Lithium Composite Oxide Cathode Voltage Stability
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Solution Overview
Problem
Lithium ion secondary batteries using lithium-rich cathode active materials face insufficient discharge capacity and voltage deterioration during charge and discharge cycles, which limits their energy density and performance.
Innovation Solution
A lithium-containing composite oxide with a specific formula (LiaiNibCocMndMeO2) is developed, where the valence of Ni is between 2.15 and 2.45, and the composition is optimized to enhance discharge capacity and suppress voltage deterioration, along with a coating of Zr, Ti, or Al on the cathode active material to improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-rich cathode active material is used to increase discharge capacity, then the discharge capacity of lithium ion secondary battery is improved, but the discharge voltage deteriorates during charge and discharge cycles
Solution Approach 1:
The patent uses a composite oxide material with specific crystal structures (R-3m and C2/m space groups) containing Li, Mn, Co, Ni, and other elements in controlled ratios. This composite structure enables the material to achieve high discharge capacity while maintaining voltage stability through the synergistic effects of multiple elements and crystal phases
Solution Approach 2:
The patent applies element-specific doping strategies where different elements (Na, Mg, Ti, Zr, Al, W, Mo) are introduced at specific sites in the crystal structure to achieve local optimization. The X-ray diffraction peak intensity ratios are controlled to ensure specific local structural characteristics that balance capacity and voltage stability
2Use of energy by moving object
If lithium-rich cathode active material is used to increase discharge capacity, then the energy density of lithium ion secondary battery is improved, but the deterioration of discharge voltage due to repetition of charge and discharge cycle increases
Solution Approach 1:
The patent precisely controls compositional parameters including the ratio of X-ray diffraction peak intensities (0.02 to 0.5), element contents (Mn content at least 0.55 in molar ratio, boron 0.001 to 3 wt%, or elements A at 0.03 to 5 wt%), and crystal structure characteristics. These parameter optimizations enable high energy density while suppressing voltage deterioration during cycling
3Ease of manufacture
If conventional lithium cathode active material (LiCoO2) is used, then the battery structure is simple and easy to manufacture, but the discharge capacity per unit mass is insufficient for downsizing requirements
Solution Approach 1:
The patent modifies the conventional LiCoO2 composition by introducing additional elements (Mn, Ni, Co in specific ratios, plus Na, Mg, Ti, Zr, Al, W, or Mo) and controlling the Li to transition metal ratio (a/(b+c+d+e) between 1.1 and 1.4). This compositional parameter change increases discharge capacity per unit mass while maintaining a manufacturing process similar to conventional materials
Solution Approach 2:
The patent creates a composite oxide structure that combines multiple transition metal elements with lithium in a layered crystal structure. This composite approach maintains the structural simplicity and manufacturability of conventional lithium cobalt oxide while achieving superior discharge capacity through the synergistic effects of multiple elements
Data Source
AI summary
To provide a lithium-containing composite oxide capable of obtaining a lithium ion secondary battery having a large discharge capacity wherein the deterioration of the discharge voltage due to repetition of a charge and discharge cycle is suppressed, a cathode active material, a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery. A lithium-containing composite oxide, which is represented by the formula I:LiaiNibCOcMndMeO2 Formula I,wherein M is at least one member selected from the group consisting of Na, Mg, Ti, Zr, Al, W and Mo, a+b+c+d+e=2, 1.1≤a/(b+c+d+e)≤1.4, 0.2≤b/(b+c+d+e)≤0.5, 0≤c/(b+c+d+e)≤0.25, 0.3≤d/(b+c+d+e)≤0.6, and 0≤e/(b+c+d+e)≤0.1, and wherein the valence of Ni is from 2.15 to 2.45.