Towards low cost, environmentally and socially responsible materials for next-generation lithium-ion batteries

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Date

2021-08

Authors

Sharma, Shyam Subramaniam

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Abstract

Rechargeable batteries are key to unlocking the potential held by both electric vehicles and clean energy technologies. However, while batteries are at the center of the clean energy revolution, they are not free of their own impacts on the planet. Here, we first provide a robust, holistic framework for researchers to use to assess these impacts for any battery material. The framework addresses four key issues present during the battery manufacturing process: (i) total energy use and emissions, (ii) toxicity, (iii) habitat destruction, and (iv) social impact. This article also includes impact assessments for three battery chemistries that are being intensely pursued: (i) LiNi₀.₈Mn₀.₁Co₀.₁O₂ (NMC811) - Graphite, (ii) LiFePO₄ (LFP)-Graphite, and (iii) aqueous Na-ion. Based on these assessments, we highlight the need to eliminate the use of cobalt and the N-methlypyrrolidone (NMP) solvent. Additionally, we demonstrate the safety benefits of low toxicity electrolyte salts and non-toxic binders. Lastly, we show the land use reductions afforded by using iron and manganese-based cathodes, sodium as the working ion, and cellulose over polyethylene separators. Based on the findings of our initial study, we propose the use of freestanding Al-based foils as low cost, environmentally friendly anodes for future Li-ion batteries. Specifically, we demonstrate the positive effect of as low as 1% silicon doping (Al₉₉.₀Si₁.₀) on the performance of a free-standing, aluminum foil anode. The Al₉₉.₀Si₁.₀ foil anode displays substantial improvements in both cycle life (> 100 cycles) and coulombic efficiency (> 99.5%) compared to pure Al in both half and full cells. Ex-situ morphological analysis with scanning electron microscopy (SEM) reveals the formation of a large, interconnected network of deep cracks in Al₉₉.₀Si₁.₀ after the initial cycle, generating nanostructured, porous aluminum “islands” supported by a pristine, unreacted aluminum substrate. We believe that this highly stable structure allows for facile lithium transport and has the capability to freely expand/contract without isolation from the base foil, preventing rapid mechanical failures of the electrode. Our results demonstrate the potential of Si-doped Al foil anodes as a low cost, sustainable battery material, and the study will stimulate further exploration of Al-alloy foil anodes.

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