Composite Cathode Material with Nanosheets for Lower Battery Voltage Drop
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Solution Overview
Problem
The voltage drop of the positive electrode active material in battery cells is too large, which hinders the improvement of energy density in batteries used in various electronic devices.
Innovation Solution
A composite positive electrode active material is developed, comprising a first lithium iron manganese phosphate type material with a nanosheet structure and a second lithium iron manganese phosphate type material with a spherical or quasi-spherical structure, where the ratio of the (010) crystal plane area of the first material is greater than that of the second material, enhancing lithium ion diffusion and forming a conductive network structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional positive electrode active material is used, then the battery cell can operate, but the voltage drop is too large which hinders energy density improvement
Solution Approach 1:
The patent employs a composite positive electrode active material consisting of lithium iron phosphate particles (spherical or quasi-spherical structure) and lithium iron manganese phosphate particles (nanosheet structure). This composite structure combines the advantages of both materials: lithium iron phosphate provides high voltage plateau and stability, while lithium iron manganese phosphate contributes to lower intrinsic resistance and improved conductivity. The synergistic effect of this composite material reduces overall voltage drop and enhances energy density
Solution Approach 2:
The patent applies local quality by creating distinct morphological regions within the composite material. The lithium iron phosphate exists as spherical or quasi-spherical particles while the lithium iron manganese phosphate forms nanosheet structures. Each component maintains its specific local structure optimized for its function: spheres provide stability and predictable electrochemical behavior, while nanosheets provide high surface area and short ion diffusion paths, reducing local resistance
2Quantity of substance
If the first lithium iron manganese phosphate type material with nanosheet structure is used, then the capacity approaches theoretical capacity, but the device complexity increases due to mixed material composition
Solution Approach 1:
The patent uses a composite material system where two well-established lithium phosphate materials are combined in specific proportions (60-95 wt% lithium iron phosphate and 5-40 wt% lithium iron manganese phosphate). This composite approach achieves capacity close to theoretical limits by leveraging the high theoretical capacity of lithium iron manganese phosphate nanosheets while maintaining the electrochemical stability and manufacturability of lithium iron phosphate spheres
Solution Approach 2:
The patent optimizes specific parameters of the composite material including the weight ratio of the two components (60-95:5-40), the particle size distribution (micro-nano scale), and the crystal plane orientation ratio A1>A2. These parameter optimizations enable the material to achieve near-theoretical capacity while maintaining manageable complexity through controlled composition rather than random mixing
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 composite material improves the energy density and rate performance of battery cells by increasing the average discharge voltage and reducing intrinsic resistance, thereby facilitating rapid lithium ion transmission and enhancing overall conductivity.
Implementation Method 1
a capacity thereof is close to a theoretical capacity; and after the first lithium iron manganese phosphate type material and the second lithium iron manganese phosphate type material are mixed to form the composite positive electrode active material, an overall capacity of the composite positive electrode active material is improved, and an average discharge voltage is improved
Implementation Method 2
the composite positive electrode active material satisfies: A1>A2. Therefore, the nanosheet structure of the first lithium iron manganese phosphate type material in the embodiment of the present application makes the area of the (010) crystal plane of the first lithium iron manganese phosphate type material larger
Data Source
AI summary
A composite positive electrode active material is disclosed. The composite positive electrode active material includes a first lithium iron manganese phosphate type material and a second lithium iron manganese phosphate type material. The first lithium iron manganese phosphate type material has a nanosheet structure, and a ratio of an area of a (010) crystal plane of the first lithium iron manganese phosphate type material to a total area of crystal planes of the first lithium iron manganese phosphate type material is A1%. The second lithium iron manganese phosphate type material has a spherical and/or quasi-spherical structure, and a ratio of an area of a (010) crystal plane of the second lithium iron manganese phosphate type material to a total area of crystal planes of the second lithium iron manganese phosphate type material is A2%. The composite positive electrode active material satisfies A1>A2.