Amorphous Materials for Lithium-Ion and Post-Lithium-Ion Batteries

Lithium-ion and post-lithium-ion batteries are important components for building sustainable energy systems. They usually consist of a cathode, an anode, an electrolyte, and a separator. Recently, the use of solid-state materials as electrolytes has received extensive attention. The solid-state electrolyte materials (as well as the electrode materials) have traditionally been overwhelmingly crystalline materials, but amorphous (disordered) materials are gradually emerging as important alternatives because they can increase the number of ion storage sites and diffusion channels, enhance solid-state ion diffusion, tolerate more severe volume changes, and improve reaction activity. To develop superior amorphous battery materials, researchers have conducted a variety of experiments and theoretical simulations. This review highlights the recent advances in using amorphous materials (AMs) for fabricating lithium-ion and post-lithium-ion batteries, focusing on the correlation between material structure and properties (e.g., electrochemical, mechanical, chemical, and thermal ones).  We  review both the conventional and the emerging characterization methods for analyzing AMs and present the roles of disorder in influencing the performances of various batteries such as those based on lithium, sodium, potassium, and zinc. Finally,  we  describe the challenges and perspectives for commercializing rechargeable AMs-based batteries.

Review and New Perspectives on Non-Layered Manganese Compounds as Electrode Material for Sodium-Ion Batteries

After more than 30 years of delay compared to lithium-ion batteries, sodium analogs are now emerging in the market. This is a result of the concerns regarding sustainability and production costs of the former, as well as issues related to safety and toxicity. Electrode materials for the new sodium-ion batteries may contain available and sustainable elements such as sodium itself, as well as iron or manganese, while eliminating the common cobalt cathode compounds and copper anode current collectors for lithium-ion batteries. The multiple oxidation states, abundance, and availability of manganese favor its use, as it was shown early on for primary batteries. Regarding structural considerations, an extraordinarily successful group of cathode materials are layered oxides of sodium, and transition metals, with manganese being the major component. However, other technologies point towards Prussian blue analogs, NASICON-related phosphates, and fluorophosphates. The role of manganese in these structural families and other oxide or halide compounds has until now not been fully explored. In this direction, the present review paper deals with the different Mn-containing solids with a non-layered structure already evaluated. The study aims to systematize the current knowledge on this topic and highlight new possibilities for further study, such as the concept of entatic state applied to electrodes.

Suppress Loss of Polysulfides in Lithium-Sulfur Battery by Regulating the Rate-Determining Step via 1T MoS2-MnO2 Covering Layer

The commercialization of lithium-sulfur batteries (LSBs) is obstructed by several technical challenges, the most severe of which is the irreversible loss of soluble polysulfide intermediates. These soluble polysulfides must be anchored or confined in the cathode side to maintain the long life of the LSBs. Here, 1T MoS₂-MnO₂/CC heterostructure functional covering layer is designed to regulate the rate-determining step from the liquid-to-solid reaction to solid-to-solid reaction. Rapid and uniform nucleation of solid Li₂S₂/Li₂S is therefore achieved, and the loss of soluble polysulfides is retarded. The Li-S batteries assembled with 1T MoS₂-MnO₂/CC covering layer therefore deliver outstanding rate capabilities even under high sulfur loads and large current rates. This study paves a novel way to suppress the polysulfides' "farewell effect" from the perspective of the kinetics.

T. J, Joseph A. Biogenic MnO2 nanoparticles derived from a Cedrus deodara pine needle extract and their composites with polyaniline/activated charcoal as an electrode material for supercapacitor applications

A ternary composite of phytogenic MnO2 nanoparticles with polyaniline (PA) and activated charcoal (AC) was designed and fabricated.

Structural transformation and electrochemical properties of a nanosized flower-like R-MnO2 cathode in a sodium battery

High-energy density and low-cost sodium-ion batteries are being sought to meet increasing energy demand. Here, R-MnO₂ is chosen as a cathode material of sodium-ion batteries owing to its low cost and high energy density. The structural transformation from the tunnel R-MnO₂ to the layered NaMnO₂ and electrochemical properties during the charge/discharge are investigated at the atomic level by combining XRD and related electrochemical experiments. Na_≤0.04MnO₂ has a tunnel R-MnO₂ phase structure, Na_≥0.42MnO₂ has a layered NaMnO₂ phase structure, and Na_0.04-0.42MnO₂ is their mixed phase. Mn³⁺ 3d⁴[t_2gβ3d_z²(1)3d_x²-y²(0)] in NaMnO₂ loses one 3d_z² electron and the redox couple Mn³⁺/Mn⁴⁺ delivers 206 mA h g^-1 during the initial charge. The case that the Fermi energy level difference between R-MnO₂ and NaMnO₂ is lower than that between the layered Na_(12-x)/12MnO₂ and NaMnO₂ makes the potential plateau of R-MnO₂ turning into NaMnO₂ lower than that of the layered Na_(12-x)/12MnO₂ to NaMnO₂. This can be confirmed by our experiment from the 1st-2nd voltage capacity profile of R-MnO₂ in EC/PC (ethylene carbonate/propylene carbonate) electrolyte. The study would give a new view of the production of sustainable sodium battery cathode materials.

An amorphous hierarchical MnO2/acetylene black composite with boosted rate performance as an anode for lithium-ion batteries

Amorphization is considered to be an effective way to enhance the electrochemical performances of electrode materials due to the existence of isotropy and numerous defects. Herein, an amorphous hierarchically structured MnO₂/acetylene black (a-MnO₂/AB) composite is successfully fabricated via a redox method and subsequent mechanical ball milling. The a-MnO₂/AB composite is composed of approximately 300 nm flower-like amorphous MnO₂ submicron spheres and acetylene black particles with a diameter of about 50 nm. The a-MnO₂/AB electrode exhibits an initial coulombic efficiency of 73.2%, excellent rate capabilities of 318 mA h g^-1 at 9.6 A g^-1, and high specific capacity retention of 1300 mA h g^-1 after 300 cycles at 1 A g^-1. The amorphous structure can provide more channels for rapid lithium-ion transmission due to the disorder and defects, and the ion-diffusion coefficient (∼5 × 10^-7 cm² s^-1) is higher than those of crystalline materials. Due to the strong interactions (Mn-O-C bonds) between MnO₂ and AB as a result of the ball milling, the composite shows low charge transport resistance and small volume changes during the discharging/charging process. This work provides a facile route for the construction of amorphous hierarchically structured Mn-based oxides as anodes for lithium-ion batteries (LIBs).

Albumin-stabilized manganese-based nanocomposites with sensitive tumor microenvironment responsivity and their application for efficient SiRNA delivery in brain tumors

Mn(iv)-Based nanoparticles (NPs) are effective in improving tumor oxygenation (hypoxia) and reducing endogenous hydrogen peroxide and acidity in the tumor region. However, the optimized reduction conditions of conventional Mn(iv)-based NPs are generally reported at pH ≤ 6.5, while the usual pH range of the tumor microenvironment (TME) is 6.5-7.0. The dissatisfactory imaging performance in the weakly acidic environment may limit their further application in tumor diagnosis. In this study, Mn(iii) was introduced in a nanoplatform, because it is reduced into Mn(ii) in weakly acidic environments. Arg-Gly-Asp (RGD) peptide-decorated bovine serum albumin (BSA) was employed as the stabilizer and scaffold to fabricate Mn(iii)- and Mn(iv)-integrated nanocomposites (RGD-BMnNPs) with suitable size, good stability, and excellent biocompatibility. The as-prepared NPs showed clear contrast enhancement at pH 6.5-6.9 in vitro as well as sensitive and rapid T₁-weighted imaging performance within the tumor region in a glioblastoma (U87MG) orthotopic model, owing to the intrinsic disproportionation reaction of Mn(iii) in the weakly acidic environment. In addition, these NPs could be used for efficient siRNA delivery. They showed superior advantages in this process, including increased tumour uptake, improved tumor accumulation and enhanced therapeutic effects with the modulation of the TME. These novel albumin-stabilized manganese-based NPs combined with efficient drug delivery capacity hold great potential to serve as intelligent theranostic agents for further clinical translation.

Catalytic manganese oxide nanostructures for the reverse water gas shift reaction

Understanding the fundamental structure-property relationships of nanomaterials is critical for many catalytic applications as they comprise of the catalyst designing principles. Here, we develop efficient synthetic methods to prepare various MnO₂ structures and investigate their catalytic performance as applied to the reverse Water Gas Shift (rWGS) reaction. We show that the support-free MnO derived from MnO₂ 1D, 2D and 3D nanostructures are highly selective (100% CO₂ to CO), thermally stable catalysts (850 °C) and differently effective in the rWGS. Up to 50% conversion is observed, with a H₂/CO₂ feed-in ratio of 1 : 1. From both experiments and DFT calculations, we find the MnO₂ morphology plays a critical role in governing the catalytic behaviors since it affects the predominant facets exposed under reaction conditions as well as the intercalation of K⁺ as a structural building block, substantially affecting the gas-solid interactions. The relative adsorption energy of reactant (CO₂) and product (CO), ΔE = E_ads(CO₂) -E_ads(CO), is found to correlate linearly with the catalytic activity, implying a structure-function relationship. The strong correlation found between E_ads(CO₂) -E_ads(CO), or more generally, E_ads(R) -E_ads(P), and catalytic activity makes ΔE a useful descriptor for characterization of efficient catalysts involving gas-solid interactions beyond the rWGS.