CN101636872A - Quick charging method of lithium based secondary battery and electronic apparatus employing it - Google Patents

Abstract

The invention provides a fast charging method for lithium series secondary batteries and electronic equipment. In the present invention, the charging current is maintained at a predetermined constant rapid charging current (S1), and when the terminal voltage V1 (S6) reaches the charging end voltage Vf', it is determined to be fully charged (S7), and the charging is completed. The voltage Vf' is set to a voltage (S5) obtained by adding a voltage drop VD (S4) to a preset initial charging end voltage Vf, wherein the voltage drop VD is determined according to the temperature T of the secondary battery. (S2) is obtained by multiplying the estimated internal resistance value (S3) and the fast charging current value. Therefore, instead of conventional CC-CV charging, while preventing overcharging, it can supply a constant large current from the beginning to the end, and quickly charge to full charge.

Description

Rapid charging method of lithium series secondary battery and electronic equipment using the method

technical field

The present invention relates to a method for rapidly charging lithium-based secondary batteries and electronic equipment using the method.

Background technique

As a typical conventional charging method for lithium-based secondary batteries, for example, a CCCV (Constant Current Constant Voltage) charging method as shown in FIG. 7 is known. In the CCCV charging method, first, when a fully charged battery can be discharged to a SOC (State Of Charge) of 0% within 1 hour, for example, at a current value of 1C, CC is performed at a current of about 0.7 to 1C ( constant current) charging. Next, after the terminal voltage of the battery reaches a predetermined end-of-charge voltage, for example, 4.2V, switching is made to CV (constant voltage) charging in which the charging current is gradually decreased to maintain the end-of-charge voltage. FIG. 7(A) is a graph showing changes in cell voltage, and FIG. 7(B) is a graph showing changes in charging current.

However, the actual situation is that even if 4.2V is applied as above, due to the influence of internal resistance, the actual charging voltage will be less than 4.2V, and it will not be possible to fully charge (full charge). Therefore, Japanese Patent Laid-Open Publication No. 11-285162 (Patent Document 1), which is a typical prior art, discloses the following content: When the unit cell voltage rises to a certain level by charging with a large current (CC), the connection and Each unit cell is arranged in parallel with the switch having a series circuit of a switch and an impedance. Then, as charging proceeds, current flows through the bypass path, thereby reducing the effect of internal resistance to fully charge the battery. On the other hand, Japanese Patent Laid-Open Publication No. 2005-185060 (Patent Document 2) discloses that whenever the voltage of the battery pack reaches Vf (the voltage of the battery body) + R (the battery body such as the protection element) When the voltage of the impedance inside and outside)×I (charging current) is reached, the current I is gradually reduced.

In the conventional techniques described above, charging to full charge while preventing overcharging can be achieved by greatly reducing the charging current at the end of charging, but there is a problem that the charging time cannot be sufficiently shortened.

Contents of the invention

The object of the present invention is to provide a rapid charging method and electronic equipment for a lithium-series secondary battery capable of preventing overcharging and rapidly charging to full charge.

The electronic equipment involved in the present invention includes: a lithium series secondary battery; a charging current supply unit for rapidly charging the lithium series secondary battery; a charging control unit for controlling the charging current supplied by the charging current supply unit; a detection unit that detects the temperature of the lithium series secondary battery; a voltage detection unit that detects a terminal voltage of the lithium series secondary battery; and a setting unit that sets a charging end voltage of the charging control unit, wherein the charging control unit the charging current supply unit supplies a predetermined constant fast charging current to the lithium series secondary battery, and when the terminal voltage detected by the voltage detecting unit reaches the charging end voltage set by the setting unit The charging current supply unit ends the supply of the quick charging current, and the setting unit includes: estimating the internal resistance value of the lithium series secondary battery based on the temperature of the lithium series secondary battery detected by the temperature detection unit. an internal resistance estimating section; and estimating an amount of voltage drop caused by the internal resistance based on the internal resistance value estimated by the internal resistance estimating section and the fast charging current value, and adding the amount of voltage drop to a preset reference voltage to calculate the above-mentioned end-of-charge voltage calculation unit.

Moreover, the rapid charging method for lithium series secondary batteries related to the present invention is used to rapidly charge lithium series secondary batteries until reaching a specified end-of-charge voltage, comprising the steps of continuously supplying a predetermined constant rapid charging A step of current flow; a step of detecting at least the temperature of the above-mentioned lithium series secondary battery; a step of estimating the internal resistance value of the above-mentioned lithium series secondary battery based on the detected temperature; based on the estimated above-mentioned internal resistance value and the above-mentioned fast charging current value , a step of estimating a voltage drop caused by the internal resistance; and a step of calculating the charging end voltage by adding the voltage drop to a preset reference voltage.

The rapid charging method for a lithium-based secondary battery and the electronic device using the method according to the present invention maintain the charging current at a predetermined constant rapid charging current instead of the conventional CC-CV charging as described above, and, Charging ends when the terminal voltage reaches the charging end voltage. Then, the charging end voltage is set to a voltage obtained by adding a voltage drop amount obtained by adding an internal resistance value estimated from the temperature of the secondary battery to a predetermined reference voltage, and the rapid charge current obtained by multiplying the values.

Therefore, overcharging can be prevented, and a constant large current can be supplied from the start to the end of charging, enabling rapid charging.

Description of drawings

FIG. 1 is a block diagram showing an electrical configuration of an electronic device according to Embodiment 1 of the present invention.

2 is a graph for explaining a change in internal resistance value against a temperature change of a non-aqueous electrolyte secondary battery (non-aqueous electrolytic secondary battery) having a heat-resistant layer between the negative electrode and the positive electrode, the heat-resistant layer adopting Porous protective film comprising resin binder and inorganic oxide filler.

FIG. 3 is a flowchart for describing in detail the charging operation of the electronic device according to Embodiment 1 of the present invention.

FIG. 4 is a graph for explaining a charging method according to Embodiment 1 of the present invention. FIG. 4(A) is a graph showing changes in cell voltage, and FIG. 4(B) is a graph showing changes in charging current.

FIG. 5 is a flowchart for explaining in detail the charging operation in the electronic device according to Embodiment 2 of the present invention.

FIG. 6 is a graph showing changes in internal resistance with respect to changes in SOC.

FIG. 7 is a graph for explaining a typical conventional charging method. FIG. 7(A) is a graph showing changes in cell voltage, and FIG. 7(B) is a graph showing changes in charging current.

8 is a block diagram showing an example of the configuration of an electronic device according to Embodiment 3 of the present invention.

FIG. 9 is a flowchart showing an example of the operation of the electronic device shown in FIG. 8 .

FIG. 10 is a block diagram showing an example of the configuration of an electronic device according to Embodiment 4 of the present invention.

FIG. 11 is a flowchart showing an example of the operation of the electronic device shown in FIG. 10 .

FIG. 12 is a flowchart showing an example of the operation of the electronic device shown in FIG. 10 .

FIG. 13 is a flowchart showing an example of the operation of the electronic device shown in FIG. 10 .

FIG. 14 is a block diagram showing a modified example of the electronic device shown in FIGS. 8 and 10 .

Detailed ways

(Example 1)

FIG. 1 is a block diagram showing an electrical configuration of an electronic device according to Embodiment 1 of the present invention. This electronic device includes a battery pack 1, a charger 2 for charging the battery pack, and a load device not shown. In FIG. 1 , the battery pack 1 is charged by the charger 2 , but the battery pack 1 may be mounted on the above-mentioned load device and charged by the load device. The battery pack 1 and the charger 2 are connected to each other through DC high-side terminals T11, T21 for power supply, communication signal terminals T12, T22, and GND terminals T13, T23 for power supply and communication signals. Even in the case where the above-mentioned load device is provided, the same terminals are provided.

In the battery pack 1, FETs 12 and 13 having different conduction forms for charging and discharging are interposed in a DC high-side charge-discharge path 11 extending from the terminal T11, and the charge-discharge path 11 is connected to the high-side of the secondary battery 14. side terminals. The low-side terminal of the secondary battery 14 is connected to the GND terminal T13 via a DC low-side charging and discharging path 15 interposed by a current detection impedance 16 that converts charging current and discharging current into voltage values.

The secondary battery 14 is configured by connecting one or more unit cells (cells) in series and parallel, and the temperature of the unit cells is detected by a temperature sensor 17 and input to an analog/digital converter 19 in the control IC 18 . And the voltage between the terminals of each unit cell is detected by the voltage detection circuit 20, and is input to the analog/digital converter 19 in the control IC18. In addition, the current value detected by the current detection impedance 16 is also input to the analog/digital converter 19 inside the control IC 18 . The analog/digital converter 19 converts each input value into a digital value (digital value), and outputs it to the control unit 21 .

The control unit 21 includes a microcomputer and its peripheral circuits, and the like. Furthermore, the control unit 21 functions as an SOC acquisition unit by executing a predetermined control program.

In addition, the control unit 21 integrates the current value detected by the current detection impedance 16 in response to each input value from the analog/digital converter 19, and converts the terminal voltage detected by the voltage detection circuit 20 into SOC, thereby The remaining capacity (SOC) of the secondary battery 14 is calculated. Next, the control unit 21 transmits from the communication unit 22 to the charger 2 via the terminals T12, T22 and T13, T23 whether there is an abnormality in the voltage and temperature of each unit cell. When charging and discharging are performed normally, the control unit 21 turns on FETs 12 and 13 to enable charging and discharging, and turns off FETs 12 and 13 to prohibit charging and discharging when an abnormality is detected.

In the charger 2 , the communication unit 32 of the control IC 30 receives the temperature and the presence or absence of abnormality, and the charging control unit 31 controls the charging current supply circuit 33 to supply the charging current. The charging current supply circuit 33 includes an AC-DC converter, a DC-DC converter, or the like. Furthermore, the charging current supply circuit 33 converts the input voltage supplied from the outside into predetermined voltage values and current values, and supplies them to the charging and discharging paths 11 and 15 via the terminals T21, T11 and T23, T13.

The charging control unit 31 includes, for example, a CPU (Central Processing Unit) that executes specified arithmetic processing, a ROM (Read Only Memory) that stores a specified control program, a RAM (Random Access Memory) that temporarily stores data, and peripheral circuits of these components. Furthermore, charging control unit 31 functions as a setting unit including an internal resistance estimating unit and an end voltage calculating unit by executing a control program stored in the ROM.

In an electronic device adopting the above structure, attention should be paid to the following points. That is, in this embodiment, when charging the secondary battery 14 quickly, the charging control unit 31 supplies a predetermined constant fast charging current I through the charging current supply circuit 33, and monitors the voltage generated by the analog/digital converter 35. The detection circuit 34 detects the voltage V1 between the terminals T21 ( T11 ) and T23 ( T13 ). Then, when the voltage V1 reaches a predetermined charging end voltage Vf', the charging current supply circuit 33 is stopped from supplying the quick charging current I.

That is, it should be noted that CV (constant voltage) charging is not performed after CC (constant current) charging as in the past, but charging is terminated directly in the state of CC (constant current) charging, and then according to the temperature detected by the temperature sensor 17 , and the unit cell temperature T input via the communication unit 22, 32 determines the charge end voltage Vf'.

Specifically, as shown in FIG. 2 , the charging control unit 31 stores in advance, as a data table, data indicating that the higher the temperature T is, the smaller the internal resistance value R of the secondary battery 14 is in a nonvolatile memory such as ROM. element. Next, when the temperature data is input from the battery pack 1 side, the charging control unit 31 reads the corresponding internal resistance value R from the above table. When there is no corresponding data in the data table, the internal resistance value R can be calculated by interpolating the previous and subsequent data, or a data that approximately expresses the change of the internal resistance value R with respect to the temperature T can be stored in advance. Formula, each time the temperature data is input, the internal resistance value R is obtained through successive calculations (successive computation).

Next, the charging control unit 31 (internal resistance estimating unit) multiplies the obtained internal resistance value R by the quick charging current value I, thereby estimating the amount of voltage drop VD due to the internal resistance. Then, charging control unit 31 (end voltage calculation unit) sets voltage Vf' obtained by adding voltage drop amount VD to initial charge end voltage Vf (reference voltage) as charge end voltage.

An open circuit voltage (OCV) when the secondary battery 14 is fully charged, that is, a full charge voltage, is set in advance as the initial charge end voltage Vf.

When the secondary battery 14 is a lithium ion secondary battery, the full charge voltage is, for example, the potential difference between the positive electrode potential and the negative electrode potential when the negative electrode potential of the secondary battery 14 is substantially 0V, that is, the terminal voltage of the secondary battery 14. . In the case of a lithium-ion secondary battery, when lithium cobalt oxide is used as the positive electrode active material, the full charge voltage is about 4.2V, and when lithium manganese oxide is used as the positive electrode active material, The full charge voltage is about 4.3V.

FIG. 3 is a flowchart for explaining in detail the above charging operation performed by the charging control unit 31 . First, in step S1, the charging control unit 31 starts supply of the quick charging current I, and in step S2, receives data on the temperature T from the battery pack 1 side. In step S3, the charging control unit 31 reads the internal resistance value R corresponding to the received data from the above-mentioned data table, or obtains the internal resistance value R through calculation, and in step S4, calculates the internal resistance value R according to I×R The amount of voltage drop VD due to the internal resistance is obtained, and then in step S5, the end-of-charge voltage Vf' is obtained from Vf+VD.

Next, in step S6, the charge control unit 31 detects the actual terminal voltage V1, and in step S7, judges whether or not the voltage V1 has reached the charge end voltage Vf' or higher. In step S7, when the voltage V1 has not reached the charging end voltage Vf' or higher, return to step S1, and the charging control unit 31 continues charging with a large current I, and when it has reached the charging end voltage Vf' or higher, transfer to step S8 , the supply of the charging current I is stopped, and when there is an indicator (indicator) or the like, a full charge display is performed.

Therefore, for example, in the case of a lithium ion secondary battery, in general, the initial charge end voltage Vf of each unit cell is set to 4.2V or 4.25V, but in this embodiment, considering the internal resistance caused by The voltage drop VD, for example, in the case of I=2A, R=25mΩ, the initial charging end voltage Vf is 4.25V or 4.3V. With this structure, it is possible to prevent overcharging, supply a constant large current I all the time, and quickly charge to full charge. FIG. 4 shows the charging method according to the present embodiment as described above. Similar to FIG. 7 , FIG. 4(A) is a graph showing changes in cell voltage, and FIG. 4(B) is a graph showing changes in charging current.

Moreover, it is more desirable that the secondary battery 14 adopts a non-aqueous electrolyte secondary battery having a heat-resistant layer formed by a porous protective film comprising a resin binder and an inorganic oxide filler (filler) between the negative electrode and the positive electrode. Battery. Such a secondary battery is disclosed, for example, in Japanese Patent Publication No. 3371301 and the like. The inorganic oxide filler is selected from alumina powder or SiO ₂ powder (silica) with a particle size in the range of 0.1 μm to 50 μm. Moreover, the thickness of the above-mentioned porous protective film is set to 0.1 μm to 200 μm, and the porous protective film is coated on the surface of the negative electrode or the positive electrode by applying a fine particle slurry (slurry) containing a resin binder and an inorganic oxide filler. formed on at least one surface of the

By using a secondary battery with such a structure, even if it reaches an overcharged state and metal lithium precipitates in a dendritic form, the heat-resistant layer can prevent a short circuit between the negative electrode and the positive electrode. Fast charging with high current I.

(Example 2)

FIG. 5 is a flowchart for explaining in detail the charging operation in the electronic device according to Embodiment 2 of the present invention. In this embodiment, the structure of the electronic device shown in FIG. 1 above can be used. In the processing of FIG. 5, the parts similar to or corresponding to the processing of FIG. Its description is omitted. It should be noted that, in this embodiment, not only the internal resistance value R but also the terminal voltage V1 and the actual capacity W of the secondary battery 14 are taken into consideration to determine the end-of-charge voltage Vf'. The above-mentioned internal resistance value R(DC-IR) not only decreases as the temperature increases as shown in Figure 2, but also changes according to the SOC (State of Charge) as shown in Figure 6. Furthermore, if the deterioration increases due to repeated charging and discharging, the internal resistance value R will increase.

Therefore, in step S2', the charging control unit 31 acquires not only the data of the unit cell temperature T but also the data of the SOC (=terminal voltage) accumulated by the control unit 21, and the data due to repeated charging managed by the control unit 21. Data of actual capacity (Ah in fully charged state) W (= degree of deterioration) decreased by discharge. Next, in step S3', the charging control unit 31 reads all these data as parameters from a table storing corresponding internal resistance values, or reads some of these data as parameters and stores corresponding internal resistance values. After the data table of the value, correct the read value through the remaining parameters to generate the value to be used in the future, etc., so as to obtain the internal resistance value R.

When estimating the internal resistance value R as described above, not only the above-mentioned unit cell temperature T but also the SOC (= terminal voltage) and the actual capacity W (= degree of deterioration) are taken into consideration, so that the above-mentioned The internal resistance R is the end-of-charge voltage Vf'.

In addition, instead of detecting the terminal voltage V1 by the voltage detection circuit 34 , data detected by the voltage detection circuit 20 on the side of the battery pack 1 may be transmitted to the charger 2 side. Moreover, in the lithium series secondary battery, as the SOC increases, the terminal voltage V1 also increases, so the terminal voltage V1 can also be used instead of the SOC value.

Moreover, in the above-described embodiment, the analog/digital converter 19 is installed on the battery pack 1 side, and the battery temperature and battery voltage information is sent to the charging control unit 31 on the charger 2 side through the communication parts 22, 32, but it may also be The charging control unit 31 is equipped with an analog/digital converter, and directly reads the above-mentioned information. Furthermore, in the above-mentioned embodiment, the charge control unit 31 is provided separately from the battery pack 1, but a battery pack equipped with a charge control function in which the charge control unit 31 is integrally formed with the battery pack 1 may also be used.

Here, Japanese Patent Laid-Open Publication No. 2005-261020 discloses that the voltage difference between OCV (open circuit voltage) and CCV (closed circuit voltage) is obtained in advance every time charging is performed, and the voltage difference is obtained at a constant current. During the charging process, the time required for the terminal voltage to rise to the voltage difference is measured, and even if it reaches the predetermined end-of-charge voltage, it will continue to charge for the above-mentioned measured time from this moment, so that it can be quickly charged to full charge without being affected by internal resistance . Furthermore, this prior art discloses that measuring the OCV and CCV just before the terminal voltage reaches the end-of-charge voltage makes it possible to cope with changes in internal resistance accompanying temperature rise due to charging.

However, this conventional technology can charge to full charge while preventing overcharge, and can shorten the charging time by switching from conventional CV charging to CC charging. However, in order to measure OCV, it is necessary to stop the supply of charging current for a period of time. , compared with this embodiment, the charging time becomes longer.

In this regard, Japanese Patent Laid-Open Publication No. 10-214643 discloses the following content: make the charging current oscillate (oscillate), measure the internal resistance according to the voltage and current values before and after, and compare the voltage drop caused by the internal resistance A corresponding voltage is added to the charging voltage. Therefore, there is no need to completely stop the charging current for the above-mentioned OCV measurement, and the charging time can be shortened to a certain extent. However, since the charging current is reduced to be less than CC, it is different from the present embodiment in which the above-mentioned constant CC is charged from the beginning to the end. However, the charging time is still longer.

(Example 3)

8 is a block diagram showing an example of the configuration of an electronic device according to Embodiment 3 of the present invention. In FIG. 8 , the same components as those of the electronic device shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The electronic device shown in FIG. 8 differs from the electronic device shown in FIG. 1 in the following points. That is, in the electronic device shown in FIG. 8 , control unit 21 a functions as charge control unit 210 , internal resistance estimation unit 211 , and end voltage calculation unit 212 .

Furthermore, the charging control unit 31a does not perform detection of the internal resistance value R, setting of the charging end voltage, or determination of whether or not charging has been completed. Moreover, the load device 4 is connected between the terminal T21 and the terminal T23. Furthermore, the discharge current of the secondary battery 4 (should be 14 ) and the current output from the charging current supply circuit 33 are supplied as the driving current of the load device 4 .

FIG. 9 is a flowchart showing an example of the operation of the electronic device shown in FIG. 8 . In addition, in the following flowcharts, the same step numbers are assigned to the same operations, and descriptions thereof will be omitted. First, for example, the full charge voltage of the secondary battery 14 is initially set as the initial charge end voltage Vf by the end voltage calculation unit 212 (step S11 ). Next, the internal resistance estimating unit 211 acquires the terminal voltage V1 detected by the voltage detection circuit 20 as an open circuit voltage V1' (step S12).

Next, internal resistance estimating unit 211 requests charging control unit 31 a to output a current having preset current value I (quick charging current) via communication units 22 and 32 . Then, a charging current of a current value I is supplied from the charging current supply circuit 33 to the secondary battery 14 in response to a control signal from the charging control unit 31a, thereby starting constant-current charging (step S13).

Next, the internal resistance estimation unit 211 acquires the current value I detected by the current detection impedance 16 and the terminal voltage V1 detected by the voltage detection circuit 20 (steps S14 and S15 ). Then, the internal resistance value R' is calculated based on the following formula (1) (step S16).

R'＝(V1-V1')/I...(1)

Next, the end voltage calculation unit 212 calculates the voltage drop amount VD based on the following formula (2) (step S17 ).

VD＝R’×I ……(2)

Next, end voltage calculation unit 212 calculates and sets charge end voltage Vf' based on the following equation (3) (step S18).

Vf’＝Vf+VD……(3)

Then, the charge control unit 210 compares the terminal voltage V1 with the charge end voltage Vf' (step S19). Next, when the terminal voltage V1 is equal to or higher than the charging end voltage Vf' (YES in step S19), the charging control unit 210 sends a charging end instruction signal to the charging control unit 31a. Then, in response to the control signal from the charging control unit 31a, the charging current supply circuit 33 stops supplying the charging current, and charging ends (step S20).

On the other hand, in step S19, when the terminal voltage V1 has not yet reached the charging end voltage Vf' (NO in step S19), the charging control unit 210 waits for 1 second, and adds 1 to the variable t for counting. (step S21).

Next, after 1 second has elapsed, charging control unit 210 compares variable t with 300 (step S22). Then, when the variable t has not yet reached 300 (No in step S22), and 5 minutes have not passed, repeat steps S14 to S19 every 1 minute, update the charging end voltage Vf', and execute the charging end judgment in step S19 .

On the other hand, when the variable t is equal to or greater than 300 (Yes in step S22), and more than five minutes have elapsed, the charging control unit 210 initializes the variable t (step S23), and sends a message to the charging control unit 31a to Indication signal that the charging current is zero. Then, in response to the control signal from the charging control unit 31a, the charging current supply circuit 33 stops supplying the charging current (step S24). Next, repeat steps S12 to S19 again, re-measure the open-circuit voltage V1', thereby correcting the change of the open-circuit voltage V1' caused by, for example, changes in the temperature environment, etc., and update the charging end voltage Vf', and execute the charging end determination in step S19 .

(Example 4)

FIG. 10 is a block diagram showing an example of the configuration of an electronic device according to Embodiment 4 of the present invention. In FIG. 10 , the same components as those of the electronic device shown in FIG. 1 and FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. The electronic device shown in FIG. 10 differs from the electronic device shown in FIG. 8 in the following points. That is, in the electronic device shown in FIG. 10 , the control unit 21 b also functions as the SOC acquisition unit 213 and the degradation detection unit 214 . Furthermore, the degradation detection unit 214 functions as an OCV acquisition unit, a CCV acquisition unit, and an actual internal resistance calculation unit. Furthermore, the operations of the internal resistance estimation unit 211b and the end voltage calculation unit 212b are different. In addition, the control unit 21 b has a nonvolatile storage element such as ROM storing a data table indicating the correspondence relationship between the temperature T and the SOC of the secondary battery 14 and the internal resistance value R of the secondary battery 14 in advance.

Since other configurations are the same as those of the electronic device shown in FIG. 9 , description thereof will be omitted, and the characteristic operation of the electronic device shown in FIG. 10 will be described. 11 , 12 , and 13 are flowcharts showing an example of the operation of the electronic device shown in FIG. 10 .

First, as in the flow chart shown in FIG. 8 , after steps S11 to S13 are executed, the actual internal resistance value R′ which is the actual internal resistance value of the secondary battery 14 is detected by the deterioration detection unit 214 (actual internal resistance calculation unit). . Fig. 12 is a flowchart showing an example of the detection operation of the actual internal resistance value R'.

The degradation detection unit 214 acquires the current value I detected by the current detection impedance 16 (step S31). Then, the degradation detection unit 214 (CCV acquisition unit) acquires the terminal voltage V1 detected by the voltage detection circuit 20 as a closed-circuit terminal voltage (step S32 ). Furthermore, the degradation detection unit 214 (OCV acquisition unit) acquires the open-circuit voltage V1' detected in step S12 as the open-circuit terminal voltage.

Next, the degradation detection unit 214 (actual internal resistance calculation unit) calculates the internal resistance value R' based on the following formula (4), and ends the detection operation of the actual internal resistance value R' (step S33).

R’＝(V1-V1’)/I……(4)

Next, return to FIG. 11 and calculate the deterioration coefficient P (step S40). FIG. 13 is a flowchart showing an example of the calculation operation of the deterioration coefficient P. First, the temperature T of the secondary battery 14 is detected by the temperature sensor 17 (step S41). Next, the SOC of the secondary battery 14 is calculated by the SOC acquiring unit 213 (step S42).

The SOC acquisition unit 213 can calculate the SOC of the secondary battery 14 by, for example, always integrating the charge and discharge current detected by the current detection impedance 16, or by converting the terminal voltage V1 of the secondary battery 14 detected by the voltage detection circuit 20 into SOC to calculate SOC.

Next, the internal resistance value R corresponding to the temperature T and SOC obtained in steps S41 and S42 is acquired by the internal resistance estimating unit 211b through, for example, a data table stored in the ROM (step S43).

Therefore, since the internal resistance value R corresponds to the internal resistance value of the secondary battery 14 when it is not deteriorated, the more serious the deterioration of the secondary battery 14 is, the greater the difference between the internal resistance value R and the actual internal resistance value R' is.

Therefore, the degree of deterioration P is calculated by the degree of deterioration calculation unit 214 so that the greater the difference between the internal resistance value R and the actual internal resistance value R', for example, the smaller the R/R', the greater the degree of deterioration (step S44) .

Specifically, the degree of deterioration P is a numerical value equal to or less than "1" acquired using, for example, a preset function or a data table, and the smaller R/R' is, the smaller the value is.

Next, returning to Fig. 11 , the end-of-charge voltage Vf' is calculated by the end-of-charge calculation unit 212b based on the following equation (5) (step S50).

Vf’＝P×Vf+VD……(5)

Accordingly, the end-of-charge voltage Vf' is corrected such that the greater the degree of deterioration indicated by the degree of deterioration P, the lower the end-of-charge voltage.

The more severe the deterioration of the lithium series secondary battery is, the easier it is to further deteriorate when the charging voltage is increased. Therefore, if the lithium-based secondary battery is charged until it reaches a constant terminal voltage regardless of the degree of deterioration, the more deteriorated the battery, the further the deterioration will be, and the deterioration will be accelerated. However, according to the electronic equipment shown in FIG. 10, since the charge end voltage Vf' is corrected so that the greater the degree of deterioration indicated by the degree of deterioration P, the lower the charge end voltage Vf', the acceleration of the secondary battery can be reduced. 14 Possibility of deterioration.

Hereinafter, since the operation of steps S19 to S24 is the same as the flowchart shown in FIG. 9 , description thereof will be omitted.

In addition, as shown in FIG. 14, charger 2c may include at least some of SOC acquisition unit 213, degradation detection unit 214, internal resistance estimation unit 211 (211b), and end voltage calculation unit 212 (212b).

That is, an electronic device according to the present invention includes: a lithium-series secondary battery; a charging current supply unit configured to quickly charge the lithium-series secondary battery; a charging control unit that controls the charging current supplied by the charging current supply unit. a temperature detection unit that detects the temperature of the lithium series secondary battery; a voltage detection unit that detects the terminal voltage of the lithium series secondary battery; and a setting unit that sets the charging end voltage of the charging control unit, wherein the charging The control unit causes the charging current supply unit to supply a predetermined constant rapid charging current to the lithium-series secondary battery, and when the terminal voltage detected by the voltage detection unit reaches the charging end set by the setting unit voltage, the charging current supply unit ends the supply of the quick charging current, and the setting unit includes: estimating the internal resistance of the lithium series secondary battery based on the temperature of the lithium series secondary battery detected by the temperature detection unit. value of the internal resistance estimating part; and based on the internal resistance value estimated by the above-mentioned internal resistance estimating part and the above-mentioned fast charging current value, the amount of voltage drop caused by the above-mentioned internal resistance is estimated, and by adding the above-mentioned voltage drop amount to the preset The end voltage calculation unit that calculates the above-mentioned end-of-charging voltage from the reference voltage.

Moreover, the rapid charging method for lithium series secondary batteries related to the present invention is used to rapidly charge lithium series secondary batteries until reaching a specified end-of-charge voltage, comprising the steps of continuously supplying a predetermined constant rapid charging A step of current flow; a step of detecting at least the temperature of the above-mentioned lithium series secondary battery; a step of estimating the internal resistance value of the above-mentioned lithium series secondary battery based on the detected temperature; based on the estimated above-mentioned internal resistance value and the above-mentioned fast charging current value , a step of estimating a voltage drop caused by the internal resistance; and a step of calculating the charging end voltage by adding the voltage drop to a preset reference voltage.

According to this configuration, conventionally, CC (constant current) charging is performed until a predetermined end-of-charge voltage is reached, and switching to CV (constant voltage) charging after reaching the end-of-charge voltage is a fast process for secondary batteries such as general lithium-ion batteries. In the charging method and the electronic device using the method, the charging control unit maintains the charging current supplied from the charging current supply unit to the battery pack at a predetermined constant quick charging current when quick charging is performed.

Furthermore, the charging control unit determines that the secondary battery is fully charged when the terminal voltage detected by the voltage detecting unit reaches the charging end voltage, and stops the charging current supply unit from supplying the rapid charging current. The end-of-charge voltage is generally not a fixed value, but is appropriately set according to battery temperature, ambient temperature, etc. In the present invention, the end-of-charge voltage is set in consideration of the amount of voltage drop due to internal resistance. Furthermore, the temperature-induced variation of this internal resistance (the higher the temperature, the smaller it is) is compensated.

Specifically, the setting unit estimates the internal resistance value of the secondary battery based on the temperature of the secondary battery detected by the temperature detection unit, and estimates the internal resistance value of the secondary battery based on the estimated internal resistance value and the previously obtained rapid charging current value. The amount of voltage drop caused by the above-mentioned internal resistance is calculated by adding the above-mentioned voltage drop amount to a preset reference voltage to calculate and set the above-mentioned end-of-charge voltage.

Therefore, the charged terminal voltage of the secondary battery is higher than the reference voltage by a voltage equivalent to the voltage drop caused by the charging current flowing through the internal resistance of the secondary battery. As a result, the open circuit voltage of the secondary battery does not Overcharging occurs when the reference voltage is exceeded. Accordingly, it is possible to supply a constant large current all the time while preventing overcharging, and perform rapid charging. Furthermore, since the internal resistance value is estimated based on the temperature of the secondary battery, charging does not need to be interrupted to measure the internal resistance value, thereby reducing the possibility of prolonging the charging time for measuring the internal resistance value.

Furthermore, preferably, the reference voltage is an open-circuit voltage when the lithium-based secondary battery is fully charged.

According to this configuration, since the lithium-based secondary battery is charged with a constant current until it is fully charged with a constant charging current, the charging time can be shortened.

Furthermore, it is preferable that the lithium-based secondary battery is a non-aqueous electrolyte secondary battery having a heat-resistant layer between the negative electrode and the positive electrode.

Furthermore, it is preferable that the heat-resistant layer is a porous protective film containing a resin binder and an inorganic oxide filler.

According to this structure, in a non-aqueous electrolyte secondary battery having a heat-resistant layer formed by a porous protective film containing a resin binder and an inorganic oxide filler between the negative electrode and the positive electrode, even if it reaches an overcharged state, , metallic lithium precipitates in a dendritic shape, and the heat-resistant layer can also prevent a short circuit between the negative electrode and the positive electrode, and is suitable for rapid charging using the above-mentioned constant current.

In particular, when the full-charge voltage, which is the open-circuit voltage when the lithium-series secondary battery is fully charged, is set as the above-mentioned reference voltage, since the closed-circuit voltage of the lithium-series secondary battery is charged to exceed the full-charge voltage, it is different from using The charging voltage is higher than that of the conventional charging method in which constant voltage charging is performed at the full charging voltage. However, due to the heat-resistant layer, sufficient safety can be ensured even if the charging voltage is higher than that of the conventional charging method.

Furthermore, it is preferable to further include an SOC obtaining unit for obtaining information indicating the SOC of the lithium-based secondary battery, and the internal resistance estimating unit further includes, in addition to the temperature of the lithium-based secondary battery, based on the temperature obtained by the SOC obtaining unit. The obtained information indicating the SOC estimates the above-mentioned internal resistance value.

The internal resistance value of lithium series secondary batteries varies not only with temperature but also with SOC. Therefore, according to this configuration, the internal resistance estimating unit estimates the internal resistance value of the lithium secondary battery using information indicating the SOC in addition to the temperature of the lithium secondary battery, thereby improving the estimation accuracy of the internal resistance value.

Furthermore, preferably, the internal resistance estimating unit estimates the internal resistance value using a temperature of the lithium-based secondary battery and a data table indicating a correspondence relationship between the SOC information and the internal resistance value.

According to this configuration, the internal resistance estimation unit can estimate the internal resistance value corresponding to the temperature of the lithium-based secondary battery detected by the temperature detection unit and the information indicating the SOC acquired by the SOC acquisition unit in the data table. The internal resistance value of the lithium series secondary battery, therefore, the estimation of the internal resistance value is easy.

Furthermore, it is preferable to further include a deterioration detecting unit that detects a degree of deterioration indicating the degree of deterioration of the lithium-based secondary battery, and the internal resistance estimating unit includes information indicating the temperature of the lithium-based secondary battery and the SOC in addition to , and also estimate the internal resistance value based on the degree of degradation detected by the degradation detection unit.

The internal resistance value of the lithium-series secondary battery varies corresponding to the degree of deterioration of the lithium-series secondary battery. Therefore, according to this configuration, the internal resistance estimating unit estimates the internal resistance value of the lithium-based secondary battery using the degree of deterioration in addition to the temperature of the lithium-based secondary battery and information indicating the SOC, so that the estimation of the internal resistance value can be improved. precision.

Furthermore, it is preferable that the deterioration detection unit includes an OCV acquisition unit configured to use the terminal voltage detected by the voltage detection unit as an open terminal when the current supplied from the charging current supply unit to the lithium-based secondary battery is zero. The CCV acquisition unit obtains the terminal voltage detected by the voltage detection unit as a closed-circuit terminal voltage when the rapid charging current is supplied from the charging current supply unit to the lithium series secondary battery; the actual internal resistance calculation unit , dividing the difference between the closed-circuit terminal voltage obtained by the CCV obtaining unit and the open-circuit terminal voltage obtained by the OCV obtaining unit by the above-mentioned fast charging current value, thereby calculating the actual internal resistance value of the lithium series secondary battery as the actual internal resistance value; and the degree of deterioration calculation unit calculates that the greater the difference between the internal resistance value estimated by the internal resistance estimation unit and the actual internal resistance value calculated by the actual internal resistance calculation unit is, the greater the degree of deterioration is. In the degree of degradation, the end voltage calculation unit corrects the end-of-charge voltage so that the end-of-charge voltage becomes lower as the degree of deterioration indicated by the degree of degradation calculated by the degree of degradation calculation unit increases.

According to this configuration, the open-circuit voltage of the lithium-based secondary battery is obtained by the OCV obtaining unit, and the closed-circuit voltage of the lithium-based secondary battery is obtained by the CCV obtaining unit. In this way, since the difference between the open circuit voltage and the closed circuit voltage is caused by the voltage drop caused by the internal resistance, the actual internal resistance calculation unit can calculate the difference between the closed circuit terminal voltage and the open circuit terminal voltage by the quick charge current value The actual internal resistance value of the lithium series secondary battery is used as the actual internal resistance value. Also, the deeper the deterioration of the lithium series secondary battery, the greater the internal resistance value.

On the other hand, since the parameters used by the internal resistance estimation unit to estimate the internal resistance value do not reflect deterioration, the internal resistance value estimated by the internal resistance estimation unit becomes the internal resistance value of a non-deteriorated lithium secondary battery. Therefore, the deeper the deterioration of the lithium-based secondary battery, the larger the difference between the internal resistance value estimated by the internal resistance estimation unit and the actual internal resistance value calculated by the actual internal resistance calculation unit. Therefore, the degree of deterioration is calculated by the degree of deterioration calculation unit so that the greater the difference between the internal resistance value estimated by the internal resistance estimation unit and the actual internal resistance value calculated by the actual internal resistance calculation unit, the greater the degree of deterioration. Then, the end-of-charge voltage is corrected by the end-voltage calculation unit so that the end-of-charge voltage becomes lower as the degree of deterioration indicated by the degree of deterioration increases.

The deeper the degree of deterioration of the lithium series secondary battery is, the easier it is to further deteriorate when the charging voltage is increased. Therefore, if the lithium-based secondary battery is charged until it reaches a constant terminal voltage regardless of the degree of deterioration, the more deteriorated the battery, the more the deterioration will increase, and the deterioration will be accelerated. However, according to this configuration, since the end-of-charge voltage is corrected so that the degree of deterioration indicated by the degree of deterioration becomes lower, the end-of-charge voltage becomes lower, and therefore, the possibility of accelerated deterioration of the lithium-based secondary battery can be reduced.

Moreover, it is more desirable that the above-mentioned rapid charging method for a lithium-series secondary battery further includes a step of detecting the degree of deterioration of the above-mentioned lithium-series secondary battery, wherein the step of estimating the internal resistance value excludes the above-mentioned lithium-series secondary battery In addition to temperature, the above-mentioned internal resistance value is also estimated from the terminal voltage and deterioration degree.

According to this configuration, for example, based on a three-dimensional table stored in advance, the internal resistance value corresponding to the temperature, terminal voltage, and degree of deterioration is read from it, or when there is no matching data, the internal resistance value is obtained by interpolation calculation , or the data of the internal resistance value corresponding to the temperature is corrected based on the terminal voltage and the degree of deterioration, and the internal resistance value is obtained in consideration of not only the temperature of the above-mentioned lithium series secondary battery but also the terminal voltage and the degree of deterioration.

Therefore, it is possible to more accurately obtain the end-of-charge voltage which is the internal resistance value of the lithium-based secondary battery.

Industrial availability

When charging lithium series secondary batteries, instead of conventional CC-CV charging, the charging current is maintained at a predetermined constant rapid charging current, and when the terminal voltage reaches the charging end voltage, it is judged to be fully charged, and, The end-of-charge voltage is set to a voltage obtained by adding a predetermined end-of-charge voltage and a voltage drop amount obtained by comparing an internal resistance value estimated from the temperature of the secondary battery with a rapid charge current value. Therefore, overcharging can be prevented, and a constant large current can be supplied all the time, and the battery can be quickly charged to full charge, which is suitable for the rapid charging of the above-mentioned lithium series secondary battery.

Claims (12)

1. An electronic device, characterized in that it comprises: Lithium series secondary batteries; A charging current supply unit, used for fast charging the lithium series secondary battery; a charging control unit that controls a charging current supplied by the charging current supply unit; a temperature detection unit for detecting the temperature of the lithium series secondary battery; a voltage detection section that detects a terminal voltage of the lithium series secondary battery; and a setting unit that sets the charging end voltage of the charging control unit, wherein, The charging control unit causes the charging current supply unit to supply a predetermined constant rapid charging current to the lithium series secondary battery, and when the terminal voltage detected by the voltage detecting unit reaches the When the charging end voltage set by the setting unit is set, the charging current supply unit is caused to stop the supply of the fast charging current, The setting unit includes: an internal resistance estimation unit that estimates an internal resistance value of the secondary battery from the temperature of the lithium-based secondary battery detected by the temperature detection unit; and Estimating the amount of voltage drop due to the internal resistance from the internal resistance value estimated by the internal resistance estimating unit and the fast charging current value, and adding the amount of voltage drop to a preset reference voltage An end voltage calculation unit that calculates the end-of-charging voltage. 2. The electronic device according to claim 1, wherein the reference voltage is an open circuit voltage when the lithium series secondary battery is fully charged. 3. The electronic device according to claim 1 or 2, wherein the lithium series secondary battery is a non-aqueous electrolyte secondary battery having a heat-resistant layer between the negative electrode and the positive electrode. 4. The electronic device according to claim 3, wherein the heat-resistant layer is a porous protective film comprising a resin binder and an inorganic oxide filler. 5. The electronic device according to any one of claims 1 to 4, further comprising: an SOC acquiring unit that acquires information indicating the SOC of the lithium-based secondary battery, The internal resistance estimation unit estimates the internal resistance value based on the information indicating the SOC acquired by the SOC acquisition unit in addition to the temperature of the lithium-based secondary battery. 6. The electronic device according to claim 5, wherein the internal resistance estimating unit uses the temperature of the lithium-series secondary battery and the correspondence relationship between the information indicating the SOC and the internal resistance value data sheet, deduce the internal resistance value. 7. The electronic device according to claim 5 or 6, further comprising: a deterioration detection section that detects a degree of deterioration indicating a degree of deterioration of the lithium series secondary battery, The internal resistance estimation unit estimates the internal resistance value based on the degree of degradation detected by the degradation detection unit, in addition to the temperature of the lithium-based secondary battery and the information indicating the SOC. 8. The electronic device according to claim 5 or 6, wherein the degradation detection unit comprises: an OCV acquisition unit that acquires a terminal voltage detected by the voltage detection unit as an open terminal voltage when the current supplied from the charging current supply unit to the lithium-series secondary battery is zero; a CCV acquisition unit that acquires a terminal voltage detected by the voltage detection unit as a closed-circuit terminal voltage when the rapid charging current is supplied from the charging current supply unit to the lithium-series secondary battery; The actual internal resistance value of the lithium-series secondary battery is calculated by dividing the difference between the closed-circuit terminal voltage obtained by the CCV obtaining unit and the open-circuit terminal voltage obtained by the OCV obtaining unit by the quick charge current value. an actual internal resistance calculation section as an actual internal resistance value; and The degree of deterioration is calculated such that the greater the difference between the internal resistance value estimated by the internal resistance estimating unit and the actual internal resistance value calculated by the actual internal resistance calculating unit, the greater the degree of deterioration. Degree Calculation Department, among them, The end voltage calculation unit corrects the end-of-charge voltage so that the end-of-charge voltage becomes lower as the degree of deterioration indicated by the degree of deterioration calculated by the degree-of-deterioration calculation unit increases. 9. The electronic device according to any one of claims 5 to 8, wherein the information indicating the SOC is a terminal voltage of the lithium-series secondary battery. 10. A fast charging method for a lithium series secondary battery, used for fast charging the lithium series secondary battery until reaching a specified end-of-charge voltage, characterized in that it comprises the following steps: the step of continuously supplying a predetermined constant fast charging current; a step of detecting at least the temperature of the secondary battery; a step of estimating the internal resistance value of the secondary battery according to the detected temperature; a step of estimating a voltage drop caused by the internal resistance based on the estimated internal resistance value and the fast charging current value; A step of calculating the charge end voltage by adding the voltage drop amount to a preset reference voltage. 11. The rapid charging method of lithium series secondary battery according to claim 10, characterized in that: said lithium series secondary battery is a non-aqueous electrolyte secondary battery with a heat-resistant layer between the negative electrode and the positive electrode. 12. The fast charging method for lithium series secondary batteries according to claim 10 or 11, further comprising: A step of detecting a degree of deterioration indicating a degree of deterioration of the lithium series secondary battery, wherein, In the step of estimating the internal resistance value, the internal resistance value is estimated from the terminal voltage and the degree of deterioration in addition to the temperature of the lithium-series secondary battery.

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