Silicon Negative Electrode Battery Pack Discharge Cut-Off Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rechargeable lithium batteries with silicon-containing active materials face rapid capacity deterioration and reduced cycle life due to volume changes during charge/discharge cycles, leading to crack formation and degradation.
Innovation Solution
A battery pack design incorporating a silicon-containing negative active material with a predetermined discharge cut-off voltage, controlled by a circuit board's charge/discharge controller, to prevent crack generation by managing lithium concentration and particle size, ensuring improved cycle life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing active material is used to increase capacity, then energy density is improved, but cycle life deteriorates due to crack formation from volume change
Solution Approach 1:
The patent applies parameter changes by controlling the discharge cut-off voltage to a specific range (2.8V to 3.0V) and managing the x value of LixSi (lithium silicide) to maintain it between 1.25 and 1.75. This parameter control prevents excessive lithium insertion that causes large volume expansion, thereby avoiding crack formation in silicon particles while preserving high capacity. The controlled parameters enable silicon to deliver high energy density without the typical cycle life degradation.
2Reliability
If graphite active material is used to ensure long cycle life, then reliability is improved, but capacity is reduced due to low energy density per unit weight
Solution Approach 1:
The patent employs composite materials by combining silicon-containing active material with carbon materials (such as graphite, amorphous carbon, or conductive carbon black) to form a composite negative electrode. The carbon component provides structural stability and crack prevention, while the silicon component delivers high capacity. This composite structure allows the battery to achieve both long cycle life (from carbon's stability) and high capacity (from silicon's high lithium insertion capability), resolving the trade-off between reliability and capacity.
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 controlled discharge cut-off voltage enhances the cycle life and capacity retention of silicon-containing negative active materials by preventing crack formation, thereby extending the battery's operational lifespan.
Implementation Method 1
a negative electrode including a silicon-containing negative active material selected from silicon, a silicon-carbon composite, and a combination thereof
Implementation Method 2
Rechargeable lithium batteries generate electrical energy due to chemical potential changes during intercalation/deintercalation of lithium ions at the positive and negative electrodes
Data Source
AI summary
A battery assembly including: at least one rechargeable lithium battery including a negative electrode including a silicon-containing negative active material selected from silicon, a silicon-carbon composite, and a combination thereof, and a positive electrode including a positive active material; a circuit board electrically connected to the battery assembly; and an outer terminal electrically connecting the battery assembly to an outer power or an outer load, wherein the circuit board includes a charge/discharge element for charging and discharging the battery assembly and a charge/discharge controller electrically connected to the battery assembly and the charge/discharge element, wherein the charge/discharge controller controls the charge and discharge of the battery assembly, and wherein a discharge cut-off voltage of the charge/discharge controller is predetermined as a voltage when LixSi present in the negative electrode during the discharge has an x value of less than or equal to about 1.25.