In-situ encapsulation of pseudocapacitive Li2TiSiO5 nanoparticles into fibrous carbon framework for ultrafast and stable lithium storage

Lithium-ion capacitors (LICs) emerge as the promising energy storage devices owing to their enhanced power density compared to batteries and superior energy density to electric double-layer capacitors. However, the wide use of graphite anodes in LICs results in intrinsic problems such as sluggish reaction kinetics and dendritic Li plating problem, while Li4Ti5O12-based electrodes exhibit low energy storage capacity and excessively high insertion potential. Herein, our research uncovers the synthesis of novel Li2TiSiO5 and carbon nanofibers (LTSO/C) via a morphology-preserved thermal transformation strategy as the high-performance anodes of LICs. LTSO/C electrodes with the unique 3D interconnected nanoarchitecture consisting of aggregation-free LTSO nanoparticles exbibit high-rate behavior (ca. 50% capacity retention from 0.1 to 10 A g−1), suitable Li+ insertion potential (0.1–1 V vs. Li/Li+), and high packing density of 1.93 g cm−3 (highly comparable to graphite and larger than Li4Ti5O12). Moreover, analysis on reaction kinetics has revealed that such high-rate performance can be attributed to the pseudocapacitive charge storage mechanism of as-synthesized LTSO/C electrodes. Afterwards, novel LICs employing LTSO/C anodes to replace graphite and Li4Ti5O12 further yield high working potential of 4.2 V and large gravimetric energy and power densities. These results thus suggest a great promise of the proposed materials selection and nanostructure design for ultrafast and stable energy storage devices.