Capacitive SoC Sensing for Swelling-Prone Lithium-Ion Pouch Cells
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Solution Overview
Problem
Lithium-ion batteries experience volume changes during charging cycles, leading to swelling and potential rupture, necessitating effective monitoring systems for automotive and other applications.
Innovation Solution
A system and method using capacitive electrodes to measure the state-of-charge of lithium-ion batteries by correlating capacitance with battery volume changes, combined with voltage-derived measurements for redundant determination, and incorporating isolator plates and a spring element to prevent pouch rupture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium-ion batteries are monitored during charging cycles, then battery safety and state-of-charge determination are improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical monitoring systems with a capacitive sensing system. By measuring capacitance changes between electrodes that respond to battery swelling, the system achieves reliable safety monitoring through electrical measurements rather than mechanical sensors, thereby improving reliability while minimizing added complexity
Solution Approach 2:
The capacitive monitoring system serves multiple functions simultaneously: it determines state-of-charge, detects battery swelling, and provides safety monitoring. This multi-functionality allows a single sensing mechanism to address multiple safety and performance concerns without proportionally increasing system complexity
2Measurement precision
If capacitive electrodes are applied to measure state-of-charge, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses capacitive electrodes as intermediary sensing elements that indirectly measure state-of-charge through capacitance changes caused by battery swelling. This intermediary approach provides precise measurement without requiring direct internal battery sensors, achieving high measurement precision while keeping the electrode system relatively simple
Solution Approach 2:
The monitoring system combines voltage-derived state-of-charge measurements with capacitively-derived measurements into a unified sensing approach. This merging of measurement methods enhances precision through redundancy and cross-validation while utilizing shared infrastructure, thereby limiting the increase in overall device complexity
3Strength
If isolator plates and spring element are used to prevent pouch rupture, then battery integrity is improved, but device complexity increases
Solution Approach 1:
The patent incorporates isolator plates and a spring element that provide mechanical cushioning and restraint before battery swelling can cause pouch rupture. This preventive structural design absorbs expansion forces and maintains pouch integrity throughout the charging cycle, improving strength while using a relatively simple mechanical restraint system
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
Accurately determines state-of-charge and prevents battery pouch rupture by measuring capacitive coupling, enabling low battery warnings and end-of-life alerts, while maintaining battery integrity.
Implementation Method 1
measuring the capacitance of the capacitive coupling and correlating the capacitance with a state-of-charge of the lithium-ion battery
Implementation Method 2
a spring element disposed between the first isolator plate and the second isolator plate, the spring element being an extension spring that resists outward movement of the first and second isolator plates
Data Source
AI summary
A system and a method for measuring a state-of-charge of a lithium-ion battery are provided. The system and the method include first and second capacitive electrodes that are applied to the exterior of a pouch-type battery cell or a battery stack, the capacitive electrodes defining a capacitive coupling. The system and method further include measuring the capacitance of the capacitive coupling and correlating the capacitance with a state-of-charge of the lithium-ion battery. The capacitively-derived state-of-charge measurement can be used in combination with a voltage-derived state-of-charge measurement, thereby providing a redundant state-of-charge determination. Other applications include low battery warnings and end-of-life warnings.