Negative Thermal Expansion Behavior Enabling Good Electrochemical-Energy-Storage Performance at Low Temperatures.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Metal-ion batteries, including lithium-ion batteries, are crucial energy storage devices.
• Poor low-temperature performance, due to limited electrochemical kinetics, hinders their use in cold climates.
• A novel strategy is needed to overcome these temperature-dependent limitations.

Purpose of the Study:

• To investigate the potential of negative-thermal-expansion (NTE) materials for enhancing low-temperature battery performance.
• To demonstrate this strategy using LiTi2(PO4)3 (LTP) as a model material.

Main Methods:

• Utilized LiTi2(PO4)3 (LTP) with a negative a-direction thermal expansion coefficient (-1.1×10^-6 K^-1).
• Synthesized carbon-coated LTP (C-LTP) to improve electrochemical properties.
• Evaluated electrochemical performance, including ion diffusivity, capacity, rate capability, and cycling stability at -10°C.

Main Results:

• C-LTP exhibited robust electrochemical performance at -10°C, retaining 84% of Li+ diffusivity and 96% of theoretical capacity compared to 25°C.
• Superior rate capability was observed, with 83% capacity retention at 5C compared to 0.5C.
• The material demonstrated excellent cycling stability, achieving 96.8% capacity retention over 1000 cycles at 2C at -10°C.

Conclusions:

• Electrochemical energy storage materials with NTE behavior offer a promising strategy for improving low-temperature battery function.
• The unique structural changes in LTP at lower temperatures, driven by NTE, facilitate ion transport and insertion.
• C-LTP presents a viable solution for high-performance, stable metal-ion batteries in demanding cold environments.