Negative Electrode Secondary Particles for Low-Resistance Battery Cycling
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Solution Overview
Problem
Conventional secondary batteries face challenges in achieving low resistance and improved cycle characteristics due to the crushing and cracking of negative electrode active material particles during charging and discharging, which is exacerbated by the need to balance pressing pressure to avoid material damage.
Innovation Solution
The use of active material secondary particles comprising negative electrode active material particles bonded together with perfluoropolyether, which helps absorb volume changes and reduces stress concentrations, thereby enhancing the structural integrity and conductivity of the negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative electrode mixture is pressed under high pressure to increase the filling ratio, then the resistance of the negative electrode is reduced, but the negative electrode active material may be crushed
Solution Approach 1:
The negative electrode active material is divided into primary particles (0.1-5.0 μm) that aggregate to form secondary particles (0.5-20.0 μm). This segmentation allows the material to achieve high filling ratio when pressed while the secondary particle structure prevents complete crushing of the active material, as the primary particles can rearrange within the secondary particle framework.
Solution Approach 2:
The invention creates a composite structure where multiple primary particles are aggregated into secondary particles with controlled morphology. This composite approach allows the negative electrode to achieve both high density (reduced resistance) and structural integrity (prevented crushing) by combining the benefits of fine particle filling with larger aggregate strength.
2Strength
If the negative electrode mixture is pressed under low pressure to avoid crushing of the negative electrode active material, then the filling ratio of the negative electrode decreases, but the resistance of the negative electrode is likely to increase
Solution Approach 1:
By segmenting the active material into primary particles that form secondary particles, the material can be pressed at lower pressures without crushing. The secondary particle structure provides a framework that allows density increase through particle rearrangement rather than particle compression, maintaining integrity while improving filling ratio.
Solution Approach 2:
The invention changes the particle size parameters by creating a bimodal distribution with primary particles (0.1-5.0 μm) and secondary particles (0.5-20.0 μm). This parameter optimization allows the material to achieve high filling ratio at lower pressing pressures, avoiding the need for high pressure that would cause crushing.
3Use of energy by moving object
If the negative electrode active material undergoes volume change during charging and discharging, then carrier ions are occluded or released, but voids or cracks may form in the negative electrode
Solution Approach 1:
The segmented structure of primary particles within secondary particles allows localized volume change accommodation. When carrier ions are occluded or released, the primary particles can expand or contract independently within the secondary particle framework, preventing the formation of voids or cracks that would compromise cycle characteristics.
Solution Approach 2:
The secondary particle structure acts as a flexible framework that can accommodate volume changes of the primary particles during charging and discharging. This flexible structure prevents the formation of voids or cracks by allowing the particle arrangement to adapt to volume changes while maintaining structural integrity.
Data Source
AI summary
Disclosed is new technology for reducing the resistance of a secondary battery and improving the cycle characteristics. In a negative electrode of the secondary battery, predetermined active material secondary particles are used. The active material secondary particles of the present disclosure comprise a plurality of negative electrode active material particles and perfluoropolyether.