Orthophosphate-Coated Cathode for High-Voltage Battery Stability
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Solution Overview
Problem
Secondary batteries with high voltage plateaus face challenges in maintaining electrochemical performance due to corrosion and stripping of transition metals, leading to reduced cycle and storage life, despite efforts to improve energy density.
Innovation Solution
A secondary battery design incorporating a positive electrode active material with a central core material coated with an orthophosphate modification layer and a non-aqueous electrolyte containing a fluorinated phosphate, which reduces metal stripping and SEI film destruction, enhancing electrochemical performance at high voltages while retaining high energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a positive electrode active material having a high voltage plateau is used to improve energy density, then the energy density of the secondary battery is improved, but corrosion of the surface of the positive electrode active material and stripping of transition metal are aggravated
Solution Approach 1:
An orthophosphate modification layer is introduced as an intermediary between the positive electrode active material and the electrolyte. This modification layer acts as a protective barrier that prevents direct contact and harmful interactions, thereby reducing surface corrosion and transition metal stripping while maintaining the high voltage plateau characteristics of the underlying active material
Solution Approach 2:
The positive electrode active material is transformed into a composite structure by coating it with orthophosphate. This composite material combines the high voltage plateau properties of the core active material with the protective and stabilizing characteristics of the orthophosphate shell, achieving both high energy density and improved stability
2Reliability
If the concentration of fluorinated phosphate in the non-aqueous electrolyte is increased to reduce dissolution of orthophosphate, then protection of central core material is improved, but kinetic performance and energy density may be affected
Solution Approach 1:
The concentration of fluorinated phosphate in the electrolyte is precisely controlled within an optimized range rather than being maximized. This parameter optimization ensures sufficient protection against orthophosphate dissolution while avoiding excessive concentrations that would impede ion transport and degrade kinetic performance
Solution Approach 2:
Instead of using a high concentration of fluorinated phosphate, a partial concentration within the optimized range is employed. This partial action approach provides adequate protection for the central core material without the detrimental effects of excessive fluoride ion concentration on electrochemical kinetics
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 cycle and storage life of secondary batteries at high voltages by reducing transition metal stripping and SEI film destruction, maintaining high energy density and kinetic performance.
Implementation Method 1
the positive electrode active material includes a central core material and a modification layer disposed on a surface of the central core material, the modification layer including an orthophosphate
Implementation Method 2
the non-aqueous electrolyte includes a fluorinated phosphate with a molecular formula Bb+m[PO1+cF3-c]c−n... dissolution of the orthophosphate can be significantly reduced
Implementation Method 3
destruction of an SEI film on a surface of a negative electrode active material is reduced
Data Source
AI summary
A secondary battery includes a positive electrode sheet having a positive electrode active material and a non-aqueous electrolyte. The positive electrode active material includes a central core material and a modification layer disposed on a surface of the central core material. The modification layer including an orthophosphate with a molecular formula Aa+x[PO4]3−y, where A denotes one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Ni, Fe, Co, Ti, Al, Cr, V, Nb, and W, 1≤a≤6, and ax=3y. The non-aqueous electrolyte includes a fluorinated phosphate with a molecular formula Bb+m[PO1+cF3-c]c−n, where B denotes one or more of Li, Na, K, Rb, Cs, Mg, Ca, and Ba, 1≤b≤2, c denotes 1 or 2, and bm=cn.