Tuning Anionic Redox Activity and Reversibility for a High‐Capacity Li‐Rich Mn‐Based Oxide Cathode via an Integrated Strategy

Abstract

When fabricating Li‐rich layered oxide cathode materials, anionic redox chemistry plays a critical role in achieving a large specific capacity. Unfortunately, the release of lattice oxygen at the surface impedes the reversibility of the anionic redox reaction, which induces a large irreversible capacity loss, inferior thermal stability, and voltage decay. Therefore, methods for improving the anionic redox constitute a major challenge for the application of high‐energy‐density Li‐rich Mn‐based cathode materials. Herein, to enhance the oxygen redox activity and reversibility in Co‐free Li‐rich Mn‐based Li1.2Mn0.6Ni0.2O2 cathode materials by using an integrated strategy of Li2SnO3 coating‐induced Sn doping and spinel phase formation during synchronous lithiation is proposed. As an Li+ conductor, a Li2SnO3 nanocoating layer protects the lattice oxygen from exposure at the surface, thereby avoiding irreversible oxidation. The synergy of the formed spinel phase and Sn dopant not only improves the anionic redox activity, reversibility, and Li+ migration rate but also decreases Li/Ni mixing. The 1% Li2SnO3‐coated Li1.2Mn0.6Ni0.2O2 delivers a capacity of more than 300 mAh g−1 with 92% Coulombic efficiency. Moreover, improved thermal stability and voltage retention are also observed. This synergic strategy may provide insights for understanding and designing new high‐performance materials with enhanced reversible anionic redox and stabilized surface lattice oxygen.

Deciphering the oxygen absorption pre-edge: a caveat on its application for probing oxygen redox reactions in batteries

“…As a result, O-K sXAS pre-edge evolution has been used overwhelmingly in a large number of publications as the evidence of the so-called oxygen redox states in battery electrodes based on TM oxides. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] On the contrary, as we pointed out directly in a recent review, 6 The importance of this debate stems from the fact that the oxygen activities in electrochemical systems hold both sides of the dilemma of stability and performance, 32 which are critical topics for materials across a wide range of energy applications, including batteries and catalytic systems. 33 Therefore, many fervent research topics on oxygen activities are in dire need of a correct interpretation of the O-K sXAS pre-edge.…”

Local Electric‐Field‐Driven Fast Li Diffusion Kinetics at the Piezoelectric LiTaO3 Modified Li‐Rich Cathode–Electrolyte Interphase

“…[1][2][3] Lithium-rich (Li-rich) materials, with the specific capacity over 260 mAh g −1 and energy density up to ≈1000 Wh kg −1 , [4] have attracted great interest in the past decades. To build the next generation LIBs with higher performances, high energy density materials are urgently pursued worldwide.…”

Function and Application of Defect Chemistry in High‐Capacity Electrode Materials for Li‐Based Batteries

“…[16a,60-61] The doping of Sn 4 + is beneficial for enlarging the interplanar spacing because Sn 4 + has a large ion radius and pillar structure in the lattice, which can improve the mobility of Li-ion. [62] W doping tends to segregate on the surface of the electrode, which can reduce the ratio of Ni/Mn and alter the valence state on the surface. [63] In addition, the formed WÀ O bonds have strong covalent bond property, which is conducive to reducing the migration of transition metal ions and the loss of surface oxygen.…”