Surface heterostructure induced by TiO2 modification in Li-rich cathode materials for enhanced electrochemical performances

Enhancing Ionic Transport and Structural Stability of Lithium-Rich Layered Oxide Cathodes via Local Structure Regulation

Lithium-rich manganese-based layered oxides (LRM) have garnered considerable attention as cathode materials due to their superior performance. However, the inherent structural degradation and obstruction of ion transport during cycling lead to capacity and voltage decay, impeding their practical applications. Herein, an Sb-doped LRM material with local spinel phase is reported, which has good compatibility with the layered structure and provides 3D Li+ diffusion channels to accelerate Li+ transport. Additionally, the strong Sb-O bond enhances the stability of the layered structure. Differential electrochemical mass spectrometry indicates that highly electronegative Sb doping effectively suppresses the release of oxygen in the crystal structure and mitigates successive electrolyte decomposition, thereby reducing structural degradation of the material. As a result of this dual-functional design, the 0.5 Sb-doped material with local spinel phases exhibits favorable cycling stability, retaining 81.7% capacity after 300 cycles at 1C, and an average discharge voltage of 1.87 mV per cycle, which is far superior to untreated material with retention values of 28.8% and 3.43 mV, respectively. This study systematically introduces Sb doping and regulates local spinel phases to facilitate ion transport and alleviate structural degradation of LRM, thereby suppressing capacity and voltage fading, and improving the electrochemical performance of batteries.

Boosting the Electrochemical Performance of Li1.2Ni0.13Co0.13Mn0.54O2 by Rough Coating with the Superionic Conductor Li7La3Zr2O12

Li-rich Mn-based layered compounds have progressed as promising cathode materials for lithium-ion batteries (LIBs) due to their relatively low cost, considerable energy storage capacity, and high operating voltage. However, they suffer critical drawbacks, such as capacity decay and inferior rate performance, which restrain their real applications. We carried out surface modification via rough coating of superionic conductor Li₇La₃Zr₂O₁₂ (LLZO) on the Li-rich Mn-based layered cathode. The cathode with a LLZO coating exhibits significantly improved electrochemical performance, which mainly benefits from the enhanced Li-ion diffusion and reduced side reactions at electrode/electrolyte interfaces via effective coating of LLZO layer. This work provides a facile and efficient way to design Li-rich Mn-based cathodes for high-energy and stable LIBs.

Surface LiMn1.4Ni0.5Mo0.1O4 Coating and Bulk Mo Doping of Li-Rich Mn-Based Li1.2Mn0.54Ni0.13Co0.13O2 Cathode with Enhanced Electrochemical Performance for Lithium-Ion Batteries

To improve the initial Coulombic efficiency, cycling stability, and rate performance of the Li-rich Mn-based Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode, the combination of LiMn_1.4Ni_0.5Mo_0.1O₄ coating with Mo doping has been successfully carried out by the sol-gel method and subsequent dip-dry process. This strategy buffers the electrodes from the corrosion of electrolyte and enhances the lattice parameter, which could inhibit the oxygen release and maintain the structural stability, thus improving the cycle stability and rate capability. After LiMn_1.4Ni_0.5Mo_0.1O₄ modification, the initial discharge capacity reaches 272.4 mAh g^-1 with a corresponding initial Coulombic efficiency (ICE) of 84.2% at 0.1C (1C = 250 mAh g^-1), far higher than those (221.5 mAh g^-1 and 68.9%) of the pristine sample. Besides, the capacity retention of the coated sample is enhanced by up to 66.8% after 200 cycles at 0.1C. Especially, the rate capability of the coated sample is 95.2 mAh g^-1 at 5C. XRD, SEM, TEM, XPS, and Raman spectroscopy are adopted to characterize the morphologies and structures of the samples. This coating strategy has been demonstrated to be an effective approach to construct high-performance energy storage devices.

Boosting potassium-storage performance via the functional design of a heterostructured Bi2S3@RGO composite

Potassium-ion batteries (PIBs) are considered a promising alternative to lithium-ion batteries (LIBs) for next-generation energy storage due to the abundance and competitive cost of potassium resources. However, the excavation and the development of proper electrodes for PIBs are still confronted with great challenges. Herein, a self-assembled bismuth sulfide microsphere wrapped with reduced graphene oxide was fabricated to form a heterostructured Bi2S3@RGO composite via a visible-light-assisted method and served as the anode for PIBs. The as-prepared Bi2S3@RGO composite presented a high reversible specific capacity of 538 mA h g-1 at 0.2 A g-1 and superior rate capability of 237 mA h g-1 at a high current density of 2 A g-1 after 300 cycles. In particular, the high capacity could be ascribed to the synergistic effect of the conversion and alloying reactions during the electrochemical processes, which was validated by ex situ X-ray diffraction. The fabrication of a unique heterostructure combining the self-assembled Bi2S3 microspheres and flexible RGO boosted the facile charge transfer, leading to the enhanced cyclic stability and rate performance.