Lithium battery cathode material

The main constituent materials of the lithium ion battery include an electrolyte, a separator, a positive and a negative material, and the like. The positive electrode material occupies a large proportion (the mass ratio of the positive and negative materials is 3:1 to 4:1), because the performance of the positive electrode material directly affects the performance of the lithium ion battery, and the cost directly determines the battery cost.

A lithium ion battery is a secondary battery system in which two different lithium intercalation compounds capable of reversibly inserting and extracting lithium ions are used as a positive electrode and a negative electrode of a battery. During charging, lithium ions are removed from the crystal lattice of the positive electrode material, inserted into the crystal lattice of the negative electrode material after passing through the electrolyte, so that the negative electrode is rich in lithium and the positive electrode is depleted in lithium; during discharge, lithium ions are released from the crystal lattice of the negative electrode material, after passing through After the electrolyte is inserted into the crystal lattice of the positive electrode material, the positive electrode is rich in lithium and the negative electrode is depleted in lithium. Thus, the difference between the positive and negative materials in the insertion and extraction of lithium ions with respect to the potential of the metal lithium is the operating voltage of the battery.

Lithium-ion battery is a new generation of green high-energy battery with excellent performance, which has become one of the key points of high-tech development. Lithium-ion batteries have the following characteristics: high voltage, high capacity, low consumption, no memory effect, no pollution, small volume, small internal resistance, less self-discharge, and more cycles. Because of its above characteristics, lithium-ion batteries have been applied to many civilian and military fields such as mobile phones, notebook computers, video cameras, and digital cameras.

Drying lithium battery cathode material by microwave drying new technology, solving the problem of drying time of conventional lithium battery cathode material drying technology, making the capital turnover slow, uneven drying, and insufficient drying depth

Specific features are:

1. Using lithium battery cathode material microwave drying equipment, fast and fast, can complete deep drying in a few minutes, the final water content can reach more than one thousandth

2. Microwave drying lithium battery cathode material, which is evenly dried and has good drying quality.

3. Microwave drying lithium battery cathode material, which is energy efficient, safe and environmentally friendly.

4. Microwave drying battery cathode material, which has no thermal inertia and the instantness of heating is easy to control, the microwave sintered lithium battery cathode material has the characteristics of fast heating rate, high energy utilization rate, high heating efficiency, safety and sanitation, and can improve the uniformity and yield of the product and improve the microstructure and properties of the sintered material.

In recent years, lithium battery related policies have been introduced to promote the establishment of upstream and downstream enterprises in the industry. The lithium battery is mainly composed of a positive electrode material, a negative electrode material, a separator and an electrolyte, and the positive electrode material accounts for more than 40% of the total cost of the lithium battery, and the performance of the positive electrode material directly affects various performance indexes of the lithium battery, so Lithium battery cathode materials occupy a central position in lithium batteries.

Lithium battery cathode materials that have been marketed at present include lithium cobaltate, lithium manganate, lithium iron phosphate and ternary materials.

With the rapid development of China's economy, the increasing demand for new materials for batteries, coupled with the strong demand for new, efficient and environmentally friendly battery materials for mobile phones, notebook computers, digital cameras, video cameras, automobiles, etc., China's new battery materials market will continue to expand. Lithium battery as the future development direction of the battery, its cathode material market development prospects are promising. At the same time, the promotion of 3G mobile phones and the large-scale commercialization of new energy vehicles will bring new opportunities for lithium battery cathode materials.

Although lithium battery cathode materials have a broad market, the outlook is very optimistic. However, lithium battery cathode materials still have certain technical bottlenecks especially the advantages of high capacitance and strong safety performance have not been fully exerted.

In fact, in the field of lithium battery cathode materials, any small technological innovation may set off a new round of market expansion. Chinese enterprises should strengthen research and development of key technologies for cathode materials, gain international leading position, and enhance core competitiveness. Take advantage of international competition.

At present, lithium batteries have low energy density. First of all, the energy density is low, the car is heavy, the space is small, and new battery materials need to be discovered. Secondly, the battery life is poor. It is said that the endurance of more than 100 kilometers is the ideal state. The actual road life is about 60 kilometers. If it is in a big city like Beijing, 60 kilometers is not enough. The third is poor security. This problem is still controversial because the materials used to make the battery are unstable and it is easy to explode.

Lithium battery anode material grasps the safety lifeline of power battery. In the lithium ion battery anode material, in addition to graphitized mesocarbon microbeads (MCMB), amorphous carbon, silicon or tin, occupy a small portion of the market, natural graphite and artificial Graphite occupies more than 90% of the market share of anode materials. In the 2011 anode material market statistics, the total global production of anode materials reached 32,000 tons, an increase of 28% compared with the same period of last year, in which both natural graphite and artificial graphite anode materials accounted for 89% of the market share. In recent years, due to the growth of electronic products, especially the application of lithium-ion batteries in the field of mobile phone tablet PCs, the corresponding positive and negative materials of batteries have increased rapidly in recent years. Graphite anode materials have been continuously from 2009 to 2011. The growth rate in three years has reached more than 25%.

In 2013, the global diaphragm demand reached 563 million square meters, which was 1.41 times of the market capacity in 2011, and the output value was about 1.7 billion US dollars. The domestic barrier film market demand was approximately 128 million square meters in 2011. China's lithium battery products have accounted for about 30% of the global market share. The market demand for domestic separators has grown in tandem with the lithium battery market.

At present, 80% of the domestic separator film consumption depends on imports, and there is still a lot of room for the demand for domestic separators. The proportion of domestic separators in the domestic market will rise rapidly. In 2013, the share of domestic separators in the domestic market is expected to exceed 30%, and in 2015 it will exceed 40%.

In summary, the development direction of lithium ion battery cathode materials is lithium iron phosphate. Although the research and development of domestic lithium iron phosphate cathode materials is in full swing, it lacks original innovative technologies. Lithium-ion battery anode materials have two development directions in the future - lithium titanate materials and silicon-based materials. The silicon-based materials developed in recent years in China can basically meet the requirements of high specific capacity, high power characteristics and long cycle life, but industrialization must also break through the constraints of process, cost and environment. China has made certain achievements in the localization of lithium ion battery separators, but there is still a long way to go to achieve mass production of high-end products. Lithium hexafluorophosphate possesses an absolute market advantage in lithium-ion battery electrolytes, but China is basically subject to Japanese technology, and its independent research and development strength is weak.

Conductive coating in battery materials

Surface treatment of battery conductive substrates with functional coatings is a breakthrough technological innovation. Carbon-coated aluminum foil/copper foil is a uniform and fine coating of aluminum nano-conductive graphite and carbon coated particles on the copper foil. It provides excellent static conductivity and collects micro-current of active material, which can greatly reduce the contact resistance between the positive/negative electrode material and the current collector, and improve the adhesion between the two, reducing the bonding. The amount of agent used, in turn, results in a significant increase in the overall performance of the battery.

The coating is water-based (aqueous agent system) and oily (organic solvent system).

Performance advantages of conductive coatings coated with carbon foil/copper foil

1. Significantly improve battery pack consistency and significantly reduce battery composition. Such as:

· Significantly reduce the dynamic internal resistance increase of the battery;

· Improve the consistency of the differential pressure of the battery pack;

· Extend battery life;

· Significantly reduce the battery composition.

2. Improve the adhesion and adhesion of the active material and the current collector, and reduce the manufacturing cost of the pole piece. Such as:

Improve the adhesion of the positive electrode material and the collector using the aqueous system;

Improve the adhesion of nanoscale or submicron cathode materials and collectors;

Improve the adhesion of lithium titanate or other high capacity anode materials and collectors;

· Improve the pass rate of the pole piece and reduce the manufacturing cost of the pole piece.

Test chart of adhesion of battery pole pieces coated with carbon foil and light foil

After the carbon-coated aluminum foil was used, the adhesion of the pole piece was increased from 10 gf to 60 gf (using a 3 M tape or a hundred-bar knife method), and the adhesion was remarkably improved.

3. Reduce polarization, increase magnification and gram capacity, and improve battery performance. Such as:

· partially reduce the proportion of binder in the active material and increase the gram capacity;

Improve the electrical contact between the active substance and the current collector;

· Reduce polarization and improve power performance.

Battery rate performance chart of different aluminum foils

Among them, C-AL is carbon coated aluminum foil, E-AL is etched aluminum foil, U-AL is light aluminum foil.

4. Protect the current collector and extend battery life. Such as:

· Prevent the collector from being corroded and oxidized;

· Increase the surface tension of the collector and enhance the easy coating performance of the collector;

? Can replace the costly etched foil or replace the original standard foil with a thinner foil.

Battery cycle graph of different aluminum foils (200 weeks)

(1) Is a light aluminum foil, (2) is an etched aluminum foil, and (3) is a carbon coated aluminum foil.

Study on anode materials for lithium batteries

As a negative electrode material of a lithium secondary battery, first, metallic lithium, followed by an alloy. However, they cannot solve the safety performance of lithium-ion batteries, which led to the birth of lithium-ion batteries with carbon materials as the negative electrode.

The negative electrode material of the polymer lithium ion battery is substantially the same as the lithium ion battery. As can be seen from the development of polymer lithium ion batteries, since the commercialization of lithium ion batteries, the following negative electrode materials have been studied: graphitized carbon materials, amorphous carbon materials, nitrides, silicon-based materials, tin-based materials, new alloys and other materials. This chapter mainly describes practical anode materials, namely graphitized carbon materials, and other anode materials are discussed.

For the practical application of the anode material, there are many factors to be considered, in addition to the reversible capacity, irreversible capacity and cycle performance, it should also include the adhesion of the anode material to the current collector ( coating properties), and the preparation of the negative electrode tab. Compaction density, volumetric capacity density, mass capacity density, etc., and these latter factors are often ignored by those engaged in the study of negative electrode materials. Of course, the conductivity and specific surface area of the negative electrode material are also factors to be considered.

Due to the variety of carbon materials, in order to better understand the anode materials, some basic knowledge about carbon materials will be introduced.

The page contains the contents of the machine translation.