Lithium Vanadium Phosphate Electrodes for High Discharge Capacity
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Solution Overview
Problem
All-solid-state batteries using solid electrolytes face challenges in achieving high discharge capacity due to uneven crystalline grain boundaries and hindered lithium ion conduction, despite improvements in charge-discharge cycle characteristics with certain electrode materials.
Innovation Solution
The use of lithium vanadium phosphate as the active material in both positive and negative electrode layers, with specific Li/V ratios and bivalent V proportions, combined with lithium aluminum titanium phosphate as the solid electrolyte, to stabilize lithium ions and enhance ion conduction, resulting in a uniform grain boundary structure and increased discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stoichiometric Li3V2(PO4)3 is used as active material for sintered body electrodes, then charge-discharge cycle characteristics are improved, but discharge capacity is reduced due to uneven grain boundaries and hindered lithium ion conduction
Solution Approach 1:
The patent changes the chemical composition parameters of lithium vanadium phosphate by controlling the Li/V ratio and the proportion of bivalent V to form a non-stoichiometric compound. This parameter adjustment allows the material to achieve both good cycle characteristics and high discharge capacity by optimizing the balance between structural stability and ion conduction properties.
Solution Approach 2:
The patent creates a composite structure within the lithium vanadium phosphate material by incorporating multiple valence states of V and controlling the Li distribution. This composite approach at the molecular level produces uniform grain boundaries while maintaining structural integrity, thereby achieving both reliability and high capacity.
2Reliability
If solid electrolyte is used instead of liquid electrolyte, then safety problems such as leakage and exhaustion are eliminated, but discharge capacity is smaller compared to liquid electrolyte batteries
Solution Approach 1:
The patent optimizes the composition parameters of the solid electrolyte and electrode materials to enhance lithium ion conduction. By adjusting the Li/V ratio and V valence state in lithium vanadium phosphate, the material achieves better interfacial contact and ion transport efficiency, thereby increasing discharge capacity while maintaining the safety advantages of solid electrolytes.
Solution Approach 2:
The patent creates local optimization at the grain boundary regions and electrode-electrolyte interfaces by controlling the distribution of Li and V valence states. This local quality enhancement improves lithium ion conduction pathways specifically where needed, maximizing capacity without compromising the overall safety benefits of the solid electrolyte system.
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
This configuration allows for stable lithium ion movement and higher discharge capacity, improving the overall performance of all-solid-state batteries by optimizing the composition and structure of the electrode and electrolyte layers.
Implementation Method 1
the movement of lithium ions in the solid electrolyte layer between the positive electrode active material layer and the negative electrode active material layer becomes easier
Implementation Method 2
the lithium ions in the lithium vanadium phosphate can stably exist in crystal lattices
Data Source
AI summary
A high discharge capacity in an all-solid-state battery in which lithium vanadium phosphate is used in a positive electrode active material layer and a negative electrode active material layer. An all-solid-state battery wherein a positive electrode active material layer and a negative electrode active material layer contain lithium vanadium phosphate, which includes a Li- and V-containing polyphosphate compound and satisfies 1.50<Li/V≤2.30, with the percentage of divalent V included in the V being 5˜80%. Thus, a high discharge capacity can be provided.