Theoretical Design On The Anti-perovskite Electrolyte For All-solid Sodium Battery

Sodium ion batteries have received widespread attention Due to the unlimited reserves and the low price of sodium resources.However,currently sodium ion batteries using organic liquid electrolyte has some safety concerns such as easy leakage and flammability.The solid electrolyte instead of organic liquid electrolyte is expected to fundamentally solve this problem and build a safer sodium ion battery system.At present,the two mature categories of oxide and sulfide solid electrolytes cannot meet the requirements of high ionic conductivity,excellent stability for sodium metal anodes,and wide voltage windows.Therefore,it is particularly important to design and develop new sodium ion solid electrolyte systems with excellent performance.Recently,a Li-riched double anti-perovskite solid electrolyte based on high-throughput calculations has the excellent ionic transportation performance and stability with Li metal compared with traditional solid electrolytes.The performance of the corresponding Na⁺anti-perovskite electrolyte is very poor,and there are few studies related to this structure.In view of this,this paper extends the modification concept to the composition optimization and design of sodium ion solid electrolyte.Based on the first-principles material genome method,a series of chemical composition regulation,structural optimization,and performance evaluation were carried out,and a series of new Na⁺solid electrolyte components with excellent performance were designed.The main contents are as follows:?1?This work proposes a new type of double anti-perovskite component-Na₆SOI₂as an ultra-fast ion conductor to addresse the problem of poor ion conductivity and diffusion activation energy in the Na⁺anti-perovskite system.The new electrolyte material can meet the standards of kinetic stability and thermodynamic stability simultaneously.On this basis,the diffusion activation energy of Na₂₅S₅O₄I₇ obtained by moderate off-stoichiometric composition is only 0.16 e V,and the ionic conductivity at room temperature can reach 10.36 m S cm^-1.At the same time,the synthesis temperature of this new solid electrolyte is lower than that of sulfide solid electrolyte,and it is electrochemically compatible with Na anodes?intrinsic voltage plateau 0-1.5V?.?2?A series of modification work was carried out on an ARP-type structure Na4OI2,which was stable at room temperature and found in the previous work,and an optimal electrolyte component Na₃Li S_0.5O_0.5I₂ for dual ion co-transportation was obtained.The diffusion activation energy of this structure is only 0.16 e V,and the room temperature ion conductivity can reach 6.3 m S cm^-1.The optimized intrinsic voltage window of the electrolyte can reach more than 2 V,and it is compatible with sodium anode both thermodynamically and electrochemically.As the voltage increases,sodium ions will be consumed,forming a series of stable compounds with little lattice mismatch.The structure when sodium ions are completely lost can be used as a cathode material compatible with electrolytes.In this way,a solid-state sodium ion battery with a gradient change in sodium ion concentration from the electrolyte to the cathode material is constructed,and its theoretical energy density can reach 320 W h kg-1.?3?Based on the sodium haloite Na₃SO₄F_0.5Cl_0.5 present in nature,the composition optimization and performance evaluation were carried out using the high-throughput material genome method,and a class of halogen-based ultra-fast ion conductors with high voltage resistance and insensitivity to water and oxygen were obtained.The ionic conductivity of the optimal composition can reach 8.167 m S cm^-1,and the diffusion activation energy is only 0.137 e V.The potential gap between the screed Na₃AO₄X and sodium anode is below 1 V,which can be considered to have a high resistence to sodium anode.And the oxidation potential can reach beyond 3.5 V,which can be matched with high-voltage cathode materials.In addition,the solid electrolyte obtained in this work is not sensitive to oxygen and water,so there is no need to strictly control the synthesis and processing environment.