Miniature Electrochemical Cell Hermetic Sealing via Ceramic Plate
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Solution Overview
Problem
Conventional miniature electrochemical cells face challenges in achieving hermetic sealing and accommodating dimensional changes due to the use of polymeric adhesive layers and lack of suitable hermetic casings for solid-state cells, especially when the cell size is below 0.5 cc, leading to issues with contamination and longevity.
Innovation Solution
A hermetic casing structure using a ceramic plate with platinum-containing fill materials and current collectors deposited via physical vapor deposition, which provides a robust and flexible seal to accommodate expansion and contraction during cycling, ensuring reliable electrical isolation and chemical compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymeric adhesive layers are used for sealing, then ease of manufacture is improved, but hermeticity and reliability deteriorate due to inconsistent prevention of contaminant ingress/egress
Solution Approach 1:
The patent employs a composite sealing structure combining ceramic plate, metal container, and conductive paste materials. The ceramic plate provides hermetic sealing properties while the metal container offers structural support. This composite approach replaces the unreliable polymeric adhesive with a multi-material construction that achieves both manufacturability and hermeticity through the inherent properties of each material.
Solution Approach 2:
The patent replaces the polymeric adhesive bonding mechanism with a sintering process that creates direct ceramic-to-metal bonds. The conductive paste is sintered to form integral electrical pathways and seals, eliminating the need for separate adhesive layers. This substitution of bonding mechanism achieves superior hermeticity while maintaining ease of manufacture through a streamlined process.
2Volume of moving object
If cell size is reduced below 0.5 cc, then miniaturization is achieved, but sealing becomes difficult as seals occupy major portion of cell volume
Solution Approach 1:
The patent utilizes a thin ceramic plate as the sealing element that closes the metal container. The ceramic plate's thin profile minimizes the volume occupied by the seal, enabling effective sealing in miniaturized cells below 0.5 cc while maintaining hermeticity. The thin-film approach allows adequate electrical isolation without compromising cell size.
Solution Approach 2:
The composite construction of metal container plus thin ceramic plate creates an efficient sealing system for miniaturized cells. The metal provides structural integrity while the ceramic provides hermetic sealing in a thin profile, optimizing the balance between seal effectiveness and cell volume for miniature applications.
3Device complexity
If solid electrolyte is used, then filling port requirements are eliminated, but dimensional changes during cycling require hermetic casings that accommodate expansion and contraction
Solution Approach 1:
The patent segments the casing into a metal container body and a separate ceramic plate closure. This segmentation allows each component to be optimized independently: the metal container provides structural support while the ceramic plate provides hermetic sealing and accommodates dimensional changes through its material properties. The segmented design enables the casing to adapt to cycling-induced dimensional changes while maintaining hermeticity.
4Reliability
If ceramic plate with via holes is used for hermetic sealing, then hermeticity is improved, but manufacturing precision is required for via hole alignment and fill material placement
Solution Approach 1:
The conductive paste is applied to the ceramic plate and then sintered in place, allowing the paste to self-align and form integral pathways through the via holes during the sintering process. The sintering operation bonds the paste to the ceramic and metal components simultaneously, reducing the need for high-precision pre-alignment of via holes and fill materials. The process leverages the self-bonding capability of the paste to achieve hermetic sealing with moderate manufacturing precision.
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 achieves a hermetic seal with a leak rate of less than 1×10−7 std. cc He/sec and accommodates dimensional changes, enhancing the longevity and reliability of miniature solid-state electrochemical cells, particularly suitable for sizes below 0.5 cc.
Implementation Method 1
an electrochemical cell which is sufficiently hermetic to prevent ingress of moisture and egress of electrolyte
Implementation Method 2
platinum-containing fill materials and current collectors deposited via physical vapor deposition
Implementation Method 3
secondary electrochemical cells activated with a solid electrolyte typically undergo expansion and contraction during charging and discharging
Data Source
AI summary
A miniature electrochemical cell having a volume of less than 0.5 cc includes a casing having a header assembly comprising a ceramic plate formed by co-firing a metallic-containing paste in first and second via holes extending through a green-state ceramic. The ceramic plate is joined to a metal ring by a gold-braze to form the header assembly that is secured to an open-ended metal container by a weld to provide the casing. The fill material resulting from sintering the metallic-containing paste provides a first conductive pathway to the anode current collector contacting an anode active material and a second conductive pathway to a cathode current collector contacting a cathode active material. A solid electrolyte activates the anode and cathode while also serving as a separator. Outer surfaces of the first and second conductive pathways are configured for electrical connection to a load.