Composite Positive Electrode Sheet for High-Rate Battery Cathodes
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Solution Overview
Problem
Secondary batteries manufactured with existing positive electrode active materials suffer from low energy density, poor kinetic performance, low cell rate performance, short cycle life, and safety concerns, particularly at low temperatures.
Innovation Solution
A positive electrode sheet is developed with a multi-layer structure comprising a first active material with a chemical formula of LiaAxMn1-yRyP1-zCzO4-nDn and a second active material of LiNibCocMn(1-b-c)O2, where A includes elements like Zn, Al, Na, and R includes elements like Ti, V, and C includes elements like B, S, Si, with specific doping to improve rate performance, cycling stability, and safety by reducing Mn dissolution and interface reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium manganese iron phosphate is used as the main positive electrode active material, then the battery has good thermal stability and safety, but the kinetic performance and cell rate performance are poor
Solution Approach 1:
The patent uses a composite positive electrode active material consisting of lithium manganese iron phosphate (providing thermal stability) and ternary materials such as lithium nickel cobalt manganese oxide or lithium cobalt oxide (providing high kinetic performance). This composite structure combines the advantages of both material systems to achieve both safety and high rate performance.
2Speed
If lithium manganese iron phosphate is mixed with ternary materials to improve kinetic performance, then the cell rate performance improves, but the energy density decreases
Solution Approach 1:
The patent optimizes the compositional parameters of the composite material, specifically controlling the content of lithium manganese iron phosphate to be 5-50 mass% and ternary materials to be 50-95 mass%. By precisely adjusting these parameters, the patent achieves high energy density while maintaining excellent rate performance.
3Ease of manufacture
If existing positive electrode active materials are used, then the manufacturing process is simple, but the cycling performance and low-temperature performance are poor
Solution Approach 1:
The patent employs a composite positive electrode active material system that maintains the simplicity of existing manufacturing processes while significantly improving cycling performance and low-temperature performance through the synergistic combination of lithium manganese iron phosphate and ternary materials.
4Device complexity
If existing positive electrode active materials are used, then the structure is simple, but the safety performance is low
Solution Approach 1:
The patent uses a composite positive electrode active material combining lithium manganese iron phosphate (with inherent thermal stability) and ternary materials. This composite structure enhances safety performance while maintaining relatively simple device structure, avoiding complex additional safety mechanisms.
Data Source
AI summary
A positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical apparatus are described. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector and having a single-layer or multi-layer structure. When the positive electrode film layer is of the single-layer structure, at least one positive electrode film layer comprises both a first positive electrode active material and a second positive electrode active material with a chemical formula of LiaAxMn1-yRyP1-zCzO4-nDn; and/or, when the positive electrode film layer is of the multi-layer structure, at least one layer of the at least one positive electrode film layer includes both a first and second positive electrode active material. The secondary battery made of the positive electrode sheet has high energy density and high battery cell rate performance.