Building Homogenous Li₂TiO₃ Coating Layer on Primary Particles to Stabilize Li‐Rich Mn‐Based Cathode Materials

Abstract

M = Co, Ni) can deliver a theoretical specific capacity exceeding 300 mAh g −1 by unlocking the anionic redox chemistry. [2] However, LRMOs are plagued by issues of low Coulombic efficiency, capacity/voltage decay and voltage hysteresis mainly due to irreversible oxygen loss and transition metal (TM) migration. [3] Oxygen loss is proposed to lower the migration barrier of transition metals, induce the formation of cracks, accelerate electrolyte decomposition, and further impose thermal runway risk. [4] Many approaches, such as composition tailoring, [5] element doping, [6] gradient concentration design [7] and surface coating, [8] have been established to stabilize LRMOs. Among them, surface coating is most straightforward to mitigate oxygen loss on charging LRMOs.For practical electrode fabrication, cathode materials are usually prepared in microspheres composed of nanosized primary particles to achieve high tap density and facilitate slurry preparation and casting on current collector. Most reported coating techniques, for example, ball milling, atomic layer deposition and wet chemistry method involving coprecipitation and calcination, often build a protective layer on the secondary particles due to weak interaction between inner primary particles and coating material. Few researches have realized effective coating on primary particles of cathode materials. [9] For example, atomic layer deposition and high temperature annealing was employed to melt coated Li 3 PO 4 layer into grain boundaries of LiNi 0.76 Mn 0.14 Co 0.10 O 2 . [9b] Besides, a conformal poly(3,4-ethylenedioxythiophene) layer was generated on both secondary and primary particles of LiNi 0.85 Co 0.10 Mn 0.05 O 2 and Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 by oxidative chemical vapor deposition. [9c] Recently, a reactive boride infusion strategy was adopted to coat Co x B on primary particles of LiNi 0.8 Co 0.1 Mn 0.1 O 2 at room temperature. [9d] However, these primary particle coating strategies are often plagued by high cost and/or complicated procedures. It is desirable to develop facile, scalable routes for surface modification of primary particles to improve the performance of LRMO cathode materials.In this study, we proposed a simple yet efficient strategy for homogenously coating Li 2 TiO 3 (LTO) on the primary particles of Li 1.08 Mn 0.54 Co 0.13 Ni 0.13 O 2 (LRMO). As a lithium-ion conducting material, LTO not only exhibits chemical and Li-rich Mn-based oxides (LRMOs) are promising cathode materials for next-generation lithium-ion batteries (LIBs) with high specific energy (≈900 Wh kg −1 ) because of anionic redox contribution. However, LRMOs suffer from issues such as irreversible release of lattice oxygen, transition metal (TM) dissolution, and parasitic cathode-electrolyte reactions. Herein, a facile, scalable route to build homogenous and ultrathin Li 2 TiO 3 (LTO) coating layer on the primary particles of LRMO through molten salt (LiCl) assisted solid-liquid reaction between TiO 2 and Li 1.08 Mn 0.54 Co 0.13 Ni 0.13 O 2 is repo...

Enhancing Thermal and High-Voltage Cycling Stability of Ni-Rich Layered Cathodes through a Ti-Doping-Induced Surface-Disordered Structure

“…The SEM results indicate that both the NMC811 and T-NMC811 samples are crystalline, and the construction process of the surface-disordered structure does not have significant effects on the particle morphology (Figure S2). Using high-resolution TEM measurements, a nano-scale amorphous coating layer was found on the surface of the T-NMC811 sample (Figure S3), which may be ascribed to the formation of lithium titanium oxides during the high-temperature calcination process. , Also, the high-temperature process will lead to the Ti element doping into the surface lattice structure . To prove the doping of the Ti element, we conducted energy-dispersive spectrometry (EDX) mapping and line scanning of TEM on a single particle to characterize the distribution of elements.…”

Scalable Nitrate Treatment for Constructing Integrated Surface Structures to Mitigate Capacity Fading and Voltage Decay of Li‐Rich Layered Oxides

“…[24] In addition, the peak II centered at around 531.3 eV and the peak III situated at 532.8 eV are attributed to Li 2 CO 3 /LiOH components and surface oxidized species. [25] As listed in Table S2, the peak area ratio of peak II and peak III in pristine is larger than that in Ce-and Y-treated samples. This indicates that, without the surface-integrated layer, the pristine sample is unstable in air and engenders more residual lithium.…”

Improving the long-term electrochemical performances of Li-rich cathode material by encapsulating a three-in-one nanolayer

“…9,10 Under high charge cut-off voltage, typically in the range of 4.5-4.8 V, more Li + ions are delithiated from the Li-rich cathode, and more transition metal (TM) ions migrate from TM sites to neighboring Li + vacancies, easily triggering layered-to-spinel phase transition, TM dissolution, and oxygen extraction. 11,12 Consequently, TM dissolution and oxygen release at high operation voltages tend to exacerbate side reactions and aid the growth of an improper solid-electrolyte interphase (SEI) layer at the cathode-electrolyte interface (CEI), leading to a rapid increase in interface impedance, depressed Li + diffusion, continuous capacity degradation, and voltage fading in repeated cycles. [13][14][15] To ameliorate the aforementioned issues, various surface treatments from physical and chemical aspects have been carried out to enhance the long-term cyclability of Li-rich materials.…”