Silicon-Carbon Anode Structure to Prevent Electrode Layer Peeling
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high efficiency and capacity due to the structural instability of irreversible additives, which lead to oxygen gas generation and reduced dispersibility in the positive electrode slurry, affecting charging and discharging efficiency and safety.
Innovation Solution
A negative electrode for lithium secondary batteries is developed, comprising a carbon material and silicon particles with controlled particle sizes, where the silicon content is limited to 40 wt% or less, and the carbon material is used as a matrix to uniformly disperse silicon particles, enhancing dispersibility and electrical conductivity while minimizing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high content of irreversible additive is used in the positive electrode to increase capacity, then the capacity increases, but the structural instability causes oxygen gas generation and reduces charging/discharging efficiency and safety
Solution Approach 1:
The patent extracts the problematic irreversible additive from the positive electrode and relocates it to the negative electrode. By placing the irreversible additive (silicon material) in the negative electrode where it can undergo controlled irreversible reactions without generating harmful oxygen gas, the patent resolves the contradiction between increasing capacity and maintaining safety/efficiency.
Solution Approach 2:
The patent creates a composite negative electrode active material comprising carbon material and silicon material. This composite structure allows the silicon to provide high capacity while the carbon matrix provides structural stability and prevents excessive expansion, thereby maintaining charging/discharging efficiency and safety while increasing overall capacity.
2Reliability
If a low content of irreversible additive (less than 5 wt%) is used to reduce irreversibility, then the irreversibility decreases, but the dispersibility in positive electrode slurry deteriorates and particle size scattering increases
Solution Approach 1:
The patent inverts the conventional approach by moving the irreversible additive from the positive electrode to the negative electrode. This inversion allows the use of higher silicon content (1-40 wt%) in the negative electrode without the dispersibility and oxygen generation problems that plague the positive electrode, thereby simultaneously improving irreversibility and maintaining compositional stability.
Solution Approach 2:
The patent creates a composite negative electrode active material with carbon material and silicon material where the carbon serves as a matrix to disperse the silicon particles. This composite structure ensures good dispersibility even at higher silicon contents (1-40 wt%), preventing particle size scattering and maintaining compositional stability during manufacturing.
3Quantity of substance
If silicon material is added to increase capacity, then the capacity increases, but the expansion and contraction causes peeling of the negative electrode mixture layer
Solution Approach 1:
The patent creates a composite structure where silicon particles (1-20 μm) are dispersed in a carbon material matrix. The carbon matrix accommodates the expansion and contraction of silicon during lithium insertion/extraction, preventing the mixture layer from peeling while maintaining good adhesion to the current collector. This composite approach allows higher silicon content (1-40 wt%) without compromising structural integrity.
Solution Approach 2:
The patent controls the particle size of silicon material within a specific range (1-20 μm) and limits the silicon content to 1-40 wt% of the total negative electrode active material. These parameter optimizations ensure that the silicon can expand and contract without causing excessive stress that would lead to peeling, while still providing high capacity.
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 solution improves the charging/discharging capacity and efficiency of the negative electrode, suppresses side reactions with the electrolyte, and prevents peeling of the negative electrode mixture layer due to expansion and contraction, resulting in enhanced battery performance and extended lifespan.
Implementation Method 1
the carbon material is used as a matrix to uniformly disperse silicon particles, enhancing dispersibility and electrical conductivity while minimizing side reactions
Implementation Method 2
prevents peeling of the negative electrode mixture layer due to expansion and contraction
Data Source
AI summary
The present disclosure relates to aA negative electrode for a lithium secondary battery and a lithium secondary battery including the same, wherein the negative electrode includes a negative electrode active material which contains a carbon material and a silicon material, contains Si in a specific content, and has a form and/or structure in which the size of each material is controlled so that it is possible to improve the charging/discharging capacity and efficiency of the negative electrode, suppress the side reaction between the negative electrode active material and the electrolyte during the charging and discharging while solving a problem of the negative electrode mixture layer peeling due to the expansion and contraction of the negative electrode active material. In addition, since the lithium secondary battery according to of the present technology includes a positive electrode containing a specific positive electrode active material and a positive electrode additive together with the negative electrode to further improve the initial charging/discharging efficiency and capacity of the battery, there is an advantage in that electrical performance of the battery is excellent.