Abstract
This work elucidates the manufacturing of lithium titanate (Li4Ti5O12, LTO) electrodes via the aqueous process using sodium carboxymethylcellulose (CMC), guar gum (GG) or pectin as binders. To avoid aluminum current collector dissolution due to the rising slurries’ pH, phosphoric acid (PA) is used as a pH-modifier. The electrodes are characterized in terms of morphology, adhesion strength and electrochemical performance. In the absence of phosphoric acid, hydrogen evolution occurs upon coating the slurry onto the aluminum substrate, resulting in the formation of cavities in the coated electrode, as well as poor cohesion on the current collector itself. Consequently, the electrochemical performance of the coated electrodes is also improved by the addition of PA in the slurries. At a 5C rate, CMC/PA-based electrodes delivered 144 mAh·g−1, while PA-free electrodes reached only 124 mAh·g−1. When GG and pectin are used as binders, the adhesion of the coated layers to the current collector is reduced; however, the electrodes show comparable, if not slightly better, electrochemical performance than those based on CMC. Full lithium-ion cells, utilizing CMC/PA-made Li[Ni0.33Mn0.33Co0.33]O2 (NMC) cathodes and LTO anodes offer a stable discharge capacity of ~120 mAh·g−1(NMC) with high coulombic efficiencies.
Highlights
The worldwide trend to develop light weight and high performance devices, such as smartphones, personal computers and tablets, demands designable and reliable power supplies
We report our investigation of full cells comprising Ni0.33 Mn0.33 Co0.33 ]O2 (NMC) as the cathode and Li4 Ti5 O12 (LTO) as the anode, both prepared via aqueous processing using natural polymeric binders
The higher adhesion strength of CMC compared to guar gum (GG) electrodes can be explained by the linear β-linkage polymer chain geometry
Summary
The worldwide trend to develop light weight and high performance devices, such as smartphones, personal computers and tablets, demands designable and reliable power supplies. A major requirement of new battery technologies is, besides key factors, like high performance, safety and low cost, the sustainability and environmental friendliness of the used components [1,2]. From this point of view, aqueous processing of LIB electrodes, i.e., utilizing only water-soluble binders, is an extremely promising approach. The alkaline nature of aqueous LTO slurries favors the corrosion of the aluminum current collector upon electrode coating [5] To avoid this issue, the use of mild acids, i.e., phosphoric (PA) and formic (FA) acids, as pH modifiers of Li[Ni0.33 Mn0.33 Co0.33 ]O2. We report our investigation of full cells comprising NMC as the cathode and LTO as the anode, both prepared via aqueous processing using natural polymeric binders
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