Structural Reinforcement through High-Valence Nb Doping to Boost the Cycling Stability of Co-Free and Ni-Rich LiNi_0.9Mn_0.1O₂ Cathode Materials

Abstract

As an important Co-free and Ni-rich layered oxide, LiNi 0.9 Mn 0.1 O 2 (NM91) has garnered significant interest as a promising cathode material for lithium-ion batteries. Despite its attractively high specific capacity, the intrinsic structural instability poses a great challenge to its electrochemical performances, especially cycling performance. In this work, we circumvent the structural instability issue of NM91 through high-valence Nb doping. Our findings reveal that high-valence Nb 5+ dopants were successfully incorporated into the lattice of LiNi 0.9 Mn 0.1 O 2 , functioning as interlayer pillars that reinforce the structure and mitigate the detrimental H2 → H3 phase transition. This results in greatly improved cycling stability and rate capability of the cathode. The discharge capacities of 1%Nb-NM91 reached 211.8 mA h g −1 at 0.1 C and 159.3 mA h g −1 at 5 C, with a retention rate of 95.6% after 100 cycles at 0.5 C, even superior to the previously reported lower Ni content counterparts, including LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and so forth. This study demonstrates that highvalence Nb doping is a promising strategy to overcome the structural instability issue in LiNi 0.9 Mn 0.1 O 2 and underscores the potential of Co-free Ni-rich layered oxides as cathode materials for 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.…”

Surface Engineering of Ni-Rich Cathodes Enables Homogeneous Doping of High-Valence Mo Ions for Li-Ion Batteries

“…Ni-rich layered oxides (LiNi x Co y Mn 1– x – y O 2 , x ≥ 0.8) are regarded as one of the most prospective cathode materials for lithium-ion batteries (LIBs) to meet the demands of rapidly advancing electric vehicles (EVs) owing to their outstanding discharge capacity and eco-friendly characteristics. − Despite these advantages, practical implementation of these Ni-rich cathodes still faces certain challenges . For instance, the electrochemical cycles induce lattice parameter changes, resulting in the accumulation of mechanical stress and the development of intergranular and intragranular cracks in the cathode material. − Consequently, the primary or secondary particles experience distortion, fragmentation, and cracking. − These cracks expose new surfaces, providing additional channels for electrolyte infiltration, which accelerates interface side reactions, leading to continuous capacity degradation of the cathode. − Furthermore, the release of lattice oxygen at high potentials jeopardizes thermal stability, and oxygen free radicals entering the electrolyte promote the oxidation and decomposition of the electrolyte, contributing to overall battery performance degradation. − …”

“…A successful method for improving stability and mitigating capacity degradation is metal cation doping. − Recent studies have highlighted the potential of doping high-valence elements, such as Nb, , Sb, Ta, and Mo, to induce a radial arrangement of primary particles by regulating crystal surface energy. Consequently, the doped cathode exhibits a conversion of uneven strain distribution into a uniform circumferential strain, effectively inhibiting local stress concentration, dissipating mechanical strain, and preventing intergranular cracks. − Moreover, the stronger metal–oxygen (M–O) bond resulting from the doping process aids in alleviating Li/Ni cation mixing and the escape of lattice oxygen, leading to Ni-rich oxides with enhanced cycle durability and thermal stability. ,, Mo has emerged as one of the most efficient agents among those that have been reported for refining primary particles over a broad range of calcination temperature .…”

“…15−18 A successful method for improving stability and mitigating capacity degradation is metal cation doping. 19−22 Recent studies have highlighted the potential of doping high-valence elements, such as Nb, 7,23 Sb, 24 Ta, 25 and Mo, 26 to induce a radial arrangement of primary particles by regulating crystal surface energy. Consequently, the doped cathode exhibits a conversion of uneven strain distribution into a uniform circumferential strain, effectively inhibiting local stress concentration, dissipating mechanical strain, and preventing intergranular cracks.…”