Silicon-Graphite Negative Electrode Adhesion via N-O Coating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges with silicon-based active materials detaching from the negative electrode current collector due to high expansion and contraction during charging and discharging, limiting adhesion and cycle performance.
Innovation Solution
A negative electrode composition comprising a silicon-based active material and a carbon-based active material, with specific nitrogen (N) and oxygen (O) content ranges, improves adhesion and prevents expansion issues, using a mixture of silicon oxide and silicon-carbon composite with controlled N and O amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase capacity, then energy density is improved, but adhesion to current collector deteriorates due to high expansion and contraction
Solution Approach 1:
The patent uses a composite material system consisting of silicon-based active material particles coated with a carbon layer containing specific amounts of nitrogen and oxygen. This composite structure combines the high capacity of silicon with the adhesion benefits of carbon-containing functional groups, resolving the contradiction between capacity and adhesion.
Solution Approach 2:
The patent changes the chemical parameters of the carbon coating by controlling the nitrogen and oxygen content within specific ranges (N: 0.1-5.0 wt%, O: 0.1-5.0 wt%). This parameter optimization modifies the surface properties to enhance adhesion while maintaining the expansion-contraction characteristics of silicon.
2Quantity of substance
If silicon-based active material undergoes expansion and contraction during charging and discharging, then capacity is improved, but detachment from current collector occurs
Solution Approach 1:
The patent employs a thin carbon coating film containing nitrogen and oxygen functional groups that flexes with the silicon particles during expansion and contraction. This flexible coating maintains structural integrity and prevents detachment, allowing the silicon to undergo volume changes while maintaining stability.
Solution Approach 2:
The carbon coating with nitrogen and oxygen acts as an intermediary layer between the silicon-based active material and the current collector. This intermediary absorbs and distributes the mechanical stress from expansion and contraction, preventing direct detachment while maintaining electrical contact.
3Reliability
If graphite is used as negative electrode active material, then adhesion is maintained, but energy density is limited due to low capacity
Solution Approach 1:
The patent creates a composite material where silicon-based particles (providing high capacity) are coated with carbon containing nitrogen and oxygen (providing adhesion). This composite achieves both high capacity and good adhesion, overcoming the limitations of pure graphite.
Solution Approach 2:
The patent applies local quality modification by coating only the silicon particles with carbon containing specific nitrogen and oxygen content, rather than using uniform graphite throughout. This localized approach maintains adhesion at the critical particle-collector interface while maximizing capacity through silicon.
Data Source
AI summary
The present invention relates to a negative electrode composition and a negative electrode, a lithium secondary battery, a battery module, and a battery pack comprising same, the composition comprising a negative electrode active material comprising a silicon-based active material and a carbon-based active material, wherein the amount of silicon-based active material is greater than 0 parts by weight and less than or equal to 10 parts by weight based on 100 parts by weight of the total negative electrode active material, the carbon-based active material comprises natural graphite and has a total amount of N and O of at least 200 ppm to 2000 ppm based on 0.01 g of the natural graphite, and the silicon-based active material comprises at least one of a silicon-carbon composite and a silicon oxide, has a total amount of N and O of 0.7% to 3.3% based on 0.01 g of the silicon-carbon composite, and has a total amount of N and O of 30% to 32% based on 0.01 g of the silicon oxide.