A Critical Review on Orthosilicate Li2MSiO4 (M= Fe, Mn) Electrode Materials for Li Ion Batteries

The development of novel electrode materials with good electrochemical performances is necessary for the expanded and varied applications of lithium-ion batteries, and this development heavily relies on cathode materials. Due to excellent thermal stability, abundance, low cost, and environmental friendliness, orthosilicate cathode materials Li2MSiO4 (M= Fe, Mn) has received a lot of attention recently. The present review article gives a glimpse into the characteristics, advantages, and recent progress of orthosilicate cathode materials. This review starts with a brief history and working mechanism of batteries, the advantages of cathode materials followed by types of cathode materials, various synthesis methods, and different techniques used for their characterization. The most current initiatives to enhance orthosilicate Li2MSiO4 type electrochemical performances were introduced in this review. We provide a critical assessment of the efficient modification techniques for the orthosilicate Li2MSiO4 type cathode materials in particular. These potential cathode materials' synthesis, structure, morphologies, and particularly electrochemical performances have been thoroughly examined. This evaluation, we hope, will clarify the sustained advancement of high-efficiency and reasonably priced Li-ion batteries&#xD.

Carbon Loaded Nano-Designed Spherically High Symmetric Lithium Iron Orthosilicate Cathode Materials for Lithium Secondary Batteries

In the present study, Li2FeSiO4 (LFS) cathode material has been prepared via a modified polyol method. The stabilizing nature of polyol solvent was greatly influenced to reduce the particle size (~50 nm) and for coating the carbon on the surface of the as-mentioned materials (~10 nm). As-prepared nano-sized Li2FeSiO4 material deliver initial discharge capacity of 186 mAh·g-1 at 1C with the coulombic efficiency of 99% and sustain up to 100 cycles with only 7 mAh·g-1 is the difference of discharge capacity from its 1st cycle to 100th cycle. The rate performance illustrates the discharge capacity 280 mAh·g-1 for lower C-rate (C/20) and 95 mAh·g-1 for higher C-rate (2C).

The Core-Shell Heterostructure CNT@Li2FeSiO4@C as a Highly Stable Cathode Material for Lithium-Ion Batteries

The reasonable design of nanostructure is the key to solving the inherent defects and realizing a high performance of Li₂FeSiO₄ cathode materials. In this work, a novel heterostructure CNT@Li₂FeSiO₄@C has been designed and synthesized and used as a cathode material for lithium-ion battery. It is revealed that the product has a uniform core-shell structure, and the thickness of the Li₂FeSiO₄ layer and the outer carbon layer is about 19 nm and 2 nm, respectively. The rational design effectively accelerates the diffusion of lithium ions, improves the electric conductivity, and relieves the volume change during the charging/discharging process. With the advantages of its specific structure, CNT@Li₂FeSiO₄@C has successfully overcome the inherent shortcomings of Li₂FeSiO₄ and shown good reversible capacity and cycle properties.

Impact of Cl Doping on Electrochemical Performance in Orthosilicate (Li2FeSiO4): A Density Functional Theory Supported Experimental Approach

Safe and high-capacity cathode materials are a long quest for commercial lithium-ion battery development. Among various searched cathode materials, Li₂FeSiO₄ has taken the attention due to optimal working voltage, high elemental abundance, and low toxicity. However, as per our understanding and observation, the electrochemical performance of this material is significantly limited by the intrinsic low electronic conductivity and slow lithium-ion diffusion, which limits the practical capacity (a theoretical value of ∼330 mAh g^-1). In this report, using first-principles density functional theory based approach, we demonstrate that chlorine doping on oxygen site can enhance the electronic conductivity of the electrode and concurrently improve the electrochemical performance. Experimentally, X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission gun scanning electron microscopy elemental mapping confirms Cl doping in Li_2-xFeSiO_4-xCl_x/C (x ≤ 0.1), while electrochemical cycling performance demonstrated improved performance. The theoretical and experimental studies collectively predict that, via Cl doping, the lithium deinsertion voltage associated with the Fe²⁺/Fe³⁺ and Fe³⁺/Fe⁴⁺ redox couples can be reduced and electronic conductivity can be enhanced, which opens up the possibility of utilization of silicate-based cathode with carbonate-based commercial electrolyte. In view of potential and electronic conductivity benefits, our results indicate that Cl doping can be a promising low-cost method to improve the electrochemical performance of silicate-based cathode materials.