Charger and method for charging lithium ion battery

Abstract

A charger (10) comprises: a voltage detection unit (12) that detects the terminal voltage of a lithium ion battery (20); a current detection unit (13) that detects the charging current going to the lithium ion battery (20); a charge / discharge control unit (11) that controls the charging / discharging of the lithium ion battery; and a communication unit (17) that communicates with a BMS (22) of the lithium ion battery. The communication unit (17) receives, from the BMS (22), information pertaining to the estimated SOC value for the lithium ion battery (20) at the present time and the ratio between the capacities of a positive electrode material and a negative electrode material, and information regarding the positive electrode potential and negative electrode potential achieved when the SOC value is a prescribed value. In the process of charging the lithium ion battery (20), the charge / discharge control unit (11) performs intermittent charging that repeats an operation of charging at a first current value for a first duration and then pausing charging for a second duration longer than the first duration. On the basis of the information received by the communication unit (17) pertaining to the ratio between the capacities of the positive electrode material and the negative electrode material and information regarding the positive electrode potential and negative electrode potential achieved when the SOC value is a prescribed value, the charge / discharge control unit (11) does not perform charging for the entirety of the process of increasing the SOC value from 0% to 100%, but performs the intermittent charging for a portion of said process.

Description

Charger, how to charge lithium-ion batteries

[0001] The present invention relates to a technology for charging and discharging a lithium-ion battery while acquiring data that allows calculation of SOC-OCV characteristics.

[0002] Patent Document 1 describes a secondary battery capacity measurement system that estimates the SOC of a secondary battery.

[0003] In a conventional system such as that disclosed in Patent Document 1, the OCV value is acquired when the SOC transitions between 0% and 100% while charging or discharging with a minute current. In the conventional system, the deterioration level of the secondary battery is estimated from the relationship data between the SOC and the OCV value acquired in this manner.

[0004] JP 2016-53564 A

[0005] However, with conventional systems and methods, it takes a long time, such as several days, to obtain data on the relationship between the SOC value and the OCV value.

[0006] Furthermore, for example, in the case of an in-vehicle battery, the discharge of the lithium-ion battery, which is a secondary battery, is controlled by a battery management system (BMS) of the lithium-ion battery so that the SOC value does not fall into a low SOC range of about 0% to 20%. For this reason, conventional systems and methods were unable to discharge the battery to the low SOC range, and were therefore unable to measure the OCV value in the low SOC range.

[0007] Therefore, an object of the present invention is to provide a charging technique that can acquire SOC-OCV characteristics that enable estimation of the degree of deterioration of a lithium-ion battery without measuring the OCV value in the low SOC region.

[0008] A charger according to one embodiment of the present invention is for charging a lithium-ion battery that uses graphite for the negative electrode, and includes a voltage detection unit that detects the terminal voltage of the lithium-ion battery, a current detection unit that detects the charging current to the lithium-ion battery, a charge / discharge control unit that controls charging / discharging of the lithium-ion battery, and a communication unit that communicates with the BMS of the lithium-ion battery.

[0009] The communication unit receives from the BMS the current estimated SOC value of the lithium ion battery, information regarding the ratio of the capacity of the positive electrode material to the negative electrode material, and information regarding the positive electrode potential and negative electrode potential when the SOC value is a predetermined value.

[0010] In the process of charging the lithium ion battery, the charge / discharge control unit performs intermittent charging by repeatedly charging the lithium ion battery for a first time at a first current value and then leaving the battery without charging for a second time longer than the first time. The charge / discharge control unit performs intermittent charging for a part of the SOC value range from 0% to 100%, without charging the entire SOC value, based on information regarding the capacity ratio between the positive electrode material and the negative electrode material received by the communication unit and information regarding the positive electrode potential and the negative electrode potential when the SOC value is a predetermined value.

[0011] This configuration utilizes the fact that the relationship between the SOC value and the OCV value has a characteristic change based on information about the ratio of the capacities of the positive and negative electrode materials of the lithium-ion battery and information about the positive and negative electrode potentials when the SOC value is a predetermined value (e.g., 100%). By charging while measuring the relationship between the SOC value and the OCV value so as to include the range of this characteristic change, the relationship between the SOC value and the OCV value can be estimated with high accuracy without charging over the entire SOC range (0% to 100%).

[0012] A method for charging a lithium-ion battery according to one embodiment of the present invention is a method for charging a lithium-ion battery using graphite for the negative electrode. When the lithium-ion battery is attached to a charger, the method acquires, from the BMS of the lithium-ion battery, the SOC value and the OCV value at the time of attaching the lithium-ion battery to the charger.

[0013] In this charging method, if the acquired SOC value is equal to or less than a first SOC value, the lithium ion battery is charged at a constant current for a first time, and after this constant current charging, the battery is left in an open state for a second time, and then an SOC-OCV data acquisition step is executed to acquire the SOC value and OCV value after the second time has elapsed.

[0014] In this charging method, when the acquired SOC value is higher than the first SOC value, a discharging step is performed in which the lithium-ion battery is discharged until the SOC value becomes equal to or lower than the first SOC value or the OCV value becomes equal to or lower than the first OCV value. After the discharging step is performed, this charging method performs an SOC-OCV data acquisition step. The SOC-OCV data acquisition step is repeatedly performed until the SOC value reaches 100%.

[0015] This method utilizes the fact that the relationship between the SOC value and the OCV value has a characteristic change based on the ratio of the capacity of the positive electrode material to the negative electrode material of the lithium-ion battery. By charging the battery while measuring the relationship between the SOC value and the OCV value so as to include the range of this characteristic change (a range including the first SOC value), it is possible to estimate the relationship between the SOC value and the OCV value with high accuracy without charging the battery over the entire SOC range (from 0% to 100%).

[0016] A method for charging a lithium-ion battery according to one embodiment of the present invention is a method for charging a lithium-ion battery using graphite for the negative electrode. When the lithium-ion battery is attached to a charger, the method acquires, from the BMS of the lithium-ion battery, the SOC value and the OCV value at the time of attaching the lithium-ion battery to the charger.

[0017] In this charging method, if the acquired SOC value is 100%, the lithium ion battery is discharged at a constant current for a first time, and after this constant current discharge, the lithium ion battery is left in an open state for a second time, and then an SOC-OCV data acquisition step is executed to acquire the SOC value and OCV value after the second time has elapsed.

[0018] The SOC-OCV data acquisition step is repeatedly performed until the SOC value reaches a first SOC value, and when the SOC value reaches the first SOC value, the lithium ion battery is charged with a continuous current and voltage.

[0019] This method utilizes the fact that the relationship between the SOC value and the OCV value has a characteristic change based on the ratio of the positive electrode material to the negative electrode material of a lithium-ion battery. By discharging while measuring the relationship between the SOC value and the OCV value so as to include the range of this characteristic change (a range including the first SOC value), it is possible to estimate the relationship between the SOC value and the OCV value with high accuracy without discharging over the entire SOC range (from 0% to 100%).

[0020] According to the present invention, it is possible to acquire the SOC-OCV characteristic that enables estimation of the deterioration level of a lithium ion battery without measuring the OCV value in the low SOC region.

[0021] FIG. 1 is a diagram showing the configuration of a charging and degradation analysis system including a charger according to a first embodiment of the present invention. FIG. 2 is a flowchart showing an example of a charging method for a lithium-ion battery according to the first embodiment of the present invention. FIG. 3 is a flowchart showing an example of a charging method for a lithium-ion battery according to the first embodiment of the present invention. FIG. 4(A) is a graph showing the relationship between the measured values ​​of the SOC-OCV characteristics and the fitting curve when using the charging method according to the first embodiment of the present invention, and FIG. 4(B) is a graph showing the relationship between the measured values ​​of the SOC-OCV characteristics and the fitting curve when using a conventional charging method. FIG. 5 is a flowchart showing an example of a charging method for a lithium-ion battery according to a second embodiment of the present invention.

[0022] [First embodiment] A charger and a charging method according to a first embodiment of the present invention will be described with reference to the drawings. The charger and the charging method of this embodiment are applied to a charger and a charging method for charging a lithium-ion battery that uses graphite as the negative electrode material.

[0023] FIG. 1 is a diagram showing the configuration of a charging and deterioration level analysis system including a charger according to a first embodiment of the present invention.

[0024] 1, the charging and deterioration level analysis system 1 includes a charger 10 and an analysis device 90. The charger 10 and the analysis device 90 are capable of data communication via a data communication IF provided in each of them.

[0025] The charger 10 includes a charge / discharge control unit 11, a voltage detection unit 12, a current detection unit 13, a communication unit 17, an electronic load 18, and a power supply circuit 19. The charger 10 also includes a positive charging terminal, a negative charging terminal, and a communication terminal.

[0026] The power supply circuit 19 is connected to an external power supply and is also connected to the charge / discharge control unit 11, etc. The power supply circuit 19 converts the external power into a predetermined DC voltage and DC current, and supplies the DC voltage and DC current to the charge / discharge control unit 11, etc.

[0027] The charge / discharge control unit 11 is connected to the positive and negative charging terminals, the communication unit 17, the electronic load 18, and an IF for data communication.

[0028] The voltage detection unit 12 is configured by a DC voltmeter and is connected between the charging positive terminal and the charging negative terminal.

[0029] The current detection unit 13 is configured by a DC ammeter and is connected in series to the wiring connecting the charge / discharge control unit 11 and the positive terminal for charging.

[0030] The communication unit 17 is connected to the communication terminal.

[0031] The electronic load 18 is connected to the charge / discharge control unit 11 .

[0032] The lithium ion battery 20 includes a battery cell 21 and a BMS 22. The lithium ion battery 20 also includes a positive terminal, a negative terminal, and a communication terminal.

[0033] The battery cell 21 is a lithium-ion battery cell that uses graphite as the negative electrode material. The positive electrode of the battery cell 21 is connected to the positive electrode terminal of the lithium-ion battery 20. The negative electrode of the battery cell 21 is connected to the negative electrode terminal of the lithium-ion battery 20.

[0034] The BMS 22 is a battery management system and is connected in parallel to the battery cells 21. The BMS 22 can detect the state of charge of the battery cells 21 and measure the SOC values ​​of the battery cells 21. The BMS 22 also stores in advance battery specifications including the ratio of positive electrode material to negative electrode material of the battery cells 21. The BMS 22 is connected to a communication terminal.

[0035] When charging the lithium ion battery 20, the lithium ion battery 20 is attached to the charger 10. This connects the positive terminal of the lithium ion battery 20 to the positive charging terminal of the charger 10. The negative terminal of the lithium ion battery 20 is connected to the negative charging terminal of the charger 10. The communication terminal of the lithium ion battery 20 is connected to the communication terminal of the charger 10.

[0036] This allows the charge / discharge control unit 11 of the charger 10 to charge or discharge the battery cells 21 of the lithium ion battery 20. In addition, the communication unit 17 of the charger 10 can communicate with the BMS 22 of the lithium ion battery 20.

[0037] Generally speaking, when charging the battery cells 21, the charge / discharge control unit 11 supplies current to the battery cells 21 by intermittent charge control or continuous charge control, which will be described later. In this way, the battery cells 21 are charged.

[0038] During this charge control, the charge / discharge control unit 11 receives feedback of the charge current value detected by the current detection unit 13 and performs charging at a predetermined constant current.

[0039] During intermittent charging control, the charge / discharge control unit 11 appropriately acquires the SOC value and also acquires the voltage detected by the voltage detection unit 12 as the OCV value, using a method described below.

[0040] When the battery cell 21 is to be discharged, the charge / discharge control unit 11 connects the battery cell 21 to the electronic load 18. This causes a current to flow from the battery cell 21 to the electronic load 18, and the electronic load 18 consumes power. This discharges the battery cell 21. The charge / discharge control unit 11 can control the amount of discharge from the battery cell 21 by controlling the discharge current value and discharge time.

[0041] The charge / discharge control unit 11 transmits the acquired SOC value and OCV value as a pair to the analysis device 90 via the IF.

[0042] The analysis device 90 includes an SOC-OCV characteristic calculation unit 91 and a deterioration level estimation unit 92. The SOC-OCV characteristic calculation unit 91 generates SOC-OCV characteristic data using the SOC value and OCV value received from the charger 10. At this time, the SOC-OCV characteristic calculation unit 91 performs curve fitting on a plurality of pairs of SOC values ​​and OCV values ​​to generate the SOC-OCV characteristic data.

[0043] The deterioration level estimation unit 92 stores in advance reference SOC-OCV characteristic data for each deterioration level corresponding to the battery specifications of the battery cell 21. The deterioration level estimation unit 92 compares the SOC-OCV characteristic data calculated by the SOC-OCV characteristic calculation unit 91 with the reference SOC-OCV characteristic data for each deterioration level based on the battery specifications of the battery cell 21. The deterioration level estimation unit 92 estimates the deterioration level of the most similar reference SOC-OCV characteristic data as the deterioration level of the battery cell 21 (lithium ion battery 20).

[0044] In this configuration, the charger 10 performs charge and discharge control as follows.

[0045] FIG. 2 is a flowchart showing an example of a method for charging a lithium ion battery according to the first embodiment of the present invention.

[0046] The charge / discharge control unit 11 detects whether the lithium-ion battery 20 is correctly attached to the charger 10. The charge / discharge control unit 11 can detect whether the lithium-ion battery 20 is correctly attached to the charger 10, for example, based on the voltage detected by the voltage detection unit 12 and the state of communication with the BMS 22 by the communication unit 17.

[0047] If the lithium-ion battery 20 is installed (S11: YES), the communication unit 17 acquires the SOC value (current estimated SOC value) and battery information of the lithium-ion battery 20 (battery cell 21) from the BMS 22 of the lithium-ion battery 20 (S12). The battery information includes the negative electrode material, the ratio of the capacity of the positive electrode material to the negative electrode material, and the positive electrode potential and the negative electrode potential when the SOC value is a predetermined value.

[0048] The communication unit 17 outputs the acquired SOC value and battery information of the lithium ion battery 20 (battery cell 21 ) to the charge / discharge control unit 11 .

[0049] The charge / discharge control unit 11 stores a first SOC value for determining charge control. The first SOC value is set based on battery information (anode material, ratio of cathode material to anode material) of the battery cell 21. More specifically, the first SOC value is set based on an SOC range that includes a voltage peak (maximum value) that occurs when a graphite intercalation compound formed by lithium ions being inserted into graphite in the anode of the battery cell 21 switches from a two-phase coexistence reaction between Stage 4 and Stage 3 to a two-phase coexistence reaction between Stage 3 and Stage 2. Alternatively, the first SOC value is set based on a range that includes a voltage peak that occurs at LixC (x = 0.5) due to the two-phase coexistence reaction of a lithium-ion battery. This peak voltage depends on the battery information, particularly the ratio of cathode material to anode material. Therefore, by acquiring battery information from the BMS 22, the charge / discharge control unit 11 can accurately determine the SOC value at which the voltage peak occurs.

[0050] For example, the first SOC value is set to be equal to or lower than the lower limit SOC value of a predetermined SOC range centered around the SOC value of this voltage peak.

[0051] The charge / discharge control unit 11 compares the first SOC value with the SOC value of the battery cell 21 acquired through the BMS 22 and the communication unit 17. If the SOC value of the battery cell 21 is equal to or lower than the first SOC value (S13: YES), the charge / discharge control unit 11 performs the next intermittent charging.

[0052] The charge / discharge control unit 11 charges the battery cells 21 of the lithium-ion battery 20 at a constant current I1 for a first time t1 (S14). After this constant current charging, the charge / discharge control unit 11 leaves the battery cells 21 in an electrically open state for a second time t2 (S15). The second time t2 is set longer than the first time t1 and is set to a time during which the voltage that temporarily rises during charging stabilizes.

[0053] Thereafter, the charge / discharge control unit 11 acquires the SOC value after the second time t2 has elapsed from the BMS 22, and acquires the voltage detected by the voltage detection unit 12 as the OCV value (S16).

[0054] The charge / discharge control unit 11 repeatedly performs intermittent charging while acquiring the SOC value and OCV value until the battery reaches full charge (SOC value is 100%) (S17: NO).

[0055] When the battery cell 21 reaches a fully charged state (SOC value is 100%), the charge / discharge control unit 11 ends charging of the battery cell 21 (S17: YES).

[0056] If the SOC value of the battery cell 21 is higher than the first SOC value (S13: NO), the charge / discharge control unit 11 performs the following control.

[0057] The charge / discharge control unit 11 discharges the battery cells 21 of the lithium-ion battery 20 using the electronic load 18 until the SOC value becomes equal to or less than the first SOC value (S18). At this time, the charge / discharge control unit 11 may use the OCV value. In this case, the charge / discharge control unit 11 discharges the battery cells 21 using the electronic load 18 until the OCV value becomes equal to or less than the first OCV value that is uniquely determined for the first SOC value.

[0058] The charge / discharge control unit 11 discharges the battery cell 21 until the SOC value (first OCV value) becomes equal to or less than the first SOC value, and then performs the above-described intermittent charge control to acquire the SOC value and the OCV value (S19).

[0059] By using this charging method, the charger 10 can obtain the SOC value and OCV value by performing intermittent charging in a portion of the battery, rather than charging the entire SOC value from 0% to 100%, based on the battery information (ratio of positive electrode material to negative electrode material) received (acquired) by the communication unit.

[0060] By including a characteristic range in the relationship between the SOC value and the OCV value, the SOC-OCV characteristic calculation unit 91 can perform highly accurate curve fitting for a plurality of pairs of SOC value and OCV value, thereby generating SOC-OCV characteristic data that accurately reflects the actual degree of deterioration of the battery cell 21, and estimating the degree of deterioration with high accuracy.

[0061] Furthermore, the above-described charging method does not require charging the entire SOC range from 0% to 100%. Therefore, by using the above-described charging method, the deterioration level of the lithium-ion battery can be estimated with high accuracy without measuring the OCV value in the low SOC range.

[0062] The charger 10 preferably further uses the following charging method.

[0063] Fig. 3 is a flowchart showing an example of a charging method for a lithium-ion battery according to the first embodiment of the present invention. The charging method shown in Fig. 3 differs from the charging method shown in Fig. 2 in the charging control in the range from a first SOC value to a second SOC value higher than the first SOC value. Other aspects of the charging method shown in Fig. 3 are the same as those of the charging method shown in Fig. 2, and a description of similar aspects will be omitted.

[0064] If the SOC value of the battery cell 21 is equal to or less than the first SOC value (S13: YES), the charge / discharge control unit 11 performs intermittent charging control based on the first time t1, constant current I1, and second time t2 shown in the above-mentioned steps S14, S15, and S16.

[0065] When the SOC value of the battery cell 21 becomes higher than the first SOC value (S21: YES), the charge / discharge control unit 11 performs the next charge control.

[0066] The charge / discharge control unit 11 sets a second SOC value that is higher than the first SOC value. Similar to the above-described first SOC value, the second SOC value is set based on battery information (negative electrode material, and the ratio of positive electrode material to negative electrode material) of the battery cell 21. For example, the first SOC value and the second SOC value are set on the low SOC value side and the high SOC value side, respectively, of the above-described SOC value of the voltage peak. Specifically, the first SOC value is set to an SOC value that is lower by a predetermined SOC value than the SOC value of the voltage peak. The second SOC value is set to an SOC value that is higher by a predetermined SOC value than the SOC value of the voltage peak.

[0067] Specifically, the charge / discharge control unit 11 charges with a constant current I1 at the third time t3 (< the first time t1), or charges with a small (constant) charging current I3 (< the constant current I1) at the first time t1 (S22).

[0068] After this constant current charging, the charge / discharge control unit 11 leaves the battery cell 21 in an electrically open state for a second time t2 (S23).

[0069] Thereafter, the charge / discharge control unit 11 acquires the SOC value after the second time t2 has elapsed from the BMS 22, and acquires the voltage detected by the voltage detection unit 12 as the OCV value (S24).

[0070] The charge / discharge control unit 11 repeatedly executes this intermittent charging until the SOC value reaches the second SOC value (S25: NO).

[0071] When the SOC value becomes equal to or greater than the second SOC value (S25: YES), the charge / discharge control unit 11 executes intermittent charging based on the above-described steps S14, S15, and S16, and repeats this intermittent power reception until the battery is fully charged.

[0072] By using this charging method, the charger 10 can increase the number of measurement points for the SOC and OCV values ​​within a range where the relationship between the SOC and OCV values ​​is characteristic. Therefore, the SOC-OCV characteristic calculation unit 91 can perform more accurate curve fitting for multiple pairs of SOC and OCV values. This makes it possible to generate SOC-OCV characteristic data that more accurately reflects the actual degree of deterioration of the battery cell 21, and to estimate the degree of deterioration with even greater accuracy.

[0073] 4A is a graph showing the relationship between the measured values ​​of the SOC-OCV characteristics and the fitting curve when using the charging method according to the first embodiment of the present invention, and FIG. 4B is a graph showing the relationship between the measured values ​​of the SOC-OCV characteristics and the fitting curve when using a conventional charging method. In FIGS. 4A and 4B, circles represent measured values, and solid lines represent fitting curves. The dashed line represents the characteristics of the negative electrode, and the dashed line represents the characteristics of the positive electrode.

[0074] As shown in Fig. 4A, by using the charging method according to the first embodiment of the present invention, the fitting curve fits the measured values ​​with high accuracy, whereas as shown in Fig. 4B, by using the conventional charging method, the fitting curve deviates from the measured values.

[0075] In this way, the charger 10 and charging method according to the first embodiment can perform highly accurate curve fitting for a plurality of pairs of SOC and OCV values, thereby generating SOC-OCV characteristic data that accurately reflects the actual degree of deterioration of the battery cell 21, and estimating the degree of deterioration with high accuracy.

[0076] [Second embodiment] A charger and a charging method according to a second embodiment of the present invention will be described with reference to the drawings. The charger and the charging method according to the second embodiment are different from the charger and the charging method according to the first embodiment in the charging method, but the configuration of the charger is the same. Therefore, a description of the configuration of the charger will be omitted, and the charging method will be described.

[0077] FIG. 5 is a flowchart showing an example of a method for charging a lithium ion battery according to the second embodiment of the present invention.

[0078] The charge / discharge control unit 11 detects whether the lithium ion battery 20 is correctly attached to the charger 10 .

[0079] If the lithium-ion battery 20 is installed (S31: YES), the communication unit 17 acquires the SOC value and battery information of the lithium-ion battery 20 (battery cell 21) from the BMS 22 of the lithium-ion battery 20 (S32). The battery information includes the negative electrode material and the ratio of the positive electrode material to the negative electrode material. The communication unit 17 outputs the acquired SOC value and battery information of the lithium-ion battery 20 (battery cell 21) to the charge / discharge control unit 11.

[0080] If the SOC value of the battery cell 21 is 100% (S33: YES), the charge / discharge control unit 11 performs the next intermittent charging.

[0081] The charge / discharge control unit 11 acquires the OCV value at this time from the voltage detection unit 12 (S34).

[0082] The charge / discharge control unit 11 discharges the battery cell 21 of the lithium ion battery 20 at a constant current I1d for a first time t1 (S35).

[0083] After this constant current charging, the charge / discharge control unit 11 leaves the battery cell 21 in an electrically open state for a second time t2 (S36).

[0084] Thereafter, the charge / discharge control unit 11 acquires the SOC value after the second time t2 has elapsed from the BMS 22, and acquires the voltage detected by the voltage detection unit 12 as the OCV value (S37).

[0085] The charge / discharge control unit 11 repeatedly executes intermittent discharge while acquiring the SOC value and OCV value until the first SOC value is reached (S38: NO).

[0086] When the SOC value reaches the first SOC value (S38: YES), the charge / discharge control unit 11 charges the battery cells 21 of the lithium ion battery 20 with a continuous current and voltage (S39).

[0087] In this way, the charger 10 and the charging method can obtain multiple pairs of SOC and OCV values, including a range where the relationship between the SOC and OCV values ​​is characteristic, even when the battery is intermittently discharged, just as in the case of the above-described intermittent charging. Therefore, the charger 10 and the charging method can generate SOC-OCV characteristic data that accurately reflects the actual degree of deterioration of the battery cell 21, and can estimate the degree of deterioration with high accuracy.

[0088] If the SOC value is not 100% (S33: NO), but is close to 100%, for example, the battery may be charged until the SOC value reaches 100%, and then the above-described intermittent discharge method may be used.

[0089] Also, if the SOC value is not 100% (S33: NO), and the SOC value is close to the second SOC value described above, for example, the battery may be discharged to below the first SOC value, and then the intermittent charging method described above may be used.

[0090] <1> A charger for charging a lithium ion battery using graphite for its negative electrode, comprising: a voltage detection unit for detecting a terminal voltage of the lithium ion battery; a current detection unit for detecting a charging current to the lithium ion battery; a charge / discharge control unit for controlling charging / discharging of the lithium ion battery; and a communication unit for communicating with a BMS of the lithium ion battery, wherein the communication unit receives from the BMS an estimated SOC value at the current time of the lithium ion battery, information about a ratio of capacities of a positive electrode material and a negative electrode material, and information about a positive electrode potential and a negative electrode potential when the SOC value is a predetermined value, and wherein the charge / discharge control unit performs intermittent charging in the process of charging the lithium ion battery by repeating an operation of charging at a first current value for a first time period and then leaving the battery for a second time period longer than the first time period without charging, a charger that performs the intermittent charging for a part of an SOC value range, without charging the entire SOC value range from 0% to 100%, based on information regarding the ratio of the capacities of the positive electrode material and the negative electrode material received by the communication unit and information regarding the positive electrode potential and the negative electrode potential when the SOC value is a predetermined value.

[0091] <2> A charging method for a lithium-ion battery using graphite in an anode, comprising: when the lithium-ion battery is attached to a charger, acquiring an SOC value and an OCV value of the lithium-ion battery at the time of attachment to the charger from a BMS of the lithium-ion battery; if the acquired SOC value is equal to or less than a first SOC value, performing an SOC-OCV data acquisition step of charging the lithium-ion battery at a constant current for a first time, leaving the lithium-ion battery in an open state for a second time after the constant current charging, and then acquiring an SOC value and an OCV value after the second time has elapsed; if the acquired SOC value is higher than the first SOC value, performing a discharging step of discharging the lithium-ion battery until the SOC value becomes equal to or less than the first SOC value or the OCV value becomes equal to or less than the first OCV value; after performing the discharging step, performing the SOC-OCV data acquisition step; and repeatedly performing the SOC-OCV data acquisition step until the SOC value reaches 100%.

[0092] <3> A method for charging a lithium-ion battery using graphite in an anode, comprising: when the lithium-ion battery is attached to a charger, acquiring an SOC value and an OCV value of the lithium-ion battery at the time of attaching the lithium-ion battery to the charger from a BMS of the lithium-ion battery; and if the acquired SOC value is 100%, performing an SOC-OCV data acquisition step of discharging the lithium-ion battery at a constant current for a first time, leaving the lithium-ion battery in an open state for a second time after the constant current discharge, and then acquiring an SOC value and an OCV value after the second time has elapsed; and repeatedly performing the SOC-OCV data acquisition step until the SOC value reaches a first SOC value; and when the SOC value reaches the first SOC value, charging the lithium-ion battery with a continuous current and voltage.

[0093] <4> The method for charging a lithium-ion battery according to <2>, wherein the SOC-OCV data acquisition step includes: setting a second SOC value higher than the first SOC value; and, within a range between the first SOC value and the second SOC value, setting a charging time shorter than the first time or setting a charging current smaller than the constant current, thereby increasing the number of measurement points for the SOC value and the OCV value within the range.

[0094] <5> The method for charging a lithium-ion battery according to <2> or <3>, wherein the range between the first SOC value and the second SOC value is a range that includes a voltage peak that occurs when a graphite intercalation compound formed by lithium ions being inserted into the graphite in the negative electrode switches from a two-phase coexistence reaction of Stage 4 and Stage 3 to a two-phase coexistence reaction of Stage 3 and Stage 2.

[0095] <6> The method for charging a lithium ion battery according to <2> or <3>, wherein the range between the first SOC value and the second SOC value is a range that includes a voltage peak generated at LixC (x = 0.5) by a two-phase coexistence reaction in the lithium ion battery.

[0096] 1: Deterioration analysis system 10: Charger 11: Charge / discharge control unit 12: Voltage detection unit 13: Current detection unit 17: Communication unit 18: Electronic load 19: Power supply circuit 20: Lithium-ion battery 21: Battery cell 90: Analysis device 91: SOC-OCV characteristic calculation unit 92: Deterioration estimation unit I1: Constant current I1d: Constant current I3: Charging current t1: First time t2: Second time t3: Third time

Claims

1. A charger for charging a lithium-ion battery using graphite for the negative electrode, comprising: a voltage detection unit for detecting the terminal voltage of the lithium-ion battery; a current detection unit for detecting the charging current to the lithium-ion battery; a charge / discharge control unit for controlling the charging / discharging of the lithium-ion battery; and a communication unit for communicating with a BMS of the lithium-ion battery, wherein the communication unit receives from the BMS an estimated SOC value of the lithium-ion battery at the present time, information regarding the ratio of the capacity of the positive electrode material to the negative electrode material, and information regarding the positive electrode potential and the negative electrode potential when the SOC value is a predetermined value, and wherein the charge / discharge control unit, in the process of charging the lithium-ion battery, performs intermittent charging by repeatedly charging the lithium-ion battery for a first time period at a first current value and then leaving the battery for a second time period longer than the first time period without charging, a charger that performs the intermittent charging for a part of an SOC value range, without charging the entire SOC value range from 0% to 100%, based on information regarding the ratio of the capacities of the positive electrode material and the negative electrode material received by the communication unit and information regarding the positive electrode potential and the negative electrode potential when the SOC value is a predetermined value.

2. A charging method for a lithium-ion battery using graphite for the negative electrode, comprising: when the lithium-ion battery is attached to a charger, acquiring from the BMS of the lithium-ion battery an SOC value and an OCV value of the lithium-ion battery at the time of attachment to the charger; if the acquired SOC value is equal to or less than a first SOC value, charging the lithium-ion battery at a constant current for a first time, leaving it in an open state for a second time after the constant current charging, and then acquiring the SOC value and OCV value after the second time has elapsed; if the acquired SOC value is higher than the first SOC value, executing a discharging step of discharging the lithium-ion battery until the SOC value becomes equal to or less than the first SOC value or the OCV value becomes equal to or less than the first OCV value; after executing the discharging step, executing the SOC-OCV data acquiring step; and repeatedly executing the SOC-OCV data acquiring step until the SOC value reaches 100%.

3. A charging method for a lithium-ion battery using graphite for the negative electrode, comprising: when the lithium-ion battery is attached to a charger, acquiring from the BMS of the lithium-ion battery an SOC value and an OCV value at the time of attaching the lithium-ion battery to the charger; if the acquired SOC value is 100%, discharging the lithium-ion battery at a constant current for a first time, leaving it in an open state for a second time after this constant current discharge, and then executing an SOC-OCV data acquisition step to acquire the SOC value and OCV value after the second time has elapsed; the SOC-OCV data acquisition step is repeatedly executed until the SOC value reaches a first SOC value; and when the SOC value reaches the first SOC value, charging the lithium-ion battery with a continuous current and voltage.

4. The method for charging a lithium-ion battery according to claim 2, characterized in that the SOC-OCV data acquisition step: sets a second SOC value higher than the first SOC value; and, in the range between the first SOC value and the second SOC value, sets a charging time shorter than the first time or sets a charging current smaller than the constant current, thereby increasing the number of measurement points for the SOC value and the OCV value within the range.

5. A method for charging a lithium-ion battery as described in claim 2 or claim 3, characterized in that the range between the first SOC value and the second SOC value is a range that includes a voltage peak that occurs when a graphite intercalation compound formed in the negative electrode by lithium ions being inserted into the graphite switches from a two-phase coexistence reaction of Stages 4 and 3 to a two-phase coexistence reaction of Stages 3 and 2.

6. The method for charging a lithium-ion battery according to claim 2 or 3, wherein the range between the first SOC value and the second SOC value is a range that includes a voltage peak generated at LixC (x = 0.5) by a two-phase coexistence reaction in the lithium-ion battery.

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