Lithium-Iron Oxide Cathode Additive Coating for Air Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in increasing capacity and reducing irreversible capacity due to volume changes in metal and metal oxide anode active materials, leading to instability and decreased performance, particularly with materials like Li6FeO4 which deteriorates quickly in air and has low electrical conductivity.
Innovation Solution
A cathode additive comprising lithium-iron oxide particles doped or undoped with hetero-elements, coated with a lithium borate-based compound, which enhances air stability and electrical conductivity, and includes a carbon coating layer and carbon nanotube-containing layer to improve irreversible capacity and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li6FeO4 is used as sacrificial positive electrode material, then high initial irreversible capacity is achieved, but air stability deteriorates quickly
Solution Approach 1:
A coating layer comprising lithium phosphate and boron-containing compound is applied on the surface of Li6FeO4 particles. This coating layer acts as an intermediary protective barrier that prevents direct contact between Li6FeO4 and air, thereby maintaining air stability while preserving the high initial irreversible capacity of the underlying Li6FeO4 material.
Solution Approach 2:
The sacrificial positive electrode material is designed as a composite structure where Li6FeO4 particles are coated with a composite coating layer containing lithium phosphate and boron-containing compounds. This composite material approach combines the high irreversible capacity of Li6FeO4 with the protective properties of the coating layer, achieving both high initial irreversible capacity and improved air stability.
2Quantity of substance
If Li6FeO4 is used as sacrificial positive electrode material, then high initial irreversible capacity is achieved, but electrical conductivity remains low
Solution Approach 1:
The coating layer comprising lithium phosphate and boron-containing compound serves as an intermediary that improves electrical conductivity at the particle level while not interfering with the high irreversible capacity mechanism. The coating facilitates better charge transfer between particles, thereby enhancing overall electrical conductivity of the electrode material.
Solution Approach 2:
The surface properties of Li6FeO4 particles are modified by applying a coating layer that changes the electrical parameters of the material. The lithium phosphate and boron-containing compound coating alters the surface conductivity characteristics, improving electron transport while maintaining the bulk material's high irreversible capacity properties.
3Quantity of substance
If metal and metal oxide anode active material is applied, then higher capacity is achieved, but volume change increases significantly
Solution Approach 1:
The patent extracts and addresses the volume change problem by applying a protective coating layer on the anode active material particles. This coating layer compensates for the volume expansion and contraction during charge-discharge cycles, allowing the use of high-capacity metal and metal oxide materials without suffering from their inherent volume change issues.
4Quantity of substance
If metal and metal oxide anode active material is applied, then higher capacity is achieved, but irreversible lithium loss increases
Solution Approach 1:
The sacrificial positive electrode material (coated Li6FeO4) performs a preliminary action by releasing lithium ions during initial charging cycles. This preliminary lithium release compensates for the irreversible lithium loss that occurs when metal and metal oxide anode materials are used, thereby enabling the use of high-capacity anodes without excessive lithium loss.
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 cathode additive exhibits high initial irreversible capacity, improved air stability, and enhanced electrical conductivity, effectively compensating for lithium loss and suppressing gas generation, thereby increasing battery lifespan and safety.
Implementation Method 1
A cathode additive comprising lithium-iron oxide particles doped or undoped with hetero-elements, coated with a lithium borate-based compound, which enhances air stability and electrical conductivity
Implementation Method 2
includes a carbon coating layer and carbon nanotube-containing layer to improve irreversible capacity and safety
Data Source
AI summary
A cathode additive for a lithium secondary battery, a manufacturing method thereof, a cathode for a lithium secondary battery including the same, and a lithium secondary battery are provided herein. The cathode additive has excellent air stability while exhibiting high initial irreversible capacity. The cathode additive includes lithium (Li)-iron (Fe) oxide particles doped or undoped with a hetero-element, and a lithium borate-based compound-containing layer formed on the lithium-iron oxide particles.