WO2023105600A1

WO2023105600A1 - Power storage cell and power storage module

Info

Publication number: WO2023105600A1
Application number: PCT/JP2021/044825
Authority: WO
Inventors: 大輔小松; 靖生鈴木; モハメドミザヌルラフマン; 信雄安東
Original assignee: 武蔵精密工業株式会社
Priority date: 2021-12-07
Filing date: 2021-12-07
Publication date: 2023-06-15

Abstract

The present invention achieves both suppression of deterioration of a first cell and suppression of reduction of the volume energy density of a power storage cell. This power storage cell comprises a first positive electrode, a second positive electrode having lower capacity and lower internal resistance than the first positive electrode, and a negative electrode. In this power storage cell, a first cell composed of the first positive electrode and the negative electrode has relatively high internal resistance and exhibits a relatively high capacitive characteristic. A second cell composed of the second positive electrode and the negative electrodes has relatively low internal resistance, and thus exhibits a relatively high output characteristic. A first capacity ratio is the ratio of the capacity of the second positive electrode to the capacity of the first positive electrode, and is 0.7-10% inclusive.

Description

Storage cell and storage module

The present invention relates to storage cells and storage modules.

Conventionally, there has been known a hybrid electric storage cell in which a negative electrode is arranged between a first positive electrode containing a transition metal oxide (lithium cobaltate, etc.) and a second positive electrode containing activated carbon (phenolic resin). (see Patent Document 1 below). In such a hybrid electric storage cell, the first cell composed of the first positive electrode and the negative electrode has relatively high internal resistance and exhibits relatively high capacity characteristics. The second cell, which is composed of the second positive electrode and the negative electrode, has relatively low internal resistance, and thus exhibits relatively high output characteristics (speeding up charging and discharging).

Japanese Patent No. 5091573

As a result of extensive studies, the inventors of the present invention have found that the conventional hybrid storage cell may not be able to suppress the deterioration of the first cell even if the second cell is provided. It was newly discovered that even if the deterioration of the second cell can be suppressed, the presence of the second cell may reduce the volumetric energy density of the storage cell.

Note that such a problem is not limited to the combination of the first positive electrode containing a transition metal oxide and the second positive electrode containing activated carbon, but is also applicable to hybrids having two positive electrodes having different capacities and internal resistances. This is also a common issue for storage cells.

An object of the present invention is to provide a storage cell that can solve the above-described problems.

(1) A storage cell disclosed in this specification includes a first positive electrode, a second positive electrode having a lower capacity and lower internal resistance than the first positive electrode, and a negative electrode. , in the storage cell, a first capacity ratio, which is a ratio of the capacity of the second positive electrode to the capacity of the first positive electrode, is 0.7% or more and 10% or less. In this electric storage cell, the first cell composed of the first positive electrode and the negative electrode has relatively high internal resistance and exhibits relatively high capacity characteristics. A second cell composed of a second positive electrode and a negative electrode has relatively low internal resistance, and thus exhibits relatively high output characteristics. Since the first capacity ratio is 0.7% or more, deterioration of the first cell due to current fluctuations can be suppressed due to the low capacity and low resistance characteristics of the second cell. Moreover, since the first capacity ratio is 10% or less, it is possible to suppress a decrease in the capacity of the storage cell due to the low capacity characteristic of the second cell. As described above, according to the present electric storage cell, it is possible to simultaneously suppress deterioration of the first cell and suppress a decrease in volumetric energy density of the electric storage cell.

(2) In the storage cell, the first capacity ratio may be 1% or more. According to this storage cell, it is possible to suppress voltage fluctuations due to charge-discharge cycles in which current fluctuations are relatively large.

(3) In the storage cell, the first positive electrode material forming the first positive electrode and the second positive electrode material forming the second positive electrode may have different characteristics. According to this electric storage cell, it is possible to give the electric storage cell both the electrode characteristics based on the first positive electrode material and the electrode characteristics based on the second positive electrode material.

(4) In the storage cell, the second capacity ratio, which is the ratio of the total capacity of the capacity of the first positive electrode and the capacity of the second positive electrode to the capacity of the negative electrode, is 10% or more and 90%. It is good also as a structure which is below. According to this storage cell, since the second capacity ratio is 90% or less, expansion and contraction of the negative electrode due to intercalation of lithium ions are suppressed, and the cycle life of the storage cell can be improved. . Moreover, since the second capacity ratio is 10% or more, it is possible to suppress a decrease in the volumetric energy density of the storage cell.

(5) In the storage cell, the second capacity ratio may be 50% or more and 75% or less. According to this energy storage cell, it is possible to more effectively suppress a decrease in the volume energy density of the energy storage cell while improving the cycle life of the energy storage cell.

(6) In the above electric storage cell, the negative electrode may be configured such that the negative electrode SOC is in the range of 10% or more and 100% or less. According to this storage cell, it is possible to suppress the decrease in the life of the storage cell due to the shortage of positive ions.

(7) In the above electric storage module, the electric storage module includes a plurality of electric storage cells, wherein at least one of the plurality of electric storage cells is the electric storage cell according to any one of (1) to (6) above. may be According to this power storage module, it is possible to achieve both suppression of deterioration of the first cells and suppression of reduction in the volumetric energy density of the power storage cells.

Explanatory diagram showing the internal configuration of the electricity storage device 1 according to the embodiment. Explanatory drawing showing the voltage change of the pre-doped storage cell 100 Explanatory diagram showing performance evaluation results Explanatory diagram showing the internal configuration of an electricity storage device 1a in a modified example of the present embodiment.

A. Embodiment:
A-1. Configuration of power storage device 1:
(Configuration of power storage device 1):
FIG. 1 is an explanatory diagram showing the internal configuration of an electricity storage device 1 according to the embodiment. FIG. 1 shows mutually orthogonal XYZ axes for specifying directions. In this specification, for the sake of convenience, the positive direction of the Z-axis is referred to as the “upward direction” and the negative direction of the Z-axis is referred to as the “downward direction”. Orientation may be set.

As shown in FIG. 1 , the power storage device 1 includes a housing 30 and power storage cells 100 . The housing 30 is a container in which an accommodation space is formed to accommodate the storage cell 100 . The housing 30 is made of metal such as aluminum, or synthetic resin that does not absorb moisture. The housing 30 is provided with a positive terminal portion 40P and a negative terminal portion 40N. For example, a part or all of the metal portion of the housing 30 may serve as either one of the positive electrode side terminal portion 40P and the negative electrode side terminal portion 40N. Moreover, the electric storage device 1 may have a configuration in which the electric storage cell 100 is housed in a bag such as a laminated film, for example.

The storage cell 100 includes a lithium ion battery (hereinafter referred to as “LIB”) that exhibits relatively high internal resistance and relatively high capacity characteristics, and a relatively low internal resistance and relatively high output characteristics. It is a so-called hybrid cell that includes a lithium ion capacitor (hereinafter referred to as “LIC”) that exhibits high performance. As described above, since the electricity storage device 1 includes the electricity storage cell 100 which is a hybrid cell, it has a large energy capacity and is capable of rapid charging and discharging. The power storage device 1 is, for example, a load leveling device for solar power generation, wind power generation, etc., an instantaneous voltage drop countermeasure device for electronic equipment typified by computers, an energy regeneration device for electric vehicles and hybrid cars, and an electric two-wheel drive. It is used as a power source, etc.

In this embodiment, the storage cell 100 has multiple LIB cells 10 and multiple LIC cells 20 . Inside the housing 30, a plurality of LIB cells 10, a plurality of LIC cells 20, and an electrolytic solution (not shown) are housed in the same space. FIG. 1 shows an arrangement state of multiple LIB cells 10 and multiple LIC cells 20 . As shown in FIG. 1, a plurality of LIB cells 10 and a plurality of LIC cells 20 are arranged side by side in a predetermined direction (the Y-axis direction in this embodiment) in the same space within the housing 30 . An electrolytic solution (not shown) is contained in the housing 30, and the LIB cell 10 and the LIC cell 20 are immersed in the electrolytic solution. Hereinafter, the direction in which the LIB cells 10 and the LIC cells 20 are arranged (the Y-axis direction) is referred to as the "cell arrangement direction". The electrolytic solution is, for example, a mixture of an electrolytic salt, an organic solvent and an additive.

Specifically, as shown in FIG. 1, the storage cell 100 includes multiple LIB positive plates 110P, multiple LIC positive plates 210P, multiple negative plates 110N, and a separator 120. LIB positive plates 110P and LIC positive plates 210P are alternately arranged one by one in the cell arrangement direction. The negative electrode plate 110N is arranged so as to be interposed between the LIB positive electrode plate 110P and the LIC positive electrode plate 210P that face each other in the cell arrangement direction. In addition, the separator 120 is interposed between the LIB positive plate 110P and the negative electrode plate 110N facing each other in the cell arrangement direction and between the LIC positive plate 210P and the negative electrode plate 110N facing each other in the cell arrangement direction. are placed in That is, the storage cell 100 has a laminated structure in which the LIB positive plate 110P, the LIC positive plate 210P, the negative electrode plate 110N, and the separator 120 are arranged side by side in a predetermined direction (the cell alignment direction in this embodiment). The LIB positive plate 110P is an example of the first positive electrode in the claims, the LIC positive plate 210P is an example of the second positive electrode in the claims, and the negative electrode plate 110N is the It is an example of a negative electrode.

The LIB positive electrode plate 110P has a positive electrode current collector 112P and a pair of LIB positive electrode

active materials

114P, 114P supported by the positive electrode current collector 112P. The positive electrode current collector 112P is aluminum foil, and porous foil such as etched foil or punched foil may be used. In addition, the positive electrode current collector 112P has a positive electrode tab protruding upward near its upper end. A pair of LIB positive electrode active materials 114P are supported on both sides of the positive electrode current collector 112P. The pair of LIB positive electrode active materials 114P are made of the same material. Examples of materials used for forming the LIB positive electrode active material 114P include lithium cobalt oxide, ternary lithium metal composite oxides (nickel manganese cobalt, etc.), lithium manganate, lithium nickel oxide, and lithium iron phosphate. The LIB positive electrode active material 114P is an example of the first positive electrode material in the claims.

The LIC positive electrode plate 210P has a positive electrode current collector 212P and a pair of LIC positive electrode

active materials

214P, 214P supported by the positive electrode current collector 212P. The positive electrode current collector 212P is aluminum foil, and porous foil such as etching foil or punching foil may be used. In addition, the positive electrode current collector 212P has a positive electrode tab protruding upward near its upper end. A pair of LIC positive electrode active materials 214P are supported on both sides of the positive electrode current collector 212P. The pair of LIC positive electrode active materials 214P are made of the same material. As a material for forming the LIC positive electrode active material 214P, for example, activated carbon such as steam activated carbon or alkali activated carbon is used. The LIC cathode active material 214P is an example of the second cathode material in the claims.

The negative electrode plate 110N has a negative electrode current collector 112N and a pair of negative electrode

active materials

114N and 114N supported by the negative electrode current collector 112N. The negative electrode current collector 112N is copper foil, and porous foil such as etched foil or punched foil may be used. In addition, the negative electrode current collector 112N has a negative electrode tab protruding upward near its upper end. A pair of negative electrode active materials 114N are supported on both sides of the negative electrode current collector 112N. The pair of negative electrode active materials 114N are made of the same material. Examples of materials used for forming the negative electrode active material 114N include graphite, silicon-based materials, hard carbon, soft carbon, and lithium titanate. The separator 120 is made of an insulating material (for example, paper, glass fiber, synthetic resin (porous polyethylene film, etc.)).

The ears of the plurality of LIB positive plates 110P and the ears of the plurality of LIC positive plates 210P are electrically connected to the positive terminal portion 40P. Ear portions of the plurality of negative electrode plates 110N are electrically connected to the negative terminal portion 40N.

With the above configuration, the LIB cell 10 is configured by the LIB positive electrode active material 114P of the LIB positive plate 110P, the negative electrode active material 114N of the negative electrode plate 110N, and the separator 120 interposed therebetween. The LIC cell 20 is composed of the LIC positive electrode active material 214P of the LIC positive plate 210P, the negative electrode active material 114N of the negative electrode plate 110N, and the separator 120 interposed therebetween. That is, the LIB cell 10 and the LIC cell 20 are connected in parallel with each other. Moreover, the storage cell 100 has a configuration in which a predetermined plurality (two in FIG. 1) of the LIB cells 10 and the LIC cells 20 are alternately arranged in the cell arrangement direction.

(Detailed configuration of storage cell 100):
In the storage cell 100, the following first condition is satisfied for the LIB positive plate 110P and the LIC positive plate 210P.
<First condition>
The first capacity ratio is 0.7% or more and 10% or less.
The first capacity ratio is the ratio of the capacity of the LIC positive plate 210P to the capacity of the LIB positive plate 110P.
Here, the capacity of the LIB positive plate 110P is a charge transfer amount (amount of electricity) when a half cell is configured by the LIB positive plate 110P, a test negative electrode, and a separator, and a charge/discharge test is performed on the half cell. . The capacity of the LIC positive plate 210P is the amount of charge transferred (amount of electricity) when a half cell is formed by the LIC positive plate 210P, the test negative electrode, and the separator, and a charge/discharge test is performed on the half cell. The test negative electrode used for these half cells has a sufficient capacity so as not to affect the measurement result of the capacity of the half cell in the charge/discharge test. In this embodiment, for example, a test negative electrode having lithium metal as a negative electrode material is used.

The charge/discharge test for measuring the capacity of each pole is as follows. First, each half cell is charged at a constant current of 0.3 C until the cell voltage reaches a set voltage (for example, 3.65 V) for full charge, and then a constant voltage charge (CCCV) of the set voltage is applied. charge) for 30 minutes to reach full charge. Next, from this fully charged state, the battery is discharged at a constant current of 1 C until the cell voltage reaches the final voltage (eg, 2.2 V at which the cell voltage begins to drop rapidly). By repeating this charging and discharging three times, the half-cell was put into a steady state, and the capacity measured when discharging for the third time was taken as the capacity of each electrode.

In the storage cell 100, it is preferable that the LIB positive plate 110P and the LIC positive plate 210P satisfy the following second condition.
<Second condition>
The first capacity ratio is 1% or more.
It should be noted that the first capacity ratio is more preferably 2% or more.

In the storage cell 100, it is preferable that the LIB positive plate 110P and the LIC positive plate 210P satisfy the following third condition.
<Third condition>
The LIB positive electrode active material 114P forming the LIB positive electrode plate 110P and the LIC positive electrode active material 214P forming the LIC positive electrode plate 210P have different characteristics.
For example, in a configuration in which lithium iron phosphate (LFP) is used as the LIB positive electrode active material 114P and activated carbon (AC) is used as the LIC positive electrode active material 214P, the LIB positive electrode plate 110P has a relatively high internal resistance, The LIC positive electrode plate 210P has relatively low internal resistance and has the characteristics of a LIC positive electrode exhibiting relatively high output characteristics. It will be.

The storage cell 100 preferably satisfies the following fourth condition.
<Fourth condition>
The second capacity ratio is 10% or more and 90% or less.
The second capacity ratio is the ratio of the total capacity of the LIB positive plate 110P and the LIC positive plate 210P to the capacity of the negative plate 110N.

The storage cell 100 preferably further satisfies the following fifth condition.
<Fifth condition>
The second capacity ratio is 50% or more and 75% or less.

The storage cell 100 preferably satisfies the following sixth condition.
<Sixth condition>
The negative electrode plate 110N is used in a range where the negative electrode SOC (state of charge) is 10% or more and 100% or less.
The storage cell 100 that satisfies the sixth condition can be realized, for example, by doping the negative electrode plate 110N with lithium ions (so-called pre-doping). FIG. 2 is an explanatory diagram showing the voltage change of the pre-doped storage cell 100. As shown in FIG. A graph G1 in FIG. 2 is a graph showing changes in potential of the positive terminal portion 40P of the storage cell 100 during charging and discharging. A graph G2 is a graph showing changes in potential of the negative electrode terminal portion 40N of the storage cell 100 during charging and discharging. As shown in FIG. 2, by doping the negative electrode plate 110N with lithium ions, the utilization region R2 of the negative electrode plate 110N in the storage cell 100 can be made smaller than the negative electrode SOC region R1 corresponding to the capacity of the negative electrode plate 110N. can be done. That is, by doping the negative electrode plate 110N with lithium ions, it is possible to adjust the negative electrode SOC utilization range (=R2/R1) of the negative electrode plate 110N. FIG. 2 illustrates voltage changes when the negative electrode SOC utilization range of the negative electrode plate 110N is 50%.

A method for specifying the range of use of the negative electrode SOC of the negative electrode plate 110N is as follows. First, the storage cell 100 in a fully charged state was disassembled, and a half cell having the same structure as that used in the charge/discharge test was produced for each of the LIB positive plate 110P, the LIC positive plate 210P, and the negative electrode plate 110N. Measure the discharge capacity of the half cell. Then, the calculation result of positive electrode capacity (=discharge capacity of LIB positive plate 110P+discharge capacity of LIC positive plate 210P)/negative electrode capacity (=discharge capacity of negative electrode plate 110N) was specified as the second capacity ratio. When the negative electrode plate 110N is doped with lithium ions, the initial discharge capacity of the negative electrode half-cell becomes larger than the positive electrode capacity. The utilization range of the negative electrode SOC can be specified from the difference between the discharge capacity and the positive electrode capacity, and the negative electrode capacity.

A-2. Performance evaluation:
Performance evaluations performed using samples of the storage cell 100 will be described below. FIG. 3 is an explanatory diagram showing performance evaluation results. Each sample has a configuration in which lithium iron phosphate is used as the LIB positive electrode active material 114P, activated carbon is used as the LIC positive electrode active material 214P, and graphite (C) is used as the negative electrode active material 114N. As shown in FIG. 3, the samples (S1 to S10) differ from each other in the first capacity ratio (%). Note that the sample S1 has a first capacity ratio of 0%, and therefore is a single LIB storage cell.

A-2-1. Sample preparation method:
Each sample of the storage cell 100 was manufactured according to the following manufacturing method. First, each electrode (LIB positive plate 110P, LIC positive plate 210P, negative electrode plate 110N) constituting a sample is produced as follows.
(Preparation of LIB positive electrode plate 110P):
Commercially available LiFePO ₄ powder (90 parts by weight), acetylene black powder (5 parts by weight), and polyvinylidene fluoride (PVdF) powder (5 parts by weight) are mixed, N-methylpyrrolidone is added, and the mixture is thoroughly stirred. The first positive electrode slurry was obtained by defoaming. This first positive electrode slurry was applied to both sides of a porous aluminum foil, dried, and pressed, and cut into a predetermined shape to obtain a LIB positive electrode plate 110P.

(Preparation of LIC positive electrode plate 210P):
Commercially available activated carbon powder (85 parts by weight) having a specific surface area of 2000 m ² /g, acetylene black powder (5 parts by weight), acrylic resin binder (6 parts by weight), and carboxymethyl cellulose (4 parts by weight) were mixed. , and pure water were added, and the slurry was sufficiently agitated to remove air bubbles, thereby obtaining a second positive electrode slurry. Both surfaces of the porous aluminum foil were coated with the second positive electrode slurry, dried, and then cut into a predetermined shape to obtain the LIC positive electrode plate 210P.

(Preparation of negative electrode plate 110N):
Commercially available artificial graphite powder (96 parts by weight), acetylene black powder (1 part by weight), and styrene-butadiene rubber (SBR) powder (2 parts by weight) are mixed, carboxymethylcellulose (1 part by weight) is added, A negative electrode slurry was obtained by sufficiently stirring and defoaming. This negative electrode slurry was applied to both sides of the porous copper foil, dried, and pressed, and cut into a predetermined shape to obtain a negative electrode plate 110N.

The LIB positive electrode plate 110P, the LIC positive electrode plate 210P, and the negative electrode plate 110N thus produced were laminated via a separator (polyethylene microporous film) to form an electrode assembly. Here, for each sample, the first capacity ratio was made different from each other by changing the number (number ratio) of the LIB positive plate 110P and the LIC positive plate 210P. Next, external terminals were welded to each of the LIB positive plate 110P, the LIC positive plate 210P, and the negative electrode plate 110N constituting the electrode assembly, and the electrode assembly was placed in a bag-like aluminum laminate. Next, an electrolytic solution was injected into the laminate, and then the opening of the laminate was vacuum-sealed to prepare a sample electric storage cell.

A-2-2. Sample volume measurement:
The capacities of the LIB positive plate 110P, the LIC positive plate 210P, and the negative electrode plate 110N were measured as follows. The negative electrode active material of the test negative electrode used for measuring the capacity of the sample is lithium. For example, a test negative electrode (Li electrode) was obtained by pressing a lithium foil cut into a predetermined shape onto a porous copper foil cut into a predetermined shape.

A half cell was constructed from the LIB positive electrode plate 110P obtained by disassembling each sample, a test negative electrode, and a separator (polyethylene microporous film). The capacity of the LIB positive electrode plate 110P was used. The LIC positive electrode plate 210P obtained by disassembling each sample, the test negative electrode, and the separator (polyethylene microporous film) constitute a half cell. It was set as the capacity of the positive electrode plate 210P. A negative electrode plate 110N obtained by disassembling each sample, a test negative electrode, and a separator (polyethylene microporous film) constitute a half cell. The capacity was 110N. Then, the first capacity ratio of each sample was obtained based on each measured capacity.

A-2-3. Various performance evaluations:

(Electric vehicle running pattern test):
A charging/discharging cycle pattern was obtained by converting the running pattern of the two electric wheels into a current value for motor drive control. This charge/discharge cycle pattern is a charge/discharge pattern in which charging with a current value of about 5 C and discharging with a current value of about 5 C are switched every predetermined time (3 seconds on average). A charge/discharge cycle test was performed using the above charge/discharge pattern using a sample of each fully charged storage cell, and the test was terminated when the sample was discharged to a predetermined voltage (2.2 V). The lower the voltage fluctuation width of the storage cell in one cycle of the charge/discharge pattern, the smaller the internal resistance of the storage cell, which means that the voltage fluctuation in the charge/discharge cycle pattern with large current fluctuations is suppressed. In this evaluation, when the voltage fluctuation rate of each sample was 70% or less of the voltage fluctuation width of sample S1 (LIB alone), it was defined as "Passed". As shown in FIG. 3, samples S1 to S3 with a first capacity ratio of less than 1% are evaluated as "Failed", and samples S4 to S10 with a first capacity ratio of 1% or more was evaluated as "Passed". From this result, it can be seen that by setting the first capacity ratio to 1% or more, the internal resistance of the storage cell is small, and the voltage fluctuation is suppressed with respect to the charging/discharging cycle pattern in which the current fluctuates sharply. When the first capacity ratio is less than 1%, the capacity of the LIC positive plate 210P is extremely small (the number of LIB positive plates 110P is small), and the current path of the LIC positive plate 210P is narrow. The electrical resistance of 210P becomes relatively large. Therefore, even in a hybrid cell, it is considered that the internal resistance of the storage cell is not reduced.

(cycle test):
For each sample, the cut-off voltage was set to 3.65 V and 2.2 V, and a charge-discharge cycle test of 1C charge and 5C discharge was performed under a temperature environment of 60°C. The higher the capacity retention rate, which is the discharge capacity of the storage cell in the current cycle with respect to the discharge capacity of the storage cell in the first cycle of the charge/discharge pattern, the more the deterioration of LIB is suppressed and the capacity of the storage cell due to the continuation of the charge/discharge cycle. It means that deterioration is suppressed. In this evaluation, when the capacity retention rate of the storage cell is higher than the capacity retention rate of the LIB cell 10, it is defined as “Passed”. As shown in FIG. 3, samples S2 to S10 having a first capacity ratio of 0.7 or more were evaluated as "Passed." From this result, it can be seen that when the first capacity ratio is 0.7 or more, the capacity retention rate of the storage cell can be made higher than the capacity retention rate of the LIB cell 10 . When the first capacity ratio is less than 0.7%, the capacity of the LIC positive plate 210P is extremely small (the number of LIB positive plates 110P is small), so the high output characteristics of the LIC cell 20 are fully exhibited. As a result, it is considered that deterioration of the LIB cell 10 cannot be suppressed.

(Volume Energy Density Test):
For each sample, a charge-discharge test was performed with a cutoff voltage of 3.65 V and 2.2 V, held at 0.3 C charge for 30 minutes, and then discharged at 1 C. After that, each storage cell was measured by the above measurement method. was measured. Then, the discharge energy was calculated from the obtained discharge curve, and the volume energy density was calculated from the electrode volume. In this evaluation, when the volume energy density was 50% or more of the volume energy density of the LIB cell 10, it was determined as "Passed". As shown in FIG. 3, samples S1 to S9 with a first capacity ratio of 1.0% or less are evaluated as "Passed", and sample S10 with a first capacity ratio exceeding 1.0% is evaluated as " Failed”. From this result, it can be seen that by setting the first capacity ratio to 10% or less, a decrease in the volumetric energy density of the storage cell is suppressed. If the first capacity ratio exceeds 10%, the capacity of the LIC positive plate 210P is relatively large (the number of LIB positive plates 110P is small), so the high capacity characteristics of the LIB are not sufficiently exhibited. As a result, it is believed that the volumetric energy density decreases.

A-3. Effect of this embodiment:
As described above, in the electric storage device 1 of the present embodiment, the electric storage cell 100 is composed of the LIB positive plate 110P and the negative electrode plate 110N. Exhibit capacity characteristics. The LIC cell 20 composed of the LIC positive plate 210P and the negative plate 110N has relatively low internal resistance, and thus exhibits relatively high output characteristics. Since the first capacitance ratio is 0.7% or more (first condition), the low capacitance and low resistance characteristics of the LIC cell 20 can suppress deterioration of the LIB cell 10 due to current fluctuations. . In addition, since the first capacity ratio is 10% or less (first condition), it is possible to prevent the capacity of the storage cell 100 from decreasing due to the low capacity characteristic of the LIC cell 20 . As described above, according to the present embodiment, both suppression of deterioration of the LIB cell 10 and suppression of decrease in the volumetric energy density of the storage cell 100 can be achieved.

In this embodiment, when the first capacity ratio is 1% or more (second condition), it is possible to suppress voltage fluctuations caused by charge-discharge cycles in which current fluctuations are relatively large. When the LIB positive electrode active material 114P constituting the LIB positive electrode plate 110P and the LIC positive electrode active material 214P constituting the LIC positive electrode plate 210P have different characteristics (third condition), the LIB positive electrode active material 114P and electrode characteristics based on the LIC positive electrode active material 214P. Also, in the manufacturing stage of the storage cell 100, the performance of each electrode can be changed according to the characteristics of the materials used as the LIB positive electrode active material 114P and the LIC positive electrode active material 214P.

If the second capacity ratio exceeds 90%, the degree of expansion and contraction of the negative electrode plate 110N due to intercalation of lithium ions from the positive electrode (LIB positive electrode plate 110P) is large. Therefore, there is a possibility that the capacity of the storage cell 100 may decrease or the internal resistance of the storage cell 100 may increase due to, for example, physical damage to the electrodes. In contrast, in the present embodiment, when the second capacity ratio is 90% or less (fourth condition), the negative electrode plate 110N resulting from intercalation of lithium ions from the positive electrode (LIB positive electrode plate 110P) expansion and contraction are suppressed, and the cycle life of the storage cell 100 can be improved.

Further, if the second capacity ratio is less than 10%, the amount of the negative electrode active material 114N that is excessively large relative to the LIB positive electrode active material 114P and the LIC positive electrode active material 214P is not used for charging and discharging. Since the amount of material increases, the volume energy density of the storage cell 100 may decrease. On the other hand, in the present embodiment, when the second capacity ratio is 10% or more (fourth condition), it is possible to suppress the volumetric energy density of the storage cell 100 from decreasing. Furthermore, when the second capacity ratio is 50% or more and 75% or less (fifth condition), it is possible to prevent the volume energy density of the storage cell 100 from decreasing while improving the cycle life of the storage cell 100. , can be suppressed more effectively.

In this embodiment, when the negative electrode SOC is used in the range of 10% or more and 100% or less (sixth condition), it is possible to suppress the decrease in the life of the storage cell 100 due to the lack of lithium ions.

A-4. Modification of this embodiment:
FIG. 4 is an explanatory diagram showing the internal configuration of an electricity storage device 1a in a modification of the present embodiment. The power storage device 1a of this modification differs from the power storage device 1 of the above-described embodiment in the configuration of the power storage cells. In the following, of the configuration of the electricity storage device 1a of this modified example, the same configurations as the configuration of the electricity storage device 1 of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

A power storage cell 100 a of this modification includes a plurality of hybrid positive electrode plates 110 Pa, a plurality of negative electrode plates 110 N, and a separator 120 . Hybrid positive electrode plates 110Pa and negative electrode plates 110N are alternately arranged one by one in the cell arrangement direction. The separator 120 is arranged so as to be interposed between the hybrid positive electrode plate 110Pa and the negative electrode plate 110N facing each other in the cell arrangement direction. That is, the storage cell 100a has a laminated structure in which the hybrid positive electrode plate 110Pa, the negative electrode plate 110N, and the separator 120 are arranged side by side in a predetermined direction (the cell alignment direction in this embodiment).

The hybrid positive electrode plate 110Pa includes a positive electrode current collector 112P, a LIB positive electrode active material 114P supported on one surface of the positive electrode current collector 112P (the surface on the Y-axis positive direction side in FIG. 4), and the positive electrode current collector 112P. and the LIC positive electrode active material 214P supported on the other surface (the surface on the Y-axis negative direction side in FIG. 4). Of the hybrid positive electrode plate 110Pa, the portion on the side to which the LIB positive electrode active material 114P is applied is an example of the first positive electrode in the claims, and the portion on the side to which the LIC positive electrode active material 214P is applied is the It is an example of the second positive electrode in the claims.

With the above configuration, the LIB cell 10 is composed of the LIB positive electrode active material 114P of the hybrid positive electrode plate 110Pa, the negative electrode active material 114N of the negative electrode plate 110N, and the separator 120 interposed therebetween. The LIC cell 20 is composed of the LIC positive electrode active material 214P of the hybrid positive electrode plate 110Pa, the negative electrode active material 114N of the negative electrode plate 110N, and the separator 120 interposed therebetween. That is, the LIB cell 10 and the LIC cell 20 are connected in parallel with each other. Further, the storage cell 100a has a configuration in which a predetermined number of LIB cells 10 and LIC cells 20 (one cell in FIG. 4) are alternately arranged in the cell alignment direction.

Even in such a configuration, by satisfying the first to sixth conditions described above, the same effect as the above embodiment can be obtained.

B. Variant:
The present invention is not limited to the above-described embodiments, and can be modified in various forms without departing from the scope of the invention. For example, the following modifications are possible.

The configuration of the electricity storage device 1 in the above embodiment is merely an example, and various modifications are possible. For example, in the above embodiment, the LIB positive electrode plate 110P and the LIC positive electrode plate 210P were exemplified as the first positive electrode and the second positive electrode. , and low internal resistance. For example, the first positive electrode and the second positive electrode are formed of the same material, and the first positive electrode and the second positive electrode have different coating amounts, densities, etc. of the electrode layers (active materials). A configuration in which a relationship is established may also be used.

In the above embodiment, the storage cell 100 includes a plurality of =LIB cells 10 and a plurality of LIC cells 20, and a predetermined number of LIB cells 10 and LIC cells 20 are arranged alternately in the cell arrangement direction. However, for example, only the LIB cells 10 or only the LIC cells may be arranged continuously in the cell arrangement direction. Also, the number of LIB cells 10 and LIC cells 20 is not limited to the same number, and the number ratio of LIB cells 10 and LIC cells 20 may be changed. Alternatively, for example, a configuration in which one LIB cell 10 and one LIC cell 20 are included in each power storage device may be used. 1 and 4 of the above embodiments, the pair of LIB negative electrode active materials 114N attached to the negative electrode plate 110N may be made of different materials.

In the above embodiment, the plurality of LIB cells 10, the plurality of LIC cells 20, and the electrolytic solution are housed in the same space. may be housed in the same space, or the LIB cell 10 and the LIC cell 20 may be housed in different spaces (cell chambers, battery cases). In the above embodiment, both the LIB cell 10 and the LIC cell 20 have a laminated structure. may be configured to have.

In the above embodiment, the configuration may be such that at least one of the second to sixth conditions is not satisfied. In addition, in a power storage module having a plurality of power storage cells, the above effect can be obtained by satisfying the first condition and further the second to sixth conditions for at least one power storage cell.

The materials that make up each member in the above embodiment are merely examples, and each member may be made of another material. In addition, the method for manufacturing the storage cell in the above embodiment is merely an example, and the storage cell may be manufactured by another manufacturing method.

1, 1a: power storage device 10: LIB cell 20: LIC cell 30: housing 40N: negative electrode side terminal portion 40P: positive electrode

side terminal portion

100, 100a: storage cell 110N: negative electrode plate 110P: LIB positive electrode plate 110Pa: hybrid positive electrode plate 112N: negative electrode current collector 112P: positive electrode current collector 114N: negative electrode active material 114P: LIB positive electrode active material 120: separator 210P: LIC positive electrode plate 212P: positive electrode current collector 214P: LIC positive electrode active material

Claims

a first positive electrode;
a second positive electrode having a lower capacity and a lower internal resistance than the first positive electrode;
a negative electrode;
A storage cell comprising
A first capacity ratio, which is a ratio of the capacity of the second positive electrode to the capacity of the first positive electrode, is 0.7% or more and 10% or less.
storage cell.
The storage cell according to claim 1,
The first capacity ratio is 1% or more,
storage cell.
The storage cell according to claim 1 or 2,
The first positive electrode material constituting the first positive electrode and the second positive electrode material constituting the second positive electrode have different characteristics,
storage cell.
The storage cell according to any one of claims 1 to 3,
A second capacity ratio, which is a ratio of the total capacity of the capacity of the first positive electrode and the capacity of the second positive electrode to the capacity of the negative electrode, is 10% or more and 90% or less.
storage cell.
The storage cell according to claim 4,
The second capacity ratio is 50% or more and 75% or less.
storage cell.
The storage cell according to any one of claims 1 to 5,
The negative electrode is used in a negative electrode SOC range of 10% or more and 100% or less,
storage cell.
A power storage module comprising a plurality of power storage cells,
At least one of the plurality of storage cells is the storage cell according to any one of claims 1 to 6,
storage module.