Lithium Manganese Phosphate Cathode Coating for Rate and Cycle Life
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Solution Overview
Problem
Lithium manganese phosphate secondary batteries suffer from poor rate performance and cycling performance due to the dissolution of manganese ions during lithium deintercalation and intercalation, leading to reduced safety and kinetic performance.
Innovation Solution
A core-shell structure positive electrode active material with specific element doping and surface coating, where the core includes Li1+xMn1-yAyP1-zRzO4 and is enveloped by a first coating layer of pyrophosphate and phosphate, and a second carbon-containing layer, along with additives in the non-aqueous electrolyte to form a polymer layer and a low-resistance CEI film, inhibiting manganese ion dissolution and promoting lithium ion migration.
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 patent applies local quality by creating a core-shell structure where the core maintains the original lithium manganese phosphate composition for stability, while the shell provides different local environments (amorphous coating for protection, carbon coating for conductivity) to address specific performance limitations in different regions of the material particle
Solution Approach 2:
The patent uses composite materials by combining lithium manganese phosphate with amorphous coating materials and carbon materials to form a composite structure. This composite approach allows the material to simultaneously exhibit the stability of lithium manganese phosphate, the protective properties of the amorphous coating, and the high conductivity of carbon, thereby improving rate performance while maintaining cycle life
2Reliability
If lithium manganese phosphate is used as positive electrode active material, then safety is improved, but kinetic performance deteriorates
Solution Approach 1:
The patent employs flexible shells and thin films by applying an amorphous coating layer on the surface of lithium manganese phosphate particles. This thin film structure provides flexible adaptation to volume changes during lithium insertion/extraction, maintains intimate contact with the electrolyte for good kinetic performance, and prevents direct exposure of the crystalline core to the electrolyte, thereby improving both safety and kinetic performance
3Stability of the object's composition
If element doping is applied to lithium manganese phosphate, then structural stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-doping element A into the lithium manganese phosphate crystal structure before the coating process. This preliminary doping step stabilizes the crystal structure in advance, reducing the need for complex post-processing and subsequent coating steps, thereby improving structural stability while controlling manufacturing complexity
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 the rate performance, cycling performance, and high-temperature stability of lithium manganese phosphate secondary batteries by reducing manganese ion dissolution and enhancing lithium ion transport, while maintaining capacity and safety performance.
Implementation Method 1
inhibiting manganese ion dissolution
Implementation Method 2
promoting lithium ion migration
Implementation Method 3
form a polymer layer and a low-resistance CEI film
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, where a positive electrode active material includes a core and a shell enveloping the core, the core including Li1+xMn1-yAyP1-zRzO4 and the shell including a first coating layer enveloping the core and a second coating layer enveloping the first coating layer, where the first coating layer includes a pyrophosphate MP2O7 and a phosphate XPO4, and the second coating layer includes carbon; and the non-aqueous electrolyte includes a first additive, the first additive including one or more from a group consisting of compounds shown in formula 1 and compounds shown in formula 2.