Lithium Manganese Phosphate Cathode Core-Shell Cladding for Cycle Stability
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Solution Overview
Problem
Lithium manganese phosphate secondary batteries exhibit poor cycling performance and high-temperature stability, necessitating improvements in rate performance and safety.
Innovation Solution
A secondary battery with a positive electrode active material featuring a core-shell structure, comprising an inner core of doped lithium manganese phosphate and a three-layer cladding system including crystalline pyrophosphates, phosphates, and carbon, along with specific additives in the non-aqueous electrolyte solution to enhance ion conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium manganese phosphate is used as positive electrode active material, then safety and cycle life are improved, but rate performance deteriorates
Solution Approach 1:
The positive electrode active material is divided into inner core and shell structure, where the inner core contains lithium manganese phosphate for long cycle life while the shell provides high-rate performance characteristics, allowing each part to optimize its function independently
Solution Approach 2:
The patent creates a composite structure combining lithium manganese phosphate with other materials in the shell layer, achieving synergistic effects that simultaneously improve both cycle life and rate performance beyond what single materials can provide
2Reliability
If lithium manganese phosphate is used as positive electrode active material, then safety is improved, but high-temperature stability deteriorates
Solution Approach 1:
The shell structure provides localized protection with different compositional characteristics tailored to address high-temperature instability at the surface while preserving the safety benefits of lithium manganese phosphate in the bulk material
3Speed
If cladding or doping is applied to lithium manganese phosphate, then rate performance is improved, but cycling performance deteriorates
Solution Approach 1:
The patent separates the functions of rate performance enhancement and cycling stability into different structural components - the shell composition optimizes rate performance while the core-shell architecture as a whole preserves cycling performance, avoiding the trade-off present in simple cladding or doping approaches
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
Significantly improves high-temperature cycling performance, storage capacity, and rate performance by reducing manganese ion dissolution and interfacial side reactions, while maintaining safety and kinetic performance.
Implementation Method 1
The first cladding layer comprises crystalline pyrophosphates and reduces the dissolution of manganese ions
Implementation Method 2
During charging and discharging of the battery, active ions (e.g., lithium ions) are intercalated and deintercalated back and forth between the positive electrode plate and the negative electrode plate
Implementation Method 3
reducing interfacial side reactions between the positive electrode active material and the electrolyte solution
Data Source
AI summary
Provided are a secondary battery, a battery module, a battery pack, and an electrical apparatus. The secondary battery comprises a positive electrode plate and a non-aqueous electrolyte solution, where the positive electrode plate comprises a positive electrode active material having a core-shell structure and comprising an inner core and a shell cladding the inner core, where the inner core has a chemical formula of Li1+xMn1−yAyP1−zRzO4, a first cladding layer comprises crystalline pyrophosphates LiaMP2O7 and/or Mb(P2O7)c, a second cladding layer comprises a crystalline phosphate XPO4, and a third cladding layer is carbon; and the non-aqueous electrolyte solution comprises a first additive comprising one or more compounds in the group consisting of a compound represented by formula 1, a compound represented by formula 2, and a compound represented by formula 3, thereby improving rate performance, cycling performance, and high-temperature stability of a lithium manganese phosphate secondary battery.