Layered-Spinel Composite Cathode for Lithium Batteries
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Solution Overview
Problem
Conventional cathode active materials in lithium batteries suffer from high initial irreversible capacities and low charge/discharge efficiencies due to their layered structures, which limit their discharge capacity and stability.
Innovation Solution
A cathode active material with a layered-spinel composite structure, represented by the formula xLi2MO3-yLiMeO2-zLi1+dM′2−dO4, where 0≦d≦0.33, 0<x<1, 0<y<1, 0<z<1, and x+y+z=1, allowing for intercalation and deintercalation of lithium, thereby increasing discharge capacities and charge/discharge efficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a layered structure cathode active material (Li2MO3-LiMeO2) is used to achieve high initial discharge capacity, then the initial discharge capacity increases, but the initial irreversible capacity increases and charge/discharge efficiency decreases
Solution Approach 1:
The cathode active material is segmented into multiple functional layers with distinct roles: the first layer (Li2MO3-LiMeO2) provides high capacity, the second layer (spinel structure) provides stability and reversibility, and the third layer (conductive coating) enhances electron transport. This segmentation allows each layer to optimize its function while working together to resolve the contradiction between high capacity and low irreversible loss.
Solution Approach 2:
The invention uses a composite material structure combining three different types of layers with complementary properties. The layered Li2MO3-LiMeO2 provides high theoretical capacity, the spinel LiMn2O4 layer provides structural stability and reversible lithium insertion/extraction, and the conductive coating layer provides excellent electron conductivity. This composite approach synergistically resolves the contradiction between high discharge capacity and low irreversible capacity.
2Quantity of substance
If the content ratio of Li2MO3 is increased to 50% or more to obtain high discharge capacity, then the discharge capacity increases, but the initial irreversible capacity increases
Solution Approach 1:
The cathode active material is segmented into multiple functional layers with distinct roles: the first layer (Li2MO3-LiMeO2) provides high capacity, the second layer (spinel structure) provides stability and reversibility, and the third layer (conductive coating) enhances electron transport. This segmentation allows each layer to optimize its function while working together to resolve the contradiction between high capacity and low irreversible loss.
Solution Approach 2:
The invention uses a composite material structure combining three different types of layers with complementary properties. The layered Li2MO3-LiMeO2 provides high theoretical capacity, the spinel LiMn2O4 layer provides structural stability and reversible lithium insertion/extraction, and the conductive coating layer provides excellent electron conductivity. This composite approach synergistically resolves the contradiction between high discharge capacity and low irreversible capacity.
3Reliability
If LiCoO2 is used as cathode active material, then the battery has good stability, but the discharge capacity is limited and cost is high
Solution Approach 1:
The invention uses a composite material structure where the spinel LiMn2O4 layer provides structural stability similar to LiCoO2, while the Li2MO3-LiMeO2 layer provides higher theoretical capacity. The conductive coating further enhances performance. This composite approach achieves both stability and high capacity, overcoming the limitations of pure LiCoO2.
Solution Approach 2:
The invention changes the chemical composition parameters by using manganese-based oxides (Li2MO3, LiMeO2, LiMn2O4) instead of cobalt-based LiCoO2. This parameter change reduces cost and increases theoretical capacity while maintaining stability through the spinel structure and conductive coating, resolving the contradiction between stability and capacity.
4Quantity of substance
If LiNixCo1−xO2 or LiNi1−x−yCoxMnymO2 is used to improve discharge capacity, then the capacity increases, but stability and reliability problems persist
Solution Approach 1:
The cathode active material is segmented into multiple functional layers with distinct roles: the first layer (Li2MO3-LiMeO2) provides high capacity, the second layer (spinel structure) provides stability and reversibility, and the third layer (conductive coating) enhances electron transport. This segmentation allows each layer to optimize its function while working together to resolve the contradiction between high capacity and low irreversible loss.
Solution Approach 2:
The invention uses a composite material structure combining three different types of layers with complementary properties. The layered Li2MO3-LiMeO2 provides high theoretical capacity, the spinel LiMn2O4 layer provides structural stability and reversible lithium insertion/extraction, and the conductive coating layer provides excellent electron conductivity. This composite approach synergistically resolves the contradiction between high discharge capacity and low irreversible 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 layered-spinel composite structure enhances lithium batteries' initial coulombic efficiencies and capacity retention ratios, overcoming the limitations of conventional materials by enabling repeated oxidation and reduction of Mn ions, thus improving charge/discharge performance.
Implementation Method 1
Mn is not additionally oxidized, and thus that oxygen is decomposed together with lithium into Li2O
Implementation Method 2
Mn is reduced to 3+
Implementation Method 3
enabling repeated oxidation and reduction of Mn ions, thus improving charge/discharge performance
Implementation Method 4
even when lithium is intercalated or deintercalated, the structural integrity of these Mn oxides is not destroyed
Data Source
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.