Spinel-Rock-Salt Composite for High-Potential Lithium Battery Stability
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Solution Overview
Problem
Lithium secondary batteries using Ni—Mn spinel-structure oxide as a high-potential positive electrode active material face capacity deterioration due to transition metal elution and nonaqueous electrolyte decomposition at high potentials, leading to reduced cycle characteristics and energy density.
Innovation Solution
A positive electrode active material comprising a nickel-and-manganese-containing composite oxide with a spinel phase and a layered rock-salt phase, where the latter efficiently absorbs acids produced during high-potential charging, suppressing transition metal elution and maintaining lithium supply, thereby enhancing durability and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Ni—Mn spinel-structure oxide is used as high-potential positive electrode active material to increase energy density, then action potential increases (4.3 V or higher vs. lithium metal), but transition metal elution occurs and battery capacity deteriorates during repeated charging and discharging
Solution Approach 1:
A protective coating layer is applied to the surface of the Ni—Mn spinel-structure oxide particles. This coating layer acts as an intermediary barrier that prevents direct contact between the spinel oxide and the nonaqueous electrolyte, thereby suppressing transition metal elution and electrolyte decomposition while maintaining high potential operation, thus improving cycle characteristics without sacrificing energy density
Solution Approach 2:
The surface composition and structure of the spinel oxide are modified by controlling synthesis parameters such as doping with other metal elements (e.g., Co, Zn, Al) or adjusting particle size and morphology. These parameter changes enhance surface stability and reduce transition metal elution at high potentials, allowing the material to maintain both high energy density and good cycle characteristics
2Use of energy by moving object
If high-potential charging is performed to improve energy density, then action potential increases, but nonaqueous electrolyte decomposes to produce additional acid (e.g., HF) which promotes transition metal elution
Solution Approach 1:
The protective coating layer serves as an intermediary barrier that physically separates the spinel oxide from the nonaqueous electrolyte. This prevents the electrolyte from decomposing at high potentials and eliminates the production of harmful acids like HF, while still allowing lithium ion transport, thus maintaining high energy density without generating harmful byproducts
Solution Approach 2:
The coating layer material is selected to be more reactive toward any produced acids than the spinel oxide surface. The acid preferentially reacts with the coating layer, converting the harmful acid into benign reaction products on the coating surface, thereby protecting the spinel oxide from acid attack and transition metal elution while maintaining high potential operation for energy density
3Use of energy by moving object
If repeated high-potential charging and discharging is performed to improve performance, then energy density increases, but temperature increases (60° C. or higher) causing lithium deactivation on negative electrode surface
Solution Approach 1:
The protective coating layer acts as a thermal barrier that reduces heat generation during high-potential charging and discharging. By suppressing side reactions between the spinel oxide and electrolyte, the coating minimizes exothermic processes, thereby controlling temperature rise and preventing lithium deactivation on the negative electrode while maintaining high energy density operation
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 proposed active material effectively stabilizes lithium supply and prevents capacity degradation even under high-potential charging conditions, improving the durability and cycle characteristics of lithium secondary batteries.
Implementation Method 1
the layered rock-salt phase efficiently absorbs the acid
Implementation Method 2
oxygen (O) may be desorbed from the nickel-and-manganese-containing composite oxide
Implementation Method 3
a part of the nonaqueous electrolyte may be oxidized and decomposed to produce an acid
Implementation Method 4
a part of the nonaqueous electrolyte may be oxidized and decomposed to produce an acid
Data Source
AI summary
A positive electrode active material for a lithium secondary battery includes a primary particle containing a spinel phase and a layered rock-salt phase. The spinel phase is formed of a nickel-and-manganese-containing composite oxide having a spinel crystal structure that includes lithium, nickel, and manganese. The layered rock-salt phase is formed of a transition metal composite oxide having a layered rock-salt crystal structure that includes lithium and at least one transition metal element. The nickel-and-manganese-containing composite oxide contains oxygen and fluorine. The transition metal composite oxide includes oxygen and fluorine.