Silicon Anode Pore Control for Battery Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon as an anode active material face significant declines in cycle characteristics due to increased surface area, leading to electrolyte decomposition and lithium inactivation, which reduces battery performance over frequent charge and discharge cycles.
Innovation Solution
The anode includes a silicon anode active material with a controlled pore structure, where the volumetric capacity of pores ranging from 3 nm to 50 nm is 0.2 cm3/g or less, measured by mercury porosimetry, and optionally includes an oxide-containing film or metal material to reduce reactivity and enhance adhesion, thereby improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is deposited as the anode active material by a vapor-phase method to increase surface area, then battery capacity is improved, but cycle characteristics easily decline due to electrolyte decomposition and lithium inactivation
Solution Approach 1:
The patent utilizes a porous anode current collector with controlled pore size (3-50 nm) and limited volumetric capacity (0.2 cm³/g or less) to provide high surface area for lithium insertion while restricting electrolyte penetration. This porous structure allows the silicon anode to maintain high capacity through increased reactive surface area while the controlled porosity prevents excessive electrolyte contact that would cause decomposition and capacity fade.
Solution Approach 2:
The patent creates a composite structure combining silicon anode material with a porous current collector substrate. This composite approach allows the silicon to provide high theoretical capacity (4199 mAh/g) while the porous current collector provides structural support and controls electrolyte interaction, achieving both high capacity and good cycle characteristics through material composition.
2Quantity of substance
If the surface area of the anode active material is increased to enhance capacity, then more lithium insertion sites are available, but electrolyte decomposition and lithium inactivation increase
Solution Approach 1:
The porous current collector with specifically controlled pore size (3-50 nm) and low volumetric capacity (0.2 cm³/g or less) provides extensive surface area for lithium insertion while the narrow pore dimensions limit electrolyte penetration depth. This creates high surface area-to-volume ratio that increases lithium insertion capacity while the restricted porosity reduces electrolyte contact, thereby minimizing decomposition reactions.
3Quantity of substance
If a porous structure is created to increase surface area, then battery capacity is enhanced, but the volumetric capacity of pores becomes too high leading to stability issues
Solution Approach 1:
The patent precisely controls the pore size parameter (3-50 nm) and volumetric capacity parameter (0.2 cm³/g or less) of the porous current collector to achieve optimal balance between surface area and stability. By adjusting these physical parameters within specific ranges, the patent maximizes surface area for lithium insertion while maintaining structural stability and preventing excessive electrolyte interaction that would compromise anode material stability.
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
This approach enhances the resistance of the anode active material to electrolyte decomposition during charge and discharge, leading to improved cycle characteristics and extended battery lifespan by reducing the surface area and increasing the stability of the anode material.
Implementation Method 1
a porous anode active material layer 22B arranged on the anode current collector 22A... including a pore group with a diameter ranging from 3 nm to 50 nm both inclusive
Data Source
AI summary
A battery capable of improving cycle characteristics is provided. An anode includes: an anode current collector, and an anode active material layer arranged on the anode current collector, in which the anode active material layer includes an anode active material including silicon (Si), and including a pore group with a diameter ranging from 3 nm to 50 nm both inclusive, and the volumetric capacity per unit weight of silicon of the pore group with a diameter ranging from 3 nm to 50 nm both inclusive is 0.2 cm3/g or less, the volumetric capacity being measured by mercury porosimetry using a mercury porosimeter.