Application Of Self-healing Materials In Photoelectric Devices

Photoelectric devices,such as sensors,actuators,and energy storage devices,have been widely used in energy,information and other high-tech fields.These devices will inevitably be subjected to mechanical stress which causes damage.Introducing self-healing properties into the photoelectric devices can lead to spontaneous healing of damages,and therefore can effectively extend the service life and improve the safety of the devices.In this thesis,we focus on the local or integral self-healing of photoelectric devices.We designed and synthesized a series of new self-healing materials and used them in optoelectric functional devices,such as dielectric actuators and lithium-sulfur batteries.The main research results are as followed:1.Dielectric elastomer actuators(DEAs)have been receiving extensive attentions due to their unparalleled combination of high energy density,high efficiency,softness,silent operation,and muscle-like performance,which are favorable for soft robotics.However,DEAs encounter safety problems due to dielectric breakdown at high electric fields.In this work,we fabricate a DEA by using Cu/Cu_xO/PDMS(polydimethylsiloxane)composite as dielectric elastomer.Due to the presence of a Cu_xO layer as the insulating layer,which blocks the formation of conductive networks and reduces the dielectric loss,the Cu/Cu_xO/PDMS film with 15 wt% content of Cu/Cu_xO exhibited a significantly higher breakdown strength(29.17 V/?m as compared to 12.50 V/?m for Cu/PDMS film).Such results are helpful for further fabrication of DEAs with improved safety.2.Although the previous work improved the breakdown strength and the safety of use,dielectric actuators are prone to be worn or partially damaged when operating at high electric fields.The introduction of self-healing features into dielectric actuators is favorable for extending its life span and security.Although many attempts have been made to produce self-healing dielectric actuators,most of them focus on the healing of either the electrode or the dielectric layers.A dielectric actuator that exhibits integral self-healing is still unprecedented.Meanwhile,realizing integral self-healing in dielectric actuator is highly challenging,because both the electrode and the dielectric layer need to be healed while the interface between the electrode and the dielectric layer should remain unaffected during the healing process.In this paper,we synthesized self-healing PDMS polymers containing different amount of polyaniline(PANI)(denoted as PDMS-PANI_n,where n represent the weight percentage of PANI)as dielectric layer and electrode respectively.PDMS-PANI_2.5 polymer exhibits good dielectric properties(?= 11.11 at 50 Hz)and was used as dielectric layer,while PDMS-PANI₂₀ polymer with high conductivity of 4.5× 10^-5 S/cm was used as electrode.As both of them have excellent self-healing ability and are compatible and diffusible to each other,the entire actuator device can still cause actuated strain after cutting and healing at room temperature for 48 h.Our strategy for realizing integral self-healing of actuator is also applicable to other electronic devices.3.Lithium-sulfur batteries,which can be applied for portable electronic devices with longer endurance,have received tremendous attention because of their high theoretical capacity and high energy density.However,both electrode volume variation and serious shuttling effects during the charge/discharge process limit the promotion of lithium-sulfur batteries.In this work,a novel self-healing PDMS polymer with dynamic disulfide bond(2S-PDMS)was designed as binders in sulfur electrodes.The disulfide bonds in 2S-PDMS molecules can reversibly break and form,facilitating the conversion of polysulfides,as evidenced by both experimental and calculated results.In addition,2S-PDMS binders with a remarkable self-healing ability and flexibility can remain the sulfur cathode integrited without cracks or damage.Consequently,the 2S-PDMS-based cathode exhibits both high capacity and excellent cycling stability,showing a specific capacity of 545.7 m Ah g^-1 at 2.0 C after 400 cycles(79.6% capacity retention).Moreover,soft-packed Li-S batteries with a high sulfur loading of 6.6 mg cm^-2 deliver a high areal capacity of 4.54 m Ah cm^-2 after 50 cycles,which verifies good flexibility and stability of the 2S-PDMS-based cathode.