Silicon-Coated Carbon Electrode Material for Lithium-Ion Batteries
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Solution Overview
Problem
Rechargeable lithium batteries with metallic lithium negative electrodes face issues like dendrite formation and increased internal resistance due to side reactions, while graphite-based electrodes offer limited energy density and mechanical integrity problems with silicon-based electrodes.
Innovation Solution
A method involving carbon particles coated with metallic silicon, achieved by applying a silicon precursor and thermally decomposing it to form a composite material with a silicon shell on carbon particles, enhancing energy density and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If metallic lithium is used as negative electrode material, then energy density is improved, but dendrite formation and internal resistance increase occur
Solution Approach 1:
The patent introduces an intermediary layer comprising fluorinated cyclic carbonate and chain carbonate between the metallic lithium negative electrode and the electrolyte solution. This intermediary layer prevents direct contact and harmful interactions while allowing lithium ion transport, thereby maintaining high energy density without dendrite formation or excessive internal resistance increase.
2Reliability
If graphite-based negative electrode is used, then dendrite formation is prevented, but energy density is reduced
Solution Approach 1:
The patent uses fluorinated cyclic carbonate and chain carbonate as an intermediary layer that enables the use of metallic lithium (which has higher energy density than graphite) while preventing the harmful effects. The intermediary layer allows lithium ion transport while blocking direct harmful interactions, achieving both high energy density and dendrite prevention.
3Quantity of substance
If silicon particles are used as active material, then lithium ion storage capacity is improved, but mechanical integrity deteriorates due to volume change
Solution Approach 1:
The patent introduces fluorinated cyclic carbonate and chain carbonate as an intermediary buffer layer between the silicon particles and the electrolyte solution. This layer accommodates the volume changes of silicon during lithiation/delithiation cycles, preventing particle breakage while maintaining high lithium ion storage capacity.
Solution Approach 2:
The intermediary layer formed by fluorinated cyclic carbonate and chain carbonate acts as a flexible protective shell around silicon particles. This thin film layer can accommodate volume expansion and contraction during lithium ion insertion and extraction, maintaining mechanical integrity while enabling high capacity.
4Strength
If nanoparticulate silicon is used, then volume change is reduced, but electrolyte consumption increases due to large specific surface area
Solution Approach 1:
The patent changes the chemical composition parameters of the intermediary layer by using fluorinated cyclic carbonate and chain carbonate with specific molecular structures. This creates an SEI layer with lower lithium ion conductivity and better stability, reducing electrolyte consumption while maintaining volume stability of nanoparticulate silicon.
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 method produces electrodes with up to three times higher lithium-ion storage capacity and similar cycle stability to nanoparticulate silicon without the associated disadvantages, maintaining mechanical integrity and reducing internal resistance.
Implementation Method 1
The precursor is electrochemically reduced on the surface of the carbon particles... thermally decomposing it to form a composite material with a silicon shell on carbon particles
Implementation Method 2
The deposition takes place by means of a cyclic voltammetry method from a solution in which a halogen-containing silicon compound such as silicon tetrachloride is contained as a silicon precursor. This precursor is electrochemically reduced on the surface of the carbon particles.
Data Source
AI summary
The invention relates to a method for producing active material for the electrode of an electrochemical element, comprising the steps of (1) providing carbon particles, (2) applying a silicon precursor onto the surface of the carbon particle and (3) thermally breaking down the silicon precursor to form metal silicon. The invention furthermore relates to an electrochemical active material that can be produced according to a said method, to an electrode having said active material, and to an electrochemical element having at least one said electrode.