The characteristics of lithium titanate as the negative electrode of lithium ion battery
Since lithium titanate itself does not provide a lithium source, it can only be matched with lithium-containing electrode materials. When used as a positive electrode, the negative electrode can only be metal lithium or lithium alloy, and the battery voltage is about 1.5V at this time. As a negative electrode, lithium manganate, ternary materials and other positive electrode materials can form a battery with a voltage of 3V, so there are not many studies and applications of lithium titanate as a positive electrode material.
The current commercial lithium-ion battery negative electrode mainly uses carbon materials, but the lithium-ion battery with carbon as the negative electrode still has some drawbacks in its application. Lithium dendrites are easy to precipitate when overcharged, causing short circuits in the battery and affecting the safety performance of the lithium battery; SEI film is easy to form, resulting in low first charge and discharge efficiency and large irreversible capacity; the platform voltage of carbon materials is low (close to metal lithium), and it is easy to cause the decomposition of the electrolyte, which brings safety hazards; the volume changes during the insertion and extraction of lithium ions, and the cycle stability is poor.
1. Compared with the traditional graphite anode, lithium titanate has obvious advantages as a lithium ion battery anode
(1) Lithium titanate has a high lithium ion diffusion coefficient (2×10-8cm2/s). Commercial buses and passenger cars can charge 90% in 5 minutes without damaging the battery.
(2) Wide temperature adaptability, the material of lithium titanate anode system has better performance at low temperature (-40℃) and high temperature (60℃). For the low temperature and high temperature regions that the graphite anode system is difficult to cross, lithium titanate has obvious advantages.
(3) SEI film is not formed on the surface of lithium titanate, and lithium ions will not be consumed in the first cycle. In addition, the material has little change in the volume of lithium ions inserted and released, which is a “zero strain material”, which will help improve the cycle life of lithium-ion batteries. In actual application testing, the cycle life of lithium titanate can reach an astonishing 30,000 times capacity retention rate of more than 80%. Under the condition of fast charging, the capacity loss is less than 10% after 3000 charge-discharge cycles. Generally, the lithium iron phosphate bus battery is replaced every 2 to 3 years, and the lithium titanate battery is replaced every 10 to 15 years.
(4) Since the potential of lithium titanate is higher than that of lithium metal, it is not easy to generate lithium dendrites on the surface of the negative electrode of lithium titanate, which avoids the potential safety hazards of lithium dendrites piercing the diaphragm during the long cycle cycle.
(5) The discharge voltage is stable, and the electrolyte is not decomposed, which improves the safety performance of lithium batteries.
2. Lithium titanate as a negative electrode also has certain defects
(1) The problem of flatulence has been hindering the application of lithium titanate batteries.
(2) Compared with other types of lithium-ion power batteries, the energy density will be lower. The specific capacity of lithium titanate is only 170mA·h/g, which is much lower than the 300mA·h/g of graphite anode, which is determined by the material structure.
(3) Compared with other types of lithium-ion power batteries, the price is relatively high.
(4) There are still differences in battery consistency, and the difference in battery consistency will gradually increase as the number of charge and discharge increases.