WO2008131631A1

WO2008131631A1 - Safety type battery

Info

Publication number: WO2008131631A1
Application number: PCT/CN2008/000096
Authority: WO
Inventors: Fenggang Zhao; Wenhui Zeng
Original assignee: Dongguan Amperex Electronics Technology Co., Ltd
Priority date: 2007-04-25
Filing date: 2008-01-14
Publication date: 2008-11-06
Also published as: CN101295802A

Abstract

A safety type lithium ion battery including an anode layer having the bigger resistance. This lithium battery includes an electrode assembly, which has an anode and a cathode, wherein the anode includes a collector and an anode layer inhering on the surface of the collector and including active substance, and the active substance of the anode layer is graphite, and the resistance of the anode layer is at the range of 0.5Ω/cm2~10Ω/cm2. Because the resistance of the anode layer is bigger, the contact resistance is smaller when shorting, and the shorting current density is also relatively smaller. Accordingly, it is not happen that the temperature instantly raises and leads to fire, and it will improve the safety of the lithium ion battery.

Description

Safety lithium ion battery

The present invention relates to the field of lithium ion battery technology, and more particularly to a safe lithium ion battery having a large resistance of an anode diaphragm.

Background technique

Lithium-ion battery is a battery with high energy density and good environmental performance, which is widely used in various portable electronic devices. A lithium ion battery generally includes a cathode sheet, a separator, and an anode sheet wound together, wherein the cathode sheet includes a cathode current collector and a membrane having a cathode active material attached thereto; the anode sheet includes an anode current collector and is attached thereto A membrane having an anode active material. The cathode current collector is generally made of aluminum foil, the anode current collector is generally made of copper foil, and the isolating diaphragm is generally made of a polypropylene and polyethylene composite film. In the production, the cathode sheet, the separator and the anode sheet are superposed and wound to obtain a battery core, and the battery core is placed in the battery package, and then the electrolyte is injected into the package and sealed to form a battery.

However, the existing lithium ion battery is flammable due to the organic electrolyte used, and its anode diaphragm generally uses a graphite material, and its electric resistance is relatively small and is also easy to burn. When a short circuit occurs inside the battery, the battery is easily caused. Burning creates a safety hazard.

Table 1 shows the safety test results of a group of existing lithium-ion batteries. The test method is as follows: The cathode current collector, the cathode diaphragm and the anode current collector and the anode diaphragm are directly contacted, respectively, and then the test results are recorded separately. .

Table I Anode piece

Short circuit test

Copper foil, anode diaphragm, aluminum foil, safer, fire

Cathode sheet

Cathode diaphragm is safer and safer

According to the results of the above tests, when the cathode current collector (aluminum foil) and the anode diaphragm are short-circuited in the cathode sheet, the temperature of the battery rises rapidly, and smoke starts to be generated, resulting in an open flame. This phenomenon is caused by: The resistance of the anode diaphragm in a common lithium-ion battery is generally

Between 0.1~0.2Q/cm ² , and the cathode diaphragm resistance is about 1.6Q/cm ² , and the anode material itself is easy to burn. Thus, when the cathode current collector is in direct contact with the anode diaphragm, the resistance is small. The current density is relatively large, resulting in a large amount of heat generation. At this time, a large amount of heat generated by the current is concentrated on the short circuit, and the anode material itself is also easy to burn, which is very likely to cause combustion, and the battery cannot pass the short circuit test described above. , posing a hidden danger to the safe use of the battery.

Summary of the invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a safe lithium ion battery, and more particularly to a safe lithium ion battery having an anodic diaphragm having a large electrical resistance to overcome the above problems.

In order to achieve the above object, the present invention provides a safe lithium ion battery, the anode piece of which has a high electrical resistance, and its electric resistance is generally from 0.5 Q/cm ^{2 to} 8 Q/cm ² . In this way, if an unexpected situation occurs, such as the metal current trapped inside the battery pierces the separator and the cathode current collector-aluminum foil contacts the anode diaphragm to cause an internal short circuit, since the anode sheet has a high resistance, the contact resistance is relatively short. Smaller, the short-circuit current density is relatively small, so that the lithium-ion battery will not suddenly rise in temperature and cause a fire, thereby improving the safety of the lithium-ion battery. Fullness.

In order to solve the above technical problems, the present invention adopts the following specific solutions:

1. Insulate one or more insulating materials in the anode sheet of the battery, such as titanium oxide (Ti0 ₂ ), silicon oxide (Si0 ₂ ), aluminum oxide (A1 ₂ 0 ₃ ) or zinc oxide (Zn0 ₂ ). material.

2. No conductive carbon powder is added to the anode film, and the amount of binder is increased at the same time. 3. Use a low conductivity graphite material and surface treatment of the graphite material with a metal oxide such as alumina (A1203) or magnesium oxide (Mg02) to reduce its conductivity. The above measures can be used alone or in combination with several schemes. After adopting the above scheme, the anode piece of the lithium ion battery has a high resistance, and the electric resistance thereof is generally 0.5Q/cm ^{2 to} 8Q/cm ² , preferably 1.4Q/cm ² , so that the battery can not be ignited in the short circuit. , can also make the battery capacity, cycle performance, etc. are basically unaffected.

BRIEF DESCRIPTION OF THE DRAWINGS:

The present invention will be further described below in conjunction with the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the structure of an anode piece of a lithium ion battery in the present invention.

Specific examples:

Embodiment 1:

The structure and manufacturing process of the safe lithium ion battery of the present invention are basically the same as those of the conventional lithium ion battery. The difference is that the following method is used in the production of the anode piece: See Fig. 1, the anode piece 1 in this experiment An anode current collector 11 and a membrane 12 having an anode active material attached thereto are included. The anode current collector 11 is generally made of copper foil. When making First, a negative electrode active material, graphite powder, 1 ^ ₀₃ with eight hydroxypropyl-methyl cellulose sodium (CMC) And styrene-butadiene rubber (SBR) are mixed, wherein sodium carboxymethylcellulose and styrene-butadiene rubber are used as binders. This mixture was dispersed in water as a solvent to obtain an anode mixed slurry. Then, the above slurry was uniformly coated on a negative electrode current collector made of a copper foil to prepare an anode sheet 1, and then cold pressed. Next, the anode sheet 1 is dried to volatilize the solvent, so that a film 12 is formed on the surface of the anode sheet, and the drying temperature can be selected as needed. Further, in addition to the coating method, the slurry may be attached to the surface of the current collector 11 by dipping, and then cold pressed, and a film 12 is formed on the surface of the current collector 11 after drying.

In order to improve the reliability of the experiment, a total of three sets of experiments were performed in the present embodiment.

experiment one

In this experiment, the mass percentage of active material, binder and insulating material in the membrane 12 is: 94.5 : 4 : 1.5, wherein the active material is: graphite, the insulating material is AL ₂ 0 ₃ , the binder is: CMC and The mixture of SBR, the mass percentage of the two in the membrane are: 1.5% and 2.5%.

Experiment 2

A second experiment the same experimental manufacturing method, except that the active material, the binder and the mass percentage of AL2〇 _3. The mass percentage of the three in this experiment is: 91.5: 4:4.5. Among them, the mass percentage of CMC and SBR in the membrane are still: 1.5% and 2.5%, respectively. Experiment 3

In this experiment an active material, a binder and a mass percentage of AL2〇 _3. The mass percentage of the three in this experiment is: 86.5: 4:9.5. Among them, the mass percentage of CMC and SBR in the membrane is still divided into: 1.5% and 2.5%.

Comparative example The comparison column also uses the experimental manufacturing method, except that the film does not contain AL20 ₃ , and the mass percentage of the active material to the binder is: 96:4. Among them, the mass percentage of CMC and SBR in the membrane are still: 1.5% and 2.5%.

Table 2 shows the experimental results of the data and resistance of the above three groups of experiments.

Table II

As can be seen from the data in the table, the resistance layer of the surface sheet of the anode sheet of the present invention is remarkably improved as compared with the current lithium ion battery. After the formation, in the fully charged state, the nail penetration test can be smoothly passed, especially after the battery is disassembled, the anode piece and the cathode current collector are directly contacted, and no smoke or fire occurs. And three lithium ion batteries in other electrochemical properties after adding AL2〇 _3, as no significant difference in the capacity, cycle characteristics, i.e., the membrane 12 in the mixing AL2〇 ₃ will not affect the performance of the lithium ion battery.

Embodiment 2:

In the second embodiment, three sets of experiments and one comparative example were also made. The experimental conditions of the three sets of experiments were basically the same as those of the first embodiment, except that A1 ₂ 0 ₃ was replaced by Ti0 ₂ , and the comparative example remained unchanged. The experimental data and experimental results are shown in Table 3.

Anode

Graphite (%) CMC ( % ) SBR ( % ) Ti0 ₂ ( % ) Diaphragm resistance (Ω/cm ² ) Experiment 4 94.5 1.5 2.5 1.5 0.95 Experiment 5 91.5 1.5 2.5 4.5 3.80 Experiment 6 86.5 1.5 2.5 9.5 6.55 Comparative Example 96.0 1.5 2.5 0 0.15

As can be seen from the data in Table 3, the three groups of lithium ion batteries in this embodiment can also greatly improve the anode film resistance after adding Ti0 ₂ , thereby improving the safety performance of the lithium ion battery, and other electrochemical properties such as capacity and cycle performance. No significant difference.

Embodiment 3

In the present embodiment, no insulating material is added to the anode film, and graphite having a low electrical conductivity is used as the anode material, and the content of the binder is appropriately increased. The percentage of graphite to binder is between 90 and 92.5: 10 to 7.5, and at the same time, the resistance of the anode film using the above substance is between 0.5 Q/cm ^{2 and} 8 Q/cm ² . After testing, the anode film using the above materials is used in the fabricated battery, and no smoke and fire will occur in the short-circuit test to meet the battery safety requirements.

It should be noted that: The inventive idea of the present invention is to improve the safety of the battery by increasing the phase resistance of the anode body, and therefore it should be considered that: by various means, in particular, several modes disclosed by the present invention, whether used alone or not Or an embodiment in which the anode film resistance is increased in combination should fall within the protection scope of the present invention.

Claims

Rights request

1, a safe lithium ion battery, the lithium ion battery comprises an electrode group, the electrode group is provided with an anode sheet and a cathode sheet, wherein the anode sheet comprises a current collector and a membrane attached with an active material on the surface of the current collector, the anode diaphragm The active material is a graphite material, and the electric resistance of the anode sheet is between 0.5 Q/cm ^{2 and} 10 Q/cm ² .

2. The safe lithium ion battery according to claim 1, wherein: the diaphragm on the surface of the anode sheet comprises: an active material, a binder, and alumina as an insulating material, the mass percentage of which is: 86.5~94.5: 4: 9.5~1.5.

3. The safe lithium ion battery according to claim 1, wherein: the diaphragm on the surface of the anode sheet comprises: an active material, a binder, and titanium oxide or silicon oxide as an insulating material, the mass percentage of the three. In: 86.5~94.5: 4: 9.5~1.5.

A safety lithium ion battery according to claim 1, wherein the surface of the graphite material as the anode diaphragm active material is coated with a layer of aluminum oxide or magnesium oxide.

5. The safe lithium ion battery according to claim 4, wherein the mass ratio of the coated graphite material to the binder is between 93 and 94.5:7 to 5.5.

6. The safe lithium ion battery according to claim 4, wherein: the binder is: a mixture of sodium carboxymethylcellulose and styrene-butadiene rubber.