Engineering novel Ni2-XCoxP structures for high performance lithium-ion storage

Phosphorus-Doped FeOF Nanoparticle-Based Cathodes for Lithium Storage

“…38 As the introduction of P alters the electronic environment of FeOF, the XPS peaks of Fe, F, O, and P all shift, indicating that the electronic structure is optimized and the Li + transport kinetics are improved. 24,30 The electronegativity of P (2.19) is lower than O (3.44) and F (3.55); the partial replacement of lattice O by P can reduce the ionicity of Fe−F and the formation of Fe−P to enhance the Li + transport rate. 15 Furthermore, the approximate concentration ratio of P in P-FeOF can be calculated by fitting the XPS peak area of P 2p; the calculation shows that the approximate concentration ratios of P are 8.85% (30 min), 9.21% (60 min), and 9.26% (90 min), respectively (calculation details in the Supporting Information).…”

“…P doping can host a large amount of Li + without significant volume change and facilitate the interfacial kinetics of Li + intercalation. 30 Therefore, the P-FeOF is expected to efficiently enhance electrochemical performance.…”

“…EDX mappings show that the Fe, O, F, and P elements are homogeneously distributed in the P-F6 sample, which further demonstrates the presence of P elements (Figure g–j). P doping can host a large amount of Li + without significant volume change and facilitate the interfacial kinetics of Li + intercalation . Therefore, the P-FeOF is expected to efficiently enhance electrochemical performance.…”

“…28,29 The weak M−P bond enhances the electrochemical activity and reversible redox reaction characteristics of electrode materials, which can improve the rate performance of LIBs. 30 Furthermore, the design of nanostructures not only shortens the electron/ion transport distance but also alleviates the volume expansion of the material, thereby effectively improving the reaction kinetics. 18 Inspired by the advantages of P doping and nanostructures, we proposed P doping in FeOF with a nanorod structure to expand the interlayer distance, increase reaction sites, and improve the reaction kinetics and structural stability to meet the requirements of the fast-charge and longcycle performance.…”

“…When using O to partially substitute F in FeF 3 , the ionicity of Fe–F is reduced and the lattice defects are increased, which can integrate the advantages of fluoride and oxide. , However, the rate performance and cycle stability of FeOF are still unsatisfactory because of the low ionic/electronic conductivities, the aggregation of Fe nanoparticles, side reactions of Fe with electrolytes, and the high electronegativity of Fe–F. , Significant efforts have been made to overcome these obstacles, including doping heteroatoms, morphology design, preparation of nanomaterials and composite structures, and so forth. ,, Ion doping has been widely regarded as an effective strategy for enhancing structural stability and improving electronic structure/properties; thus, heteroatom doping may be a straightforward way to improve electrochemical performance. − Especially, non-metal dopants might induce the reconstruction of charge distribution around the sites of the parent material, which may improve the redox activity of the material. − However, the relevant electrochemical mechanism caused by non-metal doping has not been clearly understood. Phosphorus has higher electrical conductivity and the ability to reduce the adsorption energy of Li + to facilitate the interfacial kinetics of Li + intercalation. − Moreover, introducing P into the material can alter the charge balance and endow the material with certain pseudocapacitive properties, thereby improving the rate performance of the material. , The weak M–P bond enhances the electrochemical activity and reversible redox reaction characteristics of electrode materials, which can improve the rate performance of LIBs . Furthermore, the design of nanostructures not only shortens the electron/ion transport distance but also alleviates the volume expansion of the material, thereby effectively improving the reaction kinetics .…”