Double-Layer Battery Anode Structure for Silicon Expansion Control
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Solution Overview
Problem
Existing negative electrode materials for secondary batteries, particularly silicon-based materials, face challenges in maintaining charge/discharge efficiency and structural integrity due to high volume changes during cycling, limiting the capacity and performance of lithium secondary batteries.
Innovation Solution
A negative electrode with a two-layer structure comprising a first mixture layer of carbon material and silicon oxide, and a second mixture layer of carbon material and conductive carbon-based materials, optimized in weight ratios and thicknesses, to enhance conductivity and adhesion, thereby stabilizing the electrode during charge/discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material to increase capacity, then theoretical capacity increases 10 times compared to carbon-based material, but charge/discharge efficiency decreases to 80% and volume change rate increases to 300% or more causing conductive path disconnection
Solution Approach 1:
The patent uses a composite material structure where silicon oxide particles are embedded in a carbon matrix. This composite design combines the high capacity advantage of silicon (3.8 times that of graphite) with the structural stability and conductivity of carbon, achieving both high capacity and maintained charge/discharge efficiency without the severe volume expansion problems of pure silicon
Solution Approach 2:
The carbon matrix acts as a flexible shell surrounding the silicon oxide particles, accommodating volume changes during lithiation/delithiation cycles. This shell structure prevents conductive path disconnection and maintains structural integrity, solving the problem of conductive path breakdown due to 300%+ volume change in pure silicon
2Quantity of substance
If silicon-based material is used to achieve high capacity, then energy density increases, but volume change rate reaches 300% or more during charge/discharge causing structural deterioration
Solution Approach 1:
The silicon oxide-carbon composite structure provides structural stability while maintaining high energy density. The carbon matrix constrains silicon oxide volume expansion, preventing structural deterioration during repeated charge/discharge cycles while preserving the high capacity benefits
Solution Approach 2:
The carbon matrix serves as an intermediary between the silicon oxide particles and the electrolyte, mediating the volume changes. It absorbs and distributes mechanical stress, preventing direct structural failure of the silicon oxide and maintaining long-term structural integrity
3Quantity of substance
If silicon-based material is used to maximize capacity, then theoretical capacity reaches 10 times that of carbon-based material, but conductive path disconnects during continuous charge/discharge process
Solution Approach 1:
The conductive carbon matrix provides continuous conductive pathways throughout the electrode structure, ensuring electron transport even as silicon oxide particles expand and contract. This composite design maintains conductive path continuity while utilizing the high theoretical capacity of silicon oxide
Solution Approach 2:
The carbon shell surrounding each silicon oxide particle remains flexible and adherent during volume changes, preventing conductive path disconnection. This shell maintains electrical contact between silicon oxide particles and the external circuit throughout the charge/discharge process
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 double-layer structure improves charge/discharge efficiency and maintains structural integrity, enhancing the capacity and cycle life of the secondary battery by maintaining conductive paths and reducing material separation.
Implementation Method 1
the first mixture layer includes a first carbon material and a silicon oxide as a first active materials in a weight ratio of 90 to 99:1 to 10 and a first needle type carbon-based conductive material as a first conductive material
Implementation Method 2
a first mixture layer includes a first carbon material and a silicon oxide as a first active materials in a weight ratio of 90 to 99:1 to 10
Data Source
AI summary
The technology relates to a negative electrode for a secondary battery, and a secondary battery including same. The negative electrode comprises a composite material layer having a double-layer structure, but includes silicon oxide and carbon nanotubes in only one layer, such that it is possible to increase the capacity of a battery while preventing structural deterioration of the negative electrode due to changes in electrode volume during charging and discharging.