Thin Film Battery Substrate CTE Matching
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Solution Overview
Problem
Thin-film solid-state batteries face catastrophic failure due to cracking of cathode material layers during manufacturing or early life cycles, leading to significant issues in small devices where battery replacement is not viable, resulting in loss beyond the battery's economic value.
Innovation Solution
A thin-film battery design using a glass or ceramic substrate with a coefficient of thermal expansion of 7 to 10 ppm/°K, combined with a continuous metal or metal oxide cathode current collector and a LiPON electrolyte layer, allowing for thick LiCoO2 cathode material layers that resist cracking and prevent catastrophic failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thick cathode material layers are used to increase energy density, then battery capacity is improved, but the cathode material layer becomes prone to cracking during manufacturing or early life cycles
Solution Approach 1:
The patent changes the physical parameters of the substrate by selecting glass or ceramic materials with specific coefficient of thermal expansion (CTE) values ranging from 7 to 10 ppm/°K. This parameter selection creates a CTE match between the substrate and the cathode material layer, reducing thermal stress and preventing cracking during manufacturing and operation, thereby enabling thick cathode layers without compromising reliability
Solution Approach 2:
The patent employs a composite structure consisting of a glass or ceramic substrate combined with a metal or metal oxide cathode current collector. This composite material system provides both mechanical support and thermal expansion compatibility, allowing thick cathode material layers to be deposited without cracking while maintaining structural integrity and reliability
2Weight of moving object
If smaller battery size is used to reduce device weight and volume, then portability is improved, but battery capacity is reduced
Solution Approach 1:
The patent optimizes the thickness parameter of the cathode material layer to range from 10 to 80 micrometers. This controlled thickness increase allows significantly higher lithium content and thus higher capacity in a compact form factor, enabling small batteries to achieve sufficient capacity without increasing overall device weight or volume
Solution Approach 2:
The patent uses thin-film deposition techniques to create highly dense and uniform cathode material layers with precise control over thickness and composition. This manufacturing approach maximizes the energy density per unit volume, allowing small batteries to achieve high capacity in minimal space
3Ease of manufacture
If conventional substrates are used for thin-film batteries, then manufacturing simplicity is maintained, but cathode material layer cracking occurs leading to catastrophic failure
Solution Approach 1:
The patent specifies precise CTE parameter ranges for the substrate (7 to 10 ppm/°K) and controls the thickness parameter of functional layers. These parameter specifications enable crack-free cathode material deposition while maintaining compatibility with existing thin-film manufacturing processes, achieving both reliability and ease of manufacture
Solution Approach 2:
The patent introduces a metal or metal oxide cathode current collector as an intermediary layer between the glass or ceramic substrate and the cathode material. This intermediary layer acts as a buffer that accommodates thermal expansion differences and provides a compliant substrate for thick cathode material deposition, preventing cracking while maintaining manufacturing simplicity
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 battery construction provides high energy density and reliability, reducing the likelihood of catastrophic failure and enabling smaller, more reliable power supplies for electronic devices, as the interaction between the substrate, cathode current collector, and LiPON electrolyte layer helps in maintaining the integrity of the cathode material layer.
Implementation Method 1
a glass or ceramic substrate having a coefficient of thermal expansion ('CTE') of from about 7 to about 10 ppm/° K
Implementation Method 2
a LiPON electrolyte layer superjacent to the cathode material layer
Data Source
AI summary
A thin film battery comprises a glass or ceramic substrate having a coefficient of thermal expansion (“CTE”) of from about 7 to about 10 ppm/° K, a continuous metal or metal oxide cathode current collector and having a thickness of less than about 3 micrometers, the cathode current collector being superjacent to the glass or ceramic substrate, a cathode material layer comprising lithium transition metal oxides that is a continuous film having a thickness of from about 10 to about 80 micrometers, the cathode material layer being superjacent to the cathode current collector, a LiPON electrolyte layer superjacent to the cathode material layer and having a thickness of from about 0.5 to about 4 micrometers, and an anode current collector with an optional anode material. Methods of making and using the batteries are described.