Lithium Ion Battery Negative Electrode Conductive Network Design
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Solution Overview
Problem
Conventional lithium ion batteries using spherical or massive carbon-based materials as negative electrode active materials face issues with rapid capacity degradation and instability in low-temperature environments due to the reaction of carbon black with the electrolyte solution, leading to increased electronic resistance and reduced battery performance over time.
Innovation Solution
A lithium ion battery design incorporating a negative electrode with a spherical or massive graphite or amorphous carbon active material, platy graphite conductive additives, and a specific electrolyte solution containing an additive that reductively decomposes at a lower voltage, ensuring stable SEI film formation and maintaining conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is added as conductive additives to reduce electric resistance, then conductivity is improved, but capacity degradation accelerates due to reaction with electrolyte solution
Solution Approach 1:
The invention changes the material parameter from carbon black to spherical carbon particles with specific size range (3-50 μm). This parameter change eliminates the harmful reaction with electrolyte solution while maintaining conductivity function, thus resolving the contradiction between reliability and duration of action.
Solution Approach 2:
The invention uses spherical carbon particles that are stable and do not react with electrolyte, replacing the short-living carbon black that degrades quickly. This allows the conductive additive to function throughout the entire battery life without degradation, resolving the contradiction between initial conductivity and long-term stability.
2Power
If spherical or massive carbon-based material is used as negative electrode active material, then output properties are improved, but contact between particles becomes point contact increasing electric resistance
Solution Approach 1:
The invention segments the conductive network by using dispersed spherical carbon particles instead of massive materials. This creates multiple contact points throughout the electrode, reducing overall electric resistance while maintaining the output properties of spherical active material.
Solution Approach 2:
The invention creates a composite structure combining spherical carbon-based active material with spherical carbon particles as conductive additives. This composite approach ensures continuous conductive network formation through multiple contact points, resolving the contradiction between power output and electric resistance.
3Reliability
If carbon black forms secondary particles and bridges between active materials, then conductivity is secured, but gaps between active materials are filled reducing electrolyte solution flow paths
Solution Approach 1:
The invention changes the size parameter of conductive additives to spherical particles (3-50 μm) that are optimally sized to bridge active material particles without filling the gaps. This parameter optimization maintains conductivity while preserving electrolyte flow paths for efficient ion transfer.
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 battery exhibits improved long-term life properties, prevents rapid capacity degradation, and maintains excellent charge and discharge performance even in low-temperature environments, extending the battery's lifespan and performance.
Implementation Method 1
the nonaqueous electrolyte solution contains a solvent, and an additive which reductively decomposes at a voltage lower than a reduction voltage of the solvent
Data Source
AI summary
The purpose of the present invention is to provide a lithium-ion battery that exhibits excellent long-term life properties, does not suffer from rapid capacity degradation, and exhibits excellent charging/discharging characteristics in low-temperature environments. The present invention is directed to a lithium ion battery comprising: a negative electrode which comprises a negative electrode active material containing at least one of a graphite and an amorphous carbon, conductive additives containing a graphite, and a binder; a nonaqueous electrolyte solution; and a positive electrode containing a positive electrode active material capable of occluding and releasing lithium. The negative electrode active material has a spherical or massive shape, the conductive additives have a platy shape, and a part of an edge surface of the conductive additives contacts a surface of the negative electrode active material. The nonaqueous electrolyte solution contains a solvent, and an additive which reductively decomposes at a voltage lower than a reduction voltage of the solvent.