Zinc Solid-Solved Surface on Lithium-Nickel-Cobalt Oxide
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Solution Overview
Problem
Lithium-nickel composite oxides used in nonaqueous electrolyte secondary batteries face challenges such as degraded cycle characteristics, increased resistance, and atmospheric degradation due to lithium deficiency and moisture reaction, limiting their high-energy density and cost-effectiveness for portable and electric vehicle applications.
Innovation Solution
A positive electrode active material comprising a lithium-nickel-cobalt-zinc composite oxide powder with a zinc solid-solved region on its surface, achieved through coating with a zinc compound followed by heat treatment, maintains low reaction resistance and high discharge capacity even when exposed to the atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium-nickel composite oxide is used as positive electrode active material, then cost is reduced and capacity is increased, but cycle characteristics are degraded and atmospheric degradation occurs
Solution Approach 1:
The patent applies local quality by creating a zinc-containing surface layer on the lithium-nickel-cobalt composite oxide particles. This surface layer has different composition and properties from the interior, providing atmospheric resistance locally at the surface while maintaining the high-capacity nickel-rich composition in the bulk material. The zinc content is specifically controlled to be 0.01-1.5 mass% to achieve this localized protection without compromising overall battery capacity.
Solution Approach 2:
The patent creates a composite material structure by combining lithium-nickel-cobalt composite oxide with zinc compound. This composite structure integrates the high capacity benefits of nickel-based materials with the atmospheric stability of zinc-containing compounds. The composite oxide has a dual-function structure: the core provides high capacity while the zinc-containing surface layer provides protection against atmospheric degradation and improved cycle characteristics.
2Reliability
If zinc compound is added to form zinc solid-solved region, then atmospheric resistance is improved and cycle characteristics are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent merges the coating process with the existing sintering step by conducting the zinc compound coating immediately before the sintering process. The coating and subsequent heating are combined into a sequential operation without intermediate steps. This integration allows the zinc compound to be applied and then activated in a single manufacturing flow, reducing the number of separate process steps while achieving the desired surface modification.
Solution Approach 2:
The patent utilizes parameter changes by controlling the heating temperature and atmosphere during the sintering process to achieve zinc solid solution formation. By adjusting the heating conditions (temperature, atmosphere composition, and duration), the zinc compound transforms into a zinc-containing solid solution within the oxide structure. This parameter-controlled transformation achieves the desired surface layer without requiring additional complex processing equipment or steps.
3Ease of manufacture
If lithium hydroxide remains in the positive electrode active material, then synthesis is simplified, but gelation occurs during paste preparation and gas generation occurs during charging
Solution Approach 1:
The patent applies preliminary action by removing excess lithium hydroxide through the zinc compound coating process before paste preparation. The zinc compound reacts with and removes the harmful lithium hydroxide residues during the coating step, which occurs before electrode assembly. This preliminary removal prevents gelation during subsequent paste preparation and eliminates the source of gas generation during charging, while still allowing simplified synthesis conditions.
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 lithium-nickel-cobalt-zinc composite oxide powder with a zinc solid-solved region enhances battery performance by preventing lithium deficiency and atmospheric degradation, ensuring high discharge capacity and low reaction resistance, making it suitable for both portable and electric vehicle applications.
Implementation Method 1
achieved through coating with a zinc compound followed by heat treatment
Implementation Method 2
At least a part of a surface of the lithium-nickel-cobalt-zinc composite oxide powder includes a zinc solid-solved region where zinc is solid-solved
Data Source
AI summary
A positive electrode active material for a nonaqueous electrolyte secondary battery includes a lithium-nickel-cobalt-zinc composite oxide powder that contains lithium (Li); nickel (Ni); cobalt (Co); element M, which is at least one element selected from the group consisting of manganese (Mn), vanadium (V), magnesium (Mg), molybdenum (Mo), niobium (Nb), silicon (Si), titanium (Ti), and aluminum (Al); and zinc (Zn). A molar element ratio (Li:Ni:Co:M) of the lithium-nickel-cobalt-zinc composite oxide powder satisfies Li:Ni:Co:M=z:(1-x-y):x:y (where 0.95≤z≤1.10, 0.05≤x≤0.35, and 0≤y≤0.10); a zinc content with respect to Li, Ni, Co, the element M, and oxygen in the lithium-nickel-cobalt-zinc composite oxide powder is greater than or equal to 0.01 mass % and less than or equal to 1.5 mass %; and at least a part of a surface of the lithium-nickel-cobalt-zinc composite oxide powder includes a zinc solid-solved region where zinc is solid-solved.