Design And Electrochemical Performance Of Phosphides Composite Anodes Material For Lithium/Sodium/Potassium-ion Batteries

Lithium-ion batteries?LIBs?have been widely utilized in portable devices owing to their high energy conversion rate,high energy density and low environmental pollution.However,graphite,which is used as a common anode material for LIBs,fails to meet the energy demand of electric vehicle power system because the defects such as low theoretical specific capacity.Therefore,it is of great significance that developing a negative electrode material with higher capacity and better performance to improve the energy density of LIBs.At the same time,due to the limited lithium resources of the earth,it is also important to create sodium-ion batteries?SIBs?and potassium-ion batteries?PIBs?which are potential to replace the existing LIBs as a technical reserve while developing ithium ion battery anode materials.Phosphorus-base anode materials have great potential as anode materials for lithium/sodium/potassium ion batteries because of their low cost and high theoretical capacity of 2596 mA h g^-1.However,phosphorus anode materials have to face some serious problems such as poor cycling stability and rate performance caused by poor conductivity and a large volume change rate during charge and discharge process.In this paper,the chemical porperties of phosphorous-based anode materials are improved by combing phosphorus with other elements with high conductivity to form phosphides.Through designing and regulating nanostructures,the improved phosphorous-base anodes deliver high reversible capacity,long cycle life and good rate performance.Details are as follows:Firstly,a nanorod-like iron phosphide/phosphorus-doped mesoporous carbon composite?nanorode-FeP/P-C?was designed and prepared.The creation process is mainly divided into three steps.Ferric chloride?FeCl₃?and phytic acid providing phosphorus source and carbon source were heated stirred to obtain the complex.The obtained complex was carbonized heating in a tube furnace by high temperature to obtain a Fe₂P₄O₁₂/phosphorus-doped carbon precursor(Fe₂P₄O₁₂/P-C).Then,Fe₂P₄O₁₂/P-C was recution to nanorod-FeP/P-C with pure hydrogen at high temperature.Owing to the nonorod structure of FeP and the phosphorous-doped mesoporous carbon with high specific structure area,which improves electron conductivity and reduces volume change during charge and discharge process,nanorod-FeP/P-C exhibited high reversible capacity,stable cycle performance and excellent rate performance.The LiMnCoNiO₂?nanorod-FeP/P-C full cell assembled with LiMnCoNiO₂ cathode material and nanorod-FeP/P-C anode material exhibited high working voltage and energy density.The sodium storage properties of nanorod-FeP/P-C composites were also tested.Secondly,an amorphous Se-P-C composite was prepared by plasma-assisted ball milling.In the preparation process,Se-2P/C@30h,Se-P/C@30h,Se-4P/C@30h,Se-2P/C@20h,Se-2P/C@30h?regular milling?,Se/C@30h and P/C@30h composite materials were prepared using different Se:P molar ratios and various ball-milling condition.XRD and TEM analysis result indicated that the prepared Se-2P/C@30h composite shows amorphous structure.Except Se-2P/C@30h composite material,the other prepared Se-P-C composites show characteristic peak of Se in Raman spectra,indicating that the complete reaction between Se and P in Se-2P/C@30h composite.Meanwhile,STEM-EDS and element-mapping analysis also proved that Se and P distributions were uniform in Se-2P/C@30h composites.Owing to the smallest particle size which leads to the easier reaction of active substances with Li⁺and Na⁺ions and the complete combition of Se-P phase which enhances electrical conductivity,Se-2P/C@30h electrode exhibited excellent lithium/sodium electrochemical storage performance.Finally,a potential Se-P-C potassium ion battery anode material was created based on the amorphous Se-P-C composite prepared by plasma-assisted ball milling.Among the prepared Se-P-C composites,Se-2P/C@30h electrode showed the best potassium storage performance because of the its minimum particle size,which makes the reaction of the active material and K⁺ions easier,and sufficient reaction between Se and P.Through ex-situ XRD and TEM test of Se-2P/C@30h electrode in the potassium storage state?discharge to 0.01 V?and the depotassium state?charge to 0.01 V?,it was found that KSe and K₂P₃ were formed during the potassiation process and disappeared in the depotassiation process.The reversible reaction equation:3?Se-2P?+7K?3KSe+2K₂P₃.