Single-Crystal LCO Cathode Blend for High-Voltage Stability
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Solution Overview
Problem
Existing lithium-ion secondary battery positive electrode active materials, specifically those comprising a mixture of large single-crystalline LCO powder and small polycrystalline LCO powder, exhibit insufficient high temperature and high voltage stability, as well as low powder density, leading to reduced electrode density and performance.
Innovation Solution
A positive electrode active material for lithium-ion secondary batteries is composed of a mixture of a first single-crystalline LCO powder with a higher median particle size D50 and a second single-crystalline LCO powder with a lower median particle size D50, where the volume fraction of the second powder ranges from 10% to 40%, resulting in improved stability and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mixture of large single-crystalline LCO powder and small polycrystalline LCO powder is used, then the positive electrode active material can be manufactured, but the high temperature and high voltage stability is insufficient
Solution Approach 1:
The patent changes the particle size parameter by using a bimodal distribution with D50 values of 12-25 μm and 3-8 μm, and changes the crystal structure parameter by ensuring both powders are single-crystalline. These parameter changes resolve the contradiction by achieving high temperature and high voltage stability while reducing harmful factors like Q floating and Co dissolution.
Solution Approach 2:
The patent creates a composite positive electrode active material by mixing two different single-crystalline LCO powders with different particle sizes. This composite structure combines the benefits of large particles (high density) and small particles (good stability), resolving the contradiction between reliability and harmful factors.
2Quantity of substance
If a mixture of large single-crystalline LCO powder and small polycrystalline LCO powder is used, then the positive electrode active material can be manufactured, but the powder density is low
Solution Approach 1:
The patent changes the particle size parameter by using a bimodal distribution with specific D50 ranges (12-25 μm for first powder, 3-8 μm for second powder), which optimizes the packing density. This parameter change resolves the contradiction by achieving high powder density while maintaining good electrode density.
3Ease of manufacture
If small polycrystalline LCO powder is used, then the manufacturing process can be simplified, but the high temperature and high voltage stability deteriorates
Solution Approach 1:
The patent changes the crystal structure parameter by ensuring both powders are single-crystalline, which improves high temperature and high voltage stability. Although this may increase manufacturing complexity compared to polycrystalline materials, the parameter change is necessary to achieve the desired reliability.
Data Source
AI summary
A positive electrode active material for lithium-ion secondary batteries comprises Li, Co, O, and optionally M′. M′ comprises Al and/or Ti and optionally one or more elements selected from the group consisting of Ni, Mn, B, Sr, Mg, Nb, W, F, and Zr. A molar ratio of Co to M′+Co (Co/(M′+Co)) is more than 0.90. The positive electrode active material comprises a first LCO powder and a second LCO powder that are both single-crystalline powders. The first LCO powder has a first median particle size D50A of between 12 μm and 25 μm, the second LCO powder has a second median particle size D50B of between 3 μm and 8 μm, and the volume fraction of the second LCO powder relative to the total volume of the positive electrode active material is between 10% and 40%.