Over-lithiated Composite Cathode for Stable High Capacity
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Solution Overview
Problem
Existing lithium battery positive active materials have limited electric capacity and structural instability during charging and discharging cycles, leading to decreased voltage and reduced battery lifetime.
Innovation Solution
A composite positive active material is developed, comprising an over-lithiated lithium transition metal oxide with a specific chemical formula and structure, where a metal cation is doped into the Li ion layer to stabilize the lithium ions, preventing migration and maintaining structural integrity during charge-discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li2MO3 is used as a positive active material to achieve high capacity, then the battery capacity increases, but the average voltage decreases due to transition metal atom translocation
Solution Approach 1:
The patent applies local quality by creating a composite structure where Li2MO3 and LiM'O2 have different functional roles. The Li2MO3 component provides high capacity through excessive lithium content, while the LiM'O2 component with M' in +3 oxidation state maintains structural stability and prevents voltage decay. This local differentiation of material properties within the composite resolves the contradiction between achieving high capacity and maintaining voltage.
Solution Approach 2:
The patent uses composite materials by combining Li2MO3 and LiM'O2 in a specific composite structure. The composite leverages the high capacity advantage of Li2MO3 while the LiM'O2 component provides structural stability to prevent transition metal translocation. This composite approach allows simultaneous achievement of high capacity and stable voltage characteristics.
2Quantity of substance
If Li2MO3 is used to enable intercalation of large amount of Li ions, then high capacity properties are achieved, but structural change occurs during charging/discharging cycles
Solution Approach 1:
The patent applies local quality by assigning different structural roles to different components. The Li2MO3 component accommodates large amounts of Li ions for high capacity, while the LiM'O2 component with M' in +3 oxidation state provides structural stability. This local functional differentiation allows the composite to simultaneously achieve high Li ion intercalation capacity and structural stability during cycling.
Solution Approach 2:
The patent uses composite materials to combine the high Li ion intercalation capacity of Li2MO3 with the structural stability of LiM'O2. The composite structure allows excessive lithium content in Li2MO3 to be tolerated without causing structural collapse, as the LiM'O2 component maintains structural integrity during charging and discharging cycles.
3Speed
If transition metal atoms translocate into empty Li ion sites, then Li ion mobility increases, but average voltage decreases
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the composite. The Li2MO3 component allows Li ion mobility and translocation events, while the LiM'O2 component with M' in +3 oxidation state acts as a structural anchor that prevents excessive translocation. This local differentiation maintains voltage by confining translocation effects to specific regions.
Solution Approach 2:
The patent uses composite materials to manage transition metal translocation. The LiM'O2 component in the composite acts as a structural stabilizer that limits the extent of transition metal atom translocation into Li ion sites, thereby preventing significant voltage decay while still allowing sufficient Li ion mobility for high capacity.
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 composite material enhances the battery's capacity, stability, and lifetime by suppressing changes in the discharge curve and maintaining high voltage, thereby improving overall performance.
Implementation Method 1
M'' is doped in a Li ion layer of Li2-yM''yMO3
Data Source
AI summary
A composite positive active material including an over-lithiated lithium transition metal oxide, the over-lithiated transition metal oxide including a compound represented by Formula 1 or Formula 3: [Formula 1] xLi2-yM″yMO3-(1-x)LiM′O2, [Formula 3] xLi2-yM″yMO3-x′LiM′O2-x″Li1+dM′″2-dO4, x+x′+x″=1, 0<x<1, 0<x′<1, 0<x″<1, 0<y≦1, and 0≦d≦0.33, is disclosed. A positive electrode and a lithium battery containing the composite positive active material, and a method of preparing the composite positive active material are also disclosed.