Lithium Cobaltate Cathode Coating for Cycle Stability
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Solution Overview
Problem
Current lithium secondary batteries face challenges in increasing energy density due to limitations in cathode active materials, specifically lithium cobaltate, which suffers from reduced cycle characteristics and stability issues when charging voltage is elevated, leading to decreased capacity and efficiency.
Innovation Solution
A cathode active material is developed with a complex oxide containing lithium and cobalt, coated with a layer of lithium, nickel, and manganese, where the manganese concentration is higher in the external layer, improving chemical stability and cycle characteristics while maintaining high capacity and electric potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If charging voltage is increased to improve energy density, then battery capacity and electric potential increase, but electrolyte oxidation decomposition and cobalt elution occur, reducing cycle characteristics
Solution Approach 1:
A coating layer comprising lithium nickelate and lithium manganate is applied to the surface of the cathode active material particles. This coating layer acts as an intermediary barrier between the cathode active material and the electrolyte, preventing direct harmful interactions while allowing beneficial electrochemical reactions to proceed, thereby enabling higher charging voltages without compromising cycle characteristics
Solution Approach 2:
The cathode active material is constructed as a composite structure with a core of lithium cobaltate particles and a shell of coating layer containing lithium nickelate and lithium manganate. This composite structure combines the high capacity and electric potential of lithium cobaltate with the enhanced stability of lithium nickelate and lithium manganate, resolving the contradiction between energy density and reliability
2Power
If charging voltage is increased to improve energy density, then battery electric potential increases, but electrolyte oxidation decomposition occurs, reducing charge and discharge efficiency
Solution Approach 1:
The coating layer serves as a protective intermediary that prevents direct contact between the high-potential cathode active material and the electrolyte, thereby preventing oxidation decomposition of the electrolyte while maintaining efficient lithium ion transport, which preserves charge and discharge efficiency even at elevated electric potentials
3Quantity of substance
If charging voltage is increased to improve energy density, then battery capacity increases, but cobalt is eluted from the cathode, reducing cycle characteristics
Solution Approach 1:
The coating layer comprising lithium nickelate and lithium manganate acts as a stable intermediary barrier that prevents cobalt elution from the cathode active material into the electrolyte during high-voltage charging cycles, thereby maintaining cathode composition stability while preserving battery capacity
Solution Approach 2:
The composite structure with lithium nickelate and lithium manganate coating provides enhanced compositional stability to the lithium cobaltate core, preventing cobalt elution while maintaining the high capacity characteristics of the original material
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 active material enhances the battery's capacity, electric potential, high-temperature characteristics, and cycle stability, allowing for increased charging voltage without deteriorating the electrolyte or cobalt, thus improving overall battery performance.
Implementation Method 1
the oxidizing atmosphere in the vicinity of the cathode becomes strong. In the result, the electrolyte is easily deteriorated by oxidation decomposition, or cobalt is easily eluted from the cathode
Data Source
AI summary
A cathode active material capable of increasing a capacity and improving high temperature characteristics or cycle characteristics, a method of manufacturing it, a cathode using the cathode active material, and a battery using the cathode active material are provided. In a cathode active material contained in a cathode, a coating layer is provided on at least part of complex oxide particle containing at least lithium (Li) and cobalt (Co). The coating layer is an oxide which contains lithium (Li) and at least one of nickel (Ni) and manganese (Mn).