Lithium (Li) ion batteries (LIB) are an important energy storage technology, especially for the development of electric vehicles. However, two key challenges remain: (i) increasing the energy density and (ii) reducing the cost. To enable the ubiquitous utilization of electric vehicles, it is necessary to move forward to active materials that have increased Li storage capability. Li metal anodes have extremely high theoretical specific charge capacity compared to the graphite anodes used in commercial cells. However, the problems of lithium dendrite growth and low coulombic efficiency have proven to be difficult challenges to overcome. Fundamentally, these two issues stem from the instability of the solid electrolyte interphase (SEI) layer, which is easily damaged by the large volumetric changes during battery cycling. In this work, we show that by applying a highly viscoelastic polymer to the lithium metal electrode, the morphology of the lithium deposition became significantly more uniform. At a high current density of 5 mA/cm<sup>2</sup> we obtained a flat and dense lithium metal layer, and we observed stable cycling Coulombic efficiency of ~97% maintained for more than 180 cycles at a current density of 1 mA/cm<sup>2</sup>. The demonstration of a functional soft, viscoelastic polymer coating for improving Li metal electrodeposit morphology and electrochemical cycling represents a stark, but promising, deviation from conventional understanding. It has been reported that high modulus coatings or interfaces are effective for suppressing dendrite growth. However, in this case it is not mechanical stiffness but rather the extreme softness and intrinsic polymer flow that are utilized to improve electrode uniformity.

High performance lithium metal anode with a soft and flowable polymer coating

254th National Meeting (2017)

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