All-Solid Battery Cover Layer Structure Against Reflow Peeling
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Solution Overview
Problem
Stacked all solid batteries face reliability issues due to peeling between the cover layer and internal electrodes during reflow soldering, primarily caused by tensile stress, which can lead to high reliability concerns.
Innovation Solution
The battery design incorporates a multilayer structure with a solid electrolyte layer without filler materials between the cover layers and internal electrodes, and the cover layers include a solid electrolyte and filler materials to form a bone structure, which reduces necking and enhances bonding strength, thereby minimizing peeling risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cover layer is made with solid electrolyte and filler materials to form a bone structure, then the bonding strength is enhanced and necking is reduced, but the device complexity increases due to the multilayer structure with different compositions
Solution Approach 1:
The battery structure is divided into multiple functional layers: a first cover layer with solid electrolyte and first filler materials, a solid electrolyte layer without filler materials, and a second cover layer with solid electrolyte and second filler materials. This segmentation allows each layer to be optimized for specific functions while maintaining overall structural integrity and reducing peeling during reflow soldering.
Solution Approach 2:
Different regions of the battery structure have different material compositions tailored to local requirements. The cover layers contain filler materials to enhance bonding strength and reduce necking, while the intermediate solid electrolyte layer excludes filler materials to prevent peeling at the interface with internal electrodes. This local differentiation of material properties resolves the contradiction between strength enhancement and peeling prevention.
2Reliability
If a solid electrolyte layer without filler materials is placed between the cover layer and internal electrodes, then peeling is suppressed during reflow soldering, but the manufacturing precision requirements increase due to the need for precise layer stacking
Solution Approach 1:
The solid electrolyte layer without filler materials is pre-positioned between the cover layer and internal electrodes during the stacking process, before reflow soldering occurs. This preliminary arrangement ensures that when tensile stress occurs during reflow, the peeling-resistant interface is already in place, preventing peeling without requiring real-time adjustment during soldering.
Solution Approach 2:
The battery employs composite material structures: cover layers composed of solid electrolyte and filler materials for bonding strength, combined with a pure solid electrolyte layer for peeling resistance. This composite approach allows the system to achieve both high reliability during reflow and manageable manufacturing precision through the use of compatible materials that bond well at their interfaces.
3Stability of the object's composition
If the cover layers include filler materials that are less likely to cause necking, then the volumetric expansion and contraction is absorbed during charging and discharging, but the loss of substance increases due to the additional filler materials
Solution Approach 1:
The filler materials in the cover layers are specifically selected to have different properties from the solid electrolyte, particularly in terms of necking resistance and volumetric stability. By changing the material parameters of the filler (choosing materials less likely to cause necking), the cover layers can absorb volumetric expansion and contraction during battery operation, maintaining structural stability while minimizing substance loss through controlled material selection rather than excessive material addition.
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 effectively suppresses peeling and maintains high reliability by absorbing volumetric expansion and contraction during charging and discharging, ensuring stable performance even under tensile stress during reflow soldering.
Implementation Method 1
the cover sheet including a solid electrolyte and a filler material which is less likely causes necking than the solid electrolyte
Implementation Method 2
absorbing volumetric expansion and contraction during charging and discharging
Data Source
AI summary
An all solid battery includes a multilayer structure in which each of a plurality of solid electrolyte layers and each of a plurality of internal electrodes including an electrode active material are alternately stacked, a first cover layer provided on a first end of the multilayer structure in a stacking direction, and a second cover layer provided on a second end of the multilayer structure in the stacking direction. The first cover layer and the second cover layer include a solid electrolyte and filler materials dispersed in the solid electrolyte. One of the plurality of solid electrolyte layers not including the filler materials is arranged between the first cover layer and one of the plurality of internal electrodes located closest to the first cover layer. The second cover layer directly contacts another one of the plurality of internal electrodes located closest to the second cover layer.