Dual-Modified Compact Layer and Superficial Ti Doping for Reinforced Structural Integrity and Thermal Stability of Ni-Rich Cathodes

Abstract

Nickel-rich layered oxides have been regarded as a potential cathode material for high-energy-density lithium-ion batteries because of the high specific capacity and low cost. However, the rapid capacity fading due to interfacial side reactions and bulk structural degradation seriously encumbers its commercialization. Herein, a highly stable hybrid surface architecture, which integrates an outer coating layer of TiO2&Li2TiO3 and a surficial titanium doping by incorporated Ti2O3, is carefully designed to enhance the structural stability and eliminate lithium impurity. Meanwhile, the surficial titanium doping induces a nanoscale cation-mixing layer, which suppresses transition-metal-ion migration and ameliorates the reversibility of the H2 → H3 phase transition. Also, the Li2TiO3 coating layer with three-dimensional channels promotes ion transportation. Moreover, the electrochemically stable TiO2 coating layer restrains side reactions and reinforces interfacial stability. With the collaboration of titanium doping and TiO2&Li2TiO3 hybrid coating, the sample with 1 mol % modified achieves a capacity retention of 93.02% after 100 cycles with a voltage decay of only 0.03 V and up to 84.62% at a high voltage of 3.0–4.5 V. Furthermore, the ordered occupation of Ni ions in the Li layer boosts the thermal stability by procrastinating the layered-to-rock salt phase transition. This work provides a straightforward and economical modification strategy for boosting the structural and thermal stability of nickel-rich cathode materials.

Grain-boundary engineering of Ni-rich cathodes prolongs the cycle life of Li-ion batteries

“…Subsequently, the (400) S and (440) S peaks move towards lower angles at ∼350 °C, revealing that the spinel phase starts to convert into a rock-salt phase ( Fm 3̄ m ). 43 For the pristine NCM cathode, the temperature of the phase transition drops to 200 °C and 330 °C. It is well known that phase transformations are usually accompanied by the release of lattice oxygen.…”

Enhancing the Integral Structural and Thermal Stability of Ultrahigh-Ni Cathodes via Morphology Refinement and In Situ Interfacial Engineering

“…The unit cell volume and c -axis also slightly increase, which is owing to the introduction of tungsten and fluorine. , In addition, calculation results shown in Table S2 reveal that the degree of Li + /Ni 2+ miscibility enhances from 2.22% (NCM) to 3.18% (NCM-WF1) then to 5.23% (NCM-WF2). Studies report that the introduction of high valence state ions is unfavorable for Ni 2+ to convert into Ni 3+ , and thus, more Ni 2+ migrating to the lithium layer act as a pillar, which is profitable to improve the stability and cycle life. − …”

Li2TiO3 Dopant and Phosphate Coating Improve the Electrochemical Performance of LiCoO2 at 3.0–4.6 V

“…S6, respectively, and the fitting results by the Zview2 software are shown in Table 2 and Table S4. The intersection of the starting point and the x-axis in the Nyquist plots represents the ohmic resistance (R s ), and the semicircles at high frequency and medium frequency represent the electrode surface film impedance (R f ) and charge transfer impedance (R ct ), respectively; the sloping line at low frequency reflects the Li-ion solid-state diffusion (W o ) [53]. The transfer kinetics at the interface can be reflected by the change in R ct , and the reduced charge transfer resistance benefits Li-ion diffusion [54].…”