Layered-Olivine Cathode Composition for Safer Secondary Batteries
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Solution Overview
Problem
Current lithium-ion batteries using ternary materials as positive electrode materials suffer from poor high-temperature performance, cycle performance, and structural stability, leading to safety concerns.
Innovation Solution
A secondary battery design that incorporates a positive electrode material composed of a layered structure material and an olivine structure material, with a specific mass ratio, to introduce two stages of discharge voltage platforms, reducing the discharge depth of the layered structure material and enhancing thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If ternary materials are used as positive electrode materials to achieve high energy density and high voltage platform, then the battery capacity and voltage are improved, but the high-temperature performance, cycle performance, and structural stability deteriorate
Solution Approach 1:
The patent uses a composite positive electrode material consisting of layered structure material (LiNi0.8Co0.1Mn0.1O2) and olivine structure material (LiFePO4) in a mass ratio of 95:5 to 5:95. This composite structure combines the high capacity advantages of layered materials with the thermal stability and structural stability of olivine materials, resolving the contradiction between high energy density and high-temperature performance.
2Power
If ternary materials are used as positive electrode materials to achieve high voltage platform, then the battery voltage is improved, but the structural stability deteriorates
Solution Approach 1:
The composite positive electrode material combines layered structure material (providing high voltage platform) with olivine structure material (providing structural stability). The olivine phase acts as a structural buffer that maintains overall stability while allowing the layered phase to operate at high voltage, thus resolving the contradiction between high voltage and structural stability.
3Reliability
If the discharge depth of layered structure material is reduced to improve thermal stability, then the safety performance is improved, but the battery capacity may be compromised
Solution Approach 1:
The composite structure allows the olivine phase to contribute to capacity while the layered phase operates at reduced discharge depth for improved thermal stability. The olivine material's inherent stability prevents thermal runaway even when layered material discharge is limited, thus maintaining safety while preserving acceptable capacity through the synergistic contribution of both phases.
Solution Approach 2:
The patent optimizes the mass ratio parameters of the two materials (layered:olivine from 95:5 to 5:95) to achieve the desired balance between capacity and safety. By adjusting this critical parameter, the system can be tuned to prioritize either capacity or safety depending on application requirements, while always maintaining both functions to some degree.
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 battery exhibits improved voltage and capacity retention, reduced thermal runaway risk, and enhanced safety performance by transitioning from a higher to a lower discharge voltage platform, thus addressing the limitations of ternary material batteries.
Implementation Method 1
The positive electrode material includes a first active material and a second active material. The first active material is a layered structure material. The second active material is an olivine structure material. A discharge curve of the secondary battery has a first voltage platform and a second voltage platform.
Data Source
AI summary
A secondary battery belonging to the technical field of batteries is provided. The secondary batter includes a positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet includes a positive electrode material including a first active material and a second active material. The first active material is a layered structure material, and the second active material is an olivine structure material. A mass ratio of the second active material to a sum of masses of the first active material and the second active material is 5 wt % to 30 wt %. A discharge curve of the secondary battery has a first voltage platform and a second voltage platform.