Sol–gel derived nanostructured Li2MnSiO4/C cathode with high storage capacity

Enabling the Electrochemical Performance of Maricite-NaMnPO4 and Maricite-NaFePO4 Cathode Materials in Sodium-Ion Batteries

NaMnPO4 and NaFePO4, polyanion cathode materials, exist in two different phases maricite/natrophilite and maricite/olivine, respectively. Both natrophilite NaMnPO4 and olivine NaFePO4 are electrochemically active and possess a one-dimensional tunnel for sodium-ion migration; however, these two phases are thermodynamically unstable. Therefore, they can be synthesized through an electrochemical route. On the contrary, maricite (m)-NaMnPO4 and maricite (m)-NaFePO4 are thermodynamically stable forms but have a huge activation energy of their diffusion pathways for sodium extraction and insertion in the crystal structure, which hinders electrochemical reactions. Therefore, the electrochemical behaviour of commercial m-NaMnPO4 and m-NaFePO4 has been studied to find a way for enabling them electrochemically. Ball milling and thermal/mechanical carbon coating are employed to reduce the particle size to enhance the electrochemical performance and shorten the diffusion pathway. Moreover, ball milling leads to defects and partial phase transformation. The electrochemical performance of milled-coated NaMnPO4 and NaFePO4 has been thoroughly investigated and compared. The phase transition of NaFePO4 is revealed by a differential scanning calorimeter. As a result, the achievable capacities of both cathode materials are significantly enhanced up to ∼50 mAh.g−1 via the particle size reduction as well as by carbon coating. However, the side reactions and agglomeration problems in such materials need to be minimized and must be considered to enable them for applications.

Boosting Redox-Active Sites of 1T MoS2 Phase by Phosphorus-Incorporated Hierarchical Graphene Architecture for Improved Li Storage Performances

Hybridizing and architecting two kinds of 2D nanomaterials are attractive for energy storage applications. Herein, the chemical and electronic coupling of redox active 1T MoS₂ phase with hierarchical phosphorus-doped graphene architecture (HMPGA) is accomplished by the strong interactions of 2D hybrid colloids. The spectroscopic analyses on the crystal structure, surface morphology, and composition confirm the efficient doping of phosphorus and the hybridization interaction of 1T MoS₂ with the phosphorus-incorporated graphene. The resulting HMPGA anode shows significant improvement in battery performances. The specific capacity is delivered to 1194 mAh g^-1 at 100 mA g^-1 with a cyclability of 93.3% over 600 cycles. This improvement is ascribed to the multicoupling effect arising from the abundant redox-actives sites of 1T MoS₂ phase boosted and stabilized by hierarchically architected, phosphorus-doped graphenes.

Facile Electrochemical Activity of Monoclinic Li2MnSiO4 as Potential Cathode for Li-Ion Batteries

Synthesis of pure single-phase Li₂MnSiO₄ is challenging because of its rich polymorphism. Here, we demonstrate our success in preparing crystalline pure, battery-grade monoclinic phase Li₂MnSiO₄ (LMS) employing the temperature-programmed reaction technique. Systematic analysis of the electrochemical behavior of Li₂MnSiO₄ reveals its excellent battery activity in the monoclinic phase, with an initial discharge capacity of ∼250 mAh g^-1 associated with the reversible intercalation of more than one Li⁺. The extraction of Li⁺ ions from Li₂MnSiO₄ corresponding to the oxidation of Mn²⁺ to Mn³⁺ then to Mn⁴⁺ appears as single oxidation/reduction peaks at 4.3/3.9 V in the first charge/discharge sweep of cyclic voltammogram within the potential window of 3.0-4.4 V. However, an extension of cathodic sweep to 2.5 V results in the appearance of an additional redox peak at 2.7/3.1 V vs Li⁺/Li^o due to the reversible phase transition of monoclinic phase into battery-active orthorhombic phase induced by Jahn-Teller-active Mn³⁺ as evident from ex situ X-ray diffractograms. Indeed, the reversible intercalation of Li⁺ into the newly formed phase accounts for the high specific capacity of LMS within the potential window of 2.5-4.4 V. The capacity loss in the repeated cycles of monoclinic Li₂MnSiO₄ is explained by the formation of Mn₂O₃ owing to the dissolution of Mn³⁺.

Charge/discharge characteristics of Jahn–Teller distorted nanostructured orthorhombic and monoclinic Li2MnSiO4 cathode materials

The nanostructured core Li₂MnSiO₄ and carbonous shell geometries in orthorhombic phase.

Facile preparation of a Na2MnSiO4/C/graphene composite as a high performance cathode for sodium ion batteries

A new class of Na₂MnSiO₄/C/G composite exhibits outstanding electrochemical properties when used as a cathode material for Na ion batteries.

Advances in high-capacity Li2MSiO4 (M = Mn, Fe, Co, Ni, …) cathode materials for lithium-ion batteries

This review highlights the high-capacity Li₂MSiO₄ (M = Mn, Fe, Co, Ni, …) cathode materials for lithium-ion batteries.

Synthesis and electrochemical performance of Na-modified Li2Fe0.5Mn0.5SiO4 cathode material for Li-ion batteries

Li_2−xNa_xFe_0.5Mn_0.5SiO₄/C composites have been synthesized via a refluxing-assisted solid-state reaction. They can be well indexed as two mixed polymorphs with P2₁ and Pmn2₁. Na-doping can significantly improve the capacity and the rate capability.

Custom designed nanocrystalline Li2MSiO4/reduced graphene oxide (M = Fe, Mn) formulations as high capacity cathodes for rechargeable lithium batteries

Nanocrystalline Li₂MSiO₄ (M = Fe, Mn) particles embedded between rGO sheets exhibit a capacity of 149 mAh g⁻¹ with 89% capacity retention and 210 mAh g⁻¹ with 87% retention respectively by Li₂FeSiO₄/rGO and Li₂MnSiO₄/rGO.