Controlled-valve lead-acid batteries, methods for manufacturing the same, and energy storage systems including controlled-valve lead-acid batteries.

Abstract

A controlled-valve lead-acid battery comprises at least one unit including a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material. The negative electrode plate includes a negative electrode material. The negative electrode material comprises a carbonaceous material. The specific surface area (Sc) of the carbonaceous material, based on the BET method, satisfies Sc ≥ 650 m² / g. The content (Cc) of the carbonaceous material in the negative electrode material satisfies Cc ≥ 0.5% by mass. Controlled-valve lead-acid batteries can be used, for example, in small motor vehicles or vehicles with idle stop control.

Description

Technical Field

[0001] This invention relates to a control valve type lead-acid battery and its manufacturing method, as well as an energy storage system including the control valve type lead-acid battery. Prior Technology

[0002] Besides automotive (four-wheeled cars, small motor vehicles (motorcycles, etc.) and industrial applications, control valve type (sealed) lead-acid batteries are also used in various other applications. A control valve type lead-acid battery includes a negative plate, a positive plate, a separator between the negative and positive plates, and an electrolyte. The separator is made of materials such as glass fiber nonwoven fabric. Electrode materials are contained in both the positive and negative plates. The negative electrode material contains lead as the active material, as well as carbon materials and organic shrink-proof agents.

[0003] Patent document 1 discloses a composition for the negative electrode active material of a sealed lead-acid battery, the composition comprising: a Brunauer-Emmett-Teller (BET) carbon material with a surface area of ​​150 m² / g to 2000 m² / g and a D90 value greater than 5 μm, the composition being characterized in that: based on the total weight of the composition, the amount of the carbon material is in the range of 0.1 wt% to 1.5 wt%.

[0004] Patent Document 2 discloses a lead-acid battery comprising an electrode containing carbon black oxide, the carbon black oxide having the following characteristics: a BET surface area in the range of 650 m² / g to 2100 m² / g; an oil absorption number (OAN) in the range of 35 mL / 100 g to 500 mL / 100 g; and having at least one of the following characteristics: (a) a volatile matter content of at least 5.5% by mass relative to the total mass of carbon black oxide, determined by mass loss at 950°C; (b) a total oxygen content of at least 3.5% by mass relative to the total mass of carbon black oxide; (c) a total titratable acidic group content of at least 0.5 μmol / m², determined by Boehm titration; and (d) a total titratable acidic group content of at least 0.5 mmol / g, determined by Boehm titration.

[0005] Patent document 3 discloses a negative electrode active material composition comprising: a carbon material having a surface area of ​​at least 250 m² / g; and an organic molecular shrinkage inhibitor, wherein the ratio of the carbon material to the shrinkage inhibitor in the negative electrode active material composition is in the range of 5:1 to 1:1, and the composition has a median pore size in the range of 0.8 μm to 4 μm.

[0006] Patent document 4 proposes a lead-acid battery, characterized in that: a combination of sodium lignin sulfonate with a molecular weight of 50,000 to 65,000 and an organic sulfur content of 5.5% by weight or more, and heavy oil with a specific surface area of ​​1200 m2 / g to 1300 m2 / g and a DBP oil absorption of 450 ml / g to 550 ml / g is used as the raw material in the additives of the negative electrode active material of the lead-acid battery.

[0007] Furthermore, Patent Document 5 proposes an electrode plate for a lead-acid battery, characterized in that: the active material is lead or lead dioxide, and the micropores of the active material layer in the charged state are distributed in micropore region A with a micropore diameter of 0.8μm to 10μm and micropore region B with a micropore diameter of 0.01μm to 0.2μm, each having a maximum value, and having a micropore structure with a clearly separated distribution state of at least two.

[0008] Patent document 6 discloses a lead-acid battery comprising: a separator for holding electrolyte, a positive electrode plate, a negative electrode plate, and a battery case. In the lead-acid battery, the negative electrode material of the negative electrode plate contains a bisphenol condensate, and the theoretical capacity ratio B / A of the theoretical capacity A of the positive electrode material of the positive electrode plate to the theoretical capacity B of the negative electrode material is 0.85 or more and 1.2 or less.

[0009] Patent document 7 proposes a lead-acid battery, characterized in that: in the positive electrode plate for lead-acid batteries using lead monoxide powder with an average particle size of 1μm to 10μm as the main component, lead tetroxide powder with an average particle size of 1μm to 3μm as the main component, and a pore-forming agent, the volume of fine pores with a diameter of 1μm or larger is 30% to 50% relative to the total fine pore volume.

[0010] [Existing Technical Documents]

[0011] [Patent Literature]

[0012] [Patent Document 1] Japanese Patent Publication No. 2015-537345

[0013] [Patent Document 2] Japanese Patent Publication No. 2018-522379

[0014] [Patent Document 3] Japanese Patent Publication No. 2015-534709

[0015] [Patent Document 4] Japanese Patent Laid-Open No. 2007-273367

[0016] [Patent Document 5] Japanese Patent Laid-Open No. 10-69900

[0017] [Patent Document 6] International Publication No. 2015 / 079668

[0018] [Patent Document 7] Japanese Patent Laid-Open No. 11-162456 Summary of the Invention Problems to be Solved by the Invention

[0019] Lead-acid batteries are sometimes used in a state of insufficient charge called a partial state of charge (PSOC). For example, a lead-acid battery mounted on a vehicle controlled by idle reduction (or start-stop) is used in PSOC. When a lead-acid battery is used in PSOC, stratification is likely to develop in which the specific gravity of the electrolyte in the upper part of the battery gradually decreases and the specific gravity of the electrolyte in the lower part of the battery gradually increases. If stratification develops, the accumulation of lead sulfate in the lower part of the negative electrode plate becomes significant, and sulfation that generates lead sulfate crystals is likely to occur. As a result, the capacity decreases, and due to uneven charge and discharge reactions, the electrode plates deteriorate, shortening the life of the lead-acid battery. Furthermore, in this specification, idle reduction may sometimes be abbreviated as "IS".

[0020] So far, various studies have been conducted on technologies for suppressing the accumulation of lead sulfate in lead-acid batteries for four-wheel vehicles. However, in lead-acid batteries for four-wheel vehicles controlled by IS and lead-acid batteries for small motor vehicles controlled by IS, the level of the state of charge (SOC) when switching from the load current in IS to the starting current for restarting the engine is different. Therefore, even if the technology of the previous lead-acid battery for four-wheel vehicles is applied to a lead-acid battery for a motorcycle, the effect of suppressing the accumulation of lead sulfate may not sometimes be obtained. Means for Solving the Problems

[0021] One aspect of the present invention relates to a controlled valve type lead storage battery, in which at least one cell including a positive electrode plate, a negative electrode plate, and an electrolyte is provided. The positive electrode plate includes a positive electrode material, the negative electrode plate includes a negative electrode material and a negative electrode current collector, the negative electrode material contains a carbonaceous material, and the specific surface area Sc of the carbonaceous material based on the BET method satisfies Sc≥650 m2 / g. The content Cc of the carbonaceous material in the negative electrode material satisfies Cc≥0.5 mass%, and it is used for a small motor vehicle.

[0022] Another aspect of the present invention relates to a controlled valve type lead storage battery, in which at least one cell including a positive electrode plate, a negative electrode plate, and an electrolyte is provided. The positive electrode plate includes a positive electrode material, the negative electrode plate includes a negative electrode material and a negative electrode current collector, the negative electrode material contains a carbonaceous material, and the specific surface area Sc of the carbonaceous material based on the BET method satisfies Sc≥650 m2 / g. The content Cc of the carbonaceous material in the negative electrode material satisfies Cc≥0.5 mass%, and it is used for a vehicle. The vehicle is configured such that idling stop control is performed when the state of charge (SOC) of the controlled valve type lead storage battery is above a threshold value of 90% or more, and idling stop control is not performed when the SOC of the controlled valve type lead storage battery is less than the threshold value.

[0023] Another aspect of the present invention relates to an electric power storage system, which includes: a controlled valve type lead storage battery; a vehicle that receives power supply from the controlled valve type lead storage battery; and a state of charge control unit that controls the state of charge (SOC) of the controlled valve type lead storage battery. The controlled valve type lead storage battery includes at least one cell including a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material, the negative electrode plate includes a negative electrode material and a negative electrode current collector, the negative electrode material contains a carbonaceous material, and the specific surface area Sc of the carbonaceous material based on the BET method satisfies Sc≥650 m2 / g. The content Cc of the carbonaceous material in the negative electrode material satisfies Cc≥0.5 mass%. The vehicle performs idling stop control when the state of charge (SOC) of the controlled valve type lead storage battery is above a threshold value of 90% or more, and does not perform idling stop control when the SOC of the controlled valve type lead storage battery is less than the threshold value. Advantages of the Invention

[0024] Accumulation of lead sulfate in the negative electrode plate of the controlled valve type lead storage battery can be suppressed. Brief Description of the Drawings

[0025] Figure 1 is a cross-sectional view schematically showing the structure of a lead-acid battery according to one embodiment of the present invention.

[0026] Figure 2 is a block diagram schematically illustrating the configuration of an energy storage system according to one embodiment of the present invention.

[0027] Figure 3 is a graph showing the relationship between the carbonaceous material content Cc and the amount of organic shrink-proof agent Ce added in the negative electrode material for carbonaceous materials with different BET specific surface areas Sc.

[0028] Figure 4 is a graph showing the relationship between the content of carbonaceous material Cc and the accumulation of lead sulfate.

[0029] Figure 5 is a graph showing the relationship between the BET specific surface area Sc of carbonaceous materials and the accumulation of lead sulfate. Implementation

[0030] The novel features of the invention are set forth in the appended patent claims, but both the composition and content of the invention, together with other objects and features of the invention, can be better understood from the following detailed description taken in conjunction with the drawings.

[0031] Small motor vehicles (e.g., motorcycles) pose a higher risk of falls compared to four-wheeled vehicles. Therefore, the use of liquid-cooled (vented) lead-acid batteries in small motor vehicles is limited, and in recent years there has been a trend towards using valve-regulated lead-acid batteries (VRLA). Furthermore, small motor vehicles with idle stop (IS) control have also been developed in recent years. Examples of small motor vehicles that can be equipped with VRLA include idle start-stop vehicles, micro-hybrid vehicles, and mild hybrid vehicles. Some of these already have IS control, and others are likely to have IS control in the near future. Therefore, even in VRLAs used in these small motor vehicles, the accumulation of lead sulfate in the negative plates due to use under PSOC conditions becomes a problem.

[0032] Because IS-controlled four-wheeled vehicles require high-precision control of the charging and discharging of their batteries, a Battery Management System (BMS) is included. The BMS contains a state-of-charge (SOC) control unit that manages the state of charge of the lead-acid battery. In lead-acid batteries used in IS-controlled four-wheeled vehicles, high recharge acceptance during deceleration is crucial. Therefore, the BMS's SOC control unit precisely controls the SOC of the lead-acid battery to a relatively low level (e.g., 70% or higher but less than 90%). This allows for the efficient charging of the lead-acid battery during vehicle deceleration, minimizing wasted regenerative energy. On the other hand, small motor vehicles using lead-acid batteries typically do not include a BMS and currently do not perform regenerative energy charging control. Therefore, in such small motor vehicles, the SOC of the lead-acid battery is controlled to be sufficiently high (e.g., 90% or higher) compared to that of lead-acid batteries used in four-wheeled vehicles, even during IS control. Even when charging is controlled in the manner described to achieve a high SOC, undercharging persists, leading to lead sulfate accumulation in the negative plate. Thus, the SOC under IS-controlled discharge mode differs between lead-acid batteries for four-wheeled vehicles and those for small motor vehicles. Therefore, even if lead sulfate accumulation suppression technology from four-wheeled vehicle lead-acid batteries is directly applied to lead-acid batteries for small motor vehicles, lead sulfate accumulation may not always be suppressed.

[0033] To explain more specifically, in lead-acid batteries for four-wheeled vehicles controlled by IS, if the negative electrode material contains a certain amount of carbonaceous material, the high conductivity of the carbonaceous material can achieve an effect of suppressing lead sulfate accumulation. Various carbonaceous materials exist with specific surface areas based on the BET method (hereinafter referred to as BET specific surface area). However, the effect of suppressing lead sulfate accumulation in lead-acid batteries for four-wheeled vehicles, as described above, is independent of the BET specific surface area of ​​the carbonaceous material; it becomes even greater with a higher content of carbonaceous material. Therefore, in lead-acid batteries for four-wheeled vehicles, inexpensive carbonaceous materials with smaller BET specific surface areas, such as acetylene black, are often used in the negative electrode plate. Furthermore, the aforementioned effect can be obtained similarly in both liquid lead-acid batteries and VRLA batteries.

[0034] Furthermore, it has been established that in lead-acid batteries (VABs) for small motor vehicles controlled by IS, even with a large amount of carbonaceous material having a small BET specific surface area used in the negative electrode plate, the accumulation inhibition effect of lead sulfate cannot be achieved. That is, it has been established that the behavior of the BET specific surface area of ​​carbonaceous material in inhibiting lead sulfate accumulation differs between lead-acid batteries for four-wheeled vehicles controlled by IS and VLBs for small motor vehicles controlled by IS. Previously, the difference in the behavior of the BET specific surface area of ​​carbonaceous material in these two types of lead-acid batteries for four-wheeled vehicles and VLBs for small motor vehicles was unknown.

[0035] In view of this understanding, one aspect of the VRLA of the present invention is used in small motor vehicles and includes at least one unit comprising a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material. The negative electrode plate includes a negative electrode material and a negative current collector. The negative electrode material comprises a carbonaceous material. The BET specific surface area of ​​the carbonaceous material: Sc satisfies Sc ≥ 650 m² / g. The content of carbonaceous material in the negative electrode material: Cc satisfies Cc ≥ 0.5% by mass.

[0036] Another aspect of the present invention relates to a VRLA used in a vehicle, the vehicle being configured to perform IS control when the SOC of the VRLA is above a threshold value of 90% or more, and not to perform IS control when the SOC of the VRLA is below the threshold value. The VRLA comprises at least one unit including a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material. The negative electrode plate includes a negative electrode material and a negative current collector. The negative electrode material comprises a carbonaceous material. The BET specific surface area of ​​the carbonaceous material, Sc, satisfies Sc ≥ 650 m² / g. The content of the carbonaceous material in the negative electrode material, Cc, satisfies Cc ≥ 0.5% by mass.

[0037] The present invention also includes a method for manufacturing the VRLA. The method for manufacturing VRLA includes: a step of preparing a negative electrode paste comprising lead powder, the carbonaceous material, water, and sulfuric acid; a step of forming an unchemically converted negative electrode plate by coating or filling the negative electrode paste onto a negative electrode current collector; and a step of obtaining a negative electrode plate comprising a negative electrode material and a negative electrode current collector by chemically converting the unchemically converted negative electrode plate.

[0038] The present invention also includes an energy storage system comprising the VRLA, a vehicle receiving power from the VRLA, and a charging state control unit that controls the VRLA's SOC.

[0039] Another aspect of the present invention provides an energy storage system comprising: a VRLA (Dynamic Voltage Assisted Actuator), a vehicle receiving power from the VRLA, and a state of charge control unit for controlling the SOC (State of Charge) of the VRLA. The VRLA includes at least one unit comprising a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material. The negative electrode plate includes a negative electrode material. The negative electrode material comprises a carbonaceous material. The BET specific surface area (Sc) of the carbonaceous material satisfies Sc ≥ 650 m² / g. The carbonaceous material content (Cc) in the negative electrode material satisfies Cc ≥ 0.5% by mass. In the energy storage system, IS (Inertial Control) is performed when the vehicle's VRLA SOC is above a threshold value of 90% or higher, and IS is not performed when the VRLA SOC is below the threshold value.

[0040] Small motor vehicles typically do not include a BMS. The VRLA used in small motor vehicles is configured to charge and discharge at a near-fully charged PSOC state, whether for starting or IS. More specifically, it is designed to perform IS control when the VRLA's SOC is above a threshold of 90%, and not when it is below that threshold.

[0041] According to the VRLA or energy storage system, the negative electrode material contains carbonaceous material with a BET specific surface area Sc ≥ 650 m² / g at a content Cc ≥ 0.5% by mass. Therefore, the accumulation of lead sulfate in the negative electrode plate can be suppressed. Since the charge-discharge reaction of the electrode plate proceeds more uniformly, electrode plate degradation can be suppressed. Thus, the lifespan performance of the VRLA can be improved.

[0042] In contrast, when the negative electrode material of the VRLA (or the VRLA included in the energy storage system) contains a small amount of carbonaceous material with Cc < 0.5% by mass, the accumulation of lead sulfate remains almost unchanged at Sc < 650 m² / g and Sc ≥ 650 m² / g, and the effect of inhibiting lead sulfate accumulation is almost negligible. Furthermore, when the negative electrode material contains carbonaceous material with Cc ≥ 0.5% by mass and Sc < 650 m² / g, it is almost impossible to increase Cc, and the effect of inhibiting lead sulfate accumulation is not achieved.

[0043] In lead-acid batteries for four-wheeled vehicles, when the negative electrode material contains a small amount of carbonaceous material with Cc < 0.5% by mass, the accumulation of lead sulfate remains almost unchanged at Sc < 650 m² / g and Sc ≥ 650 m² / g, and the accumulation inhibition effect of lead sulfate is also almost negligible. This is roughly the same as the results in VRLA. When the negative electrode material contains carbonaceous material with Cc ≥ 0.5% by mass, the same degree of lead sulfate accumulation inhibition effect is obtained at both Sc < 650 m² / g and Sc ≥ 650 m² / g. That is, in lead-acid batteries for four-wheeled vehicles, the accumulation inhibition effect of lead sulfate depends only on the carbonaceous material content Cc, and not on the BET specific surface area Sc of the carbonaceous material. This tendency remains unchanged in both liquid lead-acid batteries and VRLA batteries for four-wheeled vehicles. In contrast, in the VRLA (or the VRLA included in the energy storage system), the effect of inhibiting lead sulfate accumulation depends on both the content of carbonaceous material Cc and the BET specific surface area Sc of the carbonaceous material.

[0044] The details of the different mechanisms by which the BET specific surface area of ​​carbonaceous materials exhibits different behavior in inhibiting lead sulfate accumulation in VRLA and lead-acid batteries for four-wheeled vehicles, as described above, are not clear, but are speculated as follows.

[0045] In lead-acid batteries for four-wheeled vehicles charged and discharged at a lower SOC, the conductivity of the negative electrode material is lower compared to that charged and discharged at a higher SOC. Therefore, adding a certain amount of carbonaceous material to the negative electrode material significantly improves its conductivity. Furthermore, it is believed that using carbonaceous material with a high BET specific surface area (Sc) can retain a large amount of electrolyte around the lead, the active material. However, in lead-acid batteries charged and discharged at a lower SOC, the increased conductivity of the negative electrode material resulting from the addition of carbonaceous material has a greater impact than the effect of retaining a large amount of electrolyte around the lead. Consequently, regardless of the difference in BET specific surface area (Sc), including a certain amount of carbonaceous material in the negative electrode material can suppress the accumulation of lead sulfate in the negative electrode plate.

[0046] On the other hand, in the VRLA that is charged and discharged at a higher SOC, the negative electrode material is in a state containing a large amount of highly conductive lead. Therefore, even if carbonaceous material is added to the negative electrode material, the effect of increased conductivity associated with the addition of carbonaceous material is hardly observed. It is believed that in the state of high conductivity of the negative electrode material, the charge and discharge reaction is significantly affected by the ionic conductivity of the electrolyte around the lead. In VRLA, compared with liquid lead-acid batteries, there is less electrolyte around the lead. By using carbonaceous material with a BET specific surface area Sc of 650 m2 / g or more at a Cc content of 0.5% or more, a large amount of electrolyte can be maintained around the lead. This improves the ionic conductivity around the lead, and the charge and discharge reaction proceeds more smoothly. That is, it can be said that by using carbonaceous material as described, the reaction at the lead-electrolyte interface can be promoted. As a result, it is believed that the accumulation of lead sulfate in the negative electrode plate can be suppressed.

[0047] As described, the VRLA is preferably used in vehicles where IS control is performed when the SOC reaches a threshold of 90% or higher, but not when the threshold is not reached. In this case, the difference in behavior of the BET specific surface area of ​​the carbonaceous material in the inhibition of lead sulfate accumulation becomes more pronounced in the VRLA described above and in lead-acid batteries for four-wheeled vehicles. Therefore, the effect of inhibiting lead sulfate accumulation can be more effectively achieved.

[0048] Organic shrink-proof agents can also be added to the negative electrode material. In the manufacturing method of VRLA, the negative electrode paste can also contain organic shrink-proof agents. By using organic shrink-proof agents, the low-temperature high-rate (HR) discharge performance of VRLA can be improved.

[0049] When the negative electrode material contains an organic shrink-proof agent, the organic shrink-proof agent is adsorbed onto the carbonaceous material, making it difficult for the organic shrink-proof agent to exert its shrink-proof effect. If a carbonaceous material with a large specific surface area (Sc) is used, the effect of the carbonaceous material on the adsorption of the organic shrink-proof agent becomes more apparent. From the viewpoint of ensuring higher low-temperature HR discharge performance, the amount of organic shrink-proof agent added to the negative electrode material, Ce (mass %), is preferably Ce > 0.368Cc + 0.054. In this case, as the carbonaceous material, a carbonaceous material with a specific surface area (Sc) of 650 m² / g ≤ Sc ≤ 1000 m² / g can be used. Furthermore, if the amount of organic shrink-proof agent (Ce) added is controlled within the aforementioned range, the hydrogen overvoltage on the negative electrode side is within an appropriate range, but tends to increase. Therefore, even when using VRLA at higher temperatures, the charging current during constant voltage charging can be suppressed to a low level. Accompanying this, the generation of oxygen from the positive electrode plate can be suppressed, thereby suppressing the heat generated by the oxygen absorption reaction of the negative electrode material. This helps to suppress electrolyte loss, which is advantageous from the perspective of ensuring excellent lifespan performance.

[0050] The optimal addition amount of organic anti-shrinkage agent (Ce) is 0.372Cc + 0.092 ≤ Ce ≤ 0.373Cc + 0.249. Setting it to 0.372Cc + 0.092 ≤ Ce further improves low-temperature high-temperature discharge performance and inhibits electrolyte loss. Furthermore, setting it to Ce ≤ 0.373Cc + 0.249 helps prevent excessive coating of the organic anti-shrinkage agent by carbonaceous materials and lead. Maintaining the high conductivity of the negative electrode material helps suppress the decrease in charge acceptability.

[0051] In applications where VRLAs are used in small motor vehicles, unlike four-wheeled vehicles, they are typically not equipped with a BMS (Battery Management System). Because it is difficult to control charging and discharging based on temperature changes in lead-acid batteries, the performance of VRLAs is significantly affected by external temperature. Small motor vehicles can be used in various environments, from hot to cold regions. Therefore, the VRLAs used in these vehicles require an excellent balance of lead sulfate accumulation suppression, low-temperature high-temperature discharge performance, charge acceptability, and liquid reduction suppression over a wide temperature range. Ensuring a high level of balance in these multiple characteristics requires extremely advanced technology. In contrast, by using carbonaceous materials with a specific surface area Sc of 650 m² / g ≤ Sc ≤ 1000 m² / g, and by adjusting the amount of organic anti-shrinkage agent Ce according to the carbonaceous material content Cc using the formula described above, the balance of these characteristics can be precisely adjusted. Therefore, excellent performance and stable quality can be achieved even when used in various regions worldwide.

[0052] High low-temperature HR discharge performance is required for VRLAs. For example, in small motor vehicles such as motorcycles, VRLAs are sometimes started in low-temperature environments, thus requiring high low-temperature HR discharge performance. To ensure high low-temperature HR discharge performance in VRLAs, it is effective to suppress sulfation in the negative electrode. From the viewpoint of suppressing sulfation in the negative electrode, it is generally advantageous to have a large NAM / PAM ratio relative to the mass of the negative electrode material (Negative Active Material: NAM) and the positive electrode material (Positive Active Material: PAM). In contrast, in the VRLAs of one and another aspects of the present invention, it is preferable to have a small NAM / PAM ratio. More specifically, the NAM / PAM ratio is preferably <1.21. When the content of carbonaceous material Cc in the negative electrode material is 0.5% by mass or more, the accumulation of lead sulfate can be suppressed. Therefore, even with a NAM / PAM ratio of <1.21, sufficient low-temperature HR discharge performance can be ensured when the battery is not used or when the battery is in a PSOC state. On the other hand, when the carbonaceous material content (Cc) in the negative electrode material is less than 0.5% by mass, even with a NAM / PAM ratio of <1.21, the decrease in the maintenance rate of low-temperature HR discharge performance when the battery is not used or when the battery is in a PSOC state cannot be suppressed. This is believed to be because when the carbonaceous material content (Cc) is less than 0.5% by mass, in addition to fewer conductive paths, the ionic conductivity around lead is low, thus failing to sufficiently suppress the accumulation of lead sulfate, leading to sulfation.

[0053] Furthermore, by setting the NAM / PAM ratio to <1.21, the mass of the positive electrode active material contained in a given volume of positive electrode material can be relatively increased. This reduces the load per unit mass of the positive electrode active material applied to the positive electrode material by the charge-discharge reaction. Therefore, it is expected that the degradation of the positive electrode material can be suppressed, and the characteristics related to the positive electrode can be improved.

[0054] In recent years, VRLA has sometimes been required to exhibit excellent cycle characteristics (hereinafter referred to as room temperature HR cycle characteristics) during repeated charge-discharge cycles including room temperature HR discharge. For example, room temperature HR discharge is envisioned during engine acceleration. Room temperature HR discharge is generally significantly affected by the reaction at the positive electrode.

[0055] In the aforementioned VRLA, when the NAM / PAM ratio is <1.21, the positive electrode material may also contain pores with a pore size of 1 μm or more and 10 μm or less. In this specification, the pores with a pore size of 1 μm or more and 10 μm or less in the positive electrode material are sometimes referred to as first pores. The proportion of first pores in the positive electrode material can be 9% by volume or more. When the proportion of first pores is within this range, the room temperature HR cycle characteristics are significantly improved. Therefore, it is easy to balance the room temperature HR discharge performance with the cycle characteristics during repeated charge-discharge cycles including room temperature HR discharge, achieving a high level of balance between room temperature HR discharge performance and cycle life. This effect is believed to be achieved for the following reasons: First, by having a first pore proportion of 9% by volume or more, a large amount of electrolyte can be maintained in the positive electrode material, and a large number of reactive sites can be ensured in the positive electrode material. Therefore, high initial room temperature HR characteristics can be obtained. Furthermore, by having a first pore ratio of 9% or more, the diffusivity of the electrolyte in the positive electrode material is improved. Additionally, by adjusting the NAM / PAM ratio to less than 1.21, as described above, the degradation of the positive electrode material can be suppressed. It is believed that through these interactions, the room-temperature HR cycle characteristics are significantly improved.

[0056] (Explanation of terminology)

[0057] (Negative electrode material)

[0058] In a negative electrode plate, the negative electrode material is typically held within the negative current collector. The negative electrode material is the portion obtained by removing the negative current collector from the negative electrode plate. Sometimes, pads, pasting paper, or other components are attached to the negative electrode plate. Since these components (also called attachment components) are used integrally with the negative electrode plate, they are included within the negative electrode plate. When the negative electrode plate includes attachment components, the negative electrode material is the portion obtained by removing both the negative current collector and the attachment components from the negative electrode plate.

[0059] (BET specific surface area)

[0060] The specific surface area based on the Brunauer-Emmett-Teller (BET) method (BET specific surface area) refers to the specific surface area calculated using a gas adsorption method with nitrogen as the adsorbent gas and the BET formula.

[0061] (The content of carbonaceous material Cc in the negative electrode material)

[0062] The carbonaceous material content Cc refers to the mass ratio (mass %) of carbonaceous material contained in the negative electrode material, calculated from the negative electrode plate taken from a lead-acid battery in a fully charged state.

[0063] (Organic anti-shrinkage agent)

[0064] Organic anti-shrinkage agents refer to organic compounds among the following compounds, which have the function of inhibiting the shrinkage of lead, which is the negative electrode active material, during repeated charging and discharging of lead-acid batteries.

[0065] (Amount of organic shrink-proof agent added, Ce)

[0066] The amount of organic shrink-proof agent added, Ce, refers to the mass percentage (mass%) of the organic shrink-proof agent added in the negative electrode material during the preparation of the negative electrode material or negative electrode paste.

[0067] (Positive electrode material)

[0068] In a positive electrode plate, the positive electrode material is typically held within the positive current collector. The positive electrode material is the portion obtained by removing the positive current collector from the positive electrode plate. Sometimes, pads, adhesive sheets, or other components are attached to the positive electrode plate. Since these components (also called attachment components) are used integrally with the positive electrode plate, they are included within the positive electrode plate. When the positive electrode plate includes attachment components, the positive electrode material is the portion obtained by removing both the positive current collector and the attachment components from the positive electrode plate.

[0069] (Ratio of the first fine pore)

[0070] As described above, the term "first pore" refers to pores with a diameter of 1 μm or more but less than 10 μm contained in the positive electrode material. The term "ratio of the first pores in the positive electrode material" refers to the ratio (volume %) of the first pores in the total pore volume of the positive electrode material.

[0071] (NAM / PAM ratio)

[0072] The NAM / PAM ratio is the ratio of the total mass of the negative electrode material in one cell of a VRLA to the total mass of the positive electrode material in one cell. When the VRLA contains two or more cells, the total mass of the negative and positive electrode materials are the average of the total masses calculated for the two cells. When the VRLA contains three or more cells, each average is calculated based on one cell located at the end of the VRLA and one cell located near the center.

[0073] (State of Charge (SOC))

[0074] The term SOC refers to the ratio of the charged capacity to the VRLA's full charge capacity (100%). Furthermore, in this manual, a 100% full charge state for a control valve type lead-acid battery refers to the state at which charging is completed according to the conditions described in Japanese Industrial Standards (JIS) D 5302:2004, section 8.2.2 (revised March 20, 2016).

[0075] A fully charged lead-acid battery refers to a lead-acid battery that has undergone chemical conversion and has been fully charged. Full charging of a lead-acid battery after chemical conversion can be performed immediately after the conversion or after a certain period of time has elapsed since the conversion (for example, a lead-acid battery in use (preferably in the initial stage of use) can also be fully charged after chemical conversion). A battery in the initial stage of use refers to a battery that has not undergone significant deterioration since the start of use.

[0076] (SOC threshold)

[0077] The "critical limit" of SOC refers to a pre-set baseline SOC. "Reaching the critical limit" means that the SOC becomes the critical limit or is close to it. In addition, the SOC near the critical limit refers to the specified SOC below the critical limit and the specified SOC above the critical limit.

[0078] (Control valve type lead-acid batteries for small motor vehicles and small motor vehicles)

[0079] The term "VRLA for small motor vehicles" refers to the VRLA in lead-acid batteries included within the application scope of IEC 60095-7:2019 and JIS D 5302:2004. "Small motor vehicles" refers to motorcycles and motorized bicycles that utilize these VRLAs. Small motor vehicles include, for example, motorcycles, three-wheeled vehicles, ATVs (including both three-wheeled and four-wheeled vehicles), water skis, snowmobiles, and all-terrain vehicles. Furthermore, small motor vehicles may also have a VRLA for small motor vehicles mounted on top of the engine.

[0080] (Idle Stop (IS))

[0081] A vehicle with idle stop (IS) is a vehicle that uses idle stop (IS) control, including an idle stop system (IS). Sometimes the idle stop system is referred to as an ISS. An ISS is a system that controls the engine to stop when the vehicle is parked or stopped. In an ISS, during the engine stop period, the vehicle's required current is supplied by the battery on the vehicle. During the engine stop period in an ISS, when the battery's state of charge (SOC) reaches a predetermined threshold, the engine restarts. The period from when the engine stops by parking or stopping the vehicle until it restarts is called the idle stop period (IS period). During the IS period, the load current corresponding to the consumption of the vehicle's electrical system and the starting current when restarting the engine are discharged from the battery.

[0082] The VRLA and energy storage system according to embodiments of the present invention will be described in more detail below. However, the present invention is not limited to the following embodiments.

[0083] [VRLA]

[0084] (Negative electrode plate)

[0085] A negative electrode plate typically consists of a negative current collector and a negative electrode material, with the negative electrode material held in the negative current collector.

[0086] (Negative current collector)

[0087] The negative current collector can be formed by casting lead (Pb) or lead alloys, or by processing lead sheets or lead alloy sheets. Processing methods include, for example, drawing or punching. Using a grid-shaped current collector as the negative current collector is preferable because it facilitates the support of the negative electrode material.

[0088] The lead alloy used in the negative electrode current collector can be any of the Pb-Ca alloys or Pb-Ca-Sn alloys. These lead or lead alloys may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, and Cu. The negative electrode current collector may also include a surface layer. The composition of the surface layer and the inner layer of the negative electrode current collector may differ. The surface layer may be formed on a portion of the negative electrode current collector. The surface layer may also be formed on the ear portion of the negative electrode current collector. The surface layer on the ear portion may contain Sn or a Sn alloy.

[0089] (Negative electrode material)

[0090] The negative electrode material contains an essential component: a negative electrode active material (lead or lead sulfate) that exhibits capacity through a redox reaction. The negative electrode active material in the charged state is spongy lead, but unconverted negative electrode plates are typically made using lead powder. The negative electrode material also contains carbonaceous materials as additives. Furthermore, the negative electrode material may contain additives other than carbonaceous materials (organic shrink-proof agents, barium sulfate, etc.).

[0091] (Carbon-based materials)

[0092] Carbonaceous materials used as negative electrode materials include: carbon black, graphite, hard carbon, soft carbon, etc. Examples of carbon black include acetylene black, furnace black, and lamp black. Furnace black also includes Ketjen black (trade name). Graphite can be any carbonaceous material containing a graphite-type crystal structure, and can be either synthetic or natural graphite. A single carbonaceous material can be used, or a combination of two or more can be used.

[0093] Furthermore, in this specification, carbonaceous materials in which the intensity ratio (ID / IG) of the peak values ​​(D band) appearing in the Raman spectrum above 1300 cm⁻¹ and below 1350 cm⁻¹ to the peak values ​​(G band) appearing in the Raman spectrum above 1550 cm⁻¹ and below 1600 cm⁻¹ is 0 or higher and 0.9 or lower are referred to as graphite. Graphite can be either artificial graphite or natural graphite.

[0094] The BET specific surface area (Sc) of the carbonaceous material is 650 m² / g or higher. When the BET specific surface area (Sc) is less than 650 m² / g, even setting the carbonaceous material content to 0.5% by mass or higher is insufficient to adequately suppress lead sulfate accumulation in the negative electrode plate. From the viewpoint of ensuring higher suppression of lead sulfate accumulation, the BET specific surface area (Sc) is preferably 750 m² / g or higher, and can also be 800 m² / g or higher. From the viewpoint of ensuring even higher suppression of lead sulfate accumulation, the BET specific surface area (Sc) is preferably 1000 m² / g or lower.

[0095] From the viewpoint of easily controlling the BET specific surface area Sc of carbonaceous materials to the aforementioned range, the carbonaceous materials preferably include at least furnace black (especially Ketjen black). The carbonaceous materials may include furnace black (especially Ketjen black) and other carbonaceous materials. When combining two or more carbonaceous materials, the types or adjustment ratios of the combined carbonaceous materials can be selected in such a way that the overall BET specific surface area Sc of the carbonaceous materials falls within the aforementioned range.

[0096] The carbonaceous material content (Cc) in the negative electrode material is 0.5% by mass or more. When the carbonaceous material content (Cc) is less than 0.5% by mass, the effect of inhibiting lead sulfate accumulation in the negative electrode plate is independent of the BET specific surface area (Sc) of the carbonaceous material. From the viewpoint of ensuring a higher effect of inhibiting lead sulfate accumulation, the carbonaceous material content (Cc) can be 0.75% by mass or more. For example, the carbonaceous material content (Cc) can be 3% by mass or less, or 2% by mass or less.

[0097] The content Cc of carbonaceous materials can be 0.5% by mass or more and 3% by mass or less (or 2% by mass or less), or 0.75% by mass or more and 3% by mass or less (or 2% by mass or less).

[0098] (Organic anti-shrinkage agent)

[0099] As an organic shrinkage inhibitor, for example, at least one selected from the group consisting of lignin compounds and synthetic organic shrinkage inhibitors can be used.

[0100] Examples of lignin compounds include lignin and lignin derivatives. Examples of lignin derivatives include lignin sulfonic acid or its salts (alkali metal salts (sodium salts, etc.)).

[0101] The synthetic organic anti-shrinkage agents used in lead-acid batteries are usually organic condensates (hereinafter referred to as condensates). A condensate is a compound obtained through a condensation reaction. Condensates may contain aromatic compound units (hereinafter also called aromatic compound units). An aromatic compound unit is a unit derived from an aromatic compound incorporated into the condensate. That is, an aromatic compound unit is a residue of an aromatic compound. A condensate may contain units of one aromatic compound or more than two aromatic compounds.

[0102] Examples of condensates include condensates of aromatic compounds obtained using aldehyde compounds. Such condensates can be synthesized by reacting an aromatic compound with an aldehyde compound. Here, by reacting the aromatic compound with an aldehyde compound in the presence of sulfite, or by using an aromatic compound containing sulfur (e.g., bisphenol S) as the aromatic compound, a condensate containing sulfur can be obtained. For example, the sulfur content in the condensate can be adjusted by adjusting at least one of the amount of sulfite and the amount of the sulfur-containing aromatic compound. This method can also be followed when using other raw materials. The aromatic compound condensed to obtain the condensate can be one or more. Furthermore, the aldehyde compound can be an aldehyde (e.g., formaldehyde), or a condensate (or polymer) of an aldehyde. Examples of aldehyde condensates (or polymers) include paraformaldehyde, trioxane, and tetraoxymethylene. An aldehyde compound can be used alone or in combination with two or more. From the perspective of high reactivity with aromatic compounds, formaldehyde is preferred.

[0103] Aromatic compounds may contain sulfur-containing groups. That is, the condensate can be an organic polymer containing multiple aromatic rings and sulfur as a sulfur-containing group. The sulfur-containing group can be directly bonded to the aromatic ring of the aromatic compound, for example, it can also be bonded to the aromatic ring as an alkyl chain containing a sulfur group. Among the sulfur-containing groups, a stable sulfonic acid group or a sulfonyl group is preferred. The sulfonic acid group can exist in the acid form or in the salt form, such as sodium salts.

[0104] Examples of aromatic rings in aromatic compounds include benzene rings and naphthalene rings. When an aromatic compound has multiple aromatic rings, these rings can be directly bonded or linked by linking groups (e.g., alkylene groups (including alkylidene groups), ternary groups), etc. Examples of such structures include diaromatic structures (biphenyl, diphenylalkanes, diphenyl ternary, etc.).

[0105] Examples of aromatic compounds include those having the aromatic ring and functional groups (hydroxyl, amino, etc.). The functional group can be directly bonded to the aromatic ring or bonded in the form of an alkyl chain. Furthermore, the hydroxyl group also includes salts of hydroxyl groups (-OMe). The amino group also includes salts of amino groups (and salts with anions). Examples of Me include alkali metals (Li, K, Na, etc.) and Group II metals of the periodic table (Ca, Mg, etc.). Aromatic compounds may also have a sulfide group and substituents other than the aforementioned functional group (e.g., alkyl, alkoxy) in the aromatic ring.

[0106] Aromatic compounds that form the basis of aromatic compound units can be at least one selected from the group consisting of diaromatic compounds and monocyclic aromatic compounds.

[0107] Examples of diaromatic compounds include: bisphenol compounds, hydroxybiphenyl compounds, and diaromatic compounds with an amino group (such as diarylalkane compounds with an amino group, diaryl benzoyl compounds with an amino group, and biphenyl compounds with an amino group). Among these, bisphenol compounds are preferred.

[0108] Bisphenol compounds are preferably bisphenol A, bisphenol S, bisphenol F, etc. For example, the bisphenol compound may contain at least one selected from the group consisting of bisphenol A and bisphenol S. By using bisphenol A or bisphenol S, excellent shrinkage prevention effect on the negative electrode material can be obtained.

[0109] Bisphenol compounds only need to have a bisphenol skeleton, and the bisphenol skeleton can also have substituents. That is, bisphenol A only needs to have a bisphenol A skeleton, and its skeleton can also have substituents. Bisphenol S only needs to have a bisphenol S skeleton, and its skeleton can also have substituents.

[0110] As monocyclic aromatic compounds, hydroxyl monoaromatic compounds and amino monoaromatic compounds are preferred. Among them, hydroxyl monoaromatic compounds are preferred.

[0111] Examples of hydroxyl monoaromatic compounds include hydroxynaphthalene compounds and phenolic compounds. For example, phenol sulfonic acid compounds (phenol sulfonic acid or its substitutes, etc.) are preferred as phenolic compounds. Furthermore, as mentioned above, the phenolic hydroxyl group also includes a salt of the phenolic hydroxyl group (-OMe).

[0112] Examples of amino-based monoaromatic compounds include aminonaphthalene compounds and aniline compounds (aminobenzenesulfonic acid, alkylaminobenzenesulfonic acid, etc.).

[0113] As described above, the negative electrode material contains a carbonaceous material with a large BET specific surface area Sc. If such a carbonaceous material is used, the organic shrink-proof agent is adsorbed onto the carbonaceous material, and sometimes it is difficult to effectively exert the effect of the organic shrink-proof agent. From the viewpoint of more effectively exerting the effect brought about by the use of organic shrink-proof agent, the amount of organic shrink-proof agent Ce added to the negative electrode material is preferably determined according to the BET specific surface area Sc of the carbonaceous material. From the viewpoint of ensuring higher low-temperature HR discharge performance, the amount of organic shrink-proof agent Ce added to the negative electrode material is preferably Ce>0.368Cc+0.054(1). From the viewpoint of further improving the low-temperature HR discharge performance and suppressing electrolyte reduction, it is preferable to set the amount of organic shrink-proof agent Ce to 0.372Cc+0.092≦Ce(2). Furthermore, from the viewpoint of improving the effect of suppressing the decrease in charge acceptability, it is preferable to set the amount of organic anti-shrinkage agent Ce to Ce≦0.373Cc+0.249(3). Moreover, these relationships are established within the range of BET specific surface area Sc of carbonaceous materials being 650 m2 / g or more (or 750 m2 / g or more or 800 m2 / g or more) and 1000 m2 / g or less.

[0114] The relationships (1) to (3) are derived from the evaluation of low-temperature HR discharge performance, charge acceptability, and electrolyte reduction characteristics using multiple carbonaceous materials with different BET specific surface areas (Sc). More specifically, the evaluation was conducted using carbonaceous materials with BET specific surface areas (Sc) within the aforementioned range, and by varying the carbonaceous material content (Cc) and the amount of organic anti-shrinkage agent added (Ce). The relationship between the carbonaceous material content (Cc) and the amount of organic anti-shrinkage agent added (Ce) at this time is shown in Figure 3.

[0115] Furthermore, the evaluation of each characteristic is carried out through the procedure described later. Each characteristic is evaluated according to the following criteria.

[0116] (Low-temperature HR discharge performance)

[0117] a: The duration of low-temperature HR discharge is over 200 seconds.

[0118] b: The duration of low-temperature HR discharge is more than 180 seconds but less than 200 seconds.

[0119] c: The duration of cryogenic HR discharge was less than 180 seconds.

[0120] (Charging acceptance)

[0121] a: The current at the 100th second is above 0.5A and below 0.7A.

[0122] b: The current exceeds 0.7A but is below 0.8A at the 100th second.

[0123] c: The current at the 100th second is greater than 0.8A or less than 0.5A.

[0124] (Reduction of electrolyte)

[0125] a: The reduction in electrolyte amount is less than 10% of the mass.

[0126] b: The reduction in electrolyte is more than 10% by mass but less than 15% by mass.

[0127] c: The reduction in electrolyte content is more than 15% by mass.

[0128] Figure 3 shows the evaluation results obtained by comprehensively evaluating each characteristic according to the following criteria.

[0129] A: The evaluation of both low-temperature HR discharge performance and charge acceptability is a, and the evaluation of electrolyte reduction is a or b.

[0130] B: The evaluation of low-temperature HR discharge performance is b, the evaluation of charge acceptability is a, and the evaluation of electrolyte reduction is a or b, or the evaluation of both low-temperature HR discharge performance and charge acceptability is b, and the evaluation of electrolyte reduction is a.

[0131] C: Not classified as either A or B.

[0132] For the plotted data, regarding each Cc, the formula for linear approximating the points with an upper limit of comprehensive evaluation A is related to equation (3), which is Ce = 0.373Cc + 0.249. Additionally, regarding each Cc, the formula for linear approximating the points with a comprehensive evaluation B is related to equation (2), which is Ce = 0.372Cc + 0.092. For points below this formula, the formula for linear approximating the points with an upper limit of comprehensive evaluation C is related to equation (1), which is Ce = 0.368Cc + 0.054. For each approximation formula shown in Figure 3, the value represented by R² is the remainder term of the linear approximation.

[0133] As shown in Figure 3, when Ce≦0.368Cc+0.054, the low-temperature HR discharge duration is less than 180 seconds for most points. Under the condition of satisfying equation (1), a low-temperature HR discharge duration of more than 180 seconds can be obtained. Under the condition of satisfying equation (2), a longer low-temperature HR discharge duration can be obtained, and electrolyte loss can be suppressed. Under the condition of satisfying equation (3), higher charge acceptability can be obtained.

[0134] (Barium sulfate)

[0135] The negative electrode material may contain barium sulfate. The barium sulfate content in the negative electrode material may be, for example, 0.05% by mass or more, or 0.10% by mass or more. Alternatively, the barium sulfate content in the negative electrode material may be, for example, 3% by mass or less, or 2% by mass or less.

[0136] The barium sulfate content in the negative electrode material can be 0.05% by mass or more and 3% by mass or less, 0.05% by mass or more and 2% by mass or less, 0.10% by mass or more and 3% by mass or less, or 0.10% by mass or more and 2% by mass or less.

[0137] (Analysis of negative electrode material or its components)

[0138] The analytical methods for negative electrode materials or their constituent components are described below.

[0139] (1) Quantitative analysis of negative electrode materials

[0140] A fully charged lead-acid battery was disassembled to obtain the negative electrode plate for analysis. The obtained negative electrode plate was washed with water to remove sulfuric acid. Washing continued until pH test paper was pressed against the washed negative electrode plate surface and the color of the test paper did not change. The washing time was set to be no more than 2 hours. The washed negative electrode plate was dried under reduced pressure at 60℃±5℃ for approximately 6 hours. If the negative electrode plate contained attached components, these components were removed by peeling. The mass of the dried material (negative electrode plate) was measured. Next, a sample (hereinafter referred to as Sample A) was obtained by scraping and separating the negative electrode material from the negative electrode current collector. Sample A was pulverized as needed for analysis of the composition of the negative electrode material.

[0141] The negative electrode current collector is ultrasonically treated while immersed in water to remove the negative electrode material adhering to it. After washing and drying, the mass of the negative electrode current collector is measured. The mass of the negative electrode material is calculated by subtracting the mass of the negative electrode current collector from the mass of the negative electrode plate. The total mass of the negative electrode material in the unit is calculated by summing the masses of all negative electrode plates in the unit.

[0142] (2) Qualitative analysis of organic shrink-proof agents in negative electrode materials

[0143] The pulverized sample A was immersed in a 1 mol / L sodium hydroxide (NaOH) aqueous solution to extract the organic shrink-proof agent. If the extract contained multiple organic shrink-proof agents, each organic shrink-proof agent was then separated from the extract. For the separates containing each organic shrink-proof agent, insoluble components were removed by filtration, and the resulting solutions were desalted, concentrated, and dried. Desalting was performed using a desalting column, by passing the solution through an ion exchange membrane, or by placing the solution in a dialysis tube and immersing it in distilled water. The powdered sample of the organic shrink-proof agent (hereinafter referred to as sample B) was obtained by drying.

[0144] The type of organic shrink-proof agent is determined by combining the following information: infrared spectrophotometer of sample B obtained by the method described above; ultraviolet-visible absorption spectrum of sample B obtained by diluting sample B with distilled water or the like and measured by ultraviolet-visible absorbance meter; or nuclear magnetic resonance (NMR) spectrum of the solution obtained by dissolving sample B with a specified solvent such as heavy water.

[0145] (3) Quantitative analysis of carbonaceous materials and barium sulfate

[0146] For 10g of pulverized sample A, add 50ml of 20% (w / w) nitric acid and heat for about 20 minutes to dissolve the lead component as lead ions. Filter the resulting mixture to separate the carbonaceous material, barium sulfate, and other solid components.

[0147] After dispersing the obtained solid components in water to form a dispersion, components other than carbonaceous material and barium sulfate (e.g., reinforcing materials) are removed from the dispersion using a sieve. Next, the dispersion is filtered using a membrane filter whose mass has been pre-determined. The membrane filter and the filtered sample are then dried together in a desiccator at 110℃ ± 5℃. The resulting sample is a mixture of carbonaceous material and barium sulfate (hereinafter referred to as sample C). The mass of sample C (Mm) is determined by subtracting the mass of the membrane filter from the total mass of the dried sample C and the membrane filter. Then, the dried sample C and the membrane filter are placed in a crucible and heated to ashing at 1300℃ or higher. The remaining residue is barium oxide. The mass of barium oxide is converted to the mass of barium sulfate, and the mass of barium sulfate (MB) is calculated. The mass of the carbonaceous material is calculated by subtracting the mass of MB from the mass of Mm. The percentage (mass %) of each mass in sample A is determined, which serves as the content of carbonaceous material Cc and lead sulfate in the negative electrode material.

[0148] (4) BET specific surface area Sc of carbonaceous materials

[0149] (4-1) Separation of carbonaceous materials

[0150] A specified amount of pulverized sample A was collected and its mass determined. 30 mL of a 60% (w / w) nitric acid aqueous solution was added to every 5 g of sample A, and the mixture was heated at 70℃ ± 5℃. To the resulting mixture, 10 g of disodium ethylenediaminetetraacetate, 30 mL of a 28% (w / w) ammonia solution, and 100 mL of water were added to every 5 g of sample A, and heating continued until the soluble components dissolved. Sample A was pretreated as described above. The dispersion obtained through pretreatment was filtered using a membrane filter (0.1 μm pore size) to recover the solid components. The recovered sample was screened using a 500 μm sieve to remove large components (such as reinforcing materials), and the components that passed through the sieve were recovered as carbonaceous materials.

[0151] (4-2) Determination of BET specific surface area Sc

[0152] For the carbonaceous material recovered in (4-1), the BET specific surface area Sc is determined using the BET formula via gas adsorption. More specifically, the carbonaceous material is pretreated by heating it in a nitrogen stream at 150°C ± 5°C for 1 hour. Using the pretreated carbonaceous material, the BET specific surface area is determined using the following apparatus and under the following conditions, and is taken as the BET specific surface area Sc of the carbonaceous material.

[0153] Measurement apparatus: TriStar 3000 manufactured by Micromeritics

[0154] Adsorbed gas: Nitrogen gas with a purity of 99.99% or higher.

[0155] Adsorption temperature: Boiling point of liquid nitrogen (77K)

[0156] The calculation method for BET specific surface area is based on section 7.2 of JIS Z 8830:2013.

[0157] (other)

[0158] Lead-acid batteries can be manufactured by a manufacturing method that includes at least the step of obtaining the negative electrode plate.

[0159] The negative electrode plate can be obtained by a manufacturing method including the following steps: preparing a negative electrode paste containing lead powder, carbonaceous material, water and sulfuric acid; forming an unchemically converted negative electrode plate using the negative electrode paste; and chemically converting the unchemically converted negative electrode plate.

[0160] The negative electrode paste may contain organic shrink-proof agents and various additives as needed. The negative electrode paste is prepared by mixing raw materials. The organic shrink-proof agent is preferably added to the negative electrode paste in such a way that the amount Ce (mass %) of the organic shrink-proof agent in the negative electrode material satisfies the relationship described in formula (1) (preferably formula (2)). Alternatively, the organic shrink-proof agent can also be added to the negative electrode paste in such a way that the amount Ce of the organic shrink-proof agent satisfies the relationship described in formula (3).

[0161] Unconverted negative electrode plates are obtained by coating or filling a negative electrode paste onto a negative electrode current collector. The process of forming unconverted negative electrode plates may also include further curing and drying of the coating or filler obtained by coating or filling the negative electrode current collector with the negative electrode paste. Curing of the coating or filler is preferably carried out at a high temperature and high humidity above room temperature.

[0162] Chemical conversion can be achieved by charging the electrode assembly while immersing it in an electrolyte containing sulfuric acid within the battery case of a lead-acid battery. Alternatively, chemical conversion can be performed before assembling the lead-acid battery or the electrode assembly. Spongy lead is generated through chemical conversion.

[0163] (Positive electrode plate)

[0164] A positive electrode plate typically comprises a positive current collector and a positive electrode material. The positive electrode material is held in place by the positive current collector. Positive electrode plates in lead-acid batteries can be classified as paste-type, clad-type, etc. Paste-type positive electrode plates are preferred.

[0165] The positive current collector can be formed by casting lead (Pb) or lead alloys, or by processing lead sheets or lead alloy sheets. Processing methods include, for example, drawing or punching. Using a grid-shaped current collector as the positive current collector is preferable because it facilitates the mounting of the positive electrode material.

[0166] For lead alloys used in positive current collectors, Pb-Sb alloys and Pb-Ca-Sn alloys are preferred in terms of corrosion resistance and mechanical strength. The positive current collector may also include a surface layer. The composition of the surface layer and the inner layer of the positive current collector may differ. The surface layer may be formed on a portion of the positive current collector. The surface layer may also be formed only on the grid portion, only on the ear portion, or only on the frame portion of the positive current collector.

[0167] The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that exhibits capacity through a redox reaction. Other additives may be included in the positive electrode material as needed.

[0168] As described above, the ratio of the first pores in the positive electrode material is preferably 9% by volume or more, and may also be 15% by volume or more. When the ratio of the first pores is within this range, the decrease in low-temperature HR discharge performance after long-term storage of VRLA can be suppressed, and excellent room-temperature HR discharge performance and room-temperature HR cycling characteristics can be ensured. From the viewpoint of ensuring high capacity and suppressing the degradation of the positive electrode plate, the ratio of the first pores is, for example, 25% by volume or less, and may also be 20% by volume or less, or 14% by volume or less.

[0169] The ratio of the first fine pore in the positive electrode material can be 9% or more (or 15% or more) and less than 25%, 9% or more (or 15% or more) and less than 20%, or 9% or more and less than 14%.

[0170] Unconverted paste-type positive electrode plates are obtained by filling a positive electrode paste into a positive electrode current collector, followed by aging and drying. The positive electrode paste is prepared by mixing lead powder, additives, water, and sulfuric acid. For example, the ratio of the first pore size can be adjusted by regulating the amount of water and sulfuric acid used in preparing the positive electrode paste.

[0171] Positive plates are obtained by chemically converting unconverted positive plates. This chemical conversion can be performed by charging the plate group, which contains unconverted positive plates, while immersing it in an electrolyte solution containing sulfuric acid within the battery case of a lead-acid battery. Alternatively, the chemical conversion can be performed before assembling the lead-acid battery or the plate group.

[0172] The NAM / PAM ratio is, for example, 1.25 or less, or 1.21 or less. As described above, the NAM / PAM ratio is preferably less than 1.21. From the viewpoint of ensuring higher room temperature HR discharge performance, the NAM / PAM ratio is preferably 1.05 or less, and more preferably 1.04 or less. The lower limit of the NAM / PAM ratio is, for example, 0.4 or more. The NAM / PAM ratio can be adjusted, for example, by adjusting the lead content in the electrode, the electrode material density, the electrode thickness, the number of electrodes, etc.

[0173] (Analysis of positive electrode materials)

[0174] The analysis of the positive electrode material was performed using positive electrode material collected from the positive plate taken from a lead-acid battery in a fully charged state.

[0175] The positive electrode material is recovered from the positive electrode plate using the following procedure. First, a fully charged lead-acid battery is disassembled, and the obtained positive electrode plate is washed with water to remove sulfuric acid. Washing continues until pH test paper is pressed against the washed positive electrode plate surface and the color of the test paper no longer changes. The washing time is set to be no more than 2 hours. The washed positive electrode plate is then dried at 60°C ± 5°C for approximately 6 hours. After drying, if the positive electrode plate contains attached components, the attached components are removed from the positive electrode plate by peeling. An analytical positive electrode plate can be obtained in this manner.

[0176] (1) Mass of positive electrode material

[0177] Using the aforementioned positive electrode plate for analysis, and in accordance with the quantitative description of the negative electrode material, the mass of the positive electrode material is determined. The PAM / NAM ratio is then calculated based on the obtained masses of the positive and negative electrode materials.

[0178] (2) Ratio of the first fine pore

[0179] When observing the positive electrode plate for analysis from the front, the positive electrode material is collected from the top, bottom, left and right sides near the center, thereby obtaining the positive electrode material for analysis (hereinafter referred to as sample D).

[0180] Using sample D, the total micropore volume and micropore distribution were measured using a mercury porosimeter (manufactured by Shimadzu Corporation, AutoPore IV9505). From this micropore distribution, the ratio (volume %) of the volume of the first micropore in the total micropore volume was determined. This ratio represents the proportion (volume %) of the first micropore in the positive electrode material. Furthermore, the determination of the total micropore volume and micropore distribution was performed under the following conditions.

[0181] Contact angle: 130°

[0182] Surface tension: 484 dyn / cm

[0183] Pore ​​diameter: ≥0.0055μm and ≤170μm

[0184] (Isolation component)

[0185] VRLA typically includes a separator between the positive and negative electrodes. The separator comprises a non-woven fabric. This non-woven fabric is a pad made by winding glass fibers without weaving. The thickness of the separator between the negative and positive electrodes is selected based on the distance between the electrodes. The number of separator sheets is selected based on the number of electrodes.

[0186] Nonwoven fabrics are primarily composed of fibers. These fibers can include glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers (polyethylene terephthalate fibers, etc.)), and pulp fibers. Glass fibers are preferred. Nonwoven fabrics may also contain components other than fibers, such as acid-resistant inorganic powders and polymers as binders.

[0187] The average fiber diameter of the glass fiber is preferably 0.1 μm or more and 25 μm or less.

[0188] The average fiber diameter can be determined by arbitrarily selecting more than 10 fibers and taking a magnified photograph of the selected fibers. Furthermore, glass fibers can be used not only with a single fiber diameter, but also by a mixture of multiple fiber diameters (e.g., 1μm glass fibers and 10μm glass fibers).

[0189] The nonwoven fabric may contain glass fibers or other fibrous materials insoluble in the electrolyte. As fibrous materials other than glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyethylene terephthalate fibers, and other polyester fibers), pulp fibers, etc., may be used. Preferably, the nonwoven fabric is formed of fibrous materials accounting for at least 60% by mass. The proportion of glass fibers in the fibrous materials constituting the nonwoven fabric is preferably at least 60% by mass. Additionally, the nonwoven fabric may also contain inorganic powders (e.g., silica powder, glass powder, diatomaceous earth), etc.

[0190] The spacer may be made of nonwoven fabric alone. Depending on the requirements, the spacer may also be a laminate of nonwoven fabric and microporous membrane, a material bonded with nonwoven fabric and a material of the same or different kind, or a material that creates interlocking textures between nonwoven fabric and a material of the same or different kind.

[0191] Microporous membranes are porous sheets primarily composed of materials other than fibers. For example, microporous membranes can be obtained by extruding a composition containing a pore-forming agent (at least one of polymer powder and oil) into a sheet, and then removing the pore-forming agent to form fine pores. Microporous membranes preferably contain acid-resistant materials. Furthermore, microporous membranes primarily composed of polymer components are preferred. As the polymer component, polyolefins (polyethylene, polypropylene, etc.) are preferred.

[0192] (electrolyte)

[0193] The electrolyte is an aqueous solution containing sulfuric acid. The electrolyte can also be gelled for use in lead-acid batteries as needed. The electrolyte may, as needed, contain at least one selected from the group consisting of cations (e.g., metal cations) and anions (e.g., anions other than sulfate anions (such as phosphate ions)). Examples of metal cations include at least one selected from the group consisting of sodium ions, lithium ions, magnesium ions, and aluminum ions.

[0194] The specific gravity of the electrolyte in a fully charged lead-acid battery at 20°C is, for example, 1.20 or higher, or 1.25 or higher. The specific gravity of the electrolyte at 20°C is, for example, 1.35 or lower, preferably 1.32 or lower.

[0195] The specific gravity of the electrolyte in a fully charged lead-acid battery at 20°C can be above 1.20 and below 1.35, above 1.20 and below 1.32, above 1.25 and below 1.35, or above 1.25 and below 1.32.

[0196] Lead-acid batteries can be obtained by a manufacturing method comprising assembling a lead-acid battery by housing a positive electrode plate, a negative electrode plate, and an electrolyte in a battery case. In the assembly step, a separator is typically positioned between the positive and negative electrode plates. If at least one of the positive and negative electrode plates housed in the battery case is not chemically converted, the assembly step includes, after housing the positive, negative, and electrolyte in the battery case, a step of chemically converting at least one of the positive and negative electrode plates. The positive, negative, electrolyte, and separator are prepared before being housed in the battery case.

[0197] (Evaluation of lead-acid batteries)

[0198] (Accumulation of lead sulfate)

[0199] For lead-acid batteries that have been fully charged, a PSOC cycle test is conducted in an air bath at 10℃±2℃. More specifically, (a) to (i) below are considered as one charge-discharge cycle, and this cycle is repeated 10,000 times.

[0200] (a) IS discharge (1): Discharge for 20 seconds with a current value (A) that is twice the value recorded as the rated 10-hour rate capacity (Ah).

[0201] (b) Discharge equivalent to restart: Discharge for 1 second with a current value (A) that is 6 times the value recorded as the rated 10-hour rate capacity (Ah).

[0202] (c) Discharge equivalent to motor acceleration: Discharge for 0.5 seconds at a current value (A) that is 15 times the value recorded as the rated 10-hour rate capacity (Ah).

[0203] (d) Constant voltage charging (1): Set the current value (A) recorded as the rated 10-hour rate capacity (Ah) to the maximum current, and charge for 50 seconds at a constant voltage of 2.42V ± 0.03V / cell (approximately 14.52V / 6 cells).

[0204] (e)IS discharge (2): Discharge for 20 seconds with a current value (A) that is twice the value recorded as the rated 10-hour rate capacity (Ah).

[0205] (f) Discharge equivalent to restart: Discharge for 1 second with a current value (A) that is 6 times the value recorded as the rated 10-hour rate capacity (Ah).

[0206] (g) Discharge equivalent to motor acceleration: Discharge for 0.3 seconds at a current value (A) that is 20 times the value recorded as the rated 10-hour rate capacity (Ah).

[0207] (h)IS discharge (3): Discharge for 3 seconds with a current value (A) that is 8 times the value recorded as the rated 10-hour rate capacity (Ah).

[0208] (i) Constant voltage charging (2): Set the current value (A) recorded as the rated 10-hour rate capacity (Ah) to the maximum current, and charge for 100 seconds at a constant voltage of 2.42V ± 0.03V / cell (approximately 14.52V / 6 cells).

[0209] Furthermore, this cyclic test is conducted under the condition of maintaining a SOC of 90% or more as the threshold value, which can be said to be a test that simulates the IS control of small motor vehicles with a SOC of 90% or more.

[0210] The negative electrode plate was removed from the self-circulating lead-acid battery, washed with water, and dried under pressure below atmospheric pressure. Washing continued until pH test paper was pressed against the washed negative electrode plate surface and the color of the test paper did not change. The washing time was set to be no more than 2 hours. The entire negative electrode material was collected from the negative electrode plate and pulverized. Next, a sulfur analysis device (LECO S-200 model) was used to determine the sulfur content in the pulverized negative electrode material (pulverized sample). Then, the sulfur content in the lead sulfate accumulated in the negative electrode material was calculated according to the following formula.

[0211] The sulfur content in lead sulfate = (the sulfur content obtained using a sulfur analysis device) - (mass of the crushed sample (g) × amount of organic shrink-proof agent added (g / g) × sulfur content in the organic shrink-proof agent (g / g))

[0212] Next, the sulfur content in lead sulfate is converted into the amount of lead sulfate, and the lead sulfate concentration (mass%) per unit mass of the crushed sample is calculated as the accumulation of lead sulfate.

[0213] (Low-temperature HR discharge performance)

[0214] A fully charged lead-acid battery was discharged at a discharge current of 150A at -15℃±2℃ until the terminal voltage reached 1.0V / cell. The discharge time (initial low-temperature HR discharge duration) (s) was calculated. The longer the discharge duration, the better the low-temperature HR discharge performance.

[0215] After determining the initial low-temperature HR discharge duration, the lead-acid batteries were placed at 20℃±2℃. For lead-acid batteries three months and six months after the start of placement, they were charged at a constant voltage of 14.5V / cell for 16 hours at 20℃±2℃, and then discharged at a discharge current of 40A at 0℃±2℃ until the terminal voltage reached 1.0V / cell. The discharge time (low-temperature HR discharge duration) (s) at this time was calculated. The ratio (%) of the low-temperature HR discharge duration (s) after three months and six months of placement was calculated when the initial low-temperature HR discharge duration (s) was set to 100%. The reduction rate d (%) between the ratio after three months and the ratio after six months of placement was calculated by subtracting the ratio after three months from the ratio after six months of placement. The ratio obtained by multiplying the reduction rate d by 6 was then used to estimate the ratio (%) of the low-temperature HR discharge duration of the lead-acid batteries after two years of placement. This ratio was used as the maintenance rate of low-temperature HR discharge performance to evaluate the low-temperature HR discharge performance.

[0216] (Room temperature HR discharge performance)

[0217] A fully charged lead-acid battery was discharged at 25℃±2℃ with a discharge current of 40A until the terminal voltage reached 1.0V / cell. The discharge time (initial room temperature HR discharge duration) (s) and the discharge capacity (initial discharge capacity) were calculated. The longer the discharge duration, the better the room temperature HR discharge performance.

[0218] For a lead-acid battery whose initial room temperature HR discharge duration and discharge capacity have been determined, repeat the following charge and discharge cycles until the discharge capacity reaches 50% of the initial discharge capacity. Calculate the number of cycles at this point, and evaluate the room temperature HR cycle characteristics based on this number of cycles.

[0219] (Charging acceptance)

[0220] Under the following conditions, a fully charged lead-acid battery is discharged to 10% depth of discharge (DOD), allowed to rest for 1 hour, and then recharged under the following conditions. Charge acceptability is compared to the current value at the 100th second after charging begins. Furthermore, a state where the battery is discharged for 1 hour at a current value (A) that is 0.1 times the value recorded as the rated 10-hour rate capacity (Ah) is defined as DOD 10%.

[0221] Discharge: Discharge for 1 hour at a current value (A) that is 0.1 times the value recorded as the rated 10-hour rate capacity (Ah).

[0222] Charging (Charging Acceptability): Constant voltage (2.35V±0.02V / cell, maximum current 10A)

[0223] Temperature: 25℃±2℃

[0224] (Reduction of electrolyte)

[0225] The fully charged lead-acid batteries were charged at 50℃±2℃ for 100 days at a constant voltage (2.36V±0.03V / cell, maximum current 10A). During this period, the amount of electrolyte was monitored, and the percentage of the reduced electrolyte mass to the initial electrolyte mass was determined as the amount of electrolyte reduction.

[0226] The VRLA can also be combined with a vehicle that receives power from the VRLA and a state of charge (SOC) control unit that controls the VRLA to form an energy storage system. This invention also includes such an energy storage system.

[0227] As described, the VRLA is preferably used in vehicles where IS control is performed when the SOC reaches a threshold of 90% or higher, and not when the threshold is not reached. In this case, when the VRLA's SOC is below the threshold, the charging state control unit charges the VRLA with a constant voltage until the specified SOC is reached. This allows for easy improvement of the VRLA's SOC even in vehicles without a BMS.

[0228] The charging status control unit can start VRLA charging when the SOC is below a specified threshold value, or when the SOC is above a specified threshold value.

[0229] The VRLA is charged at a constant voltage during engine operation. During this time, the alternator operates and generates electricity to charge the VRLA at a constant voltage. To prevent overcharging of the VRLA during constant voltage charging, a charging voltage is set. For example, if the VRLA's State of Charge (SOC) exceeds a threshold value and reaches that threshold, the vehicle's engine does not stop, but continues charging from the alternator at the constant voltage. Therefore, the VRLA's SOC is controlled to remain above the threshold value.

[0230] In the aforementioned VRLA, charging at a constant voltage can also be performed at 2.30V / cell or higher (preferably 2.33V / cell or higher) and 2.45V / cell or lower. For example, in the case of a lead-acid battery comprising six cells connected in series, it is ideal to charge at a constant voltage of 13.80V or higher (preferably 14.0V or higher) and 14.7V or lower.

[0231] The constant voltage charging voltage is determined as follows: For vehicles that receive power from the VRLA, the battery voltage during constant voltage charging of the VRLA is measured using a voltmeter (manufactured by HIOKI, MEMORY HiLOGGER, LR8400) and converted into the voltage per single cell.

[0232] Figure 1 is a schematic cross-sectional view showing the structure of a control valve type lead-acid battery according to an embodiment of the present invention.

[0233] In Figure 1, the lead-acid battery 1B includes a battery case 10 that houses an array of electrode plates 11 and an electrolyte (not shown). The upper opening of the battery case 10 is sealed by a cover 12B. The array of electrode plates 11 is formed by stacking multiple negative electrode plates 2 and positive electrode plates 3 separated by a separator 4.

[0234] Each of the plurality of negative plates 2 has an upwardly protruding current-collecting lug (not shown) on its upper part. Each of the plurality of positive plates 3 also has an upwardly protruding current-collecting lug (not shown) on its upper part. Furthermore, the lugs of the negative plates 2 are connected to each other as a single unit by a negative electrode strip (not shown). Similarly, the lugs of the positive plates 3 are also connected to each other as a single unit by a positive electrode strip (not shown). The negative electrode strip is connected to a negative terminal (not shown) serving as an external terminal, and the positive electrode strip is connected to a positive terminal (not shown) serving as an external terminal.

[0235] The battery compartment 10 is divided into multiple (three in the example) independent cell chambers 10r, each cell chamber 10r housing a group of electrode plates 11. The cover 12B has batch exhaust chambers 14r communicating with each cell chamber via exhaust holes 15. Each batch exhaust chamber 14r includes fewer exhaust valves 13 than the number of cell chambers (one in the example). If the internal pressure of the batch exhaust chamber 14r exceeds a predetermined upper limit, the exhaust valve 13 opens, releasing gas from the batch exhaust chamber 14r to the outside. When the internal pressure of the batch exhaust chamber 14r is below the upper limit, oxygen generated in the positive electrode plate 3 is reduced to water at the negative electrode plate 2 of any cell chamber 10r. Figure 1 shows a case where a cover including one exhaust valve 13 is used in the batch exhaust chamber 14r, but this is not a limitation; a cover including an independent exhaust valve for each cell chamber can also be used.

[0236] Figure 2 is a schematic block diagram illustrating an energy storage system with the aforementioned configuration. The energy storage system 20 includes: a control valve-type lead-acid battery A, a vehicle 30 receiving power from the lead-acid battery A, and a state-of-charge (SOC) control unit 40 for controlling the SOC of the lead-acid battery A. The state-of-charge control unit 40 includes a charging control unit 41 for controlling the charging of the lead-acid battery A. The vehicle 30 is an idle-stop vehicle (IS vehicle) including an idle-stop (IS) control unit 50 based on an idle-stop (IS) system (ISS). When the SOC of the lead-acid battery A is controlled (IS controlled) to maintain a threshold value of 90% or higher, the state-of-charge control unit 40 charges the lead-acid battery A at a constant voltage of 2.30V / cell or higher and 2.45V / cell or lower when the SOC of the lead-acid battery A reaches the threshold value during the IS period.

[0237] The following describes a lead-acid battery, a manufacturing method, and an energy storage system of one aspect and another aspect of the present invention.

[0238] (1) A control valve type lead-acid battery, wherein the control valve type lead-acid battery comprises at least one unit including a positive electrode plate, a negative electrode plate and an electrolyte, the positive electrode plate comprising a positive electrode material, the negative electrode plate comprising a negative electrode material and a negative current collector, the negative electrode material comprising a carbonaceous material, the specific surface area of ​​the carbonaceous material based on the BET method: Sc satisfies Sc≧650m2 / g, and the content of the carbonaceous material in the negative electrode material: Cc satisfies Cc≧0.5% by mass%, for use in small motor vehicles.

[0239] (2) A control valve type lead-acid battery, wherein the control valve type lead-acid battery comprises at least one unit including a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the positive electrode plate includes a positive electrode material, the negative electrode plate includes a negative electrode material and a negative current collector, the negative electrode material comprises a carbonaceous material, the specific surface area of ​​the carbonaceous material based on the BET method: Sc satisfies Sc≧650m2 / g, the content of the carbonaceous material in the negative electrode material: Cc satisfies Cc≧0.5% by mass%, and is used in a vehicle, wherein the vehicle is configured to: perform idle stop control when the state of charge of the control valve type lead-acid battery is above a threshold value of 90% or more, and not perform idle stop control when the state of charge of the control valve type lead-acid battery is below the threshold value.

[0240] (3) In (1) or (2), an organic shrink-proof agent may also be added to the negative electrode material.

[0241] (4) In (3), the specific surface area Sc can satisfy 650m2 / g≦Sc≦1000m2 / g, and the amount of organic anti-shrinkage agent added in the negative electrode material: Ce (mass%) can satisfy Ce>0.368Cc+0.054.

[0242] (5) In (4), the amount of Ce added can satisfy 0.372Cc+0.092≦Ce≦0.373Cc+0.249.

[0243] (6) A method for manufacturing a control valve type lead-acid battery, wherein the method comprises: a step of preparing a negative electrode paste comprising lead powder, the carbonaceous material, water, and sulfuric acid; a step of forming an unchemically converted negative electrode plate by coating or filling the negative electrode paste onto the negative electrode current collector; and a step of obtaining the negative electrode plate comprising the negative electrode material and the negative electrode current collector by chemically converting the unchemically converted negative electrode plate.

[0244] (7) In (6), the negative electrode paste may further contain an organic anti-shrinkage agent, the specific surface area Sc may satisfy 650m2 / g≦Sc≦1000m2 / g, and the amount of organic anti-shrinkage agent added in the negative electrode material: Ce (mass%) may satisfy Ce>0.368Cc+0.054.

[0245] (8) In (7), the amount of Ce added can satisfy 0.372Cc+0.092≦Ce≦0.373Cc+0.249.

[0246] (9) An energy storage system, the energy storage system comprising: a control valve type lead-acid battery; a vehicle receiving power from the control valve type lead-acid battery; and a charging state control unit controlling the charging state (SOC) of the control valve type lead-acid battery, the control valve type lead-acid battery having at least one unit including a positive electrode plate, a negative electrode plate, and an electrolyte, the positive electrode plate including a positive electrode material, the negative electrode plate including a negative electrode material and a negative current collector, the negative electrode material comprising a carbonaceous material, the specific surface area (Sc) of the carbonaceous material based on the BET method satisfying Sc ≥ 650 m2 / g, the content (Cc) of the carbonaceous material in the negative electrode material satisfying Cc ≥ 0.5% by mass, the vehicle performing idle stop control when the SOC of the control valve type lead-acid battery is above a threshold value of 90%, and not performing idle stop control when the SOC of the control valve type lead-acid battery is below the threshold value.

[0247] (10) In (9), the charging state control unit can charge the control valve lead-acid battery with a constant voltage when the SOC of the control valve lead-acid battery is not at the threshold value.

[0248] (11) In (10), the charging under constant voltage can be performed at 2.30V / cell or higher (preferably 2.33V / cell or higher) and 2.45V / cell or lower.

[0249] (12) In any one of (1) to (11), the specific surface area Sc can be 750 m2 / g or more, or 800 m2 / g or more.

[0250] (13) In any one of (1)~(3), (6), and (9)~(12), the specific surface area Sc may be less than 1000m2 / g.

[0251] (14) In any one of (1) to (13), the content Cc of the carbonaceous material can be 0.75% by mass or more.

[0252] (15) In any one of (1) to (14), the content of the carbonaceous material Cc may be less than 3% by mass or less than 2% by mass.

[0253] (16) In any one of (1) to (15), the ratio of the mass of the negative electrode material to the mass of the positive electrode material: the NAM / PAM ratio may be less than 1.25 or less than 1.21.

[0254] (17) In any one of (1) to (16), the mass ratio of the negative electrode material to the mass of the positive electrode material: the NAM / PAM ratio may be 0.4 or higher.

[0255] (18) In any one of (1) to (17), the ratio of the mass of the negative electrode material to the mass of the positive electrode material is: NAM / PAM ratio can satisfy NAM / PAM ratio < 1.21.

[0256] (19) In (18), the positive electrode material may include a first fine pore having a pore diameter of 1 μm or more and 10 μm or less, and the proportion of the first fine pore in the positive electrode material may be 9% or more by volume.

[0257] (20) In (19), the ratio of the first fine pores may be less than 25% by volume, less than 20% by volume, or less than 14% by volume.

[0258] (21) In the above (19), the ratio of the first fine pores can be 15% or more by volume.

[0259] (22) In (21), the ratio of the first fine pores may be less than 25% by volume or less than 20% by volume.

[0260] (23) In any one of (1) to (22), the negative electrode material may contain barium sulfate.

[0261] (24) In (23), the content of barium sulfate in the negative electrode material can be more than 0.05% by mass or more than 0.10% by mass.

[0262] (25) In (23) or (24), the content of barium sulfate in the negative electrode material may be less than 3% by mass or less than 2% by mass.

[0263] (26) In any one of (1) to (25), the specific gravity of the electrolyte in the lead-acid battery in a fully charged state at 20°C may be 1.20 or more, or 1.25 or more.

[0264] (27) In any one of (1) to (26), the specific gravity of the electrolyte in the lead-acid battery in a fully charged state at 20°C may be less than 1.35 or less than 1.32.

[0265] [Example]

[0266] The present invention will now be described in detail based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0267] Controlled valve lead-acid battery A1 and controlled valve lead-acid batteries R1 to R3

[0268] The following procedure is used to manufacture a control valve type lead-acid battery.

[0269] (a) Fabrication of the negative electrode plate

[0270] Lead powder, barium sulfate, carbonaceous material, organic shrinkage inhibitor (sodium lignosulfonate), and an appropriate amount of sulfuric acid aqueous solution are mixed to obtain a negative electrode paste. The carbonaceous material is then mixed such that the content of the carbonaceous material, determined by the aforementioned procedure, is the value shown in Table 1. Carbon black with a BET specific surface area Sc, determined by the aforementioned procedure, is used as the carbonaceous material. The amount of organic shrinkage inhibitor added, Ce, is adjusted such that the content of the carbonaceous material, Cc, and the amount of organic shrinkage inhibitor added, Ce, satisfy equations (1) and (2).

[0271] The negative electrode paste is filled into the mesh of the extended grid made of Pb-Ca-Sn alloy, and then cured and dried to obtain a negative electrode plate that has not undergone chemical conversion.

[0272] (b) Fabrication of the positive electrode plate

[0273] Lead powder, used as raw material, is mixed with sulfuric acid aqueous solution to obtain a positive electrode paste. The positive electrode paste is filled into the mesh of an extended grid made of Pb-Ca-Sn alloy, and then cured and dried to obtain a positive electrode plate that has not undergone chemical conversion.

[0274] (c) Assembly of lead-acid batteries

[0275] Four unconverted negative electrode plates and three unconverted positive electrode plates are used, with a separator placed between the negative and positive electrode plates. The negative and positive electrode plates are stacked alternately to form an electrode plate group. As the separator, a glass fiber nonwoven sheet is used.

[0276] The electrode assembly and electrolyte are housed together in a polypropylene battery case to assemble a lead-acid battery. The assembled battery undergoes chemical conversion to complete a VRLA (VRLA for small motor vehicles). The VRLA has a rated voltage of 12V and a rated 10-hour rate capacity of 5Ah. The specific gravity of the electrolyte after chemical conversion is 1.32. The negative electrode material after chemical conversion contains 0.5% by mass of barium sulfate. Furthermore, the ratio of the first micropores in the positive electrode material, determined by the aforementioned procedure, is 0.9% by volume. Additionally, the NAM / PAM ratio, determined by the aforementioned procedure, is 1.21.

[0277] Liquid lead-acid batteries R4 to R7

[0278] Similar to lead-acid battery A1, unchemically converted negative and positive plates are fabricated. The unchemically converted negative plates are housed in a bag-shaped separator made of a microporous membrane of polyethylene. Otherwise, similar to lead-acid battery A1, plate groups are formed, and the lead-acid battery is assembled. Chemical conversion is then performed on the assembled battery to complete a liquid-filled lead-acid battery (lead-acid battery for four-wheeled vehicles). The rated voltage of the lead-acid battery is 12V, and the rated 10-hour rate capacity is 5Ah.

[0279] [Accumulation of lead sulfate]

[0280] For the controlled valve lead-acid battery (VRLA) A1 and controlled valve lead-acid batteries (VRLA) R1 to R3, the accumulation of lead sulfate in the negative plate is measured by performing charge and discharge cycles including PSOC cycles using the aforementioned procedure.

[0281] For liquid lead-acid batteries R4 to R7, after full charging, a PSOC cycle test was conducted at 10℃±2℃. More specifically, (a) to (f) below were treated as one cycle, and repeated for 10 cycles. The lead-acid batteries were disassembled, and the amount of lead sulfate accumulated in the negative plate was determined. The amount accumulated was determined in the same manner as in the case of VRLA. Furthermore, the charge and discharge at 1S corresponds to (b) and (c).

[0282] (a) Depth of discharge (DOD) adjustment (DOD 50%): Discharge for 2.5 hours at a current value (A) that is 4 times the rated 20-hour rate capacity (Ah).

[0283] (b) Constant voltage charging: Using the current value (A) of the rated capacity (preferably the rated 20-hour rate capacity) (Ah) as the maximum current, charge at a constant voltage of 2.35V ± 0.02V / cell for 40 minutes.

[0284] (c) Discharge (DOD 17.5%): Discharge for 30 minutes at a current value (A) that is 7 times the rated 20-hour rate capacity (Ah).

[0285] (d) Full charge: Use a current value (A) that is twice the rated 20-hour rate capacity (Ah) as the maximum current, and charge for 18 hours at a constant voltage of 2.67V ± 0.03V / cell.

[0286] (e) 20-hour rate discharge: Discharge at a current value (A) of the rated capacity (preferably the rated 20-hour rate capacity) (Ah) until the termination voltage reaches 1.75V / cell.

[0287] (f) Full charge: Use a current value (A) that is twice the value of the rated capacity (preferably the rated 20-hour rate capacity) (Ah) as the maximum current, and charge for 24 hours at a constant voltage of 2.67V ± 0.03V / cell.

[0288] The results for lead-acid battery A1 and lead-acid batteries R1 to R7 are shown in Table 1. A1 is the example, and R1 to R7 are comparative examples.

[0289]

[0290] As shown in Table 1, in liquid lead-acid batteries for four-wheeled vehicles, in both cases where the carbonaceous material content (Cc) is less than 0.5% by mass and more than 0.5% by mass, almost no difference was found in the accumulation of lead sulfate based on the BET specific surface area (Sc) of the carbonaceous material (comparison of R4 and R5, comparison of R6 and R7). In liquid lead-acid batteries for four-wheeled vehicles, if the carbonaceous material content (Cc) increases, the accumulation of lead sulfate decreases, regardless of the BET specific surface area (Sc) of the carbonaceous material (comparison of R4 and R5 with R6 and R7). Furthermore, these results are for liquid lead-acid batteries, but the same trend is observed in the case of VRLA batteries for four-wheeled vehicles.

[0291] In contrast, in VRLA for small motor vehicles, when the carbonaceous material content (Cc) is less than 0.5% by mass, almost no difference was found in the accumulation of lead sulfate due to the BET surface area (Sc) of the carbonaceous material (comparison of R2 and R3). Furthermore, when the BET surface area (Sc) is less than 650 m² / g, even increasing the carbonaceous material content (Cc) did not significantly change the accumulation of lead sulfate (comparison of R3 and R1). However, if carbonaceous material with a BET surface area (Sc) of 650 m² / g or more is used with a Cc content of 0.5% by mass or more, the accumulation of lead sulfate can be significantly reduced (comparison of A1 and R1, comparison of A1 and R2).

[0292] As described above, the BET specific surface area Sc, which inhibits lead sulfate accumulation, exhibits significantly different behavior in lead-acid batteries for four-wheeled vehicles with IS control at a lower SOC and in VRLAs for small motor vehicles with IS control at a higher SOC.

[0293] Controlled valve lead-acid batteries A2 to A7 and controlled valve lead-acid batteries R8 to R9

[0294] The carbonaceous material was mixed such that the content Cc of the carbonaceous material determined by the aforementioned procedure was the value shown in Table 2. As the carbonaceous material, carbon black with a BET specific surface area Sc of 800 m² / g, determined by the aforementioned procedure, was used. The amount Ce of the organic shrink-proof agent was adjusted such that the carbonaceous material content Cc and the amount Ce of the organic shrink-proof agent satisfied equations (1) and (2). In addition, a control valve type lead-acid battery was manufactured in the same manner as lead-acid battery A1, and the accumulation of lead sulfate was evaluated. The results are shown in Table 2 and Figure 4. A2 to A7 are examples, and R8 and R9 are comparative examples.

[0295]

[0296] As shown in Table 2 and Figure 4, a high level of lead sulfate accumulation inhibition can be obtained when the carbonaceous material content Cc in the negative electrode material is 0.5% by mass or higher. Based on these results and the results in Table 1, it is believed that when the carbonaceous material content Cc is 0.5% by mass or higher, the difference in the behavior of the BET specific surface area Sc that leads to the lead sulfate accumulation inhibition effect in lead-acid batteries for four-wheeled vehicles and VRLA batteries for small motor vehicles is as described.

[0297] Controlled valve lead-acid batteries A8 to A11 and controlled valve lead-acid batteries R10 to R12

[0298] The carbonaceous material was mixed such that the content Cc of the carbonaceous material obtained by the procedure described above was the value shown in Table 3. As the carbonaceous material, carbon black, or carbon black and graphite, was used such that the BET specific surface area Sc obtained by the procedure described above was the value shown in Table 3. The amount Ce of the organic anti-shrinkage agent added was adjusted such that the content Cc of the carbonaceous material and the amount Ce of the organic anti-shrinkage agent added satisfied Equations (1) and (2). Apart from these, a lead-acid battery was manufactured in the same manner as lead-acid battery A1, and the accumulation of lead sulfate was evaluated. The results are shown in Table 3 and Figure 5. A8 to A11 are examples, and R10 to R12 are comparative examples.

[0299]

[0300] R10-R12:VRLA

[0301] A8-A11:VRLA

[0302] As shown in Table 3 and Figure 5, when the BET specific surface area Sc of the carbonaceous material is between 650 m² / g and 1000 m² / g, the accumulation of lead sulfate in the negative electrode plate is low and almost constant. Therefore, when the negative electrode material contains carbonaceous materials with a BET specific surface area Sc in this range, it is easy to achieve a balance between battery characteristics such as high-response discharge performance, charge acceptability, and electrolyte reduction suppression.

[0303] Controlled valve lead-acid batteries A21~A56 and R21

[0304] The carbonaceous material and the organic shrink-proof agent were mixed such that the content Cc of the carbonaceous material and the amount Ce of the organic shrink-proof agent, as determined by the aforementioned procedure, were the values ​​shown in Table 4. As the carbonaceous material, carbon black with a BET specific surface area Sc, as determined by the aforementioned procedure, was used, and the values ​​shown in Table 4 were also used. Apart from these, the lead-acid battery was manufactured in the same manner as lead-acid battery A1. For the lead-acid battery, the low-temperature HR discharge performance (low-temperature HR discharge duration (seconds)), charge acceptance (current at 100 seconds (A)), and electrolyte reduction were evaluated using the aforementioned procedure. Regarding electrolyte reduction, the evaluation was conducted according to the criteria A to C described below.

[0305] A: The reduction in electrolyte amount is less than 10% of the mass.

[0306] B: The reduction in electrolyte is more than 10% by mass but less than 15% by mass.

[0307] C: The reduction in electrolyte content is more than 15% by mass.

[0308] The results are shown in Table 4 and Figure 3. Figure 3 shows the relationship between the amount of organic anti-shrinkage agent (Ce) and the content of carbonaceous material (Cc) for the negative electrode materials of each lead-acid battery shown in Table 4. A21–A56 are examples, and R21 is a comparative example.

[0309]

[0310] According to Table 4 and Figure 3, from the viewpoint of ensuring high low-temperature HR discharge performance (specifically, a low-temperature HR discharge duration of 180 seconds or more), Ce > 0.368Cc + 0.054 is preferred. From the viewpoint of ensuring even higher low-temperature HR discharge performance while suppressing electrolyte reduction, Ce ≤ 0.372Cc + 0.092 ≤ Ce is preferred. From the viewpoint of ensuring higher charge acceptability, Ce ≤ 0.373Cc + 0.249 is preferred.

[0311] Controlled valve lead-acid batteries A61 to A66 and controlled valve lead-acid batteries R31 to R36

[0312] The carbonaceous material and organic shrink-proof agent were mixed such that the carbonaceous material content Cc, determined by the aforementioned procedure, was the value shown in Table 5. As the carbonaceous material, carbon black with a BET specific surface area Sc, determined by the aforementioned procedure, was used, and the value in Table 5 was also obtained. The amount of organic shrink-proof agent added, Ce, was adjusted within the range of 0.372Cc + 0.092 ≤ Ce ≤ 0.373Cc + 0.249. The ratio of the first pore size was adjusted to the value shown in Table 1 by adjusting the concentration and amount of the sulfuric acid aqueous solution used in preparing the negative electrode paste. The NAM / PAM ratio, determined by the aforementioned procedure, was adjusted as shown in Table 5. Apart from these, a lead-acid battery was manufactured in the same manner as lead-acid battery A1, and the low-temperature HR discharge performance, charge acceptance, electrolyte reduction, low-temperature HR discharge performance retention, initial room-temperature HR discharge performance, and room-temperature HR cycle characteristics were evaluated using the aforementioned procedure. Electrolyte reduction was evaluated according to the aforementioned criteria. The results are shown in Table 5. Furthermore, the room temperature HR discharge performance and room temperature HR cycle characteristics are expressed as values ​​with the R31 result of the lead-acid battery set to 100%. A61~A66 are examples, and R31~R36 are comparative examples.

[0313]

[0314] As shown in Table 5, when the negative electrode material contains carbonaceous material with a BET specific surface area of ​​650 m² / g or more at a content of 0.5% by mass (Cc), and the NAM / PAM ratio is ≤1.21, a high retention rate of low-temperature HR discharge performance can be ensured. That is, high low-temperature HR discharge performance can be maintained even with long-term use. Even if the NAM / PAM ratio is reduced (e.g., NAM / PAM ratio <1.21), high low-temperature HR discharge performance can still be obtained, thus the volume ratio of the positive electrode material can be relatively increased, thereby improving the room-temperature HR discharge performance. By reducing the utilization rate of the positive electrode active material contained in the positive electrode material, the room-temperature HR cycle characteristics can be improved. On the other hand, when the content of carbonaceous material (Cc) is less than 0.5% by mass, if the NAM / PAM ratio decreases, the retention rate of low-temperature HR discharge performance decreases.

[0315] Furthermore, when the negative electrode material contains carbonaceous material with a BET specific surface area of ​​650 m² / g or more in a content of Cc of 0.5% by mass or more, the room temperature HR cycle characteristics are lower when the ratio of the first fine pores in the positive electrode material is 8% by volume, compared to when the content of carbonaceous material Cc is less than 0.5% by mass. However, if the ratio of the first fine pores is 9% by volume or more, a higher room temperature HR cycle characteristic can be ensured when the content of carbonaceous material Cc is 0.5% by mass or more.

[0316] The present invention has been described with respect to preferred embodiments, but this disclosure is not intended to be limiting. Various modifications and variations will undoubtedly become apparent to those skilled in the art upon reading this disclosure. Therefore, the appended patent scope should be interpreted as encompassing all modifications and variations without departing from the true spirit and scope of the invention.

[0317] [Industrial Applicability]

[0318] VRLA is suitable for use in small motor vehicles or IS vehicles, etc. Furthermore, these applications are merely illustrative and not limited to these uses.

[0319] A, 1B: Lead-acid battery

[0320] 2: Negative electrode plate

[0321] 3: Positive plate

[0322] 4: Isolation components

[0323] 10: Battery compartment

[0324] 10r: Unit Room

[0325] 11: Plate Group

[0326] 12B: Cover

[0327] 13: Exhaust valve

[0328] 14r: Batch exhaust chamber

[0329] 15: Exhaust port

[0330] 20: Energy Storage System

[0331] 30: Vehicles

[0332] 40: Charging Status Control Unit

[0333] 41: Charging control unit

[0334] 50: Idle Stop (IS) Control Unit

Claims

1. A control valve type lead-acid battery, wherein the control valve type lead-acid battery comprises at least one unit including a positive electrode plate, a negative electrode plate, and an electrolyte, the positive electrode plate comprising a positive electrode material, the negative electrode plate comprising a negative electrode material and a negative current collector, the negative electrode material comprising a carbonaceous material, the specific surface area Sc of the carbonaceous material based on the Buerter method satisfying Sc ≥ 650 m² / g, the content Cc of the carbonaceous material in the negative electrode material satisfying Cc ≥ 0.5% by mass, the mass ratio NAM / PAM of the negative electrode material relative to the mass of the positive electrode material satisfying NAM / PAM ratio < 1.21, and is used in small motor vehicles.

2. A control valve type lead-acid battery, comprising at least one unit including a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the positive electrode plate includes a positive electrode material, the negative electrode plate includes a negative electrode material and a negative current collector, the negative electrode material comprises a carbonaceous material, the specific surface area Sc of the carbonaceous material based on the Buerter method satisfies Sc ≥ 650 m² / g, the content Cc of the carbonaceous material in the negative electrode material satisfies Cc ≥ 0.5% by mass, the mass ratio NAM / PAM of the negative electrode material relative to the mass of the positive electrode material satisfies NAM / PAM ratio < 1.21, and is used in a vehicle, wherein the vehicle is configured to: perform idle stop control when the state of charge (SOC) of the control valve type lead-acid battery is above a threshold value of 90% or more, and not perform idle stop control when the state of charge of the control valve type lead-acid battery is below the threshold value.

3. The control valve type lead-acid battery as claimed in claim 1 or 2, wherein the specific surface area Sc is less than 1000 m2 / g.

4. The control valve type lead-acid battery as claimed in claim 1 or 2, wherein the content Cc is less than 3% by mass.

5. The control valve type lead-acid battery as claimed in claim 1 or 2, wherein the content Cc is less than 2% by mass.

6. The control valve type lead-acid battery as claimed in claim 1 or 2, wherein an organic shrink-proof agent is further added to the negative electrode material.

7. The control valve type lead-acid battery as claimed in claim 6, wherein the specific surface area Sc satisfies 650m² / g≦Sc≦1000m² / g, and the amount of organic anti-shrinkage agent added in the negative electrode material, Ce (mass%), satisfies Ce>0.368Cc+0.

054.

8. The control valve type lead-acid battery as claimed in claim 7, wherein the added amount Ce satisfies 0.372Cc+0.092≦Ce≦0.373Cc+0.

249.

9. The control valve type lead-acid battery as claimed in claim 1 or 2, wherein the positive electrode material comprises a first pore having a pore size of 1 μm or more and 10 μm or less, and the proportion of the first pore in the positive electrode material is 9% by volume or more.

10. A method for manufacturing a control valve type lead-acid battery, comprising manufacturing a control valve type lead-acid battery as described in claim 1 or 2, the method comprising: The steps for preparing a negative electrode paste comprising lead powder, the carbonaceous material, water, and sulfuric acid; The steps include: forming an unchemically converted negative electrode plate by coating or filling the negative electrode paste onto the negative electrode current collector; and obtaining the negative electrode plate comprising the negative electrode material and the negative electrode current collector by chemically converting the unchemically converted negative electrode plate.

11. A method for manufacturing a control valve type lead-acid battery as claimed in claim 10, wherein the negative electrode paste further comprises an organic anti-shrinkage agent, the specific surface area Sc satisfies 650 m² / g ≤ Sc ≤ 1000 m² / g, and the amount of the organic anti-shrinkage agent added in the negative electrode material, Ce (mass %), satisfies Ce > 0.368Cc + 0.

054.

12. A method for manufacturing a control valve type lead-acid battery as claimed in claim 11, wherein the amount of Ce added satisfies 0.372Cc+0.092≦Ce≦0.373Cc+0.

249.

13. An energy storage system, the energy storage system comprising: Control valve type lead-acid battery; The vehicle receives power from the control valve type lead-acid battery; The system includes a charging state control unit that controls the state of charge (SOC) of the control valve type lead-acid battery. The control valve type lead-acid battery has at least one unit including a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material, and the negative electrode plate includes a negative electrode material and a negative current collector. The negative electrode material contains carbonaceous material, and the specific surface area Sc of the carbonaceous material based on the Bouert method satisfies Sc ≥ 650 m² / g. The content Cc of the carbonaceous material in the negative electrode material satisfies Cc ≥ 0.5% by mass, and the mass ratio NAM / PAM of the negative electrode material relative to the mass of the positive electrode material satisfies NAM / PAM < 1.

21. The vehicle performs idle stop control when the SOC of the control valve type lead-acid battery is above a threshold value of 90%, and does not perform idle stop control when the state of charge of the control valve type lead-acid battery is below the threshold value.

14. The energy storage system as claimed in claim 13, wherein the charging state control unit charges the control valve lead-acid battery at a constant voltage when the SOC of the control valve lead-acid battery is below the threshold value.

15. The energy storage system as claimed in claim 14, wherein the charging at the constant voltage is performed at a voltage of 2.30V / cell or higher and 2.45V / cell or lower.

Images