rechargeable lithium-ion cell state of charge and defectxa0detection by in-situ inside-out magnetic resonance imaging - lithium ion cell

When and why does a rechargeable battery lose capacity or damage?
This is a difficult question to answer.
However, it is at the heart of advances in consumer electronics, electric vehicles and electrical storage.
The difficulty is related to the limited amount of information that people can get from the cell without the need to disassemble the cell and perform a destructive analysis of it.
Here, we demonstrate that measuring the small induced magnetic field changes inside the battery can be used to evaluate the level of lithium-incorporated electrode materials and to diagnose certain cell defects that may occur during assembly.
The measurement speed is fast, the completed and unfinished batteries can be measured, and most importantly, the batteries compatible with the commercial design requirements of the conductive shell can be non-destructive measured.
Among the many important energy solutions, batteries are a key enabling technology that is an integral part of advances in storage for portable electronics, electric vehicles and power grids.
Ongoing demand for high-powered batteries
The desire for energy capacity and fast charging and discharging equipment presents some daunting engineering and scientific challenges.
Ensuring equipment safety is an important consideration and needs to be addressed with care.
Due to battery and battery failures, some industry leaders have experienced unforeseen setbacks, such as those recently seen on the swelling issue of Samsung Note 7 devices or iPhone 8.
One of the main reasons for this problem to reappear, and one of the main reasons for the slow progress of battery technology, is that it is difficult to track defects inside the battery in a non-destructive way during operation. X-
Ray CT is a successful technology to scan the battery, but it is relatively slow, so it is generally not suitable for high throughput or in-situ applications. Furthermore, X-
The diagnosis provided by Ray CT is primarily a component with a large density of cells and does not provide insight into subtle chemical or physical changes in internal materials.
The recently developed acoustic technology seems to be a promising approach to the non-destructive representation of cell behavior throughout the cell life cycle, and its sensitivity to important cell behavior is currently being studied.
Magnetic resonance (MR)
Several techniques have been developed to measure several different cell properties.
A fundamental limitation that is difficult to overcome under typical operating conditions is that the conductor is opaque to radio frequency radiation.
Typically, the battery housing is made of conductive materials such as polymer-
Lined aluminum in bags or laminated batteries, but the electrodes also exclude the use of conventional MR for real or commercial purposes
Type cell geometry.
Nevertheless, Mr. Li provides important insights into electrolyte behavior
Use custom-made shoot growth and other electro-chemical effects
Built-in battery, allowing easy RF access.
Here we demonstrate a MR technique that overcomes these limitations and provides cell diagnostics that do not require rf access to the interior of the cell.
This technique is based on imaging the induction or permanent magnetic field produced by the cell and connecting it to the process inside the cell.
The reason why this magnetic field information is so rich is that magnetic x is related to the material, and the resulting magnetic field depends on the distribution of the material within the cell, which changes during cell operation.
Magnetic properties also depend on the electronic structure of the material, so there may be a significant change in magnetic properties during redox reactions, such as battery charging or discharging.
Therefore, the measurement of the magnetic sensitivity can produce detailed information about the oxidation state of the material in the electrolytic device to gain an in-depth understanding of the charge state (SOC)
The battery and its failure mechanism.
In addition, the magnetic sensitivity of many widely used electrode materials, such as LiMnO, LiFePO, LiCoO and LiNiMnCoO, depends on their lithium state.
Graphite is a popular anode material with strong anti-magnetic properties and a high degree of heterosexual polarization.
In this case, with the Li-embedded structure, the interlayer distance in graphite increases, and the polarization rate and its heterogeneity decrease significantly.
This effect depends largely on the stage (
Graphite layers between each lithium layer)
The lithium is obtained.
When the battery is placed into an external magnetic field, the magnetic field generated by the battery is monitored, thus providing the ability to monitor the electro-chemical process in situ.
In addition, the distribution of magnetic materials inside the cell affects the spatial change of the magnetic field it produces, so it is also sensitive to the precise structure of the cell.
In this way, measurements of magnetic fields can be used to screen physical defects in cells.
The MR method provides the ability to measure minor changes in the magnetic field map, for example, by using phase-
Map imaging or specific NMR probes. In the phase-
Map imaging method to obtain multiple images at different Echo Times (TEs)
It is also used to reconstruct the spatial variation of the induced resonance frequency shift from the evolution of the signal phase.
In this way, a very accurate field map can be obtained
Sensitivity of μ t order of magnitude
Because in the end, the magnetic field change is measured, in addition to measuring the magnetic properties of the device, one can also measure the current distribution in the same way, for example, in the slack stage between charging steps, or during charging or discharging.
In this paper, we show how to use MR in Li-ion pouch cell.
When the battery is charged, the field changes in a highly predictable way.
For example, these results can be used to infer the average oxidation state of the Cathode composition as a charge function.
To demonstrate the potential of this technology, it is important to understand the precise structure of cells and materials used and to explore the different types of defects that may occur during construction.
Therefore, we measured cells in their original state, and also those with specific defects.
This approach enables us to demonstrate certain types of identification of these defects through non-invasive MR methods.