Ni-Rich Layered Cathode Coating for Stable Li-O Interlayer Spacing
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining excellent electrochemical properties, particularly at high-voltage operations due to instability in positive electrode active materials, leading to degradation in lifetime and capacity characteristics.
Innovation Solution
A lithium secondary battery design featuring a positive electrode with a lithium composite transition metal oxide powder having a layered structure, where nickel accounts for 50-75% of transition metals, and a doping element like Zr and Co, with a surface coating layer, exhibiting a minimal 3% change in Li-O interlayer spacing during charging and discharging, as measured by in-situ high-temperature XRD using synchrotron radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If LiCoO2 is used as positive electrode active material, then high operating voltage and excellent capacity characteristics are achieved, but thermal stability deteriorates and cost increases
Solution Approach 1:
The patent uses LiNi0.8Co0.1Mn0.1O2 composite material that combines nickel for high capacity, cobalt for catalytic activity, and manganese for thermal stability. This composite approach achieves high operating voltage while improving thermal stability compared to pure LiCoO2
Solution Approach 2:
The patent applies different elements to different functional requirements within the same material structure - nickel in the octahedral sites for capacity, cobalt for voltage maintenance, and manganese for structural stability, creating local functional optimization throughout the crystal structure
2Quantity of substance
If LiNiO2 is used as positive electrode active material, then reversible capacity is improved, but thermal stability deteriorates causing battery rupture risk
Solution Approach 1:
The patent creates LiNi0.8Co0.1Mn0.1O2 by combining nickel-based material (for capacity) with cobalt and manganese (for stability), achieving a balance where high reversible capacity is maintained while thermal stability is significantly improved compared to pure LiNiO2
Solution Approach 2:
Cobalt and manganese act as intermediary elements that mediate between nickel's high capacity and its thermal instability, with cobalt providing catalytic activity for lithium insertion/extraction and manganese providing structural framework stability
3Reliability
If NCM-based lithium oxides are used to improve thermal stability, then thermal stability is improved, but structural stability deteriorates under high-voltage operation leading to lifetime degradation
Solution Approach 1:
The patent optimizes the stoichiometric parameters of the LiNi0.8Co0.1Mn0.1O2 composition and controls synthesis parameters (temperature, time, atmosphere) to achieve a balanced structure that maintains stability under high-voltage conditions while retaining thermal stability benefits
Solution Approach 2:
The patent creates local structural optimization through element distribution in the crystal lattice, with manganese providing structural framework stability and cobalt providing local catalytic sites, creating regions with different functional properties that collectively maintain overall structural stability
4Quantity of substance
If charging voltage is increased to improve capacity, then capacity characteristics are improved, but surface instability increases due to side reactions with electrolyte
Solution Approach 1:
A coating layer is applied as an intermediary barrier between the LiNi0.8Co0.1Mn0.1O2 positive electrode material and the electrolyte, preventing direct contact and side reactions at high charging voltages while allowing lithium ion transport, thus maintaining surface stability during high-capacity operation
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 configuration enhances the battery's electrochemical performance and stability at high voltages, improving capacity and lifetime characteristics by minimizing structural changes and preventing electrolyte reactions.
Implementation Method 1
lithium ions are repeatedly intercalated and deintercalated through charging and discharging
Implementation Method 2
the lithium-oxygen (Li-O) interlayer spacing is measured by in-situ high-temperature XRD measuring instrument using synchrotron radiation
Implementation Method 3
the lithium-oxygen (Li-O) interlayer spacing is measured by in-situ high-temperature XRD measuring instrument using synchrotron radiation
Data Source
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AI summary
Provided is a lithium secondary battery which includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode includes, as a positive electrode active material, a lithium composite transition metal oxide powder having a layered structure and a nickel content accounting for 50 atm% to 75 atm% of total transition metals, and wherein the lithium composite transition metal oxide powder undergoes a 3% or less change in lithium-oxygen (Li-O) interlayer spacing (i.e., LiO6 slab thickness) in a state-of-charge (SOC) range of 58% to 86%.