Layered Silicon-Graphite Anode Binders for Stable Lithium Cells
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Solution Overview
Problem
Lithium secondary batteries face challenges in mechanical stability and lifespan due to mechanical deformation caused by changes in anode binders, which affect the battery's capacity and output.
Innovation Solution
A lithium secondary battery design featuring a multi-layered anode active material structure with a first layer using a styrene-butadiene rubber (SBR) binder and a second layer using an acryl-based binder, along with a mixture of silicon and graphite-based active materials, to enhance adhesion and suppress electrode expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the anode binder is changed to accommodate new anode materials, then the battery capacity and output can be improved, but mechanical deformation of the anode occurs and stability deteriorates
Solution Approach 1:
The patent divides the anode binder system into multiple functional layers: a first binder layer (SBR-based) providing mechanical stability and adhesion to the current collector, and a second binder layer (acryl-based) enabling high capacity of silicon-based materials. This segmentation allows each binder to optimize its function without compromising overall anode stability.
Solution Approach 2:
The patent uses composite binder materials combining different polymer types (SBR and acryl-based binders) with complementary properties. The SBR binder provides elasticity and adhesion, while the acryl-based binder offers strong bonding to silicon materials, creating a composite system that achieves both high capacity and mechanical stability.
2Productivity
If silicon-based active material is used to increase capacity, then the battery output is improved, but electrode expansion and mechanical deformation occur
Solution Approach 1:
The patent applies different binder properties to different regions and functions: the SBR binder layer provides mechanical support and volume accommodation near the current collector, while the acryl-based binder layer provides strong adhesion in the region of maximum silicon material concentration. This local differentiation of binder properties allows the electrode to accommodate silicon expansion while maintaining structural integrity.
Solution Approach 2:
The patent designs the binder system to anticipate and accommodate the expansion of silicon-based materials during lithium insertion. The SBR binder's elastic properties and the layered structure provide pre-configured volume accommodation space, preventing mechanical deformation before it occurs during battery cycling.
3Device complexity
If a single binder type is used to simplify the structure, then the device complexity is reduced, but adhesion strength and mechanical stability are compromised
Solution Approach 1:
The patent segments the binder function into distinct layers with specialized roles. The first layer uses SBR binder optimized for adhesion to the current collector and providing mechanical stability, while the second layer uses acryl-based binder optimized for bonding to silicon-based active materials. This functional segmentation achieves superior overall adhesion strength compared to a single binder system.
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 improves mechanical and chemical stability, prevents electrode wrinkling, and enhances capacity and output by maintaining adhesion strength and controlling silicon-based active material expansion.
Implementation Method 1
a first anode binder containing a styrene-butadiene-based rubber (SBR) binder
Implementation Method 2
a second anode binder containing an acryl-based binder
Implementation Method 3
Each of the first anode active material and the second anode active material includes a silicon-based active material... to suppress electrode expansion
Data Source
Figure 1~2
AI summary
According to the present inventive concept, a lithium secondary battery includes a cathode, a separator, and an anode including an anode current collector and an anode active material layer formed on the anode current collector and facing the cathode with the separator interposed therebetween. The anode active material layer includes a first anode active material layer formed on the anode current collector and including a first anode active material and a first anode binder containing a styrenebutadiene-based rubber (SBR) binder and a second anode active material layer formed on the first anode active material layer and including a second anode active material and a second anode binder containing a acryl-based binder. Each of the first anode active material and the second anode active material includes a silicon-based active material and a graphite-based material and contains 2 to 9.5 parts by weight of silicon with respect to the 100 part by weight of the graphite-based active material.