Layered Positive Electrode Structure for Low-Temperature Li Battery Output
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, high operating voltage, and high conductivity, particularly in low-temperature conditions.
Innovation Solution
A positive electrode for rechargeable lithium batteries is designed with a layered structure comprising a first active material layer of monolithic particles and a second active material layer of aggregated particles, both made from olivine-based lithium compounds, with specific elemental compositions and varying binder and conductive material contents to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-layer electrode structure is used, then the device complexity is low, but the energy density and conductivity are insufficient
Solution Approach 1:
The positive electrode is divided into two distinct layers: a first active material layer containing single particles and a second active material layer containing secondary particles. This segmentation allows each layer to contribute differently to the overall performance, with the first layer providing high conductivity and the second layer providing high capacity, thereby resolving the contradiction between energy density and structural simplicity.
Solution Approach 2:
The electrode uses a composite structure combining two types of active material layers with different particle morphologies and chemical compositions. The first layer uses particles with specific elemental ratios (Fe:Li:B1 > 2:1:0.5) while the second layer uses particles with different ratios (Fe:Li:B2 > 3:1:0.5), creating a composite material system that achieves both high energy density and maintained conductivity.
2Power
If conventional active materials are used, then the manufacturing process is simple, but the operating voltage and conductivity are insufficient
Solution Approach 1:
The invention modifies the chemical composition parameters of the active materials by controlling the ratios of Fe, Li, and B elements in each layer. The first layer maintains Fe:Li:B1 > 2:1:0.5 while the second layer uses Fe:Li:B2 > 3:1:0.5. These parameter changes optimize the operating voltage and conductivity without fundamentally changing the manufacturing process, thus resolving the contradiction between performance and ease of manufacture.
3Quantity of substance
If high capacity materials are used, then the energy density increases, but the low-temperature performance deteriorates
Solution Approach 1:
Different regions of the electrode (first layer vs. second layer) are assigned different particle characteristics tailored to their specific functions. The first layer uses particles optimized for conductivity and low-temperature performance, while the second layer uses particles optimized for high capacity. This local quality differentiation allows the electrode to achieve high overall capacity while maintaining reliable low-temperature performance.
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 electrode structure achieves high energy density, high operating voltage, and improved conductivity, particularly at low temperatures, enhancing the overall performance of rechargeable lithium batteries.
Implementation Method 1
These batteries generate electrical energy through redox reactions that take place as lithium ions are intercalated into or deintercalated from the positive electrode and the negative electrode
Data Source
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AI summary
A positive electrode for a rechargeable lithium battery includes a current collector, a first active material layer on the current collector, and a second active material layer on the first active material layer. The first active material layer includes a first particle that may be in the form of a single particle, and the second active material layer includes a second particle that may be in the form of a secondary particle. The first particle includes a compound of Formula 1, and the second particle includes a compound of Formula 2. Also disclosed is a rechargeable lithium battery including the same.