Design and characterization of a polymer/oxide hybrid electrolyte for Li|NMC622 battery application

Summary:

Lithium metal is among the most promising anode materials for high energy battery application [1] but is known to eventually suffer from dendrite growth upon cycling. Thus, research efforts to prevent inhomogeneous lithium deposits including exploitation of solid electrolytes increased over the last years. While oxide-based electrolytes feature high ionic conductivity and oxidative stability, polymer electrolytes afford sufficient mechanical flexibility and good processability, rendering them promising classes of materials. In particular, single-ion conducting polymers, with only Li+ ions as mobile species enable high transference numbers and reduced polarization effects, potentially mitigating dendrite growth.[2,3] Consequently, single-ion conducting polymer electrolytes exhibit stable plating and stripping against lithium metal in Li||Li cells for hundreds of hours,[4,5] though quasi-solid polymer electrolytes may exploit organic solvents as “transporter molecules” that make up more than 50% of the total weight from the polymer electrolyte.[4,5] In an effort to decrease the required solvent contents, ceramic particles were systematically added to a reported quasi-solid polymer system,[6] thereby significantly limiting the solvent uptake of the introduced hybrid electrolytes (40 wt.% in comparison to 140 wt.% for the pure polymer electrolyte). Notably, hybrid electrolytes with optimized composition retain a very promising ionic conductivity of 0.7 mS cm 1 at 40 °C, after oxide particle surfaces were silane modified, in this way improving the interfaces among the particles and the polymer matrix. In summary, the hybrid electrolyte facilitates robust cycling of Li|NMC622 cells for over 500 cycles at 40°C and a rate of 0.5C, whereas corresponding polymer electrolytes without ceramic particles suffer from rapid fading of the specific capacities.

References:
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