Facile synthesis of LiAl0.1Mn1.9O4 as cathode material for lithium ion batteries: towards rate and cycling capabilities at an elevated temperature

Enhanced Cycling Stability through Erbium Doping of LiMn₂O₄ Cathode Material Synthesized by Sol-Gel Technique

In this work, LiMn_2−xEr_xO₄ (x ≤ 0.05) samples were obtained by sol-gel processing with erbium nitrate as the erbium source. XRD measurements showed that the Er-doping had no substantial impact on the crystalline structure of the sample. The optimal LiMn_1.97Er_0.03O₄ sample exhibited an intrinsic spinel structure and a narrow particle size distribution. The introduction of Er³⁺ ions reduced the content of Mn³⁺ ions, which seemed to efficiently suppress the Jahn–Teller distortion. Moreover, the decreased lattice parameters suggested that a more stable spinel structure was obtained, because the Er³⁺ ions in a ErO₆ octahedra have stronger bonding energy (615 kJ/mol) than that of the Mn³⁺ ions in a MnO₆ octahedra (402 kJ/mol). The present results suggest that the excellent cycling life of the optimal LiMn_1.97Er_0.03O₄ sample is because of the inhibition of the Jahn-Teller distortion and the improvement of the structural stability. When cycled at 0.5 C, the optimal LiMn_1.97Er_0.03O₄ sample exhibited a high initial capacity of 130.2 mAh g⁻¹ with an excellent retention of 95.2% after 100 cycles. More significantly, this sample showed 83.1 mAh g⁻¹ at 10 C, while the undoped sample showed a much lower capacity. Additionally, when cycled at 55 °C, a satisfactory retention of 91.4% could be achieved at 0.5 C after 100 cycles with a first reversible capacity of 130.1 mAh g⁻¹.

Sol-Gel Synthesis of Silicon-Doped Lithium Manganese Oxide with Enhanced Reversible Capacity and Cycling Stability

A series of silicon-doped lithium manganese oxides were obtained via a sol-gel process. XRD characterization results indicate that the silicon-doped samples retain the spinel structure of LiMn₂O₄. Electrochemical tests show that introducing silicon ions into the spinel structure can have a great effect on reversible capacity and cycling stability. When cycled at 0.5 C, the optimal Si-doped LiMn₂O₄ can exhibit a pretty high initial capacity of 140.8 mAh g^-1 with excellent retention of 91.1% after 100 cycles, which is higher than that of the LiMn₂O₄, LiMn_1.975Si_0.025O₄, and LiMn_1.925Si_0.075O₄ samples. Moreover, the optimal Si-doped LiMn₂O₄ can exhibit 88.3 mAh g^-1 with satisfactory cycling performance at 10 C. These satisfactory results are mainly contributed by the more regular and increased MnO₆ octahedra and even size distribution in the silicon-doped samples obtained by sol-gel technology.

Enhanced Cycling Stability of LiCuxMn1.95-xSi0.05O₄ Cathode Material Obtained by Solid-State Method

The LiCu_xMn_1.95−xSi_0.05O₄ (x = 0, 0.02, 0.05, 0.08) samples have been obtained by a simple solid-state method. XRD and SEM characterization results indicate that the Cu-Si co-doped spinels retain the inherent structure of LiMn₂O₄ and possess uniform particle size distribution. Electrochemical tests show that the optimal Cu-doping amount produces an obvious improvement effect on the cycling stability of LiMn_1.95Si_0.05O₄. When cycled at 0.5 C, the optimal LiCu_0.05Mn_1.90Si_0.05O₄ sample exhibits an initial capacity of 127.3 mAh g⁻¹ with excellent retention of 95.7% after 200 cycles. Moreover, when the cycling rate climbs to 10 C, the LiCu_0.05Mn_1.90Si_0.05O₄ sample exhibits 82.3 mAh g⁻¹ with satisfactory cycling performance. In particular, when cycled at 55 °C, this co-doped sample can show an outstanding retention of 94.0% after 100 cycles, whiles the LiMn_1.95Si_0.05O₄ only exhibits low retention of 79.1%. Such impressive performance shows that the addition of copper ions in the Si-doped spinel effectively remedy the shortcomings of the single Si-doping strategy and the Cu-Si co-doped spinel can show excellent cycling stability.

Research progress on design strategies, synthesis and performance of LiMn2O4-based cathodes

In this work, we review recent progress in structural design, designing composites with graphene/carbon nanotubes, crystalline doping, and coatings for improving the electrochemical performance of LiMn₂O₄-based cathode materials.