JP2017054739A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery capable of appropriately operating a current interruption mechanism while maintaining good battery performance. A secondary battery according to the present invention has a wound electrode body (20) including a positive electrode having a positive electrode active material layer (54) and a negative electrode having a negative electrode active material layer (64), a battery case, and the internal pressure of the battery case is predetermined. A current cutoff mechanism that operates when the pressure exceeds a predetermined pressure and a gas generating agent that generates gas at a predetermined temperature or higher are provided. At least one of a portion of the positive electrode located on the outermost periphery of the wound electrode body 20 and a portion of the negative electrode located on the outermost periphery of the wound electrode body 20 includes the positive electrode active material. There is an electrode active material layer non-forming portion 90 where the material layer 54 or the negative electrode active material layer 64 is not formed, and the gas generating agent is contained in the electrode active material layer non-forming portion 90. It is arranged so that the content of the agent is a predetermined amount or more. [Selection diagram] Fig. 4

Description

  The present invention relates to a secondary battery.

  In recent years, lithium secondary batteries, nickel metal hydride batteries and other secondary batteries (storage batteries) have become increasingly important as power sources for mounting on vehicles or as power sources for personal computers and portable terminals. In particular, a secondary battery that is lightweight and has a high energy density is preferably used as a high-output power source for mounting on a vehicle. One typical structure of such a lithium secondary battery is a sealed secondary battery (sealed battery) in which a battery case containing an electrode body and an electrolyte is sealed.

  By the way, when this type of secondary battery (typically a lithium secondary battery) is charged, an overcurrent may be supplied to the battery, resulting in overcharging. In order to stop the progress of such overcharge, a battery having a current cutoff mechanism that cuts off a charging current when a gas pressure inside the battery (internal pressure of the battery case) exceeds a predetermined value has been proposed. In general, when a battery is overcharged, a nonaqueous solvent or the like of the electrolytic solution is electrolyzed to generate gas and heat. The current interruption mechanism can prevent further overcharge by detecting this gas and cutting the charging path of the battery. Further, in Patent Document 1, in a secondary battery having a current interruption mechanism that operates by increasing the internal pressure of the battery, a microcapsule is disposed in the electrode body, and a gas generating agent such as cyclohexylbenzene is included in the microcapsule. Is described. According to such a configuration, when the battery temperature rises during overcharge, gas is generated from the gas generating agent in the microcapsule, and the microcapsule bursts, thereby increasing the internal pressure of the battery case at once. Thereby, the current interruption mechanism can be operated at an appropriate timing.

JP 2013-004305 A

However, generally, even if the battery temperature rises due to an overcharged state, the temperature distribution in the battery may be uneven. For this reason, depending on the location where the gas generating agent is disposed, the temperature increase may be delayed or may not increase to a temperature at which the gas generating agent generates gas. According to the technique of Patent Document 1, since the gas generating agent (microcapsule) is arranged in the electrode body, the gas generating agent (microcapsule) hinders the movement of charge carriers (for example, lithium ions), and the battery Resistance sometimes increased.
When the battery is overcharged and the battery temperature rises while maintaining good battery performance, it is desirable to efficiently generate gas from the gas generating agent and to properly operate the current interruption mechanism. The present invention solves the above problems.

  When the present inventors diligently studied the temperature distribution of the battery in the overcharged state, when the battery is in the overcharged state, the positive electrode active material layer, the negative electrode active material layer, and the wound core in which the separator is laminated It has been found that the part tends to be hot (the temperature tends to rise).

Therefore, in order to solve the above problems, according to the present invention, a positive electrode having a positive electrode active material layer on a positive electrode current collector, a negative electrode having a negative electrode active material layer on a negative electrode current collector, and the positive electrode and the negative electrode are electrically connected. A wound electrode body having a separator to be isolated from each other, an electrolyte, a battery case containing the electrode body and the electrolyte, an external terminal electrically connected to the electrode body, and an internal pressure of the battery case are predetermined. A secondary battery is provided that includes a current interrupting mechanism that interrupts electrical connection between the electrode body and an external terminal when the pressure rises above a given pressure.
The secondary battery includes at least one of a positive electrode portion positioned on the outermost periphery of the wound electrode body in the positive electrode and a negative electrode portion positioned on the outermost periphery of the wound electrode body in the negative electrode. Has an electrode active material layer non-formed portion where the positive electrode active material layer or the negative electrode active material layer is not formed, and the electrode active material layer non-formed portion is filled with gas when a predetermined temperature is reached. A gas generating agent to be generated is arranged. Here, the content of the gas generating agent in the secondary battery is expressed by the following formula:
X ≧ 32.9 × (P2 / T2-P1 / T1) × V / R
(Where X is the amount (g) of the gas generating agent in the secondary battery, P1 is the internal pressure (MPa) of the battery case at the time of battery construction, and P2 is the internal pressure (MPa) of the battery case at which the current interruption mechanism operates. Set value, T1 is the battery temperature (K) at the time of battery construction, T2 is the set value of the battery temperature (K) at which the current interruption mechanism operates, V is the volume of the remaining space in the battery case (cm ³ ), R: gas Constant (J / K · mol).)
It is set to comprise.

According to such a configuration, the gas generating agent is disposed at a location where the battery tends to become hot when the battery is overcharged. For this reason, gas can be efficiently generated from the gas generating agent, and the internal pressure of the battery case can be quickly increased. Thereby, the current interruption mechanism can be operated at an appropriate timing.
Further, since the gas generating agent is disposed on the outermost periphery of the electrode body, it has little influence on the movement of charge carriers between the positive and negative electrode active material layers. For this reason, it is possible to suppress deterioration in battery performance (for example, increase in battery resistance) due to the gas generating agent in the battery.
That is, according to the present invention, it is possible to provide a secondary battery that can appropriately operate the current interrupting mechanism during overcharge while maintaining good battery performance during normal operation.

It is a perspective view which shows typically the external shape of the secondary battery which concerns on one Embodiment. It is a longitudinal cross-sectional view which follows the II-II line | wire in FIG. It is a schematic diagram which shows the structure of the wound electrode body which concerns on one Embodiment. It is sectional drawing which shows typically a part of structure of the winding electrode body which concerns on one Embodiment.

Hereinafter, the present invention will be described in detail by taking a lithium secondary battery as an example as a secondary battery according to an embodiment of the present invention with reference to the drawings as appropriate. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, the lithium secondary battery is an example, and the technical idea of the present invention is also applied to other secondary batteries (for example, sodium secondary batteries) provided with other charge carriers (for example, sodium ions).
In the following drawings, members / parts having the same action are described with the same reference numerals, and redundant descriptions may be omitted or simplified. Further, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship.

  In the present specification, the “secondary battery” generally refers to a battery that can be repeatedly charged and discharged, such as a so-called chemical battery such as a lithium secondary battery, a sodium secondary battery, and a nickel hydride secondary battery, and an electric double layer capacitor. It is a term encompassing the physical battery. In the present specification, the “lithium secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier (supporting salt, supporting electrolyte) and is charged and discharged by the movement of lithium ions between the positive and negative electrodes.

  FIG. 1 shows a lithium secondary battery (lithium ion secondary battery) 100 according to an embodiment of the present invention. As shown in FIG. 2, in the lithium secondary battery 100, the wound electrode body 20 is housed in a battery case (that is, an outer container) 30 together with an electrolyte (not shown).

  The shape of the battery case 30 is not particularly limited, and may be, for example, a cylindrical shape or a cubic shape (box shape). The battery case 30 is, for example, as shown in FIGS. 1 and 2, a box-shaped (that is, a bottomed rectangular parallelepiped) case body having an opening at one end (corresponding to the upper end in a normal use state of the battery). 32 and a lid 34 that seals the opening of the case body 32. As shown in the figure, the lid 34 is provided with external terminals (a positive terminal 42 and a negative terminal 44) for external connection so that a part of the terminals protrudes from the lid 34 to the outside of the battery 100. Yes. Further, the lid 34 is provided with a safety valve 36 set to release the internal pressure in the battery case and an injection port (not shown) for injecting the electrolyte into the battery case. As a material of such a battery case, for example, a metal material (for example, aluminum) that is lightweight and has good thermal conductivity is suitable.

  The battery case 30 of the secondary battery disclosed herein includes a pressure-actuated current interrupt device (CID: Current Interrupt Device) that forcibly cuts off the charging current when the pressure in the battery case exceeds a predetermined pressure. ). Generally, when a secondary battery is overcharged, an electrolyte component (for example, a non-aqueous solvent) is electrolyzed to generate gas. The pressure type current interruption mechanism cuts off the charging current to the battery and stops the progress of overcharge when the internal pressure of the battery case exceeds a predetermined level due to the generation of this gas. In this embodiment, as shown in FIG. 2, the current interruption mechanism 80 includes a current interruption mechanism 80 between the positive electrode current collector 52 and the positive electrode terminal 42 so that the battery current conduction path in the positive electrode 50 is interrupted. Is provided.

  As shown in FIGS. 2 and 3, the wound electrode body 20 is formed by laminating a long positive electrode 50 and a long negative electrode 60 with two long separators 70 ( It is wound in the longitudinal direction. In the present embodiment, the wound electrode body 20 has a flat shape. The wound electrode body 20 is formed by, for example, laminating and winding the positive electrode 50, the negative electrode 60, and the separator 70, and then winding the wound body in one direction orthogonal to the winding axis (typically, the side surface). It can be formed into a flat shape by crushing (from the direction) and pressing it.

  The positive electrode 50 includes a long positive electrode current collector 52 and a positive electrode active material layer including at least a positive electrode active material formed along one side or both sides (here, both surfaces) of the positive electrode current collector 52 along the longitudinal direction. 54. As the positive electrode current collector 52, for example, an aluminum foil or the like can be suitably used.

Examples of the positive electrode active material include lithium composite metal oxides such as a layered structure and a spinel structure (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiFePO _4, etc.). The positive electrode active material layer 54 can include components other than the active material, such as a conductive material and a binder. As the conductive material, carbon black such as acetylene black (AB) and other (such as graphite) carbon materials can be suitably used. As the binder, PVdF or the like can be used.

  Such a positive electrode 50 is prepared by, for example, dispersing a positive electrode active material and a material used as necessary in an appropriate solvent (for example, N-methyl-2-pyrrolidone) to prepare a paste-like (slurry) composition. The composition can be formed by applying an appropriate amount of the composition to the surface of the positive electrode current collector 52 and then drying it. Moreover, the properties (for example, average thickness, active material density, porosity, etc.) of the positive electrode active material layer 54 can be adjusted by performing an appropriate press treatment as necessary.

  The negative electrode 60 includes a long negative electrode current collector 62 and a negative electrode active material layer including at least a negative electrode active material formed along the longitudinal direction on one or both surfaces (here, both surfaces) of the negative electrode current collector 62. 64. As the negative electrode current collector 62, for example, a copper foil or the like can be suitably used.

  Examples of the negative electrode active material include a carbon material having a graphite structure (layered structure) at least partially, lithium transition metal nitride, and the like. Carbon materials such as so-called graphitic materials (graphite), non-graphitizable carbon materials (hard carbon), graphitizable carbon materials (soft carbon), and materials having a combination of these are preferably used. obtain. Among these, graphite particles such as natural graphite can be preferably used. Moreover, the negative electrode active material layer 64 may contain components other than the active material, such as a binder and a thickener. As the binder, styrene butadiene rubber (SBR) or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

  Such a negative electrode 60 is prepared by, for example, dispersing a negative electrode active material and a material used as necessary in an appropriate solvent (for example, water) to prepare a paste-like (slurry) composition. After the amount is applied to the surface of the negative electrode current collector 62, it can be formed by drying. Further, the properties (for example, average thickness, active material density, porosity, etc.) of the negative electrode active material layer 64 can be adjusted by performing an appropriate press treatment as necessary.

  Examples of the separator 70 include a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer).

  Although not particularly limited, in the present embodiment, the positive electrode 50 has the positive electrode current collector 52 exposed without forming the positive electrode active material layer 54 along the edge on one side in the width direction of the positive electrode current collector 52. The exposed positive electrode current collector exposed end 53 is set. Similarly, in the negative electrode 60, the negative electrode current collector exposed end portion 63 where the negative electrode current collector 62 is exposed without forming the negative electrode active material layer 64 along the edge portion on one side in the width direction of the negative electrode current collector 62. Is set. As shown in FIGS. 2 and 3, the wound electrode body 20 has the positive electrode current collector exposed end portion 53 and the negative electrode current collector exposed end portion 63 outward from both ends in the winding axis direction. It may have been rolled over and rolled up so as to protrude. As a result, a wound core in which the positive electrode 50, the negative electrode 60, and the separator 70 are laminated and wound is formed at the center of the wound electrode body 20 in the winding axis direction. Further, as shown in FIG. 2, the positive electrode 50 and the negative electrode 60 have a positive electrode current collector exposed end 53 and a positive electrode terminal 42 (for example, made of aluminum) electrically connected via a positive electrode current collector plate 42a. The negative electrode current collector exposed end 63 and the negative electrode terminal 44 (for example, made of nickel) can be electrically connected via the negative electrode current collector plate 44a. The positive and negative electrode current collector plates 42a and 44a and the positive and negative electrode current collector exposed end portions 53 and 63 (typically the positive and negative electrode current collectors 52 and 62) are respectively formed by, for example, ultrasonic welding or resistance welding. Can be joined.

  Further, in the secondary battery 100 disclosed herein, as shown in FIGS. 3 and 4, the positive electrode portion of the positive electrode 50 located on the outermost periphery of the wound electrode body 20, and the negative electrode 60 An electrode active material layer non-formed portion 90 in which the positive electrode active material layer 54 or the negative electrode active material layer 64 is not formed is set in at least one of the negative electrode portions located on the outermost periphery of the wound electrode body 20. Is done. When the positive electrode active material layer 54 (or the negative electrode active material layer 64) is the positive electrode 50 (or the negative electrode 60) formed on both surfaces of the positive electrode current collector 52 (or the negative electrode current collector 62), the electrode active material layer The non-formed portion 90 may be set on at least one side of the positive electrode 50 (or the negative electrode 60).

  At least a part of the electrode active material layer non-forming portion 90 includes a gas generating agent that generates gas when a predetermined temperature (for example, 125 ° C. or higher, typically 130 ° C. or higher) is reached (FIGS. 3 and 3). 4 in the gas generant arrangement part 92). For this reason, from the viewpoint of ensuring a wide area in which the gas generating agent is disposed, the electrode active material layer non-formed portion 90 is formed on both the positive electrode 50 and the negative electrode 60 (more preferably, both of the positive electrode 50 and the negative electrode 60). It is preferable that the electrode active material layer non-formed portion 90 is formed on both surfaces of the positive electrode 50 (or the negative electrode 60) (more preferably, gas is generated on both surfaces of the positive electrode 50 or the negative electrode 60). Preferably). More preferably, the electrode active material layer non-formation portion 90 (more preferably, the gas generating agent disposition portion 92) is set so as to make one round of the outermost circumference of the wound electrode body 20. In particular, since the temperature rise during overcharge is large (rapid), a gas generating agent is suitably disposed in a portion corresponding to the winding core of the wound electrode body 20 (preferably near the center in the winding axis direction). obtain.

As the gas generating agent, for example, an organic foaming agent (thermal decomposition foaming agent) that generates a gas (typically nitrogen gas, carbon dioxide gas, etc.) by thermal decomposition at a predetermined temperature or higher can be preferably used. Examples of such organic blowing agents include p, p′-oxybisbenzenesulfonyl hydrazide (OBSH), azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), and the like. These may be used alone or in combination of two or more.
In the case where the organic foaming agent (thermal decomposition foaming agent) is disposed in the electrode active material layer non-forming portion 90 (gas generating agent disposing portion 92), an auxiliary agent (foaming aid) that promotes the decomposition of the organic foaming agent. An agent) may be further provided in the electrode active material layer non-forming portion 90 (gas generating agent disposing portion 92). By providing such an auxiliary agent (foaming auxiliary agent), the decomposition temperature of the gas generating agent (organic foaming agent) can be lowered, and the temperature at which the gas generating agent begins to generate gas can be adjusted to a desired temperature. Such an auxiliary agent (foaming auxiliary agent) is not particularly limited, and examples thereof include urea, zinc stearate, calcium stearate, calcium carbonate, and zinc oxide.

  The method of disposing the gas generating agent (and auxiliary agent) in the electrode active material layer non-forming portion 90 (gas generating agent disposing portion 92) is not particularly limited. For example, a binder (binder) is applied to the surface of the positive electrode current collector 52 or the negative electrode current collector 62 exposed in the electrode active material layer non-forming portion 90, and a gas generating agent (and An auxiliary agent) may be arranged. The said binder is not specifically limited, The binder (for example, PVdF, SBR, etc.) normally used for a secondary battery can be used.

The amount (g) of the gas generating agent disposed in the electrode active material layer non-forming portion 90 (gas generating agent disposing portion 92) is such that the content (g) of the gas generating agent in the secondary battery is as follows. formula:
X ≧ 32.9 × (P2 / T2-P1 / T1) × V / R
It is set to comprise. Here, X is the amount (g) of the gas generating agent in the secondary battery, P1 is the internal pressure (MPa) of the battery case at the time of battery construction, and P2 is the internal pressure (MPa) of the battery case at which the current interrupting mechanism operates. Value, T1 is the battery temperature (K) at the time of battery construction, T2 is the set value of the battery temperature (K) at which the current interrupting mechanism operates, V is the volume of the remaining space in the battery case (cm ³ ), R: gas constant (J / K · mol). Here, the volume of the remaining space is a volume of a space other than the volume occupied by battery components such as the electrode body and the electrolyte in the internal volume of the battery case. By containing the gas generating agent satisfying the above formula in the secondary battery, a sufficient amount of gas for operating the CID can be secured quickly when the battery is overcharged.

The property of the electrolyte is not particularly limited, and may be liquid, gel, or solid. Typically, a nonaqueous electrolytic solution containing a supporting salt in an organic solvent (nonaqueous solvent) can be used.
As the non-aqueous solvent, organic solvents such as various carbonates, ethers, esters, nitriles, sulfones, and lactones that are used in an electrolytic solution of a general lithium secondary battery can be used. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like.
As the supporting salt, the same salt as that of a general lithium secondary battery can be used. For example, a lithium salt of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ or the like (preferably LiPF ₆ ) can be used. Moreover, the suitable range of the density | concentration of the supporting salt in electrolyte can be set to 0.7 mol / L-1.3 mol / L (for example, 1.1 mol / L).

  In addition, the secondary battery 100 causes a decomposition / polymerization reaction on the positive electrode active material when the battery is overcharged in the battery case, thereby consuming a charging current and suppressing the battery charging reaction. And / or an overcharge inhibitor known to be capable of generating gas (typically hydrogen gas) to increase the internal pressure of the battery. Such an overcharge inhibitor generally can generate heat (polymerization heat) when the above-described polymerization reaction occurs, and thus can contribute to a rapid increase in the temperature in the battery when the battery is overcharged. Such an overcharge preventing agent can contain the same overcharge preventing agent as that used in conventional secondary batteries. For example, cyclohexylbenzene (CHB), biphenyl (BP), and the like can be used. .

  The secondary battery disclosed here is a battery capable of appropriately operating a current interruption mechanism (CID) at the time of overcharging while maintaining good battery performance during normal operation, and has high battery performance and safety. Can be compatible. Therefore, although the said battery can be utilized for various uses, it can use suitably as a drive power supply mounted in a vehicle, for example using such a property. The type of vehicle is not particularly limited, and examples include plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), electric trucks, motorbikes, electric assist bicycles, electric wheelchairs, electric railways, and the like. . Therefore, according to the present invention, there is provided a vehicle equipped with any of the secondary batteries disclosed herein, preferably as a power source. The secondary battery provided in the vehicle may be in the form of an assembled battery in which a plurality of secondary batteries are connected.

  Several examples (test examples) relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the specific examples.

  The lithium secondary batteries according to Examples 1 to 6 were constructed by the following materials and processes.

[Construction of lithium secondary battery]
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (LNCM) as a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder are combined with LNCM: AB : PVdF = 90: 8: 2 was mixed with N-methylpyrrolidone (NMP) at a mass ratio to prepare a paste-like (slurry) positive electrode active material layer forming composition. This composition was applied to both sides of a long aluminum foil (positive electrode current collector) in a band shape, dried and pressed to produce a positive electrode.

  Next, natural graphite (C) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener, C: SBR: CMC = 98: 1: A paste-like (slurry) negative electrode active material layer forming composition was prepared by dispersing in water at a mass ratio of 1. This composition was applied in a strip shape on both sides of a long copper foil (negative electrode current collector), dried and pressed to prepare a negative electrode.

  The positive electrode and the negative electrode prepared by the above-described method are overlapped in the longitudinal direction via two separators (average thickness 25 μm) having a three-layer structure in which a porous polypropylene layer is formed on both sides of the porous polyethylene layer. A flat wound electrode body was produced by crushing and ablating after winding in the direction (Example 1).

Next, the wound electrode body and the nonaqueous electrolyte were accommodated in a rectangular battery case (made of aluminum), and a lithium secondary battery according to Example 1 was constructed. As the non-aqueous electrolyte, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of EC: DMC: EMC = 1: 1: 1 is used as a supporting salt. Of LiPF ₆ dissolved at a concentration of 1 mol / L was used. That is, in the battery according to Example 1, no gas generating agent was disposed in the battery (indicated by “-” in the corresponding column of Table 1).

<Example 2>
With respect to the positive electrode and the negative electrode, when the wound electrode body is produced, an electrode active material layer non-formation part in which the positive electrode active material layer and the negative electrode active material layer are not provided is provided at the outermost part of the wound electrode body. A positive electrode and a negative electrode were produced using the same materials and processes as in Example 1 except that. And the polyvinylidene fluoride (PVdF) as a binder was apply | coated to the said electrode active material layer non-formation part, and pp 'oxybisbenzene sulfonyl hydrazide (OBSH) as a gas generating agent was arrange | positioned on this PVdF. And the wound electrode body which concerns on Example 2 is produced with the material and process similar to the said Example 1 except having used the positive electrode and negative electrode which have arrange | positioned this gas generating agent, The lithium secondary battery which concerns on Example 2 Built.
Here, the amount of the gas generating agent disposed in the lithium secondary battery is expressed by the following formula (I):
X ≧ 32.9 × (P2 / T2-P1 / T1) × V / R (I)
In addition, the value shown below was employ | adopted for X, P1, P2, T2, T1, V, and R in the said Formula (I) (it is the same also about the below-mentioned Examples 3-6).
X is the amount (g) of the gas generating agent in the secondary battery.
P1 is the internal pressure of the battery case at the time of battery construction, and was 0.1 MPa here.
P2 is a set value of the internal pressure of the battery case where the CID operates, and is set to 0.8 MPa here.
T1 is a battery temperature at the time of battery construction, and was 298.15 K (25 ° C.) here.
T2 is a set value of the battery temperature (K) at which the CID operates. Here, T2 is set to 393.15K (120 ° C.).
V is the volume (cm ³ ) of the remaining space in the battery case, and was 50 cm ³ here.
R is a gas constant (J / K · mol), which is 8.31.
It was set as the quantity which satisfy | fills.

<Example 3>
The lithium secondary battery according to Example 3 was prepared by the same material and process as in Example 2 except that the amount of the gas generating agent (OBSH) disposed in the lithium secondary battery was changed to an amount not satisfying the above formula (I). The next battery was built.

<Example 4>
The same positive electrode and negative electrode as in Example 1 were prepared. And it is a part of separator, Comprising: The gas generating agent (OBSH) is arrange | positioned in the part located in the outermost periphery of this winding electrode body when constructing a winding electrode body, It is the same as that of the said Example 1 A lithium secondary battery according to Example 4 was constructed using the materials and processes described above. The content of the gas generating agent in the secondary battery satisfies the above formula (I).

<Example 5>
A gas generating agent (OBSH) was mixed in the positive electrode active material layer forming composition and the negative electrode active material layer forming composition, so that the gas generating agent was disposed in the positive electrode active material layer and the negative electrode active material layer. A lithium secondary battery according to Example 5 was constructed using the same materials and processes as in Example 1 above. The content of the gas generating agent in the secondary battery satisfies the above formula (I).

<Example 6>
The gas generating agent (OBSH) is made of the same material and process as in Example 1 except that the gas generating agent (OBSH) is disposed between the electrode body and the battery case lid (here, the surface of the positive electrode current collector plate and the negative electrode current collector plate). A lithium secondary battery according to Example 6 was constructed. The content of the gas generating agent in the secondary battery satisfies the above formula (I).

<Resistance measurement>
Each of the lithium secondary batteries according to Examples 1 to 6 is charged with 60% SOC (State of Charge) by constant current and constant voltage (CC-CV) charging in a room temperature (about 25 ° C.) environmental atmosphere. Adjusted to the condition. Thereafter, discharging was performed at 25 ° C. with a current value of 10 C for 10 seconds, and IV resistance was calculated from a voltage drop amount 10 seconds after the start of discharging. A battery having a measured resistance value larger than the resistance value of Example 1 was evaluated as “x”, and a battery having a resistance value of Example 1 or less was evaluated as “◯”. The results are shown in Table 1. In addition, the reference example 1 was described as “−”.

<Overcharge test>
Each of the lithium secondary batteries according to Examples 1 to 6 was charged in a room temperature (about 25 ° C.) environment atmosphere to reach 10 V at a current value of 3 C, and the operation of CID was examined. A battery in which CID normally operated was evaluated as “◯”, and a battery in which CID did not operate normally (inoperative or delayed in operation) was evaluated as “x”. The results are shown in Table 1.

As shown in Table 1, the secondary battery shown in Example 2 had a lower battery resistance than the secondary battery according to Example 1. On the other hand, the secondary battery according to Example 5 had higher battery resistance than the secondary battery according to Example 1. This is considered that the gas generating agent arranged in the active material layer hinders the movement of the charge carrier.
Further, in the secondary battery shown in Example 2, the CID operated appropriately (relatively early) during overcharge. On the other hand, in the secondary batteries according to Examples 1, 3, 4, and 6, the CID did not operate properly. Since the secondary battery according to Example 1 does not include a gas generating agent in the battery, and the secondary battery according to Example 3 has a low gas generating agent content in the battery, the amount of gas generated is insufficient. Think. Moreover, the secondary battery which concerns on Example 4 and Example 6 thinks that the temperature rise of the location which has arrange | positioned the overcharge gas generating agent was inadequate, or the temperature rise of the said location was delayed.
That is, according to the present invention, while maintaining high battery performance (suppressing an increase in resistance), the amount of gas generated during overcharge can be increased (gas is generated quickly from the generating agent), and the current is interrupted. It was confirmed that the mechanism can operate properly.

  As mentioned above, although the specific example of this invention was demonstrated in detail, the said embodiment and Example are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

20 Winding electrode body 30 Battery case 32 Battery case body 34 Cover body 36 Safety valve 42 Positive electrode terminal 42a Positive electrode current collector plate 44 Negative electrode terminal 44a Negative electrode current collector plate 50 Positive electrode 52 Positive electrode current collector 53 Positive electrode current collector exposed end 54 Positive electrode Active material layer 60 Negative electrode 62 Negative electrode current collector 63 Negative electrode current collector exposed end 64 Negative electrode active material layer 70 Separator 80 Current interruption mechanism (CID)
90 Electrode active material layer non-formation part 92 Gas generant arrangement part 100 Secondary battery (lithium secondary battery)

Claims (1)

A wound electrode body having a positive electrode having a positive electrode active material layer on the positive electrode current collector, a negative electrode having a negative electrode active material layer on the negative electrode current collector, and a separator for electrically isolating the positive electrode and the negative electrode;
Electrolyte,
A battery case containing the wound electrode body and the electrolyte;
An external terminal electrically connected to the wound electrode body;
When the internal pressure of the battery case rises above a predetermined pressure, a secondary battery comprising a current interruption mechanism that interrupts electrical connection between the wound electrode body and the external terminal,
At least one of the positive electrode portion positioned on the outermost periphery of the wound electrode body in the positive electrode and the negative electrode portion positioned on the outermost periphery of the wound electrode body in the negative electrode is provided with the positive electrode active portion. There is an electrode active material layer non-formed part in which the material layer or the negative electrode active material layer is not formed,
In the part where the electrode active material layer is not formed, a gas generating agent that generates gas when a predetermined temperature is reached is disposed,
Here, the content of the gas generating agent in the secondary battery is expressed by the following formula:
X ≧ 32.9 × (P2 / T2-P1 / T1) × V / R
(Where X is the amount (g) of the gas generating agent in the secondary battery, P1 is the internal pressure (MPa) of the battery case at the time of battery construction, and P2 is the internal pressure (MPa) of the battery case at which the current interruption mechanism operates. Set value, T1 is the battery temperature (K) at the time of battery construction, T2 is the set value of the battery temperature (K) at which the current interruption mechanism operates, V is the volume of the remaining space in the battery case (cm ³ ), R: gas Constant (J / K · mol).)
A secondary battery set to include:

Images