Spinel lithium manganate (LiMn 2 O 4 ) is a promising cathode material for lithium-ion batteries (LIBs) due to its non-toxicity, cost-effectiveness, and recyclability. However, its development is hindered by rapid capacity degradation and structural collapse caused by Jahn-Teller distortion and Mn-ions dissolution. In this work, a dual-functional LaNiO 3 coating on LiMn 2 O 4 particles was introduced to prevent direct contact with the F-containing electrolyte, meanwhile, apply compressive stress on the surface of LiMn 2 O 4 , suppressing surface MnO 6 octahedra distortion and preserving cubic symmetry during deep charge-discharge cycles. The strong La–O bonds can strengthen interface Mn–O bonds and increase the activation energy for Mn-ions disproportionation and acid erosion, thus reducing Mn-ions dissolution. Additionally, LaNiO 3 can serve as a conductive synapse to improve conductivity of LiMn 2 O 4 and optimize the Li + migration pathway at the electrode-electrolyte interface, reducing the migration potential barrier of Li + . Electrochemical tests show that the 1 wt% LaNiO 3 -coated LiMn 2 O 4 cathode achieves an initial discharge capacity of 130.37 mAh/g with a capacity retention of 92.27% after 600 cycles. This performance is significantly superior to that of the unmodified LiMn 2 O 4 , which only exhibits an initial capacity of 115.63 mAh/g and a retention of 79.55%. This work offers an effective strategy to enhance LiMn 2 O 4 stability and capacity and provides a theoretical basis for using perovskite materials in surface modification.
Yana Liu,Yu Zhu,Qinke Tang,Xinkang Shen,Yunfeng Zhu,Jiguang Zhang,Jun Wang,Zhixin Ba,Wenrong Cai,Yuting Huang,Xiaohui Hu
(3DOM) LaNiO 3 catalysts were successfully synthesized and significantly improved the hydrogen storage kinetics of MgH 2 . MgH 2 -5 wt% 3DOM LaNiO 3 can rapidly absorb 5.91 wt% H 2 at 175 °C within 500 s and desorb 6.37 wt% H 2 within 500 s at 300 °C, its hydrogen absorption and desorption rates are 10 and 11 times higher than MgH 2 -5 wt% Nano LaNiO 3 , respectively. This remarkable enhancement is primarily due to its unique 3DOM structure and the synergistic effect of highly dispersed LaH 3 and Mg 2 Ni/Mg 2 NiH 4 formed in situ during the ball milling and first de/re-hydrogenation process. 3DOM structure catalysts are fragile which can make the catalyst distribution more uniform during ball milling process, giving rise to the significantly improved catalytic activity. The theoretical calculation results show that Mg 2 Ni/LaH 3 heterostructure can greatly reduce the hydrogen adsorption energy to −0.768 eV and the heterogeneous interface induces the charge redistribution between Mg 2 Ni and LaH 3 , resulting in a small amount of negative charge accumulating on the surface of Mg 2 Ni. Moreover, highly dispersed LaH 3 and Mg 2 Ni/Mg 2 NiH 4 in the MgH 2 matrix create a multiphase interface, which can provide more active sites and a variety of pathways for hydrogen diffusion. Above reasons contribute to the excellent synergistic catalytic performance of in situ formed LaH 3 and Mg 2 Ni/Mg 2 NiH 4 on MgH 2 . These discoveries hold scientific value for the design and preparation of highly active catalysts using 3DOM materials for hydrogen storage in light-metal hydrides, especially in MgH 2 .
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