Secondary Battery Electrolyte Buffer Structure for Electrode Swelling
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Solution Overview
Problem
Lithium secondary batteries using lithium metal or silicon particles as negative electrodes face issues with charge capacity due to the expansion and contraction of the negative electrode during charging and discharging, leading to voids that prevent effective electrolyte contact, resulting in reduced durability and uneven resistance.
Innovation Solution
A secondary battery design with a space forming member that absorbs and discharges electrolyte between the electrode laminated body and the exterior body, allowing for expansion and contraction, ensuring consistent electrolyte distribution and preventing contact with seals during thermal fusion, thereby improving durability and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal or silicon particles are used as negative electrode active material to improve charge capacity, then the charge capacity increases, but the negative electrode thickness greatly increases during charging and decreases during discharging, leading to lowered electricity charging and discharging characteristics
Solution Approach 1:
The patent applies local quality by creating a moss-like structure in specific regions of the negative electrode where lithium metal accumulates. This structure provides localized void spaces that allow electrolytic solution penetration, ensuring that the areas with greatest thickness variation maintain proper electrolyte contact for reliable charging and discharging
Solution Approach 2:
The negative electrode is segmented into active material particles (lithium metal or silicon particles) dispersed throughout the electrode structure. This segmentation allows the electrode to accommodate volume changes through particle-level transformations rather than requiring uniform thickness changes across the entire electrode
2Quantity of substance
If the negative electrode active material layer is formed with separated lithium changing from particle state to moss-like state, then charge capacity increases, but voids easily occur in the layer, causing portions to not contact electrolytic solution and reducing charge capacity
Solution Approach 1:
The moss-like structure creates localized void spaces within the negative electrode active material layer. These voids are strategically formed in regions where lithium metal accumulates, ensuring that electrolytic solution can penetrate and contact active material portions that would otherwise be isolated, maintaining uniform electrolyte distribution and stable charge capacity
3Reliability
If excess electrolytic solution is accommodated in the battery case at rest to prevent contact with electrodes, then electrolytic solution insufficiency is solved, but it becomes difficult to supply electrolytic solution to voids in the negative electrode active material layer
Solution Approach 1:
The battery case is designed with dynamic expansion and contraction capabilities in the lamination direction. During charging when the negative electrode expands, the case contracts to create space for electrolytic solution to flow into voids. During discharging when the electrode contracts, the case expands to accommodate excess electrolyte, maintaining continuous electrolyte supply to active material
Solution Approach 2:
The battery case volume parameters are changed dynamically through expansion and contraction in the lamination direction. This parameter change creates pressure differential that drives electrolytic solution flow into and out of voids in the negative electrode, ensuring proper electrolyte distribution without requiring the case to be rigid
4Ease of manufacture
If the battery case is rigid to maintain structure, then manufacturing is easier, but the electrolytic solution cannot move promptly when the negative electrode dissolves, leading to uneven electrolyte distribution and increased resistance
Solution Approach 1:
The battery case transitions from a rigid structure to a dynamic structure capable of expansion and contraction in the lamination direction. This dynamic capability allows the case to respond to electrode volume changes, maintaining proper electrolyte distribution and preventing resistance increase while remaining manufacturable through standard battery assembly processes
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 design enhances the durability and charge capacity of lithium secondary batteries by maintaining even electrolyte distribution and preventing liquid leaks, while also improving energy density and cycle characteristics.
Implementation Method 1
a space forming member forming an electrolytic solution temporary storing space that is able to absorb and discharge an electrolytic solution is disposed between at least one side surface, extending in lamination directions, of an electrode laminated body
Implementation Method 2
the exterior body is able to expand and contract or deform in lamination directions of the electrode laminated body
Data Source
AI summary
A secondary battery according to the present invention is a secondary battery including: an electrode laminated body comprising a positive electrode and a negative electrode laminated with each other via a separator; an electrolytic solution; and an exterior body accommodating the electrode laminated body and the electrolytic solution, in which a thickness of the negative electrode changes due to charging and discharging of electricity, the exterior body is able to expand and contract or deform in lamination directions of the electrode laminated body, and a space forming member forming an electrolytic solution temporary storing space that is able to absorb and discharge the electrolytic solution is disposed between at least one side surface, extending in the lamination directions, of the electrode laminated body and an inner surface of the exterior body.