Silicon-Graphite Composite Anode for Lithium Battery Capacity
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Solution Overview
Problem
Rechargeable lithium batteries face limitations in capacity, efficiency, and cycle life due to the low energy density of graphite-based negative active materials and the inefficiencies of oxide-based negative active materials.
Innovation Solution
Incorporating a silicon-based negative active material in the range of 3-20 wt% with a carbon-based material, and using a positive electrode with a combination of lithium cobalt-based and lithium nickel cobalt manganese-based oxides, optimized for charge and discharge efficiency, to enhance the battery's discharge profile and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If graphite is used as negative active material, then charge-discharge efficiency is improved, but capacity is limited due to low energy density
Solution Approach 1:
The patent uses a composite negative active material comprising graphite (70-97 wt%) and silicon oxide (3-30 wt%). Graphite provides high charge-discharge efficiency while silicon oxide contributes to increased capacity. The composite structure allows both materials to work synergistically, resolving the contradiction between efficiency and capacity.
2Quantity of substance
If oxide negative active material is used, then capacity is improved, but charge-discharge efficiency deteriorates
Solution Approach 1:
The patent creates a composite negative active material where silicon oxide (providing high capacity) is combined with graphite (providing high efficiency). The graphite component ensures efficient charge-discharge performance while the silicon oxide component increases overall capacity, thus resolving the contradiction between capacity and efficiency.
3Quantity of substance
If silicon-based negative active material is used to increase capacity, then battery swelling occurs due to reaction with electrolyte at high discharge voltage
Solution Approach 1:
The patent uses graphite as an intermediary material in the composite negative active material. Graphite acts as a buffer that reacts with the electrolyte in a controlled manner, preventing direct and excessive reaction between silicon oxide and electrolyte that would cause battery swelling. This intermediary approach allows silicon oxide to contribute to capacity while mitigating its harmful side effects.
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 solution results in a rechargeable lithium battery with improved capacity, efficiency, and cycle-life characteristics, balancing capacity and efficiency through the use of silicon-based and carbon-based materials, and optimizing the positive electrode composition.
Implementation Method 1
a lithium-transition element composite oxides being capable of intercalating lithium
Implementation Method 2
rechargeable lithium batteries use an organic electrolyte solution and have twice or more the discharge voltage than that of conventional batteries
Data Source
AI summary
In an aspect, a rechargeable lithium battery including a negative electrode including a silicon-based negative active material is disclosed.