Hybrid Vehicle Li-Ion Cell Charge Method Preventing Metal Deposition
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Solution Overview
Problem
In hybrid electric vehicles, rapid and continuous charging of lithium ion secondary cells can lead to metal Li deposition on the negative electrode, causing capacity deterioration and discomfort due to unstable idling, while existing charging methods either fail to prevent this or compromise comfort.
Innovation Solution
A method that splits the charging period into multiple split charging periods and non-charging periods, with at least one instance of suspension or discharging during the non-charging periods, ensuring each split charging period is at least 40 seconds long, to diffuse Li ions and prevent metal Li deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid and continuous charging is performed on the lithium ion secondary cell while the hybrid electric vehicle stops running, then the storage amount of the cell can be quickly restored, but metal Li deposits on the negative electrode surface causing capacity deterioration
Solution Approach 1:
The charging period is divided into multiple split charging periods and non-charging periods. Each split charging period lasts at least 40 seconds, followed by a non-charging period where suspension or discharging occurs. This segmentation prevents continuous rapid charging, allowing Li ions to diffuse properly and preventing metal Li deposition while still achieving relatively quick overall charging.
2Reliability
If existing charging methods are used to prevent metal Li deposition, then cell capacity is preserved, but vehicle idling becomes unstable and riding comfort is compromised
Solution Approach 1:
The charging control device dynamically adjusts charging parameters based on the hybrid electric vehicle's running state. When the vehicle is stopped, charging is performed with split charging periods of at least 40 seconds followed by non-charging periods. When the vehicle is running, continuous charging can be performed. This dynamic adaptation maintains vehicle stability while preventing metal Li deposition.
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 effectively suppresses capacity reduction and stabilizes vehicle idling, maintaining comfort by ensuring Li ions are diffused, thus preventing metal Li deposition and maintaining electrical capacity.
Implementation Method 1
Li ions that are not incorporated into the negative electrode are deposited as metal Li on the surface of the negative electrode due to the diffusion control of Li ions on the negative electrode surface
Data Source
AI summary
Provided is a lithium ion secondary cell charge method including: a step S1 which judges whether a physical amount value corresponding to an accumulation amount of a lithium ion secondary cell is lowered to a first predetermined value; a step S2 which judges whether a hybrid vehicle is in a travel stop state; and charge steps S5 to SA which divide a charge period K into two or more divided charge periods KC1, KC2 and a non-charge period KR between the divided charge periods, so that charge is performed during the divided charge periods KC1, KC2 while the hybrid vehicle is in the travel stop state and charge stop or discharge is performed during the non-charge period KR, wherein each of the divided charge periods KC1, KC2 is not shorter than 40 seconds.