Lithium Manganese Phosphate Cathode Doping for Rate and Cycle Stability
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Solution Overview
Problem
Lithium manganese phosphate cathode active materials exhibit poor rate performance and cycle performance, necessitating improvements in energy density, stability, and safety.
Innovation Solution
A secondary battery with a cathode active material of the form LiaAxMn1-yByP1-zCzO4-nDn, where A, B, C, and D are doped elements at specific sites in LiMnPO4, combined with a non-aqueous electrolyte containing a lithium salt and an isocyanate-based additive to reduce lattice change rate, surface activity, and manganese ion dissolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium manganese phosphate cathode active material is used, then safety and cycle life are improved, but rate performance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the doping amounts of multiple elements (A: 0.01-0.1 mol, B: 0.01-0.5 mol, C: 0.01-0.1 mol, D: 0.01-0.1 mol) in the cathode active material formula LiaAxMn1-yByP1-zCzO4-nDn. This multi-parameter optimization resolves the contradiction by adjusting compositional parameters to achieve both improved cycle life and enhanced rate performance simultaneously.
Solution Approach 2:
The patent creates a composite doped structure by incorporating four different elements (A, B, C, D) into the lithium manganese phosphate lattice. This composite approach combines the benefits of each dopant: A elements improve structural stability for cycle life, while B elements enhance electron conductivity for rate performance, thereby resolving the technical contradiction through material composition design.
2Reliability
If lithium manganese phosphate cathode active material is used, then safety is improved, but energy density deteriorates
Solution Approach 1:
The patent resolves this contradiction by changing the compositional parameters of the cathode active material through controlled doping. By optimizing the amounts of elements A, B, C, and D within specific ranges, the material achieves improved safety through structural stabilization while maintaining or enhancing energy density through improved electrochemical performance and reduced side reactions.
Solution Approach 2:
The patent applies local quality by introducing dopants at specific lattice sites to create localized structural improvements. The doping elements are distributed throughout the cathode material structure to locally enhance stability and electrochemical properties, allowing the material to maintain high energy density while improving overall safety through localized structural optimizations.
3Duration of action of stationary object
If lithium manganese phosphate cathode active material is used, then cycle life is improved, but high temperature stability deteriorates
Solution Approach 1:
The patent resolves this contradiction by changing the compositional parameters through multi-element doping. The specific doping amounts (A: 0.01-0.1 mol, B: 0.01-0.5 mol, C: 0.01-0.1 mol, D: 0.01-0.1 mol) are optimized to simultaneously improve cycle life and high temperature stability by stabilizing the crystal structure against thermal degradation while maintaining long-term cycling performance.
Solution Approach 2:
The patent creates a composite doped structure that combines multiple elements to achieve synergistic effects. The composite material incorporates elements A, B, C, and D that work together to provide both cycle life improvement through structural stabilization and high temperature stability through enhanced thermal resistance, resolving the contradiction between duration and compositional stability.
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 enhances rate performance, cycle stability, and high-temperature stability, while improving the gram capacity and compacted density of the cathode material, thereby enhancing the overall performance of lithium-ion batteries.
Implementation Method 1
Without wishing to be bound by theory, it is believed that the performance improvement of lithium manganese phosphate is related to reducing the lattice change rate of lithium manganese phosphate and reducing surface activity during lithium deintercalation
Implementation Method 2
Mn-site doping can also effectively reduce surface activity, thereby inhibiting the dissolution of manganese ions and the interface side reaction between the cathode active material and the electrolyte
Implementation Method 3
inhibiting the dissolution of manganese ions and the interface side reaction between the cathode active material and the electrolyte
Data Source
AI summary
A secondary battery, a battery module, a battery pack, and an electric device. The secondary battery includes a cathode piece and a non-aqueous electrolyte, in which, the cathode piece includes a cathode active material, and the cathode active material has a chemical formula represented by LiaAxMn1-yByP1-zCzO4-nDn; the non-aqueous electrolyte includes a first lithium salt and a first additive, optionally, the first lithium salt is one or more selected from the group consisting of LiN(CmF2m+1SO2)(CnF2n+1SO2) and Li(FSO2)2N, m and n represent positive integers; the first additive includes one or more of a compound represented by Formula 1. Using the cathode active material and/or a combination of the cathode active material and the non-aqueous electrolyte improves the rate performance, cycle performance, and high temperature stability of the lithium manganese phosphate secondary battery.