Wire-Type Anode with Graphite Buffer Layer for Secondary Batteries
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Solution Overview
Problem
Secondary batteries face challenges with flexible cable-type designs prone to short circuits due to external impacts and electrode expansion issues, and metal-based anode active materials hinder lithium ion diffusion, restricting battery capacity.
Innovation Solution
An anode design featuring a wire-type current collector with a metal-based anode active material layer and a graphite-based composite layer, including a conductive layer, which enhances electrochemical reactivity and stress resistance by using a mixture of graphite, conductive materials, and polymer binders to facilitate lithium ion diffusion and prevent material isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a metal-based anode active material layer is made thick to increase battery capacity, then the capacity increases, but lithium ion diffusion becomes difficult and capacity is substantially restricted
Solution Approach 1:
The anode active material layer is divided into two distinct layers: a metal-based anode active material layer (containing Si, Sn, or their alloys) and a graphite-based anode composite layer. This segmentation allows each layer to perform its specialized function - the metal-based layer provides high capacity while the graphite-based layer facilitates lithium ion diffusion, resolving the contradiction between capacity and ion diffusion rate.
Solution Approach 2:
The invention uses a composite structure combining metal-based active materials (Si, Sn, or their alloys) with graphite-based active materials in a layered configuration. This composite material approach leverages the high capacity of metal-based materials while incorporating the excellent lithium ion diffusion properties of graphite, thereby achieving both high capacity and fast ion diffusion.
2Quantity of substance
If Si or Sn is used as anode active material to increase capacity, then the capacity increases, but the active material may peel off due to expansion and shrinkage during charging and discharging
Solution Approach 1:
The invention creates a composite anode structure where metal-based active materials (Si, Sn, or their alloys) are combined with graphite-based active materials. The graphite component provides structural stability and accommodates the expansion and shrinkage of the metal-based material during lithium insertion and extraction, preventing peeling while maintaining high capacity.
Solution Approach 2:
The graphite-based anode composite layer contains porous structures that can accommodate the volume expansion of metal-based active materials during charging. This porous architecture provides buffer space for expansion and contraction cycles, maintaining electrode integrity and preventing material peeling while preserving high capacity.
3Adaptability or versatility
If a cable-type secondary battery structure is used to achieve flexible shapes, then adaptability increases, but the battery becomes prone to short circuits due to external physical impact and twist
Solution Approach 1:
The invention employs a flexible pouch-shaped casing made of aluminum laminate sheet that encapsulates the electrode assembly. This flexible shell provides mechanical protection against external physical impacts and twists while maintaining the cable-type battery's shape adaptability for various mobile device configurations, thereby improving reliability without sacrificing versatility.
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 anode design improves battery capacity and energy density by buffering volume expansion, enhancing lithium ion transfer, and reducing side reactions, while maintaining high energy density and stability against mechanical stress.
Implementation Method 1
it is difficult for lithium ions to diffuse in the anode active material layer, thereby substantially restricting the capacity of batteries
Implementation Method 2
the active material may peel off due to the expansion and shrinkage of electrodes caused by the repeated charging and discharging
Data Source
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AI summary
The present invention relates to an anode for a secondary battery, comprising: a wire-type current collector; a metal-based anode active material layer formed on the surface of the wire-type current collector, and comprising a metallic active material; and a graphite-based anode composite layer formed on the surface of the metal-based anode active material layer, and comprising a mixture of a graphite-based active material, a conductive material and a first polymer binder. The anode of the present invention has the metal-based anode active material layer together with the graphite-based anode composite layer acting as a buffer, thereby preventing the metallic active material from being isolated or released even if excessive volume expansion occurs during charging and discharging processes. Also, the graphite-based anode composite layer has good affinity with an organic electrolyte solution to compensate the defect of the metallic active material having low affinity with an organic electrolyte solution.