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.

Mitigating Voltage Decay via Chemo‐Mechanical Decoupling Enabled by a Rigid‐Soft Gradient Interphase in Li‐Rich Layered Oxides

“…Notably, this low-energy feature remains stronger in LLO-MZC after full discharge, whereas it decays more severely in LLO, signifying that the rigid-soft gradient interphase stabilizes oxygen redox activity and limits irreversible loss of lattice oxygen. This trend is further corroborated by the statistical comparison of integrated low-energy pre-edge intensity in Figure 6c, evidencing a smaller irreversible depletion of oxygen-related electronic states in LLO-MZC, which aligns with the stabilized anionic redox expected from the chemically fortified outer layer of the gradient framework [68].…”

Boosting Electrochemical Performance of Lithium-Rich Manganese-Based Cathode Materials through a Dual Modification Strategy with Defect Designing and Interface Engineering

“…The distinct lattice fringes with an interplanar spacing of 0.475 nm are indexed to the (003) planes of R3̅ m or (001) planes of C2/m. 54 The FFT pattern coordinating with the SPSR (signed with an orange square) of the HRTEM image can also justify the above results. In addition, a similar configuration of lattice fringes can be found in CN-LMNC (Figure 4c).…”

“…The HRTEM image, united fast Fourier transform (FFT) patterns, and signal profile of the selected region (SPSR) of LMNC are displayed in Figure a. The distinct lattice fringes with an interplanar spacing of 0.475 nm are indexed to the (003) planes of R 3̅ m or (001) planes of C 2/ m . The FFT pattern coordinating with the SPSR (signed with an orange square) of the HRTEM image can also justify the above results.…”

Improving the Electrochemical Performance of a Lithium-Rich Layered Cathode with an In Situ Transformed Layered@Spinel@Spinel Heterostructure

“…The lattice oxygen loss in the LLO and LSS samples charged to 4.8 V in the initial cycle is characterized as shown in Figure g–i. In Figure g–i, the blue and pink regions represent electrolyte oxidation and oxygenated deposited species, respectively . The same lattice oxygen O 2– (the green region) peak as shown in Figure d–f decreases.…”

“…In Figure 5g−i, the blue and pink regions represent electrolyte oxidation and oxygenated deposited species, respectively. 42 The same lattice oxygen O 2− (the green region) peak as shown in Figure 5d−f decreases. In addition, a weak peak appears at 531 eV (the red region), which can be attributed to the existence of formal O 2 2− species or to undercoordinated oxygen atoms.…”