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Advanced materials: Fe (Ⅱ) rich antler coral like porous lifeo2-x anode materials with first effect higher than 90% for lithium ion batteries

wallpapers News 2020-11-14
As anode materials of lithium-ion batteries

has attracted much attention due to its high specific capacity high safety low cost environmental friendliness. Different from traditional embedded materials metal oxide can store lithium reversibly through conversion reaction mechanism which greatly increases its lithium storage capacity which is 2-3 times of that of traditional commercial graphite anode. Among them iron oxide is a transition metal oxide anode material which is widely studied at present its volume specific capacity is more than 6 times of commercial fossil ink material showing a good application development prospect in the field of small battery. However poor cycle stability low first coulomb efficiency have always been the key problems restricting the practical application of iron oxide anode materials. The first coulomb efficiency of iron oxides is generally lower than 80% which is mainly due to the formation of Fe Li2O complexes after lithium intercalation. The low conductivity strong Li-O bond of Li2O can make the reverse reaction difficult to occur. In addition the formation of SEI film the decomposition of electrolyte consume a lot of lithium ions which is also an important factor causing the first low coulomb efficiency. For all batteries with limited lithium sources this problem is particularly prominent. Therefore improving the first coulomb efficiency of iron oxide is very important for its practical application. However so far no effective method has been found to improve the first coulomb efficiency of iron oxides.

to solve the above problems Liu Yongfeng pan Hongge of School of materials of Zhejiang University innovatively used LiH as lithium source to chemically pre lithium Fe2O3 through solid-state heating reaction. The porous (II) (II) FeO 2 can be reduced to (II) FeO 2 the (II) FeO 2 can be reduced to (II) FeO 2. Its compact porous structure is not only conducive to lithium ion transport but also can effectively buffer the volume change in the process of intercalation / delithiation maintain the effective utilization of active substances structural integrity inhibit the surface side reaction improve the cycle stability of the material. More importantly the electronic conductivity of lifeo2-x is improved by the presence of Fe (II). The Fe nanocrystals produced by reduction during the first lithium intercalation process are obviously refined the lithium product presents a composite structure of Fe nanocrystals (< 10 nm) uniformly distributed in the amorphous Li2O matrix. The refinement uniform distribution of Fe nanocrystals can effectively improve the interdiffusion performance of Fe / Li2O interface promote Fe nanocrystals to more effectively catalyze the reduction of Li2O thus improving the reversibility of the conversion reaction obtain the first coulomb efficiency up to 90.2%. This study not only reveals the influence mechanism of morphology lattice defects of oxide anode materials on its electrochemical capacity reversibility of conversion reaction but also provides an effective method to improve the first coulomb efficiency of transition metal oxide anode materials provides a new idea for the structural design of other conversion reaction materials the improvement of electrochemical performance induced by defects.

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