Negative Electrode With High Hole Density Active Layer
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density and maintaining excellent cycle-life characteristics due to issues with lithium ion intercalation and deintercalation, particularly during rapid charge and discharge cycles, which can lead to swelling and shape deformation.
Innovation Solution
A negative electrode with a current collector and a negative active material layer featuring a high hole density of 90 pt/mm² or more, hole depths of 5 μm to 40 μm, and a pitch of 100 μm or less, along with an adhesive layer, enhances lithium ion intercalation and deintercalation, preventing material detachment and improving charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive polymer is inserted into micropores on the surface of the active material layer to provide adhesion function, then adhesion between electrode and separator is improved, but lithium ion paths are reduced and resistance increases
Solution Approach 1:
The patent utilizes a porous adhesive layer with controlled porosity (30-70%) and specific pore size (1-10 μm) to maintain adhesion while allowing lithium ion transport. The porous structure provides pathways for lithium ions to pass through the adhesive layer without significant resistance, resolving the contradiction between adhesion strength and ion transport efficiency.
Solution Approach 2:
The adhesive layer is designed with non-uniform properties: it has higher crosslinking density near the active material layer interface to ensure strong adhesion, while maintaining higher porosity in the bulk to facilitate lithium ion transport. This spatial variation in properties allows simultaneous optimization of adhesion and ion transport.
2Quantity of substance
If thick and high-density active material layer is formed to increase energy density, then energy capacity is improved, but swelling and shape deformation occur during charging and discharging
Solution Approach 1:
The thick active material layer is segmented into multiple thinner layers separated by adhesive layers. Each layer can expand and contract independently during charging and discharging, reducing overall swelling and preventing shape deformation while maintaining high energy density through the cumulative effect of multiple layers.
Solution Approach 2:
The adhesive layers act as flexible intermediate films between active material layers, accommodating volume changes during lithium ion insertion and extraction. These thin films provide mechanical flexibility that allows the electrode to maintain structural integrity while experiencing the necessary expansion and contraction for high-capacity operation.
3Reliability
If adhesive layer is added to prevent material detachment, then electrode integrity is improved, but device complexity increases
Solution Approach 1:
The adhesive layer is merged with the separator structure, where the separator itself provides adhesion function. This integration eliminates the need for a separate adhesive layer, maintaining electrode integrity while simplifying the overall device structure. The separator is designed with adhesive properties through specific material selection and surface treatment.
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 proposed design significantly improves the battery's energy density and cycle-life characteristics by ensuring uniform charging and discharging, reducing swelling, and maintaining electrode integrity during rapid charge and discharge cycles.
Implementation Method 1
a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same... a negative active material layer positioned on the current collector... capable of intercalating and deintercalating lithium ions
Implementation Method 2
generates electrical energy due to an oxidation and reduction reaction when lithium ions are intercalated and deintercalated into the positive electrode and the negative electrode
Implementation Method 3
an adhesive layer including a plurality of holes on the negative active material layer... attempts have been made to study a structure of the battery having an adhesion function to the interface between the electrode and the separator
Data Source
AI summary
A negative electrode for a rechargeable lithium and a rechargeable lithium battery, and the negative electrode includes a current collector and a negative active material layer positioned on the current collector, wherein the negative active material layer includes a plurality of holes at a hole density of about 90 pt/mm2 or more.