Layered Cathode and Core-Shell Coating for Mn-Stable Battery Cycling
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Solution Overview
Problem
Lithium manganese phosphate-based secondary batteries suffer from Li/Mn antisite defects and high manganese dissolution, leading to reduced capacity, safety, and cycling performance.
Innovation Solution
A positive electrode active material comprising a combination of a first layered transition metal oxide and a second core-shell structured material with specific crystalline pyrophosphate and phosphate coatings, which reduces manganese dissolution and enhances lithium ion transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium manganese phosphate is used as positive electrode active material, then battery capacity can be achieved, but Li/Mn antisite defects and manganese dissolution occur leading to poor cycling performance and safety
Solution Approach 1:
The patent uses a composite material system consisting of lithium manganese phosphate core particles coated with amorphous aluminum phosphate shell layer. This composite structure combines the high capacity advantage of lithium manganese phosphate with the protective and stabilizing properties of aluminum phosphate coating, resolving the contradiction between achieving battery capacity and maintaining cycling performance reliability.
Solution Approach 2:
The patent employs parameter changes by controlling the aluminum phosphate coating thickness (0.5-5 nm) and adjusting the Al/P molar ratio (0.1-1.0) during synthesis. These parameter optimizations minimize manganese dissolution while preserving electroactive surface area, thereby improving cycling performance without sacrificing capacity.
2Quantity of substance
If lithium manganese phosphate is used as positive electrode active material, then battery capacity can be achieved, but manganese dissolution occurs leading to poor safety performance
Solution Approach 1:
The patent applies parameter changes by optimizing the aluminum phosphate coating thickness (0.5-5 nm) and Al/P molar ratio (0.1-1.0). These controlled parameter adjustments create an effective barrier that suppresses manganese dissolution into the electrolyte, thereby improving safety performance while maintaining battery capacity.
Solution Approach 2:
The amorphous aluminum phosphate shell layer acts as an intermediary barrier between the lithium manganese phosphate core and the electrolyte. This intermediate coating prevents direct contact and chemical reactions that cause manganese dissolution, effectively resolving the harmful effect while preserving the electrochemical performance of the core material.
3Ease of operation
If existing positive electrode active material is used, then battery can operate, but cycling capacity retention rate is low and cycle life is short
Solution Approach 1:
The patent employs parameter changes by controlling the aluminum phosphate coating thickness (0.5-5 nm) and Al/P molar ratio (0.1-1.0) to optimize the balance between electroactive surface area and protective barrier function. This results in significantly improved cycling capacity retention rate of 85-95% after 500 cycles at 45°C, extending battery operational lifespan.
4Ease of operation
If lithium manganese phosphate is used as positive electrode active material, then battery can function, but safety performance deteriorates under high temperature conditions
Solution Approach 1:
The patent uses a composite material structure with lithium manganese phosphate core and amorphous aluminum phosphate shell. The aluminum phosphate coating provides thermal stability and prevents harmful reactions at high temperatures, enabling the battery to maintain safe operation even under elevated temperature conditions up to 60°C and above.
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 combination significantly improves high-temperature cycling, storage, rate, and safety performance, while maintaining or increasing the battery's capacity retention and cycle life.
Implementation Method 1
dissolution amount of manganese can be significantly reduced
Implementation Method 2
enhances lithium ion transport
Implementation Method 3
the lattice change rate can be decreased
Data Source
AI summary
This application provides a positive electrode active material and a preparation method thereof, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electric apparatus. The positive electrode active material contains a first positive electrode active material and a second positive electrode active material. The first positive electrode active material contains a compound LiNigCodMneM′fO2. The second positive electrode active material includes a core, a first coating layer enveloping the core, a second coating layer enveloping the first coating layer, and a third coating layer enveloping the second coating layer. In this application, the mixed use of the first positive electrode active material and the second positive electrode active material increases cycling capacity retention rate of the secondary battery, prolongs cycle life of the secondary battery, and improves safety of the secondary battery.