Graphite Anode Layer Alignment for Stable Lithium Intercalation
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Solution Overview
Problem
Graphite powder used in negative electrodes of secondary batteries has edge planes facing various directions, leading to inefficient lithium intercalation, varying lithium amounts, decreased active material density, and increased irreversible capacity due to electrolyte film formation, resulting in reduced discharge capacity and electrode deterioration.
Innovation Solution
The use of graphite with graphene layers aligned parallel to the electric field direction in the battery, terminated with functional groups like —O—Si, —O—P, or —O-M, to enhance lithium insertion and extraction efficiency, reduce edge defects, and maintain high active material density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If graphite powder is mixed with binder and conductive additive to form negative electrode active material layer, then the electrode can be manufactured with proper structure, but lithium intercalation efficiency decreases because edge planes face various directions
Solution Approach 1:
The invention changes the orientation parameter of graphite edge planes from random distribution to aligned orientation parallel to the electric field direction. This is achieved by controlling the stacking direction of graphene layers during graphite synthesis, transforming the edge plane orientation parameter to maximize lithium intercalation efficiency while maintaining manufacturability
Solution Approach 2:
The invention uses composite material structure where graphite particles are composed of stacked graphene layers with controlled orientation. The composite structure of multiple graphene layers forming oriented graphite particles allows both manufacturing feasibility and high lithium intercalation efficiency
2Ease of manufacture
If graphite powder with random edge plane orientation is used, then manufacturing is easier, but the amount of inserted and extracted lithium varies leading to electrode deterioration
Solution Approach 1:
The invention changes the orientation parameter of graphite edge planes from random to aligned parallel to electric field direction. This parameter change ensures uniform lithium insertion/extraction amounts across all graphite particles, preventing electrode deterioration while maintaining ease of manufacturing oriented graphite structures
Solution Approach 2:
Instead of trying to control lithium insertion to match random graphite orientation, the invention inverts the approach by orienting the graphite edge planes uniformly parallel to the electric field direction. This inversion of control strategy from controlling lithium to controlling graphite orientation resolves the reliability issue
3Ease of manufacture
If graphite powder is used and mixed with binder and conductive additive, then electrode structure is formed, but active material density decreases
Solution Approach 1:
The invention changes the orientation parameter of graphite crystallites to align edge planes parallel to electric field direction. This orientation parameter change increases the proportion of effective edge planes available for lithium intercalation, thereby increasing active material density while maintaining electrode structure formation capability
4Productivity
If graphite powder with large specific surface area is used, then more edge planes are available for lithium insertion, but irreversible capacity increases due to excessive film formation
Solution Approach 1:
The invention changes the orientation parameter of graphite edge planes to align parallel to electric field direction. This parameter change increases the effective surface area for reversible lithium insertion while reducing the surface area exposed to electrolyte that would form irreversible films, thereby maximizing productive lithium capacity while minimizing energy loss
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 allows for efficient lithium insertion and extraction, stabilizes the graphene edges, reduces variability in lithium amount, and maintains high output and capacity while minimizing the need for electrolyte impregnation.
Implementation Method 1
Graphite is a layered compound in which a plurality of graphene layers is stacked in parallel to each other by van der Waals forces
Implementation Method 2
lithium is inserted between the plurality of graphene layers to form a lithium-graphite intercalation compound, and lithium is occluded (intercalated) between the graphene layers
Implementation Method 3
lithium is released (deintercalated) when the secondary battery is discharged
Implementation Method 4
on the edge plane including the edges of the plurality of graphene layers, a film called a solid electrolyte interphase is formed at the time of initial charging and lithium is consumed due to the formation of the film
Data Source
AI summary
A secondary battery in which graphite that is an active material can occlude and release lithium efficiently is provided. Further, a highly reliable secondary battery in which the amount of lithium inserted and extracted into/from graphite that is an active material is prevented from varying is provided. The secondary battery includes a negative electrode including a current collector and graphite provided over the current collector, and a positive electrode. The graphite includes a plurality of graphene layers. Surfaces of the plurality of graphene layers are provided substantially along the direction of an electric field generated between the positive electrode and the negative electrode.