Enhanced electrochemical performance of perovskite LaNiO3 coating on Li1.2Mn0.54Ni0.13Co0.13O2 as cathode materials for Li-ion batteries

Improving Fast Charging-Discharging Performances of Ni-Rich LiNi0.8Co0.1Mn0.1O2 Cathode Material by Electronic Conductor LaNiO3 Crystallites

Fast charging-discharging is one of the important requirements for next-generation high-energy Li-ion batteries, nevertheless, electrons transport in the active oxide materials is limited. Thus, carbon coating of active materials is a common method to supply the routes for electron transport, but it is difficult to synthesize the oxide-carbon composite for LiNiO₂-based materials which need to be calcined in an oxygen-rich atmosphere. In this work, LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) coated with electronic conductor LaNiO₃ (LNO) crystallites is demonstrated for the first time as fast charging-discharging and high energy cathodes for Li-ion batteries. The LaNiO₃ succeeds in providing an exceptional fast charging-discharging behavior and initial coulombic efficiency in comparison with pristine NCM811. Consequently, the NCM811@3LNO electrode presents a higher capacity at 0.1 C (approximately 246 mAh g⁻¹) and a significantly improved high rate performance (a discharge specific capacity of 130.62 mAh g⁻¹ at 10 C), twice that of pristine NCM811. Additionally, cycling stability is also improved for the composite material. This work provides a new possibility of active oxide cathodes for high energy/power Li-ion batteries by electronic conductor LaNiO₃ coating.

Harmonious Dual-Riveting Interface Induced from Niobium Oxides Coating Toward Superior Stability of Li-Rich Mn-Based Cathode

Ni²⁺/Ni⁴⁺ and O^2-/O_n^2- redoxs endow the Li-rich layered oxide of Li_1.2Mn_0.6Ni_0.2O₂ (LMNO) with a considerable specific capacity and higher voltage. However, during the repeated de-/lithiation, the constant structure degradation initiated from transition metal ion dissolvement and oxygen escape leads to rapid capacity decay, which severely hinders the commercial application of LMNO. Herein, Nb₂O₅ and LiNbO₃ are fabricated on the outside of the LMNO substrate. With the appropriate ion radius, a small amount of Nb⁵⁺ enters the substrate, which could enlarge the crystal spacing and facilitate the fast Li⁺ transfer and, more importantly, change the valence state of Mn and induce the formation a Fd3̅m transition phase on the interface between the coating layer and the interior LMNO. Density functional theory (DFT) calculation has proven that the transition phase could build double-way chemical bonds both inside and outside, and the LiNbO₃ coated LMNO composite (LMNO@LNO) possesses a more stable and harmonious interface due to the higher bonding strength between LiNbO₃ and the transition phase. Therefore, LMNO@LNO demonstrates the most outstanding rate capability and long-tern cycling stability (decay rate of 0.041% per cycle during 1000 cycling at 5 C). This work provides a new inspiration for the coating materials selection and the interface stability research for the LMNO cathodes.

Temperature-Controlled Synthesis of Li- and Mn-Rich Li1.2Mn0.54Ni0.13Co0.13O2 Hollow Nano/Sub-Microsphere Electrodes for High-Performance Lithium-Ion Battery

The calcination temperature plays a significant role in the structural, textural, and energy-storage performance of metal oxide nanomaterials in Li-ion battery application. Here, we report the formation of well-crystallized homogeneously dispersed Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere architectures through a simple cost-effective coprecipitation and chemical mixing route without surface modification for improving the efficiency of energy storage devices. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere cathode materials are calcined at 800, 900, 950, and 1000 °C. Among them, Li1.2Mn0.54Ni0.13Co0.13O2 calcined at 950 °C exhibits a high discharge capacity (277 mAh g-1 at 0.1C rate) and excellent capacity retention (88%) after 50 cycles and also delivers an excellent discharge capacity of >172 mAh g-1 at 5C rate. Good electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2-950 is directly related to the optimized size of its primary particles (85 nm) (which constitute the spherical secondary particle, ∼720 nm) and homogeneous cation mixing. Higher calcination temperature (≥950 °C) leads to an increase of the primary particle size, poor cycling stability, and inferior rate capacity of Li1.2Mn0.54Ni0.13Co0.13O2 due to smashing of quasi-hollow spheres upon repeated lithium ion intercalations/deintercalations. Therefore, Li1.2Mn0.54Ni0.13Co0.13O2-950 is a promising electrode for the next-generation high-voltage and high-capacity Li-ion battery application.

Surface-Functionalized Coating for Lithium-Rich Cathode Material To Achieve Ultra-High Rate and Excellent Cycle Performance

Although the lithium-rich cathode material Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, as a promising cathode material, has a high specific capacity, it suffers from capacity decay and discharge voltage decay during cycling. In this work, the specific capacity and discharge voltage of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ are stabilized by surface-functionalized LiCeO₂ coating. We have conducted LiCeO₂ coating via a mild synchronous lithium strategy to protect the electrode surface from electrolyte attack. This optimized LiCeO₂ coating has high Li⁺ conductivity and abundant oxygen vacancies. The results demonstrate that 3% LiCeO₂-coated Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ exhibits the highest capacity retention rate at 1, 2, and 5 C after 200 cycles, which were 84.3%, 85.4%, and 86.3%, respectively. The discharge specific capacity was almost 1.3, 1.4, and 1.4 times that of the pristine electrode. In addition, the 3% LiCeO₂ electrode exhibited the least voltage decay of 0.409, 0.497, and 0.494 V at 1, 2, and 5 C, which was only about half of the pristine electrode. It should not be overlooked that the 3% LiCeO₂ electrode still exhibits a high capacity at high current densities of 1250 mA g^-1 (5 C) and 2500 mA g^-1 (10 C), and its specific discharge capacities are 190.5 and 160.6 mAh g^-1, respectively. These outstanding electrochemical properties benefit from surface-functionalized LiCeO₂ coatings. To better understand the mechanism of oxygen loss of lithium-rich materials, we propose the lattice oxygen migration path of the LiCeO₂-coated electrodes during the cycle. Our research provides a possible solution to the poor rate capability and cycle performance of cathode materials through surface-functionalized coatings.