Lithium-Ion Conductivity Epitaxial Layer Contributing to the Structure and Cycling Stability of LiMn₂O₄ Cathodes

Abstract

A critical challenge in the commercialization of spinel lithium manganate materials is the bulk structure damage and capacity degradation due to manganese dissolution during battery operation. Hence, Li 3 PO 4 with good ionic conductivity was homogeneously deposited on the surface of spinel lithium manganate by the sol−gel method, aiming to improve the stability and cycling of the spinel structure by an epitaxial layer. The structural and electrochemical characterizations reveal that the presence of the Li 3 PO 4 epitaxial coating prevents the direct contact of the cathode surface and electrolyte, thus enhancing the stability of the structure and reducing the extent of manganese dissolution. Further studies have shown that the contribution of the Li 3 PO 4 layer promotes the diffusion coefficient of lithium ions, which increases from 7.89 × 10 −12 to 4.43 × 10 −11 cm 2 s −1 . Meanwhile, the Li 3 PO 4 coating regulates the concentration of oxygen vacancies on the surface of the spinel, effectively reducing the transfer resistance and increasing the electronic conductivity to 3.50 × 10 −5 cm −1 . Specifically, the discharge specific capacity of the 1.0 wt % Li 3 PO 4modified electrode is still 115.4 mAh g −1 after 300 cycles, with the capacity retention increased to 90.8%. Even at a high rate of 10C, it still demonstrates excellent rate capability, with the discharge specific capacity more elevated than that of the unmodified material at about 40 mAh g −1 . This strategy can simultaneously solve the interfacial instability and bulk structure degradation, thus improving the electrochemical performance of lithium manganate materials.

Homogeneous Adsorption of Multiple Potassiation Products of Red Phosphorus Anode toward Stable Potassium Storage

“…The thin, uniform, and flat carbon layer would be more conducive to the migration of K + and effectively alleviate the huge volume expansion of RP in the process of repeated potassiation/depotassiation, so as to improve the cycle stability of the battery. 22,23 1l,n, S3c and S4c, insets), which is in concordance with the XRD results that the composites are amorphous. In conclusion, the TEM and EDS elemental mapping analyses demonstrated that MPc anchored on RP successfully induced a uniform distribution of the carbon layer on the RP surface, which effectively addressed the issue of incomplete encapsulation of RP by the carbon layer.…”

“…Nevertheless, in comparison with RP/C, where the carbon layer was agglomerated on the RP surface, the agglomeration of the carbon layer in MPc@RP/C was significantly suppressed. The thin, uniform, and flat carbon layer would be more conducive to the migration of K + and effectively alleviate the huge volume expansion of RP in the process of repeated potassiation / depotassiation, so as to improve the cycle stability of the battery. , The selected area electron diffraction (SAED) of particles for the composites shows what are typical amorphous halos (Figures l,n, S3c and S4c, insets), which is in concordance with the XRD results that the composites are amorphous. In conclusion, the TEM and EDS elemental mapping analyses demonstrated that MPc anchored on RP successfully induced a uniform distribution of the carbon layer on the RP surface, which effectively addressed the issue of incomplete encapsulation of RP by the carbon layer.…”

Degradation Mechanisms of Electrodes Promotes Direct Regeneration of Spent Li‐Ion Batteries: A Review

“…[69,146,147] Peng et al [148] discovered that the S-LMO possesses a highly ordered structural domain with lattice fringe spacing of 0.47 nanometers, which related to the (003) crystallographic planes of the LMO. [149] They also found that the spent cathode had distinct disordered regions, amorphous phases, and corrosion holes in addition to the structure of the spinel LMO (Figure 10d,e). During the cycling process, these undesirable phases, which exhibit no electrochemical activity, cause a diminishment of capacity and an increasement in impedance.…”