Operando Investigation of Silicon Anodes During Electrochemical Cycling in Li-ion Batteries.

Silicon (Si) is recognized as a promising anode material for next-generation anodes due to its high capacity. However, large volume expansion and active particle pulverization during cycling rapidly deteriorate the battery performance. The relationship between Si anode particle size and particle pulverization, and the structure evolution of Si particles during cycling is not well understood. In this study, a quantitative, time-resolved "operando" small angle X-ray scattering (SAXS) investigation into the morphological change of unwrapped and reduced graphene oxide (rGO) wrapped Si nanoparticles (Si@rGO) is conducted with respect to the operating voltage. The results provide a clear picture of Si particle size change and the role of nonrigid rGO in mitigating Si volume expansion and pulverization. Further, this study demonstrates the advantage of "operando" SAXS in electrochemical environments as compared to other approaches.

Recycle, Recover and Repurpose Strategy of Spent Li-ion Batteries and Catalysts: Current Status and Future Opportunities.

The disposal of hazardous waste of any form has become a great concern for the industrial sector due to increased environmental awareness. The increase in usage of hydroprocessing catalysts by petrochemical industries and lithium-ion batteries (LIBs) in portable electronics and electric vehicles will soon generate a large amount of scrap and create significant environmental problems. Like general electronic wastes, spent catalysts and LIBs are currently discarded in municipal solid waste and disposed of in landfills in the absence of policy and feasible technology to drive alternatives. Such inactive catalyst materials and spent LIBs not only contain not only hazardous heavy metals but also toxic and carcinogenic chemicals. Besides polluting the environment, these systems (spent catalysts and LIBs) contain valuable metals such as Ni, Mo, Co, Li, Mn, Rh, Pt, and Pd. Therefore, the extraction and recovery of these valuable metals has significant importance. In this Review, we have summarized the strategies used to recover valuable (expensive) as well as cheap metals from secondary resources-especially spent catalysts and LIBs. The first section contains the background and sources of LIBs and catalyst scraps with their current recycling status, followed by a brief explanation of metal recovery methods such as pyrometallurgy, hydrometallurgy, and biometallurgy. The recent advances achieved in these methods are critically summarized. Thus, the Review provides a guide for the selection of adequate methods for metal recovery and future opportunities for the repurposing of recovered materials.

Reversible Intercalation of Multivalent Al3+ Ions into Potassium-Rich Cryptomelane Nanowires for Aqueous Rechargeable Al-Ion Batteries.

The development of new battery technology that utilizes abundant electrode materials that are environmentally benign is an important area of research. To alleviate the reliance on Li-ion batteries new energy storage mechanisms are urgently needed. To address these issues, MnO2 nanowires were investigated as a possible electrode material for use in rechargeable Al ion batteries that can operate in aqueous conditions. The use of this type of material and an aqueous electrolyte ensures safe operation as well as easy recycling of spent batteries. A potassium-rich cryptomelane structure was presented, and a new mechanism of electrochemical energy storage was elucidated based on the intercalation and deintercalation of small-radius Al3+ ions interchanging with larger K+ ions in the cryptomelane MnO2 nanowires, which was supported by DFT calculations. This first-time use of a cryptomelane MnO2 cathode for an aqueous Al ion system yielded a discharge capacity of 109 mAh g-1 , which indicates the potential commercial viability of rechargeable aqueous Al-ion batteries.

Re-evaluation of experimental measurements for the validation of electronic band structure calculations for LiFePO4 and FePO4.

Experimental measurements used to validate previous electronic band structure calculations for olivine LiFePO4 and its delithiated phase, FePO4, have been re-investigated in this study. Experimental band gaps of LiFePO4 and FePO4 have been determined to be 6.34 eV and 3.2 eV by electron energy loss spectroscopy (EELS) and UV-Vis-NIR diffusion reflectance spectroscopy, respectively. X-ray photoemission (XPS) and Raman spectroscopy show that the surfaces of very carefully synthesized LiFePO4 display Li-depletion, which affects optical reflectance determinations. Based on these experimental measurements, functionals for density functional theory (DFT) calculations of the electronic properties have been revisited. Overall, electronic structures of LiFePO4 and FePO4 calculated using sX-LDA show the best self-consistent match to combined experimentally determined parameters. Furthermore, the open-circuit voltages of the LiFePO4 half-cell have been interpreted in terms of both Fermi levels and Gibbs free energies, which provides additional support for the electronic band structures determined by this research.

New Spin on Organic Radical Batteries-An Isoindoline Nitroxide-Based High-Voltage Cathode Material.

Organic electrode materials are a highly promising and environmentally benign class of battery materials with radical polymers being at the forefront of this research. Herein, we report the first example of the 1,1,3,3-tetramethylisoindolin-2-yloxyl class of nitroxides as an organic electrode material and the synthesis and application of a novel styrenic nitroxide polymer, poly(5-vinyl-1,1,3,3-tetramethylisoindolin-2-yloxyl) (PVTMIO). The polymer was synthesized from the precursor monomer, 2-methoxy-5-vinyl-1,1,3,3-tetramethylisoindoline, and subsequent oxidative deprotection yielded the electroactive radical species. Cyclic voltammetry revealed a high oxidation potential of 3.7 V versus Li, placing it among the top of the nitroxide class of electrode materials. The suitability of PVTMIO for utilization in a high-voltage organic radical battery was confirmed with a discharge capacity of 104.7 mAh g-1, high rate performance, and stability under cycling conditions (90% capacity retention after 100 cycles), making it one of the highest reported organic p-dopable cathode materials.