An ultrahigh efficiency electrochemical actuator

Electrochemical actuators (EAs) with capabilities of triggering large deformation are attracting great interests because of their low stimulation voltage and high durability. However, porous electrode structures (PESs) with either a large unexpected strain or small-size inserted ions lead to small actuation strain and low energy transduction efficiency. To address this problem, an ideal electrode material, namely, pyrolytic graphite (PG), with an anisotropic densely stacked electrode structure (ASES), was proposed, and the optimal insertion ion, namely, AlCl₄⁻ with a large radius, was selected. Simulations show that an ASES presents an increased actuation strain and effectively eliminates unexpected strain. In addition, the insertion of AlCl₄⁻ into the graphite layers can lead to a directionally large volume expansion (>230%) due to the low energy barrier and large ionic radius. Experimental results reveal that the PG can expand/contract repeatedly with a high linear strain of ≈48% under a zero stress and ≈32% under a load of 2.5 MPa. EAs based on PG and AlCl₄⁻ achieve excellent actuation efficiency with an energy density of 105.89 J cm ⁻³, power density of 0.35 W cm⁻³ and a high electromechanical transduction efficiency of up to 14.30%. This design method provides a significant way to develop high-performance EAs.