Graphene Composite Oxide Electrode for Lithium-Ion Batteries
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Solution Overview
Problem
Lithium-ion secondary batteries face limitations in increasing discharge capacity and energy density due to high resistance in lithium-containing composite oxides.
Innovation Solution
Incorporating graphenes with lithium-containing composite oxides of olivine structure, where the b-axis of flat single crystal particles intersects with the positive electrode current collector, reducing internal resistance and enhancing ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium-containing composite oxides are used as positive electrode active materials, then thermal stability is improved, but resistance increases limiting discharge capacity and energy density
Solution Approach 1:
The patent uses composite materials by combining lithium-containing composite oxides (olivine structure) with graphene sheets. The graphene acts as a conductive matrix that compensates for the high resistance of the lithium-containing composite oxides, while maintaining their thermal stability. This composite structure enables both high discharge capacity and energy density by improving electron transport pathways.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous structure where graphene is specifically distributed around lithium-containing composite oxide particles. The graphene provides localized high conductivity regions that facilitate ion and electron transport at critical interfaces, while the olivine structure particles maintain their inherent thermal stability in specific zones.
2Quantity of substance
If particle diameters of active materials are reduced to increase discharge capacity, then ion intercalation and deintercalation are improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the positive electrode active material into small olivine structure particles (5-50 nm in b-axis direction) that are individually dispersed within the graphene matrix. This segmentation increases the total surface area for ion intercalation while the graphene framework provides a simple manufacturing approach by acting as a pre-formed conductive network that facilitates particle assembly.
3Power
If proportion of conduction auxiliary agent is increased to reduce resistance, then power is improved, but discharge capacity decreases due to reduced active material proportion
Solution Approach 1:
The patent changes the parameter of conduction auxiliary agent from traditional materials to graphene, which has superior electrical conductivity. This allows using a smaller proportion of conduction auxiliary agent (5-20 wt%) while achieving the same or better conductivity enhancement, thereby maintaining higher proportions of active material for discharge capacity.
Solution Approach 2:
Graphene serves as an intermediary that simultaneously provides conduction pathways and structural support. It mediates between the lithium-containing composite oxide particles and the electrolyte, facilitating both electron transport (improving power) and ion transport (maintaining discharge capacity) without requiring large amounts of inactive conduction material.
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 increases discharge capacity and power density while enabling faster charging and discharging, achieving theoretical discharge capacity.
Implementation Method 1
lithium ions are easily diffused between the current collector and the electrolyte
Implementation Method 2
The use of the graphene for a conduction auxiliary agent allows an increase in proportion of a positive electrode active material in the positive electrode active material layer and a reduction in resistance of the positive electrode active material layer
Data Source
AI summary
To provide a lithium-ion secondary battery having higher discharge capacity and higher energy density and a manufacturing method thereof. The lithium-ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer provided over the positive electrode current collector. In the positive electrode active material layer, graphenes and lithium-containing composite oxides are alternately provided. The lithium-containing composite oxide is a flat single crystal particle in which the length in the b-axis direction is shorter than each of the lengths in the a-axis direction and the c-axis direction. Further, the lithium-containing composite oxide is provided over the positive electrode current collector so that the b-axis of the single crystal particle intersects with a surface of the positive electrode current collector.