Sodium-Ion Cell Formation Electrolyte for Stable SEI Cycling
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Solution Overview
Problem
The formation of the solid electrolyte interphase (SEI) in sodium ion batteries is unstable, leading to irreversible capacity loss and poor cycling stability, hindering the performance of sodium ion batteries.
Innovation Solution
A method for forming a battery cell with a carbon anode, sodium cathode, and an electrolyte solution containing an alkali-metal bis(oxalato)borate salt, using specific charging and discharging protocols at controlled temperatures and C-rates, along with an organic solvent like pyrrolidone and phosphoric acid esters, to optimize SEI formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte systems are used in sodium ion batteries, then the batteries can operate, but the SEI formation is unstable leading to irreversible capacity loss and poor cycling stability
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte system by using alkali-metal bis(oxalato)borate salts with pyrrolidone and phosphoric acid ester compounds, which fundamentally alters the SEI formation mechanism to achieve stable SEI and eliminate irreversible capacity loss
Solution Approach 2:
The patent employs a composite electrolyte system combining alkali-metal bis(oxalato)borate salt with specific organic solvents (pyrrolidone and phosphoric acid ester compounds), creating a synergistic effect that produces a stable SEI layer and improves cycling stability
2Reliability
If the SEI layer is formed to protect the anode, then cycling stability improves, but irreversible capacity loss occurs during SEI formation
Solution Approach 1:
The patent performs a preliminary formation cycle at elevated temperature (40-80°C) to pre-form a stable SEI layer before normal operation, which prevents subsequent electrolyte decomposition and eliminates continuous capacity loss during cycling
Solution Approach 2:
The patent changes the temperature parameter during formation cycle (elevated to 40-80°C) and uses specific electrolyte composition to control SEI formation kinetics, achieving a stable SEI that prevents ongoing capacity degradation
3Reliability
If lithium ion-based batteries are used, then market dominance and performance are achieved, but resource scarcity and environmental friendliness deteriorate
Solution Approach 1:
The patent replaces scarce lithium resources with abundant sodium resources, using a cost-effective electrolyte system based on alkali-metal bis(oxalato)borate salts that is both economically viable and environmentally friendly
Solution Approach 2:
The patent changes the fundamental chemical parameter from lithium-based to sodium-based battery chemistry, using alkali-metal bis(oxalato)borate electrolytes that enable high-performance sodium ion batteries with reduced environmental impact
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 method results in a stable SEI that enhances discharge capacity and coulombic efficiency, providing a low-cost, fluorine-free electrolyte system with improved cycling performance.
Implementation Method 1
sodium ions are transferred from a cathode to an anode through an electrolyte during charging and then from the anode to the cathode during discharging
Implementation Method 2
The SEI layer should ideally act as a passivation layer, preventing more electrolyte decomposition
Data Source
AI summary
Described is a method of forming a battery cell, the method includes;in a battery cell, the battery cell comprising a carbon containing anode, a sodium containing cathode and an electrolyte solution comprising an alkali-metal bis(oxalato)borate salt, wherein the alkali metal ion is selected from sodium (Na+) and potassium (K+) and an organic solvent comprising a pyrrolidone and/or a phosphoric acid ester compound,performing a first formation cycle by fully charging and discharging the battery cell, and;wherein the formation cycle is carried out at a temperature within the range of from >25° C. and 100° C.