Cathode Active Material Oxygen Control for Higher Initial Capacity
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Solution Overview
Problem
Lithium-ion secondary batteries using lithium-transition metal composite oxides as cathode active materials face challenges in achieving improved initial capacity.
Innovation Solution
A cathode active material with a stoichiometric oxygen content of 1.9 or more, comprising alternate layers of transition metals (such as nickel, cobalt, and manganese) and lithium, is produced by firing a raw material in an atmosphere with an oxygen partial pressure of 1.1 atm or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the raw material is fired under conventional oxygen partial pressure (less than 1.1 atm), then the production cost and equipment complexity are reduced, but the stoichiometric oxygen content of the cathode active material is insufficient (less than 1.9), resulting in poor initial capacity
Solution Approach 1:
The patent changes the oxygen partial pressure parameter from conventional levels (less than 1.1 atm) to a specific higher range (1.1-6.0 atm) during the firing process. This parameter change directly increases the stoichiometric oxygen content of the cathode active material from less than 1.9 to 1.9 or more, thereby improving initial capacity while maintaining structural stability
Solution Approach 2:
The patent applies an oxygen-rich atmosphere (oxygen partial pressure of 1.1-6.0 atm) during firing, which acts as a strong oxidizing environment. This accelerated oxidation ensures sufficient oxygen incorporation into the cathode active material structure, achieving a stoichiometric oxygen content of 1.9 or more and preventing oxygen deficiency that would otherwise limit initial capacity
2Productivity
If the oxygen partial pressure is increased to 1.1 atm or more to improve stoichiometric oxygen content, then the initial capacity is improved, but the equipment complexity and production cost increase
Solution Approach 1:
The patent modifies the oxygen partial pressure parameter to a specific range (1.1-6.0 atm) that optimizes the balance between initial capacity improvement and equipment requirements. This controlled parameter change achieves sufficient oxygen content (stoichiometric oxygen ≥ 1.9) without requiring excessively high pressures, thereby limiting equipment complexity increases
Solution Approach 2:
The patent applies a moderate increase in oxygen partial pressure (1.1-6.0 atm) rather than extreme high pressure. This partial action approach provides sufficient oxygen for achieving stoichiometric oxygen content of 1.9 or more and improving initial capacity, while avoiding the need for complex high-pressure equipment that would be required for much higher pressure applications
3Productivity
If the stoichiometric oxygen content is increased to 1.9 or more, then the initial capacity is improved, but the crystal structure stability may be compromised
Solution Approach 1:
The patent carefully controls the oxygen partial pressure within a specific range (1.1-6.0 atm) during firing to achieve stoichiometric oxygen content of 1.9 or more. This controlled parameter change ensures sufficient oxygen for high initial capacity while preventing excessive oxygen that could cause structural distortion or phase transitions, thereby maintaining crystal structure stability
Solution Approach 2:
The patent achieves the target stoichiometric oxygen content of 1.9 or more through moderate oxygen partial pressure (1.1-6.0 atm) rather than extreme oxygen enrichment. This partial action approach provides just enough oxygen to improve initial capacity while avoiding oxygen excess that would compromise crystal structure stability, thus resolving the contradiction between capacity improvement and structural stability
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 increased stoichiometric oxygen content stabilizes the octahedral structure of the transition metal layers, enhancing lithium ion insertion and resulting in improved initial capacity of the lithium-ion secondary battery.
Implementation Method 1
firing, in an atmosphere containing oxygen, a raw material of the cathode active material containing lithium and at least one kind of transition metal selected from among nickel, cobalt, and manganese
Data Source
AI summary
A cathode active material includes a crystal structure including an alternate arrangement of transition metal layers and lithium layers. The transition metal layers include at least one kind of transition metal selected from nickel, cobalt and manganese. In the cathode active material, a stoichiometric oxygen content is 1.9 or more.