Pinhole-Free Solid State Electrolytes via Plasma Treatment
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Solution Overview
Problem
Solid state electrolytes, such as LiPON, have limited ionic conductivity and are prone to pinholes, which compromise the functionality of thin film batteries and electrochromic devices, leading to reduced breakdown voltage and potential short circuits.
Innovation Solution
Incorporating thin layers or particles of transition metal oxides, silicon, or silicon oxide into the electrolyte stack, combined with plasma treatment to enhance ionic conductivity and reduce pinhole density, using methods like physical vapor deposition and plasma-induced ion bombardment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PVD RF sputtering is used to deposit LiPON electrolyte films, then the films can be formed, but pinholes appear in the films leading to reduced breakdown voltage and potential short circuits
Solution Approach 1:
The patent applies preliminary plasma treatment to the substrate and deposited LiPON films before final deposition completion. This preliminary plasma exposure modifies the surface properties and fills pinholes proactively, preventing their formation or minimizing their impact before the film structure is finalized, thereby improving breakdown voltage without requiring excessive film thickness
Solution Approach 2:
The patent systematically varies deposition parameters including RF power, deposition rate, film thickness, and plasma treatment conditions to optimize the balance between film quality and pinhole formation. By changing these parameters, the patent achieves pinhole-free films at appropriate thicknesses without compromising ionic conductivity or requiring excessive material deposition
2Manufacturing precision
If thicker LiPON films are deposited to minimize pinholes, then pinhole density decreases, but manufacturing cost increases due to lower throughput and higher material consumption
Solution Approach 1:
The patent replaces the purely mechanical approach of depositing thicker films to eliminate pinholes with a plasma-based chemical/physical treatment approach. Plasma treatment actively modifies the film structure and fills pinholes in-situ, allowing thin films to achieve pinhole-free quality without requiring excessive thickness, thereby maintaining high throughput and reducing material consumption
Solution Approach 2:
The patent introduces plasma as an intermediary treatment between deposition steps. This plasma intermediary actively processes the deposited film, filling pinholes and improving film quality without requiring the film to be excessively thick, thus resolving the contradiction between achieving pinhole-free films and maintaining manufacturing productivity
3Productivity
If RF power is increased during sputtering to improve deposition rate, then throughput increases, but pinhole density increases significantly
Solution Approach 1:
The patent applies plasma treatment as a preliminary and intermediate step during the deposition process. This plasma treatment proactively addresses pinhole formation by modifying the film structure and filling voids, allowing higher RF power to be used for faster deposition without the penalty of increased pinhole density, as the plasma treatment compensates for the increased pinhole formation tendency
Solution Approach 2:
The patent converts the harmful effect of high RF power (increased pinhole formation) into a beneficial process by using plasma treatment to selectively remove or fill pinholes. The plasma treatment transforms the defective high-rate deposited film into a high-quality film, allowing the system to benefit from high deposition rates while eliminating the harmful pinhole effect
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
Significantly increases ionic conductivity of solid state electrolytes, achieving pinhole-free films with improved lithium ion mobility and reduced resistance, enhancing the performance of electrochemical devices like thin film batteries and electrochromic devices.
Implementation Method 1
inducing and maintaining a plasma in the vicinity of the substrate to provide ion bombardment of the deposited layer of electrolyte
Implementation Method 2
The conventional method used to deposit LiPON is physical vapor deposition (PVD) radio frequency (RF) sputtering
Implementation Method 3
physical vapor deposition (PVD) radio frequency (RF) sputtering of a Li3PO4 target
Data Source
AI summary
The present invention relates to vacuum-deposited solid state electrolyte layers with high ionic conductivity in electrochemical devices, and methods and tools for fabricating said electrolyte layers. An electrochemical device may comprise solid state electrolytes with incorporated thin layers and/or particles of transition metal oxides, silicon, silicon oxide, or other suitable materials that will induce an increase in ionic conductivity of the electrolyte stack (for example, materials with which lithium is able to intercalate), or mixtures thereof. An improvement in ionic conductivity of the solid state electrolyte is expected which is proportional to the number of incorporated layers or a function of the distribution uniformity and density of the particles within the electrolyte. Embodiments of the present invention are applicable to solid state electrolytes in a broad range of electrochemical devices including thin film batteries, electrochromic devices and ultracapacitors. The solid state electrolyte layers may be nominally pinhole-free.