Sodium-Ion Cell Discharge Thresholds for Safe Low-Charge Storage
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Solution Overview
Problem
Existing sodium-ion batteries face challenges in achieving a safe state of charge for storage and transportation, as discharging to low voltages can lead to internal short circuits, thermal runaway, and capacity fade.
Innovation Solution
A process involving discharging sodium-ion cells to a minimum cell operating voltage of less than -0.1V at a discharge rate of C/<10, followed by maintaining the cell at a voltage of 1V or less, to achieve a state of charge from 20% or less, enhancing safety and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sodium-ion cells are discharged to low voltages (0V or close to 0V) to achieve safe storage and transportation, then cell safety is improved, but internal short circuits and thermal runaway risks increase
Solution Approach 1:
The patent changes the voltage parameter from conventional 0V cutoff to a negative voltage threshold (less than -0.1V). This parameter change enables the cell to be discharged to a state that is safe for storage and transportation while preventing the harmful effects of over-discharge such as copper dissolution and internal short circuits.
Solution Approach 2:
The patent applies preliminary anti-action by pre-establishing a negative voltage threshold (less than -0.1V) that prevents copper dissolution and internal short circuit formation before they can occur. This preemptive measure stops the harmful chain reaction before it starts, ensuring cell safety during storage and transportation.
2Reliability
If discharge rate is reduced to C/100 to achieve proper state of charge, then cell safety is improved, but preparation time increases to 100 hours
Solution Approach 1:
The patent changes the voltage parameter to a negative threshold (less than -0.1V), which allows for faster discharge rates (C/10 to C/1) while still achieving the safe state of charge. This parameter change eliminates the need for extremely slow discharge rates and the associated 100-hour preparation time.
Solution Approach 2:
The patent uses voltage threshold feedback (less than -0.1V) to control the discharge process. This feedback mechanism allows the discharge to proceed at faster rates while automatically stopping when the safe threshold is reached, thereby reducing preparation time without compromising cell safety.
3Productivity
If discharge rate is increased to reduce preparation time, then productivity is improved, but electrochemical performance deteriorates due to capacity fade
Solution Approach 1:
The patent changes the voltage parameter to a negative threshold (less than -0.1V), which enables the use of higher discharge rates (C/10 to C/1) without causing capacity fade or deteriorating electrochemical performance. This parameter change allows fast preparation while maintaining cell quality.
Solution Approach 2:
The patent replaces the conventional mechanical approach of using extremely slow discharge rates (C/100) with an electrochemical approach using negative voltage thresholds. This substitution allows for faster discharge rates while still achieving the desired safe state of charge without compromising electrochemical performance.
4Reliability
If cells are discharged to 0V to achieve safe state, then storage safety is improved, but copper dissolution occurs leading to capacity loss
Solution Approach 1:
The patent changes the voltage parameter from 0V to a negative threshold (less than -0.1V). This parameter change ensures that the cell is discharged to a safe state for storage while preventing copper dissolution, as the negative voltage threshold stops the electrochemical reactions that cause copper to dissolve into the electrolyte.
Solution Approach 2:
The patent applies preliminary anti-action by pre-establishing a negative voltage threshold (less than -0.1V) that prevents copper dissolution before it can occur. This preemptive measure stops the harmful chain reaction of copper dissolution and subsequent capacity loss while still achieving safe storage conditions.
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 process allows for the safe storage and transportation of sodium-ion cells by reducing the state of charge to a safer level, preventing risks associated with lithium-ion batteries, and maintaining the electrochemical performance and life expectancy of the cells.
Implementation Method 1
When a sodium-ion (or lithium-ion) battery is charging, Na+ (or Li+) ions de-intercalate from the cathode and insert into the anode. Meanwhile charge balancing electrons pass from the cathode through the external circuit containing the charger and into the anode of the battery.
Implementation Method 2
They are both reusable secondary batteries that comprise an anode (negative electrode), a cathode (positive electrode) and an electrolyte material, both are capable of storing energy, and they both charge and discharge via a similar reaction mechanism.
Data Source
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AI summary
The invention relates to a process for providing a sodium-ion cell and/or a sodium-ion battery which is in a state of charge from about 20% or less. Sodium-ion cells and/or sodium-ion batteries are also disclosed.