Core-Shell Lithium Manganese Phosphate Cathode for Rate Performance
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Solution Overview
Problem
Lithium manganese phosphate-based secondary batteries suffer from poor rate performance, limiting their commercial application due to low manganese ion migration and interfacial side reactions.
Innovation Solution
A lithium manganese phosphate positive electrode active material with a core-shell structure is developed, where the core is doped with elements A and R, and coated with crystalline pyrophosphate, phosphate, and carbon layers, along with a specific non-aqueous electrolyte composition to enhance manganese ion stability and lithium ion transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium manganese phosphate is used as positive electrode active material, then high capacity and good safety are achieved, but rate performance is poor
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core maintains the original lithium manganese phosphate composition for high capacity, while the shell contains multiple coating layers (amorphous alumina, crystalline phosphate, and carbon) with different functions. The amorphous alumina layer provides initial protection, the crystalline phosphate layer enhances ion transport, and the carbon layer improves conductivity, collectively solving the rate performance issue without compromising safety.
Solution Approach 2:
The patent employs composite materials by combining lithium manganese phosphate core with multiple coating layers forming a composite shell structure. This composite approach integrates the advantages of different materials: the protective properties of alumina, the ion-conducting properties of crystalline phosphate, and the conductivity of carbon, thereby improving rate performance while maintaining the inherent safety of lithium manganese phosphate.
2Quantity of substance
If lithium manganese phosphate is used as positive electrode active material, then high capacity is achieved, but poor rate performance restricts commercial application
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core maintains the original lithium manganese phosphate composition for high capacity, while the shell contains multiple coating layers (amorphous alumina, crystalline phosphate, and carbon) with different functions. The amorphous alumina layer provides initial protection, the crystalline phosphate layer enhances ion transport, and the carbon layer improves conductivity, collectively solving the rate performance issue without compromising safety.
Solution Approach 2:
The patent uses intermediary materials in the form of coating layers that mediate between the lithium manganese phosphate core and the electrolyte. The amorphous alumina and crystalline phosphate layers act as intermediaries that facilitate lithium ion transport, while the carbon layer serves as an intermediary that enhances electronic conductivity, thereby improving rate performance without reducing capacity.
3Ease of manufacture
If lithium manganese phosphate is used as positive electrode active material, then low cost is achieved, but poor rate performance limits commercial application
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core maintains the original lithium manganese phosphate composition for high capacity, while the shell contains multiple coating layers (amorphous alumina, crystalline phosphate, and carbon) with different functions. The amorphous alumina layer provides initial protection, the crystalline phosphate layer enhances ion transport, and the carbon layer improves conductivity, collectively solving the rate performance issue without compromising safety.
Solution Approach 2:
The patent employs parameter changes by modifying the surface properties of lithium manganese phosphate through controlled coating processes. The parameters include coating thickness (5-50 nm for amorphous alumina, 2-20 nm for crystalline phosphate), crystallinity control, and composition ratios, which are optimized to improve rate performance while maintaining cost-effectiveness and using conventional manufacturing techniques.
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 solution significantly improves high-temperature cycling performance, cycling stability, and rate performance by reducing manganese ion dissolution and interfacial side reactions, while maintaining good chemical stability and oxidation resistance.
Implementation Method 1
the pyrophosphate coating layer in hindering the manganese ion dissolution and the ability of the phosphate coating layer in conducting lithium ions, reducing the interfacial side reactions
Implementation Method 2
the ability of the phosphate coating layer in conducting lithium ions
Implementation Method 3
the third coating layer is carbon
Data Source
AI summary
This application provides a secondary battery, a battery module, a battery pack, and an electric apparatus. The secondary battery includes a positive electrode plate and a non-aqueous electrolyte. The positive electrode plate includes a positive electrode active material having a core-shell structure, the positive electrode active material including a core and a shell enveloping the core. A chemical formula of the core is Li1+xMn1−yAyP1-zRzO4. A is one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge. R is one or more elements selected from B, Si, N, and S. The first coating layer includes a crystalline pyrophosphate LiaMP2O7 and/or Mb(P2O7)c. The second coating layer includes a crystalline phosphate XPO4. The third coating layer is carbon. The non-aqueous electrolyte includes a first solvent, the first solvent including one or more of the compounds represented by formula 1.