Insight into the Fast‐Rechargeability of a Novel Mo_1.5W_1.5Nb₁₄O₄₄ Anode Material for High‐Performance Lithium‐Ion Batteries

Abstract

Wadsley–Roth phased niobates are promising anode materials for lithium‐ion batteries, while their inherently low electrical conductivity still limits their rate‐capability. Herein, a novel doped Mo1.5W1.5Nb14O44 (MWNO) material is facilely prepared via an ionothermal‐synthesis‐assisted doping strategy. The detailed crystal structure of MWNO is characterized by neutron powder diffraction and aberration corrected scanning transmission electron microscope, unveiling the full occupation of Mo6+‐dopant at the t1 tetrahedral site. In half‐cells, MWNO exhibits enhanced fast‐rechargeability. The origin of the improved performance is investigated by ultraviolet–visible diffuse reflectance spectroscopy, density functional theory (DFT) computation, and electrochemical impedance spectroscopy, revealing that bandgap narrowing improves the electrical conductivity of MWNO. Furthermore, operando X‐ray diffraction elucidates that MWNO exhibits a typical solid‐solution phase conversion‐based lithium‐ion insertion/extraction mechanism with reversible structural evolution during the electrochemical reaction. The boosted lithium‐ion diffusivity of MWNO, due to the Mo6+/W6+ doping effect, is confirmed by a galvanostatic intermittent titration technique and DFT. With the simultaneously enhanced electrical conductivity and lithium‐ion diffusivity, MWNO successfully demonstrates its fast‐rechargeability and practicality in the LiNi0.5Mn1.5O4‐coupled full‐cells. Therefore, this work illustrates the potential of ionothermal synthesis in energy storage materials and provides a mechanistic understanding of the doping effect on improving material's electrochemical performance.

Crystallographic Insight of Reduced Lattice Volume Expansion in Mesoporous Cu2+‐Doped TiNb2O7 Microspheres during Li+ Insertion

“…© 2023 Wiley-VCH GmbH valence states of Nb 4+ /Nb 5+ , Nb 3+ /Nb 4+ , and Ti 3+ /Ti 4+ . [26,37,[53][54][55] By comparing the peak intensity, position and stability delivered by TNO, 5Cu-TNO and 5Cu-TNO@NC anodes at three different cycles (initial state; 1000th, and 2000th), the Cu 2+ doping significantly improves the reversibility of the resulting 5Cu-TNO and 5Cu-TNO@NC anodes even after 2000 cycles. The CV tests conducted at different scanning rates (0.2-1.0 mV s −1 ) further demonstrate that the Cu 2+ doping and N-doped carbon coating enhance the pseudocapacitive effect of TiNb 2 O 7 since the amount of pseudocapacitive charge storage contribution by TNO is much lower than those by 5Cu-TNO and 5Cu-TNO@ NC (Figures S13 and S14, Supporting Information).…”

Enhanced Energy Storage Performance of Zr-Doped TiNb2O7 Nanospheres Prepared by the Hydrolytic Method

“…The plot of the potential versus log(D Li + ) is shown in Figure 6b,d. According to Fick's second law, 46 the calculation formula of D Li + is as follows 47 i k j j j j j y { z z z z z i k j j j j j y…”

“…The plot of the potential versus log( D Li + ) is shown in Figure b,d. According to Fick’s second law, the calculation formula of D Li + is as follows D normalL normali + = 4 π τ true( m normalb V normalM M normalB S true) true( normalΔ E normalS normalΔ E τ true) 2 where τ represents the constant current pulse; m b , V M , M B , and S stand for the mass of the active material in the electrode, molar volume, molar mass, and surface area of the electrode, respectively. Δ Ε S is the voltage difference in the current pulse process; Δ Ε τ is the voltage difference in the galvanostatic titration process .…”

Designing strategies of advanced electrode materials for high-rate rechargeable batteries

“…5c). Recently, an ionothermal-synthesis-assisted doping strategy was proposed by Dai et al 149 to prepare the Mo 1.5 W 1.5 Nb 14 O 44 anode. Based on the highly similar ionic sizes of the Mo 6+ and W 6+ cations, the W–R phase structure can be ensured.…”