WO2012063286A1

WO2012063286A1 - Secondary battery

Info

Publication number: WO2012063286A1
Application number: PCT/JP2010/006601
Authority: WO
Inventors: 中島　潤二
Original assignee: 三菱重工業株式会社
Priority date: 2010-11-10
Filing date: 2010-11-10
Publication date: 2012-05-18

Abstract

Separator films of PE or PP which have been conventionally used oxidize and degrade. The possibility that, as a result, insulation properties are reduced or lifetime performance decreases has not been resolved. Furthermore, with conventional battery configurations, there has been a tradeoff between capacity and output so that it has been difficult to achieve high output. In an electrolyte system, there has been the problem that, as a result of temperature dependency of an electrolyte, performance at a low temperature has deteriorated so that desired performance could not be achieved. Furthermore, as a result of the expansion of specific applications, quick-recharge is being desired for recharge as well. In the separator according to the present invention, by configuring thereof so as to support a material containing ceramic material and elemental phosphorous in a nonwoven fabric, it is possible to continuously maintain insulation in a an expected environment and to improve safety.

Description

Secondary battery

The present invention relates to a secondary battery excellent in performance and safety.

A battery is a device that converts the chemical energy of a chemical substance inside into electrical energy through an electrochemical redox reaction. In recent years, it has been used around the world for portable electronic devices such as electronics, communications, and computers. From now on, it will be used as a large battery for mobiles such as electric vehicles and stationary equipment for power load leveling systems. It is expected to be put into practical use and is becoming an increasingly important key device.

Among them, lithium-ion secondary batteries have brought great spread. This lithium ion secondary battery uses a positive electrode having a lithium-containing transition metal composite oxide as an active material and a material capable of inserting and extracting lithium, such as lithium metal, lithium alloy, metal oxide, or carbon. The main components are a negative electrode, an electrolyte, and a separator.

As an example, in a lithium ion secondary battery, lithium ions emitted from a lithium metal composite oxide used as a positive electrode during initial charging move to a graphite electrode used as a negative electrode and are inserted between the graphite electrodes. At this time, since lithium is highly reactive, a thin film layer is formed on the surface of the graphite negative electrode. Such a layer is called a SEI (Solid-Electrolyte-Interface) layer. Once formed, the SEI layer serves as an ion tunnel and allows only lithium ions to pass through. By such a protective film having an ion tunnel effect, the structure of the graphite negative electrode can be prevented from collapsing due to an electrolytic solution or the like.

Once the SEI layer is formed, the lithium ions again do not side-react with the graphite negative electrode or other substances, and the amount of lithium ions in the electrolyte is reversibly maintained, ensuring stable charge / discharge. The However, depending on the voltage (high voltage), gases such as CO, CO ₂ , CH ₄ , C ₂ H ₆ are generated during the above-described SEI formation reaction due to decomposition of the carbonate-based organic solvent, This causes the problem that the thickness of the battery expands during charging. In addition, in a fully charged state at a certain voltage (high voltage), the SEI layer gradually collapses as time passes during high temperature storage, and the side reaction in which the exposed negative electrode surface reacts with the surrounding electrolyte continues. Will occur. At this time, due to continuous gas generation, the internal pressure of the battery rises, and as a result, the thickness of the battery increases. Furthermore, the PE and PP separator films used in the past are oxidized and deteriorated. As a result, there is a risk that the insulation performance is lowered, the life performance is lowered, and there is a possibility that a spark will run on the gas methane or oxygen when the internal pressure rises due to a short circuit and there is a possibility of ignition.

The same applies to the case where sodium is used instead of lithium in the positive electrode.

In addition, conventional polymer film separators such as PE and PP have a risk of shrinking and short-circuiting at high temperatures.

As a result, problems such as battery deformation due to battery swelling and heat generation, charge / discharge efficiency of the battery are reduced, and battery life is shortened due to a decrease in battery energy density.

In order to solve these problems, attempts have been made to ensure battery performance by using a nonwoven fabric in which a ceramic material and polymer particles are supported as a separator of a lithium ion secondary battery.
Patent Document 1: Japanese Translation of PCT Publication No. 2009-507353

However, even when the separator according to the method described in Patent Document 1 is used, increasing the operating voltage that can be used due to the influence of the polymer particles contained does not provide sufficient battery performance and safety during high-temperature storage. In addition, a chemical reaction may occur at the interface between the polymer particles and the active material contained, and further, contact with the polymer particles and the copper foil of the negative electrode current collector plate may cause copper damage and affect the life. all right. Furthermore, it was found that the separator was clogged due to melting of the polymer particles during storage at high temperature, and the output characteristics were deteriorated.

Therefore, the present invention has been made to solve these problems, and the problem is that it is particularly excellent in performance, can simultaneously improve capacity and high output performance, and can expand the specification temperature range. Furthermore, it is an object of the present invention to provide a battery having excellent safety because an internal short circuit hardly occurs without contracting the separator.

As a result of investigations to solve the above problems, by carrying a material containing a ceramic material and phosphorus element on a nonwoven fabric as a separator, it becomes a stable battery even at a high positive potential, and can realize high output and high capacity. Since the specification temperature range can be expanded, and insulation can be secured stably against heat, the present invention is obtained which is a highly safe battery.

That is, the secondary battery of the present invention basically has a separator carrying a material containing a ceramic material and a phosphorus element in a nonwoven fabric, and the content ratio of the ceramic material is 50 wt% or more and 96 wt% or less, The ceramic material is Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , BaTiO ₃ , AlPO ₄ , ZrPO ₄ , AlF ₃ . Furthermore, it is characterized by containing a polymer fiber having cellulose or an acrylic group. The nonwoven fabric material is characterized by comprising materials such as PET (polyethylene terephthalate), PP (polypropylene), PPS (polyphenylene sulfite), mica (mica) and the like.

As a result, the capacity and high output performance can be improved at the same time, the specification temperature range can be expanded, and the separator is not shrunk, internal short circuit is less likely to occur, and it is safer and prevents copper damage. A battery having a long life can be obtained.

In the case of a sodium ion battery, it is similarly established by replacing Na with Li.

According to the battery of the present invention, high output and high capacity can be achieved at the same time, copper damage is suppressed, and the life is improved by being excellent in liquid retention. Further, safety can be improved because the temperature rise in the battery can be suppressed, it is flame retardant and non-flammable, and it does not shrink at high temperatures like a film, thereby preventing a short circuit. Furthermore, even if the battery itself is exposed to a high temperature, safety can be ensured by suppressing ion migration and cutting off the current by vitrification or the like.

According to the battery of the present invention, charging and discharging can be stably performed even in a high operating voltage region (4.45 V or more).

This battery has a high voltage and a high capacity, can exhibit excellent charge / discharge performance, life, and rate performance (output characteristics), and can be used without problems even under high voltage and high temperature storage. Furthermore, since generation | occurrence | production of decomposition gas is suppressed, a highly safe battery can be obtained and it is a highly practical thing.

FIG. 1 is a schematic configuration diagram of a separator of the present invention. FIG. 2 is a table summarizing the battery conditions of this example. FIG. 3 is a table showing the performance of the battery in each example of this example.

A preferred embodiment of the present invention will be described below with reference to FIG.

First, the separator which is the gist of the present invention is formed by supporting at least a nonwoven material 1 with a ceramic material 2 and a material 3 containing a phosphorus element.

Even if the nonwoven fabric 1 and the ceramic material 2 are exposed to a high temperature, the film-like separator does not shrink and short-circuit internally, and is flame retardant and non-flammable, thereby improving safety. In addition, it has been confirmed that the diffusion rate is improved when ions move on the ceramic surface, and high output and rapid charging can be realized.

Moreover, when phosphorus (P) 3 is contained, holes are generated and an acceptor function is generated at the interphase interface. As a result, the elimination reaction is improved, and a semiconductor intermediate layer having ion conductivity is formed on the surface of the active material (both positive electrode and negative electrode). Therefore, the positive electrode active material itself and the contacting electrolyte and electrolyte are prevented from being oxidized by a high voltage.

¡Since it has excellent liquid retention, its life is also improved. Further, since the liquid injection property is improved, the manufacturing tact is also improved.

As a result, it has been possible to achieve both high output, rapid charging and high capacity, which have been conventionally difficult due to trade-offs. Due to the effect of phosphorus, an increase in the internal pressure of the battery and a swelling of the battery can due to a gasification reaction during high temperature standing and high voltage charging are suppressed, battery performance stability is improved, and size change is suppressed. In addition, since the separator has flame retardancy or nonflammability and does not shrink at high temperatures, a battery having excellent safety can be obtained. In addition, the specification temperature range is expanded, and further, it relates to a lithium ion secondary battery or sodium ion secondary battery separator having excellent life characteristics, and a lithium ion secondary battery or sodium ion secondary battery including the separator. .

Examples are shown below to clarify the features of the present invention, but the present invention is not limited to these examples.

The positive electrode contains an active material capable of inserting and removing lithium ions or sodium ions. As the active material, lithium nickel manganate, lithium manganate, lithium nickelate, nickel cobalt lithium manganate, lithium manganese phosphate, lithium iron manganate, lithium manganese titanate and their modified products (coinciding with metals such as aluminum and magnesium) And composite oxides such as those using sodium instead of lithium. In particular, those containing manganese are preferable. As binder, PVdF, PTFE, P (VdF / HFP) and modified acrylonitrile rubber particle binder (such as BM-520B manufactured by Nippon Zeon Co., Ltd.) as a base material are soluble in carboxymethylcellulose (CMC) and soluble It may be combined with a modified acrylonitrile rubber (such as BM-720H manufactured by Nippon Zeon Co., Ltd.). As the conductive agent, acetylene black, ketjen black, and various graphites may be used alone or in combination.

The negative electrode includes an active material capable of inserting and removing lithium ions or sodium ions. As the active material, metallic lithium, various natural graphites and artificial graphite, silicon-based composite materials such as silicide, silicon oxide-based materials, titanium alloy-based materials, and various alloy composition materials can be used. As a binder, from the viewpoint of improving the lithium ion acceptability, SBR and a modified product thereof are used in combination with a cellulose resin such as CMC and added in a small amount. Like the positive electrode, acrylic resin, PVdF, PTFE or P (VdF / HFP) is used. It is more preferable that

As for the electrolyte, the lithium salts include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , One or two selected from the group consisting of LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , LiCl, LiI, LiBETI, LiTFS The above can be mixed and used.
The concentration of the lithium salt is preferably 0.01 mol / l or more and lower than the saturated state. It has been found that when the lithium salt concentration is less than 0.01 mol / l, there is almost no dissociated lithium ion, so that the ion transmission force is insufficient and the performance is extremely lowered. On the other hand, in the saturated state, lithium is precipitated and the constituent materials such as electrodes are deformed.

As solvents, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), fluorinated ethylene carbonate (FEC), trifluoromethylcyclohexane (TFMCH), bistrifluoromethanesulfonylimide (TFSI), succinonitrile (SN), fluorinated phosphonitrile trimer and the like can also be used. In addition, in order to ensure stability during overcharge, vinylene carbonate (VC), cyclohexylbenzene (CHB), propane sultone (PS), propylene sulfite (PRS), ethylene sulfite (ES), and the like and their modified products It is also possible to use.

When phosphorus (P) is contained, holes are generated and an acceptor function is generated at the interphase interface. Thereby, it is considered that a semiconductor intermediate layer having ion conductivity is formed on the surface of the active material (both positive electrode and negative electrode). Therefore, the positive electrode active material itself and the contacting electrolyte and electrolyte are prevented from being oxidized by a high voltage.

Further, when zinc (Zn) is added, the acceptor function is further strengthened.

Potential conversion at nano level (energy that relaxes high potential) follows the transition probability W = W ₀ e ^{−r / Rd} (where Rd is the donor's Bohr radius), where r is the distance between the donor and the acceptor. Therefore, the degree of oxidation inhibition can be controlled by the size and amount of the P-containing material 3 to be added. However, there is a possibility of tradeoff with the reaction rate, that is, resistance and rate characteristics, and the size and amount are determined by optimizing the addition amount.

It is preferable to use a lithium salt or a sodium salt having a low lattice energy, a high degree of dissociation, an excellent ionic conductivity, and a good thermal stability and oxidation resistance.

The present invention is not limited to the examples shown below.

In addition, the following batteries were allowed to stand for a certain period of time after injecting the electrolyte in a dry air environment, and then subjected to a precharge process for about 20 minutes at a current corresponding to 0.1 C. A process of leaving aging in a 60 ° C. environment for 1 day is assumed.

(Nail penetration safety)
With respect to the fully charged battery, a heat generation state and an appearance were observed when a 2.7 mm diameter iron round nail was penetrated at a speed of 5 mm / second in a normal temperature environment.

Example 1
In Example 1, 10% by weight of propylene carbonate (PC), 10% by weight of fluorinated ethylene carbonate (FEC), 60% by weight of dimethyl carbonate (DMC), and 15% by weight of succinonitrile (SN) as organic solvents Lithium bistrifluoromethanesulfonylimide (LiTFSI) was used in a mixed solvent of 5% by weight, and LiPF ₆ was dissolved as a lithium salt at 1 mol / L to obtain an electrolyte for a lithium ion battery. However, it is not limited to this composition.

The positive electrode uses LiMnO ₂ formed on an Al foil. At the time of forming the positive electrode, an appropriate amount of each of acrylene black as a conductive agent and an acrylic resin as a binder is mixed. The negative electrode is made of a copper foil formed by mixing half of artificial graphite and natural graphite. When forming the negative electrode, an appropriate amount of styrene butadiene rubber resin (SBR) and a thickener cellulose (cmc) are applied and mixed as a binder.

The separator is a coating material in which the skeleton of the nonwoven fabric 1 is PET fiber, and α-Al ₂ O ₃ is mixed as a ceramic material 2 with an acrylic resin (for example, BM-520B manufactured by Nippon Zeon Co., Ltd.) at a 96: 4 weight ratio. The non-woven fabric is impregnated with AlPO ₄ which is phosphorus-containing material 3 having a weight 1/7 of the weight of Al ₂ O ₃ and dispersed, and heated to remove the solvent.

(Example 2)
In Example 1, the nonwoven fabric 1 is replaced with PET, and fibers made of PP are used.

(Example 3)
In Example 1, the nonwoven fabric 1 is replaced with PET and fibers of PPS material are used.

Example 4
In Example 1, the nonwoven fabric 1 is made of mica (mica) material instead of PET. For example, Neobest manufactured by Olivest Co., Ltd. is used.

(Example 5)
In Example 1, instead of Al ₂ O ₃ which is the ceramic material 2, SiO ₂ is used.

(Example 6)
In Example 1, anatase TiO ₂ is used in place of Al ₂ O ₃ which is the ceramic material 2.

(Example 7)
In Example 1, ZrO ₂ is used in place of Al ₂ O ₃ which is the ceramic material 2.

(Example 8)
In Example 1, BaTiO ₃ is used instead of Al ₂ O ₃ which is the ceramic material 2.

Example 9
In Example 1, in place of the Al ₂ O ₃ is a ceramic material 2, using AlPO _4, a solid powder and only AlPO _4.

(Example 10)
In Example 9, ZrPO ₄ is used instead of AlPO ₄ .

(Example 11)
In contrast to Example 1, a material obtained by impregnating a paint in which AlF ₃ is added to 1/10 weight of Al ₂ O ₃ weight is used.

(Example 12)
In Example 1, the nonwoven fabric 1 is entangled with cellulose fibers, and the average pore diameter before the cellulose is used is 0.6 μm, and the average pore diameter is 0.2 μm. However, the hole diameter is not limited to this.

(Example 13)
In Example 1, the ratio of Al ₂ O ₃ and acrylic resin was 50:50 by weight.

(Comparative Example 1)
In Example 1, the ratio of Al ₂ O ₃ and acrylic resin was 49:51 by weight.

(Comparative Example 2)
In Example 1, the ratio of Al ₂ O ₃ and acrylic resin was 97: 3 by weight.

(Comparative Example 3)
In Example 1, a separator having the same thickness and a PE film was used.

In Example 1, it was confirmed that the positive electrode obtained the same tendency with other materials regardless of LiMnO ₂ . The same applies to the negative electrode.

Furthermore, it has been confirmed that the same is true when Na is used instead of Li.

FIG. 2 shows a table summarizing the battery conditions of this example.

Also, the performance of the battery in each example of this example is shown in FIG.

The battery of the present invention also operated at −40 ° C., but it does not have the structure of the present invention, such as a comparative example, a structure that does not contain phosphorus, such as no phosphorus, or that uses a film separator. It did not work at -40 ° C.

The secondary battery according to the present invention has excellent performance and is useful as a highly safe and high-performance power source.

Claims

In an ion secondary battery composed of a positive electrode made of composite lithium oxide or composite sodium oxide, a negative electrode made of a material capable of holding lithium or sodium, a separator, and an electrolyte solution or solid electrolyte made of a nonaqueous solvent, A secondary battery in which the separator carries a material containing a ceramic material and a phosphorus element in a nonwoven fabric
The secondary battery according to claim 1, wherein the ceramic material-containing weight ratio of the separator is 50 wt% or more and 96 wt% or less.
The secondary battery according to claim 1, wherein the ceramic material contains at least alumina (Al 2 O 3 ).
The secondary battery according to claims 1 to 3, wherein the ceramic material contains at least silica (SiO 2 ).
The secondary battery according to any one of claims 1 to 4, wherein the ceramic material contains at least titanium oxide (TiO 2 ).
The secondary battery according to any one of claims 1 to 5, wherein the ceramic material contains at least zirconia (ZrO 2 ).
The secondary battery according to any one of claims 1 to 6, wherein the ceramic material contains at least barium titanate (BaTiO 3 ).
The secondary battery according to any one of claims 1 to 7, wherein the separator contains at least aluminum phosphate AlPO 4 .
The secondary battery according to any one of claims 1 to 8, wherein the separator contains at least zirconium phosphate ZrPO 4 .
The secondary battery according to any one of claims 1 to 9, wherein the separator contains at least aluminum fluoride AlF 3 .
The secondary battery according to claim 1, wherein the nonwoven fabric is made of a material containing cellulose.
The secondary battery according to any one of claims 1 to 11, wherein the nonwoven fabric is made of a material containing polymer fibers having an acrylic group.
The secondary battery according to claim 1, wherein the nonwoven fabric is made of a material containing polyethylene terephthalate (PET).
The secondary battery according to claim 1, wherein the nonwoven fabric is made of a material containing polypropylene (PP).
The secondary battery according to claim 1, wherein the non-woven fabric is made of a material containing polyphenylene sulfide (PPS).
The secondary battery according to any one of claims 1 to 15, wherein the nonwoven fabric is made of a material containing mica.
The secondary battery according to any one of claims 1 to 16, wherein the specified voltage uses a range of 4.45V or more when charged.