SVO Battery Insulation Layout Against Lithium Dendrite Shorting
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Solution Overview
Problem
Lithium dendrite formation in Silver Vanadium Oxide (SVO) batteries used in implantable medical devices leads to internal shorting, which is not adequately prevented by existing insulation structures, posing a reliability risk due to manufacturing variations and mechanical disturbances.
Innovation Solution
A battery design with an anode-cathode alignment where the lithium anode is recessed from the cathode edge in critical areas, combined with a robust insulation scheme using overmolded feedthrough insulation and insulating boots to create a shield impenetrable to the electrolyte, preventing lithium dendrite formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing insulation structures (simple overlapping fit or interference joint) are used, then the battery can be manufactured with standard tolerances, but lithium dendrites can still form through openings and cause shorting failures
Solution Approach 1:
The insulation structure is divided into multiple segments: an insulating boot covering the cell stack, feedthrough insulation covering the feedthrough assembly, and an insulating grommet at the interface. Each segment provides localized insulation, and together they create comprehensive protection against dendrite formation without requiring a single complex structure.
Solution Approach 2:
The insulation components are nested within each other to create layered protection. The insulating grommet is positioned at the interface between the insulating boot and feedthrough insulation, with each layer providing additional protection. This nested arrangement ensures that dendrites cannot penetrate through gaps between components.
2Ease of manufacture
If insulation joints with fit variations are used, then manufacturing is easier with standard tolerances, but openings are left for dendrites to form
Solution Approach 1:
The insulating grommet is made of a compliant material that can deform elastically to accommodate fit variations between the insulating boot and feedthrough insulation. This flexible shell maintains continuous insulation coverage despite manufacturing tolerances, preventing openings that would allow dendrite formation while remaining easy to manufacture and assemble.
3Device complexity
If the anode is aligned with the cathode edge, then the battery structure is simpler, but lithium dendrites can form between exposed anode surfaces and cathode edges
Solution Approach 1:
The anode-cathode alignment is optimized locally at critical areas where dendrite formation is most likely. The anode is recessed relative to the cathode edge at these specific locations, while maintaining proper alignment elsewhere. This localized adjustment provides enhanced protection without requiring complete redesign of the entire alignment structure.
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
A battery includes a case having a feedthrough port, a feedthrough assembly disposed in the feedthrough port, and a cell stack disposed within the case. The feedthrough port includes an inner conductor and an insulator core separating the inner conductor from the case. The cell stack includes an anode, a cathode, and a separator insulating the anode from the cathode, wherein the anode and cathode are offset from one another. An insulating boot surrounding the cell stack insulates the cell stack from the case. The insulating boot has an opening configured to receive therein the feedthrough assembly, which may include overmolded insulation. The interior surfaces and interior walls of the battery case may be thermal spray-coated with a dielectric material to prevent lithium dendrite formation between cathode and anode surfaces.