Single-Crystal Li-Ion Cathode Composition for Lower Irreversible Capacity
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Solution Overview
Problem
Existing positive electrode active materials for lithium-ion rechargeable batteries, particularly those containing Al and B elements, suffer from low initial discharge capacity, high irreversible capacity, and high internal resistance at 50% state of charge, which limits their electrochemical performance.
Innovation Solution
A positive electrode active material powder comprising Li, M′ (with Ni between 60.0 and 75.0 mol %, Co between 0.0 and 20.0 mol %, Mn between 0.0 and 35.0 mol %, and D elements like Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, Zn, and Zr, with Al and B and W content between 0.1 and 5.0 mol %, exhibiting single-crystalline morphology and specific molar ratios, as determined by ICP and XPS analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If positive electrode active material comprises Al and B elements as in prior art, then the material can be manufactured, but it exhibits low initial discharge capacity and high irreversible capacity
Solution Approach 1:
The patent changes the chemical composition parameters by introducing W element and optimizing the Al:B ratio. Specifically, the material comprises Al in amount of 0.01-5.0 mol%, B in amount of 0.01-5.0 mol%, and W in amount of 0.01-5.0 mol% relative to total transition metal content, with Al/B molar ratio between 0.1 and 10. These parameter changes resolve the contradiction by achieving higher initial discharge capacity while reducing irreversible capacity loss compared to prior art containing only Al and B.
Solution Approach 2:
The patent creates a composite positive electrode active material combining multiple elements (Al, B, W) with specific ratios. The composite structure comprises lithium nickel manganese cobalt oxide (NMC) as base material with Al, B, and W additives in optimized proportions. This composite approach resolves the technical contradiction by synergistically combining the benefits of different elements to achieve both high initial discharge capacity and low irreversible capacity.
2Reliability
If positive electrode active material comprises Al and B elements, then the material structure can be formed, but it exhibits high internal resistance at 50% state of charge
Solution Approach 1:
The patent optimizes manufacturing parameters by controlling the amounts of Al, B, and W elements within specific ranges (0.01-5.0 mol% each) and maintaining Al/B molar ratio between 0.1 and 10. These parameter changes reduce internal resistance at 50% state of charge while preserving manufacturability through conventional ceramic processing techniques.
Solution Approach 2:
The patent applies local quality by concentrating Al, B, and W elements at specific sites within the material structure rather than uniform distribution. The elements are localized at grain boundaries and surface regions where they most effectively reduce internal resistance, while maintaining the overall NMC crystal structure integrity for ease of manufacture.
Data Source
AI summary
A positive electrode active material for batteries which comprises Li, M′, and oxygen, wherein M′ comprises: Ni in a content a between 60.0 mol % and 75.0 mol %; Co in a content x between 0.0 mol % and 20.0 mol %; Mn in a content y between 0.0 mol % and 35.0 mol %, a dopant D in a content z between 0.0 mol % and 2.0 mol %, Al, B and W in a total content c between 0.1 mol % and 5.0 mol %, wherein the active material has an Al content AlA, a B content BA, and a W content WA, wherein a, x, y, z, c, AlA, BA and WA are measured by ICP, wherein AlA, BA and WA, wherein the positive electrode active material, when measured by XPS analysis, shows an average Al fraction AlB, an average B fraction BB and an average W fraction WB, wherein AlB/AlA, BB/BA, and WB/WA are all larger than 1.0, and wherein the positive electrode active material is a single crystalline powder.