Synergetic effects of cation (K+) and anion (S2−)-doping on the structural integrity of Li/Mn-rich layered cathode material with considerable cyclability and high-rate capability for Li-ion batteries

Recent Progress and Challenges of Li-Rich Mn-Based Cathode Materials for Solid-State Lithium-Ion Batteries

Li-rich Mn-based (LRM) cathode materials, characterized by their high specific capacity (>250 mAh g-¹) and cost-effectiveness, represent promising candidates for next-generation lithium-ion batteries. However, their commercial application is hindered by rapid capacity degradation and voltage fading, which can be attributed to transition metal migration, lattice oxygen release, and the toxicity of Mn ions to the anode solid electrolyte interphase (SEI). Recently, the application of LRM cathode in all-solid-state batteries (ASSBs) has garnered significant interest, as this approach eliminates the liquid electrolyte, thereby suppressing transition metal crosstalk and solid-liquid interfacial side reactions. This review first examines the historical development, crystal structure, and mechanisms underlying the high capacity of LRM cathode materials. It then introduces the current challenges facing LRM cathode and the associated degradation mechanisms and proposes solutions to these issues. Additionally, it summarizes recent research on LRM materials in ASSBs and suggests strategies for improvement. Finally, the review discusses future research directions for LRM cathode materials, including optimized material design, bulk doping, surface coating, developing novel solid electrolytes, and interface engineering. This review aims to provide further insights and new perspectives on applying LRM cathode materials in ASSBs.

Hollow porous carbon nanospheres containing polar cobalt sulfide (Co9S8) nanocrystals as electrocatalytic interlayers for the reutilization of polysulfide in lithium-sulfur batteries

HYPOTHESIS

The introduction of functional interlayers for efficient anchoring of lithium polysulfides has received significant attention worldwide.

EXPERIMENTS

A facile wet-chemical method was adopted to obtain hollow porous carbon nanospheres (HPCNSs) impregnated with metallic and polar cobalt sulfide (Co₉S₈) nanocrystals (abbreviated as "Co₉S₈@HPCNS"). The prepared nanocrystals were employed as electrocatalytic interlayers via separator coating for the efficient capture and reutilization of polysulfide species in Li-S batteries. The HPCNSs were synthesized via the polymerization method followed by carbonization and template removal. The Co₉S₈ nanocrystals were impregnated inside the HPCNSs, followed by heat treatment in a reducing atmosphere.

FINDINGS

The porous structure of the CNS enables the efficient percolation of the electrolyte, in addition to accommodating unwanted volume fluctuations during redox processes. Furthermore, the metallic Co₉S₈ nanocrystals improve the electronic conductivity and enhance the polarity of the CNS towards the polysulfide. Correspondingly, the Li-S cells featuring Co₉S₈@HPCNS as electrocatalytic interlayers and regular sulfur (S) electrodes display improved electrochemical performance such as reasonable rate performance and prolonged cycling stability at different current rates (0.1, 0.5, and 1.0 C). Therefore, we anticipate that the rational design strategy proposed herein will provide significant insights into the synthesis of advanced materials for various energy storage applications.

Integrating a Ferroelectric Interface with a Well-Tuned Electronic Structure in Lithium-Rich Layered Oxide Cathodes for Enhanced Lithium Storage

Li-rich layered oxides (LLOs) are considered promising candidates for new high-energy-density cathode materials for next-generation power batteries. However, their large-scale applications are largely hindered by irreversible Li/O loss, structural degradation, and interfacial side reactions during cycling. Herein, we demonstrate an integration strategy that tunes the electronic structure by La/Al codoping and constructs a ferroelectric interface on the LLOs surface through Bi_0.5Na_0.5TiO₃ (BNT) coating. Experimental characterization reveals that the synergistic effect of the ferroelectric interface and the well-tuned electronic structure can not only promote the diffusion of Li⁺ and hinder the migration of O^n- but also suppress the lattice volume changes and reduce interfacial side reactions at high voltages up to 4.9 V vs Li⁺/Li. As a result, the modified material shows enhanced initial capacities and retention rates of 224.4 mAh g^-1 and 78.57% after 500 cycles at 2.0-4.65 V and 231.7 mAh g^-1 and 85.76% after 200 cycles at 2.0-4.9 V at 1C, respectively.

Na doping into Li-rich layered single crystal nanoparticles for high-performance lithium-ion batteries cathodes

Lithium-rich layered manganese-based cathodes (LRLMOs) with first-class energy density (∼1000 W h kg^-1) have attracted wide attention. Nevertheless, the weak cycle stability and bad rate capability obstruct their large-scale commercial application. Here, single crystal Li_1.2-xNa_xNi_0.2Mn_0.6O₂(x = 0, 0.05, 0.1, 0.15) nanoparticles are designed and successfully synthesized due to the single crystal structure with smaller internal stress and larger ionic radius of Na. The synergistic advantages of single crystal structure and Na doping are authenticated as cathodes for Li ion batteries (LIBs), which can consolidate the crystallographic structure and be benefit for migration of lithium ion. Among all the Na doping single crystals, Li_1.1Na_0.1Ni_0.2Mn_0.6O₂cathode possesses supreme cycling life and discharge capacity at large current density. To be more specific, it exhibits a discharge capacity of 264.2 mAh g^-1after 50 charge and discharge cycles, higher than that of undoped material (214.9 mAh g^-1). The discharge capacity of Li_1.1Na_0.1Ni_0.2Mn_0.6O₂cathode at 10 C (1 C = 200 mA g^-1) is enhanced to 160.4 mAh g^-1(106.7 mAh g^-1forx = 0 sample). The creative strategy of Na doping single crystal LRLMOs might furnish an idea to create cathode materials with high energy and power density for next generation LIBs.