JP2006261093A - Non-aqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous secondary battery which prevents overcharge and sharp object breakage from causing ignition and explosion even under special environment and the like due to increasing the capacity of a unit cell or assembling the unit cells and is excellent in safety. <P>SOLUTION: A separator of the non-aqueous secondary battery is composed in a plurality of layers, and a non-aqueous electrolyte of the non-aqueous secondary battery is doped with an aromatic compound having a benzene ring and/or a phosphagen derivative. The non-aqueous electrolyte is doped preferably with both of the aromatic compound and the phosphagen derivative, where a mass ratio of the aromatic compound to the electrolyte is 3 to 15%, and a mass ratio of the phosphagen derivative to the electrolyte is 1 to 15%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-aqueous secondary battery, and more particularly to a high-capacity non-aqueous secondary battery having a unit cell capacity exceeding 1.5 Ah.

  2. Description of the Related Art In recent years, electronic devices have become rapidly portable and cordless, and there is a strong demand for secondary batteries that are small and lightweight, have high capacity, and high voltage as power sources for driving these devices. In this respect, non-aqueous electrolyte secondary batteries, particularly lithium ion secondary batteries, are particularly expected as batteries having high energy density. However, as the energy becomes higher, it becomes difficult to ensure the safety of the battery, and an abnormal situation at the time of overcharging causes ignition and explosion, which is very dangerous.

  Therefore, conventionally, improvement of various separators, flame-retardant or non-flammable electrolytes containing additives such as phosphazene compounds as disclosed in Patent Document 1, physical safety mechanism (current cutoff valve, vent vent), etc. Safety measures are taken. Moreover, as disclosed in Patent Documents 2 to 4, many means for ensuring the safety of the unit cell during overcharge by adding an aromatic compound to the electrolytic solution are also used.

  In addition, even in abnormal situations such as damage to the battery due to sharp objects, ignition and rupture may occur, resulting in a very dangerous state. A substance uncoated part is provided or a metal foil is inserted. In addition, safety measures are taken such as mixing various additives into the electrolytic solution and forming an electrode surface coating by aging or the like.

As another method, Patent Document 5 discloses a technique in which two types of separators are arranged between electrodes in order to prevent a large current from flowing due to a short circuit due to nail penetration or the like. Further, in Patent Documents 6 and 7, an extensible film is provided on the electrode surface or the battery container, and when the nail is stabbed, the film is stretched together with the nail or the like and is sandwiched between the electrodes. What prevents flow is disclosed.
JP 2002-83628 A JP 05-036439 A JP 2001-015155 A JP 2004-006164 A JP-A-10-302749 JP 2000-21386 A JP 2002-151159 A

  However, when the battery size is increased, especially when the capacity is increased, the conventional safety measures cannot follow the enormous amount of heat generated during overcharging, and there is a possibility of ignition and explosion. In addition, when multiple large-sized and high-capacity unit cells are connected to form an assembled battery, heat from the unit cells is accumulated in the assembled battery case, and overcharging proceeds in a high-temperature environment, resulting in ignition. there is a possibility. In addition, when the protection circuit fails, the unit cell is exposed to an overcharged state. At that time, the charger power supply voltage varies depending on the number of units connected in series in the assembled battery, and the unit cell has 12V, 30V, 50V, Voltage is applied at various levels of 100V. And the unit cell overcharged state changes depending on the upper limit voltage, and it is difficult to ensure safety especially at 50V or more.

  On the other hand, in small batteries (small capacity) for portable terminals of about 500 mAh, there are many means for ensuring unit cell safety during overcharge by adding an aromatic compound to the electrolyte as in Patent Documents 2 to 4. It is used. However, with this safety measure, it becomes difficult to prevent dangers such as ignition and explosion during overcharge as the capacity of the unit cell increases. In particular, the occurrence of problems becomes significant when the capacity exceeds 1.5 Ah. It was.

  This seems to be due to the following reasons. Usually, an aromatic compound having a benzene ring starts a polymerization decomposition reaction on the surface of the positive electrode in the vicinity of 4.2 V to 4.7 V to constitute a polymer polymerization film. Further, the gas generated at the same time causes a phenomenon in which the separator is locally peeled from the positive electrode, which makes it difficult for lithium ions to move between the positive electrode and the negative electrode. Therefore, the charging current in the secondary battery is suppressed. On the other hand, the part where the separator does not peel from the positive electrode is in contact with the surface of the positive electrode for a while, but the porous film separator that is generally used shrinks and dissolves due to the exothermic reaction when the polymerization proceeds. However, the positive electrode polymerized film is destroyed, and the positive electrode and the negative electrode may cause an internal short circuit in an unstable state of 4.2 V (full charge) or more, resulting in ignition and rupture.

  In addition, when the battery has a high energy density and a high capacity, the conventional safety measures cannot suppress the enormous amount of heat generated at the time of internal short-circuiting when the unit cell is destroyed by sharps, and there is a problem that ignition and explosion occur. there were. For example, when a sharp object such as a nail pierces a unit cell, the separator between the positive and negative electrodes enters the crack of the electrode together with the sharp object, and covers the electrode. Otherwise, there is a problem of internal short circuit between the positive and negative electrodes. As a measure for preventing an internal short circuit when a sharp object is stuck in a unit cell, a method of increasing the thickness of the separator can be considered. For example, 25 μm is usually doubled to 50 μm. However, even with a thicker separator, when a sharp object is pierced, the separator does not tear uniformly and cannot completely cover the electrode, so that there is a possibility of contact with the electrode. In this case, if an internal short circuit occurs through a sharp object, boiling of the electrolyte solution due to an enormous amount of heat generation or positive electrode thermal runaway may be induced, resulting in a large amount of smoke, rupture, or ignition.

  In addition, there is a risk that the risk of battery rupture due to a puncture accident of a unit cell may increase due to a decrease in heat dissipation due to high temperature environment such as midsummer or battery assembly.

  On the other hand, according to the methods as disclosed in Patent Documents 5 to 7, although there is a certain effect as a measure against unit cell destruction by sharps, in a high-capacity battery, even if a minute short circuit occurs, the thermal runaway of the positive electrode As a result, the battery falls into a dangerous state, which is insufficient as a safety measure.

  The present invention has been made in view of the above-mentioned problems of the prior art, and when a unit cell is increased in energy, capacity, or assembled battery, even if it is in a special environment such as a high temperature environment, the thermal runaway of the battery The purpose is to prevent.

  That is, the first object of the present invention is to provide a non-aqueous secondary battery that is excellent in safety even when overcharge occurs due to a failure of an electronic circuit. Another object of the present invention is to provide a non-aqueous secondary battery that prevents ignition and rupture when a sharp object is damaged and is excellent in safety.

  The present invention relates to a non-aqueous two-component battery in which a negative electrode containing an active material capable of occluding and releasing lithium ions and a positive electrode containing a lithium-containing oxide are laminated or wound through a separator and housed in a container with a non-aqueous electrolyte. In the secondary battery, the separator is composed of a plurality of layers, and a non-aqueous secondary battery in which an aromatic compound having a benzene ring is added to the electrolyte is provided.

  Further, the present invention provides a non-contained structure in which a negative electrode containing an active material capable of occluding and releasing lithium ions and a positive electrode containing a lithium-containing oxide are laminated or wound through a separator and stored in a storage container together with a non-aqueous electrolyte. In the water secondary battery, the separator is composed of a plurality of layers, and a non-aqueous secondary battery in which a phosphazene derivative is added to the electrolyte is provided.

  According to the non-aqueous secondary battery of the present invention, the separator is composed of a plurality of layers, and an aromatic compound having a benzene ring is added to the electrolyte, so that even when the capacity is increased, the safety at the time of overcharge is achieved. Can be improved. Similarly, by forming a separator with a plurality of layers and adding a phosphazene derivative to the electrolyte, safety can be improved in the case of damage due to sharp objects such as nails, even in a battery with an increased capacity.

  Furthermore, by adding both the aromatic compound and the phosphazene derivative, particularly excellent safety can be realized.

  Hereinafter, embodiments of the non-aqueous secondary battery of the present invention will be described. FIG. 1 schematically shows the appearance and the inside of a nonaqueous secondary battery 10 of the present invention, in which a laminate 12 in which negative electrodes and positive electrodes are alternately laminated via a separator composed of a plurality of layers. Represents the state of being accommodated in the aluminum laminate container 14 together with the non-aqueous electrolyte. Here, the negative electrode, the positive electrode, the separator, and the nonaqueous electrolyte are not shown.

  The negative electrode has a negative electrode active material, a conductive auxiliary agent and a binder such as polyvinylidene fluoride and polytetrafluoroethylene applied in a paste form with a solvent, dried, and dried to a thickness of 30 to 300 μm. It is produced by forming a negative electrode active material-containing coating film. The negative electrode active material is not particularly limited, but it is preferable to use carbon materials such as graphite, pyrolytic carbons, cokes, and glassy carbons that can be doped and dedoped with lithium ions. It is preferable to use a copper foil having a thickness of 5 to 60 μm for the current collector. Further, the negative electrode lead terminal 18 is electrically connected to the negative electrode current collector, and is led out of the container 14.

The positive electrode is also manufactured in the same manner as the negative electrode. Examples of the positive electrode active material include lithium cobalt oxide such as LiCoO ₂ , lithium manganese oxide such as LiMn ₂ O ₄ , and lithium nickel oxide such as LiNiO _2. Lithium composite oxides exemplified by these materials are preferably used. Co, Mn, or Ni of these active materials may be substituted with other elements, respectively, or a plurality of active materials may be mixed and used. Further, as the positive electrode current collector, an aluminum foil having a thickness of 5 to 60 μm is suitable, and the positive electrode lead terminal 16 is electrically connected to the positive electrode current collector and led out of the housing container 14.

  In the present invention, a multilayer separator is interposed between the positive electrode and the negative electrode. The individual separators constituting each layer may be a laminated body that is laminated and integrated, or may be a simple laminate of two or more independent separators. The material of each layer is not particularly limited, such as polyethylene, polypropylene, a fusion of polyethylene and polypropylene, polyethylene terephthalate, polybutylene terephthalate, etc., but the air permeability is 600 (s / 100 ml) or less and the thickness of one separator layer is 5 μm. It is preferably ˜50 μm and a porosity of 30% to 80%. In particular, the air permeability is more preferably 300 (s / 100 ml) or less, the thickness of one separator layer is more preferably 30 μm or less, and the porosity is 45% to 70%. Preferably, at least one layer is in this range.

  Also, the form of each layer of the separator is not particularly limited, and a woven fabric, a non-woven fabric (for example, composed of fibers and having no directionality), a porous film (for example, taking a film resin at the time of manufacture) Any one having a directional property such as a different heat shrinkage rate in a direction and a direction perpendicular thereto can be used, and each layer has the same form as a combination of nonwoven fabrics or porous films. There may be different forms such as a combination of a nonwoven fabric and a porous film.

  When the material and form are different on both sides of the separator, the effect may vary depending on the arrangement. In the case where the porosity is different on both sides of the separator, it is desirable to dispose the separator so that the porosity on the positive electrode side is higher than the porosity on the negative electrode side. Here, when the nonwoven fabric faces both the positive electrode and the negative electrode, it is desirable that the porosity of the separator on the positive electrode side is 60% or more, and the porosity of the separator on the negative electrode side is lower than 60%. . When the porous film faces both the positive electrode and the negative electrode, the porosity of the separator on the positive electrode side should be 50% or more, and the porosity of the separator on the negative electrode side should be lower than 50%. desirable. However, if the porosity is too low, the cycle performance, the low temperature performance, and the load performance are remarkably reduced due to insufficient amount of the electrolyte, so the porosity should be 30% or more.

  With the above arrangement, the liquid retention of the positive electrode separator is increased, and more aromatic additives can be held on the positive electrode surface. For this reason, a strong film is produced on the positive electrode and a large amount of gas is generated. The generated gas promotes peeling between the separator layers and between the separator and the negative electrode, and the effect of preventing thermal runaway of the positive electrode is enhanced. On the other hand, heat generation due to decomposition of the electrolyte in the negative electrode can be suppressed by reducing the liquid retention on the negative electrode side.

  For the same reason as described above, in the case of a combination of a nonwoven fabric and a porous film, it is desirable to dispose the nonwoven fabric on the positive electrode side. Even when a phosphazene derivative is added, if the liquid retention property of the positive electrode separator is high, the thermal stability of the positive electrode is increased, and thus the safety can be further improved.

  Furthermore, when the flatness differs between both surfaces of the separator, it is desirable to dispose the separator so that the unevenness of the separator surface on the negative electrode side is smaller than that on the positive electrode side, and the surface with better flatness is on the negative electrode side. If the flatness of the separator surface on the negative electrode side becomes high, the gas generated at the time of abnormality will easily peel off the gap between the negative electrode and the separator or between each layer of the separator, stopping the electrode reaction, This is because it increases the safety.

As the non-aqueous electrolyte used in the present invention, a solute such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ was dissolved in an organic solvent such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate. Examples thereof, or those obtained by mixing a resin and a cross-linking agent into a gel or solidifying it, can be exemplified by a liquid electrolyte (so-called electrolytic solution). preferable. These nonaqueous electrolytes are further added with at least one additive selected from aromatic compounds having a benzene ring and phosphazene derivatives.

  The aromatic compound is not particularly limited as long as it decomposes in the vicinity of 4.2 V to 4.7 V to generate gas, and polymerizes to form a film on the positive electrode surface, and includes toluene, xylene, Illustrative examples include alkylbenzenes such as cyclohexylbenzene, aromatic halogens, aromatic amines, aromatic carboxylic acids, and biphenyl, which are selected from biphenyl and cyclohexylbenzene from the viewpoint of film formation. At least one compound or a derivative thereof (such as a fluorine-substituted product) is preferably used.

  In addition, as the phosphazene derivative, both a cyclic type and a chain type can be used. However, in consideration of battery characteristics such as load characteristics, those having a cyclic structure represented by the following general formula are preferably used. It is done.

ただし、側鎖Ｒは、
１）−ＣＨ_３、−ＣＨ_２ＣＨ_３などの炭素数１〜１０のアルキル基（ただし、水素の一部または全部がフッ素などのハロゲン元素で置換されていてもよい）
２）−ＯＣＨ_３、−ＯＣＨ_２ＣＨ_３、−ＯＣ_６Ｈ_５、−ＯＣＨ_２ＯＣＨ_２ＣＨ_３などの炭素数１〜１０のアルコキシ基（ただし、水素の一部または全部がフッ素などのハロゲン元素で置換されていてもよい）
３）−ＣＯＯＣＨ_３、−ＣＯＯＣＨ_２ＣＨ_３、−ＣＯＯＣ_６Ｈ_５などの炭素数１〜１０のカルボキシル基（ただし、水素の一部または全部がフッ素などのハロゲン元素で置換されていてもよい）
４）−ＣＯＣＨ_３、−ＣＯＣＨ_２ＣＨ_３、−ＣＯＣ_６Ｈ_５などの炭素数１〜１０のカルボニル基（ただし、水素の一部または全部がフッ素などのハロゲン元素で置換されていてもよい）
５）−Ｃ_６Ｈ_５、−Ｃ_６Ｈ_４ＣＨ_３、−Ｃ_６Ｈ_５（ＣＨ_３）_２などの炭素数１〜１２のアリール基（ただし、水素の一部または全部がフッ素などのハロゲン元素で置換されていてもよい）
６）−ＣＨ＝ＣＨ_２、−ＣＨ＝ＣＨ_２Ｃ_２Ｈ_５、−ＣＨ＝ＣＨ_２Ｃ_６Ｈ_５などの炭素数１〜１０のビニル基（ただし、水素の一部または全部がフッ素などのハロゲン元素で置換されていてもよい）
７）水素またはフッ素、塩素などのハロゲン元素
のいずれかであって、６個のＲは互いに同じであっても異なっていてもよい。

However, the side chain R is
₁₎ -CH 3, alkyl group having 1 to 10 carbon atoms, such as _-CH 2 CH ₃ (although some hydrogen or all may be substituted with a halogen element such as fluorine)
2) Alkoxy groups having 1 to 10 carbon atoms such as —OCH ₃ , —OCH ₂ CH ₃ , —OC ₆ H ₅ , —OCH ₂ OCH ₂ CH ₃ (however, part or all of hydrogen is a halogen element such as fluorine) May be substituted)
_{3) -COOCH 3, -COOCH 2 CH} 3, -COOC 6 H 5 carboxyl group having 1 to 10 carbon atoms, such as (but part of hydrogen or all may be substituted with a halogen element such as fluorine)
4) A carbonyl group having 1 to 10 carbon atoms such as —COCH ₃ , —COCH ₂ CH ₃ , —COC ₆ H ₅ (however, part or all of hydrogen may be substituted with a halogen element such as fluorine)
5) an aryl group having 1 to 12 carbon atoms such as —C ₆ H ₅ , —C ₆ H ₄ CH ₃ , —C ₆ H ₅ (CH ₃ ) ₂ (provided that part or all of hydrogen is halogen such as fluorine) May be substituted with an element)
6) A vinyl group having 1 to 10 carbon atoms such as —CH═CH ₂ , —CH═CH ₂ C ₂ H ₅ , —CH═CH ₂ C ₆ H ₅ (provided that part or all of hydrogen is fluorine or the like) May be substituted with a halogen element)
7) Any of hydrogen, halogen elements such as fluorine and chlorine, and six Rs may be the same or different from each other.

  The addition amount of the additive is preferably 2% to 15% (mass ratio) with respect to the electrolyte solution for aromatic compounds, and 1% to 15% (mass ratio) with respect to the electrolyte solution for phosphazene derivatives. ). Moreover, it is desirable to add both of these compounds.

  The above-described negative electrode and positive electrode are formed into a laminated body 12 with a separator interposed therebetween, and the laminated body 12 is left as it is or is wound and enclosed in a storage container 14 together with a non-aqueous electrolyte. Battery 10 is produced. As the container 14, a can such as aluminum or SUS, or an exterior material obtained by laminating a thin metal foil of these materials with nylon, polyethylene, or polypropylene can be used.

  In the present invention, the separator is composed of a plurality of layers so that the separators 2 and 6 sufficiently cover the nail 4 even when a sharp object such as the nail 4 is stuck in the battery as shown in FIG. Therefore, an internal short circuit between the positive and negative electrodes via the nail 4 can be prevented.

  On the other hand, when a sharper object such as a cutter is stuck in the battery, short-circuit prevention at the separator becomes insufficient, and short-circuiting between the positive and negative electrodes, which are partially exposed, is likely to occur. However, since the thermal stability of the positive electrode is improved by adding the phosphazene derivative to the electrolyte, thermal runaway of the positive electrode due to the short circuit can be prevented.

  Tables 1 and 2 show the overcharge test results of the non-aqueous secondary battery according to one embodiment of the present invention. In this overcharge test, four types of nonaqueous secondary batteries in which the conditions of the separator inserted between each positive electrode and negative electrode forming the laminate are changed are used. One is a non-woven fabric formed from polypropylene fibers, which uses one or two sheets having an air permeability of 7 (s / 100 ml), a thickness of 25 μm, and a porosity of 70%. The other is one made of a polypropylene porous film, having a permeability of 500 (s / 100 ml), a thickness of 25 μm, and a porosity of 54%.

Further, in each condition, LiPF ₆ was dissolved at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio (mass ratio) of 50:50, and biphenyl as an aromatic compound was further dissolved. A non-aqueous electrolyte was used that was added at a mass ratio of 0% (no addition), 3%, 5%, and 10%.

  Each battery formed in this way was fully charged with a constant current of 2A (0.2C) and a constant voltage of 4.2V, then discharged to 3V with a constant current of 2A, and a non-aqueous battery with a capacity of 10Ah. A secondary battery was obtained. The results of the overcharge test performed using this battery are as shown in Table 1.

  The tests shown in Table 1 were conducted under a charging method: 10 A (1 C) constant current / 12 V constant voltage, and an environmental temperature: room temperature (20 ° C.). Five batteries were used for each condition. Thus, it was confirmed whether abnormalities were observed after the test.

  Furthermore, using the non-aqueous secondary battery produced in the same manner as in the above example, the environmental temperature is set to 20 ° C. to 40 ° C., assuming that there is a problem due to a decrease in heat dissipation when charging as a battery pack in summer. The overcharge test was conducted by changing the upper limit voltage from 12V to 100V. The test results were as shown in Table 2. The test was conducted at a charging method: 10 A (1 C) constant current / 100 V constant voltage and an environmental temperature: 40 ° C., and in the same manner as in the test of Table 1, five batteries were used for each condition. Confirmed whether or not.

  Tables 1 and 2 show the number of batteries in which abnormalities were found in each of the above tests.

  According to this overcharge test result, as shown in Tables 1 and 2, even a single cell of a large capacity non-aqueous secondary battery such as a capacity of 10 Ah used in the test or a combination battery obtained by combining a plurality of them. It was confirmed that safety was ensured even when exposed to a very dangerous state of overcharging. This is because it was impossible for one separator to withstand overcharge in spite of the presence of the additive, but using two separators seems to have caused the following new functions.

  That is, by overcharging, the aromatic compound in the electrolyte starts a polymerization decomposition reaction on the surface of the positive electrode, and is integrated with the separator to form a polymer polymerization film on the surface of the positive electrode. The other separator is peeled off from the separator integrated with the separator, and the separator is also peeled off from the negative electrode. For this reason, since there is no portion where the positive electrode and the negative electrode are in close contact with each other through the separator, the risk that the separator is melted due to the exothermic reaction due to the concentration of the charging current is reduced.

  Table 3 shows the nail penetration test results of the nonaqueous secondary battery according to another embodiment of the present invention, and Table 4 shows the cutter penetration test results.

  In addition, in the above test, instead of the non-aqueous electrolyte used in Example 1, phoslite (trade name, manufactured by Bridgestone), which is a cyclic phosphazene derivative represented by the above general formula, was used in a mass ratio of 0% (none Addition) A battery manufactured in the same manner as each battery of Example 1 was used except that the nonaqueous electrolyte added at a ratio of 2%, 3%, 5%, and 10% was used.

  The respective batteries were charged and discharged in the same manner as in Example 1 to obtain a non-aqueous secondary battery having a capacity of 10 Ah.

  In addition, the nail penetration test shown in Table 3 was conducted by passing a battery through a battery at room temperature (20 ° C.) with a nail diameter of 3 mm and a nail penetration speed of 1 mm / s. Used to check if any abnormalities were observed after the test. In addition, the cutter penetration test shown in Table 4 was conducted by inserting a cutter with a blade width of 9 mm into the battery surface at an arbitrary speed at room temperature (20 ° C.), and using 5 batteries for each condition. Thus, it was confirmed whether abnormalities were observed after the test. Further, Table 5 shows the test results obtained by changing the room temperature in Table 4 from 20 ° C. to 40 ° C., assuming a decrease in heat dissipation when an assembled battery is used.

  Tables 3 to 5 show the number of batteries in which abnormality was observed in each of the above tests.

  As is clear from the results of Tables 3 to 5, even in the case of a single battery or a combination battery with poor heat dissipation, which is a combination of a plurality of cells, safety that does not cause an abnormality such as ignition or rupture at the time of battery destruction due to sharp damage It was confirmed that a high-performance battery could be constructed.

  Hereinafter, Table 6 shows the overcharge test result, the nail penetration test result, and the cutter penetration test result of the non-aqueous secondary battery according to still another example of the present invention.

  The above test was performed using a non-aqueous electrolyte in which 3% by weight of biphenyl and 3% by weight of phoslite were added instead of the non-aqueous electrolyte used in Example 1, and the separator was configured as follows. Was carried out using a battery produced in the same manner as in Example 1. That is, in Example 3, two sheets of non-woven fabric similar to Example 1 were stacked to form a separator, two porous films similar to Example 1 were stacked to form a separator, and the non-woven fabric and porous film Three types of batteries were prepared, one by one, and a non-woven fabric on the positive electrode side and a porous film on the negative electrode side to form a separator.

  The respective batteries were charged and discharged in the same manner as in Example 1 to obtain a non-aqueous secondary battery having a capacity of 10 Ah.

  The overcharge test shown in Table 6 is performed at a charging method: 10 A (1 C) constant current / 100 V constant voltage, and the ambient temperature: room temperature (20 ° C.). The nail penetration test is performed at room temperature (20 ° C.). The battery was penetrated at a diameter of 3 mm and a nail penetration speed of 1 mm / s, and the cutter penetration test was performed at a room temperature (20 ° C.) by inserting a cutter with a blade width of 9 mm into the battery surface at an arbitrary speed. Five batteries were used for each test, and it was confirmed whether abnormality was recognized after the test.

  Further, Table 7 also shows the results of performing the same test as described above by changing the room temperature from 20 ° C. to 40 ° C., assuming that the heat dissipation is reduced due to the battery assembly.

  Tables 6 and 7 show the number of batteries in which abnormality was found in each of the above tests.

  As is clear from the results in Tables 6 and 7, even a single cell of a large-capacity non-aqueous secondary battery with high capacity and high energy density or a combination battery with a combination of a plurality of them that has poor heat dissipation, It was confirmed that particularly high safety can be ensured by adding an aromatic compound having a phosphazene derivative and a phosphazene derivative to a non-aqueous electrolyte.

It is the schematic which shows the external appearance of the non-aqueous secondary battery of this invention. It is the schematic which shows a mode that the separator has covered the nail when the nail stabbed in the non-aqueous secondary battery.

Explanation of symbols

2 1st sheet separator 4 Nail 6 2nd sheet separator 10 Non-aqueous secondary battery 12 Laminated body 14 Container 16 Positive electrode lead terminal 18 Negative electrode lead terminal

Claims (15)

  In a non-aqueous secondary battery in which a negative electrode including an active material capable of inserting and extracting lithium ions and a positive electrode including a lithium-containing oxide are stacked or wound through a separator and stored in a storage container together with a non-aqueous electrolyte. A non-aqueous secondary battery, wherein the separator is composed of a plurality of layers, and an aromatic compound having a benzene ring is added to the electrolyte.   The non-aqueous secondary battery according to claim 1, wherein a phosphazene derivative is added to the electrolyte. The non-aqueous secondary battery according to claim 2, wherein the phosphazene derivative is a cyclic compound represented by the following general formula (1).

However, the side chain R is
₁₎ -CH 3, alkyl group having 1 to 10 carbon atoms, such as _-CH 2 CH ₃ (although some hydrogen or all may be substituted with a halogen element such as fluorine)
2) Alkoxy groups having 1 to 10 carbon atoms such as —OCH ₃ , —OCH ₂ CH ₃ , —OC ₆ H ₅ , —OCH ₂ OCH ₂ CH ₃ (however, part or all of hydrogen is a halogen element such as fluorine) May be substituted)
_{3) -COOCH 3, -COOCH 2 CH} 3, -COOC 6 H 5 carboxyl group having 1 to 10 carbon atoms such as (although some hydrogen or all may be substituted with a halogen element such as fluorine)
4) A carbonyl group having 1 to 10 carbon atoms such as —COCH ₃ , —COCH ₂ CH ₃ , —COC ₆ H ₅ (however, part or all of hydrogen may be substituted with a halogen element such as fluorine)
5) an aryl group having 1 to 12 carbon atoms such as —C ₆ H ₅ , —C ₆ H ₄ CH ₃ , —C ₆ H ₅ (CH ₃ ) ₂ (provided that part or all of hydrogen is halogen such as fluorine) May be substituted with an element)
6) A vinyl group having 1 to 10 carbon atoms such as —CH═CH ₂ , —CH═CH ₂ C ₂ H ₅ , —CH═CH ₂ C ₆ H ₅ (provided that part or all of hydrogen is fluorine or the like) May be substituted with a halogen element)
7) Any of hydrogen, halogen elements such as fluorine and chlorine, and six Rs may be the same or different from each other.   The non-aqueous secondary battery according to claim 2 or 3, wherein the addition amount of the phosphazene derivative is 1 to 15% by mass ratio with respect to the electrolyte.   The nonaqueous secondary battery according to any one of claims 1 to 4, wherein an addition amount of the aromatic compound having a benzene ring is 2 to 15% by mass ratio with respect to the electrolyte.   The nonaqueous secondary battery according to claim 1, wherein the aromatic compound having a benzene ring is at least one compound selected from biphenyl and cyclohexylbenzene or a derivative thereof.   In a non-aqueous secondary battery in which a negative electrode including an active material capable of inserting and extracting lithium ions and a positive electrode including a lithium-containing oxide are stacked or wound through a separator and stored in a storage container together with a non-aqueous electrolyte. A non-aqueous secondary battery, wherein the separator is composed of a plurality of layers, and a phosphazene derivative is added to the electrolyte. The non-aqueous secondary battery according to claim 7, wherein the phosphazene derivative is a cyclic compound represented by the following general formula (2).

However, the side chain R is
₁₎ -CH 3, alkyl group having 1 to 10 carbon atoms, such as _-CH 2 CH ₃ (although some hydrogen or all may be substituted with a halogen element such as fluorine)
2) Alkoxy groups having 1 to 10 carbon atoms such as —OCH ₃ , —OCH ₂ CH ₃ , —OC ₆ H ₅ , —OCH ₂ OCH ₂ CH ₃ (however, part or all of hydrogen is a halogen element such as fluorine) May be substituted)
_{3) -COOCH 3, -COOCH 2 CH} 3, -COOC 6 H 5 carboxyl group having 1 to 10 carbon atoms such as (although some hydrogen or all may be substituted with a halogen element such as fluorine)
4) A carbonyl group having 1 to 10 carbon atoms such as —COCH ₃ , —COCH ₂ CH ₃ , —COC ₆ H ₅ (however, part or all of hydrogen may be substituted with a halogen element such as fluorine)
5) an aryl group having 1 to 12 carbon atoms such as —C ₆ H ₅ , —C ₆ H ₄ CH ₃ , —C ₆ H ₅ (CH ₃ ) ₂ (provided that part or all of hydrogen is halogen such as fluorine) May be substituted with an element)
6) A vinyl group having 1 to 10 carbon atoms such as —CH═CH ₂ , —CH═CH ₂ C ₂ H ₅ , —CH═CH ₂ C ₆ H ₅ (provided that part or all of hydrogen is fluorine or the like) May be substituted with a halogen element)
7) Any of hydrogen, halogen elements such as fluorine and chlorine, and six Rs may be the same or different from each other.   The non-aqueous secondary battery according to claim 7 or 8, wherein the addition amount of the phosphazene derivative is 1 to 15% by mass with respect to the electrolyte.   The non-water according to any one of claims 1 to 9, wherein the separator is a laminated body in which the same kind or different kinds of separators are laminated and integrated, or two or more separators of the same kind or different kinds are stacked. Secondary battery.   The separator is a non-woven fabric having an air permeability of 300 (s / 100 ml) or less, a porosity of 30% to 80%, and a thickness of 5 μm to 50 μm, and an air permeability of 600 (s / 100 ml). The non-water according to claim 10, wherein the non-water is composed of at least one selected from porous films having a porosity of 30% to 80% and a thickness of 5 μm to 50 μm. Secondary battery.   The non-aqueous secondary battery according to claim 11, wherein a material of the separator is at least one selected from polyethylene, polypropylene, a fusion of polyethylene and polypropylene, polyethylene terephthalate, and polybutylene terephthalate.   The nonaqueous secondary battery according to claim 1, wherein the separator has a higher porosity on the positive electrode side than on the negative electrode side. The nonaqueous secondary battery according to any one of claims 1 to 13, wherein in the separator, the unevenness on the negative electrode side surface is smaller than the unevenness on the positive electrode side surface. The nonaqueous secondary battery according to claim 1, wherein the negative electrode active material is a carbon material.

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