CN115015384A - In-situ detection method and system for liquid metal battery - Google Patents

In-situ detection method and system for liquid metal battery Download PDF

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CN115015384A
CN115015384A CN202210546669.5A CN202210546669A CN115015384A CN 115015384 A CN115015384 A CN 115015384A CN 202210546669 A CN202210546669 A CN 202210546669A CN 115015384 A CN115015384 A CN 115015384A
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liquid metal
metal battery
battery
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王玮
邹秉辰
蒋凯
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Huazhong University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/043—Analysing solids in the interior, e.g. by shear waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2437—Piezoelectric probes
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    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M10/39—Accumulators not provided for in groups H01M10/05-H01M10/34 working at high temperature
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Abstract

The invention discloses an in-situ detection method and a system of a liquid metal battery, which belong to the technical field of battery detection and comprise the following steps: in the normal operation process of the liquid metal battery, transmitting an ultrasonic signal to the liquid metal battery through an ultrasonic module; the ultrasonic module is coupled with the bottom of the liquid metal battery and used for transmitting ultrasonic waves and receiving reflected echo signals; receiving an echo signal reflected by the liquid metal battery through an ultrasonic module, extracting the echo signal reflected by the interface between the anode and the electrolyte from the echo signal, and calculating the amplitude variation of the echo signal; determining the alloying degree of the anode according to the corresponding relation between the amplitude variation calibrated in advance and the alloying degree of the anode; according to the pre-calibrated amplitude variation and dischargeThe corresponding relation of the capacity determines the current discharge capacity C of the battery 1 (ii) a According to
Figure DDA0003649433070000011
And estimating the state of charge (SoC). The invention can realize accurate detection of the alloying/dealloying process of the anode in the liquid metal battery under the condition of not disassembling the battery.

Description

In-situ detection method and system for liquid metal battery
Technical Field
The invention belongs to the technical field of battery detection, and particularly relates to an in-situ detection method and system for a liquid metal battery.
Background
Liquid metal batteries are a novel electrochemical energy storage technology, and generally adopt liquid metals with smaller electronegativity, such as Li, Na, Ca and Mg, as a negative electrode, liquid metals/alloys with larger electronegativity as a positive electrode, and inorganic molten salt as an electrolyte, so that a three-layer full liquid structure is spontaneously formed due to density difference and incompatibility. The full-liquid structure can effectively avoid the problems of electrode structure deformation and dendritic crystal growth of the traditional solid electrode in the circulating process, so that the liquid metal battery has an ultra-long service life, and meanwhile, the excellent rate performance of the battery is also endowed by the rapid mass transfer dynamics of a liquid/liquid interface.
Different from the insertion/extraction reaction of the traditional lithium ion battery, the electrochemical reaction of the liquid metal battery in the circulating process is the alloying/dealloying process of the anode, the alloy solid grows on the anode/electrolyte interface during discharging, and dealloying on the anode side is converted into a liquid electrode during charging. The construction of the full liquid phase structure of the battery needs high working temperature, the electrode material has the characteristic of sensitivity to water and oxygen and needs a sealed battery structure, and the whole battery takes stainless steel with the thickness of about 3mm as a shell, so that the in-situ analysis and monitoring means aiming at the alloying process of the liquid metal battery is very limited. The in-situ detection technology applied to other electrochemical energy storage systems, such as in-situ XRD, in-situ SEM, neutron imaging and the like, has the problems of high cost, complex equipment, low penetrating power, requirement for additionally designing a battery structure and the like, and cannot be applied to a liquid metal battery with high-temperature operation and sealed structure.
In the patent application document with application publication number CN 112903950 a, a device for high-temperature in-situ nondestructive testing of a liquid metal battery is disclosed, when the battery works, rays, ultrasonic waves and electromagnetic waves enter from an incident window and an incident hole of the device, penetrate out from a transmission hole and a transmission window after passing through a detection sample, and are collected by an external detector and then subjected to subsequent analysis. The entrance window and the entrance hole of the device are parallel to the cell sealing component. The device can realize the nondestructive detection of the microstructure and the morphology of part of the component in the operation process of the battery and analyze the corrosion process of the liquid metal electrode and the molten salt electrolyte to key parts of the battery. But the ray and the electromagnetic wave cannot penetrate through the stainless steel shell of the battery; if the ultrasonic wave enters from the incident hole of the device, the ultrasonic wave cannot be transmitted to the battery anode/electrolyte interface, so that the device cannot realize in-situ observation of the electrochemical reaction process of the surface of the anode in the liquid metal battery. And because the design structure restriction, the same device can't detect, analyze the liquid metal battery of different volumes, correspondingly, also can't detect, analyze the battery of different capacities, has certain limitation in the application.
The accurate prediction of the State of Charge (SoC) of a battery is a theoretical basis and technical support for realizing long-term safe operation of the battery, and the SoC is a State variable inside the battery and cannot be directly measured. In the current research on liquid metal batteries, the ampere-hour integration method for estimating the SoC of a single battery is mainly calculated by an electrochemical test program according to SoC definition, and the method is influenced by accumulated errors and battery state changes, and inevitably deviates from a true value in a long-term test of one cycle. The method for estimating the SoC by establishing the model according to the equivalent circuit needs to establish a precise and effective battery equivalent model and identify unknown parameters in the model. In 2017, Wang Dai Lei and the like propose a method for estimating the state of charge of a liquid metal battery by adopting an extended Kalman filtering algorithm based on a second-order Thevenin model, wherein the estimation error is less than 4% in the actual working condition test (DOI: 10.13334/j.0258-8013. pcsee.160520). In 2019, Liu et al propose a liquid metal battery state of charge estimation method using an adaptive unscented Kalman filtering method, and the root mean square error when the method is used for estimating the battery SoC is only 0.2145(DOI:10.1016/j. aponergy.2019.05.032). The methods for estimating the SoC of the liquid metal battery based on the equivalent circuit have advantages and disadvantages, and are not widely applied.
In the patent application document with application publication number CN 106772063 a, a method and a device for monitoring SoC and soh (state of health) of a battery by using sound waves are disclosed, the invention utilizes ultrasonic waves to penetrate the battery, collects acoustic parameters after the sound waves penetrate the battery, and establishes a relationship between the acoustic parameters and the battery state so as to realize real-time analysis of the battery state. However, since the ultrasonic wave is attenuated to a greater extent in the gas, the signal collected after the ultrasonic wave is transmitted is weak for the liquid metal battery containing the gas, and therefore, the ultrasonic wave transmission method is not suitable for the liquid metal battery containing the gas; in addition, since the ultrasonic wave sequentially penetrates through each interface in the cell during the transmission process, the method of transmitting the acoustic wave cannot analyze the change of a specific interface in the cell including multiple interfaces. The device disclosed in the invention or the device disclosed in the chinese invention patent CN 107238804 a cannot be applied to a liquid metal battery with an asymmetric top-bottom configuration and a sealed structure assembled at the top end, and cannot monitor the state of the liquid metal battery.
Generally, no in-situ detection method suitable for the alloying process of the liquid metal battery and the SoC of the liquid metal battery exists at present.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides an in-situ detection method and system for a liquid metal battery, and aims to realize accurate detection of the alloying/dealloying process of a positive electrode in the liquid metal battery under the condition that the liquid metal battery is not disassembled.
To achieve the above object, according to one aspect of the present invention, there is provided an in-situ detection method of a liquid metal battery, including the steps of:
(S1) transmitting an ultrasonic signal to the liquid metal battery through the ultrasonic module in a normal operation process of the liquid metal battery; the ultrasonic module is coupled with the bottom of the liquid metal battery and used for transmitting ultrasonic waves and receiving reflected echo signals;
(S2) receiving the echo signal reflected by the liquid metal battery through the ultrasonic module, and extracting the echo signal reflected by the interface between the positive electrode and the electrolyte therefrom as a target echo signal;
(S3) calculating the amplitude variation of the target echo signal, and determining the alloying degree of the positive electrode according to the corresponding relation between the amplitude variation calibrated in advance and the alloying degree of the positive electrode.
According to the liquid metal battery, the ultrasonic module is coupled with the bottom of the liquid metal battery, and the ultrasonic wave is transmitted from the bottom of the liquid metal battery to the interior of the liquid metal battery; different from the traditional ultrasonic transmission detection, the invention receives and analyzes the echo signal reflected by the interior of the battery at the bottom of the battery and discriminates the echo signal reflected by the positive electrode/electrolyte interface; experiments show that the echo signal reflected at the interface of the anode/electrolyte can accurately reflect the interface change, and the amplitude variation of the echo signal has a specific corresponding relation with the anode alloying degree. The invention does not need to disassemble the battery in the detection process, and is a nondestructive in-situ detection method. In general, the method can realize accurate detection of the alloying/dealloying process of the anode in the liquid metal battery under the condition of not disassembling the liquid metal battery, and has important significance for researching the change process of the anode in the charge and discharge process of the liquid metal battery and analyzing the mechanism of the electrochemical reaction of the liquid metal battery.
Further, the amplitude variation calculation method includes:
converting the target echo signal into a voltage signal;
respectively calculating the peak value max [ y ] of the voltage signal of the liquid metal battery in the discharge state ch (t 1 ≤t f ≤t 2 ，t 3 ≤t d ≤t 4 )]And valley value min [ y ch (t 1 ≤t≤t 2 ，t 3 ≤t d ≤t 4 )]And a liquid metalPeak value max [ y ] of voltage signal of battery in non-discharge state ch (t 1 ≤t f ≤t 2 ，t d ＝0)]And valley value min [ y ch (t 1 ≤t f ≤t 2 ，t d ＝0)]；
According to
Figure BDA0003649433050000041
And calculating the amplitude variation.
According to the invention, the amplitude variation calculated by the method can accurately reflect the difference between echo signals reflected by the ultrasonic waves at the specific interface inside the battery in the discharging state and the non-discharging state, so that the change of the anode/electrolyte interface in the battery is accurately reflected, and the accuracy of the subsequent analysis result for the anode alloying degree is further improved.
Further, the step (S3) further includes:
determining the current discharge capacity C of the liquid metal battery according to the corresponding relation between the amplitude variation and the discharge capacity which are calibrated in advance 1 ；
According to
Figure BDA0003649433050000051
Estimating the state of charge (SoC) of the liquid metal battery;
wherein, C 0 Indicating the nominal discharge capacity of the liquid metal battery.
Experiments show that the amplitude variation of the echo signal reflected at the positive electrode/electrolyte interface has a specific corresponding relation with the discharge capacity of the battery, the discharge capacity of the battery is determined based on the echo signal and the corresponding relation calibrated in advance, the charge state of the battery is estimated based on the discharge capacity, and the accurate estimation of the charge state of the liquid metal battery can be realized while the alloying degree of the positive electrode is accurately detected.
Further, before the step (S2), the method further includes: adjusting signal parameters of the ultrasonic signals to enable the difference between the flight time of echo signals reflected by the interface between the anode and the electrolyte and the flight time of echo signals and clutter signals reflected by other interfaces to be larger than a preset threshold value;
the signal parameters include at least one of:
gain, transmit voltage, pulse width, repetition frequency.
Before the target echo signal is detected, the difference between the flight time of the echo signal reflected by the interface between the anode and the electrolyte and the flight time of the echo signal and the clutter signal reflected by other interfaces is larger (larger than a preset threshold value) by adjusting the parameters of the ultrasonic signal, so that the target echo signal can be obviously distinguished from other echo signals and clutter signals, and the target echo signal can be conveniently and accurately extracted subsequently.
According to another aspect of the present invention, there is provided an in-situ detection system for a liquid metal battery, comprising: the device comprises a battery tester, an ultrasonic module and a control module;
the battery tester is respectively connected with the anode and the cathode of the liquid metal battery to be tested and is used for applying current to the liquid metal battery so as to ensure that the liquid metal battery normally operates;
the ultrasonic module is coupled with the bottom of the liquid metal battery and used for transmitting ultrasonic waves and receiving reflected echo signals;
the control module is connected with the ultrasonic module and used for extracting an echo signal reflected by the interface between the anode and the electrolyte from the echo signal reflected by the liquid metal battery to serve as a target echo signal;
and the control module is also used for calculating the amplitude variation of the target echo signal and determining the alloying degree of the anode according to the corresponding relation between the amplitude variation calibrated in advance and the alloying degree of the anode.
Further, the amplitude variation calculation method includes:
converting the target echo signal into a voltage signal;
respectively calculating the peak value max [ y ] of the voltage signal of the liquid metal battery in the discharge state ch (t 1 ≤t f ≤t 2 ，t 3 ≤t d ≤t 4 )]And valley value min [ y ch (t 1 ≤t≤t 2 ，t 3 ≤t d ≤t 4 )]And the peak value max [ y ] of the voltage signal of the liquid metal battery in the undischarged state ch (t 1 ≤t f ≤t 2 ，t d ＝0)]And valley value min [ y ch (t 1 ≤t f ≤t 2 ，t d ＝0)]；
According to
Figure BDA0003649433050000061
And calculating the amplitude variation.
Further, the control module is further configured to determine a current discharge capacity C of the liquid metal battery according to a corresponding relationship between the amplitude variation and the discharge capacity calibrated in advance 1 (ii) a And according to
Figure BDA0003649433050000062
Estimating the state of charge (SoC) of the liquid metal battery;
wherein, C 0 Indicating the nominal discharge capacity of the liquid metal battery.
Further, the ultrasonic module comprises an ultrasonic probe and a wedge matched with the ultrasonic probe.
In the invention, the ultrasonic module comprises the ultrasonic probe and a wedge block matched with the ultrasonic probe, and the use of the wedge block can eliminate a detection blind area on the surface of the probe caused by irregular shape of a sound field, thereby further improving the detection accuracy.
Further, the ultrasonic module also comprises a cooling structure fixed at the bottom of the liquid metal battery.
In the detection system provided by the invention, the ultrasonic module also comprises a cooling structure fixed at the bottom of the liquid metal battery, so that the detection precision can be prevented from being influenced because the contact temperature of the battery and the ultrasonic probe exceeds the working temperature range of the ultrasonic probe.
Furthermore, the ultrasonic probe is a single crystal probe, a phased array linear array probe or a phased array probe.
Generally speaking, by the technical scheme of the invention, a contact type ultrasonic reflection detection method is adopted, and the interface reaction change of the anode/electrolyte interface in the liquid metal battery is detected in real time by analyzing the echo signal generated by a specific interface under the conditions of not disassembling the battery and not influencing the operation of the battery, so that the in-situ detection of the alloying/dealloying degree of the anode of the liquid metal battery is realized, and the in-situ detection of the state of charge (SoC) of the liquid metal battery is further realized.
The invention does not need to design a special detection device, effectively overcomes the problem that the complex structure of the liquid metal battery influences the detection of the battery, can detect the interface reaction change of the anode/electrolyte interface in the battery in real time under the condition of not influencing the operation of the battery, and has important significance for researching the anode change process in the charge-discharge cycle of the liquid metal battery and analyzing the mechanism of the electrochemical reaction of the liquid metal battery. Meanwhile, compared with other nondestructive in-situ detection methods, the contact type ultrasonic reflection detection method is simple and convenient, does not need to additionally design a complex detection structure, can detect liquid metal batteries with different capacities, and provides a new idea for the field of battery detection.
Drawings
Fig. 1 is a flowchart of an in-situ detection method for a liquid metal battery according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an in-situ detection method for a Li | | | Ga room-temperature liquid metal battery provided in an embodiment of the present invention;
FIG. 3 is a schematic diagram of a theoretical propagation path of ultrasonic waves inside a liquid metal battery according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a relationship between the amplitude of the echo signal of the Li | | | Ga room-temperature liquid metal battery anode/electrolyte interface and the discharge capacity provided in the embodiment of the present invention;
fig. 5 is a two-dimensional ultrasonic imaging of the Li | | | Ga room-temperature liquid metal battery provided in the embodiment of the present invention;
fig. 6 is a three-dimensional ultrasonic imaging of continuous variation during discharging of the Li | | | Ga room-temperature liquid metal battery positive electrode/electrolyte interface provided in an embodiment of the present invention;
fig. 7 is a schematic diagram of Li | | | Bi high-temperature liquid metal battery detection provided in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In order to solve the technical problem that the conventional liquid metal battery detection method cannot effectively realize in-situ detection of the anode alloying/dealloying process in the battery circulation process, the invention provides an in-situ detection method and a system of a liquid metal battery, and the overall thought of the method is as follows: by utilizing the strong penetrating power and the rapid propagation characteristic of ultrasonic waves, a contact type ultrasonic detection method is adopted, ultrasonic waves are emitted from the bottom of the battery to the interior of the battery, echo signals reflected by a battery anode/electrolyte interface in the detection process are obtained in real time, the continuous observation of the anode/electrolyte interface is realized, and the reflected echo signals of the anode under different alloying degrees are calibrated by determining detection parameters, so that the detection of the alloying degree of the battery anode is realized by utilizing the detected echo signals; on the basis, the reflected echo signals of the battery under each different SoC are calibrated by determining the detection parameters, so that the current SoC of the battery is estimated by using the amplitude of the echo signals.
The following are examples.
Example 1:
in this embodiment, the detected liquid metal battery is a Li | | Ga room-temperature liquid metal battery;
referring to fig. 1 and 2, the present embodiment includes the following steps:
(S1) transmitting an ultrasonic signal to the liquid metal battery through the ultrasonic module in a normal operation process of the liquid metal battery; the ultrasonic module is coupled with the bottom of the liquid metal battery and used for transmitting ultrasonic waves and receiving reflected echo signals;
referring to fig. 2, in the present embodiment, the battery is normally operated by applying a test current to the battery through a battery tester connected to both the positive electrode and the negative electrode of the battery; optionally, in this embodiment, the discharge current is set to 7mA, so that the Li | | | Ga liquid metal battery starts to discharge; through the battery tester, the battery voltage can be acquired in real time in the detection process;
referring to fig. 2, in the embodiment, the ultrasonic module includes an ultrasonic probe and a wedge matched with the ultrasonic probe, the lower bottom surface of the wedge of the probe/wedge is connected with the bottom of the Li | | Ga liquid metal battery, and the probe and the battery are fully coupled by adopting silicon oil or other ultrasonic coupling agents; optionally, in this embodiment, the ultrasonic probe in the ultrasonic module is specifically a 5MHz ultrasonic longitudinal wave single crystal probe;
the wedge block in the ultrasonic module is used for eliminating a detection blind area with irregular noise on the near surface of the probe, so that the detection accuracy is ensured; the ultrasonic module is integrally coupled with the bottom of the battery, so that air can be isolated between the ultrasonic probe and the battery, the ultrasonic probe and the battery are tightly combined, and the ultrasonic waves emitted by the probe can enter the battery;
when the ultrasonic wave is incident from the bottom of the liquid metal battery, theoretically, the ultrasonic wave passes through three interfaces (taking a full-charge state as an example) of a positive current collector/positive electrode interface, a positive electrode/electrolyte interface and an electrolyte/negative electrode interface from bottom to top in sequence, and due to the fact that acoustic impedances of media on two sides of the interfaces are different, transmission and reflection behaviors occur at each interface, as shown in fig. 3; the three interfaces, interface 1, interface 2 and interface 3 in fig. 3;
(S2) receiving the echo signal reflected by the liquid metal battery through an ultrasonic module, and extracting the echo signal reflected by the interface between the anode and the electrolyte from the echo signal as a target echo signal;
in order to realize continuous observation of the anode/electrolyte interface of the battery and detect the alloying degree of the anode, the embodiment only analyzes the echo signal reflected by the anode/electrolyte interface; in practical application, after receiving echo signals reflected by a battery, echo signals reflected by different interfaces can be distinguished according to the flight time of ultrasonic signals;
in order to facilitate accurate extraction of the echo signal reflected by the positive electrode/electrolyte interface, as a preferred embodiment, in this embodiment, before the step (S2), one or more signal parameters such as gain, transmission voltage, pulse width, repetition frequency, etc. of the ultrasonic signal are further adjusted, so that the difference between the flight time of the echo signal reflected by the interface between the positive electrode and the electrolyte and the flight times of the echo signal reflected by other interfaces and the clutter signal is greater than a preset threshold, thereby making the echo signal reflected by the positive electrode/electrolyte interface clearly distinguished from other echo signals or clutter signals;
(S3) the amplitude variation of the target echo signal is calculated, and the alloying degree of the positive electrode is determined according to the corresponding relation between the amplitude variation calibrated in advance and the alloying degree of the positive electrode.
In the embodiment, the positive electrode of the (semi) liquid metal battery is gallium metal Ga which can be maintained in a liquid state at room temperature, the working temperature of the battery is within the working temperature range of the ultrasonic probe, and the ultrasonic probe can be directly contacted with the bottom of the battery; optionally, the embodiment adopts a simple ultrasonic longitudinal wave single crystal probe to analyze the receiving voltage of the echo signal. In the discharge process of the battery, the amplitude of an echo signal belonging to a positive electrode/electrolyte interface changes, and experiments show that the amplitude variation of the echo signal can accurately reflect the interface change, and the amplitude variation of the echo signal has a specific corresponding relation with the alloying degree of the positive electrode; it is easy to understand that, because the dealloying process of the positive electrode is the reverse process of the alloying process, the detection of the alloying degree of the positive electrode reflects the dealloying degree of the positive electrode to a certain extent.
Based on the above theoretical analysis, in this embodiment, the positive electrode/electrolyte interface echo signal is detected in advance through the above steps (S1) and (S2) for the Li | | | Ga liquid metal battery with known positive electrode alloying degree, and the amplitude variation is calculated, so as to determine the amplitude variation corresponding to different alloying degrees of different positive electrodes, and complete the calibration; based on the calibration result, the corresponding anode alloying degree can be determined according to the amplitude variation of the echo signal amplitude of the anode/electrolyte interface of the battery to be detected.
Considering that the degree of alloying of the positive electrode is related to the discharge state of the battery, as a preferred embodiment, the present embodiment calculates the amount of change in the amplitude of the target echo signal as follows:
converting the target echo signal into a voltage signal;
respectively calculating the peak value max [ y ] of the voltage signal of the liquid metal battery in the discharge state ch (t 1 ≤t f ≤t 2 ，t 3 ≤t d ≤t 4 )]And valley value min [ y ch (t 1 ≤t≤t 2 ，t 3 ≤t d ≤t 4 )]And the peak value max [ y ] of the voltage signal of the liquid metal battery in the undischarged state ch (t 1 ≤t f ≤t 2 ，t d ＝0)]And valley value min [ y ch (t 1 ≤t f ≤t 2 ，t d ＝0)]；
According to
Figure BDA0003649433050000111
And calculating the amplitude variation.
In the above formula, y ch Receiving voltage (V) for echo signals, wherein the voltage (V) is in positive correlation with the echo amplitude; t is t f As time of flight, t 1 ≤t f ≤t 2 Representing the selection of the echo signal area belonging to the anode/electrolyte interface; t is t 3 0 denotes discharge start time, t 4 Is the discharge cut-off time; t is t d Indicating a certain moment in the discharge process, t d 0 represents the discharge start time; book blockAccording to the embodiment, the amplitude variation calculated in the manner can accurately reflect the difference between echo signals reflected by ultrasonic waves of the battery in a discharging state and an undischarged state, so that the change of a positive electrode/electrolyte interface in the battery is accurately reflected, and the accuracy of a subsequent analysis result for the alloying degree of the positive electrode is further improved.
Further research shows that the amplitude variation δ calculated in the above manner has a specific corresponding relationship with the battery discharge capacity, for example, in the embodiment, in the Li | | Ga liquid metal battery, the amplitude variation of the echo signal reflected by the anode/electrolyte interface has a relatively obvious linear relationship with the battery discharge capacity, as shown in fig. 4, so that the current battery discharge capacity can be inferred by calculating the δ value at a certain moment in the discharge process, thereby estimating the SoC of the battery; as a preferable embodiment, the step (S3) of the present embodiment further includes:
determining the current discharge capacity C of the liquid metal battery according to the corresponding relation between the amplitude variation and the discharge capacity which are calibrated in advance 1 ；
According to
Figure BDA0003649433050000112
Estimating the state of charge (SoC) of the liquid metal battery;
wherein, C 0 Indicating the nominal discharge capacity of the liquid metal battery.
The calibration mode of the corresponding relation between the amplitude variation of the target echo signal and the discharge capacity is similar to the calibration mode of the corresponding relation between the amplitude variation and the anode alloying degree, namely for the Li | | Ga liquid metal battery with the known charge state, the amplitude variation of the target echo signal is detected by the mode, so that the amplitude variation corresponding to different discharge capacities is determined, and the calibration is completed.
It should be noted that, in practical applications, when the liquid metal battery is another type of battery, the correspondence between the amplitude variation and the positive electrode alloying degree and the correspondence between the amplitude variation and the discharge capacity need to be recalibrated.
Generally speaking, in the embodiment, the ultrasonic module coupled with the bottom of the liquid metal battery transmits the ultrasonic waves from the bottom of the liquid metal battery to the inside of the liquid metal battery, and the ultrasonic waves have strong penetrating power and are tightly combined with the battery in an air-isolating manner in a coupling contact manner, so that the transmitted ultrasonic waves can enter the battery; different from the traditional ultrasonic transmission detection, the echo signal reflected by the interior of the battery is received at the bottom of the battery for analysis, and the echo signal reflected by the positive electrode/electrolyte interface is screened out; the alloying degree is determined and the charge state of the battery is estimated based on the echo signal and the corresponding relation calibrated in advance, and the accurate detection of the alloying degree and the charge state of the positive electrode can be realized.
Different ultrasonic probes can emit ultrasonic waves with different specific frequencies, the higher the ultrasonic frequency is, the higher the detection resolution is, but the penetrating power is weakened, and the ultrasonic detection method needs to be selected and adjusted according to the actual detection effect of the battery. Considering that the working temperature of the liquid metal battery of most systems is high and exceeds the Curie temperature of a piezoelectric crystal in the ultrasonic probe, when the probe cannot be directly contacted with the bottom of the battery, a simple cooling structure can be added between the probe/wedge block integral structure and the battery, so that the temperature of the contact part of the battery and the ultrasonic probe is reduced to be within the working temperature range of the ultrasonic probe; at this time, in order to avoid the introduction of a temperature reduction structure and influence on the intensity of the ultrasonic wave entering the battery, a low-frequency ultrasonic probe can be selected to enhance the penetrating power of the ultrasonic wave.
Example 2:
in this embodiment, the detected liquid metal battery is a Li | | Ga room-temperature liquid metal battery;
the present embodiment is similar to embodiment 1, except that in this embodiment, the ultrasonic probe in the ultrasonic module is specifically a 5MHz phased array linear array probe, and the present embodiment performs two-dimensional imaging on the longitudinal section direction of the battery while completing in-situ detection of the alloying degree of the positive electrode in the battery and the state of charge of the battery, so as to position the positive electrode/electrolyte interface of the battery, as shown in fig. 5.
Example 3:
in this embodiment, the detected liquid metal battery is a Li | | Ga room-temperature liquid metal battery;
this embodiment is similar to embodiment 1, except that in this embodiment, the ultrasonic probe in the ultrasonic module is specifically a 5MHz phased array ultrasonic probe, and in this embodiment, while completing in-situ detection of the alloying degree of the positive electrode in the battery and the state of charge of the battery, the inside of the battery is three-dimensionally acoustically imaged, the positive electrode/electrolyte interface is intercepted, the change of the interface in the discharging process is directly observed, and the alloying process is analyzed, as shown in fig. 6.
Example 4:
in this embodiment, the detected liquid metal battery is a Li | | Ga room-temperature liquid metal battery;
referring to fig. 2, the present embodiment includes: the device comprises a battery tester, an ultrasonic module and a control module;
the battery tester is respectively connected with the anode and the cathode of the liquid metal battery to be tested and is used for applying current to the liquid metal battery so as to ensure that the liquid metal battery normally operates;
the ultrasonic module is coupled with the bottom of the liquid metal battery and used for transmitting ultrasonic waves and receiving reflected echo signals;
the control module is connected with the ultrasonic module and used for extracting an echo signal reflected by the interface between the anode and the electrolyte from the echo signal reflected by the liquid metal battery to be used as a target echo signal;
the control module is also used for calculating the amplitude variation of the target echo signal and determining the alloying degree of the anode according to the corresponding relation between the amplitude variation calibrated in advance and the alloying degree of the anode; in this embodiment, the control module is implemented by the computer in fig. 2;
referring to fig. 2, in the present embodiment, the ultrasonic module includes an ultrasonic probe and a wedge matched with the ultrasonic probe, and an ultrasonic signal transmitter/receiver shown in fig. 2; the wedge block is used for eliminating a detection blind area with irregular noise on the near surface of the probe and ensuring the detection accuracy; in actual measurement, the whole probe/wedge block is coupled with the bottom of the liquid metal battery through an ultrasonic coupling agent such as silicone oil, and through coupling, air is isolated between the ultrasonic probe and the battery and the ultrasonic probe and the battery are tightly combined, so that ultrasonic waves emitted by the probe can enter the battery.
Similarly to the above method embodiments, in this embodiment, the amplitude variation calculation manner includes:
converting the target echo signal into a voltage signal;
respectively calculating the peak value max [ y ] of the voltage signal of the liquid metal battery in the discharge state ch (t 1 ≤t f ≤t 2 ，t 3 ≤t d ≤t 4 )]And valley value min [ y ch (t 1 ≤t≤t 2 ，t 3 ≤t d ≤t 4 )]And the peak value max y of the voltage signal of the liquid metal battery in the undischarged state ch (t 1 ≤t f ≤t 2 ，t d ＝0)]And valley value min [ y ch (t 1 ≤t f ≤t 2 ，t d ＝0)]；
According to
Figure BDA0003649433050000141
Calculating the amplitude variation;
in this embodiment, the control module is further configured to determine the current discharge capacity C of the liquid metal battery according to a corresponding relationship between the amplitude variation and the discharge capacity calibrated in advance 1 (ii) a And according to
Figure BDA0003649433050000142
Estimating the state of charge (SoC) of the liquid metal battery;
wherein, C 0 Indicating the nominal discharge capacity of the liquid metal battery.
In this embodiment, the specific implementation of the signal analysis performed by the control module can refer to the description in embodiment 1, and will not be repeated here.
Example 5:
in this embodiment, the detected liquid metal battery is a Li | | | Bi liquid metal battery;
the present embodiment is similar to embodiment 4, except that, considering that the operating temperature of the Li | | | Bi liquid metal battery is higher than the curie temperature of the piezoelectric crystal inside the ultrasonic probe, referring to fig. 7, in order to ensure the normal operation of the ultrasonic probe, in the present embodiment, the ultrasonic module includes an ultrasonic probe and a matched wedge, and a cooling structure is further disposed between the whole probe/wedge and the bottom of the battery; in this embodiment, the cooling structure can be cooled by air cooling or water cooling;
in order to avoid the introduction of the cooling structure and influence on the intensity of the ultrasonic wave entering the battery, in this embodiment, the frequency of the ultrasonic wave emitted by the ultrasonic probe is 2MHz, and the ultrasonic probe may be a single crystal probe, a phased array linear array probe, or a phased array probe.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. An in-situ detection method of a liquid metal battery is characterized by comprising the following steps:
(S1) transmitting an ultrasonic signal to the liquid metal battery through an ultrasonic module in a process of normal operation of the liquid metal battery; the ultrasonic module is coupled with the bottom of the liquid metal battery and used for transmitting ultrasonic waves and receiving reflected echo signals;
(S2) receiving the echo signal reflected by the liquid metal battery through the ultrasonic module, and extracting therefrom an echo signal reflected by an interface between the positive electrode and the electrolyte as a target echo signal;
(S3) calculating the amplitude variation of the target echo signal, and determining the alloying degree of the positive electrode according to the corresponding relation between the amplitude variation calibrated in advance and the alloying degree of the positive electrode.
2. The in-situ detection method of a liquid metal battery of claim 1, wherein the amplitude variation calculation comprises:
converting the target echo signal into a voltage signal;
respectively calculating the peak value max [ y ] of the voltage signal of the liquid metal battery in the discharge state ch (t 1 ≤t f ≤t 2 ，t 3 ≤t d ≤t 4 )]And valley value min [ y ch (t 1 ≤t≤t 2 ，t 3 ≤t d ≤t 4 )]And a peak value max [ y ] of the voltage signal of the liquid metal battery in an undischarged state ch (t 1 ≤t f ≤t 2 ，t d ＝0)]And valley value min [ y ch (t 1 ≤t f ≤t 2 ，t d ＝0)]；
According to the following
Figure FDA0003649433040000011
And calculating the amplitude variation.
3. The in-situ detection method of a liquid metal battery as claimed in claim 2, wherein said step (S3) further comprises:
determining the current discharge capacity C of the liquid metal battery according to the corresponding relation between the amplitude variation and the discharge capacity which are calibrated in advance 1 ；
According to
Figure FDA0003649433040000012
Estimating the state of charge (SoC) of the liquid metal battery;
wherein, C 0 Represents the rated discharge capacity of the liquid metal battery.
4. The in-situ detection method for liquid metal battery as claimed in any one of claims 1-3, further comprising, before the step (S2): adjusting signal parameters of the ultrasonic signals to enable the difference between the flight time of echo signals reflected by the interface between the anode and the electrolyte and the flight time of echo signals and clutter signals reflected by other interfaces to be larger than a preset threshold value;
the signal parameter comprises at least one of:
gain, transmit voltage, pulse width, repetition frequency.
5. An in-situ detection system for a liquid metal battery, comprising: the device comprises a battery tester, an ultrasonic module and a control module;
the battery tester is respectively connected with the anode and the cathode of the liquid metal battery to be tested and is used for applying current to the liquid metal battery so as to ensure that the liquid metal battery normally operates;
the ultrasonic module is coupled with the bottom of the liquid metal battery and used for transmitting ultrasonic waves and receiving reflected echo signals;
the control module is connected with the ultrasonic module and used for extracting an echo signal reflected by an interface between the anode and the electrolyte from the echo signal reflected by the liquid metal battery to serve as a target echo signal;
the control module is further configured to calculate an amplitude variation of the target echo signal, and determine the alloying degree of the positive electrode according to a corresponding relationship between a pre-calibrated amplitude variation and the alloying degree of the positive electrode.
6. The in-situ detection system for a liquid metal battery of claim 5, wherein the amplitude variation calculation comprises:
converting the target echo signal into a voltage signal;
respectively calculating the peak value max [ y ] of the voltage signal of the liquid metal battery in the discharge state ch (t 1 ≤t f ≤t 2 ，t 3 ≤t d ≤t 4 )]And valley value min [ y ch (t 1 ≤t≤t 2 ，t 3 ≤t d ≤t 4 )]And a peak value max [ y ] of the voltage signal of the liquid metal battery in an undischarged state ch (t 1 ≤t f ≤t 2 ，t d ＝0)]And valley value min [ y ch (t 1 ≤t f ≤t 2 ，t d ＝0)]；
According to
Figure FDA0003649433040000031
And calculating the amplitude variation.
7. The in-situ detection system for a liquid metal battery of claim 6, wherein the control module is further configured to determine a current discharge capacity C of the liquid metal battery according to a pre-calibrated correspondence between an amplitude variation and a discharge capacity 1 (ii) a And according to
Figure FDA0003649433040000032
Estimating the state of charge (SoC) of the liquid metal battery;
wherein, C 0 Represents the rated discharge capacity of the liquid metal battery.
8. The in-situ detection system for the liquid metal battery as recited in any one of claims 5 to 7, wherein the ultrasonic module comprises an ultrasonic probe and a wedge matched with the ultrasonic probe, and an ultrasonic signal emitter and an ultrasonic signal receiver.
9. The in situ detection system of a liquid metal battery of claim 8, wherein the ultrasound module further comprises a cooling structure secured to a bottom of the liquid metal battery.
10. The in situ liquid metal cell inspection system of claim 8, wherein the ultrasonic probe is a single crystal probe, a phased array linear probe, or a phased array probe.
CN202210546669.5A 2022-05-18 2022-05-18 In-situ detection method and system for liquid metal battery Pending CN115015384A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115683411A (en) * 2023-01-03 2023-02-03 深圳平创半导体有限公司 Method for monitoring contact pressure of semiconductor device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115683411A (en) * 2023-01-03 2023-02-03 深圳平创半导体有限公司 Method for monitoring contact pressure of semiconductor device

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