Doping-Induced Pre-Transformation to Extend Solid-Solution Regimes in Li-Ion Batteries

Abstract

In many intercalation electrodes of Li-ion batteries, lithiation induces distortive structural transformations with substantial implications for stress accumulation, capacity loss, and degraded rate performance. Here, we dope a phase-transforming electrode to stabilize a structure bearing considerable similarities to the initially lithiated phase. In this "pre-transformation" approach, demonstrated based on Mo-doping of V 2 O 5 , the thermodynamic penalty associated with the phase transformation is paid in part during materials' synthesis rather than the charge/discharge of a battery. Mo-doping alters Li−V 2 O 5 thermodynamics to unlock extended solid-solution lithiation regimes with modulated interplanar separations. Specifically, Mo-doping reduces structural distortions during charge/discharge processes, diminishes coherency stresses, and yields a substantially modified intercalation phase diagram. Operando synchrotron X-ray diffraction and chemical lithiation results in conjunction with phase-field modeling demonstrate the promise of doping-induced structural distortions to entirely alter phase evolution and improve electrochemistry−mechanics coupling in phase-transforming cathodes.

R-Nb2O5 has an ‘idealized’ V2O5 structure and Wadsley–Roth-like structural stability during Li-ion battery cycling

“…The symmetric cycling processes on discharge and charge are in contrast to those of the 'parent' compounds of R-Nb 2 O 5 , ReO 3 and V 2 O 5 , in which extensive and irreversible atomic structure changes during the rst lithiation result in signicant differences in the prole shape of the rst discharge and following cycles. 29,30,35 At faster cycling rates, electrochemical curves show good reversibility and similar electrochemical features to those aer cycling at slower rates, as well as lower capacities and higher overpotentials. Changes in cycling features with increasing rate are evident in Fig.…”

“…The symmetric cycling processes on discharge and charge are in contrast to those of the ‘parent’ compounds of R -Nb 2 O 5 , ReO 3 and V 2 O 5 , in which extensive and irreversible atomic structure changes during the first lithiation result in significant differences in the profile shape of the first discharge and following cycles. 29,30,35…”

“…27,28 Like ReO 3 , V 2 O 5 also undergoes polyhedral rotations during lithiation that result in extensive atomic structure changes. 29,30 V 2 O 5 has layers composed of edge-and cornersharing [VO 5 ] square pyramids (Fig. 1d).…”

Phase Engineering and Synchrotron-Based Study on Two-Dimensional Energy Nanomaterials

“…(c,d) Phase transformation diagrams of Mo 0.125 V 1.875 O 5 and V 2 O 5 . Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

Chemistry–mechanics–geometry coupling in positive electrode materials: a scale-bridging perspective for mitigating degradation in lithium-ion batteries through materials design

“…Such an approach with extended reversible solid-solution lithiation has been recently observed for Mo-doped V 2 O 5 wherein Mo alloying induces a pre-transformation to a distorted phase that is similar in structure to the lithiated phase. 175 Conceptually, the potential efficacy of improving electrochemical performance by tuning electronic structure has also been demonstrated by the tunnel-structured ζ-V 2 O 5 polymorph. 14,153 Compared to α-V 2 O 5 , ζ-V 2 O 5 has broader, more degenerate d-bands, which gives rise to a lower effective mass and a resulting increase in the mobility of the coupled polaron diffusion phenomena.…”