JP2015060669A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery capable of properly actuating a current interruption mechanism.SOLUTION: A nonaqueous electrolyte secondary battery includes: an electrode body 20 including a positive electrode 50, a negative electrode and a separator 70; a nonaqueous electrolyte containing a gas generating agent; and a current interruption mechanism. A LiMnPO-containing layer 80 containing LiMnPOis arranged between a positive electrode active material layer 54 and the separator 70.

Description

  The present invention relates to a secondary battery (non-aqueous electrolyte secondary battery) provided with a non-aqueous electrolyte.

  Lithium ion secondary batteries and other non-aqueous electrolyte secondary batteries are becoming increasingly important as on-vehicle power supplies or personal computers and portable terminals. In particular, a lithium ion secondary battery that is lightweight and obtains a high energy density is preferably used as a high-output power source mounted on a vehicle. When the nonaqueous electrolyte secondary battery is overcharged, excessive charge carriers are released from the positive electrode, and excessive charge carriers are inserted in the negative electrode. For this reason, both the positive electrode and the negative electrode are thermally unstable. When both the positive electrode and the negative electrode become thermally unstable, the organic solvent of the electrolytic solution is eventually decomposed, and a rapid exothermic reaction occurs, thereby impairing the stability of the battery.

  To solve this problem, for example, the battery case is equipped with a current interruption mechanism that interrupts charging when the gas pressure inside the battery exceeds a predetermined pressure, and gas is generated when a predetermined overcharge state is reached in the electrolyte. A non-aqueous electrolyte secondary battery to which a gas generating agent is added is disclosed (for example, Patent Document 1). As such a gas generating agent, for example, cyclohexylbenzene (CHB) or biphenyl (BP) is used. CHB and BP activate the polymerization reaction during overcharge and generate hydrogen gas. Thereby, the pressure in a battery case becomes high, an electric current interruption mechanism act | operates, and an overcharge electric current is interrupted | blocked.

JP 2006-324235 A

  As described above, a gas generating agent such as CHB or BP activates a polymerization reaction at the time of overcharge of about 4.35V to 4.6V to generate gas. In this case, in order to generate a sufficient amount of gas at the time of overcharging, it is preferable to maintain the voltage range (for example, about 4.35V to 4.6V) in which the gas generation of the gas generating agent occurs as long as possible. However, in the conventional nonaqueous electrolyte secondary battery, the voltage tends to increase rapidly when overcharged, and it is difficult to maintain the voltage range in which gas generation of the gas generating agent occurs. The present invention solves the above problems.

The non-aqueous electrolyte secondary battery provided by the present invention includes a positive electrode in which a positive electrode active material layer is held on a positive electrode current collector, a negative electrode in which a negative electrode active material layer is held on a negative electrode current collector, and the positive electrode An electrode body including a separator interposed between the negative electrode, a battery case that houses the electrode body, an external terminal that is provided in the battery case and connected to the electrode body, and is housed in the battery case A non-aqueous electrolyte containing a gas generating agent that reacts at a voltage equal to or higher than a predetermined voltage to generate gas, and when the internal pressure of the battery case becomes higher than a predetermined pressure, the electrode body and the external A current interrupting mechanism for interrupting electrical connection with the terminal. Then, the between the positive electrode active material layer and the separator, LiMnPO ₄ containing layer containing LiMnPO ₄ is disposed.

By disposing the LiMnPO ₄ -containing layer between the positive electrode active material layer and the separator in this manner, the overcharge (SOC (State of Charge) region exceeding 100%, typically 100% to 140% SOC. The voltage rise in the region) becomes gradual, and the voltage range in which gas generation of the gas generating agent occurs during overcharge can be maintained long. Thereby, when it will be in an overcharge state, the gas generation amount by a gas generating agent can be ensured more appropriately, and a current interruption mechanism can be operated appropriately.

It is a figure which shows an example of the structure of a nonaqueous electrolyte secondary battery. It is a schematic diagram which shows a part of cross section which cut | disconnected the wound electrode body to radial direction. It is a figure which shows the charge curve of the conventional lithium ion secondary battery. It is a figure which shows the charge curve of the lithium ion secondary battery which concerns on one Embodiment. Is a graph showing the relationship between the maximum temperature of the basis weight and battery LiMnPO _4.

Hereinafter, preferred embodiments of the present invention will be described. 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.
In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a so-called storage battery such as a lithium ion secondary battery and a power storage element such as an electric double layer capacitor. The “non-aqueous electrolyte secondary battery” refers to a battery provided with a non-aqueous electrolyte (typically, an electrolyte containing a supporting salt (supporting electrolyte) in a non-aqueous solvent). The “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as electrolyte ions and is charged and discharged by the movement of lithium ions between positive and negative electrodes. The electrode active material refers to a material capable of reversibly occluding and releasing chemical species (lithium ions in a lithium ion secondary battery) serving as a charge carrier.

  Hereinafter, a non-aqueous secondary battery according to an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected suitably to the member and site | part which show | play the same effect | action. Each drawing is schematically drawn and does not necessarily reflect the real thing. Each drawing shows an example only and does not limit the present invention unless otherwise specified. Hereinafter, embodiments of the present invention will be described by taking as an example the case where the present invention is applied to a lithium ion secondary battery, but it is not intended to limit the application target of the present invention.

  FIG. 1 shows a lithium ion secondary battery 100 according to an embodiment of the present invention. As shown in FIG. 1, the lithium ion secondary battery 100 includes a wound electrode body 20 and a battery case 30. As shown in FIG. 1, a lithium ion secondary battery 100 according to an embodiment of the present invention includes a flat rectangular battery case 20 having a flat wound electrode body 20 together with a liquid electrolyte (electrolytic solution) (not shown). That is, it is accommodated in the exterior container 30.

  The battery case 30 has a box-shaped (that is, bottomed rectangular parallelepiped) case body 32 having an opening at one end (corresponding to the upper end in a normal use state of the battery), and the opening attached to the opening. It is comprised from the cover body 34 which consists of a rectangular-shaped plate member which plugs up a part. The material of the battery case 30 is exemplified by aluminum, for example. As shown in FIG. 1, a positive electrode terminal 42 and a negative electrode terminal 44 for external connection are formed on the lid 34. A safety valve 36 is formed between both terminals 42 and 44 of the lid 34.

  The wound electrode body 20 includes a long sheet-like positive electrode (positive electrode sheet 50) and a long sheet-like negative electrode (negative electrode sheet 60) similar to the positive electrode sheet 50, in total, two long sheet-like separators (separators). 70).

  The positive electrode sheet 50 includes a strip-shaped positive electrode current collector 52 and a positive electrode active material layer 54. For the positive electrode current collector 52, for example, a strip-shaped aluminum foil having a thickness of about 15 μm is used. A positive electrode active material layer non-forming portion 52 a is set along an edge portion on one side in the width direction of the positive electrode current collector 52. In the illustrated example, the positive electrode active material layer 54 is held on both surfaces of the positive electrode current collector 52 except for the positive electrode active material layer non-forming portion 52 a set in the positive electrode current collector 52. The positive electrode active material layer 54 includes a positive electrode active material, a conductive material, and a binder.

As the positive electrode active material, a material used as a positive electrode active material of a lithium ion secondary battery can be used. Examples of cathode active materials include lithium transition metal oxides such as LiNiCoMnO ₂ (lithium-nickel-cobalt-manganese composite oxide). For example, an oxide represented by LiNi _{0.3 + m} Mn _{0.3 + n} Co _0.4-mn O ₂ is exemplified as the layered lithium transition metal oxide. In the above formula, m satisfies 0 ≦ m ≦ 0.4, and n satisfies 0 ≦ n ≦ 0.4 (where m + n <0.4). Preferable examples include LiNi _1/3 Mn _1/3 Co _1/3 O ₂ that contains Ni, Mn, and Co at approximately the same ratio. A conductive material such as acetylene black (AB) can be mixed with the positive electrode active material. In addition to the positive electrode active material and the conductive material, a binder such as polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), or carboxymethyl cellulose (CMC) can be added. A positive electrode active material layer forming composition (paste) can be prepared by dispersing these in a suitable dispersion medium and kneading. The positive electrode active material layer 54 is formed by applying the positive electrode active material layer forming composition to the positive electrode current collector 52, drying it, and pressing it to a predetermined thickness.

  The negative electrode sheet 60 includes a strip-shaped negative electrode current collector 62 and a negative electrode active material layer 64. For the negative electrode current collector 62, for example, a strip-shaped copper foil having a thickness of about 10 μm is used. On one side in the width direction of the negative electrode current collector 62, a negative electrode active material layer non-formation part 62a is set along the edge. The negative electrode active material layer 64 is held on both surfaces of the negative electrode current collector 62 except for the negative electrode active material layer non-forming portion 62 a set in the negative electrode current collector 62. The negative electrode active material layer 64 includes a negative electrode active material, a thickener, a binder, and the like.

  As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion secondary batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon. And like a positive electrode, this negative electrode active material is disperse | distributed to a suitable dispersion medium with binders, such as PVDF, SBR, and CMC (it can function also as a thickener), and is kneaded, The composition for negative electrode active material layer formation A product (paste) can be prepared. The negative electrode active material layer 64 is formed by applying this negative electrode active material layer forming composition to the negative electrode current collector 62, drying it, and pressing it to a predetermined thickness.

The separator 70 is a member that separates the positive electrode sheet 50 and the negative electrode sheet 60. In this example, the separator 70 is composed of a strip-shaped base material having a predetermined width and having a plurality of minute holes. Examples of the base material include a sheet material having a single layer structure (for example, a single layer structure of polyethylene) made of a porous polyolefin-based resin, or a sheet material having a laminated structure (for example, a three-layer structure of polypropylene, polyethylene, and polypropylene). Can be used. A LiMnPO ₄ containing layer 80 is formed on one side of the separator 70. This will be described later.

  The wound electrode body 20 is attached to electrode terminals 42 and 44 attached to the battery case 30 (in this example, the lid body 34). The wound electrode body 20 is housed in the battery case 30 in a state where the wound electrode body 20 is flatly pushed and bent in one direction orthogonal to the winding axis. In the wound electrode body 20, the positive electrode active material layer non-formed portion 52 a of the positive electrode sheet 50 and the negative electrode active material layer non-formed portion 62 a of the negative electrode sheet 60 protrude on the opposite sides in the winding axis direction. Among these, one electrode terminal 42 is fixed to the positive electrode active material layer non-forming portion 52 a of the positive electrode current collector 52 via the positive electrode current collector plate 42 a, and the other electrode terminal 44 is the negative electrode current collector 62. The negative electrode active material layer non-forming portion 62a is fixed via a negative electrode current collector plate 44a. The wound electrode body 20 is accommodated in the flat internal space of the case body 32. The case body 32 is closed by the lid 34 after the wound electrode body 20 is accommodated.

As the electrolytic solution (non-aqueous electrolytic solution), the same non-aqueous electrolytic solution conventionally used for lithium ion secondary batteries can be used without any particular limitation. Such a nonaqueous electrolytic solution typically has a composition in which a supporting salt is contained in a suitable nonaqueous solvent. As the non-aqueous solvent, for example, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, or the like can be used. Moreover, as said support salt, lithium salts, such as LiPF ₆ , can be used, for example.

  The non-aqueous electrolyte contains, for example, a gas generating agent that reacts and generates gas when the battery voltage becomes equal to or higher than a predetermined voltage. As such a gas generating agent, for example, cyclohexylbenzene (CHB) or biphenyl (BP) can be used. For example, when CHB or BP is overcharged at about 4.35V to 4.6V, the polymerization reaction is activated to generate hydrogen gas. The amount of the gas generating agent added to the non-aqueous electrolyte is preferably about 0.05% by mass or more and 4.0% by mass or less, for example.

  Further, as described above, in the lithium ion secondary battery 100, a gas generating agent is added to the electrolytic solution. For example, when the battery is overcharged at about 4.35V to 4.6V, gas is generated. The pressure inside becomes high. The current interruption mechanism 90 is a mechanism that interrupts the current path when the pressure in the battery case becomes abnormally high. In this embodiment, as shown in FIG. 1, the current interruption mechanism 90 is constructed inside the positive electrode terminal 42 so that the conduction path of the battery current in the positive electrode is interrupted.

  Hereinafter, the lithium ion secondary battery 100 will be described in more detail. FIG. 2 schematically shows a cross section of the positive electrode sheet 50 and the separator 70 overlapped in the wound electrode body 20 taken along the winding axis direction (for example, the width direction of the positive electrode sheet 50).

As shown in FIG. 2, in the wound electrode body 20, a LiMnO ₄ containing layer 80 is disposed between the positive electrode active material layer 54 and the separator 70. In this embodiment, the LiMnPO ₄ containing layer 80 is formed on the surface of the separator 70. The LiMnPO ₄ -containing layer 80 is formed on the surface facing the positive electrode active material layer 54 on the front and back of the separator 70. The LiMnPO ₄ containing layer 80 contains LiMnPO ₄ .

LiMnPO included in LiMnPO ₄ containing layer 80 ₄ is a lithium manganese phosphate as a main component an olivine phosphate compound of lithium can occlude and release. The shape (outer shape) of LiMnPO ₄ is not particularly limited. From the viewpoint of mechanical strength, ease of production, etc., generally spherical LiMnPO ₄ particles can be preferably used.

Here, FIG. 3 shows a charging curve of a conventional lithium ion secondary battery not provided with the LiMnPO ₄ containing layer (a graph showing a transition of voltage with respect to a change in SOC). On the other hand, FIG. 4 shows a charging curve of a lithium ion secondary battery in which a LiMnPO ₄ containing layer is disposed between the positive electrode active material layer and the separator.

As shown in FIG. 3, in the lithium ion secondary battery in which the LiMnPO ₄ containing layer is not provided, the voltage tends to rapidly increase when overcharged (for example, a region where the SOC exceeds 100%). A gas generating agent such as CHB or BP activates the polymerization reaction during overcharge of about 4.35 V to 4.6 V, and generates gas. For this reason, if the voltage suddenly rises during overcharge, the reaction time of the gas generating agent cannot be ensured sufficiently, and the amount of gas generated by the gas generating agent may be insufficient.

In contrast, as shown in FIGS. 1, 2, and 4, in the lithium ion secondary battery 100 disclosed herein, a LiMnPO ₄ containing layer 80 is disposed between the positive electrode active material layer 54 and the separator 70. According to the configuration, when the battery is overcharged (for example, a region where the SOC exceeds 100%), the voltage gradually increases, and the charging curve includes a plateau region indicating a gradual voltage increase (for example, SOC 100% of the charging curve in FIG. 4). ~ 150% part) appears. In the lithium ion secondary battery 100 having such characteristics, a voltage range (for example, about 4.35V to 4.6V) in which gas generation of the gas generating agent occurs during overcharge can be maintained for a long time. Thereby, when it will be in an overcharge state, the gas generation amount by a gas generating agent can be ensured more appropriately, and the electric current interruption mechanism 90 can be operated appropriately.

The mass (weight per unit area) of LiMnPO ₄ per unit area of the positive electrode current collector 52 is not particularly limited, but if the basis weight of LiMnPO ₄ is too small, the above-described effect of suppressing voltage increase during overcharging becomes insufficient. There is a case. From this point of view, it is appropriate to set it to approximately 0.25 mg / cm ² or more (for example, 0.25 mg / cm ² or more and 1 mg / cm ² or less), preferably 0.5 mg / cm ² or more, more preferably Is 0.75 mg / cm ² or more. On the other hand, if the basis weight of LiMnPO ₄ is too large, battery capacity and input / output characteristics may be reduced. From this point of view, it is generally appropriate to the 1.2 mg / cm ² or less, preferably 1 mg / cm ² or less.

As the volume density of LiMnPO ₄ contained in LiMnPO ₄ containing layer 80 is not particularly limited, it is generally 1.8 g / ^{m 3} or more (e.g., 1.8 g / ^{m 3} or more 2.8 g / ^{m 3} or less) Is preferably 2 g / m ³ or more, and more preferably 2.2 g / m ³ or more. If the density of LiMnPO ₄ is too small, it is necessary to increase the film thickness of the LiMnPO ₄ -containing layer 80, so that the battery capacity may be disadvantageous. On the other hand, if the density of LiMnPO ₄ is too large, the air permeability of the LiMnPO ₄ -containing layer 80 is lowered (lithium ions are difficult to pass through), and the battery characteristics may be deteriorated.

The film thickness of the LiMnPO ₄ -containing layer 80 is not particularly limited, but is appropriately about 2 μm to 10 μm, preferably 2 μm to 6 μm. Further, the Gurley value of the LiMnPO ₄ containing layer 80 is not particularly limited, but it is appropriate to set it to about 100 (sec / 100 cm ³ ) or more and 160 (sec / 100 cm ³ ) or less, preferably 100 (sec / 100 cm ^3). ) 110 (sec / 100 cm ³ ) or more. In addition, the Gurley value of the LiMnPO ₄ containing layer 80 shall be measured according to JIS L 1096: 2010 “Fabric and knitted fabric test method”.

The LiMnPO ₄ containing layer 80 can contain a material other than LiMnPO _{4 as} necessary. An inorganic filler is illustrated as such a material. A material that can constitute the inorganic filler used in the LiMnPO ₄ containing layer 80 is preferably a material that has high electrical insulation and a higher melting point than the separator 70. Examples thereof include inorganic compounds such as alumina, alumina hydrate (boehmite), magnesia, titania, silica, zirconia, zinc oxide, iron oxide, ceria and yttria. These inorganic materials may be used individually by 1 type, and may be used in combination of 2 or more types. By containing such a material of the inorganic filler in LiMnPO ₄ containing layer 80, heat resistance and mechanical strength of the LiMnPO ₄ containing layer 80 is improved. Therefore, it is possible to effectively prevent thermal contraction that may occur when overcharging or when a short circuit occurs. The shape (outer shape) of the inorganic filler is not particularly limited. From the viewpoints of mechanical strength, manufacturability, etc., generally spherical inorganic filler particles can be preferably used.

The LiMnPO ₄ containing layer 80 may contain a binder. The binder used for the LiMnPO ₄ containing layer 80 is preferably a binder having high affinity with the separator 70. When the composition for forming the LiMnPO ₄ containing layer 80 is an organic solvent-based solvent (for example, NMP), it is preferable to use a binder that is dispersed or dissolved in the organic solvent-based solvent. Preferable examples include polyvinylidene fluoride (PVdF).

Although not particularly limited, it is preferable that the proportion of LiMnPO ₄ of total LiMnPO ₄ containing layer is approximately 25 mass% or more (typically 25 to 100% by weight), is about 50 to 100 wt% It is preferable. Moreover, in the LiMnPO ₄ containing layer having a composition containing an inorganic filler, the proportion of the inorganic filler in the LiMnPO ₄ containing layer can be, for example, 75% by mass or less (eg, 1% by mass to 75% by mass), and approximately 50% by mass. % Or less, more preferably about 25% by mass or less. Further, when containing LiMnPO ₄ and an inorganic filler other than LiMnPO ₄ containing layer-forming components (e.g., binder) is preferably set to be lower than or equal to the total content of about 10% by weight thereof optional ingredients, about 5 wt% or less ( For example, approximately 1 to 5% by mass) is preferable.

Next, a method for forming the LiMnPO ₄ containing layer 80 according to the present embodiment will be described. As the LiMnPO ₄ -containing layer-forming coating material for forming the LiMnPO ₄ -containing layer 80, a paste (including slurry or ink, including the same in the following) in which LiMnPO ₄ , an inorganic filler and a solvent are mixed and used is used. It is done. By applying an appropriate amount of this paste-like paint to the surface of the separator 70 and further drying, the LiMnPO ₄ containing layer 80 can be formed. N-methylpyrrolidone (NMP) is illustrated as a solvent used for the paint for forming a LiMnPO ₄ -containing layer.

The evaluation cell (lithium ion secondary battery) provided with the LiMnPO ₄ containing layer according to the present invention was constructed, and the maximum battery temperature and output characteristics when the current interruption mechanism was activated during the battery overcharge test were evaluated. . A specific method will be described below.

Here, the positive electrode of the evaluation cell was produced as follows. LiNiCoMnO ₂ powder as a positive electrode active material, AB as a conductive material, and PVdF as a binder are mixed in NMP so that the mass ratio of these materials becomes 93: 4: 3, and used for the positive electrode active material layer A composition was prepared. This positive electrode active material layer composition was applied in a strip shape on both sides of a long sheet of aluminum foil and dried to prepare a positive electrode sheet having a positive electrode active material layer provided on both sides of the positive electrode current collector.

  The negative electrode of the evaluation cell was produced as follows. A negative electrode active material layer composition was prepared by dispersing graphite as a negative electrode active material, SBR as a binder, and CMC as a thickener in water so that the mass ratio of these materials was 98: 1: 1. Prepared. This composition for negative electrode active material layers was apply | coated on both surfaces of the elongate sheet-like copper foil, and the negative electrode sheet by which the negative electrode active material layer was provided on both surfaces of the negative electrode collector was produced.

The separator with the LiMnPO ₄ containing layer of the evaluation cell was produced as follows. LiMnPO ₄ powder, boehmite powder as an inorganic filler, and PVdF as a binder were dispersed in NMP to prepare a paint for forming a LiMnPO ₄ containing layer. This LiMnPO ₄ -containing layer forming coating was applied to the surface (one side) of a separator (a porous polyethylene (PE) sheet was used) and dried to form a LiMnPO ₄ -containing layer.

As a non-aqueous electrolyte for the evaluation cell, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 3: 4: 3, and LiPF as a supporting salt. ₆ was used at a concentration of about 1 mol / liter. As the non-aqueous electrolyte, a gas generator with 4% by mass of CHB added was used.

The positive electrode sheet and the negative electrode sheet were wound through two separators to produce a wound body, and the wound body was crushed from the lateral direction to produce a flat wound electrode body. At that time, the LiMnPO ₄ containing layer formed on the surface of the separator was disposed so as to face the positive electrode active material layer. The wound electrode body thus obtained was housed in a box-shaped battery case (in this case, an aluminum battery case was used) together with the electrolyte, and the opening of the battery case was sealed. Thus, the lithium ion secondary battery of the evaluation cell was constructed. The lithium ion secondary battery includes a current interruption mechanism 90 (see FIG. 1). The rated capacity of such a lithium ion secondary battery is 20 Ah.

<Samples 1-6>
In this example, the LiMnPO ₄ containing layer was formed by changing the blending ratio of LiMnPO ₄ and alumina. Table 1 shows the basis weight of each sample of LiMnPO ₄ and alumina.

  In order to evaluate the overcharge behavior of the lithium ion secondary batteries of Samples 1 to 6, each battery was charged until the current interruption mechanism was activated, and the maximum temperature of the battery when the current interruption mechanism was activated was examined. It was. The battery temperature was measured by attaching a thermocouple to the outer surface of the battery. The results are shown in Table 1 and FIG.

  In addition, in order to evaluate the output characteristics of the lithium ion secondary batteries of Samples 1 to 6, each battery was placed in a thermostatic bath at −10 ° C., and low output discharge was performed at 250 W, 300 W, and 350 W. The output value (W) output in 5 seconds was calculated from the time when the voltage reached 0.0 V and the output value at that time. The results are shown in Table 1 and FIG.

As shown in Table 1 and FIG. 5, in Sample 1, the LiMnPO ₄ layer disposed between the positive electrode active material layer and the separator does not contain LiMnPO ₄ . In Sample 1, since the time until the current interrupting mechanism was activated was long, the battery temperature during overcharging reached 185 ° C. On the other hand, in Samples 2 to 6, LiMnPO ₄ is contained in the LiMnPO ₄ layer disposed between the positive electrode active material layer and the separator. In Samples 2 to 6, the current interruption mechanism operated efficiently, so that the battery temperature during overcharging was lower than that of Sample 1. In the case of the battery used here, the battery temperature tended to decrease as the basis weight of LiMnPO ₄ increased. From the viewpoint of efficiently operating the current interruption mechanism, the basis weight of LiMnPO ₄ is suitably 0.25 mg / cm ² or more, preferably 0.5 mg / cm ² or more, particularly preferably 0.8. 75 mg / cm ² or more.

In Samples 2 to 5, the basis weight of LiMnPO ₄ is set to 1 mg / cm ² or less. In Samples 2 to 5, the output at low temperature was approximately 300 W, and good characteristics were exhibited. On the other hand, in sample 6, the basis weight of LiMnPO ₄ is set to 1.25 mg / cm ² . In Sample 6, the output at low temperature was less than 285 W, and the characteristics were deteriorated compared to Samples 2-5. From the viewpoint of improving the output characteristics at low temperatures, the basis weight of LiMnPO ₄ are appropriate to below 1.2 mg / cm ^2, is preferably 1 mg / cm ² or more, particularly preferably 0.9 mg / cm ² or less.

Although the lithium ion secondary battery according to one embodiment of the present invention has been described above, the secondary battery according to the present invention is not limited to any of the above-described embodiments, and various modifications can be made. For example, in the above-described embodiment, the case where the LiMnPO ₄ containing layer 80 is formed on the surface of the separator 70 is exemplified, but the present invention is not limited to this. The LiMnPO ₄ containing layer 80 may be formed on the surface of the positive electrode active material layer 54. Even in this case, the above-described effects can be obtained.

20 Winding electrode body 30 Battery case 50 Positive electrode sheet 52 Positive electrode current collector 54 Positive electrode active material layer 60 Negative electrode sheet 62 Negative electrode current collector 64 Negative electrode active material layer 70 Separator 80 LiMnPO ₄ containing layer 90 Current blocking mechanism 100 Lithium ion secondary battery

Claims (1)

An electrode body comprising: a positive electrode in which a positive electrode active material layer is held on a positive electrode current collector; a negative electrode in which a negative electrode active material layer is held on a negative electrode current collector; and a separator interposed between the positive electrode and the negative electrode; ,
A battery case that houses the electrode body;
An external terminal provided in the battery case and connected to the electrode body;
A non-aqueous electrolyte containing a gas generating agent that is contained in the battery case, reacts at a voltage equal to or higher than a predetermined voltage, and generates a gas;
When the internal pressure of the battery case becomes higher than a predetermined pressure, a current interruption mechanism that interrupts electrical connection between the electrode body and the external terminal,
Wherein between the positive electrode active material layer and the separator, LiMnPO ₄ containing layer containing LiMnPO ₄ is disposed, a non-aqueous electrolyte secondary battery.

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