JP6791702B2 - Rechargeable battery module - Google Patents

Description

The present invention relates to a deterioration estimation method and a deterioration estimation device, for example, in a secondary battery module used as a power source for an automobile.

In recent years, lithium ion secondary batteries have been used as a power source for electric vehicles and hybrid vehicles. Lithium-ion secondary batteries for automobiles are required to have high output, high energy density, and long life.

In addition, there is an idea that lithium-ion secondary batteries can be used for a long life from the viewpoint of control. Therefore, it is also required to accurately grasp the deteriorated state of the lithium ion secondary battery and appropriately control it based on the deteriorated state.

In order to solve the above problems, Patent Document 1 discloses an estimation method for estimating the deterioration state of the secondary battery used.

Patent No. 5466564

In Patent Document 1, the deterioration state of the battery is estimated by converting the usage conditions subdivided according to the temperature and the charging state (SOC: State Of Charge) into a single reference deterioration mode.

However, in the method of Patent Document 1, since the condition not assuming actual running is used as the reference deterioration mode, the deterioration prediction does not take into consideration the variation for each battery.

Therefore, an object of the present invention is to solve the above problems. Specifically, it is an object of the present invention to provide a deterioration prediction method and a deterioration prediction device in consideration of variations among batteries.

In order to solve the above problems, the secondary battery module in the present invention includes a secondary battery, a current measuring unit that measures the current of the secondary battery, a temperature measuring unit that measures the temperature of the secondary battery, and time. The calculation unit includes a timer for measuring the above, and a calculation unit for calculating the current time integration amount and the SOC range of the secondary battery from the measured current and the time by the timer, and the calculation unit calculates the SOC range. When, separately for each category that combines the temperature range including the measured temperature, the current changes in the degradation rate of the secondary battery was recorded against time integration amount, the first at a given the SOC range the current time integrated amount in a temperature range, converts the current time integrated amount in a second temperature range corresponding to the deterioration rate for the current time integrated amount, then, in a second temperature range, relative to the current time integrated amount calculating a deterioration rate in accordance with changes in the degradation rate of the secondary battery.

Further, in the secondary battery module of the present invention, when a predetermined voltage value is exceeded from the secondary battery, the measuring unit for measuring the voltage of the secondary battery, and the measured voltage, the upper limit value of the used SOC range is lowered.

According to the present invention, deterioration can be predicted without going through a reference deterioration mode that does not assume actual driving, so that more accurate deterioration prediction can be performed.

External perspective view of a square secondary battery An exploded perspective view of a square secondary battery An exploded perspective view of the wound electrode group Block conceptual diagram of the secondary battery module 1 according to this embodiment Classification table of current integrated amount corresponding to temperature-SOC of this embodiment Cycle characteristic diagram corresponding to the classification table of this embodiment Control flowchart of this embodiment The figure explaining the method of the iterative operation Method of calculating total deterioration rate using FIG.

Hereinafter, Example 1 will be described.

FIG. 1 is an external perspective view of the square secondary battery 100.

The square secondary battery 100 includes a battery can 1 and a lid (battery lid) 6. The battery can 1 has a side surface and a bottom surface having a pair of opposing wide surfaces having a relatively large area and a pair of opposing narrow surfaces having a relatively small area, and an opening 1a above the side surface (FIG. 2). ) .

The winding group 3 (FIG. 2) is housed in the battery can 1, and the opening 1a of the battery can 1 is sealed by the battery lid 6. The battery lid 6 has a substantially rectangular flat plate shape, and is welded so as to close the upper opening 1a of the battery can 1 to seal the battery can 1. The battery lid 6 is provided with a positive electrode external terminal 12 and a negative electrode external terminal 14 . The winding group 3 is charged via the positive electrode external terminal 12 and the negative electrode external terminal 14 , and power is supplied to the external load. A gas discharge valve 10 is integrally provided on the battery lid 6, and when the pressure inside the battery container rises, the gas discharge valve 10 opens to discharge gas from the inside, and the pressure inside the battery container is reduced. As a result, the safety of the square secondary battery 100 is ensured.

FIG. 2 is an exploded perspective view of the square secondary battery 100 .

The battery can 1 of the prismatic secondary battery 100 has a rectangular bottom surface 1d, a rectangular cylindrical side surface 1b which rises from the bottom 1d, and an opening 1a, which is open upward at the upper end of the side surface 1b .. The winding group 3 is housed in the battery can 1 via the insulating protective film 2.

Since the winding group 3 is wound in a flat shape, it has a pair of curved portions having a semicircular cross section facing each other and a flat surface portion continuously formed between the pair of curved portions. ing. The winding group 3 is inserted into the battery can 1 from one curved portion side so that the winding axis direction is along the lateral width direction of the battery can 1, and the other curved portion side is arranged on the upper opening side.

The positive electrode foil exposed portion 32c of the winding group 3 is electrically connected to the positive electrode external terminal 12 provided on the battery lid 6 via the positive electrode current collector plate (current collector terminal) 24 . Further, the negative electrode foil exposed portion 34c of the winding group 3 is electrically connected to the negative electrode external terminal 14 provided on the battery lid 6 via the negative electrode current collector plate (current collector terminal) 44 . Thus, from outside winding assembly 3 via a positive current collector plate 24 and negative electrode current collector plate 44 is supplied electric power to the external load, the winding assembly 3 via a positive current collector plate 24 and negative electrode terminal plate 44 The generated power is supplied and charged.

A gasket 5 and an insulating plate 7 are provided on the battery lid 6 in order to electrically insulate the positive electrode current collector plate 24 and the negative electrode current collector plate 44 , and the positive electrode external terminal 12 and the negative electrode external terminal 14 from the battery lid 6, respectively. Has been done. Further, after injecting the electrolytic solution into the battery can 1 from the liquid injection port 9, the liquid injection plug 11 is joined to the battery lid 6 by laser welding to seal the liquid injection port 9, and the square secondary battery 100 is sealed. To do.

Here, examples of the material for forming the positive electrode external terminal 12 and the positive electrode current collector plate 24 include an aluminum alloy, and examples of the material for forming the negative electrode external terminal 14 and the negative electrode current collector plate 44 include a copper alloy. Examples of the material for forming the insulating plate 7 and the gasket 5 include resin materials having insulating properties such as polybutylene terephthalate, polyphenylene sulfide, and perfluoroalkoxy fluororesin.

Further, the battery lid 6 is provided with a liquid injection port 9 for injecting an electrolytic solution into the battery container, and the liquid injection port 9 is a liquid injection plug after injecting the electrolytic solution into the battery container. Sealed by 11. Here, as the electrolytic solution to be injected into the battery container, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF6) is dissolved in a carbonic acid ester-based organic solvent such as ethylene carbonate is applied. can do.

The positive electrode external terminal 12 and the negative electrode external terminal 14 have a welded joint portion to be welded to a bus bar or the like. The welded joint has a rectangular parallelepiped block shape that protrudes upward from the battery lid 6, and has a configuration in which the lower surface faces the surface of the battery lid 6 and the upper surface is parallel to the battery lid 6 at a predetermined height position. Have.

The positive electrode connection portion 12 a and the negative electrode connection portion 14 a are cylinders whose tips protrude from the lower surfaces of the positive electrode external terminal 12 and the negative electrode external terminal 14 , respectively, and whose tips can be inserted into the positive electrode side through hole 26 and the negative electrode side through hole 46 of the battery lid 6. It has a shape. The positive electrode connection portion 12a and the negative electrode connection portion 14a penetrate the battery lid 6 and penetrate the inside of the battery can 1 rather than the positive electrode current collector plate 24 , the positive electrode current collector plate base 21 of the negative electrode current collector plate 44 , and the negative electrode current collector plate base 41. The positive electrode external terminal 12 , the negative electrode external terminal 14 , the positive electrode current collector plate 24 , and the negative electrode current collector plate 44 are integrally fixed to the battery lid 6 by projecting to the side and crimping the tip. A gasket 5 is interposed between the positive electrode external terminal 12 , the negative electrode external terminal 14, and the battery lid 6, and an insulating plate is interposed between the positive electrode current collector plate 24 , the negative electrode current collector plate 44, and the battery lid 6. 7 is intervened.

The positive electrode current collector plate 24 and the negative electrode current collector plate 44 are a rectangular plate-shaped positive electrode current collector plate base portion 21 , a negative electrode current collector plate base portion 41, and a positive electrode current collector plate base portion 21 arranged so as to face the lower surface of the battery lid 6. , It is bent at the side end of the negative electrode current collector plate base 41 and extends toward the bottom surface along the wide surface of the battery can 1 to the positive electrode foil connecting portion 32c and the negative electrode foil connecting portion 34c of the winding group 3. It has a positive electrode side connection end 22 and a negative electrode side connection end 42 that are connected so as to face each other and overlap each other. The positive electrode current collector plate base 22 and the negative electrode current collector plate base 42 are formed with a positive electrode connection portion 22 , a positive electrode side opening hole 23 through which the negative electrode connection portion 42 is inserted, and a negative electrode side opening hole 41 , respectively.

The insulating protective film 2 is wound around the winding group 3 with the direction along the flat surface of the winding group 3 and orthogonal to the winding axis direction of the winding group 3 as the central axis direction. The insulating protective film 2 is made of a single sheet or a plurality of film members made of synthetic resin such as PP (polypropylene), and is in a direction parallel to the flat surface of the winding group 3 and orthogonal to the winding axis direction. Has a length that can be wound as a winding center.

FIG. 3 is an exploded perspective view showing a state in which a part of the wound electrode group is unfolded.

The winding group 3 is configured by winding the negative electrode 32 and the positive electrode 34 in a flat shape with a separator 33 in between. In the winding group 3, the outermost electrode is the negative electrode 32, and the separator 35 is wound on the outer side thereof. The separators 33 and 35 have a role of insulating between the positive electrode 31 and the negative electrode 32.

Negative electrode mixture 32b of negative electrode 32 is coated portion is larger in the widthwise direction than the portion cathode mixture 34b of the positive electrode 34 is applied, thereby a portion electrode mixture 34b is applied is always negative It is configured to be sandwiched between the portions where the mixture 32b is applied. The positive electrode foil exposed portion 34c and the negative electrode foil exposed portion 32c are bundled at a flat surface portion and connected by welding or the like. The separator 33 is wider in the width direction than the portion coated with the negative electrode mixture 32b, but is wound at a position where the metal foil surface at the end is exposed at the positive electrode foil exposed portion 34c and the negative electrode foil exposed portion 32c. Therefore, it does not hinder the case of bundling and welding.

The positive electrode electrode 34 has a positive electrode active material mixture on both sides of the positive electrode foil which is a positive electrode current collector, and the positive electrode foil is not coated with the positive electrode active material mixture on one end in the width direction of the positive electrode foil. An exposed portion 34c is provided.

The negative electrode electrode 32 has a negative electrode active material mixture on both sides of the negative electrode electrode foil which is a negative electrode current collector, and a negative electrode foil in which the negative electrode active material mixture is not applied to the other end in the width direction of the positive electrode electrode foil. An exposed portion 32c is provided. The positive electrode foil exposed portion 34c and the negative electrode foil exposed portion 32c are regions where the metal surface of the electrode foil is exposed, and are wound so as to be arranged at positions on one side and the other side in the winding axis direction.

Regarding the negative electrode 32, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) was added as a binder to 100 parts by weight of the amorphous carbon powder as the negative electrode active material, and N was added as a dispersion solvent. -Methylpyrrolidone (hereinafter referred to as NMP) was added and kneaded to prepare a negative electrode mixture. This negative electrode mixture was applied to both sides of a copper foil (negative electrode electrode foil) having a thickness of 10 μm, leaving welded portions (negative electrode uncoated portions). Then, through the drying, pressing, and cutting steps, a negative electrode 32 having a thickness of 70 μm in the negative electrode active material coating portion containing no copper foil was obtained.

In this embodiment, the case where amorphous carbon is used as the negative electrode active material has been illustrated, but the present invention is not limited to this, and natural graphite capable of inserting and removing lithium ions and various artificial graphite materials are used. , A carbonaceous material such as coke, a compound such as Si or Sn (for example, SiO, TiSi2, etc.), or a composite material thereof, and the particle shape thereof is particularly limited to scaly, spherical, fibrous, lumpy, etc. It is not something that is done.

Regarding the positive electrode electrode 34 , 10 parts by weight of scaly graphite as a conductive material and 10 parts by weight of PVDF as a binder were added to 100 parts by weight of lithium manganate (chemical formula LiMn2O4) as a positive electrode active material. NMP was added as a dispersion solvent and kneaded to prepare a positive electrode mixture. This positive electrode mixture was applied to both sides of an aluminum foil (positive electrode electrode foil) having a thickness of 20 μm, leaving welded portions (positive electrode uncoated portions). Then, through a drying, pressing, and cutting steps, a positive electrode 34 having a thickness of 90 μm in the positive electrode active material coating portion containing no aluminum foil was obtained.

Further, in the present embodiment, the case where lithium manganate is used as the positive electrode active material has been illustrated, but other lithium manganate having a spinel crystal structure, a lithium manganese composite oxide obtained by partially substituting or doping with a metal element, or a layered layer. Lithium cobalt oxide or lithium titanate having a crystal structure or a lithium-metal composite oxide obtained by substituting or doping a part of these with a metal element may be used.

Further, in the present embodiment, the case where PVDF is used as a binder for the coated portion of the positive electrode electrode 34 and the negative electrode electrode 32 has been illustrated, but polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, and nitrile rubber have been exemplified. , Styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latex, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, polymers such as acrylic resin, and mixtures thereof. Can be used. Further, as the shaft core, for example, a resin sheet having a higher bending rigidity than any of the positive electrode 34 , the negative electrode 32 , and the separators 33 and 35 can be used.

Subsequently, the block conceptual diagram of the secondary battery module 101 according to the present embodiment will be described with reference to FIG. The secondary battery module 101 of the present embodiment is configured by connecting a plurality of square secondary batteries 100 in series and including a control circuit such as a calculation unit 107. The current measuring means 104 is connected to the series circuit, and detects the current flowing through the series circuit.

Then, the current information detected by the current measuring means 104 is transmitted to the calculation unit 107. On the other hand, the voltage measuring means 103 is provided in parallel with this series circuit. The voltage information measured by the voltage detecting means 103 is also output to the calculation unit 107.

Further, the temperature information of the square secondary battery 100 and the time information output from the timer 106 are input to the calculation unit 107. Then, the calculation unit 107 calculates the SOC from this information and records the value so as to be associated with the classification table 108 of the current time integrated total amount value. By adopting such a method, the actual data of the square secondary battery 100 currently in use can be accumulated.

FIG. 5 is a table for associating the temperature with the SOC range, and the current time integration amount is stored for each. This data is stored in a storage unit (not shown) stored in the battery controller as A1, A2, A3, B1, B2, ... C3. In this embodiment, a 3 × 3 matrix will be used for explanation, but as the number of matrices increases, more accurate deterioration prediction becomes possible. On the other hand, the smaller the number of matrices, the smaller the calculation load.

Further, the present embodiment has an approximate expression of a deterioration curve corresponding to each temperature-SOC range as shown in FIG. Therefore, it is possible to perform the control as shown in FIG. 7, and it is possible to predict the deterioration without going through the reference deterioration mode that does not assume the actual running. Therefore, it is possible to perform more accurate deterioration prediction.

Subsequently, the control method of the present embodiment will be described with reference to FIG. 7.

First, in step S1, the deterioration rate is calculated by using an approximate expression of the deterioration curve from the current-time integration amount of A1 having an SOC range of 0 to 30% and a temperature of -30 to 25 ° C.

Then, in step S2, the current-time integrated amount X1 corresponding to the deterioration amount calculated in step S1 is calculated from the approximate expression of the deterioration curve having an SOC range of 0 to 30% and a temperature of 25 to 45 ° C.

After that, in step S3, the current time integrated amount X1 calculated in step S2, the SOC range 0 to 30%, and the current time integrated amount A2 at a temperature of 25 to 45 ° C. are added, and the SOC range 0 to 30% and the temperature 25 to 25 to The deterioration rate is calculated from the approximate expression of the deterioration curve at 50 ° C.

Finally, the SOC range 50 to 100% and the current time integration amount C3 at a temperature of 45 to 60 ° C. are added to the current time integration amount X8 calculated by iterative calculation as described in step S4, and the SOC range 50 The total deterioration rate is calculated from the approximate expression of the deterioration curve at ~ 100% and the temperature of 45 to 60 ° C.

FIG. 8 is a diagram showing a repeating calculation order. In the present embodiment, the calculation is performed in the order of A1, A2, A3, then B1, B2, B3, and finally C1, C2, C3. On the other hand, if it is within the same SOC range, it is not necessary to be particular about the calculation order, and the calculation may be performed in order from B1 instead of calculating in order from A1, or may be calculated in order from C1.

FIG. 9 is a diagram visually showing the calculations of C2 to C3 in FIG. In this way, the final total deterioration rate is calculated by converting the deterioration rate at C2 into the current-time integration amount X8 of the deterioration formula corresponding to C3, adding C3 further, and substituting it into the deterioration formula. It will be.

By controlling as described above, deterioration can be predicted without going through a reference deterioration mode that does not assume actual driving. Therefore, it is possible to perform more accurate deterioration prediction.

The first embodiment will be briefly summarized. The deterioration prediction device described in the present invention includes a secondary battery, a voltage measuring unit that measures the voltage of the secondary battery, a current measuring unit that measures the current of the secondary battery, and a secondary from the measured current and voltage. In the deterioration prediction device having a calculation unit for calculating the current time integration amount and the used SOC range of the battery, the calculation unit calculates the current time integration amount in the first temperature range and the second temperature range in the predetermined SOC range. , The current time integration amount in the first temperature range is converted into the current time integration amount in the second temperature range, and the total value of the current time integration amount in the second temperature range and the converted current time integration amount. It is characterized in that the total deterioration rate is calculated using. With such a configuration, deterioration can be predicted without going through a reference deterioration mode that does not assume actual driving. Therefore, it is possible to perform more accurate deterioration prediction.

1 ... Battery can, 1a ... Opening, 2 ... Insulation protective film, 3 ... Winding group, 4A ... Positive electrode current collector, 4B ... Negative electrode current collector, 5 ... Gasket, 6 ... Battery lid, 6A ... Positive electrode side penetration Holes, 6B ... Negative electrode side through holes, 7 ... Insulating plate, 8A ... Positive electrode external terminal, 8B ... Negative electrode external terminal, 9 ... Liquid injection port, 10 ... Gas discharge valve, 11 ... Liquid injection plug, 12A ... Positive electrode connection, 12B ... Negative electrode connection part, 21 ... Side surface, 22 ... Bottom surface, 31 ... Positive electrode, 31a ... Positive electrode foil, 31b ... Positive electrode mixture, 31c ... Positive electrode foil exposed part, 32 ... Negative electrode, 32a ... Negative electrode foil, 32b ... Negative electrode Mixture, 32c ... Negative electrode foil exposed part, 31d ... Positive electrode foil connection part, 32d ... Negative electrode foil connection part, 33 ... Separator, 100 ... Square secondary battery, 101 ... Secondary battery module, 103 ... Voltage measuring means, 104 ... Current measuring means, 107 ... Calculation unit, 108 ... Table

Claims (1)

In the secondary battery module
With a secondary battery
A current measuring unit that measures the current of the secondary battery,
A temperature measuring unit that measures the temperature of the secondary battery,
With a timer to measure time,
It is provided with a calculation unit that calculates the current time integration amount and SOC range of the secondary battery from the measured current and the time by the timer.
The calculation unit
And calculated the SOC range is divided for each category that combines the temperature range including the measured temperature, and record the changes in the degradation rate of the secondary battery with respect to the current time integrated amount,
The current-time integrated amount in the first temperature range in the predetermined SOC range is converted into the current-time integrated amount in the second temperature range corresponding to the deterioration rate with respect to the current-time integrated amount.
Thereafter, the second secondary battery module for calculating the temperature range, the transition to therefore deterioration rate of deterioration rate of the secondary battery with respect to the current time integrated amount of.

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