Silicon Anode Material Coating Structure for Stable Slurry and Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon as a negative electrode material face challenges such as cracking, electrolyte decomposition, and reduced cycle characteristics due to the expansion and contraction of the active material, leading to instability during mass production of the slurry and decreased battery capacity.
Innovation Solution
A negative electrode active material comprising silicon compound particles coated with an intermediate layer containing a Li compound different from Li silicate and/or a metal oxide/hydroxide, followed by an outermost carbon layer, to enhance Li diffusibility and conductivity, improving stability and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a negative electrode active material to improve battery capacity, then the battery capacity increases significantly, but the negative electrode active material becomes prone to cracking during charge-and-discharge
Solution Approach 1:
The patent applies composite materials by combining silicon particles with carbon materials (such as graphite, amorphous carbon, or carbon nanotubes) to form a composite negative electrode active material. The carbon component provides structural stability and prevents cracking while the silicon component delivers high capacity, thus resolving the contradiction between capacity improvement and cracking resistance
Solution Approach 2:
The patent employs a carbon coating layer as a flexible shell surrounding the silicon particles. This carbon shell accommodates the volume expansion and contraction of silicon during charge-and-discharge cycles, preventing surface cracking while maintaining electrical conductivity and enabling the high capacity of silicon to be realized
2Quantity of substance
If the negative electrode active material is used to improve battery capacity, then the reaction area increases, but the electrolyte liquid is consumed due to decomposition reactions
Solution Approach 1:
The carbon coating layer serves as an intermediary between the silicon particles and the electrolyte liquid. It allows ionic transport while preventing direct contact between the silicon surface and electrolyte, thereby suppressing decomposition reactions and electrolyte consumption while still enabling the high capacity of silicon to be utilized
3Quantity of substance
If a carbon material is disposed on the surface of silicon oxide particles to provide high battery capacity, then the conductivity improves, but the manufacturing complexity increases
Solution Approach 1:
The patent merges the functions of carbon coating (for conductivity and structural stability) and silicon oxide core (for capacity) into a single composite material structure. This integrated approach simplifies manufacturing compared to multi-step processes, as the carbon-silicon oxide composite can be prepared in one synthesis step while achieving both high capacity and good conductivity
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 proposed structure enhances Li diffusibility and conductivity, leading to improved initial efficiency, battery capacity, and stability during mass production, while maintaining sufficient cycle characteristics.
Implementation Method 1
enhance Li diffusibility
Implementation Method 2
enhance conductivity
Implementation Method 3
negative electrode active material involved in charge-and-discharge reactions
Data Source
AI summary
A negative electrode active material contains negative electrode active material particles, in which the negative electrode active material particles include silicon compound particles containing Li silicate, an intermediate layer coating a surface of the silicon compound particles, the intermediate layer containing a Li compound different from Li silicate, being adjacent to a portion of the surface of the silicon compound particles, and/or a metal oxide and/or a metal hydroxide, being adjacent to at least a portion of the surface of the silicon compound particles, and an outermost carbon layer coating the intermediate layer. The negative electrode active material can improve initial efficiency to increase battery capacity, and increase stability during the mass production of the slurry while realizing sufficient battery cycle characteristics.