LMP Cathode Core-Shell Coating for High-Temperature Battery Cycling
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Solution Overview
Problem
Lithium manganese phosphate (LMP) cathode active materials exhibit poor rate performance, cycling performance, and high-temperature stability, despite their higher safety and longer cycling life compared to other cathode active materials.
Innovation Solution
A novel LMP cathode active material with a core-shell structure is developed, incorporating a doped core and multiple coating layers, including crystalline pyrophosphate and phosphate layers, along with a non-aqueous electrolyte containing specific lithium salts and additives to reduce manganese ion dissolution and enhance lithium ion conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LMP cathode active materials are used, then safety and cycling life are improved, but rate performance deteriorates
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where the core is doped LMP (Li1+xMn1-yAyP1-zRzO4) and the shell consists of multiple coating layers including crystalline pyrophosphate and phosphate layers. This composite structure combines the high safety and cycling life of LMP with improved rate performance through the dopants and conductive coating layers.
Solution Approach 2:
The patent applies local quality by doping specific elements (A and R) at specific positions (Mn and P sites) within the LMP lattice structure, and by applying different coating layers with specific functions (pyrophosphate for stability, phosphate for ion conduction, carbon for conductivity) at the surface. This localized modification optimizes different regions for different functions.
2Reliability
If LMP cathode active materials are used, then safety is improved, but cycling performance deteriorates
Solution Approach 1:
The patent uses composite materials by combining doped LMP core with multiple functional coating layers. The crystalline pyrophosphate and phosphate coating layers protect the LMP core from degradation during cycling while maintaining safety characteristics, thus improving cycling performance without compromising safety.
Solution Approach 2:
The patent applies beforehand cushioning by pre-coating the LMP core with protective layers (crystalline pyrophosphate and phosphate) before battery assembly. These coating layers act as protective barriers that prevent direct contact between the LMP and electrolyte, cushioning against degradation during cycling operations.
3Productivity
If coating or doping is applied to LMP, then rate performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the coating structure into distinct functional layers: an inner crystalline pyrophosphate layer for structural stability, a middle crystalline phosphate layer for ion conduction, and an outer carbon layer for electrical conductivity. This segmented approach allows each layer to be optimized independently while simplifying the overall manufacturing process through systematic layer-by-layer construction.
4Duration of action of stationary object
If multiple coating layers are added to LMP, then cycling performance is improved, but device complexity increases
Solution Approach 1:
The patent segments the protective shell into functionally distinct layers: crystalline pyrophosphate for structural stability, crystalline phosphate for lithium ion conduction, and carbon for electrical conductivity. This segmentation allows each layer to perform its specific function efficiently, improving cycling performance while maintaining a systematic and manageable structure.
Solution Approach 2:
The patent applies universality by designing a multi-functional coating system where each layer serves multiple purposes: the crystalline pyrophosphate provides structural stability and protects against manganese dissolution, the crystalline phosphate enables lithium ion conduction and further protection, and the carbon layer provides electrical conductivity and additional protection. This multi-functionality reduces the need for separate components.
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 and storage performance of secondary batteries by reducing manganese ion dissolution, inhibiting interfacial side reactions, and maintaining capacity and rate performance.
Implementation Method 1
The pyrophosphate and phosphate with a specified crystallinity can give full play to an ability of the pyrophosphate coating layer to hinder the dissolution of manganese ions
Implementation Method 2
the excellent lithium ion conduction of the phosphate coating layer
Implementation Method 3
the reduction of interfacial side reactions
Implementation Method 4
facilitate well lattice matching between the pyrophosphate coating layer and the phosphate coating layer to allow tight bonding between the two coating layer
Data Source
AI summary
Provided are a secondary battery, a battery module, a battery pack, and an electric device. The secondary battery includes: a positive electrode sheet and a non-aqueous electrolyte, where the positive electrode sheet includes a cathode active material with a core-shell structure, and the cathode active material includes a core and a shell covering the core; the core has a chemical formula of Li1+xMn1-yAyP1-zRzO4; where the first coating layer includes a crystalline pyrophosphate LiaMP2O7 and/or a crystalline pyrophosphate Mb(P2O7)c, the second coating layer includes a crystalline phosphate XPO4, and the third coating layer is carbon; and the non-aqueous electrolyte includes a first lithium salt and a first additive, where the first lithium salt includes one or more selected from the group consisting of LiN(CmF2m+1SO2)(CnF2n+1SO2) and Li(FSO2)2N, where m and n each are a positive integer.