Whisker-like Active Material Amorphous Shell Adhesion
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Solution Overview
Problem
The challenge is to enhance the adhesion between a whisker-like active material and a current collector in power storage devices to prevent separation during charging and discharging, thereby improving charge/discharge cycle characteristics and capacity.
Innovation Solution
A power storage device is developed using a whisker-like active material with an amorphous outer shell and a crystalline core, where a thin mixed layer of 50 nm or less is formed between the active material and the current collector, enhancing adhesion and conductivity, and the active material layer is manufactured using a low-pressure chemical vapor deposition method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a whisker-like active material is used to increase charge/discharge capacity, then the capacity is improved, but the adhesion between the active material and current collector deteriorates
Solution Approach 1:
The patent employs a composite structure consisting of a crystalline core and an amorphous outer shell in the whisker-like active material. The crystalline core provides structural stability and high capacity, while the amorphous outer shell enhances adhesion to the current collector and accommodates volume changes during lithium ion occlusion and release, thereby resolving the contradiction between capacity and adhesion.
Solution Approach 2:
Different regions of the whisker-like active material are given different properties: the core region is crystalline for high capacity, while the outer shell region is amorphous for strong adhesion. This local differentiation of material properties allows each region to fulfill its specific function, simultaneously achieving high capacity and strong adhesion.
2Reliability
If the mixed layer thickness is increased to improve adhesion, then the adhesion is improved, but the charge/discharge cycle characteristics deteriorate
Solution Approach 1:
The patent optimizes the thickness parameter of the mixed layer to 50 nm or less, which is a critical threshold value. At this thin thickness, the mixed layer provides sufficient adhesion while minimizing its negative impact on charge/discharge cycle characteristics. This precise parameter control resolves the contradiction between adhesion and cycle life.
3Reliability
If a thick mixed layer is formed to enhance adhesion, then the adhesion is improved, but the conductivity deteriorates
Solution Approach 1:
The patent controls the mixed layer thickness to 50 nm or less, maintaining it within an optimal range that balances adhesion and conductivity. The thin mixed layer provides adequate mechanical bonding while preserving electrical conductivity pathways, thus resolving the contradiction between adhesion and power.
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 configuration results in improved adhesion, maintaining high charge/discharge capacity and cycle characteristics, reducing the risk of active material separation and enhancing the durability of the power storage device.
Implementation Method 1
a material which can occlude and release ions serving as carriers, such as carbon or silicon, is used. In particular, silicon has attracted attention because it has a higher theoretical capacity than carbon and is advantageous in increasing the capacities of power storage devices.
Implementation Method 2
the active material layer is manufactured using a low-pressure chemical vapor deposition method
Data Source
AI summary
To provide a power storage device having excellent charge/discharge cycle characteristics and a high charge/discharge capacity. The following electrode is used as an electrode of a power storage device: an electrode including a current collector and an active material layer provided over the current collector. The active material layer includes a plurality of whisker-like active material bodies. Each of the plurality of whisker-like active material bodies includes at least a core and an outer shell provided to cover the core. The outer shell is amorphous, and a portion between the current collector and the core of the active material bodies is amorphous. Note that a metal layer may be provided instead of the current collector, the active material bodies do not necessarily have to include the core, and a mixed layer may be provided between the current collector and the active material layer.