Single-Crystal Ni-Rich Cathode Composition for Low Irreversible Capacity
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Solution Overview
Problem
Existing positive electrode active materials for lithium-ion rechargeable batteries have low initial discharge capacity (DQ1) and high irreversible capacity (IRRQ), particularly when the nickel content is high, as seen in materials like lithium nickel manganese cobalt oxide (NMC) powders.
Innovation Solution
A positive electrode active material comprising Li, Ni, Co, Mn, D (where D includes elements like Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, Zn, W, and Zr), Al, and B, with a nickel content between 70.0 mol % and 95.0 mol %, and total Al and B content between 0.1 mol % and 5.0 mol %, forming a single-crystalline powder with specific atomic and molar fractions, optimized for improved electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the nickel content in the positive electrode active material is increased to improve discharge capacity, then the initial discharge capacity increases, but the irreversible capacity loss increases
Solution Approach 1:
The patent optimizes the nickel content parameter within a specific range (70-95 mol%) and combines it with aluminum and boron dopants to change the material's electrochemical parameters, achieving high discharge capacity while controlling irreversible capacity loss through precise compositional control
Solution Approach 2:
The patent creates a composite positive electrode active material containing lithium, nickel, cobalt, manganese, aluminum, and boron elements. This composite approach allows the material to benefit from nickel's high capacity while aluminum and boron mitigate the irreversible capacity loss, resolving the contradiction between high power and low energy loss
2Power
If the nickel content is increased to achieve higher discharge capacity, then the discharge capacity improves, but the material stability deteriorates
Solution Approach 1:
The patent introduces aluminum and boron dopants at specific local positions within the crystal structure to modify local properties. These dopants stabilize the crystal structure in regions where high nickel content would otherwise cause instability, allowing high overall nickel content while maintaining local structural integrity
Solution Approach 2:
The patent carefully controls the nickel content parameter within 70-95 mol% and combines it with aluminum and boron dopant parameters to optimize both discharge capacity and material stability. This parameter optimization ensures high capacity while preventing structural degradation
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 70.0 mol % and 95.0 mol %; Co in a content x between 0.0 mol % and 25.0 mol %; Mn in a content y between 0.0 mol % and 25.0 mol %, a dopant D in a content z between 0.0 mol % and 2.0 mol %, Al and B in a total content c between 0.1 mol % and 5.0 mol %, wherein the active material has an Al content AlA and a B content BA, wherein a, x, y, z, c, AlA and BA are measured by ICP, wherein AlA, and BA are expressed as molar fractions compared to the sum of a and x and y, wherein the positive electrode active material, when measured by XPS analysis, shows an average Al fraction AlB and an average B fraction BB, wherein the ratio AlB/AlA>1.0, wherein the ratio BB/BA>1.0, and wherein the positive electrode active material is a single-crystalline powder.