11. Li-ion battery separators – today’s solid electrolytes

Why “liquid” Li-ion cells are actually “semi-solid” hybrids.

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Paper discussing separator tortuosity by Gasteiger group

Voltage drop can be as high as 0.18V (losses: >15% of total energy) across a 16 micron separator if battery is operated at 5C.

Today’s “liquid cells” are in fact solid/liquid hybrids where liquid electrolytes make up only 30% to 40% of the volume between anode and cathode. Separators are the porous polymeric membranes which (electrically) insulate the anode from the cathode. They house the ionically conductive liquid electrolyte in their empty pores and govern the energy density, cycle life and safety of lithium ion cells even though they are inert components. This 2018 Nature paper discusses the role of separators as well as several critical parameters used to characterize them, such as effective conductivity, transfer coefficients, diffusion constants, porosity, tortuosity, Gurley values, permeability and others.

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2 thoughts on “11. Li-ion battery separators – today’s solid electrolytes

  1. inorganic materials based separator films could be the best candidates for thermal stability avoiding any short circuits between anode and cathode, I am related with separator films for lithium ion battery
    we believe, the electrospun technology could be beneficial in this regard

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