1.Definition of lithium titanate battery
The battery that uses lithium titanate as the anode material is called lithium titanate battery. Lithium titanate can form 2.4V or 1.9V lithium ion secondary battery with lithium manganate, ternary material or lithium iron phosphate and other cathode materials. In addition, it can also be used as a positive electrode to form a 1.5V lithium secondary battery with metal lithium or lithium alloy negative electrode.
2.Structure of lithium titanate
Lithium titanate is a kind of compound, its appearance is white powder, its melting point is 1520-1564 ℃, it is insoluble in water, and has strong melting property. It can be used for titanium-containing glaze raw materials, a small amount of melting properties, can be used as a flux.
The chemical formula of lithium titanate is Li4Ti5O12, which is a composite oxide composed of metallic lithium and low-potential transition metal titanium. It belongs to the AB2X4 series and can be described as a spinel solid solution.
The biggest feature of Li4Ti5O12 is its “zero strain”. The so-called “zero strain” means that the crystal lattice constant and volume change are very small when lithium ions are inserted or extracted, less than 1%. In the charge and discharge cycle, this “zero strain” can avoid structural damage due to the back and forth stretching of the electrode material, thereby improving the cycle performance and service life of the electrode, reducing the specific capacity degradation caused by the cycle, and has a very good Resistance to overcharge and overdischarge. Therefore, lithium titanate is also called “zero strain material”.
Structure of lithium titanate Battery Cell
Positive electrode: lithium iron phosphate, lithium manganate or ternary material, lithium nickel manganate.
Negative electrode: lithium titanate material.
Separator: Lithium battery separator with carbon as the negative electrode.
Electrolyte: Lithium battery electrolyte with carbon as the negative electrode.
Battery case: Lithium battery case with carbon as negative electrode.
- Lithium titanate characteristics
Lithium titanate (LTO) material is used as a negative electrode material in the battery. Due to its own characteristics, it is easy to interact with the electrolyte and produce gas during the charge and discharge cycle reaction. Therefore, ordinary lithium titanate The battery is prone to flatulence, leading to swelling of the battery cell, and a significant decrease in electrical performance, which greatly reduces the theoretical cycle life of the lithium titanate battery. The test data shows that ordinary lithium titanate batteries will have flatulence after about 1 500-2 000 cycles, leading to failure in normal use, which is also an important reason that restricts the large-scale application of lithium titanate batteries.
The performance improvement of lithium titanate (LTO) battery is a comprehensive manifestation of the performance improvement of individual materials and the organic integration of key materials. In response to the requirements for fast charging and long service life, in addition to the negative electrode material, other key raw materials (including positive electrode material, separator, and electrolyte) of lithium-ion batteries, combined with special engineering process experience, have finally formed ” The “flatulence” lithium titanate LpTO battery product was first implemented in batches on electric buses.
The test data shows that under the conditions of 6C charge, 6C discharge, and 100% DOD, the cycle life of the lithium titanate LpTO battery exceeds 25,000 times, the remaining capacity exceeds 80%, and the flatulence generated by the battery is not obvious. Affects its life; and the actual application of Chongqing fast-charging pure electric buses also shows that after the batteries are assembled, the electrical performance is also quite excellent, which can ensure the daily commercial operation of pure electric buses.
4.Classification of lithium titanate batteries
According to the appearance: prismatic lithium titanate battery，cylindrical lithium titanate battery and pouch lithium titanate battery
5.Advantages of lithium titanate battery
1) Long cycle life
During charging and discharging of lithium titanate batteries, the insertion and deintercalation of lithium ions will hardly cause changes in the crystal structure of lithium titanate, so it has almost no effect on the structure of lithium titanate materials. The stable 3D structure of lithium titanate provides super Long cycle life. Because of this, lithium titanate is also called “zero strain material”
2) Safe and stable
The discharge voltage of lithium titanate is stable, and when it is put into the electrolyte, the reaction activity is low, the SEI diaphragm is hardly produced, and the metal lithium crystal branch is hardly produced, which improves the safety and stability of lithium batteries.
3) High charging rate
Lithium titanate has a three-dimensional lithium ion conduction path, and has a high lithium ion diffusion coefficient (2*10-8cm2/s), so it can provide a faster charge and discharge rate. While shortening the charging time, the impact on battery cycle life is small.
4) Wide temperature range
It can work normally in the range of -40℃-50℃.
The use of electric vehicles instead of fuel vehicles is the best choice to solve urban environmental pollution. Among them, lithium-ion power batteries have attracted wide attention from researchers. In order to meet the requirements of electric vehicles for vehicle-mounted ion power batteries, the development of high safety and good rate performance And the long-lived anode material is its hot spot and difficulty.
Commercial lithium-ion battery negative electrodes mainly use carbon materials, but there are still some disadvantages in the application of lithium batteries with carbon as the negative electrode:
- Lithium dendrites are easy to precipitate during overcharging, causing battery short circuit and affecting the safety performance of lithium battery;
- It is easy to form SEI film, which leads to low first charge and discharge efficiency and large irreversible capacity;
- That is, the platform voltage of carbon materials is low (close to metal lithium), and it is easy to cause the decomposition of electrolyte, which brings safety risks.
- The volume changes greatly in the process of lithium ion insertion and extraction, and the cycle stability is poor.
Compared with carbon materials, spinel-type Li4Ti5O12 has obvious advantages: - It is a zero strain material with good cycle performance;
- The discharge voltage is stable, and the electrolyte will not be decomposed, which improves the safety performance of lithium batteries;
- Compared with carbon anode materials, lithium titanate has a high lithium ion diffusion coefficient (2*10-8cm2/s), and can be charged and discharged at a high rate.
- The potential of lithium titanate is higher than that of pure metal lithium, and it is not easy to produce lithium dendrites, which provides a basis for ensuring the safety of lithium batteries.
6.Disadvantages of lithium titanate battery
- Compared with other types of lithium-ion power batteries, the energy density will be lower.
- The problem of flatulence has been hindering the application of lithium titanate batteries.
- The price is higher than other types of lithium-ion power batteries.
- There are still differences in battery consistency, and the difference in battery consistency will gradually increase as the number of charge and discharge increases.
7.Application of Lithium titanate battery
The lithium titanate battery has a working voltage of 2.4V, a maximum voltage of 3.0V, and a charging current greater than 2C (that is, a current that is twice the battery capacity value).
Due to the high safety, high stability, long life and environmental protection characteristics of lithium titanate, the main applications are:
1) For military applications, applications requiring high safety, high stability and long-term cycles, energy storage and aerospace, Japanese torpedoes have used lithium titanate batteries, so deep diving and unmanned aerial vehicles will also have considerable development. , Will also be used first in extremely cold areas
2) Transportation, widely used in racing cars, new energy vehicles, electric motorcycles and electric buses
3) Grid, energy storage system
4) Industry
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