Secondary Battery Activation Pressing for Stable Silicon SEI
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Solution Overview
Problem
The challenge is to stabilize the formation of a solid electrolyte interface (SEI) layer in secondary batteries using silicon-based active materials, which are prone to volume expansion and contraction during charging and discharging, leading to cracks, gas production, and deteriorated lifespan characteristics.
Innovation Solution
A method involving the formation of a secondary battery structure with a silicon-based negative electrode, followed by a pressing process at 1.5 MPa to 3.5 MPa during activation through charging and discharging, to control volume expansion and maintain appropriate porosity for stable SEI layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are used in the negative electrode, then the capacity and energy density are significantly improved, but volume expansion occurs during charging and discharging causing active material particles to crack and lifespan characteristics to deteriorate
Solution Approach 1:
A silane-based coating layer is formed on the surface of the silicon-based active material particles. This coating layer acts as a flexible protective shell that can accommodate volume expansion during lithiation while preventing particle cracking and maintaining structural integrity during delithiation, thereby improving lifespan characteristics while preserving high capacity
Solution Approach 2:
The negative electrode uses a composite structure combining silicon-based active material particles with a silane-based coating layer. This composite material approach leverages the high capacity of silicon while the silane coating provides structural stability and prevents degradation, resolving the contradiction between high capacity and long lifespan
2Quantity of substance
If silicon-based active materials are used in the negative electrode, then the energy density is improved, but volume expansion causes active material particles to crack and contact between particles to be broken
Solution Approach 1:
The silane-based coating layer forms a flexible protective shell around silicon-based active material particles. This shell accommodates volume expansion during charging (lithiation) without causing particle cracking, and maintains particle integrity during discharging (delithiation), thereby preserving both high energy density and particle strength
Solution Approach 2:
The silane-based coating layer is formed beforehand on the surface of silicon-based active material particles to provide cushioning against volume expansion stress. This pre-formed protective layer prevents particle cracking before it can occur, maintaining particle integrity throughout charge-discharge cycles while preserving high energy density
3Stability of the object's composition
If a new surface is continuously generated due to volume expansion and contraction, then the SEI layer formation reaction continuously occurs, but gas production increases and local resistance increases due to excessive SEI layer formation
Solution Approach 1:
The silane-based coating layer acts as a stable protective shell that prevents continuous generation of new surfaces during volume expansion and contraction. By maintaining surface stability, the coating layer prevents continuous SEI layer formation reactions, thereby reducing gas production and avoiding excessive local resistance while still allowing necessary SEI layer formation for stable lithium ion passage
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 suppresses volume expansion, prevents cracking, minimizes gas production, and maintains electrolyte presence, thereby improving the lifespan characteristics of the battery.
Implementation Method 1
the silicon-based active materials have not been commonly used due to having a problem in which volume expansion occurs due to charging and discharging
Implementation Method 2
the electrolyte solution reacts with a lithium salt on a surface of the negative electrode to produce compounds such as Li2Co3, Li2O, LiOH, and the like. These compounds form a kind of passivation layer on the surface of the negative electrode, and the passivation layer is referred to as a solid electrolyte interface layer
Implementation Method 3
Through the activation process, lithium is intercalated into a negative electrode comprised in the secondary battery
Data Source
AI summary
The present invention relates to a method of manufacturing a secondary battery comprising the steps of: forming a secondary battery structure comprising an electrode assembly comprising a negative electrode, a positive electrode, and a separator and an electrolyte solution, and activating the secondary battery structure by charging and discharging for at least one cycle while pressing the secondary battery structure at 1.5 MPa to 3.5 MPa, wherein the negative electrode comprises a silicon-based active material.