Effects of Metal Ions on the Structural and Thermal Stabilities of Li[Ni[sub 1−x−y]Co[sub x]Mn[sub y]]O[sub 2] (x+y≤0.5) Studied by In Situ High Temperature XRD

Abstract

Highly crystalline Li[Ni1−x−yCoxMny]normalO2 (x+y⩽0.5) (Li[Ni0.6Co0.2Mn0.2]normalO2 , Li[Ni0.55Co0.15Mn0.3]normalO2 , and Li[Ni0.5Co0.25Mn0.25]normalO2 ) were synthesized through a coprecipitation method. The capacities of the prepared samples were proportional to the amount of Ni in the host structure. The thermogravimetric analysis (TGA) and in situ high-temperature–X-ray diffraction (HT-XRD) analysis revealed that changes in the amount of manganese ions in the host structure profoundly affect the structural stability of the samples with x+y⩽0.5 . Li[Ni0.55Co0.15Mn0.3]normalO2 , containing the highest manganese content (y=0.3) , showed the most stable structural integrity among the samples as confirmed by in situ HT-XRD. The electrochemical performances of the samples in Ni amount (0.5⩽1−x−y⩽0.6) with the variation of Co (0.15⩽x⩽0.25) did not significantly vary under the test conditions (3.0–4.3V) . The small increase of Mn ions plays an important role in preservation of its initial structural symmetry during the high-temperature heating as well as electrochemical cycling. Furthermore, the structural stability has a relationship with the thermal stability and the electrochemical stability, especially at an elevated temperature (55°C) . On the basis of the differential scanning calorimetry and TGA results, the Li[Ni0.55Co0.15Mn0.3]normalO2 sample demonstrated improved thermal stability compared to the other samples.

A Novel Cathode Material with a Concentration‐Gradient for High‐Energy and Safe Lithium‐Ion Batteries

“…Figure 8a shows single‐crystal electron diffraction from the Li[Ni 0.8 Co 0.2 ]O 2 electrode after 50 cycles. As reported earlier, Li[Ni 0.8 Co 0.2 ]O 2 transformed to a spinel structure during cycling 21, 22. The electron diffraction pattern is indexed to the (001) zone of the spinel structure, exhibiting a fourfold symmetry.…”

Improved Rate Capability and Thermal Stability of LiNi0.5Co0.2Mn0.3O2 Cathode Materials via Nanoscale SiP2O7 Coating

“…[19][20][21][22], but increasing the Mn content increased the charge transfer resistance, resulting in decreased electrochemical performance (rate capability). On the contrary, increasing Mn content preserves initial structural integrity during the high-temperature heating as well as electrochemical cycling [23]. However, none of previous studies have not been reported to solve both rate capability at higher rates and thermal stability of the Ni-based cathode materials simultaneously.…”

Properties of LiNi0.8Co0.1Mn0.1O2 as a high energy cathode material for lithium-ion batteries

“…The poor capacity retention for LiNi 0.8 Co 0.1 Mn 0.1 O 2 is characteristic of Ni-rich cathode materials due to the structural transformation near the surface region. The spontaneous reduction of Ni 3+ to stable Ni 2+ and the evolution of oxygen species from the surface also contributes to the formation of LiOH and Li 2 CO 3 on the surface [18,41].…”