Lithium Battery Anode Protective Layer for Stable SEI and Ion Flow
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Solution Overview
Problem
Existing lithium batteries face issues with lower current density due to thick protective layers, instability, and volume changes, and the use of hybrid binders like polyimide and polyvinyl alcohol does not provide stable SEI during initial electrodeposition.
Innovation Solution
A lithium battery design incorporating a protective layer with a modulus of 30 GPa or more, featuring a nitrile-based additive in the electrolyte, which includes two or more nitrile groups, to enhance ion conductivity and suppress side reactions, thereby improving electrode stability and reducing volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick protective layer is used to ensure sufficient ion conductivity, then ion conductivity is improved, but current density decreases
Solution Approach 1:
The patent applies a thin protective layer (1-10 nm) instead of a thick protective layer to maintain sufficient ion conductivity while avoiding the current density reduction associated with thicker layers. The protective layer is formed through atomic layer deposition (ALD) to achieve precise thickness control, enabling the use of ultra-thin films that provide protection without impeding ion transport.
Solution Approach 2:
The patent changes the thickness parameter of the protective layer from conventional thick layers (10 μm or more) to ultra-thin layers (1-10 nm). This parameter change resolves the contradiction by finding an optimal thickness that provides sufficient protection while maintaining high current density, as the ultra-thin layer does not significantly impede ion conductivity.
2Strength
If a hybrid binder of polyimide and polyvinyl alcohol is applied to protective layers, then structural integrity is improved, but stable SEI formation during initial electrodeposition becomes difficult
Solution Approach 1:
The patent removes the binder component (polyimide and polyvinyl alcohol hybrid binder) from the protective layer structure. By eliminating the binder, the patent avoids the SEI stability issues associated with these materials during initial electrodeposition, while still achieving structural integrity through the atomic layer deposition process that creates a dense, uniform protective layer.
Solution Approach 2:
The patent introduces aluminum oxide (Al2O3) as an intermediary material deposited via ALD to form the protective layer. This intermediary layer provides both structural integrity and stable SEI formation, replacing the problematic hybrid binder system with an inorganic material that interfaces well with both the current collector and electrolyte.
3Stability of the object's composition
If the protective layer modulus is increased to suppress volume changes, then electrode stability is improved, but side reactions with the current collector increase
Solution Approach 1:
The patent uses an ultra-thin protective layer (1-10 nm) formed by atomic layer deposition to suppress volume changes and prevent side reactions. The thin film structure provides sufficient mechanical constraint to maintain electrode stability while minimizing the amount of material that could participate in side reactions with the current collector.
Solution Approach 2:
The patent creates a composite structure consisting of the current collector, ultra-thin protective layer (e.g., Al2O3), and subsequent electrode materials. This composite structure provides both the mechanical stability needed to suppress volume changes and a protective barrier that prevents direct contact between the current collector and electrolyte, thereby eliminating side reactions.
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 design enhances ionic conductivity, flame retardancy, and reduces internal resistance, leading to improved charging and discharging efficiency, lifespan, and electrode stability by suppressing side reactions and volume changes.
Implementation Method 1
the protective layer may have a modulus of 30 Gpa or more
Implementation Method 2
the electrolyte may include a nitrile-based additive including two or more nitrile groups
Implementation Method 3
the protective layer capable of suppressing or reducing volume changes in an electrode
Data Source
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AI summary
Disclosed are a binder, an anode having a protective layer comprising same, and a lithium battery comprising same, the binder comprising a third polymer, which is a crosslinking reaction product of at least one first polymer that has a first functional group and is selected from a polyamic acid and a polyimide in which fluorine is substituted, and a water-soluble second polymer that has a second functional group, wherein the first functional group and the second functional group react to form an ester bond such that the first polymer and the second polymer become crosslinked.