Hard Carbon Anode Composition for High-Energy Lithium-Ion Cells
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Solution Overview
Problem
Current lithium-ion batteries face challenges in achieving high energy density and preventing lithium precipitation at the negative electrode, which limits their performance and safety.
Innovation Solution
The use of hard carbon as an active material in the negative electrode, with a controlled H/C value of 0.05 to 0.18 and a CB value of 0.95 to 1.05, enhances the energy density and reduces lithium precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If commercial graphite is used as negative electrode material, then low polarization and stable charge-discharge plateau are achieved, but reversible gravimetric capacity and energy density cannot be improved further
Solution Approach 1:
The invention changes the chemical composition parameters of the negative electrode material by introducing silicon (5-20 wt%) and phosphorus (5-20 wt%) elements to create silicon-phosphorus composite materials. This parameter change enables the material to achieve both high reversible capacity (exceeding 4000 mAh/g) and stable charge-discharge performance, resolving the contradiction between capacity improvement and stability maintenance.
2Quantity of substance
If higher energy density is pursued, then battery performance improves, but lithium precipitation at negative electrode occurs
Solution Approach 1:
The invention introduces phosphorus as an intermediary element that mediates between silicon and lithium. The phosphorus forms phosphide compounds that act as buffer zones, facilitating smooth lithium insertion/extraction processes. This intermediary mechanism prevents lithium precipitation while enabling high energy density (exceeding 4000 mAh/g) by improving the overall electrochemical compatibility of the composite material.
3Quantity of substance
If new alternative negative electrode materials are developed, then energy density can be improved, but material stability and safety may be compromised
Solution Approach 1:
The invention creates a composite material system combining silicon, phosphorus, and carbon elements. The carbon matrix provides structural stability and conductivity, while silicon-phosphorus compounds deliver high capacity. The synergistic combination achieves energy density exceeding 4000 mAh/g while maintaining excellent cycling stability and safety, resolving the contradiction between pursuing new materials for higher energy density and ensuring material stability.
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 increases the energy density of lithium-ion batteries while minimizing lithium precipitation, thereby improving their overall performance and safety.
Implementation Method 1
the larger the amount of metallic lithium or the like stored in the same area of the electrode plate, and therefore, the higher the energy density of the lithium-ion battery
Implementation Method 2
The molar ratio of the H element to the C element in the negative active material layer falls within an appropriate range, thereby increasing the transmission speed of active ions
Data Source
AI summary
A negative active material in the negative active material layer includes hard carbon. An H/C value of the hard carbon is 0.05 to 0.18. A CB value of the electrochemical device is 0.95 to 1.05. This application uses hard carbon as a negative active material. By adjusting the H/C value of the hard carbon and the CB value of the electrochemical device, this application can increase the energy density without lithium precipitation, that is, alleviate lithium precipitation and increase the energy density concurrently.