Compressible Cathode 3D Battery Structure for Swelling Reliability
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Solution Overview
Problem
Rocking chair secondary batteries face reliability and cycle life issues due to electrode expansion and contraction during charging and discharging, leading to electrical shorts and battery failures.
Innovation Solution
The implementation of a secondary battery design with an electrode assembly that includes anode and cathode structures arranged in an alternating sequence, separated by an electrically insulating microporous separator, and constrained by a set of electrode constraints to restrain growth, allowing for efficient ion movement while managing expansion and contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are allowed to expand and contract freely during charging and discharging, then the battery can maintain good electrochemical performance, but the electrodes will experience mechanical strain leading to electrical shorts and battery failure
Solution Approach 1:
The patent applies flexible thin film constraints (compliance layers) that can deform elastically to accommodate electrode expansion and contraction while maintaining structural integrity. These compliance layers are designed with appropriate mechanical properties to flex with the electrodes during cycling, preventing delamination and electrical shorts while maintaining reliable battery operation
Solution Approach 2:
The patent modifies mechanical parameters by introducing compliance layers with specific elastic moduli and thicknesses that are optimized to match the mechanical properties of the electrodes. By carefully selecting material parameters and geometric dimensions, the constraints can accommodate volume changes during charging/discharging while preventing harmful mechanical failure
2Reliability
If constraint structures are added to restrain electrode growth, then reliability and cycle life are improved, but device complexity increases
Solution Approach 1:
The patent merges the constraint function with existing battery components by integrating compliance layers into the electrode assembly structure. Rather than adding separate external constraints, the compliance layers are incorporated as part of the electrode stack itself, combining the structural support and mechanical constraint functions into a unified assembly that maintains simplicity while improving cycle life
3Quantity of substance
If anode structures expand during charging, then more carrier ions can be stored increasing energy density, but the expansion causes mechanical strain and potential battery failure
Solution Approach 1:
Flexible compliance layers are positioned adjacent to the anode structures to provide mechanical support during expansion. These thin film constraints allow the anode to expand and contract while maintaining structural integrity, enabling high carrier ion storage capacity without compromising mechanical strength or causing electrode failure
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
This design enhances energy density, reliability, and cycle life by mitigating strain and failure risks through controlled expansion and contraction of electrodes, improving the battery's performance and longevity.
Implementation Method 1
an electrically insulating microporous separator material electrically separating members of the anode and cathode structure populations
Implementation Method 2
charging the secondary battery such that an expansion in cross-sectional area of the anode active material layers in the members of the population of anode structures compresses the compressible cathode active material layers
Data Source
AI summary
A secondary battery for cycling between a charged and a discharged state is provided. The secondary battery has an electrode assembly having a population of anode structures, a population of cathode structures, and an electrically insulating microporous separator material. The electrode assembly also has a set of electrode constraints that at least partially restrains growth of the electrode assembly. Members of the anode structure population have a first cross-sectional area, A1 when the secondary battery is in the charged state and a second cross-sectional area, A2, when the secondary battery is in the discharged state, and members of the cathode structure population have a first cross-sectional area, C1 when the secondary battery is in the charged state and a second cross-sectional area, C2, when the secondary battery is in the discharged state, where A1 is greater than A2, and C1 is less than C2.