O2-Type Cathode Material for High-Voltage Li-Ion Capacity Stability
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in achieving high discharge capacity and stable charge-discharge characteristics at high voltages due to the transition of the O3 structure to a spinel structure, and cobalt, which is scarce and expensive, is often used in positive electrode active materials.
Innovation Solution
A positive electrode active material with an O2-type layered structure and specific composition Li a Na b Mn c M d O (2 ± α) is developed, where M includes Ni, Al, Ti, Sn, Zr, Nb, or Mo, and is produced by ion exchange from an Na-doped precursor with a P2-type layered structure, maintaining stability at high voltages and enhancing discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the voltage during charging is increased to increase discharge capacity, then the discharge capacity is improved, but the O3 structure transitions to a spinel structure causing charge-discharge characteristics to deteriorate
Solution Approach 1:
The patent changes the crystal structure parameter from O3 to O2-type layered structure, which maintains structural stability at high charging voltages and prevents transition to spinel structure, thereby maintaining good charge-discharge characteristics while enabling high discharge capacity
Solution Approach 2:
The patent uses a composite positive electrode active material containing Li, Na, Mn, and additive elements (Ni, Al, Ti, Sn, Zr, Nb, W, or Mo) in specific ratios, creating a composite structure that combines the advantages of different elements to achieve both high discharge capacity and structural stability
2Quantity of substance
If Co is used in the positive electrode active material to enhance discharge capacity and discharge rate characteristics, then the battery properties are improved, but the cost increases and resource scarcity becomes a problem
Solution Approach 1:
The patent replaces expensive and scarce Co with more abundant and cheaper elements such as Mn combined with additive elements (Ni, Al, Ti, Sn, Zr, Nb, W, or Mo), creating a cost-effective positive electrode active material that maintains high discharge capacity and excellent discharge rate characteristics
Solution Approach 2:
The patent changes the compositional parameters by eliminating Co and using alternative element combinations with specific ratios, achieving the desired performance without relying on scarce and expensive Co resources
3Reliability
If the O2-type layered structure is used as the main phase to maintain structural stability at high voltage, then charge-discharge characteristics are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent employs a two-step manufacturing process where Na is first doped into the precursor to form a P2-type layered structure, then Li is introduced through ion exchange. This preliminary Na doping step facilitates the formation of the desired O2-type layered structure and simplifies the overall manufacturing process
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 new active material allows charging at high voltages with high discharge capacity and excellent discharge rate characteristics, avoiding the use of cobalt and maintaining structural stability, thus improving battery performance.
Implementation Method 1
substituting an Na atom in the Na-doped precursor with an Li atom by ion exchange
Data Source
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AI summary
A positive electrode active material includes, as a main phase, an O2-type layered structure attributable to space group P63mc, and has a composition represented by a composition formula LiaNabMncMdO(2 ± α) (in the composition formula, M represents one or more additive elements selected from the group consisting of Ni, Al, Ti, Sn, Zr, Nb, W, and Mo, the additive elements including at least Ni, and a to d and α satisfy 0.7 ≤ a ≤ 1.33, 0 < b < 0.1, 0.7 < c < 0.9, 0.9 < c + d <1.1, 4 ≤ c/d ≤ 12, and 0 ≤ α ≤ 0.3).