[Abstract] Polymer lithium-ion batteries are known as chemical energy sources for the first century in the Second Site. Polymeric ion batteries have extremely high requirements for flexible packaging technology. Soft packaging technology has an important influence on battery capacity and cycle life. This article focuses on the general requirements of polymer lithium-ion batteries for flexible packaging technology, describes the difficulties of flexible packaging technology in this area, describes the development trend of flexible packaging materials in the field of polymer lithium-ion batteries, and predicts the development potential of flexible packaging materials in the field of batteries. .
[Keywords] soft packaging technology, packaging design, flexible packaging materials, lithium-ion polymer batteries Introduction The energy that the battery can output depends on the specific capacity of the active material and the voltage of the single cell. Lithium metal is the material with the highest specific capacity among all metals, and the output voltage of the battery pair composed of C is as high as 3.6 V. These properties are unmatched by other metals. Therefore, people began to pay attention to lithium battery research very early. Because the metal hammer is very lively, use it directly to make the battery, the safety is extremely poor, so people mainly study the lithium ion rechargeable battery. In 1990, the world’s first production line for producing lithium-ion secondary batteries was established in Japan. In a short period of seven or eight years, lithium-ion batteries will soon be used in mobile phones and laptops due to their light weight, large capacity, long cycle life (greater than 1000 points), and no memory effect (which can be used with charge without affecting performance). Such areas as the use of batteries have expanded and are living in absolute advantages. In 1996, the polymer lithium-ion battery was successfully developed in the laboratory. Given that the polymer lithium-ion battery has almost all the advantages of the lithium-ion battery, it has better advantages in terms of weight, shape and safety of the battery, and thus has more advantages. A wide range of applications has caused a sensation in the world's battery industry and has been hailed as a chemical energy source for the 21st century. Countries around the world, especially Japan and the United States, have invested heavily in research and industrialization. Xiamen Baolong Industry Co., Ltd. is the first company in China to produce polymer lithium-ion batteries. The current battery production scale and the level of applied soft packaging technology are equivalent to the most developed countries.
1. Polymer lithium-ion batteries From the perspective of electrochemical reactions, there is no difference between polymer lithium-ion batteries and lithium-ion batteries, and even electrode materials and electrolytes used in polymer lithium-ion batteries are the same as lithium-ion batteries. However, there are no mobile electrolytes inside the polymer lithium-ion battery. The battery can be made into extremely thin sheets and various shapes. The single-cell battery can be made 0.6mm thick, so that the battery is required to be lightweight, small-quantity or In fields where there are strict requirements on the shape, such as mobile phones, notebook computers, camcorders, military portable tools, DVD players, and even electric vehicles, polymer batteries have more extensive application advantages and prospects.
The successful development of polymer lithium-ion batteries mainly lies in the solution of three major technologies, namely film manufacturing technology, lamination technology and flexible packaging technology. Membrane technology solves the problem that batteries cannot contain liquid electrolytes; lamination technology solves the problem of monolithic battery formation and monolithic battery assembly; flexible packaging technology makes the cell sheet a battery and the battery has a polymeric ion All the advantages of the battery.
2. The impact of flexible packaging materials on polymer lithium-ion batteries Polymer batteries ultimately rely on the use of flexible packaging materials to form batteries. Strictly speaking, it cannot be called “packaging†because in the field of polymer lithium-ion batteries, the “soft packaging material†forms a battery core together with the contents, and the battery core is assembled to form a battery. Therefore, the “soft packaging material†can be Think of it as an integral part of the battery. However, the material it uses is the common packaging material for people, and it really does play a role in protecting the contents. Therefore, people are still used to calling it "packaging." Just because the flexible packaging material can be seen as an integral part of the battery, it has an important influence on the performance of the battery. When the content of water and oxygen in the battery reaches a certain level, the capacity of the polymer lithium-ion battery will become smaller, the voltage drop will increase, the battery will not be charged, the battery will not be discharged, and the cycle life will decline. This may eventually lead to the failure of the battery. . The flexible packaging material achieves the maintenance of the battery performance by blocking water and oxygen. Therefore, the barrier property of the flexible packaging material has an important influence on the battery. In addition, some of the organic substances in the flexible packaging material may dissolve in the electrolyte to cause electrochemical reactions and destroy the performance of the battery; if the electrolyte is swollen by the flexible packaging material, the mixing ratio of the electrolyte will be changed, which is unfavorable for the battery performance.
3. General Requirements for Polymeric Ion Batteries for Flexible Packaging Materials The flexible packaging material used for polymer lithium-ion batteries is an aluminum-plastic composite film. The general requirements are as follows:
1 has excellent heat sealing polymer lithium-ion battery is very sensitive to high temperatures, the general use temperature is lower than 60 °C, requiring flexible packaging materials in the heat sealing strength is sufficient, the lower the heat sealing temperature, the better. In general, the heat sealing temperature should not exceed 150°C. When a higher heat sealing temperature is used, appropriate edge cooling measures must be used to prevent conduction and radiation during heat sealing from damaging the battery.
2 The heat-sealable material does not react with the plating solution The inner layer material of the flexible packaging material can neither be dissolved by the electrolyte nor swell with the electrolyte. If the flexible packaging material is dissolved by the electrolyte, since the working voltage of the battery is as high as 3.6V or more, the dissolved components will undergo electrochemical reaction to generate gas; if the flexible packaging material swells the electrical liberation, the concentration of the electrolyte will be changed and the battery will be affected. Performance.
3 Water-blocking and oxygen-barrier performances with high weight Water vapor permeability coefficient requirement is 10-4~10-6g/m2·d·1atm
Oxygen permeability coefficient required to reach 10-1~10-3cm3/m2·d·1atm
4 High flexibility and mechanical strength The production and assembly of polymer lithium-ion batteries puts higher requirements on the flexibility of flexible packaging materials; and the safety guarantee during use ensures the mechanical strength and heat sealing strength of flexible packaging materials. Made high demands.
5 has a good ability to withstand the electrolyte bubble resistance Flexible packaging materials in the packaging of batteries, long-term storage and turnover, the electrolyte can not leak phenomenon.
4. Difficulties in flexible packaging technology From the general requirements of the polymer ion battery described above for flexible packaging materials, it can be found that the flexible packaging material required for manufacturing has high difficulty:
First of all, the requirements for barrier properties of flexible packaging materials are 10,000 times higher than those of common aluminum-plastic composite materials. Such high barrier properties are difficult to meet with the requirements of ordinary composite materials and composite technologies. It is generally necessary to use extremely thick aluminum foil and use a composite material of 4 to 7 layers in order to apply a variety of composite technologies. For example, in the same material production process, it may be necessary to adopt the dry complex method, the extrusion method, the continuous extrusion compound method, the triple extrusion method, the thermal compound method or the rogue compound method, and the multi-layer co-extrusion method. In this way, higher requirements are placed on the production technology of flexible packaging materials.
Second, the choice of composite inner heat seal material. The electrolyte used in polymer lithium-ion batteries consists of a variety of esters that make up the organic electrolyte, in which the electrolyte is hydrolyzed in the presence of moisture to form highly acidic substances. According to the principle of similar compatibility, ester-based organic materials and many heat-sealable materials have swellability. Low-melting heat-sealable materials that do not react with the electrolyte and must have sufficiently strong acid resistance are more difficult to find.
In addition, the design of packaging materials is difficult. In the process of designing flexible packaging materials, it is necessary to ensure that the above-mentioned five requirements are satisfied, but also to ensure that the production of flexible packaging materials can be achieved, but also to take into account the impact of flexible packaging materials on polymer lithium-ion batteries and the development of polymer lithium-ion batteries Trends (in order to continuously develop the required flexible packaging materials) are more difficult.
Finally, the quality of flexible packaging materials has a long period of time. The water resistance required by the polymer lithium ion battery. Oxygen barrier performance exceeds the minimum accuracy of the tester in the packaging field, so it is difficult to quantitatively test the developed flexible packaging material. What is generally used today is the final determination of the actual packaging battery. According to the inspection characteristics of the battery and the degree of influence of the flexible packaging material on the battery and the impact rate, it is generally required that the final test of the compliance of the flexible packaging material lasts for more than three months.
5. The development trend of flexible packaging materials The development trend of flexible packaging materials is determined by the development trend of polymer lithium-ion batteries and the expansion of their application areas. There are two trends in the development of polymer lithium ions: one trend is the development of batteries in the direction of miniaturization and thinning; the other is the development of large-capacity and high-power charge and discharge. The former requires that the required flexible packaging material develop in a thinner and more flexible direction under the premise of barrier property; the latter requires that the barrier property of the flexible packaging material develops to a higher direction and the degree of interaction with the electrolyte is smaller. The direction of development. These two trends show that the selection of packaging materials, the requirements for packaging composite technology, and especially the structural design of packaging materials are more demanding. As soft packaging materials are the last quality assurance gate for battery molding, the impact on battery performance is also Great, therefore, in addition to the progress of the active materials and manufacturing processes required for batteries, the development and application of polymer lithium-ion batteries will largely depend on the development of flexible packaging technology and its materials.
6. The development potential of China's flexible packaging materials At present, China's mobile phone users have exceeded 50 million; in 1999 the country's notebook computers have all used lithium-ion batteries; portable camcorders, DVD players and other batteries are very large. If a polymer lithium-ion battery is used, the annual value of the flexible packaging material required is 2.3 billion yuan; the battery for electric vehicles (electric vehicles, electric motorcycles, and electric bicycles) is a huge market for batteries, and the polymer lithium-ion battery is The most popular battery in development, if successfully developed, will use 500,000 yuan in flexible packaging materials consumed in the domestic battery industry each year. At present, although only the polymer lithium-ion battery of Xiamen Baolong Industrial Co., Ltd. has achieved industrial scale production, nearly ten companies have already invested in projects or are in pilot production stage, and flexible packaging technology is an important factor that restricts the development of these enterprises. technical problem. Whether it is to promote the research process of lithium polymer batteries or as a flexible packaging material market, the research of flexible packaging technology in this field is very necessary. In foreign countries, there are specialized research institutes for flexible packaging technology for lithium polymer batteries, and only a handful of people in the country are engaged in this research. The research and application of flexible packaging materials should become an important part of the research and production of polymer lithium-ion batteries. (Author: Xiamen Baolong Industrial Co., Ltd. Shi Baoqing)
[Keywords] soft packaging technology, packaging design, flexible packaging materials, lithium-ion polymer batteries Introduction The energy that the battery can output depends on the specific capacity of the active material and the voltage of the single cell. Lithium metal is the material with the highest specific capacity among all metals, and the output voltage of the battery pair composed of C is as high as 3.6 V. These properties are unmatched by other metals. Therefore, people began to pay attention to lithium battery research very early. Because the metal hammer is very lively, use it directly to make the battery, the safety is extremely poor, so people mainly study the lithium ion rechargeable battery. In 1990, the world’s first production line for producing lithium-ion secondary batteries was established in Japan. In a short period of seven or eight years, lithium-ion batteries will soon be used in mobile phones and laptops due to their light weight, large capacity, long cycle life (greater than 1000 points), and no memory effect (which can be used with charge without affecting performance). Such areas as the use of batteries have expanded and are living in absolute advantages. In 1996, the polymer lithium-ion battery was successfully developed in the laboratory. Given that the polymer lithium-ion battery has almost all the advantages of the lithium-ion battery, it has better advantages in terms of weight, shape and safety of the battery, and thus has more advantages. A wide range of applications has caused a sensation in the world's battery industry and has been hailed as a chemical energy source for the 21st century. Countries around the world, especially Japan and the United States, have invested heavily in research and industrialization. Xiamen Baolong Industry Co., Ltd. is the first company in China to produce polymer lithium-ion batteries. The current battery production scale and the level of applied soft packaging technology are equivalent to the most developed countries.
1. Polymer lithium-ion batteries From the perspective of electrochemical reactions, there is no difference between polymer lithium-ion batteries and lithium-ion batteries, and even electrode materials and electrolytes used in polymer lithium-ion batteries are the same as lithium-ion batteries. However, there are no mobile electrolytes inside the polymer lithium-ion battery. The battery can be made into extremely thin sheets and various shapes. The single-cell battery can be made 0.6mm thick, so that the battery is required to be lightweight, small-quantity or In fields where there are strict requirements on the shape, such as mobile phones, notebook computers, camcorders, military portable tools, DVD players, and even electric vehicles, polymer batteries have more extensive application advantages and prospects.
The successful development of polymer lithium-ion batteries mainly lies in the solution of three major technologies, namely film manufacturing technology, lamination technology and flexible packaging technology. Membrane technology solves the problem that batteries cannot contain liquid electrolytes; lamination technology solves the problem of monolithic battery formation and monolithic battery assembly; flexible packaging technology makes the cell sheet a battery and the battery has a polymeric ion All the advantages of the battery.
2. The impact of flexible packaging materials on polymer lithium-ion batteries Polymer batteries ultimately rely on the use of flexible packaging materials to form batteries. Strictly speaking, it cannot be called “packaging†because in the field of polymer lithium-ion batteries, the “soft packaging material†forms a battery core together with the contents, and the battery core is assembled to form a battery. Therefore, the “soft packaging material†can be Think of it as an integral part of the battery. However, the material it uses is the common packaging material for people, and it really does play a role in protecting the contents. Therefore, people are still used to calling it "packaging." Just because the flexible packaging material can be seen as an integral part of the battery, it has an important influence on the performance of the battery. When the content of water and oxygen in the battery reaches a certain level, the capacity of the polymer lithium-ion battery will become smaller, the voltage drop will increase, the battery will not be charged, the battery will not be discharged, and the cycle life will decline. This may eventually lead to the failure of the battery. . The flexible packaging material achieves the maintenance of the battery performance by blocking water and oxygen. Therefore, the barrier property of the flexible packaging material has an important influence on the battery. In addition, some of the organic substances in the flexible packaging material may dissolve in the electrolyte to cause electrochemical reactions and destroy the performance of the battery; if the electrolyte is swollen by the flexible packaging material, the mixing ratio of the electrolyte will be changed, which is unfavorable for the battery performance.
3. General Requirements for Polymeric Ion Batteries for Flexible Packaging Materials The flexible packaging material used for polymer lithium-ion batteries is an aluminum-plastic composite film. The general requirements are as follows:
1 has excellent heat sealing polymer lithium-ion battery is very sensitive to high temperatures, the general use temperature is lower than 60 °C, requiring flexible packaging materials in the heat sealing strength is sufficient, the lower the heat sealing temperature, the better. In general, the heat sealing temperature should not exceed 150°C. When a higher heat sealing temperature is used, appropriate edge cooling measures must be used to prevent conduction and radiation during heat sealing from damaging the battery.
2 The heat-sealable material does not react with the plating solution The inner layer material of the flexible packaging material can neither be dissolved by the electrolyte nor swell with the electrolyte. If the flexible packaging material is dissolved by the electrolyte, since the working voltage of the battery is as high as 3.6V or more, the dissolved components will undergo electrochemical reaction to generate gas; if the flexible packaging material swells the electrical liberation, the concentration of the electrolyte will be changed and the battery will be affected. Performance.
3 Water-blocking and oxygen-barrier performances with high weight Water vapor permeability coefficient requirement is 10-4~10-6g/m2·d·1atm
Oxygen permeability coefficient required to reach 10-1~10-3cm3/m2·d·1atm
4 High flexibility and mechanical strength The production and assembly of polymer lithium-ion batteries puts higher requirements on the flexibility of flexible packaging materials; and the safety guarantee during use ensures the mechanical strength and heat sealing strength of flexible packaging materials. Made high demands.
5 has a good ability to withstand the electrolyte bubble resistance Flexible packaging materials in the packaging of batteries, long-term storage and turnover, the electrolyte can not leak phenomenon.
4. Difficulties in flexible packaging technology From the general requirements of the polymer ion battery described above for flexible packaging materials, it can be found that the flexible packaging material required for manufacturing has high difficulty:
First of all, the requirements for barrier properties of flexible packaging materials are 10,000 times higher than those of common aluminum-plastic composite materials. Such high barrier properties are difficult to meet with the requirements of ordinary composite materials and composite technologies. It is generally necessary to use extremely thick aluminum foil and use a composite material of 4 to 7 layers in order to apply a variety of composite technologies. For example, in the same material production process, it may be necessary to adopt the dry complex method, the extrusion method, the continuous extrusion compound method, the triple extrusion method, the thermal compound method or the rogue compound method, and the multi-layer co-extrusion method. In this way, higher requirements are placed on the production technology of flexible packaging materials.
Second, the choice of composite inner heat seal material. The electrolyte used in polymer lithium-ion batteries consists of a variety of esters that make up the organic electrolyte, in which the electrolyte is hydrolyzed in the presence of moisture to form highly acidic substances. According to the principle of similar compatibility, ester-based organic materials and many heat-sealable materials have swellability. Low-melting heat-sealable materials that do not react with the electrolyte and must have sufficiently strong acid resistance are more difficult to find.
In addition, the design of packaging materials is difficult. In the process of designing flexible packaging materials, it is necessary to ensure that the above-mentioned five requirements are satisfied, but also to ensure that the production of flexible packaging materials can be achieved, but also to take into account the impact of flexible packaging materials on polymer lithium-ion batteries and the development of polymer lithium-ion batteries Trends (in order to continuously develop the required flexible packaging materials) are more difficult.
Finally, the quality of flexible packaging materials has a long period of time. The water resistance required by the polymer lithium ion battery. Oxygen barrier performance exceeds the minimum accuracy of the tester in the packaging field, so it is difficult to quantitatively test the developed flexible packaging material. What is generally used today is the final determination of the actual packaging battery. According to the inspection characteristics of the battery and the degree of influence of the flexible packaging material on the battery and the impact rate, it is generally required that the final test of the compliance of the flexible packaging material lasts for more than three months.
5. The development trend of flexible packaging materials The development trend of flexible packaging materials is determined by the development trend of polymer lithium-ion batteries and the expansion of their application areas. There are two trends in the development of polymer lithium ions: one trend is the development of batteries in the direction of miniaturization and thinning; the other is the development of large-capacity and high-power charge and discharge. The former requires that the required flexible packaging material develop in a thinner and more flexible direction under the premise of barrier property; the latter requires that the barrier property of the flexible packaging material develops to a higher direction and the degree of interaction with the electrolyte is smaller. The direction of development. These two trends show that the selection of packaging materials, the requirements for packaging composite technology, and especially the structural design of packaging materials are more demanding. As soft packaging materials are the last quality assurance gate for battery molding, the impact on battery performance is also Great, therefore, in addition to the progress of the active materials and manufacturing processes required for batteries, the development and application of polymer lithium-ion batteries will largely depend on the development of flexible packaging technology and its materials.
6. The development potential of China's flexible packaging materials At present, China's mobile phone users have exceeded 50 million; in 1999 the country's notebook computers have all used lithium-ion batteries; portable camcorders, DVD players and other batteries are very large. If a polymer lithium-ion battery is used, the annual value of the flexible packaging material required is 2.3 billion yuan; the battery for electric vehicles (electric vehicles, electric motorcycles, and electric bicycles) is a huge market for batteries, and the polymer lithium-ion battery is The most popular battery in development, if successfully developed, will use 500,000 yuan in flexible packaging materials consumed in the domestic battery industry each year. At present, although only the polymer lithium-ion battery of Xiamen Baolong Industrial Co., Ltd. has achieved industrial scale production, nearly ten companies have already invested in projects or are in pilot production stage, and flexible packaging technology is an important factor that restricts the development of these enterprises. technical problem. Whether it is to promote the research process of lithium polymer batteries or as a flexible packaging material market, the research of flexible packaging technology in this field is very necessary. In foreign countries, there are specialized research institutes for flexible packaging technology for lithium polymer batteries, and only a handful of people in the country are engaged in this research. The research and application of flexible packaging materials should become an important part of the research and production of polymer lithium-ion batteries. (Author: Xiamen Baolong Industrial Co., Ltd. Shi Baoqing)
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