Sodium-Containing Oxide Cathode for Stable High-Potential Lithium-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous lithium ion secondary batteries face issues with decomposition of the crystal structure and decreased reversibility when lithium is extracted from LiCoO2 at high composition ratios, leading to low discharge capacity density and poor cycle performance, especially when charged to high potentials.
Innovation Solution
A nonaqueous electrolyte secondary battery using a positive electrode active material of sodium-containing oxide NaALiBMO2±α, where 0.5≦A≦1.1, 0≦B≦0.3, and 0≦α≦0.3, belonging to the P63/mmc space group, which maintains a stable crystal structure even at high lithium extraction, thereby achieving high charge-discharge capacity density and good cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium is extracted from LiCoO2 at high composition ratios (x=0.5 or more), then discharge capacity density is improved, but crystal structure decomposition and reversibility decrease occur
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode active material from conventional LiCoO2 to a lithium-containing layered compound with formula Li1-xM1-yMn1/3Co1/3Mn1/3O2, where M is a transition metal. By adjusting the composition ratios (x, y) and introducing additional transition metals, the patent achieves both high discharge capacity density (160 mAh/g or more) and maintained crystal structure stability during charging to high potentials (5.0 V vs. Li/Li+).
Solution Approach 2:
The patent employs a composite layered compound structure combining multiple transition metals (Mn, Co, and at least one of Ni, Fe, or Cu) in specific ratios. This composite material approach allows the positive electrode active material to achieve high capacity while maintaining structural integrity, as the different metal elements work synergistically to prevent Jahn-Teller distortion and crystal structure decomposition during lithium extraction.
2Use of energy by moving object
If LiCoO2 is charged to high potentials (5.0 V vs. Li/Li+), then energy density is improved, but discharge capacity density significantly decreases due to poor cycle performance
Solution Approach 1:
The patent modifies the positive electrode active material composition to Li1-xM1-yMn1/3Co1/3Mn1/3O2 with optimized parameters (x=0.05-0.20, y=0.01-0.10) that enable stable operation at high charging potentials (5.0 V vs. Li/Li+) without significant capacity loss. The modified composition maintains reversible lithium extraction and insertion, preserving discharge capacity density while achieving high energy density.
Solution Approach 2:
The patent introduces transition metals (Ni, Fe, or Cu) that can tolerate high oxidation states and structural stress, effectively acting as sacrificial elements that protect the overall crystal structure from decomposition during high-potential charging. These additional metal elements absorb the structural stress, allowing the material to maintain its capacity over repeated charge-discharge cycles at high potentials.
3Ease of manufacture
If sodium containing layered compounds are used for ion exchange, then synthesis ease is improved, but discharge capacity density is low (about 130 mAh/g)
Solution Approach 1:
The patent performs preliminary ion exchange by first synthesizing sodium-containing layered compounds with the desired layered structure, then exchanging sodium ions with lithium ions in a controlled manner. This preliminary structuring with sodium facilitates easier synthesis of the complex layered structure, which is subsequently optimized through lithium ion exchange to achieve high discharge capacity density (160 mAh/g or more) while maintaining the synthesis advantages.
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 sodium-containing oxide with a stable crystal structure ensures high charge-discharge capacity density and maintains performance even after repeated charging to high potentials, resulting in a nonaqueous electrolyte secondary battery with high capacity and good cycle performance.
Implementation Method 1
transfer of lithium ions between a positive electrode and a negative electrode causes charges and discharges
Implementation Method 2
the sodium containing oxide contains NaALiBMO2±α (0.5≦A≦1.1, 0≦B≦0.3, and 0≦α≦0.3) that belongs to a space group P63/mmc of a hexagonal system... the crystal structure is unlikely to decomposition even though the NaALiBMO2±α is charged to high potentials
Data Source
AI summary
A positive electrode active material is made of sodium containing oxide. The sodium containing oxide contains NaALiBMO2±α that belongs to a space group P63/mmc of a hexagonal system, where the M includes at least one of manganese (Mn) and cobalt (Co). In the NaALiBMO2±α, the composition ratio A of sodium (Na) is not less than 0.5 and not more than 1.1, the composition ratio B of lithium (Li) is larger than 0 and not more than 0.3, and the α is not less than 0 and not more than 0.3.