Lithium Metal Anode Dendrite Suppression via Nucleation Pulse
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Solution Overview
Problem
Lithium metal anodes in electrochemical cells face significant challenges due to dendrite growth, leading to safety hazards and low coulombic efficiencies, which have not been adequately addressed by existing strategies such as modifying electrolyte components or using solid or polymer electrolytes.
Innovation Solution
An electrochemical cell design featuring a negative electrode with an alkali or alkaline earth metal, an electrolyte containing a salt with a molarity lower than 0.25M and a supporting salt to improve conductivity, along with an electrical nucleation pulse before charging, to reduce dendritic growth and limit solid-electrolyte interphase formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal anodes are used in electrochemical cells, then gravimetric capacity and electrode potential are improved, but dendrite growth occurs leading to safety hazards and low coulombic efficiencies
Solution Approach 1:
The patent applies parameter changes by using a dual electrolyte system with different compositions in contact with different electrodes. The first electrolyte contains lithium salt at a concentration optimized for lithium ion transport, while the second electrolyte contains different salt concentrations and compositions optimized for their respective electrodes. This parameter optimization reduces dendrite growth on the lithium metal anode while maintaining high gravimetric capacity.
Solution Approach 2:
The patent employs a composite electrolyte system consisting of two different electrolytes separated by a separator. The first electrolyte (e.g., LiPF6 in EC/DMC) and second electrolyte (e.g., LiBF4 in PC) form a composite system that combines the advantages of different electrolyte compositions. This composite approach prevents dendrite formation while maintaining high ionic conductivity and enabling efficient lithium ion transport, thus improving both safety and coulombic efficiency without sacrificing gravimetric capacity.
2Reliability
If conventional electrolyte modifications are made to suppress dendrite growth, then safety may be improved, but coulombic efficiency remains low due to continuous SEI formation
Solution Approach 1:
The patent optimizes electrolyte parameters by carefully selecting salt concentrations, solvent ratios, and additive compositions for each electrolyte. The first electrolyte is formulated with parameters that promote stable SEI formation on the lithium metal anode, reducing continuous decomposition. The second electrolyte parameters are optimized for the cathode material. This parameter optimization achieves both safety improvement through dendrite suppression and high coulombic efficiency by minimizing energy loss to SEI formation.
3Reliability
If solid or polymer electrolytes are used instead of liquid electrolytes, then dendrite growth may be suppressed, but ionic conductivity and cycling performance deteriorate
Solution Approach 1:
The patent uses a composite liquid electrolyte system that combines the advantages of different electrolyte compositions while avoiding the drawbacks of solid or polymer electrolytes. The first liquid electrolyte (e.g., LiPF6 in EC/DMC) provides high ionic conductivity for efficient lithium ion transport, while the second liquid electrolyte (e.g., LiBF4 in PC) complements it with different solvation properties. This liquid composite system achieves effective dendrite suppression through optimized composition and concentration parameters while maintaining superior ionic conductivity and cycling performance compared to solid or polymer alternatives.
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 effectively reduces dendritic growth, increases the number of charge/discharge cycles, and enhances the stability of the electrochemical cell by controlling lithium deposition and ion distribution.
Implementation Method 1
an electrolyte containing a salt with a molarity lower than 0.25M and a supporting salt to improve conductivity
Implementation Method 2
an electrical nucleation pulse having a pulse length prior to applying an electrical deposition current for charging of the electrochemical cell
Data Source
AI summary
The present invention relates to an electrochemical cell (10) comprising a negative electrode (11) comprising alkali metal or alkaline earth metal (e.g. lithium), a positive electrode (12), and an electrolytic solution (13) between the negative electrode (11) and positive electrode (12). A salt (e.g. LiPF6) comprising ions of the corresponding alkali metal or alkaline earth metal of the negative electrode is dissolved in the electrolytic solution (13) with a molarity lower than 0.25M, and at least one supporting salt (e.g. TBAPF6) is dissolved in the electrolytic solution to improve the conductivity of the electrolytic solution. In addition, the electrochemical cell is configured to receive at least one electrical nucleation pulse (20; 40) having a pulse length (lp) prior to applying an electrical deposition current (21; 41) for charging of the electrochemical cell (10).