Development of a Novel Acoustic Based State-of-Charge Sensor (SOC) for Lithium-Ion Batteries
Lead Research Organisation:
University of Warwick
Department Name: WMG
Abstract
Our proposal aims to assess the feasibility of embedding novel, miniature acoustic sensors directly within the structure of a lithium ion battery (LIB) to provide a direct measure of retained energy or state of charge (SOC). The term SOC defines the level of stored energy in the battery relative to its rated capacity and is often expressed as a percentage (0-100%).
Context
The UK's vision for transport by 2050 must be net-zero at the point of use. This requirement mandates the electrification of multiple sectors and the use of battery technology to replace traditional fossil fuels. A complete battery system will often consist of many hundreds of lithium-ion batteries (LIBs) combined electrically. Manufacturing variations, combined with the impact of interconnection resistance and temperature differences between individual batteries makes the measurement of SOC a highly challenging task and one where there is no current solution. SOC uncertainty underpins considerable complexity and cost when scaling-up battery components into complete systems, e.g., for electric vehicles (EVs). The problem is more acute for future all-electric aircraft. Regulatory bodies mandate that because of this uncertainty, redundancy must be included, in the form of additional battery capacity, to ensure safe aircraft operation. UCL has pioneered the use of ultrasound imaging to LIBs, as it provides very fast (sub-second) data collection via a relatively low-cost platform. Deploying the technique within a LIB is challenging and calls for a fundamentally different approach. This project will develop a new miniature acoustic sensor that can be embedded within the LIB as a single sensor or array to provide a non-electrochemical means of SOC measurement.
Objective
To develop and validate a proof-of-concept demonstration for how a low-profile piezoelectric transducer can be used as a non-electrochemical SOC sensor. Methods of integrating the sensor within the internal structure of the LIB that do not adversely affect sensor and battery operation will be defined.
Applications
The significant scientific contribution of this research to both sensor and battery development, includes but is not constrained too:
- Sensor: Low-profile ultrasonic sensors capable of withstanding insertion within the harsh environment of a lithium-ion battery will highlight new opportunities in the development of acoustic transducers.
- Battery Monitoring: The inclusion of an acoustic sensor within the internal structure of a battery will underpin new methods of diagnostics and prognostics and will further support the creation of a battery circular economy.
- Battery Manufacturing: The ability to manufacture a battery with embedded instrumentation has the potential to create a new classification of 'smart battery' for high-value and safety-critical applications.
- Battery Safety: The ability to measure the microstructure and SOC of the battery as internal temperature and gas pressure evolves will highlight new innovations in battery design and the selection of materials that comprise the electrolyte, electrical separator and electrodes.
Context
The UK's vision for transport by 2050 must be net-zero at the point of use. This requirement mandates the electrification of multiple sectors and the use of battery technology to replace traditional fossil fuels. A complete battery system will often consist of many hundreds of lithium-ion batteries (LIBs) combined electrically. Manufacturing variations, combined with the impact of interconnection resistance and temperature differences between individual batteries makes the measurement of SOC a highly challenging task and one where there is no current solution. SOC uncertainty underpins considerable complexity and cost when scaling-up battery components into complete systems, e.g., for electric vehicles (EVs). The problem is more acute for future all-electric aircraft. Regulatory bodies mandate that because of this uncertainty, redundancy must be included, in the form of additional battery capacity, to ensure safe aircraft operation. UCL has pioneered the use of ultrasound imaging to LIBs, as it provides very fast (sub-second) data collection via a relatively low-cost platform. Deploying the technique within a LIB is challenging and calls for a fundamentally different approach. This project will develop a new miniature acoustic sensor that can be embedded within the LIB as a single sensor or array to provide a non-electrochemical means of SOC measurement.
Objective
To develop and validate a proof-of-concept demonstration for how a low-profile piezoelectric transducer can be used as a non-electrochemical SOC sensor. Methods of integrating the sensor within the internal structure of the LIB that do not adversely affect sensor and battery operation will be defined.
Applications
The significant scientific contribution of this research to both sensor and battery development, includes but is not constrained too:
- Sensor: Low-profile ultrasonic sensors capable of withstanding insertion within the harsh environment of a lithium-ion battery will highlight new opportunities in the development of acoustic transducers.
- Battery Monitoring: The inclusion of an acoustic sensor within the internal structure of a battery will underpin new methods of diagnostics and prognostics and will further support the creation of a battery circular economy.
- Battery Manufacturing: The ability to manufacture a battery with embedded instrumentation has the potential to create a new classification of 'smart battery' for high-value and safety-critical applications.
- Battery Safety: The ability to measure the microstructure and SOC of the battery as internal temperature and gas pressure evolves will highlight new innovations in battery design and the selection of materials that comprise the electrolyte, electrical separator and electrodes.
Technical Summary
Current lithium-ion batteries (LIBs) are purely passive devices. Valuable understanding of performance, degradation and battery safety can be achieved by integrating mechatronic feature e.g., the capability of sensing, communication or control hardware directly within the battery; forming a new derivative of battery called a "smart-cell".
Within the next decade, the demand for smart LIBs will accelerate, driven by the uptake in personalised sustainable urban transport. The UK's Advanced Propulsion Centre (APC) states that future transport solutions will require batteries, augmented by smart sensors and Artificial Intelligence (AI) to meet operational, environmental and life targets.
Problem: Current battery management systems use mathematical models and algorithms to estimate battery state-of-charge (SOC) or energy capacity. In a battery system (e.g. used within an electric vehicle) that contains hundreds of individual batteries, SOC estimation becomes increasingly challenging. In terms of understanding battery operation, traditional parameters such as temperature, voltage and current, are inadequate to identify the onset of physical ageing phenomena (e.g., material defects or the onset of li-plating through high power charging). SOC uncertainty underpins considerable complexity and cost when scaling-up battery components into complete systems.
Solution: Acoustic sensing has been pioneered to support LIB diagnostics at laboratory-scale. Deployment in-situ will only be possible through miniaturisation of the piezoelectric transducers, and its internal instrumentation within a LIB. No experimental data exists on the feasibility of this concept to base new sensor designs. Through the novel integration of low-profile transducers developed as part of this project this highly valuable technique can be advanced a step closer to real world applications.
Within the next decade, the demand for smart LIBs will accelerate, driven by the uptake in personalised sustainable urban transport. The UK's Advanced Propulsion Centre (APC) states that future transport solutions will require batteries, augmented by smart sensors and Artificial Intelligence (AI) to meet operational, environmental and life targets.
Problem: Current battery management systems use mathematical models and algorithms to estimate battery state-of-charge (SOC) or energy capacity. In a battery system (e.g. used within an electric vehicle) that contains hundreds of individual batteries, SOC estimation becomes increasingly challenging. In terms of understanding battery operation, traditional parameters such as temperature, voltage and current, are inadequate to identify the onset of physical ageing phenomena (e.g., material defects or the onset of li-plating through high power charging). SOC uncertainty underpins considerable complexity and cost when scaling-up battery components into complete systems.
Solution: Acoustic sensing has been pioneered to support LIB diagnostics at laboratory-scale. Deployment in-situ will only be possible through miniaturisation of the piezoelectric transducers, and its internal instrumentation within a LIB. No experimental data exists on the feasibility of this concept to base new sensor designs. Through the novel integration of low-profile transducers developed as part of this project this highly valuable technique can be advanced a step closer to real world applications.
