Flaky Silicon Negative Electrode with Silicate Binder
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries, particularly lithium ion batteries, face challenges in maintaining cycle characteristics due to the expansion and contraction of silicon particles in the negative electrode, leading to stress, cracking, and decreased capacity over repeated charge and discharge cycles.
Innovation Solution
A negative electrode for non-aqueous electrolyte secondary batteries is developed, featuring a mixture layer with flaky silicon particles and a silicate binder, where the silicon particles are packed in the thickness direction to relax stress and the silicate provides stable bonding and lithium ion conductivity, enhancing cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative electrode active material to increase capacity, then battery capacity is improved, but cycle characteristics deteriorate due to expansion and contraction causing stress and cracking
Solution Approach 1:
The silicon particles are divided into flaky shapes with specific aspect ratios rather than using conventional spherical or irregular shapes. This segmentation approach allows the particles to expand and contract in a controlled manner along specific crystallographic directions, reducing internal stress and preventing cracking during charge-discharge cycles while maintaining high lithium ion capacity.
Solution Approach 2:
The invention changes the shape parameter of silicon particles from spherical/irregular to flaky with controlled aspect ratios. This parameter change enables the silicon to accommodate volume expansion during lithiation by orienting the flaky structure appropriately, thereby improving cycle characteristics while preserving the high capacity benefit of silicon.
2Reliability
If flaky silicon particles are used to relax stress, then cycle characteristics are improved, but manufacturing complexity increases due to specific particle shape requirements
Solution Approach 1:
The invention specifies particular parameter ranges for the flaky silicon particles (aspect ratio between 2-10, thickness 1-10 μm) that can be achieved through conventional particle processing techniques. By defining these specific parameter ranges, the patent balances the need for stress relaxation during cycling with the practical constraints of manufacturing flaky-shaped particles at scale.
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 significantly improves the cycle characteristics of non-aqueous electrolyte secondary batteries by reducing stress on silicon particles, suppressing cracking, and maintaining lithium ion absorption and release efficiency, thereby extending battery life and performance.
Implementation Method 1
the binder includes a silicate
Implementation Method 2
a negative electrode active material capable of electrochemically absorbing and releasing lithium ions
Implementation Method 3
the silicon particles are packed in the thickness direction to relax stress
Data Source
AI summary
A negative electrode for a non-aqueous electrolyte secondary battery includes a negative electrode current collector, and a negative electrode mixture layer supported on the negative electrode current collector. The negative electrode mixture layer includes a negative electrode active material capable of electrochemically absorbing and releasing lithium ions, a binder, and a conductive agent. The negative electrode active material includes flaky silicon particles, and the binder includes a silicate.