Conductive Target Material for Lithium Ion Electrolyte Deposition
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Solution Overview
Problem
Conventional lithium ion electrolyte layer deposition using monophasic lithium compound targets, such as lithium phosphate, limits the use of DC and pulsed DC sputtering processes due to low electrical conductivity, resulting in restricted deposition rates and potential inhomogeneity, complexity, and reduced thermal shock stability.
Innovation Solution
A conductive target material comprising predominantly one lithium compound, preferably lithium phosphate, with a high proportion of elemental carbon (>50%) forms a biphasic microstructure, enhancing electrical and thermal conductivity, stability, and process stability, while maintaining low costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional monophasic lithium compound targets are used, then the target material maintains electrical insulation properties suitable for electrolyte layers, but the electrical conductivity of the target material is too low for DC and pulsed DC sputtering processes
Solution Approach 1:
The patent applies composite materials by combining lithium compound particles with conductive carbon particles to create a biphasic target material. The carbon phase provides electrical conductivity enabling DC sputtering, while the lithium compound phase ensures the deposited layer maintains its electrolyte properties with low electrical conductivity and high ion conductivity.
Solution Approach 2:
The patent applies local quality by creating distinct phases within the target material where carbon particles are distributed throughout the lithium compound matrix. The carbon provides localized conductivity pathways necessary for DC sputtering operation, while the lithium compound regions maintain the chemical composition needed for forming insulating electrolyte layers with high ion conductivity.
2Manufacturing precision
If multiple lithium and phosphorus compounds are used in the target material, then the desired layer composition can be achieved, but the process complexity and production costs increase significantly
Solution Approach 1:
The patent applies taking out by extracting the carbon conductivity function from complex multi-compound lithium-phosphorus systems and implementing it through simple carbon addition to a single lithium compound. This separates the conductivity enhancement function from the composition control function, allowing straightforward DC sputtering with maintained layer composition precision.
3Productivity
If multiple chemical compounds with different thermal properties are used in the target material, then the desired electrical conductivity is achieved, but the thermal shock stability and mechanical strength are reduced
Solution Approach 1:
The patent applies homogeneity by using a single lithium compound phase combined with carbon particles, creating a more uniform thermal structure compared to multi-compound systems. This homogeneous composition with different phases provides adequate electrical conductivity through carbon while maintaining thermal shock stability and mechanical strength through the consistent thermal properties of the single lithium compound matrix.
4Productivity
If multiple chemical compounds are used in the target material, then conductivity can be improved, but the sputtering rates of different compounds vary making constant layer thickness difficult to achieve
Solution Approach 1:
The patent applies parameter changes by transitioning from multi-compound systems with different sputtering rates to a single lithium compound system where only the carbon content parameter varies. This uniform base material ensures consistent sputtering behavior and layer thickness, while carbon particles provide the necessary electrical conductivity for DC sputtering operation.
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 conductive target material allows for high deposition rates, improved thermal shock stability, and reduced costs by enabling efficient DC or pulsed DC sputtering with a 5- to 10-fold increase in deposition rate and optimized electrical conductivity, ensuring consistent layer properties.
Implementation Method 1
the deposition of such lithium ion electrolyte layers is accomplished by means of an RF/HF (radio frequency/high frequency) reactive sputtering process
Implementation Method 2
are used in physical vapour deposition (PVD) systems for deposition of lithium ion electrolyte layers
Implementation Method 3
the carbon present occurs predominantly, with a proportion of greater than 50%, in elemental form
Implementation Method 4
the sputtering of a lithium phosphate target with the involvement of nitrogen and/or oxygen during the deposition operation forms nitrogen-containing LiPON layers having a high ion conductivity
Data Source
AI summary
The present invention relates to a conductive target material comprising essentially one lithium compound, preferably lithium phosphate, and carbon, and also typical impurities. The invention further relates to a process for producing a conductive target material and to the use thereof.