Lithium Ion Battery Cathode Surface Gradient for Cycle Life
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Solution Overview
Problem
Conventional lithium ion secondary batteries with lithium composite oxides, such as LixCoO2 and LixNiO2, face challenges in maintaining cycle life performance, especially under intermittent charge and discharge cycles with long rest times, as they are prone to electrolyte decomposition and structural instability, leading to reduced battery lifetime.
Innovation Solution
A lithium ion secondary battery design incorporating a positive electrode with a lithium composite oxide represented by LivNi1-w-x-y-zCowCaxMgyMzO2, where elements like Co, Ca, and Mg are incorporated into the nickel-based oxide to form a solid solution, and further distributed more in the surface layer, enhancing thermal stability and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium composite oxide mainly composed of nickel (LixNiO2) is used as positive electrode active material, then cost is reduced, but reactivity with electrolyte increases and crystal structure stability decreases
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of elements Mc (Ca, Mg) within the active material particles, with higher concentration at the surface layer portion compared to the inner portion. This localized distribution provides enhanced electrolyte resistance and structural stability at the surface where electrolyte contact occurs, while maintaining the cost-effective nickel-based composition in the bulk material.
Solution Approach 2:
The patent employs composite materials by incorporating multiple elements (Ni, Co, Ca, Mg, and optionally Mn, Al, B, W, Nb, Ta, In, Mo, Sn, Ti, Zr, or Y) into a solid solution structure. This multi-element composite approach combines the cost advantages of nickel with the stabilizing effects of other elements, achieving both economical and performance benefits.
2Stability of the object's composition
If elements are incorporated to form solid solution, then crystal structure stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the concentration ranges of various elements in the solid solution. Specifically, it defines precise compositional parameters (0 < x ≤ 0.2, 0 < y ≤ 0.1, 0 < z ≤ 0.05, 0 ≤ w ≤ 0.3, 0.85 ≤ v ≤ 1.25) that balance crystal structure stability with manufacturing feasibility, avoiding overly complex formulations while achieving sufficient performance improvement.
3Object-affected harmful factors
If element Mc is distributed more in surface layer portion, then electrolyte decomposition is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements local quality by establishing a specific elemental distribution pattern where elements Mc (Ca, Mg) are concentrated in the surface layer portion of active material particles. This localized enrichment provides targeted protection against electrolyte decomposition at the particle surface, while the overall manufacturing process remains feasible through controlled synthesis methods.
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
This approach significantly improves the intermittent cycle performance of lithium ion secondary batteries by stabilizing the crystal structure and reducing electrolyte decomposition, leading to extended battery life even under conditions with prolonged rest times.
Implementation Method 1
incorporating a different element in the lithium composite oxide to form a solid solution to stabilize the crystal structure of the lithium composite oxide
Implementation Method 2
a coating film comprising a specific metal oxide is formed on the positive electrode active material surface
Implementation Method 3
a non-aqueous electrolyte; the positive electrode including active material particles
Data Source
AI summary
The positive electrode of the lithium ion secondary battery includes active material particles containing a lithium composite oxide represented by:LivNi1-w-x-y-zCowCaxMgyMzO2 (0.85≦v≦1.25, 0<w≦0.75, 0<x≦0.1, 0<y≦0.1, 0≦z≦0.75, 0<w+x+y+z≦0.80, and element M is an element other than Co, Ca, and Mg), and(i) when 0<z, element M includes element Me of at least one selected from the group consisting of Mn, Al, B, W, Nb, Ta, In, Mo, Sn, Ti, Zr, and Y; and element Mc of at least one selected from the group consisting of Ca, Mg, and element Me is distributed more in the surface layer portion compared with the inner portion of the active material particles, and(ii) when 0=z, element Mc of at least one selected from the group consisting of Ca and Mg is distributed more in the surface layer portion compared with the inner portion of the active material particles.