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.

Spinel Li Mn_(2)O_(4)integrated with coating and doping by Sn self-segregation

The development of high-performance and low-cost cathode materials is of great significance for the progress in lithium-ion batteries.The use of Co and even Ni is not conducive to the sustainable and healthy development of the power battery industry owing to their high cost and limited resources.Here,we report LiMn_(2)O_(4)integrated with coating and doping by Sn self-segregation.Auger electron energy spectrum and soft X-ray absorption spectrum show that the coating is Sn-rich LiMn_(2)O_(4),with a small Sn doping in the bulk phase.The integration strategy can not only mitigate the Jahn–Teller distortion but also effectively avoid the dissolution of manganese.The as-obtained product demonstrates superior high initial capacities of 124 mAh·g^(-1)and 120 mAh·g^(-1)with the capacity retention of 91.1%and 90.2%at 25℃and55℃after 50 cycles,respectively.This novel material-processing method highlights a new development direction for the progress of cathode materials for lithium-ion batteries.

Electrochemical process for recovery of metallic Mn from waste LiMn_(2)O_(4)-based Li-ion batteries in NaCl−CaCl_(2)melts

new method is proposed for the recovery of Mn via the direct electrochemical reduction of LiMn_(2)O_(4) from the waste of lithium-ion batteries in NaCl−CaCl_(2) melts at 750°C.The results show that the LiMn_(2)O_(4) reduction process by the electrochemical method on the coated electrode surface occurs in three steps:Mn(IV)→Mn(III)→Mn(II)→Mn.The products of this electro-deoxidation are CaMn2O4,MnO,(MnO)x(CaO)1−x,and Mn.Metal Mn appears when the electrolytic voltage increases to 2.6 V,which indicates that increasing the voltage may promote the deoxidation reaction process.With the advancement of the three-phase interline(3PI),electric deoxygenation gradually proceeds from the outer area of the crucible to the core.At high voltage,the kinetic process of the reduction reaction is accelerated,which generates double 3PIs at different stages.

Challenges and modification strategies of high-voltage cathode materials for Li-ion batteries

Li-ion batteries(LIBs)have gained wide recognition as effective energy storage devices and power supply sources due to their exceptional volumetric energy density,mass energy density and cycling performance.The cathode materials,a key component of LIBs,play a crucial role in determining the electrochemical performance of these batteries.Therefore,there is an increasing demand to explore and investigate suitable high-energy electrode materials that can provide greater capacity and output voltage for the next generation of LIBs.This paper aims to provide a comprehensive overview of the latest researches on five typical high-voltage cathode materials.Specifically,this review will focus on the detailed analysis of their crystalline structures,reaction mechanisms during cycling,current research status and strategies aimed at improving or enhancing their overall electrochemical performance.Overall,the insights presented in this review will help researchers design and develop high-energy cathode materials with improved performance for the next generation of LIBs.