Abstract
Sensitive and accurate diagnostic technologies with magnetic sensors are of great importance for identifying and localizing defects of rechargeable solid batteries using noninvasive detection. We demonstrate a microwave-free alternating current (AC) magnetometry method with negatively charged NV centers in diamond based on a cross-relaxation feature between nitrogen-vacancy (NV) centers and individual substitutional nitrogen (P1) centers occurring at 51.2 mT. We apply the technique to non-destructively image solid-state batteries. By detecting the eddy-current-induced magnetic field of the battery, we distinguish a defect on the external electrode and identify structural anomalies within the battery body. The achieved spatial resolution is μμμ360μm. The maximum magnetic field and phase shift generated by the battery at the modulation frequency of 5 kHz are estimated as 0.04 mT and 0.03 rad respectively.
Highlights
Sensitive and accurate diagnostic technologies with magnetic sensors are of great importance for identifying and localizing defects of rechargeable solid batteries using noninvasive detection
We demonstrate all-optical alternating current (AC) magnetometry to detect the secondary field as a function of position
ΔR = R2m sin2 + (R0 cos(φ0) − Rm cos)2, where δφ indicates the phase shifts generated by the battery, δR is the amplitude contrast generated by the battery, R0 and φ0 are the background-corresponding amplitude and phase of the lock-in amplifier (LIA), respectively, and Rm and φm are the measured lock-in amplitude and the phase, respectively
Summary
Sensitive and accurate diagnostic technologies with magnetic sensors are of great importance for identifying and localizing defects of rechargeable solid batteries using noninvasive detection. In [11], a microwave-free eddy-current imaging device based on NV centers in diamond was demonstrated making use of a NV–NV cross-relaxation feature between 0 and 20 mT. The imaged sample is an all-ceramic multilayer solid-state battery produced by TDK Corporation. It incorporates inner electrodes, electrolyte and external electrodes. The secondary field is anti-parallel to the primary field and exhibits a phase delay These quantities relate to a number of characteristics in the imaged sample, such as shape, dimensions, conductivity and susceptibility. A radio-frequency (RF) coil is made from copper wire of 0.1 mm diameter It has five turns and is wound around the diamond to provide a modulation field to both the diamond and battery. The LIA is connected to the computer, and R and θ are recorded along with the position of the battery (the 3D translation stage)
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