Cation-Disordered Rock-Salt Lithium Titanium Oxyfluoride Anode Enabling High-Rate Li-Ion Storage Through a 3D Percolation Network

TL;DR

A new lithium titanium oxyfluoride anode enables fast and efficient lithium-ion storage with high capacity and performance in batteries.

Contribution

A novel cation-disordered anode material with a 3D percolation network enables pseudocapacitive Li+ storage at low potentials.

Findings

The DRX-LixTiOF2 anode delivers a high reversible capacity of ~310 mAh g−1 and a rate capability exceeding 64.4 C.

Monte Carlo simulations show that a 3D percolation network enables fast Li+ migration with low energy barriers.

A lithium-ion capacitor with this anode achieves 4.0 V cell voltage, 197.9 Wh kg−1 energy density, and 50,000 W kg−1 power density.

Abstract

A novel low-potential cation-disordered rock-salt lithium titanium oxyfluoride (DRX-LixTiOF2) anode synthesized via electrochemically induced transformation enables pseudocapacitive Li+ storage extending down to 0.1 V vs. Li+/Li and delivers a high reversible capacity of ~ 310 mAh g−1 and an ultrahigh rate capability exceeding 64.4 C.Monte Carlo simulations reveal that the pseudocapacitive characteristics of DRX-LixTiOF2 anode originate from a three-dimensional percolation network that facilitates fast Li+ migration with low energy barriers, enabled by a cation/anion-disordered structure arising from the mixed occupancy of Li/Ti cations and O/F anions.The lithium-ion capacitor assembled with this DRX-LixTiOF2 anode and an activated carbon cathode exhibits exceptional performance: a 4.0 V operating voltage, a high energy density of 197.9 Wh kg−1 and an ultrahigh power density of 50,000 W kg−1.

A novel low-potential cation-disordered rock-salt lithium titanium oxyfluoride (DRX-LixTiOF2) anode synthesized via electrochemically induced transformation enables pseudocapacitive Li+ storage extending down to 0.1 V vs. Li+/Li and delivers a high reversible capacity of ~ 310 mAh g−1 and an ultrahigh rate capability exceeding 64.4 C.

Monte Carlo simulations reveal that the pseudocapacitive characteristics of DRX-LixTiOF2 anode originate from a three-dimensional percolation network that facilitates fast Li+ migration with low energy barriers, enabled by a cation/anion-disordered structure arising from the mixed occupancy of Li/Ti cations and O/F anions.

The lithium-ion capacitor assembled with this DRX-LixTiOF2 anode and an activated carbon cathode exhibits exceptional performance: a 4.0 V operating voltage, a high energy density of 197.9 Wh kg−1 and an ultrahigh power density of 50,000 W kg−1.

The online version contains supplementary material available at 10.1007/s40820-026-02123-w.

Pseudocapacitive materials employ rapid, non-diffusion-limited faradaic processes to store charge, demonstrating significant potential for fast-charging batteries and supercapacitors. However, the high redox potentials of existing pseudocapacitive anodes substantially lower the overall cell voltage and energy density. Here, a cation-disordered rock-salt lithium titanium oxyfluoride (DRX-LixTiOF2, 0 < x < 2) is reported to reversibly accommodate approximately 1.19 mol of Li+ (~ 310 mAh g−1) and delivers high-rate performance (exceeding 64.4 C) via pseudocapacitive Li+ storage within a low potential window extending down to 0.1 V vs. Li+/Li. This pseudocapacitive behavior is characterized by several structural and electrochemical features: the absence of phase transformation during Li+ intercalation, quasi-rectangular cyclic voltammetry curves, sloping charge/discharge profiles and a surface-controlled current response. We further reveal that the pseudocapacitive characteristics originate from a three-dimensional percolation network that facilitates fast Li+ migration with low energy barriers, enabled by a cation/anion-disordered structure arising from the mixed occupancy of Li/Ti cations and O/F anions. Owing to its low operating potential and high-rate capability, DRX-LixTiOF2 allows a lithium-ion capacitor to attain 4.0 V cell voltage and achieve energy and power densities several times higher than those obtained with conventional anodes, such as battery-type Li4Ti5O12 or pseudocapacitive materials like Nb2O5 and TiO2.

The online version contains supplementary material available at 10.1007/s40820-026-02123-w.

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