WO2014128904A1

WO2014128904A1 - Battery control circuit, battery system, and movable body and power storage system equipped with same

Info

Publication number: WO2014128904A1
Application number: PCT/JP2013/054447
Authority: WO
Inventors: 章軍司; 晋山内; 小西　宏明; 孝亮馮
Original assignee: 株式会社日立製作所
Priority date: 2013-02-22
Filing date: 2013-02-22
Publication date: 2014-08-28

Abstract

Provided are a lithium-ion secondary battery control system capable of increasing the output of a battery system, the battery system, and a movable body and a power storage system equipped with the battery system. The battery system according to the present invention is characterized by having a lithium-ion secondary battery in which a solid solution is used as a positive electrode active material and a battery control circuit for controlling the charging and discharging of the lithium-ion secondary battery, wherein the control circuit has: an open circuit voltage (OCV) ratio calculation unit for calculating an open circuit voltage (OCV) ratio from two kinds of open circuit voltage (OCV) information in the increasing and decreasing directions of the state-of-charge (SOC) of the lithium-ion secondary battery; a resistance estimation unit for, based on the open circuit voltage (OCV) ratio information calculated by the open circuit voltage (OCV) ratio calculation unit, estimating a resistance value; and an allowable maximum output calculation unit for, based on the resistance value calculated by the resistance estimation unit, calculating an allowable maximum output.

Description

Battery control circuit, battery system, and mobile body and power storage system including the same

The present invention relates to a battery control circuit for controlling a lithium ion secondary battery, a battery system using the lithium ion secondary battery as a storage medium, and a mobile body and an electric power storage system including the battery system.

In recent years, due to concerns about the prevention of global warming and the depletion of fossil fuels, there are high expectations for electric vehicles that require less energy for driving and power generation systems that use natural energy such as sunlight and wind power. However, these technologies have the following technical problems and are not widely used.

The problem with electric vehicles is that the energy density of the drive battery is low and the mileage with one charge is short. On the other hand, the problem of the power generation system using natural energy is that the amount of power generation is large and a large-capacity power storage means is required for leveling the output, resulting in high costs. In any technique, a secondary battery having a low energy density and a high energy density is required.

Since lithium ion secondary batteries have a higher energy density per weight than other secondary batteries such as nickel metal hydride batteries and lead batteries, they are expected to be applied to electric vehicles and power storage systems. However, in order to meet the demand for electric vehicles and power storage systems, higher energy density is required. In order to increase the energy density of the battery, it is necessary to increase the energy density of the positive electrode and the negative electrode.

Li ₂ MO ₃ —LiM′O ₂ solid solution is expected as a high energy density positive electrode active material. M is one or more elements selected from Mn, Ti, and Zr, and M ′ is one or more elements selected from Ni, Co, Mn, Fe, Ti, Zr, Al, Mg, Cr, and V. It is. Hereinafter, the Li ₂ MO ₃ —LiM′O ₂ solid solution is abbreviated as a solid solution positive electrode active material.

A solid solution in which Li ₂ MO ₃ having a layered structure and electrochemically inactive and LiM′O ₂ having a layered structure and electrochemically active is mixed at the time of initial charge is 4.4 V (relative to lithium metal). Thereafter, all the potentials are expressed by potentials exceeding lithium metal) and are activated by charging at a potential exceeding 200 mAh / g, and are high-capacity positive electrode active materials that can exhibit a large electric capacity exceeding 200 mAh / g (see Patent Document 1). . Therefore, a battery using a solid solution positive electrode active material can achieve high energy density.

Further, in Non-Patent Document 1, when the ratio x of Li ₂ MO ₃ is as low as 0.1, a high capacity exceeding 200 mAh / g cannot be obtained, and when x is 0.3 to 0.7, It is disclosed that a high capacity can be obtained.

Non-Patent Document 2 discloses that Li ₂ MO ₃ alone does not provide a sufficient capacity unless the specific surface area is made very small, and the deterioration is severe in the case of a high specific surface area. For this reason, if the ratio of Li ₂ MO ₃ is too high, it does not function as an electrode, so that a high capacity is obtained and the ratio x of Li ₂ MO ₃ that functions appropriately as an electrode is 0.3 to 0.7. Presumed to be in range.

US Pat. No. 7,468,223

The solid solution positive electrode active materials described in the above cited references have a problem that the electrode resistance is high because the Li ion diffusion coefficient and the electronic conductivity are low. Therefore, in the case of a high capacity battery system using a solid solution positive electrode active material for the positive electrode, high output cannot be obtained due to high resistance. Therefore, in the case of such a high-capacity battery system, a high output cannot be obtained particularly during charging, and the charging time becomes long.

The present invention has been made to solve the above-described problems, and in particular, provides a battery control circuit, a battery system, and a mobile body and a power storage system including the battery control circuit that enable high input / output of the battery system. For the purpose.

The battery system according to the present invention includes xLi ₂ MO _3- (1-x) LiM′O ₂ (where 0.3 <x <0.7, and M is at least one selected from Mn, Ti, and Zr). And M ′ is at least one selected from Ni, Co, Mn, Fe, Ti, Zr, Al, Mg, Cr, and V), and a lithium ion secondary battery using a solid solution expressed as a positive electrode active material And a battery control circuit that controls charging / discharging of the lithium ion secondary battery, and the control circuit is configured to control the charging state (SOC) increasing direction and the charging state (SOC) decreasing direction of the lithium ion secondary battery. An open circuit voltage (OCV) ratio calculation unit calculated from various types of open circuit voltage (OCV) information and a resistance based on the open circuit voltage (OCV) ratio information calculated by the open circuit voltage (OCV) ratio calculation unit Resistance to estimate value And tough, and having a permissible maximum output calculating section tolerated maximum output operation on the basis of the resistance value calculated by the resistance estimator.

In the present invention, even when a solid solution positive electrode active material is used, it is an object to provide a battery control circuit, a battery system, a mobile body including the same, and a power storage system having a reduced charging time.

Schematic configuration diagram of a battery control circuit as an embodiment of the present invention and a battery system including the same Schematic configuration diagram of a conventional battery control circuit and a battery system including the same OCV when changing SOC Resistance when changing SOC Correlation between resistance ratio and OCV ratio Schematic configuration diagram of an electric vehicle equipped with a battery system In schematic configuration diagram of power generation system with battery system

Hereinafter, embodiments of the battery system according to the present invention will be described. However, the present embodiment is an embodiment for explaining the present invention in detail, and is not limited to the present embodiment unless departing from the gist of the present invention, and can be implemented with appropriate modifications. Of course.

As a result of studying to solve the above-described problems, the solid solution positive electrode active material has a resistance value other than the open circuit potential OCV (Open Circuit Voltage) when the SOC (State Of Of Charge) is increased and decreased. It was also found that there is hysteresis, and that the resistance value has a correlation with the open circuit potential OCV.

The cause of the hysteresis is unknown, but due to the hysteresis of the resistance value, the resistance value may differ even at the same SOC and temperature depending on the charge / discharge history.

Specifically, when the SOC is increased from the state where the SOC is 0 to 20% and the SOC is increased, the SOC is decreased from the state where the SOC is discharged from the state where the SOC is approximately 80 to 100%. The resistance is low when the SOC is around 30%.

In addition, when the SOC is reduced by discharging from a state near SOC 70%, the resistance at a SOC near 30% is lower than when the SOC is decreased by discharging from a state near SOC 90%. It becomes close to the resistance when SOC is increased by charging from SOC 0%.

Further, with respect to the OCV, the SOC is reduced to about 30% when the discharge is reduced from the SOC 70% and the SOC is decreased, compared to the case where the SOC is reduced from the SOC 90% and the SOC is decreased. The OCV at is close to when SOC is increased by charging from SOC 0%.

When the SOC is changed in the increasing direction with the maximum SOC width in the battery application (specifically, when the SOC is changed from 0% to 90%, the low resistance state is defined) SOC = q% When OCV is changed to OCV _{q, B} , resistance value is R _{q, B,} and the SOC is changed in the decreasing direction with the maximum SOC width in the battery application (specifically, the SOC is changed from 90% to 0%) The OCV at SOC = q% is defined as OCV _{q, A} , the resistance value is R _{q, A,} and the OCV at SOC = q% after a certain charge / discharge history is defined as OCV _q , When the resistance value is R _q , an OCV when the SOC is changed in a decreasing direction with a wide SOC width, an OCV ratio indicating a closeness to the resistance value, and a resistance ratio are defined by the following equations.
[Equation 1]
OCV ratio x = (OCV _{q, B} −OCV _q ) / (OCV _{q, B} −OCV _{q, A} )
[Equation 2]
Resistance ratio y = (R _{q, B} -R _q ) / (R _{q, B} -R _{q, A} )
The OCV ratio and the resistance ratio have a correlation. Note that the OCV ratio and the resistance ratio were calculated based on the case where the SOC was changed at the maximum SOC width in the battery application. However, if the SOC width is sufficiently wide, the maximum SOC width in the battery application Also good.

Therefore, the battery control circuit according to the present invention has xLi ₂ MO _3- (1-x) LiM′O ₂ (where 0.3 <x <0.7, and M is selected from Mn, Ti, and Zr). Lithium ion using a solid solution represented by at least one kind and M ′ as at least one selected from Ni, Co, Mn, Fe, Ti, Zr, Al, Mg, Cr, and V) as a positive electrode active material Two types of OCV, a high resistance state and a low resistance state, which are obtained by measuring the resistance of the lithium ion secondary battery and the hysteresis characteristics of the OCV in advance, with a battery system using a secondary battery as a power storage medium as a control target. A storage unit that stores calculation parameters, two types of resistance calculation parameters, and an OCV-resistance correlation parameter indicating a correlation between the OCV ratio and the resistance ratio, and a current obtained during operation of the battery system SOC calculating means for calculating the SOC of the lithium ion secondary battery at the time of obtaining the information based on information such as voltage, OCV calculating means for calculating OCV when no current is flowing, and the calculated OCV An OCV ratio calculation means for calculating an OCV ratio from two kinds of OCVs of a high resistance state and a low resistance state, the calculated SOC and OCV ratio, two kinds of resistance calculation parameters, an OCV-resistance correlation parameter, and the like were measured. Battery control parameter calculation means for calculating a control parameter of the battery system to be output externally based on information such as temperature is provided.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, this embodiment is an illustration and this invention is not limited to embodiment illustrated below.

First, a power storage system 100 according to the present invention will be described with reference to FIG. The power storage system 100 according to the present invention includes a battery system 10 and a host system 6 that acquires power information of the battery system 10.

The battery system 10 includes a lithium ion secondary battery 7 and a battery control circuit 1 that measures and estimates the state of the lithium ion secondary battery 7. As a result of measuring and estimating the state of the lithium ion secondary battery 7, the battery control circuit 1 outputs the obtained parameters such as the allowable maximum output W and SOC to the host system 6, and the host system 6 is based on the information. This is a system that controls charging / discharging of the lithium ion secondary battery 7 by limiting the load applied to the battery system 10.

Subsequently, details of the battery control circuit 1 will be described. The battery control circuit 1 includes a storage unit 2, a calculation unit 3, a temperature information acquisition unit 11, a current information acquisition unit 12, and a voltage information acquisition unit 13. In addition, the memory | storage part 2 is comprised with memory and the calculating part 3 is comprised with CPU. The temperature information acquisition unit 11, the current information acquisition unit 12, and the voltage information acquisition unit 13 acquire temperature, current, and voltage information measured from the lithium ion secondary battery 7, respectively.

These pieces of information are each output to the calculation unit 3.

The calculation unit 3 includes an SOC calculation unit 14, an OCV calculation unit 15, an OCV ratio calculation unit 16, and a battery control parameter calculation unit 5.

The SOC calculation unit 14 calculates the SOC of the lithium ion secondary battery 7 based on the current information acquired from the current information acquisition unit 12 described above. On the other hand, the OCV calculation unit 15 receives the voltage information acquired by the voltage information acquisition unit 13 and the SOC information calculated by the SOC calculation unit 14.

Further, the OCV calculation unit 15 receives the high resistance state OCV calculation parameter P1A and the low resistance state OCV calculation parameter P1B stored in advance in the storage unit 2. Based on the voltage information, the SOC information, the high resistance state OCV calculation parameter P1A, and the low resistance state OCV calculation parameter P1B, the OCV calculation unit calculates the OCV. The OCV ratio calculation unit 16 calculates an OCV ratio based on the calculated OCV.

The battery control parameter calculation unit 5 includes a resistance estimation unit 17 and an allowable maximum output calculation unit 18. The battery control parameter calculation unit 5 includes temperature information obtained from the temperature information acquisition unit 11, SOC information calculated by the SOC calculation unit 14, OCV ratio x obtained by the OCV ratio calculation unit, and a storage unit 2, the high resistance state resistance calculation parameter R1A, the low resistance state resistance calculation parameter R1B, and the OCV-resistance correlation parameter PS1 are input.

The resistance estimation unit 17 includes the SOC information calculated by the SOC calculation unit 14, the OCV ratio x calculated by the OCV ratio calculation unit 16, the high resistance state resistance calculation parameter R1A, the low resistance state resistance calculation parameter R1B, and OCV. A resistance correlation parameter PS1 is input. The resistance estimation unit 17 calculates the resistance Rr1 based on these pieces of information.

The allowable maximum output calculation unit 18 receives the resistance Rr1 calculated by the resistance estimation unit 17, the SOC information calculated by the SOC calculation unit 14, and the OCV ratio x calculated by the OCV ratio calculation unit 16. Then, the allowable maximum output calculation unit 18 calculates the allowable maximum output W based on these pieces of information.

Subsequently, a solid solution positive electrode active material is used as the positive electrode active material of the lithium ion secondary battery 7 controlled by the battery control circuit 1 according to the present invention. Other than the above, a lithium ion secondary battery having the same basic configuration as the conventional one can be adopted. For example, a configuration in which a positive electrode, a negative electrode, and a separator that is sandwiched between the positive electrode and the negative electrode and impregnated with an organic electrolyte can be employed. In addition, the separator impregnated with the organic electrolyte solution has an ionic conductivity through which lithium ions (Li ⁺ ) pass, preventing a short circuit by separating the positive electrode and the negative electrode. Furthermore, the positive electrode is composed of a positive electrode active material, a conductive material, a binder, a current collector, and the like. In addition, the battery control circuit according to the present invention measures and estimates the battery operating status and battery status, and outputs information related to the battery status to the outside. The information to be output externally includes at least the allowable power of the battery.

On the other hand, FIG. 2 shows a schematic configuration diagram of a battery control circuit 101 and a battery system 110 including the battery control circuit 101 as a comparative example. A configuration different from the present invention is a storage unit 102 and a calculation unit 103. Therefore, since these configurations are different, the power storage system 200 is also configured differently from the power storage system 100 of the present invention.

In the battery control circuit 101 of the comparative example, the storage unit 102 does not hold the high resistance state OCV calculation parameter P1A and the low resistance state OCV calculation parameter P1B, and has only one OCV calculation parameter P2. Similarly, there is no high resistance state resistance calculation parameter R1A and low resistance state resistance calculation parameter R1B, and there is only one resistance calculation parameter P2.

Also, there is no OCV-resistance correlation parameter PS1. On the other hand, the calculation unit 103 does not include the OCV ratio calculation unit 17.

Information that can always be measured in the battery system 110 is mainly voltage, current, and temperature. Further, the allowable maximum power of the battery, which is important information in the battery system 110, is calculated using at least the resistance and the OCV as inputs. In the state where the battery is operated in accordance with the host system 6, the resistance and the OCV cannot be measured except when the measurement conditions are satisfied, and therefore it is necessary to estimate from the information that can be always measured.

As shown in FIG. 2, the conventional battery control circuit 101 holds the OCV calculation parameter P2 and the resistance calculation parameter R2 acquired in advance in the storage unit 102. Then, the battery control parameter calculation unit 105 in the calculation unit 103 executes the calculation to estimate the resistance value from the resistance calculation parameter Rr2, the SOC at that time, the temperature, and the like.

In the conventional lithium ion secondary battery 107 that does not include the solid solution positive electrode active material as the positive electrode active material, there is a correlation between the SOC and the OCV. Therefore, using the SOC and the OCV calculation parameter P2 obtained by current integration, , OCV is calculated, and battery control parameters such as allowable power of the battery are calculated using the OCV and the calculated resistance value. The calculated battery control parameters such as allowable power are output to the host system 106 to limit the load on the lithium ion secondary battery 107.

On the other hand, as shown in FIG. 1, the battery control circuit 1 of the present embodiment has two types of OCV calculation parameters P1 (high resistance state P1A and low resistance state P1B) acquired in advance and two types of OCV calculation parameters P1. The storage unit 2 stores a resistance calculation parameter R1 (high resistance state R1A, low resistance state R1B), an OCV-resistance correlation parameter PS1 indicating a correlation between the OCV ratio and the resistance ratio.

Then, in addition to the battery control parameter calculation in the battery control parameter calculation unit 5, the calculation unit 3 calculates the OCV by the OCV calculation unit 15, and executes the OCV ratio calculation by the OCV ratio calculation unit 16. The OCV calculation unit 15 calculates the OCV using a known technique when a condition is satisfied such as when no current is flowing. The OCV ratio calculation unit 15 calculates the OCV ratio x from the OCV calculated by the OCV calculation, the SOC at the time of measuring the OCV, and the OCV calculation P1 (high resistance state P1A, low resistance state P1B). To do. The OCV ratio x is output to the storage unit 2 and held in the storage unit 2.

The battery control parameter calculation unit 5 calculates the resistance ratio y from the OCV ratio x and the OCV-resistance correlation parameter PS1. In addition, the resistance calculation parameter R1 (high resistance state R1A, low resistance state R1B), The resistance value estimation unit 17 calculates an estimated resistance value Rr1 from the SOC, temperature, and the like at the time, and further calculates battery control parameters such as allowable power using the estimated resistance value Rr1. Battery control parameters such as the calculated resistance value and allowable power are output to the host system 6.

Thereby, according to the present embodiment, when the resistance of the solid solution positive electrode active material is low, the allowable power is not unnecessarily limited, and thus a high output can be obtained. Further, when the resistance is high, the allowable power is not underestimated, so that safety and reliability are improved.

In addition, since the host system can obtain an appropriate estimated value of the battery resistance, the reliability of current control for satisfying the required power is improved.

The resistance calculation parameter R1 (high resistance state R1A, low resistance state R1B) is updated in accordance with the deterioration of the battery. Also in the conventional battery system, the resistance calculation parameter R1 is updated according to deterioration, and the existing technology can be used.

Also, the SOC can be calculated by integrating the current values.

As described above, in the conventional battery control circuit as described above, control is generally performed assuming that the resistance state of the battery is one type. Therefore, when allowable power control is performed for a battery system using a secondary battery with hysteresis in resistance value, assuming that the resistance is higher than actual, high output can be obtained due to power limitation of the battery control circuit. It becomes impossible. Conversely, when the allowable power control is performed assuming a state of lower resistance than actual, an output exceeding the power limit is permitted. Furthermore, it is difficult to predict the current to satisfy the output in the control system in the higher order of the battery system that determines the output from the battery.

On the other hand, according to the present invention, a battery control circuit, a battery system, and a battery control circuit that can be controlled in accordance with the resistance state of the solid solution positive electrode active material in the lithium ion secondary battery and can increase the output of the battery system. A mobile body and a power storage system including the same can be provided. Moreover, since the highly accurate resistance value can be used for various controls using the estimated resistance value, the stability and reliability of the control are improved. Furthermore, the stability and reliability of the current / output control are also improved in the control system of the battery system.
《Experimental example》
Below, the experiment example of the battery system using the battery control circuit which concerns on this invention is shown.
(Preparation of positive electrode using solid solution positive electrode active material)
0.5Li ₂ MnO ₃ -0.5LiNi _1/3 Co _1/3 Mn _1/3 O ₂ solid solution positive electrode active material, carbon-based conductive material, N-methyl-2-pyrosinone (NMP) in advance The dissolved binder was mixed at a mass percent (%) ratio of 85: 10: 5, respectively, and the uniformly mixed slurry was applied onto an aluminum foil current collector with a thickness of 20 μm. Then, it dried at 120 degreeC and compression-molded so that the electrode density might be 2.3 g / cm < ³ > with a press.
(Production of lithium ion secondary battery)
Next, production of a lithium ion secondary battery will be described. The battery control circuit according to the present invention can be applied to control of any shape of a lithium ion secondary battery such as a cylindrical shape, a flat shape, a square shape, a coin shape, a button shape, and a sheet shape. The negative electrode has a lower discharge potential and higher capacity. The negative electrode is preferably made of lithium metal, carbon having a low discharge potential, Si, Sn having a large weight specific capacity, or lithium titanate (Li4Ti5O12) having high safety. Various materials can be used.

A lithium ion secondary battery was produced using the above-described positive electrode, negative electrode, separator, and electrolytic solution (electrolyte). Here, lithium metal is used for the negative electrode, a PP (polypropylene) porous ion conductive and insulating separator is used for the separator, and the nonaqueous organic solvent ethylene carbonate (electrolyte) is used as the electrolyte (electrolyte). EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) mixed at a volume ratio of 1: 2: 2 were used in which 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) was dissolved. .
(Resistance evaluation of lithium ion secondary battery)
The lithium ion secondary battery was charged to 4.6 V with a constant current / constant potential charge of 0.05 C, and then discharged to 2.5 V with a constant current of 0.05 C. Here, “charging / discharging rate 1C” means that, when the battery is charged from a fully discharged state, 100% charging is completed in one hour, and when the battery is discharged from a fully charged state. Completing 100% discharge in 1 hour. That is, the charging or discharging speed is 100% per hour. Therefore, 0.05 C means that the speed of charging or discharging is 5% per hour.

Thereafter, the open circuit voltage and the voltage drop amount ΔV after 10 seconds at the time of 0.1C rate discharge were measured at 25 ° C. while changing the SOC, and ΔV / current = resistance R was calculated. The amount of change in SOC was 10%, and after changing the SOC, it was relaxed in an open circuit state for 2 hours before measuring the amount of voltage drop after 10 seconds during 0.1 C rate discharge.

First, the SOC was changed from (1) 0% → 90% → 0%. Then, the OCV and resistance at 0% → 90% were functionalized to calculate the OCV calculation parameter P1B and the resistance calculation parameter R1B for the low resistance state. Further, the OCV and resistance at 90% → 0% were functionalized to calculate the OCV calculation parameter P1A and the resistance calculation parameter R1A for the high resistance state.

Next, change the SOC in two ways: (2) 0% → 70% → 30% → 70% → 0%, (3) 0% → 50% → 30% → 50% → 0% The open circuit voltage OCV and the voltage drop amount ΔV after 10 seconds during 0.1C rate discharge were measured, and the resistance was calculated. Then, the OCV ratio and the resistance ratio were calculated using the obtained open circuit voltage OCV and resistance, two kinds of OCV calculation parameters P1, and the resistance calculation parameter R1.

In FIG. 3 and FIG. 4, the fill data (black triangle, black square, black circle) is the data that increased the SOC, and the white data (white triangle, white square, white circle) decreased the SOC. Data.

FIG. 3 is a diagram showing a change in resistance when the SOC is changed by the methods (1) to (3) described above. It can be seen that the resistance is different and has hysteresis even when the SOC is changed in the increasing direction and when the SOC is changed in the decreasing direction.

Further, the smaller the change width of the SOC, the smaller the difference in hysteresis, and the resistance value when changing the SOC of (2) and (3) in the direction of decreasing changes in the direction of increasing the SOC of (1). It was a value between the resistance value in the case of the change and the OCV and the resistance value in the case of changing in the direction of decreasing the SOC. More specifically, it can be seen that the hysteresis is the largest under the condition (1) and the smallest under the condition (3).

On the other hand, FIG. 4 is a diagram showing a change in the open circuit voltage OCV when the SOC is changed by the methods (1) to (3). Similar to the data shown in FIG. 3, it can be seen that the open circuit voltage OCV is different and has hysteresis even when the SOC is changed in the increasing direction and when the SOC is changed in the decreasing direction. . Similarly to the hysteresis of the resistance, the SOC is changed by a smaller width than the condition (1) where the SOC is changed by a large width. The conditions (2) and (3) are the width of the hysteresis of the OCV. Is small.

FIG. 5 is a diagram showing the relationship between the OCV ratio and the resistance ratio when the SOC is changed by the methods (2) and (3). The OCV ratio x and the resistance ratio y in (2) and (3) have a correlation of y = x ² as shown in the figure.

It can be seen that the resistance ratio y can be calculated from the OCV ratio x using the above relational expression. The resistance value can be estimated using the calculated resistance ratio and the resistance value when the SOC is changed by the method (1). In order to measure the criterion of the hysteresis of the OCV and the resistance value, it is desirable that the range of the SOC to be changed is sufficiently wide, and it is desirable to change the maximum SOC width in the battery application. It is not limited to the value. The relational expression between the OCV ratio x and the resistance ratio y is considered to be affected by the material composition and the battery shape, and the present invention is not limited to this value. This test result can also be applied to the resistance on the charging side.
(Calculation of allowable power)
Next, the allowable maximum output calculation was executed at a point of 30% when the SOC increased during the measurement of (2). The OCV at that time is estimated based on the OCV ratio x and the SOC, the resistance Rr1 is calculated from the resistance ratio y, the resistance calculation parameters R1A, R1B, and the SOC, and the allowable maximum output W is calculated from the OCV and the resistance Rr1. The allowable minimum voltage was 3.0V. For comparison, an allowable maximum output calculation was also performed based on the resistance values in the high resistance state and the low resistance state. Further, the allowable maximum output was calculated from the actually measured OCV and resistance value.

Table 1 shows the maximum allowable output W calculated.

The value calculated by the present invention is close to 18.0 mW with respect to the value of 17.1 mW calculated from the actually measured OCV and resistance value Rr1, which is an appropriate output limit value.

On the other hand, the value calculated based on the resistance in the high resistance state is 12.8 mW, which is smaller than necessary, and the output of the system is small. Further, the value calculated based on the low resistance state is 36.5 mW, which is a value more than double, and greatly exceeds the value to be limited, which may cause a system abnormality. Therefore, by using the present invention, it is possible to appropriately limit the output even when a solid solution positive electrode active material is used.
(Current control by host system 6)
In the battery control circuit 1 of this embodiment, the estimated resistance value at the point where the SOC is 30% is output to the host system 6 externally. In the host system 6, a current for obtaining a power value of 10 mW assumed as necessary power was calculated based on the received resistance.

Table 2 shows the calculated current value based on the resistance value calculated according to the present invention and, for example, when the measured resistance is used, when the high resistance state is used, and when the low resistance state is set. A comparison of the cases with

In the present embodiment, the current value is close to the current based on the actually measured resistance. On the other hand, when the high resistance state is used, the current is smaller than the value to be calculated, and control takes time. Further, when the low resistance state is used, it is considerably larger than the value to be calculated and there is a risk of overshoot. Therefore, by using the present invention, it is possible to control the current value even when a solid solution positive electrode active material is used.
(Application example of battery system)
A battery system 10 including a battery control circuit 1 according to the present invention includes a hybrid railway vehicle that runs on a diesel engine and a motor, an electric vehicle that runs on a motor using a battery as an energy source, a hybrid vehicle that runs on an engine and a motor, It can be applied to various vehicles such as a plug-in hybrid vehicle that can charge a battery from a battery, a fuel cell vehicle that extracts power from a chemical reaction between hydrogen and oxygen, and a power source for various mobile objects such as a robot using a battery as an energy source.

FIG. 6 shows an example of application to the drive system of the electric vehicle 30. Electric power is supplied from the battery system 10 to the motor 20 via a motor controller (not shown), and the electric vehicle 30 is driven. Further, the electric power regenerated by the motor 20 during deceleration is stored in the battery system 10 via the motor controller. According to this embodiment, since the output density of the secondary battery is improved by mounting the battery system 10 including the battery control circuit according to the present invention, the output of the drive system of the electric vehicle 30 is improved. Further, since the allowable power during charging can be increased, the charging time is shortened.

In addition to the illustrated vehicles, vehicles can be widely applied to forklifts, on-site transportation vehicles such as factories, electric wheelchairs, various satellites, rockets, submarines, etc. It is applicable without limitation.

A battery system including a battery control circuit according to the present invention includes a power storage power source (power storage) for a power generation system using natural energy, such as a solar battery that converts solar light energy into electric power, or wind power generation that generates power using wind power. System). FIG. 7 shows a schematic configuration of a power generation system 300 using natural energy.

In the power generation system 300 using natural energy such as a wind power generator 310 or a solar cell (not shown), the amount of power generation varies greatly depending on weather conditions. Therefore, in order to realize a stable power supply, the load of the power system 320 It is necessary to charge / discharge electric power from the power storage system (power storage power source) 100 in accordance with the above. By applying the battery system 10 including the battery control circuit 1 according to the present invention to the power storage system 100, a necessary output can be obtained with a small number of secondary batteries, and the cost of the power generation system 300 is reduced. be able to.

In addition, although the power generation system 300 using a solar cell and a wind power generator was illustrated here, application to an electric power storage system is not limited to this, The electric power system mounted in large ships, such as a tanker, a factory, etc. It can be widely applied to power storage systems such as private power generation systems.

To summarize the present invention, the battery system of the present invention is calculated from two types of open circuit voltage (OCV) information of the lithium ion secondary battery in a charging state (SOC) increasing direction and a charging state (SOC) decreasing direction. An open circuit voltage (OCV) ratio calculation unit, a resistance estimation unit that estimates a resistance value based on open circuit voltage (OCV) ratio information calculated by the open circuit voltage (OCV) ratio calculation unit, and the resistance estimation An allowable maximum output calculation unit that calculates an allowable maximum output based on the resistance value calculated by the unit. Therefore, even if a solid body having hysteresis is used as the positive electrode active material, control according to the resistance state is possible. Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Battery control circuit 2 Memory | storage part 3 Calculation part 5 Battery control parameter calculation part 6 Host system 7 Lithium ion secondary battery 10 Battery system 11 Temperature information acquisition part 12 Current information acquisition part 13 Voltage information acquisition part 14 SOC calculation part 15 OCV calculation Unit 16 OCV ratio calculation unit 17 resistance estimation unit 18 allowable maximum output calculation unit 100 power storage system

Claims

xLi 2 MO 3- (1-x) LiM′O 2 (where 0.3 <x <0.7, M is at least one selected from Mn, Ti and Zr, M ′ is Ni, A lithium ion secondary battery using a solid solution represented by (Co, Mn, Fe, Ti, Zr, Al, Mg, Cr, V) as a positive electrode active material;
In the battery system having a battery control circuit for controlling charging and discharging of the lithium ion secondary battery,
The control circuit includes:
An open circuit voltage (OCV) ratio calculation unit calculated from two types of open circuit voltage (OCV) information in a charging state (SOC) increasing direction and a charging state (SOC) decreasing direction of the lithium ion secondary battery;
A resistance estimator for estimating a resistance value based on the open circuit voltage (OCV) ratio information calculated by the open circuit voltage (OCV) ratio calculator;
A battery system comprising: an allowable maximum output calculation unit that calculates an allowable maximum output based on the resistance value calculated by the resistance estimation unit.
The battery system according to claim 1,
The control circuit has a storage unit,
The battery unit has two types of open circuit voltage (OCV) calculation parameters, a charging state (SOC) increasing direction and a charging state (SOC) decreasing direction.
The battery system according to claim 2,
The battery unit has two types of resistance calculation parameters, a charging state (SOC) increasing direction and a charging state (SOC) decreasing direction.
The battery system according to claim 3,
The battery system, wherein the storage unit has a correlation parameter between the open circuit voltage (OCV) ratio information and the resistance ratio information.
A moving body comprising the battery system according to claim 4.
An electric power storage system comprising the battery system according to claim 4.