Lithium Titanates: the most powerful battery material ever!

Lithium titanate is an inorganic compound with the molecular formula Li4Ti5O12. It is white powder and insoluble in water. The melting point is 1520~1564℃. Lithium titanate has a strong fluxing property.

Lithium titanate basic information

CAS: 12031-82-2 EINECS: 234-759-6

Density: 3.418g /cm3

Refractive index: 2.087 (589.3 nm)

Appearance: Powder

Color: Off - white

Water solubility: keep it Insoluble in water.

Electrode materials: lithium titanate powder

Lithium titanate (Li4Ti5O12) is a composite oxide of lithium metal and low potential transition metal titanium, which has a defective spinel structure. In the 1970s, it was used as a superconducting material for a large number of studies. In the late 1980s, it was used as a cathode material for lithium-ion batteries. However, because of its low potential and low specific energy relative to lithium (theoretical specific capacity of 175mAh/g), it failed to attract widespread attention. 

In 1996, K.Zaghib, a Canadian researcher, proposed for the first time that lithium titanate material could be used as a negative electrode and a high-voltage positive electrode to form a lithium-ion battery, and a carbon electrode to form an asymmetric supercapacitor. Later, Xiao Chai and others also used it as a lithium ion anode material to carry out research. However, it was not until around 1999 that people started a lot of research on Li4Ti5O12 as the anode material of lithium ion battery.

Lithium titanate with spinel structure is known as "zero-strain" material because its lattice constant hardly changes during lithium incalation. Its theoretical lithium incalation potential is 1.55V(vs. Li+/Li) and theoretical specific capacity is 175mAh/g, which has the following advantages:

(1) The structure will not change during the charging and discharging process;

(2) Compared with Li+/Li, the discharge voltage is close to 1.55V, which does not react with electrolyte and is not easy to cause lithium metal precipitation;

(3) The diffusion coefficient of lithium ion (2×10-8cm2/s) is one order of magnitude higher than that of the carbon negative electrode;

(4) Coulomb high efficiency, non-toxic raw materials, cheap, suitable for environmental protection and large-scale development;

(5) Good chemical stability and simple preparation, as the anode material of lithium-ion power battery, it is expected to solve the fast charging performance and safety performance of lithium-ion battery, and has a good development and application prospect.

Lithium titanate structure and properties

Li4Ti5O12 has spinel structure and space group is Fd3m, in which O2- is located at 32E and constitutes FCC lattice, part of Li+ is located in the 8A gap of tetrahedron, and the remaining Li+ and Ti4+ are located in the 16D gap of octahedron. Therefore, Its structural formula is as follows: [Li] 8A [Li1/3Ti5/3] 16D [O4] 32E, lattice constant A =0.836nm.

When the foreign Li+ is embedded in the lattice of Li4Ti5O12, these Li+ begin to occupy the 16C position, and the original Li+ in the tetrahedral 8A position starts to migrate to the octahedral 16C position, and eventually all the 16C positions are occupied by Li+. The [Li2] 16C [Li1/3Ti5/3] 16D [O4] 32eChemicalbook forms a rock-salt structure, so its capacity is mainly limited by the number of octahedral voids that can accommodate Li+. Obviously, Li+ and Ti4+ in the 16D position of the octahedron have nothing to do with the disembedding of Li+, but Li+ in the 8A position of the tetrahedron enters the 16C position of the octahedron. 

Therefore, the lattice constant is not changed after the original spinel structure is embedded in Li+, and the electrode potential remains unchanged. The phase transition of the charging and discharging process can be expressed by the equation [Li] 8A [LI1/3Ti5/3] 16D [O4] 32E + XE -+xLi+→ [Li1+ X] 16C [LI1/3Ti5/3] 16D [O4] 32E. The reaction product Li7Ti5O12 is light blue. Due to the appearance of Ti4+ and Ti3+ valence changes, its electronic conductivity is good, and the electrical conductivity is about 10-2s /cm.

Preparation of lithium titanate powder 

1. The amount of metanotitanic acid and lithium hydroxide reaction, after filtration, separation, drying. Appropriate amount of TiO2 and Li2CO3 can be heated to about 950℃ to prepare.

2. The amount of metanotitanic acid and lithium hydroxide reaction, after filtration, separation, drying.

Lithium titanate uses

It is used for titanium-containing glaze raw materials, and can be used as fluxing agent. It has no volume change in charge and discharge reaction and has good cycling performance. It is regarded as "zero strain material" and can be used as a secondary battery material.

Modified with lithium titanate powder

At present, the conductivity and electrochemical performance of Li4Ti5O12 electrode materials are mainly improved by metal ion doping, carbon coating, carbon and metal composite and nanoparticle preparation.

1. Metal ion doping Li4Ti5O12 Metal ion doping on the one hand can reduce the lithium immobilization potential of Li4Ti5O12 composite, on the other hand can improve the conductivity of the composite.

2. Carbon coating Li4Ti5O12 can improve the electronic conductivity of Li4Ti5O12 material, thus improving the electrochemical performance of the material.

3.Li4Ti5O12 and carbon or metal composite research found that the preparation of Li4Ti5O12 and carbon or metal composite research found that the preparation of Li4Ti5O12 and carbon or metal composite material can effectively improve the Li4TChemicalbooki5O12 multiplier performance.

4. Reducing Li4Ti5O12 particle size reducing Li4Ti5O12 particle size can shorten the diffusion path of lithium ion, so that Li4Ti5O12 multiplier performance is significantly improved; However, when Li4Ti5O12 particles are too small, the discharge platform is shortened due to the solid solution effect, and the larger reactive active area leads to the irreversible capacity increase, especially when the discharge potential of the material is low. 

Recently, people preparation is composed of a nanoscale particle micron grade secondary particles of Li4Ti5O12, superior materials not only have a nanoscale particles of charging and discharging properties, specific surface area of the secondary particles significantly at the same time, the irreversible capacity decreases, and tap density increases, the micron grade secondary particles Li4Ti5O12 has great application value.