Negative Electrode Voltage Control for Silicon Swelling Management
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Solution Overview
Problem
Lithium-ion batteries and other electrochemical apparatuses face challenges in achieving high volumetric energy density while maintaining a long service life due to significant volume swelling of silicon negative electrode materials during cycling, which affects their endurance and safety.
Innovation Solution
The electrochemical apparatus employs a combination of first and second active materials with different discharge and charge cut-off voltages in various time periods to optimize the participation of each material in the discharge process, reducing swelling and extending the service life, and includes a control method to adjust these voltages based on the state of health parameters such as internal resistance and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon negative electrode materials are used to increase volumetric energy density, then the volumetric energy density is improved, but significant volume swelling occurs during cycling which reduces service life
Solution Approach 1:
The negative electrode active material is divided into two segments: a first active material (graphite) and a second active material (silicon). This segmentation allows the silicon component to contribute to high volumetric energy density while the graphite component provides structural stability, thereby resolving the contradiction between energy density and service life.
Solution Approach 2:
The patent dynamically changes the discharge and charge cut-off voltage parameters based on the state of health of the electrochemical apparatus. By adjusting these voltage parameters, the capacity contribution of the silicon material is optimized at different stages, reducing volume swelling effects while maintaining high energy density performance.
2Quantity of substance
If the discharge cut-off voltage is set within the first voltage range, then more active material participates in discharge improving energy density, but the service life is reduced due to increased swelling
Solution Approach 1:
The patent implements dynamic adjustment of discharge and charge cut-off voltages based on the state of health of the electrochemical apparatus. The voltage parameters are not fixed but change over time, allowing the system to maximize capacity participation when healthy and reduce swelling stress as it ages, thereby resolving the contradiction between energy density and service life.
Solution Approach 2:
The patent divides the operational life into different time periods with different voltage settings. During early periods, higher capacity utilization is allowed, while in later periods, voltage parameters are adjusted to reduce stress on the materials, creating a periodic action pattern that balances energy density and service life.
3Productivity
If the electrochemical apparatus operates at higher capacity to improve energy density, then the volumetric energy density increases, but the swelling of active materials accelerates reducing durability
Solution Approach 1:
The patent changes the operational voltage parameters based on the state of health and cycling history of the apparatus. By dynamically adjusting the discharge and charge cut-off voltages, the system optimizes the balance between capacity utilization and material stress, allowing high energy density operation when durable and reducing stress as durability decreases.
Solution Approach 2:
The patent uses the state of health of the electrochemical apparatus as feedback to adjust the discharge and charge cut-off voltages. This feedback mechanism allows the system to adapt its operational parameters based on the actual condition of the materials, maximizing energy density while preventing excessive swelling that would reduce durability.
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 enhances the volumetric energy density and extends the service life of the electrochemical apparatus by managing the participation of active materials and adjusting operational parameters, ultimately improving user experience and safety by preventing damage from excessive swelling.
Implementation Method 1
the electrochemical apparatus operates at a first discharge cut-off voltage and a first charge cut-off voltage during a first time period; the electrochemical apparatus operates at a second discharge cut-off voltage and a second charge cut-off voltage during a second time period
Data Source
AI summary
A negative electrode active material of the electrochemical apparatus includes a first active material and a second active material; where a gram capacity of the first active material is less than that of the second active material; a discharge operating voltage range of the first active material includes a first voltage range that is not greater than an upper limit of a discharge operating voltage of the second active material; the electrochemical apparatus operates at a first discharge cut-off voltage and a first charge cut-off voltage during a first time period; the electrochemical apparatus operates at a second discharge cut-off voltage and a second charge cut-off voltage during a second time period; and the first discharge cut-off voltage and the second discharge cut-off voltage are both within the first voltage range.