作者：王海
关键字：TiO2, amorphous carbon, pseudocapacitance, lithium-ion batteries, anode materials
论文来源：期刊
具体来源：ACS Applied Materials & Interfaces
发表时间：2019年

Both nanocrystals and carbon materials have attracted considerable

attention in the field of lithium-ion batteries (LIBs), due to their fast

kinetics for lithium storage or long-life cycles. However, the easy aggregation

of nanocrystals and high-temperature doping process of carbon materials

seriously hindered their application in LIBs. Here we report the development of

unprecedented TiO_2-x@C nanocomposite electrodes through a unique

"melting-low temperature pyrolysis" strategy. It is found that in

this composite structure, the continuous and interconnected three-dimensional

amorphous carbon framework (3DCF) was closely connected by TiO₂

nanocrystals by Ti-O-C covalent bonding, forming robust 3D network

architectures. Interestingly, we found that TiO₂ nanocrystals can

greatly improve the pseudocapacitance of TiO_2-x@C nanocomposite

electrodes with increasing cycles, which significantly exceeded previously

reported TiO2-based anodes and carbon materials. Furthermore, for

the first time, the unusual improvement of pseudocapacitance of TiO_2-x@C

electrodes were carefully investigated by means of dQ/dV curves and electrochemical

kinetic analysis to reveal the extra contribution of lithium storage. 3DCF, a

“lithium ion reservoir”, possesses an unexpected capacity enhancement behavior

that is triggered by TiO2 nanocystals, and exhibited bicontinuous

pathways for both rapid ions and electrons transport.  In this case, TiO2 nanocrystals

stabilizing 3DCF acted as a conductive agent during charge and discharge. Our findings

confirm that 3DCF triggered by TiO2 nanocrystals boosted electrochemical

performance of TiO2-x@C nanocomposite electrodes, especially the

pseudocapacitance enhancement. The unique characteristics of ingenious

combination of TiO2 nanocrystals and amorphous carbon materials make

them obtain superior electrochemical properties in all known TiO_2-x

and carbon-based anodes (289 mAh g-1 at 5 A g^-1 after

4000 cycles). Above all, our findings reveal previously ignored fundamental

aspects of pseudocapacitance improvement of nanocomposite electrodes, and offer

new hope for structural design and carbon coating process of high-performance

anode materials.