Positive Electrode Additive Chemistry for Low-Gas Lithium Cathodes
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Solution Overview
Problem
Lithium secondary batteries face limitations in developing positive electrode additives with high irreversible capacity, leading to side reactions and gas generation during charging/discharging, which degrade battery performance and safety.
Innovation Solution
A positive electrode for lithium secondary batteries incorporating a specific positive electrode additive represented by Formula 1, with controlled X-ray diffraction and EXAFS peaks, and a lithium metal composite oxide, to reduce side reactions and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional irreversible additive (Li6CoO4) is used to provide high irreversible capacity, then battery capacity is improved, but side reactions and oxygen gas generation occur during charging/discharging
Solution Approach 1:
The patent changes the chemical composition parameters of the irreversible additive by introducing multiple metal elements (Ni, Co, Mn, Zn) in specific ratios. The additive has the general formula Li6-x-y-z-aNi_xCo_yMn_zO4 with controlled element concentrations (0.1≤x,y,z≤0.4 and x+y+z≤1.0), which modifies the crystal structure and chemical stability to reduce oxygen release while maintaining irreversible capacity.
Solution Approach 2:
The patent creates a composite irreversible additive material combining multiple metal oxides (NiO, CoO, MnO, ZnO) with lithium oxide in a specific composite structure. This multi-element composite approach leverages the synergistic effects of different metals to enhance structural stability and suppress side reactions while providing sufficient irreversible capacity.
2Productivity
If irreversible additive remains unreacted after initial charging, then battery assembly is completed faster, but side reactions occur during subsequent charging/discharging
Solution Approach 1:
The patent optimizes the chemical composition parameters to ensure complete reaction during initial charging. The specific ratio control of metal elements (x+y+z≤1.0) and the use of multiple reactive metals create an additive that reacts more completely and uniformly during activation, eliminating residual unreacted material that would cause later side reactions.
Solution Approach 2:
The patent designs the additive composition to create a uniform and complete reaction pattern during initial charging. By controlling the metal element distribution and reactivity, the additive ensures consistent reaction across all particles, preventing localized unreacted regions that would otherwise cause subsequent side reactions.
3Ease of manufacture
If lithium oxide by-products are present in slurry composition, then additive preparation is simpler, but viscosity increases and uniform electrode application becomes difficult
Solution Approach 1:
The patent controls the composition parameters of the irreversible additive to minimize by-product formation. By precisely controlling the metal element ratios and total concentration (x+y+z≤1.0), the additive produces minimal lithium oxide by-products during synthesis, ensuring the slurry maintains appropriate viscosity for uniform electrode coating.
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 improves battery safety and electrical performance by minimizing side reactions and gas generation, enhancing charge/discharge capacity and cycle life.
Implementation Method 1
the positive electrode mixture layer has one or more peaks shown at 19.1±0.5°, 36.6±0.5°, 38.7±0.5°, 42.4±0.5° and 44.8±0.5°, represented by 2θ, in X-ray diffraction (XRD) measurement
Implementation Method 2
the positive electrode mixture layer may have peak(s) at one or more of 1.4±0.5 Å, 2.4±0.5 Å, 4.45±0.5 Å, 4.6±0.5 Å, 5.1±0.1 Å and 5.2±0.1 Å in extended X-ray absorption fine-structure (EXAFS) analysis
Data Source
AI summary
The present technology provides a positive electrode for a lithium secondary battery and a lithium secondary battery including the same. In the positive electrode, a positive electrode additive represented by Formula 1 is contained in a positive electrode mixture layer, and specific X-ray diffraction (XRD) and/or extended X-ray absorption fine-structure (EXAFS) peak(s) are controlled for cobalt remaining in the positive electrode mixture layer after initial charging to SOC 100% to have a specific oxidation number, thereby reducing side reactions caused by the irreversible additive, that is, the positive electrode additive, and reducing the amount of gas such as oxygen generated during charging/discharging. Therefore, the lithium secondary battery has an excellent effect of improving battery safety and electrical performance.