AUTHOR=Luo Hao , Tang Yijun , Xiang Zeying , Wu Pinghui , Li Zhizhong 

TITLE=Cl− Doping Strategy to Boost the Lithium Storage Performance of Lithium Titanium Phosphate

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.00349

DOI=10.3389/fchem.2020.00349

ISSN=2296-2646

ABSTRACT=<p>Because of energy storage limitations and the high demand for energy, aqueous rechargeable lithium batteries (ARLBs) are receiving widespread attention due to their excellent performance and high safety. Lithium titanium phosphate (LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>) exhibits the potential to serve as anodes for ARLBs because it has a three-dimensional channel and a stable structure. We employed an anion (Cl<sup>−</sup>) doping strategy to boost the lithium storage performance of LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>. A series of LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C composites doped with Cl<sup>−</sup> on <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>PO</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> were successfully synthesized with a sol-gel technique as anodes for ARLBs. The effects of chlorine doping with different content on the properties of LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3−<italic>x</italic></sub>Cl<sub>3<italic>x</italic></sub>/C (<italic>x</italic> = 0.05, 0.10, and 0.15) were investigated systematically. The doping of chlorine in appropriate amounts did not significantly impact the main structure and morphology of LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C. However, chlorine doping greatly increased the performance of LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C. LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>2.9</sub>Cl<sub>0.3</sub>/C (LCl-10) showed the best electrochemical properties. It delivered a discharge capacity of 108.5 and 85.5 mAh g<sup>−1</sup> at 0.5 and 15°C, respectively, with an increase of 13.2 and 43.3 mAh g<sup>−1</sup> compared to blank LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> (LCl). In addition, the discharge capacity of LCl-10 was maintained at 61.3% after 1,000 cycles at 5°C, implying an apparent improvement compared to LCl (35.3%). Our study showed that a chlorine-doped LiTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/C composite is a potential anode for high-performance ARLBs.</p>