Battery Characterization via Eddy-Current Imaging with Nitrogen-Vacancy Centers in Diamond

At a Glance

Metadata	Details
Publication Date	2021-03-30
Journal	Applied Sciences
Authors	Xue Zhang, Georgios Chatzidrosos, Yinan Hu, Huijie Zheng, Arne Wickenbrock
Institutions	GSI Helmholtz Centre for Heavy Ion Research, Helmholtz Institute Mainz
Citations	25
Analysis	Full AI Review Included

Executive Summary

This research demonstrates a highly sensitive, microwave-free eddy-current imaging (ECI) technique utilizing Nitrogen-Vacancy (NV) centers in diamond for non-destructive evaluation (NDE) of solid-state batteries.

Core Value Proposition: Provides a non-invasive method to identify and localize structural anomalies (defects, impurities, crevices) inside and outside rechargeable solid-state batteries with high spatial resolution.
Sensing Mechanism: Employs all-optical AC magnetometry based on the narrow cross-relaxation feature between NV centers and substitutional nitrogen (P1) centers, occurring at a bias field of 51.2 mT.
Performance Metrics: Achieved a magnetic sensitivity of 40 nT / sqrt(Hz) with a 100 kHz bandwidth, suitable for rapid industrial inspection.
Spatial Resolution: The system demonstrated a spatial resolution of 360 ± 2 µm (FWHM), limited primarily by the 0.1 mm distance between the sensor and the battery.
Defect Differentiation: By varying the AC modulation frequency (1 kHz to 40 kHz), the technique successfully differentiated between external electrode defects and internal anomalies (e.g., a 1 mm brass impurity and a crevice).
Quantified Results: The maximum secondary magnetic field generated by the battery at 5 kHz was measured to be 0.04 mT, with a corresponding phase shift of 0.03 rad.

Technical Specifications

Parameter	Value	Unit	Context
Sensor Type	NV Centers	N/A	Negatively charged, Type-Ib diamond
Diamond Dimensions	3.0 x 3.0 x 0.4	mm³	HPHT grown, (111)-cut
Initial Nitrogen Conc.	less than 110	ppm	Before electron irradiation and annealing
Cross-Relaxation Field (NV-P1)	51.2	mT	Feature used for AC magnetometry
Working Bias Field	52.5	mT	Optimized detection point
Magnetic Sensitivity	40	nT / sqrt(Hz)	Estimated noise sensitivity
Bandwidth	100	kHz	Expandable up to MHz
Spatial Resolution (FWHM)	360 ± 2	µm	Limited by sensor-sample distance
Sensor-Sample Distance	0.1	mm	Distance between battery and diamond
Primary AC Field Amplitude (B_primary)	0.48	mT	Modulated field for LIA detection
Modulation Frequencies Tested	1, 5, 10, 40	kHz	Used for depth differentiation
Max Secondary Field (B_secondary)	0.04	mT	Generated by battery at 5 kHz
Max Phase Shift (δφ)	0.03	rad	Generated by battery at 5 kHz
Battery Type	All-ceramic multilayer	N/A	Solid-state battery (TDK Corporation)
Battery Dimensions	4.0 x 3.0 x 1.0	mm³	Sample size
Temperature Dependence (NV-P1 shift)	-1.34	µT/K	Expected drift at room temperature

Key Methodologies

The experiment employed an all-optical, microwave-free AC magnetometry setup to perform eddy-current imaging on a solid-state battery sample.

Optical Pumping and Stabilization:
- A continuous-wave green laser (532 nm) was used to continuously pump the NV centers into the m_s = 0 spin projection via radiative and nonradiative transitions.
- A light-power stabilization loop (using a photodiode, PID controller, and AOM) was implemented to minimize noise from laser intensity fluctuations.
Magnetic Field Setup:
- A custom electromagnet (EM) provided the necessary background DC bias field, set to 52.5 mT, to align with the NV-P1 cross-relaxation feature (51.2 mT).
- An RF coil (5 turns, 0.1 mm copper wire) provided the oscillating primary AC magnetic field (B_primary = 0.48 mT) used to induce eddy currents in the battery.
Eddy Current Induction and Detection:
- The oscillating primary field induced eddy currents in the conductive components of the battery (electrodes, electrolyte). These currents generated a secondary magnetic field (B_secondary) anti-parallel to B_primary.
- The NV centers detected the total magnetic field (B_primary + B_secondary), causing a modulation in the red photoluminescence (PL) signal.
- A Lock-In Amplifier (LIA) detected the amplitude (R) and phase (θ) of the PL modulation, using the AC coil frequency (1 kHz to 40 kHz) as the reference.
Sample Scanning and Imaging:
- The solid-state battery sample was placed 0.1 mm from the diamond sensor and mounted on a motorized 3D translation stage.
- The battery was scanned across the transverse (y-z) plane to generate spatially resolved maps of the LIA amplitude and phase.
Defect Analysis and Calibration:
- By increasing the modulation frequency, the skin depth (δ) of the eddy currents was reduced, allowing differentiation between surface features (visible at 1 kHz) and internal structural anomalies (impurities and crevices, visible at 5 kHz and 20 kHz).
- The measured LIA amplitude and phase were calibrated using a reference formula to estimate the absolute magnetic field and phase shift generated by the battery.

Commercial Applications

This diamond-based ECI technology offers significant advantages in fields requiring high-resolution, non-contact inspection of conductive materials.

Battery Manufacturing and Quality Assurance:
- High-speed, non-destructive screening of solid-state batteries for internal defects (e.g., delamination, cracks, electrolyte voids, or foreign metallic impurities).
- Characterization of external electrode integrity and uniformity.
Battery Research and Development (R&D):
- Mapping complex magnetic susceptibility (χ_m) to study dissipative processes and material properties within electrodes and electrolytes.
- Depth-resolved analysis of battery components by tuning the AC modulation frequency and corresponding skin depth.
Advanced Materials Inspection:
- Non-contact evaluation of conductive thin films, microelectronic components, and printed circuit boards for structural flaws or current path anomalies.
Quantum Sensing and Metrology:
- Development of robust, compact, all-optical magnetometers for industrial environments, leveraging the wide temperature range and high sensitivity of NV diamond sensors.

View Original 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.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app11073069

References

2016 - Microwave-free magnetometry with nitrogen-vacancy centers in diamond [Crossref]
2013 - Nanometer scale thermometry in a living cell [Crossref]
2014 - Dynamic strain-mediated coupling of a single diamond spin to a mechanical resonator [Crossref]
2012 - Stable three-axis nuclear-spin gyroscope in diamond [Crossref]
2012 - Gyroscopes based on nitrogen-vacancy centers in diamond [Crossref]
2011 - Electric-field sensing using single diamond spins [Crossref]
2014 - Magnetic induction tomography using an all-optical 87Rb atomic magnetometer [Crossref]
2016 - Electromagnetic induction imaging with a radio-frequency atomic magnetometer [Crossref]
2016 - Microwave-free magnetometry with nitrogen-vacancy centers in diamond [Crossref]