Operando monitoring of dendrite formation in lithium metal batteries via ultrasensitive tilted fiber Bragg grating sensors

Lithium(Li)dendrite growth significantly deteriorates the performance and shortens the operation life of lithium metal batteries.Capturing the intricate dynamics of surface localized and rapid mass transport at the electrolyte–electrode interface of lithium metal is essential for the understanding of the dendrite growth process,and the evaluation of the solutions mitigating the dendrite growth issue.Here we demonstrate an approach based on an ultrasensitive tilted fiber Bragg grating(TFBG)sensor which is inserted close to the electrode surface in a working lithium metal battery,without disturbing its operation.Thanks to the superfine optical resonances of the TFBG,in situ and rapid monitoring of mass transport kinetics and lithium dendrite growth at the nanoscale interface of lithium anodes have been achieved.Reliable correlations between the performance of different natural/artificial solid electrolyte interphases(SEIs)and the time-resolved optical responses have been observed and quantified,enabling us to link the nanoscale ion and SEI behavior with the macroscopic battery performance.This new operando tool will provide additional capabilities for parametrization of the batteries’electrochemistry and help identify the optimal interphases of lithium metal batteries to enhance battery performance and its safety.

In situ plasmonic optical fiber detection of the state of charge of supercapacitors for renewable energy storage

In situ and continuous monitoring of electrochemical activity is key to understanding and evaluating the operation mechanism and efficiency of energy storage devices.However,this task remains challenging.For example,the present methods are not capable of providing the real-time information about the state of charge(SOC)of the energy storage devices while in operation.To address this,a novel approach based on an electrochemical surface plasmon resonance(SPR)optical fiber sensor is proposed here.This approach offers the capability of in situ comprehensive monitoring of the electrochemical activity(the electrode potential and the SOC)of supercapacitors(used as an example).The sensor adopted is a tilted fiber Bragg grating imprinted in a commercial single-mode fiber and coated with a nanoscale gold film for high-efficiency SPR excitation.Unlike conventional“bulk”detection methods for electrode activity,our approach targets the“localized”(sub-μm-scale)charge state of the ions adjacent to the electrode interface of supercapacitors by monitoring the properties of the SPR wave on the fiber sensor surface located adjacent to the electrode.A stable and reproducible correlation between the real-time charge–discharge cycles of the supercapacitors and the optical transmission of the optical fiber has been found.Moreover,the method proposed is inherently immune to temperature cross-talk because of the presence of environmentally insensitive reference features in the optical transmission spectrum of the devices.Finally,this particular application is ideally suited to the fundamental qualities of optical fiber sensors,such as their compact size,flexible shape,and remote operation capability,thereby opening the way for other opportunities for electrochemical monitoring in various hard-to-reach spaces and remote environments.

Operando optical fiber monitoring of nanoscale and fast temperature changes during photo-electrocatalytic reactions

In situ and continuous monitoring of thermal effects is essential for understanding photo-induced catalytic processes at catalyst's surfaces.However,existing techniques are largely unable to capture the rapidly changing temperatures occurring in sub-μm layers at liquid-solid interfaces exposed to light.To address this,a sensing system based on a gold-coated conventional single-mode optical fiber with a tilted fiber Bragg grating inscribed in the fiber core is proposed and demonstrated.The spectral transmission from these devices is made up of a dense comb of narrowband resonances that can differentiate between localized temperatures rapid changes at the catalyst's surface and those of the environment.By using the gold coating of the fiber as an electrode in an electrochemical reactor and exposing it to light,thermal effects in photo-induced catalysis at the interface can be decoded with a temperature resolution of 0.1℃and a temporal resolution of 0.1 sec,without perturbing the catalytic operation that is measured simultaneously.As a demonstration,stable and reproducible correlations between the light-to-heat conversion and catalytic activities over time were measured for two different catalysis processes(linear and nonlinear).These kinds of sensing applications are ideally suited to the fundamental qualities of optical fiber sensors,such as their compact size,flexible shape,and remote measurement capability,thereby opening the way for various thermal monitoring in hard-to-reach spaces and rapid catalytic reaction processes.