O2-Type Cathode Material to Resist High-Voltage Spinel Transition
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Solution Overview
Problem
Existing lithium-ion secondary battery positive electrode active materials with Co transition to spinel structures at high charging voltages, leading to deteriorated charge-discharge characteristics, and Co is expensive and in limited supply.
Innovation Solution
A positive electrode active material with an O2-type layered structure and a composition represented by LiaNabMncMdO(2±α), where M includes Ni and other additive elements, allowing charging at high voltages without Co.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Co-containing positive electrode active material is used to enhance discharge capacity, then discharge capacity is improved, but charge-discharge characteristics deteriorate at high voltage due to spinel structure transition
Solution Approach 1:
The invention removes Co from the positive electrode active material composition entirely, extracting the problematic element that causes spinel structure transition at high voltage. The material achieves high discharge capacity without Co by using a specific O2-type layered structure with Li, Na, Mn, and additive elements, thereby eliminating the reliability issue while maintaining the desired discharge capacity.
Solution Approach 2:
The invention changes the crystal structure parameter from O3-type to O2-type layered structure, and adjusts the composition parameters (a, b, c, d, α) to specific ranges. This parameter change stabilizes the structure at high voltage and prevents spinel transition, thereby maintaining good charge-discharge characteristics while achieving high discharge capacity.
2Quantity of substance
If Co is used in positive electrode active material to improve battery performance, then discharge capacity and discharge rate characteristics are enhanced, but manufacturing cost increases due to expensive and limited Co resources
Solution Approach 1:
The invention extracts Co from the material composition completely, eliminating dependence on this expensive and scarce resource. The high discharge capacity is achieved through optimized composition of abundant elements (Li, Na, Mn, Ni, Al, Ti, Sn, Zr, Nb, W, Mo) and the specific O2-type layered structure, thereby reducing manufacturing cost while maintaining performance.
Solution Approach 2:
The invention replaces expensive Co with cheaper alternative elements that can achieve similar or better performance. The use of abundant elements like Mn combined with additive elements (Ni, Al, Ti, etc.) in specific proportions provides a cost-effective solution that eliminates the need for expensive Co while maintaining high discharge capacity.
3Quantity of substance
If charging voltage is increased to enhance discharge capacity, then energy density is improved, but crystal structure transitions to spinel form causing performance deterioration
Solution Approach 1:
The invention changes the crystal structure to O2-type layered structure with specific composition parameters, which fundamentally alters the structural stability characteristics. This parameter change enables the material to maintain structural integrity at high charging voltages, preventing spinel transition and allowing high voltage charging while preserving good charge-discharge characteristics.
Solution Approach 2:
The invention creates a composite material system with Li, Na, Mn, and additive elements (Ni, Al, Ti, Sn, Zr, Nb, W, Mo) in specific proportions. This composite structure synergistically enhances crystal structure stability at high voltage, preventing spinel transition while enabling high discharge capacity through the combined effects of the different elements.
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 material maintains high discharge capacity and excellent discharge rate characteristics, even at high current densities, and does not require Co, thus addressing resource constraints and cost issues.
Implementation Method 1
substituting an Na atom in the Na-doped precursor with an Li atom by ion exchange
Data Source
AI summary
A positive electrode active material, including: a main phase including an O2-type layered structure attributable to space group P63mc; and a composition represented by a formula LiaNabMncMdO(2±α), where M represents one or more additive elements selected from the group consisting of Ni, Al, Ti, Sn, Zr, Nb, W, and Mo, the additive elements include at least Ni, and a, b, c, d and a satisfy 0.7≤a≤1.33, 0<b<0.1, 0.7<c<0.9, 0.9<c+d<1.1, 4≤c/d≤12, and 0≤α≤0.3. A method of producing the positive electrode active material, including: preparing an Na-doped precursor which has a crystal phase having a P2-type layered structure attributable to space group P63/mmc and includes Na, Mn, and the additive element M; and substituting an Na atom in the Na-doped precursor with an Li atom.