JP5327531B2 - Nonaqueous electrolyte battery electrode and nonaqueous electrolyte battery - Google Patents

Description

  The present invention relates to a nonaqueous electrolyte battery electrode and a nonaqueous electrolyte battery.

  With the widespread use of electronic devices such as notebook computers, mobile phones, and digital cameras, the demand for secondary batteries for driving these electronic devices is increasing. In recent years, the power consumption of these electronic devices has increased with the progress of higher functionality, and miniaturization is expected, so high energy density and high output density are required for secondary batteries. It has been. As secondary batteries that can achieve high energy density and high output density, non-aqueous electrolyte secondary batteries such as lithium ion batteries are considered promising.

  However, lithium-ion batteries use highly chemically active lithium, highly flammable electrolytes, and lithium transition metal composite oxides with low stability in overcharged states as battery materials. Furthermore, it is known that when charging is continued, a chemical reaction between the battery materials proceeds rapidly, and there is a safety problem that the battery generates heat or ignites (thermal runaway). For this reason, it is necessary to stop charging promptly before reaching the overcharged state.

  From such a problem, various methods for suppressing overcharge of the lithium ion battery have been studied, and disclosed in, for example, Patent Documents 1 and 2.

  In Patent Document 1, as a technique for increasing the resistance of an electrode due to a temperature rise associated with overcharging, cutting off a charging current and suppressing overcharging, an electrode mixture layer made of a positive electrode material or a negative electrode material, a current collector, In the electrode having the laminated structure, an electrode containing thermally expandable microcapsules in the electrode mixture layer or along the interface between the electrode mixture layer and the current collector is disclosed.

  Patent Document 2 discloses an exposed portion of a positive electrode current collector as a technique for suppressing an overcharge by causing an internal short circuit between a positive electrode and a negative electrode due to a potential increase accompanying overcharge and leaking a charge current. And the secondary battery which provided the metal which melt | dissolves in a non-aqueous electrolyte when the battery voltage exceeds a predetermined voltage on the surface of the part facing the exposed part of the negative electrode current collector is disclosed.

  However, in the electrode described in Patent Document 1, the microcapsules contained in the electrode mixture layer or along the interface between the electrode mixture layer and the current collector expand due to temperature rise, and the electrode mixture and the collector are collected. By peeling the electric body, the resistance of the electrode is increased, the charging current is cut off, and overcharging is suppressed. As in the example, the microcapsule has a foaming start (current cut-off) temperature of 125 ° C. or higher. Because of the high temperature, the porous synthetic resin film of polyolefin polymer (polyethylene, polypropylene) generally used as a separator shrinks and melts before the start of foaming of microcapsules, causing internal short circuit between the positive and negative electrodes However, the battery may cause heat generation and thermal runaway. In addition, the lithium transition metal composite oxide is overcharged until the foaming temperature is reached, and the stability of the lithium transition metal composite oxide is further reduced. is there.

  In the secondary battery described in Patent Document 2, when the overcharged state exceeds a predetermined potential, the metal provided at the exposed portion of the positive electrode current collector is dissolved in the electrolyte, and the negative electrode current collector facing the dissolved metal It is deposited on the exposed portion of the metal to cause an internal short circuit between the positive electrode and the negative electrode, thereby forming a path for leaking the charging current, thereby preventing overcharging. Since the deposition state differs and it is difficult to control the state of the internal short circuit, if the degree of the internal short circuit is large, the battery may cause heat generation and thermal runaway.

JP 2001-332245 A JP 2006-222077 A

  SUMMARY OF THE INVENTION The present invention has been completed in view of the above circumstances, and a problem to be solved is to provide a nonaqueous electrolyte battery electrode and a nonaqueous electrolyte battery used in a nonaqueous electrolyte battery capable of suppressing overcharge. And

  In order to solve the above-mentioned problems, the present inventors have studied the electrode, and as a result, have come to make the present invention.

That is, the electrode for a non-aqueous electrolyte battery according to claim 1 of the present invention includes a positive electrode in which a positive electrode mixture layer having a positive electrode active material is formed on a current collector, and a negative electrode mixture layer having a negative electrode active material. there a non-aqueous electrolyte battery electrode for use in non-aqueous electrolyte battery comprising a negative electrode formed on a current collector, a non-aqueous electrolyte, a positive electrode, a positive electrode mixture layer and the current collector between, it has a potential dissolution agent layer having a potential dissolving agent which dissolves at a predetermined potential, which is the upper limit voltage or a potential indicated by the positive electrode active material, the potential dissolution agent, the following formula 6 formula or formula 10 formula It is a compound represented by these.

  According to claim 1, in the electrode for a non-aqueous electrolyte battery of the present invention, a potential solubilizer layer made of a potential solubilizer that dissolves at a predetermined potential is formed between the electrode mixture layer and the current collector. Yes. The potential solubilizer that forms this potential solubilizer layer is a substance that dissolves at a predetermined potential, and therefore dissolves when the potential of the electrode exceeds a predetermined potential due to overcharge or the like. When the potential dissolving agent dissolves, electrical conduction between the electrode mixture layer and the current collector cannot be obtained. That is, when the potential dissolving agent is dissolved, the electrode mixture layer and the current collector are peeled off and are not in contact with each other, and the resistance of the electrode is increased. When the resistance of the electrode increases, the current passing through the electrode (charging current) is interrupted. As a result, further increase in the potential of the electrode and further progress of charging (overcharge) can be suppressed. Thereby, the nonaqueous electrolyte battery electrode of the present invention does not cause overcharge, heat generation, and thermal runaway. Thus, the electrode for nonaqueous electrolyte batteries of the present invention exhibits the effect of suppressing the occurrence of problems due to overcharging.

  The electrode for a non-aqueous electrolyte battery according to claim 2 is used for a positive electrode having a positive electrode active material capable of occluding and releasing lithium ions in claim 1. That is, according to claim 2, the nonaqueous electrolyte battery electrode of the present invention can be more effective when used for the positive electrode of a lithium ion battery.

In the non-aqueous electrolyte battery electrode according to the present invention , the predetermined potential at which the potential dissolving agent is dissolved is a potential equal to or higher than the upper limit potential indicated by the positive electrode active material . The predetermined potential at which the potential solubilizer dissolves is equal to or higher than the upper limit potential indicated by the positive electrode active material, so that when the nonaqueous electrolyte battery electrode of the present invention is used as a positive electrode, the potential increases to a predetermined potential or higher. The effect which can suppress that is exhibited. Here, the predetermined potential is preferably a potential of 0.1 V or more from the upper limit potential indicated by the positive electrode active material, and more preferably a potential of 0.2 V or more.

In the electrode for a non-aqueous electrolyte battery of the present invention, the potential solubilizer is a compound represented by the following chemical formula 6 or chemical formula 10 .

（Ｘ及びＹは、硫黄原子、酸素原子、メチレン基から選択され、ＸとＹは同じであっても異なっていてもよい。）

(X and Y are selected from a sulfur atom, an oxygen atom, and a methylene group, and X and Y may be the same or different.)

When the potential dissolving agent is composed of the compound represented by the chemical formula (6), the above effect can be more exhibited. The potential solubilizer may be a compound represented by the general formula shown in Chemical Formula 6 (for example, a compound of the following Chemical Formulas 7 to 9) or a mixture of a plurality of types. Any of them may be used.

The electrode for a nonaqueous electrolyte battery according to claim 3 is characterized in that, in claim 1 , the potential dissolving agent is bisethylenedithiotetrathiafulvalene. According to the third aspect , when the potential dissolving agent is bisethylenedithiotetrathiafulvalene (compound of the above chemical formula 8), the above effect can be more exhibited.

（Ｒ１〜Ｒ４のそれぞれは、水素、炭素数１〜４のアルキル基より独立して選択され、Ｒ１〜Ｒ４の少なくともひとつは、下記化１１式で表される構造のいずれかである。ｎは、自然数であり、独立して選択可能である。）

(Each of R1 to R4 is independently selected from hydrogen and an alkyl group having 1 to 4 carbon atoms, and at least one of R1 to R4 is any one of structures represented by the following formula 11. It is a natural number and can be selected independently.)

（化１１（１）〜（３）は、化学式中の＊の部分が、化１０式中のベンゼン環中の炭素原子と結合する。化１１（１）〜（３）中のＲは、−Ｈ、−ＯＨ、−ＣＨ_３、−ＮＨ_２のいずれかである。化１１（１）〜（３）中のＹは、−（ＣＨ_２）ｍ−基（ｍは、０〜１０の整数）であり、ｍが１以上のときは、Ｙを構成するメチレン基の一つ以上が、下記化１２（１）〜（１０）で表される基の少なくともひとつに置換されていてもよい。）

(In the chemical formulas 11 (1) to (3), the part * in the chemical formula is bonded to the carbon atom in the benzene ring in the chemical formula 10. R in the chemical formulas 11 (1) to (3) is- Any one of H, —OH, —CH ₃ , and —NH ₂ Y in Chemical Formulas 11 (1) to (3) is a — (CH ₂ ) m— group (m is an integer of 0 to 10); And when m is 1 or more, one or more of the methylene groups constituting Y may be substituted with at least one of the groups represented by the following chemical formulas 12 (1) to (10).

The electrode for a non-aqueous electrolyte battery according to claim 4 is characterized in that, in claim 1 , the potential solubilizer is a compound represented by the following chemical formula (13).

According to Claim 4 , the effect of Claim 1 can be exhibited more because the potential dissolving agent is composed of the compound represented by Formula 13.

The electrode for a non-aqueous electrolyte battery according to claim 5 is characterized in that in any one of claims 1 to 4 , the potential dissolving agent layer has a thickness of 50 μm or less. According to the fifth aspect , the thickness of the electric potential dissolving agent layer is 50 μm or less. Thereby, it is suppressed that resistance of the electrode for nonaqueous electrolyte batteries of the present invention becomes large. Specifically, the potential solubilizer has a larger resistance value than the current collector, and as the thickness thereof increases, the resistance of the potential solubilizer layer increases and the resistance of the electrode for the nonaqueous electrolyte battery increases. Becomes larger. And when the thickness of the potential dissolving agent layer exceeds 50 μm, the resistance of the electrode itself becomes excessively large. The potential solubilizer layer may be at least as thick as the contact between the electrode mixture layer and the current collector can be regulated by the gap formed after dissolution, and is preferably about 1 μm or more.

The electrode for a nonaqueous electrolyte battery according to claim 6 is the electrode according to any one of claims 1 to 5 , wherein the positive electrode active material has the structural formula Li _1-Z α (α is CoO ₂ , MnO ₂ , Mn ₂ O _4. , NiO ₂ ) or Li _1-Z βPO ₄ (β is Fe, Mn) (Z is a number of 0 to 1), and has a lithium transition metal composite oxide containing one or more compounds. . According to Claim 6 , the effect of Claims 1-5 can be exhibited more by using the electrode for nonaqueous electrolyte batteries of this invention for the positive electrode of a lithium ion battery.

Nonaqueous electrolyte battery according to claim 7, further comprising a positive electrode of a non-aqueous electrolyte battery electrode according to any one of claims 1 to 6, a negative electrode, a nonaqueous electrolytic solution, the It is characterized by.

As described above, the electrode for a non-aqueous electrolyte battery according to any one of claims 1 to 5 is an electrode in which occurrence of problems due to overcharging is suppressed, and the battery of the present invention includes the electrode. Since it is the battery used, the effect which suppresses generation | occurrence | production of the malfunction by overcharge is exhibited.

2 is a schematic diagram illustrating a configuration of a positive electrode for a lithium ion secondary battery according to Example 1. FIG. 1 is a schematic diagram showing a configuration of a coin-type lithium ion secondary battery of Example 1. FIG.

  Hereinafter, the nonaqueous electrolyte battery electrode and the nonaqueous electrolyte battery of the present invention will be described.

  The electrode for a non-aqueous electrolyte battery of the present invention has a positive electrode mixture layer having a positive electrode active material formed on a current collector and a negative electrode mixture layer having a negative electrode active material formed on the current collector. An electrode used for a non-aqueous electrolyte battery comprising a negative electrode and a non-aqueous electrolyte.

(Positive electrode)
The positive electrode active material contained in the positive electrode mixture layer is not particularly limited, and a conventionally known positive electrode active material can be used. Examples of the positive electrode active material include a lithium transition metal composite oxide capable of releasing lithium ions. Examples of the lithium transition metal composite oxide include the compounds described in claim 8, and examples thereof include LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li ₍ CoO ₂ , LiFeO ₂ , LiFePO ₄ , LiMnPO _4. Here, the positive electrode active material is not limited to these compounds, and the lithium transition metal composite oxide is not only used alone, but also a plurality of them. One or more of lithium manganese-containing composite oxide, lithium nickel-containing composite oxide, lithium cobalt-containing composite oxide, and lithium iron-containing composite oxide can be used. It is preferable that

  The positive electrode mixture layer is prepared by mixing the positive electrode active material, the binder, and the conductive additive in a solvent such as water or NMP, and then applying the mixture on the surface of the current collector (on the potential solubilizer layer). Can be formed. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, lithium polyacrylate, EPDM, SBR, NBR, and fluororubber. Examples of the conductive assistant include ketjen black, acetylene black, carbon black, graphite, carbon nanotube, and amorphous carbon.

  The current collector is not particularly limited, and a current collector made of a conventionally known material can be used. For example, aluminum, stainless steel, nickel plated steel, etc. can be mentioned.

(Negative electrode)
The negative electrode active material contained in the negative electrode mixture layer is not particularly limited, and a conventionally known negative electrode active material can be used. As the negative electrode active material, for example, compounds capable of inserting and extracting lithium ions can be used alone or in combination. Examples of the compound capable of inserting and extracting lithium ions include metal materials such as lithium, alloy materials containing silicon and tin, graphite, coke, organic polymer compound fired bodies, and carbon materials such as amorphous carbon. it can. These active materials can be used not only alone but also as a mixture of two or more thereof. For example, when a lithium metal foil is used as the negative electrode active material, it can be formed by pressure bonding the lithium foil to the surface of a current collector made of a metal such as copper. On the other hand, when an alloy material or a carbon material is used as the negative electrode active material, the negative electrode active material, a binder, a conductive additive, etc. are mixed in a solvent such as water or NMP, and then on a current collector made of a metal such as copper. It can be applied and formed.

  The binder is desirably formed of a polymer material, and is preferably a material that is chemically and physically stable in the atmosphere in the secondary battery. For example, polyvinylidene fluoride, polytetrafluoroethylene, lithium polyacrylate, EPDM, SBR, NBR, fluororubber, and the like can be given. Examples of the conductive assistant include ketjen black, acetylene black, carbon black, graphite, carbon nanotube, and amorphous carbon.

  The current collector is not particularly limited, and a current collector made of a conventionally known material can be used. For example, aluminum, stainless steel, nickel plated steel, etc. can be mentioned.

(Nonaqueous electrolyte)
The nonaqueous electrolytic solution is not particularly limited, and a conventionally known nonaqueous electrolytic solution can be used. Examples of the non-aqueous electrolyte include a solution in which a supporting salt is dissolved in a solvent such as an organic solvent, an ionic liquid that is liquid itself, and a solution in which the supporting salt is further dissolved in the ionic liquid.

  As an organic solvent, the organic solvent used for the electrolyte solution of a lithium secondary battery can be mention | raise | lifted, for example. As the organic solvent, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, oxolane compounds and the like can be used. In particular, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like, and mixed solvents thereof are suitable. Among these organic solvents mentioned in the examples, in particular, it is possible to use one or more non-aqueous solvents selected from the group consisting of carbonates and ethers, so that the solubility, dielectric constant, viscosity, and stability of the supporting salt are increased. And the battery charge / discharge efficiency is also high.

An ionic liquid will not be specifically limited if it is an ionic liquid normally used for the electrolyte solution of a lithium secondary battery. For example, examples of the cation component of the ionic liquid include N-methyl-N-propylpiperidinium and dimethylethylmethoxyammonium cation, and examples of the anion component include BF ₄ ⁻ , N (SO ₂ CF ₃ ) ₂ ^—. Etc.

The supporting salt used in the nonaqueous electrolytic solution is not particularly limited. For example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSCN, LiClO ₄ , LiAlCl ₄ , NaClO ₄ , BClO ₄ And salt compounds such as NaI and derivatives thereof. Among these, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ One or more selected from the group consisting of a derivative of SO ₂ ) (C ₄ F ₉ SO ₂ ), a derivative of LiCF ₃ SO _3, a derivative of LiN (CF ₃ SO ₂ ) _{2 and} a derivative of LiC (CF ₃ SO ₂ ) ₃ It is preferable to use a salt from the viewpoint of electrical characteristics.

(battery)
It is preferable to interpose a separator that is a member that achieves both electrical insulation and ion conduction between the positive electrode and the negative electrode. When the electrolyte is liquid, the separator also serves to hold the liquid electrolyte. Examples of the separator include porous synthetic resin films, particularly porous films made of polyolefin polymers (polyethylene, polypropylene) and glass fibers, and nonwoven fabrics. Furthermore, it is preferable that the separator has a larger size than the positive electrode and the negative electrode for the purpose of ensuring the insulation between the positive electrode and the negative electrode.

  Components such as a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator are housed in some case to form a non-aqueous electrolyte battery. At this time, the case is not particularly limited, and can be made of a known material and form.

(Production method)
The manufacturing method of the electrode for nonaqueous electrolyte batteries and the nonaqueous electrolyte battery of the present invention is not particularly limited. For example, an electrode can be manufactured by applying and drying a paste containing a potential solubilizer on the surface of the current collector to form a potential solubilizer layer, and forming an electrode mixture layer on the surface. Then, a battery can be manufactured by a conventionally known method using this electrode.

  The potential solubilizer layer is formed by mixing the above-described potential solubilizer, a binder, a conductive additive and the like in a solvent such as water and NMP, and then applying the mixture on a current collector and drying. Examples of the binder used for the potential solubilizer layer include polyvinylidene fluoride, polytetrafluoroethylene, lithium polyacrylate, EPDM, SBR, NBR, and fluororubber. Examples of the conductive assistant include ketjen black, acetylene black, carbon black, graphite, carbon nanotube, and amorphous carbon.

  More specifically, the case where the electrode for a non-aqueous electrolyte battery of the present invention is used for a positive electrode of a lithium ion battery will be described.

  First, a paste is prepared by dispersing a potential dissolving agent (bisethylenedithiotetrathiafulvalene), a binder (PTFE), and a conductive additive (CMC) in a solvent (water). The prepared paste is applied to the surface (one side or both sides) of the positive electrode current collector (aluminum current collector foil), dried, and compressed. Thereby, a positive electrode current collector having a potential dissolving agent layer having a predetermined thickness is manufactured.

  Thereafter, a paste is prepared by dispersing a positive electrode active material (lithium transition metal composite oxide), a binder (acetylene black), and a conductive additive (PVDF) in a solvent (NMP). The prepared paste is applied, dried and compressed on the surface of the potential solubilizer layer of the positive electrode current collector. As a result, a positive electrode mixture layer was formed on the surface of the potential dissolving agent layer. That is, the nonaqueous electrolyte battery electrode (lithium ion battery positive electrode) of the present invention is produced.

  Next, the metal foil (negative electrode active material) which consists of lithium was pressed and crimped | bonded in the state arrange | positioned on the surface of the negative electrode collector (copper foil). Thereby, the negative electrode was manufactured.

  The positive electrode and the negative electrode are cut into a predetermined size and sealed in a case together with a non-aqueous electrolyte in a state of being laminated via a separator. Thereby, a lithium ion battery is manufactured.

  Hereinafter, the present invention will be specifically described with reference to examples.

Example 1
First, 94 parts by mass of bisethylenedithiotetrathiafulvalene (manufactured by Tokyo Chemical Industry Co., Ltd.) represented by the above chemical formula 8, 3 parts by mass of polytetrafluoroethylene (PTFE), and carboxymethylcellulose (CMC) 3 parts by mass were prepared, and water was added to mix and disperse to prepare a homogeneous paste. This paste was applied to the surface (one side) of an aluminum current collector (50 μm), dried and pressed to produce a potential solubilizer layer on the surface of the current collector. The thickness of the prepared potential solubilizer layer was 80 μm including the thickness of the current collector. That is, the thickness of the potential dissolving agent layer was 30 μm.

Next, 82 parts by mass of LiFePO ₄ , 10 parts by mass of acetylene black, and 8 parts by mass of polyvinylidene fluoride (PVDF) were prepared, and normal methylpyrrolidone (NMP) was added, mixed, dispersed, and homogeneous A paste was prepared. This paste was applied on the potential solubilizer layer prepared above, dried, pressed, and then cut into a predetermined size to produce a positive electrode. The thickness of the produced positive electrode including the aluminum current collector and the potential solubilizer layer was 170 μm. The positive electrode of this example was formed on a current collector having a thickness of 50 μm, a potential solubilizer layer having a thickness of 30 μm formed on the current collector, and a potential solubilizer layer as shown in FIG. And a positive electrode mixture layer having a thickness of 90 μm.

(Preparation of negative electrode)
A lithium metal foil with a thickness of 300 μm was pressure-bonded to a copper current collector and cut into a predetermined size to produce a negative electrode.

(Preparation of non-aqueous electrolyte)
Ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7, and LiPF ₆ as a supporting electrolyte is dissolved in the mixed organic solvent so as to have a concentration of 1 mol / L. A water electrolyte was used.

(Evaluation of positive electrode)
As the evaluation of the positive electrode, the dissolution behavior of the potential solubilizer layer was confirmed. Specifically, first, a three-electrode cell using the positive electrode as a working electrode, a negative electrode as a counter electrode, and lithium metal as a reference electrode was prepared, and a potentio / galvanostat device (manufactured by solartron, model 1480 multistat) was used. Thus, the sweep was performed at a sweep rate of 10 mV / s and a potential range of 2.5 to 4.2 V.

  At the time of sweeping, generation of a blue melt was confirmed from the positive electrode surface at about 3.7V. This lysate is a potential solubilizer constituting the potential solubilizer layer. That is, the potential solubilizer (bisethylenedithiotetrathiafulvalene) constituting the potential solubilizer layer dissolves at a potential of approximately 3.7V. Then, the positive electrode mixture layer was peeled off from the current collector due to the dissolution of the potential solubilizer layer, and was brought up. As a result, it was confirmed that the positive electrode mixture layer was lifted (peeled) from the current collector, whereby the positive electrode of this example had increased resistance between the positive electrode mixture layer and the current collector.

(Production of coin-type battery)
A plate-shaped electrode body was formed by laminating the positive electrode and the negative electrode with a polypropylene separator interposed therebetween. At this time, the positive electrode and the negative electrode were laminated in a state where the respective mixture layers were opposed to each other with a separator interposed therebetween. The obtained flat electrode body was inserted into the case and held in the case. Then, after inject | pouring the said electrolyte solution in the case holding the flat electrode body, the case was sealed and sealed. Thereby, the coin-type battery of this example was manufactured. The configuration of the coin-type battery of this example is shown in FIG.

  In the battery 1 of this example, a polyethylene porous film having a thickness of 25 μm was used as the separator 7. In the battery 1 of the present embodiment, the case in which the electrode body and the like are accommodated includes a positive electrode case 50 and a negative electrode case 51, each of which is formed of stainless steel. The positive electrode case 50 and the negative electrode case 51 also function as a positive electrode terminal and a negative electrode terminal. Between the positive electrode case 50 and the negative electrode case 51, a gasket 6 made of polypropylene is interposed to ensure sealing and insulation between the bipolar cases 50 and 51.

  The battery 1 of the present embodiment is a coin type battery having a diameter of 19 mm and a thickness of 3 mm, which is configured as described above.

(Initial capacity)
The initial discharge capacity of the battery 1 of the present embodiment, 3.6V until a constant current charge at a current value of 0.1 mA / cm ^2, a constant current discharge at a current value of 0.1 mA / cm ² to 2.0V This was repeated five times, and the capacity obtained in the last discharge was defined as the initial capacity.

(Battery evaluation)
As an evaluation of the battery of this example, the current interruption effect during battery overcharge was observed. The current interruption effect at the time of overcharge of the battery was implemented by confirming the discharge capacity characteristics and charge / discharge behavior of the battery when the upper limit voltage at the time of charge was changed.

Specifically, after performing constant current constant voltage charging to 3.6 V at a current value of 0.1 mA / cm ² for 24 hours, constant current discharge was performed at a current value of 0.1 mA / cm ² . The discharge capacity at the time of discharge was almost the same as the initial capacity, and it was possible to charge and discharge again after the test.

And after performing the constant current constant voltage charge to 4.2V for 24 h with the electric current value of 0.1 mA / cm < ² >, the constant current discharge was carried out with the electric current value of 0.1 mA / cm < ² >. The discharge capacity at this time was only 0.8% of the initial capacity.

  According to the above results, when charging was performed at 3.6 V, which is a voltage equal to or lower than the upper limit potential (3.6 V) of the positive electrode (positive electrode active material) of the battery of this example, no decrease in discharge capacity was observed. High battery performance as a lithium ion battery could be demonstrated. Then, when charging was performed at 4.2 V, which is a potential (voltage) larger than the upper limit potential of the positive electrode (positive electrode active material) of the battery of this example, the discharge capacity disappeared and the battery did not function. This is because the potential of the positive electrode becomes equal to or higher than the potential at which the potential solubilizer layer dissolves, and the potential solubilizer layer dissolves. That is, the positive electrode mixture layer peels off from the current collector and does not come into contact, and does not function as the positive electrode. As a result, subsequent charging / discharging became impossible.

  As described above, it was confirmed that the battery of this example was a battery capable of exhibiting performance as a lithium ion battery and capable of suppressing overcharge during normal charging and discharging.

(Example 2)
First, 90 parts by mass of bisethylenedithiotetrathiafulvalene (same as Example 1), 4 parts by mass of acetylene black, 3 parts by mass of PTFE, and 3 parts by mass of CMC were prepared, and water was added. Were mixed and dispersed to prepare a homogeneous paste. This paste was applied to the surface (one side) of an aluminum current collector (50 μm), dried and pressed to produce a potential solubilizer layer on the surface of the current collector. The thickness of the prepared potential solubilizer layer was 80 μm including the thickness of the current collector. That is, the thickness of the potential dissolving agent layer was 30 μm.

Next, 82 parts by mass of LiFePO ₄ , 10 parts by mass of acetylene black, and 8 parts by mass of PVDF were prepared, and NMP was added and mixed and dispersed to prepare a homogeneous paste. This paste was applied on the above-mentioned potential solubilizer layer, dried, pressed, and then cut into a predetermined size to produce a positive electrode. The thickness of the produced positive electrode was 170 μm including the aluminum current collector and the potential solubilizer layer. That is, as shown in the cross-section of FIG. 1, the positive electrode of this example has a current collector with a thickness of 50 μm, a potential solubilizer layer with a thickness of 30 μm formed on the current collector, and a potential solubilizer layer. The formed positive electrode mixture layer having a thickness of 90 μm.

Thereafter, a battery was produced in the same manner as in Example 1 except that the above positive electrode was used. Then, in the same manner as in Example 1, the current interruption effect during overcharging was evaluated. As a result, after performing constant current / constant voltage charging to 3.6V at a current value of 0.1 mA / cm ² for 24 hours, the discharge capacity at the time of constant current discharge at a current value of 0.1 mA / cm ² is initial. Almost the same as the capacity, it was possible to charge and discharge again after the test. However, after performing constant current / constant voltage charging to 4.2 V at a current value of 0.1 mA / cm ² for 24 hours, the discharge capacity when the constant current is discharged at a current value of 0.1 mA / cm ² is the initial capacity. Thus, it was confirmed that the battery function was lost after the test. That is, it was confirmed that the current interruption effect was working during overcharge. That is, also in the present example, as in the case of Example 1, it was confirmed that the battery can suppress overcharge.

(Example 3)
Prepare 94 parts by mass of bisethylenedithiotetrathiafulvalene (same as Example 1), 3 parts by mass of PTFE, and 3 parts by mass of CMC, add water to mix and disperse, and prepare a homogeneous paste. Prepared. This paste was applied to one side of an aluminum current collector (50 μm), dried and pressed to prepare a potential dissolving agent layer. The thickness of the prepared potential solubilizer layer was 80 μm including the aluminum current collector. That is, the thickness of the potential dissolving agent layer was 30 μm.

Next, 82 parts by mass of LiNiO ₂ , 10 parts by mass of acetylene black, and 8 parts by mass of PVDF were prepared, and NMP was added and mixed and dispersed to prepare a homogeneous paste. This paste was applied on the above-mentioned potential solubilizer layer, dried, pressed, and then cut into a predetermined size to produce a positive electrode. The thickness of the produced positive electrode including the current collector made of aluminum and the potential solubilizer layer was 140 μm. That is, the positive electrode of this example is a 50 μm thick current collector, a 30 μm thick potential solubilizer layer formed on the current collector, and a 60 μm thick positive electrode mixture formed on the potential solubilizer layer. Layer.

Thereafter, a battery was produced in the same manner as in Example 1 except that the above positive electrode was used. Then, in the same manner as in Example 1, the current interruption effect during overcharging was evaluated. As a result, after performing constant current / constant voltage charging to 3.6V at a current value of 0.1 mA / cm ² for 24 hours, the discharge capacity at the time of constant current discharge at a current value of 0.1 mA / cm ² is initial. Almost the same as the capacity, it was possible to charge and discharge again after the test. However, after performing constant current / constant voltage charging to 4.2 V at a current value of 0.1 mA / cm ² for 24 hours, the discharge capacity when the constant current is discharged at a current value of 0.1 mA / cm ² is the initial capacity. Thus, it was confirmed that the battery function was lost after the test. That is, it was confirmed that the current interruption effect was working during overcharge. That is, also in the present example, as in the case of Example 1, it was confirmed that the battery can suppress overcharge.

(Comparative Example 1)
82 parts by mass of LiFePO ₄ , 10 parts by mass of acetylene black, and 8 parts by mass of PVDF were prepared, and NMP was added and mixed and dispersed to prepare a homogeneous paste. This paste was applied to one side of an aluminum current collector (50 μm), dried, pressed, and then cut into a predetermined size to produce a positive electrode. The thickness of the positive electrode produced was 140 μm including the aluminum current collector and the potential solubilizer layer.

Thereafter, a battery was produced in the same manner as in Example 1 except that the above positive electrode was used. Then, in the same manner as in Example 1, the current interruption effect during overcharging was evaluated. As a result, after performing constant current / constant voltage charging to 3.6V at a current value of 0.1 mA / cm ² for 24 hours, the discharge capacity at the time of constant current discharge at a current value of 0.1 mA / cm ² is initial. Almost the same as the capacity, it was possible to charge and discharge again after the test. Moreover, even after 24h constant current constant voltage charging to 4.2V at a current value of 0.1 mA / cm ^2, discharge capacity when the constant current discharge at a current value of 0.1 mA / cm ² initial Almost the same as the capacity, it was possible to charge and discharge again after the test.

  The battery of this comparative example was not provided with a potential solubilizer layer like the battery of the example, and the current interruption effect during overcharge was not confirmed. For this reason, the battery of this comparative example may cause heat generation or ignition (thermal runaway) when overcharge occurs.

(Comparative Example 2)
NMP is added to 22 parts by mass of bisethylenedithiotetrathiafulvalene (same as Example 1), 60 parts by mass of LiFePO ₄ , 10 parts by mass of acetylene black, and 8 parts by mass of PVDF, mixed and dispersed to be homogeneous. Paste was prepared. This paste was applied to one side of an aluminum current collector (50 μm), dried, pressed, and then cut into a predetermined size to produce a positive electrode. The thickness of the positive electrode produced was 140 μm including the aluminum current collector and the potential solubilizer layer.

Thereafter, a battery was produced in the same manner as in Example 1 except that the above positive electrode was used. Then, in the same manner as in Example 1, the current interruption effect during overcharging was evaluated. As a result, after performing constant current / constant voltage charging to 3.6V at a current value of 0.1 mA / cm ² for 24 hours, the discharge capacity at the time of constant current discharge at a current value of 0.1 mA / cm ² is initial. Although it was almost the same as the capacity, it was possible to charge and discharge again after the test, but after performing constant current constant voltage charging to 4.2 V at a current value of 0.1 mA / cm ² for 24 hours, the charge was 0. The discharge capacity at the time of constant current discharge at a current value of 1 mA / cm ² was 82% of the initial capacity, and although the discharge capacity was reduced, it was possible to charge / discharge again after the test.

  In the battery of this comparative example, the electric potential solubilizer is dispersed in the positive electrode mixture layer, and even if the electric potential solubilizer is dissolved during overcharge, the amount of electrical connection between the positive electrode active material and the current collector is small. It does not drop significantly. That is, in the battery of this comparative example, the current interruption effect at the time of overcharging was not obtained to the extent that the overcharging of the battery was suppressed. For this reason, as in Comparative Example 1, the battery of this comparative example may cause heat generation or ignition (thermal runaway) when overcharge occurs.

(result)
From the evaluation results of each Example and Comparative Example, the positive electrode has a potential solubilizer layer between the electrode mixture layer and the current collector, so that the potential solubilizer layer is dissolved by the potential increase during overcharge, and the positive electrode It was confirmed that the mixture layer was peeled off from the current collector and floated, and the resistance between the positive electrode mixture layer and the current collector was increased. As a result, it was possible to cut off the current flowing through the battery during overcharging, and it was confirmed that the progress of overcharging could be suppressed. That is, it was confirmed that the battery of each example was a non-aqueous electrolyte battery (lithium ion secondary battery) excellent in safety.

Example 4
First, 94 parts by mass of the compound shown in the following chemical formula 14, 94 parts by mass of PTFE and 3 parts by mass of CMC were mixed with water and dispersed to prepare a homogeneous paste. This paste was applied to the surface (one side) of an aluminum current collector (50 μm), dried and pressed to produce a potential solubilizer layer on the surface of the current collector. The thickness of the prepared potential solubilizer layer was 70 μm including the thickness of the current collector. That is, the thickness of the potential dissolving agent layer was 20 μm.

次に、ＬｉＦｅＰＯ₄を８２質量部、アセチレンブラックを１０質量部、そしてポリフッ化ビニリデン（ＰＶＤＦ）を８質量部に対し、ノルマルメチルピロリドン（ＮＭＰ）を加え、混合、分散させて均質なペーストを調製した。このペーストを上記で作製した電位溶解剤層の上に塗布し、乾燥、プレス後、所定のサイズに裁断することで正極を作製した。作製した正極の厚みはアルミニウム製の集電体、電位溶解剤層を含め１６０μｍであった。すなわち、本実施例の正極は、厚さ５０μｍの集電体、集電体上に形成された厚さ３０μｍの電位溶解剤層、電位溶解剤層上に形成された厚さ９０μｍの正極合剤層、からなる。

Next, normal methylpyrrolidone (NMP) is added to 82 parts by mass of LiFePO ₄ , 10 parts by mass of acetylene black, and 8 parts by mass of polyvinylidene fluoride (PVDF), and mixed and dispersed to prepare a homogeneous paste. did. This paste was applied on the potential solubilizer layer prepared above, dried, pressed, and then cut into a predetermined size to produce a positive electrode. The thickness of the positive electrode produced was 160 μm including the aluminum current collector and the potential solubilizer layer. That is, the positive electrode of this example is a 50 μm thick current collector, a 30 μm thick potential solubilizer layer formed on the current collector, and a 90 μm thick positive electrode mixture formed on the potential solubilizer layer. Layer.

  Then, except having used said positive electrode, the battery was produced by the method similar to Example 1, and the lithium ion secondary battery of a present Example was manufactured.

  Also in this example, the positive electrode has a potential solubilizer layer between the electrode mixture layer and the current collector, and cuts off the current flowing to the battery during overcharge as in Examples 1-3. Therefore, it was confirmed that the lithium ion secondary battery was excellent in safety.

1: Coin-type battery 2: Positive electrode 20: Positive electrode current collector 21: Potential solubilizer layer 22: Positive electrode mixture layer 3: Negative electrode 30: Negative electrode current collector 4: Electrolytic solution 50: Positive electrode case 51: Negative electrode case 6: Gasket 7: Separator

Claims (7)

A positive electrode in which a positive electrode mixture layer having a positive electrode active material is formed on a current collector, a negative electrode in which a negative electrode mixture layer having a negative electrode active material is formed on a current collector, and a non-aqueous electrolyte. An electrode for a non-aqueous electrolyte battery used for a non-aqueous electrolyte battery,
The positive electrode, the between positive electrode mixture layer and the current collector, with a potential dissolution agent layer having a potential dissolving agent which dissolves at a predetermined potential above the positive electrode active upper potential limit potential higher than indicated substance And
The electrode for a non-aqueous electrolyte battery , wherein the potential dissolving agent is a compound represented by the following chemical formula 1 or chemical formula 2 .

(X and Y are selected from a sulfur atom, an oxygen atom, and a methylene group, and X and Y may be the same or different.)

(Each of R1 to R4 is independently selected from hydrogen and an alkyl group having 1 to 4 carbon atoms, and at least one of R1 to R4 is any one of structures represented by the following chemical formula 3. n is It is a natural number and can be selected independently.)

(In the chemical formulas 3 (1) to (3), the part * in the chemical formula is bonded to the carbon atom in the benzene ring in the chemical formula 2. R in the chemical formulas 3 (1) to (3) is- Any one of H, —OH, —CH ₃ , and —NH ₂ Y in Chemical Formulas 3 (1) to (3) is a — (CH ₂ ) _m — group (m is an integer of 0 to 10); And when m is 1 or more, one or more of the methylene groups constituting Y may be substituted with at least one of the groups represented by the following chemical formulas 4 (1) to (10).

  The electrode for a non-aqueous electrolyte battery according to claim 1, which is used for a positive electrode having a positive electrode active material capable of inserting and extracting lithium ions. The electrode for a non-aqueous electrolyte battery according to claim 1 , wherein the potential solubilizer is bisethylenedithiotetrathiafulvalene. The electrode for a non-aqueous electrolyte battery according to claim 1, wherein the potential dissolving agent is a compound represented by the following chemical formula (5 ) .

(M and p are each independently selected from integers from 0 to 10. n is a natural number and is independently selected from m and p.) The electrode for a non-aqueous electrolyte battery according to claim 1 , wherein the potential solubilizer layer has a thickness of 50 μm or less. The positive electrode active material has a structural formula of Li _1-Z α (α is CoO ₂ , MnO ₂ , Mn ₂ O ₄ , NiO ₂ ) or Li _1-Z βPO ₄ (β is Fe, Mn) (Z is 0 to 1). The electrode for nonaqueous electrolyte batteries in any one of Claims 1-5 which have a lithium transition metal complex oxide in which 1 or more types of compounds shown by these are included. A non-aqueous electrolyte battery comprising: a positive electrode comprising the non-aqueous electrolyte battery electrode according to claim 1 ; a negative electrode; and a non-aqueous electrolyte.

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