Mitigating the Jahn-Teller distortion driven by the spin-orbit coupling of lithium manganate cathode

Spinel LiMn_(2)O_(4)is recognized as one of the most competitive cathode candidates for lithium-ion batteries ascribed to environmentally benign and rich sources.However,the wholesale application of LiMn_(2)O_(4)is predominately plagued by its severe capacity degradation,mainly associated with the innate Jahn-Teller effect.Herein,single-crystalline LiMn_(2)O_(4)with Eu^(3+) doping is rationally designed to mitigate the detrimental Jahn-Teller distortion by tuning the chemical environment of MnO_(6) octahedra and accommodating localized electron,based on the unique aspheric flexible 4f electron orbit of rare-earth metal ions.Notably,the stretching of MnO_(6) octahedron stemmed from the Jahn-Teller effect in Eu-doped LiMn_(2)O_(4)is effectively suppressed,confirmed by theoretical calculation.Meanwhile,the structural stability of the material has been significantly enhanced due to the robust Mn–O band coherency and weakened phase transition,proved by synchrotron radiation absorption spectrum and operando X-ray diffraction.The corresponding active cathode manifests superior long-cycle stability after 300 loops at 2C and displays only a 0.011%capacity drop per cycle even at 5C.Given this,this modification tactic sheds new light on achieving superior long-cycle performances by suppressing distortion in various cathode materials.

Methods of improving the initial Coulombic efficiency and rate performance of both anode and cathode materials for sodium-ion batteries

Sodium-ion batteries(SIBs) have gained more scientists’ interest, owing to some facts such as the natural abundance of Na, the similarities of physicochemical characteristics between Li and Na. The irreversible Na+ions consumption during the first cycle of charge/discharge process(due to the formation of the solid electrolyte interface(SEI) on the electrode surface and other irreversible reactions) is the factor that determines high performance SIBs and largely reduces the capacity of the full cell SIBs. Thus, the initial coulombic efficiency(ICE) of SIBs for both anode and cathode materials, is a key parameter for high performance SIBs, and the point is to increase the transport rate of the Na+ions. Therefore, developing SIBs with high ICE and rate performance becomes vital to boost the commercialization of SIBs. Here we provide a review on the methods to improve the ICE and the rate performance, by summarizing some methods of improving the ICE and rate performance of the anode and cathode materials for SIBs, and end by a conclusion with some perspectives and recommendations.