High-Thermal- and Air-Stability Cathode Material with Concentration-Gradient Buffer for Li-Ion Batteries

Abstract

Delivery of high capacity with high thermal and air stability is a great challenge in the development of Ni-rich layered cathodes for commercialized Li-ion batteries (LIBs). Herein we present a surface concentration-gradient spherical particle with varying elemental composition from the outer end LiNiCoMnO (NCM) to the inner end LiNiCoAlO (NCA). This cathode material with the merit of NCM concentration-gradient protective buffer and the inner NCA core shows high capacity retention of 99.8% after 200 cycles at 0.5 C. Furthermore, this cathode material exhibits much improved thermal and air stability compared with bare NCA. These results provide new insights into the structural design of high-performance cathodes with high energy density, long life span, and storage stability materials for LIBs in the future.

An Improved High-rate Discharging Performance of “Unbalanced” LiFePO₄ Cathodes with Different LiFePO₄ Loadings by a Grid-patterned Micrometer Size-holed Electrode Structuring

“…[5][6][7] In order to improve the durability of LIBs, the development of battery materials that have a high durability, such as cathode and anode active materials, electrolyte and additives added to the electrolyte solution has been accomplished. [8][9][10] For example, the degradation mechanisms of electrode materials have already been reported for LiMn 2 O 4 11 and LiNi x Co y Al z O 2 (NCA). 12 Not only the degradation of electrode materials in LIBs but also the imbalance in capacity of the cathode and anode in a cell causes the decrease in LIBs' performance.…”

The Formation, Detriment and Solution of Residual Lithium Compounds on Ni-Rich Layered Oxides in Lithium-Ion Batteries

“…As shown in Figure 5A-E, hydrophobic polydimethylsiloxane (PDMS) coated NCM811, with a strong M−O−Si covalent bond, exhibited the enhanced air storage stability (Doo et al, 2019). Additionally, octadecyl phosphate (OPA) can be utilized to form a hydrophobic self-assembled monolayer on the surface of Ni-rich cathode Cycling performance of (D) pristine NCA and (E) CGCS after air exposure with a relative humidity of about 30% for different numbers of days between 3.0 and 4.3 V. Adapted from [Shi et al, 2017] with permission from American Chemical Society. (F) Schematic view of the core-shell structure and preparation process of gradient Ni-rich cathode material; (G) CV curves for gradient Ni-rich cathode material before and after 90-days air exposure.…”

“…Constructing gradient materials, with low a Ni concentration outer surface and high Ni content inner core, provides the answer. By changing the proportion of transition metal ions at different periods of coprecipitation, Shi et al synthesized a surface concentrationgradient spherical Ni-rich cathode material with diverse elemental composition, in which the core inside was LiNi 0.80 Co 0.15 Al 0.05 O 2 and the surface was composed of LiNi 1/ 3 Co 1/3 Mn 1/3 O 2 ( Figures 7A, B) (Shi et al, 2017). Compared to the pristine LiNi 0.80 Co 0.15 Al 0.05 O 2 , the gradient material presented significantly enhanced air stability ( Figures 7D, E) and excellent cycling performance ( Figures 7C).…”

Thermal safety studies of high energy density lithium‐ion batteries under different states of charge

“…However, before considering enhanced energy density, the safety of a LIB with a higher‐specific‐capacity material system must be accounted for . Researchers have therefore carried out in‐depth work in this area . Ni‐rich oxides provide a very high specific capacity of approximately 212 mAh g −1 with a Ni:Mn:Co ratio of 8:1:1 but suffer inherent impediments to high rate performance due to low Li diffusion rates .…”

“…20,21 Researchers have therefore carried out in-depth work in this area. [22][23][24] Ni-rich oxides provide a very high specific capacity of approximately 212 mAh g −1 with a Ni:Mn:Co ratio of 8:1:1 but suffer inherent impediments to high rate performance due to low Li diffusion rates. 25,26 The latter is caused by cation mixing because of the similar radii of Li + (0.076 nm) and Ni 2+ (0.069 nm), which leads to a higher activation energy barrier and structural instability.…”