Ta Doping Improves the Cyclability and Rate Performance of a Nickel-Rich NCA Cathode via Promoted Electronic and Cationic Conductivity

Abstract

NCA layered cathode materials are characterized by low cost and high reversible specific capacity compared with olivine and spinel cathodes. However, the high Ni content also leads to poor cyclability. In this paper, other than the mechanism reported by another group, we proposed the increase in electronic and cationic conductivity of Ta-doped LiNi0.94Co0.04Al0.02O2 cathode material could be the other reason for the promoted electrochemical behavior. DFT calculation revealed that the increased amount of electrons near Fermi energy which reduces the bandgap (from 1.2953 eV to 1.2171 eV) of Ta-NCA can be ascribed to the enhanced electronic conductivity. Such improvement later leads to reduced polarization and therefore the cyclability of the half cell is increased. Meanwhile, the suppressed H2–H3 phase transition, is also found to be responsible for the promoted cyclic performance. For the Ta-NCA cathode, the capacity retention after 100 cycles is promoted from 42.11% to 93.62% (from 81.16 mAh·g–1 to 181.54 mAh·g–1). Ta doping also increases the Li diffusion coefficient due to the expanded interplanar spacing of the Li slab. For Ta-NCA cathode with a promoted diffusion coefficient of 3.11 × 10–11 cm2·s–1, the specific capacity at 5C is increased from 118.51 mAh·g–1 to 158.47 mAh·g–1. Both the increase in cyclability and rate behavior indicate the high potential of the Ta-NCA cathode material in high-energy lithium-ion batteries.

B/Al Codoped/Coated Ultra-High Nickel Cobalt-Free Material with Excellent High Voltage/Rate Cycle Stability

“…Figure j and Table S2 show the comparison of the cycling performance of the optimized NM90-1%AB material with related nickel-rich cathode materials (Ni ≥ 0.9) at different current densities and cycles in recent years. ,− It is very intuitive to find that the cycling stability and rate performances of the optimized NM90-1%AB material are superior to those reported materials, highlighting the outstanding advantages of B/Al codoping/coating modification.…”

Review—Advancements in Synthesis Methods for Nickel-Rich NCA Cathode Materials: Optimizing Synthesis Conditions and Their Impact on Electrochemical Performances for Next-Generation Lithium Batteries

“…27 Nickel-rich NCA can promote better by raising the valent of dopant elements. For example, Yanyan Liu et al 72 but it also improves the cyclability resulted by the high Ni content. Such dopants also improve the electric and cationic conductivity, resulting in less polarization and hence increased cyclability of nickel-rich NCA materials.…”

“…Such dopants also improve the electric and cationic conductivity, resulting in less polarization and hence increased cyclability of nickel-rich NCA materials. 72 Few works have systematically explored anionic doping. Nickelrich NCA cathode materials were doped with a variety of negative ions including Br , − Cl , − S , 2− F , − and PO .…”

Comprehensive Study of Ti and Ta Co‐Doping in Ni‐Rich Cathode Material LiNi0.8Mn0.1Co0.1O2 Towards Improving the Electrochemical Performance

“…Moreover, Ti‐doping can improve the structure stability and effectively suppress the undesirable phase transition [20–22] . Whereas, optimal level of Ta 5+ (0.64 Å) cations play a crucial role in minimizing Li + /Ni 2+ cation mixing, reducing the primary particle size, and improving the electronic conductivity that would synergistically improve electrochemical performance and long cycling structural stability of Ni‐rich NMC cathodes [23,24] . It has been well documented that after Ta doping, the energy of the (001) facets is lowered, which affects the primary particle morphology, resulting in a preferential growth of elongated/radially oriented primary particles thus helping better rate performance by enhancing charge transfer kinetics [25–28] …”

“…[20][21][22] Whereas, optimal level of Ta 5 + (0.64 Å) cations play a crucial role in minimizing Li + /Ni 2 + cation mixing, reducing the primary particle size, and improving the electronic conductivity that would synergistically improve electrochemical performance and long cycling structural stability of Ni-rich NMC cathodes. [23,24] It has been well documented that after Ta doping, the energy of the (001) facets is lowered, which affects the primary particle morphology, resulting in a preferential growth of elongated/radially oriented primary particles thus helping better rate performance by enhancing charge transfer kinetics. [25][26][27][28] Several methods have been used to synthesize cathode materials, including solid-state reaction, [29] spray-drying, [30] carbonate coprecipitation, [31] and hydroxide coprecipitation (HCP).…”