Binary Lithium Additive in Dense Carbon Matrix for Li-Ion Conductivity
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Solution Overview
Problem
Current cathode lithium-supplementing materials for lithium-ion batteries face challenges such as low electronic and ion conductivity, poor stability, and difficulty in de-intercalating lithium during charging, leading to reduced capacity and storage stability.
Innovation Solution
A binary lithium-supplementing additive comprising a carbon matrix with a dense carbon layer and dispersed binary lithium material (LiaXb) is developed, where 1≤a≤3 and 1≤b≤3, and X is F, S, N, B, P, or Se, with a porosity of 0.1%-1% and a weight content of 40 wt. %-80 wt. %, forming a pomegranate-like structure for enhanced conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pure lithium-supplementing materials such as LiF are used, then lithium content is high, but electronic conductivity and ion conductivity are low, and de-intercalation during charging is difficult
Solution Approach 1:
The patent uses composite materials by combining lithium-containing compounds (such as LiF, Li2SiO3, Li2SiO2N) with conductive carbon materials (graphite, amorphous carbon, conductive polymers). This composite structure maintains high lithium content while the carbon component provides electronic conductivity pathways and facilitates lithium de-intercalation during charging, resolving the contradiction between lithium content and conductivity performance
Solution Approach 2:
The conductive carbon material acts as an intermediary between the lithium-containing compounds and the electrolyte. It mediates the charge transfer process by providing electron conduction pathways and facilitating lithium ion extraction, enabling the lithium-supplementing material to function effectively without requiring the lithium compound itself to have high electronic conductivity
2Quantity of substance
If lithium-supplementing components are loaded in porous carbon material, then lithium distribution can be improved, but molten lithium metal is difficult to uniformly load into pores, and after reaction with gas, particles become large with long migration distance
Solution Approach 1:
The patent changes the physical state parameter of lithium from molten metal to lithium-containing compounds (such as LiF, Li2SiO3, Li2SiO2N) that can be processed in solid or solution state. This parameter change enables uniform distribution within carbon matrix pores without the handling difficulties of molten lithium, and prevents particle agglomeration that occurs when molten lithium reacts with gas
Solution Approach 2:
The patent creates local quality differences by using different types of carbon materials (graphite, amorphous carbon, conductive polymers) with different pore structures and conductivities in different regions of the composite. This allows optimized lithium distribution and conduction pathways while maintaining manufacturability, as the local carbon structure can be tailored to match the lithium compound placement
3Reliability
If elemental metal particles are dispersed in lithium-supplementing material, then conductivity can be improved, but lithium element and CoF3 have high viscosity under melting, making uniform mixing difficult
Solution Approach 1:
The patent changes the processing state from molten metal mixing to solid-state or solution-based mixing of lithium-containing compounds with carbon materials. This parameter change eliminates the viscosity issues of molten lithium and CoF3, enabling uniform mixing while still achieving good conductivity through the carbon network structure
Solution Approach 2:
The patent uses carbon materials (which are abundant and inexpensive) as the primary conductive component rather than relying on expensive metal particles. The carbon matrix provides sufficient conductivity while being easier to mix uniformly with lithium-containing compounds, sacrificing the superior conductivity of metal particles for the benefit of manufacturing ease and cost
4Reliability
If carbon source is carbonized at high temperature during in-situ coating, then carbon matrix forms, but carbon source reacts with lithium source to form non-electrochemically active lithium carbonate
Solution Approach 1:
The patent applies preliminary action by pre-mixing the lithium-containing compounds with the carbon source before carbonization. This ensures that the lithium compounds are already positioned within or on the carbon matrix structure before the high-temperature treatment, so that when carbonization occurs, the lithium is protected from reacting with external carbon to form inactive lithium carbonate, as the carbon is already in its final matrix form
Data Source
AI summary
A binary lithium-supplementing additive, including: a carbon matrix and a binary lithium-supplementing material dispersed in the carbon matrix. At least a carbon layer on a surface of the carbon matrix is a dense carbon layer, and the binary lithium-supplementing material has a molecular formula of LiaXb, in which, 1≤a≤3, 1≤b≤3, and X is any one selected from F, S, N, B, P, O, and Se. The binary lithium-supplementing material contained in the binary lithium-supplementing additive is rich in lithium, thereby maintaining the abundance of lithium ions in the battery system and improving the first charge-discharge efficiency and overall electrochemical performance of the battery. The binary lithium-supplementing material is dispersed in the carbon matrix to ensure uniform dispersion and stability of the binary lithium-supplementing material, so as to achieve a stable lithium-supplementing effect.