Silicon Oxide Carbon Composite Negative Electrode for Battery Cycle Stability
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Solution Overview
Problem
Lithium ion secondary batteries face limitations in increasing capacity due to insufficient negative electrode capacity when using only carbon materials, necessitating the use of non-carbon materials like silicon or silicon oxide in combination with carbon to enhance performance.
Innovation Solution
A negative electrode active material comprising a mixture of carbon, first silicon oxide particles with a carbon layer, and second silicon oxide particles, where the mass ratio and discharge capacity ratios are specifically optimized to maintain effective charge/discharge cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If only carbon materials are used in the negative electrode, then the electrode structure is simple and manufacturing is easy, but the negative electrode capacity is insufficient
Solution Approach 1:
The patent applies composite materials by combining carbon materials with silicon oxide particles to create a negative electrode active material that achieves both high capacity and structural stability. The carbon material provides a stable framework while silicon oxide particles contribute to increased capacity through lithium insertion/extraction reactions.
2Quantity of substance
If non-carbon materials like silicon oxide are added to increase capacity, then the negative electrode capacity increases, but the charge/discharge cycle characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating a heterogeneous structure where silicon oxide particles are distributed within a carbon material matrix. The carbon material provides structural stability and conductivity in regions where silicon oxide undergoes volume changes, while silicon oxide particles provide high capacity in their local regions through lithium insertion/extraction reactions.
Solution Approach 2:
The patent uses composite materials combining carbon material and silicon oxide particles, where the carbon component maintains structural integrity during charge/discharge cycles while the silicon oxide component provides enhanced capacity. This composite structure prevents the deterioration of cycle characteristics that would occur with pure silicon oxide.
3Quantity of substance
If silicon oxide particles are used to enhance capacity, then the energy density increases, but the electrode structure stability decreases due to volume expansion
Solution Approach 1:
The patent applies the counterweight principle by using carbon material as a structural framework that counterbalances the volume expansion of silicon oxide particles during lithium insertion. The carbon matrix constrains the silicon oxide particles, preventing excessive expansion that would lead to electrode structure degradation while allowing the silicon oxide to contribute its high capacity.
Solution Approach 2:
The patent employs the flexible shell principle by using the carbon material as a flexible matrix that can accommodate the volume changes of silicon oxide particles. The carbon structure acts as a confining medium that maintains electrode integrity while allowing the silicon oxide to expand and contract during charge/discharge cycles.
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 optimized negative electrode active material maintains excellent charge/discharge cycle characteristics over a long period, preventing capacity degradation and ensuring efficient energy storage in lithium ion secondary batteries.
Implementation Method 1
a carbon layer that covers the surface of the first silicon oxide particle
Implementation Method 2
a first discharge capacity associated with the carbon material and the carbon particle of the second particle is referred to as CpC, and a second discharge capacity associated with the first silicon oxide particle of the first particles and the second silicon oxide particle of the second particles is referred to as CpSO
Data Source
AI summary
A negative electrode active material includes a carbon material; a plurality of first particles including a first silicon oxide particle and a carbon layer and a plurality of second particles including a carbon particle and a second silicon oxide particle, and when a first mass of the first silicon oxide particle per gram of the negative electrode active material is referred to as M1 gram, and a second mass of the second silicon oxide particle per gram of the negative electrode active material is referred to as M2 grams, 0.40≤M1/(M1+M2)≤0.85 is satisfied, and when a first discharge capacity associated with the carbon material and the carbon particle is referred to as CpC, and a second discharge capacity associated with the first silicon oxide particle and the second silicon oxide particle is referred to as CpSO, 0.15≤CpSO/(CpC+CpSO)≤0.5 is satisfied.