Silicon-Carbon Anode Layering for Battery Capacity and Cycle Life
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in increasing the capacity and cycle characteristics due to the deterioration of silicon-containing materials when the utilization rate of the negative electrode is enhanced, leading to a decrease in open-circuit potential and accelerated material degradation.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a negative electrode with a mixture layer divided into two regions, where the first region near the surface contains a high-stability silicon oxide composite material with small Si particles and the second region near the current collector contains a lithium-ion conductive composite material, optimizing the mass ratios of these materials to maintain a stable open-circuit potential and suppress material deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the utilization rate of the negative electrode is increased to increase battery capacity, then the battery capacity increases, but the open-circuit potential decreases to 70 mV or less and the Si-containing material deteriorates
Solution Approach 1:
The negative electrode mixture layer is divided into a first region (surface side, T/2 thickness) and a second region (current collector side, T/2 thickness). The first composite material is preferentially placed in the first region while the second composite material is preferentially placed in the second region, creating a segmented structure that addresses different functional requirements in different zones of the electrode.
Solution Approach 2:
Different composite materials are strategically distributed to different regions of the negative electrode based on local functional requirements. The first composite material with higher stability is concentrated in the surface region where it can maintain open-circuit potential, while the second composite material is concentrated in the deeper region near the current collector.
2Use of energy by moving object
If deep charging is performed on Si to increase capacity utilization, then the open-circuit potential decreases to 70 mV or less, but the crystal region of Si reacts with lithium and accelerates material deterioration
Solution Approach 1:
The first composite material acts as an intermediary between the electrolyte and the second composite material. By placing the more stable first composite material in the surface region (first region), it serves as a protective layer that mediates the interaction between lithium ions and the Si-containing materials, reducing direct harmful reactions while still allowing capacity utilization.
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 configuration improves the cycle characteristics and capacity of the battery by utilizing the high-stability first composite material preferentially and minimizing the deterioration of the second composite material, resulting in enhanced charge and discharge efficiency and prolonged battery life.
Implementation Method 1
the use of silicon (Si) containing materials alloying with lithium is expected as a negative electrode active material with a high theoretical capacity density
Data Source
AI summary
A non-aqueous electrolyte secondary battery, wherein a negative electrode includes a negative electrode mixture layer having a thickness T and a negative electrode current collector, the negative electrode active material includes carbon and Si-containing materials, wherein when the negative electrode mixture layer is divided into a first region having a thickness of T/2 on the surface side of the negative electrode and a second region having a thickness of T/2 on the negative electrode collector side, a mass ratio of the first to the second composite material contained in the first region is >1, a mass ratio of the first composite to the second composite material contained in the second region is <1, and, in a fully charged condition, an open circuit potential of the negative electrode is 0 V or more and 70 mV or less with respect to a lithium metal.