Ti 2 Nb 2 x O 4+5 x compounds are very popular negative-electrode materials for lithium-ion batteries due to their high specific capacities, safe operating potentials and high cycling stability. Nevertheless, their poor electronic conductivities and insufficient Li + diffusion coefficients limit the rate capabilities. Herein, we explore highly conductive CrNb 11 O 29 with a high theoretical capacity (401 mAh g −1 ) and an open Wadsley–Roth shear structure as a new intercalating negative-electrode material having the same advantages of Ti 2 Nb 2 x O 4+5 x but a high rate capability. CrNb 11 O 29 nanorods (CrNb 11 O 29 -R) with lengths of 500–1000 nm and very small diameters of 30–50 nm are prepared based on a novel hydrothermal method . Due to the free electrons in Cr-3d orbitals and the large ionic radius of Cr 3+ , CrNb 11 O 29 exhibits a high electronic conductivity and large Li + diffusion coefficients , respectively. In-situ X-ray diffraction analyses confirm its high structural stability . These conductivity, structural and architectural advantages in CrNb 11 O 29 -R lead to its significant pseudocapacitive contribution (82.0% at 1.1 mV s −1 ), prominent rate capability (high reversible capacities of 343 mAh g −1 at 0.1C and 228 mAh g −1 at 10C), and outstanding cycling stability (only 8.9% capacity loss at 10C over 400 cycles).
Yanling Dong,Hanqing Li,Biao Zhang,Fugui Zhao,Feng Gao,Dong Liu
Microsized silicon (μSi) anodes take advantage of low-cost, high tap density, and high theoretical capacity (∼4200 mAh g–1). However, poor cycle stability is presented because of huge volume change during cycling, which seriously limits their practical application in commercial lithium-ion batteries. Herein, a tough composite network combining high electronic and ionic conductivity is developed to stabilize the operation of the μSi anode. The resultant μSi electrode exhibits a high capacity of 3789.0 mAh g–1 with a high initial Coulombic efficiency (ICE) of 92.2% at 100 mA g–1, high-rate capability (1636.0 mAh g–1 at 3 A g–1), and good cycle stability with a high capacity retention of 92.0% from 1908.7 mAh g–1 at 15th to 1755.9 mAh g–1 at 135th cycle under 2 A g–1. The excellent electrochemical performance is attributed to the high stretchability (560%) of the 3D structure of the composite network, which can preserve the integral electrode structure, providing rapid electronic conductivity and ionic conductivity during cycling and resulting in outstanding electrochemical performance. This work offers a facile strategy for the development of a tough network combining high electronic and ionic conductivity to enhance the electrochemical performance of high-capacity Si anodes and beyond for energy-dense batteries.
3D interconnected graphene nanocapsules (IGNCs) were prepared by a template strategy coupled with in-situ chemical activation technique via using diverse polycyclic aromatic molecules as building blocks for supercapacitors . Benefiting from the synergistic effects of nano-MgO-template and in-situ KOH activation, the 3D IGNCs feature seemingly incompatible advantages of conductive and porous properties, possessing interconnected thin networks for high electron conduction, short hierarchical pores for fast ion transport, and abundant accessible active sites for ion adsorption. The specific surface area, pore size and pore volume mainly depend on the mass of raw materials and the annealing temperatures. When evaluated as electrodes for supercapacitors, IGNCs exhibit remarkably enhanced electrochemical characteristics such as high capacitance, good rate performance and cycle stability. This work opens up a facile way for high-efficiency preparation of 3D IGNCs from diverse aromatic hydrocarbon sources for energy storage to substitute conventional porous carbons .
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