Cyclic Coulometry for Concurrent Battery Efficiency and Resistance Measurement
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Solution Overview
Problem
Current battery evaluation methods, such as high-precision coulometry, are limited in accurately measuring cycle life and durability of lithium-ion batteries due to their inability to concurrently measure coulombic efficiency and internal resistance growth, and require lengthy testing cycles, making it difficult to optimize battery design for various applications.
Innovation Solution
The implementation of cyclic coulometry systems that generate symmetric charge and discharge currents, adjust charge or discharge times to maintain cell voltage at a setpoint, and measure electrical parameters to generate performance metrics, including coulombic efficiency and equivalent series resistance, allowing for concurrent measurement and optimization of battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional high-precision coulometry is used to measure battery performance, then coulombic efficiency can be measured with high accuracy, but internal resistance growth cannot be measured concurrently and testing requires lengthy cycles
Solution Approach 1:
The patent combines multiple measurement functions (coulombic efficiency measurement and internal resistance measurement) into a single cyclic coulometry system. The system simultaneously performs charge-discharge cycling while measuring both coulombic efficiency and equivalent series resistance, eliminating the need for separate lengthy testing protocols and enabling concurrent acquisition of multiple battery performance parameters.
Solution Approach 2:
The cyclic coulometry system is designed to perform multiple functions: it measures coulombic efficiency, tracks internal resistance growth, and characterizes battery performance under various cycling conditions. This multi-functional approach allows a single system to replace multiple specialized testing devices and protocols, significantly improving testing productivity while maintaining measurement precision.
2Ease of operation
If fixed current cycling is applied to test battery cycle life, then the testing process is simple to implement, but it cannot provide comprehensive insights into battery performance under varying operating conditions
Solution Approach 1:
The system transitions from static fixed-current cycling to dynamic cyclic coulometry where current direction alternates between charge and discharge phases. The system dynamically adjusts measurement parameters during cycling, enabling comprehensive performance characterization under varying operating conditions while maintaining operational simplicity through automated control.
Solution Approach 2:
The cyclic coulometry system varies multiple parameters including current direction, measurement timing, and cycling conditions to comprehensively characterize battery performance. By systematically changing these parameters during testing, the system provides insights into battery behavior under diverse operating conditions without significantly complicating the testing process.
3Reliability
If lengthy testing cycles are used to accurately assess battery cycle life, then reliable cycle life data can be obtained, but the iteration process for optimizing battery chemistry becomes extremely time-consuming
Solution Approach 1:
The cyclic coulometry system enables continuous measurement of battery performance parameters throughout the cycling process. By continuously monitoring coulombic efficiency and internal resistance rather than performing discrete lengthy tests, the system accelerates data acquisition while maintaining the reliability needed for accurate cycle life assessment and rapid chemistry optimization.
Solution Approach 2:
The system creates a controlled, repeatable testing environment that isolates battery performance variables. This standardized cyclic coulometry approach provides consistent, reliable data across different battery formulations, enabling rapid comparison and optimization of battery chemistries without the time penalty of varied lengthy testing protocols.
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
This approach provides a more comprehensive understanding of battery cycle life by concurrently measuring coulombic efficiency and internal resistance growth, enabling faster iteration in battery chemistry and design optimization, and offering insights into battery performance under different conditions.
Implementation Method 1
coulometry is an electrochemical technique that measures the total coulombs of electricity consumed or produced during electrochemical reactions
Implementation Method 2
the total charge, Q, passed through the electrochemical cells is calculated by integrating the current as a function of time
Data Source
AI summary
Systems, devices, and methods of diagnosing an electrochemical cell using cyclic coulometry are discussed. An exemplary battery diagnostic system comprises a current generator to generate symmetric charge current and discharge current to excite an electrochemical cell, and a cyclic coulometer to evaluate performance of the electrochemical cell. The cyclic coulometer can adjust at least one of a charge time for applying the charge current, or a discharge time for applying the discharge current, to keep a monitored cell voltage toward a specific setpoint. The adjustment of charge or discharge time can be achieved by changing a current switch timing for reversing current from a first to a second current direction. The cyclic coulometer measures one or more electrical parameters during the charge or discharge cycle, and generates a performance metric using the measured electrical parameters.