Abstract
Dendrite growth threatens the safety of batteries by piercing the ion-transporting separators between the cathode and anode. Finding a dendrite-suppressing material that combines high modulus and high ionic conductance has long been considered a major technological and materials science challenge. Here we demonstrate that these properties can be attained in a composite made from Kevlar-derived aramid nanofibres assembled in a layer-by-layer manner with poly(ethylene oxide). Importantly, the porosity of the membranes is smaller than the growth area of the dendrites so that aramid nanofibres eliminate 'weak links' where the dendrites pierce the membranes. The aramid nanofibre network suppresses poly(ethylene oxide) crystallization detrimental for ion transport, giving a composite that exhibits high modulus, ionic conductivity, flexibility, ion flux rates and thermal stability. Successful suppression of hard copper dendrites by the composite ion conductor at extreme discharge conditions is demonstrated, thereby providing a new approach for the materials engineering of solid ion conductors.
Highlights
Dendrite growth threatens the safety of batteries by piercing the ion-transporting separators between the cathode and anode
Many problems related to the stability of cathodes and anodes remain to be resolved, more attention needs to be paid to the ion-conducting membranes (ICMs) separating them
As the industry is continuously pushing for higher energy density, the mechanical properties of internal components become essential as never before. Their brittleness of the Li-based ceramics, reflecting the fundamental conflict between the two essential materials properties[6], makes it difficult to incorporate Li-based ceramics into battery packs. Their safety concerns associated with cracking of ceramic separators necessitate thicker ICMs with increased internal resistance leading to energy losses
Summary
Dendrite growth threatens the safety of batteries by piercing the ion-transporting separators between the cathode and anode. Free-standing (PEO/ANF)n membranes were sandwiched between two lithium metal electrodes and housed in a CR2032 coin battery cell. The impregnation with lithium triflate (often used in Li batteries as electrolyte) did not change the mechanical properties of the (PEO/ANF)[200] composite.
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