Multilayer Positive Electrode Structure for Low-Resistance Li Batteries
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density, high capacity, and improved binding force between the positive active material layer and the current collector, leading to increased resistance and difficulty in electrode plate preparation.
Innovation Solution
A positive electrode for rechargeable lithium batteries is designed with a multilayer structure comprising a first active material layer containing olivine structured compounds and a second active material layer with layered compounds, along with specific particle sizes and binders to enhance binding force and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional single-layer positive active material layer is used, then the electrode structure is simple, but the binding force with the current collector is insufficient and resistance is high
Solution Approach 1:
The positive active material layer is divided into multiple layers (first positive active material layer and second positive active material layer) with different compositions and functions. The first layer contains olivine structured compounds for strong binding with the current collector, while the second layer contains layered compounds for high capacity, thereby resolving the contradiction between binding force and structural simplicity.
Solution Approach 2:
The patent uses composite materials with different crystal structures (olivine and layered) in different layers. The olivine structured compounds in the first layer provide strong binding force with the current collector, while the layered compounds in the second layer provide high capacity, achieving both strong binding and reduced resistance through material composition optimization.
2Quantity of substance
If particle size is reduced to improve capacity, then capacity increases, but binding force decreases and electrode plate preparation becomes difficult
Solution Approach 1:
Different particle sizes are used in different layers to optimize local functions. The first layer uses smaller particles (average diameter 0.5-5 μm) for strong binding with the current collector, while the second layer uses larger particles (average diameter 5-20 μm) for high capacity. This local differentiation resolves the contradiction between capacity and binding force.
Solution Approach 2:
The patent transitions from a single-layer structure to a multi-layer structure, adding a dimensional aspect to particle size distribution. By arranging different sized particles in different layers rather than mixing them uniformly, the patent achieves both strong binding (through small particles in contact with current collector) and high capacity (through larger particles in the second layer).
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 multilayer structure improves the binding force with the current collector, facilitating electrode plate preparation and reducing resistance, resulting in batteries with enhanced capacity, lifetime, and operating voltage.
Implementation Method 1
a positive electrode and a negative electrode, each including an active material that allows intercalation and deintercalation of lithium ions
Implementation Method 2
Rechargeable lithium batteries produce electrical energy from redox reactions that take place as lithium ions are intercalated into or deintercalated from the positive electrode and the negative electrode
Data Source
AI summary
A positive electrode for a rechargeable lithium battery includes a current collector, a first active material layer on the current collector, with the including first particles, second particles, a first binder, and a first conductive material. The positive electrode also includes a second active material layer on the first active material layer, the second active material layer including third particles, a second binder, and a second conductive material. The first particles are an olivine structured compound, the second particles are a layered compound, the third particles are an olivine structured compound. The first particle includes a plurality of first primary particles aggregated together, the first particles have an average diameter of about 3 μm to about 10 μm, and the first primary particles have an average diameter of about 200 nm or less. The third particles are single particles, and the third particles have an average particle diameter of about 100 nm to about 2 μm.