WO2012172586A1 - リチウム二次電池 - Google Patents
リチウム二次電池 Download PDFInfo
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- WO2012172586A1 WO2012172586A1 PCT/JP2011/003325 JP2011003325W WO2012172586A1 WO 2012172586 A1 WO2012172586 A1 WO 2012172586A1 JP 2011003325 W JP2011003325 W JP 2011003325W WO 2012172586 A1 WO2012172586 A1 WO 2012172586A1
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- carbonate
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- secondary battery
- carbon dioxide
- ion secondary
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/572—Means for preventing undesired use or discharge
- H01M50/574—Devices or arrangements for the interruption of current
- H01M50/578—Devices or arrangements for the interruption of current in response to pressure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2200/00—Safety devices for primary or secondary batteries
- H01M2200/20—Pressure-sensitive devices
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a lithium ion battery.
- Lithium secondary batteries have a high energy density and are widely used in notebook computers and mobile phones, taking advantage of their characteristics.
- interest in electric vehicles has increased from the viewpoint of preventing global warming due to an increase in carbon dioxide, and the application of lithium secondary batteries as a power source has been studied.
- Patent Documents 1 and 2 disclose techniques for adding an aromatic compound to a battery to increase safety during overcharge.
- Patent Documents 3 and 4 disclose technologies for improving safety during overcharging by mixing lithium carbonate with a positive electrode in a lithium battery having a current cutoff valve that cuts off current when the internal pressure increases.
- lithium carbonate is electrochemically decomposed at a positive electrode at a high potential, generating carbon dioxide gas, increasing the internal pressure of the battery, and operating the current cutoff valve to improve battery safety during overcharge.
- the reaction potential of lithium carbonate is as high as 4.8 V to 5.0 V vs. Li / Li +, and the reaction starts at the end of overcharge, so in some cases, before lithium carbonate reacts
- the battery may run out of heat.
- lithium carbonate has a problem of low stability due to potential. As described above, when only lithium carbonate (single) is used as the gas generating agent, various problems occur.
- the lithium ion secondary battery having the electrolyte solution has an aromatic compound
- the positive electrode includes a carbon dioxide generating agent, said carbon dioxide generating agents have the general formula a X CO A lithium ion secondary battery represented by 3 or A y HCO 3 .
- A is an alkali metal having an atomic number of 11 or more, or an alkaline earth metal having an atomic number of 4 or more.
- X is 2 when A is an alkali metal, and is 1 when A is an alkaline earth metal.
- Y is 1 when A is an alkali metal and 0.5 when alkaline earth metal.
- the said aromatic compound is a lithium ion secondary battery which is (Formula 1), (Formula 2), or benzene.
- R 1 is hydrogen or a hydrocarbon group, and when R 1 is a hydrocarbon group, m is 5 or less.
- R 2 to R 4 in (Formula 1) are H or a hydrocarbon group.
- (Formula 2) is a compound in which an aromatic compound is substituted with an alicyclic hydrocarbon.
- R 1 is hydrogen or a hydrocarbon group.
- m is 5 or less
- n is 1 or more and 14 or less.
- the technology of the present invention makes it possible to operate the current cut-off valve in the early stage of overcharge, so that the safety of the battery can be improved. Furthermore, since it is possible to use an inexpensive carbonate or bicarbonate, the cost of the battery can be reduced. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.
- the reaction potential of lithium carbonate is as high as 4.8V to 5.0V vs. Li / Li + and the reaction starts at the end of overcharge, so overcharge It can be said that there is a problem in the responsiveness to.
- lithium carbonate is known as a substance that can be electrochemically decomposed to generate carbon dioxide gas that can be applied to lithium secondary batteries. Even when other carbonates or bicarbonates such as sodium carbonate or sodium bicarbonate are used, these substances are hardly decomposed electrochemically, and as a result, safety cannot be ensured during overcharge. Moreover, lithium carbonate is more expensive than sodium carbonate and sodium hydrogen carbonate, and causes the cost of the battery to increase. Furthermore, when lithium carbonate is used, battery performance such as high-temperature storage characteristics decreases. Therefore, when the amount of lithium carbonate is reduced, a decrease in battery performance can be suppressed, but safety against overcharging is reduced.
- the current cutoff valve is operated at the initial stage of overcharge by combining an aromatic compound that reacts when an electric potential is higher than a certain level by an electrochemical reaction and a compound that generates protons and a compound that generates carbon dioxide gas. Can do.
- the aromatic compound 2 generates protons in the vicinity of the positive electrode 1 by the potential due to overcharging of the battery. Protons generated from the aromatic compound 2 cause a neutralization reaction with a compound that generates carbon dioxide to generate carbon dioxide.
- the generated carbon dioxide gas can stop charging by operating the battery shut-off valve.
- the aromatic compound that reacts with an electrochemical reaction to generate an acid when the potential becomes a certain level or higher is specifically (formula 1), (formula 2) and benzene.
- the operating potential of a lithium ion secondary battery is generally 2.5 to 4.3V. When it becomes 4.5V or more, it is overcharged. In order to prevent overcharge, it is preferable to generate gas when the battery voltage becomes 4.5 V or higher. However, in order to respond more quickly to overcharge and generate protons, the reaction potential of the aromatic compound is more preferably 4.4 V or more and 4.8 V or less. If this value is exceeded, it may not be possible to quickly respond to overcharge. Moreover, when it falls below this value, a reaction may occur during normal battery operation, which may lead to deterioration of the battery.
- the above operating potential and overcharge voltage vary depending on other designs such as active materials used in lithium ion secondary batteries. For this reason, it is preferable to adjust the reaction potential of the aromatic compound according to the operating voltage of the battery.
- the reaction potential of the aromatic compound can be adjusted by changing the functional group.
- the present invention is also useful in that the potential of carbon dioxide gas generation can be made dependent on the reaction potential of an aromatic compound capable of adjusting the reaction potential without depending only on the reaction potential of the gas generating agent.
- (Formula 1) is a compound in which at least one of the aromatic compounds is substituted with an alicyclic hydrocarbon.
- R 1 is hydrogen or a hydrocarbon group.
- the hydrocarbon group is an aliphatic hydrocarbon group (C n H 2n + 1 ), an alicyclic hydrocarbon group (C n H 2n-1 ), or an aromatic hydrocarbon group.
- Aliphatic hydrocarbon groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, dimethylethyl, pentyl, hexylyl, heptyl, octyl, isooctyl, decyl, undecyl , Dodecyl group, and alicyclic hydrocarbon group include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group and the like.
- An aromatic hydrocarbon group is a functional group having 20 or less carbon atoms that satisfies the Huckle rule. Moreover, n of (Formula 1) is 1 or more and 14 or less. When R 1 is a hydrocarbon group, m in (Formula 1) is 5 or less.
- R 1 to R 4 are hydrogen or a hydrocarbon group.
- the hydrocarbon group is an aliphatic hydrocarbon group (C n H 2n + 1 ), an alicyclic hydrocarbon group (C n H 2n-1 ), or an aromatic hydrocarbon group.
- Aliphatic hydrocarbon groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, dimethylethyl, pentyl, hexylyl, heptyl, octyl, isooctyl, decyl, undecyl , Dodecyl group, and alicyclic hydrocarbon group include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group and the like.
- An aromatic group is a functional group having 20 or less carbon atoms that satisfies the Huckel rule.
- R 1 is a hydrocarbon group
- m in (Formula 2) is 5 or less.
- the addition amount of (Formula 1), (Formula 2) and benzene is 0 or more and 50 wt%, preferably 0.01 or more and 10 wt% or less with respect to the electrolytic solution.
- the addition amount By optimizing the addition amount, both battery performance and safety during overcharging, which is an effect of the present invention, can be achieved.
- These aromatic compounds may be used individually by 1 type, and may be used in combination of multiple types.
- a compound that generates carbon dioxide gas can generate a carbon dioxide gas by causing a neutralization reaction with protons generated from the aromatic compound. Therefore, the compound that generates carbon dioxide gas is not limited to a compound that generates carbon dioxide gas by electric potential, such as lithium carbonate, and various compounds that generate carbon dioxide gas by neutralization reaction with protons are used. Can do.
- the compound that generates carbon dioxide gas by the neutralization reaction is a carbonate or hydrogen carbonate represented by the general formulas A X CO 3 and A y HCO 3 .
- A is an alkali metal having an atomic number of 11 or more or an alkaline earth metal having an atomic number of 4 or more.
- x is 2 when A is an alkali metal, and 1 when A is an alkaline earth metal.
- y is 1 when A is an alkali metal, and 0.5 when it is an alkaline earth metal.
- Examples include cesium, beryllium bicarbonate, magnesium bicarbonate, calcium bicarbonate, strontium bicarbonate, and barium bicarbonate.
- sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, bicarbonate Strontium and barium bicarbonate are preferably used.
- the carbon dioxide generator one or more of the above materials may be used. You may use said material together with lithium carbonate. When using together, 10 wt% or more and 80 wt% or less are preferable. If it is less than 10 wt%, it is difficult to exhibit the effect of suppressing overcharge, and if it is greater than 80 wt%, the high-temperature storage characteristics may deteriorate.
- the carbon dioxide generating agent is not limited to a compound that generates carbon dioxide by a potential, it is preferably stable with respect to the potential. Lithium carbonate or the like having high reactivity with respect to the potential may cause a reaction depending on the potential of the battery, which may lead to deterioration of the battery.
- Examples of the carbon dioxide gas generator having high stability with respect to electric potential include sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, magnesium hydrogen carbonate, and calcium hydrogen carbonate.
- the compound that generates carbon dioxide gas is preferably sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, sodium hydrogen carbonate or the like from the viewpoint of price.
- the carbon dioxide generating agent is present at the positive electrode.
- a compound that generates carbon dioxide gas is added to a slurry solution in which a positive electrode active material, a conductive agent, a binder, and other additives are mixed, and the mixture is stirred. It can be applied by a blade method or the like.
- a method of spraying fine particles of a carbon dioxide generating agent on the positive electrode a method of applying a carbon dioxide generating agent again on a positive electrode prepared by mixing a gas generating agent, or the like can be used.
- the amount (X) of the carbon dioxide generating agent is (0 ⁇ X ⁇ 50 wt%), preferably (0 ⁇ X ⁇ 5 wt%) with respect to the positive electrode (positive electrode active material + conductive material + binder). By defining X, it is possible to achieve both battery performance and the effects of the present invention.
- the carbonate and bicarbonate (E) and lithium carbonate (F) can be mixed and used.
- the ratio of E and F (F / (E + F)) in the case of using a mixture is 0 ⁇ F / (E + F) ⁇ 1.
- the positive electrode in the present invention is capable of inserting and extracting lithium ions, and is represented by a general formula of LiMO 2 (M is a transition metal), for example, LiCoO 2 , LiNiO 2 , LiMn 1/3 Ni 1/3.
- An oxide having a layered structure such as Co 1/3 O 2 , LiMn 0.4 Ni 0.4 Co 0.2 O 2 , and a part of M is Al, Mg, Mn, Fe, Co, Cu, Zn, Al, Ti, Examples thereof include oxides substituted with at least one metal element selected from the group consisting of Ge, W, and Zr.
- Examples thereof include oxides of Mn having a spinel type crystal structure such as LiMn 2 O 4 and Li 1 + x Mn 2 ⁇ x O 4 .
- LiFePO 4 having a olivine structure or LiMnPO 4 can also be used.
- the negative electrode in the present invention is a graphitized material obtained from natural graphite, petroleum coke, coal pitch coke, etc., heat treated at a high temperature of 2500 ° C. or higher, mesophase carbon or amorphous carbon, carbon fiber, lithium
- a metal to be alloyed or a material having a metal supported on the surface of carbon particles is used.
- a metal or alloy selected from lithium, silver, aluminum, tin, silicon, indium, gallium, and magnesium can be used as a negative electrode.
- lithium titanate can also be used.
- the electrolytic solution in the present invention is a solution in which a supporting electrolyte is dissolved in a nonaqueous solvent.
- the nonaqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte, but the following are preferable. It is an organic solvent such as diethyl carbonate, dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, propylene carbonate, ⁇ -butyl lactone, tetrohydrofuran, dimethoxyethane, etc., and these can be used alone or in combination. Further, vinylene carbonate or vinyl ethylene carbonate having an unsaturated double bond in the molecule can be mixed and used.
- the supporting electrolyte in the present invention is not particularly limited as long as it is soluble in a non-aqueous solvent, but the following are preferable. That is, LiPF 6 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 6 SO 2 ) 2 , LiClO 4 , LiBF 4 , LiAsF 6 , LiI, LiBr, LiSCN, Li 2 B 10 Cl 10 , LiCF 3 CO 2 or the like, and one kind or a mixture of two or more kinds can be used.
- a general gas release valve that opens at a predetermined internal pressure as described in Patent Document 5 or Patent Document 6 can be used. Since this gas release valve is opened at a pressure not higher than the battery burst pressure by the gas pressure that rises rapidly during thermal runaway, and the gas is selectively released from this valve to the outside of the battery can, a lithium ion battery having a gas release valve However, even if the internal pressure of the battery rises, the possibility that the battery can burst and the contents are scattered around is suppressed. Further, the gas release valve has a structure in which the electric circuit is cut off by being deformed and separated.
- FIG. 2 is a diagram of a lithium ion secondary battery 6 having a general current cutoff valve 7.
- ⁇ Method for producing electrode> Lithium cobaltate, conductive carbon, and polyvinylidene fluoride were mixed at a ratio of 95: 2.5: 2.5% by weight, and charged into N-methyl-2-pyrrolidone to prepare a slurry solution. Then, after adding a carbon dioxide generator and stirring, the slurry was applied to an aluminum foil having a thickness of 20 ⁇ m by a doctor blade method and dried.
- ⁇ Negative electrode> Artificial graphite and polyvinylidene fluoride were mixed at a ratio of 95: 5% by weight and charged into N-methyl-2-pyrrolidone to prepare a slurry solution.
- the slurry was applied to a copper foil having a thickness of 20 ⁇ m by a doctor blade method and dried.
- a separator was inserted between the positive electrode and the negative electrode and wound.
- the wound body was inserted into a battery can for 18650. Thereafter, an electrolytic solution was injected and sealed.
- operates by an internal pressure rise was applied to the upper part of a battery can. Thereafter, charge and discharge were repeated for 3 cycles at a current value of 200 mA in the range of 3.0 V to 4.2 V.
- the current value of discharge at the third cycle was defined as the battery capacity.
- the produced battery was charged to 4.2 V, then placed in a high temperature bath at 60 ° C. and stored for 10 days. Thereafter, the battery was cooled to room temperature, discharged once to 3.0 V, and then charged and discharged at a current value of 200 mA in the range of 3.0 V to 4.2 V.
- the discharge capacity at that time was defined as the battery capacity after the storage test.
- the carbon dioxide generator added to the positive electrode was Na 2 CO 3 , and the amount added was 3 wt% with respect to the weight of the positive electrode.
- the battery capacity was 2010 mAh
- the battery capacity after the high-temperature storage test was 1890 mAh.
- the current cutoff valve operated at 4.6V. As a result of the overcharge test, there was no rupture / ignition, and the overall judgment was “good”.
- FIG. As a result of battery evaluation, the battery capacity was 2010 mAh, and the battery capacity after the high-temperature storage test was 1885 mAh.
- the current cutoff valve operated at 4.6V.
- Example 4 In Example 2, but using NaHCO 3 instead of Na 2 CO 3, and examined in the same manner as in Example 2. As a result of battery evaluation, the battery capacity was 2009 MAH, and the battery capacity after the high temperature storage test was 1891 mAh. During the overcharge test, the current cutoff valve operated at 4.6V. As a result of the overcharge test, there was no rupture / ignition, and the overall judgment was “good”.
- Example 5 In Example 2, as a carbon dioxide generating agent, but using a mixture of Na 2 CO 3 and Li 2 CO 3, were examined in the same manner as in Example 2.
- the battery capacity was 2008 mAh
- the battery capacity after the high-temperature storage test was 1885 mAh.
- the current cutoff valve operated at 4.6V.
- there was no rupture / ignition and the overall judgment was “good”.
- Example 6 In Example 5, examination was performed in the same manner as in Example 5 except that the composition ratio (F / (E + F)) was set to 0.1. As a result of battery evaluation, the battery capacity was 2010 mAh, and the battery capacity after the high-temperature storage test was 1890 mAh. During the overcharge test, the current cutoff valve operated at 4.6V. As a result of the overcharge test, there was no rupture / ignition, and the overall judgment was “good”.
- Example 2 A battery was fabricated in the same manner as in Example 3 except that the gas generating agent was not used.
- the battery capacity was 2010 mAh, and the battery capacity after the high temperature storage test was 1900 mAh.
- Comparative Example 3 In the comparative example 2, it examined like the comparative example 2 except having made the density
- the battery capacity was 2001 mAh, and the battery capacity after the high temperature storage test was 1850 mAh.
- As a result of the overcharge test no ignition was observed, but since bursting was observed, the overall judgment was x.
- Example 4 In Example 1, without adding an aromatic compound, except using Li 2 CO 3 as gassing inhibitors, it was investigated in the same manner as in Example 1. The battery capacity was 1995 mAh, and the battery capacity after the high temperature storage test was 1860 mAh. As a result of the overcharge test, no ignition was observed, but since bursting was observed, the overall judgment was x.
- Comparative Example 5 (Comparative Example 5) In Comparative Example 4, examination was performed in the same manner as in Comparative Example 4 except that the amount of Li 2 CO 3 was 1.0 wt%. The battery capacity was 2001 mAh, and the battery capacity after the high temperature storage test was 1865 mAh. As a result of the overcharge test, no ignition was observed, but since bursting was observed, the overall judgment was x.
- Comparative Examples 2 and 3 are examples in which no carbon dioxide generator was added. As a result of the experiment, the current cutoff valve did not operate. In Comparative Examples 2 and 3, the gas that operates the current cutoff valve is hydrogen generated from an aromatic compound. The reason why the electric valve did not operate is considered that hydrogen was insufficient to operate the current cutoff valve due to the nature of the gas.
- Comparative Examples 4 and 5 are examples in which no aromatic compound was added. As a result of the experiment, the current cutoff valve operated, but the operating potential was as high as 5.0 and 5.1V.
- Examples 1 to 6 are examples in which an aromatic compound and a gas generating agent are combined. As a result of the experiment, the current cutoff valve was operated and its operating potential was 4.6V. In Examples 1 to 6, it can be seen that the battery shut-off valve operates at a lower potential than Comparative Examples 4 and 5, and the response to overcharge is higher.
- Example 2 the result of Example 2 was good.
- the response to overcharge and the high-temperature storage characteristics were good. Since the gas generating agent Na 2 CO 3 is more stable than LiCO 3 , it is considered that the decrease in battery performance is suppressed as compared with Examples 5 and 6. When the amount of LiCO 3 added is small, it is difficult to exert an overcharge suppressing effect. Further, it is considered that the high temperature storage characteristics are lowered when the addition amount is increased.
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Abstract
Description
また、前記芳香族化合物は、(式1),(式2)、またはベンゼンであるリチウムイオン二次電池。
以下、実施例を挙げて本発明をさらに具体的に説明するが、本発明はこれらの実施例に限定されるものではない。また、本実施例の結果を表1にまとめた。
<正極>
コバルト酸リチウム,導電材炭素,ポリフッ化ビニリデンを95:2.5:2.5重量%の割合で混合し、N-メチル-2-ピロリドンに投入混合して、スラリー状の溶液を作製した。その後、炭酸ガス発生剤を加えて撹拌後、該スラリーを厚さ20μmのアルミニウム箔にドクターブレード法で塗布し、乾燥した。
人造黒鉛とポリフッ化ビニリデンを95:5重量%の割合で混合し、N-メチル-2-ピロリドンに投入混合して、スラリー状の溶液を作製した。該スラリーを厚さ20μmの銅箔にドクターブレード法で塗布し、乾燥した。
正極と負極の間にセパレータを挿入し、捲回した。その捲回体を18650用の電池缶に挿入した。その後、電解液を注入し封止した。なお、電池缶の上部には、内圧上昇により作動する電流遮断機構を適用した。その後、3.0V~4.2Vの範囲で、200mAの電流値で、3サイクル充放電を繰り返した。3サイクル目の放電の電流値を電池容量とした。
過充電評価用に別途作製した電池を予め4.2Vに充電した。その後、2000mAの電流値で5.0Vまで過充電した。5.0Vに到達したあとは、5.0Vの定電位で充電を継続し、電流値が50mAになるまで行った。過充電試験は、破裂・発火両方が無い場合を、試験合格とし、総合判定○と表記した。破裂・発火両方、もしくはどちらか一方のみが起きた場合は、試験不合格とし、総合判定×と表記した。
芳香族化合物A(式1、R1=H、R2,3=Me、R4=H)を、電解液(電解質塩:LiPF6,溶媒:EC/DMC/EMC=1:1:1体積比,電解質塩濃度1mol/L)に、2.0wt%になるように加え電解液を準備した。また、正極に加えた炭酸ガス発生剤は、Na2CO3を用い、添加量は正極重量に対し3wt%にした。電池評価の結果、電池容量は2010mAhであり、高温保存試験後の電池容量は1890mAhであった。過充電試験中、4.6Vで電流遮断弁が作動した。過充電試験の結果、破裂・発火は無く、総合判定は○であった。
実施例1において、芳香族化合物Aの代わりに芳香族化合物B(式1、R1=H、R2=Me、R3=Et、R4=H)を用いること以外は、実施例1と同様に検討した。電池評価の結果、電池容量は2010mAhであり、高温保存試験後の電池容量は1900mAhであった。過充電試験中、4.6Vで電流遮断弁が作動した。過充電試験の結果、破裂・発火は無く、総合判定は○であった。
実施例1において、芳香族化合物Aの代わりに芳香族化合物C(式2、R1=H,n=4)を用いること以外は、実施例1と同様に検討した。電池評価の結果、電池容量は2010mAhであり、高温保存試験後の電池容量は1885mAhであった。過充電試験中、4.6Vで電流遮断弁が作動した。過充電試験の結果、破裂・発火は無く、総合判定は○であった。
実施例2において、Na2CO3の代わりにNaHCO3を用いること以外は、実施例2と同様に検討した。電池評価の結果、電池容量は2009MAHであり、高温保存試験後の電池容量は1891mAhであった。過充電試験中、4.6Vで電流遮断弁が作動した。過充電試験の結果、破裂・発火は無く、総合判定は○であった。
実施例2において、炭酸ガス発生剤として、Na2CO3とLi2CO3を混合して用いること以外は、実施例2と同様に検討した。なお、Na2CO3(E)とLi2CO3(F)の組成比(F/(E+F))は0.8であった。電池評価の結果、電池容量は2008mAhであり、高温保存試験後の電池容量は1885mAhであった。過充電試験中、4.6Vで電流遮断弁が作動した。過充電試験の結果、破裂・発火は無く、総合判定は○であった。
実施例5において、組成比(F/(E+F))を0.1にすること以外は、実施例5と同様に検討した。電池評価の結果、電池容量は2010mAhであり、高温保存試験後の電池容量は1890mAhであった。過充電試験中、4.6Vで電流遮断弁が作動した。過充電試験の結果、破裂・発火は無く、総合判定は○であった。
芳香族化合物とガス発生剤を用いずに電池を作製した。電池容量は2010mAhであり、高温保存試験後の電池容量は1901mAhであった。過充電試験の結果、破裂,発火がみられ、総合判定は×であった。
ガス発生剤を用いないこと以外は実施例3と同様に電池を作製した。電池容量は2010mAhであり、高温保存試験後の電池容量は1900mAhであった。過充電試験の結果、破裂,発火がみられ、総合判定は×であった。
比較例2において、芳香族化合物の濃度を3wt%にすること以外は、比較例2と同様に検討した。電池容量は2001mAhであり、高温保存試験後の電池容量は1850mAhであった。過充電試験の結果、発火は見られなかったが、破裂がみられたため、総合判定は×であった。
実施例1において、芳香族化合物を添加せず、また、ガス発生抑制剤としてLi2CO3を用いること以外は、実施例1と同様に検討した。電池容量は1995mAhであり、高温保存試験後の電池容量は1860mAhであった。過充電試験の結果、発火は見られなかったが、破裂がみられたため、総合判定は×であった。
比較例4において、Li2CO3の量を1.0wt%にすること以外は、比較例4と同様に検討した。電池容量は2001mAhであり、高温保存試験後の電池容量は1865mAhであった。過充電試験の結果、発火は見られなかったが、破裂がみられたため、総合判定は×であった。
2 芳香族化合物
3 リチウムイオン二次電池
4 電流遮断弁
Claims (6)
- リチウムイオンを吸蔵・放出可能な正極と、
リチウムイオンを吸蔵・放出可能な負極と、
前記正極と前記負極との間に配置されたセパレータと、
電解液と、
電池内圧の上昇に応じて作動する電流遮断機構と、
を有するリチウムイオン二次電池において、
前記電解液は、芳香族化合物を有し、
前記正極は、炭酸ガス発生剤を有し、
前記炭酸ガス発生剤は、一般式AXCO3またはAyHCO3で表わされるリチウムイオン二次電池。
(Aは、原子番号11以上のアルカリ金属、または、原子番号4以上のアルカリ土類金属である。xは、Aがアルカリ金属の場合は2であり、アルカリ土類金属の場合は1である。yは、Aがアルカリ金属の場合1であり、アルカリ土類金属の場合は、0.5である。) - 請求項1において、
前記芳香族化合物は、4.4V以上,4.8V以下の電位において、プロトンを生じる化合物であるリチウムイオン二次電池。 - 請求項1ないし請求項3のいずれかにおいて、
前記電解液は、前記芳香族化合物を、前記電解液に対して0.01以上10wt%以下含むリチウムイオン二次電池。 - 請求項1ないし請求項4のいずれかにおいて、
前記炭酸ガス発生剤は、炭酸ナトリウム,炭酸カリウム,炭酸マグネシウム,炭酸カルシウム,炭酸水素ナトリウム,炭酸水素カリウム,炭酸水素マグネシウム,炭酸水素カルシウムのいずれか一種を少なくとも含むリチウムイオン二次電池。 - 請求項1ないし請求項5のいずれかにおいて、
前記炭酸ガス発生剤は、炭酸リチウムを10%wt以上80wt%以下含むリチウムイオン二次電池。
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PCT/JP2011/003325 WO2012172586A1 (ja) | 2011-06-13 | 2011-06-13 | リチウム二次電池 |
US14/125,822 US20140170448A1 (en) | 2011-06-13 | 2011-06-13 | Lithium-ion secondary battery |
KR1020137032767A KR20140013069A (ko) | 2011-06-13 | 2011-06-13 | 리튬 이차 전지 |
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JP2017142892A (ja) * | 2016-02-08 | 2017-08-17 | 日立オートモティブシステムズ株式会社 | リチウムイオン二次電池および蓄電装置 |
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US20140093759A1 (en) * | 2011-06-13 | 2014-04-03 | Hitachi, Ltd. | Lithium-ion secondary battery |
KR102237952B1 (ko) * | 2017-07-28 | 2021-04-08 | 주식회사 엘지화학 | 이차전지용 양극 및 이를 포함하는 리튬 이차전지 |
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- 2011-06-13 US US14/125,822 patent/US20140170448A1/en not_active Abandoned
- 2011-06-13 WO PCT/JP2011/003325 patent/WO2012172586A1/ja active Application Filing
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