LiF Coated Carbon Negative Electrode for Lithium Battery Safety
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Solution Overview
Problem
Lithium secondary batteries using carbon-based negative electrodes face challenges with rapid charging capability and safety issues during overcharge and high-temperature exposure due to the formation of a thick solid electrolyte interface (SEI) and potential for short circuits.
Innovation Solution
A negative electrode with a carbon-based active material layer coated with a LiF layer containing amorphous LiF in amounts of 30 mol % or more, which helps regulate SEI thickness, enhance rapid charging, and improve safety by acting as a protective and insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick SEI is formed on the surface of the negative electrode to prevent lithium ion reactions and act as an ion tunnel, then safety is improved, but rapid charging capability is reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the SEI layer by incorporating LiF compounds (specifically LiF, Li3PO4, and Li2SiO3) in controlled ratios. This compositional parameter change modifies the SEI properties to achieve both safety and rapid charging capability, resolving the contradiction between thick SEI for safety and thin SEI for rapid charging.
Solution Approach 2:
The patent creates a composite SEI layer by combining multiple lithium compounds (LiF, Li3PO4, Li2SiO3) with carbon-based active material. This composite structure provides both the protective function of a thick SEI and the ion conductivity needed for rapid charging, simultaneously addressing both requirements.
2Duration of action of stationary object
If carbon-based compound is used as negative electrode active material to maintain structural and electrical properties, then cycle life is improved, but safety at overcharge and high temperature is lacking
Solution Approach 1:
The patent introduces LiF-containing compounds as an intermediary protective layer between the carbon-based active material and the electrolyte. This intermediary SEI layer acts as a barrier that prevents direct contact and harmful reactions at high temperatures and overcharge conditions, while allowing normal operation and maintaining cycle life.
Solution Approach 2:
The patent applies preliminary protective action by forming a stable LiF-containing SEI layer before harmful reactions can occur. This pre-formed protective barrier prevents thermal runaway and short circuits during overcharge and high-temperature conditions, addressing safety concerns before they manifest.
3Productivity
If LiF layer is formed on negative electrode active material layer to regulate SEI thickness, then rapid charging capability is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating LiF-containing compounds directly into the electrode manufacturing process before battery assembly. The LiF layer is formed in advance during electrode production, simplifying the overall manufacturing process compared to post-assembly treatments, while still achieving the desired SEI thickness control for rapid charging.
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 LiF layer enables stable rapid charging, reduces calorific values during overcharge and high-temperature exposure, and enhances short-circuit safety, maintaining excellent cycle performance and safety at overcharge and high-temperature conditions.
Implementation Method 1
a LiF layer which is formed on the negative electrode active material layer and comprises amorphous LiF
Implementation Method 2
enhance short-circuit safety, maintaining excellent cycle performance and safety at overcharge and high-temperature conditions
Data Source
AI summary
A negative electrode for a lithium secondary battery, in which a LiF layer comprising amorphous LiF in an amount of 30 mol % or more is formed on a negative electrode active material layer comprising a carbon-based active material, a lithium secondary battery comprising the same, and a preparation method thereof.