With the increasing applications of lithium ion batteries in energy storage, electric vehicles and hybrid electric vehicles, it’s required to improve the energy density, safety, rate capability and cycling stability of the batteries. Spinel Li₄Ti₅O₁₂ is a promising anode material for lithium-ion batteries which possesses good Li⁺ insertion and de-insertion reversibility with negligible structure change, high safety and rate capability, excellent cycle stability^1-2. While the theoretical capacity of it, 175 mAh g^-1, is slightly low. Meanwhile, it’s observed gassing during storage or cycling³, limitting its application.It was found that the surface coating could be an effective method to solve the swelling problem and be beneficial to the electrochemical performance⁴.

In this paper, we investigated the effect of titanate coupling reagent TCA-K38S as electrolyte additive on the performance of Li₄Ti₅O₁₂. TCA-K38S, isopropyl tri-(dioctylpyrophosphate) titanate, is a liquid monoalkoxy pyrophosphate titanate, usually used as coupling agent not only finorganic fillers with resins, but also fnon-polar materials with polar materials, the structural formula is shown in Fig.1. The electrolyte used in this work are 1.2 mol LiPF₆ in EC/ EMC solvents ((3:7 by volume), the TCA-K38S was added at 1wt.% and 3 wt.% to the electrolyte solution. Fig.2 shows the cycling performance of Li₄Ti₅O₁₂ batteries with different amounts of the TCA-K38S additive at various rates. It can be seen that the specific capacity of batteries with 1wt.% additive is 180 mAh g^-1 at the first discharge and stable in 170mAh g^‑1 at 0.2 C, comparied to 162mAh g^-1 and 158mAh g^‑1 at 0.2 C when it’s without additives.

Acknowledgements

The project was supported by the National High Technology Research and Development Program of China (863) (2013AA050902) and Shanghai Science and Technology Development Fund (15DZ2282000, 14JC1491800) .

References

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