Mixed Cathode Active Material to Reduce Mn Dissolution
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Solution Overview
Problem
Secondary batteries using lithium manganese phosphate as a positive electrode active material suffer from Li/Mn antisite defects, severe manganese dissolution, leading to poor cycling capacity retention, short cycle life, and safety concerns due to high interfacial side reactions and low energy density.
Innovation Solution
A positive electrode active material comprising a mixture of a layered transition metal oxide and a doped lithium manganese phosphate compound, with specific elemental doping at Li, Mn, P, and O sites, enhancing lithium ion transport and reducing antisite defects, thereby improving cycling performance, safety, and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium manganese phosphate is used as positive electrode active material, then the battery can be manufactured with existing processes, but Li/Mn antisite defects occur and manganese dissolution is severe, leading to poor cycling performance and safety
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core contains LiMnPO4 particles with specific doping elements (Al, Mg, Ti) to reduce Li/Mn antisite defects, while the outer shell consists of a protective coating layer that suppresses manganese dissolution. This localized structural differentiation addresses both the manufacturability of the core material and the reliability requirements of the protective shell.
Solution Approach 2:
The patent employs composite materials by combining doped LiMnPO4 particles with a protective coating material to form a core-shell composite structure. The composite integrates the advantages of the doped core (reduced antisite defects) and the protective shell (suppressed manganese dissolution), thereby improving cycling performance while maintaining manufacturability through existing coating processes.
2Ease of manufacture
If lithium manganese phosphate is used as positive electrode active material, then the battery can be manufactured with existing processes, but manganese dissolution is severe causing low safety performance
Solution Approach 1:
The protective shell is applied locally on the surface of the doped LiMnPO4 particles to specifically address manganese dissolution at the particle-electrolyte interface, while the bulk material maintains its original composition for manufacturability. This localized protection approach improves safety performance without requiring complete material replacement.
Solution Approach 2:
The patent converts the harmful effect of manganese dissolution into a benefit by using controlled doping elements (Al, Mg, Ti) that, when present in specific amounts, actually suppress manganese dissolution. The doping process transforms the potential harm of material instability into a protective mechanism that enhances safety performance.
3Ease of manufacture
If lithium manganese phosphate is used as positive electrode active material, then the battery can be manufactured with existing processes, but interfacial side reactions are high leading to poor cycling capacity retention
Solution Approach 1:
The protective shell is applied locally on the particle surface to specifically address interfacial side reactions at the electrode-electrolyte interface, while the bulk material maintains its original composition for manufacturability. This localized protection reduces interfacial side reactions without requiring complete material replacement, thereby improving cycling capacity retention.
Solution Approach 2:
The composite structure of doped LiMnPO4 core with protective shell coating reduces interfacial side reactions by providing a stable interface between the active material and electrolyte. The composite integrates the electrochemical activity of the core with the protective properties of the shell, improving cycling capacity retention while maintaining manufacturability.
4Ease of manufacture
If lithium manganese phosphate is used as positive electrode active material, then the battery can be manufactured with existing processes, but energy density is low
Solution Approach 1:
The patent applies parameter changes by optimizing the doping element concentrations (Al: 0.01-0.1 mol fraction, Mg: 0.01-0.1 mol fraction, Ti: 0.01-0.1 mol fraction) and the protective shell thickness to balance manufacturability with energy density improvement. The controlled parameter adjustments enhance material performance without requiring process overhaul.
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 enhances the cycling capacity retention, extends the cycle life, and improves the safety and energy density of secondary batteries by leveraging the complementary advantages of the mixed materials, reducing manganese dissolution and interfacial side reactions.
Implementation Method 1
enhancing lithium ion transport
Implementation Method 2
doping a specific amount of a specific element at the Li, Mn, P, and O sites of the compound LiMnPO4
Data Source
AI summary
This application provides a mixed 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 includes a first positive electrode active material and a second positive electrode active material, where the first positive electrode active material includes a compound LiNibCodMneMfO2, and the second positive electrode active material includes a compound LiaAxMn1-yByP1-zC2O4-nDn. In this application, with the first positive electrode active material and the second positive electrode active material mixed, the cycling capacity retention rate of the secondary battery is improved, the cycle life of the secondary battery is extended, and the safety of the secondary battery is improved.