Layered-Spinel Cathode Material for Lithium Batteries
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Solution Overview
Problem
Conventional cathode active materials in lithium batteries, such as LiCoO2, have limited discharge capacity and stability issues due to high irreversible capacity, leading to low initial charge/discharge efficiencies.
Innovation Solution
A layered-spinel composite structure lithium metal oxide, represented by the formula (0.6-a)Li[Li1/3Mn2/3]O2 - 0.4LiNi1-b-c Co b Mn c O2 - a/2LiMn2 O4, where 0<b<0.5, 0<c<0.5, and 0<a<0.6, allows for intercalation and deintercalation of lithium, enhancing discharge capacities and charge/discharge efficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as cathode active material, then electrochemical potential and cost are improved, but discharge capacity is limited to about 140 mAh/g
Solution Approach 1:
The patent uses a composite oxide with layered structure xLi2MO3·(1-x)LiMeO2 where M is predominantly Mn and Me is a transition metal. This composite structure combines the advantages of different materials to achieve both high electrochemical potential and high discharge capacity exceeding 140 mAh/g.
Solution Approach 2:
The patent optimizes the composition parameters x and the metal elements M and Me to achieve desired performance. By adjusting the ratio of Li2MO3 to LiMeO2 and selecting appropriate transition metals, the discharge capacity is enhanced while maintaining electrochemical stability.
2Quantity of substance
If Li is removed from LiCoO2 to increase discharge capacity, then capacity is improved, but structural stability deteriorates making Li1-xCoO2 inherently unstable
Solution Approach 1:
The composite oxide structure xLi2MO3·(1-x)LiMeO2 provides structural stability while enabling high discharge capacity. The layered structure with specific metal compositions maintains integrity during lithium intercalation and deintercalation, preventing the instability issues of Li1-xCoO2.
Solution Approach 2:
The patent introduces a composite oxide structure that acts as an intermediary between LiCoO2 and high-capacity materials. This intermediate structure provides the stability of LiCoO2 while enabling the high capacity of lithium-rich compositions through controlled lithium extraction.
3Quantity of substance
If the content ratio of Li2MO3 is increased to 50% or more to obtain high discharge capacity, then discharge capacity is improved, but initial irreversible capacity is increased reducing initial efficiency
Solution Approach 1:
The patent optimizes the composition parameter x to balance discharge capacity and initial efficiency. By carefully selecting x and the metal compositions, the initial irreversible capacity is minimized while maintaining high discharge capacity, improving initial charge/discharge efficiency.
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 layered-spinel composite structure increases discharge capacities and charge/discharge efficiencies, reducing irreversible capacity and maintaining high coulombic efficiency, as demonstrated by charge/discharge experiments showing improved capacity retention and efficiency compared to conventional materials.
Implementation Method 1
allows for intercalation and deintercalation of lithium
Implementation Method 2
charge/discharge experiments showing improved capacity retention and efficiency
Data Source
Figure 1
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Figure 2B
AI summary
Cathode active materials including lithium composite metal oxides having layered-spinel composite structures are provided. The lithium metal oxide may be represented by the formula xLi2MO3-yLiMeO2-zLi1+dM'2-dO4, in which 0≤d≤0.33, 0<x<1, 0<y<1, 0<z<1 and x+y+z=1. In the formula M is selected from Mn, Ti, Zn, and combinations thereof. Me is selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr, B and combinations thereof. M' is selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr, B, and combinations thereof. The cathode active materials have layered-spinel composite structures in which lithium can be intercalated and deintercalated. Lithium batteries including the cathode active materials show high initial coulombic efficiencies and high capacity retention ratios.