Porous Silicon-Carbon Anode Composition for High-Loading Li-Ion Cells
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Solution Overview
Problem
Existing rechargeable batteries face challenges in achieving high capacity loading without compromising electrode performance, particularly in terms of capacity, fast charging, and long cycle stability, due to unclear optimal composite formulations and processing methods for carbon-based composite particles.
Innovation Solution
A lithium-ion battery anode composition is developed using a porous composite particle comprising carbon and silicon, characterized by specific domain sizes and ratios derived from atomic pair distribution functions, with a silicon-to-carbon weight ratio ranging from 5:1 to 1:5, and a Brunauer-Emmett-Teller specific surface area between 1 to 40 m2/g, enhancing electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher capacity loading is used in battery electrodes, then battery cell energy density increases, but electrode performance deteriorates (poor cycling stability, high resistance)
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the center contains silicon particles (high capacity) and the outer shell contains porous carbon material (conductivity and stability). This spatial differentiation allows different regions to perform different functions: the silicon core provides high capacity loading while the carbon shell maintains electrode performance, cycling stability, and electrical conductivity even at high capacity loadings up to 16 mAh/cm2.
Solution Approach 2:
The patent uses composite materials by combining silicon particles with porous carbon material to form a core-shell composite structure. This composite approach allows the electrode to simultaneously achieve high capacity loading from silicon and good performance characteristics from the carbon shell, resolving the contradiction between quantity and reliability.
2Reliability
If conductive carbon is distributed within the bulk of composite particles, then charge storage performance improves, but optimal formulation and processing methods remain unclear
Solution Approach 1:
The patent applies segmentation by dividing the composite particle into distinct functional zones: a central core region containing silicon particles and an outer shell region containing porous carbon material. This segmentation provides clarity in formulation by assigning specific materials to specific regions, making the composite structure easier to design and process while achieving good charge storage performance.
Solution Approach 2:
The patent implements local quality by placing conductive carbon specifically in the outer shell region rather than uniformly throughout the bulk. This localized distribution optimizes electrical conductivity at the particle surface where electrochemical reactions occur, while simplifying the overall formulation approach by confining carbon to a specific region.
3Quantity of substance
If electrode capacity loading becomes moderate to high, then energy density increases, but electrode performance becomes particularly poor (cycling stability, resistance)
Solution Approach 1:
The patent applies beforehand cushioning by pre-coating silicon particles with a porous carbon shell before assembling the electrode. This protective carbon shell is formed in advance to cushion and accommodate the significant volume expansion of silicon during lithiation, preventing particle fracture and maintaining electrode integrity even at high capacity loadings, thereby preserving cycling stability and performance.
Solution Approach 2:
The patent uses composite materials to create a core-shell structure where silicon particles are embedded in a porous carbon matrix. This composite structure allows the electrode to achieve high capacity loading while the carbon component maintains electrical conductivity and structural stability, preventing performance degradation at high loadings.
Data Source
AI summary
In an aspect, a lithium-ion battery anode composition comprises a porous composite particle comprising carbon (C) and an active material comprising silicon (Si), wherein the carbon is characterized by a domain size (r), as estimated from an atomic pair distribution function G(r) obtained from a synchrotron x-ray diffraction measurement of the porous composite particle, ranging from around 10 Å (1 nm) to around 60 Å (6 nm). In a further aspect, a carbon material for use in making an anode composition for use in a Li-ion battery is characterized by a domain size (r), as estimated from an atomic pair distribution function G(r) obtained from a synchrotron x-ray diffraction measurement of the carbon material, ranging from around 10 Å (1 nm) to around 60 Å (6 nm).