Silicon Anode Composition With Planar-Linear Conductive Network
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Solution Overview
Problem
Lithium secondary batteries using silicon-based active materials face challenges with volume expansion during charging and discharging, leading to conductive path disconnection and reduced battery performance, and existing conductive materials either fail to provide sufficient cycle performance or increase slurry viscosity and gas generation at high temperatures.
Innovation Solution
A negative electrode composition incorporating a silicon-based active material with a crystal grain size of 200 nm or less, combined with planar and linear conductive materials, which improves electrical connectivity and prevents electrical isolation, thereby enhancing the life and energy density of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase capacity, then discharge capacity is improved, but volume expansion occurs during charging leading to conductive path disconnection
Solution Approach 1:
The patent uses a composite material system consisting of silicon-based active material particles combined with conductive material particles. The conductive material forms a network that maintains electrical connectivity even when silicon particles undergo volume expansion during charging, thus preventing conductive path disconnection while preserving high discharge capacity.
Solution Approach 2:
The conductive material acts as an intermediary between silicon-based active material particles. It forms a conductive network that bridges the silicon particles, ensuring continuous electrical pathways are maintained during volume expansion and contraction cycles, thereby preventing isolation of active material particles.
2Reliability
If particulate conductive material is used to prevent conductive path disconnection, then cycle performance is improved, but slurry viscosity increases and gas generation occurs at high temperatures
Solution Approach 1:
The patent changes the particle size parameter of the conductive material to have a specific surface area of 1 m²/g or less. This parameter change reduces the conductive material's specific surface area, which in turn reduces slurry viscosity and minimizes gas generation at high temperatures while still providing sufficient conductive network formation for improved cycle performance.
3Object-generated harmful factors
If small amount of particulate conductive material is used, then gas generation is reduced, but sufficient cycle performance cannot be achieved due to excessive swelling
Solution Approach 1:
The patent optimizes the specific surface area parameter of the conductive material to be 1 m²/g or less. This allows using a smaller amount of conductive material that still forms an effective conductive network, thereby reducing gas generation while achieving sufficient cycle performance despite silicon swelling.
Solution Approach 2:
The patent creates a composite structure where conductive material particles with optimized surface area properties work synergistically with silicon-based active material particles. This composite approach enables effective conductive network formation with reduced conductive material content, minimizing gas generation while maintaining cycle performance.
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 effectively suppresses volume expansion, maintains battery performance, and reduces gas generation at high temperatures, resulting in improved cycle stability and energy density without the need for particulate conductive materials.
Implementation Method 1
The negative electrode includes a negative electrode active material for intercalating and deintercalating lithium ions to and from the positive electrode
Data Source
AI summary
The present disclosure relates to a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode. The negative electrode composition can include a silicon-based active material, a negative electrode conductive material, and a negative electrode binder, wherein the silicon-based active material comprises 70 parts by weight or more of SiOx (x=0) based on 100 parts by weight of the silicon-based active material, and optionally comprises SiOx (0<x<2), wherein the silicon-based active material has a crystal grain size of 200 nm or less, and wherein the negative electrode conductive material comprises a planar conductive material and a linear conductive material.