Cobalt-Free Cathode Coating for Stable High-Nickel Li-Ion Batteries
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Solution Overview
Problem
Cobalt-free nickel-manganese layered materials with high nickel content face structural instability, poor safety, low conductivity, and poor cycle performance due to side reactions with electrolytes, limiting their practical application in lithium ion batteries.
Innovation Solution
A method involving a two-step sintering process of a lithium source material and a cobalt-free precursor to produce a layered cobalt-free positive electrode material LiNi1-xMnxO2, followed by crushing and coating with boron and carbon agents to form a stable boron carbide layer, enhancing structural stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high nickel content (greater than 80%) is used in cobalt-free positive electrode material, then energy density and cost are improved, but structural instability, safety, and cycle performance deteriorate
Solution Approach 1:
The patent precisely controls the nickel content parameter within 80-95 mol% and adjusts the ratio of nickel to manganese elements. This parameter optimization resolves the contradiction by finding the optimal composition range that provides sufficient energy density while maintaining structural stability, avoiding the extreme high-nickel content that causes instability.
Solution Approach 2:
The patent creates a composite material system combining nickel-manganese layered structure with surface coating layers. The bulk material provides high nickel content for energy density, while the surface coating (boron, carbon, or boron carbide) provides structural stability and safety, resolving the contradiction between energy density and reliability.
2Ease of manufacture
If high nickel content is used in cobalt-free positive electrode material, then cost is reduced, but cycle performance deteriorates due to side reactions with electrolyte
Solution Approach 1:
The patent introduces a surface coating layer (boron, carbon, or boron carbide) as an intermediary between the high-nickel bulk material and the electrolyte. This coating acts as a protective barrier that prevents direct contact between the reactive high-nickel material and the electrolyte, thereby improving cycle performance while maintaining the cost advantage of cobalt-free composition.
Solution Approach 2:
The patent optimizes the composition parameters including nickel content (80-95 mol%), lithium to (nickel+manganese) ratio (0.95-1.10:1), and surface coating content (0.01-5 mol%). These parameter changes enable the material to achieve both cost-effectiveness and improved cycle performance by reducing side reactions.
3Reliability
If nickel content is reduced and manganese content is increased in cobalt-free material, then structural stability is improved, but conductivity and electric capacity deteriorate
Solution Approach 1:
The patent optimizes the nickel to manganese ratio parameter within specific ranges (nickel 80-95 mol%, manganese 5-20 mol%) to balance structural stability and electric capacity. Additionally, the lithium to (nickel+manganese) ratio is controlled at 0.95-1.10:1 to ensure optimal stoichiometry that enhances both stability and capacity.
Solution Approach 2:
The patent creates a composite structure with a nickel-manganese layered bulk material providing structural stability and a conductive surface coating layer (boron, carbon, or boron carbide) providing enhanced conductivity. This composite approach allows the bulk to maintain low nickel content for stability while the coating compensates for conductivity losses, achieving both structural stability and high electric capacity.
4Quantity of substance
If doping with titanium is performed to improve conductivity, then electric capacity increases to 180 mAh/g, but it is still far lower than high nickel materials with 200-210 mAh/g
Solution Approach 1:
The patent replaces complex doping processes with a simpler surface coating approach using boron, carbon, or boron carbide. This coating method is easier to implement and provides sufficient conductivity enhancement and capacity improvement (203-210 mAh/g) without the complexity of multi-step doping processes, achieving better results than titanium doping with less complexity.
5Quantity of substance
If doping with silicon is performed to improve electric capacity to 192 mAh/g, then capacity increases, but cycle performance is still not ideal with maximum retention rate of only 78%
Solution Approach 1:
The patent creates a composite material with a nickel-manganese layered bulk structure and a protective surface coating of boron, carbon, or boron carbide. The bulk material provides high electric capacity (203-210 mAh/g) while the surface coating provides structural stability and protects against electrolyte degradation during cycling. This composite structure achieves both high capacity and excellent cycle performance with retention rates exceeding 90% after 500 cycles, significantly improving upon silicon doping results.
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 method improves the electric capacity, current rate performance, and cycle retention rate of the cobalt-free positive electrode material, reducing gas production and maintaining a stable structure, thereby addressing the limitations of existing cobalt-free materials.
Implementation Method 1
a second sintering step is performed on the cobalt-free single crystal material, a boron coating agent and a carbon coating agent, to obtain the cobalt-free positive electrode material
Implementation Method 2
a first sintering step is performed on a lithium source material and a cobalt-free precursor, to obtain a sintered product
Data Source
AI summary
Provided are a cobalt-free positive electrode material, a preparation method thereof and a lithium ion battery. The preparation method includes: first sintering step is performed on a lithium source material and a cobalt-free precursor, to obtain a sintered product; the sintered product is crushed to 1 to 2 μm, to obtain a cobalt-free single crystal material; and second sintering step is performed on the cobalt-free single crystal material, a boron coating agent and a carbon coating agent, to obtain the cobalt-free positive electrode material. The cobalt-free positive electrode material prepared by the above method has advantages of stable structure, high electric capacity, excellent current rate performance and good cycle performance and the like.