Lithium-Ion Battery Charging Pulse Impedance Reduction
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Solution Overview
Problem
Current quick charging methods for lithium-ion secondary batteries face challenges in both the initial and final stages of charging, as increasing the charge current leads to reduced capacity and shortened battery life due to internal stress and overvoltage, and attempting to increase current in the final stage is difficult due to high voltage limitations.
Innovation Solution
A charging device and method that applies a first current pulse with a peak value higher than the initial charge current before switching to constant voltage charging, using a calculator to determine the optimal time based on the lithium-ion secondary battery's internal impedance and temperature, allowing for increased charge current in the constant voltage stage without exceeding voltage limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large current is applied in the initial stage of charging to achieve quick charging, then charging speed is improved, but battery life and charge/discharge capacity are reduced due to internal stress and overvoltage
Solution Approach 1:
The charging process is divided into multiple stages: initial charging at controlled current, a pause period allowing impedance reduction, and final charging at increased current. This segmentation allows the battery to undergo structural changes during the pause, enabling higher current tolerance in the final stage without compromising battery health.
Solution Approach 2:
A pause period is introduced before the final charging stage to allow the battery's internal impedance to reduce naturally. This preliminary action prepares the battery structure (particularly the carbon material stage structure) to withstand higher currents in the subsequent final charging stage, preventing the harmful effects that would occur if high current were applied immediately.
2Productivity
If the charge current is increased in the final stage of charging to achieve quick charging, then charging speed is improved, but the high voltage makes it difficult to exceed the upper limit voltage
Solution Approach 1:
The battery's internal impedance is changed through the pause period, allowing the operating parameters (current and voltage) to be adjusted in the final charging stage. The reduced impedance enables higher current flow at controlled voltage levels, achieving quick charging in the final stage without exceeding voltage limits.
3Productivity
If a pause period is introduced before final charging to reduce internal impedance, then charging efficiency is improved, but charging time is increased due to the pause
Solution Approach 1:
The pause period, which initially appears to be a time loss, is converted into a beneficial phase where the battery's internal structure naturally adjusts and impedance reduces. This natural process prepares the battery for more efficient charging, and the time invested during the pause is recovered through accelerated charging in the final stage.
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 reduces the internal impedance of the battery, enabling faster and more efficient charging by increasing the charge current in the constant voltage stage, thus shortening the overall charging time without compromising battery health.
Implementation Method 1
a positive electrode material includes LixCoO2
Implementation Method 2
the internal impedance of the lithium-ion secondary battery is reduced by applying a current pulse at least once
Data Source
AI summary
A charging device for charging a lithium-ion secondary battery based on at least a constant voltage method is provided. In the charging device, before starting charging with a constant voltage or while performing charging with a constant voltage, a first current pulse having a peak current value i1 larger than a charge current value i0 is applied at least once.