Regulating Anion Redox and Cation Migration to Enhance the Structural Stability of Li-Rich Layered Oxides

Abstract

Lithium-rich manganese-based layered oxide cathodes (LLOs) with oxygen redox reactions are considered to be potential candidates for the next generation of high-energy-density Li-ion batteries. However, the oxygen redox process that enables ultrahigh specific capacity usually leads to irreversible O 2 release and cation migration, which induce structure degradation and severe capacity/ voltage losses and thus limit the commercial application of LLOs. Herein, we successfully synthesized chlorine (Cl)-doped Co-free LLOs (Li 1.2 Mn 0.53 Ni 0.27 O 1.976 Cl 0.024 ) and analyzed the effect of anion doping on oxygen redox and structure stability of LLOs. Cl doping has been proven to decrease the irreversible lattice oxygen loss to enhance the redox reversibility of oxygen and inhibit the transition-metal migration during cycles, which substantially enhances the capacity and voltage retention and improves the rate capability during cycling. This work provides new insights for the development of high-performance TM oxide cathode materials with reversible oxygen redox.

Insights into the Enhanced Structural and Thermal Stabilities of Nb-Substituted Lithium-Rich Layered Oxide Cathodes

“…Clearly, the LLONb sample shows a reduced R ct value (Table S4), suggesting that Nb doping is conducive to electron transfer and Li + deintercalation across the interface. The Li + diffusion coefficient ( D Li+ ) is also obtained by calculating the cyclic voltammogram (CV) collected at different scanning rates based on the Randles–Sevcik equation, as shown in Figures e,f and S8. The Li + diffusion coefficients of oxidation and reduction during charge and discharge process for LLONb are 6.321 × 10 –11 and 1.879 × 10 –11 , respectively, both of which are higher than those of LLO, indicating that Nb doping can promote the diffusion of Li + ion in the LLONb electrode.…”

Multi-dimensional correlation of layered Li-rich Mn-based cathode materials

“…The simulated local structure (right) around the boracic polyanion, showing that the M-O bonds are lengthened due to the strong B-O bond [182] . (E) Schematic illustration of Li-rich layered material with composited LiMn 6 and SbNi 6 superstructures [186] . (F) (i) Length of TM-O (Cl) bonds of Li 1.2 Mn 0.53 Ni 0.27 O 2 (LMNO) and Li 1.2 Mn 0.53 Ni 0.27 O 1.976 Cl 0.024 (LMNOC), (ii) energy barriers of TM migrating from the TM layer to the Li layer and (iii) operando differential electrochemical mass spectrometry curves of O 2 for LMNO and LMNOC [187] .…”

“…In addition, the conversion of the layered structure to the spinel phase during cycling was inhibited, which finally improved the electrochemical performance. Li et al [186] successfully prepared Li(Li 1/6 Mn 1/3 Ni 1/3 Sb 1/6 )O 2 materials with mixed Li@Mn 6 and Sb@Ni 6 superstructure elements [Figure 13E]. The study found that the coordination environment of local oxygen changes, which reduces the energy barrier for Li + diffusion and provides additional capacity.…”

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

“…Based on the above analysis, the key issue to improve lithium-rich layered oxide performance is to inhibit the phase transition and the irreversible release of lattice oxygen during the initial cycle. A great many modification studies have been carried out to improve the electrochemical performance of lithium-rich layered oxides. ,, To overcome these problems, many approaches have been investigated, such as material pretreatment, − cationic doping, − anion doping, − surface coating, − and core–shell structure. − In all the above strategies, the core–shell structure has been extensively studied because of the fact that no inactive component is introduced and the synergistic effect between the core component and the shell component is beneficial to improve the performance of the electrode. On the one hand, shell components can protect the host material from electrolyte corrosion and reduce the interfacial side reactions.…”

“…A great many modification studies have been carried out to improve the electrochemical performance of lithium-rich layered oxides. 4,13,14 To overcome these problems, many approaches have been investigated, such as material pretreatment, 15−17 cationic doping, 18−20 anion doping, 21−23 surface coating, 24−26 and core−shell structure. 27−29 In all the above strategies, the core−shell structure has been extensively studied because of the fact that no inactive component is introduced and the synergistic effect between the core component and the shell component is beneficial to improve the performance of the electrode.…”