Li-Ion Electrolyte Composition Balancing Resistance and Dendrites
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges with high direct current resistance and metal dendrite formation, which affect power and cycling performance, necessitating improvements in electrolyte composition to balance these factors.
Innovation Solution
Incorporating alkali metal ions with larger ionic radii and a film-forming additive into the electrolyte, with specific mass ratios and porosity controls, to facilitate lithium-ion transport and form a uniform inorganic solid electrolyte interface (SEI) film, reducing direct current resistance and suppressing dendrites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional electrolyte composition is used, then battery structure is simple, but direct current resistance is high and power performance is poor
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing alkali metal ions (Na+, K+, Cs+) with larger ionic radii than lithium ions, and controlling their mass percentage (0.01-5%) relative to film-forming additives. This parameter change facilitates lithium-ion transport channels and reduces direct current resistance, thereby improving power performance without excessive complexity
Solution Approach 2:
The patent creates a composite electrolyte system combining traditional lithium salts with alkali metal ion salts and film-forming additives. This composite approach leverages the synergistic effects of different ionic species to enhance lithium-ion conductivity and reduce resistance while maintaining manageable composition complexity
2Power
If electrolyte composition is optimized for power performance, then direct current resistance decreases, but metal dendrites may form
Solution Approach 1:
The patent introduces film-forming additives as intermediary substances that react with alkali metal ions to form protective SEI films on the electrode surfaces. These intermediary films serve as barriers that prevent direct contact between alkali metal ions and electrodes, thereby suppressing dendrite formation while still allowing optimized ion transport for reduced resistance
Solution Approach 2:
The patent creates localized protective layers (SEI films) at the electrode-electrolyte interfaces through the interaction of alkali metal ions and film-forming additives. This local modification of interface quality prevents dendrite formation at critical locations while maintaining bulk electrolyte properties optimized for low resistance
3Power
If alkali metal ions are added to improve lithium-ion transport, then power performance improves, but interfacial side reactions increase
Solution Approach 1:
The patent uses film-forming additives as intermediaries that preferentially react with alkali metal ions to form stable SEI films. This intermediary reaction prevents direct harmful interactions between alkali metal ions and electrode surfaces, thereby suppressing interfacial side reactions while preserving the beneficial lithium-ion transport enhancement
4Reliability
If film-forming additive amount is increased to suppress dendrites, then safety improves, but direct current resistance increases
Solution Approach 1:
The patent optimizes the mass percentage ratio of alkali metal ions to film-forming additives within specific ranges (0.01-5% for alkali metal ions, with controlled B/A ratios). This precise parameter control ensures sufficient film formation for safety while preventing excessive additive content that would increase resistance and degrade power performance
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 solution enhances power performance and cycling stability by improving lithium-ion transport, mitigating dendrites, and inhibiting interfacial reactions, thereby balancing the dynamics and safety of the battery.
Implementation Method 1
introducing alkali metal ions with a metal ionic radius greater than a radius of lithium ions into the electrolyte facilitates the formation of favorable channels for lithium-ion transport during charge/discharge of the lithium-ion secondary battery, thereby reducing the direct current resistance
Implementation Method 2
introducing the film-forming additive into the electrolyte facilitates the formation of a uniform and dense inorganic SEI film at an interface between the negative electrode plate and the electrolyte can effectively suppress metal dendrites
Implementation Method 3
The inorganic SEI film is also capable of further inhibiting interfacial side reactions between the electrolyte and the negative electrode plate, improving the cycling performance of the lithium-ion secondary battery
Data Source
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AI summary
A lithium-ion secondary battery (5) and an electric apparatus are provided. The lithium-ion secondary battery (5) includes an electrolyte. The electrolyte includes alkali metal ions having an ionic radius greater than a radius of lithium ions and a film-forming additive. Based on a total mass of the electrolyte, a mass percentage A of the alkali metal ions and a mass percentage B of the additive satisfy 0.10≤B/A≤6×104.The lithium-ion secondary battery (5) exhibits a low direct current resistance and excellent cycling performance.