[셀] Chinese to work on cold-resistant lithium titanium phosphate batteries
출처 : BatteryIndustry (2025.1.23)
The performance of lithium-ion batteries drops sharply in cold environments. Lithium titanium phosphate could provide a remedy. Chinese researchers have now demonstrated its suitability as an electrode material.
It is true that the cooling problems of current lithium-ion cell chemistries can be partially remedied, for example with additional battery heaters, improved electrolytes or electrode coatings. However, this increases the complexity, usually also the costs and can reduce performance, according to a press release from Informationsdienst Wissenschaft.
A team from Donghua University and Fudan University in Shanghai as well as Inner Mongolia University in Hohhot have chosen a different approach for their work: Instead of treating the symptoms of the “cold problem” with measures such as battery heating, they want to solve the cause. In electrochemical terms, the reduced performance in the cold is due to the slower diffusion of lithium ions within the electrode material.
According to an article published in the German scientific journal ‘Angewandte Chemie’, they have investigated materials with negative thermal expansion as electrode materials. Most materials expand with increasing temperature and contract when cold. Such materials with negative thermal expansion (NTE) do exactly the opposite, they expand when cold.
One such material is lithium titanium phosphate (LTP) with the formula LiTi2(PO4)3. In the laboratory, the researchers were able to demonstrate properties that give LTP good properties at low temperatures. The special crystal structure not only enables the storage of lithium ions, but also expands along one of the crystal axes during cooling.
“Through spectrometric and electron microscopic analyses as well as computer calculations, the team discovered that the vibration modes of the atoms change at low temperatures. For example, special transverse vibrations of certain oxygen atoms occur more frequently. This increases the distances between them, enlarging the lattice cavities and thus facilitating the storage and transport of lithium ions,” the press release states.
For the tests, the LTP was coated with carbon, resulting in so-called C-LTP. Specifically, at -10 degrees Celsius, 84 per cent of the diffusion rate of the value at 25 degrees could still be demonstrated. And because the open crystal structure of C-LTP at low temperatures should ensure a lower volume expansion of the cell during charging and discharging – even at low temperatures. The study therefore mentions a better cycle stability of C-LTP at -10 degrees (96.8 % capacity retention over 1000 cycles at 2 C).
Current research has identified materials with negative thermal expansion as a promising approach as an electrode material in lithium-ion batteries for cold environments. But it is still just that: a promising approach for further research, and not yet a material that will replace battery heating in electric cars in the foreseeable future.