Battery Charge Control via Ion Diffusion Rate Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Secondary batteries, particularly lithium ion batteries, face rapid degradation and reduced charge/discharge efficiency due to reversible Li loss, leading to decreased cycle characteristics and energy density, with existing control methods failing to adequately address these issues.
Innovation Solution
A charge and discharge control device and method that determine the ion diffusion rate and time-integrated overcharged amount of the negative electrode, using this information to optimize charge conditions and control current and voltage applications, thereby minimizing degradation and maintaining energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness and density of the electrode are increased to achieve high capacity, then the battery capacity is improved, but rapid degradation occurs due to reversible Li loss
Solution Approach 1:
The control device performs preliminary estimation of the time-integrated overcharged amount before degradation occurs, using ion diffusion rate and charge condition data. This allows preventive control actions to be taken before reversible Li loss and degradation become significant, thereby maintaining both high capacity and good cycle characteristics.
Solution Approach 2:
The system continuously monitors charge conditions and ion diffusion rates, calculates the time-integrated overcharged amount, and uses this feedback to adjust charging parameters. This closed-loop control prevents overcharging that leads to reversible Li loss while maximizing battery capacity utilization.
2Reliability
If charge/discharge control is performed to suppress reversible Li loss, then cycle characteristics are improved, but volumetric energy density is lowered
Solution Approach 1:
Instead of using fixed voltage thresholds for charge control, the system dynamically adjusts charging parameters based on the calculated time-integrated overcharged amount. This allows the battery to operate at higher energy densities while preventing degradation through adaptive control, rather than conservative fixed limits.
Solution Approach 2:
The control strategy transitions from static voltage threshold control to dynamic control based on real-time estimation of overcharged amount. This dynamic approach allows maximum energy utilization while preventing degradation, as control actions are adjusted continuously based on actual battery state rather than fixed limits.
3Reliability
If internal resistance is used to control charge/discharge, then degradation promotion regions are avoided, but available energy density is lowered due to detection of non-degradation resistance increases
Solution Approach 1:
The system extracts and isolates the specific degradation-related component of resistance change by estimating the time-integrated overcharged amount separately from other resistance effects. This allows control actions to target only degradation prevention without being triggered by non-degradation resistance increases, thereby maintaining available energy density.
Solution Approach 2:
Instead of directly controlling based on total internal resistance measurements that conflate degradation and non-degradation effects, the system creates a separate estimation model for overcharged amount that specifically captures degradation mechanisms. This separate 'copy' of the degradation state allows precise control without sacrificing energy density.
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 solution effectively suppresses reversible Li loss and improves cycle characteristics without lowering volumetric energy density, extending the battery's lifespan and performance.
Implementation Method 1
a determination unit that determines an ion diffusion rate responsible for electric conduction in a secondary battery
Implementation Method 2
a phenomenon in which the amount of Li that moves between a positive electrode and a negative electrode and exchanges electrons decreases
Data Source
AI summary
A charge and discharge control device is provide. The charge and discharge control device includes a determination circuitry configured to determine an ion diffusion rate associated with electric conduction in a secondary battery, and determine a time integrated value of an overcharged amount of an active material based on the ion diffusion rate and a charge condition; an evaluation circuitry configured to evaluate the charge condition of the secondary battery based on a determination result obtained by the determination circuitry; and a charge and discharge controller configured to control state of current application and voltage application to the secondary battery at a time of charging or discharging the secondary battery based on an evaluation result obtained by the evaluation circuitry.