Li-Ion Positive Electrode Composite Conduction Aid Design
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving a balance between high charge/discharge rate characteristics and inhibiting oxidative decomposition of non-aqueous electrolytic solutions, particularly when using non-graphitizable carbon as a conduction aid.
Innovation Solution
A positive electrode combination material is developed, comprising a spinel-type lithium-nickel-manganese oxide active material, carbon black, and non-graphitizable carbon, with specific surface area ratios optimized to enhance electron conductivity and prevent oxidative decomposition, including a ratio of 6.5 to 70 for the surface area of carbon black to non-graphitizable carbon and a total surface area of 90 to 400 cm2/cm2 per unit coated area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-graphitizable carbon is used as conduction aid to inhibit oxidative decomposition of solvent, then reliability is improved, but charge/discharge rate characteristics deteriorate
Solution Approach 1:
The patent uses a composite conduction aid system combining non-graphitizable carbon (to inhibit oxidative decomposition) with graphitizable carbon or conductive metal oxide (to restore charge/discharge rate characteristics). This composite approach allows both functions to coexist: the non-graphitizable carbon provides oxidation resistance while the graphitizable carbon or conductive metal oxide ensures high electron conductivity for fast charge/discharge rates.
2Use of energy by moving object
If positive electrode active material producing 4.5V or higher is used to increase energy density, then use of energy is improved, but oxidative decomposition of solvent increases
Solution Approach 1:
The patent introduces non-graphitizable carbon as an intermediary substance between the high-potential positive electrode active material and the non-aqueous electrolytic solution. This intermediary forms a protective interface that prevents direct contact and oxidative decomposition between the solvent and electrode, enabling safe use of high-voltage materials that would otherwise cause solvent decomposition.
3Productivity
If surface area of conduction aid is increased to improve charge/discharge rate, then productivity is improved, but oxidative decomposition of solvent worsens
Solution Approach 1:
The patent creates a composite conduction aid structure where non-graphitizable carbon (providing oxidation resistance) and graphitizable carbon or conductive metal oxide (providing high surface area for fast electron transfer) work together. The optimal ratio balance ensures sufficient surface area for high charge/discharge rates while maintaining oxidation resistance through the non-graphitizable carbon component.
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 achieves improved charge/discharge rate characteristics while inhibiting oxidative decomposition, maintaining a balance between high operating voltage and energy density, and reducing gas generation.
Implementation Method 1
The conduction aid has a first conduction aid composed of carbon black and a second conduction aid composed of non-graphitizable carbon
Implementation Method 2
a positive electrode active material that produces a potential of 4.5 V or higher on the basis of metal lithium
Data Source
AI summary
A positive electrode for a lithium ion secondary battery. The positive electrode includes a positive electrode combination material having a positive electrode active material that produces a potential of 4.5 V or higher on the basis of metal lithium, a first conduction aid of carbon black, a second conduction aid of non-graphitizable carbon, and a binder. A ratio (SC1/SC2) of a surface area SC1 of the first conduction aid to a surface area SC2 of the second conduction aid is 6.5 to 70, and a sum SE of a surface area SA of the positive electrode active material in the positive electrode combination material and a surface area SC of the first conduction aid and the second conduction aid is 90 cm2/cm2 to 400 cm2/cm2 or less per unit coated area of the positive electrode combination material.