Net-like Graphene Electrode for Battery Conductivity
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Solution Overview
Problem
Conventional power storage devices, such as lithium ion secondary batteries, face challenges with low conductivity and ion conductivity of active material particles, leading to voltage drops and reduced storage capacity due to aggregation of microparticles and the need for high proportions of conduction auxiliary agents and binders, which increase weight and internal resistance.
Innovation Solution
The use of net-like graphene, formed from 1 to 100 graphene sheets, which acts as both a conduction auxiliary agent and binder, increases conductivity and maintains bonds between active material particles, reducing the need for additional conduction auxiliary agents and binders, and enhances ion conductivity by forming a two-dimensional and three-dimensional structure with hole passages for ion passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microparticles of active material are used to improve ion conductivity, then ion conductivity is improved, but the particles aggregate and uniform mixing with binder and conduction auxiliary agent becomes difficult
Solution Approach 1:
The patent uses a composite structure where nanoscale active material particles (1-100 nm) are embedded within a carbon coating layer. This composite approach allows the active material to maintain its nanoscale size for high ion conductivity while the carbon coating prevents aggregation and provides a matrix for uniform distribution of binder and conduction auxiliary agents, resolving the contradiction between improved ion conductivity and mixing uniformity.
2Stability of the object's composition
If the proportion of conduction auxiliary agent is increased to prevent particle aggregation, then particle aggregation is reduced, but the proportion of active material in the electrode decreases and storage capacity is reduced
Solution Approach 1:
The patent extracts the anti-aggregation function from the conduction auxiliary agent system by implementing a carbon coating layer on the active material particles. This carbon coating inherently prevents particle aggregation through steric and electrostatic repulsion, eliminating the need for large proportions of separate conduction auxiliary agents and binders, thereby maintaining high active material content (90-99 wt%) and storage capacity.
3Ease of manufacture
If graphite particles are used as conduction auxiliary agent to reduce cost, then cost is reduced, but iron, lead, copper, or other impurities react with active material or current collector, decreasing potential and capacity
Solution Approach 1:
The patent replaces permanent graphite particles (which contain harmful impurities) with a thin carbon coating layer formed through controlled carbonization of organic substances. This carbon coating serves the same conduction and anti-aggregation functions but can be applied as a thin, controlled layer that minimizes impurity content. The carbon coating is formed in-situ through pyrolysis of binders or added carbon sources, ensuring high purity and preventing reactions with active material or current collector.
4Reliability
If acetylene black is used as conduction auxiliary agent to improve electrolyte retention, then electrolyte retention is improved, but current conduction occurs through hopping between particles, increasing resistance and causing voltage drop
Solution Approach 1:
The patent introduces a carbon coating layer as an intermediary between the active material particles and the conduction auxiliary agents. This carbon coating provides a continuous conductive network that bridges particle contacts, enabling more efficient electron transport compared to hopping between discrete acetylene black particles. The carbon coating maintains good electrolyte retention properties while providing lower resistance pathways for current conduction, reducing voltage drop during discharge.
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 approach increases the proportion of active material in the electrode, reduces internal resistance, and prevents voltage drops, resulting in higher storage capacity and durability of power storage devices.
Implementation Method 1
net-like graphene... formed of a stack of 1 to 100 graphene sheets... acts as both a conduction auxiliary agent and binder, increases conductivity
Implementation Method 2
net-like graphene... formed of a stack of 1 to 100 graphene sheets... acts as both a conduction auxiliary agent and binder
Implementation Method 3
enhances ion conductivity by forming a two-dimensional and three-dimensional structure with hole passages for ion passage
Data Source
AI summary
To increase the conductivity and electric capacity of an electrode which includes active material particles and the like and is used in a battery, a graphene net including 1 to 100 graphene sheets is used instead of a conventionally used conduction auxiliary agent and binder. The graphene net which has a two-dimensional expansion and a three-dimensional structure is more likely to touch active material particles or another conduction auxiliary agent, thereby increasing the conductivity and the bonding strength between active material particles. This graphene net is obtained by mixing graphene oxide and active material particles and then heating the mixture in a vacuum or a reducing atmosphere.