Li-Ion Battery Pressure Sensor for Accurate State of Charge
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Solution Overview
Problem
Lithium-ion batteries with flat or shallowly sloping open-circuit potential (OCP) pose challenges for accurate state of charge (SOC) determination, as existing methods like coulomb counting and OCP measurement are inherently inaccurate, necessitating an alternative technique for improved SOC estimation.
Innovation Solution
A lithium sulfur battery system equipped with a pressure sensor connected to the positive electrode, a processor, and memory to correlate pressure signals with state of charge, allowing for more accurate SOC determination and overpressure condition monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If chemistries with phase-change materials are used to achieve high specific energy, then specific energy is improved, but OCP becomes flat or shallowly sloping making SOC estimation difficult
Solution Approach 1:
The patent introduces an intermediary substance (gas or liquid electrolyte) that transmits pressure changes from the phase-change material to a pressure sensor. This mediator enables indirect measurement of SOC through pressure signals, bypassing the limitation of flat OCP while maintaining the high specific energy benefits of phase-change materials.
Solution Approach 2:
The patent replaces the electrical measurement system (OCP measurement) with a mechanical measurement system (pressure sensing). By substituting the measurement mechanism from electrical to mechanical domain, the system can accurately determine SOC in batteries with flat OCP characteristics, resolving the contradiction between high specific energy and SOC estimation accuracy.
2Productivity
If coulomb counting technique is used for SOC estimation, then it works well at high current or short times, but accuracy deteriorates over time due to measurement errors and side reactions
Solution Approach 1:
The patent implements a feedback mechanism where pressure sensor readings continuously provide real-time SOC information that can correct drift in coulomb counting estimates. The system uses the pressure-SOC correlation to periodically recalibrate the SOC estimate, maintaining accuracy over extended periods while preserving the rapid response capability at high currents.
3Measurement precision
If pressure sensor is added to the battery system for SOC determination, then SOC estimation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent designs the pressure sensing system to serve multiple functions: SOC estimation, overpressure detection, and potential temperature monitoring. By making the pressure sensor multi-functional, the added complexity is justified by the multiple benefits gained, reducing the relative impact of the complexity increase while achieving improved SOC estimation accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides enhanced accuracy in state of charge estimation and overpressure detection by utilizing pressure signals from the lithium sulfur battery, overcoming the limitations of flat OCP in lithium-ion batteries.
Implementation Method 1
a pressure sensor in fluid connection with the second electrode
Data Source
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AI summary
An electrochemical battery system in one embodiment includes a first electrode, a second electrode spaced apart from the first electrode, a separator positioned between the first electrode and the second electrode, an active material within the second electrode, a pressure sensor in fluid connection with the second electrode, a memory in which command instructions are stored, and a processor configured to execute the command instructions to obtain a pressure signal from the pressure sensor associated with the pressure within the second electrode, and to identify a state of charge of the electrochemical battery system based upon the pressure signal.