Green Strategy to Single Crystalline Anatase TiO₂ Nanosheets with Dominant (001) Facets and Its Lithiation Study toward Sustainable Cobalt-Free Lithium Ion Full Battery

Abstract

A green hydrothermal strategy starting from the Ti powders was developed to synthesis a new kind of well dispersed anatase TiO₂ nanosheets (TNSTs) with dominant (001) facets, successfully avoiding using the HF by choosing the safe substitutes of LiF powder. In contrast to traditional approaches targeting TiO₂ with dominant crystal facets, the strategy presented herein is more convenient, environment friendly and available for industrial production. As a unique structured anode applied in lithium ion battery, the TNSTs could exhibit an extremely high capacity around 215 mAh g^–1 at the current density of 100 mA g^–1 and preserved capacity over 140 mAh g^–1 enduring 200 cycles at 400 mA g^–1. As a further step toward commercialization, a model of lithiating TiO₂ was built for the first time and analyzed by the electrochemical characterizations, and full batteries employing lithiated TNSTs as carbon-free anode versus spinel LiNi_<i>x</i>Mn_2–<i>x</i>O₄ (x = 0, 0.5) cathode were configured. The full batteries of TNSTs/LiMn₂O₄ and TNSTs/LiNi_0.5Mn_1.5O₄ have the sustainable advantage of cost-effective and cobalt-free characteristics, and particularly they demonstrated high energy densities of 497 and 580 Wh kg_anode^–1 (i.e., 276 and 341 Wh kg_cathode^–1) with stable capacity retentions of 95% and 99% respectively over 100 cycles. Besides the intriguing performance in batteries, the versatile synthetic strategy and unique characteristics of TNSTs may promise other attracting applications in the fields of photoreaction, electro-catalyst, electrochemistry, interfacial adsorption photovoltaic devices etc