LiNiMnCoO2 Positive Electrode Material for High-Capacity Batteries
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Solution Overview
Problem
Existing positive electrode active materials for non-aqueous electrolyte secondary batteries face challenges in achieving high capacity while ensuring safety, as high Ni content leads to low volume resistivity and safety issues, and low Ni content results in low capacity and reactivity.
Innovation Solution
A positive electrode active material with a specific molar ratio of Ni, Mn, and Co, combined with lithium, is developed, featuring a controlled molar ratio and production method to achieve a suitable volume resistivity and high capacity, including a two-step baking process in a rotary kiln and furnace to minimize oxygen deficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the Ni content is increased to provide high capacity, then the capacity is improved, but the volume resistivity becomes excessively low which impairs battery safety
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molar ratios of Ni, Mn, and Co within specific ranges (Ni: 0.45-0.65, Mn: 0.15-0.35, Co: 0.15-0.25) and adjusting the Li ratio (0.95-1.05) to achieve optimal balance between capacity and safety. This systematic parameter optimization resolves the contradiction by finding the sweet spot where high Ni content provides sufficient capacity while maintaining adequate volume resistivity for safety.
Solution Approach 2:
The patent employs composite materials by creating a multi-element composite oxide system (Li-Ni-Mn-Co-O) where different metals serve complementary functions. Ni provides high capacity, Mn stabilizes the structure and prevents oxygen deficiency, and Co enhances electronic conductivity. This composite approach allows the material to simultaneously achieve high capacity and maintain safety through synergistic effects of multiple elements.
2Reliability
If the Ni content is decreased to maintain volume resistivity and safety, then the battery safety is improved, but the capacity decreases
Solution Approach 1:
The patent employs composite materials to compensate for reduced Ni content by leveraging the synergistic effects of Mn and Co. The Mn-rich portions provide structural stability and prevent oxygen deficiency, while Co-rich portions maintain electronic conductivity. This composite strategy allows the material to maintain safety at lower Ni content while minimizing capacity loss through the contributions of other elements.
Solution Approach 2:
The patent applies parameter changes by adjusting the overall metal ratio and individual element ratios to optimize the balance between safety and capacity. By controlling the Ni content within 0.45-0.65 and adjusting Mn and Co accordingly, the patent achieves adequate volume resistivity for safety while maintaining sufficient capacity through optimized composition parameters.
3Reliability
If a two-step baking process is used to minimize oxygen deficiency and improve safety, then the battery safety is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the baking process into two distinct steps with different temperature ranges and atmospheric conditions. The first step (lower temperature, oxygen atmosphere) removes organic residues and prevents oxygen deficiency, while the second step (higher temperature, inert atmosphere) completes sintering and forms the final crystal structure. This segmented approach minimizes oxygen deficiency and improves safety despite increased process complexity.
Solution Approach 2:
The patent uses preliminary action by performing the first baking step in an oxygen atmosphere before the second step to pre-prevent oxygen deficiency. This preliminary oxidation treatment ensures that oxygen is incorporated into the crystal structure early in the process, preventing oxygen vacancies that would compromise safety. This preliminary action is crucial for achieving the desired safety level.
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 solution provides a non-aqueous electrolyte secondary battery with enhanced capacity and safety by maintaining a suitable volume resistivity and preventing oxygen deficiency, thereby improving battery performance and cycle characteristics.
Implementation Method 1
the electronic conductivity of the composite oxide becomes low and the reactivity of the electrode decreases
Implementation Method 2
a two-step baking process in a rotary kiln and furnace to minimize oxygen deficiency
Data Source
AI summary
A positive electrode active material for a non-aqueous electrolyte secondary battery is provided. The positive electrode active material includes a composite oxide containing lithium and metal M other than lithium, and M contains Ni, Mn, and Co. The molar ratio of Ni to the total of Ni, Mn, and Co is from 0.45 to 0.65, and the molar ratio of Mn to the total of Ni, Mn, and Co is from 0.15 to 0.35. The positive electrode active material has a pressed density under a compression of 60 MPa of 3.3 g/cm3 or more and 4.3 g/cm3 or less. The positive electrode active material has a volume resistivity under a compression of 60 MPa of 100 Ω·cm or more and less than 1000 Ω·cm.