In-situ Detection Of Dendrite Growth In Lithium Battery Using Tilted Fiber Grating Sensors

Due to its rich storage and high-volume energy density,lithium ion battery is the first choice for mobile electronic devices.With the energy density of embedded lithium compounds approaching the limit,lithium anode with high capacity,high efficiency and low potential has become a research hotspot.It is challenged by short cycle life caused by short circuit of lithium dendrite and reactivity of electrolyte.The quantitative distribution and chemical morphology of lithium ions are difficult to detect.The current technology cannot read the working status information in real time during the operation,and some methods have limited measurement conditions.We need to find a new,nondestructive real-time in situ detection method.Optical fiber sensor has low cost,small size,no pollution to the battery,can withstand the battery internal electrolyte corrosion and not by the battery generated noise interference,is expected to be directly embedded in the battery to achieve detection.The in-situ detection technology of optical fiber battery is proposed in this paper,which provides a new analysis method and detection tool for the electrochemical reaction interface analysis on the electrode surface of the battery and the formation and mechanism of lithium dendrite.The innovation achievements mainly include the following two parts:(1)a reflective inclined fiber Bragg grating sensor probe is designed and developed,which solves the key technology of implantation of lithium battery of fiber sensor,attaches the fiber sensor probe to the electrode surface,and realizes in-situ real-time reading of spectral signals in the charging and discharging process of lithium battery.(2)the three-stage rule between "free lithium ion supplement" and "solid lithium dendrite growth" was found in the process of lithium dendrite growth,which provided in-situ data support for the dendrite growth mechanism.Dendrite growth and dissolution will occur on the electrode surface during constant current charging and discharging of the battery.The three-stage law of dendrite growth on the electrode surface is discovered and verified by monitoring the intensity change of the fiber cutoff mode and using the microscope as the assistant.In the first stage,ion consumption dominates,and lichen-like dendrites of lithium appear.In the second stage,ion consumption and ion supplementation tend to be consistent,and dendritic lithium dendrites appear.In the third stage,the ion-complement increased,and the lithium dendrite presented popcorn growth.At the same time,different electrolytes,different spatial positions,different current conditions,multiple cycles of charging and discharging were also tested.The growth and dissolution process of lithium dendrites were directly demonstrated through spectral data,which proved that the optical fiber sensing probe made by the detector has a fast response speed,accurate and stable detection ability.