China lithium battery materials development and four trends
In the past ten years, China has made great progress in the development of lithium battery materials, but it must also be seen that there is still a certain gap between China’s lithium battery technology and international advanced technology. The future development of lithium batteries will focus on the advancement of battery materials and the upgrading and continuous iteration of battery materials.
As the core material of the lithium battery industry chain, the localization of these battery materials and continuous technological progress are of great significance for China’s lithium battery technology to be at the forefront of the world.
Table of Contents
China’s lithium battery materials and technologies are developing rapidly
Lithium is the metal element with the smallest atomic weight in the periodic table of chemical elements, and it is also the metal with the smallest density, the smallest electrochemical equivalent, and the lowest electrode potential. Lithium batteries have become the mainstream today, with the following advantages:
● High specific energy. In terms of mass specific energy and volume specific energy, lithium batteries are more than three times higher than lead-acid batteries.
● Long cycle life. Generally, the number of cycles of lead-acid batteries is about 400 to 600 times, which is lower than that of lithium batteries.
● Wide charging power range. It can be fast charged at 1~3C, and the charging efficiency is above 85%, which will be further improved with the continuous progress of electric control technology;
● High rate discharge performance. The rate discharge of lithium batteries is higher than that of lead-acid batteries. Ordinary lithium batteries can achieve 2-3C discharge, and there are lithium batteries with high rate discharge capabilities.
China has also made a comprehensive scientific and technological plan for the development of lithium batteries, and issued a series of policies to lay a good foundation for the development of lithium batteries. Generally speaking, the global technology sources of lithium batteries are mainly Japan, China, and South Korea, among which Japan has an advantage in the research patents of lithium battery materials.
Focusing on lithium battery materials, it is necessary to increase investment in high-energy density, low-cost, safer, and lightweight battery materials for a period of time to carry out research and development and research. Make China break through the key battery materials manufacturing technology of the whole lithium battery industry chain as soon as possible, form large-scale production, and continuously have new battery materials iterations and technology iterations.
Development of several lithium battery materials
High nickel cathode materials
In battery materials, the ternary cathode materials are divided into nickel-cobalt-aluminate lithium (NCA) and nickel-cobalt lithium manganate (NCM). As the nickel content increases, the battery capacity of the ternary cathode material increases, while the cycle performance deteriorates. The advantage of high nickel cathode material is that it has a high specific capacity and is an excellent choice for power batteries. Although high nickel has the advantage of high specific capacity, it often leads to poor cycle performance due to structural and surface changes. Correspondingly, the main problems of high-nickel cathode materials include:
● Difficult to synthesize materials with stoichiometric ratio; ● High total alkali content, easy to react with CO2 and moisture in the air; ● Poor thermal stability and safety.
Therefore, it is necessary to carry out research on the modification technology of high-nickel ternary cathode materials to improve their performance. The production process of high-nickel ternary cathode materials includes the following steps: lithiation mixing, potting, calcining, crushing, grading, impurity removal, packaging, etc. The difference from ordinary ternary materials is mainly that the raw material requirements are high, the process is more complicated, and the preparation is difficult, so its cost is relatively higher.
Although there has been development in the past two years, the overall market share of high-nickel ternary cathode materials is not large, high-nickel production capacity is being released, the market is gradually advancing the application of high-nickel ternary materials, and its technology is also constantly improving.
Solid electrolyte
Among the lithium battery materials, solid electrolyte instead of liquid electrolyte is considered to be an important means to solve the safety problem of lithium-ion battery as power. Lithium-ion batteries generally use flammable organic electrolytes. When used as electric power batteries, overcharging or accidental collisions may cause the electrolyte to catch fire and cause safety accidents. The advantage of the liquid electrolyte is that it can maximize the contact area between the electrode and the electrolyte to reduce the electrochemical impedance.
However, liquid electrolytes have disadvantages such as low thermodynamic stability, poor Li+ conductivity, concentration polarization, narrow operating temperature range, easy fire, and easy leakage. In contrast, the advantages of solid electrolytes in battery materials include good safety, good machinability, simplified battery structure, wide operating temperature range, good chemical and electrochemical stability, and long cycle life. However, solid electrolytes also face problems that need to be solved: most Li+ conduction efficiency is very low; they cannot exist stably with metallic lithium.
The electrochemical impedance is large due to the limited contact area between the electrolyte and the electrodes. Solid electrolytes are not compatible with cathode and anode battery materials in terms of electrochemical and chemical stability. At present, the research around solid electrolytes is ongoing, and the materials of solid electrolytes will continue to improve and make more breakthroughs.
Silicon anode materials
Commercial lithium ion battery anode materials are mainly graphite, but the specific capacity of this type of battery material is very low, and the high-rate charge and discharge performance is poor. The theoretical specific capacity of single silicon anode material is 4200mA·h/g, more than ten times that of natural graphite; the working voltage is as low as 0.3V. In order to achieve a higher specific capacity of lithium-ion batteries to meet the needs of power batteries, a lot of research has been invested in silicon anode battery materials. Silicon-based is an important research hotspot at present, and is considered to be one of the most potential anode materials.
However, silicon-based anodes have large capacity and large volume changes in battery materials. At present, additives and other means are mainly used to improve the gram capacity, cycle stability and liquid absorption capacity of the anode material. At present, during the charge-discharge cycle, the silicon anode material will cause a huge volume change due to lithium intercalation and delithiation, which will lead to the pulverization and peeling of the active material, which will reduce the cycle performance of the electrode.
By developing silicon-carbon composite anode materials, it is possible to effectively avoid the pulverization of silicon due to excessive volume expansion during charging and discharging. In addition, carbon as coating battery materials can effectively stabilize the interface between the electrode material and the electrolyte. Therefore, silicon-carbon composites are expected to replace graphite as the anode for next-generation high-energy-density lithium-ion batteries.
Lithium battery binder
In lithium battery materials, the role of the special binder for lithium batteries is to bond and maintain electrode active materials, enhance the electronic contact between electrode active materials and conductive agents, active materials and current collectors, and better stabilize the structure of pole pieces . Since the volume of the cathode and anode of the lithium battery will expand or shrink during charging and discharging, the binder is required to play a certain buffering role.
The coating film containing the active material does not detach from the current collector or generate cracks. Although the amount of binder used is small, its binder performance has a great influence on the normal production and final performance of lithium-ion batteries, and it is a very important auxiliary battery materials in the battery industry.
Lithium battery special binders in battery materials are mainly divided into two categories: one is oil-soluble binders, using organic solvents as dispersants; the other is water-based binders, using water as dispersants. The performance of the binder directly affects the performance of the battery, so a suitable lithium battery binder requires low resistance and stable performance in the electrolyte. Binders play an important role in improving the cycle performance of batteries, rapid charge and discharge capabilities, and reducing the internal resistance of batteries.
Four major trends in the future development of lithium battery materials
The technical progress of lithium batteries mainly comes from the innovation and application research of key battery materials, and the main research and development direction is still focused on lithium-ion battery materials. This will bring a new breakthrough to the safety performance of the battery. The development trend of lithium battery materials is mainly reflected in the following four main aspects:
● One is the cathode material, which is mainly developed based on high-nickel ternary materials, through which high-nickel ternary materials can increase energy density while reducing costs and increasing stability.
● The second is the anode material. New high-capacity anode materials represented by silicon-carbon composite materials are the future development trend.
● The third is the electrolyte, which is mainly aimed at the problem of poor high-temperature stability of traditional electrolytes, researching new electrolytes, gradually developing towards polymer electrolytes, and finally developing towards all-solid electrolytes. In battery materials, the research, development and application of solid electrolyte materials will be of great significance to improve the performance of lithium batteries, reduce production costs, and improve stability and safety.
● The fourth is a new generation of water-based binder. More research will be developed in the direction of different water-based copolymer binders, in the direction of a new generation of multi-component copolymer binders that are resistant to high and low temperatures, and in the direction of more excellent anti-aging properties. In the future, research on water-based binders will become one of the important directions for the preparation of lithium-ion battery electrodes in lithium battery materials.
China lithium battery materials development and four trends
In the past ten years, China has made great progress in the development of lithium battery materials, but it must also be seen that there is still a certain gap between China’s lithium battery technology and international advanced technology. The future development of lithium batteries will focus on the advancement of battery materials and the upgrading and continuous iteration of battery materials.
As the core material of the lithium battery industry chain, the localization of these battery materials and continuous technological progress are of great significance for China’s lithium battery technology to be at the forefront of the world.
China’s lithium battery materials and technologies are developing rapidly
Lithium is the metal element with the smallest atomic weight in the periodic table of chemical elements, and it is also the metal with the smallest density, the smallest electrochemical equivalent, and the lowest electrode potential. Lithium batteries have become the mainstream today, with the following advantages:
● High specific energy. In terms of mass specific energy and volume specific energy, lithium batteries are more than three times higher than lead-acid batteries.
● Long cycle life. Generally, the number of cycles of lead-acid batteries is about 400 to 600 times, which is lower than that of lithium batteries.
● Wide charging power range. It can be fast charged at 1~3C, and the charging efficiency is above 85%, which will be further improved with the continuous progress of electric control technology;
● High rate discharge performance. The rate discharge of lithium batteries is higher than that of lead-acid batteries. Ordinary lithium batteries can achieve 2-3C discharge, and there are lithium batteries with high rate discharge capabilities.
China has also made a comprehensive scientific and technological plan for the development of lithium batteries, and issued a series of policies to lay a good foundation for the development of lithium batteries. Generally speaking, the global technology sources of lithium batteries are mainly Japan, China, and South Korea, among which Japan has an advantage in the research patents of lithium battery materials.
Focusing on lithium battery materials, it is necessary to increase investment in high-energy density, low-cost, safer, and lightweight battery materials for a period of time to carry out research and development and research. Make China break through the key battery materials manufacturing technology of the whole lithium battery industry chain as soon as possible, form large-scale production, and continuously have new battery materials iterations and technology iterations.
Development of several lithium battery materials
High nickel cathode materials
In battery materials, the ternary cathode materials are divided into nickel-cobalt-aluminate lithium (NCA) and nickel-cobalt lithium manganate (NCM). As the nickel content increases, the battery capacity of the ternary cathode material increases, while the cycle performance deteriorates. The advantage of high nickel cathode material is that it has a high specific capacity and is an excellent choice for power batteries. Although high nickel has the advantage of high specific capacity, it often leads to poor cycle performance due to structural and surface changes. Correspondingly, the main problems of high-nickel cathode materials include:
● Difficult to synthesize materials with stoichiometric ratio;
● High total alkali content, easy to react with CO2 and moisture in the air;
● Poor thermal stability and safety.
Therefore, it is necessary to carry out research on the modification technology of high-nickel ternary cathode materials to improve their performance. The production process of high-nickel ternary cathode materials includes the following steps: lithiation mixing, potting, calcining, crushing, grading, impurity removal, packaging, etc. The difference from ordinary ternary materials is mainly that the raw material requirements are high, the process is more complicated, and the preparation is difficult, so its cost is relatively higher.
Although there has been development in the past two years, the overall market share of high-nickel ternary cathode materials is not large, high-nickel production capacity is being released, the market is gradually advancing the application of high-nickel ternary materials, and its technology is also constantly improving.
Solid electrolyte
Among the lithium battery materials, solid electrolyte instead of liquid electrolyte is considered to be an important means to solve the safety problem of lithium-ion battery as power. Lithium-ion batteries generally use flammable organic electrolytes. When used as electric power batteries, overcharging or accidental collisions may cause the electrolyte to catch fire and cause safety accidents. The advantage of the liquid electrolyte is that it can maximize the contact area between the electrode and the electrolyte to reduce the electrochemical impedance.
However, liquid electrolytes have disadvantages such as low thermodynamic stability, poor Li+ conductivity, concentration polarization, narrow operating temperature range, easy fire, and easy leakage. In contrast, the advantages of solid electrolytes in battery materials include good safety, good machinability, simplified battery structure, wide operating temperature range, good chemical and electrochemical stability, and long cycle life. However, solid electrolytes also face problems that need to be solved: most Li+ conduction efficiency is very low; they cannot exist stably with metallic lithium.
The electrochemical impedance is large due to the limited contact area between the electrolyte and the electrodes. Solid electrolytes are not compatible with cathode and anode battery materials in terms of electrochemical and chemical stability. At present, the research around solid electrolytes is ongoing, and the materials of solid electrolytes will continue to improve and make more breakthroughs.
Silicon anode materials
Commercial lithium ion battery anode materials are mainly graphite, but the specific capacity of this type of battery material is very low, and the high-rate charge and discharge performance is poor. The theoretical specific capacity of single silicon anode material is 4200mA·h/g, more than ten times that of natural graphite; the working voltage is as low as 0.3V. In order to achieve a higher specific capacity of lithium-ion batteries to meet the needs of power batteries, a lot of research has been invested in silicon anode battery materials. Silicon-based is an important research hotspot at present, and is considered to be one of the most potential anode materials.
However, silicon-based anodes have large capacity and large volume changes in battery materials. At present, additives and other means are mainly used to improve the gram capacity, cycle stability and liquid absorption capacity of the anode material. At present, during the charge-discharge cycle, the silicon anode material will cause a huge volume change due to lithium intercalation and delithiation, which will lead to the pulverization and peeling of the active material, which will reduce the cycle performance of the electrode.
By developing silicon-carbon composite anode materials, it is possible to effectively avoid the pulverization of silicon due to excessive volume expansion during charging and discharging. In addition, carbon as coating battery materials can effectively stabilize the interface between the electrode material and the electrolyte. Therefore, silicon-carbon composites are expected to replace graphite as the anode for next-generation high-energy-density lithium-ion batteries.
Lithium battery binder
In lithium battery materials, the role of the special binder for lithium batteries is to bond and maintain electrode active materials, enhance the electronic contact between electrode active materials and conductive agents, active materials and current collectors, and better stabilize the structure of pole pieces . Since the volume of the cathode and anode of the lithium battery will expand or shrink during charging and discharging, the binder is required to play a certain buffering role.
The coating film containing the active material does not detach from the current collector or generate cracks. Although the amount of binder used is small, its binder performance has a great influence on the normal production and final performance of lithium-ion batteries, and it is a very important auxiliary battery materials in the battery industry.
Lithium battery special binders in battery materials are mainly divided into two categories: one is oil-soluble binders, using organic solvents as dispersants; the other is water-based binders, using water as dispersants. The performance of the binder directly affects the performance of the battery, so a suitable lithium battery binder requires low resistance and stable performance in the electrolyte. Binders play an important role in improving the cycle performance of batteries, rapid charge and discharge capabilities, and reducing the internal resistance of batteries.
Four major trends in the future development of lithium battery materials
The technical progress of lithium batteries mainly comes from the innovation and application research of key battery materials, and the main research and development direction is still focused on lithium-ion battery materials. This will bring a new breakthrough to the safety performance of the battery. The development trend of lithium battery materials is mainly reflected in the following four main aspects:
● One is the cathode material, which is mainly developed based on high-nickel ternary materials, through which high-nickel ternary materials can increase energy density while reducing costs and increasing stability.
● The second is the anode material. New high-capacity anode materials represented by silicon-carbon composite materials are the future development trend.
● The third is the electrolyte, which is mainly aimed at the problem of poor high-temperature stability of traditional electrolytes, researching new electrolytes, gradually developing towards polymer electrolytes, and finally developing towards all-solid electrolytes. In battery materials, the research, development and application of solid electrolyte materials will be of great significance to improve the performance of lithium batteries, reduce production costs, and improve stability and safety.
● The fourth is a new generation of water-based binder. More research will be developed in the direction of different water-based copolymer binders, in the direction of a new generation of multi-component copolymer binders that are resistant to high and low temperatures, and in the direction of more excellent anti-aging properties. In the future, research on water-based binders will become one of the important directions for the preparation of lithium-ion battery electrodes in lithium battery materials.
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