deactivation at the negative electrode 13 proceeds. On the other hand, when the negative electrode potential En is higher than 0.2 V based on the lithium electrode, a sufficient battery capacity may not be obtained. The parameter updating unit 580 determines the optimum battery charging/discharging conditions after the capacity recovery process by the method described above.
[実施形態の動作]
図5は、制御部570で実行される制御プログラムのフローチャートである。
図5において処理がステップS2に進むと、充放電処理部572は、通常のアプリケーションに応じた電池パック510の充放電運転を行う。その際、充放電処理部572は、電圧Ev(図3参照)または電池電圧Epn(図1参照)と、放電量Qと、を所定のサンプリング期間毎に記録する。 [Operation of Embodiment]
FIG. 5 is a flow chart of a control program executed by thecontrol unit 570. As shown in FIG.
When the process proceeds to step S2 in FIG. 5, the charging/dischargingprocessing unit 572 performs charging/discharging operation of the battery pack 510 according to the normal application. At that time, the charge/discharge processing unit 572 records the voltage Ev (see FIG. 3) or the battery voltage Epn (see FIG. 1) and the discharge amount Q for each predetermined sampling period.
図5は、制御部570で実行される制御プログラムのフローチャートである。
図5において処理がステップS2に進むと、充放電処理部572は、通常のアプリケーションに応じた電池パック510の充放電運転を行う。その際、充放電処理部572は、電圧Ev(図3参照)または電池電圧Epn(図1参照)と、放電量Qと、を所定のサンプリング期間毎に記録する。 [Operation of Embodiment]
FIG. 5 is a flow chart of a control program executed by the
When the process proceeds to step S2 in FIG. 5, the charging/discharging
次に、処理がステップS4に進むと、充放電曲線取得部582は、先述の充放電曲線解析によって、電池パック510の劣化状態、すなわち電池パック510の容量低下状況を把握する。次に、処理がステップS6に進むと、容量回復処理部574は、電池パック510の劣化状態に応じて、電池パック510の容量回復量を決定する。さらに、ステップS6において、容量回復処理部574は、決定した容量回復量に基づいて、電池パック510の過放電条件を決定する。
Next, when the process proceeds to step S4, the charge/discharge curve acquisition unit 582 grasps the state of deterioration of the battery pack 510, that is, the state of decrease in the capacity of the battery pack 510, by the charge/discharge curve analysis described above. Next, when the process proceeds to step S<b>6 , capacity recovery processing unit 574 determines the capacity recovery amount of battery pack 510 according to the state of deterioration of battery pack 510 . Furthermore, in step S6, capacity recovery processing unit 574 determines an overdischarge condition for battery pack 510 based on the determined capacity recovery amount.
次に、処理がステップS8に進むと、容量回復処理部574は、容量回復処理を行う。すなわち、決定された過放電条件に基づいて、電池パック510を過放電させる。また、充放電処理部572は、電圧Ev(図3参照)または電池電圧Epn(図1参照)と、放電量Qと、を所定のサンプリング期間毎に記録する。次に、処理がステップS10に進むと、パラメータ更新部580は、過放電した後の電池パック510の負極充放電曲線を取得し、その解析を行う。より詳細には、充放電曲線取得部582が図6の電池電圧Epnの充放電曲線を取得し、相関関係取得部584が放電量Q(または充電率)と負極電位Enとの相関関係、すなわち図6の負極電位Enの充放電曲線を取得する。そして、放電量取得部586が、平坦部PT1に対応する放電量Qまたは充電率の範囲を取得する。
Next, when the process proceeds to step S8, the capacity recovery processing section 574 performs capacity recovery processing. That is, battery pack 510 is over-discharged based on the determined over-discharge condition. Also, the charge/discharge processing unit 572 records the voltage Ev (see FIG. 3) or the battery voltage Epn (see FIG. 1) and the discharge amount Q for each predetermined sampling period. Next, when the process proceeds to step S10, parameter updating unit 580 acquires the negative electrode charge/discharge curve of battery pack 510 after overdischarge and analyzes it. More specifically, the charge/discharge curve acquisition unit 582 acquires the charge/discharge curve of the battery voltage Epn in FIG. A charge/discharge curve of the negative electrode potential En in FIG. 6 is obtained. Then, the discharged amount acquisition unit 586 acquires the discharged amount Q or the range of the charging rate corresponding to the flat portion PT1.
次に、処理がステップS12に進むと、パラメータ更新部580のパラメータ決定部588は、通常のアプリケーションに応じた充放電運転(ステップS2)において、負極電位Enが適切な範囲になるように、制御パラメータを更新する。好ましくは、パラメータ更新部580は、負極電位Enが、平坦部PT1における負極電位En1よりも高くならないように、制御パラメータを更新する。
Next, when the process proceeds to step S12, the parameter determining unit 588 of the parameter updating unit 580 controls the negative electrode potential En to be within an appropriate range in the charge/discharge operation (step S2) according to the normal application. Update parameters. Preferably, parameter updating section 580 updates the control parameters so that negative potential En does not become higher than negative potential En1 in flat portion PT1.
ステップS12が終了すると、処理はステップS2に戻り、制御部570は、通常のアプリケーションに応じた電池パック510の充放電運転を行う。その際、制御部570は、更新された制御パラメータに基づいて電池パック510の充放電を行う。
When step S12 ends, the process returns to step S2, and the control unit 570 performs charge/discharge operation of the battery pack 510 according to normal applications. At that time, control unit 570 charges and discharges battery pack 510 based on the updated control parameters.
[加熱処理]
上述したステップS8の容量回復処理においては、電池加熱部514によって一時的に電池セル・モジュール512を加熱し、容量回復反応速度を高めてもよい。電池加熱部514としては、例えばPTヒータのように、通電による電気エネルギーを熱エネルギーに変換するヒータを適用することができる。より詳細には、非加熱時における電池温度を環境温度Tamb(図示せず)とし、電池加熱部514を用いて回復処理を促進するために適した加熱温度TR(図示せず)まで電池温度を上昇させるとよい。そして、電流制御装置550から、パルス状の電流を電池パック510に供給することで、回復処理を進行させるとよい。 [Heat treatment]
In the capacity recovery process of step S8 described above, thebattery heating unit 514 may temporarily heat the battery cell module 512 to increase the capacity recovery reaction speed. As the battery heating unit 514, for example, a heater such as a PT heater that converts electric energy by energization into thermal energy can be applied. More specifically, the battery temperature when not heated is set to the ambient temperature T amb (not shown), and the battery heating unit 514 is used to heat the battery to a heating temperature T R (not shown) suitable for promoting recovery processing. It is advisable to raise the temperature. Then, it is preferable to advance the recovery process by supplying a pulsed current from the current control device 550 to the battery pack 510 .
上述したステップS8の容量回復処理においては、電池加熱部514によって一時的に電池セル・モジュール512を加熱し、容量回復反応速度を高めてもよい。電池加熱部514としては、例えばPTヒータのように、通電による電気エネルギーを熱エネルギーに変換するヒータを適用することができる。より詳細には、非加熱時における電池温度を環境温度Tamb(図示せず)とし、電池加熱部514を用いて回復処理を促進するために適した加熱温度TR(図示せず)まで電池温度を上昇させるとよい。そして、電流制御装置550から、パルス状の電流を電池パック510に供給することで、回復処理を進行させるとよい。 [Heat treatment]
In the capacity recovery process of step S8 described above, the
電池温度を高めることで、回復にかかるLiイオン拡散や皮膜分解反応が促進され、短時間での回復処理が実現できる。また、電池内部でのLiイオン拡散が促進されることで電池の面内方向ないし厚み方向でのLiイオン分布が均一化されるため、回復処理も電池内で均一化し、結果として長寿命となることが期待できる。ただし、常に電池セル温度を高い状態に保つと、電池内での劣化反応が継続的に進行するため、回復処理後は加熱処理を停止し、リチウムイオン電池の温度を環境温度Tambまで下げることが望ましい。温度を下げる方法については特に限定されないが、自然放冷の他、冷媒や空気を用いた強制冷却で温度を下げることもできる。
By increasing the battery temperature, diffusion of Li ions and film decomposition reaction required for recovery are promoted, and recovery can be performed in a short period of time. In addition, since the diffusion of Li ions inside the battery is promoted, the Li ion distribution in the in-plane direction or thickness direction of the battery is made uniform, so the recovery process is also made uniform within the battery, resulting in a long life. can be expected. However, if the battery cell temperature is kept high all the time, the deterioration reaction in the battery will continue to progress. is desirable. Although the method for lowering the temperature is not particularly limited, the temperature can be lowered by forced cooling using refrigerant or air in addition to natural cooling.
最適な環境温度Tambについて特に限定されるものでないが、電池内部の劣化を抑制するという観点で、40℃未満であることが望ましく、さらに、25℃未満であることが望ましい。電池を使用する外気温の影響で環境温度Tambが10℃未満となることもあり、電池自体の出力性能を低下させる要因となるが、本発明の回復処理には特に影響はない。最適な加熱温度TRについても特に限定されるものではない。Li拡散性や皮膜分解反応速度の促進という観点から、40℃以上であることが望ましく、60℃以上であるとさらに加速されるため望ましい。80℃以上となると反応速度が増すものの、電池を構成する部材そのものへの悪影響も懸念される。
The optimum environmental temperature T amb is not particularly limited, but from the viewpoint of suppressing deterioration inside the battery, it is preferably less than 40°C, and more preferably less than 25°C. The environmental temperature T amb may be less than 10° C. due to the influence of the outside air temperature in which the battery is used, which may cause the output performance of the battery itself to decrease, but does not particularly affect the recovery process of the present invention. The optimum heating temperature T R is also not particularly limited. From the viewpoint of promoting the Li diffusibility and film decomposition reaction rate, the temperature is preferably 40° C. or higher, and is preferably 60° C. or higher because the temperature is further accelerated. If the temperature is 80° C. or higher, the reaction rate increases, but there is concern about adverse effects on the members themselves that constitute the battery.
特に電解質の耐熱性が低い材料であると、加熱温度TRを高くすると、電解質が揮発し、ないし、電気化学的に分解されやすくなる。そのため、耐熱性の高い電解質材料を用いることで本実施形態の二次電池システムの効果が得られやすい。加熱温度TRにおいて電解質が揮発し電池膨れが生じると回復処理が適切に進行しないため、電解質の揮発温度は高いことが望まれる。具体的には、加熱温度TRよりも高い揮発温度を示すことが望ましく、より望ましくは100℃を超える揮発温度を有することが望ましい。具体的な材料としては前述のイオン液体、溶媒和イオン液体を用いた電解質を用いることができる。
In particular, when the heat resistance of the electrolyte is low, increasing the heating temperature T R makes the electrolyte volatilize or easily decompose electrochemically. Therefore, by using an electrolyte material with high heat resistance, the effect of the secondary battery system of the present embodiment can be easily obtained. If the electrolyte volatilizes at the heating temperature T R and the battery swells, the recovery process does not proceed properly, so a high volatilization temperature of the electrolyte is desired. Specifically, it desirably exhibits a volatilization temperature higher than the heating temperature T R , and more desirably has a volatilization temperature exceeding 100°C. As a specific material, the electrolyte using the above-described ionic liquid or solvated ionic liquid can be used.
また、リチウムイオン電池セルの温度を加熱温度TR以上に高める方法として、電池パック510の内部の電池加熱部514ではなく、電池セル・モジュール512の充放電に伴う自己発熱を利用してもよい。リチウムイオン電池の正極と負極の間でやり取りされる通常の充電、放電反応では、電池内部の抵抗(Rcell)、充放電電流(Ibat)に従い、IbatRcell
2であらわされるジュール発熱が発生する。例えば、リチウムイオン電池セルへの急速充電や外部電源への大電流放電時の自己発熱で電池温度がTRを超える際に回復処理を進めることでも同様の効果が得られる。
In addition, as a method of raising the temperature of the lithium ion battery cell to the heating temperature T R or higher, instead of using the battery heating unit 514 inside the battery pack 510, self-heating accompanying charging and discharging of the battery cell module 512 may be used. . In normal charging and discharging reactions exchanged between the positive and negative electrodes of a lithium-ion battery, Joule heating represented by I bat R cell Occur. For example, the same effect can be obtained by proceeding with the recovery process when the battery temperature exceeds T R due to self-heating during rapid charging of the lithium ion battery cell or discharge of large current to the external power supply.
[実施例]
以下、好適な実施例について説明する。
本実施例においては、図2の電池セル構成で、電池パック510(図3参照)としてリチウムイオン電池を試作した。試作したリチウムイオン電池では、揮発温度が20℃のカーボネート溶媒適用の有機電解質を用いた。具体的にはカーボネート系溶媒に1Mの濃度でLiPF6を溶解させたものを用いた。溶媒組成は、エチルカーボネート(EC):ジメチルカーボネート(DMC)= 1:2とした。正極にLiNi1/3Co1/3Mn1/3O2、負極に黒鉛を用いたラミネートセルを作製した。Al集電箔の両面に正極材、Cu集電箔の両面に負極材を塗布し、対向する負極/正極容量比が1.3となるようにした。所定の形状に正極と負極を打ち抜いた後、ポリオレフィン素材の多孔質基材と正極、負極を積層した。正極の容量は片面で約80mAhになり、負極の容量は片面で約90mAhになるように設計した。初期化後の電池パック510の容量は約280mAhであった。 [Example]
Preferred embodiments are described below.
In this example, a lithium-ion battery was experimentally produced as a battery pack 510 (see FIG. 3) with the battery cell configuration shown in FIG. In the prototype lithium ion battery, an organic electrolyte with a carbonate solvent having a volatilization temperature of 20° C. was used. Specifically, a solution obtained by dissolving LiPF6 at a concentration of 1M in a carbonate-based solvent was used. The solvent composition was ethyl carbonate (EC):dimethyl carbonate (DMC)=1:2. A laminate cell was fabricated using LiNi1/3Co1/3Mn1/3O2 for the positive electrode and graphite for the negative electrode. A positive electrode material was applied to both sides of the Al current collecting foil, and a negative electrode material was applied to both sides of the Cu current collecting foil, so that the opposing negative electrode/positive electrode capacity ratio was 1.3. After punching out the positive electrode and the negative electrode into a predetermined shape, the porous base material of polyolefin material, the positive electrode, and the negative electrode were laminated. The capacity of the positive electrode was designed to be about 80 mAh on one side, and the capacity of the negative electrode was designed to be about 90 mAh on one side. The capacity ofbattery pack 510 after initialization was about 280 mAh.
以下、好適な実施例について説明する。
本実施例においては、図2の電池セル構成で、電池パック510(図3参照)としてリチウムイオン電池を試作した。試作したリチウムイオン電池では、揮発温度が20℃のカーボネート溶媒適用の有機電解質を用いた。具体的にはカーボネート系溶媒に1Mの濃度でLiPF6を溶解させたものを用いた。溶媒組成は、エチルカーボネート(EC):ジメチルカーボネート(DMC)= 1:2とした。正極にLiNi1/3Co1/3Mn1/3O2、負極に黒鉛を用いたラミネートセルを作製した。Al集電箔の両面に正極材、Cu集電箔の両面に負極材を塗布し、対向する負極/正極容量比が1.3となるようにした。所定の形状に正極と負極を打ち抜いた後、ポリオレフィン素材の多孔質基材と正極、負極を積層した。正極の容量は片面で約80mAhになり、負極の容量は片面で約90mAhになるように設計した。初期化後の電池パック510の容量は約280mAhであった。 [Example]
Preferred embodiments are described below.
In this example, a lithium-ion battery was experimentally produced as a battery pack 510 (see FIG. 3) with the battery cell configuration shown in FIG. In the prototype lithium ion battery, an organic electrolyte with a carbonate solvent having a volatilization temperature of 20° C. was used. Specifically, a solution obtained by dissolving LiPF6 at a concentration of 1M in a carbonate-based solvent was used. The solvent composition was ethyl carbonate (EC):dimethyl carbonate (DMC)=1:2. A laminate cell was fabricated using LiNi1/3Co1/3Mn1/3O2 for the positive electrode and graphite for the negative electrode. A positive electrode material was applied to both sides of the Al current collecting foil, and a negative electrode material was applied to both sides of the Cu current collecting foil, so that the opposing negative electrode/positive electrode capacity ratio was 1.3. After punching out the positive electrode and the negative electrode into a predetermined shape, the porous base material of polyolefin material, the positive electrode, and the negative electrode were laminated. The capacity of the positive electrode was designed to be about 80 mAh on one side, and the capacity of the negative electrode was designed to be about 90 mAh on one side. The capacity of
上記の電池パック510の劣化試験として、45℃環境で充放電サイクルを300回繰り返し、充放電曲線解析を実行したところ、負極内のリチウムイオンの失活により電池容量が初期容量の70%(約200mAh)低下することが確認された。そこで、容量回復処理として正極電位と負極電位の差分(Ep-En)が-1Vとなるように過電圧電流を供給することで容量が初期容量の3%に相当する10mAh改善することを確認した。その後、再度充放電曲線解析を実行したところ、負極の第一平坦部の電位が0.108VvsLi/Li+であることが明らかとなったため、充放電時の負極電位がこれを下回らないように充放電パターンを更新した。その後、100サイクル繰り返した後の電池容量は初回効率の70%を維持しており、容量回復処理とその後の充放電制御パラメータ更新工程で寿命を25%増加できることが分かった。
As a deterioration test of the battery pack 510 described above, charge-discharge cycles were repeated 300 times in a 45° C. environment, and charge-discharge curve analysis was performed. 200 mAh) was confirmed to decrease. Therefore, it was confirmed that the capacity was improved by 10 mAh, which corresponds to 3% of the initial capacity, by supplying an overvoltage current so that the difference between the positive electrode potential and the negative electrode potential (Ep-En) was -1 V as a capacity recovery process. After that, when the charge-discharge curve analysis was performed again, it was found that the potential of the first flat portion of the negative electrode was 0.108 V vs Li / Li +, so the negative electrode potential during charging and discharging should not fall below this. Updated pattern. After that, it was found that the battery capacity after repeating 100 cycles maintained 70% of the initial efficiency, and the life could be increased by 25% in the capacity recovery process and the subsequent charge/discharge control parameter update process.
[比較例]
次に、比較例について説明する。
本比較例では、電池セルの構成は上述の実施例と同様であり、容量回復処理で初期容量の3%分だけ性能を改善させる段階までは上述の実施例1と同様である。但し、比較例では、充放電制御パラメータを更新せず、負極の電位が、第一平坦部の電位を下回る(0.05V)まで充放電を繰り返した。その結果、容量回復処理の後10サイクルの間に、電池容量が初回効率の70%を下回り、容量回復処理の効果がほとんど見られない結果となった。 [Comparative example]
Next, a comparative example will be described.
In this comparative example, the configuration of the battery cell is the same as in the above-described example, and the steps up to the step of improving the performance by 3% of the initial capacity in the capacity recovery process are the same as in the above-described first example. However, in the comparative example, charging and discharging were repeated until the potential of the negative electrode fell below the potential of the first flat portion (0.05 V) without updating the charging and discharging control parameter. As a result, during 10 cycles after the capacity recovery treatment, the battery capacity fell below 70% of the initial efficiency, resulting in almost no effect of the capacity recovery treatment.
次に、比較例について説明する。
本比較例では、電池セルの構成は上述の実施例と同様であり、容量回復処理で初期容量の3%分だけ性能を改善させる段階までは上述の実施例1と同様である。但し、比較例では、充放電制御パラメータを更新せず、負極の電位が、第一平坦部の電位を下回る(0.05V)まで充放電を繰り返した。その結果、容量回復処理の後10サイクルの間に、電池容量が初回効率の70%を下回り、容量回復処理の効果がほとんど見られない結果となった。 [Comparative example]
Next, a comparative example will be described.
In this comparative example, the configuration of the battery cell is the same as in the above-described example, and the steps up to the step of improving the performance by 3% of the initial capacity in the capacity recovery process are the same as in the above-described first example. However, in the comparative example, charging and discharging were repeated until the potential of the negative electrode fell below the potential of the first flat portion (0.05 V) without updating the charging and discharging control parameter. As a result, during 10 cycles after the capacity recovery treatment, the battery capacity fell below 70% of the initial efficiency, resulting in almost no effect of the capacity recovery treatment.
[実施形態の効果]
以上のように好適な実施形態によれば、二次電池システム500は、一または複数の電池セル100を有する二次電池(512)と、二次電池(512)に対する充電または二次電池(512)からの放電を行う際の電流または電圧の制御条件を規定する制御パラメータに基づいて、二次電池(512)に対する充電処理または二次電池(512)からの放電処理を行う充放電処理部572と、二次電池(512)に対する容量回復処理を行う容量回復処理部574と、容量回復処理の状況に応じて、制御パラメータを更新するパラメータ更新部580と、を備える。このように、容量回復処理の状況に応じて、制御パラメータを更新することにより、二次電池システム500を長寿命化を実現できる。 [Effects of Embodiment]
As described above, according to the preferred embodiment, thesecondary battery system 500 includes a secondary battery (512) having one or more battery cells 100, and a charge or secondary battery (512) for the secondary battery (512). ), the charge/discharge processing unit 572 performs charge processing for the secondary battery (512) or discharge processing from the secondary battery (512) based on control parameters that define current or voltage control conditions when discharging from the secondary battery (512). , a capacity recovery processing unit 574 that performs capacity recovery processing for the secondary battery (512), and a parameter update unit 580 that updates control parameters according to the status of the capacity recovery processing. In this way, by updating the control parameters in accordance with the state of the capacity recovery process, it is possible to extend the life of the secondary battery system 500 .
以上のように好適な実施形態によれば、二次電池システム500は、一または複数の電池セル100を有する二次電池(512)と、二次電池(512)に対する充電または二次電池(512)からの放電を行う際の電流または電圧の制御条件を規定する制御パラメータに基づいて、二次電池(512)に対する充電処理または二次電池(512)からの放電処理を行う充放電処理部572と、二次電池(512)に対する容量回復処理を行う容量回復処理部574と、容量回復処理の状況に応じて、制御パラメータを更新するパラメータ更新部580と、を備える。このように、容量回復処理の状況に応じて、制御パラメータを更新することにより、二次電池システム500を長寿命化を実現できる。 [Effects of Embodiment]
As described above, according to the preferred embodiment, the
また、電池セル100はリチウムイオン電池であり、容量回復処理は、電池セル100の端子電圧を2.0V以下に維持する処理を含むと一層好ましい。このように、電池セル100の端子電圧を2.0V以下に維持することにより、負極表面の皮膜を分解することができ、電池セル100の性能を回復することができる。
Further, it is more preferable that the battery cell 100 is a lithium ion battery and the capacity recovery process includes a process of maintaining the terminal voltage of the battery cell 100 at 2.0 V or less. By maintaining the terminal voltage of the battery cell 100 at 2.0 V or less in this manner, the film on the surface of the negative electrode can be decomposed, and the performance of the battery cell 100 can be recovered.
また、電池セル100は、充電率の変化に対して負極電位Enが第1の電位(En1)で一定になる範囲を含む充電率の領域である第1の平坦部(PT1)と、充電率の変化に対して、第1の電位(En1)よりも低い第2の電位(En2)で負極電位Enが一定になる範囲を含む充電率の領域である第2の平坦部(PT2)と、が現れる性質を有するものであり、制御パラメータは、二次電池(512)の上限電圧を指定する上限電圧指定パラメータを含むものであり、パラメータ更新部580は、各々の電池セル100における負極電位Enが第1の電位(En1)以上になるように上限電圧指定パラメータを更新する機能を有すると一層好ましい。これにより、負極電位Enを高めに保つことができ、長時間に渡って好ましい性能を保つことができる。
In addition, the battery cell 100 has a first flat portion (PT1), which is a charging rate region including a range in which the negative electrode potential En is constant at the first potential (En1) with respect to changes in the charging rate, and a charging rate a second flat portion (PT2), which is a charging rate region including a range in which the negative electrode potential En is constant at a second potential (En2) lower than the first potential (En1) with respect to changes in The control parameters include an upper limit voltage designation parameter that designates the upper limit voltage of the secondary battery (512), and the parameter updating unit 580 updates the negative electrode potential En is more than the first potential (En1), it is more preferable to have a function to update the upper limit voltage designation parameter. As a result, the negative electrode potential En can be kept high, and favorable performance can be maintained for a long period of time.
また、電池セル100はリチウムイオン電池であり、第1の電位(En1)はリチウム電極基準で0.1V以上0.2V以下の電位であると一層好ましい。これにより、リチウムイオン電池である電池セル100に対して、長時間に渡って好ましい性能を保つことができる。
Further, it is more preferable that the battery cell 100 is a lithium ion battery and the first potential (En1) is a potential of 0.1 V or more and 0.2 V or less based on the lithium electrode. As a result, the battery cell 100, which is a lithium ion battery, can maintain favorable performance over a long period of time.
また、パラメータ更新部580は、充電処理または放電処理における二次電池(512)に流れる電流または二次電池(512)に現れる電圧に基づいて、二次電池(512)の充放電曲線を取得する充放電曲線取得部582と、充放電曲線に基づいて、充電率と負極電位Enとの相関関係を取得する相関関係取得部584と、相関関係に基づいて第1の平坦部(PT1)と第2の平坦部(PT2)に対応する充電率を取得する放電量取得部586と、取得した充電率に基づいて、負極電位Enが第1の電位(En1)以上になる充電率範囲で二次電池(512)を充放電させる制御パラメータを決定するパラメータ決定部588と、を備えると一層好ましい。これにより、充放電曲線に基づいた適切な制御パラメータを決定することができる。
Also, the parameter updating unit 580 acquires the charge/discharge curve of the secondary battery (512) based on the current flowing through the secondary battery (512) or the voltage appearing in the secondary battery (512) during the charging process or discharging process. a charge/discharge curve acquisition unit 582; a correlation acquisition unit 584 that acquires the correlation between the charging rate and the negative electrode potential En based on the charge/discharge curve; 2, and based on the obtained charging rate, the negative electrode potential En is the first potential (En1) or higher in the charging rate range where the secondary It is more preferable to have a parameter determination unit 588 that determines control parameters for charging and discharging the battery (512). This makes it possible to determine appropriate control parameters based on the charge/discharge curve.
また、充放電処理部572は、二次電池(512)の放電中に二次電池(512)の端子電圧が所定の放電停止電圧以下になると放電を停止させるものであり、容量回復処理は、電池セル100の端子電圧を放電停止電圧よりも低い電圧に維持する処理を含むと一層好ましい。これのように電池セル100の端子電圧を放電停止電圧よりも低い電圧に維持することにより、負極表面の皮膜を適切に分解することができる。
In addition, the charge/discharge processing unit 572 stops discharging when the terminal voltage of the secondary battery (512) drops below a predetermined discharge stop voltage during discharge of the secondary battery (512). It is more preferable to include a process for maintaining the terminal voltage of the battery cell 100 at a voltage lower than the discharge stop voltage. By maintaining the terminal voltage of the battery cell 100 at a voltage lower than the discharge stop voltage in this manner, the film on the surface of the negative electrode can be appropriately decomposed.
[変形例]
本発明は上述した実施形態に限定されるものではなく、種々の変形が可能である。上述した実施形態は本発明を理解しやすく説明するために例示したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、上記実施形態の構成に他の構成を追加してもよく、構成の一部について他の構成に置換をすることも可能である。また、図中に示した制御線や情報線は説明上必要と考えられるものを示しており、製品上で必要な全ての制御線や情報線を示しているとは限らない。実際には殆ど全ての構成が相互に接続されていると考えてもよい。上記実施形態に対して可能な変形は、例えば以下のようなものである。 [Modification]
The present invention is not limited to the embodiments described above, and various modifications are possible. The above-described embodiments are illustrated for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. Further, other configurations may be added to the configurations of the above embodiments, and part of the configurations may be replaced with other configurations. Also, the control lines and information lines shown in the drawings are those considered to be necessary for explanation, and do not necessarily show all the control lines and information lines necessary on the product. In practice, it may be considered that almost all configurations are interconnected. Possible modifications to the above embodiment are, for example, the following.
本発明は上述した実施形態に限定されるものではなく、種々の変形が可能である。上述した実施形態は本発明を理解しやすく説明するために例示したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、上記実施形態の構成に他の構成を追加してもよく、構成の一部について他の構成に置換をすることも可能である。また、図中に示した制御線や情報線は説明上必要と考えられるものを示しており、製品上で必要な全ての制御線や情報線を示しているとは限らない。実際には殆ど全ての構成が相互に接続されていると考えてもよい。上記実施形態に対して可能な変形は、例えば以下のようなものである。 [Modification]
The present invention is not limited to the embodiments described above, and various modifications are possible. The above-described embodiments are illustrated for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. Further, other configurations may be added to the configurations of the above embodiments, and part of the configurations may be replaced with other configurations. Also, the control lines and information lines shown in the drawings are those considered to be necessary for explanation, and do not necessarily show all the control lines and information lines necessary on the product. In practice, it may be considered that almost all configurations are interconnected. Possible modifications to the above embodiment are, for example, the following.
(1)上記実施形態においては、電池セル100として、リチウムイオン電池のセルを適用した例を説明した。しかし、電池セル100はリチウムイオン電池に限定されるものではなく、種々の二次電池を適用することができる。
(1) In the above embodiment, an example in which a lithium-ion battery cell is applied as the battery cell 100 has been described. However, the battery cell 100 is not limited to a lithium ion battery, and various secondary batteries can be applied.
(2)上記実施形態における制御部570のハードウエアは一般的なコンピュータによって実現できるため、図5に示したフローチャート、その他上述した各種処理を実行するプログラム等を記憶媒体に格納し、または伝送路を介して頒布してもよい。
(2) Since the hardware of the control unit 570 in the above embodiment can be realized by a general computer, the flowchart shown in FIG. may be distributed via
(3)図5に示した処理、その他上述した各処理は、上記実施形態ではプログラムを用いたソフトウエア的な処理として説明したが、その一部または全部をASIC(Application Specific Integrated Circuit;特定用途向けIC)、あるいはFPGA(Field Programmable Gate Array)等を用いたハードウエア的な処理に置き換えてもよい。
(3) The processing shown in FIG. 5 and each of the other processing described above are described as software processing using a program in the above embodiment, but some or all of them are ASIC (Application Specific Integrated Circuit; It may be replaced with hardware processing using FPGA (Field Programmable Gate Array) or the like.
100 電池セル
500 二次電池システム
512 電池セル・モジュール(二次電池)
572 充放電処理部
574 容量回復処理部
580 パラメータ更新部
582 充放電曲線取得部
584 相関関係取得部
586 放電量取得部
588 パラメータ決定部
En 負極電位
En1 負極電位(第1の電位)
En2 負極電位(第2の電位)
PT1 平坦部(第1の平坦部)
PT2 平坦部(第2の平坦部) 100battery cell 500 secondary battery system 512 battery cell module (secondary battery)
572 charge/discharge processing unit 574 capacity recovery processing unit 580 parameter update unit 582 charge/discharge curve acquisition unit 584 correlation acquisition unit 586 discharge amount acquisition unit 588 parameter determination unit En negative electrode potential En1 negative electrode potential (first potential)
En2 negative electrode potential (second potential)
PT1 flat part (first flat part)
PT2 flat part (second flat part)
500 二次電池システム
512 電池セル・モジュール(二次電池)
572 充放電処理部
574 容量回復処理部
580 パラメータ更新部
582 充放電曲線取得部
584 相関関係取得部
586 放電量取得部
588 パラメータ決定部
En 負極電位
En1 負極電位(第1の電位)
En2 負極電位(第2の電位)
PT1 平坦部(第1の平坦部)
PT2 平坦部(第2の平坦部) 100
572 charge/
En2 negative electrode potential (second potential)
PT1 flat part (first flat part)
PT2 flat part (second flat part)
Claims (5)
- リチウムイオン電池セルである一または複数の電池セルを有する二次電池と、
前記二次電池に対する充電または前記二次電池からの放電を行う際の電流または電圧の制御条件を規定する制御パラメータに基づいて、前記二次電池に対する充電処理または前記二次電池からの放電処理を行う充放電処理部と、
前記二次電池に対して、前記電池セルの端子電圧を2.0V以下に維持する処理を含む容量回復処理を行う容量回復処理部と、
前記容量回復処理の状況に応じて、前記制御パラメータを更新するパラメータ更新部と、を備える
ことを特徴とする二次電池システム。 a secondary battery having one or more battery cells that are lithium ion battery cells;
Charging processing for the secondary battery or discharging processing from the secondary battery is performed based on control parameters that define current or voltage control conditions when charging or discharging the secondary battery. A charge and discharge processing unit that performs
a capacity recovery processing unit that performs capacity recovery processing including processing for maintaining the terminal voltage of the battery cell at 2.0 V or less for the secondary battery;
A secondary battery system, comprising: a parameter updating unit that updates the control parameter according to the status of the capacity recovery process. - 前記電池セルは、充電率の変化に対して負極電位が第1の電位で一定になる範囲を含む前記充電率の領域である第1の平坦部と、前記充電率の変化に対して、前記第1の電位よりも低い第2の電位で前記負極電位が一定になる範囲を含む前記充電率の領域である第2の平坦部と、が現れる性質を有するものであり、
前記制御パラメータは、前記二次電池の上限電圧を指定する上限電圧指定パラメータを含むものであり、
前記パラメータ更新部は、各々の前記電池セルにおける前記負極電位が前記第1の電位以上になるように前記上限電圧指定パラメータを更新する機能を有する
ことを特徴とする請求項1に記載の二次電池システム。 The battery cell has a first flat portion that is the region of the charging rate including a range in which the negative electrode potential is constant at a first potential with respect to changes in the charging rate, and the A second flat portion, which is a region of the charging rate including a range in which the negative electrode potential is constant at a second potential lower than the first potential, appears,
The control parameter includes an upper limit voltage designation parameter that designates an upper limit voltage of the secondary battery,
2. The secondary battery according to claim 1, wherein the parameter updating unit has a function of updating the upper limit voltage specifying parameter so that the negative electrode potential in each of the battery cells becomes equal to or higher than the first potential. battery system. - 前記パラメータ更新部は、
前記充電処理または前記放電処理における前記二次電池に流れる電流または前記二次電池に現れる電圧に基づいて、前記二次電池の充放電曲線を取得する充放電曲線取得部と、
前記充放電曲線に基づいて、前記充電率と前記負極電位との相関関係を取得する相関関係取得部と、
前記相関関係に基づいて前記第1の平坦部と前記第2の平坦部に対応する前記充電率を取得する放電量取得部と、
取得した前記充電率に基づいて、前記負極電位が前記第1の電位以上になる充電率範囲で前記二次電池を充放電させる前記制御パラメータを決定するパラメータ決定部と、を備える
ことを特徴とする請求項2に記載の二次電池システム。 The parameter updating unit
a charge/discharge curve acquisition unit that acquires a charge/discharge curve of the secondary battery based on the current flowing through the secondary battery or the voltage appearing in the secondary battery in the charging process or the discharging process;
a correlation acquisition unit that acquires a correlation between the charging rate and the negative electrode potential based on the charge/discharge curve;
a discharge amount acquiring unit that acquires the charging rate corresponding to the first flat portion and the second flat portion based on the correlation;
a parameter determining unit that determines the control parameter for charging and discharging the secondary battery within a charging rate range in which the negative electrode potential is equal to or higher than the first potential, based on the obtained charging rate. The secondary battery system according to claim 2. - 前記充放電処理部は、前記二次電池の放電中に前記二次電池の端子電圧が所定の放電停止電圧以下になると放電を停止させるものであり、
前記容量回復処理は、前記電池セルの端子電圧を前記放電停止電圧よりも低い電圧に維持する処理を含む
ことを特徴とする請求項2に記載の二次電池システム。 The charge/discharge processing unit stops discharging when the terminal voltage of the secondary battery becomes equal to or lower than a predetermined discharge stop voltage during discharging of the secondary battery,
The secondary battery system according to claim 2, wherein the capacity recovery process includes a process of maintaining the terminal voltage of the battery cell at a voltage lower than the discharge stop voltage. - コンピュータを、
リチウムイオン電池セルである一または複数の電池セルを有する二次電池に対する充電または前記二次電池からの放電を行う際の電流または電圧の制御条件を規定する制御パラメータに基づいて、前記二次電池に対する充電処理または前記二次電池からの放電処理を行う充放電処理手段、
前記二次電池に対して、前記電池セルの端子電圧を2.0V以下に維持する処理を含む容量回復処理を行う充放電処理手段、
前記容量回復処理の状況に応じて、前記制御パラメータを更新するパラメータ更新手段、
として機能させるためのプログラム。 the computer,
Based on control parameters that define current or voltage control conditions when charging or discharging a secondary battery having one or more battery cells that are lithium ion battery cells, the secondary battery Charging and discharging processing means for performing charging processing for or discharging processing from the secondary battery,
charging and discharging processing means for performing capacity recovery processing including processing for maintaining the terminal voltage of the battery cell at 2.0 V or less for the secondary battery;
parameter update means for updating the control parameter according to the status of the capacity recovery process;
A program to function as
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JP2011165453A (en) * | 2010-02-09 | 2011-08-25 | Hitachi Vehicle Energy Ltd | Lithium ion secondary battery system and lithium ion secondary battery |
JP2015012680A (en) * | 2013-06-28 | 2015-01-19 | 日立オートモティブシステムズ株式会社 | Secondary battery system |
JP2021139788A (en) * | 2020-03-06 | 2021-09-16 | 株式会社日立ハイテク | Battery characteristic determination device and secondary battery system |
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JP2011159545A (en) * | 2010-02-02 | 2011-08-18 | Toyota Motor Corp | Charge/discharge control device of lithium ion secondary battery |
JP2011165453A (en) * | 2010-02-09 | 2011-08-25 | Hitachi Vehicle Energy Ltd | Lithium ion secondary battery system and lithium ion secondary battery |
JP2015012680A (en) * | 2013-06-28 | 2015-01-19 | 日立オートモティブシステムズ株式会社 | Secondary battery system |
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