3D Battery Electrode Constraints for Cycling Expansion Control
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Solution Overview
Problem
The expansion and contraction of electrodes in rocking chair batteries during cycling lead to electrical shorts and battery failures, affecting reliability and cycle life.
Innovation Solution
Implementing a set of electrode constraints, including primary and secondary growth constraint systems, to restrain the macroscopic expansion of electrodes, with a ratio of electrode assembly dimensions at least 2:1, and using materials that can accept more than one mole of carrier ions per mole of electrode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrodes are designed to accept multiple moles of carrier ions per mole of electrode active material, then energy density is improved, but electrode expansion and contraction during cycling increases leading to electrical shorts and battery failures
Solution Approach 1:
The electrode assembly is segmented into multiple individual electrodes that are constrained independently by growth constraints. Each electrode can expand and contract within its constrained space, preventing macroscopic expansion while maintaining the ability to accept multiple moles of carrier ions. This segmentation allows high energy density materials to be used without causing battery failure from uncontrolled expansion.
Solution Approach 2:
Growth constraints act as intermediary structures between the electrode active material and the battery enclosure. These constraints mediate the expansion and contraction forces generated by high-capacity electrode materials, allowing the electrodes to undergo volume changes during cycling without transmitting harmful macroscopic expansion to the battery structure, thus preventing electrical shorts while enabling high energy density.
2Quantity of substance
If electrode active material is designed to accept more than one mole of carrier ion per mole of electrode active material, then capacity is improved, but macroscopic expansion of electrode assembly increases
Solution Approach 1:
The electrode assembly is divided into multiple individual electrodes, each constrained by growth constraints. This segmentation allows the electrode material to undergo volume changes at the micro-scale while preventing macroscopic volume increase of the overall assembly, enabling high-capacity materials to be used without significant expansion.
Solution Approach 2:
Growth constraints function as flexible restraining structures that allow controlled deformation of electrode material during ion insertion/extraction. These constraints accommodate the volume changes associated with high-capacity materials (accepting more than one mole of carrier ions) while preventing macroscopic expansion of the electrode assembly, thus maintaining compact battery design.
3Adaptability or versatility
If electrodes are allowed to expand and contract freely during cycling, then electrode flexibility is maintained, but electrical shorts and battery failures occur
Solution Approach 1:
Growth constraints are designed as flexible restraining structures that allow electrode material to expand and contract during cycling while preventing excessive macroscopic expansion. The constraints maintain appropriate mechanical coupling between electrodes, ensuring electrical connectivity is preserved while preventing electrical shorts caused by uncontrolled expansion and contraction.
Solution Approach 2:
The electrode assembly incorporates growth constraints that create a composite structure combining flexible electrode material with restraining constraint elements. This composite design allows the electrode to maintain flexibility for ion transport while the constraint structure prevents harmful macroscopic expansion, thus improving reliability without sacrificing electrode adaptability.
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
Improves energy density, reliability, and cycle life of batteries by controlling electrode expansion and contraction, reducing failure incidence.
Implementation Method 1
both the positive and negative electrodes comprise materials into which a carrier ion inserts and extracts
Implementation Method 2
The set of electrode constraints includes a primary constraint system comprising first and second primary growth constraints and at least one primary connecting member... wherein the primary constraint system restrains growth of the electrode assembly in the longitudinal direction
Data Source
AI summary
A secondary battery is provided for cycling between a charged and a discharged state, the secondary battery including a battery enclosure, an electrode assembly, carrier ions, a non-aqueous liquid electrolyte within the battery enclosure, and a set of electrode constraints. The set of electrode constraints includes a primary constraint system having first and second primary growth constraints and at least one primary connecting member, the first and second primary growth constraints separated from each other in the longitudinal direction, wherein the primary constraint array restrains growth of the electrode assembly in the longitudinal direction such that any increase in the Feret diameter of the electrode assembly in the longitudinal direction over 20 consecutive cycles of the secondary battery is less than 20%. The set of electrode constraints further includes a secondary constraint system having first and second secondary growth constraints connected by at least one secondary connecting member, wherein the secondary constraint system at least partially restrains growth of the electrode assembly in a second direction upon cycling of the secondary battery.