Sodium-Ion Cell Storage and Transportation via State of Charge Control
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Solution Overview
Problem
Sodium-ion batteries face challenges in safe storage and transportation due to potential overheating, fire, or explosion risks when fully discharged, and existing solutions do not adequately address the stability and discharge capacity retention of these cells over time.
Innovation Solution
A process for constructing sodium-ion cells involving a positive electrode, negative electrode, and electrolyte, with controlled charge/discharge operations to maintain a state of charge between 0% to 20%, preferably 0%, to ensure safe storage and transportation, using impure or household-grade materials for current collectors and employing carbon-coated metals to enhance stability and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-ion batteries are stored in a fully discharged state or cycled down to 0 Volts, then the cell voltage is minimized, but copper dissolution occurs from the negative electrode current collector leading to decreased discharge capacity and shortened cycle life
Solution Approach 1:
The patent changes the material parameter of the negative electrode current collector from copper to copper-coated aluminium. This material substitution allows the battery to be discharged to 0 Volts without copper dissolution, as the aluminium substrate does not suffer from the same electrochemical instability at low potentials. The copper coating maintains electrical conductivity while the aluminium provides structural stability during full discharge cycles.
Solution Approach 2:
The patent employs a composite structure of copper coating on aluminium substrate for the negative electrode current collector. This composite material combines the high electrical conductivity of copper with the electrochemical stability of aluminium at low potentials. The copper layer provides necessary conductivity for electron transport while the aluminium substrate prevents dissolution issues that occur with pure copper at 0 Volt states.
2Ease of manufacture
If conventional lithium-ion batteries are transported and stored, then commercial use is enabled, but safety hazards occur including smoke production, extreme heat, fire, or explosion particularly when charged
Solution Approach 1:
The patent changes the electrochemical system from lithium-ion to sodium-ion chemistry. Sodium-ion batteries operate at different voltage ranges and electrochemical potentials that inherently reduce the risk of thermal runaway and safety hazards. The sodium-based electrolyte and electrode materials exhibit greater thermal stability and lower reactivity compared to their lithium counterparts, eliminating the severe safety concerns associated with charged lithium-ion battery transportation.
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 process enables sodium-ion cells to be safely stored and transported for extended periods without capacity loss, reduced risk of overheating or explosion, and allows for repeated cycling without detrimental effects on discharge capacity, using low-grade materials like household aluminum, which is cost-effective and commercially advantageous.
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
employing carbon-coated metals to enhance stability and adhesion
Data Source
AI summary
The invention relates to a process for making sodium-ion cells, particularly sodium-ion cells which are capable of safe storage and/or transportation, comprising the steps: a) constructing a sodium-ion cell comprising a positive electrode, a negative electrode and an electrolyte, optionally performing one more charge/discharge operations on the sodium-ion cell; and b) treating the sodium-ion cell to ensure that it is in a state of charge of from 0% to 20%.