Secondary Battery High-Rate Discharge Control for eVTOL
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Solution Overview
Problem
Electric aerial vehicles experience temporary deterioration in secondary batteries due to high discharge rates during takeoff, leading to increased internal resistance and ion concentration imbalances, which affects output performance.
Innovation Solution
A battery system with a secondary battery and a battery control unit that controls high-rate discharge, utilizing a positive electrode with a first active material (lithium nickel cobalt manganese oxide) and a second active material (lithium manganese iron phosphate) to manage ion distribution and reduce internal resistance through controlled heat generation during high-rate discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-rate discharge is performed during takeoff, then power output is improved, but temporary deterioration occurs due to ion concentration imbalance
Solution Approach 1:
The battery control unit performs preliminary heating of the secondary battery before high-rate discharge during takeoff. This preliminary action prevents temporary deterioration by ensuring ions are in a mobile state before the high discharge rate begins, allowing the battery to deliver high power without suffering from ion concentration imbalance
2Power
If high-rate discharge is performed during takeoff, then power output is improved, but internal resistance increases temporarily
Solution Approach 1:
The battery control unit heats the secondary battery in advance before the high-rate discharge phase. This preliminary heating action reduces internal resistance before high power demand occurs, enabling improved power output without the harmful temporary increase in internal resistance that would otherwise occur
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 ensures high output performance by suppressing temporary deterioration, maintaining low internal resistance, and extending battery life by optimizing ion distribution and utilization rates of the active materials.
Implementation Method 1
the temperature of the secondary battery is increased, so that the secondary battery can be discharged at a high rate in a state where the internal resistance of the secondary battery is reduced
Data Source
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AI summary
A battery system is mounted on an electric vehicle. The battery system includes a secondary battery (2) and a battery control unit. The battery control unit controls the secondary battery (2) to perform a high-rate discharge when the electric vehicle is started. A positive electrode (4) of the secondary battery (2) has a first active material (41) and a second active material (42). The second active material (42) has a high resistance region in which a resistance is higher than that of the first active material (41) in a high-rate discharge region which is the SOC region of the secondary battery (2) where high-rate discharge is performed at startup time. The secondary battery (2) is configured so that, when high-rate discharge is performed at startup time, after the utilization rate of the second active material (42) becomes higher than the utilization rate of the first active material (41), the utilization rate of the first active material (41) becomes higher than the utilization rate of the second active material (42).