Li-Ion Battery Core-Shell Cathode for Heat Suppression
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Solution Overview
Problem
Lithium ion secondary batteries with lithium composite oxides containing nickel as the main component face challenges in curbing abnormal heat generation during internal short-circuits, particularly at high temperatures, due to reactive nickel species and electrolyte decomposition reactions, which affect safety and reliability.
Innovation Solution
A lithium ion secondary battery design featuring a positive electrode with a core of lithium-nickel composite oxide (LixNi1-y-zCoyMezO2) and a surface layer containing nickel oxide with a NaCl-type crystal structure and a second lithium-nickel composite oxide, where element Me (such as Al, Mn, or Mg) is distributed more on the surface, converting side reaction active points into electrochemically inactive oxides to prevent oxygen desorption and electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium composite oxide containing nickel as main component is used, then cost is reduced, but abnormal heat generation occurs during internal short-circuit
Solution Approach 1:
The patent applies local quality by creating a surface layer with different composition and properties from the core. The surface layer contains nickel oxide with NaCl-type crystal structure and second lithium-nickel composite oxide, which are specifically designed to be electrochemically inactive and suppress side reactions, while the core maintains high capacity lithium-nickel composite oxide composition.
Solution Approach 2:
The patent uses composite materials by combining lithium-nickel composite oxide with nickel oxide and second lithium-nickel composite oxide in a core-shell structure. This composite structure allows the battery to benefit from both the high capacity of lithium-nickel composite oxide and the safety of the inactive surface layer that prevents abnormal heat generation.
2Ease of manufacture
If lithium composite oxide containing nickel is used, then cost is reduced, but reliability decreases due to electrolyte decomposition reaction
Solution Approach 1:
The surface layer is designed with specific local quality to prevent electrolyte decomposition. It contains nickel oxide with NaCl-type crystal structure and element M distributed on the surface, creating a protective barrier that is electrochemically inactive and prevents contact between the electrolyte and reactive nickel species in the core.
Solution Approach 2:
The surface layer acts as an intermediary between the electrolyte and the lithium-nickel composite oxide core. This intermediate layer prevents direct interaction between the electrolyte and reactive nickel species, thereby suppressing electrolyte decomposition reactions while allowing lithium ion transport.
3Object-affected harmful factors
If surface layer is added to prevent side reactions, then safety is improved, but high-rate performance at low temperature deteriorates
Solution Approach 1:
The patent optimizes parameters including the thickness of the surface layer, the composition ratios of nickel oxide and second lithium-nickel composite oxide, and the distribution of element M on the surface. These parameter changes ensure the surface layer is thin enough to allow lithium ion transport at low temperatures while being thick enough to suppress side reactions.
Solution Approach 2:
The surface layer has localized quality differences with element M concentrated on the outer surface and nickel oxide with NaCl-type structure in the inner part of the surface layer. This gradient structure allows optimized lithium ion transport at the outer surface while maintaining side reaction suppression in the inner region.
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 design enhances safety during internal short-circuits by reducing heat generation without compromising high-rate performance at low temperatures, as the surface layer modifications effectively curb side reactions while maintaining battery capacity and performance.
Implementation Method 1
nickel oxide with the nickel oxidation number of 3 or less... converting side reaction active points into electrochemically inactive oxides to prevent oxygen desorption and electrolyte decomposition
Implementation Method 2
Lithium ion secondary batteries, a typical example of non-aqueous electrolyte secondary batteries, have high electromotive force and high energy density
Data Source
AI summary
Active material particles of a lithium ion secondary battery includes at least a first lithium-nickel composite oxide: LixNi1-y-zCoyMezO2 (where 0.85≦̸x≦̸1.25, 0<y≦̸0.5, 0≦̸z≦̸0.5, 0<y+z≦̸0.75, and element Me is at least one selected from the group consisting of Al, Mn, Ti, Mg, and Ca) forming a core portion thereof. The surface layer portion of the active material particles includes nickel oxide having the NaCl-type crystal structure or a second lithium-nickel composite oxide, and further includes element M not forming the crystal structure of the first lithium-nickel composite oxide. Element M is at least one selected from the group consisting of Al, Mn, Mg, B, Zr, W, Nb, Ta, In, Mo, and Sn.