Lithium Composite Metallic Oxide Core-Shell Structure for High Voltage Stability
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Solution Overview
Problem
Lithium composite metallic oxides used in high-voltage secondary batteries face challenges in maintaining capacity and stability due to insufficient resistance to high voltage, with existing methods like doping, forming protective films, and altering surface compositions not fully addressing the issue.
Innovation Solution
A lithium composite metallic oxide with a high manganese portion and metallic oxidation portion, expressed by LiaNibCocMndDeOf, where the composition ratio between Ni, Co, and Mn is optimized in the superficial layer, and a metallic oxidation portion acts as a protective film, enhancing stability and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doping an active material with an element of different species is performed to improve resistance to high voltage, then the resistance to high voltage is improved, but the Li storage capacity decreases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core portion contains the doped lithium composite metallic oxide with high voltage resistance, and the superficial layer contains undoped or differently doped material with high Li storage capacity. This allows different regions to have different functions: the core provides stability and resistance to degradation, while the superficial layer provides capacity.
Solution Approach 2:
The patent segments the active material into distinct portions: a core portion and a superficial layer portion. The core portion is doped with elements like Al or Zr to provide high voltage resistance, while the superficial layer is designed to maximize Li storage capacity. This segmentation allows each portion to be optimized for its specific function without compromising the other.
2Reliability
If a protective film is formed on the surface of an active material to prevent contact with electrolytic solution, then degradation from electrolytic solution contact is inhibited, but electric resistance increases
Solution Approach 1:
The patent uses a thin superficial layer (1-10 nm thick) that acts as a protective interface between the core active material and the electrolytic solution. This thin film is sufficient to prevent direct contact and degradation while being thin enough to maintain good electrical conductivity, thus avoiding the harmful effect of increased electric resistance.
Solution Approach 2:
The patent creates a composite structure where the core portion (lithium composite metallic oxide) is combined with a superficial layer that has different properties. The composite structure provides both protection from electrolytic solution degradation and maintains electrical conductivity, resolving the contradiction between protection and conductivity.
3Reliability
If the composition of an active material in the superficial layer is changed to increase Al composition, then theoretical desirability is achieved, but marked advantageous effect is not observed
Solution Approach 1:
The patent optimizes the thickness of the superficial layer to be within a specific range (1-10 nm) and controls the composition ratios of elements in both the core and superficial layer. By carefully adjusting these parameters, the patent achieves both high voltage resistance and high capacity maintained rate, overcoming the limitation of previous approaches that only changed composition without optimizing thickness and ratio.
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 lithium composite metallic oxide maintains a satisfactory Li storage capacity and capacity retention rate even under high voltage conditions, with the high manganese portion and metallic oxidation layer improving stability and inhibiting degradation during charging and discharging.
Implementation Method 1
making a protective film on the surface of an active material with a salt of phosphoric acid, and preventing the active material from contacting directly with an electrolytic solution
Implementation Method 2
degradations of the active material accompanied by charging and discharging operations, namely, accompanied by the absorption and release of Li
Data Source
AI summary
A lithium composite metallic oxide expressed by: LiaNibCocMndDeOf (where 0.2≤“a”≤1.5, “b”+“c”+“d”+“e”=1, 0<“e”<1, “D” is at least one of the following elements: Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf and Rf, and 1.7≤“f”≤2.1), and including: a high manganese portion, which is made of a metallic oxide including Ni, Co and Mn at least and of which the composition ratio between Ni, Co and Mn is expressed by Ni:Co:Mn=g:h:i (note that “g”+“h”+“i”=1, 0<“g”<1, 0<“h”<“c”, and “d”<“i”<1), in a superficial layer thereof; and a metallic oxidation portion in an outermost superficial layer of the high manganese portion.