Operando Calorimetry Informs the Origin of Rapid Rate Performance in Microwave-Prepared TiNb2O7 Electrodes

Abstract

<div>The shear-phase compound TiNb<sub>2</sub>O<sub>7</sub> has recently emerged as a safe and high-volumetric density replacement for graphite anodes in lithium ion batteries. An appealing feature of TiNb<sub>2</sub>O<sub>7</sub> is that it retains capacity even at high cycling rates. Here we demonstrate that phase pure and crystalline TiNb<sub>2</sub>O<sub>7</sub> can be rapidly prepared using a high-temperature microwave synthesis method. Studies of the charging and discharging of this material, including through operando calorimetry, permit key thermodynamic parameters to be revealed. The nature of heat generation is dominated by Joule heating, which sensitively changes as the conductivity of the electrode increases with increasing lithiation. The enthalpy of mixing, obtained from operando calorimetry, is found to be small across the different degrees of lithiation pointing to the high rate of lithium ion diffusion at the origin of rapid rate performance.</div>

Redox Mechanisms, Structural Changes, and Electrochemistry of the Wadsley–Roth LixTiNb2O7 Electrode Material

“…11 TiNb 2 O 7 has since displayed the capability to supply high power densities at high charge rates. 24,25 Despite an increased interest in Wadsley−Roth phases as anodes in Li-ion batteries, [14][15][16]18,26,27 there is still a limited understanding of the electronic, thermodynamic, and structural properties of these phases as a function of the degree of Li insertion. This paper examines the full lithiation profile of TiNb 2 O 7 using first-principles statistical mechanics calculations to understand the redox mechanisms and their effect on the structural properties and Li site preferences.…”

Microwave‐assisted synthesis and electrochemical characterization of TiNb2O7microspheres as anode materials for lithium‐ion batteries

“…The energy conversion process is considered to enhance the reaction rate of compound formation. Thus, microwave‐assisted synthesis improves the phase purity and crystallinity of TiNb 2 O 7 powders 30,34,36 . The sample is identified to possess the Wadsley–Roth shear structure with C 2/ m space group 36 …”

“…Thus, microwave‐assisted synthesis improves the phase purity and crystallinity of TiNb 2 O 7 powders 30,34,36 . The sample is identified to possess the Wadsley–Roth shear structure with C 2/ m space group 36 …”

Li2ZnTi3O8anode: design from material to electrode and devices

“…In the microwave heating process, the microwave absorbing agent absorbs microwave energy and then converts microwave energy into heat to sinter the materials in a few minutes. 72,73 Li et al synthesized LZTO via a microwave reaction and investigated the effects of the microwave power on the electrochemical performance of LZTO. 42 In a typical process, TiO 2 , Li 2 CO 3 , and Zn(CH 3 COO) 2 •2H 2 O as the raw materials were ball-milled, then pressed into pellets, and finally heated in a domestic microwave oven at different microwave powers using Super P as the absorbing agent.…”