Silicon Anode Cladding with Carbon and Sulfur for Longer Cycle Life
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Solution Overview
Problem
Existing silicon negative electrode active materials for secondary batteries face challenges in energy density and cycle life due to volume expansion and low conductivity, necessitating improved performance.
Innovation Solution
A negative electrode active material is developed comprising a silicon inner core clad with a carbon-containing layer and an elemental sulfur layer, which enhances conductivity and ion-conducting performance, forming an artificial Solid Electrolyte Interphase (SEI) film to protect the silicon surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon negative electrode active materials are used to achieve high theoretical specific capacity, then energy density is improved, but volume expansion occurs during cycling which reduces cycle life
Solution Approach 1:
The patent applies nested structure by placing silicon inner core inside a carbon-containing layer, which is in turn enclosed by an elemental sulfur layer. This multi-layer nested configuration allows the silicon core to expand and contract during lithium insertion/extraction while being constrained and protected by the surrounding layers, thereby maintaining high energy density from the silicon while improving cycle life through structural stability.
Solution Approach 2:
The patent creates a composite material system consisting of silicon inner core, carbon-containing layer, and elemental sulfur layer. This composite structure combines the high capacity advantage of silicon with the structural stability and conductivity benefits of carbon and sulfur, resolving the contradiction between achieving high energy density and maintaining long cycle life.
2Use of energy by moving object
If silicon negative electrode active materials are used to achieve high theoretical specific capacity, then energy density is improved, but conductivity remains low which increases impedance
Solution Approach 1:
The patent constructs a composite material where silicon inner core is combined with carbon-containing layer and elemental sulfur layer. The carbon and sulfur components provide excellent electrical conductivity that compensates for the low conductivity of pure silicon, thereby reducing impedance while maintaining the high energy density contribution from the silicon core.
Solution Approach 2:
The carbon-containing layer and elemental sulfur layer act as intermediary substances between the silicon inner core and the electrolyte. These intermediary layers improve overall conductivity and facilitate charge transfer, thereby reducing impedance while allowing the silicon core to maintain its high capacity function.
3Use of energy by moving object
If silicon negative electrode active materials are used to achieve high theoretical specific capacity, then energy density is improved, but the silicon surface is damaged by electrolyte which shortens cycle life
Solution Approach 1:
The patent uses nested structure with silicon inner core protected by carbon-containing layer and elemental sulfur layer. This nested configuration creates a protective barrier that shields the silicon surface from direct contact with electrolyte, preventing electrolyte damage while allowing the silicon to deliver its high energy density potential.
Solution Approach 2:
The carbon-containing layer and elemental sulfur layer serve as intermediary protective barriers between the silicon inner core and the electrolyte. These intermediary layers prevent harmful electrolyte components from directly attacking the silicon surface, thereby preserving the silicon structure and extending cycle life while maintaining high energy density.
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 Si/C/S composite system increases energy density and prolongs cycle life by buffering volume changes, improving conductivity, and preventing electrolyte damage, leading to enhanced lithium storage capacity and reduced impedance.
Implementation Method 1
forming an artificial Solid Electrolyte Interphase (SEI) film to protect the silicon surface
Implementation Method 2
buffering volume changes
Implementation Method 3
improving conductivity
Data Source
AI summary
Provided are a negative electrode active material and a preparation method thereof, as well as a secondary battery having the same, and a battery module, a battery pack and an electrical apparatus. The negative electrode active material of the present application comprises: a silicon inner core; a first cladding layer clad on the surface of the silicon inner core, wherein the first cladding layer is a carbon-containing layer; and a second cladding layer clad on the surface of the first cladding layer, wherein the second cladding layer is an elemental sulfur layer. By using the negative electrode active material of the present application, the energy density of the secondary battery can be improved, and the cycle life can be prolonged.