Silicon-Anode Battery Charging Profile for Fast Charge Cycle Life
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Solution Overview
Problem
Charging non-aqueous electrolyte secondary batteries with silicon compounds as a negative electrode active material faces challenges of cracking due to high currents, leading to deteriorated cycle characteristics, while low currents result in prolonged charging times.
Innovation Solution
A charging method involving multiple stages with controlled current values, including a first charging step at a first constant current, a second charging step at a lower current, and a large current step, optimized by empirical expressions to balance efficiency and cycle characteristics, specifically for batteries with a carbon-silicon compound mix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If charging current is increased to reduce charging time, then productivity is improved, but the silicon compound cracks and cycle characteristics deteriorate
Solution Approach 1:
The charging process is divided into multiple stages with different current values. The charging method applies a first constant current value for initial charging, then switches to a second constant current value when the battery capacity reaches a specific threshold (when Q1/Q ≥ 0.05), and finally transitions to a large current charging step. This segmentation allows the battery to be charged efficiently without causing silicon compound cracking during critical phases.
Solution Approach 2:
The charging current is dynamically adjusted based on the battery's state of charge. The method monitors battery capacity in real-time and changes current values at specific thresholds. This dynamic adjustment ensures that high current is applied only when safe (when silicon compound stress is low), while protecting the silicon compound structure during vulnerable charging phases.
2Reliability
If charging current is reduced to prevent silicon compound cracking, then cycle characteristics are maintained, but charging time increases
Solution Approach 1:
The charging process is divided into multiple stages with different current values. The charging method applies a first constant current value for initial charging, then switches to a second constant current value when the battery capacity reaches a specific threshold (when Q1/Q ≥ 0.05), and finally transitions to a large current charging step. This segmentation allows the battery to be charged efficiently without causing silicon compound cracking during critical phases.
Solution Approach 2:
The charging method changes the current parameter based on battery capacity thresholds. By monitoring the ratio Q1/Q and switching current values at specific thresholds (0.05, 0.1, 0.2), the method optimizes the balance between charging speed and silicon compound protection, achieving both fast charging and maintained cycle characteristics.
3Productivity
If high current charging is applied from the beginning, then charging efficiency is improved, but initial irreversible capacity increases due to silicon compound damage
Solution Approach 1:
The method applies a preliminary charging phase with controlled current (first and second constant current values) before transitioning to large current charging. This preliminary action prepares the battery by initially charging it at lower currents when the silicon compound is more vulnerable, preventing damage and reducing initial irreversible capacity loss before high-current charging begins.
Solution Approach 2:
The charging current is dynamically adjusted based on the battery's state of charge. The method monitors battery capacity in real-time and changes current values at specific thresholds. This dynamic adjustment ensures that high current is applied only when safe (when silicon compound stress is low), while protecting the silicon compound structure during vulnerable charging phases.
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 method enables efficient charging in a short time while maintaining favorable cycle characteristics by minimizing silicon compound cracking and optimizing lithium ion occlusion.
Implementation Method 1
a silicon compound such as silicon oxide represented by SiO x can occlude more lithium ions per unit volume than a carbon material such as graphite
Data Source
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AI summary
A charging method of a non-aqueous electrolyte secondary battery involves a first charging step in which, defining x as the ratio of the capacity of a silicon compound to the rated capacity Q(0.1 ≤ x ≤ 0.5), a battery capacity Q1st that satisfies the expression below is charged at a first fixed current value; and a high current charging step in which, after completion of the first charging step, charging is performed at a fixed current value higher than the first fixed current value. Expression: 0.38x - 0.063 - α ≤ Q1st / Q ≤ 0.38x + 0.163 + α (α = 0.1)