High-Nickel Cathode Material With Spinel Transition for Thermal Stability
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Solution Overview
Problem
Lithium secondary batteries with high nickel content face challenges in maintaining structural and chemical stability, leading to rapid degradation and reduced lifetime characteristics, especially at high temperatures, due to exothermic reactions and cation mixing.
Innovation Solution
A lithium secondary battery design incorporating a positive electrode active material with a lithium composite transition metal oxide having a layered structure that transforms into a spinel structure at 300°C or more in a fully charged state, utilizing Ti and W as doping elements, which enhances thermal stability and electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content (50 at% or more) is used in the positive electrode active material, then capacity implementation is improved, but structural stability and chemical stability decrease leading to rapid degradation
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of doping elements within the particle structure. The doping elements (Ti, Zr, Hf) are concentrated at the surface region rather than being uniformly distributed, providing localized stabilization where it is most needed to prevent degradation while maintaining high nickel content in the bulk for capacity.
Solution Approach 2:
The patent creates a composite material system by combining high-nickel NCM (Ni0.80Co0.08Mn0.12O2) with doping elements (Ti, Zr, Hf) in specific proportions. This composite approach allows the material to exhibit both high capacity from the nickel-rich base and enhanced stability from the doping elements, particularly through the formation of a stabilized surface layer.
2Quantity of substance
If high nickel content (80 at% or more) is used in the positive electrode active material, then capacity is further improved, but lifetime characteristics are rapidly degraded at high temperature due to cation mixing and irreversible phase transformation
Solution Approach 1:
The patent applies preliminary anti-action by pre-doping the high-nickel NCM material with stabilizing elements (Ti, Zr, Hf) before battery operation. This preliminary stabilization prevents cation mixing and irreversible phase transformation that would otherwise occur during cycling, particularly at high temperatures, thereby extending lifetime while maintaining high capacity.
Solution Approach 2:
The patent modifies the compositional parameters of the positive electrode active material by precisely controlling the nickel content (0.80 ≤ a < 0.95) and doping element concentrations ([b+d] ≥ 0.05 and [c+e] ≥ 0.05). These parameter changes optimize the balance between capacity and lifetime characteristics at high temperature.
3Reliability
If doping with metal element is performed to improve structural stability, then thermal structural stability is improved, but capacity is decreased and resistance increases at high temperatures
Solution Approach 1:
The patent resolves this contradiction by concentrating doping elements at the surface region rather than uniformly distributing them throughout the particle. This localized doping provides thermal structural stability where it is most needed (at the surface) while minimizing the doping element content in the bulk, thereby preserving capacity.
Solution Approach 2:
The patent optimizes the doping element concentration parameters with specific ranges: [b+d] ≥ 0.05 and [c+e] ≥ 0.05, where b and c are base doping elements and d and e are additional doping elements. These parameter constraints ensure sufficient structural stability while limiting capacity loss from excessive doping.
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 battery exhibits minimized capacity reduction and resistance increase at high temperatures, maintaining stable electrochemical performance and extending the battery's lifetime characteristics.
Implementation Method 1
the layered structure of the positive electrode active material is phase-transformed into a spinel structure at a temperature of 300° C. or more in a fully charged state
Data Source
AI summary
Provided is a lithium secondary battery including 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 % or more of total transition metals, and wherein the layered structure of the positive electrode active material is phase-transformed into a spinel structure at a temperature of 300° C. or more in a fully charged state.