Surface Modification of Ni-Rich LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Material by Tungsten Oxide Coating for Improved Electrochemical Performance in Lithium-Ion Batteries

Abstract

Ni-rich NCM-based positive electrode materials exhibit appealing properties in terms of high energy density and low cost. However, these materials suffer from different degradation effects, especially at their particle surface. Therefore, in this work, tungsten oxide is evaluated as a protective inorganic coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM-811) positive electrode materials for lithium-ion battery (LIB) cells and investigated regarding rate capability and cycling stability under different operation conditions. Using electrochemical impedance spectroscopy, the interfacial resistance of uncoated and coated NCM-811 electrodes is explored to study the impact of the coating on lithium-ion diffusion. All electrochemical investigations are carried out in LIB full cells with graphite as a negative electrode to ensure better comparability with commercial cells. The coated electrodes show an excellent capacity retention for the long-term charge/ discharge cycling of NCM-811-based LIB full cells, i.e., 80% state-of-health after more than 800 cycles. Furthermore, the positive influence of the tungsten oxide coating on the thermal and structural stability is demonstrated using postmortem analysis of aged electrodes. Compared to the uncoated electrodes, the surface-modified electrodes show less degradation effects, such as particle cracking on the electrode surface and improvement of the thermal stability of NCM-811 in the presence of electrolyte.

Realizing Superior Cycle Stability of a Ni‐Rich Layered LiNi0.83Co0.12Mn0.05O2 Cathode with a B2O3 Surface Modification

“…Among these cathode materials, nickel‐rich (Ni‐rich) layered oxides LiNi x M 1‐x O 2 (M=Co, Mn, Al/Mn, x≥0.8) have received wide attention due to their high energy density, low cost and outstanding cycling and thermal stability . The high Ni content of LiNi x M 1‐x O 2 possesses a theoretical capacity of 275 mAh g −1 ; for example, the discharge capacity of LiNi 0.8 Co 0.1 Mn 0.1 O 2 can deliver 200 mAhg −1 within 2.5–4.3 V . A low Co and Mn content is beneficial for reducing cost and improving cycling stability.…”

Hierarchical porous LiNi1/3Co1/3Mn1/3O2 with yolk–shell-like architecture as stable cathode material for lithium-ion batteries

“…These are primarily attributed to (1) more severe Li + /Ni 2+ cation mixing that can trigger phase transitions; (2) the formation of surface lithium-containing residuals (e.g., LiOH, Li 2 CO 3 ) that can not only build accumulative resistance hindering the charge transfer at the interface of electrode/electrolyte but also generate gas (O 2 , CO, CO 2 ) during cycling; (3) the formation of oxygen species due to the reactions of highly reactive Ni 4+ at delithiation status with electrolyte, concomitantly with structural evolutions. [17][18][19] By far, LiNi 1/3 Co 1/3 Mn 1/3 O 2 which shows advantages of better structural and thermal stability and more stable cycling stability over those Ni-rich NCM cathode materials, has been deemed as the most ideal cathode material because of its overall modest performance. 20 However, drawbacks including the fatal capacity degradation in terms of long cycles and inferior rate capability especially at high C-rates as a result of sluggish lithium ions diffusion ($10 À11 cm 2 s À1 ) 21,22 have impeded its wide spread usage in high-power applicants.…”

Surface regulation enables high stability of single-crystal lithium-ion cathodes at high voltage

“…Therefore doping strategies would consequently decrease specific capacity. Another issue was recently raised that uneven stresses, observed in cycles driven at high voltage, induced intragranular cracks in polycrystalline, which exacerbated structural collapse and capacity loss in Ni-rich NCM [12][13][14] . To solve the deficiencies caused by different reasons, creative strategies are necessary to improve structural stability in NCM particles 15 .…”