Advanced Functional Materials:Li2S/Li2Se Application of hybrid protective layer in stabilizing lithium metal anode

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Because of its high theoretical specific capacity low electrode potential

lithium metal is regarded as the most potential anode material to improve the energy density of lithium-ion batteries. However the dendrite growth in lithium-ion batteries seriously limits its practical application. The unstable SEI on the surface of lithium metal is the main factor leading to its dendrite growth. Therefore it is an effective strategy to construct a stable protective layer with high ionic conductivity on the surface of lithium metal to promote the uniform deposition of lithium ions inhibit the dendrite growth. The reaction of highly active lithium with gas is an effective method to build a uniform stable protective layer on the surface of lithium metal but the melting point of lithium metal is low (180 ℃) so this method is often limited to the boiling point of the precursor. Therefore it is still a challenge to explore a mild easy-to-use method to form a protective layer with high ionic conductivity.

Professor Yu Yan's research group of University of science technology of China designed a kind of mixed Li2S / li2se (LSSE) artificial protective layer for stabilizing lithium metal anode. Lithium sulfide has been widely studied as a protective layer with high ionic conductivity to inhibit the growth of lithium dendrite. Based on the study of lithium sulfide a low boiling compound ses2 (118 ℃) was used as the precursor of gas evaporation a uniform mixed Li2S / li2se (LSSE) artificial protective layer was obtained on the surface of lithium metal by a simple low temperature gas-solid (ses2 gas / Li) reaction method. The first principles calculations show that li2se has different crystal orientations (100 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 110 [111]) have lower ion transfer energy indicating that the introduction of li2se can further improve the ionic conductivity of Li2S system because the boiling point of compound selenium sulfide is much lower than that of elemental sulfur elemental selenium the experimental method of preparing mixed Li2S / li2se protective layer is simpler than that of pure Li2S li2se. On the one h the stable LSSE protective layer can improve the surface ion conductivity on the other h it can passivate the reaction between lithium metal organic electrolyte thus promoting the uniform deposition of lithium ion effectively inhibiting the dendrite growth preventing the reaction between lithium polysulfide lithium metal in lithium sulfur battery thus reducing the loss of active sulfur. The hybrid SEI protects the lithium metal（ LSSe@Li ）Under the condition of current density of 1.5macm-2 lithium stripping capacity of 3mahcm-2 the symmetrical cell realized 900 h dendrite free cycle. When the electrode is used in LiFePO4 battery 460 cycles can be achieved at 1C current density. In contrast the capacity of pure lithium metal anode decreases obviously after 250 cycles. LSSe@Li When applied to lini0.6co0.2mn0.2o2 full cell lithium sulfur full cell better cycle performance rate performance are obtained.

this work provides an idea of using low boiling point compounds to construct mixed ion conductive protective layer which can be used for reference in the research of inorganic layer modification on lithium metal surface. The research results were published in the international authoritative journal of advanced materials (100fmi: 20210.0012).

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