Li-ion Cathode Precursor Ion Exchange for Energy Density
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Solution Overview
Problem
Current Li-ion battery technology faces challenges with high-energy density cathode materials like HE-NCM, which have impedance, voltage profile, and stability issues, limiting their commercial viability.
Innovation Solution
A precursor for Li-ion cathode materials with a composition of LixAy(MnaNibMc)O2+d, where x+y is between 1.1 and 1.5, and A represents Na, K, or Cs, is synthesized using a two-step co-precipitation/solid state process, followed by ion-exchange to produce IE-HE-NCM with improved inter-layer spacings and reduced ion exchange extent, lowering processing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-energy NCM cathode materials are used to increase capacity, then energy density is improved, but impedance and stability issues worsen
Solution Approach 1:
A coating layer comprising at least one of a metal oxide, metal hydroxide, metal carbonate, or metal hydroxycarbonate is applied to the surface of the NCM cathode material particles. This coating acts as an intermediary between the NCM particles and the electrolyte, stabilizing the surface chemistry and reducing impedance while preserving the high capacity characteristics of the NCM material
2Ease of manufacture
If conventional solid state synthesis is used to produce HE-NCM, then manufacturing simplicity is maintained, but rate capability and cycling stability worsen
Solution Approach 1:
The synthesis process is divided into two distinct stages: (1) co-precipitation to form a precursor with controlled morphology and composition, followed by (2) thermal treatment to achieve the final HE-NCM phase. This segmentation allows optimization of each stage independently, improving rate capability and cycling stability while maintaining manufacturing feasibility
3Productivity
If ion exchange is used to improve rate capability and cycling stability, then performance is improved, but processing cost increases
Solution Approach 1:
The co-precipitation process is designed to pre-form a precursor with optimal morphology, composition, and surface characteristics that closely resemble the final HE-NCM product. This preliminary action reduces the extent of ion exchange required, thereby improving rate capability and cycling stability while minimizing processing costs
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 approach results in higher rate capability, cycling stability, and energy density, while reducing processing costs and enabling greater control over morphology and properties of the final cathode materials.
Implementation Method 1
a Li-ion cathode material that is synthesized by ion-exchange from the precursor
Data Source
AI summary
Li-ion cathode materials with improved performance characteristics and precursors to prepare such materials are disclosed. The precursors consist of complex, mixed alkali transition metal oxides of the formula LixAy(MnaNibMc)O2+d, where M represents one or more selected from transition metal elements beside Ni and Mn, and the groups IIA and IIIA elements of the periodic table, x is between 1 and 1.4, y is between 0.1 and 0.5, and x+y is between 1.1 and 1.5, a+b+c=1, the value of d depends on the proportions and average oxidation states of the cation elements Li, A, Mn, Ni and M such that the combined positive charge of the cation elements is balanced by the number of oxygen anions, A represents one or more elements selected from Na, K and Cs. The Li-ion cathode materials are produced by exchange of element(s) A for Li under mild conditions to limit the degree of structural reorganization that occurs during the reaction.