Three-Layer Encapsulation for Thin Film Lithium-Ion Batteries
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Solution Overview
Problem
Thin film lithium-ion batteries face challenges with self-discharge and reduced service life due to sensitivity to humidity and mechanical stresses from volume variations during charge and discharge cycles, leading to encapsulation failures and reduced performance.
Innovation Solution
A three-layer encapsulation system comprising an electrically insulating material deposited by atomic layer deposition, a parylene or polyimide layer, and a protective epoxy resin or polyurethane layer to create a hermetic, impermeable barrier that protects against oxygen and humidity, while allowing for slight dimensional changes and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If thin film lithium-ion batteries use metallic lithium anodes with thin electrolyte films to achieve high energy density, then energy density improves, but self-discharge increases due to leak currents at electrode edges
Solution Approach 1:
The patent applies edge coating with conductive material (graphite, lithium phosphate, or lithium titanate) to seal the edges of thin film batteries. This creates a protective barrier at the electrode edges where leak currents occur, preventing the creeping short circuit that causes self-discharge while maintaining the thin film structure necessary for high energy density
Solution Approach 2:
The patent uses composite edge coatings combining conductive materials (graphite, lithium phosphate, or lithium titanate) with the thin film battery structure. This composite approach provides both edge sealing to prevent leak currents and maintains electrical conductivity for battery operation
2Quantity of substance
If anode materials undergo cyclic volume variation during charge and discharge to enable lithium ion insertion and extraction, then battery capacity improves, but mechanical and electrical contacts between layers deteriorate
Solution Approach 1:
The patent selects anode materials with specific properties (lithium phosphate, lithium titanate, or graphite) that have different volume expansion characteristics compared to conventional metallic lithium. These materials undergo more controlled and reversible volume changes during cycling, maintaining mechanical integrity and electrical contact stability while preserving battery capacity
3Reliability
If encapsulation systems are made rigid to prevent cracks from cyclic volume variation, then encapsulation integrity improves, but the system cannot accommodate dimensional changes of the battery
Solution Approach 1:
The patent employs flexible encapsulation materials (polymer films, elastomers, or composite flexible structures) that can stretch and deform elastically during battery volume changes. This flexibility prevents crack formation while maintaining encapsulation integrity, accommodating the cyclic dimensional variations that occur during charge and discharge
4Ease of manufacture
If active materials are exposed to air and humidity for manufacturing and operation, then battery assembly becomes easier, but spontaneous reaction with water forms LiOH leading to capacity loss
Solution Approach 1:
The patent implements hermetic encapsulation using impermeable barrier layers (metallic films, ceramic coatings, or composite barrier structures) that create an inert protective environment around the active materials. This prevents moisture and oxygen penetration, stopping the spontaneous formation of LiOH and associated capacity loss while allowing standard manufacturing processes
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 encapsulation system significantly extends the service life of thin film lithium-ion batteries by preventing degradation from humidity and mechanical stresses, reducing self-discharge, and ensuring reliable operation over a longer period.
Implementation Method 1
a first covering layer composed of an electrically insulating material deposited by atomic layer deposition
Implementation Method 2
a third covering layer deposited on the second covering layer in such a way as to protect the second encapsulation layer, namely from oxygen
Data Source
AI summary
Systems, methods, and apparatus for encapsulating objects like that of microelectronic components and batteries. The system includes three successive layers that include a first covering layer composed of an electrically insulating material deposited by atomic layer deposition, which at least partly covers the object, a second covering layer that includes parylene and/or polyimide, and which is disposed on the first covering layer, and a third covering layer deposited on the second covering layer in such a way as to protect the second encapsulation layer, namely, with respect to oxygen, and thereby increase the service life of the object.